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Eberhard Schlatter - One of the best experts on this subject based on the ideXlab platform.
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proximal tubular secretion of creatinine by Organic Cation Transporter oct2 in cancer patients
Clinical Cancer Research, 2012Co-Authors: Giuliano Ciarimboli, Jason A. Sprowl, Cynthia S Lancaster, Vivian Massmann, Denise Guckel, Ron H J Mathijssen, Hermann Pavenstädt, Ryan M. Franke, Eberhard Schlatter, Wenjian YangAbstract:Purpose: Knowledge of Transporters responsible for the renal secretion of creatinine is key to a proper interpretation of serum creatinine and/or creatinine clearance as markers of renal function in cancer patients receiving chemotherapeutic agents. Experimental Design: Creatinine Transport was studied in transfected HEK293 cells in vitro and in wild-type mice and age-matched Organic Cation Transporter 1 and 2–deficient [Oct1/2(−/−)] mice ex vivo and in vivo . Clinical pharmacogenetic and Transport inhibition studies were done in two separate cohorts of cancer patients. Results: Compared with wild-type mice, creatinine clearance was significantly impaired in Oct1/2(−/−) mice. Furthermore, creatinine inhibited Organic Cation Transport in freshly isolated proximal tubules from wild-type mice and humans, but not in those from Oct1/2(−/−) mice. In a genetic association analysis ( n = 590), several polymorphisms around the OCT2/ SLC22A2 gene locus, including rs2504954 ( P = 0.000873), were significantly associated with age-adjusted creatinine levels. Furthermore, in cancer patients ( n = 68), the OCT2 substrate cisplatin caused an acute elevation of serum creatinine ( P = 0.0083), consistent with inhibition of an elimination pathway. Conclusions: Collectively, this study shows that OCT2 plays a decisive role in the renal secretion of creatinine. This process can be inhibited by OCT2 substrates, which impair the usefulness of creatinine as a marker of renal function. Clin Cancer Res; 18(4); 1101–8. ©2012 AACR .
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regulation of Organic Cation Transport in isolated mouse proximal tubules involves complex changes in protein trafficking and substrate affinity
Cellular Physiology and Biochemistry, 2012Co-Authors: Denise Guckel, Giuliano Ciarimboli, Hermann Pavenstädt, Eberhard SchlatterAbstract:This study characterizes the complex mechanisms of acute regulation of Organic Cation (OC) Transport across the basolateral membrane of isolated mouse proximal tubules. The fluorescent substrate ASP(+), 4-(-4-(dimethylamino) styryl-N-methylpyridinium, was used to quantify OC Transport using a microtiter plate based fluorescence reader method. Inhibition of phosphatidylinositol-3-kinase, of p56 tyrosine kinase, stimulation of PKC and inhibition of PKA reduced ASP(+)-uptake. ASP(+)-kinetic and Dixon plot analyses revealed effects on Transporter trafficking as explanation for the inhibition of ASP(+)-uptake by these pathways. Angiotensin II (AII) via stimulation of Ca(2+)/calmodulin increased ASP(+)-uptake. This effect aroused from an altered substrate affinity. Bafilomycin, an inhibitor of the vacuolar H(+)-ATPase and thus endosomal and lysosomal function, reduced ASP(+)-uptake, but did not prevent the AII effect on ASP(+)-uptake. Bafilomycin seemed to diminish the recycling rate of OCTs and hence to reduce the amount of Transporters in the membrane. AII via Ca(2+)/calmodulin increased the substrate affinity of the remaining OCTs. The involvement of the cytoskeleton in acute regulation of OCTs became obvious as colchicine induced inhibition of microtubule polymerisation reduced ASP(+)-uptake. Acute regulation of mouse OCTs mostly involves changes in trafficking from and to the plasma membrane and only in the case of AII/CaM changes in substrate affinity.
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properties and regulation of Organic Cation Transport in freshly isolated mouse proximal tubules analyzed with a fluorescence reader based method
Pflügers Archiv: European Journal of Physiology, 2011Co-Authors: Svenja K. Holle, Giuliano Ciarimboli, Hermann Pavenstädt, Bayram Edemir, Ute Neugebauer, Eberhard SchlatterAbstract:The main elimination site of Organic Cations (OCs) is the renal proximal tubule (PT). OC Transporters (OCT) accept endogenous and exogenous substances and xenobiotics. As transgenic mouse models are increasingly used in translational medicine, functional properties with special focus on regulation of OCT of isolated mouse PTs were studied with a new fluorescence reader-based method, which allows studying larger numbers of tubules per kidney. OC Transport across the basolateral membrane of PTs from male mice was measured as initial uptake of the fluorescent dye 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP). A microtiter plate fluorescence reader was used to semi-automatically analyze OC Transport in freshly isolated tubules. Relative mRNA expression of OCT1/OCT2/OCT3 in PTs was 1/0.3/0.01 and did not vary from S1 to S3 segments. ASP was Transported by PTs with a Km of 6 μM. It was inhibited by TEA, TPA, or cimetidine (IC50 = 5, 19, or 53 μM, respectively). Angiotensin II stimulated ASP uptake (+63%), while stimulation of PKC reduced (−37%) OC Transport. Inhibition of p56lck tyrosine kinase (−60%), of PI3K (−36%), of Ca2+/calmodulin (−25%), or of PKA (−33%) reduced OC Transport. In PTs from OCT1/2−/− mice ASP uptake was reduced to ~20%. Using this fluorescence reader-based method, we report substrate specificities and a complex pattern of acute regulation of OC Transport in isolated mouse PTs. Compared to isolated human PTs or rat and human OCT isoforms expressed in HEK293-cells, OC Transport across the basolateral membrane of freshly isolated mouse PTs shows similarities but also specific differences.
