The mood-stabilizing agents lithium and valproate robustly increase the levels of the neuroprotective protein bcl-2 in the CNS

Valproic acid inhibits substance P-induced activation of protein kinase C epsilon and expression of the substance P receptor

The neuropeptide substance P (SP) has been hypothesized to be involved in the etiopathology of affective disorders. This hypothesis is based on the findings that neurokinin-1-receptor antagonists have antidepressant effects in depressed patients and that SP may worsen mood. In this study, we investigated the effect of the mood-stabilizing agents valproic acid (VPA), carbamazepine, and lithium on SP-induced gene expression. As a model system, we used primary rat astrocytes and human astrocytoma cells, which both express functional SP-receptors and, upon stimulation with SP, synthesize interleukin-6 (IL-6), a cytokine which has been shown to be elevated during the acute depressive state. We found that VPA dose-dependently inhibited SP-induced IL-6 synthesis which was seen with pre-incubation periods of 30 min, 3, 7 and 14 days, whereas carbamazepine and lithium showed no inhibitory effect. The inhibitory effect of VPA was not mediated by inhibition of the stress-regulated kinases p38 and p42/44 (Erk1/2) but by inhibition of protein kinase C epsilon activation. Furthermore, VPA down-regulated the expression of the substance P receptor (neurokinin(NK)-1-receptor) as assessed by real-time PCR. Whether both mechanisms contribute to the mood-stabilizing properties of VPA has to be evaluated in further studies.

Valproic acid enhances axonal regeneration and recovery of motor function after sciatic nerve axotomy in adult rats

It has recently been demonstrated that valproic acid (VPA) robustly promotes neurite outgrowth, activates the extracellular signal regulated kinase pathway, and increases growth cone-associated protein 43 and bcl-2 levels in cultured human neuroblastoma SH-SY5Y cells. We hypothesized that VPA could also enhance peripheral nerve regeneration in adult animals. To test this hypothesis, we examined the effects of VPA (300 mg/kg daily for 16 weeks) on sciatic axonal regeneration following single or conditional axotomies in rats. The results showed that in VPA-treated rats there was a significant increase in the total numbers of regenerated myelinated nerve fibers and reinnervated muscle fibers in comparison with those rats not treated with VPA. As measured by sciatic function index and toe spread index, the motor function of the reinnervated hind limbs of rats receiving single axotomy without VPA treatment significantly improved at week 8 and reached plateau levels at about week 11, whereas the motor function of the reinnervated hind limbs of rats receiving single axotomy plus VPA and rats receiving conditional axotomy with or without VPA treatment significantly improved at week 4 and reached plateau levels at about week 8; there was no significant difference of the motor function among the three later groups. The results demonstrated that VPA is able to enhance sciatic nerve regeneration and recovery of motor function in adult rats, suggesting the potential clinical application of VPA for the treatment of peripheral nerve injury in humans.

Attenuation of N-methyl-D-aspartate-mediated cytoplasmic vacuolization in primary rat hippocampal neurons by mood stabilizers

Recent post-mortem and brain imaging studies suggest that decreased neuronal and glial densities may account for cell loss in vulnerable brain regions such as the hippocampus and the frontal cortex in patients with bipolar disorder. Investigations into the mechanisms of action of mood stabilizers suggest that these drugs may regulate the expression of neuroprotective genes and protect against excitotoxicity. In this study, we characterized the ultrastructural appearance of rat hippocampal neurons pretreated with mood stabilizers and then exposed to the glutamate receptor agonist N-methyl-D-aspartate. Using transmission electron microscopy we found that rat hippocampal neurons exposed to 0.5 mM N-methyl-D-aspartate for 10 min produced more cytoplasmic vacuolization than in control neurons. Chronic treatment with mood stabilizers, lithium, valproate or carbamazepine for 7 days at therapeutically relevant concentrations fully attenuated N-methyl-D-aspartate-mediated cytoplasmic vacuolization. These results suggest that inhibition of neurotoxicity may be involved in the action of mood stabilizers.

Anti-epileptic drugs as possible neuroprotectants in cerebral ischemia

Many similarities exist between cerebral ischemia and epilepsy regarding brain-damaging and auto-protective mechanisms that are activated following the injurious insult. Therefore, drugs that are effective in minimizing seizure-induced brain damage may also be useful in minimizing ischemic injury. Use of such drugs in stroke victims may have important clinical and financial advantages. Therefore, the authors conducted a Medline search of studies involving the use of anti-epileptic drugs (AEDs) as possible neuroprotectants and summarize the data. Most AEDs have been tested in animal models of focal or global ischemia and some were already tested in humans, for a possible neuroprotective effect. The existing data is rather scant and insufficient but it appears that only drugs that have multiple mechanisms of action seem to have some potential in conferring a degree of neuroprotection that could be clinically applicable to stroke patients. In conclusion, some of the newer AEDs show promise as possible neuroprotectants in the setup of acute ischemic stroke but more studies are needed before clinical trials in humans could be undertaken.

Postinsult treatment with lithium reduces brain damage and facilitates neurological recovery in a rat ischemia/reperfusion model

Lithium has long been a primary drug used to treat bipolar mood disorder, even though the drug's therapeutic mechanisms remain obscure. Recent studies demonstrate that lithium has neuroprotective effects against glutamate-induced excitotoxicity in cultured neurons and in vivo. The present study was undertaken to examine whether postinsult treatment with lithium reduces brain damage induced by cerebral ischemia. We found that s.c. injection of lithium dose dependently (0.5-3 mEq/kg) reduced infarct volume in the rat model of middle cerebral artery occlusionreperfusion. Infarct volume was reduced at a therapeutic dose of 1 mEq/kg even when administered up to 3 h after the onset of ischemia. Neurological deficits induced by ischemia were also reduced by daily administration of lithium over 1 week. Moreover, lithium treatment decreased the number of neurons showing DNA damage in the ischemic brain. These neuroprotective effects were associated with an up-regulation of cytoprotective heat shock protein 70 (HSP70) in the ischemic brain hemisphere as determined by immunohistochemistry and Western blotting analysis. Lithium-induced HSP70 up-regulation in the ischemic hemisphere was preceded by an increase in the DNA binding activity of heat shock factor 1, which regulates the transcription of HSP70. Physical variables and cerebral blood flow were unchanged by lithium treatment. Our results suggest that postinsult lithium treatment reduces both ischemia-induced brain damage and associated neurological deficits. Moreover, the heat shock response is likely to be involved in lithium's neuroprotective actions. Additionally, our studies indicate that lithium may have clinical utility for the treatment of patients with acute stroke.

