Translating advances in the molecular basis of schizophrenia into novel cognitive treatment strategies

The presence and severity of cognitive symptoms, including working memory, executive dysfunction and attentional impairment, contributes materially to functional impairment in schizophrenia. Cognitive symptoms have proven resistant to both first- and second-generation antipsychotic drugs. Efforts to develop a consensus set of cognitive domains that are both disrupted in schizophrenia and are amenable to cross-species validation (e.g. the NIMH CNTRICS and RDoC initiatives) are an important step towards standardisation of outcome measures that can used in preclinical testing of new drugs. While causative genetic mutations have not been identified, new technologies have identified novel genes as well as hitherto candidate genes previously implicated in the pathophysiology of schizophrenia and/or mechanisms of antipsychotic efficacy. This review comprises a selective summary of these developments, particularly phenotypic data arising from preclinical genetic models for cognitive dysfunction in schizophrenia, with the aim of indicating potential new directions for pro-cognitive therapeutics

Exploration of the NRG-ErbB genetic pathway for biomarkers of Clozapine mediated symptom remission and symptom severity in treatment-resistant schizophrenia

© 2017 Dr Md Shaki MostaidSchizophrenia is a disabling mental health disorder that is characterized by positive symptoms (delusions, hallucinations etc.), negative symptoms (apathy, social withdrawal, emotional blunting etc.) and cognitive deficits (impaired memory, lack of attention etc.). Current pharmacological treatment includes typical and atypical antipsychotics but 20-30% of patients do not adequately respond to these treatments and are thus defined as treatment-resistant. Clozapine is indicated for the treatment of treatment-resistant schizophrenia (TRS). However, biomarkers of clozapine mediated symptom remission and symptom severity in TRS have yet to be identified. One promising biomarker is neuregulin 1 (NRG1), a growth factors that activates ErbB receptor tyrosine kinases and initiates the NRG-ErbB signalling pathway, which plays a key role in neurodevelopment. Genomic, transcriptomic, and proteomic abnormalities in NRG-ErbB pathway have been linked to schizophrenia and clozapine has been shown to modulate NRG1 gene and protein expression. Thus, NRG-ErbB pathway gene and protein expression profiles, as well as genetic variation, may serve as biomarkers for clozapine mediated symptom remission and symptom severity.  In this thesis, we will present our investigation of the peripheral gene and protein expression levels of NRG-ErbB pathway genes in TRS patients and healthy controls and how they relate to clozapine mediated symptom remission as well as symptom severity. In addition, we will discuss the role genetic polymorphisms in NRG1 play in regulating its gene and protein expression. Finally, we will present results from healthy peripheral blood mononuclear cells exposed in vitro to clozapine for 24 hours and seven days and discuss the effects of clozapine on NRG-ErbB pathway gene and protein expression. Chapter 1 contains systematic review of scientific literatures and justifies the main 3 goals of the thesis. Chapter 2 of this thesis aimed at investigation of the candidate SNPs and microsatellites within the NRG1 gene among 16,720 patients, 20,449 controls, and 2,157 family trios via a meta-analytic procedure. We found significant association for three polymorphisms at the 5’ end (rs62510682, rs35753505, and 478B14-848) and two (rs2954041 and rs10503929) at the 3’ end of the NRG1 with schizophrenia. We could not find association for haplotypes. Chapter 3 aimed to assess the peripheral expression pattern of major NRG1 mRNA isoforms in whole blood and NRG1-β1 protein in serum in patients with TRS to find clinically useful biomarkers of clozapine mediated symptom severity and symptom remission. Using RT-qPCR we found upregulation of three NRG1 mRNA isoforms (NRG1 EGFα, NRG1 EGFβ, NRG1 typeI(Ig2)) in whole blood in TRS patients. However, protein assay via ELISA showed lower level of serum NRG1-β1 in TRS patients but it was confounded by smoking. Expression of NRG1 EGFα, NRG1 EGFβ was also negatively correlated with age of illness onset. In Chapter 4, we continued to examine the peripheral mRNA expression pattern of the major NRG-ErbB pathway downstream signaling genes in TRS patients and controls to see if increased expression in ligands leads to overexpression of receptors and subsequent upregulation of the full pathway in treatment-resistant schizophrenia. We found that five mRNA transcripts (ErbB3, PIK3CD, AKT1, P70S6K, eIF4EBP1) were upregulated in TRS patients, although only one (P70S6K) survived after correction for multiple comparisons. Moreover, investigation of the clinical factors revealed that expression of ErbB2, PIK3CD, PIK3R3, AKT1, mTOR, and P70S6K were negatively correlated with duration of illness. Chapter 5 summarises the main findings of the thesis, its relevance to previous literature, advancement of knowledge, implications and future steps in investigation of the NRG-ErbB genetic pathway for suitable biomarkers in schizophrenia, more specifically treatment-resistant schizophrenia

