Mechanism Of Relieve Effect Of Arginine On The Inflammatory Responses Induced By Lipopolysaccharide In Lactating Cows

The lipopolysaccharide (LPS) associated with grain-induced subacute rumen acidosis (SARA) would translocate into the peripheral blood circulation and excited the systemic inflammatory responses, which will adversely affect the cow’s health and milk quality. In this study, SARA-induced inflammatory state was imitated thought LPS stimulates the lactating cows, then following trail in vivo and in vitro were conducted to investigate the alleviation and its possible mechanism that arginine regulates the inflammation. This study included two experiments.Trial 1, the aim of this experimnet was to research the effect of arginine on lactating cow’s inflammation induced by jugular vein LPS infusion. Eight Mid and Late lactation Holstein cows were used in a replicated 4×4 Latin square design balanced for residual effects with 15-d periods. The treatments were randomly distributed as jugular vein infusion of(1) physiological saline (Con), (2) physiological saline including18 g/d/L Arg (Arg), (3) physiological saline including 0.2μg/kg/d LPS (LPS), (4) physiological saline including 18 g/d/L Arg and 0.2 μg/kg/d LPS (LPS+Arg). The results shows as follows:1) arginine reduced the LPS-induced increase of IL-1β, IL-6, TNF-a, LBP, WBC, AST and iNOS.2) MDA content was decreased, GSH-PX activity and total antioxidant ability were increased after arginine infusion in the dairy cows stimulated by LPS.3) Arginine infusion increased the plasma content of Gly, Leu, Ile, Phe, Arg, Ala, Val, Lys, Met and total free amino acids in LPS-stimulated cow’s jugular vein, and the difference of Gly, Leu, Ile, Phe was extremely significant.4) Arginine infusion increased DMI, milk yield, and protein yield, fat yield, fat percentage and αS1-CN, aS2-CN, β-CN, total casein yield, decreased the milk somatic cell count (SCC) and whey protein content in LPS-stimulated cow’ milk. The results indicated that arginine has the capacity to alleviate the inflammation in lactating cow induced by LPS.Trial 2, the purpose of this experimnet was to investigate the possible mechanism that arginine regulates the inflammation. The cells were divided into four groups, stimulated with or without LPS (10 μg/mL) and treated with or without arginine (100 μg/mL) for 12 h. The concentration of proinflammatory cytokines, inducible nitric oxidesynthase (iNOS), mammalian target of rapamycin (mTOR), and Toll-like receptor 4 (TLR4) signaling pathways as well as the casein was determined. The results showed that arginine reduced the LPS-induced production like IL-1β, IL-6, TNF-a, and iNOS. Though the expression of NF-κB was attenuated and the mTOR signaling pathway was upregulated, arginine had no effect on TLR4 expression. In addition, the results show that the content of β-casein and the total casein were enhanced after arginine was supplemented in LPS-induced BMECs. The results indicated that arginine relieves the inflammatory reaction induced by LPS and enhance the concentration of β-casein and the total casein via inhibiting the NF-κB signaling pathway, Arg/NO signaling pathway, moreover, it is able to regulate the inflammation thought the PI3K/AKT/mTOR signaling pathway.