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cisplatin nephrotoxicity is critically mediated via the human Organic Cation Transporter 2
American Journal of Pathology, 2005Co-Authors: Giuliano Ciarimboli, Hermann Koepsell, Detlef Lang, Hansjurgen Piechota, Jochen Zisowsky, Hermann Pavenstädt, Ulrich Jaehde, Thomas Ludwig, Jörg Haier, Eberhard SchlatterAbstract:Cis- platin is an effective anti-neoplastic agent, but it is also highly nephrotoxic. Here, we clearly identify the human Organic Cation Transporter 2 (hOCT2) as the critical Transporter for cis- platin nephrotoxicity in isolated human proximal tubules and offer a potential mechanism for reducing nephrotoxicity in clinical practice. Interaction of cis- platin with hOCT2 in kidney or hOCT1 in liver was investigated with the fluorescent Cation 4-[4-(dimethyl-amino)styril]-methylpyridinium in stably transfected HEK293 cells and for the first time in tissues physiologically expressing these Transporters, human proximal tubules, and human hepatocyte couplets. Cis- platin (100 μmol/L) inhibited Transport via hOCT2-HEK293 but not hOCT1-HEK293. In human proximal tubules cis- platin competed with basolateral Organic Cation Transport, whereas it had no effect in tubules from a diabetic kidney or in hepatocytes. In hOCT2-HEK293 cells treated for 15 hours, incubation with cis- platin induced apoptosis, which was completely suppressed by contemporaneous incubation with the hOCT2 substrate cimetidine (100 μmol/L). These findings demonstrate that uptake of cis- platin is mediated by hOCT2 in renal proximal tubules, explaining its organ-specific toxicity. A combination of cis- platin with other substrates that compete for hOCT2 offers an effective option to decrease nephrotoxicity in the clinical setting.
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Regulation of Organic Cation Transport
Pflügers Archiv, 2005Co-Authors: Giuliano Ciarimboli, Eberhard SchlatterAbstract:Transport of Organic Cations (OC) is important for the recycling of endogenous OC and also a necessary step for detoxifiCation of exogenous OC in the body. Even though the identifiCation and characterisation of numerous OC Transporters in recent years has allowed the elucidation of molecular mechanisms underlying OC Transport, elucidation of the regulation of this Transport is just beginning. This review summarises the general properties of OC Transport and then analyses the literature on the regulation of these processes. Studies on short- and long-term regulation of OC Transport are considered separately. Important aspects of short-term regulation have been clarified and the regulatory pathways of several OC Transporters have been characterised. Short-term regulation appears to be Transporter subtype-, tissue- and species-dependent and to involve Transporter phosphorylation. Transporter phosphorylation may alter the affinity for substrates or/and expression on the plasma membrane. Even though several studies have shown long-term regulation of OC Transport, the pathophysiological meaning of these changes are not well understood. In this case, regulation seems to be subtype-, tissue- and gender-specific. Further research is necessary to clarify this important issue of regulation of OC Transport.
Giuliano Ciarimboli - One of the best experts on this subject based on the ideXlab platform.
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Mouse Organic Cation Transporter 1 determines properties and regulation of basolateral Organic Cation Transport in renal proximal tubules
Pflügers Archiv - European Journal of Physiology, 2014Co-Authors: Philipp Klassen, Vivian Massmann, Denise Guckel, Hermann Pavenstädt, Svenja K. Holle, Bayram Edemir, Giuliano CiarimboliAbstract:The proximal tubule of mouse kidney expresses mouse Organic Cation Transporter 1 (mOCT1), mOCT2, and much less mOCT3. Therefore, mOCT-mediated Transport across the basolateral membrane of proximal tubules reflects properties of at least mOCT1 and mOCT2. Here, we unraveled substrate affinities and modulation of Transport activity by acute regulation by protein kinases on mOCT1 and mOCT2 separately and compared these findings with those from isolated proximal tubules of male and female mOCT2^−/− mice. These data are also compared to our recent reports on isolated tubules from wild-type and mOCT1/2 double knockout (mOCT1/2^−/−) mice. OCT-mediated Transport in proximal tubules of mOCT2^−/− mice was only 20 % lower compared to those isolated from wild-type mice. While mOCT1 was regulated by all five pathways examined [protein kinase A (PKA), protein kinase C (PKC), p56^lck, phosphoinositide 3-kinase (PI3K), and calmodulin (CaM)], mOCT2 activity was modulated by PKA, p56^lck, and CaM only, however, in the same direction. As mOCT-mediated Transport across the basolateral membrane of mOCT2^−/− mice expressing only mOCT1 and to a small amount mOCT3 was identical to that observed for tubules isolated from wild-type mice and to that observed for human embryonic kidney 293 (HEK293) cells stably expressing mOCT1, mOCT1 represents the relevant paralog for OCT-dependent Organic Cation Transport in the mouse kidney. Gender does not play a major role in expression and activity of renal OCT-mediated Transport in the mouse. Properties of mouse OCT considerably differ from those of rat or human origin, and thus, observations made in these rodents cannot directly be transferred to the human situation.
