Shedding and repair of renal cell membranes following drug-induced nephrotoxicity in humans.

Nephrotoxic drugs may account for approximately at least 20% of clinically observed cases of acute renal failure in whom tubular lethal or sublethal damage is a predominant finding. Acute toxic tubular cell injury is characterized by loss of cellular polarization, intrinsic energy deficiency, calcium overload, release of toxic proteases and free oxygen radicals, derangement of the cytoskeleton, and vacuolar transformation of brush border microvilli. These events may finally lead to irreversible cell death. Shedding of membrane enzymes and cytoskeletal components in urine (kidney tissue proteinuria) may serve as a noninvasive early marker for assessing tubular cell injury. Successful recovery of renal function depends on early repair of lethally or sublethally damaged nephrons, in which intrinsic nephrogenic adaptive and proliferative responses cooperate in concert with auto/para/-juxtacrine growth promoting factors and cytokines. Exogenously administered growth factors may enhance renal cell recovery, as shown in animal models. Increased expression of immediate early genes in tubular cells after renal injury reflects the ongoing mitogenic activity necessary for reepithelialization and remodeling (new, polarized, differentiated cells). Further progress in understanding the molecular mechanisms of renal tubular injury will probably influence the diagnostic modalities and therapeutic approaches to acute drug induced renal failure.