The aim of this study was to confirm the renoprotective effect of xanthine oxidoreductase (XOR) inhibitor, topiroxostat, compared with another XOR inhibitor, febuxostat, under decreased angiotensin II type 1a (AT1a) receptor expression in the model of renal injury caused by adenine. To evaluate the degree of tubular damage using urinary liver-type fatty acid-binding protein (L-FABP) under decreased AT1a expression, we used AT1a receptor knockdown hetero and human L-FABP chromosomal transgenic (Tg) mice (AT1a+/-L-FABP+/-). Male AT1a+/-L-FABP+/- mice were divided into two groups: the adenine diet group (n = 40) was given a diet containing only 0.2% w/w adenine, and the normal diet group (n = 5) was given a normal diet. When renal dysfunction was confirmed in the adenine diet group 4 weeks after starting the diet, the adenine diet group was further divided into five groups. The adenine diet group (n = 8) was continuously given only the adenine diet. Each group receiving high-dose (3 mg/kg) or low-dose (1 mg/kg) topiroxostat (Topiroxostat-H group, n = 8, Topiroxostat-L group, n = 8) or febuxostat (Febuxostat-H group, n = 8, Febuxostat-L group, n = 8) was given the adenine diet including the drug for another 4 weeks. The levels of renal XOR, renal dysfunction, urinary L-FABP, tubulointerstitial damage, hypoxia, and oxidative stress were decreased or attenuated after treatment with topiroxostat or febuxostat compared with the adenine diet group. Furthermore, antioxidant capacity was maintained owing to these treatments.
In conclusion, topiroxostat and febuxostat attenuated renal damage under decreased AT1a expression in the adenine-induced renal injury model.