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) Li X, Law JW, Lee AY
Semaphorin 5A and plexin-B3 regulate human glioma cell motility and morphology through Rac1 and the actin cytoskeleton.
Oncogene. 2011 Jun 27;
Semaphorins are implicated in glioma progression, although little is known about the underlying mechanisms. We have reported plexin-B3 expression in human gliomas, which upon stimulation by Sema5A causes significant inhibition of cell migration and invasion. The concomitant inactivation of Rac1 is of mechanistic importance because forced expression of constitutively active Rac1 abolishes these inhibitory effects. Furthermore, Sema5A induces prominent cell collapse and ramification of processes reminiscent of astrocytic morphology, which temporally associate with extensive disassembly of actin stress fibers and disruption of focal adhesions, followed by accumulation of actin patches in protrusions. Mechanistically, Sema5A induces transient protein kinase C (PKC) phosphorylation of fascin-1, which can reduce its actin-binding/bundling activities and temporally parallels its translocation from cell body to extending processes. PKC inhibition or fascin-1 knockdown is sufficient to abrogate Sema5A-induced morphological differentiation, whereas the process is hastened by forced expression of fascin-1. Intriguingly, Sema5A induces re-expression of glial fibrillary acidic protein (GFAP), which when silenced restricts differentiation of glioma cells to bipolar instead of multipolar morphology. Therefore, we hypothesize complementary functions of fascin-1 and GFAP in the early and late phases of Sema5A-induced astrocytic differentiation of gliomas, respectively. In summary, Sema5A and plexin-B3 impede motility but promote differentiation of human gliomas. These effects are plausibly compromised in high-grade human astrocytomas in which Sema5A expression is markedly reduced, hence leading to infiltrative and anaplastic characteristics. This is evident by increased invasiveness of glioma cells when endogenous Sema5A is silenced. Therefore, Sema5A and plexin-B3 represent potential novel targets in counteracting glioma progression.Oncogene advance online publication, 27 June 2011; doi:10.1038/onc.2011.256. [PubMed Citation] [Order full text from Infotrieve]

2) Creson TK, Austin DR, Shaltiel G, McCammon J, Wess J, Manji HK, Chen G
Lithium treatment attenuates muscarinic M(1) receptor dysfunction.
Bipolar Disord. 2011 May;13(3):238-49.
Creson TK, Austin DR, Shaltiel G, McCammon J, Wess J, Manji HK, Chen G. Lithium treatment attenuates muscarinic M(1) receptor dysfunction. Bipolar Disord 2011: 13: 238-249. � 2011 The Authors. Journal compilation � 2011 John Wiley & Sons A/S. Objective:? Altered muscarinic acetylcholine receptor levels and receptor-coupled signaling processes have been reported in mood disorders. M(1) , one of five muscarinic receptor subtypes, couples to the phospholipase C/protein kinase C and extracellular signal-regulated kinase (ERK) pathways. Mood stabilizers regulate these pathways. MicroRNAs (miRNAs) are small noncoding RNAs that suppress translation in a sequence-selective manner. Lithium downregulates several miRNAs, including let-7b and let-7c. One predicted target of let-7b and let-7c is the M(1) receptor. We hypothesized that miRNAs regulate M(1) receptor translation, and that disrupted M(1) expression leads to aberrant behaviors and disrupted downstream signaling pathways that are rescued by lithium treatment. Methods:? The effects of miRNAs and chronic treatment with mood stabilizers on M(1) levels were tested in primary cultures and in rat frontal cortex. Effects of M(1) ablation and chronic treatment with mood stabilizers on several signaling cascades and M(1) -modulated behaviors were examined in wild-type and M(1) knockout mice. Results:? Let-7b, but not let-7c, negatively regulated M(1) levels. Chronic treatment with lithium, but not valproate, increased M(1) levels in the rat cortex. M(1) knockout mice exhibit ERK pathway deficits and behavioral hyperactivity; chronic treatment with lithium attenuated these deficits and hyperactivity. Conclusions:? Lithium treatment can affect M(1) receptor function through intracellular signaling enhancement and, in situations without M(1) ablation, concomitant receptor upregulation via mechanisms involving miRNAs. Muscarinic dysfunction may contribute to mood disorders, while M(1) receptors and the downstream ERK pathway may serve as potential therapeutic targets for alleviating manic symptoms such as psychomotor hyperactivity. [PubMed Citation] [Order full text from Infotrieve]

