| Weaning is the physiological process that animals must undergo.The mature animal will survive during the weaning process.In order to increase the efficiency of sow production and utilization rate of tillers,and reduce the production costs of piglets,the “early weaning stress in pigs” was artificially induced in large-scale breeding,which will lead to the inadequacy of the intestinal development and injury of the intestinal barrier system of piglets,induce the intestinal inflammation,which in turn decreases the resistance of disease,finally leading to sluggish growth and the inducation of intestinal inflammation and even diarrhea,which seriously affects the economic efficiency of pigs.The intestinal epithelial of layer animal serves as the first line of defense for the intestinal lumen and is used to protect pigs from harmful microorganisms,toxins,or antigens in the small intestine lumen.When the intestinal barrier is destroyed in early weaning,intestinal permeability is increased,the toxins,bacteria or feed-related antigens will penetrate the epithelial layer and cause inflammation.The intestinal mucosal epithelial cells(IEC)have the most vigorous metabolism and have a developed endoplasmic reticulum structure,and IEC is sensitive for sustaing by endoplasmic reticulum stressors such as intestinal commensal flora and mucosal inflammatory mediators.At present,studies have been reported on the occurrence of endoplasmic reticulum stress in livers induced by early weaning in piglets,but whether intestinal endoplasmic reticulum stress can be induced in “early weaning stress in pigs” has not been reported.Previous studies in our laboratory showed that ?-carotene can promote the growth of weaned piglets at 28 days,enhance the immunity of piglets,and reduce the intestinal inflammation induced by weaning.Therefore,on the basis of previous studies,animal husbandry were used to regulate the physiological function of animals in this experiment,the effects of ?-carotene on the inflammation and endoplasmic reticulum stress of piglets' intestinal epithelial cells induced by early weaning stress were observed,the aim of this experiment were study the protective effects of ?-carotene on the growth and intestinal health of early weaned piglets and reveal the mechanism of its protective effect on piglet weaning stress.60 newborn piglets were randomly divided into four groups.The piglets were weighed at 0 d,14 d,22 d,and 28 d after birth,respectively.Three piglets were randomly selected to collect blood and intestinal samples from each group for detection of pro-inflammatory cytokines and growth factors in blood and,for detection of the related genes and protein expression of pro-inflammatory cytokines,endoplasmic reticulum stress in the intestine at 1 d,3 d,7 d after weaning,respectively.The results showed that the average daily weight gain of early weaning piglets was significantly reduced,and ?-carotene significantly increased the average daily weight gain,while ?-carotene significantly increased serum IGF-1 concentration.It significantly increased IGF-1 mRNA levels both in jejunum and ileum of piglets.In terms of inflammation,?-carotene reduced the levels of serum inflammatory cytokines IL-1?,IL-6,IL-10 and TNF-? in early-weaned piglets to a certain extent,and it decreased the mRNA levels of intestinal inflammatory factor TNF-? and NF-?B.?-carotene significantly reduced the level of NF-?B protein phosphorylation in duodenum,jejunum and ileum in weaned piglets.In terms of intestinal mucosal morphology,In terms of intestinal mucosal morphology,?-carotene increased villus height and decreased crypt depth in early-weaned piglets.?-carotene significantly reduced the expression of XBP1 and CHOP protein in the duodenum.?-carotene reduced the expression of GRP78,XBP1 and CHOP proteins in the jejunum and ileum.These results suggest that early weaning stress induces inflammation and endoplasmic reticulum stress in intestinal epithelial cells of piglets,and that ?-carotene can alleviate intestinal epithelial cell inflammation and endoplasmic reticulum stress in early weaning piglets.Forty Wistar rats of 21 days of age were selected as the object to establish a protective model of ?-carotene on LPS-induced rat inflammation.The protective effect of ?-carotene on LPS-induced inflammation in rats was examined by ELISA,fluorescence quantitative PCR and western blot.The results showed that ?-carotene significantly reduced LPS-induced serum inflammatory cytokines and intestinal inflammatory cytokines IL-1?,IL-6,TNF-? mRNA expression levels.It significantly decreased LPS-induced expression of p-NF-?B,XBP1 and caspase-12.These results further demonstrate that ?-carotene can alleviate intestinal inflammation,endoplasmic reticulum stress and apoptosis,consistent with the results of early weaned piglets.The mouse macrophages(RAW264.7)and neonatal pig jejunal epithelial cells(IPEC-J2)were selected as the research subjects.The protective models of ?-carotene on LPS-induced RAW264.7 inflammation and tunicamycin(TM)-induced IPEC-J2 endoplasmic reticulum stress were established to study the mechanism of ?-carotene.The results showed that ?-carotene significantly reduced the expression of TNF-?,IL-1? and IL-6 mRNA and the expression of p-NF-?B,p-IRE1 and XBP1 protein induced by LPS.?-carotene may partly regulate the inflammatory response through the p-IER1-XBP1 signaling pathway.?-carotene down-regulated TM induced the expression of GRP78 and p-PERK,but the down-regulation of NF-?B and CHOP was not significantly different from that of LPS group.The above results indicate that ?-carotene can relieve endoplasmic reticulum stress and may partially relieve apoptosis by down-regulating the expression of CHOP protein. |
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