TNFα-initiated oxidative/nitrative stress mediates cardiomyocyte apoptosis in traumatic animals

Abstract

Whole body non-penetrating trauma causes myocardial infarction in humans and mechanical trauma (MT) results in cardiac dysfunction in animals. Our recent study demonstrated that incubation of cardiomyocytes with plasma isolated from MT animals causes significant cardiomyocyte apoptosis that can be blocked by neutralization of TNFalpha. The present study attempted to obtain direct in vivo evidence to support that overproduction of TNFalpha plays a causative role in trauma-induced cardiomyocyte apoptosis. Non-lethal MT caused significant TNFalpha overproduction (2.4-fold at 1.5 h after MT) and increased cardiomyocyte apoptosis (starting 3 h and peaking 12 h after MT). Pharmacological inhibition of TNFalpha with etanercept or TNFalpha gene deletion reduced post-trauma myocyte apoptosis (P<0.01). Expression of iNOS and NADPH oxidase, overproduction of NO and O2-, and excessive protein nitration in the MT heart were all significantly reduced in etanercept-treated or TNFalpha-/- mice, suggesting that oxidative/nitrative stress may contribute to TNFalpha-initiated myocyte apoptosis in MT hearts. Additional experiments demonstrated that inhibiting iNOS (1400W) or NADPH oxidase (apocynin), or scavenging peroxynitrite (FP15) significantly reduced myocyte apoptosis in MT animals (P<0.01). Collectively, these data demonstrated that non-lethal mechanical trauma caused significant TNFalpha production that in turn stimulated myocardial apoptosis via oxidative/nitrative stress.