The renin-angiotensin system blockade does not prevent renal interstitial fibrosis induced by aristolochic acids.

BACKGROUND: Experimental aristolochic acid nephropathy (AAN), characterized by interstitial fibrosis, tubular atrophy, and chronic renal failure, was reported after 35-day injections of aristolochic acids (AA) to salt-depleted male Wistar rats. The link between renal fibrosis and the renin-angiotensin system (RAS) in this model remains unknown. METHODS: We investigated the impact of sodium diets (low and normal), of RAS inhibition with enalapril (ENA) alone, or combined with candesartan (CSN) for 35 days, and ENA + CSN for 65 days on AAN development. At the end of each observation period, blood pressure and renal angiotensin-converting enzyme activity were measured, as well as renal functional impairment (plasma creatinine increase, proteinuria) and histologic lesions (interstitial fibrosis, monocytes/macrophages infiltration, myofibroblasts collagens type I and IV, proliferating cells). RESULTS: Sodium intake did not modify renal functional and morphologic impairment induced by AA. The RAS blockade by ENA or ENA + CSN in rats receiving AA did not result in any statistical difference in terms of renal failure, proteinuria, and interstitial fibrosis on day 35 or 65. On day 35, the monocytes/macrophages infiltration was significantly decreased by two-fold when ENA (P < 0.01) or ENA + CSN (P < 0.01) was given from day 0. CONCLUSION: Our data demonstrate that RAS modulation by salt depletion and pharmacologic blockade do not influence renal failure and interstitial fibrosis in the rat model of AAN. We suggest that pathways of interstitial renal fibrosis may be independent of RAS at least in some conditions.

Aristolochic acids induce chronic renal failure with interstitial fibrosis in salt-depleted rats.

Chinese-herb nephropathy (CHN) is a rapidly progressive renal fibrosis associated with the intake of a Chinese herb (Aristolochia fangchi) containing nephrotoxic and carcinogenic aristolochic acids (AA). This study attempted to reproduce the main features of human CHN (renal failure, tubular atrophy, and interstitial fibrosis) in a rat model similar to that of cyclosporin-induced nephropathy. Salt-depleted male Wistar rats received daily subcutaneous injections of either 1 mg/kg body wt AA (low-dose AA group), 10 mg/kg body wt AA (high-dose AA group), or vehicle (control group) for 35 d. On days 10 and 35, assessment of renal function, measurements of urinary excretion of glucose, protein, and leucine aminopeptidase, and histologic analyses were performed (six rats euthanized/group). High-dose AA induced glucosuria, proteinuria, and elevated serum creatinine levels and reduced leucine aminopeptidase enzymuria on days 10 and 35, whereas low-dose AA had no significant effect. Tubular necrosis associated with lymphocytic infiltrates (day 10) and tubular atrophy surrounded by interstitial fibrosis (day 35) were the histologic findings for the high-dose AA-treated rats. In both AA groups, urothelial dysplasia was also observed, as well as fibrohistiocytic sarcoma at the injection site. A short-term model of AA-induced renal fibrosis was established in salt-depleted Wistar rats. These results support the role of AA in human CHN and provide a useful model for examination of the pathophysiologic pathways of renal fibrosis.