Abstract 108: Sex Differences in Stroke-induced Lymphocyte Responses in the Gut Epithelia

Abstract

Introduction: Stroke is a sexually dimorphic disease. Notably, emerging evidence suggests that stroke leads to gut dysbiosis and pathological shifts in the gut microbiota. However, little is known about how the gut epithelial surface maintains homeostasis after stroke. In this study, we isolated intraepithelial lymphocytes (IELs), which are mainly CD8 + T cells and do not need priming against antigens, as well as intestinal epithelial cells (IECs). We examined their responses to stroke-induced gut epithelial damage. Methods: C57BL/6 (2-3 months) mice of both sexes were subjected to either 60-minute middle cerebral artery occlusion or sham surgery. At day 7 after stroke, IECs and IELs, which are intercalated between IECs, were isolated from mouse colonic tissues using Percoll density gradients. RNA was isolated from the cells and amplified to quantitate expression levels of cell-specific genes for antibacterial proteins and chemotactic cytokines. Tissues were then used for histological analysis by hematoxylin and eosin staining and bacterial fluorescence in situ hybridization (FISH). Results: Stroke caused significant colonic damage in male mice, compared to female mice. Bacterial FISH demonstrated microbial encroachment into the host gut epithelium in males after stroke; whereas female mice maintained spatial segregation between the host gut and bacteria. Stroke increased expression levels of pro-inflammatory cytokine genes in male IELs including IL-1β (28.3 fold increase, P <0.05), KC or CXCL1 (5.8 fold increase, P <0.05) and MIP2α or CXCL2 (9.9 fold increase, P <0.05) after stroke compared with sham mice. Additionally, both IELs and IECs of male stroke mice exhibited an up-regulation of antimicrobial protein gene, regenerating islet-derived protein 3 (Reg3γ, P <0.05). This pattern of up-regulation, however, was not present in female mice. Conclusions: This is the first study that demonstrates robust sex differences in lymphocyte responses at the gut mucosal surface between males and females following stroke. The closer proximity of the gut microbiota with the host may direct gene expression related to microbial responses in the injured epithelium after brain injury. Our study provides novel insight into host-microbial homeostasis in stroke.