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Drug Interactions

Organic Anion Transporter 3 Mediated Interactions in a Renal Proximal Tubule Epithelial Cellular Model: Effects of Mycophenolate and Prednisolone

121: Organic Anion Transporter 3 Mediated Interactions in a Renal Proximal Tubule Epithelial Cellular Model: Effects of Mycophenolate & Prednisolone

Monday, September 9, 2024
5:00 PM – 7:00 PM ET
Statement of Purpose, Innovation or Hypothesis: Kidney transplant patients are prescribed life-long maintenance immunosuppression for preventing graft rejection. Mycophenolic acid (MPA) and prednisone (which is converted to the active drug prednisolone) are commonly administered as combinatorial anti-rejection therapy in transplant recipients. This patient population is also subjected to polypharmacy, being prescribed a variety of medications for the management of co-morbid conditions such as cardiovascular disease and infectious complications. A large proportion of co-administered medications are excreted by the organic anion transporter 3 (OAT3) as a part of their renal clearance process. The objective of this study was to investigate the effects of immunosuppressants (i.e., MPA and prednisolone) on the uptake activities of OAT3 in a human renal conditionally immortalized proximal tubule epithelial cellular model (ciPTEC).

Description of Methods & Materials: ciPTEC (Cell4Pharma) cells overexpressing OAT3 at passages 51-55 were seeded into 24-well plates (155,800 cells per well). Fluorescein (0.4 – 5.6 µg/mL exposure over 10 minutes) uptake into ciPTEC cells was used as a selective probe marker for OAT3 activities. To test the inhibition and induction effects of immunosuppressants on OAT3-mediated fluorescein uptake, ciPTEC cells were co-incubated with MPA (4 µg/mL for 10 minutes; physiological concentration; potential inhibitor) or pre-incubated with prednisolone (0.2, 0.8, 2.0 µg/mL for 3 days, physiological concentrations; potential inducer). As positive inhibitory controls, cells were co-exposed to fluorescein and known OAT3 inhibitors (i.e., probenecid 25.7 µg/mL or diclofenac 124.1 µg/mL for 10 minutes). Fluorescein uptake was quantified by a fluorescence microplate reader (excitation 485nm / emission 535nm). The data were expressed as mean ± standard deviation.

Data & Results: Concentration-dependent uptake of fluorescein into ciPTEC OAT3 cells was evident, and 1.1 µg/mL over 10 minutes represented the initial velocity condition. MPA reduced the fluorescein uptake by 31.2 ± 5.1% (p < 0.005, N=4), whereas probenecid and diclofenac reduced fluorescein uptake by 41.1±7.7% (p < 0.001, N=4) and 42.5±1.3% (p < 0.0001, N=4), respectively, when compared to the control. Prednisolone (0.2, 0.8, and 2.0 µg/mL, N=4 for each concentration) pre-treatment for 3 days increased fluorescein uptake by 25.6±14.7% (p > 0.05), 27.3±15.6% (p > 0.05), and 44.2±8.4% (p < 0.05) compared to the control, respectively. 

Interpretation, Conclusion or Significance: We have developed a mechanistic in vitro renal model suitable for characterizing the OAT3-mediated pharmacokinetic interactions involving commonly prescribed immunosuppressants. Further investigations are ongoing to determine the enzyme kinetics of OAT3 modulation and the effects of MPA or prednisolone on specific drugs that are frequently co-prescribed in kidney transplant recipients.

Disclosures:

Citations/References:

Additional Information/Authors: Not Applicable