l-Arginine Inhibits Apoptosis of Ovine Intestinal Epithelial Cells through the l-Arginine–Nitric Oxide Pathway

Abstract

ABSTRACT Background In nonruminants, many of the biological roles of l-arginine (Arg) at the intestinal level are mediated through the Arg–nitric oxide (Arg–NO) pathway. Whether the Arg–NO pathway is involved in controlling the immune response and viability in ovine intestinal epithelial cells (IOECs) is unclear. Objectives The current study aimed to examine the role of the Arg–NO pathway in apoptosis, antioxidant capacity, and mitochondrial function of IOECs. Methods The IOECs were incubated in Arg-free DMEM supplemented with 150 μM Arg (CON) or 300 μM Arg (ARG) alone or with 350 μM Nw-nitro-l-arginine methyl ester hydrochloride (l-NAME) (CON + NAME, ARG + NAME) for 24 h. The reactive oxygen species (ROS) concentration, antioxidant capacity, and cell apoptotic percentage were determined. Results Arg supplementation decreased (P < 0.05) the ROS concentration (38.9% and 22.7%) and apoptotic cell percentage (57.2% and 54.8%) relative to the CON and CON + NAME groups, respectively. Relative to the CON and ARG treatments, the l-NAME administration decreased (P < 0.05) the mRNA abundance of superoxide dismutase 2 (32% and 21.3%, respectively) and epithelial NO synthase (36% and 29.1%, respectively). Arg supplementation decreased (P < 0.05) the protein abundance of apoptosis antigen 1 (FAS) (52.0% and 43.9%) but increased (P < 0.05) those of nuclear respiratory factor 1 (31.3% and 22.9%) and inducible NO synthase (35.2% and 41.8%) relative to the CON and CON + NAME groups, respectively. Conclusions The inhibition of apoptosis in IOECs due to the increased supply of Arg is associated with the mitochondria- and FAS-dependent pathways through the activity of the Arg–NO pathway. The findings help elucidate the role of the Arg–NO pathway in IOEC growth and apoptosis.