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

IntroductionInfection and inflammation elevate circulating pro-inflammatory cytokines that can affect renal drug clearance. Accordingly, we sought to (i) quantify the extent of modulation of renal drug-metabolizing enzymes and transporters (DMETs) by cytokines and (ii) identify the mechanism(s) underlying these effects. MethodsFresh primary human proximal tubular epithelial cells (PTECs) were cultured on extracellular matrix-coated Transwells. PTECs were exposed every 24 h, for 48 h, to IL-6, IL-1{beta}, TNF-, IFN-{gamma}, 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. Individual activity of OAT1-4, OCT2, and OCTN1 was measured. To determine mechanisms of these effects, selective MAPK/NF-{kappa}B inhibitors (ERK [PD98059], p38MAPK [SB203580], JNK [SP600125], and NF-{kappa}B [PDTC]), individually or as a cocktail, were used. IL-6, soluble IL-6 receptor (sIL-6R), and IL-6 + sIL-6R were used to probe endogenous/exogenous IL-6 classic versus trans-signaling. ResultsIL-1{beta} was the predominant modulator, downregulating mRNA expression of OAT1-3, OCT2, OAT4, MATE2-K, MRP2, and OATP4C1, and upregulating mRNA expression of OCTN1 and MRP3. TNF- downregulated OAT1-3 mRNA expression to an extent similar to IL-1{beta}, but did not affect other transporters. Activity changes for the major uptake transporters mirrored mRNA directionality. MAPK/NF-{kappa}B blockade by the inhibitor cocktail reduced IL-6 secretion while completely reversing the IL-1{beta}-driven downregulation of OAT1-3 mRNA. JNK inhibition alone restored OAT1/3 mRNA. Inhibition of p38MAPK blunted OAT2 mRNA downregulation. OCTN1 mRNA induction required NF-{kappa}B. Downregulation of OAT4/OCT2 mRNA was largely MAPK/NF-{kappa}B-independent. IL-6 alone, sIL-6R alone, or IL-6 + sIL-6R did not reproduce IL-1{beta}-driven changes in transporter mRNA. ConclusionsIL-1{beta} is the principal driver of cytokine-mediated regulation of human renal transporters in PTECs via JNK/p38MAPK/NF-{kappa}B nodes. These mechanistic, exposure-verified data provide inputs for physiologically based pharmacokinetic predictions of renal secretory clearance and pathway-mediated drug interactions during inflammation. Visual Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/690608v1_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@177e372org.highwire.dtl.DTLVardef@1f56bc4org.highwire.dtl.DTLVardef@17612e3org.highwire.dtl.DTLVardef@d2291f_HPS_FORMAT_FIGEXP M_FIG C_FIG Translational StatementSystemic inflammation increases cytokine concentrations and alters drug pharmacokinetics. Yet, cytokine regulation of renal drug transporters remains poorly defined, even though the kidney clears many anti-infective drugs via active secretion. Using an optimized primary human proximal tubular epithelial cell model that preserves expression and function of major renal transporters, we found that IL-1{beta} is the predominant cytokine that downregulates the mRNA and activity of OAT1-3, OCT2, and OAT4, while upregulating the mRNA and activity of OCTN1. We further showed that IL-1{beta}-driven downregulation of OAT1/3 occurs through JNK signaling, OAT2 through p38MAPK, and OCTN1 through NF-{kappa}B. These data provide quantitative inputs for physiologically based pharmacokinetic models to predict how inflammation alters renal transporter-mediated drug clearance, informing dose adjustment and risk assessment for disease-drug and drug-drug interactions in patients with inflammatory kidney disease or systemic infections. They also highlight signaling nodes where anti-inflammatory therapies might inadvertently modify renal drug transport.