Intracellular pH regulation in isolated rat bile duct epithelial cells.

Strazzabosco, Mario; Mennone, Albert; Boyer, James L.

doi:10.1172/jci115160

Cited by 107 publications

(115 citation statements)

References 42 publications

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“…11,12 Phosphorylation and opening of a cAMP-dependent Cl Ϫ channel, the cystic fibrosis transmembrane conductance regulator (CFTR), 13 causes Cl Ϫ efflux to the ductular lumen. This appears to stimulate an apical Na ϩ -independent Cl Ϫ /HCO 3 Ϫ anion exchange (AE), 14 with HCO 3 Ϫ efflux and Cl Ϫ influx, that is facilitated by the outside to inside transmembrane gradient of Cl Ϫ at relatively high intracellular HCO 3 Ϫ concentration. [10][11][12]15,16 Several bicarbonate transporters, most of them encoded by the SLC4 and SLC26 gene families, 17 have been described to exert AE activity.…”

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confidence: 99%

Bicarbonate-rich choleresis induced by secretin in normal rat is taurocholate-dependent and involves AE2 anion exchanger

et al. 2006

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Canalicular bile is modified along bile ducts through reabsorptive and secretory processes regulated by nerves, bile salts, and hormones such as secretin. Secretin stimulates ductular cystic fibrosis transmembrane conductance regulator (CFTR)-dependent Cl ؊ efflux and subsequent biliary HCO 3 ؊ secretion, possibly via Cl ؊ /HCO 3 ؊ anion exchange (AE). However, the contribution of secretin to bile regulation in the normal rat, the significance of choleretic bile salts in secretin effects, and the role of Cl ؊ /HCO 3 ؊ exchange in secretin-stimulated HCO 3 ؊ secretion all remain unclear. Here, secretin was administered to normal rats with maintained bile acid pool via continuous taurocholate infusion. Bile flow and biliary HCO 3 ؊ and Cl ؊ excretion were monitored following intrabiliary retrograde fluxes of saline solutions with and without the Cl ؊ channel inhibitor 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) or the Cl ؊ /HCO 3 ؊ exchange inhibitor 4,4 -diisothiocyanatostilbene-2,2 -disulfonic acid (DIDS). Secretin increased bile flow and biliary excretion of HCO 3 ؊ and Cl ؊ . Interestingly, secretin effects were not observed in the absence of taurocholate. Whereas secretin effects were all blocked by intrabiliary NPPB, DIDS only inhibited secretin-induced increases in bile flow and HCO 3 ؊ excretion but not the increased Cl ؊ excretion, revealing a role of biliary Cl ؊ /HCO 3 ؊ exchange in secretininduced, bicarbonate-rich choleresis in normal rats. Finally, small hairpin RNA adenoviral constructs were used to demonstrate the involvement of the Na ؉ -independent anion exchanger 2 (AE2) through gene silencing in normal rat cholangiocytes. AE2 gene silencing caused a marked inhibition of unstimulated and secretin-stimulated Cl ؊ /HCO 3 ؊ exchange. In conclusion, maintenance of the bile acid pool is crucial for secretin to induce bicarbonate-rich choleresis in the normal rat and that this occurs via a chloride-bicarbonate exchange process consistent with AE2 function. (HEPATOLOGY 2006;43:266-275.) S ecretin is known to induce bicarbonate-rich hydrocholeresis in many animal species. 1-7 Its interaction with a G-protein-coupled receptor selectively localized to the epithelial bile duct cells 8 results in increased intracellular levels of cyclic adenosine monophosphate (cAMP) [cAMP] i 7,9,10 and protein kinase A activation. 11,12 Phosphorylation and opening of a cAMP-dependent Cl Ϫ channel, the cystic fibrosis transmembrane conductance regulator (CFTR), 13 causes Cl Ϫ efflux to the ductular lumen. This appears to stimulate an apical Na ϩ -independent Cl Ϫ /HCO 3 Ϫ anion exchange (AE), 14 with HCO 3 Ϫ efflux and Cl Ϫ influx, that is facilitated by the outside to inside transmembrane gradient of Cl Ϫ at relatively high intracellular HCO 3 Ϫ concentration. [10][11][12]15,16 Several bicarbonate transporters, most of them encoded by the SLC4 and SLC26 gene families, 17 have been described to exert AE activity. A decade ago, we localized one of those polypeptides, the SLC4A2 or AE2, 18 to the apical membrane in...

