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N F LaRusso

Publications and source records attributed to N F LaRusso.

At least 37 records · Page 2Linked to original sources
PubMed2000

Rab3D, a small GTP-binding protein implicated in regulated secretion, is associated with the transcytotic pathway in rat hepatocytes.

Rab3 isotypes are expressed in regulated secretory cells. Here, we report that rab3D is also expressed in rat hepatocytes, classic models for constitutive secretion. Using reverse transcriptase polymerase chain reaction (RT-PCR) with primers specific for rat rab3D, we amplified a 151 base pair rab3D fragment from total RNA extracted from primary cultures of rat hepatocytes. Immunoblot analysis using polyclonal antibodies to peptides representing the N- and C-terminal hypervariable regions of murine rab3D recognized a protein of approximately 25 kd in hepatocyte lysates, hepatic subcellular fractions, and tissue extracts. The distribution of rab3D was primarily cytosolic; however, only membrane-associated rab3D significantly bound guanosine triphosphate (GTP) in overlay assays. Several lines of investigation indicate that rab3D is associated with the transcytotic pathway. First, rab3D was enriched in a crude vesicle carrier fraction (CVCF), which includes transcytotic carriers. Vesicular compartments immunoisolated from the CVCF on magnetic beads coated with anti-rab3D antibody were enriched in the transcytosed form of the polymeric IgA receptor (pIgA-R), but lacked not only the pIgA-R precursor form associated with the secretory pathway, but also a Golgi marker protein. Second, indirect immunofluorescence on frozen liver sections and in polarized cultured hepatocytes localized rab3D-positive sites at or near the apical plasma membrane and to the pericanalicular cytoplasm. Finally, cholestasis induced by bile duct ligation (BDL), a manipulation known to slow transcytosis, caused rab3D to accumulate in the pericanalicular cytoplasm of cholestatic hepatocytes. Our results indicate that rab3D plays a role in the regulation of apically directed transcytosis in rat hepatocytes.

Animals↗
PubMed2000

The utility of CA 19-9 in the diagnoses of cholangiocarcinoma in patients without primary sclerosing cholangitis.

OBJECTIVES: The diagnosis of cholangiocarcinoma is often difficult, making management approaches problematic. A reliable serum tumor marker for cholangiocarcinoma would be a useful additional diagnostic test. Previous studies have demonstrated that elevated serum concentrations of CA 19-9, a tumor-associated antigen, have good sensitivity and specificity for cholangiocarcinoma in patients with primary sclerosing cholangitis. However, the value of this tumor marker for cholangiocarcinoma unassociated with primary sclerosing cholangitis is unclear. Thus, the aims of this study were to determine the usefulness of a serum CA 19-9 determination in the diagnosis of de novo cholangiocarcinoma. METHODS: We prospectively measured serum CA 19-9 concentrations in patients with cholangiocarcinoma (n = 36), nonmalignant liver disease (n = 41), and benign bile duct strictures (n = 26). Serum CA 19-9 concentrations were measured by an immunoradiometric assay (CIS Bio International) without knowledge of the clinical diagnosis. RESULTS: The sensitivity of a CA 19-9 value >100 U/ml in diagnosing cholangiocarcinoma was 53%. When compared with the nonmalignant liver disease and the benign bile duct stricture groups, the true negative rates were 76% and 92%, respectively. Patients with unresectable cholangiocarcinoma had significantly greater mean CA 19-9 concentrations compared to patients with resectable cholangiocarcinoma. CONCLUSIONS: These data suggest that the serum CA 19-9 determination is a useful addition to the available tests for the differential diagnosis of cholangiocarcinoma.

Bile Duct Neoplasms↗
PubMed2000

A pilot study of pentoxifylline for the treatment of primary sclerosing cholangitis.