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proximal tubular secretion of creatinine by Organic Cation Transporter oct2 in cancer patients
Clinical Cancer Research, 2012Co-Authors: Giuliano Ciarimboli, Jason A. Sprowl, Cynthia S Lancaster, Vivian Massmann, Denise Guckel, Ron H J Mathijssen, Hermann Pavenstädt, Ryan M. Franke, Eberhard Schlatter, Wenjian YangAbstract:Purpose: Knowledge of Transporters responsible for the renal secretion of creatinine is key to a proper interpretation of serum creatinine and/or creatinine clearance as markers of renal function in cancer patients receiving chemotherapeutic agents. Experimental Design: Creatinine Transport was studied in transfected HEK293 cells in vitro and in wild-type mice and age-matched Organic Cation Transporter 1 and 2–deficient [Oct1/2(−/−)] mice ex vivo and in vivo . Clinical pharmacogenetic and Transport inhibition studies were done in two separate cohorts of cancer patients. Results: Compared with wild-type mice, creatinine clearance was significantly impaired in Oct1/2(−/−) mice. Furthermore, creatinine inhibited Organic Cation Transport in freshly isolated proximal tubules from wild-type mice and humans, but not in those from Oct1/2(−/−) mice. In a genetic association analysis ( n = 590), several polymorphisms around the OCT2/ SLC22A2 gene locus, including rs2504954 ( P = 0.000873), were significantly associated with age-adjusted creatinine levels. Furthermore, in cancer patients ( n = 68), the OCT2 substrate cisplatin caused an acute elevation of serum creatinine ( P = 0.0083), consistent with inhibition of an elimination pathway. Conclusions: Collectively, this study shows that OCT2 plays a decisive role in the renal secretion of creatinine. This process can be inhibited by OCT2 substrates, which impair the usefulness of creatinine as a marker of renal function. Clin Cancer Res; 18(4); 1101–8. ©2012 AACR .
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regulation of Organic Cation Transport in isolated mouse proximal tubules involves complex changes in protein trafficking and substrate affinity
Cellular Physiology and Biochemistry, 2012Co-Authors: Denise Guckel, Giuliano Ciarimboli, Hermann Pavenstädt, Eberhard SchlatterAbstract:This study characterizes the complex mechanisms of acute regulation of Organic Cation (OC) Transport across the basolateral membrane of isolated mouse proximal tubules. The fluorescent substrate ASP(+), 4-(-4-(dimethylamino) styryl-N-methylpyridinium, was used to quantify OC Transport using a microtiter plate based fluorescence reader method. Inhibition of phosphatidylinositol-3-kinase, of p56 tyrosine kinase, stimulation of PKC and inhibition of PKA reduced ASP(+)-uptake. ASP(+)-kinetic and Dixon plot analyses revealed effects on Transporter trafficking as explanation for the inhibition of ASP(+)-uptake by these pathways. Angiotensin II (AII) via stimulation of Ca(2+)/calmodulin increased ASP(+)-uptake. This effect aroused from an altered substrate affinity. Bafilomycin, an inhibitor of the vacuolar H(+)-ATPase and thus endosomal and lysosomal function, reduced ASP(+)-uptake, but did not prevent the AII effect on ASP(+)-uptake. Bafilomycin seemed to diminish the recycling rate of OCTs and hence to reduce the amount of Transporters in the membrane. AII via Ca(2+)/calmodulin increased the substrate affinity of the remaining OCTs. The involvement of the cytoskeleton in acute regulation of OCTs became obvious as colchicine induced inhibition of microtubule polymerisation reduced ASP(+)-uptake. Acute regulation of mouse OCTs mostly involves changes in trafficking from and to the plasma membrane and only in the case of AII/CaM changes in substrate affinity.
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properties and regulation of Organic Cation Transport in freshly isolated mouse proximal tubules analyzed with a fluorescence reader based method
Pflügers Archiv: European Journal of Physiology, 2011Co-Authors: Svenja K. Holle, Giuliano Ciarimboli, Hermann Pavenstädt, Bayram Edemir, Ute Neugebauer, Eberhard SchlatterAbstract:The main elimination site of Organic Cations (OCs) is the renal proximal tubule (PT). OC Transporters (OCT) accept endogenous and exogenous substances and xenobiotics. As transgenic mouse models are increasingly used in translational medicine, functional properties with special focus on regulation of OCT of isolated mouse PTs were studied with a new fluorescence reader-based method, which allows studying larger numbers of tubules per kidney. OC Transport across the basolateral membrane of PTs from male mice was measured as initial uptake of the fluorescent dye 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP). A microtiter plate fluorescence reader was used to semi-automatically analyze OC Transport in freshly isolated tubules. Relative mRNA expression of OCT1/OCT2/OCT3 in PTs was 1/0.3/0.01 and did not vary from S1 to S3 segments. ASP was Transported by PTs with a Km of 6 μM. It was inhibited by TEA, TPA, or cimetidine (IC50 = 5, 19, or 53 μM, respectively). Angiotensin II stimulated ASP uptake (+63%), while stimulation of PKC reduced (−37%) OC Transport. Inhibition of p56lck tyrosine kinase (−60%), of PI3K (−36%), of Ca2+/calmodulin (−25%), or of PKA (−33%) reduced OC Transport. In PTs from OCT1/2−/− mice ASP uptake was reduced to ~20%. Using this fluorescence reader-based method, we report substrate specificities and a complex pattern of acute regulation of OC Transport in isolated mouse PTs. Compared to isolated human PTs or rat and human OCT isoforms expressed in HEK293-cells, OC Transport across the basolateral membrane of freshly isolated mouse PTs shows similarities but also specific differences.
