ERK phosphorylation mediates sildenafil-induced myocardial protection against ischemia-reperfusion injury in mice

Abstract

Sildenafil, a selective inhibitor of phosphodiesterase type 5, induces powerful protection against myocardial ischemia-reperfusion injury through activation of cGMP-dependent protein kinase (PKG). We further hypothesized that PKG-dependent activation of survival kinase ERK may play a causative role in sildenafil-induced cardioprotection via induction of endothelial nitric oxide synthase (eNOS)/inducible nitric oxide synthase (iNOS) and Bcl-2. Our results show that acute intracoronary infusion of sildenafil in Langendorff isolated mouse hearts before global ischemia-reperfusion significantly reduced myocardial infarct size (from 29.4 +/- 2.4% to 15.9 +/- 3.0%; P < 0.05). Cotreatment with ERK inhibitor PD98059 abrogated sildenafil-induced protection (31.8 +/- 4.4%). To further evaluate the role of ERK in delayed cardioprotection, mice were treated with sildenafil (ip) 24 h before global ischemia-reperfusion. PD98059 was administered (ip) 30 min before sildenafil treatment. Infarct size was reduced from 27.6 +/- 3.3% in controls to 7.1 +/- 1.5% in sildenafil-treated mice (P < 0.05). The delayed protective effect of sildenafil was also abolished by PD98059 (22.5 +/- 2.3%). Western blots revealed that sildenafil significantly increased phosphorylation of ERK1/2 and GSK-3beta and induced iNOS, eNOS, Bcl-2, and PKG activity in the heart 24 h after treatment. PD98059 inhibited the enhanced expression of iNOS, eNOS, and Bcl-2 and the phosphorylation of GSK-3beta. PD98059 had no effect on the sildenafil-induced activation of PKG. We conclude that these studies provide first direct evidence that PKG-dependent ERK phosphorylation is indispensable for the induction of eNOS/iNOS and Bcl-2 and the resulting cardioprotection by sildenafil.

Dexmedetomidine protects the heart against ischemia-reperfusion injury by an endothelial eNOS/NO dependent mechanism

“…For example, evidence shows that PKG can protect cells from IR injury by activating signaling cascades that delay mPTP opening [60][61][62].…”

Induction of cardioprotection by small netrin-1-derived peptides

“…2). Several previous studies have shown that activated ERK1/2 mediates protection against I/R injury (11,18). Moreover, mice expressing an unphosphorylatable (S1179A) form of eNOS show more severe infarction than wild-type mice (1).…”

Overexpression of cGMP-dependent protein kinase I (PKG-I) attenuates ischemia-reperfusion-induced kidney injury

“…PKG-I is expressed in vascular smooth muscle cells, cardiomyocytes, endothelial cells, mesangial cells, renal tubular cells, macrophages, and other cell types (9). Recent studies demonstrated the protective effect of the cGMP/PKG signaling pathway on IR injury in the heart as well as in cardiomyocytes through several mechanisms such as regulation of mitochondria K ATP channels or enhanced phosphorylation of Akt, ERK, and glycogen synthase kinase (GSK)-3␤ (5,11,13) . However, whether PKG displays a protective effect on kidney IR injury is unknown.…”