3) Xuqian W, Kanghua L, Weihong Y, Xi Y, Rongping D, Qin H, Fangtian D, Chunhua Zhao R
Intraocular Transplantation of Human Adipose-Derived Mesenchymal Stem Cells in a Rabbit Model of Experimental Retinal Holes.
Ophthalmic Res. 2011 Apr 5;46(4):199-207.
Aims: To investigate whether human adipose-derived mesenchymal stem cell (hAD-MSC) transplantation would ameliorate the healing process of a rabbit model of retinal holes. Methods: Retinal holes were made in the left eyes of 20 New Zealand white rabbits and randomly filled by hAD-MSCs (transplantation group) or phosphate-buffered saline (control group), respectively. Frequency-domain optical coherence tomography (OCT) scan was performed on days 2, 4, 12, 20 and 32 postoperatively, and immunofluorescence was performed on days 12 and 32 to further identify the cell types of the injured area. Results: Frequency-domain OCT scan showed that the mean center thickness of the reconstructed tissue reached a normal level on day 12 in the transplantation group, while in the control group, the mean center thickness was normal on day 32. Furthermore, compared to the control group where only anti-glial fibrillary acidic protein-labeled glial-like cells were detected, donor-derived opsin-positive photoreceptor-like cells and protein kinase C-positive bipolar-like cells were sporadically found in the transplantation group. Conclusions: Transplanted hAD-MSCs could engraft in the retinal hole of a rabbit model, and clearly accelerated the healing process and ameliorated injury recovery. [PubMed Citation] [Order full text from Infotrieve]

4) Peng L, Li B, Du T, Wang F, Hertz L
Does conventional anti-bipolar and antidepressant drug therapy reduce NMDA-mediated neuronal excitation by downregulating astrocytic GluK2 function?
Pharmacol Biochem Behav. 2011 Apr 2;
Chronic treatment with anti-bipolar drugs (lithium, carbamazepine, and valproic acid) down-regulates mRNA and protein expression of kainate receptor GluK2 in mouse brain and cultured astrocytes. It also abolishes glutamate-mediated, Ca(2+)-dependent ERK(1/2) phosphorylation in the astrocytes. Chronic treatment with the SSRI fluoxetine enhances astrocytic GluK2 expression, but increases mRNA editing, abolishing glutamate-mediated ERK(1/2) phosphorylation and [Ca(2+)](i) increase, which are shown to be GluK2-mediated. Neither drug group affects Glu4/Glu5 expression necessary for GluK2's ionotropic effect. Consistent with a metabotropic effect, the PKC inhibitor GF 109203X and the IP(3) inhibitor xestospongin C abolish glutamate stimulation in cultured astrocytes. In CA1/CA3 pyramidal cells in hippocampal slices, activation of extrasynaptic GluK2 receptors, presumably including astrocytic, metabotropic GluK2 receptors, causes long-lasting inhibition of slow neuronal afterhyperpolarization mediated by Ca(2+)-dependent K(+) flux. This may be secondary to the induced astrocytic [Ca(2+)](i) increase, causing release of 'gliotransmitter' glutamate. Neuronal NMDA receptors respond to astrocytic glutamate release with enhancement of excitatory glutamatergic activity. Since reduction of NMDA receptor activity is known to have antidepressant effect in bipolar depression and major depression, these observations suggest that the inactivation of astrocytic GluK2 activity by antidepressant/anti-bipolar therapy ameliorates depression by inhibiting astrocytic glutamate release. A resultant strengthening of neuronal afterhyperpolarization may cause reduced NMDA-mediated activity. [PubMed Citation] [Order full text from Infotrieve]

