Adaptive responses of renal organic anion transporter 3 (OAT3) during cholestasis

2008 ◽  
Vol 295 (1) ◽  
pp. F247-F252 ◽  
Author(s):  
Jiarong Chen ◽  
Tomohiro Terada ◽  
Ken Ogasawara ◽  
Toshiya Katsura ◽  
Ken-ichi Inui
Keyword(s):  
Bile Acids ◽  
Cholic Acid ◽  
Molecular Mechanisms ◽  
Competitive Inhibition ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Specific Substrate ◽  
Renal Secretion ◽  
Sd Rats ◽  
Anion Transporter

During cholestasis, bile acids are mainly excreted into the urine, but adaptive renal responses to cholestasis, especially molecular mechanisms for renal secretion of bile acids, have not been well understood. Organic anion transporters (OAT1 and OAT3) are responsible for membrane transport of anionic compounds at the renal basolateral membranes. In the present study, we investigated the pathophysiological roles of OAT1 and OAT3 in terms of renal handling of bile acids. The Eisai hyperbilirubinemic rats (EHBR), mutant rats without multidrug resistance-associated protein 2, showed higher serum and urinary concentrations of bile acids, compared with Sprague-Dawley (SD) rats (wild type). The protein expression level of rat OAT3 was significantly increased in EHBR compared with SD rats, whereas the expression of rat OAT1 was unchanged. The transport activities of rat and human OAT3, but not OAT1, were markedly inhibited by various bile acids such as chenodeoxycholic acid and cholic acid. Cholic acid, glycocholic acid, and taurocholic acid, which mainly increased during cholestasis, are transported by OAT3. The plasma concentration of β-lactam antibiotic cefotiam, a specific substrate for OAT3, was more increased in EHBR than in SD rats despite upregulation of OAT3 protein. This may be due to the competitive inhibition of cefotiam transport by bile acids via OAT3. In conclusion, the present study clearly demonstrated that OAT3 is responsible for renal secretion of bile acids during cholestasis and that the pharmacokinetic profile of OAT3 substrates may be affected by cholestasis.

scholarly journals Molecular Mechanisms for Species Differences in Organic Anion Transporter 1, OAT1: Implications for Renal Drug Toxicity

2018 ◽  
Vol 94 (1) ◽  
pp. 689-699 ◽  
Author(s):  
Ling Zou ◽  
Adrian Stecula ◽  
Anshul Gupta ◽  
Bhagwat Prasad ◽  
Huan-Chieh Chien ◽  
...  
Keyword(s):  
Drug Toxicity ◽  
Molecular Mechanisms ◽  
Species Differences ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Anion Transporter

scholarly journals Renal secretion of hydrochlorothiazide involves organic anion transporter 1/3, organic cation transporter 2, and multidrug and toxin extrusion protein 2-K

2019 ◽  
Vol 317 (4) ◽  
pp. F805-F814
Author(s):  
Jia Yin ◽  
David J. Wagner ◽  
Bhagwat Prasad ◽  
Nina Isoherranen ◽  
Kenneth E. Thummel ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Organic Cation ◽  
Organic Anion ◽  
Organic Cation Transporter ◽  
Tubular Secretion ◽  
Organic Anion Transporter ◽  
Anion Transporters ◽  
Anion Transporter ◽  
Organic Cation Transporter 2 ◽  
Toxin Extrusion

Hydrochlorothiazide (HCTZ) is the most widely used thiazide diuretic for the treatment of hypertension either alone or in combination with other antihypertensives. HCTZ is mainly cleared by the kidney via tubular secretion, but the underlying molecular mechanisms are unclear. Using cells stably expressing major renal organic anion and cation transporters [human organic anion transporter 1 (hOAT1), human organic anion transporter 3 (hOAT3), human organic cation transporter 2 (hOCT2), human multidrug and toxin extrusion 1 (hMATE1), and human multidrug and toxin extrusion 2-K (hMATE2-K)], we found that HCTZ interacted with both organic cation and anion transporters. Uptake experiments further showed that HCTZ is transported by hOAT1, hOAT3, hOCT2, and hMATE2-K but not by hMATE1. Detailed kinetic analysis coupled with quantification of membrane transporter proteins by targeted proteomics revealed that HCTZ is an excellent substrate for hOAT1 and hOAT3. The apparent affinities ( Km) for hOAT1 and hOAT3 were 112 ± 8 and 134 ± 13 μM, respectively, and the calculated turnover numbers ( kcat) were 2.48 and 0.79 s−1, respectively. On the other hand, hOCT2 and hMATE2-K showed much lower affinity for HCTZ. The calculated transport efficiency ( kcat/ Km) at the single transporter level followed the rank order of hOAT1> hOAT3 > hOCT2 and hMATE2-K, suggesting a major role of organic anion transporters in tubular secretion of HCTZ. In vitro inhibition experiments further suggested that HCTZ is not a clinically relevant inhibitor for hOAT1 or hOAT3. However, strong in vivo inhibitors of hOAT1/3 may alter renal secretion of HCTZ. Together, our study elucidated the molecular mechanisms underlying renal handling of HCTZ and revealed potential pathways involved in the disposition and drug-drug interactions for this important antihypertensive drug in the kidney.

