Norcantharidin modulates development of dendritic cells and prolongs skin allograft survival

To examine the effects of norcantharidin (NCTD) on development of human myeloid dendritic cells (DCs) in vitro and in skin allograft transplantation in vivo.

Human CD14(+) monocytes were isolated and triggered differentiation and maturation toward myeloid DCs with and without NCTD. The cell morphology, viability, cell death, expression of surface markers and co-stimulatory molecules, allostimulatory activity, and cytokine production were examined for characterization of DCs. The rejection of mice skin allograft model was used to translate the in vitro effect of cantharidin (CTD) and NCTD on DCs.

DCs developed in the presence of NCTD showed decreased viability, cell death with necrosis, and lower expression of CD1a and CD83. DCs triggered in the presence of NCTD possessed a greater allostimulatory activity in naive CD4(+)CD45RA(+) T cells. NCTD modulated DCs through calcineurin phosphatase but not through mammalian target of rapamycin or downstream molecule p70S6 kinase. In vivo, NCTD caused accumulation and co-localization of antigen-presenting cells and regulatory T cells in the interfollicular area of the recipients' spleens. CTD and NCTD prolonged skin allograft survival along with less severe histopathological inflammatory reactions. CTD, but not NCTD, treatment caused elevation of serum alanine aminotransferase and evident mortality of the recipients.

NCTD modulated the differentiation and maturation of human myeloid DCs and caused deviation of standard DC differentiation toward a tolerogenic phenotype through calcineurin phosphatase inhibition. In vivo, both drugs effectively prolonged skin allograft survival. NCTD was less toxic than CTD, and thus, has potential for development as an immunosuppressant for transplant rejection.