Hydrogen sulfide regulates cardiac sarcoplasmic reticulum Ca2 + uptake via KATP channel and PI3K/Akt pathway

Abstract

AimsTo investigate the effects of hydrogen sulfide (H2S) on calcium uptake activity of the rat cardiac sarcoplasmic reticulum (SR) and possible signaling. Main methodsCrude SR was isolated after treatment with H2S, then SR Ca2+ uptake and SR Ca2+-ATPase (SERCA) activity was measured by the isotopic tracer method. The possible roles of the KATP channel and PI3K/Akt and SR-membrane protein phospholamban (PLB) pathway were analyzed by specific blockers, and target protein activation was assayed by measuring protein phosphorylation. Key findingsExogenous H2S lowered Ca2+ uptake into the SR time or concentration dependently, which was associated with decreased SERCA activity. Inhibiting endogenous H2S production by DL-propargylglycine increased SR Ca2+ uptake and SERCA activity. H2S inhibition of PLB phosphorylation was through SERCA activity and was reversed by two PI3K inhibitors, wortmannin and LY294002. Glibenclamide (a KATP channel blocker) blocked the inhibitory effects of H2S on PLB and Akt phosphorylation. Pinacidil (a KATP channel opener) reduced the phosphorylation of PLB and reversed the effects of DL-propargylglycine. H2S preconditioning increased PLB phosphorylation but did not affect SERCA activity. SignificanceEndogenous H2S transiently and reversibly inhibits SR Ca2+ uptake in rat heart SR because of downregulated SERCA activity associated with PLB phosphorylation by the PI3K/Akt or KATP channel. The transient negative regulation of SR Ca2+ uptake and the L-type Ca2+ channel contributes to Ca2+ cycle homeostasis, which might be an important molecular mechanism in ischemic diseases.