Down-regulation of expression and function of the rat liver Na+/bile acid cotransporter in extrahepatic cholestasis

Gartung, Carsten; Ananthanarayanan, Meenakshisundaram; Rahman, M. Azizur; Schuele, Stephan; Nundy, Surajit; Soroka, Carol J.; Stolz, Andrew; Suchy, Frederick J.; Boyer, James L.

doi:10.1053/gast.1996.v110.pm8536857

Cited by 237 publications

(168 citation statements)

References 5 publications

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“…22 These discrepancies may be related to strain differences and/or the severity of the cholestatic injury after 7 versus 14 days of CBDL. Ntcp, Oatp1, and Oct1 protein expression decreased in both wild-type and Mrp4Ϫ/Ϫ CBDL mice as previously reported in CBDL rats 21,23,26 and mice, 28,29 although Ntcp reached statistical significance only in the Mrp4Ϫ/Ϫ group (Fig. 4A-B).…”

Section: Cbdl Results In More Liversupporting

confidence: 86%

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Mrp4−/− mice have an impaired cytoprotective response in obstructive cholestasis

et al. 2006

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Mrp4 is a member of the multidrug resistance-associated gene family that is expressed on the basolateral membrane of hepatocytes and undergoes adaptive upregulation in response to cholestatic injury or bile acid feeding. However, the relative importance of Mrp4 in a protective adaptive response to cholestatic injury is not known. To address this issue, common bile duct ligation (CBDL) was performed in wild-type and Mrp4؊/؊ mice and animals followed for 7 days. Histological analysis and serum aminotransferase levels revealed more severe liver injury in the absence of Mrp4 expression. Western analyses revealed that Mrp4, but not Mrp3, was significantly increased after CBDL in wild-type mice. Serum bile acid levels were significantly lower in Mrp4؊/؊ mice than in wild-type CBDL mice, whereas serum bilirubin levels were the same, suggesting that Mrp4 was required to effectively extrude bile acids from the cholestatic liver. Mrp3 and Ost␣-Ost␤ were upregulated in Mrp4؊/؊ mice but were unable to compensate for the loss of Mrp4. High-performance liquid chromatography analysis on liver extracts revealed that taurine tetrahydroxy bile acid/beta-muricholic acid ratios were increased twofold in Mrp4؊/؊ mice. In conclusion, hepatic Mrp4 plays a unique and essential protective role in the adaptive response to obstructive cholestatic liver injury. ( M ultidrug resistance-associated protein 4 (MRP4) (ABCC4) is an ATP-dependent organic anion transporter with broad substrate specificity. [1][2][3] It is a member of the ABC transporter superfamily 4 and is expressed in a variety of epithelia, including the basolateral and apical plasma membranes of the liver and kidneys, respectively. 5-7 However, this array of substrates and specific tissue localization have not provided insight into Mrp4 function in vivo.Mrp4 was first suggested to play a role in the adaptive response to the hepatic overload of bile acids following the genetic deletion of farnesoid X receptor (FXR), a bile acid sensor. 8,9 A subsequent study suggested that Mrp4 was not elevated upon feeding the hydrophobic bile acid, lithocholic acid. 10 Despite this finding, other studies have demonstrated that hepatic Mrp4 is upregulated in both rats and mice after bile duct ligation 6,11 and in pediatric patients with progressive familial intrahepatic cholestasis. 12 Recent studies demonstrate that MRP4 functions as an efflux pump for bile acids together with glutathione. 13 Further support for a role for MRP4 in hepatic bile acid overload is the recent demonstration that Mrp4 is upregulated by the constitutive androstane receptor. 14 Constitutive androstane receptor is a member of the nuclear hormone receptor superfamily that is required to elevate serum bile acids during cholestatic injury. 15 Cholestatic injury in mice, rats, and humans can also result in adaptive responses in other basolateral transporters. Examples include Mrp3, which is primarily a bilirubin conjugate transporter and also a constitutive androstane receptor target, 15 and the recently described heterodi...

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Section: Cbdl Results In More Liversupporting

confidence: 86%

“…Ntcp mRNA was significantly downregulated after CBDL (Fig. 3) as described in rats 23 and mice. 24 However, there were no significant changes in Mrp2 mRNA in any of the experimental groups as described previously in mice, 11 in contrast to rat liver following CBDL 25,26 (Fig.…”

Section: Cbdl Results In More Liversupporting

confidence: 60%

Mrp4−/− mice have an impaired cytoprotective response in obstructive cholestasis

et al. 2006

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“…Current concepts assume mechanisms that would limit intracellular accumulation of potentially toxic bile salts under cholestatic conditions. 17,28,32 This includes down-regulation of Ntcp 33 or OATPs 34 at the basolateral membrane in order to limit bile salt uptake, or upregulation of Mrp4, 34 Mrp3, 35 and OSTa/b, 12 which may enhance bile salt secretion back into the systemic circulation. Bile salt inflow to the liver may increase considerably under pathophysiological conditions, but may also reach physiological concentrations of up to 150 lmol/L (in rat).…”

