Protein Kinase C (PKC ) and Bipolar Disorder -- Neurotransmitter.net

(Updated 8/25/04)

[For more information on the relationship between mood stabilizers and protein kinase C (PKC), please click here.]

Hahn CG, Friedman E.
Abnormalities in protein kinase C signaling and the pathophysiology of bipolar disorder.
Bipolar Disord 1999 Dec;1(2):81-6
"Protein kinase C (PKC) is a group of calcium and phospholipid-dependent enzymes, which plays a pivotal role in cell signaling systems. Recently accumulated evidence indicates that alterations in PKC activity play a significant role in the pathophysiology of bipolar disorder. A number of laboratories investigated the effect of mood stabilizers on the regulation of PKC activity in bipolar patients, in animals, and in cultured cells. Following chronic lithium treatment, PKC activation was significantly reduced in rat brains, as measured by the translocation of cytoplasmic PKC to the membrane compartment, or by quantitative binding of the PKC ligand, PDBu. The effect of the therapeutic concentration of lithium in attenuating PKC-dependent intracellular parameters was also demonstrated in cultured cells. More importantly, alterations in platelet PKC was shown in bipolar patients during the manic state of the illness. In comparison to patients with major depressive disorder, schizophrenia, or healthy controls, PKC activity was significantly increased in manic patients, suggesting that changes in PKC may be an illness-specific marker. Interestingly, enhanced PKC activity during mania was suppressed following mood-stabilizer treatment as manic symptoms improved. In parallel to the findings in platelets, postmortem studies demonstrate that membrane-associated PKC and stimulation-induced translocation of cytosolic enzyme to the membrane were also increased in frontal cortex of bipolar patients. Other studies suggest alterations in other signal transduction mechanisms in bipolar disorder. These include alterations in G protein activation, phosphatidylinositol (PI) signaling, cyclic AMP formation, and intracellular calcium homeostasis. The alterations of PKC activity in bipolar disorder may be related to changes in these other intracellular signaling mechanisms. Alternatively, the changes of PKC activity may be the core pathology of the illness. More studies are required to further characterize the association of PKC changes with bipolar disorder, using a proper neuronal model." [Abstract]

Wang HY, Friedman E.
Enhanced protein kinase C activity and translocation in bipolar affective disorder brains.
Biol Psychiatry 1996 Oct 1;40(7):568-75
"Protein kinase C (PKC) activity and its redistribution were determined in the frontal cortices of postmortem brains of bipolar affective disorder subjects and age-, sex-, and postmortem time-matched controls. Membrane and cytosolic PKC activity was determined by histone phosphorylation using [32P]-adenosine triphosphate as substrate. Specific PKC isozyme levels were assessed by Western blot analysis using antipeptide antibodies. Brain membrane-associated PKC activity was higher in bipolar vs. control tissue. An examination of the specific PKC isozymes in cortical homogenates revealed that cytosolic alpha- and membrane-associated gamma- and zeta PKC isozymes were elevated in cortices of bipolar affective disorder subjects, whereas cytosolic epsilon PKC was found to be reduced. In control brain slices, incubation with 1 mumol/L phorbol 12-myristate 13-acetate (PMA) caused an increase in membrane PKC activity, whereas cytosolic enzyme activity was decreased. This redistribution of the enzyme by PMA was markedly potentiated in brain slices of bipolar subjects. The results suggest that PKC-mediated phosphorylation is increased in brains of subjects with bipolar affective illness." [Abstract]

Wang H, Friedman E.
Increased association of brain protein kinase C with the receptor for activated C kinase-1 (RACK1) in bipolar affective disorder.
Biol Psychiatry 2001 Sep 1;50(5):364-70
"BACKGROUND: Membrane protein kinase C (PKC) activity is increased in frontal cortex of subjects with bipolar affective disorder, and lithium was demonstrated to inhibit PKC translocation to membranes. Protein kinase C is anchored to the membrane via the receptor for activated C kinase-1 (RACK1), suggesting that interactions between these proteins may be altered in bipolar disease. METHODS: The levels of RACK1 coimmunoprecipitating with PKC isozymes were compared in homogenates of frontal cortex slices from postmortem bipolar subjects and matched control subjects. RESULTS: Receptor for activated C kinase-1 was located exclusively in membranes and, in control brains, the levels of RACK1 that coimmunoprecipitated with most PKC isozymes were increased by stimulation with the PKC activator, phorbol 12-myristate, 13-acetate (PMA). The association of RACK1 with membrane gammaPKC and zetaPKC was increased under basal conditions in bipolar relative to control brains. Stimulation with PMA increased the amount of RACK1 that coimmunoprecipitated with the alpha, beta, gamma, delta, and varepsilonPKC isozymes, but not zetaPKC, in bipolar tissues over that elicited in control tissues. CONCLUSIONS: These data suggest that the increased association of RACK1 with PKC isozymes may be responsible for the increases in membrane PKC and in its activation that were previously observed in frontal cortex of bipolar affective disorder brains." [Abstract]

Escriba PV, Garcia-Sevilla JA.
Parallel modulation of receptor for activated C kinase 1 and protein kinase C-alpha and beta isoforms in brains of morphine-treated rats.
Br J Pharmacol 1999 May;127(2):343-8
"1. Receptor for activated C kinase 1 (RACK1) is an intracellular receptor for protein kinase C (PKC) that regulates the cellular enzyme localization. Because opiate drugs modulate the levels of brain PKC (Ventayol et al., 1997), the aim of this study was to assess in parallel the effects of morphine on RACK1 and PKC-alpha and beta isozymes densities in rat brain frontal cortex by immunoblot assays. 2. Acute morphine (30 mg kg(-1), i.p., 2 h) induced significant increases in the densities of RACK1 (33%), PKC-alpha (35%) and PKC-beta (23%). In contrast, chronic morphine (10-100 mg kg(-1), i.p., 5 days) induced a decrease in RACK1 levels (22%), paralleled by decreases in the levels of PKC-alpha (16%) and PKC-beta (16%). 3. Spontaneous (48 h) and naloxone (2 mg kg(-1), i.p., 2 h)-precipitated morphine withdrawal after chronic morphine induced marked up-regulations in the levels of RACK1 (38-41%), PKC-alpha (51-52%) and PKC-beta (48-62%). 4. In the same brains and for all combined treatments, there were significant positive correlations between the density of RACK1 and those of PKC-alpha (r=0.85, n = 35) and PKC-beta (r=0.75, n=32). 5. These data indicate that RACK1 is involved in the short- and long-term effects of morphine and in opiate withdrawal, and that RACK1 modulation by morphine or its withdrawal is parallel to those of PKC-alpha and beta isozymes. Since RACK1 facilitates the PKC substrate accessibility, driving its cellular localization, the coordinate regulation of the PKC/RACK system by morphine could be a relevant molecular mechanism in opiate addiction." [Abstract]