OBJECTIVE: There is no effective therapy for patients with primary sclerosing cholangitis (PSC). Rats with experimental small bowel bacterial overgrowth develop hepatobiliary injury similar to PSC. The hepatobiliary injury results from peptidoglycan-polysaccharide-mediated activation of Kupffer cells, release of cytokines such as tumor necrosis factor (TNF-alpha), and is prevented by pentoxifylline. Our aims were to assess the safety and effects of pentoxifylline on symptoms and biochemical liver tests in patients with PSC. METHODS: A total of 20 patients with clinical, cholangiographic, and histological features of PSC of varying severity were treated with pentoxifylline sustained release (SR) tablets (400 mg q.i.d.) for < or = 1 yr. Serum alkaline phosphatase, aspartate aminotransferase, and bilirubin were monitored every 3 months for 1 year; serum TNF-alpha and TNF receptor subtypes I and II were assessed at baseline and 1 year. RESULTS: Of 20 patients, 16 tolerated pentoxifylline and completed the study. Two patients were withdrawn because of severe nausea, and two patients were noncompliant with medication and withdrew. Pentoxifylline did not significantly alter symptoms of fatigue or pruritus, serum liver tests, serum TNF-alpha or TNF receptor levels. CONCLUSIONS: In the current regimen, pentoxifylline alone does not significantly improve symptoms or liver tests in patients with PSC.

Administration, Oral↗
PubMed2000

A revised natural history model for primary sclerosing cholangitis.

OBJECTIVE: To describe a natural history model for primary sclerosing cholangitis (PSC) that is based on routine clinical findings and test results and eliminates the need for liver biopsy. PATIENTS AND METHODS: Using the Cox proportional hazards analysis, we created a survival model based on 405 patients with PSC from 5 clinical centers. Independent validation of the model was undertaken by applying it to 124 patients who were not included in the model creation. RESULTS: Based on the multivariate analysis of 405 patients, a risk score was defined by the following formula: R = 0.03 (age [y]) + 0.54 loge (bilirubin [mg/dL]) + 0.54 loge (aspartate aminotransferase [U/L]) + 1.24 (variceal bleeding [0/1]) - 0.84 (albumin [g/dL]). The risk score was used to obtain survival estimates up to 4 years of follow-up. Application of this model to an independent group of 124 patients showed good correlation between estimated and actual survival. CONCLUSIONS: A new model to estimate patient survival in PSC includes more reproducible variables (age, bilirubin, albumin, aspartate aminotransferase, and history of variceal bleeding), has accuracy comparable to previous models, and obviates the need for a liver biopsy.

Adult↗
PubMed1999

GUDC inhibits cytochrome c release from human cholangiocyte mitochondria.

Although ursodeoxycholic acid (UDC) is considered effective treatment for primary biliary cirrhosis (PBC), its mechanism of action is unclear. We tested the hypothesis that UDC is taken up by cholangiocytes and inhibits caspase 3-dependent apoptosis. We used the human cholangiocyte cell line (H69) and assessed it for expression and function of an apical sodium-dependent bile acid transporter (ASBT) by RT-PCR and uptake of tritiated taurocholic acid. We experimentally induced apoptosis in H69 cells using beauvericin (BV) and determined caspase 3 activation using a fluorogenic substrate and mitochondrial cytochrome c release (CC) into the cytosol by immunoblot analysis. We found that a functional ASBT is expressed by H69 cells as demonstrated by RT-PCR and bile acid uptake studies. Exposure of H69 cells to BV induced apoptosis in 39.4 +/- 1.3% of cells at 2 h (0.23 +/- 0.2% in controls). In contrast, when H69 cells were preincubated with GUDC (50 mM) for 24 h and then exposed to BV, apoptosis was inhibited by 23% (P < 0.03). In cholangiocytes pretreated with GUDC for 24 h and those treated with BV for 2 h, caspase 3-like activity was reduced by 79% and mitochondrial CC release was inhibited. In summary, the human cholangiocyte cell line H69 possesses a functional bile acid transporter, and GUDC decreases BV-induced apoptosis and inhibits activity of caspase 3 protease by blocking CC release from mitochondria. These preliminary results are consistent with our hypothesis that the beneficial effect of UDC on PBC may involve decreased apoptosis after GUDC uptake by cholangiocytes.

