Arginine alleviates Clostridium perfringens α toxin-induced intestinal injury in vivo and in vitro via the SLC38A9/mTORC1 pathway

Introduction Clostridium perfringens α toxin is a main virulence factor responsible for gut damage in animals. Arginine is a functional amino acid exhibiting significant immunoregulatory activities. However, the effects and immunoregulatory mechanisms of arginine supplementation on α toxin-induced intestinal injury remain unclear. Methods In vivo , 256 male Arbor Acres chickens were randomly assigned to a 2×2 factorial arrangement, involving diet treatments (with or without 0.3% arginine supplementation) and immunological stress (with or without α toxin challenge). In vitro , IEC-6 cells were treated with or without arginine in the presence or absence of α toxin. Moreover, IEC-6 cells were transfected with siRNA targeting mTOR and SLC38A9 to explore the underlying mechanisms. Results and discussion The results showed that in vivo , arginine supplementation significantly alleviated the α toxin-induced growth performance impairment, decreases in serum immunoglobulin (Ig)A and IgG levels, and intestinal morphology damage. Arginine supplementation also significantly reduced the α toxin-induced increase in jejunal proinflammatory cytokines interleukin (IL)-1β , IL-6 and IL-17 mRNA expression. Clostridium perfringens α toxin significantly decreased jejunal mechanistic target of rapamycin (mTOR) and solute carrier family 38 member 9 ( SLC38A9) mRNA expression, while arginine supplementation significantly increased mTOR and SLC38A9 mRNA expression. In vitro , arginine pretreatment mitigated the α toxin-induced decrease in cell viability and the increase in cytotoxicity and apoptosis. Arginine pretreatment also alleviated the α toxin-induced upregulation of mRNA expression of inflammation-related cytokines IL-6 , C-X-C motif chemokine ligand ( CXCL ) 10 , CXCL11 and transforming growth factor-β ( TGF-β ), as well as apoptosis-related genes B-cell lymphoma-2 associated X protein ( Bax ), B-cell lymphoma-2 ( Bcl-2 ), B-cell lymphoma-extra large ( Bcl-XL ) and cysteinyl aspartate specific proteinase 3 ( Caspase-3 ) and the ratio of Bax to Bcl-2 . Arginine pretreatment significantly increased the α toxin-induced decrease in mTOR , SLC38A9 , eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 ( 4EBP1 ) and ribosomal protein S6 kinase ( S6K ) mRNA expression. Knockdown SLC38A9 and mTOR largely abrogated the positive effects of arginine pretreatment on α toxin-induced intracellular changes. Furthermore, SLC38A9 silencing abolished the increased mTOR mRNA expression caused by arginine pretreatment. In conclusion, arginine administration attenuated α toxin-induced intestinal injury in vivo and in vitro , which could be associated with the downregulation of inflammation via regulating SLC38A9/mTORC1 pathway.