Proximal Tubular Vacuolization and Hypersensitivity to Drug-Induced Nephrotoxicity in Male Mice With Decreased Expression of the NADPH-Cytochrome P450 Reductase

The effect of variations in the expression of cytochrome P450 reductase (CPR or POR) is determined in mice with decreased POR expression to identify potential vulnerabilities in people with low POR expression. There is an age-dependent appearance of increasing vacuolization in the proximal tubules of the renal cortex in 4- to 9-month-old male (but not female) Cpr-low (CL) mice. These mice have low POR expression in all cells of the body and upregulation of lysosome-associated membrane protein 1 expression in the renal cortex. Vacuolization is also seen in extrahepatic CL and extrarenal CL male mice, but not in mice with tissue-specific Por deletion in liver, intestinal epithelium, or kidney. The occurrence of vacuolization is accompanied by increases in serum blood-urea-nitrogen levels. Male CL mice are hypersensitive to cisplatin- and gentamicin-induced renal toxicity at 3 months of age, before proximal tubular (PT) vacuoles are detectable. At doses that do not cause renal toxicity in wild-type mice, both drugs cause substantial increases in serum blood-urea-nitrogen levels and PT vacuolization in male but not female CL mice. The hypersensitivity to drug-induced renal toxicity is accompanied by increases in circulating drug levels. These novel findings demonstrate deficiency of renal function in mice with globally reduced POR expression and suggest that low POR expression may be a risk factor for drug-induced nephrotoxicity in humans.