Activin receptor-like kinase 7 mediates high glucose-induced H9c2 cardiomyoblast apoptosis through activation of Smad2/3

Abstract

Cardiomyocyte apoptosis is an important pathological change of diabetic cardiomyopathy. How the elevated glucose levels cause cell apoptosis remains unknown. The aim of our study was to investigate whether activin receptor-like kinase 7 (ALK7)-Smad2/3 signaling pathway plays an important role in high glucose-induced cardiomyocyte apoptosis. H9c2 cardiomyoblasts and neonatal rat cardiomyocytes were treated with 33mmol/l glucose. The expression of ALK7, Smad2 and Smad3 were inhibited by small interfering RNA respectively. The level of ALK7, total Smad2/3, phosphorylated Smad2/3, B-cell lymphoma-2 (Bcl-2) and cleaved Caspase3 were evaluated using western blot. The apoptosis rate was detected by flow cytometer. High glucose treatment caused the apoptosis of H9c2 cardiomyocyte and the inhibition of Smad2 or Smad3 attenuated this apoptosis. ALK7 existed in both H9c2 cardiomyoblasts and neonatal rat cardiomyocytes and high ambient glucose upregulated its expression. The increased expression level of cleaved Caspase3 and apoptosis rate and decreased expression of Bcl-2 were reversed after ALK7 was inhibited. The expression of phosphorylated Smad2/3 also decreased after the knockdown of ALK7. Our findings suggest that ALK7 mediates high ambient glucose-induced H9c2 cardiomyoblasts apoptosis through the activation of Smad2/3.

Keywords: ALK; ActRII; Activin receptor-like kinase 7; Apoptosis; B-cell lymphoma-2; BMPs; Bcl-2; Cardiomyocyte; DCM; DMEM; Dulbecco's modified Eagle's medium; FBS; GDF; Glucose; Smad2/3; TGF-β; X-linked inhibitor of apoptosis protein; XIAP; activin receptor-like kinase; activin type II receptors; bone morphogenetic proteins; diabetic cardiomyopathy; fetal bovine serum; growth and differentiation factors; siRNA; small interfering RNA; transforming growth factor-β.