title: Hydrogen sulfide regulates Na+/H+ exchanger activity via stimulation of phosphoinositide 3-kinase/Akt and protein kinase G pathways.
abstract: Intracellular pH (pH(i)) is an important endogenous modulator of cardiac function. Inhibition of Na(+)/H(+) exchanger-1 (NHE-1) protects the heart by preventing Ca(2+) overload during ischemia/reperfusion. Hydrogen sulfide (H(2)S) has been reported to produce cardioprotection. The present study was designed to investigate the pH regulatory effect of H(2)S in rat cardiac myocytes and evaluate its contribution to cardioprotection. It was found that sodium hydrosulfide (NaHS), at a concentration range of 10 to 1000 μM, produced sustained decreases in pH(i) in the rat myocytes in a concentration-dependent manner. NaHS also abolished the intracellular alkalinization caused by trans-(±)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]benzeneacetamide methane-sulfonate hydrate (U50,488H), which activates NHEs. Moreover, when measured with an NHCl(4) prepulse method, NaHS was found to significantly suppress NHE-1 activity. Both NaHS and cariporide or [5-(2-methyl-5-fluorophenyl)furan-2-ylcarbonyl]guanidine (KR-32568), two NHE inhibitors, protected the myocytes against ischemia/reperfusion injury. However, coadministration of NaHS with KR-32568 did not produce any synergistic effect. Functional study showed that perfusion with NaHS significantly improved postischemic contractile function in isolated rat hearts subjected to ischemia/reperfusion. Blockade of phosphoinositide 3-kinase (PI3K) with 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), Akt with Akt VIII, or protein kinase G (PKG) with (9S,10R,12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]]enzodiazocine-10-carboxylic acid, methyl ester (KT5823) significantly attenuated NaHS-suppressed NHE-1 activity and/or NaHS-induced cardioprotection. Although KT5823 failed to affect NaHS-induced Akt phosphorylation, Akt inhibitor did attenuate NaHS-stimulated PKG activity. In conclusion, this work demonstrated for the first time that H(2)S produced cardioprotection via the suppression of NHE-1 activity involving a PI3K/Akt/PKG-dependent mechanism.
authors.affiliation: Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Li-Fang
authors.initials: LF
authors.lastname: Hu
authors.forename: Yu
authors.initials: Y
authors.lastname: Li
authors.forename: Kay Li
authors.initials: KL
authors.lastname: Neo
authors.forename: Qian Chen
authors.initials: QC
authors.lastname: Yong
authors.forename: Shiau Wei
authors.initials: SW
authors.lastname: Lee
authors.forename: Benny Kwong Huat
authors.initials: BK
authors.lastname: Tan
authors.forename: Jin-Song
authors.initials: JS
authors.lastname: Bian
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D027963:Chloride-Bicarbonate Antiporters / Q000378:metabolism; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D006146:Guanidines / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000819:agonists*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013440:Sulfides / Q000494:pharmacology*; D013450:Sulfones / Q000494:pharmacology
chemical_list: D000889:Anti-Arrhythmia Agents; D027963:Chloride-Bicarbonate Antiporters; D006146:Guanidines; D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; D013440:Sulfides; D013450:Sulfones; C093376:sodium-hydrogen exchanger regulatory factor; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; C093373:cariporide; D058539:Phosphatidylinositol 3-Kinase; C494920:Akt1 protein, rat; D051057:Proto-Oncogene Proteins c-akt; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; C025451:sodium bisulfide