title: Rapid pacing of embryoid bodies impairs mitochondrial ATP synthesis by a calcium-dependent mechanism--a model of in vitro differentiated cardiomyocytes to study molecular effects of tachycardia.
abstract: Tachycardia may cause substantial molecular and ultrastructural alterations in cardiac tissue. The underlying pathophysiology has not been fully explored. The purpose of this study was (I) to validate a three-dimensional in vitro pacing model, (II) to examine the effect of rapid pacing on mitochondrial function in intact cells, and (III) to evaluate the involvement of L-type-channel-mediated calcium influx in alterations of mitochondria in cardiomyocytes during rapid pacing. In vitro differentiated cardiomyocytes from P19 cells that formed embryoid bodies were paced for 24 h with 0.6 and 2.0 Hz. Pacing at 2.0 Hz increased mRNA expression and phosphorylation of ERK1/2 and caused cellular hypertrophy, indicated by increased protein/DNA ratio, and oxidative stress measured as loss of cellular thiols. Rapid pacing additionally provoked structural alterations of mitochondria. All these changes are known to occur in vivo during atrial fibrillation. The structural alterations of mitochondria were accompanied by limitation of ATP production as evidenced by decreased endogenous respiration in combination with decreased ATP levels in intact cells. Inhibition of calcium inward current with verapamil protected against hypertrophic response and oxidative stress. Verapamil ameliorated morphological changes and dysfunction of mitochondria. In conclusion, rapid pacing-dependent changes in calcium inward current via L-type channels mediate both oxidative stress and mitochondrial dysfunction. The in vitro pacing model presented here reflects changes occurring during tachycardia and, thus, allows functional analyses of the signaling pathways involved.
authors.affiliation: Institute of Clinical Chemistry, Department of Pathobiochemistry, Otto-von-Guericke University Magdeburg, and Division of Cardiology, University Hospital Magdeburg, Germany.
authors.forename: Lorenz
authors.initials: L
authors.lastname: Schild
authors.forename: Alicja
authors.initials: A
authors.lastname: Bukowska
authors.forename: Andreas
authors.initials: A
authors.lastname: Gardemann
authors.forename: Pamela
authors.initials: P
authors.lastname: Polczyk
authors.forename: Gerburg
authors.initials: G
authors.lastname: Keilhoff
authors.forename: Michael
authors.initials: M
authors.lastname: Täger
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Dudley
authors.forename: Helmut U
authors.initials: HU
authors.lastname: Klein
authors.forename: Andreas
authors.initials: A
authors.lastname: Goette
authors.forename: Uwe
authors.initials: U
authors.lastname: Lendeckel
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000096:biosynthesis* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002304:Cardiac Pacing, Artificial; D002454:Cell Differentiation; D019069:Cell Respiration / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006984:Hypertrophy; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D018384:Oxidative Stress / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013610:Tachycardia / Q000503:physiopathology*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D012333:RNA, Messenger; D013438:Sulfhydryl Compounds; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D014700:Verapamil; D019950:Mitogen-Activated Protein Kinase 1; D002118:Calcium