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new clues for nephrotoxicity induced by ifosfamide preferential renal uptake via the human Organic Cation Transporter 2
Molecular Pharmaceutics, 2011Co-Authors: Giuliano Ciarimboli, Hermann Pavenstädt, Svenja K. Holle, Beate Vollenbrocker, Yohannes Hagos, Stefan Reuter, Gerhard Burckhardt, Stefan Bierer, Edwin Herrmann, Rainer RossiAbstract:Anticancer treatment with ifosfamide but not with its structural isomer cyclophosphamide is associated with development of renal Fanconi syndrome leading to diminished growth in children and bone problems in adults. Since both cytotoxics share the same principal metabolites, we investigated whether a specific renal uptake of ifosfamide is the basis for this differential effect. First we studied the interaction of these cytotoxics using cells transfected with Organic anion or Cation Transporters and freshly isolated murine and human proximal tubules with appropriate tracers. Next we determined changes in membrane voltage in proximal tubular cells to understand their differentiated nephrotoxicity. Ifosfamide but not cyclophosphamide was significantly Transported into cells expressing human Organic Cation Transporter 2 (hOCT2) while both did not interact with Organic anion Transporters. This points toward a specific interaction of ifosfamide with hOCT2, which is the main OCT isoform in human kidney. In isolated human proximal tubules ifosfamide also interacted with Organic Cation Transport. This interaction was also seen in isolated mouse proximal tubules; however, it was absent in tubules from OCT-deficient mice, illustrating the biological importance of this selective Transport. Ifosfamide decreased the viability of cells expressing hOCT2, but not that of control cells. Coadministration of cimetidine, a known competitive substrate of hOCT2, completely prevented this ifosfamide-induced toxicity. Finally, ifosfamide but not cyclophosphamide depolarized proximal tubular cells. We propose that the nephrotoxicity of ifosfamide is due to its selective uptake by hOCT2 into renal proximal tubular cells, and that coadministration of cimetidine may be used to prevent ifosfamide-induced nephrotoxicity.
K J Ullrich - One of the best experts on this subject based on the ideXlab platform.
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luminal Transport system for choline in relation to the other Organic Cation Transport systems in the rat proximal tubule
Pflügers Archiv: European Journal of Physiology, 1996Co-Authors: K J Ullrich, G RumrichAbstract:The efflux of [3H] choline+ from the proximal tubular lumen was measured by using the stop-flow microperfusion method. The 2-s efflux of [3H] choline+ follows kinetics with a Michaelis constant, Km = 0.18 mmol · 1−1, maximal flux, Jmax = 0.43 pmol · cm−1· s−1 and a permeability term = 38.0 μm2 · s−1. Replacement of Na+ by N-methyl-D-glucamine+ or Li+, or a change of luminal pH do not alter choline+ efflux. Replacement of Na+ by Cs+ inhibits 2-s choline+ (0.01 mmol · l−1) efflux by 22% and replacement by K+ inhibits by 49%, indicating that the electrical potential difference across the brush border membrane acts as driving force for choline+ Transport. Comparing the apparent luminal inhibitory constant values for choline (app. Ki,l,choline+) with the chemical structure of inhibiting substrates, it was found that the inhibitory potency of amines with high pKa values, i.e. high basicity, and of quaternary ammonium compounds (tetraethyl to tetrahexylammonium) increases with their hydrophobicity in a similar manner as was observed previously against the contraluminal N1-methylnicotinamide (NMeN+) Transporter and the luminal H+/Organic Cation (N-methyl-4-phenylpyridinium) (MPP+) exchanger. Independently of their hydrophobicity, an increase in the inhibitory potency of the homologous series of aminoquinolines against the choline+ Transporter was observed with increasing pKa values, i.e. increasing basicity, as was found previously against the two other Organic Cation Transporters. A third parameter influencing the interaction with the choline+ Transporter is the presence of two amino groups with high pKa values or one amino group and a permanent positive charge, as is documented with the two-ring aminostyryl and rhodamine compounds, as well as three-ring aminoacridine, aminophenanthrene and cyanine compounds. Thus with the aminostyryl, pyridinium +, rhodamine, phenanthridium+ and cyanine+ dyes app. Ki,1,choline+ values of between 0.01 and 0.07 mmol·l−1 have been found. A fourth parameter influencing the choline+ Transporter is the presence of an OH group on the C atom next to that bearing the N atom (as in choline+) or an ester-OCOR group (acetylcholine+, butyrylcholine+) or a thioester-SCOR-group (acetylthiocholine+, butyrylthiocholine+); or an-OP(OH)2(OR) group (glycerylphosphoryl-choline+), resulting in app. Ki,1,choline+ values of 0.3–1.0 mmol · l−1. Thus the substrates for the luminal choline+ Transporter have general features in common with the luminal H+/Organic Cation exchanger and the contraluminal Organic Cation Transporter, i.e. hydrophobicity and basicity. Additional parameters for interaction are an OH (or similar) group positioned a favourable distance from the N atom or a second amino/ammonium group in multi-ring compounds.
