Catherine Toben

Schizophrenia is a neurodevelopmental psychiatric disorder characterized by symptoms of psychosis, thought disorder, and flattened affect. Immune mechanisms are associated with schizophrenia, though the precise nature of this relationship (causal, correlated, consequential) and the mechanisms involved are not fully understood. To elucidate these mechanisms, we conducted a transcriptome‐wide Mendelian randomization study using gene expression exposures from 29 human cis‐eQTL data sets encompassing 11 unique immune cell types, available from the eQTL catalog. These analyses highlighted 196 genes, including 67 located within the human leukocyte antigen (HLA) region. Enrichment analyses indicated an overrepresentation of immune genes, which was driven by the HLA genes. Stringent validation and replication steps retained 61 candidate genes, 27 of which were the sole causal signals at their respective loci, thereby representing strong candidate effector genes at known risk loci. We highlighted L3HYPDH as a potential novel schizophrenia risk gene and DPYD and MAPK3 as candidate drug repurposing targets. Furthermore, we performed follow‐up analyses focused on one of the candidate effectors, interferon regulatory transcription factor 3 (IRF3), which coordinates interferon responses to viral infections. We found evidence of shared genetic etiology between schizophrenia and autoimmune diseases at the IRF3 locus, and a significant enrichment of IRF3 chromatin binding at known schizophrenia risk loci. Our findings highlight a novel schizophrenia risk gene, potential drug repurposing opportunities, and provide support for IRF3 as a schizophrenia hub gene, which may play critical roles in mediating schizophrenia‐autoimmune comorbidities and the impact of infections on schizophrenia risk.

Background: Schizophrenia is a neurodevelopmental psychiatric disorder characterised by symptoms of psychosis, thought disorder, and flattened affect. Immune mechanisms are associated with schizophrenia, though the precise nature of this relationship (i.e., causal, correlated, consequential) and the mechanisms involved are not fully understood. Methods: To elucidate these mechanisms, we conducted a transcriptome-wide Mendelian randomization study using gene expression exposures from 29 human cis -eQTL datasets encompassing 11 unique immune cell types, all publicly available from the eQTL catalogue. Results: These analyses highlighted 196 genes, including 67 located within the human leukocyte antigen (HLA) region. Enrichment analyses indicated an over-representation of immune genes, which was driven by the HLA genes. Stringent validation and replication steps retained 61 candidate genes, 27 of which were the sole causal signals at their respective loci, thereby representing strong candidate effector genes at known risk loci. We highlighted L3HYPDH as a potential novel schizophrenia risk gene and DPYD and MAPK3 as candidate drug repurposing targets. Futhermore, we performed follow-up analyses focused on one of the candidate effectors, interferon regulatory transcription factor 3 ( IRF3 ), which coordinates interferon responses to viral infections. We found evidence of shared genetic aetiology between schizophrenia and autoimmune diseases at the IRF3 locus, and a significant enrichment of IRF3 chromatin binding at known schizophrenia risk loci. Conclusions: Our findings highlight a novel schizophrenia risk gene, potential drug repurposing opportunities, and provide support for IRF3 as a schizophrenia hub gene, which may play critical roles in mediating schizophrenia-autoimmune comorbidities and the impact of viral infections on schizophrenia risk.

Interleukin 6 (IL-6) is a multifunctional cytokine with both pro- and anti-inflammatory properties with a heritability estimate of up to 61%. The circulating levels of IL-6 in blood have been associated with an increased risk of complex disease pathogenesis. We conducted a two-staged, discovery and replication meta genome-wide association study (GWAS) of circulating serum IL-6 levels comprising up to 67 428 (n_discovery = 52 654 and n_replication = 14 774) individuals of European ancestry. The inverse variance fixed effects based discovery meta-analysis, followed by replication led to the identification of two independent loci, IL1F10/IL1RN rs6734238 on chromosome (Chr) 2q14, (P_combined = 1.8 × 10⁻¹¹), HLA-DRB1/DRB5 rs660895 on Chr6p21 (P_combined = 1.5 × 10⁻¹⁰) in the combined meta-analyses of all samples. We also replicated the IL6R rs4537545 locus on Chr1q21 (P_combined = 1.2 × 10⁻¹²²). Our study identifies novel loci for circulating IL-6 levels uncovering new immunological and inflammatory pathways that may influence IL-6 pathobiology.

Physical exercise (PE) and environmental enrichment (EE) can modulate immunity. However, the differential effects of short-term PE, EE, and PE + EE on neuroimmune mechanisms during normal aging has not been elucidated. Hence, a cohort of 3-, 8-, and 13-month-old immunologically unchallenged C57BL/6 wild-type mice were randomly assigned to either Control, PE, EE, or PE + EE groups and provided with either no treatment, a running wheel, a variety of plastic and wooden objects alone or in combination with a running wheel for seven weeks, respectively. Immunohistochemistry and 8-color flow cytometry were used to determine the numbers of dentate gyrus glial cells, and the proportions of CD4⁺and CD8⁺T cell numbers and their subsets from cervical lymph nodes, respectively. An increase in the number of IBA1⁺microglia in the dentate gyrus at 5 and 10 months was observed after EE, while PE and PE + EE increased it only at 10 months. No change in astroglia number in comparison to controls were observed in any of the treatment groups. Also, all treatments induced significant differences in the proportion of specific T cell subsets, i.e., CD4⁺and CD8⁺T naïve (T_N), central memory (T_CM), and effector memory (T_EM) cells. Our results suggest that in the short-term, EE is a stronger modulator of microglial and peripheral T cell subset numbers than PE and PE + EE, and the combination of short-term PE and EE has no additive effects.

The purpose of this randomized controlled trial was to determine the effects of resistance training (RT) on markers of inflammation and immune function in breast cancer survivors. Thirty-nine breast cancer survivors were randomly assigned to a RT (n = 20) or control (n = 19) group. RT performed supervized exercise three times per week. Natural killer cell (NK) and natural killer T-cell (NKT) function, and markers of inflammation (serum TNF-α, IL-6, IL-10, and CRP) were measured before and after training. Changes in NK and NKT cell function were analyzed using ANCOVA, with the change score the dependent variable, and the baseline value of the same variable the covariate. Effect sizes (ES) were calculated via partial eta-squared. We found a significant reduction, and large associated ESs, in the RT group compared to the control group for change in NK cell expression of TNF-α (p = 0.005, ES = 0.21) and NKT cell expression of TNF-α (p = 0.04, ES = 0.12). No differences were observed in any serum marker. Significant improvements in all measurements of strength were found in RT compared to control (p < 0.001; large ESs ranging from 0.32 to 0.51). These data demonstrate that RT has a beneficial effect on the NK and NKT cell expression of TNF-α indicating that RT may be beneficial in improving the inflammatory profile in breast cancer survivors.