5) Moretti M, Valvassori SS, Steckert AV, Rochi N, Benedet J, Scaini G, Kapczinski F, Streck EL, Zugno AI, Quevedo J
Tamoxifen effects on respiratory chain complexes and creatine kinase activities in an animal model of mania.
Pharmacol Biochem Behav. 2011 Apr;98(2):304-10.
The present study aimed to investigate the effects of tamoxifen (TMX) on locomotor behavior and on the activities of mitochondrial respiratory chain complexes and creatine kinase (CK) in the brain of rats subjected to an animal model of mania induced by d-amphetamine (D-AMPH)-reversion and prevention protocols. The D-AMPH administration increased locomotor activity in saline-treated rats under prevention and reversion treatment; furthermore, there was evident reduction in the locomotion in the D-amphetamine group treated with TMX. D-AMPH significantly decreased the activity of mitochondrial respiratory chain complexes in saline-treated rats in prefrontal cortex, hippocampus, striatum and amygdala in both prevention and reversion treatment. Depending on the cerebral area and evaluated complex, TMX was able to prevent and reverse this impairment. A decrease in CK activity was also verified in the brain of rats when D-AMPH was administrated in both experiments; the administration of TMX reversed but not prevented the decrease in CK activity induced by D-AMPH. The present study demonstrated that TMX reversed and prevented the alterations in behavioral and energy metabolism induced by D-AMPH (alterations were also observed in bipolar disorder), reinforcing the need for more studies about inhibitors of PKC as possible targets for new medications in the treatment of bipolar disorder. [PubMed Citation] [Order full text from Infotrieve]

6) Galeotti N, Ghelardini C
Antidepressant phenotype by inhibiting the phospholipase Cβ(1)--protein kinase Cγ pathway in the forced swim test.
Neuropharmacology. 2011 May;60(6):937-43.
Although great advances have recently been made in the study of signal transduction, the pathogenesis of affective disorders is still unknown. There is mounting evidence suggesting that elevated phosphoinositide-protein kinase C (PI-PKC) signal transduction pathway may be a pathophysiological feature of bipolar and major depressive disorders. The aim of the present study was to further investigated the phospholipase C-protein kinase C (PLC-PKC) cascade by evaluating the effect produced by an acute blockade of this intracellular pathway at PLC and PKC level. Adult male mice were administered with pharmacological inhibitors of PLC or PKC and then subjected to the forced swim test (FST), an animal model which emulates the behavioural despair paradigm of depression. In this study we also tested the hypothesis that it might be possible to selectively modulate depressive behaviour by inhibiting the expression of specific PLC and PKC isoforms by means of specific antisense oligonucleotides (aODNs). Administration of the PLC inhibitors neomycin and U73122 as well as of the PKC inhibitors calphostin C�and chelerytrine dose-dependently reduced the immobility time in the FST producing an antidepressant-like behaviour. Selective knockdown of the PLC?(1) and PKC? isoforms also induced an antidepressant phenotype. Conversely, the inhibition of the expression of PLC?(3) was unable to modify the immobility time values. The PLC and PKC modulators used, at the highest effective doses, altered neither locomotor activity nor motor coordination. We demonstrate that selective blockade of PLC?(1)-PKC? signalling pathway produces an antidepressant-like phenotype in mice. [PubMed Citation] [Order full text from Infotrieve]

7) Perlis RH, Huang J, Purcell S, Fava M, Rush AJ, Sullivan PF, Hamilton SP, McMahon FJ, Schulze TG, Schulze T, Potash JB, Zandi PP, Willour VL, Penninx BW, Boomsma DI, Vogelzangs N, Middeldorp CM, Rietschel M, N�then M, Cichon S, Gurling H, Bass N, McQuillin A, Hamshere M, Craddock N, Sklar P, Smoller JW
Genome-wide association study of suicide attempts in mood disorder patients.
Am J Psychiatry. 2010 Dec;167(12):1499-507.
[PubMed Citation] [Order full text from Infotrieve]

