Regulation mechanism of AT1R/miR-26a pathway in hypertensive vascular remodeling

Abstract

Objective To elucidate the important role and molecular mechanism of AT1R/miR-26a pathway in hypertensive vascular remodeling. Methods ① Eight-week-old male spontaneously hypertensive rats (SHRs) were randomly divided into losartan group [gavage with losartan 20 mg/(kg·d) for 8 weeks], prazosin group [gavage with prazosin 5 mg/(kg·d) for 8 weeks], SHR control group [gavage with pure water 10 mL/(kg·d) for 8 weeks], with 8 animals in each groups. Six eight-week-old male WKY rats served as normal control group [gavage with pure water 10 mL/(kg·d) for 8 weeks]. All rats in each group were measured for systolic blood pressure (SBP) through tail artery in 3 to 5 d before and during the intervention period until the end of treatment. ② After the rats were anesthetized, the thoracic aorta were harvested for detecting the expression level of miR-26a by real-time quantitative polymerase chain reaction (qPCR). ③ The thoracic aorta was embedded in paraffin, and sectioned for HE and Masson staining, α-actin and PCNA immunohistochemistry. ④ The expression of AT1R, TGFβ1, p-smad3 and CTGF in the thoracic aorta were detected by Western blotting. ⑤ The rat thoracic aortic smooth muscle cells (VSMCs) at 3 to 9 passages were divided into AngⅡ treatment group (VSMCs+AngⅡ, AngⅡ10-7 mol/L, treated for 24 h), and control group (VSMC+Ctrl). qPCR was used to detect the expression level of miR-26a, and the expression of smad3 and p-smad3 was observed by Western blotting. Results ① At the end of treatment received, SBP was significantly lower in the losartan and prazosin groups than the SHR control group, but all of them were obviously higher than that of normal control group (P 0.05). ②The expression of miR-26a in the thoracic aorta was notably higher in the losartan and prazosin groups than the SHR control group, but statistically lower than the normal control group (P < 0.05), and that of the losartan group was higher than that of the prazosin group (P < 0.05). ③ Media thickness/lumen diameter (MT/LD), collagen volume fraction (CVF), and smooth muscle cell proliferation index in the losartan and prazosin groups were remarkably lower than those in the SHR control group (P < 0.05), and those in the losartan group were lower than those of the prazosin group. The normal control group had no obvious thickening of the vascular wall, with well-arranged smooth muscle cells, and regular morphology of the nucleus, and no significant collagen fiber deposition. ④The expression levels of AT1R, p-smad3, TGFβ1 and CTGF in the thoracic aorta were significantly lower in the losartan and prazosin groups than the SHR control group (P < 0.05). Although those in the losartan group were lower than those of the prazosin group (P < 0.05), the levels in the both group were higher than those of normal control group (P < 0.05). ⑤The expression of miR-26a was significantly lower, and that of p-smad3 was higher in VSMC+AngⅡ group when compared with VSMC+Ctrl group (P < 0.05). Conclusion miR-26a prevents blood pressure from rising and has a protective effect in the process of hypertensive vascular remodeling. Blocking AT1 receptor may improve the remodeling by up-regulating miR-26a.

Keywords

• hypertension
• vascular remodeling
• microrna-26a
• at1 receptor