Dose-dependent stimulation/inhibition effects of cyclosporin A on lysosomal cathepsin activities in cultured proximal tubule cells.
The effects of cyclosporin A on the activities of lysosomal cysteine proteinases (cathepsin B, H, L+B) in LLC-Pk1 cells were investigated to elucidate their potential role in cyclosporin A-induced nephrotoxicity. Cyclosporin A at lower doses (0.1--1,000 ng/ml) stimulated cathepsin B, H, L+B. In contrast, at a higher dose (10,000 ng/ml), it inhibited these proteinase activities associated with a reduction in protein degradation. In line with the altered proteinase activities, cellular protein content was decreased at the lower dose (10 ng/ml) and increased at the higher dose. The higher dose of cyclosporin A also enhanced cellular lipid peroxide content after an exposure of 4 and 10 h. Co-incubation with superoxide dismutase (40 U/ml) did not ameliorate the inhibition of cathepsin B activity induced by the high dose of cyclosporin A. On the contrary, the calcium channel blocker verapamil (10(-6) M) prevented this inhibition. In conclusion, cyclosporin A exerts a dose-dependent biphasic effect on lysosomal cysteine proteinase activities. A rise in cytosolic Ca2+ concentration, but not an enhanced lipid peroxidation, may be involved in the suppression of cathepsin B activity induced by the higher dose of cyclosporin A. These studies raise the possibility that alterations of tubular proteinase activity may play a role in the cyclosporin A-induced nephrotoxicity.
Division of Nephrology, University of Wurzburg, Germany.
H
H
Ling
S
S
Vamvakas
L
L
Schaefer
L
L
Schramm
L
L
Paczek
J
J
Daemmrich
R M
RM
Schaefer
A
A
Heidland
D000001:Calcimycin / Q000494:pharmacology; D002401:Cathepsin B / Q000378:metabolism; D056655:Cathepsin H; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism*; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology* / Q000633:toxicity; D003546:Cysteine Endopeptidases / Q000378:metabolism; D010450:Endopeptidases; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000633:toxicity; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D008054:Lipid Peroxides / Q000378:metabolism; D008247:Lysosomes / Q000201:enzymology; D008858:Microscopy, Phase-Contrast; D011506:Proteins / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D004791:Enzyme Inhibitors; D008054:Lipid Peroxides; D011506:Proteins; D000001:Calcimycin; D016572:Cyclosporine; D014700:Verapamil; D013482:Superoxide Dismutase; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; D056668:Cathepsin L; D056655:Cathepsin H