Lithium enhances long-term potentiation independently of hippocampal neurogenesis in the rat dentate gyrus

We measured the temporal and spatial profiles of neural precursor cells, hippocampal long-term potentiation (LTP), and signaling molecules in neurogenesis-induced adult rats. Chronic lithium treatment produced a significant 54% and 40% increase in the numbers of bromodeoxyuridine [BrdU(+)] cells after 12 h and 28 days, respectively, after treatment completion in the dentate gyrus (DG). Both LTP obtained from slices perfused with artificial cerebrospinal fluid (ACSF-LTP) and LTP recorded in the presence of bicuculline (bicuculline-LTP) were significantly greater in the lithium group than in the saline controls. Although the number of BrdU(+) cells, approximately 90% of which were double-labeled with a neural marker neuronal nuclear protein, were markedly increased in the granule cell layer (GCL) 28 days after the completion of the 28-day lithium treatment, the magnitude of LTP observed at this time was similar to that observed 12 h after completing the 28-day lithium treatment. However, protein levels of calcium and calmodulin-dependent protein kinase II, p-Elk and TrkB were highly elevated until 28 days after the 28-day lithium treatment. Acute lithium treatment for 2 days also enhanced LTP, which was accompanied by the elevated expression of p-CREB, but not by neurogenesis. Our results suggest that the enhancement of LTP is independent of the increased number of neurons per se and it is more closely associated with key molecules, which are probably involved in neurogenesis.

Finding the intracellular signaling pathways affected by mood disorder treatments

Postmortem and brain imaging studies have revealed structural changes and cell loss in cortico-limbic regions of the brain in bipolar disorder and major depression. Consistent with these findings, mood stabilizers such as lithium ion and valproic acid, which are used to treat bipolar disorder, as well as antidepressants and electroconvulsive therapy have recently been shown to activate interconnected intracellular signaling pathways that promote neurogenesis and synaptic plasticity. These insights should assist in understanding the pathophysiology of severe mood disorders as well as aid in the development of more effective treatments.

Chronic lithium enhances hippocampal long-term potentiation, but not neurogenesis, in the aged rat dentate gyrus

We investigated the hippocampal long-term potentiation (LTP), neurogenesis, and the activation of signaling molecules in the 20-month-old aged rats following chronic lithium treatment. Chronic lithium treatment produced a significant 79% increase in the numbers of BrdU(+) cells after treatment completion in the dentate gyrus (DG). Both LTP obtained from slices perfused with artificial cerebrospinal fluid (ACSF-LTP), and LTP recorded in the presence of bicuculline (bicuculline-LTP) were significantly greater in the lithium group than in the saline controls. Our results show that as with young rats, chronic lithium can substantially increase LTP and the number of BrdU(+) cells in the aged rats. However, neurogenesis, assessed by colocalization of NeuN and BrdU, was not detected in the aged rat DG subjected to chronic lithium treatment. Therefore, it is concluded that the increase in LTP and the number of BrdU(+) cells might not be associated with increases in neurogenesis in the granule cell layer of the DG. Lithium might has a beneficial effects through other signaling pathways in the aged brain.

Chronic lithium treatment antagonizes glutamate-induced decrease of phosphorylated CREB in neurons via reducing protein phosphatase 1 and increasing MEK activities

The cyclic AMP response element binding protein (CREB) has major roles in mediating adaptive responses at glutamatergic synapses and in the neuroprotective effects of neurotrophins. CREB has been implicated as a potential mediator of antidepressant actions. In vitro, chronic lithium treatment has been shown to promote neuronal cell survival. In the present study, we have used cultures of cerebellar granule neurons to analyze the effects of acute and chronic lithium treatment on the response to toxic concentrations of glutamate. Such concentrations of glutamate decrease the phosphorylation of CREB at serine(133) in an N-methyl-D-aspartate (NMDA) receptor-dependent manner. Chronic, but not acute, lithium treatment suppresses glutamate-induced decreases in phosphorylated CREB, and transfection studies indicate that chronic lithium, in the presence of a glutamate stimulus, markedly increases CRE-driven gene expression. Experiments with selected pharmacological reagents indicate that the glutamate-induced decreases in phosphorylated CREB are regulated primarily by protein phosphatase 1. Chronic lithium treatment not only decreases protein phosphatase 1 activity under these circumstances, but also augments glutamate-induced increases in MEK activity. PD 98059, a MEK inhibitor, prevents chronic lithium treatment from increasing phosphorylated CREB levels in glutamate-treated neurons. We conclude from these results that chronic lithium treatment is permissive for maintaining higher phosphorylated CREB levels in the presence of glutamate in part by decreasing protein phosphatase 1 activity and in part by increasing MEK activity. Higher levels of phosphorylated CREB and CRE-responsive genes such as bcl-2 may be responsible for lithium's reported effects on neuronal survival.

Valproate inhibits oxidative damage to lipid and protein in primary cultured rat cerebrocortical cells

Valproate is often prescribed as a long-term therapeutic mood stabilizing agent for individuals with bipolar disorder. Although research suggests that this drug may produce a neuroprotective effect, its neuroprotective mechanism is not yet clear. The purpose of this study was to determine if valproate provides a neuroprotective effect against damage caused by oxidative stress in primary cultured rat cerebral cortical cells. We found that chronic treatment with valproate at therapeutically relevant concentrations for 7 days inhibited lipid peroxidation and protein oxidation induced by treatment with 0.25 mM oxidant FeCl(3) for 90 min, indicating that valproate inhibits oxidative damage to lipid and protein. Our results suggest that chronic treatment with valproate may protect neuronal cells from damage caused by oxidative stress and that neuroprotection from oxidative damages may be involved in the mechanism of action of valproate. Supporting this possibility are recent findings that chronic treatment with valproate increased the expression of endoplasmic reticulum stress protein GRP78 and antiapoptotic factor bcl-2 in rat cerebral cortex. Since GRP78 binds Ca(2+) and folds damaged protein, bcl-2 stabilizes mitochondrial transmembrane potential and inhibits cytochrome C release, and both GRP78 and bcl-2 have been shown to inhibit oxyradical accumulation, together these findings indicate that valproate may target one or more of these processes in order to produce neuroprotective effects.