OAT2 catalyses efflux of glutamate and uptake of orotic acid

2011 ◽  
Vol 436 (2) ◽  
pp. 305-312 ◽  
Author(s):  
Christian Fork ◽  
Tim Bauer ◽  
Stefan Golz ◽  
Andreas Geerts ◽  
Jessica Weiland ◽  
...  
Keyword(s):  
Orotic Acid ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Specific Substrate ◽  
Efflux Transporter ◽  
Anion Transporter ◽  
293 Cells ◽  
Solute Carrier ◽  
Laser Capture ◽  
Glutamate Efflux

OAT (organic anion transporter) 2 [human gene symbol SLC22A7 (SLC is solute carrier)] is a member of the SLC22 family of transport proteins. In the rat, the principal site of expression of OAT2 is the sinusoidal membrane domain of hepatocytes. The particular physiological function of OAT2 in liver has been unresolved so far. In the present paper, we have used the strategy of LC (liquid chromatography)–MS difference shading to search for specific and cross-species substrates of OAT2. Heterologous expression of human and rat OAT2 in HEK (human embryonic kidney)-293 cells stimulated accumulation of the zwitterion trigonelline; subsequently, orotic acid was identified as an excellent and specific substrate of OAT2 from the rat (clearance=106 μl·min−1·mg of protein−1) and human (46 μl·min−1·mg of protein−1). The force driving uptake of orotic acid was identified as glutamate antiport. Efficient transport of glutamate by OAT2 was directly demonstrated by uptake of [3H]glutamate. However, because of high intracellular glutamate, OAT2 operates as glutamate efflux transporter. Thus expression of OAT2 markedly increased the release of glutamate (measured by LC-MS) from cells, even without extracellular exchange substrate. Orotic acid strongly trans-stimulated efflux of glutamate. We thus propose that OAT2 physiologically functions as glutamate efflux transporter. OAT2 mRNA was detected, after laser capture microdissection of rat liver slices, equally in periportal and pericentral regions; previous reports of hepatic release of glutamate into blood can now be explained by OAT2 activity. A specific OAT2 inhibitor could, by lowering plasma glutamate and thus promoting brain-to-blood efflux of glutamate, alleviate glutamate exotoxicity in acute brain conditions.

scholarly journals Multiple Drug Transporters Are Involved in Renal Secretion of Entecavir

2016 ◽  
Vol 60 (10) ◽  
pp. 6260-6270 ◽  
Author(s):  
Xi Yang ◽  
Zhiyuan Ma ◽  
Sisi Zhou ◽  
Yayun Weng ◽  
Hongmei Lei ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Organic Cation ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Multiple Drug ◽  
Renal Secretion ◽  
Renal Tubular Cells ◽  
Anion Transporter ◽  
Chronic Hepatitis B Virus ◽  
In Cells

ABSTRACTEntecavir (ETV) is a first-line antiviral agent for the treatment of chronic hepatitis B virus infection. Renal excretion is the major elimination path of ETV, in which tubular secretion plays the key role. However, the secretion mechanism has not been clarified. We speculated that renal transporters mediated the secretion of ETV. Therefore, the aim of our study was to elucidate which transporters contribute to the renal disposition of ETV. Our results revealed that ETV (50 μM) remarkably reduced the accumulation of probe substrates in MDCK cells stably expressing human multidrug and toxin efflux extrusion proteins (hMATE1/2-K), organic cation transporter 2 (hOCT2), and carnitine/organic cation transporters (hOCTNs) and increased the substrate accumulation in cells transfected with multidrug resistance-associated protein 2 (hMRP2) or multidrug resistance protein 1 (hMDR1). Moreover, ETV was proved to be a substrate of the above-described transporters. In transwell studies, the transport of ETV in MDCK-hOCT2-hMATE1 showed a distinct directionality from BL (hOCT2) to AP (hMATE1), and the cellular accumulation of ETV in cells expressing hMATE1 was dramatically lower than that of the mock-treated cells. The accumulation of ETV in mouse primary renal tubular cells was obviously affected by inhibitors of organic anion transporter 1/3 (Oat1/3), Oct2, Octn1/2, and Mrp2. Therefore, the renal uptake of ETV is likely mediated by OAT1/3 and OCT2 while the efflux is mediated by MATEs, MDR1, and MRP2, and OCTN1/2 may participate in both renal secretion and reabsorption.

