Hydrogen Sulfide Alleviates Lipid Peroxidation-Mediated Carbonyl Stress in Uranium-Intoxicated Kidney Cells via Nrf2/ARE Signaling

Objective: To explore the protective effects and underlying mechanisms of H 2 S against lipid peroxidation-mediated carbonyl stress in the uranium-treated NRK-52E cells. Methods: Cell viability was evaluated using CCK-8 assay. Apoptosis was measured using flow cytometry. Reagent kits were used to detect carbonyl stress markers malondialdehyde, 4-hydroxynonenal, thiobarbituric acid reactive substances, and protein carbonylation. Aldehyde-protein adduct formation and alcohol dehydrogenase, aldehyde dehydrogenase 2, aldo-keto reductase, nuclear factor E2-related factor 2 (Nrf2), and cystathionine β-synthase (CBS) expression were determined using western blotting or real-time PCR. Sulforaphane (SFP) was used to activate Nrf2. RNA interference was used to inhibit CBS expression. Results: GYY4137 (an H 2 S donor) pretreatment significantly reversed the uranium-induced increase in carbonyl stress markers and aldehyde-protein adducts. GYY4137 effectively restored the uranium-decreased Nrf2 expression, nuclear translocation, and ratio of nuclear to cytoplasmic Nrf2, accompanied by a reversal of the uranium-decreased expression of CBS and aldehyde-metabolizing enzymes. The application of CBS siRNA efficiently abrogated the SFP-enhanced effects on the expression of CBS, Nrf2 activation, nuclear translocation, and ratio of nuclear to cytoplasmic Nrf2 and concomitantly reversed the SFP-enhanced effects of the uranium-induced mRNA expression of aldehyde-metabolizing enzymes. Simultaneously, CBS siRNA reversed the SFP-mediated alleviation of the uranium-induced increase in reactive aldehyde levels, apoptosis rates, and uranium-induced cell viability. Conclusion: H 2 S induces Nrf2 activation and nuclear translocation, which modulates the expression of aldehyde-metabolizing enzymes and the CBS/H 2 S axis. Simultaneously, the Nrf2-controlled CBS/H 2 S axis may at least partially promote Nrf2 activation and nuclear translocation. These events form a cycle-regulating mode through which H 2 S attenuates the carbonyl stress-mediated NRK-52E cytotoxicity triggered by uranium.