Enhancing neuronal plasticity and cellular resilience to develop novel, improved therapeutics for difficult-to-treat depression

There is growing evidence from neuroimaging and ostmortem studies that severe mood disorders, which have traditionally been conceptualized as neurochemical disorders, are associated with impairments of structural plasticity and cellular resilience. It is thus noteworthy that recent preclinical studies have shown that critical molecules in neurotrophic signaling cascades (most notably cyclic adenosine monophosphate [cAMP] response element binding protein, brain-derived neurotrophic factor, bcl-2, and mitogen activated protein [MAP] kinases) are long-term targets for antidepressant agents and antidepressant potentiating modalities. This suggests that effective treatments provide both trophic and neurochemical support, which serves to enhance and maintainnormal synaptic connectivity, thereby allowing the chemical signal to reinstate the optimal functioning of critical circuits necessary for normal affective functioning. For many refractory patients, drugs mimicking "traditional" strategies, which directly or indirectly alter monoaminergic levels, may be of limited benefit. Newer "plasticity enhancing" strategies that may have utility in the treatment of refractory depression include N-methyl-D-aspartate antagonists, alpha-amino-3-hydroxy-5-methylisoxazole propionate (AMPA) potentiators, cAMP phosphodiesterase inhibitors, and glucocorticoid receptor antagonists. Small-molecule agents that regulate the activity f growth factors, MAP kinases cascades, and the bcl-2 family of proteins are also promising future avenues. The development of novel, nonaminergic-based therapeutics holds much promise for improved treatment of severe, refractory mood disorders.

Congenitally learned helpless rats show abnormalities in intracellular signaling

BACKGROUND

Affective disorders and the drugs used to treat them lead to changes in intracellular signaling. We used a genetic animal model to investigate to what extent changes in intracellular signal transduction confer a vulnerability to mood or anxiety disorders.

METHODS

Levels of gene expression in a selectively bred strain of rats with a high vulnerability to develop congenitally learned helplessness (cLH), a strain highly resistant to the same behavior (cNLH) and outbred Sprague-Dawley (SD) control animals were compared using quantitative reverse transcription polymerase chain reaction.

RESULTS

Congenitally learned helpless animals had a 24%-30% reduced expression of the cyclic adenosine monophosphate response element binding protein messenger ribonucleic acid (mRNA) in the hippocampus and a 40%-41% increased level of the antiapoptotic protein bcl-2 mRNA in the prefrontal cortex compared to cNLH and SD rats. Other significant changes included changes in the expression levels of the alpha catalytic subunit of protein kinase A, glycogen synthase kinase 3beta, and protein kinase C epsilon.

CONCLUSIONS

Congenitally learned helpless animals show evidence of altered signal transduction and regulation of apoptosis compared to cNLH and SD control animals.

Family-based association study of 76 candidate genes in bipolar disorder: BDNF is a potential risk locus. Brain-derived neutrophic factor

Identification of the genetic bases for bipolar disorder remains a challenge for the understanding of this disease. Association between 76 candidate genes and bipolar disorder was tested by genotyping 90 single-nucleotide polymorphisms (SNPs) in these genes in 136 parent-proband trios. In this preliminary analysis, SNPs in two genes, brain-derived neurotrophic factor (BDNF) and the alpha subunit of the voltage-dependent calcium channel were associated with bipolar disorder at the P<0.05 level. In view of the large number of hypotheses tested, the two nominally positive associations were then tested in independent populations of bipolar patients and only BDNF remains a potential risk gene. In the replication samples, excess transmission of the valine allele of amino acid 66 of BDNF was observed in the direction of the original result in an additional sample of 334 parent-proband trios (T/U=108/87, P=0.066). Resequencing of 29 kb surrounding the BDNF gene identified 44 additional SNPs. Genotyping eight common SNPs identified three additional markers transmitted to bipolar probands at the P < 0.05 level. Strong LD was observed across this region and all adjacent pairwise haplotypes showed excess transmission to the bipolar proband. Analysis of these haplotypes using TRANSMIT revealed a global P value of 0.03. A single haplotype was identified that is shared by both the original dataset and the replication sample that is uniquely marked by both the rare A allele of the original SNP and a novel allele 11.5 kb 3'. Therefore, this study of 76 candidate genes has identified BDNF as a potential risk allele that will require additional study to confirm.

Regulation of c-Jun N-terminal kinase, p38 kinase and AP-1 DNA binding in cultured brain neurons: roles in glutamate excitotoxicity and lithium neuroprotection

In rat cerebellar granule cells, glutamate induced rapid activation of c-Jun N-terminal kinase (JNK) and p38 kinase to phosphorylate c-Jun (at Ser63) and p53 (at Ser15), respectively, and a subsequent marked increase in activator protein-1 (AP-1) binding that preceded apoptotic death. These glutamate-induced effects and apoptosis could largely be prevented by long-term (7 days) pretreatment with 0.5-2 mm lithium, an antibipolar drug. Glutamate's actions could also be prevented by known blockers of this pathway, MK-801 (an NMDA receptor blocker), SB 203580 (a p38 kinase inhibitor) and curcumin (an AP-1 binding inhibitor). The concentration- and time-dependent suppression of glutamate's effects by lithium and curcumin correlated well with their neuroprotective effects. These results suggest a prominent role of JNK and p38, as well as their downstream AP-1 binding activation and p53 phosphorylation in mediating glutamate excitotoxicity. Moreover, the neuroprotective effects of lithium are mediated, at least in part, by suppressing NMDA receptor-mediated activation of the mitogen-activated protein kinase pathway.

Dose-related effects of chronic antidepressants on neuroprotective proteins BDNF, Bcl-2 and Cu/Zn-SOD in rat hippocampus

It has been proposed that antidepressants have neuroprotective effects on hippocampal neurons. To further test this hypothesis, brain-derived neurotrophic factor (BDNF), B cell lymphoma protein-2 (Bcl-2), and copper-zinc superoxide dismutase (Cu/Zn-SOD) were examined immunohistochemically in hippocampal neurons of Sprague-Dawley rats following daily treatment with 5 or 10 mg/kg of amitriptyline or venlafaxine for 21 days. At 5 mg/kg, both amitriptyline and venlafaxine increased the intensity of BDNF immunostaining in hippocampal pyramidal neurons, and the intensity of Bcl-2 immunostaining in hippocampal mossy fibers, but did not alter the Cu/Zn-SOD immunoreactivity. The high dose of venlafaxine, however, decreased the intensity of BDNF immunostaining in all subareas of the hippocampus and increased the intensity of Cu/Zn-SOD immunostaining in the dentate granular cell layer. The high dose of amitriptyline increased the intensity of Cu/Zn-SOD immunostaining, but did not affect the immunoreactivity of Bcl-2 or BDNF. These findings suggest that the chronic administration of amitriptyline or venlafaxine at 5 mg/kg, but not 10 mg/kg, may be neuroprotective to hippocampal neurons. These dose-related effects of antidepressant drugs on hippocampal neurons may have relevance to disparate findings in the field.

