L-Theanine delays D-galactose-induced senescence by regulating the cell cycle and inhibiting apoptosis in rat intestinal cells

Background Intestinal senescence is associated with several aging-related diseases. l -Theanine (LTA) has demonstrated great potential as an antioxidant and anti-senescence agent. In this study, we investigated the regulatory effect of LTA on cellular senescence using an in vitro model of d -galactose ( d -Gal)-induced senescence in the rat epithelial cell line IEC-6. Results We confirmed that treatment of IEC-6 cells with 40 mg/mL d -Gal for 48 h resulted in the successful development of the senescent cell model. Compared with d -Gal alone, both LTA preventive and delayed intervention increased cell viability and the ratio of JC-1 monomers to aggregates, increased the antioxidant capacity, and decreased advanced glycation end product (AGE) levels and the overall number of senescent cells. Preventive and delayed intervention with 1000 μM LTA alleviated the d -Gal-induced cell cycle arrest by regulating p38, p53, CDK4, and CDK6 expression at the mRNA and protein levels and further induced CycD1 protein. Moreover, LTA preventive intervention reduced apoptosis to a greater degree than delayed intervention by upregulating the expression of the receptors of AGEs, Bax, Bcl-2, and NF-κB at the mRNA and protein levels. Conclusion Therefore, our findings indicate that LTA intervention could attenuate senescence in IEC-6 cells by regulating the cell cycle and inhibiting apoptosis. This article is protected by copyright. All rights reserved.