Abstract
The aim of this study was to identify the role of the precursor of the brain-derived neurotrophic factor (pro-BDNF) in myocardial hypoxia/reoxygenation injury (H/R) and to address the underlying mechanisms. For this purpose, myocardial microvascular endothelial cells (MMECs) exposed to a high concentration of glucose (30 mM) for 48 h were subjected to 4 h of hypoxia followed by 2 h of reoxygenation. Terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining and flow-cytometric analysis were performed to detect apoptosis. Cell scratch and capillary-like-structure formation assays were employed to evaluate cell function. The levels of apoptosis-related proteins were evaluated by Western blotting and immunofluorescence assays. Our results showed that H/R resulted in MMEC injury, as indicated by significant increases in TUNEL-positive cell numbers and a reduction in MMEC migration and in capillary-like-structure formation coupled with increased pro-BDNF protein expression. In addition, overexpression of pro-BDNF in MMECs via a viral vector led to increased pro-BDNF expression, and this upregulation induced apoptosis. Mechanistic experiments revealed that H/R did not influence BDNF, JNK, and caspase 3 expression, but upregulated pro-BDNF, p75NTR, sortilin, phospho-JNK, and cleaved caspase 3 protein levels. In contrast, neutralization of endogenous pro-BDNF with an antibody significantly attenuated H/R-induced upregulation of pro-BDNF, p75NTR, sortilin, p-JNK, and cleaved caspase 3 protein levels, indicating that p75NTR-sortilin signaling and activation of JNK and caspase 3 may be involved in these effects. In conclusion, H/R-induced injury may be mediated by pro-BDNF, at least in part through the regulation of p75NTR-sortilin signaling and activation of JNK and caspase 3.
Highlights
Diabetes mellitus (DM), a potent and prevalent risk factor of ischemic heart disease, has received increasing attention globally
After exposure to high concentration of glucose (HG), hypoxia/reoxygenation injury (H/R) caused a significant increase in the proportion of TUNEL-positive cells as compared to myocardial microvascular endothelial cells (MMECs) not subjected to H/R, indicating that H/R induced MMEC apoptosis (Figures 1(a)–1(c))
These results indicate that H/R exerted a proapoptotic effect and upregulated the pro-brain-derived neurotrophic factor (BDNF) protein
Summary
Diabetes mellitus (DM), a potent and prevalent risk factor of ischemic heart disease, has received increasing attention globally. DM increased myocardial susceptibility to ischemia/reperfusion- (I/R-) caused irreversible destruction, characterized by deficient oxygen supply and subsequent restoration of blood flow [5,6,7,8]. Microvascular disturbances are a vital feature of myocardial reperfusion injury [9]. A basic component of myocardial microcirculation, were first harmed by reperfusion injury followed by damage to cardiomyocytes after restoration of the cardiac microcirculation and played a vital role in the preservation of cardiomyocytes after reperfusion injury [9, 13]. The potential mechanisms responsible for the adverse effects caused by apoptosis and endothelial dysfunction after endothelial injury induced by hyperglycemia with I/R insults remain an enigma
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