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Cytochrome P450s metabolize the naturally occurring nephrotoxin aristolochic acid. Using liver-specific cytochrome P450 reductase-null mice we found that a low but lethal dose of aristolochic acid I was ineffective in wild-type mice. Induction of hepatic CYP1A by 3-methylcholanthrene pretreatment markedly increased the survival rate of wild type mice given higher doses and these mice were protected from aristolochic acid I-induced renal injury. Clearance of aristolochic acid I in null mice was slower compared to control and the 3-methylcholanthrene-pretreated wild type mice. The levels of aristolochic acid I in the kidney and liver were much higher in null mice but much lower in 3-methylcholanthrene-treated compared to control wild type mice. Hepatic microsomes from 3-methylcholanthrene-treated wild type mice had greater activity compared to untreated mice. Finally, aristolochic acid I was more cytotoxic than its major metabolite aristolactam I and this cytotoxicity was decreased in human renal tubular epithelial HK2 cells in the presence of a reconstituted hepatic microsome-cytosol (S9) system. These results indicate that hepatic P450s play an important role in metabolizing aristolochic acid I into less toxic metabolites and thus have a detoxification role in aristolochic acid I-induced kidney injury.

Background/Aims: Angiotensin (Ang) II plays vital roles in vascular inflammation and remodeling in hypertension. Phenotypic transformation of vascular smooth muscle cells (VSMCs) is a major initiating factor for vascular remodeling. The present study was designed to determine the roles of NLRP3 inflammasome activation in Ang II-induced VSMC phenotypic transformation and vascular remodeling in hypertension. Methods: Primary VSMCs from the aorta of NLRP3 knockout (NLRP3^-/-) mice and wild-type (WT) mice were treated with Ang II for 24 h. Subcutaneous infusion of Ang II via osmotic minipump for 2 weeks was used to induce vascular remodeling and hypertension in WT and NLRP3^-/- mice. Results: NLRP3 gene deletion attenuates Ang II-induced NLRP3 inflammasome activation, phenotypic transformation from a contractile phenotype to a synthetic phenotype and proliferation in primary mice VSMCs. Ang II-induced hypertension and vascular remodeling in WT mice were attenuated in NLRP3^-/- mice. Furthermore, Ang II-induced NLRP3 inflammasome activation, phenotypic transformation and proliferating cell nuclear antigen (PCNA) upregulation were inhibited in the media of aorta of NLRP3^-/- mice. Conclusions: NLRP3 inflammasome activation contributes to Ang II-induced VSMC phenotypic transformation and proliferation as well as vascular remodeling and hypertension.