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confidence: 99%

Bicarbonate-rich choleresis induced by secretin in normal rat is taurocholate-dependent and involves AE2 anion exchanger

et al. 2006

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“…Differences in untreated PBC and con-ulation (usually through Cl 0 influx and HCO 0 3 efflux, which leads to intracellular acidification). 8,20,21 Reduced AE2 extrols were even more striking when the sum of structure scores, referred to as the immunoreactivity index for AE2, pression could alter pH status within the cells, leading to antigenic changes (for example, changes in protein strucwas considered in each preparation (Fig. 1).…”

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confidence: 99%

Decreased anion exchanger 2 immunoreactivity in the liver of patients with primary biliary cirrhosis

et al. 1997

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Organic and inorganic anions participate in the generation Chloride-bicarbonate anion exchanger 2 (AE2) is exof the osmotic force responsible for the bile acid-independent pressed in a variety of tissues, including the liver and flow. 4,5 Secretion of bicarbonate to the bile appears to occur salivary glands, where it may participate in the generathrough Na / -independent chloride-bicarbonate anion extion of hydroionic fluxes into secretions. We have prechangers (AE), and AE proteins are thought to play an imviously reported decreased hepatic levels of AE2 mesportant role in the formation of canalicular and ductular senger RNA in patients with primary biliary cirrhosis bile. 6-9 (PBC), a cholestatic condition frequently associated AE proteins are encoded by a family of genes, three of with pluriglandular exocrine failure. Here we investiwhich (AE1, AE2, and AE3 genes) are now well charactergated the expression of AE2 protein in the liver of PBC ized. 10,11 AE1 (also referred to as band-3 protein) is expressed patients. Using a monoclonal antibody against an AE2 in erythroid cell membranes and in the kidney. AE3 messenpeptide, immunohistochemistry was performed on liver ger RNA (mRNA) has been described in excitable tissues such biopsy specimens from subjects with normal liver (n Å as nervous system and cardiac muscle. AE2 protein (or corre-7), patients with PBC (n Å 13), and patients with cirrhosponding transcript) has been encountered in a variety of sis or cholestasis other than PBC (n Å 17 and 11, respectissues, including the liver and secretory epithelia, where it tively). Immunostaining was graded from 0 to 7, is thought to participate in the generation of hydroionic according to its intensity and distribution. AE2 immunofluxes into secretions. Using a monoclonal antibody against reactivity was observed in normal livers, as previously AE2 developed in our laboratory, we have found that AE2 reported, and in many pathological liver biopsy speciimmunoreactivity localizes to both canaliculi and the luminal mens, being mainly restricted to canaliculi and the lumiside of bile duct epithelial cells. 12 This apical location of AE2 nal membrane of terminal and interlobular bile ducts.is consistent with its participation in bile formation and with Canalicular and ductular scores were significantly recurrent models of biliary bicarbonate secretion and secretinduced in the PBC group compared with each control stimulated ductular choleresis. 13,14 group (normal liver and cirrhosis or cholestasis other PBC is frequently associated with pluriglandular exocrine than PBC), whereas no differences in immunoreactivity failure. 15,16 We hypothesized that abnormalities in bicarbonscores were observed among control groups. When four ate transport mechanisms could underlie both the cholestasis patients with primary sclerosing cholangitis (PSC) were and the exocrine failure that characterize this disease. We analyzed, they also differed from those with PBC. These have already reported a reduction in the levels of AE2 mRNA results su...

