Peroxynitrite-induced α-actinin nitration and contractile alterations in isolated human myocardial cells

Attila Borbély, Attila Tóth, István Édes, László Virág, Julius Gy Papp, András Varró, Walter J. Paulus, Jolanda Van Der Velden, Ger J.M. Stienen, Zoltán Papp*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Objective: Peroxynitrite-mediated myocardial protein nitration has been associated with a depressed cardiac pump function. In the present study, an attempt was made to elucidate the molecular background of peroxynitrite-evoked alterations in the human myocardium. Methods: Isometric force generation was measured in permeabilized human ventricular myocytes and biochemical methods were employed to identify the proteins affected by peroxynitrite-induced nitrotyrosine formation. Results: The maximal Ca2+-activated isometric force (pCa = 4.75) decreased to zero with increasing concentrations of peroxynitrite in a concentration-dependent manner (IC50: 55 ± 4 μM; based on a total of 75 myocytes). However, there were no differences before and after the application of 50 μM peroxynitrite in the Ca 2+-sensitivity of force production (pCa50: 5.89 ± 0.02 and 5.86 ± 0.04), in the steepness of the Ca2+-force relationship (nHill: 2.22 ± 0.11 and 2.42 ± 0.25), and in the actin-myosin turnover kinetics (ktr at saturating [Ca2+]: 1.14 ± 0.03 1/s and 1.05 ± 0.07 1/s) (P > 0.05). Nevertheless, 50 μM peroxynitrite greatly deteriorated the cross-striation pattern and induced a slight, but significant, increase in the passive force component (from 2.1 ± 0.1 to 2.5 ± 0.2 kN/m2; n = 57 cells), reflecting ultrastructural alterations. Western immunoblots revealed that 50 μM peroxynitrite selectively induced the nitration of a protein with an apparent molecular mass of about 100 kDa. Subsequent immunoprecipitation assays identified this nitrated protein as α-actinin, a major Z-line protein. Conclusions: These results suggest α-actinin as a novel target for peroxynitrite in the human myocardium; its nitration induces a contractile dysfunction, presumably by decreasing the longitudinal transmission of force between adjacent sarcomeres.

Original languageEnglish
Pages (from-to)225-233
Number of pages9
JournalCardiovascular Research
Volume67
Issue number2
DOIs
Publication statusPublished - 1 Aug 2005

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