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luminal Transport system for h Organic Cations in the rat proximal tubule kinetics dependence on ph specificity as compared with the contraluminal Organic Cation Transport system
Pflügers Archiv: European Journal of Physiology, 1995Co-Authors: C David, G Rumrich, K J UllrichAbstract:The efflux of radiolabelled Organic Cations from the tubular lumen into proximal tubular cells was investigated by using the stop-flow microperfusion method. The efflux rate increased in the sequence: N1-methylnicotinamide (NMeN+) < cimetidine < tetraethylammonium (TEA+) < N-methyl-4-phenylpyridinium (MPP+). Preloading the animals by i.v. infusion or pre perfusion of the peritubular capillaries with NMeN+ increased the efflux rate of MPP+. Luminal efflux was also augmented when the tubular solution was made alkaline with HCO3−or phosphate, whereby HCO3−is more effective than phosphate. Replacement of Na+ by Cs+ showed no effect. With i.v. preloading the animals with NMeN+ and with 25 mM HCO3−in the luminal perfusate the 2-s efflux follows kinetics with a Michaelis constant Km=0.21 mmol/l and maximal flux Jmax=0.42 pmol · cm−1 · s−1 and a permeability term with P=37.7 μm2 · s−1. Comparing the apparent luminal inhibitory constant values for MPP+\((Ki_{l,MPP^ + } )\) with the apparent contraluminal \(Ki_{cl,NMeN^ + }\) values of substrates of homologous series, it was found that (1) limitation by molecular size occurs at the contraluminal cell side earlier than at the luminal cell side; (2) affinity increases with hydrophobicity of the substrates at the luminal cell side, with a steeper or equal slope than at the contraluminal cell side; (3) affinity increases with basicity (i.e. pKa values) at the luminal cell side with a steeper slope than at the contraluminal cell side. Taken together, substrates with low hydrophobicity and low basicity interact at the luminal cell side more weakly than at the contraluminal cell side. On the other hand large, hydrophobic substrates have, at the luminal cell side, a higher affinity than at the contraluminal cell side. Many substrates, however, have equal affinity at the luminal and contraluminal cell sides.
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bisubstrates substances that interact with both renal contraluminal Organic anion and Organic Cation Transport systems ii zwitterionic substrates dipeptides cephalosporins quinolone carboxylate gyrase inhibitors and phosphamide thiazine carboxylates nonionizable substrates steroid hormones and cyclophosphamides
Pflügers Archiv: European Journal of Physiology, 1993Co-Authors: K J Ullrich, G Rumrich, C David, Gunter FritzschAbstract:In order to test what chemical structure is required for a substrate to interact not only with the contraluminal Organic anion (p-aminohippurate, PAH) Transporter, but also with the Organic Cation (N1-methylnicotinamide, NMeN, or tetraethylammonium, TEA) Transporter, the stop-flow peritubular capillary perfusion method was applied and app. Ki values were evaluated. Zwitterionic hydrophobic dipeptides not only interact with PAH but also with NMeN Transport although with lower inhibitory potency (Ki,PAH = 0.2-1.4; Ki,NMeN 6-14 mmol/l). Amongst the zwitterionic cephalosporins, which all inhibit PAH Transport, the amino cephalosporin analogue cefadroxil was identified to interact also with NMeN Transport (Ki,PAH = 3.0, Ki,NMeN = 11.2 mmol/l). All zwitterionic naphthyridine and oxochinoline gyrase inhibitors tested inhibit NMeN Transport with app. Ki,NMeN values between 1.2 mmol/l and 4.7 mmol/l; the naphthyridine analogues show a good inhibitory potency against PAH Transport (Ki,PAH approximately 0.4 mmol/l), the piperazine-containing quinolone analogues have a moderate inhibitory potency (Ki,PAH = 1.1-2.5 mmol/l) and the piperazine-containing pipemidic acid did not inhibit PAH Transport at all. Zwitterionic thiazolidine carboxylate phosphamides also interact with both Transporters (app. Ki,PAH approximately 3.0; app. Ki,NMeN approximately 18.0 mmol/l). The nonionizable oxo- and hydroxy-group-containing corticosteroid hormones also interact with the two Transporters. (a) An OH group in position 21 is necessary for interaction with the PAH Transporter, but not for interaction with the TEA Transporter. (b) Introduction of an OH group in position 17 alpha abolishes interaction with the TEA Transporter, but has different effects with the PAH Transporter. (c) Introduction of an OH group in position 6 abolishes interaction with both, the PAH and the TEA Transporter. (d) A change of the side-group in position 11 of corticosterone from -OH to -H to = O enhances interaction with the PAH Transporter but has no effect on the interaction with the TEA Transporter. Nonionizable 4- or 5-androstene analogues inhibit both Transporters with app. Ki between 0.16 mmol/l and 0.64 mmol/l, if the steroids are soluble in a concentration greater than 1 mmol/l. Nonionizable oxazaphosphorins with more than one chloroethyl group interact with the PAH Transporter with app. Ki between 0.84 mmol/l and 4.9 mmol/l and with the NMeN Transporter with app. Ki between 3.2 mmol/l and 18.7 mmol/l. Thus a substrate interacts with both Transporters if it is sufficiently hydrophobic, possesses acidic and/or electron-attracting plus basic and/or electron-donating groups, or possesses several electron-attracting nonionizable groups (O, OH, Cl). A certain spatial arrangement of the interacting groups seems to be necessary.