Vawter MP, Freed WJ, Kleinman JE.
Neuropathology of bipolar disorder.
Biol Psychiatry 2000 Sep 15;48(6):486-504
"The literature on the neuropathology of bipolar disorder (BD) is reviewed. Postmortem findings in the areas of pathomorphology, signal transduction, neuropeptides, neurotransmitters, cell adhesion molecules, and synaptic proteins are considered. Decreased glial numbers and density in both BD and major depressive disorder (MDD) have been reported, whereas cortical neuron counts were not different in BD (in Brodmann's areas [BAs] 9 and 24). In contrast, MDD patients showed reductions in neuronal size and density (BA 9, BA 47). There are a number of findings of alterations in neuropeptides and monoamines in BD brains. Norepinephrine turnover was increased in several cortical regions and thalamus, whereas the serotonin metabolite, 5-hydroxyindoleacetic acid, and the serotonin transporter were reduced in the cortex. Several reports further implicated both cyclic adenosine monophosphate and phosphatidylinositol (PI) cascade abnormalities. G protein concentrations and activity increases were found in the occipital, prefrontal, and temporal cortices in BD. In the PI signal cascade, alterations in PKC activity were found in the prefrontal cortex. In the occipital cortex, PI hydrolysis was decreased. Two isoforms of the neural cell adhesion molecules were increased in the hippocampus of BD, whereas the synaptic protein marker, synaptophysin, was not changed. The findings of glial reduction, excess signal activity, neuropeptide abnormalities, and monoamine alterations suggest distinct imbalances in neurochemical regulation. Possible alterations in pathways involving ascending projections from the brain stem are considered. Larger numbers of BD brains are needed to further refine the conceptual models that have been proposed, and to develop coherent models of the pathophysiology of BD." [Abstract]

Suzuki K, Kusumi I, Akimoto T, Sasaki Y, Koyama T.
Altered 5-HT-Induced Calcium Response in the Presence of Staurosporine in Blood Platelets from Bipolar Disorder Patients.
Neuropsychopharmacology. 2003 Jun;28(6):1210-4.
"We have reported that the platelet intracellular calcium (Ca) mobilization after stimulation by serotonin (5-HT) is specifically enhanced in bipolar disorder among various psychiatric disorders, compared with that in normal control. To explore the mechanisms of enhanced Ca response to 5-HT in the platelets, we first examined the relation between the 5HT-elicited Ca mobilization and 5-HT(2A) receptor density using the platelets from 13 normal subjects. From this study, we found no significant correlation between two measures. Then, we investigated the effects of staurosporine, a protein kinase C (PKC) inhibitor, on Ca response to 5-HT in platelets from patients with major depressive disorder (unipolar), bipolar disorder, and normal controls. While 5-HT-induced Ca mobilization, in the presence of 100 nM staurosporine, was significantly attenuated in normal controls and patients with major depressive disorder, the inhibitory effect of staurosporine was not observed in bipolar disorder. These results suggest that the failure in inhibiting the platelet intracellular Ca response to 5-HT in bipolar disorder may be related to increased activity of PKC rather than increased 5-HT(2A) receptor number. Moreover, the trend of the Ca response towards staurosporine may become a specific biological marker for unipolar-bipolar dichotomy." [Abstract] [Full Text]

Friedman E, Hoau-Yan-Wang, Levinson D, Connell TA, Singh H.
Altered platelet protein kinase C activity in bipolar affective disorder, manic episode.
Biol Psychiatry 1993 Apr 1;33(7):520-5 [Abstract]

Wang HY, Markowitz P, Levinson D, Undie AS, Friedman E.
Increased membrane-associated protein kinase C activity and translocation in blood platelets from bipolar affective disorder patients.
J Psychiatr Res 1999 Mar-Apr;33(2):171-9
"BACKGROUND: recent investigations have suggested that the phosphoinositide (PI) signal transduction system may be involved in the pathophysiology of bipolar affective disorders. Earlier studies in our laboratory have implicated altered PKC-mediated phosphorylation in bipolar affective disorder and in the clinical action of lithium. In the present study, we compared PKC activity and its translocation in platelets from subjects with bipolar affective disorder and three other groups. METHODS: subjects included 44 with bipolar disorder (acute manic episode), 25 with acute major depression, 23 with schizophrenia in acute exacerbation and 43 controls free of personal or family history of an Axis I disorder. Blood platelet membrane and cytosol PKC activity was measured before and after in vitro stimulation with serotonin (5-HT), thrombin and the direct PKC activator, PMA. In addition, we examined 5-HT-, thrombin- and PMA-elicited translocations of PKC isozymes from cytosol to the membrane in platelets of control subjects. RESULTS: in the basal state, manic subjects demonstrated higher membrane PKC activity than depressive and control subjects. The ratio of membrane to cytosol PKC activity was significantly higher in manic (1.10), as compared to control (0.84), depressed (0.93) or schizophrenic (0.93) subjects. Stimulation of platelets with 5-HT in vitro, resulted in greater membrane to cytosol ratio in the manic subjects compared to the three other groups. The responsiveness of platelets to PMA and thrombin was greater for manic subjects than for depressed and schizophrenic subjects, but not greater than the controls. In this measure both the schizophrenic and depressive groups were less active than controls. The results also demonstrate that platelets contain alpha-, beta-, delta- and zeta-PKC isozymes. While alpha- and beta-PKC isoforms were translocated from cytosol to membrane in response to serotonin, PMA and thrombin, serotonin also elicited the redistribution of delta-PKC and thrombin also activated zeta-PKC. CONCLUSION: the results demonstrate that a heightened PKC-mediated signal transduction is associated with acute mania and suggest a decreased transduction in patients with unipolar depression or schizophrenia." [Abstract]

Young LT, Wang JF, Woods CM, Robb JC.
Platelet protein kinase C alpha levels in drug-free and lithium-treated subjects with bipolar disorder.
Neuropsychobiology 1999;40(2):63-6
"Recent studies suggest that protein kinase C (PKC), particularly the alpha isoform, plays an important role in the action of lithium. There is, however, little evidence from patients with bipolar disorder (BD) to support this effect. The present investigation carried out comparative studies of PKC levels in platelets obtained from BD subjects including those with and without lithium treatment. All subjects met DSM-IV criteria for BD type I confirmed by structured interview (SCID-IV). Levels of PKC-alpha isoform in platelets from controls and from BD subjects were measured with immunoblotting analysis. No significant differences were found between controls, drug-free or lithium-treated BD subjects on membrane or cytosolic levels of PKC-alpha or in the membrane-to-cytosol ratio of this protein. The present study suggests that levels of PKC-alpha do not change in the peripheral tissues of BD subjects with or without lithium treatment." [Abstract]

Pandey GN, Dwivedi Y, SridharaRao J, Ren X, Janicak PG, Sharma R.
Protein kinase C and phospholipase C activity and expression of their specific isozymes is decreased and expression of MARCKS is increased in platelets of bipolar but not in unipolar patients.
Neuropsychopharmacology 2002 Feb;26(2):216-28
"Phospholipase C (PLC) and protein kinase C (PKC) are important components of the phosphoinositide (PI) signaling system. To examine if the abnormalities observed in the PI signaling system of patients with affective disorders, reported in previous studies, are related to abnormalities in one or more of its components, we studied PKC, PI-PLC activity, the expression of their specific isozymes, and expression of myristoylated alanine-rich C-kinase substrate (MARCKS) in platelets obtained from 15 drug-free hospitalized patients with bipolar disorder and 15 with major depressive disorder (unipolar) and from 15 nonhospitalized normal control subjects. We observed a significant decrease in PI-PLC and PKC activity and the expression of selective PKC alpha, betaI, betaII, and PLC delta(1) isozymes in membrane and cytosol fraction of platelets from bipolar but not unipolar patients. On the other hand, the level of MARCKS was significantly increased in membrane and cytosol fraction of platelets from patients with bipolar but not unipolar disorders. These results suggest that alterations in PKC, PLC, and MARCKS may be involved in the pathophysiology of bipolar illness." [Abstract]

