title: Pyruvate restores β-adrenergic sensitivity of L-type Ca(2+) channels in failing rat heart: role of protein phosphatase.
abstract: Oxidative stress plays a major role in the pathogenesis of heart failure, where the contractile response to β-adrenergic stimulation is profoundly depressed. This condition involves L-type Ca(2+) channels, but the mechanisms underlying their impaired adrenergic regulation are unclear. Thus the present study explored the basis for impaired adrenergic control of Ca(2+) channels in a rat infarction model of heart failure. Patch-clamp recordings of L-type Ca(2+) current (I(Ca,L)) from ventricular myocytes isolated from infarcted hearts showed a blunted response to intracellular cAMP that was reversed by treatment with exogenous pyruvate. Biochemical studies showed that basal and cAMP-stimulated protein kinase A activities were similar in infarcted and sham-operated hearts, whereas molecular analysis also found that binding of protein kinase A to the α(1C) subunit of voltage-gated Ca(2+) channel isoform 1.2 was not different between groups. By contrast, protein phosphatase 2A (PP2A) activity and binding to α(1C) were significantly less in infarcted hearts. The PP2A inhibitor okadaic acid markedly increased I(Ca,L) in sham-operated myocytes, but this response was significantly less in myocytes from infarcted hearts. However, pyruvate normalized I(Ca,L) stimulation by okadaic acid, and this effect was blocked by inhibitors of thioredoxin reductase, implicating a functional role for the redox-active thioredoxin system. Our data suggest that blunted β-adrenergic stimulation of I(CaL) in failing hearts results from hyperphosphorylation of Ca(2+) channels secondary to oxidation-induced impairment of PP2A function. We propose that the redox state of Ca(2+) channels or PP2A is controlled by the thioredoxin system which plays a key role in Ca(2+) channel remodeling of the failing heart.
authors.affiliation: Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198, USA.
authors.forename: Ming-Qi
authors.initials: MQ
authors.lastname: Zheng
authors.forename: Xun
authors.initials: X
authors.lastname: Li
authors.forename: Kang
authors.initials: K
authors.lastname: Tang
authors.forename: Neeru M
authors.initials: NM
authors.lastname: Sharma
authors.forename: Todd A
authors.initials: TA
authors.lastname: Wyatt
authors.forename: Kaushik P
authors.initials: KP
authors.lastname: Patel
authors.forename: Lie
authors.initials: L
authors.lastname: Gao
authors.forename: Keshore R
authors.initials: KR
authors.lastname: Bidasee
authors.forename: George J
authors.initials: GJ
authors.lastname: Rozanski
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006321:Heart / Q000187:drug effects*; D006333:Heart Failure / Q000378:metabolism* / Q000503:physiopathology; D006439:Hemodynamics / Q000502:physiology; D047468:Immunoprecipitation; D008297:Male; D032342:Muscle Cells / Q000187:drug effects; D009203:Myocardial Infarction / Q000473:pathology; D010084:Oxidation-Reduction; D010749:Phosphoprotein Phosphatases / Q000502:physiology*; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000378:metabolism; D019289:Pyruvic Acid / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D013879:Thioredoxins / Q000378:metabolism / Q000502:physiology
chemical_list: D000318:Adrenergic beta-Agonists; D020746:Calcium Channels, L-Type; D011943:Receptors, Adrenergic, beta; D013879:Thioredoxins; D019289:Pyruvic Acid; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2
keywords: L-type Ca2+ channel; PP2a; pyruvate; thioredoxin