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Bisubstrates: substances that interact with renal contraluminal Organic anion and Organic Cation Transport systems. I. Amines, piperidines, piperazines, azepines, pyridines, quinolines, imidazoles, thiazoles, guanidines and hydrazines.
Pflugers Archiv : European journal of physiology, 1993Co-Authors: K J Ullrich, G Rumrich, C David, G FritzschAbstract:In order to evaluate whether N-containing substrates interact with the Organic "anion" (p-aminohippurate, PAH) or only with the Organic "Cation" (N1-methylnicotinamide, NMeN) Transport system or with both, the stop-flow peritubular capillary microperfusion method was applied in the rat kidney in situ and the apparent Ki values of several classes or Organic substrate against contraluminal NMeN and PAH Transport were determined. Organic "anion" and Organic "Cation" Transport are in inverted commas because neither Transporter sees the degree of ionization in bulk solution, and they also accept nonionizable substrates [Ullrich KJ, Rumrich G (1992) Pflügers Arch 421:286-288]. Amines must be sufficiently hydrophobic (phenylethylamine, piperidine, piperazine) in order to interact with NMeN Transport. Additional Cl, Br, NO2 or other electronegative groups render them inhibitory towards PAH Transport also. Such bisubstrate amines were identified as follows: metoclopramide, bromopride, diphenhydramine, bromodiphenhydramine, verapamil, citalopram, ketamine, mefloquine, ipsapirone, buspirone, trazodone, H7 and trifluoperazine. Imidazole analogues interact with both Transporters if they bear sufficiently hydrophobic alkyl or aryl groups or electronegative sidegroups. Bisubstrate imidazole analogues are tinidazole, pilocarpine, clonidine, azidoclonidine and cimetidine. Pyridines and thiazoles interact with the NMeN Transporter if they have an additional ring-attached NH2 group. Again with an additional Cl, Br, or NO2 group the aminopyridines and aminothiazoles also become inhibitors for the PAH Transporter. Amongst the guanidines only substances with several electronegative side-groups such as guanfacine, amiloride, benzylamiloride and ranitidine, interact with both Transporters. Amongst the phenylhydrazines only 4-bromophenylhydrazine interacts with the NMeN Transporter and 4-nitrophenylhydrazine with both Transporters. Quinoline (isoquinoline) and its amino and hydroxy analogues interact with both Transporters, their pKa values correlate directly with the affinity to the NMeN Transporter and reciprocally with their affinity to the PAH Transporter. In experiments with labelled substrates only the sufficiently hydrophilic cimetidine, amiloride and ranitidine show a saturable Transport, which can be inhibited by probenecid (apalcillin) and tetraethylammonium in an additive manner. The highly hydrophobic substrates verapamil, citalopram, imipramine, diltiazem and clonidine enter the cell very fast in an unsaturable and uninhibitable manner, apparently in the undissociated form, since N-methyl-4-phenylpyridinium, which--disregarding its ionization--is similarly hydrophobic, shows a Transport behaviour similar to that of tetraethylammonium [Ullrich et al. (1991) Pflügers Arch 419:84-92]. Ethidium bromide and dimidium bromide, which have a permanent Cationic quaternary nitrogen and two sufficiently electronegative NH2 groups, also interact with both Transporters.(ABSTRACT TRUNCATED AT 400 WORDS)
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contraluminal Transport of Organic Cations in the proximal tubule of the rat kidney
Pflügers Archiv: European Journal of Physiology, 1991Co-Authors: K J Ullrich, G Rumrich, C David, F Papavassiliou, Gunter FritzschAbstract:In order to study the characteristics of contraluminal Organic Cation Transport from the blood site into proximal tubular cells the stopped-flow capillary perfusion method was applied. The disappearance of N1-[3H]methylnicotinamide (NMeN+) and [3H]tetraethylammonium (TEA+) at different concentrations and contact times was measured and the following parameters evaluated: Km,NMeN = 0.54 mmol/l, Jmax,NMeN = 0.4 pmol s−1 cm−1; Km,TEA = 0.16 mmol/l, Jmax,TEA = 0.8 pmol s−1 cm−1. TEA+ inhibited NMeN+ Transport and NMeN+ the uptake of TEA+. Thereby, the Ki values for inhibition correspond closely to the Km values for uptake. Similar inhibitory potencies of ten Organic Cation against TEA+ and NMeN+ Transport provide further evidence for a common Transport system. Omission of HCO 3 − , or Na+ and addition of K+ (with or without Ba2+) reduce NMeN+ Transport, while omission of K+ (with or without valinomycin) or addition of thiocyanate has no effect. Since the manoeuvres that depolarize contraluminal electrical potential difference reduce NMeN+ Transport, cell-negative electrical potential difference is suggested as a driving force for contraluminal Organic Cation Transport from the interstitium into the cell. Furthermore, the inhibitory potency (app. Ki values) of homologous series of primary, secondary, tertiary and hydroxy amines as well as of mono- and bisquarternary ammonium compounds against NMeN+ Transport was tested. The inhibitory potency increased in the sequence methyl tetrapentyl- > tetrahexyl- > tetraheptyl > tetraoctylammonium. Introducing two OH groups into triethylamine reduces the inhibitory potency while introduction of two OH groups into diethylamine or three OH groups into triethylamine abolishes the inhibitory potency as a result of reduced hydrophobicity. With choline (trimethylethanolamine) and its analogues the reversed correlation between Ki,NMeN and log octanol was also seen. Molecules with a similar hydrophobic moiety to those of the monoammonium compounds, but with two ammonium groups, showed only a small or no inhibitory potency against NMeN+ Transport. The data indicate that (a) hydrophobic moieties are important for the interaction with the contraluminal Organic Cation Transporter, and (b) the size of the molecule can be a limiting factor. The reduced or missing interaction of the bisquarternary compound might be caused either by the second charge and/or reduced hydrophobicity and/or too large size of a molecule.
