Rooibos tea (Aspalathus linearis) extract protects against air particulate matter induced hepatic oxidative stress in Nrf2-independent manner

Diesel exhaust particles (DEP) are a typical example of air particulate matter generated into the environment from industrial, residential and vehicular diesel engines. Studies have implicated the induction of oxidative stress in the adverse health effect of DEP. In this study, the effect of aqueous rooibos extract (RE) on DEP-induced hepatic oxidative stress was examined and the role of Nrf2-regulation in this effect was evaluated. Wistar rats were divided into 4 groups of 5 rats/group and were administered 0.7 mg/kg DEP subcutaneously and 50 mg/kg RE orally. Group one was given vehicle (saline and DMSO), group two was administered with RE for 4 weeks, group three was given RE for 2 weeks followed by concomitant administration of RE and DEP for further 2 weeks and group four was given DEP twice a week at the last 2 weeks of treatment. Malondialdehyde (MDA), Conjugated dienes (CDs) and GSH levels were determined in the liver homogenate. AST and ALT activities were assayed in the serum and RT-qPCR was used to quantify the gene expression of Nrf2 and HO-1 in the liver. Results showed that RE pre-treatment significantly (p