Cyclosporine, but not FK 506 and rapamycin, enhances cell proliferation in mouse medullary thick ascending cultured cells

Cyclosporine stimulates Na+-K+-Cl- cotransport activity in cultured mouse medullary thick ascending limb cells

BACKGROUND

Cyclosporine (CsA) has been shown to alter the activity of plasma membrane transporters in kidney epithelial cells. In this study, we have investigated the effects of CsA on Na+,K+-ATPase and Na+-K+-Cl- cotransport activities in cultured cells derived from microdissected mouse medullary thick ascending limb (mTAL) cells.

METHODS

Experiments were carried out on subcultured confluent mouse TAL cells. Reverse transcription-polymerase chain reaction experiments showed that they expressed the mNKCC2 electroneutral Na+-K+-Cl- cotransporter and ROM-K1 and ROMK2 potassium channel mRNA. Western blotting also revealed the presence of the 40 kD ROMK protein using an anti-ROMK antibody. The effect of CsA (100 ng/mL) on ion transport was assessed by measuring the influx and efflux of rubidium (86Rb+) and 36Cl-, used as tracers of K+ and Cl- movements, on cells grown on Petri dishes or permeable filters.

RESULTS

CsA inhibited by 38% the ouabain-sensitive component of 86Rb+ influx mediated by the Na+,K+-ATPase pumps. CsA also increased by 38% the ouabain-resistant furosemide-sensitive component (Or-Fs) of 86Rb+ influx, reflecting the Na+-K+-Cl- cotransport activity and stimulated the basolateral efflux of 36Cl- from mTAL cells grown on filters. The CsA-stimulated basal efflux of Cl- was prevented by the basal addition of the Cl- channel blocker 5-nitro-2-(3-phenylpropylamino) benzoate (NPPB, 10-4 mol/L). Apical addition of the K+ channel blocking agent Ba2+ (10-4 mol/L) partially prevented the CsA-stimulated basal efflux of Cl-. Adding Ba2+ to the luminal side of cells grown on Petri dishes also prevented the rise in apical 86Rb+ efflux and the increased Or-Fs component of 86Rb+ influx caused by CsA.

CONCLUSION

These results indicated that CsA may stimulate the Na+-K+-Cl- cotransport activity and also suggested that this immunosuppressive agent may interfere in the recycling of apical K+ in this model of cultured mouse TAL cells.

Cyclosporine induces different responses in human epithelial, endothelial and fibroblast cell cultures

BACKGROUND

Nephrotoxicity, accelerated atherosclerosis, and graft vascular disease are common complications of cyclosporine long-term treatment characterized by a wide disruption of organ architecture with increased interstitial areas and accumulation of extracellular matrix (ECM). How cyclosporine induces these changes is not clear, but it is conceivable that they are the sum of changes induced at the cell level.

METHODS

We studied the effects of cyclosporine on human endothelial (HEC), epithelial (HK-2), and fibroblast (MRC5) cells. Cell proliferation was evaluated by cell counting, apoptosis and collagen production by enzyme-linked immunosorbent assay, and nitric oxide by measuring the concentration of nitrite/nitrate in the cell supernatant. (alpha1)I and (alpha2)IV collagen, matrix metalloprotease-9 (MMP9), and tissue inhibitors of metalloprotease-1 (TIMP-1) mRNA levels were measured by reverse transcription-polymerase chain reaction. Proteolytic activity was evaluated by zymography.

RESULTS

Cyclosporine showed a marked antiproliferative and proapoptotic effect on endothelial and epithelial cells. Fibroblast growth was not affected by cyclosporine. Nitric oxide was up-regulated by cyclosporine in epithelial cells and fibroblasts but not in endothelial cells. (alpha1)I and (alpha2)IV collagen synthesis was increased in cyclosporine-treated endothelial and epithelial cells, respectively. Proteolytic activity was increased in endothelial and epithelial cells. TIMP-1 mRNA was up-regulated by cyclosporine in fibroblasts.

CONCLUSIONS

Our results demonstrate that cyclosporine exhibits an antiproliferative effect on endothelial and epithelial cells. This effect is associated with induction of apoptosis probably via nitric oxide up-regulation in epithelial cell cultures. Cyclosporine treatment induces ECM accumulation by increasing collagen synthesis in endothelial and epithelial cells and reducing its degradation by up-regulating TIMP-1 expression in fibroblasts. We conclude that cyclosporine affects cell types differently and that the disruption of organ architecture is the result of multiple effects at the cell level.