The Role Of HIF1-? And MiR-21 In Ischemic Postconditioning Protects Against Intestinal Ischemia/reperfusion Injury

Background:Intestinal ischemia/reperfusion can lead to tissue damage associated with inflammation and mucosal apoptosis.Ischemic postconditioning,a series of repeated,brief,intermittent periods of ischemia and reperfusion,has beneficial effects against ischemia/reperfusion induced injury in the heart and intestine,although the underlying mechanisms remain unclear.Purpose:The purpose of this study is to evaluate the involvement of hypoxia inducible factor-1 alpha(HIF-la)and microRNA-21(miR-21)in the protective effects of ischemic postconditioning in rat's model of ischemia/reperfusion induced by superior mesenteric artery occlusion and reopening.Methods:Rats were randomly divided into the following groups:1)sham group,n = 6;2)I/R group,n = 12;3)ischemic postconditioning + I/R group,n = 18;4)anti-miR-21+ I/R group,n = 6;5)anti-miR-21 + ischemic postconditioning + I/R group,n = 6;6)2ME + ischemic postconditioning + I/R group,n = 6;7)2ME + anti-miR-21 +ischemic postconditioning + I/R group,n = 6.Sham-operation group,in which superior mesenteric artery was separated,but without occlusion;I/R group,for which superior mesenteric artery occlusion time was 60 minutes and reperfusion time was 2 hours;ischemic postconditioning,in which superior mesenteric artery was occluded by 3 cycles of 30 seconds reperfusion before another reperfusion as described previously.Intestinal epithelial cells(IEC-6)were obtained from American Type Culture Collection.Hypoxia was induced by culturing cells in a modular incubator equipped with an O2 sensor,which enabled the mixing of N2 and air to achieve hypoxic conditions(10%or 2%O2 and 5%CO2 balanced with N2).For reoxygenation,cells were transferred to normoxic conditions.Results:Ischemic postconditioning decreased ischemia/reperfusion injury and suppressed apoptosis in the intestinal tissues of model rats concomitant with the induction of HIF-1? and the upregulation of miR-21.In vitro experiments in the intestinal epithelial cell line IEC-6 showed that hypoxia induced miR-21 and this effect was abolished by silencing of HIF1-?,confirming the induction miR-21 by HIF1-?.Knockdown of miR-21 or inhibition of HIF1-? abolished the IPostC mediated attenuation of intestinal injury and apoptosis,and the downregulation of programmed cell death 4(PDCD4)and Fas-L.Conclusions:A potential mechanism underlying the protective effect of ischemic postconditioning involving the induction of miR-21 by HIF1-? and the attenuation of apoptosis via the downregulation of PDCD4 and Fas-L.