Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 375, Issue 6, pp 383–392

Pharmacological evidence for altered src kinase regulation of ICa,L in patients with chronic atrial fibrillation

  • Maura Greiser
  • Christian R. Halaszovich
  • Dirk Frechen
  • Peter Boknik
  • Ursula Ravens
  • Dobromir Dobrev
  • Andreas Lückhoff
  • Ulrich Schotten
Original Article

DOI: 10.1007/s00210-007-0174-6

Cite this article as:
Greiser, M., Halaszovich, C.R., Frechen, D. et al. Naunyn-Schmied Arch Pharmacol (2007) 375: 383. doi:10.1007/s00210-007-0174-6

Abstract

A reduction in l-type Ca2+ current (ICa,L) contributes to electrical remodeling in chronic atrial fibrillation (AF). Whether the decrease in ICa,L is solely due to a reduction in channel proteins remains controversial. Protein tyrosine kinases (PTK) have been described as potent modulators of ICa,L in cardiomyocytes. We studied α1Cl-type Ca2+ channel subunit expression and the regulation of ICa,L by PTK in chronic AF using PTK inhibitors: genistein, a nonselective inhibitor of PTK, and 4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo-3,4-d-pyrimidine (PP1), a selective inhibitor of src kinases. Furthermore, type-1 and type-2A protein phosphatase activity was measured with phosphorylase as substrate in whole-cell lysates derived from atrial tissue of AF patients. Right atrial appendages were obtained from patients undergoing open-heart surgery. Protein levels of α1Cl-type Ca2+ channel subunit were determined using Western blot analysis and normalized to the protein amounts of calsequestrin as internal control. The protein concentrations of α1C did not differ between AF and sinus rhythm (SR; α1C/calsequestrin: 1.0 ± 0.1 and 1.2 ± 0.2, respectively, n = 8 patients). In cardiomyocytes from patients in SR (n = 20 patients), genistein and PP1 both evoked similar increases in ICa,L from 3.0 ± 0.3 to 6.1 ± 0.8 pA/pF and from 2.8 ± 0.4 to 6.1 ± 0.6 pA/pF, respectively. In cells from AF patients (n = 10 patients), basal ICa,L was significantly lower. In this case, genistein lead to the same relative increase in ICa,L as in SR cells (from 1.46 ± 0.30 to 3.2 ± 1.0 pA/pF), whereas no increase was elicited by PP1 suggesting impaired regulation of ICa,L by src kinases in AF. Total and type 1 and type 2A-related phosphatase activities were higher in tissue from patients with chronic AF compared to SR (4.8 ± 0.4, 2.1 ± 0.2, and 2.7 ± 0.4 nmol/mg/min and 3.6 ± 0.4, 1.3 ± 0.2, and 2.4 ± 0.3 nmol/mg/min, respectively, n = 7 patients per group). Downregulation of ICa,L in AF is not due to a reduction in l-type Ca2+ channel protein expression. Indirect evidence for an impaired src kinase regulation of ICa,L together with an increased phosphatase activity suggests that a complex alteration in the kinase/phosphatase balance leads to ICa,L dysregulation in chronic AF.

Keywords

Atrial fibrillation Electrical remodeling l-Type calcium current Protein kinases Cardiomyocytes 

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Maura Greiser
    • 1
    • 1
  • Christian R. Halaszovich
    • 1
  • Dirk Frechen
    • 2
  • Peter Boknik
    • 4
  • Ursula Ravens
    • 3
  • Dobromir Dobrev
    • 3
  • Andreas Lückhoff
    • 1
  • Ulrich Schotten
    • 5
  1. 1.Institut für PhysiologieUniversitätsklinikum AachenAachenGermany
  2. 2.Medizinische Klinik IUniversitätsklinikum AachenAachenGermany
  3. 3.Institut für PharmakologieTechnische Universität DresdenDresdenGermany
  4. 4.Institut für PharmakologieWestfälische Wilhelms-Universität MünsterMunsterGermany
  5. 5.Department of PhysiologyMaastricht UniversityMaastrichtThe Netherlands
  6. 6.Department of PhysiologyMaastricht UniversityMaastrichtThe Netherlands