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FK506-induced kidney tubular cell injury
A Moutabarrik1, M Ishibashi, M Fukunaga
1Department of Urology, Osaka University Hospital, Japan.
Abstract:
Some renal changes associated with cyclosporine, such as tubular vacuolization and glomerular thrombosis, have also been reported with FK506. Furthermore, FK506 therapy is associated with a decrease in glomerular filtration rate and renal plasma flow and an increase in renal vascular resistance. We studied the in vitro tubular cell sensitivity to FK506 in comparison with CsA, the ultrastructural changes induced by FK506 and CsA, and the effect of both drugs on tubular cell growth in vitro. We also investigated whether FK506 and CsA induced endothelin-1 (ET-1) secretion of cultured tubular cells and whether this stimulatory effect coincided with a change in the endothelin systemic synthesis. Exposure of tubular cells to high concentrations of FK506 or CsA (10, 50, 100 microM) induced a time- and dose-dependent cell injury in vitro. The damage induced by FK506 and CsA was characterized by a direct cytotoxic effect on tubular cells, as expressed by release of 3H thymidine from prelabeled cells, N-acetyl-beta-D-glucosaminidase release, and cell detachment. Ultrastructural changes (vacuolizations, swelling, and mitochondrial enlargement) and inhibition of the growth of cultured tubular cells were also observed at high concentrations of FK506 and CsA. Low concentrations of FK506 and CsA (1, 0.1, 0.01, 0.001 microM) were not cytotoxic and induced only a minimal inhibitory effect on the growth of tubular cells in vitro. We demonstrated that FK506 (1, 0.1, 0.01 microM) time-dependently stimulated the secretion of endothelin by cultured tubular cells. CsA 10, 1, 0.1, 0.01 also exerted an enhancing effect on ET-1 secretion in cultured tubular cells. We observed that the concentration of CsA that induced the most important enhancing effect was 10 or 100 times higher than that required for FK506 to observe the same effect. The concentrations of FK506 or CsA that induced ET-1 secretion were not cytolytic for tubular cells in vitro. FK506- or CsA-treated rats showed an increase in serum level of ET-1 in comparison with the control. Through the stimulatory effect on endothelin secretion by tubular cells, FK506 and CsA may induce a perturbation of renal hemodynamics. Concentrations of FK506 and CsA, higher than established serum levels but close to those reached in tissues, are cytotoxic for tubular cells and induced ultrastructural changes and a significant delayed regeneration.
Insights
Both FK506 and cyclosporine (CsA) can cause kidney damage by affecting tubular cells and increasing endothelin-1 (ET-1) secretion. High drug concentrations are cytotoxic, while lower concentrations stimulate ET-1, potentially altering renal hemodynamics.
Area of Science:
- Nephrology
- Pharmacology
- Cell Biology
Background:
- FK506 and cyclosporine (CsA) are immunosuppressants with known nephrotoxic effects.
- Renal changes like tubular vacuolization and glomerular thrombosis are associated with both drugs.
- FK506 therapy can decrease glomerular filtration rate and renal plasma flow, increasing renal vascular resistance.
Purpose of the Study:
- To compare the in vitro sensitivity of tubular cells to FK506 and CsA.
- To investigate the ultrastructural changes induced by FK506 and CsA in tubular cells.
- To determine the effect of FK506 and CsA on tubular cell growth and endothelin-1 (ET-1) secretion.
Main Methods:
- In vitro exposure of cultured tubular cells to varying concentrations of FK506 and CsA.
- Assessment of cell injury through 3H thymidine release, N-acetyl-beta-D-glucosaminidase release, and cell detachment.
- Evaluation of ultrastructural changes via microscopy.
- Measurement of ET-1 secretion in cultured cells and serum levels in treated rats.
Main Results:
- High concentrations (10-100 microM) of FK506 and CsA induced time- and dose-dependent tubular cell injury, characterized by cytotoxicity, ultrastructural changes, and inhibited growth.
- Low concentrations (0.001-1 microM) of FK506 and CsA were not cytotoxic but stimulated ET-1 secretion.
- FK506 and CsA treatment in rats led to increased serum ET-1 levels.
- CsA required higher concentrations than FK506 to achieve similar ET-1 secretion enhancement.
Conclusions:
- FK506 and CsA exhibit direct cytotoxicity to tubular cells at high concentrations, causing ultrastructural damage and delayed regeneration.
- Both drugs stimulate ET-1 secretion from tubular cells at concentrations below cytotoxic levels.
- The stimulation of ET-1 secretion by FK506 and CsA may contribute to renal hemodynamic perturbations.
- These findings highlight the complex nephrotoxic mechanisms of FK506 and CsA, involving both direct cellular damage and modulation of vasoactive substances.