A Human Renal Proximal Tubule Cell Line with Stable Organic Anion Transporter 1 and 3 Expression Predictive for Antiviral-Induced Toxicity

Membrane transporters and receptors are responsible for balancing nutrient and metabolite levels to aid body homeostasis. Here, we report that proximal tubule cells in kidneys sense elevated endogenous, gut microbiome-derived, metabolite levels through EGF receptors and downstream signaling to induce their secretion by up-regulating the organic anion transporter-1 (OAT1). Remote metabolite sensing and signaling was observed in kidneys from healthy volunteers and rats in vivo, leading to induced OAT1 expression and increased removal of indoxyl sulfate, a prototypical microbiome-derived metabolite and uremic toxin. Using 2D and 3D human proximal tubule cell models, we show that indoxyl sulfate induces OAT1 via AhR and EGFR signaling, controlled by miR-223. Concomitantly produced reactive oxygen species (ROS) control OAT1 activity and are balanced by the glutathione pathway, as confirmed by cellular metabolomic profiling. Collectively, we demonstrate remote metabolite sensing and signaling as an effective OAT1 regulation mechanism to maintain plasma metabolite levels by controlling their secretion.

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Liver X receptor activation downregulates organic anion transporter 1 (OAT1) in the renal proximal tubule

AJP Renal Physiology ◽

10.1152/ajprenal.00341.2011 ◽

2012 ◽

Vol 302 (5) ◽

pp. F552-F560 ◽

Cited By ~ 11

Author(s):

Suticha Kittayaruksakul ◽

Sunhapas Soodvilai ◽

Nithi Asavapanumas ◽

Chatchai Muanprasat ◽

Varanuj Chatsudthipong

Keyword(s):

Proximal Tubule ◽

Organic Anion ◽

Basolateral Membrane ◽

Receptor Activation ◽

Inhibitory Effect ◽

Renal Proximal Tubule ◽

Organic Anion Transporter ◽

Anion Transporter ◽

X Receptors ◽

Lxr Agonists

Liver X receptors (LXRs) play an important role in the regulation of cholesterol by regulating several transporters. In this study, we investigated the role of LXRs in the regulation of human organic anion transporter 1 (hOAT1), a major transporter localized in the basolateral membrane of the renal proximal tubule. Exposure of renal S2 cells expressing hOAT1 to LXR agonists (TO901317 and GW3965) and their endogenous ligand [22(R)-hydroxycholesterol] led to the inhibition of hOAT1-mediated [14C]PAH uptake. This inhibition was abolished by coincubation of the above agonists with 22(S)-hydroxycholesterol, an LXR antagonist. Moreover, it was found that the effect of LXR agonists was not mediated by changes in intracellular cholesterol levels. Interestingly, the inhibitory effect of LXRs was enhanced in the presence of 9- cis retinoic acid, a retinoic X receptor agonist. Kinetic analysis revealed that LXR activation decreased the maximum rate of PAH transport ( Jmax) but had no effect on the affinity of the transporter ( Kt). This result correlated well with data from Western blot analysis, which showed the decrease in hOAT1 expression following LXR activation. Similarly, TO901317 inhibited [14C]PAH uptake by the renal cortical slices as well as decreasing mOAT1 protein expression in mouse kidney. Our findings indicated for the first time that hOAT1 was downregulated by LXR activation in the renal proximal tubule.

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Organic anion transporter 3 (Slc22a8) is a dicarboxylate exchanger indirectly coupled to the Na+gradient

AJP Renal Physiology ◽

10.1152/ajprenal.00405.2002 ◽

2003 ◽

Vol 284 (4) ◽

pp. F763-F769 ◽

Cited By ~ 133

Author(s):

Douglas H. Sweet ◽

Lauretta M. S. Chan ◽

Ramsey Walden ◽

Xiao-Ping Yang ◽

David S. Miller ◽

...

Keyword(s):

Proximal Tubule ◽

Organic Anion ◽

Renal Proximal Tubule ◽

Organic Anion Transporter ◽

Xenopus Laevis Oocytes ◽

Estrone Sulfate ◽

Anion Transporter ◽

Renal Proximal Tubule Cells ◽

Rat Renal Cortical Slices ◽

Cortical Slices

Basolateral uptake of organic anions in renal proximal tubule cells is indirectly coupled to the Na+ gradient through Na+-dicarboxylate cotransport and organic anion/dicarboxylate exchange. One member of the organic anion transporter (OAT) family, Oat1, is expressed in the proximal tubule and is an organic anion/dicarboxylate exchanger. However, a second organic anion carrier, Oat3, is also highly expressed in the renal proximal tubule, but its mechanism is unclear. Thus we have assessed Oat3 function in Xenopus laevis oocytes and rat renal cortical slices. Probenecid-sensitive uptake of p-aminohippurate (PAH, an Oat1 and Oat3 substrate) and estrone sulfate (ES, an Oat3 substrate) in rat Oat3-expressing oocytes was significantly trans-stimulated by preloading the oocytes with the dicarboxylate glutarate (GA). GA stimulation of ES transport by oocytes coexpressing rabbit Na+-dicarboxylate cotransporter 1 and rat Oat3 was significantly inhibited when the preloading medium contained Li+ or methylsuccinate (MS) or when Na+ was absent. All these treatments inhibit the Na+-dicarboxylate cotransporter, but not rat Oat3. Li+, MS, and Na+ removal had no effect when applied during the ES uptake step, rather than during the GA preloading step. Concentrative ES uptake in rat renal cortical slices was also demonstrated to be probenecid and Na+ sensitive. Accumulation of ES was stimulated by GA, and this stimulation was completely blocked by probenecid, Li+, MS, taurocholate, and removal of Na+. Thus Oat3 functions as an organic anion/dicarboxylate exchanger that couples organic anion uptake indirectly to the Na+ gradient.

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