Manji HK, Chen G.
PKC, MAP kinases and the bcl-2 family of proteins as long-term targets for mood stabilizers.
Mol Psychiatry 2002;7 Suppl 1:S46-56
"The complexity of the unique biology of bipolar disorder--which includes the predisposition to episodic, and often progressive, mood disturbance--and the dynamic nature of compensatory processes in the brain, coupled with limitations in experimental design, have hindered our ability to identify the underlying pathophysiology of this fascinating neuropsychiatric disorder. Although we have yet to identify the specific abnormal genes in mood disorders, recent studies have implicated critical signal transduction pathways as being integral to the pathophysiology and treatment of bipolar disorder. In particular, a converging body of preclinical data has shown that chronic lithium and valproate, at therapeutically relevant concentrations, regulate the protein kinase C signaling cascade. This has led to the investigation of the antimanic efficacy of tamoxifen (at doses sufficient to inhibit protein kinase C), with very encouraging preliminary results. A growing body of data also suggests that impairments of neuroplasticity and cellular resilience may also underlie the pathophysiology of bipolar disorder. It is thus noteworthy that mood stabilizers, such as lithium and valproate, indirectly regulate a number of factors involved in cell survival pathways--including cAMP response element binding protein, brain derived neurotrophic factor, bcl-2 and mitogen-activated protein kinases--and may thus bring about some of their delayed long-term beneficial effects via under-appreciated neurotrophic effects. The development of novel treatments, which more directly target molecules involved in critical central nervous system cell survival and cell death pathways, has the potential to enhance neuroplasticity and cellular resilience, thereby modulating the long-term course and trajectory of these devastating illnesses." [Abstract]

Chen G, Masana MI, Manji HK.
Lithium regulates PKC-mediated intracellular cross-talk and gene expression in the CNS in vivo.
Bipolar Disord 2000 Sep;2(3 Pt 2):217-36
"It has become increasingly appreciated that the long-term treatment of complex neuropsychiatric disorders like bipolar disorder (BD) involves the strategic regulation of signaling pathways and gene expression in critical neuronal circuits. Accumulating evidence from our laboratories and others has identified the family of protein kinase C (PKC) isozymes as a shared target in the brain for the long-term action of both lithium and valproate (VPA) in the treatment of BD. In rats chronically treated with lithium at therapeutic levels, there is a reduction in the levels of frontal cortical and hippocampal membrane-associated PKC alpha and PKC epsilon. Using in vivO microdialysis, we have investigated the effects of chronic lithium on the intracellular cross-talk between PKC and the cyclic AMP (cAMP) generating system in vivo. We have found that activation of PKC produces an increase in dialysate cAMP levels in both prefrontal cortex and hippocampus, effects which are attenuated by chronic lithium administration. Lithium also regulates the activity of another major signaling pathway the c-Jun N-terminal kinase pathway--in a PKC-dependent manner. Both Li and VPA, at therapeutically relevant concentrations, increase the DNA binding of activator protein 1 (AP-1) family of transcription factors in cultured cells in vitro, and in rat brain ex vivo. Furthermore, both agents increase the expression of an AP-1 driven reporter gene, as well as the expression of several endogenous genes known to be regulated by AP-1. Together, these results suggest that the PKC signaling pathway and PKC-mediated gene expression may be important mediators of lithium's long-term therapeutic effects in a disorder as complex as BD." [Abstract]
Chen, G, Manji, HK, Hawver, DB, Wright, CB, Potter, WZ
Chronic sodium valproate selectively decreases protein kinase C alpha and epsilon in vitro
J Neurochem 1994 63: 2361-2364
"Valproic acid (VPA) is a fatty acid antiepileptic with demonstrated antimanic properties, but the molecular mechanism or mechanisms underlying its therapeutic efficacy remain to be elucidated. In view of the increasing evidence demonstrating effects of the first-line antimanic drug, lithium, on protein kinase C (PKC), we investigated the effects of VPA on various aspects of this enzyme. Chronic exposure (6-7 days) of rat C6 glioma cells to "therapeutic" concentrations (0.6 mM) of VPA resulted in decreased PKC activity in both membrane and cytosolic fractions and increased the cytosol/membrane ratio of PKC activity. Western blot analysis revealed isozyme-selective decreases in the levels of PKC alpha and epsilon (but not delta or zeta) in both the membrane and cytosolic fractions after chronic VPA exposure; VPA added to reaction mixtures did not alter PKC activity or 3H-phorbol ester binding. Together, these data suggest that chronic VPA indirectly lowers the levels of specific isozymes of PKC in C6 cells. Given the pivotal role of PKC in regulating neuronal signal transduction and modulating intracellular cross-talk between neurotransmitter systems, the specific decreases in PKC alpha and epsilon may play a role in the antimanic effects of VPA." [Abstract]

Manji HK, Etcheberrigaray R, Chen G, Olds JL.
Lithium decreases membrane-associated protein kinase C in hippocampus: selectivity for the alpha isozyme.
J Neurochem 1993 Dec;61(6):2303-10
"We investigated the effects of lithium on alterations in the amount and distribution of protein kinase C (PKC) in discrete areas of rat brain by using [3H]phorbol 12,13-dibutyrate quantitative autoradiography as well as western blotting. Chronic administration of lithium resulted in a significant decrease in membrane-associated PKC in several hippocampal structures, most notably the subiculum and the CA1 region. In contrast, only modest changes in [3H]phorbol 12,13-dibutyrate binding were observed in the various other cortical and subcortical structures examined. Immunoblotting using monoclonal anti-PKC antibodies revealed an isozyme-specific 30% decrease in hippocampal membrane-associated PKC alpha, in the absence of any changes in the labeling of either the beta (I/II) or gamma isozymes. These changes were observed only after chronic (4 week) treatment with lithium, and not after acute (5 days) treatment, suggesting potential clinical relevance. Given the critical role of PKC in regulating neuronal signal transduction, lithium's effects on PKC in the limbic system represent an attractive molecular mechanism for its efficacy in treating both poles of manic-depressive illness. In addition, the decreased hippocampal membrane-associated PKC observed in the present study offers a possible explanation for lithium-induced memory impairment." [Abstract]
Soares JC, Chen G, Dippold CS, Wells KF, Frank E, Kupfer DJ, Manji HK, Mallinger AG.
Concurrent measures of protein kinase C and phosphoinositides in lithium-treated bipolar patients and healthy individuals: a preliminary study.
Psychiatry Res 2000 Aug 21;95(2):109-18
"This study examined the hypothesis that lithium inhibits the PI signaling pathway in humans during in vivo administration by concurrently measuring PKC isozymes and platelet membrane phosphoinositides in lithium-treated patients and healthy individuals. The platelet membrane and cytosolic levels of PKC alpha, beta I, beta II, delta, and epsilon were measured using Western blotting. The relative platelet membrane contents of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP), and phosphatidylinositol-4,5-bisphosphate (PIP(2)) were measured with two-dimensional thin-layer chromatography. Nine euthymic lithium-treated bipolar subjects and 11 healthy control subjects were studied. Compared to control subjects, lithium-treated bipolar patients had significantly lower levels of cytosolic PKC alpha isozyme (t-test=-3.24, d.f.=17, P=0.01) and PIP(2) platelet membrane levels (t-test=-2.51, d.f.=18, P=0.02), and a trend toward reduced levels of cytosolic PKC beta II isozyme (t=-2.17, d.f.=17, P=0.05). There was no significant correlation between PIP(2) and any of the PKC isozymes. These preliminary findings suggest that chronic lithium treatment may decrease the levels of both cytosolic PKC alpha isozyme and membrane PIP(2) in platelets of bipolar disorder patients." [Abstract]
Seung Kim HF, Weeber EJ, Sweatt JD, Stoll AL, Marangell LB.
Inhibitory effects of omega-3 fatty acids on protein kinase C activity in vitro.
Mol Psychiatry 2001 Mar;6(2):246-8
"Preliminary clinical data indicate that omega-3 fatty acids may be effective mood stabilizers for patients with bipolar disorder. Both lithium and valproic acid are known to inhibit protein kinase C (PKC) activity after subchronic administration in cell culture and in vivo. The current study was undertaken to determine the effects of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on protein kinase C phosphotransferase activity in vitro. Various concentrations of DHA, EPA, and arachidonic acid (AA) were incubated with the catalytic domain of protein kinase C beta from rat brain. Protein kinase C activity was measured by quantifying incorporation of (32)P-PO(4) into a synthetic peptide substrate. Both DHA and EPA, as well as the combination of DHA and EPA, inhibited PKC activity at concentrations as low as 10 micromol l(-1). In contrast, arachidonic acid had no effect on PKC activity. Thus, PKC represents a potential site of action of omega-3 fatty acids in their effects on the treatment of bipolar disorder." [Abstract]
Morishita S, Aoki S, Watanabe S.
Different effect of desipramine on protein kinase C in platelets between bipolar and major depressive disorders.
Psychiatry Clin Neurosci 1999 Feb;53(1):11-5
"Protein kinase C (PKC) activity was investigated in platelets from affective disorder subjects and healthy volunteers. The PKC activity of platelets incubated with desipramine was determined in vitro. The PKC activity of the major depressive disorder subjects and healthy volunteers was inhibited by desipramine, whereas that of the bipolar disorder subjects showed both inhibition and activation. In addition, the base PKC activity incubation with antidepressants of the major depressive disorder patients was significantly higher than of the bipolar disorder patients. These preliminary results suggest that the function of PKC may, at least in part, be associated with the mechanism of affective disorder." [Abstract]

