Hydrogen sulfide restores cardioprotective effects of remote ischemic preconditioning in aged rats via HIF-1α/Nrf2 signaling pathway

The present study explored the therapeutic potential of hydrogen sulfide (H(2)S) in restoring aging-induced loss of cardioprotective effect of remote ischemic preconditioning (RIPC) along with the involvement of signaling pathways. The left hind limb was subjected to four short cycles of ischemia and reperfusion (IR) in young and aged male rats to induce RIPC. The hearts were subjected to IR injury on the Langendorff apparatus after 24 h of RIPC. The measurement of lactate dehydrogenase, creatine kinase and cardiac troponin served to assess the myocardial injury. The levels of H(2)S, cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), nuclear factor erythroid 2-related factor 2 (Nrf2), and hypoxia-inducible factor (HIF-1α) were also measured. There was a decrease in cardioprotection in RIPC-subjected old rats in comparison to young rats along with a reduction in the myocardial levels of H(2)S, CBS, CSE, HIF-1α, and nuclear: cytoplasmic Nrf2 ratio. Supplementation with sodium hydrogen sulfide (NaHS, an H(2)S donor) and l-cysteine (H(2)S precursor) restored the cardioprotective actions of RIPC in old hearts. It increased the levels of H(2)S, HIF-1α, and Nrf2 ratio without affecting CBS and CSE. YC-1 (HIF-1α antagonist) abolished the effects of NaHS and l-cysteine in RIPC-subjected old rats by decreasing the Nrf2 ratio and HIF-1α levels, without altering H(2)S.The late phase of cardioprotection of RIPC involves an increase in the activity of H(2)S biosynthetic enzymes, which increases the levels of H(2)S to upregulate HIF-1α and Nrf2. H(2)S has the potential to restore aging-induced loss of cardioprotective effects of RIPC by upregulating HIF-1α/Nrf2 signaling.