Kenichi Inui - One of the best experts on this subject based on the ideXlab platform.
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importance of the multidrug and toxin extrusion mate slc47a family to pharmacokinetics pharmacodynamics toxicodynamics and pharmacogenomics
British Journal of Pharmacology, 2011Co-Authors: Atsushi Yonezawa, Kenichi InuiAbstract:The renal Organic Cation Transport system mediates the tubular secretion of Cationic compounds including drugs, toxins and endogenous metabolites into urine. It consists of a membrane potential-dependent Organic Cation Transporter at the basolateral membrane and an H+/Organic Cation antiporter at the brush-border membrane. In 2005, human multidrug and toxin extrusion MATE1/SLC47A1 was identified as a mammalian homologue of bacterial NorM. Thereafter, human MATE2-K/SLC47A2 and rodent MATE were found. Functional characterization revealed that MATE1 and MATE2-K were H+/Organic Cation antiporter, mediating the renal tubular secretion of Cationic drugs in cooperation with the basolateral Organic Cation Transporter OCT2. Recently, substrate specificity, transcription mechanisms, structure, polymorphisms, in vivo contributions and clinical outcomes on MATE have been investigated intensively. In this review, we summarize recent findings on MATE1/SLC47A1 and MATE2-K/SLC47A2 and discuss the importance of these Transporters to the pharmacokinetics, pharmacodynamics/toxicodynamics and pharmacogenomics of Cationic drugs.
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altered pharmacokinetics of Cationic drugs caused by down regulation of renal rat Organic Cation Transporter 2 slc22a2 and rat multidrug and toxin extrusion 1 slc47a1 in ischemia reperfusion induced acute kidney injury
Drug Metabolism and Disposition, 2008Co-Authors: Takanobu Matsuzaki, Kenichi Inui, Takafumi Morisaki, Wakako Sugimoto, Koji Yokoo, Daisuke Sato, Hiroshi Nonoguchi, Kimio Tomita, Tomohiro Terada, Akinobu HamadaAbstract:In the proximal tubules of rat (r) kidney, the polyspecific Organic Cation Transporters (OCTs), rOCT1 and rOCT2, mediate the baso-lateral uptake of various Organic Cations, including many drugs, toxins, and endogenous compounds, and the apical type of H+/ Organic Cation antiporter, rat multidrug and toxin extrusion 1 (rMATE1), mediate the efflux of Organic Cations. Renal clearances of H2 receptor antagonists, including famotidine, were reported to be decreased in patients with kidney disease. Therefore, acute kidney injury (AKI) could influence renal excretion and disposition of Organic Cations accompanied by the regulation of Organic Cation Transporters. The aim of this study was to investigate the pharmacokinetic alteration of Cationic drugs and the expression of tubular Organic Cation Transporters, rOCT1, rOCT2, and rMATE1, in ischemia/reperfusion (I/R)-induced AKI rats. I/R-induced AKI increased the plasma concentration of i.v. administrated famotidine, a substrate for rOCT1 and rOCT2, or tetraethylammonium (TEA), a substrate for rOCT1, rOCT2, and rMATE1. The areas under the plasma concentration curves for famotidine and TEA were 2- and 6-fold higher in I/R rats than in sham-operated rats, respectively. The accumulation of TEA into renal slices was significantly decreased, suggesting that Organic Cation Transport activity at the basolateral membranes was reduced in I/R rat kidney. The protein expressions of basolateral rOCT2 and luminal rMATE1 were down-regulated in I/R rat kidneys. These data suggest that the urinary secretion of Cationic drugs via epithelial Organic Cation Transporters is decreased in AKI.