Gould TD, Manji HK.
Signaling networks in the pathophysiology and treatment of mood disorders.
J Psychosom Res. 2002 Aug;53(2):687-97.
"Over the past decade, the focus of research into the pathophysiology of mood disorders (bipolar disorder and unipolar depression in particular) has shifted from an interest in the biogenic amines to an emphasis on second messenger systems within cells. Second messenger systems rely on cell membrane receptors to relay information from the extracellular environment to the interior of the cell. Within the cell, this information is processed and altered, eventually to the point where gene and protein expression patterns are changed. There is a preponderance of evidence implicating second messenger systems and their primary contact with the extracellular environment, G proteins, in the pathophysiology of mood disorders. After an introduction to G proteins and second messenger pathways, this review focuses on the evidence implicating G proteins and two second messenger systems-the adenylate cyclase (cyclic adenosine monophosphate, cAMP) and phosphoinositide (protein kinase C, PKC) intracellular signaling cascades-in the pathophysiology and treatment of bipolar disorder and unipolar depression. Emerging evidence implicates changes in cellular resiliency, neuroplasticity and additional cellular pathways in the pathophysiology of mood disorders. The systems discussed within this review have been implicated in neuroplastic processes and in modulation of many other cellular pathways, making them likely candidates for mediators of these findings." [Abstract]

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Recent Bipolar Disorder & PKC Research
1) Costa BL, Fawcett R, Li GY, Safa R, Osborne NN
Orally administered epigallocatechin gallate attenuates light-induced photoreceptor damage.
Brain Res Bull. 2008 Jul 1;76(4):412-23.
EGCG, a major component of green tea, has a number of properties which includes it being a powerful antioxidant. The purpose of this investigation was to deduce whether inclusion of EGCG in the drinking water of albino rats attenuates the effect of a light insult (2200lx, for 24h) to the retina. TUNEL-positive cells were detected in the outer nuclear layer of the retina, indicating the efficacy of the light insult in inducing photoreceptor degeneration. Moreover, Ret-P1 and the mRNA for rhodopsin located at photoreceptors were also significantly reduced as well as the amplitude of both the a- and b-waves of the electroretinogram was also reduced showing that photoreceptors in particular are affected by light. An increase in protein/mRNA of GFAP located primarily to M�ller cells caused by light shows that other retinal components are also influenced by the light insult. However, antigens associated with bipolar (alpha-PKC), ganglion (Thy-1) and amacrine (GABA) cells, in contrast, appeared unaffected. The light insult also caused a change in the content of various proteins (caspase-3, caspase-8, PARP, Bad, and Bcl-2) involved in apoptosis. A number of the changes to the retina caused by a light insult were significantly attenuated when EGCG was in the drinking water. The reduction of the a- and b-waves and photoreceptor specific mRNAs/protein caused by light were significantly less. In addition, EGCG attenuated the changes caused by light to certain apoptotic proteins (especially at after 2 days) but did not appear to significantly influence the light-induced up-regulation of GFAP protein/mRNA. It is concluded that orally administered EGCG blunts the detrimental effect of light to the retina of albino rats where the photoreceptors are primarily affected. [PubMed Citation] [Order full text from Infotrieve]

2) Squassina A, Manchia M, Manconi F, Piccardi M, Ardau R, Chillotti C, Severino G, Del Zompo M
A case-control association study of the PDLIM5 gene and bipolar disorder in a Sardinian sample.
Psychiatr Genet. 2008 Jun;18(3):128-32.
OBJECTIVES: PDLIM5 (ENH, LIM protein) [Postsynaptic Density-95/discs large/Zone occludens-1 (PDZ) and Lin-11, Isl-1, Mec-3 (LIM) domain 5;] is an adaptor protein that selectively binds protein kinase C-epsilon (PKC epsilon) to N-type Ca channels in brain neurons. As it has been suggested that alterations in protein kinase C activity might be involved in the pathophysiology of bipolar disorder (BD), PDLIM5 might play an important role in modulating susceptibility to the disease. Earlier investigations have reported altered expression of the PDLIM5 gene in postmortem brains and leukocytes of patients with BD. In a recent study, positive association for PDLIM5 single nucleotide polymorphisms (SNPs) was shown in a Japanese bipolar sample. The aim of our study was to investigate the association between PDLIM5 SNPs and BD in a case-control sample. METHODS: We genotyped SNPs rs10008257 (SNP1), rs2433320 (SNP2) and rs2433322 (SNP3) located within the 5' region of the gene in a sample that comprises of 300 bipolar patients and 300 healthy controls of Sardinian ancestry. RESULTS: In single-marker analysis, no association was found for any of the SNPs tested. After correction for multiple testing, haplotype analysis showed slight statistically significant association for a rare haplotype of SNPs 1 and 2. Although the findings presented in this paper do not provide strong evidence that the PDLIM5 gene significantly affects the pathophysiology of BD, they suggest that rare variants within the promoter region of the gene may have a marginal effect on the disorder. Further investigation on independent samples and different populations is warranted. [PubMed Citation] [Order full text from Infotrieve]

