Study On The Effect Of Salmonella Typhimurium Stimulation On Chicken Duodenal Epithelial Cell Proliferation And Apoptosis

Small intestine is not only a place for the digestion and absorption of nutrients, but also is a place for immunization. The balance between intestinal epithelial cell proliferation and apoptosis plays an important role in the homeostasis and maintenance of the integrity of the intestinal barrier. Infection-induced colitis, clinically results in disorder in apoptosis and proliferation and destroys the function of small intestine. Lipopolysacride(LPS) found in mammals, the main component of the outer cell wall of Salmonella, can activate TLR4 signaling pathway and acceleate apoptosis in intestinal epithelial cells, while inhibiting cell proliferation. However the studies regarding the impact of TLR4 on chicken intestinal epithelial cell proliferation and apoptosis induced by Salmonella infection has not been reported. Therefore, in the present study,one-day-old Kebao broilers were treated with Salmonella typhimurium or LPS to induce the imbalance between duodenal epithelial cell proliferation and apoptosis. The expression of TLR4 was studied also.IThe main contents and results are as follows: 1. Effect of LPS or Salmonella typhimurium stimulation on epithelial cell proliferation in chicken duodenumIn order to study the effect of Salmonella infection on epithelial cell proliferation in chicken duodenum, the chickens were infected with LPS or Salmonella typhimurium. Immunohistochemical staining techniques were used to study the changes of distribution and expression of PCNA in chicken duodenum. The results of control group showed that PCNA was mainly distributed in the duodenal mucosa, submucosa, muscularis and serosa and it was mainly present in the nucleus. Moreover, a large number of positive cells were located in mucosal epithelium, lamina propria and intestinal glands. After Salmonella or LPS stimulation, PCNA expression levels were decreased in chicken duodenum. Compared with the control group, after 12 h, 72 h, and 120 h of LPS stimulation, PCNA expression was significantly reduced(p <0.05); after 6h, 12 h, 24 h, 36 h, 72 h and 120 h of Salmonella infection, PCNA expression were significantly lower(p <0.05). The above results show that when Salmonella typhimurium invade the body, it inhibits the intestinal epithelial cells proliferation and damage the function of intestinal mucosal barrier. 2.Effect of LPS or Salmonella typhimurium stimulation on epithelial cell apoptosis in chicken duodenalIn order to study the effect of Salmonella infection on epithelial cell apoptosis in chicken duodenum, the chickens were infected with LPS or Salmonella typhimurium stimulation. Immunohistochemical staining techniques were used to study the changes of distribution and expression of anti-DNA was found in chicken duodenum. The results of control group showed that apoptotic cells were mainly distributed in the duodenal mucosa, submucosa, muscularis and serosa. Moreover, a large number of positive cells were located in mucosal epithelium, lamina propria and intestinal glands. After LPS or Salmonella stimulation, apoptotic cells expressions were increased in chicken duodenum. Compared with the control group, after 12 h and 24 h of LPS stimulation, anti-DNA expression was significantly increased(p <0.05); after 6h, 12 h, 24 h, 36 h, 72 h and 120 h of Salmonella infection, the apoptosis was significantly enhanced(p <0.05). The above results show that when Salmonella typhimurium invade the body, it promote intestinal epithelial cell apoptosis and causes the destruction of the intestinal barrier. 3. Effect of LPS or Salmonella typhimurium stimulation on the expression of TLR4 in chicken duodenumIn order to study the effect of Salmonella infection on chicken duodenal epithelial cells, the chickens were infected with LPS or Salmonella typhimurium stimulation. Immunohistochemical staining and Q-PCR techniques were used to study the changes of the distribution and expression of expression of TLR4 receptors was studied in chicken duodenum. The results of control group showed that TLR4 receptors were mainly distributed in the duodenal mucosa, while its expression was less in submucosa, muscularis and serosa. Moreover, a large number of positive cells were located in mucosal epithelium, lamina propria and intestinal glands. After LPS or Salmonella stimulation, TLR4 expression levels were increased. Compared with the control group, after 2h, 12 h, and 72 h of LPS stimulation, the expression of TLR4 was significantly increased(p <0.05); after 6h, 12 h, 24 h, 36 h and 72 h of Salmonella stimulation, the expression of TLR4 was significantly increased(p <0.05). This study suggests that, when Salmonella typhimurium invade the body, it destroys the balance of duodenal epithelial cell proliferation and apoptosis via activation of TLR4, and hence the function of intestinal barrier.