Regulation of Renal Transporters by Pro-Inflammatory Cytokines in Human Proximal Tubular Epithelial Cells: Identification of the Perpetrator and Mechanisms.

Infection and inflammation elevate circulating pro-inflammatory cytokines that can affect renal drug clearance. Accordingly, we sought to (i) quantify cytokine-mediated modulation of renal drug-metabolizing enzymes and transporters (DMETs) and (ii) identify the underlying mechanism(s). Fresh primary human proximal tubular epithelial cells (PTECs) were cultured on extracellular matrix-coated Transwells and exposed for 48 h to IL-6, IL-1β, TNF-α, IFN-γ, IL-4, or IL-10 (0.1 or 1 ng/mL), individually or as a cocktail. mRNA expression of 25 renal DMETs was quantified by RT-qPCR, and activity of OAT1-4, OCT2, and OCTN1 was measured. Mechanisms were probed using selective MAPK/NF-κB inhibitors targeting ERK, p38MAPK, JNK, and NF-κB. IL-6 classic and trans-signaling were evaluated using IL-6 and soluble IL-6 receptor (sIL-6Rα). IL-1β was the predominant modulator, downregulating OAT1-3, OCT2, OAT4, MATE2-K, MRP2, and OATP4C1 mRNA and upregulating OCTN1 and MRP3 mRNA. TNF-α downregulated OAT1-3 mRNA but had minimal effects on other transporters. Uptake activity changes mirrored mRNA directionality. MAPK/NF-κB blockade completely reversed IL-1β-driven OAT1-3 mRNA downregulation while reducing IL-6 secretion. JNK inhibition restored OAT1/3 mRNA, whereas p38MAPK inhibition attenuated OAT2 suppression. NF-κB inhibition reduced OCTN1 induction. In contrast, IL-6, sIL-6Rα, or their combination did not reproduce IL-1β-driven transporter changes. These data identify IL-1β as the principal driver of cytokine-mediated regulation of human renal transporters in PTECs via JNK/p38MAPK/NF-κB nodes. These mechanistic, exposure-verified data may inform future translational modeling of renal secretory clearance during inflammation.