L-arginine stimulates cell proliferation and prevents LPS-induced death of intestinal cell

摘要

Abstract This study tested the hypothesis that L-arginine (Arg) stimulates cell proliferation and prevents LPS-induced damage of intestinal cell. Intestinal porcine epithelial cells (IPEC-1) were cultured for 4 days in Arg-free Dulbecco's modified Eagle's-F12 Ham medium (DMEM-F12) containing 10, 100 or 350 μM Arg and 0 or 20 ng/ml lipopolysaccharide (LPS). Cell numbers, protein concentrations, protein synthesis and degradation, mTOR signaling pathway and TLR4 signaling pathway were determined. Without LPS treating, IPEC-1 cells exhibited a growth of time-dependent and dose dependent manner. IPEC-1 Cells exposed to 20 ng/ml LPS exhibited lower survival rate and lower protein concentrations, compared with the corresponsive Arg dose treatments. But addition of 100 and 350 μM Arg to culture medium reduced LPS-induced cell death and increased protein concentrations of LPS treated IPEC-1 Cells, in comparison with 10 μM Arg treated cells. Furthermore, supplementation of 100 and 350 μM Arg improved the protein synthesis and reduced the protein degradation of IPEC-1 cells. LPS treating had negative effects on the protein synthesis and degradation, but supplementing 100 and 350 μM Arg attenuated these effects. Compared with 10 μM Arg treatment, addition of 100 or 350 μM Arg to culture medium increased relative protein levels for phosphorylated mTOR and phosphorylated S6K and reduced the relative TLR4 and phosphorylated NFκB levels in LPS treated IPEC-1 cells. These results demonstrate a protective effect of Arg against LPS-induced enterocyte damage involving the protein synthesis and degradation and the mTOR and TLR4 signaling pathway, which support the solutions to prevent intestinal endotoxin-induced injury and inflammatory disease in neonates.