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hormonal regulation of Organic Cation Transporter oct2 expression in rat kidney
FEBS Letters, 2000Co-Authors: Yumiko Urakami, Hideyuki Saito, Masahiro Okuda, Kenichi InuiAbstract:Rat (r) OCT2 was identified as the second member of the Organic Cation Transporter (OCT) family, and is predominantly expressed in the kidney. We reported previously that rOCT2 was responsible for the gender differences in renal basolateral membrane Organic Cation Transport activity. As renal rOCT2 expression in males is much higher than that in females, we hypothesized that rOCT2 expression may be under the control of sex hormones. Treatment of male and female rats with testosterone significantly increased the expression levels of rOCT2 mRNA and protein in the kidney, whereas estradiol treatment moderately decreased the expression levels of rOCT2. There was no regulation of renal rOCT1 mRNA expression by testosterone or estradiol. Treatment of male and female rats with testosterone significantly stimulated the tetraethylammonium (TEA) accumulation by renal slices, whereas estradiol treatment caused a decrease in the TEA accumulation by slices from male but not female rats. The present findings suggested that testosterone up-regulates renal rOCT2 expression and estradiol moderately down-regulates rOCT2.
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Gender differences in expression of Organic Cation Transporter OCT2 in rat kidney
FEBS letters, 1999Co-Authors: Yumiko Urakami, Hideyuki Saito, Masahiro Okuda, Nobuhiko Nakamura, Kazushige Takahashi, Yukiya Hashimoto, Kenichi InuiAbstract:The Organic Cation Transporter (OCT) mediates transloCation of various Cationic molecules including drugs, toxins and endogenous substances. We examined gender differences in the expression of rat (r) OCT2 in the kidney. Slices and basolateral membrane vesicles of male rat kidney showed a higher Transport activity for tetraethylammonium than those of female rat kidney. The expression levels of rOCT2 mRNA and protein in the kidney of males were much higher than those in females. There was no gender difference in mRNA expression of rOCT1 and rOCT3. These findings suggest that rOCT2 is responsible for the gender differences in renal basolateral membrane Organic Cation Transport activity.
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Molecular mechanisms of Organic Cation Transport in OCT2-expressing Xenopus oocytes.
Biochimica et Biophysica Acta, 1999Co-Authors: Masahiro Okuda, Yumiko Urakami, Hideyuki Saito, Kenichi InuiAbstract:Abstract The molecular mechanisms of Organic Cation Transport by rat OCT2 was examined in the Xenopus oocyte expression system. When extracellular Na+ ions were replaced with K+ ions, uptake of tetraethylammonium (TEA) by OCT2-expressing oocytes was decreased, suggesting that TEA uptake by OCT2 is dependent on membrane potential. Kinetic analysis revealed that the decreased TEA uptake by ion substitution was caused at least in part by decreased substrate affinity. AcidifiCation of extracellular buffer resulted in decreased uptake of TEA, whereas TEA efflux from OCT1- and OCT2-expressing oocytes was not stimulated by inward proton gradient, in consistent with basolateral Organic Cation Transport in the kidney. Inhibition of TEA uptake by various Organic Cations revealed that apparent substrate spectrum of OCT2 was similar with that of OCT1. However, the affinity of procainamide to OCT1 was higher than that to OCT2. Uptake of 1-methyl-4-phenylpyridinium was stimulated by OCT2 as well as OCT1, but uptake of levofloxacin, a zwitterion, was not stimulated by both OCTs. These results suggest that OCT2 is a multispecific Organic Cation Transporter with the characteristics comparable to those of the basolateral Organic Cation Transporter in the kidney.
Shuvo Roy - One of the best experts on this subject based on the ideXlab platform.
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apical shear stress enhanced Organic Cation Transport in human oct2 mate1 transfected madin darby canine kidney cells involves ciliary sensing
Journal of Pharmacology and Experimental Therapeutics, 2019Co-Authors: Aishwarya Jayagopal, Paul Brakeman, Peter Soler, Nicholas Ferrell, William H Fissell, Deanna L Kroetz, Shuvo RoyAbstract:Active Transport by renal proximal tubules plays a significant role in drug disposition. During drug development, estimates of renal excretion are essential to dose determination. Kidney bioreactors that reproduce physiologic cues in the kidney, such as flow-induced shear stress, may better predict in vivo drug behavior than do current in vitro models. In this study, we investigated the role of shear stress on active Transport of 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (ASP+) by Madin-Darby canine kidney cells exogenously expressing the human Organic Cation Transporters Organic Cation Transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1). Cells cultured in a parallel plate under continuous media perfusion formed a tight monolayer with a high barrier to inulin. In response to increasing levels of shear stress (0.2-2 dynes/cm2), cells showed a corresponding increase in Transport of ASP+, reaching a maximal 4.2-fold increase at 2 dynes/cm2 compared with cells cultured under static conditions. This Transport was inhibited with imipramine, indicating active Transport was present under shear stress conditions. Cells exposed to shear stress of 2 dynes/cm2 also showed an increase in RNA expression of both transfected human and endogenous OCT2 (3.7- and 2.0-fold, respectively). Removal of cilia by ammonium sulfate eliminated the effects of shear on ASP+ Transport at 0.5 dynes/cm2 with no effect on ASP+ Transport under static conditions. These results indicate that shear stress affects active Transport of Organic Cations in renal tubular epithelial cells in a cilia-dependent manner.