Comparison of the Pharmacological Efficacies of Immunosuppressive Drugs Evaluated by the ATP Production and Mitochondrial Activity in Human Lymphocytes

Abstract

The lymphocyte immunosuppressant sensitivity test (LIST) using patient peripheral lymphocytes can predict the therapeutic efficacy of immunosuppressive drugs used in renal transplantation. We have evaluated the pharmacological efficacy of drugs by using the LIST with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, which measures the cellular mitochondrial activity. The LIST with the MTT assay requires a relatively large amount of blood. As such, we developed a new assay for examining drug sensitivity with a CellTiter-Glo assay, which measures the amount of cellular ATP to help increase the assay's sensitivity and reduce the amount of blood needed. Renal transplant recipients generally receive either cyclosporine or tacrolimus, in addition to mycophenolate mofetil and methylprednisolone, as an immunosuppressive therapy to prevent acute rejection. We evaluated the pharmacological efficacy of these immunosuppressive agents with both the MTT and CellTiter-Glo assays using the peripheral blood mononuclear cells of 21 healthy volunteers. Furthermore, we also examined the relationship between these immunosuppressive agents' pharmacological efficacy and the results of the MTT and CellTiter-Glo assays. The IC50 values for cyclosporine, tacrolimus, mycophenolic acid, and methylprednisolone were significantly correlated between the MTT and CellTiter-Glo assays. The amount of blood cells required for LIST with the CellTiter-Glo assay was able to be reduced to 25% of the amount required for the previously established LIST with the MTT assay procedure. We concluded from these observations that the LIST with the CellTiter-Glo assay should be used instead of the MTT assay for carrying out individualized immunosuppressive therapy in renal transplantation patients.

Keywords: 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay; CellTiter-Glo assay; Lymphocyte immunosuppressant sensitivity test (LIST); Peripheral blood mononuclear cells (PBMCs).

Figure 1

Representative lymphocyte immunosuppressant sensitivity test (LIST) determined by MTT and CellTiter-Glo assays. Typical dose–response curves for cyclosporine (A), tacrolimus (B), mycophenolic acid (C), and methylprednisolone (D) on concanavalin A-stimulated blastogenesis of peripheral blood mononuclear cells (PBMCs) from one healthy subject estimated by the LIST, followed by MTT and CellTiter-Glo assay procedures.

Figure 2

Correlation between immunosuppressant drug IC₅₀ by MTT and CellTiter-Glo assays. (A) The relationship between the cyclosporine IC₅₀ values obtained by the LIST procedure with the MTT and CellTiter-Glo assays in the PBMCs of 21 healthy subjects. A significant correlation was observed between these values by the Kendall and Spearman coefficient correlation (r = 0.511 by Kendall test, p = 0.001; r = 0.683 by Spearman test, p = 0.001). (B) The relationship between the tacrolimus IC₅₀ values obtained by the LIST with the MTT and CellTiter-Glo assays in the PBMCs of 21 healthy subjects. A significant correlation was observed between these values by the Kendall and Spearman coefficient correlation (r = 0.555 by Kendall test, p = 0.001; r = 0.697 by Spearman test, p = 0.001). (C) The relationship between the mycophenolic acid IC₅₀ values obtained by the LIST with the MTT and CellTiter-Glo assays in the PBMCs of 21 healthy subjects. A significant correlation was observed between these values by the Kendall and Spearman coefficient correlation (r = 0.359 by Kendall test, p = 0.029; r = 0.508 by Spearman test, p = 0.019). (D) The relationship between the methylprednisolone IC₅₀ values obtained by the LIST procedure with the MTT and CellTiter-Glo assays in the PBMCs of 21 healthy subjects. A significant correlation was observed between these values by the Kendall and Spearman coefficient correlation (r = 0.489 by Kendall test, p = 0.002; r = 0.637 by Spearman test, p = 0.002).