Febuxostat ameliorates angiotensin II-induced aortic fibrosis via suppressing macrophage-derived TGF-β expression

Abstract

[background] A xanthine oxidase (XO) inhibitor, febuxostat (FEB) is often used in patients with hyperuricemia. Several reports have suggested that uric acid contributes to endothelial dysfunction and kidney injury. Because XO produces hydrogen peroxide with uric acid in the nucleic acid metabolism, XO inhibitors can also have the anti-oxidative properties. From these reasons, XO inhibitors have the possibilities to suppress cardiovascular diseases. Actually, the effects of FEB on cardiovascular events have been examined in several clinical trials and several basic researches have suggested that FEB suppressed cardiac fibrosis and renal inflammation, however, those mechanisms remain unclear. In this study, we investigated the effects of FEB on angiotensin II (Ang II)-induced vascular remodeling.

[methods] To induce vascular remodeling, Ang II (2.0 mg/kg/day) was infused for 2 weeks by a sc implanted osmotic minipump. FEB (10 mg/kg/day, p.o.) was administrated for 2 weeks. Aortic fibrosis was assessed by EVG staining. Macrophage infiltration in aorta was investigated by immunostaining with F4/80 antibody and XO antibody. In our in vitro studies, mouse macrophage RAW264.7 cells (RAW) and mouse embryonic fibroblasts (MEF) were used. Protein expression and mRNA expression were assessed by Western blotting and quantitative real time-PCR, respectively.

[results] FEB administration suppressed Ang II-induced blood pressure elevation and aortic fibrosis, however it did not affect medial thickening of the aortae. Immunostaining showed that Ang II-induced macrophage infiltration in aorta tended to be suppressed by FEB, and XO was mainly colocalized in macrophages, not in fibroblasts. TGF-β1 mRNA expression was induced in aorta in Ang II alone group, but not in Ang II+FEB group. Ang II induced α-SMA positive fibroblasts in the aortic wall, but FEB suppressed them. In our in vitro studies, XO expression was induced in Ang II stimulation alone, but not in Ang II+FEB in RAW. TGF-β1 mRNA expression was induced by Ang II, but it was suppressed by FEB in RAW. TGF-β1 mRNA expression in MEF was not induced by Ang II and was lower than that in RAW.

[conclusions] Our results suggested that FEB ameliorates angiotensin II-induced aortic fibrosis via suppressing macrophage-derived TGF-β expression.