Anti-inflammatory effect of cyclosporin a on human skin mast cells

We have examined the effects of cyclosporin A (CsA) and cyclosporin H (CsH), which bind with different affinity to cyclophilin, to evaluate the role of this protein in the release of preformed (histamine) and de novo synthesized (prostaglandin D₂[PGD₂]) mediators of inflammatory reactions from human skin mast cells (HSMC). CsA (2.4-800 nM)inhibited (5-60%) histamine release from HSMC challenged with anti-IgE. CsA exerted little, if any, inhibitory effect on histamine release from HSMC challenged with compound A23187 and substance P, whereas it completely suppressed A23187-induced histamine release from human basophils. Inhibition of histamine release from HSMC challenged with anti-IgE was extremely rapid and was not abolished by washing (three times) the cells before anti-IgE challenge. CsA (2.4-800 nM) markedly inhibited (25-70%) the de novo synthesis of PGD₂ from HSMC challenged with anti-IgE. CsH, which has an extremely low affinity for cyclophilin, had no effect on skin mast-cell mediator release. These data suggest that CsA is a potent anti-inflammatory agent acting on HSMC, presumably by interacting with cyclophilin.