Mood stabilizers in Alzheimer's disease: symptomatic and neuroprotective rationales

OBJECTIVE

This paper provides a case study of 'reverse translational research', in which empirical clinical trials focused on relieving psychopathological symptoms of Alzheimer's disease (AD) ultimately led to mechanism-based trials addressing aspects of the underlying pathophysiology of Alzheimer's disease. AD is multi-dimensional in nature, characterized not only by cognitive and functional decline but by neuropsychiatric symptoms that develop commonly and are associated with considerable morbidity. There have been a large number of empirical trials of various pharmacological agents to reduce these symptoms, such as agitation. Although antipsychotics are used most frequently for agitation, the usual effect size is modest, and there is a range of tolerability and/or safety issues, leading to the hope that alternatives can be found. Furthermore, most clinical trials addressing psychopathology have not been mechanism-based and none have attempted an alternative approach, namely, to delay or prevent the emergence of psychopathology.

FINDINGS

The evidence of clinical trials is reviewed regarding the safety, tolerability, and apparent efficacy of the mood stabilizers carbamazepine and valproate for agitation associated with AD. Possible mechanisms of action of valproate are reviewed, leading to the surprising conclusion that neuroprotective properties may account for some of its clinical effects. These mechanisms (including activation of wnt-dependent signaling and upregulation of bcl-2, among others) may be particularly relevant for long-term treatment of AD.

CONCLUSIONS

These clinical and mechanistic findings were combined in the development of a novel clinical trial examining whether chronic valproate therapy can attenuate the clinical progression of AD, which will be implemented by the Alzheimer's Disease Cooperative Study. The design addresses valproate's potential to delay or prevent the onset of agitation in patients lacking agitation to begin with, as well as to slow progressive decline in cognition and daily functioning.

Lithium induces brain-derived neurotrophic factor and activates TrkB in rodent cortical neurons: an essential step for neuroprotection against glutamate excitotoxicity

Mechanisms underlying the therapeutic effects of lithium for bipolar mood disorder remain poorly understood. Recent studies demonstrate that lithium has neuroprotective actions against a variety of insults in vitro and in vivo. This study was undertaken to investigate the role of the brain-derived neurotrophic factor (BDNF)/TrkB signaling pathway in mediating neuroprotection of lithium against glutamate excitotoxicity in cortical neurons. Pretreatment with either lithium or BDNF protected rat cerebral cortical neurons from glutamate excitotoxicity. The duration of treatment required to elicit maximal neuroprotection by BDNF (1 day) was much shorter than that by lithium (6 days). K252a, an inhibitor of Trk tyrosine kinases, and a BDNF neutralizing antibody suppressed the neuroprotective effect of lithium. Treatment of cortical neurons with lithium increased the cellular BDNF content in 3 days and the phosphorylation of TrkB at Tyr490 in 5 days, suggesting that long-term lithium administration enhances BDNF expression/secretion, leading to the activation of TrkB receptor. Lithium failed to protect against glutamate excitotoxicity in cortical neurons derived from homozygous and heterozygous BDNF knockout mice, although lithium fully protected cortical neurons prepared from wild type mice littermates. Taken together, these data suggest that the BDNF/TrkB pathway plays an essential role in mediating the neuroprotective effect of lithium.

Mood stabilizer psychopharmacology

Mood stabilizers represent a class of drugs that are efficacious in the treatment of bipolar disorder. The most established medications in this class are lithium, valproic acid, and carbamazepine. In addition to their therapeutic effects for treatment of acute manic episodes, these medications often are useful as prophylaxis against future episodes and as adjunctive antidepressant medications. While important extracellular effects have not been excluded, most available evidence suggests that the therapeutically relevant targets of this class of medications are in the interior of cells. Herein we give a prospective of a rapidly evolving field, discussing common effects of mood stabilizers as well as effects that are unique to individual medications. Mood stabilizers have been shown to modulate the activity of enzymes, ion channels, arachidonic acid turnover, G protein coupled receptors and intracellular pathways involved in synaptic plasticity and neuroprotection. Understanding the therapeutic targets of mood stabilizers will undoubtedly lead to a better understanding of the pathophysiology of bipolar disorder and to the development of improved therapeutics for the treatment of this disease. Furthermore, the involvement of mood stabilizers in pathways operative in neuroprotection suggests that they may have utility in the treatment of classical neurodegenerative disorders.

PKC, MAP kinases and the bcl-2 family of proteins as long-term targets for mood stabilizers

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.

Low glial numbers in the amygdala in major depressive disorder

BACKGROUND

Functional imaging studies implicate the prefrontal cortex and amygdala in major depressive disorder and bipolar disorder, and glial decreases have been reported in the prefrontal cortex. Here, glia and neurons were counted in the amygdala and entorhinal cortex in major depressive disorder, bipolar disorder, and control cases.

METHODS

Tissue blocks from major depressive disorder (7), bipolar disorder (10), and control (12) cases, equally divided between right and left, were cut into 50 microm sections and stained with the Nissl method. One major depressive disorder and all but two bipolar disorder cases had been treated with lithium or valproate. Neurons and glia were counted using stereological methods.

RESULTS

Glial density and the glia/neuron ratio were substantially reduced in the amygdala in major depressive disorder cases. The reduction was mainly accounted for by counts in the left hemisphere. No change was found in neurons. Average glia measures were not reduced in bipolar disorder cases; however, bipolar disorder cases not treated with lithium or valproate had significant glial reduction. Similar but smaller changes were found in the entorhinal cortex.

CONCLUSIONS

Glia are reduced in the amygdala in major depressive disorder, especially on the left side. The results suggest that lithium and valproate may moderate the glial reduction.

Increased gray matter volume in lithium-treated bipolar disorder patients

Lithium's neurotrophic effects have been reported in several in vitro and ex vivo studies. Preliminary human studies with magnetic resonance imaging (MRI) and spectroscopy have recently provided evidence of lithium-induced increases in gray matter volumes and N-acetyl-aspartate levels. In order to further examine the hypothesis that lithium treatment would relate to detectable increases in gray matter brain content, we blindly measured gray and white matter volumes in MRI images of 12 untreated and 17 lithium-treated bipolar patients and 46 healthy controls. Using multivariate analysis of covariance with age and gender as covariates, we found that total gray matter volumes were significantly increased in lithium-treated (747.9 +/- 69.8 cm(3)) compared with untreated patients (639.2 +/- 91.2 cm(3); F = 10.6; d.f. = 1, 25; P = 0.003) and healthy individuals (675.8 +/- 61.8 cm(3); F = 17.4; d.f. = 1, 59; P < 0.001), suggesting in vivo effects of lithium on gray matter, which could possibly reflect lithium's neurotrophic effects.