Meta-analysis supports GWAS-implicated link between GRM3 and schizophrenia risk

Genome-wide association study (GWAS) evidence has identified the metabotropic glutamate receptor 3 (GRM3) gene as a potential harbor for schizophrenia risk variants. However, previous meta-analyses have refuted the association between GRM3 single-nucleotide polymorphisms (SNPs) and schizophrenia risk. To reconcile these conflicting findings, we conducted the largest and most comprehensive meta-analysis of 14 SNPs in GRM3 from a total of 11 318 schizophrenia cases, 13 820 controls and 486 parent-proband trios. We found significant associations for three SNPs (rs2237562: odds ratio (OR)=1.06, 95% confidence interval (CI)=1.02-1.11, P=0.017; rs13242038: OR=0.90, 95% CI=0.85-0.96, P=0.016 and rs917071: OR=0.94, 95% CI=0.91-0.97, P=0.003). Two of these SNPs (rs2237562, rs917071) were in strong-to-moderate linkage disequilibrium with the top GRM3 GWAS significant SNP (rs12704290) reported by the Schizophrenia Working Group of the Psychiatric Genomics Consortium. We also found evidence for population stratification related to rs2237562 in that the 'risk' allele was dependent on the population under study. Our findings support the GWAS-implicated link between GRM3 genetic variation and schizophrenia risk as well as the notion that alleles conferring this risk may be population specific

An Interleukin-1 beta (IL1B) haplotype linked with psychosis transition is associated with IL1B gene expression and brain structure

We investigated IL1B genetic variation previously associated with risk for transition to psychosis for its association with gene expression in human post-mortem dorsolateral prefrontal cortex (DLPFC) from 74 (37 schizophrenia, 37 control) individuals and brain structure in 92 (44 schizophrenia, 48 control) living individuals. The IL1B A-G-T ‘risk for psychosis transition’ haplotype (rs16944|rs4848306|rs12621220) was associated with upregulation of IL1B mRNA expression in the DLPFC as well as reduced total grey matter and left middle frontal volumes and enlarged left lateral ventricular volume. Our results suggest IL1B genetic variation may confer psychosis risk via elevated mRNA expression and/or brain structure abnormalities

Meta-analysis reveals associations between genetic variation in the 5' and 3' regions of Neuregulin-1 and schizophrenia

Genetic, post-mortem and neuroimaging studies repeatedly implicate neuregulin-1 (NRG1) as a critical component in the pathophysiology of schizophrenia. Although a number of risk haplotypes along with several genetic polymorphisms in the 5' and 3' regions of NRG1 have been linked with schizophrenia, results have been mixed. To reconcile these conflicting findings, we conducted a meta-analysis examining 22 polymorphisms and two haplotypes in NRG1 among 16 720 cases, 20 449 controls and 2157 family trios. We found significant associations for three polymorphisms (rs62510682, rs35753505 and 478B14-848) at the 5'-end and two (rs2954041 and rs10503929) near the 3'-end of NRG1. Population stratification effects were found for the rs35753505 and 478B14-848(4) polymorphisms. There was evidence of heterogeneity for all significant markers and the findings were robust to publication bias. No significant haplotype associations were found. Our results suggest genetic variation at the 5' and 3' ends of NRG1 are associated with schizophrenia and provide renewed justification for further investigation of NRG1's role in the pathophysiology of schizophrenia