Reabsorption of bile acids regulated by FXR-OATP1A2 is the main factor for the formation of cholesterol gallstone

2020 ◽  
Vol 319 (3) ◽  
pp. G303-G308
Author(s):  
Jingli Cai ◽  
Zhaowen Wang ◽  
Guiming Chen ◽  
Dapeng Li ◽  
Jun Liu ◽  
...  
Keyword(s):  
Bile Acids ◽  
Cholesterol Gallstone ◽  
Organic Anion ◽  
Farnesoid X Receptor ◽  
Organic Anion Transporter ◽  
Anion Transporter ◽  
First Time ◽  
Main Factor

For the first time, our results indicate that the axis of farnesoid X receptor-organic anion transporter polypeptide 1A2 that physiologically regulates the reabsorption of bile acids might play an important role in the regulation of the composition of bile acids and make contribution to the development of cholelithiasis.

scholarly journals OATP1B3-1B7, a novel organic anion transporting polypeptide, is modulated by FXR ligands and transports bile acids

2019 ◽  
Vol 317 (6) ◽  
pp. G751-G762 ◽  
Author(s):  
Vanessa Malagnino ◽  
Janine Hussner ◽  
Ali Issa ◽  
Angela Midzic ◽  
Henriette E. Meyer zu Schwabedissen
Keyword(s):  
Endoplasmic Reticulum ◽  
Bile Acid ◽  
Bile Acids ◽  
Smooth Endoplasmic Reticulum ◽  
Organic Anion ◽  
Farnesoid X Receptor ◽  
Organic Anion Transporter ◽  
Organic Anion Transporting Polypeptide ◽  
Anion Transporter ◽  
Solute Carrier

Organic anion transporting polypeptide (OATP) 1B3–1B7 (LST-3TM12) is a member of the OATP1B [solute carrier organic anion transporter ( SLCO) 1B] family. This transporter is not only functional but also expressed in the membrane of the smooth endoplasmic reticulum of hepatocytes and enterocytes. OATP1B3–1B7 is a splice variant of SLCO1B3 in which the initial part is encoded by SLCO1B3, whereas the rest of the mRNA originates from the gene locus of SLCO1B7. In this study, we not only showed that SLCO1B3 and the mRNA encoding for OATP1B3–1B7 share the 5′ untranslated region but also that silencing of an initial SLCO1B3 exon lowered the amount of SLCO1B3 and of SLCO1B7 mRNA in Huh-7 cells. To validate the assumption that both transcripts are regulated by the same promoter we tested the influence of the bile acid sensor farnesoid X receptor (FXR) on their transcription. Treatment of Huh-7 and HepaRG cells with activators of this known regulator of OATP1B3 not only increased SLCO1B3 but also OATP1B3–1B7 mRNA transcription. Applying a heterologous expression system, we showed that several bile acids interact with OATP1B3–1B7 and that taurocholic acid and lithocholic acid are OATP1B3–1B7 substrates. As OATP1B3–1B7 is located in the smooth endoplasmic reticulum, it may grant access to metabolizing enzymes. In accordance are our findings showing that the OATP1B3–1B7 inhibitor bromsulphthalein significantly reduced uptake of bile acids into human liver microsomes. Taken together, we report that OATP1B3–1B7 transcription can be modulated with FXR agonists and antagonists and that OATP1B3–1B7 transports bile acids. NEW & NOTEWORTHY Our study on the transcriptional regulation of the novel organic anion transporting polypeptide (OATP) 1B3–1B7 concludes that the promoter of solute carrier organic anion transporter ( SLCO) 1B3 governs SLCO1B3–1B7 transcription. Moreover, the transcription of OATP1B3–1B7 can be modulated by farnesoid X receptor (FXR) agonists and antagonists. FXR is a major regulator in bile acid homeostasis that links OATP1B3–1B7 to this physiological function. Findings in transport studies with OATP1B3–1B7 suggest that this transporter interacts with the herein tested bile acids.

