Genomics and epigenomics in novel schizophrenia drug discovery: translating animal models to clinical research and back

A Review of Switching Strategies for Patients with Schizophrenia Comorbid with Metabolic Syndrome or Metabolic Abnormalities

Metabolic syndrome (MetS) in patients with schizophrenia occurs 2-3 times more frequently than in the general population. Antipsychotic medication is a primary risk factor for patients with MetS. In particular, the widely used second-generation antipsychotics can affect glucose and lipid metabolism and can induce insulin resistance and other metabolic abnormalities through various receptors. Notably, the metabolic risks of various antipsychotics may differ because of their different pharmacological affinity to MetS-related receptors. Several previous studies have shown that switching from high to low metabolic risk antipsychotics may improve patients' metabolic parameters. The current review aims to discuss the strategies for switching antipsychotic medications and the impact on metabolic abnormalities in patients with schizophrenia.

Clozapine-induced transcriptional changes in the zebrafish brain

Clozapine is an atypical antipsychotic medication that is used to treat schizophrenia patients who are resistant to other antipsychotic drugs. The molecular mechanisms mediating the effects of clozapine are not well understood and its use is often associated with severe side-effects. In this study, we exposed groups of wild-type zebrafish to two doses of clozapine (‘low’ (20 µg/L) and ‘high’ (70 µg/L)) over a 72-h period, observing dose-dependent effects on behaviour. Using RNA sequencing (RNA-seq) we identified multiple genes differentially expressed in the zebrafish brain following exposure to clozapine. Network analysis identified co-expression modules characterised by striking changes in module connectivity in response to clozapine, and these were enriched for regulatory pathways relevant to the etiology of schizophrenia. Our study highlights the utility of zebrafish as a model for assessing the molecular consequences of antipsychotic medications and identifies genomic networks potentially involved in schizophrenia.

Schizophrenia, cannabis use and Catechol-O-Methyltransferase (COMT): Modeling the interplay on cognition

Cognitive impairments are considered core features of schizophrenia and are recognized as the most important predictors of functional outcome and quality of life. A better study of the mechanisms underlying the cognition is of extreme relevance. Literature has shown that several genetic and environmental factors affect cognitive performance. In particular, the interaction between Catechol-O-Methyltransferase (COMT) gene and cannabis use has gained increasing attention in the past years. Based on these premises, the present study, aimed to analyze the interplay between cannabis use and COMT polymorphism on cognitive performance in a sample of 135 patients with chronic schizophrenia. Patients were assessed for neurocognitive measures with a broad battery, genotyped for COMT Val158Met polymorphism from peripheral blood sample, and evaluated with a semi-structured interview in order to establish the history of cannabis abuse. Results showed a significant interaction effect between COMT polymorphism and cannabis use on verbal fluency and speed of processing. The analysis revealed significant differences between subjects COMT Val/Val homozygous and Met carriers with history of cannabis use, with a better performance on both tasks among the Met carriers group. These data are in line with literature on healthy subjects that suggests a more detrimental effect of cannabis among subjects with Val/Val genotype. In conclusions, results highlight the need to better disentangle the biological pathways in which cannabis use and COMT are converging, as possible treatment targets, as well as the importance to assess these factors in clinical to optimize individualized interventions.

[Epigenetic research of cognitive deficit in schizophrenia: some methodological considerations]

AIM

To highlights the problems of assessing cognitive deficits in schizophrenia, relevant to the epigenetic, as well as a wide range of other approaches to the search for biological bases of cognition.

MATERIAL AND METHODS

The literature on the weaknesses in the evaluation of cognitive functions in patients with schizophrenia are summarized and discussed. The analysis is illustrated by our experience in developing a cognitive battery and a sample to examine relationships between DNA methylation in blood cells and cognitive deficits in schizophrenia.

RESULTS AND CONCLUSION

It has been shown that to assess cognitive deficits in patients and to reduce the influence of confounders in epigenetic analysis it is necessary (1) to use a battery with the existing co-normative data in the target population, which allows to evaluate representativeness of control and patients included in the study sample, (2) to verify the theoretically driven battery structure using normative population and a cohort of patients, (3) to balance groups of cases and controls on the number, age and sex, for which an individual matching of cases and controls is best suited, (4) to conduct an additional statistical analysis controlling for education and smoking.

