CBL knockdown protects cardiomyocytes against hypoxia-reoxygenation injury by downregulating GRB2 expression

Myocardial ischemia-reperfusion injury (MIRI) is an event that follows a myocardial infarction. As such, close observation and appropriate patient management is paramount in the treatment process of interventional surgery. The pathogenesis of MIRI has not been fully elucidated. Therefore, the aim of the present study was to explore of novel targets for MIRI treatment whilst also determining their possible underlying mechanism of action. The plasma samples used in the present study were collected from 30 patients with ischemic cardiomyopathy and 30 healthy volunteers. H9c2 rat cardiomyoblasts were subjected to hypoxia and reoxygenation (H/R) modeling to establish an in vitro MIRI model. Initially, the expression levels of Cbl proto-oncogene (CBL) in ICM heart tissue, normal heart tissue, H/R-induced H9c2 cells and normal H9c2 cells were detected using quantitative PCR and western blotting. With the application of Cell Counting Kit-8, western blotting and Tunnel assay, the proliferation, oxidative stress and apoptosis of H/R-induced cells were assessed. Moreover, co-IP assay was employed to testify the interaction between CBL and GRB2. The present study revealed that CBL expression was upregulated in patients with ischemic cardiomyopathy and H/R-induced H9c2 cells in comparison with that in normal heart tissue and normal H9c2 cells, respectively. The genetic silence of CBL using small interfering RNA promoted the proliferation and oxidative stress of H/R-induced cells but repressed the apoptosis. The full-length wild-type of growth factor receptor-bound protein 2 (GRB2) was ligated into pcDNA3.1 to achieve GRB2 overexpression, which revealed that GRB2 overexpression reversed the effects of CBL knockdown on cells, suggesting that it may mediate these processes downstream. In conclusion, under hypoxic conditions, CBL knockdown promoted the proliferation and antioxidant capacity of cardiomyocytes whilst inhibiting apoptosis, by downregulating GRB2 expression. These findings revealed the underlying mechanism of action of this pathway, which can be exploited for the prevention or treatment of MIRI.