Inhibition of phospholipase C-{gamma}1 augments the decrease in cardiomyocyte viability by H2O2

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 291; no. 2; p. H854
• Main Authors: Mangat, Rabban, Singal, Tushi, Dhalla, Naranjan S, Tappia, Paramjit S
• Format: Journal Article
• Language: English
• Published: 01.08.2006
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.01205.2005

1 Department of Human Nutritional Sciences, Faculty of Human Ecology, 2 Department of Physiology, Faculty of Medicine, and 3 Department of Human Anatomy and Cell Science, University of Manitoba, and Institute of Cardiovascular Sciences, St. Boniface Hospital Research Centre, Winnipeg, Canada Submitted 14 November 2005 ; accepted in final form 23 February 2006 The present study was conducted to examine the role of a major cardiac phospholipase C (PLC) isozyme, PLC- 1 , in cardiomyocytes during oxidative stress. Left ventricular cardiomyocytes were isolated by collagenase digestion from adult male Sprague-Dawley rats (250–300 g) and treated with 20, 50, and 100 µM H 2 O 2 for 15 min. A concentration-dependent (up to 50 µM) increase in the mRNA level and membrane protein content of PLC- 1 was observed with H 2 O 2 treatment. Furthermore, PLC- 1 was activated in response to H 2 O 2 , as revealed by an increase in the phosphorylation of its tyrosine residues. There was a marked increase in the phosphorylation of the antiapoptotic protein Bcl-2 by H 2 O 2 ; this change was attenuated by a PLC inhibitor, U-73122. Although both protein kinase C (PKC)- and - protein contents were increased in the cardiomyocyte membrane fraction in response to H 2 O 2 , PKC- activation, unlike PKC- , was attenuated by U-73122 (2 µM). Inhibition of PKC- with inhibitory peptide (0.1 µM) prevented Bcl-2 phosphorylation. Moreover, different concentrations (0.05, 0.1, and 0.2 µM) of this peptide augmented the decrease in cardiomyocyte viability in response to H 2 O 2 . In addition, a decrease in cardiomyocyte viability, as assessed by trypan blue exclusion, due to H 2 O 2 was also seen when cells were pretreated with U-73122 and was as a result of increased apoptosis. It is therefore suggested that PLC- 1 may play a role in cardiomyocyte survival during oxidative stress via PKC- and phosphorylation of Bcl-2. cardiomyocyte viability; phospholipase C; signal transduction Address for reprint requests and other correspondence: P. S. Tappia, Laboratory of Cardiac Membrane Biology, Institute of Cardiovascular Sciences, St. Boniface Hospital Research Centre (R3020), 351 Tache Ave., Winnipeg, Manitoba, Canada R2H 2A6 (e-mail: ptappia{at}sbrc.ca )