Interactions between psychotropics, anaesthetics and electroconvulsive therapy: implications for drug choice and patient management

Despite many predictions that electroconvulsive therapy (ECT) would be replaced by pharmacotherapy, ECT has remained an invaluable adjunct in the management of severe psychiatric disease. Both pharmacotherapy and ECT continue to be used extensively, and will frequently be administered concurrently. The majority of patients requiring ECT will need anaesthesia; therefore, interactions could conceivably occur between the psychotropic drugs, ECT and the anaesthetic agents utilised. In managing an anaesthetic for ECT the effects of the anaesthetic agents and other medications on seizure intensity are important determinants influencing outcome. With regard to the antidepressants, tricyclic antidepressants (TCAs) and ECT can be combined safely and beneficially. More care is required when ECT is administered in the setting of a monoamine oxidase inhibitor (MAOI), especially the older irreversible varieties and in patients recently placed on MAOI therapy. Of the anticonvulsants and mood stabilisers, lithium and ECT given concurrently add significant risk of delirium and/or organic syndromes developing. Possible concerns with valproate, carbamazepine, lamotrigine, gabapentin and topiramate are that they may inhibit seizure activity. Additionally, carbamazepine may prolong the action of suxamethonium (succinylcholine). The combination of antipsychotics and ECT is well tolerated, and may in fact be beneficial. As regards the anxiolytics, benzodiazepines have anticonvulsant properties that might interfere with the therapeutic efficacy of ECT. CNS stimulants on the other hand may prolong seizures as well as produce dysrhythmias and elevate blood pressure. Calcium channel antagonists should be used with great care to avoid significant cardiovascular depression. The anaesthesiologist should therefore remain vigilant at all times, as untoward responses during ECT might occur suddenly due to interactions between psychotropics, anaesthetic agents and/or ECT.

Evaluation of neuroprotection by lithium and valproic acid against ouabain-induced cell damage

BACKGROUND

The pathophysiology of manic-depression may be associated with dysregulation of ion homeostasis. Ouabain is a potent inhibitor of the sodium-potassium adenosine triphosphatase and has been purported to mimic abnormalities seen in acute mania. As manic episodes are believed to be neurotoxic and mood stabilizers have recently been implicated as neuroprotectants, it is of interest to determine if lithium and valproic acid antagonize ouabain-induced neurotoxicity.

METHODS

Human neuroblastoma SH-SY5Y cells were differentiated for 12 days then pretreated with lithium or valproic acid for 24 h and then challenged with a 10 microM ouabain insult. Cellular damage was assessed with lactate dehydrogenase (LDH) release, and apoptotic potential of ouabain was evaluated with DNA fragmentation.

RESULTS

Ouabain significantly increased LDH release after 72 h of treatment. Lithium pretreatment at 1 mM diminished ouabain-induced LDH release. Valproic acid alone at 100 and 1000 micrograms/mL significantly increased LDH release from the cells. Furthermore, it significantly potentiated ouabain-induced LDH release. DNA fragmentation suggests that ouabain induces apoptosis.

CONCLUSIONS

Lithium at the therapeutic level of 1 mM limits the extent of cellular damage caused by 10 microM ouabain in SH-SY5Y cells as measured by LDH release. Valproic acid alone at the therapeutic concentration of 100 micrograms/mL induces LDH release and does not prevent ouabain-induced LDH release.

Efficacy of current antiepileptics to prevent neurodegeneration in epilepsy models

Results of experiments performed in animal epilepsy models and human epilepsy during the past decade indicate that the epileptic brain is not a stable neuronal network, but undergoes modifications caused by the underlying etiology and/or recurrent seizures. In many forms of epilepsy, such as temporal lobe epilepsy, the underlying etiologic factor triggers a cascade of events (epileptogenesis) leading to spontaneous seizures and cognitive decline. In some patients, the condition progresses, due in part to recurrent seizures. The current treatment of epilepsy focuses exclusively on preventing or suppressing seizures, which are symptoms of the underlying disease. Now, however, we are beginning to understand the underlying neurobiology of the epileptic process, as well as factors that might predict the risk of progression in individual patients. Thus, there are new opportunities to develop neuroprotective and antiepileptogenic treatments for patients who, if untreated, would develop drug-refractory epilepsy associated with cognitive decline. These treatments might improve the long-term outcome and quality-of-life of patients with epilepsy. Here we review the available data regarding the neuroprotective effects of antiepileptic drugs (AEDs) at different phases of the epileptic process. Analysis of published data suggests that initial-insult modification and prevention of the progression of seizure-induced damage are candidate indications for treatment with AEDs. An understanding of the molecular mechanisms underlying the progression of epileptic process will eventually show what role AEDs have in the neuroprotective and antiepileptogenic treatment regimen.

Neuroprotective effects of lithium in cultured cells and animal models of diseases

Lithium, the major drug used to treat manic depressive illness, robustly protects cultured rat brain neurons from glutamate excitotoxicity mediated by N-methyl-D-aspartate (NMDA) receptors. The lithium neuroprotection against glutamate excitotoxiciy is long-lasting, requires long-term pretreatment and occurs at therapeutic concentrations of this drug. The neuroprotective mcchanisms involve inactivation of NMDA receptors, decreased expression of pro-apoptotic proteins, p53 and Bax, enhanced expression of the cytoprotective protein, Bcl-2, and activation of the cell survival kinase, Akt. In addition, lithium pretreatment suppresses glutamate-induced loss of the activities of Akt, cyclic AMP-response element binding protein (CREB), c-Jun - N-terminal kinase (JNK) and p38 kinase. Lithium also reduces brain damage in animal models of neurodegenerative diseases in which excitotoxicity has been implicated. In the rat model of stroke using middle cerebral artery occlusion, lithium markedly reduces neurologic deficits and decreases brain infarct volume even when administered after the onset of ischemia. In a rat Huntington's disease model, lithium significantly reduces brain lesions resulting from intrastriatal infusion of quinolinic acid, an excitotoxin. Our results suggest that lithium might have utility in the treatment of neurodegenerative disorders in addition to its common use for the treatment of bipolar depressive patients.

Regulation of ER stress proteins by valproate: therapeutic implications

OBJECTIVES

This paper reviews results of our studies examining the regulation of endoplasmic reticulum (ER) stress proteins by valproate (VPA). and discusses the possible implications in bipolar disorder.

METHODS

Our previous studies in the field are reviewed along with relevant literature.

RESULTS

Using differential display PCR, we identified GRP78 as a VPA-regulated gene in rat cerebral cortex. We also showed that other members of the ER stress proteins family, GRP94 and calreticulin, are also upregulated by VPA. Immunohistochemistry identified that ER stress proteins are increased in frontal and parietal cortex, as well as regions of the hippocampus in rat brain following chronic treatment with VPA.

