MiR-146a protects small intestine against ischemia/reperfusion injury by down-regulating TLR4/TRAF6/NF-κB pathway

Previous studies reported that miR-146a was involved in small intestine ischemia-reperfusion (I/R) injury, but the mechanism is largely vague. Here, we aimed to identify the change of miR-146a in patients with mesenteric ischemia and explore the potential regulatory mechanism of miR-146a in intestine epithelial cells survival under ischemia and I/R injury. The plasma of 20 patients with mesenteric ischemia and 25 controls was collected to examine the miR-146a expression by qPCR. Rat intestinal epithelial cells (IEC-6) and 24 male Sprague-Dawley rats were included to build ischemia and I/R model in vitro and in vivo. The qPCR results showed that miR-146a decreased both in the plasma of patients with mesenteric ischemia and in IEC-6 cells and rat small intestine tissues in ischemia and I/R model compared to controls. Both the in vitro and in vivo results showed that I/R resulted in more severe apoptotic injury than ischemia. Cleaved-caspase 3, TLR4, TRAF6, and nuclear NF-kappa B p65 were up-regulated accompanying reduced XIAP and SOCS3 expression in intestinal ischemia and I/R injury. After up-regulation of miR-146a in IEC-6 cells, increased cell survival and decreased cell apoptosis were observed, concomitant with decreased cleaved-caspase 3 and down-regulated TLR4/TRAF6/NF-kappa B pathway. What is more, this protective effect was blocked by TRAF6 overexpression and increased nuclear NF-kappa B p65 nuclear. Taken together, this study revealed that miR-146a expression was decreased in small intestine ischemia and I/R injury. And miR-146a improves intestine epithelial cells survival under ischemia and I/R injury through inhibition TLR4, TRAF6, and p-I kappa B alpha, subsequently leading to decreased NF-kappa B p65 nuclear translocation.