Anti-Bacterial Agents↗
PubMed1999

Recurrence of primary sclerosing cholangitis following liver transplantation.

Recurrence of primary sclerosing cholangitis (PSC) following liver transplantation has been suggested; however, it has not been fully defined because of numerous complicating factors and the lack of diagnostic criteria. In the present study, we investigated the recurrence of PSC by developing strict criteria and applying them to a large cohort of PSC patients who underwent liver transplantation. Between March 1985 and June 1996, 150 PSC patients underwent liver transplantation at the Mayo Clinic; mean follow up was 55 months. The incidence of nonanastomotic biliary strictures and hepatic histologic findings suggestive of PSC were compared between patients transplanted for PSC and a non-PSC transplant control group. Our definition of recurrent PSC was based on characteristic cholangiographic and histologic findings that occur in nontransplant PSC patients. By using strict criteria, 30 patients with other known causes of posttransplant nonanastomotic biliary strictures were excluded leaving 120 patients for analysis of recurrence of PSC. We found evidence of PSC recurrence after liver transplantation in 24 patients (20%). Of these, 22 out of 24 patients showed characteristic features of PSC on cholangiography and 11 out of 24 had compatible hepatic histologic abnormalities with a mean time to diagnosis of 360 and 1,350 days, respectively. Both cholangiographic and hepatic histologic findings suggestive of PSC recurrence were seen in nine patients. The higher incidence and later onset of nonanastomotic biliary strictures in patients with PSC compared with a non-PSC control group is supportive of the fact that PSC does recur following liver transplantation. We were unable to identify specific clinical risk factors for recurrent PSC, and the overall patient and graft survival in patients with recurrent PSC was similar to those without evidence of recurrence. Our observations provide convincing evidence that PSC frequently recurs in the hepatic allograft using strict inclusion and exclusion criteria.

Adult↗
PubMed1999

The relative role of the Child-Pugh classification and the Mayo natural history model in the assessment of survival in patients with primary sclerosing cholangitis.

The Child-Pugh classification is a simple, convenient prognostic measure in patients with liver cirrhosis. We investigated the relative role of the Child-Pugh classification and the Mayo model in the assessment of survival in patients with primary sclerosing cholangitis (PSC). Of the 173 patients described in the original Mayo PSC natural history model, 147 patients had sufficient information in the medical record to allow computation of the Child-Pugh score. We used our most recent modification of the Mayo model to compute the risk score, based on patient's age, serum levels of bilirubin, albumin, and aspartate aminotransferase and history of variceal bleeding. Using the risk score (R), patients were divided into the low- (R < 0), intermediate- (0 </= R < 2), and high-risk (R >/= 2) groups. Kaplan-Meier estimates and proportional hazards analysis were used to evaluate the two prognostic models. Although there was a statistically significant correlation between the Child-Pugh and Mayo risk scores, two-thirds of the patients had a Child-Pugh score of 5 or 6 and a relatively wide range of risk scores (-1.1-4.3). The probability of survival for 7 years in patients in the low-, intermediate-, and high-risk groups was 92%, 74%, and 40% for Child-Pugh class A (n = 96) and 100%, 62%, and 28% for Child-Pugh class B patients (n = 44), respectively. There were only a small number (n = 7) of Child-Pugh class C patients. In our age-adjusted multivariate analysis, each unit increase in the Mayo risk score was associated with a 2.5-fold increase in the risk of death (95% confidence interval: 1.8-3.4, P <.01), whereas Child-Pugh classification had no significant impact on survival (Child-Pugh B vs. A: risk ratio = 1.1 [95% confidence interval: 0.6-2.0]; Child-Pugh C versus A: risk ratio = 0.6 [95% confidence interval: 0. 2-1.8]). In contrast to the Child-Pugh classification, which was developed for advanced liver cirrhosis, the Mayo model provides valid survival information, particularly in patients early in the course of PSC.

Adult↗
PubMed1999

Long-term results of patients undergoing liver transplantation for primary sclerosing cholangitis.

