Hydrogen sulfide protects cells against oxidative stress through modifying the redox status of thioredoxin

Hydrogen sulfide (H 2 S) is a gaseous mediator with multi-faced biological activities. It protects cells against oxidative stress, but the mechanisms involved are still poorly understood. Using an in vitro model of oxidative cell injury, we explored the potential mechanisms. (1) Exposure of glomerular podocytes to adriamycin, an anti-tumor drug, induced P38-mediated oxidative cell injury, as evidenced by the increased reactive oxygen species (ROS) generation, oxidative activation of ASK and P38, as well as the prevention of cell death by an antioxidant, NADPH oxidase inhibitor, and P38 inhibitor. (2) Supplement of podocytes with H 2 S donor NaHS blunted the activation of ASK/P38 signaling pathway and protected cells from adriamycin-induced oxidative cell injury. It also alleviated cell damage elicited by H 2 O 2 , superoxide, thioredoxin (Trx) inhibitor PX12, and Trx reductase inhibitor auranofin. (3) Given the importance of Trx in the regulation of ASK/P38 signaling pathway, we focused on Trx. H 2 S did not affect the protein level of Trx and TXNIP (a negative regulator of Trx), but it promoted the dissociation of TXNIP from Trx. Furthermore, it prevented the H 2 O 2 -induced formation of Trx dimers in a way similar to DTT. Moreover, it increased the conversion of Trx from the oxidized form to the reduced form. (4) In HepG2 cells, inhibition of the H 2 S-producing enzyme CSE increased Trx oxidation and exaggerated Trx reductase inhibitor-induced cell death. Consistently, the promotion of endogenous H 2 S production through the supplement of cells with L-cysteine exerted the opposite effects. Collectively, our study indicates that H 2 S inhibits oxidative activation of ASK/P38 signaling pathway and mitigates oxidative cell injury through a mechanism involving its regulation on Trx redox status. Our study thus provides novel mechanistic insight into the anti-oxidative actions of H 2 S and suggests that it could be used to prevent and treat oxidative cell injury.