Inflammatory cytokines in depression: Neurobiological mechanisms and therapeutic implications

Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) in the 9p21 gene desert associated with coronary artery disease (CAD) and type 2 diabetes. Despite evidence for a role of the associated interval in neighbouring gene regulation, the biological underpinnings of these genetic associations with CAD or type 2 diabetes have not yet been explained. Here we identify 33 enhancers in 9p21; the interval is the second densest gene desert for predicted enhancers and six times denser than the whole genome (P < 6.55 × 10(-33)). The CAD risk alleles of SNPs rs10811656 and rs10757278 are located in one of these enhancers and disrupt a binding site for STAT1. Lymphoblastoid cell lines homozygous for the CAD risk haplotype show no binding of STAT1, and in lymphoblastoid cell lines homozygous for the CAD non-risk haplotype, binding of STAT1 inhibits CDKN2BAS (also known as CDKN2B-AS1) expression, which is reversed by short interfering RNA knockdown of STAT1. Using a new, open-ended approach to detect long-distance interactions, we find that in human vascular endothelial cells the enhancer interval containing the CAD locus physically interacts with the CDKN2A/B locus, the MTAP gene and an interval downstream of IFNA21. In human vascular endothelial cells, interferon-γ activation strongly affects the structure of the chromatin and the transcriptional regulation in the 9p21 locus, including STAT1-binding, long-range enhancer interactions and altered expression of neighbouring genes. Our findings establish a link between CAD genetic susceptibility and the response to inflammatory signalling in a vascular cell type and thus demonstrate the utility of genome-wide association study findings in directing studies to novel genomic loci and biological processes important for disease aetiology.

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9p21 DNA variants associated with coronary artery disease impair interferon-γ signalling response

Mood disorders, such as major depressive disorder (MDD) and bipolar disorder (BPD), are the most prevalent psychiatric conditions, and are also among the most severe and debilitating. However, the precise neurobiology underlying these disorders is currently unknown. One way to combat these disorders is to discover novel biomarkers for them. The development of such biomarkers will aid both in the diagnosis of mood disorders and in the development of effective psychiatric medications to treat them. A number of preclinical studies have suggested that the brain-derived neurotrophic factor (BDNF) plays an important role in the pathophysiology of MDD. In 2003, we reported that serum levels of BDNF in antidepressant-naive patients with MDD were significantly lower than those of patients medicated with antidepressants and normal controls, and that serum BDNF levels were negatively correlated with the severity of depression. Additionally, we found that decreased serum levels of BDNF in antidepressant-naive patients recovered to normal levels associated with the recovery of depression after treatment with antidepressant medication. This review article will provide an historical overview of the role played by BDNF in the pathophysiology of mood disorders and in the mechanism of action of therapeutic agents. Particular focus will be given to the potential use of BDNF as a biomarker for mood disorders. BDNF is initially synthesized as a precursor protein proBDNF, and then proBDNF is proteolytically cleaved to the mature BDNF. Finally, future perspectives on the use of proBDNF as a novel biomarker for mood disorders will be discussed.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1440-1819.2010.02113.x

Brain-derived neurotrophic factor as a biomarker for mood disorders: an historical overview and future directions.

Context: Brain-derived neurotrophic factor (BDNF) plays a pivotal role in the pathophysiology of suicidal behavior andBDNF levels are decreased in the brain and plasma of suicide subjects. So far, the mechanisms leading to downregulation of BDNF expression are poorly understood. Objectives: To test the hypothesis that alterations of DNA methylation could be involved in the dysregulation of BDNF gene expression in the brain of suicide subjects. Design: Three independent quantitative methylation techniques were performed on postmortem samples of brain tissue. BDNF messenger RNA levels were determined by quantitative real-time polymerase chain reaction. Setting: Academic medical center. Patients or Other Participants: Forty-four suicide completers and 33 nonsuicide control subjects of white ethnicity.

https://jamanetwork.com/journals/jamapsychiatry/articlepdf/210623/yoa90071_258_267.pdf

Increased BDNF promoter methylation in the Wernicke area of suicide subjects.

Cytokine and cytokine receptor gene polymorphisms and their functionality

Introduction: Recent post-mortem studies of suicide victims have implicated brain-derived neurotrophic factor (BDNF) in suicide. Therefore, it was decided to examine the possible ro

Association of Polymorphism (Val66Met) of Brain-Derived Neurotrophic Factor with Suicide Attempts in Depressed Patients

Interleukin-1beta (IL-1beta) activates inflammatory mediator cascades and has been implicated in the pathogenesis of several diseases. Single nucleotide polymorphisms (SNPs) of the IL1B promoter have been associated with various inflammatory diseases. We recently reported that IL1B gene transcription was influenced by four promoter SNPs, and that individual SNP function in vitro was governed by haplotype context. In the present study we tested the in vivo relevance of this observation by comparing IL1B promoter haplotype-pairs with IL-1beta protein levels in 900 gingival tissue fluid samples. Three SNPs (-511, -1464, -3737) defined four IL1B promoter haplotypes that occurred in the study population and could be assigned unambiguously to each chromosome. The four haplotypes defined ten haplotype-pairs of which four pairs, representing 57% of the population, were associated with 28-52% higher IL-1beta protein levels in vivo. Two of these pairs, characterized by homozygosity for the common allele at -3737, were also associated with raised serum levels of C-reactive protein (p = 0.02). We validated these findings in stimulated peripheral blood mononuclear cells (PBMCs) from a separate population (N = 70). PBMCs with IL1B haplotype-pairs associated with higher in vivo levels of IL-1beta produced 86-287% more IL-1beta in vitro than the reference group. We believe that this is the first demonstration of a relationship between in vivo levels of an inflammatory mediator and gene promoter haplotypes on both chromosomes. These findings may apply to other inducible genes and could provide a logical framework for exploring disease risk related to genetic variability in pathogenic mediators.

IL1B gene promoter haplotype pairs predict clinical levels of interleukin-1beta and C-reactive protein.

The objective was to investigate whether genotypes, haplotypes and haplotype-pairs of interleukin (IL) gene cluster are associated with risk of Myocardial Infarction (MI) at young age and with the release of IL-1B and expression of tissue factor pro-coagulant activity (TFPCA), after stimulation in vitro with lipopolysaccharide (LPS) of human peripheral blood mononuclear cells (PBMCs). Patients with MI at young age, frequency-matched for age, sex and recruitment centre, with healthy population-based controls and PBMCs from healthy volunteers were studied. Five single nucleotide polymorphisms (SNPs), identifying two haplotype-blocks, in IL-1B gene and one SNP in IL-1A and IL-RA genes were genotyped. In multivariate analyses, haplotype A2 (122) and A4 (112) were associated with decreased risk of MI [OR = 0.62 (95% CI = 0.40–0.95), p = 0.01; OR = 0.69 (95% CI = 0.51–0.92), p = 0.03, respectively]. Haplotype-pair A2/A2 showed significant reduction in the risk of MI [OR = 0.38 (95% CI = 0.18–0.81); p = 0.01]. H...

Monica de Gaetano

Papers

Association of Polymorphism (Val66Met) of Brain-Derived Neurotrophic Factor with Suicide Attempts in Depressed Patients

IL1B gene promoter haplotype pairs predict clinical levels of interleukin-1beta and C-reactive protein.

Interleukin 1 gene cluster, myocardial infarction at young age and inflammatory response of human mononuclear cells.