3) Squassina A, Congiu D, Manconi F, Manchia M, Chillotti C, Lampus S, Severino G, Zompo MD
The PDLIM5 gene and lithium prophylaxis: An association and gene expression analysis in Sardinian patients with bipolar disorder.
Pharmacol Res. 2008 May;57(5):369-73.
A number of studies support the notion that lithium interacts with the protein kinase C (PKC) pathway, an important mediator of several intracellular responses to neurotransmitter signaling. PDLIM5 (PDZ and LIM domain 5; LIM) is an adaptor protein that selectively binds the isozyme PKC(varepsilon) to N-type Ca(2+) channels in neurons. We tested for an association between three single nucleotide polymorphisms (SNPs) at the PDLIM5 gene and lithium prophylaxis in a Sardinian sample comprised of 155 bipolar patients treated with lithium. In order to evaluate whether PDLIM5 expression interacts with lithium response, we carried out gene expression analysis in lymphoblastoid cells of 30 bipolar patients. No association was shown between PDLIM5 polymorphisms and lithium response. When PDLIM5 expression was evaluated, no significant differences were detected between Full Responders to lithium (total score>/=7) and other patients (total score[PubMed Citation] [Order full text from Infotrieve]

4) Choudhary SK, Archin NM, Margolis DM
Hexamethylbisacetamide and disruption of human immunodeficiency virus type 1 latency in CD4(+) T cells.
J Infect Dis. 2008 Apr 15;197(8):1162-70.
BACKGROUND: Novel therapeutic approaches are needed to attack persistent proviral human immunodeficiency type 1 (HIV-1) infection. Hexamethylbisacetamide (HMBA), a hybrid bipolar compound, induces expression of the HIV-1 promoter in the long terminal repeat (LTR) region in a Tat-independent manner but mimics the effect of Tat, overcoming barriers to LTR expression and increasing the processivity of LTR transcription complexes. METHODS: We studied alterations in cellular factors and their LTR occupancy induced by HMBA in models of latent HIV-1 infection. We measured the induction of viral outgrowth by HMBA in resting CD4(+) T cells from aviremic HIV-1-infected donors. RESULTS: HMBA induced outgrowth of HIV-1 from resting CD4(+) T cells recovered from aviremic patients treated with antiretroviral therapy (ART). HMBA triggered cyclin-dependent kinase 9 (CDK9) recruitment to the LTR, a key factor in the induction of efficient HIV-1 expression, via an unexpected interaction with the transcription factor Sp1. The availability of Sp1 and Sp1 DNA binding sites were necessary for HMBA-induced CDK9 recruitment and LTR expression. HMBA signaling via both protein kinase C mu and phosphatidylinositol 3-kinase appeared to contribute to LTR induction. CONCLUSIONS: The novel mechanism through which HMBA disrupts latent HIV-1 infection involves 2 cellular kinases that may be therapeutically exploited to induce expression of persistent proviral HIV-1. [PubMed Citation] [Order full text from Infotrieve]

5) Catapano LA, Manji HK
Kinases as drug targets in the treatment of bipolar disorder.
Drug Discov Today. 2008 Apr;13(7-8):295-302.
Bipolar disorder is one of the most severely debilitating of all medical illnesses, and is increasingly recognized as a major public health problem. For many patients with bipolar disorder, current pharmacotherapy is insufficient. Exciting recent data suggest that regulation of signaling molecules may be involved in the pathophysiology of the disorder, and in the mechanisms of action of mood stabilizers and antidepressants. Through our developing understanding of the biochemical targets of effective medications, several potential targets for new therapies have emerged. This short review will focus on two of the most promising such targets: glycogen synthase-3 and protein kinase C. [PubMed Citation] [Order full text from Infotrieve]

6) Yildiz A, Guleryuz S, Ankerst DP, Ong�r D, Renshaw PF
Protein kinase C inhibition in the treatment of mania: a double-blind, placebo-controlled trial of tamoxifen.
Arch Gen Psychiatry. 2008 Mar;65(3):255-63.
CONTEXT: Findings that protein kinase C (PKC) activity may be altered in mania, and that both lithium carbonate and valproate sodium inhibit PKC-associated signaling in brain tissue, encourage development of PKC inhibitors as candidate antimanic agents. OBJECTIVE: To perform a controlled test of antimanic efficacy of the centrally active PKC inhibitor tamoxifen citrate. DESIGN: Three-week, randomized, double-blind, placebo-controlled, parallel-arms trial. SETTING: A university medical center inpatient psychiatric unit in Izmir, Turkey. PATIENTS: Sixty-six patients aged 18 to 60 years, diagnosed as having DSM-IV bipolar I disorder on the basis of the Structured Clinical Interview for DSM-IV, currently in a manic or mixed state, with or without psychotic features, with initial scores on the Young Mania Rating Scale (YMRS) greater than 20. INTERVENTION: Treatment with tamoxifen or identical placebo tablets for up to 3 weeks. Adjunctive lorazepam was allowed up to 5 mg/d. MAIN OUTCOME MEASURES: Primary: change in YMRS scores; secondary: change in Clinical Global Impressions-Mania scores, weekly ratings of depression and psychosis, and adjunctive use of lorazepam. RESULTS: The 21-day trial was completed by 29 of 35 subjects randomized to receive tamoxifen (83%) and 21 of 31 given placebo (68%) (P = .25). Intent-to-treat analysis of available measures on all 66 subjects indicated that tamoxifen treatment yielded mean decreases in scores on the YMRS and Clinical Global Impressions-Mania of 5.84 and 0.73 point per week, respectively, compared with mean increases of 1.50 and 0.10 point per week, respectively, with placebo; both drug-placebo contrasts differed significantly (P < .001). CONCLUSIONS: Tamoxifen demonstrated antimanic properties and was remarkably well tolerated. The findings encourage further clarification of the role of PKC in the pathophysiologic mechanism of bipolar I disorder and development of novel anti-PKC agents as potential antimanic or mood-stabilizing agents. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00411203 and isrctn.org Identifier: ISRCTN97160532. [PubMed Citation] [Order full text from Infotrieve]

7) Seelan RS, Khalyfa A, Lakshmanan J, Casanova MF, Parthasarathy RN
Deciphering the lithium transcriptome: microarray profiling of lithium-modulated gene expression in human neuronal cells.
Neuroscience. 2008 Feb 19;151(4):1184-97.
The mechanisms underlying lithium's therapeutic efficacy in the chronic treatment of bipolar disorder are not clearly understood. Useful insights can be obtained by identifying genes that are differentially regulated during chronic lithium treatment. Toward this end, we have used microarray technology to identify mRNAs that are differentially expressed in a human neuronal cell line that has been continuously maintained in therapeutic levels of lithium for 33 days. Significantly, unlike other transcriptomes where predominantly rodent cells were used and a limited number of genes probed, we have used human cells probed with more extensive 44,000 gene microarrays. A total of 671 differentially regulated transcripts, after correcting for false discovery rates, were identified, of which 347 and 324, respectively, were found to be up- and downregulated. Peroxiredoxin 2 (PRDX2), an antioxidant enzyme, was the most upregulated while tribbles homolog 3 (TRB3), a pro-apoptotic protein, was the most downregulated, implying a beneficial effect of lithium on neuronal cells. Several of the most highly regulated genes are novel, uncharacterized and encode proteins of unknown function. Differentially expressed genes associated with phosphoinositide metabolism include those encoding phosphatidyl inositol 4-phosphate 5-kinase type II alpha (PIP5K2A), WD repeat domain, phosphoinositide interacting 1 protein (WIPI49), tribbles homolog 3 (TRB3) and sorting nexin 14 (SNX14). A protein interactome using some of the saliently regulated genes identified protein kinase C (PKC) as a major target for lithium action while a global analysis of all 671 differentially expressed genes identified the mitogen-activated protein kinase pathway as the most regulated. The list of highly regulated genes, besides encoding putative targets for antimanic agents, should prove useful in defining novel pathways, or to better understand the mechanisms, underlying the mood stabilization process. [PubMed Citation] [Order full text from Infotrieve]

