Effects of Heat Stress on Duodenal Mucosal Structure,HIF-1 and Its Related Protein Expression in Congjiang Xiang Pigs
The aim of this study was to investigate the effects of heat stress(HS)on the duodenal mucosal barrier structure and the character of hypoxia inducible factor 1(HIF-1)expression and regulation in Congjiang Xiang pigs.Twenty-four fattening pigs were divided into 6 groups ran-domly,the control group(Con)kept under normal conditions,and the other 5 groups were trea-ted with heat stress for 6,12,24,48,72 h),respectively.Rectal temperature and respiratory rate were measured during treatment,and the duodenum of each group was collected at the end of the experiment.The change of duodenal tissue structure and goblet cell number in each group were observed with hematoxylin-eosin staining(HE)and alcian blue-periodate Schiff reaction(AB-PAS).The apoptosis cell of duodenal was detected by TUNEL staining.Real-time fluores-cence quantification(qRT-PCR),Western blot and immunohistochemistry were used to detect the expression changes of tight junction related proteins,HIF-1 and its upstream regulatory fac-tors respectively.The results showed that,compared with the control group,HS could induce rectal temperature and respiratory rate increase,and the villus height kept decreasing with exten-sion of HS time,while the crypt depth increased synchronously,the ratio of villus height/gland depth and the expression of Occludin and ZO-1 decreased significantly.On the contrary,the number of goblet cells kept increasing.TUNEL showed the apoptosis rate of group HS 72 h was significantly higher than that of control group(P＜0.001).The positive expression of HIF-1αwas mainly observed in small intestinal epithelial cells,and which expression enhanced at HS 72 h,the trend was as same as which HIF-1α mRNA and protein expression.The character of HSP90 expression were basically consistent with HIF-1α while the profile of PHD-2 was obvious-ly the opposite.These results indicated that HS could induce apoptosis of small intestinal epithe-lial cells and damage duodenal mucosal barrier.The increase of HIF-1 expression is closely relat-ed to the apoptosis of small intestine cells,and may be regulated by both HSP90 and PHD-2.
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