Extracellular FKBP12 Inhibits Tacrolimus Translocation to Peripheral Blood Mononuclear Cells Reducing...

Area of Science:

• Immunology
• Pharmacology
• Transplantation Medicine

Background:

• Tacrolimus is a vital immunosuppressant in transplantation, requiring precise blood concentration management.
• Peripheral blood mononuclear cell (PBMC) tacrolimus levels may better indicate immunosuppressive activity than whole blood levels.
• Extracellular FK506-binding protein (FKBP)12, a tacrolimus-binding protein, was investigated for its role in T-cell suppression.

Purpose of the Study:

• To investigate the impact of extracellular FKBP12 on tacrolimus-mediated T-cell suppression.
• To understand how extracellular FKBP12 influences tacrolimus accumulation within PBMCs.
• To explore the implications for therapeutic drug monitoring in transplantation.

Main Methods:

• Human whole blood and purified PBMCs were stimulated to induce cytokine production.
• Tacrolimus accumulation in PBMCs was quantified using supercritical fluid chromatography-tandem mass spectrometry.
• The effect of varying extracellular FKBP12 concentrations on tacrolimus activity was assessed.

Main Results:

• Tacrolimus inhibited cytokine release in a dose-dependent manner.
• Extracellular FKBP12 significantly attenuated tacrolimus's inhibitory effect on cytokine release.
• Extracellular FKBP12 reduced intracellular tacrolimus concentrations, indicating binding and reduced T-cell uptake.

Conclusions:

• Extracellular FKBP12 impacts tacrolimus pharmacodynamics, affecting drug distribution and efficacy.
• Monitoring PBMC tacrolimus concentrations is important.
• Considering extracellular FKBP12 levels may refine therapeutic drug monitoring and personalize immunosuppressive therapy in transplant recipients.