Section: Discussionmentioning

confidence: 99%

Short-term feedback regulation of bile salt uptake by bile salts in rodent liver

et al. 2012

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The sodium taurocholate cotransporting polypeptide (Ntcp) is the major bile salt uptake transporter at the sinusoidal membrane of hepatocytes. Short-term feedback regulation of Ntcp by primary bile salts has not yet been investigated in vivo. Subcellular localization of Ntcp was analyzed in Ntcp-transfected HepG2-cells by flow cytometry and in immunofluorescence images from tissue sections by a new automated image analysis method. Net bile salt uptake was investigated in perfused rat liver by a pulse chase technique. In Flag-Ntcp-EGFP (enhanced green fluorescent protein) expressing HepG2-cells, taurochenodeoxycholate (TCDC), but not taurocholate (TC), induced endocytosis of Ntcp. TCDC, but not TC, caused significant internalization of Ntcp in perfused rat livers, as shown by an increase in intracellular Ntcp immunoreactivity, whereas Bsep distribution remained unchanged. These results correlate with functional studies. Rat livers were continuously perfused with 100 mu mol/L of TC. 25 mu mol/L of TCDC, taurodeoxycholate (TDC), tauroursodeoxycholate (TUDC), or TC were added for 30 minutes, washed out, followed by a pulse of (3)[H]-TC. TCDC, but not TDC, TUDC, or TC significantly increased the amount of (3)[H]-TC in the effluent, indicating a reduced sinusoidal net TC uptake. This effect was sensitive to chelerythrine (protein kinase C inhibitor) and cypermethrin (protein phosphatase 2B inhibitor). Phosphoinositide 3-kinase (PI3K) inhibitors had an additive effect, whereas Erk1/2 (extracellular signal activated kinase 1/2), p38MAPK, protein phosphatase 1/2A (PP1/2A), and reactive oxygen species (ROS) were not involved. Conclusion: TCDC regulates bile salt transport at the sinusoidal membrane by protein kinase C-and protein phosphatase 2B-mediated retrieval of Ntcp from the plasma membrane. During increased portal bile salt load this mechanism may adjust bile salt uptake along the acinus and protect periportal hepatocytes from harmful bile salt concentrations

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“…Male SpragueDawley rats (200 -230 g) were obtained from Charles River (Wilmington, MA) and underwent BDL or sham operation as previously described. 21,23 Animals were sacrificed at 3, 7, and 14 days and tissues were harvested for Western analysis, real-time reverse transcriptase-mediated polymerase chain reaction (RT-PCR), and immunofluorescence studies. Tissues for immunofluorescence were snap frozen in freon that had been cooled in liquid nitrogen.…”

Section: Methodsmentioning

confidence: 99%

Down-regulation of the organic cation transporter 1 of rat liver in obstructive cholestasis

et al. 2004

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The liver plays a major role in biotransformation and elimination of various therapeutic agents and xenobiotics, many of which are organic cations and substrates of the organic cation transporter 1 (Oct1, Slc22a1). Oct1 is expressed at the basolateral membranes of hepatocytes and proximal renal tubules. Although Oct1 is the major uptake mechanism in hepatocytes for many pharmaceutical compounds, little is known about the effects of liver injury on this process. Our aim was to investigate the effects of obstructive cholestasis on Oct1 expression and function in liver and kidney. The effects of bile duct ligation (BDL) on Oct1 protein, messenger RNA (mRNA) expression, and tissue localization were determined in rat liver and kidney with Western analysis, real-time reverse transcriptase-mediated polymerase chain reaction (RT-PCR), and immunofluorescence. To assess Oct1 function, the model substrate tetraethylammonium ([ 14 C]TEA) was administered intravenously to BDL and control rats and distribution of radioactivity was determined. Oct1 protein significantly decreased in cholestatic livers to 42.1 ؎ 17.7% (P < .001), 15.5 ؎ 4.7% (P < .05), and 8.6 ؎ 2.7% (P < .05) of controls after 3, 7, and 14 days, respectively, but not in kidneys. Hepatic Oct1 mRNA decreased to 77.2 ؎ 12.7%, 40.7 ؎ 8.1% (P < .05), and 50.3 ؎ 7.5% (P < .05) 3, 7, and 14 days after BDL, respectively. Tissue immunofluorescence corroborated these data. Hepatic accumulation of [ 14 C]TEA in 14-day BDL rats was reduced to 29.6 ؎ 10.9% of controls (P < .0005). In conclusion, obstructive cholestasis down-regulates Oct1 and impairs Oct1-mediated uptake in rat liver, suggesting that hepatic uptake of small cationic drugs may be impaired in cholestatic liver injury. (HEPATOLOGY 2004;39:1382-1389

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Down-regulation of expression and function of the rat liver Na+/bile acid cotransporter in extrahepatic cholestasis

Cited by 237 publications

References 5 publications

Mrp4−/− mice have an impaired cytoprotective response in obstructive cholestasis

Mrp4−/− mice have an impaired cytoprotective response in obstructive cholestasis

Short-term feedback regulation of bile salt uptake by bile salts in rodent liver

Down-regulation of the organic cation transporter 1 of rat liver in obstructive cholestasis

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