Sexual dimorphism of the planum temporale in schizophrenia: A MRI study

OBJECTIVE

Anatomical alterations in the superior temporal gyrus have been consistently reported in patients with schizophrenia, and they have mostly been linked to positive symptoms, including hallucinations and thought disorders. The superior temporal gyrus is considered one of the most asymmetric and lateralized structure of the human brain, and the process of lateralization seems to vary according to gender in the normal population. However, although it has been consistently suggested that patients with schizophrenia did not show normal brain lateralization in several regions, only few studies investigated it in the superior temporal gyrus and its sub-regions considering the effects of gender. In this context, the aim of this study was to evaluate sexual dimorphism in superior temporal gyrus volumes in a sample of patients with schizophrenia compared to age- and gender-matched healthy controls.

METHODS

A total of 72 right/left-handed males (40 schizophrenia patients and 32 healthy controls) and 45 right/left-handed females (18 schizophrenia patients and 27 healthy controls) underwent clinical evaluation and a 1.5T magnetic resonance imaging scan. Gray and white matter volumes of regions of interest within the superior temporal gyrus were manually detected, including the Heschl's gyrus and the planum temporale.

RESULTS

Female patients with schizophrenia presented a reduction in left planum temporale gray matter volumes ( F = 4.58, p = 0.03) and a lack of the normal planum temporale asymmetry index ( t = 0.27; p = 0.79) compared to female controls ( t = 5.47; p = 0.001). No differences were found between males for any volumes or laterality indices. Finally, in female patients with schizophrenia, Heschl's gyrus gray and white matter volumes negatively correlated with positive symptoms ( r = -0.56, p = 0.01).

CONCLUSION

Our results showed that sexual dimorphism plays a key role on planum temporale in schizophrenia, underlining the importance of gender as a modulator of brain morphology and lateralization of schizophrenia.

The loss-of-function of DNA methyltransferase 1 by siRNA impairs the growth of non-small cell lung cancer with alleviated side effects via reactivation of RASSF1A and APC in vitro and vivo

Hypermethylation of tumor suppressor genes (TSGs) promoters by DNA methyltransferase (DNMT) can be observed in almost all cancers which represent a hallmark of carcinogenesis, including lung cancer. DNMT inhibitors (e.g.5-Aza-CR/CdR) reactivate TSGs to exert anti-cancer activity and have been applied into the clinical. However, it is cytotoxic even at low concentrations, which might be not directly related to DNA methylation. We here investigated an alternative strategy in the lung cancer therapy and aimed to estimate and compare its efficiency and side effects of knockdown of DNMT1 in vitro and in vivo. Lung cancer tissues (n=20) showed enhanced expression of DNMT1 than corresponding non-neoplastic tissues. Similar results were found in lung cancer cell lines A549 and H538. The treatment of 5-Aza-CR or knockdown of DNMT1 in vitro could inhibit the expressions of DNMT1 but restore the TSGs expressions including the Ras association domain family 1A (RASSF1A) and the adenomatous polyposis coli (APC) via the demethylation of its promoter region, which results in the decreased proliferation, increased apoptosis and impaired ability of migration. Importantly, knockdown of DNMT1 by siRNA in vivo also effectively demethylated the RASSF1A and APC promoter, elevated their expressions and limited tumor growth, which functioned like 5-Aza-CR but with alleviated side effects, suggesting that knockdown of DNMT1 might be potential strategy for the treatment of lung cancer with better tolerability.

Microbiota and Neurological Disorders: A Gut Feeling

In the past century, noncommunicable diseases have surpassed infectious diseases as the principal cause of sickness and death, worldwide. Trillions of commensal microbes live in and on our body, and constitute the human microbiome. The vast majority of these microorganisms are maternally derived and live in the gut, where they perform functions essential to our health and survival, including: digesting food, activating certain drugs, producing short-chain fatty acids (which help to modulate gene expression by inhibiting the deacetylation of histone proteins), generating anti-inflammatory substances, and playing a fundamental role in the induction, training, and function of our immune system. Among the many roles the microbiome ultimately plays, it mitigates against untoward effects from our exposure to the environment by forming a biotic shield between us and the outside world. The importance of physical activity coupled with a balanced and healthy diet in the maintenance of our well-being has been recognized since antiquity. However, it is only recently that characterization of the host-microbiome intermetabolic and crosstalk pathways has come to the forefront in studying therapeutic design. As reviewed in this report, synthetic biology shows potential in developing microorganisms for correcting pathogenic dysbiosis (gut microbiota-host maladaptation), although this has yet to be proven. However, the development and use of small molecule drugs have a long and successful history in the clinic, with small molecule histone deacetylase inhibitors representing one relevant example already approved to treat cancer and other disorders. Moreover, preclinical research suggests that epigenetic treatment of neurological conditions holds significant promise. With the mouth being an extension of the digestive tract, it presents a readily accessible diagnostic site for the early detection of potential unhealthy pathogens resident in the gut. Taken together, the data outlined herein provide an encouraging roadmap toward important new medicines and companion diagnostic platforms in a wide range of therapeutic indications.