CONCLUSIONS

Regulation of ER stress proteins by VPA may prove to be important to the mechanism of action of the drug. The neuroprotective role of these proteins may also prove to be involved in the pathophysiology of bipolar disorder.

Cell pathology in bipolar disorder

OBJECTIVES

The objective of this paper is to review findings of morphometric postmortem studies conducted on tissues from subjects with bipolar disorder (BPD) to demonstrate that impairments of cell morphology and resilience may underlie the neurobiology of BPD.

METHODS

Reports of alterations in number, density and size of neurons and glial cells in BPD are reviewed. Owing to the low number of postmortem studies on cellular pathology in BPD, abstracts of recent symposia are also discussed.

RESULTS AND CONCLUSIONS

In BPD. significant reductions in the volume of several brain regions, as well as region- and layer-specific reductions in the number, density and/or size of neurons and glial cells have been demonstrated. Moreover, the results of recent clinical and preclinical studies investigating the molecular and cellular targets of mood stabilizing and antidepressant medications provide intriguing possibilities that impairments in neuroplasticity and cellular resilience may underlie the neurobiology of BPD. Future studies will likely examine the role of both genetic and environmental factors in the pathogenesis and cellular changes in BPD.

Anatomical MRI findings in mood and anxiety disorders

OBJECTIVE

In vivo structural magnetic resonance imaging (MRI) studies have evaluated the brain anatomy of various psychiatric disorders, allowing the investigation of putative abnormal brain circuits possibly involved in the patophysiology of psychiatric disorders. Here we reviewed the structural MRI literature in mood and anxiety disorders.

METHODS

All anatomical MRI studies evaluating mood and anxiety disorder patients were identified through a comprehensive Medline search conducted for the period from 1966 to January 2002, and a manual search of bibliographic cross-referencing complemented the Medline search.

RESULTS

Differential patterns of anatomical brain abnormalities appear to be involved in subtypes of mood disorders, with hippocampus and basal ganglia being abnormal in unipolar disorder, and amygdala and cerebellum in bipolar disorders, suggesting that these two mood disorders are biologically distinct. As for anxiety disorders, orbital frontal regions and basal ganglia have been reported to be anatomically abnormal in obsessive-compulsive disorder, temporal lobe was found to be abnormally reduced in panic disorder, and abnormal hippocampus shrinkage was shown in posttraumatic stress disorder.

CONCLUSIONS

The structural MRI findings reviewed here suggest abnormalities in specific brain regions participating in proposed neuroanatomic models possibly involved in the pathophysiology of mood disorders and anxiety disorders. Nonetheless, available MRI studies have suffered from limitations related to relatively small patient samples and involvement of medicated patients, and were largely cross-sectional investigations. Therefore, longitudinal MRI studies involving more sizeable samples of drug-free patients, patients at first episode of illness or at high risk for mood or anxiety disorders, associated to genetic studies, are likely to be extremely valuable to separate state from trait brain abnormalities and to characterize further the pathophysiology of these disorders.

The neurobiology of bipolar disorder: focus on signal transduction pathways and the regulation of gene expression

OBJECTIVE

This article presents an overview of signal transduction pathways and reviews the research undertaken to study these systems in clinically relevant samples from patients with bipolar disorder (BD).

METHOD

We reviewed the published findings from studies of postmortem brain tissue and blood samples from patients with BD.

RESULTS

Although the exact biochemical abnormalities have yet to be identified, the presented findings strongly suggest that BD may be due, at least in part, to abnormalities in signal transduction mechanisms. In particular, altered levels or function, or both, of G-protein alpha subunits and effector molecules such as protein kinase A (PKA) and protein kinase C (PKC) have consistently been associated with BD both in peripheral cells and in postmortem brain tissue, while more recent studies implicate disruption in novel second-messenger cascades, such as the ERK/MAPK pathway.

CONCLUSIONS

Despite the difficulties inherent in biochemical studies of clinically relevant tissue samples, numerous investigations have illuminated the signal transduction mechanisms in patients with BD. These studies also suggest that BD may be due to the interaction of many abnormalities. In this context, novel techniques enabling the study of gene expression promise to assist in untangling these complex interactions, through visualizing the end result of these changes at the level of gene transcription.

Lithium suppresses excitotoxicity-induced striatal lesions in a rat model of Huntington's disease

Huntington's disease is a progressive, inherited neurodegenerative disorder characterized by the loss of subsets of neurons primarily in the striatum. In this study, we assessed the neuroprotective effect of lithium against striatal lesion formation in a rat model of Huntington's disease in which quinolinic acid was unilaterally infused into the striatum. For this purpose, we used a dopamine receptor autoradiography and glutamic acid decarboxylase mRNA in situ hybridization analysis, methods previously shown to be adequate for quantitative analysis of the excitotoxin-induced striatal lesion size. Here we demonstrated that subcutaneous injections of LiCl for 16 days prior to quinolinic acid infusion considerably reduced the size of quinolinic acid-induced striatal lesion. Furthermore, these lithium pre-treatments also decreased the number of striatal neurons labeled with the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay. Immunohistochemistry and western blotting demonstrated that lithium-elicited neuroprotection was associated with an increase in Bcl-2 protein levels. Our results raise the possibility that lithium may be considered as a neuroprotective agent in treatment of neurodegenerative diseases such as Huntington's disease.

The role of CREB and other transcription factors in the pharmacotherapy and etiology of depression

Psychiatric diseases are genetically complex and consequently, altered programs of gene expression have been hypothesized as the molecular basis of psychopathology. Since transcription factors represent the final communicative link between receptor activation and the orchestration of programs of gene expression, they are prime targets for studies on both the pharmacotherapy and the etiology of depression. The cyclic AMP response element binding protein (CREB) and the glucocorticoid receptor (GR) are altered by chronic treatment with antidepressants. Since it is phosphorylated CREB (pCREB) that determines its transcriptional activity, it is pertinent that some antidepressants have been shown to reduce pCREB in brain in vivo and in tissue culture in vitro. Moreover, pCREB is down-regulated in human fibroblasts from patients with major depression and in postmortem brain of suicide victims with a history of depression. With regard to GR, its mRNA, immunoreactivity, density and cytoplasmic-nuclear translocation are increased by antidepressants. While transcription factor mediated programs of gene expression relevant to either the pharmacotherapy or the etiology of depression are still largely elusive, studies utilizing modern technologies such as differential display and cDNA microarrays promise to lead eventually to the identification of structure and function of psychopathologically relevant target genes.

