Effect of cyclosporins A, G, and H on normal and ichthyotic keratinocyte growth in culture

Influence of Cyclosporin A on human gingival keratinocytes in vitro

PURPOSE

Gingival hyperplasia is a well known side effect of Cyclosporine A therapy. The aetiology of this is not totally understood and there is debate whether it is hyperplasia of the gingival epithelium or of the submucosal connective tissue, or both, and what roles play factors like age and gender of the patients, duration and dosage of the drug.

MATERIAL AND METHODS

The influence of different Cyclosporine A concentrations (10(-6) g/ml; 5 x 10(-7) g/ml; 10(-9) g/ml) and of no medication (controls) on growth and proliferation of cultured human gingival keratinocytes was investigated after a culture period of 3, 6 and 9 days. Cell proliferation was assessed by counting anti Ki-67 stained nuclei, cell growth by counting total number of nuclei and by the EZ4U-assay.

RESULTS

There was no significant correlation of the cell proliferation rate and cellular growth with either gender (p > 0.568) or duration of medication (p > 0.876); but Cyclosporine A concentration showed a highly significant influence on cellular growth (p = 0.0001). Inhibition of cell growth was dependent on drug dosage, but a low concentration of 10(-9) g/ml even stimulated cell growth.

CONCLUSIONS

There is evidence that Cyclosporine A in low concentrations (10(-9) g/ml as applied in long-term therapy) stimulates gingival keratinocyte growth and therefore might be related to hyperplasia of the gingiva. However, high Cyclosporine A concentrations may inhibit cell growths and factors like gender of the patient did not show any influence in-vitro.

Cyclosporine A up-regulates angiotensin II receptors and calcium responses in human vascular smooth muscle cells

BACKGROUND

The most widely used immunosuppressive drug for preventing graft rejection and treating autoimmune diseases is currently cyclosporine A (CsA). However, CsA also causes vasoconstriction, which is considered to be at the origin of CsA-induced nephrotoxicity and hypertension. To evaluate the cellular basis for these side effects, we studied the influence of CsA on the regulation of the free cytosolic Ca2+ concentration ([Ca2+]c) in cultured human vascular smooth muscle cells (SMCs).

METHODS

SMCs were isolated from the medial layer of human aorta. [Ca2+]c regulation was studied by fluorimetry with fura 2 and by measuring 45Ca2+ effluxes. Angiotensin II (Ang II) receptors were detected by [125I]Ang II binding.

RESULTS

Pretreatment of human SMCs for 24 hours with CsA in its therapeutic concentration range (0. 1 to 10.0 microM) had no effect on basal [Ca2+]c, but increased the [Ca2+]c elevation and 45Ca2+ efflux when cells were stimulated with Ang II. Half-maximal effects occurred at approximately 1 microM CsA. The CsA effects on [Ca2+]c were accompanied by a nearly twofold increase in Ang II receptor number, whereas no change in affinity to Ang II was observed. CsA did not alter endothelin-1- or thapsigargin-induced 45Ca2+ efflux. Increases in both Ca2+ responses and [125I]Ang II binding were attenuated by the transcriptional inhibitor actinomycin D. The effects of CsA did not appear to be mediated by calcineurin inhibition because cyclosporine H, which is not immunosuppressive, also increased the Ang II-induced 45Ca2+ efflux.

CONCLUSION

These data suggest that CsA preferentially up-regulates the transcription of Ang II receptors, which very likely leads to vasoconstriction in vivo and could be at the origin of CsA-induced hypertension and nephrotoxicity in humans.

Comparative evaluation of in vitro and in vivo immunosuppressive potential of cyclosporin G with cyclosporin A and FK-506

Cyclosporin G (CsG), a promising cyclosporin A (CsA) analogue, was examined and compared with two reference immunosuppressive drugs: CsA and FK-506, regarding their inhibitory effects on different lymphocyte activation pathways as well as on graft-versus-host reaction (GvHR) across differences at major or minor histocompatibility loci. The results showed that, at different concentrations, CsG efficiently inhibited proliferation induced by alloantigens (mixed lymphocyte culture), mitogens (concanavalin A, pokeweed mitogen) and the combination of phorbol myristate acetate + ionomycin, to the same extent as observed with CsA and FK-506. It was also shown that CsG exhibited the same strong inhibitory effects as the two other immunosuppressants upon stimulation triggered by viral (MLs-1a) or bacterial (staphylococcal enterotoxin B) superantigen. Determination of IL-2 activity in the supernatant of MLC also confirmed similar strong inhibitory effects, exerted by CsG compared to CsA and FK-506. In systemic and local GvHR across major or minor histocompatibility barriers, CsG as well as CsA and FK-506 presented an equivalent immunosuppressive potential. In conclusion, from various experiments involving different modes of activation, it was shown that CsG was as strongly immunosuppressive as CsA and FK-506.