The effect of add-on memantine on global function and quality of life in schizophrenia: A randomized, double-blind, controlled, clinical trial

Background:

Schizophrenia severely influences function and quality of life. The benefit of newer antipsychotics in improving the quality of life in schizophrenia still remains controversial. The aim of the present study is to evaluate the effect of memantine on global function and quality of life in patients with schizophrenia.

Materials and Methods:

This was a randomized controlled trial on inpatient cases of schizophrenia in Noor University Hospital, Isfahan, Iran. A number of 64 patients were selected through sequential sampling; patients were randomly allocated in intervention and placebo groups. The intervention group was treated with memantine plus previously administered, stabled-dose, atypical antipsychotic, while the control group received placebo plus previously administered, stabled-dose, atypical antipsychotic. Memantine administration was initiated at 5 mg daily; the dosage was increased at weekly intervals by 5 mg and finally up-titrated to 20 mg daily within 4 weeks. All patients were assessed by means of Global Assessment of Functioning (GAF) and quality of life scale (QLS) initially and every four weeks to the end of the 12^th week.

Results:

Analysis of baseline GAF and QLS scores showed no significant differences between the two groups (P = 0.081 and P = 0.225, respectively). GAF and QLS scores increased in both groups; but it was higher in the intervention group. The difference between the two groups was statistically significant. (P < 0.001 and P < 0.001, respectively) memantine was well tolerated, with no significant side effects.

Conclusion:

Add-on memantine was significantly effective in improving the global function of patients as well as their quality of life.

Insights into the origin of DNA methylation differences between monozygotic twins discordant for schizophrenia

Background

DNA methylation differences between monozygotic twins discordant for schizophrenia have been previously reported. However, the origin of methylation differences between monozygotic twins discordant for schizophrenia is not clear. The findings here argue that all DNA methylation differences may not necessarily represent the cause of the disease; rather some may result from the effect of antipsychotics.

Methods

Methylation differences in rat brain regions and also in two pairs of unrelated monozygotic twins discordant for schizophrenia have been studied using genome-wide DNA methylation arrays at Arraystar Inc. (Rockville, Maryland, USA). The identified gene promoters showing significant alterations to DNA methylation were then further characterized using ingenuity pathway analysis (Ingenuity System Inc, CA, USA).

Results

Pathway analysis of the most significant gene promoter hyper/hypomethylation revealed a significant enrichment of DNA methylation changes in biological networks and pathways directly relevant to neural development and psychiatric disorders. These included HIPPO signaling (p = 3.93E-03) and MAPK signaling (p = 4.27E-03) pathways involving hypermethylated genes in schizophrenia-affected patients as compared to their unaffected co-twins. Also, a number of significant pathways and networks involving genes with hypomethylated gene promoters have been identified. These included CREB signaling in neurons (p = 1.53E-02), Dopamine-DARPP32 feedback in cAMP signaling (p = 7.43E-03) and Ephrin receptors (p = 1.13E-02). Further, there was significant enrichment for pathways involved in nervous system development and function (p = 1.71E-03-4.28E-02).

Conclusion

The findings highlight the significance of antipsychotic drugs on DNA methylation in schizophrenia patients. The unique pathways affected by DNA methylation in the two pairs of monozygotic twins suggest that patient-specific pathways are responsible for the disease; suggesting that patient-specific treatment strategies may be necessary in treating the disorder. The study reflects the need for developing personalized medicine approaches that take into consideration epigenetic variations between patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s40303-015-0013-5) contains supplementary material, which is available to authorized users.