Reno- and hepato-protective effect of allopurinol after renal ischemia/reperfusion injury: Crosstalk between xanthine oxidase and peroxisome proliferator-activated receptor gamma signaling

Renal ischemia/reperfusion (I/R) is a common cause of acute kidney injury and remote liver damage is an ultimate negative outcome. Current treatments for I/R typically involve the use of antioxidants and anti-inflammatory to protect against oxidative stress and inflammation. Xanthine oxidase (XO) and PPAR-γ contribute to renal I/R-induced oxidative stress; however, the crosstalk between the two pathways remains unexplored. In the present study, we report that XO inhibitor, allopurinol (ALP), protects kidney and liver after renal I/R by PPAR-γ activation. Rats with renal I/R showed reduced kidney and liver functions, increased XO, and decreased PPAR-γ. ALP increased PPAR-γ expression and improved liver and kidney functions. ALP also reduced inflammation and nitrosative stress indicated by reduction in TNF-α, iNOS, nitric oxide (NO), and peroxynitrite formation. Interestingly, rats co-treated with PPAR-γ inhibitor, BADGE, and ALP showed diminished beneficial effect on renal and kidney functions, inflammation, and nitrosative stress. This data suggests that downregulation of PPAR-γ contributes to nitrosative stress and inflammation in renal I/R and the use of ALP reverses this effect by increasing PPAR-γ expression. In conclusion, this study highlights the potential therapeutic value of ALP and suggests targeting XO-PPAR-γ pathway as a promising strategy for preventing I/R injury.

Entacapone scavenges peroxynitrite and protects against kidney and liver injuries induced by renal ischemia/reperfusion in rats

BACKGROUND

Acute kidney injury (AKI), secondary to renal ischemia/reperfusion (I/R), is a serious problem associated with high mortality. The pathophysiology of AKI after renal I/R involves peroxynitrite production; hence, scavenging this metabolite may rescue AKI. Entacapone is a catechol-O-methyl transferase (COMT) inhibitor which elicits antioxidant activity by scavenging peroxynitrite. Therefore, we hypothesized that the peroxynitrite scavenging activity of entacopone protects against AKI after renal I/R injury in rats.

METHODS

Male Wistar rats were given either entacapone or a well-known peroxynitrite scavenger (FeTPPS) daily for 10 days before I/R procedures. I/R was induced by occluding both renal pedicles for 45 min followed by reperfusion for 24 h.

RESULTS

Pre-treatment with either entacapone or FeTPPS improved renal function as indicated by a significant reduction in serum creatinine and urea when compared to I/R group (P < 0.05). I/R injury increased renal levels of NO (4-folds, P < 0.05), iNOS (4-folds, P < 0.05), and 3-nitrotyrosine (5-folds, P < 0.05) compared to sham control. These effects were abrogated in animals pre-treated with entacapone or FeTPPS before being subjected to I/R (P < 0.05). In addition, entacapone or FeTPPS significantly inhibited I/R-induced elevation in renal TNF-α levels (78% and 58%, respectively) and caspase-3 activity (72% and 56%, respectively) indicating the reduction of both inflammation and apoptosis in the kidney (P < 0.05). The two drugs also improved kidney and liver functions in rats with renal I/R injury.

CONCLUSION

Our study showed that entacapone and FeTPPS protected against AKI and remote liver damage associated with renal I/R and this effect might be due to scavenging peroxynitrite and reducing nitrosative stress.