Gene expression differences in bipolar disorder revealed by cDNA array analysis of post-mortem frontal cortex

Previous studies have implicated a number of biochemical pathways in the etiology of bipolar disorder (BD). However, the precise abnormalities underlying this disorder remain to be established. To investigate novel factors that may be important in the pathophysiology of BD, we utilized cDNA expression arrays to examine differences in expression of up to 1200 genes known to be involved in potentially relevant biochemical processes. This investigation was undertaken in post-mortem samples of frontal cortex tissue from patients with BD and matched controls, obtained (n = 10/group) from the Stanley Foundation Neuropathology Consortium. Results include significant (greater than 35% change in signal intensity) differences between BD and controls in a number of genes (n = 24). Selected targets were analyzed by RT-PCR, which confirmed a decrease in transforming growth factor-beta1 (TGF-beta 1), and an increase in both caspase-8 precursor (casp-8) and transducer of erbB2 (Tob) expression in BD. We further observed a significant decrease of TGF-beta 1 mRNA levels in BD by RT-PCR in individual post-mortem samples. Given the neuroprotective role attributed to this inhibitory cytokine, our results suggest that the down-regulation of TGF-beta 1 may lead to various neurotoxic insults potentially involved in the etiology of certain mood disorders.

The multifaceted roles of glycogen synthase kinase 3beta in cellular signaling

Glycogen synthase kinase-3beta (GSK3beta) is a fascinating enzyme with an astoundingly diverse number of actions in intracellular signaling systems. GSK3beta activity is regulated by serine (inhibitory) and tyrosine (stimulatory) phosphorylation, by protein complex formation, and by its intracellular localization. GSK3beta phosphorylates and thereby regulates the functions of many metabolic, signaling, and structural proteins. Notable among the signaling proteins regulated by GSK3beta are the many transcription factors, including activator protein-1, cyclic AMP response element binding protein, heat shock factor-1, nuclear factor of activated T cells, Myc, beta-catenin, CCAAT/enhancer binding protein, and NFkappaB. Lithium, the primary therapeutic agent for bipolar mood disorder, is a selective inhibitor of GSK3beta. This raises the possibility that dysregulation of GSK3beta and its inhibition by lithium may contribute to the disorder and its treatment, respectively. GSK3beta has been linked to all of the primary abnormalities associated with Alzheimer's disease. These include interactions between GSK3beta and components of the plaque-producing amyloid system, the participation of GSK3beta in phosphorylating the microtubule-binding protein tau that may contribute to the formation of neurofibrillary tangles, and interactions of GSK3beta with presenilin and other Alzheimer's disease-associated proteins. GSK3beta also regulates cell survival, as it facilitates a variety of apoptotic mechanisms, and lithium provides protection from many insults. Thus, GSK3beta has a central role regulating neuronal plasticity, gene expression, and cell survival, and may be a key component of certain psychiatric and neurodegenerative diseases.

Emerging therapeutic targets in bipolar mood disorder

Bipolar mood disorder is a chronic, severe and life-threatening psychiatric illness, whose underlying pathophysiology is still obscure. Lithium is the mainstay of treatment for this illness, with robust acute antimanic and long-term prophylactic effects. Over the past decade, valproate has been another medication shown to have possibly similar mood-stabilising properties to lithium, in double-blind controlled trials. Nonetheless, among patients suffering from bipolar disorder, a substantial percentage appears to respond poorly to currently available pharmacological therapies, including lithium, valproate, carbamazepine and other newer compounds, clearly demonstrating that there is a substantial need for improved therapeutic agents. Very significant effort has been made in the past several years to elucidate the cellular mechanisms by which lithium and valproate produce their therapeutic effects. The available evidence points to a modulatory action of these compounds over multiple neural biochemical pathways and most investigations have found relevant actions of mood stabilisers on intracellular signal transduction mechanisms. Moreover, it has been shown in recent years that lithium and valproate lead to long-term changes in neural plasticity, with eventual neurotrophic and neuroprotective effects. Although these actions are not fully understood, stimulation of transcription factors and effects on gene expression are potentially involved. The search for the mechanisms of action of well-established mood-stabilisers has helped to reveal promising molecular targets to test novel therapeutic approaches. This review will examine the current investigations on the diverse biochemical and molecular pathways regulated by either lithium or valproate and highlight the potential cellular targets for the development of novel mood stabilisers.

The mood stabilizer valproic acid activates mitogen-activated protein kinases and promotes neurite growth

The mood-stabilizing agents lithium and valproic acid (VPA) increase DNA binding activity and transactivation activity of AP-1 transcription factors, as well as the expression of genes regulated by AP-1, in cultured cells and brain regions involved in mood regulation. In the present study, we found that VPA activated extracellular signal-regulated kinase (ERK), a kinase known to regulate AP-1 function and utilized by neurotrophins to mediate their diverse effects, including neuronal differentiation, neuronal survival, long term neuroplasticity, and potentially learning and memory. VPA-induced activation of ERK was blocked by the mitogen-activated protein kinase/ERK kinase inhibitor PD098059 and dominant-negative Ras and Raf mutants but not by dominant-negative stress-activated protein kinase/ERK kinase and mitogen-activated protein kinase kinase 6 mutants. VPA also increased the expression of genes regulated by the ERK pathway, including growth cone-associated protein 43 and Bcl-2, promoted neurite growth and cell survival, and enhanced norepinephrine uptake and release. These data demonstrate that VPA is an ERK pathway activator and produces neurotrophic effects.

Effect of lithium on phosphoinositide metabolism in human brain: a proton decoupled (31)P magnetic resonance spectroscopy study

BACKGROUND

The objective of our study was to evaluate whether lithium increases brain phosphomonoester (PME) levels in human subjects.

METHODS

Proton decoupled (31)P magnetic resonance spectra were obtained from eight healthy volunteers before and after the administration of lithium carbonate, 450 mg b.i.d., for 7 and 14 days.

RESULTS

Pairwise comparisons of the mole percent PME revealed a significant increase from baseline at day 7 and day 14 of lithium administration.

CONCLUSIONS

An increase in PME concentration with 7 and 14 days of lithium administration in the human brain in vivo was observed. Because the inositol-1-monophosphate contributes to the PME peak, this result suggests that some of the initial actions of lithium may occur through a reduction of myo-inositol, which in turn may initiate a cascade of secondary changes at different levels of signal transduction process and gene expression in brain, effects that are ultimately responsible for the therapeutic benefits of lithium.