8) O'Brien BJ, Hirano AA, Buttermore ED, Bhat MA, Peles E
Localization of the paranodal protein Caspr in the mammalian retina.
Mol Vis. 2010;16:1854-63.
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9) Amrollahi Z, Rezaei F, Salehi B, Modabbernia AH, Maroufi A, Esfandiari GR, Naderi M, Ghebleh F, Ahmadi-Abhari SA, Sadeghi M, Tabrizi M, Akhondzadeh S
Double-blind, randomized, placebo-controlled 6-week study on the efficacy and safety of the tamoxifen adjunctive to lithium in acute bipolar mania.
J Affect Disord. 2011 Mar;129(1-3):327-31.
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10) Machado-Vieira R, Salvadore G, DiazGranados N, Ibrahim L, Latov D, Wheeler-Castillo C, Baumann J, Henter ID, Zarate CA
New therapeutic targets for mood disorders.
ScientificWorldJournal. 2010;10:713-26.
Existing pharmacological treatments for bipolar disorder (BPD) and major depressive disorder (MDD) are often insufficient for many patients. Here we describe a number of targets/compounds that clinical and preclinical studies suggest could result in putative novel treatments for mood disorders. These include: (1) glycogen synthase kinase-3 (GSK-3) and protein kinase C (PKC), (2) the purinergic system, (3) histone deacetylases (HDACs), (4) the melatonergic system, (5) the tachykinin neuropeptides system, (6) the glutamatergic system, and (7) oxidative stress and bioenergetics. The paper reviews data on new compounds that have shown antimanic or antidepressant effects in subjects with mood disorders, or similar effects in preclinical animal models. Overall, an improved understanding of the neurobiological underpinnings of mood disorders is critical in order to develop targeted treatments that are more effective, act more rapidly, and are better tolerated than currently available therapies. [PubMed Citation] [Order full text from Infotrieve]

11) Ali SM, Ahmad A, Shahabuddin S, Ahmad MU, Sheikh S, Ahmad I
Endoxifen is a new potent inhibitor of PKC: a potential therapeutic agent for bipolar disorder.
Bioorg Med Chem Lett. 2010 Apr 15;20(8):2665-7.
Protein kinase C (PKC) plays a major role in regulation of both pre and postsynaptic neurotransmission. Excessive activation of PKC results in symptoms related to bipolar disorder. Tamoxifen, a widely used breast cancer drug is known to inhibit PKC and demonstrate antimanic properties in human. We describe herein the synthesis of endoxifen, a tamoxifen active metabolite and compared its PKC inhibitory activity with that of tamoxifen. Endoxifen exhibited fourfold higher potency compared to tamoxifen. [PubMed Citation] [Order full text from Infotrieve]

12) Pavan C, Vindigni V, Michelotto L, Rimessi A, Abatangelo G, Cortivo R, Pinton P, Zavan B
Weight gain related to treatment with atypical antipsychotics is due to activation of PKC-β.
Pharmacogenomics J. 2010 Oct;10(5):408-17.
Atypical antipsychotics (APDs) are currently used in clinical practice for a variety of mental disorders such as schizophrenia, bipolar disorder and severe behavioral disturbances. A well-known disadvantage of using these compounds is a propensity for weight gain, resulting frequently in obesity. The mechanisms underlying pharmacologically induced weight gain are still controversial. The objective of this study was to evaluate in vitro the effects of different APDs on adipogenic events in cultured human pre-adipocytes and in rat muscle-derived stem cells (MDSCs), aiming to identify a common intracellular event contributable to these drugs. Culture behavior was evaluated in terms of cell proliferation, lipid accumulation, gene expression and morphological features. Results indicate that APDs influence adipogenic events through changes in the differentiation and proliferation of pre-adipocytes and MDSCs that are brought on by protein kinase C-? (PKC-?) activation. These data identify a signaling route that could be a potential target of pharmacological approaches for preventing the weight gain associated with APD treatment. [PubMed Citation] [Order full text from Infotrieve]

