l-Theanine alleviates heat stress-induced impairment of immune function by regulating the p38 MAPK signalling pathway in mice

Abstract

L-Theanine can regulate the immune system's function and inflammatory responses under heat stress via activation of the p38 MAPK signalling pathway.

Abstract

With the current trend of global warming, heat stress-induced impairment could seriously endanger human health. l-Theanine is a non-protein amino acid in tea with various biological activities, including immunoregulatory, anti-anxiety, and anti-oxidation. However, its effect on immune function under heat stress and the underlying mechanism are currently unclear. In this study, male BALB/c mice were used as experimental objects to explore the effect of l-theanine on heat stress-induced changes in immune function and its mechanism. Three doses of l-theanine were used: low (100 mg kg ⁻¹ d ⁻¹), medium (200 mg kg ⁻¹ d ⁻¹), and high (400 mg kg ⁻¹ d ⁻¹). Treatment with l-theanine could attenuate the heat stress-induced reductions in body weight and feed intake in mice, alleviate damage in the liver and jejunum, and inhibit the inflammatory factors IL-6, IL-1β, and TNF-α. Aspartate aminotransferase and alanine transaminase activity levels and the malondialdehyde content decreased, while the IgA, IgM, and IgG contents increased in response to l-theanine. It is possible that l-theanine affects the P38 signalling pathway and inhibits the increase in p-P65/P65 caused by the overexpression of HSP27 and regulation of PPAR-γ and Foxp3 proteins, thereby alleviating immune dysfunction caused by heat stress.