4-Methylpyrazole-mediated inhibition of Cytochrome P450 2E1 protects renal epithelial cells, but not bladder cancer cells, from cisplatin toxicity.

Cisplatin is an effective chemotherapeutic drug for the treatment of bladder cancer, though cisplatin-induced nephrotoxicity (CIN) occurs in approximately 20-30% of patients, limiting its clinical use. Evidence has shown that cytochrome P450 2E1 (CYP2E1), a drug metabolism enzyme expressed in proximal tubules, mediates the production of reactive oxygen species (ROS) during cisplatin-induced injury. Previously, we showed that the repurposed drug 4-methylpyrazole (4MP; fomepizole) blocks CYP2E1 activity and prevents acetaminophen-induced liver injury. Here, we investigated the potential protective effects of 4MP against CIN. Male and female C57BL/6J mice were treated with a single 20 mg/kg dose of cisplatin for 3 days (acute) or 9 mg/kg/week for 4 weeks (repeated dosing regimen) with or without a co-treatment of 50 mg/kg 4MP. Our findings revealed that acute treatment with cisplatin induced severe histological tubular damage and elevated plasma BUN and creatinine levels in male mice, but not in female mice. This difference correlated with higher basal CYP2E1 expression in the kidneys of male mice compared to female mice. We also found that cisplatin increased renal CYP2E1 activity and that inhibition of CYP2E1 with 4MP significantly reduced cisplatin induced cell death in male mice and primary normal human kidney cells. By contrast, human bladder cancer cells do not express CYP2E1, and treatment with 4MP did not interfere with cisplatin anti-cancer effects in human bladder cancer HTB9 cells. This study highlights the critical role of CYP2E1 in CIN and suggests that its inhibition with 4MP in the kidney is a potential prophylactic therapeutic option to prevent CIN in bladder cancer patients without affecting its anti-neoplastic effect.