8) Lepagnol-Bestel AM, Maussion G, Boda B, Cardona A, Iwayama Y, Delezoide AL, Moalic JM, Muller D, Dean B, Yoshikawa T, Gorwood P, Buxbaum JD, Ramoz N, Simonneau M
SLC25A12 expression is associated with neurite outgrowth and is upregulated in the prefrontal cortex of autistic subjects.
Mol Psychiatry. 2008 Apr;13(4):385-97.
Autism is a neurodevelopmental disorder with a strong genetic component, probably involving several genes. Genome screens have provided evidence of linkage to chromosome 2q31-q33, which includes the SLC25A12 gene. Association between autism and single-nucleotide polymorphisms in SLC25A12 has been reported in various studies. SLC25A12 encodes the mitochondrial aspartate/glutamate carrier functionally important in neurons with high-metabolic activity. Neuropathological findings and functional abnormalities in autism have been reported for Brodmann's area (BA) 46 and the cerebellum. We found that SLC25A12 was expressed more strongly in the post-mortem brain tissues of autistic subjects than in those of controls, in the BA46 prefrontal cortex but not in cerebellar granule cells. SLC25A12 expression was not modified in brain subregions of bipolar and schizophrenic patients. SLC25A12 was expressed in developing human neuronal tissues, including neocortical regions containing excitatory neurons and neocortical progenitors and the ganglionic eminences that generate neocortical inhibitory interneurons. At mid-gestation, when gyri and sulci start to develop, SLC25A12 molecular gradients were identified in the lateral prefrontal and ventral temporal cortex. These fetal structures generate regions with abnormal activity in autism, including the dorsolateral prefrontal cortex (BA46), the pars opercularis of the inferior frontal cortex and the fusiform gyrus. SLC25A12 overexpression or silencing in mouse embryonic cortical neurons also modified dendrite length and the mobility of dendritic mitochondria. Our findings suggest that SLC25A12 overexpression may be involved in the pathophysiology of autism, modifying neuronal networks in specific subregions, such as the dorsolateral prefrontal cortex and fusiform gyrus, at both pre- and postnatal stages. [PubMed Citation] [Order full text from Infotrieve]

9) Mathew SJ, Manji HK, Charney DS
Novel Drugs and Therapeutic Targets for Severe Mood Disorders.
Neuropsychopharmacology. 2008 Jan 2;
Monoaminergic-based drugs remain the primary focus of pharmaceutical industry drug discovery efforts for mood disorders, despite serious limitations regarding their ability to achieve remission. The quest for novel therapies for unipolar depression and bipolar disorder has generally centered on two complementary approaches: (1) understanding the presumed therapeutically relevant biochemical targets of currently available medications, and using that knowledge to design new drugs directed at both direct biochemical targets and downstream targets that are regulated by chronic drug administration; and (2) developing pathophysiological models of the illness to design therapeutics to attenuate or prevent those pathological processes. This review describes several promising drugs and drug targets for mood disorders using one or both of these approaches. Agents interacting with non-catecholamine neurotransmitter systems with particular promise for unipolar and bipolar depression include excitatory amino acid neurotransmitter modulators (eg, riluzole, N-methyl-D-aspartate antagonists, and AMPA receptor potentiators) and neuropeptide antagonists (targeting corticotropin releasing factor-1 and neurokinin receptors). Potential antidepressant and mood-stabilizing agents targeting common intracellular pathways of known monoaminergic agents and lithium/mood stabilizers are also reviewed, such as neurotrophic factors, extracellular receptor-coupled kinase (ERK) mitogen-activated protein (MAP) kinase and the bcl-2 family of proteins, and inhibitors of phosphodiesterase, glycogen synthase kinase-3, and protein kinase C. A major thrust of drug discovery in mood disorders will continue efforts to identify agents with rapid and sustained onsets of action (such as intravenous administration of ketamine), as well as identify drugs used routinely in non-psychiatric diseases for their antidepressant and mood-stabilizing properties.Neuropsychopharmacology advance online publication, 2 January 2008; doi:10.1038/sj.npp.1301652. [PubMed Citation] [Order full text from Infotrieve]

10) Zarate CA, Singh JB, Carlson PJ, Quiroz J, Jolkovsky L, Luckenbaugh DA, Manji HK
Efficacy of a protein kinase C inhibitor (tamoxifen) in the treatment of acute mania: a pilot study.
Bipolar Disord. 2007 Sep;9(6):561-70.
OBJECTIVES: Considerable preclinical biochemical and behavioral data suggest that protein kinase C inhibition would bring about antimanic effects. Notably, the structurally highly dissimilar antimanic agents lithium and valproate, when administered in therapeutically relevant paradigms, attenuate protein kinase C [corrected] function. There is currently only one relatively selective protein kinase C inhibitor that crosses the blood-brain barrier available for human use--tamoxifen. Our group recently conducted a single-blind study with tamoxifen in acute mania and found that it significantly decreased manic symptoms within a short period of time (3-7 days). In this study, we investigated whether antimanic effects can be achieved with a protein kinase C inhibitor in subjects with mania. METHODS: In a double-blind, placebo-controlled study, 16 subjects with bipolar disorder, manic or mixed, with or without psychotic features, were randomly assigned to receive tamoxifen (20-140 mg/day; n = 8) or placebo (n = 8) for three weeks. Primary efficacy was assessed by the Young Mania Rating Scale. RESULTS: Subjects on tamoxifen showed significant improvement in mania compared to placebo as early as five days, an effect that remained significant throughout the three-week trial. The effect size for the drug difference was very large (d = 1.08, 95% confidence interval 0.45-1.71) after three weeks (p = 0.001). At study endpoint, response rates were 63% for tamoxifen and 13% for placebo (p = 0.12). CONCLUSIONS: Antimanic effects resulted from a protein kinase C inhibitor; onset occurred within five days. Large, controlled studies with selective protein kinase C inhibitors in acute mania are warranted. [PubMed Citation] [Order full text from Infotrieve]

11) Mazza M, Di Nicola M, Della Marca G, Janiri L, Bria P, Mazza S
Bipolar disorder and epilepsy: a bidirectional relation? Neurobiological underpinnings, current hypotheses, and future research directions.
Neuroscientist. 2007 Aug;13(4):392-404.
A number of studies have demonstrated that affective disorders in epilepsy represent a common psychiatric comorbidity; however, most of the classic neuropsychiatric literature focuses on depression, which is actually prominent, but little is known about bipolar depression, and very little about mania, in epilepsy. Biochemical, structural, and functional abnormalities in primary bipolar disorder could also occur secondary to seizure disorders. The kindling paradigm, invoked as a model for understanding seizure disorders, has also been applied to the episodic nature of bipolar disorder. In bipolar patients, changes in second-messenger systems, such as G-proteins, phosphatidylinositol, protein kinase C, myristoylated alanine-rich C kinase substrate, or calcium activity have been described, along with changes in c-fos expression. Common mechanisms at the level of ion channels might include the antikindling and the calcium-antagonistic and potassium outward current-modulating properties of antiepileptic drugs. All these lines of research appear to be converging on a richer understanding of neurobiological underpinnings between bipolar disorder and epilepsy. Mania, which is the other side of the coin in affective disorders, may represent a privileged window into the neurobiology of mood regulation and the neurobiology of epilepsy itself. Future research on intracellular mechanisms might become decisive for a better understanding of the similarities between these two disorders. [PubMed Citation] [Order full text from Infotrieve]

