Lymphotoxin receptor beta expression by neutrophils prevents metabolic activation and colitis pathogenesis

Abstract

Abstract Inflammatory bowel disease, while multifactorial, is largely characterized by an exacerbated intestinal immune activation. However, the critical mechanisms regulating immune activation remain to be fully defined. We have previously reported that a member of the TNF superfamily, TNFSF14 (LIGHT), and its interaction with the lymphotoxin beta receptor (LTβR), is required for preventing severe disease in a mouse model of dextran sulfate sodium (DSS) induced colitis. Thus, we aimed to determine the cell type and mechanism critical to LTβR mediated protection from DSS-induced colitis. Employing the use of LTβRfl/fl mice and tissue-specific Cre-mediated deletion, we found that neutrophils were a critical LTβR expressing cell type. Mrp8-Cre driven deletion of neutrophil LTβR expression resulted in exacerbated DSS-induced colitis and drastically increased colonic neutrophil accumulation. Mechanistically, RNASeq analysis of neutrophils revealed transcriptional alterations in genes associated with cellular metabolism, and mitochondrial function in particular. Ex vivo studies of bone marrow neutrophils from LTβRfl/fl x Mrp8-Cre mice, compared to Cre-controls, revealed increased mitochondrial mass and number, as well as elevated mitochondrial ROS production. Subsequent metabolic studies demonstrated that LTβR deficient neutrophils exhibited elevated mitochondrial respiration and glycolysis. Interestingly, these increased levels of mitochondrial mass, ROS production and glycolytic activity persist in LTβR deficient colonic neutrophils during DSS-induced colitis. In sum, our results demonstrate that neutrophil LTβR signaling plays a critical role in the immune activation associated with DSS-induced colitis.