Glutamine protects cardiomyocytes from hypoxia/reoxygenation injury under high glucose conditions through inhibition of the transforming growth factor-beta 1-Smad3 pathway

摘要

Activation of transforming growth factor-beta 1 (TGF-beta 1)-Smad3 pathway aggravates myocardial ischemia/reperfusion injury (IRI). We previously showed that glutamine (Gin) protects cardiomyocytes from hypoxia/reoxygenation (H/R) injury under high glucose (HG) conditions. The aim of this study was to investigate whether Gln exerts its protective effect in H/R via inhibiting TGF-beta 1-Smad3 pathway. In vitro, H9c2 rat cardiomyocytes were treated with Gln with HG (33 mM) and/or H/R. We also performed in vivo experiments in which we treated normal and diabetic rats with Gln or solvent control following IRI. We assessed protein levels of TGF-beta 1, total Smad3, phosphorylated (p)-Smad3 and cleaved caspase-3 in H9c2 cells and rat myocardium by Western blotting. H9c2 cells treated with HG + H/R exhibited high apoptosis rates, as well as a highly activated TGF-beta 1-Smad3 pathway. TGF-beta 1 receptor inhibitor (SB431542) or Smad3 inhibitor (SIS3) reduced HG + H/R induced apoptosis. Similarly, Gln supplementation alleviated apoptosis and decreased p-Smad3 levels. However, Gln's protective effect was significantly weakened by TGF-beta 1. Diabetic rats treated with Gin had improved hemodynamics, smaller infarct size after IRI, and a significant decrease in TGF-beta 1-Smad3 pathway activation. We conclude that Gln inhibits HG + H/R induced activation of the TGF-beta 1-Smad3 pathway and decreases cell apoptosis in cardiomyocytes. (C) 2016 Elsevier Inc. All rights reserved.