Peripheral transcription of NRG-ErbB pathway genes are upregulated in treatment-resistant schizophrenia

Investigation of peripheral gene expression patterns of transcripts within the NRG-ErbB signaling pathway, other than neuregulin-1 (NRG1), among patients with schizophrenia and more specifically treatment-resistant schizophrenia (TRS) is limited. The present study built on our previous work demonstrating elevated levels of NRG1 EGFα, EGFβ, and type I(Ig2) containing transcripts in TRS by investigating 11 NRG-ErbB signaling pathway mRNA transcripts (NRG2, ErbB1, ErbB2, ErbB3, ErbB4, PIK3CD, PIK3R3, AKT1, mTOR, P70S6K, eIF4EBP1) in whole blood of TRS patients (N = 71) and healthy controls (N = 57). We also examined the effect of clozapine exposure on transcript levels using cultured peripheral blood mononuclear cells (PBMCs) from 15 healthy individuals. Five transcripts (ErbB3, PIK3CD, AKT1, P70S6K, eIF4EBP1) were significantly elevated in TRS patients compared to healthy controls but only expression of P70S6K (Pcorrected = 0.018), a protein kinase linked to protein synthesis, cell growth, and cell proliferation, survived correction for multiple testing using the Benjamini-Hochberg method. Investigation of clinical factors revealed that ErbB2, PIK3CD, PIK3R3, AKT1, mTOR, and P70S6K expression were negatively correlated with duration of illness. However, no transcript was associated with chlorpromazine equivalent dose or clozapine plasma levels, the latter supported by our in vitro PBMC clozapine exposure experiment. Taken together with previously published NRG1 results, our findings suggest an overall upregulation of transcripts within the NRG-ErbB signaling pathway among individuals with schizophrenia some of which attenuate over duration of illness. Follow-up studies are needed to determine if the observed peripheral upregulation of transcripts within the NRG-ErbB signaling pathway are specific to TRS or are a general blood-based marker of schizophrenia

Pharmacokinetics and Bioavailability Study of a Prednisolone Tablet as a Single Oral Dose in Bangladeshi Healthy Volunteers

The aim of the study was to assess the pharmacokinetic and bioavailability of 2 formulations of 5-mg prednisolone tablets, reference product (Teva UK Limited) and Pred (Eskayef Bangladesh Ltd) as test product. The open-label, randomized, 2-way crossover studies were conducted on 14 healthy subjects. Participants were assigned to receive both products as a single dose (20 mg formulations, 4 × 5 mg tablets) followed by a 2 weeks’ washout period. Following oral administration, samples were obtained at various time intervals and analyzed for prednisolone concentrations using a validated high-performance liquid chromatography assay method with ultraviolet detection. The obtained values for test and reference products were 683.00 ± 94.54 ng/mL and 635.16 ± 125.57 ng/mL for C max ; 2716.54 ± 196.28 ng·h/mL and 2780.5 ± 119.73 ng·h/mL for AUC 0-12 ; 3284.36 ± 138.12 ng·h/mL and 3317.96 ± 133.95 ng·h/mL for AUC 0-∞ , respectively. From the paired Student t test, no significant differences between 2 formulations were observed ( P > .05). The 90% confidence intervals of C max , AUC 0-12 , and AUC 0-∞ were found to be 99.0% to 100.9%, 99.4% to 100.5%, and 99.9% to 101.3%, respectively. Finally, it can be concluded that Pred (Test) of Eskayef Bangladesh Ltd and prednisolone (Reference) of Teva UK Limited are bioequivalent and interchangeable