Cytotoxic and genotoxic effects of high concentrations of the immunosuppressive drugs cyclosporine and tacrolimus in MRC-5 cells

Abstract

Immunosuppressive drugs are used to suppress immune system activity in transplant patients and reduce the risk of organ rejection. The present study evaluated the potential cytotoxic, genotoxic and mutagenic of the immunosuppressive drugs cyclosporine (CsA) and tacrolimus (FK-506) on normal human fibroblasts (MRC-5 cells). Based on plasma concentrations of the immunosuppressive drugs, which were obtained from the records of kidney transplant patients at the Kidney Institute of Londrina, Brazil, 11 concentrations of each immunosuppressive were chosen to evaluate cell viability using the MTT assay. From these results, CsA and FK-506 concentrations of 135, 300, 675, and 1520ng/ml and 8, 16, 24, and 32ng/ml, respectively, were evaluated using (i) the comet assay, (ii) the nuclear division index (NDI), (iii) the micronucleus test (CBMN) and (iv) cell proliferation curves generated by quantifying cell numbers and protein levels. In this study, 1520 to 3420ng/ml CsA decreased cell viability after 48h of exposure. Genotoxic effects were observed only with a concentration of 1520ng/ml after 3h of exposure and with concentrations of 675 and 1520ng/ml after 24h of exposure. Mutagenic effects were observed only for the concentration of 1520ng/ml. FK-506 decreased cell viability after 72h of exposure for concentrations up to 20ng/ml; genotoxic effects were observed with concentrations up to 8ng/ml for both treatment times (3 and 24h) and mutagenic effects were observed with concentrations of 24 and 32ng/ml after 24h of treatment. The cell proliferation curves demonstrated the absence of cytostatic effects of these drugs, and these data were confirmed by the NDI analysis. Our results suggest that concentrations lower than 300ng/ml of CsA and 16ng/ml of FK-506 are safe for use, as they did not induce genotoxic and mutagenic damage or affect MRC-5 cell viability and proliferation.