349 BILE ACIDS DOWNREGULATE THE HUMAN HEPATIC ORGANIC ANION TRANSPORTER 7

2012 ◽  
Vol 56 ◽  
pp. S141-S142
Author(s):  
C. Jüngst ◽  
K. Klein ◽  
J.J. Eloranta ◽  
G.A. Kullak-Ublick
Keyword(s):  
Bile Acids ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Anion Transporter

scholarly journals Indoxyl Sulfate Contributes to mTORC1-Induced Renal Fibrosis via The OAT/NADPH Oxidase/ROS Pathway

Toxins ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 909
Author(s):  
Takehiro Nakano ◽  
Hiroshi Watanabe ◽  
Tadashi Imafuku ◽  
Kai Tokumaru ◽  
Issei Fujita ◽  
...  
Keyword(s):  
Nadph Oxidase ◽  
Renal Fibrosis ◽  
Molecular Mechanisms ◽  
Epithelial Mesenchymal Transition ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Indoxyl Sulfate ◽  
Uremic Toxin ◽  
Mesenchymal Transition ◽  
Anion Transporter

Activation of mTORC1 (mechanistic target of rapamycin complex 1) in renal tissue has been reported in chronic kidney disease (CKD)-induced renal fibrosis. However, the molecular mechanisms responsible for activating mTORC1 in CKD pathology are not well understood. The purpose of this study was to identify the uremic toxin involved in mTORC1-induced renal fibrosis. Among the seven protein-bound uremic toxins, only indoxyl sulfate (IS) caused significant activation of mTORC1 in human kidney 2 cells (HK-2 cells). This IS-induced mTORC1 activation was inhibited in the presence of an organic anion transporter inhibitor, a NADPH oxidase inhibitor, and an antioxidant. IS also induced epithelial–mesenchymal transition of tubular epithelial cells (HK-2 cells), differentiation of fibroblasts into myofibroblasts (NRK-49F cells), and inflammatory response of macrophages (THP-1 cells), which are associated with renal fibrosis, and these effects were inhibited in the presence of rapamycin (mTORC1 inhibitor). In in vivo experiments, IS overload was found to activate mTORC1 in the mouse kidney. The administration of AST-120 or rapamycin targeted to IS or mTORC1 ameliorated renal fibrosis in Adenine-induced CKD mice. The findings reported herein indicate that IS activates mTORC1, which then contributes to renal fibrosis. Therapeutic interventions targeting IS and mTORC1 could be effective against renal fibrosis in CKD.

Bile acids downregulate the human hepatic organic anion transporter 7

2012 ◽  
Vol 50 (01) ◽  
Author(s):  
C Jüngst ◽  
K Klein ◽  
J Eloranta ◽  
G Kullak-Ublick
Keyword(s):  
Bile Acids ◽  
Organic Anion ◽  
Organic Anion Transporter ◽  
Anion Transporter

Hepatocyte nuclear factor-4α regulates the human organic anion transporter 1 gene in the kidney

2007 ◽  
Vol 292 (6) ◽  
pp. F1819-F1826 ◽  
Author(s):  
Ken Ogasawara ◽  
Tomohiro Terada ◽  
Jun-ichi Asaka ◽  
Toshiya Katsura ◽  
Ken-ichi Inui
Keyword(s):  
Promoter Activity ◽  
Molecular Mechanisms ◽  
Organic Anion ◽  
Critical Role ◽  
Direct Repeat ◽  
Organic Anion Transporter ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Mobility Shift ◽  
Anion Transporter

Human organic anion transporter 1 (OAT1, SLC22A6), which is localized to the basolateral membranes of renal tubular epithelial cells, plays a critical role in the excretion of anionic compounds. OAT1 is regulated by various pathophysiological conditions, but little is known about the molecular mechanisms regulating the expression of OAT1. In the present study, we investigated the transcriptional regulation of OAT1 and found that hepatocyte nuclear factor (HNF)-4α markedly transactivated the OAT1 promoter. A deletion analysis of the OAT1 promoter suggested that the regions spanning −1191 to −700 base pairs (bp) and −140 to −79 bp were essential for the transactivation by HNF-4α. These regions contained a direct repeat separated by two nucleotides (DR-2), which is one of the consensus sequences binding to HNF-4α, and an inverted repeat separated by eight nucleotides (IR-8), which was recently identified as a novel element for HNF-4α, respectively. An electrophoretic mobility shift assay showed that HNF-4α bound to DR-2 and IR-8 under the conditions of HNF-4α overexpression. Furthermore, under normal conditions, HNF-4α bound to IR-8, and a mutation in IR-8 markedly reduced the OAT1 promoter activity, indicating that HNF-4α regulates the basal transcription of OAT1 via IR-8. This paper reports the first characterization of the human OAT1 promoter and the first gene in the kidney whose promoter activity is regulated by HNF-4α.

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