13) Barbier E, Wang JB
Anti-depressant and anxiolytic like behaviors in PKCI/HINT1 knockout mice associated with elevated plasma corticosterone level.
BMC Neurosci. 2009;10:132.
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14) Herrick S, Evers DM, Lee JY, Udagawa N, Pak DT
Postsynaptic PDLIM5/Enigma Homolog binds SPAR and causes dendritic spine shrinkage.
Mol Cell Neurosci. 2010 Feb;43(2):188-200.
Dendritic spine morphology is thought to play important roles in synaptic development and plasticity, and morphological derangements in spines are correlated with several neurological disorders. Here, we identified an interaction between Spine-Associated RapGAP (SPAR), a postsynaptic protein that reorganizes actin cytoskeleton and drives dendritic spine head growth, and PDLIM5/Enigma Homolog (ENH), a PDZ-LIM (postsynaptic density-95/Discs large/zona occludens 1-Lin11/Isl-1/Mec3) family member. PDLIM5 has been implicated in susceptibility to bipolar disorder, major depression, and schizophrenia, but its function in neurological disease is poorly understood. We show that PDLIM5 is present in the postsynaptic density, where it promotes decreased dendritic spine head size and longer, filopodia-like morphology. Conversely, RNA interference against PDLIM5 or loss of PDLIM5 interaction with SPAR caused increased spine head diameter. Furthermore, PKC activation promoted delivery of PDLIM5 into dendritic spines and increased its spine colocalization with SPAR. These data reveal new postsynaptic functions for PDLIM5 in shrinkage of dendritic spines that may be relevant to its association with psychiatric illness. [PubMed Citation] [Order full text from Infotrieve]

15) Hains AB, Vu MA, Maciejewski PK, van Dyck CH, Gottron M, Arnsten AF
Inhibition of protein kinase C signaling protects prefrontal cortex dendritic spines and cognition from the effects of chronic stress.
Proc Natl Acad Sci U S A. 2009 Oct 20;106(42):17957-62.
The prefrontal cortex r regulates behavior, cognition, and emotion by using working memory. Prefrontal functions are impaired by stress exposure. Acute, stress-induced deficits arise from excessive protein kinase C (PKC) signaling, which diminishes prefrontal neuronal firing. Chronic stress additionally produces architectural changes, reducing dendritic complexity and spine density of cortico-cortical pyramidal neurons, thereby disrupting excitatory working memory networks. In vitro studies have found that sustained PKC activity leads to spine loss from hippocampal-cultured neurons, suggesting that PKC may contribute to spine loss during chronic stress exposure. The present study tested whether inhibition of PKC with chelerythrine before daily stress would protect prefrontal spines and working memory. We found that inhibition of PKC rescued working memory impairments and reversed distal apical dendritic spine loss in layer II/III pyramidal neurons of rat prelimbic cortex. Greater spine density predicted better cognitive performance, the first direct correlation between pyramidal cell structure and working memory abilities. These findings suggest that PKC inhibitors may be neuroprotective in disorders with dysregulated PKC signaling such as bipolar disorder, schizophrenia, post-traumatic stress disorder, and lead poisoning--conditions characterized by impoverished prefrontal structural and functional integrity. [PubMed Citation] [Order full text from Infotrieve]

