A1935 Modulation of TRPV4 by apigenin ameliorates renal fibrosis in DOCA salt hypertensive rats

Abstract

Objectives: Hypertension contributes to chronic renal damage. Apigenin, an effective anti-hypertensive flavone, acts as antagonist of transient receptor potential vanilloid 4 (TRPV4). Here, we aimed to investigate whether apigenin ameliorates hypertension-induced renal fibrosis and its underlying mechanism. Methods: Male Sprague-Dawley rats, 2-month-old TRPV4 knockout mice (TRPV4−/−) and their wild-type littermates were used to established deoxycorticosterone acetate (DOCA)–salt-induced hypertension model and received 0.2% apigenin diet for 4 weeks. The tail-cuff blood pressure (BP) was measured. Renal fibrosis was assessed by Histological staining and protein levels of fibrotic markers TGF-β1, p-Smad2/3, CTGF, COL1a1, and COL3a1 detected by western blot. Expression of TRPV4 was analyzed in kidney and renal mesangial cell. Cytosolic free Ca2+ was measured by fluorospectrometers. Results: Apigenin signifcantly attenuated hypertension-induced renal fibrosis, which was accompanied by reduced expression of TGF-β1/Smad2/3 signaling proteins. The inhibitory effect of apigenin on renal fibrosis is independent of blood pressure reduction. Immunochemistry, cell-attached patch clamp and fluorescent Ca2+ imaging results indicated that TRPV4 was expressed and activated by apigenin in both the kidney and renal cells. Importantly, knockout of TRPV4 in mice abolished the beneficial effects of apigenin that were observed in the DOCA–salt hypertensive rats. Additionally, apigenin directly inhibited activation of the TGF-β1/Smad2/3 signaling pathway in different renal tissues through activation of TRPV4 regardless of the type of pro-fibrotic stimulus. Conclusion: Dietary apigenin ameliorates hypertension-induced renal fibrosis through directly inhibiting the TGF-β1/Smad2/3 pathway in a TRPV4-dependent manner.