Liver transplantation is the only effective therapeutic option for patients with end-stage liver disease due to primary sclerosing cholangitis (PSC). In this study, we analyzed a single center's experience with 150 consecutive PSC patients who received 174 liver allografts. Mean follow-up was 55 months. Actuarial patient survival at 1, 2, 5, and 10 years was 93.7%, 92.2%, 86.4%, and 69.8%, respectively, whereas graft survival was 83.4%, 83.4%, 79.0%, and 60. 5%, respectively. The main indication for retransplantation was hepatic artery thrombosis, and the major cause of death was severe infection. Patients with PSC had a higher incidence of acute cellular and chronic ductopenic rejection compared to a non-PSC control group. Chronic ductopenic rejection adversely affected patient and graft survival. Biliary strictures, both anastomotic and nonanastomotic, were frequent and occurred in 16.2% and 27.2% of patients, respectively. The incidence of recurrent PSC was 20%. A negative impact on patient survival was not seen in patients with either postoperative biliary strictures or recurrence of PSC. Six patients (4%) had cholangiocarcinoma and 1 patient died related to recurrence of malignant disease. Seventy-eight percent of PSC patients had associated inflammatory bowel disease, most commonly chronic ulcerative colitis, which did not adversely impact patient outcome posttransplantation. Nine patients required proctocolectomy after liver transplantation; 5 because of intractable symptoms related to inflammatory bowel disease and 4 due to the development of colorectal carcinoma/high-grade dysplasia. Our data show that liver transplantation provides excellent long-term patient and graft survival for patients with end-stage PSC.

Cause of Death↗
PubMed1999

Cholangiocarcinomas express Fas ligand and disable the Fas receptor.

Cholangiocarcinoma is a highly-malignant adenocarcinoma originating from cholangiocytes. Current concepts support escape from immune surveillance using aberrant expression of Fas ligand (FasL) and dysregulation of receptor (FasR) signaling as a potential mechanism for tumor progression. Our aims were to determine if altered expression of FasR and FasL or changes in expression of FLICE inhibitor (I-FLICE) allow cholangiocarcinoma cells to escape immune surveillance. Human cholangiocarcinoma cell lines were evaluated for the functional expression of FasR and FasL by (1) quantitating apoptosis after incubation of cells with agonistic antibodies and (2) an in vitro cell death assay involving coculture of cholangiocarcinoma cells with Fas-sensitive thymocytes. I-FLICE antisense treatment was performed by stable transfection with complementary DNA (cDNA) for I-FLICE in the reverse orientation. We found that normal cholangiocytes in vivo express FasL. Human cholangiocarcinoma cell lines express both FasL and FasR and I-FLICE. FasL expressed by cholangiocarcinomas in vitro induced lymphocyte cell death (70% after 24 hours). Despite the expression of FasR, exposure of the cells to agonistic antibodies (500 ng/mL) induced only minimal apoptosis in the Jurkat cells. Antisense treatment of cholangiocarcinomas in vitro with I-FLICE reduced protein expression of I-FLICE by 90% to 95% and increased Fas-mediated apoptosis 2-fold. We concluded that cholangiocarcinomas escape immune surveillance either by disabling FasR signaling through the expression of I-FLICE and/or increased FasL expression to induce apoptosis of invading T cells. Reduction of I-FLICE expression in cholangiocarcinoma cells restored Fas-mediated apoptosis. Therapeutic maneuvers to inhibit expression of I-FLICE may aid in the treatment of cholangiocarcinoma.

Antibodies, Monoclonal↗
PubMed1999

Time course of histological progression in primary sclerosing cholangitis.