16) Carroll LS, Williams NM, Moskvina V, Russell E, Norton N, Williams HJ, Peirce T, Georgieva L, Dwyer S, Grozeva D, Greene E, Farmer A, McGuffin P, Morris DW, Corvin A, Gill M, Rujescu D, Sham P, Holmans P, Jones I, Kirov G, Craddock N, O'Donovan MC, Owen MJ
Evidence for rare and common genetic risk variants for schizophrenia at protein kinase C, alpha.
Mol Psychiatry. 2010 Nov;15(11):1101-11.
We earlier reported a genome-wide significant linkage to schizophrenia at chromosome 17 that was identified in a single pedigree (C702) consisting of six affected, male siblings with DSM-IV schizophrenia and prominent mood symptoms. In this study, we adopted several approaches in an attempt to map the putative disease locus. First, mapping the source of linkage to chromosome 17 in pedigree C702. We refined the linkage region in family C702 to a 21-marker segment spanning 11.7?Mb at 17q23-q24 by genotyping a total of 50 microsatellites across chromosome 17 in the pedigree. Analysis of data from 1028 single nucleotide polymorphisms (SNPs) across the refined linkage region identified a single region of homozygosity present in pedigree C702 but not in 2938 UK controls. This spanned ~432?kb of the gene encoding protein kinase C, alpha (PRKCA), the encoded protein of which has been implicated in the pathogenesis of psychiatric disorders. Analysis of pedigree C702 by oligonucleotide-array comparative genome hybridization excluded the possibility that this region of homozygosity was because of a deletion. Mutation screening of PRKCA identified a rare, four-marker haplotype (C-HAP) in the 3' untranslated region of the gene, which was present in the homozygous state in all six affected members of pedigree C702. No other homozygotes were observed in genotype data for a total of 6597 unrelated Europeans (case N=1755, control N=3580 and parents of probands N=1262). Second, association analysis of C702 alleles at PRKCA. The low-frequency haplotype (C-HAP) showed a trend for association in a study of unrelated schizophrenia cases and controls from the UK (661 cases, 2824 controls, P=0.078 and odd ratio (OR)=1.9) and significant evidence for association when the sample was expanded to include cases with bipolar (N=710) and schizoaffective disorder (N=50) (psychosis sample: 1421 cases, 2824 controls, P=0.037 and OR=1.9). Given that all the affected members of C702 are male, we also undertook sex-specific analyses. This revealed that the association was strongest in males for both schizophrenia (446 male cases, 1421 male controls, P=0.008 and OR=3.9) and in the broader psychosis group (730 male cases, 1421 male controls, P=0.008 and OR=3.6). Analysis of C-HAP in follow-up samples from Ireland and Bulgaria revealed no evidence for association in either the whole sample or in males alone, and meta-analysis of all male psychosis samples yielded no significant evidence of association (969 male cases, 1939 male controls, 311 male probands P=0.304 and OR=1.4). Third, association mapping of the pedigree C702 linkage region. Independent of pedigree C702, genotype data from the Affymetrix 500k GeneChip set were available for 476 patients with schizophrenia and 2938 controls from the United Kingdom. SNPs in PRKCA showed evidence for association with schizophrenia that achieved gene-wide significance (P=0.027). Moreover, the same SNP was the most significantly associated marker out of the 1028 SNPs genotyped across the linkage region (rs873417, allelic P=0.0004). Follow-up genotyping in samples from Ireland, Bulgaria and Germany did not show consistent replication, but meta-analysis of all samples (4116 cases and 6491 controls) remained nominally significant (meta-analysis P=0.026, OR=1.1). We conclude that, although we have obtained convergent lines of evidence implicating both rare and common schizophrenia risk variants at PRKCA, none of these is individually compelling. However, the evidence across all approaches suggests that further study of this locus is warranted. [PubMed Citation] [Order full text from Infotrieve]

17) Large CH, Di Daniel E, Li X, George MS
Neural network dysfunction in bipolar depression: clues from the efficacy of lamotrigine.
Biochem Soc Trans. 2009 Oct;37(Pt 5):1080-4.
One strategy to understand bipolar disorder is to study the mechanism of action of mood-stabilizing drugs, such as valproic acid and lithium. This approach has implicated a number of intracellular signalling elements, such as GSK3beta (glycogen synthase kinase 3beta), ERK (extracellular-signal-regulated kinase)/MAPK (mitogen-activated protein kinase) or protein kinase C. However, lamotrigine does not seem to modulate any of these targets, which is intriguing given that its profile in the clinic differs from that of valproic acid or lithium, with greater efficacy to prevent episodes of depression than mania. The primary target of lamotrigine is the voltage-gated sodium channel, but it is unclear why inhibition of these channels might confer antidepressant efficacy. In healthy volunteers, we found that lamotrigine had a facilitatory effect on the BOLD (blood-oxygen-level-dependent) response to TMS (transcranial magnetic stimulation) of the prefrontal cortex. This effect was in contrast with an inhibitory effect of lamotrigine when TMS was applied over the motor cortex. In a follow-up study, a similar prefrontal specific facilitatory effect was observed in a larger cohort of healthy subjects, whereas valproic acid inhibited motor and prefrontal cortical TMS-induced BOLD response. In vitro, we found that lamotrigine (3-10 microM) enhanced the power of gamma frequency network oscillations induced by kainic acid in the rat hippocampus, an effect that was not observed with valproic acid (100 microM). These data suggest that lamotrigine has a positive effect on corticolimbic network function that may differentiate it from other mood stabilizers. The results are also consistent with the notion of corticolimbic network dysfunction in bipolar disorder. [PubMed Citation] [Order full text from Infotrieve]

