Project description:Schizophrenia is a chronic mental illness that is among the world’s top twenty causes of years lost to disability according to the global burden of disease 2019 (10.1016/S0140-6736(20)30925-9). Positive symptoms, including hallucinations and delusions in schizophrenia, often improved with conventional antipsychotic medication, which exerts its therapeutic effects mainly by antagonizing the dopamine D2 receptors. Haloperidol was one of the first antipsychotics to be approved by the FDA, and it is since then widely used for the treatment of psychotic disorders including schizophrenia. Despite its high affinity for dopamine D2 receptors, it has been shown that haloperidol interacts with other receptors, such as dopamine D3 and D4 receptors, α-adrenergic receptor 1 and to some extent 5HT2A. Dopaminergic dysfunction is known for decades to be involved in the pathophysiology of schizophrenia, but only recently has the striatum been implicated in such devasting disorder. The dorsal striatum is a brain region involved in motor, cognitive and motivational functions, highly impacted by antipsychotic drugs. Particularly, it is well-recognized that chronic haloperidol administration has a tremendous impact on striatal synaptic plasticity, by changing the volume of dorsal striatum, the number of striatal neurons and the synaptic morphology, both in humans and rodents. Despite the overwhelming evidence correlating chronic haloperidol administration with striatum alterations, so far, the exact striatal synaptic mechanism by which haloperidol exerts its beneficial effects remains unclear. Although dopamine D2 receptor blockade can be achieved within hours after haloperidol administration, the onset of action is delayed by weeks. Thus, it is crucial to better understand the neuronal mechanism behind the delayed clinical effects of haloperidol to improve the treatment outcome. Using proteomic analysis and whole-cell patch-clamp recordings (Figure 1), we demonstrate for the first time a possible mechanism by which haloperidol may be contributing to its beneficial long-term therapeutic effect. Specifically, we demonstrate that modulation of D2-MSNs by chronic haloperidol administration leads to a slow remodeling of D1-neurons that may be responsible for its positive therapeutic effects.

Project description:Antipsychotic drugs are commonly used to treat psychosis, mood disorders, and anxiety. While there is indirect evidence that some component of the antipsychotic effect of these drugs may involve modulation of dopamine transmission, their mechanism of action is poorly understood. We hypothesized that antipsychotic drugs mediate their effects via epigenetic modulation. Here we tested the effect of an antipsychotic, olanzapine, on the methylation status of genes following chronic treatment. These effects have been revealed through significantly increased (p<0.01) DNA methylation of genes involved in dopaminergic and non-dopaminergic pathways including the glutamatergic, GABAergic, cholinergic, neuregulin and ErbB signaling pathways. The affected genes included GLS in hippocampus, NR1 in cerebellum and GLUD1 and NR2B in liver. Further, from a set of genes in the 22q11.2 micro-deletions that has been previously implicated in psychosis, 22 genes showed increased methylation following olanzapine treatment. Ingenuity Pathway Analysis (IPA) revealed that chronic olanzapine treatment significantly affected several important pathways such as CREB and CDK5 signaling (p=1.4E-05). Also, DNA replication, recombination and repair, cellular movement and cell cycle have been identified as the top networks affected by olanzapine. The results suggest that these downstream effects, aside from D2 blockade, may play a critical role in the biological actions of antipsychotics. These include altered expressions of relevant genes involved in GABAergic, glutamatergic, cholinergic, neuregulin and ErbB signaling pathways. Epigenetic mechanisms involving changes in DNA methylation could, therefore, explain the delay and individualized non-specificity of biological effects of olanzapine. The results also suggest that DNA methylation may play a role in the process of therapeutic efficacy of olanzapine by altering the transcriptome via tissue-specific methylation of genes involved in schizophrenia signaling pathways. comparison of olanzapine treated rats vs. control rats for genome-wide DNA methylation changes

Project description:Antipsychotic drugs are commonly used to treat psychosis, mood disorders, and anxiety. While there is indirect evidence that some component of the antipsychotic effect of these drugs may involve modulation of dopamine transmission, their mechanism of action is poorly understood. We hypothesized that antipsychotic drugs mediate their effects via epigenetic modulation. Here we tested the effect of an antipsychotic, olanzapine, on the methylation status of genes following chronic treatment. These effects have been revealed through significantly increased (p<0.01) DNA methylation of genes involved in dopaminergic and non-dopaminergic pathways including the glutamatergic, GABAergic, cholinergic, neuregulin and ErbB signaling pathways. The affected genes included GLS in hippocampus, NR1 in cerebellum and GLUD1 and NR2B in liver. Further, from a set of genes in the 22q11.2 micro-deletions that has been previously implicated in psychosis, 22 genes showed increased methylation following olanzapine treatment. Ingenuity Pathway Analysis (IPA) revealed that chronic olanzapine treatment significantly affected several important pathways such as CREB and CDK5 signaling (p=1.4E-05). Also, DNA replication, recombination and repair, cellular movement and cell cycle have been identified as the top networks affected by olanzapine. The results suggest that these downstream effects, aside from D2 blockade, may play a critical role in the biological actions of antipsychotics. These include altered expressions of relevant genes involved in GABAergic, glutamatergic, cholinergic, neuregulin and ErbB signaling pathways. Epigenetic mechanisms involving changes in DNA methylation could, therefore, explain the delay and individualized non-specificity of biological effects of olanzapine. The results also suggest that DNA methylation may play a role in the process of therapeutic efficacy of olanzapine by altering the transcriptome via tissue-specific methylation of genes involved in schizophrenia signaling pathways.

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Gene expression changes following chronic antipsychotic exposure in single cells from mouse striatum

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