OBJECTIVE: The aim of this study was to determine the time course over which patients with primary sclerosing cholangitis (PSC) progress through the histological stages of the disease. METHODS: One hundred seven patients with PSC who had at least two liver biopsies were identified. The stage information from two consecutive biopsies formed one observation and a continuous time Markov model was used to describe the rate of progression between biopsies. RESULTS: Three hundred seven liver biopsies were performed in the 107 patients giving a total of 200 observations. At 1 yr, 42% of patients in stage II disease progress, 66% at 2 yr, and 93% at 5 yr; whereas 14% of patients in stage III progress at 1 yr, 25% at 2 yr, and 52% at 5 yr. The frequency of progression of stage I disease could not be determined because of the small number of patients in stage I. Regression of histological stage was observed in 30 of 200 total observations (15%), and in 30 of 85 observations (35%) in which there was a change in stage. CONCLUSIONS: These data regarding histological progression in PSC may be potentially helpful in determining the number of patients and length of time necessary to appreciate a treatment effect in clinical trials. However, the high degree of sampling variability in PSC may restrict the usefulness of serial liver biopsies as a means of evaluating treatment efficacy.

Adolescent↗
PubMed1999

Secretin induces the apical insertion of aquaporin-1 water channels in rat cholangiocytes.

Aquaporin-1 (AQP1) water channels are present in the apical and basolateral plasma membrane domains of bile duct epithelial cells, or cholangiocytes, and mediate the transport of water in these cells. We previously reported that secretin, a hormone known to stimulate ductal bile secretion, increases cholangiocyte osmotic water permeability and stimulates the redistribution of AQP1 from an intracellular vesicular pool to the cholangiocyte plasma membrane. Nevertheless, the target plasma membrane domain (i.e., basolateral or apical) for secretin-regulated trafficking of AQP1 in cholangiocytes is unknown, as is the functional significance of this process for the secretion of ductal bile. In this study, we used primarily an in vivo model (i.e., rats with cholangiocyte hyperplasia induced by bile duct ligation) to address these issues. AQP1 was quantitated by immunoblotting in apical and basolateral plasma membranes prepared from cholangiocytes isolated from rats 20 min after intravenous infusion of secretin. Secretin increased bile flow (78%, P < 0.01) as well as the amount of AQP1 in the apical cholangiocyte plasma membrane (127%, P < 0.05). In contrast, the amount of AQP1 in the basolateral cholangiocyte membrane and the specific activity of an apical cholangiocyte marker enzyme (i.e., gamma-glutamyltranspeptidase) were unaffected by secretin. Similar observations were made when freshly isolated cholangiocytes were directly exposed to secretin. Immunohistochemistry for AQP1 in liver sections from secretin-treated rats showed intensified staining at the apical region of cholangiocytes. Pretreatment of rats with colchicine (but not with its inactive analog beta-lumicolchicine) inhibited both the increases of AQP1 in the cholangiocyte plasma membrane (94%, P < 0.05) and the bile flow induced by secretin (54%, P < 0.05). Our results in vivo indicate that secretin induces the microtubule-dependent insertion of AQP1 exclusively into the secretory pole (i.e., apical membrane domain) of rat cholangiocytes, a process that likely accounts for the ability of secretin to stimulate ductal bile secretion.

Animals↗
PubMed1999

Cryptosporidium parvum induces apoptosis in biliary epithelia by a Fas/Fas ligand-dependent mechanism.

Although the clinical features of sclerosing cholangitis from opportunistic infections of the biliary tree in patients with acquired immunodeficiency syndrome (AIDS) are well known, the mechanisms by which associated pathogens, such as Cryptosporidium parvum, cause disease are obscure. Using an in vitro model of biliary cryptosporidiosis, we observed that C. parvum induces apoptosis in cultured human biliary epithelia. Both caspase protease inhibitors and neutralizing antibodies to either Fas receptor (Fas) and Fas ligand (FasL) inhibited this process; neutralizing antibodies to other apoptotic cytokines [interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta (TGF-beta)] had no effect. C. parvum stimulated FasL membrane surface translocation, increased both FasL and Fas protein expression in infected biliary epithelia, and induced a marked increase of soluble FasL (but not IL-1beta, TNF-alpha, and TGF-beta) in supernatants from infected cells. When a coculture model is used in which infected and uninfected cell populations were physically separated by a semipermeable membrane, both uninfected biliary epithelia and uninfected Fas-sensitive Jurkat cells (but not a Fas-resistant Jurkat cell line) underwent apoptosis when cocultured with infected biliary epithelia. Moreover, both a neutralizing antibody to FasL and a metalloprotease inhibitor blocked the apoptosis in uninfected cocultured cells. Activation of caspase activity was also observed in uninfected cocultured biliary epithelia. The data suggest that C. parvum induces apoptosis in biliary epithelia by a Fas/FasL-dependent mechanism involving both autocrine and paracrine pathways. These observations may be relevant to both the pathogenesis and therapy of the cholangitis seen in AIDS patients with biliary cryptosporidiosis.