Cloning and expression pattern of a novel PEBP2 beta-binding protein (charged amino acid rich leucine zipper-1[Crl-1]) in the mouse

PEBP2 beta/Cbf beta is the beta subunit of PEBP2/Cbf, which has been demonstrated to have important biological activities in hematopoiesis and osteogenesis. However, PEBP2 beta is ubiquitously expressed, suggesting that PEBP2 has other additionally important physiological activities. In an effort to elucidate other possible functions for PEBP2, we have isolated a novel gene that encodes a PEBP2 beta-interacting protein from a mouse cDNA library. We have called this gene Crl-1 for charged amino acid rich leucine zipper-1 (Crl-1) because it is rich in charged amino acids and contains a putative leucine zipper region. Expression studies in a 17.5 days post-coitum mouse embryo demonstrated Crl-1 expression mainly in the olfactory bulb and cerebral cortex. Post-natally, Crl-1 expression was additionally observed in the cerebellar cortex with strong expression in the hippocampus. These findings show that this novel PEBP2 beta-interacting protein is expressed mainly in subsets of neuronal cells, suggesting that Crl-1 plays some role in the developing mouse brain.

Reductions in neuronal and glial density characterize the dorsolateral prefrontal cortex in bipolar disorder

BACKGROUND

Bipolar disorder (BPD) is a mental illness in which depression and mania typically alternate, and both phases can present with psychotic features. The symptomatology of BPD, therefore, resembles major depressive disorder (MDD) and schizophrenia (SCHZ), posing diagnostic dilemmas. Distinct alterations in cellular architecture of the dorsolateral prefrontal cortex distinguish SCHZ and MDD, whereas the cellular neuropathology of BPD has not been studied.

METHODS

Dorsolateral prefrontal area 9 was analyzed using a three-dimensional morphometric method in postmortem brains from 10 BPD patients and 11 matched nonpsychiatric control subjects.

RESULTS

Area 9 in BPD was characterized by reduced neuronal density in layer III (16%-22%) and reduced pyramidal cell density in layers III and V (17%-30%). A 19% reduction in glial density was found in sublayer IIIc coupled with enlargement and changes in shape of glial nuclei spanning multiple layers.

CONCLUSIONS

The morphologic signature of BPD, i.e., decreased neuronal and glial density in association with glial hypertrophy, is distinct from previously described elevations in neuronal density in SCHZ, instead resembling the reductions in cell density found in MDD. Thus, the neuropathologic distinctions between BPD and SCHZ are indicative of separate mental illnesses, each with a unique morphologic disturbance of specific neural circuits.

The cellular neurobiology of depression

Major depressive disorders, long considered to be of neurochemical origin, have recently been associated with impairments in signaling pathways that regulate neuroplasticity and cell survival. Agents designed to directly target molecules in these pathways may hold promise as new therapeutics for depression.

Lithium-related genetics of bipolar disorder

Lithium is a potent prophylactic medication and mood stabilizer in bipolar disorder. However, clinical outcome is variable, and its therapeutic effect manifests after a period of chronic treatment, implying a progressive and complex biological response process. Signal transduction systems known to be perturbed by lithium involve phosphoinositide (PI) turnover, activation of the Wnt pathway via inhibition of glycogen synthase kinase-3beta (GSK-3beta), and a growth factor-induced, Akt-mediated signalling that promotes cell survival. These pathways, acting in synergy, probably prompt the amplification of lithium signal causing such immense impact on the neuronal network. The sequencing of the human genome presents an unparallelled opportunity to uncover the full molecular repertoire involved in lithium action. Interrogation of high-resolution expression microarrays and protein profiles represents a strategy that should help accomplish this goal. A recent microarray analysis on lithium-treated versus untreated PC12 cells identified multiple differentially altered transcripts. Lithium-perturbed genes, particularly those that map to susceptibility regions, could be candidate risk-conferring factors for mood disorders. Transcript and protein profiling in patients could reveal a lithium fingerprint for responsiveness or nonresponsiveness, and a signature motif that may be diagnostic of a specific phenotype. Similarly, lithium-sensitive gene products could provide a new generation of pharmacological targets.

The mechanism of lithium action: state of the art, ten years later

Lithium is an effective drug for both treatment and prophylaxis of bipolar disorder. However, the mechanism of lithium action is still unknown. The inositol depletion hypothesis is supported by biochemical and behavioral data in rats, but primate inositol levels are higher than in rodents and may obviate the effects of depletion. Inhibition of 5HT autoreceptors by lithium is supported by biochemical and behavioral data in rats but would seem more related to lithium's antidepressant than to its antimanic or prophylactic effects. Lithium induces increases in levels of the anti-apoptotic factor Bcl-2. This effect could be most relevant for treatment of neurodegenerative disorders. Lithium inhibits glycogen synthase kinase-3, which is involved in a wide range of signal transduction pathways. However, this lithium effect occurs at high concentrations and may be more relevant for its toxic effect. Lithium in low concentrations induces accumulation of PAP, which affects several cellular processes including RNA processing. However, PAP phosphatase is present more in peripheral tissues than in brain. This lithium effect could explain some of its peripheral side effects. Chronic lithium administration upregulates glutamate reuptake and thus decreases glutamate availability in synapse. Glutamate is an excitatory neurotransmitter and its reduction could exert an antimanic effect. Biochemical and clinical experiments are necessary to determine the key mechanism of lithium efficacy in treatment and prophylaxis of affective disorders.

Inhibitory effects of omega-3 fatty acids on protein kinase C activity in vitro

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.

Overexpression of neuronal pentraxin 1 is involved in neuronal death evoked by low K(+) in cerebellar granule cells

Mature cerebellar granule cells in culture die by a process that requires new RNA and protein synthesis when deprived of depolarizing concentrations of potassium. We investigated gene expression during the early phase of the cell death program evoked by potassium deprivation. Using a differential gene display technique, we isolated a cDNA that was increased by potassium deprivation. This cDNA was homologous to the 3' mRNA end of neuronal pentraxin 1 (NP1), a gene encoding a secreted glycoprotein whose expression is restricted to the nervous system. Reverse-Northern and Northern blot analyses confirmed that treatment with low potassium induces overexpression of NP1 mRNA, with a subsequent increase in NP1 protein levels. Time-course studies indicated that overexpression of NP1 protein reaches a maximum after 4 h of exposure to potassium deprivation and 4 h before significant cell death. Incubation of cerebellar granule cells with an antisense oligodeoxyribonucleotide directed against NP1 mRNA reduced low potassium-evoked NP1 protein levels by 60% and attenuated neuronal death by 50%, whereas incubation with the corresponding sense oligodeoxyribonucleotide was ineffective. Furthermore, acute treatment with lithium significantly inhibited both overexpression of NP1 and cell death evoked by low potassium. These results indicate that NP1 is part of the gene expression program of apoptotic cell death activated by nondepolarizing culture conditions in cerebellar granule cells.