Corl Benjamin A, Odle Jack, Niu Xiaomei, Moeser Adam J, Gatlin Lori A, Phillips Oulayvanh T, Blikslager Anthony T, Rhoads J Marc
Department of Animal Sciences, North Carolina State University, Raleigh, NC 27695, USA.
J Nutr. 2008 Jan;138(1):24-9. doi: 10.1093/jn/138.1.24.
We previously showed that phosphorylation of p70 S6 kinase (p70(S6k)) in the intestine is increased during viral enteritis. In this study, we hypothesized that during rotavirus infection, oral Arg, which stimulates p70(S6k) activation, will further stimulate intestinal protein synthesis and mucosal recovery, whereas the p70(S6k) inhibitor rapamycin (Rapa) will inhibit mucosal recovery. Newborn piglets were fed a standard milk replacer diet supplemented with Arg (0.4 g x kg(-1) x d(-1), twice daily by gavage), Rapa (2 mg x m(-2) x d(-1)), Arg + Rapa, or saline (controls). They were infected on d 6 of life with porcine rotavirus. Three days postinoculation, we measured the piglets' body weight, fecal rotavirus excretion, villus-crypt morphology, epithelial electrical resistance in Ussing chambers, and p70(S6k) activation by Western blotting and immunohistochemistry. We previously showed a 2-fold increase in jejunal protein synthesis during rotavirus diarrhea. In this experiment, Arg stimulated jejunal protein synthesis 1.3-fold above standard medium, and the Arg stimulation was partially inhibited by Rapa. Small bowel stimulation of p70(S6k) phosphorylation and p70(S6k) levels were inhibited >80% by Rapa. Immunohistochemistry revealed a major increase of p70(S6k) and ribosomal protein S6 phosphorylation in the crypt and lower villus of the infected piglets. However, in Arg-treated piglets, p70(S6k) activation occurred over the entire villus. Jejunal villi of the Rapa-treated group showed inactivation of p70(S6k) and a decrease in mucosal resistance (reflecting increased permeability), the latter of which was reversed by Arg. We conclude that, early in rotavirus enteritis, Arg has no impact on diarrhea but augments intestinal protein synthesis in part by p70(S6k) stimulation, while improving intestinal permeability via a mammalian target of rapamycin/p70(S6k)-independent mechanism.
我们之前发现，病毒性肠炎期间肠道中p70 S6激酶（p70(S6k)）的磷酸化水平会升高。在本研究中，我们假设在轮状病毒感染期间，口服精氨酸（Arg）可刺激p70(S6k)活化，进而进一步刺激肠道蛋白质合成和黏膜恢复，而p70(S6k)抑制剂雷帕霉素（Rapa）则会抑制黏膜恢复。新生仔猪喂食添加了Arg（0.4 g·kg⁻¹·d⁻¹，每天两次经口灌胃）、Rapa（2 mg·m⁻²·d⁻¹）、Arg + Rapa或生理盐水（对照组）的标准代乳粉日粮。在出生后第6天用猪轮状病毒感染它们。接种后3天，我们测量了仔猪的体重、粪便轮状病毒排泄量、绒毛-隐窝形态、尤斯灌流小室中的上皮电阻，以及通过蛋白质免疫印迹法和免疫组织化学检测的p70(S6k)活化情况。我们之前发现轮状病毒腹泻期间空肠蛋白质合成增加了2倍。在本实验中，Arg刺激空肠蛋白质合成比标准培养基高出1.3倍，且Arg的刺激作用被Rapa部分抑制。Rapa使小肠中p70(S6k)磷酸化和p70(S6k)水平的刺激作用抑制了80%以上。免疫组织化学显示，感染仔猪的隐窝和绒毛下部p70(S6k)和核糖体蛋白S6磷酸化显著增加。然而，在经Arg处理的仔猪中，p70(S6k)活化发生在整个绒毛上。Rapa处理组的空肠绒毛显示p70(S6k)失活且黏膜抵抗力降低（反映通透性增加），而Arg可逆转后者。我们得出结论，在轮状病毒肠炎早期，Arg对腹泻无影响，但部分通过刺激p70(S6k)增加肠道蛋白质合成，同时通过一种不依赖雷帕霉素哺乳动物靶点/p70(S6k)的机制改善肠道通透性。