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“…Characterization of Mouse BDCC-Immunocytochemistry using cytokeratin-19 or CFTR antibody (6,8,11) was performed in BDCCs 48 -72 h after plating. Immunofluorescent images of the mouse BDCCs, immunostained with cytokeratin-19 or CFTR antibody, were obtained using an Olympus IX-70 inverted fluorescent microscope (Olympus America, Inc., Melville, NY) with a cooled charge-coupled device video camera (Hamamatsu Photonics Systems, Bridgewater, NJ) connected to a Power Mac computer with image analysis software (Improvision, Inc., Boston, MA).…”

Section: Materials-bovinementioning

confidence: 99%

“…In addition, these findings also indicate that there is a functioning non-CFTR chloride conductance pathway(s) present in CF cholangiocytes, which can mediate RVD in these cells. (7,8). Isotonic and hypotonic solution compositions are as described previously (4).…”

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Impaired Regulatory Volume Decrease in Freshly Isolated Cholangiocytes from Cystic Fibrosis Mice

Cho

Siegrist

Zinzow

2004

Journal of Biological Chemistry

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Various K ؉ and Cl ؊ channels are important in cell volume regulation and biliary secretion, but the specific role of cystic fibrosis transmembrane conductance regulator in cholangiocyte cell volume regulation is not known. The goal of this research was to study regulatory volume decrease (RVD) in bile duct cell clusters (BDCCs) from normal and cystic fibrosis (CF) mouse livers. Mouse BDCCs without an enclosed lumen were prepared as described (Cho, W. K. (2002) Am. J. Physiol. 283, G1320 -G1327). The isotonic solution consisted of HEPES buffer with 40% of the NaCl replaced with isomolar amounts of sucrose, whereas hypotonic solution was the same as isotonic solution without sucrose. The cell volume changes were indirectly assessed by measuring cross-sectional area (CSA) changes of the BDCCs using quantitative videomicroscopy. Exposure to hypotonic solutions increased relative CSAs of normal BDCCs to 1.20 ؎ 0.01 (mean ؎ S.E., n ‫؍‬ 50) in 10 min, followed by RVD to 1.07 ؎ 0.01 by 40 min. Hypotonic challenge in CF mouse BDCCs also increased relative CSA to 1.20 ؎ 0.01 (n ‫؍‬ 53) in 10 min but without significant recovery. Coadministration of the K ؉ -selective ionophore valinomycin restored RVD in CF mouse BDCCs, suggesting that the impaired RVD was likely from a defect in K ؉ conductance. Moreover, this valinomycin-induced RVD in CF mice was inhibited by 5-nitro-2 -(3-phenylpropylamino)-benzoate, indicating that it is not from nonspecific effects. Neither cAMP nor calcium agonists could reverse the impaired RVD seen in CF cholangiocytes. Our conclusion is that CF mouse cholangiocytes have defective RVD from an impaired K ؉ efflux pathway, which could not be reversed by cAMP nor calcium agonists.Under physiological conditions, osmoregulation plays a crucial role in cholangiocytes, which are exposed to various osmotic stresses from the uptake of solutes and electrolytes and bile secretion (1, 2). A recent study on a human cholangiocarcinoma cell line (3), as well as our results in a study on primary bile duct cell clusters (BDCCs) 1 from normal mouse livers (4), indicates that cholangiocytes can regulate their cell volumes back to base line from hypotonicity-induced swelling. As in other cell types, these adaptive mechanisms of regulatory volume decrease (RVD) in cholangiocytes are mediated by certain K ϩ and Cl Ϫ conductances (3, 4).Cystic fibrosis (CF) is the most common inherited multisystem disease in the Caucasian population and is caused by a defect in the cystic fibrosis transmembrane conductance regulator (CFTR). Many CF patients develop a spectrum of hepatobiliary diseases that are thought to be due to secretory dysfunctions from the CFTR Cl Ϫ channel defects. In recent years, CF liver diseases have become the second most common cause of mortality in CF patients as they live longer, but the underlying pathophysiological mechanisms are not well understood. Recent immunocytochemical studies of the liver have shown that CFTR is expressed only on the bile duct epithelium but not on hepatocytes (5). The CFTR is...

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Intracellular pH regulation in isolated rat bile duct epithelial cells.

Cited by 107 publications

References 42 publications

Bicarbonate-rich choleresis induced by secretin in normal rat is taurocholate-dependent and involves AE2 anion exchanger

Bicarbonate-rich choleresis induced by secretin in normal rat is taurocholate-dependent and involves AE2 anion exchanger

Decreased anion exchanger 2 immunoreactivity in the liver of patients with primary biliary cirrhosis

Impaired Regulatory Volume Decrease in Freshly Isolated Cholangiocytes from Cystic Fibrosis Mice

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