Potential Molecular and Cellular Mechanism of Psychotropic Drugs

Psychiatric disorders are among the most debilitating of all medical illnesses. Whilst there are drugs that can be used to treat these disorders, they give sub-optimal recovery in many people and a significant number of individuals do not respond to any treatments and remain treatment resistant. Surprisingly, the mechanism by which psychotropic drugs cause their therapeutic benefits remain unknown but likely involves the underlying molecular pathways affected by the drugs. Hence, in this review, we have focused on recent findings on the molecular mechanism affected by antipsychotic, mood stabilizing and antidepressant drugs at the levels of epigenetics, intracellular signalling cascades and microRNAs. We posit that understanding these important interactions will result in a better understanding of how these drugs act which in turn may aid in considering how to develop drugs with better efficacy or increased therapeutic reach.

Repeated electroconvulsive seizure induces c-Myc down-regulation and Bad inactivation in the rat frontal cortex

Repeated electroconvulsive seizure (ECS), a model for electroconvulsive therapy (ECT), exerts neuroprotective and proliferative effects in the brain. This trophic action of ECS requires inhibition of apoptotic activity, in addition to activation of survival signals. c-Myc plays an important role in apoptosis of neurons, in cooperation with the Bcl-2 family proteins, and its activity and stability are regulated by phosphorylation and ubiquitination. We examined c-Myc and related proteins responsible for apoptosis after repeated ECS. In the rat frontal cortex, repeated ECS for 10 days reduced the total amount of c-Myc, while increasing phosphorylation of c-Myc at Thr58, which reportedly induces degradation of c-Myc. As expected, ubiquitination of both phosphorylated and total c-Myc increased after 10 days ECS, suggesting that ECS may reduce c-Myc protein level via ubiquitination-proteasomal degradation. Bcl-2 family proteins, caspase, and poly(ADP-ribose) polymerase (PARP) were investigated to determine the consequence of down-regulating c-Myc. Protein levels of Bcl-2, Bcl-X(L), Bax, and Bad showed no change, and cleavage of caspase-3 and PARP were not induced. However, phosphorylation of Bad at Ser-155 and binding of Bad to 14-3-3 increased without binding to Bcl-X(L) after repeated ECS, implying that repeated ECS sequesters apoptotic Bad and frees pro-survival Bcl-X(L). Taken together, c-Myc down-regulation via ubiquitination-proteasomal degradation and Bad inactivation by binding to 14-3-3 may be anti-apoptotic mechanisms elicited by repeated ECS in the rat frontal cortex. This finding further supports the trophic effect of ECS blocking apoptosis as a possible therapeutic effect of ECT.

Haloperidol and clozapine differentially regulate signals pstream of glycogen synthase kinase 3 in the rat frontal cortex

Glycogen synthase kinase 3 (GSK3) was recently suggested to be a potential target of psychotropics used in psychiatric illnesses such as schizophrenia and bipolar disorder. Relevant studies have found that antipsychotic drugs regulate GSK3 activity via an increase in either inhibitory serine phosphorylation or amount of GSK3 after acute or subchronic treatment. Recent evidence shows that GSK3 is regulated by dopaminergic or serotonergic systems implicated in the pathophysiology and treatment mechanisms of schizophrenia and bipolar disorder. Therefore, antipsychotics may regulate GSK3 via antagonizing dopaminergic or serotonergic activity. However, the signaling pathway that is involved in GSK3 regulation by dopaminergic or serotonergic systems has not been well established. Haloperidol is a typical antipsychotic with potent dopamine D(2) receptor antagonism. Clozapine is an atypical antipsychotic with potent serotonin 5HT(2) receptor antagonism. We injected rats with haloperidol or clozapine and examined the phosphorylation and amount of GSK3alpha/beta and its well-known upstream regulators Akt and Dvl in the rat frontal cortex by Western blotting. Both haloperidol and clozapine induced Ser21/9 phosphorylation of GSK3GSK3alpha/beta. Haloperidol increased the Ser473 phosphorylation of Akt transiently, whereas clozapine maintained the increase for 1 h. Haloperidol did not affect the phosphorylation and amount of Dvl, whereas clozapine increased both phosphorylation and the amount of Dvl. Our results suggest that GSK3 activity may be regulated by both typical and atypical antipsychotics and that Akt or Dvl, depending on the D(2)- or 5HT(2)- receptor antagonism properties of typical and atypical antipsychotics, mediate the regulation differently.

Regulation of the Circadian Gene CLOCK Expression by KCl Depolarization in B35 Rat Neuroblastoma Cells / 신경정신의학

OBJECTIVES: To investigate the effects of KCl on regulation of circadian gene CLOCK expression, we observed whether induction of CLOCK is influenced by KCl depolarization in B35 rat neuroblastoma cells. METHODS: B35 rat neuroblastoma cells were grown in Dulbecco's modified Eagle's medium supplemented with 10% FBS and 1% penicillin-streptomycin in a 37 degrees C humidified incubator with 5% CO2. Inhibitors including cycloheximide and actinomycin D were pretreated 1 hour before treatment with 50mM KCl. Immunoblotting with anti-CLOCK antibody was done. RESULTS: CLCOK is induced by 50 mM KCl in B35 Rat Neuroblastoma cells, and a maximal induction in CLOCK level reached peak at 8 to 20 hours. The pretreatment of cycloheximide and actinomycin D prevented the induction of CLOCK by 50 mM KCl. CONCLUSION: We suggest that KCl depolarization may play critical roles in several aspects of the circadian gene CLOCK expression.

Search of Altered Gene Expression after Chronic Administration of Olanzapine in the Rat Frontal Cortex using cDNA Microarray / 대한정신약물학회지

OBJECTIVE: cDNA microarray is a convenient molecular technology that enables to search for gene expression in large scale. To explore the effect of antipsychotics on the gene expression in the brain, we applied cDNA microarray and searched for differentially expressed genes in the olanzapine-treated rat frontal cortex. METHODS: We administered olanzapine (4 mg/kg/day, IP) to S-D rats for 14days, and dissected the frontal cortex to examine. We analyzed altered gene expression from microarray, and screened up- or down-regulated genes. Their changes were confirmed by RT-PCR. RESULTS: Three down-regulated and one up-regulated genes were screened by triplicate cDNA microarray analysis. Among them, translocase of the inner mitochondrial membrane 23 (TIM23) was confirmed in RT-PCR. The expression of TIM23 mRNA was significantly increased in olanzapine-treated rat frontal cortex. CONCLUSION: This is the first report of up-regulated gene expression of TIM23 by antipsychotics in the rat brain. TIM23 is the essential component of mitochondrial biogenesis. From this result, we suggest that antipsychotic effect may be related to the improvement of mitochondrial dysfunction in the brain.