Inhibition of phospholipase C-γ₁augments the decrease in cardiomyocyte viability by H₂O₂

Abstract

The present study was conducted to examine the role of a major cardiac phospholipase C (PLC) isozyme, PLC-gamma 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 microM H2O2 for 15 min. A concentration-dependent (up to 50 microM) increase in the mRNA level and membrane protein content of PLC-gamma 1 was observed with H2O2 treatment. Furthermore, PLC-gamma 1 was activated in response to H2O2, 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 H2O2; this change was attenuated by a PLC inhibitor, U-73122. Although both protein kinase C (PKC)-delta and -epsilon protein contents were increased in the cardiomyocyte membrane fraction in response to H2O2, PKC-epsilon activation, unlike PKC-delta, was attenuated by U-73122 (2 microM). Inhibition of PKC-epsilon with inhibitory peptide (0.1 microM) prevented Bcl-2 phosphorylation. Moreover, different concentrations (0.05, 0.1, and 0.2 microM) of this peptide augmented the decrease in cardiomyocyte viability in response to H2O2. In addition, a decrease in cardiomyocyte viability, as assessed by trypan blue exclusion, due to H2O2 was also seen when cells were pretreated with U-73122 and was as a result of increased apoptosis. It is therefore suggested that PLC-gamma 1 may play a role in cardiomyocyte survival during oxidative stress via PKC-epsilon and phosphorylation of Bcl-2.

Tribulosin protects rat hearts from ischemia/reperfusion injury

“…It has been suggested that targeted disruption of the PKCε gene leads to loss of the cardioprotective effect of ischemic preconditioning [22,23] . A PKCε-inhibitory peptide efficiently inhibited Bcl-2 phosphorylation and augmented hydrogen peroxide-induced apoptosis in a concentration-dependent manner in rat cardiocytes [24] . In our study, PKCε expression increased after using tribulosin.…”

Multiple roles of phosphoinositide-specific phospholipase C isozymes

“…However, observations made using signallingrestricted receptors and PLC-γ1 null fibroblasts support the idea that PLC-γ1 is not required for growth factor-stimulated proliferation (28,(116)(117)(118). More definitive roles for PLC-γ1 have been established in the regulation of cellular differentiation and survival programmes (119)(120)(121). Recently, several studies implicated PLC-γ1 as a determinant of the directionality of cell movement towards EGF and proposed that it can couple to the actin polymerisation machinery via multiple routes including regulation of coffilin and Rac/Cdc42 GTPases (122).…”

Reactive Oxygen Species in Inflammation and Tissue Injury

“…Direct oxidative modification of the regulatory domain results in increased PKC activity (143). ROS can also regulate PKC activation by generating different mediators and cofactors, including PLC and PLD (267,438). Oxidant-mediated activation of PKC also occurred through phosphorylation of distinct residues of different PKC isoforms (224).…”