title: Oxidation of myofilament protein sulfhydryl groups reduces the contractile force and its Ca2+ sensitivity in human cardiomyocytes.
abstract: This study sought to characterize the relation between the oxidation of protein sulfhydryl (SH) groups and Ca2+-activated force production in the human myocardium. Triton-permeabilized left ventricular cardiomyocytes from donor hearts were exposed to an oxidative (2,2'-dithiodipyridine, DTDP) agent in vitro, and the changes in isometric force, its Ca2+ sensitivity, the cross-bridge-sensitive rate constant of force redevelopment at saturating [Ca2+] (k(tr,max)), and protein SH oxidation were monitored. DTDP (0.1-10 mM for 2 min) oxidized the myocardial proteins and diminished the Ca2+-activated force with different concentration dependences (EC(50,SH) = 0.17 +/- 0.02 mM and EC(50,force) = 2.46 +/- 0.22 mM; mean +/- SEM). The application of 2.5 mM DTDP decreased the maximal Ca2+-activated force (to 64%), its Ca2+ sensitivity (DeltapCa(50) = 0.22 +/- 0.02), and the steepness of the Ca2+-force relation (n(Hill), from 2.01 +/- 0.08 to 1.76 +/- 0.08). These changes were paralleled by reductions in the free SH content of the proteins (to 15%) and in k(tr,max) (to 75%). SH-specific labeling identified SH oxidation of myosin light chain 1 and actin at DTDP concentrations at which the changes in the contractile parameters occurred. Our data suggest that SH oxidation in selected myofilament proteins diminishes the Ca2+-activated force and its Ca2+ sensitivity through an impaired Ca2+ regulation of the actin-myosin cycle in the human heart.
authors.affiliation: Division of Clinical Physiology, University of Debrecen, Debrecen, Hungary.
authors.forename: Zita
authors.initials: Z
authors.lastname: Hertelendi
authors.forename: Attila
authors.initials: A
authors.lastname: Tóth
authors.forename: Attila
authors.initials: A
authors.lastname: Borbély
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Galajda
authors.forename: Jolanda
authors.initials: J
authors.lastname: van der Velden
authors.forename: Ger J M
authors.initials: GJ
authors.lastname: Stienen
authors.forename: István
authors.initials: I
authors.lastname: Edes
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Papp
mesh_terms: D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives / Q000494:pharmacology; D008841:Actin Cytoskeleton / Q000378:metabolism*; D000328:Adult; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D004220:Disulfides / Q000494:pharmacology; D005260:Female; D006801:Humans; D047468:Immunoprecipitation; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000378:metabolism
chemical_list: D004220:Disulfides; D011506:Proteins; D013438:Sulfhydryl Compounds; C001105:2,2'-dipyridyl disulfide; D015082:2,2'-Dipyridyl; D002118:Calcium