Animals↗
PubMed1998

Cholangiocyte-specific rat liver proteins identified by establishment of a two-dimensional gel protein database.

The liver is composed of a variety of cells that form a functional unit involved in uptake, synthesis, metabolism, and secretion. Until recently, most studies examining liver function did not analyze the specific proteins expressed or functions performed by the multiple individual cell types that constitute the hepatic mass. In the last decade, novel isolation methods have been developed that allow the purification of liver cell populations highly enriched in one type of liver cell. Here, we present a detailed two-dimensional (2-D) protein map of rat bile duct epithelial cells (i.e., cholangiocytes) using a recently developed isolation procedure. In addition, we identify 27 major cholangiocyte proteins either by comparison to maps of known rat liver proteins (based on pI and Mr) or by tryptic digestion and microsequencing. Finally, we compare the relative abundance of individual proteins present in cholangiocytes to whole liver as well as hepatocyte-specific proteins. Our results show that cholangiocytes express a unique array of individual proteins. The cholangiocyte 2-D protein pattern is markedly different from that of isolated rat hepatocytes or whole rat liver, with high levels of proteins previously known to be expressed by cholangiocytes (e.g., cytokeratins, actins) as well as protein not previously demonstrated to be expressed at high levels (e.g., annexin V, selenium binding protein). We conclude that this cholangiocyte-derived, 2-D protein map will be a crucial resource for studies directed at our understanding of cholangiocyte physiology and pathobiology.

Animals↗
PubMed1998

Anatomy of the human biliary system studied by quantitative computer-aided three-dimensional imaging techniques.

The branching geometry of the normal, cholangiographically identifiable human biliary tree was studied with an innovative computer-aided three-dimensional (3D) imaging technique. In addition, a serially sectioned conventional paraffin block from a normal donor liver was used to create and quantitatively study a microscopic 3D image. Finally, a geometric model was developed to estimate the enlargement of biliary surfaces imparted by microvilli. The images created by these techniques could be viewed in stationary modes or rotating around any preselected axis. Approximately 7 (+/-3) intrahepatic duct orders were cholangiographically identified. Computerized measurements of the images from three normal livers suggested that the mean total volume of duct orders 1 to 7 shown in the cholangiograms was 16.6 cm3. The volume of the entire macroscopic duct system was estimated to be between 14 and 24 cm3 (mean, 20.4 cm3), with an internal surface of 336 to 575 cm2 (mean, 398 cm2). A geometric model based on electron micrographs suggested that this surface is magnified approximately 5.5-fold by the presence of microvilli. Volume and surface area (SA) measurements of all ducts in the same orders increased nearly exponentially from the first toward the seventh branching order (i.e., from the hilus toward the periphery of the liver), and probably beyond. The microscopic computerized reconstruction of a septal bile duct with its tributaries also allowed volume measurements; the imaged duct system represented 2.7% of the portal tract volume. The data presented herein may help to better evaluate branching patterns of the biliary tree and, eventually, the quantitative aspects of site-restricted cholangiocyte function and their role in the development of biliary diseases.

Biliary Tract↗
PubMed1998

Cryptosporidium parvum is cytopathic for cultured human biliary epithelia via an apoptotic mechanism.

