Mitochondrial Complex II In Intestinal Epithelial Cells Regulates T-cell Mediated Immunopathology

Summary Intestinal epithelial cell (IEC) damage by T cells contributes to alloimmune, autoimmune and iatrogenic diseases such as graft-versus-host disease (GVHD), inflammatory bowel disease (IBD) and immune checkpoint blockade (ICB) mediated colitis, respectively. Despite significant advances in understanding the aberrant biology of T cells in these diseases, little is known about how the fundamental biological processes of the target IECs influence the disease severity. Here, through analyses of metabolic pathways of IECs, we identified disruption of oxidative phosphorylation without a concomitant change in glycolysis and an increase in succinate levels in several distinct in vivo models of T cell mediated gastrointestinal damage such as GVHD, IBD and ICB mediated colitis. Metabolic flux studies, complemented by imaging and protein analyses identified a critical role for IEC intrinsic succinate dehydrogenase A (SDHA), a component of mitochondrial complex II, in causing these metabolic alterations that contributed to the severity of intestinal damage. The critical mechanistic role of IEC intrinsic SDHA was confirmed by complementary chemical and genetic reduction of SDHA and with IEC specific deletion of SDHA. Further in vitro and in vivo mechanistic studies demonstrated that loss of SDHA in IECs was mediated by the perforin-granzyme from the T cells. The loss of SDHA was also validated in human clinical samples. These data identify a critical role for the alteration of the IEC specific mitochondrial complex II component SDHA in the regulation of the severity of T cell mediated intestinal diseases.