18) Mallinger AG, Thase ME, Haskett R, Buttenfield J, Luckenbaugh DA, Frank E, Kupfer DJ, Manji HK
Verapamil augmentation of lithium treatment improves outcome in mania unresponsive to lithium alone: preliminary findings and a discussion of therapeutic mechanisms.
Bipolar Disord. 2008 Dec;10(8):856-66.
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19) Ou Y, Ruan Y, Cheng M, Moser JJ, Rattner JB, van der Hoorn FA
Adenylate cyclase regulates elongation of mammalian primary cilia.
Exp Cell Res. 2009 Oct 1;315(16):2802-17.
The primary cilium is a non-motile microtubule-based structure that shares many similarities with the structures of flagella and motile cilia. It is well known that the length of flagella is under stringent control, but it is not known whether this is true for primary cilia. In this study, we found that the length of primary cilia in fibroblast-like synoviocytes, either in log phase culture or in quiescent state, was confined within a range. However, when lithium was added to the culture to a final concentration of 100 mM, primary cilia of synoviocytes grew beyond this range, elongating to a length that was on average approximately 3 times the length of untreated cilia. Lithium is a drug approved for treating bipolar disorder. We dissected the molecular targets of this drug, and observed that inhibition of adenylate cyclase III (ACIII) by specific inhibitors mimicked the effects of lithium on primary cilium elongation. Inhibition of GSK-3beta by four different inhibitors did not induce primary cilia elongation. ACIII was found in primary cilia of a variety of cell types, and lithium treatment of these cell types led to their cilium elongation. Further, we demonstrate that different cell types displayed distinct sensitivities to the lithium treatment. However, in all cases examined primary cilia elongated as a result of lithium treatment. In particular, two neuronal cell types, rat PC-12 adrenal medulla cells and human astrocytes, developed long primary cilia when lithium was used at or close to the therapeutic relevant concentration (1-2 mM). These results suggest that the length of primary cilia is controlled, at least in part, by the ACIII-cAMP signaling pathway. [PubMed Citation] [Order full text from Infotrieve]

20) Zarate CA, Manji HK
Protein kinase C inhibitors: rationale for use and potential in the treatment of bipolar disorder.
CNS Drugs. 2009;23(7):569-82.
Bipolar disorder is one of the most severely debilitating of all medical illnesses. For a large number of patients, outcomes are quite poor. The illness results in tremendous suffering for patients and their families and commonly impairs functioning and workplace productivity. Risks of increased morbidity and mortality, unfortunately, are frequent occurrences as well. Until recently, little has been known about the specific molecular and cellular underpinnings of bipolar disorder. Such knowledge is crucial for the prospect of developing specific targeted therapies that are more effective and that have a more rapid onset of action than currently available treatments. Exciting recent data suggest that regulation of certain signalling pathways may be involved in the aetiology of bipolar disorder and that these pathways may be profitably targeted to treat the disorder. In particular, mania is associated with overactive protein kinase C (PKC) intracellular signalling, and recent genome-wide association studies of bipolar disorder have implicated an enzyme that reduces the activation of PKC. Importantly, the current mainstays in the treatment of mania, lithium (a monovalent cation) and valproate (a small fatty acid) indirectly inhibit PKC. In addition, recent clinical studies with the relatively selective PKC inhibitor tamoxifen add support to the relevance of the PKC target in bipolar disorder. Overall, a growing body of work both on a preclinical and clinical level indicates that PKC signalling may play an important role in the pathophysiology and treatment of bipolar disorder. The development of CNS-penetrant PKC inhibitors may have considerable benefit for this devastating illness. [PubMed Citation] [Order full text from Infotrieve]