Effects of miR-21 on hypertensive rats through PTEN/PI3K/Akt/mTOR signaling pathway

Y.-J. Shi, W. Xu, Y.-F. Han, J.-X. Li, L.-L. Niu, Y.-D. Chen

Department of Cardiology, Chinese PLA General Hospital, Beijing, China. cyundai@vip.163.com

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• Cardiology

OBJECTIVE: The aim of this study was to investigate the effects of micro-ribonucleic acid (miR)-21 on hypertensive rats through the phosphatase and tensin homolog deleted on chromosome ten (PTEN)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway.
MATERIALS AND METHODS: A total of 10 spontaneously hypertensive rats (SHRs) were selected as the model group. Meanwhile, 10 rats with the same age were enrolled in the normal control group. Real Time-fluorescence quantitative Polymerase Chain Reaction (qRT-PCR) was performed to detect the mRNA level of miR-21 in rats of the SHR model group and control group. The tail arterial diastolic pressure of rats in the awake and resting state was measured in both groups, respectively. Pathological sections were prepared to evaluate pathological changes in myocardial tissues. Subsequently, myocardial cells were isolated, cultured and transfected with miR-21 mimics and miR-21 inhibitor, respectively. Transfection efficiency was verified using fluorescence quantitative PCR. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay was utilized to determine the apoptosis level of myocardial cells. Furthermore, the expression levels of the signaling pathway-related proteins were detected via Western blotting assay.
RESULTS: Fluorescence quantitative PCR results revealed that the expression level of miR-21 was significantly higher in the SHR model group (p<0.05). The diastolic pressure increased markedly in the SHR model group when compared with that in the control group (p<0.05). Subsequent hematoxylin and eosin (HE) staining indicated apparent myocardial tissue injury in the SHR model group (p<0.05). After transfection, the results showed that miR-21 inhibitor could effectively down-regulate the expression level of miR-21 in myocardial cells (p<0.05). Meanwhile, TUNEL staining revealed that the number of apoptotic cells in the miR-21 inhibitor group was remarkably higher than that of the other two groups (p<0.05). In addition, Western blotting results manifested that the protein expression levels of PTEN, PI3K, Akt and mTOR were significantly lower in the miR-21 mimics group (p<0.05), whereas was remarkably higher in the miR-21 inhibitor group (p<0.05).
CONCLUSIONS: MiR-21 is involved in regulating the pathological symptoms and myocardial cell apoptosis in hypertensive rats through the PTEN/PI3K/Akt/mTOR signaling pathway.

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