While the clinical features of sclerosing cholangitis secondary to opportunistic infections of the biliary tree in patients with acquired immunodeficiency syndrome (AIDS) are well known, the mechanisms by which microbial pathogens such as Cryptosporidium parvum associated with this syndrome actually cause disease are obscure. We established an in vitro model of biliary cryptosporidiosis employing a human biliary epithelial cell line. Using morphological and biochemical techniques, we examined the interaction of C. parvum with cultured human cholangiocytes. When the apical plasma membrane of polarized, confluent monolayers of human biliary epithelial cells was exposed to C. parvum oocysts that had been excysted in vitro, sporozoites attached to and invaded the cells in a time-, dose-, temperature-, and pH-dependent manner. The infectious process was both plasma membrane domain- and cell-specific, because no attachment or invasion occurred when the basolateral membrane of cholangiocytes was exposed to the parasite, or when a human hepatocyte cell line (HepG2) was used. Time-lapse video microscopy and scanning electron microscopy (SEM) showed that sporozoite attachment was rapid, involved extensive cholangiocyte membrane ruffling, and culminated in parasite penetration into a tight-fitting vacuole formed by invagination of the plasma membrane similar to those found in naturally occurring infection in vivo. Transmission electron microscopy (TEM) showed that C. parvum organisms formed parasitophorus vacuoles and were able to undergo a complete reproductive cycle, forming both asexual and sexual reproductive stages. Unexpectedly, direct cytopathic effects were noted in infected monolayers, with widespread programmed cell death (i.e., apoptosis) of biliary epithelial cells as assessed both morphologically and biochemically beginning within hours after exposure to the organism. The novel finding of specific cytopathic invasion of biliary epithelia by C. parvum may be relevant to the pathogenesis and possible therapy of the secondary sclerosing cholangitis seen in AIDS patients with biliary cryptosporidiosis.

Animals↗
PubMed1998

Purinergic regulation of acid/base transport in human and rat biliary epithelial cell lines.

Biliary epithelial cells (cholangiocytes) are responsible for rapid regulation of bile volume and alkalinity. Secretin and other hormones raising intracellular cyclic adenosine monophosphate (cAMP) concentrations promote biliary HCO3 secretion by stimulating apical Cl- channels and Cl-/HCO3- exchange (AE2). Cholangiocyte ion transport may also be stimulated by locally acting mediators; for example, adenosine 5'-triphosphate (ATP), a secretagogue that can be released into the bile by hepatocytes and cholangiocytes, activates Cl- conductances and Na+/H+ exchange (NHE) in cholangiocyte cell lines. To further explore the role of extracellular ATP in the paracrine regulation of carrier mechanisms regulating cholangiocyte H+/HCO3- secretion, we investigated the effects of nucleotides on intracellular pH regulation (measured by microfluorimetry with 2'7'-bis(2-carboxyethyl)-5,6,carboxyfluorescein [BCECF]) in human (MZ-ChA-1) and rat (NRC-1) cholangiocyte cell lines. In MZ-ChA-1 cells, 10 mol/L ATP, uridine 5'-triphosphate (UTP), and ATPgammas significantly increased NHE activity. The pharmacological profile of agonists was consistent with that anticipated for receptors of the P2Y2 class. ATP did not increase AE2 activity, but, when given to cells pretreated with agents raising intracellular cAMP, had a synergistic stimulatory effect that was inhibited by amiloride. To assess the polarity of purinergic receptors, monolayers of NRC-1 cells were exposed to apical or basolateral nucleotides. Apical administration of purinergic agonists, but not adenosine, increased basolateral NHE activity (ATPgammaS > UTP > ATP). Basolateral administration of purinergic agonists induced a weaker activation of NHE, which was instead strongly stimulated by adenosine and by adenosine receptor agonists (NECA = R-PIA = S-PIA). In conclusion, this study demonstrates that, consistent with the proposed role for biliary ATP in paracrine and autocrine control of cholangiocyte ion secretion, extracellular ATP stimulates cholangiocyte basolateral NHE activity through P2Y2 receptors that are predominantly expressed at the apical cell membrane.

Adenosine↗