miR-181c-5p Exacerbates HypoxiaReoxygenation-Induced Cardiomyocyte Apoptosis via Targeting PTPN4

Abstract EN

Background.

Activation of cell apoptosis is a major form of cell death during myocardial ischemia/reperfusion injury (I/RI).

Therefore, examining ways to control cell apoptosis has important clinical significance for improving postischemic recovery.

Clinical evidence demonstrated that miR-181c-5p was significantly upregulated in the early phase of myocardial infarction.

However, whether or not miR-181c-5p mediates cardiac I/RI through cell apoptosis pathway is unknown.

Thus, the present study is aimed at investigating the role and the possible mechanism of miR-181c-5p in apoptosis during I/R injury by using H9C2 cardiomyocytes.

Methods and Results.

The rat origin H9C2 cardiomyocytes were subjected to hypoxia/reoxygenation (H/R, 6 hours hypoxia followed by 6 hours reoxygenation) to induce cell injury.

The results showed that H/R significantly increased the expression of miR-181c-5p but not miR-181c-3p in H9C2 cells.

In line with this, in an in vivo rat cardiac I/RI model, miR-181c-5p expression was also significantly increased.

The overexpression of miR-181c-5p by its agomir transfection significantly aggravated H/R-induced cell injury (increased lactate dehydrogenase level and reduced cell viability) and exacerbated H/R-induced cell apoptosis (greater cleaved caspases 3 expression, Bax/Bcl-2 and more TUNEL-positive cells).

In contrast, inhibition of miR-181c-5p in vitro had the opposite effect.

By using computational prediction algorithms, protein tyrosine phosphatase nonreceptor type 4 (PTPN4) was predicted as a potential target gene of miR-181c-5p and was verified by the luciferase reporter assay.

The overexpression of miR-181c-5p significantly attenuated the mRNA and protein expression of PTPN4 in H9C2 cardiomyocytes.

Moreover, knockdown of PTPN4 significantly aggravated H/R-induced enhancement of LDH level, cleaved caspase 3 expression, and apoptotic cell death, which mimicked the proapoptotic effects of miR-181c-5p in H9C2 cardiomyocytes.

Conclusions.

These findings suggested that miR-181c-5p exacerbates H/R-induced cardiomyocyte injury and apoptosis via targeting PTPN4 and that miR-181c-5p/PTPN4 signaling may yield novel strategies to combat myocardial I/R injury.