Effect of oxidant stress on growth factor stimulation of proliferation in cultured human proximal tubule cells.

Restoring kidney function after injury involves cell migration and proliferation, processes that are yet to be precisely defined. Because epidermal growth factor (EGF) and insulin-like growth factor-1 (IGF-1) promote recovery from acute renal failure, we used SV-40 immortalized human proximal tubule cells to examine the effects of these growth factors on cell proliferation after peroxide injury (1.5 mM for 1 hour). ATP levels decreased to approximately 15% of control values immediately after injury but returned to nearly normal levels after 4 hours of recovery. Under control conditions, both EGF and IGF-1 stimulated proliferation and their effects were additive. However, 20-24 hours after injury, while IGF-1 stimulated proliferation, EGF was no longer effective nor was the combination of EGF and IGF-1. Although the EGF receptor was decreased 20 hours after injury, the lack of IGF-1 effect could not be explained by loss of the IGF-1 receptor, which remained unchanged after peroxide injury. Thus, the mechanism responsible for the blunting of the IGF-1 effect on proliferation following injury remains speculative. However, we conclude that the effects of growth factors under control conditions may not predict their effects after injury.

The actin cytoskeleton and integrin expression in the recovery of cell adhesion after oxidant stress to a proximal tubule cell line (JTC-12).

This study examines the role of the actin cytoskeleton and integrin expression in the recovery of cell adhesion in the proximal tubule cell line JTC-12 after peroxide injury. The cells were exposed to 10, 20, or 50 mM hydrogen peroxide for 10 min and then allowed to recover. Viability measurements by trypan blue exclusion confirmed that the injury was largely nonlethal with 85% viability at 1 h even at 50 mM peroxide. ATP levels fell immediately after the peroxide incubation in all groups to approximately 10% of normal, but already showed some recovery by 1 h and full recovery in the 10 and 20 mM groups by 24 h. Cell adhesion to extracellular matrix immediately after injury was depressed at 20 and 50 mM peroxide, but by 12 h was abnormal only at 50 mM peroxide and at 24 h was essentially normal at all peroxide concentrations. Immediately after exposure to 10 mM peroxide, there were subtle abnormalities in the actin cytoskeleton (thickening of fibrils) as assessed by phalloidin staining, with more pronounced effects at 20 and 50 mM. At 1 h, many cells showed collapse of the actin cytoskeleton to the periphery. There was some recovery at 4 h; by 12 h, the actin cytoskeleton showed further recovery, although was still abnormal (coarsened microfilaments), especially at 20 and 50 mM peroxide. By 24 h, the actin cytoskeleton showed only subtle coarsening. Integrin surface expression was assessed by flow cytometry. The alpha6 subunit on cells exposed to 20 mM peroxide was unchanged at 1 h and 4 h, but by 12 h had increased to 118.5+/-4.5% and by 24 h to 146+/-13.4% of control levels. The expression of the beta1 and alphaVbeta3 integrins remained unchanged. Thus, despite coarsening of the actin cytoskeleton and depressed ATP levels, cell adhesion recovered from oxidant stress. Abnormal cell adhesion after injury was not a consequence of a decrease in integrin expression, and recovery of cell adhesion was not a consequence of the modest and selective increase in integrin expression.

HIV-associated renal disease in London hospitals.

We report experience from London hospitals which further illustrates the heterogeneous nature of HIV-associated nephropathy (HIVAN). Nineteen HIV-positive patients underwent renal biopsy from 1992 to 1994. Fourteen were male, five female. Eleven were Afro-Caribbean, 7 Caucasian and 1 Asian. Eleven patients had classical HIVAN with proteinuria, rapidly progressive renal failure and features of focal and segmental glomerulosclerosis (FSGS) on renal biopsy, and three of these had associated tubulo-interstitial nephritis (TIN). One further patient had TIN and tubular changes suggestive of HIVAN but no glomeruli were present in the biopsy. Other biopsy findings were of focal proliferative glomerulonephritis and TIN (1 patient), pauci-immune crescentic glomerulonephritis and TIN (1 patient), membranous nephropathy (1 patient), membranoproliferative nephropathy (1 patient) and haemolytic uraemic syndrome (2 patients). Of 11 patients with FSGS, seven died with median survival of 8 months (range 23 days-46 months) and five are still alive after median follow-up of 18 months (range 10-22 months). Of patients with glomerular disease other than FSGS, five died, with median survival of 3 months (range 1-27 months) and two have survived (10 and 27 months, respectively). Thirteen patients had renal failure, 10 of whom had FSGS. In 10 cases renal failure was acute and in two was the presenting feature of HIV infection. Thirteen patients underwent renal replacement therapy. Four received haemodialysis, and all died within one month. Nine patients received CAPD. Two were able to discontinue dialysis. Of the remaining seven, five died with median survival of 8 months (range 1.3-40 months) and two are alive 1 and 10 months after beginning dialysis.(ABSTRACT TRUNCATED AT 250 WORDS)