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

Aims: To investigate the effects of hydrogen sulfide (H2S) on calcium uptake activity of the rat cardiac sarcoplasmic reticulum (SR) and possible signaling. Main methods: Crude 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 K-ATP 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 findings: Exogenous 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 K-ATP, channel blocker) blocked the inhibitory effects of H2S on PLB and Akt phosphorylation. Pinacidil (a K-ATP 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. Significance: Endogenous 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 K-ATP 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. Crown Copyright (C) 2012 Published by Elsevier Inc. All rights reserved.