12) Einat H, Yuan P, Szabo ST, Dogra S, Manji HK
Protein kinase C inhibition by tamoxifen antagonizes manic-like behavior in rats: implications for the development of novel therapeutics for bipolar disorder.
Neuropsychobiology. 2007;55(3-4):123-31.
RATIONALE: In the context of bipolar disorder (BPD) research it was demonstrated that administration of the structurally dissimilar mood stabilizers lithium and valproate produced a striking reduction in protein kinase C (PKC) in rat brain. In a small clinical study, tamoxifen (a PKC inhibitor) had antimanic efficacy. However, both lithium and valproate exert many biochemical changes and attribution of therapeutic relevance to any molecular findings needs to be based on linking them to behavioral effects. OBJECTIVES: The present study was designed to explore such relationship by studying the effects of PKC inhibition in amphetamine-induced behavioral animal models of mania and changes in GAP-43. METHODS: The effects of two daily tamoxifen (1 mg/kg) i.p. injections on acute or chronic (7 injections) amphetamine (0.5 mg/kg) -induced behaviors and GAP-43 phosphorylation were tested. RESULTS: The study demonstrates that tamoxifen significantly reduced amphetamine-induced hyperactivity in a large open field without affecting spontaneous activity levels and normalized amphetamine-induced increase in visits to the center of an open field (representing risk-taking behavior). Tamoxifen also attenuated amphetamine-induced phosphorylation of GAP-43, a result that is consistent with the behavioral findings. CONCLUSIONS: These results support the possibility that PKC signaling may play an important role in the pathophysiology and treatment of BPD. These findings may have direct clinical implications as they offer a new avenue for attempts to develop more specific drugs for the disorder. [PubMed Citation] [Order full text from Infotrieve]

13) Rosenberg G
The mechanisms of action of valproate in neuropsychiatric disorders: can we see the forest for the trees?
Cell Mol Life Sci. 2007 Aug;64(16):2090-103.
After more than 40 years of clinical use, the mechanisms of action of valproate in epilepsy, bipolar disorder and migraine are still not fully understood. However, recent findings reviewed here shed new light on the cellular effects of valproate. Beyond the enhancement of gamma-aminobutyric acid-mediated neurotransmission, valproate has been found to affect signalling systems like the Wnt/beta-catenin and ERK pathways and to interfere with inositol and arachidonate metabolism. Nevertheless, the clinical relevance of these effects is not always clear. Valproate treatment also produces marked alterations in the expression of multiple genes, many of which are involved in transcription regulation, cell survival, ion homeostasis, cytoskeletal modifications and signal transduction. These alterations may well be relevant to the therapeutic effects of valproate, and result from its enhancement of activator protein-1 DNA binding and direct inhibition of histone deacetylases, and possibly additional, yet unknown, mechanism(s). Most likely, both immediate biochemical and longer-term genomic influences underlie the effects of valproate in all three indications. [PubMed Citation] [Order full text from Infotrieve]

14) Puthussery T, Fletcher EL
Neuronal expression of P2X3 purinoceptors in the rat retina.
Neuroscience. 2007 Apr 25;146(1):403-14.
P2X3 purinoceptors are involved in fast, excitatory neurotransmission in the nervous system, and are expressed predominantly within sensory neurons. In this study, we examined the cellular and synaptic localization of the P2X3 receptor subunit in the retina of the rat using immunofluorescence immunohistochemistry and pre-embedding immunoelectron microscopy. In addition, we investigated the activity of ecto-ATPases in the inner retina using an enzyme cytochemical method. The P2X3 receptor subunit was expressed in the soma of a subset of GABA immunoreactive amacrine cells, some of which also expressed protein kinase C-alpha. In addition, punctate immunoreactivity was observed within both the inner and outer plexiform layers of the retina. Double labeling studies showed that P2X3 receptor puncta were associated with both rod and cone bipolar cell axon terminals in the inner plexiform layer. Ultrastructural studies indicated that P2X3 receptor subunits were expressed on putative A17 amacrine cells at sites of reciprocal synaptic input to the rod bipolar cell axon terminal. Moreover, we observed P2X3 immunolabeling on amacrine cell processes that were associated with cone bipolar cell axon terminals and other conventional synapses. In the outer retina, P2X3 immunoreactivity was observed on specialized junctions made by putative interplexiform cells. Ecto-ATPase activity was localized to the inner plexiform layer on the extracellular side of all plasma membranes, but was not apparent in the ganglion cell layer or the inner nuclear layer, suggesting that ATP dephosphorylation occurs exclusively in synaptic regions of the inner retina. These data provide further evidence that purines participate in retinal transmission, particularly within the rod pathway. [PubMed Citation] [Order full text from Infotrieve]

15) Bellon A, Ort�z-L�pez L, Ram�rez-Rodr�guez G, Ant�n-Tay F, Ben�tez-King G
Melatonin induces neuritogenesis at early stages in N1E-115 cells through actin rearrangements via activation of protein kinase C and Rho-associated kinase.
J Pineal Res. 2007 Apr;42(3):214-21.
Melatonin increases neurite formation in N1E-115 cells through microtubule enlargement elicited by calmodulin antagonism and vimentin intermediate filament reorganization caused by protein kinase C (PKC) activation. Microfilament rearrangement is also a necessary process in growth cone formation during neurite outgrowth. In this work, we studied the effect of melatonin on microfilament rearrangements present at early stages of neurite formation and the possible participation of PKC and the Rho-associated kinase (ROCK), which is a downstream kinase in the PKC signaling pathway. The results showed that 1 nm melatonin increased both the number of cells with filopodia and with long neurites. Similar results were obtained with the PKC activator phorbol 12-myristate 13-acetate (PMA). Both melatonin and PMA increased the quantity of filamentous actin. In contrast, the PKC inhibitor bisindolylmaleimide abolished microfilament organization elicited by either melatonin or PMA, while the Rho inhibitor C3, or the ROCK inhibitor Y27632, abolished the bipolar neurite morphology of N1E-115 cells. Instead, these inhibitors prompted neurite ramification. ROCK activity measured in whole cell extracts and in N1E-115 cells was increased in the presence of melatonin and PMA. The results indicate that melatonin increases the number of cells with immature neurites and suggest that these neurites can be susceptible to differentiation by incoming extracellular signals. Data also indicate that PKC and ROCK are involved at initial stages of neurite formation in the mechanism by which melatonin recruits cells for later differentiation. [PubMed Citation] [Order full text from Infotrieve]

