Study on toxicological aspects of crystal-mediated nephrotoxicity induced by FYX-051, a xanthine oxidoreductase inhibitor, in rats

Nephroprotective effects of (-)-α-bisabolol against ischemic-reperfusion acute kidney injury

BACKGROUND

Ischemia/reperfusion (I/R) in kidney is commonly related to acute kidney injury (AKI), essentially through oxidative stress. (-)-α-Bisabolol is a sesquiterpene isolated from the essential oil of a variety of plants, including chamomile, which has important antioxidant activity.

STUDY DESIGN

This study intends to evaluate the nephroprotective activity of (-)-α-bisabolol (Bis) in both in vivo and in vitro models of kidney I/R.

METHODS

Male Wistar rats were submitted to right nephrectomy, followed by ischemia by clamping of the renal artery in the left kidney for 60min. and 48h of reperfusion. The animals were treated orally with Bis (100mg/kg) or vehicle for 24h after reperfusion, and placed in metabolic cages, to evaluate water consumption, diuresis, urinary osmolality, classic biochemical markers and urinary KIM-1 (kidney injury molecule-1). Additionally, the left kidney was collected for histological evaluation and determination of glutathione (GSH) and Thiobarbituric Acid Reactive Substances (TBARS) levels. Tubular epithelial cells LLC-MK2 were used to assess Bis effect on in vitro I/R, by MTT assay. It was performed the cellular respiration tests by flow cytometry: evaluation of the production of cytoplasmic reactive oxygen species by DCFH-DA assay and mitochondrial transmembrane potential analysis with the dye rhodamine 123.

RESULTS

I/R caused alterations in diuresis, water intake, urinary osmolality, plasmatic creatinine, urea and uric acid, creatinine clearance, proteinuria and microalbuminuria. Treatment with Bis ameliorated all of these parameters. Also, KIM-1 level enhanced by I/R was also diminished in groups treated with Bis. The histological examination showed that Bis attenuated the morphological changes caused by I/R, markedly vascular congestion and intratubular deposits of proteinaceous material. Additionally, Bis was able to reduce the changes observed in TBARS and GSH levels in kidney tissue. In in vitro assay, Bis was capable to partially protect the cell lineage against cell damage induced by I/R.

CONCLUSION

(-)-α-Bisabolol has a nephroprotective effect in kidney I/R, with antioxidant effect. Moreover, this result seems to be associated to a direct protective effect on tubular epithelia.

Mechanistic insights into xanthine oxidoreductase from development studies of candidate drugs to treat hyperuricemia and gout

Xanthine oxidoreductase (XOR), which is widely distributed from humans to bacteria, has a key role in purine catabolism, catalyzing two steps of sequential hydroxylation from hypoxanthine to xanthine and from xanthine to urate at its molybdenum cofactor (Moco). Human XOR is considered to be a target of drugs not only for therapy of hyperuricemia and gout, but also potentially for a wide variety of other diseases. In this review, we focus on studies of XOR inhibitors and their implications for understanding the chemical nature and reaction mechanism of the Moco active site of XOR. We also discuss further experimental or clinical studies that would be helpful to clarify remaining issues.