title: Further study on the role of HSP70 on Ca2+ homeostasis in rat ventricular myocytes subjected to simulated ischemia.
abstract: We hypothesized that activation of heat shock protein 70 (HSP70) by preconditioning, which is known to confer delayed cardioprotection, attenuates the impaired handling of Ca(2+) at multiple sites. To test the hypothesis, we determined how the ryanodine receptor (RyR), sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA), and Na(+)/Ca(2+) exchanger (NCX) handled Ca(2+) in rat ventricular myocytes preconditioned with a kappa-opioid receptor agonist, U50488H (UP), followed by blockade of HSP70 with a selective antisense oligonucleotide and subsequently subjected to simulated ischemia. We determined the following: 1) the Ca(2+) transients induced by electrical stimulation and caffeine, which provide the overall picture of Ca(2+) homeostasis; 2) expression of RyR, SERCA, and NCX; and 3) Ca(2+) fluxes via NCX by the use of (45)Ca(2+) in the rat ventricular myocyte. We found that UP increased the activity of RyR, SERCA, and NCX and the expression of RyR and SERCA. These effects led to increases in the release of Ca(2+) from the sarcoplasmic reticulum via RyR and in the removal of Ca(2+) from the cytoplasm by reuptake of Ca(2+) to the SR via SERCA and by extrusion of Ca(2+) out of the cell via NCX. UP also reduced mitochondrial Ca(2+) accumulation. All of the effects of UP were either abolished or significantly attenuated by blockade of HSP70 synthesis with a selective antisense oligonucleotide. The results are evidence that activation of HSP70 by preconditioning improves the ischemia-impaired Ca(2+) homeostasis at multiple sites in the heart, which may be responsible, at least partly, for attenuated Ca(2+) overload, improved recovery in contractile function, and cardioprotection.
authors.affiliation: Muscular and Neurodegenerative Disease Unit, University of Genoa and G. Gaslini Pediatric Institute, Genoa, Italy.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Kenneth W L
authors.initials: KW
authors.lastname: Kam
authors.forename: Gudrun H
authors.initials: GH
authors.lastname: Borchert
authors.forename: Gennadi M
authors.initials: GM
authors.lastname: Kravtsov
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Ballard
authors.forename: Tak Ming
authors.initials: TM
authors.lastname: Wong
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002478:Cells, Cultured; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006352:Heart Ventricles / Q000166:cytology*; D006706:Homeostasis; D007511:Ischemia; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019831:Sodium-Calcium Exchanger / Q000378:metabolism
chemical_list: D000959:Antihypertensive Agents; D018840:HSP70 Heat-Shock Proteins; D016376:Oligonucleotides, Antisense; D010726:Phosphodiesterase Inhibitors; D019831:Sodium-Calcium Exchanger; D002110:Caffeine; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium