Molecular pathological evaluation of clusterin in a rat model of unilateral ureteral obstruction as a possible biomarker of nephrotoxicity.

In the present study, to determine the validity of considering clusterin as a possible biomarker of nephrotoxicity, the expression and distribution of clusterin in the rat UUO kidney were investigated. Real-time RT-PCR revealed an immediate increase in the clusterin mRNA level in the kidney, within 6 hours after UUO, and also maintenance of the mRNA expression level from day-1 to day-3 was 60-fold higher in the UUO kidney than in the sham kidney. ISH analysis revealed clusterin mRNA signals in the UUO renal tubular epithelium, whereas no signal was observed in the sham kidney. Detection of clusterin-alpha and -beta was conducted using the subtype-specific antibodies, by both of western blotting and immunohistochemistry. Although clusterin-alpha was predominant in the UUO urine, only faint signals were noted at the brush border of the tubular epithelium or intraductal. On the other hand, strong signals of clusterin-beta were detected in the UUO kidney homogenate, and the molecule was localized in the renal tubular epithelium. These results suggest that clusterin was translated in the renal tubular epithelium after de novo expression induced by renal injury. Thus, detection of clusterin mRNA and clusterin-beta in the kidney or clusterin-alpha in the urine may be useful for predicting nephrotoxicity.