16) Akimoto T, Kusumi I, Suzuki K, Masui T, Koyama T
Effects of valproate on serotonin-induced intracellular calcium mobilization in human platelets.
J Psychiatry Neurosci. 2007 Jan;32(1):17-22.
OBJECTIVE: Valproate (VPA) is effectively used in the treatment of bipolar disorder, although the mechanism of action is unclear. In patients with bipolar disorder, 5-hydroxytryptamine (5-HT)-induced intraplatelet calcium (Ca) mobilization has been shown to be enhanced. METHODS: We examined the effect of VPA on 5-HT-induced Ca response in the platelets of normal subjects, in the presence of a calmodulin antagonist W-7 (N-[6-aminohexyl]-5-chloro-1-naphthalenesulfonamide), a protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) or PKC inhibitors staurosporine and bisindolylmaleimide II. RESULTS: VPA inhibited the 5-HT-induced Ca response in a concentration-dependent manner. For calmodulin pathways, W-7 enhanced the 5-HT-stimulated Ca response, which was not affected by VPA. For PKC pathways, PMA reduced the Ca response, although both PKC inhibitors had no effect. PMA, staurosporine or bisindolylmaleimide II reversed the inhibitory effect of VPA on the Ca response, while W-7 did not modify it. CONCLUSION: These findings suggest the possibility that the mechanism of action of VPA may be partly related to PKC signalling. [Free Full Text] [PubMed Citation] [Order full text from Infotrieve]

17) Pandey GN, Ren X, Dwivedi Y, Pavuluri MN
Decreased protein kinase C (PKC) in platelets of pediatric bipolar patients: effect of treatment with mood stabilizing drugs.
J Psychiatr Res. 2008 Jan;42(2):106-16.
Pediatric bipolar disorder (PBD) is a major public health concern, however, its neurobiology is poorly understood. We, therefore, studied the role of protein kinase C (PKC) in the pathophysiology of bipolar illness. We determined PKC activity and immunolabeling of various PKC isozymes (i.e., PKC alpha, PKC betaI, PKC betaII, and PKC delta) in the cytosol and membrane fractions of platelets obtained from PBD patients and normal control subjects. PKC activity and PKC isozymes were also determined after 8 weeks of pharmacotherapy of PBD patients (n=16) with mood stabilizers. PKC activity and the protein expression of PKC betaI and betaII, but not PKC alpha or PKC delta, were significantly decreased in both membrane as well as cytosol fractions of platelets obtained from medication-free PBD patients compared with normal control subjects. Eight weeks of pharmacotherapy resulted in significantly increased PKC activity but no significant changes in any of the PKC isozymes in PBD patients. These results indicate that decreases of specific PKC isozymes and decreased PKC activity may be associated with the pathophysiology of PBD and that pharmacotherapy with mood stabilizing drugs results in an increase and normalization of PKC activity along with improvement in clinical symptoms. [PubMed Citation] [Order full text from Infotrieve]

18) Zahir T, Klassen H, Tomita M, Young MJ
Sorbitol causes preferential selection of Muller glial precursors from late retinal progenitor cells in vitro.
Mol Vis. 2006;12:1606-14.
PURPOSE: The replacement of glucose by sorbitol in growth medium causes selection of astroglial cells from heterogeneous primary cultures derived from the brains of newborn mice. The present study was undertaken to investigate the effects of sorbitol on in vitro selection of M�ller glial precursors from expanded late retinal progenitor cells (RPCs). METHODS: RPCs used in these studies were isolated from the neural retina of postnatal day one green fluorescent protein (GFP) transgenic mice. The resulting GFP positive neurospheres were dissociated into a single cell suspension and grown on poly-D-lysine/laminin coated tissue culture flasks or slides to generate adherent RPCs. These adherent cells were treated with glucose free medium containing 25 mM sorbitol for 7 days and the expression of retinal-specific cell markers was determined by immunocytochemistry, reverse transcriptase polymerase chain reaction (RT-PCR) and immunoblot analysis RESULTS: In vitro studies showed that sorbitol treatment of late RPCs altered cellular morphology. Immunocytochemical studies showed an increase in the proportion of cells expressing glial cell markers, most of which co-expressed CRALBP, GFAP, and vimentin. An increase in the proportion of cells expressing PKCalpha, a bipolar cell marker, was also observed. RT-PCR analysis showed down-regulation of nestin transcripts with a concomitant increase in CRALBP, GFAP, vimentin and PKCalpha. These findings were confirmed by immunoblot analysis, where down-regulation of nestin expression with simultaneous up-regulation of CRALBP, GFAP and PKCalpha was observed. CONCLUSIONS: Sorbitol treatment of multipotent late RPCs, in the absence of glucose, results in the preferential selection of M�ller glial precursors and their subsequent differentiation into cells that morphologically resemble M�ller cells and co-express multiple glial markers. [Free Full Text] [PubMed Citation] [Order full text from Infotrieve]

19) Akimoto T, Kusumi I, Suzuki K, Koyama T
Effects of calmodulin and protein kinase C modulators on transient Ca2+ increase and capacitative Ca2+ entry in human platelets: relevant to pathophysiology of bipolar disorder.
Prog Neuropsychopharmacol Biol Psychiatry. 2007 Jan 30;31(1):136-41.
Disturbed intracellular calcium (Ca(2+)) homeostasis has been implicated in bipolar disorder, which mechanisms may be involved in the dysregulation of protein kinase C (PKC) and calmodulin systems. In this study, we investigated a transient intracellular Ca(2+) increase induced by thapsigargin, an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPase pump (SERCA), and a capacitative Ca(2+) entry followed by addition of extracellular Ca(2+), in the presence or absence of PKC/calmodulin modulators in the platelets of healthy subjects in order to elucidate the role of SERCA in Ca(2+) homeostasis and to assess how both PKC and calmodulin systems regulate the two Ca(2+) responses. Moreover, we also examined the thapsigargin-elicited transient Ca(2+) increase and capacitative Ca(2+) entry in patients with mood disorders. PKC and calmodulin systems have opposite regulatory effects on the transient Ca(2+) increase and capacitative Ca(2+) entry in the platelets of normal subjects. The inhibitory effect of PKC activation on capacitative Ca(2+) entry is significantly increased and the stimulatory effect of PKC inhibition is significantly decreased in bipolar disorder compared to major depressive disorder and normal controls. These results suggest the possibility that increased PKC activity may activate the inhibitory effect of capacitative Ca(2+) entry in bipolar disorder. However, this is a preliminary study using a small sample, thus further studies are needed to examine the PKC and calmodulin modulators on the capacitative Ca(2+) entry in a larger sample. [PubMed Citation] [Order full text from Infotrieve]

20) McNamara RK, Ostrander M, Abplanalp W, Richtand NM, Benoit SC, Clegg DJ
Modulation of phosphoinositide-protein kinase C signal transduction by omega-3 fatty acids: implications for the pathophysiology and treatment of recurrent neuropsychiatric illness.
Prostaglandins Leukot Essent Fatty Acids. 2006 Oct-Nov;75(4-5):237-57.
The phosphoinositide (PI)-protein kinase C (PKC) signal transduction pathway is initiated by pre- and postsynaptic Galphaq-coupled receptors, and regulates several clinically relevant neurochemical events, including neurotransmitter release efficacy, monoamine receptor function and trafficking, monoamine transporter function and trafficking, axonal myelination, and gene expression. Mounting evidence for PI-PKC signaling hyperactivity in the peripheral (platelets) and central (premortem and postmortem brain) tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, coupled with evidence that PI-PKC signal transduction is down-regulated in rat brain following chronic, but not acute, treatment with antipsychotic, mood-stabilizer, and antidepressant medications, suggest that PI-PKC hyperactivity is central to an underlying pathophysiology. Evidence that membrane omega-3 fatty acids act as endogenous antagonists of the PI-PKC signal transduction pathway, coupled with evidence that omega-3 fatty acid deficiency is observed in peripheral and central tissues of patients with schizophrenia, bipolar disorder, and major depressive disorder, support the hypothesis that omega-3 fatty acid deficiency may contribute to elevated PI-PKC activity i