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Biomedical subjects

Raoul Poupon

Publications and source records attributed to Raoul Poupon.

At least 55 records · Page 3Linked to original sources
PubMed2003

Ursodeoxycholic acid therapy and the risk of colorectal adenoma in patients with primary biliary cirrhosis: an observational study.

Ursodeoxycholic acid (UDCA) is the first-line treatment for primary biliary cirrhosis (PBC). The long-term administration of UDCA might indirectly favor colon carcinogenesis by increasing the fecal excretion of secondary bile acids or, in contrast, it might inhibit colon carcinogenesis, as demonstrated in animal models. In patients with PBC, we examined the effect of prolonged UDCA administration on the prevalence and recurrence of colorectal adenoma and on the proliferation of colon epithelial cells. One hundred fourteen patients (103 women, 11 men; mean age, 55 years) with PBC, were enrolled in a colonoscopic surveillance program. The prevalence of colon adenoma was compared in patients already treated with UDCA (mean duration 46 months) at the time of colonoscopy (treated group, n = 52) and in patients undergoing colonoscopy just prior to treatment initiation (untreated group, n = 62). The recurrence of adenoma following removal (mean follow-up, 35 months) was compared between UDCA-treated patients and appropriate age- and gender-matched controls (2/1) selected from a cohort of 205 patients undergoing polypectomy. Epithelial cell proliferation was assessed using anti-Ki67 antibodies on colon biopsies from both treated and untreated patients. Treated and untreated patients displayed similar demographic characteristics. The prevalence of colorectal adenomas was 13% in the treated group versus 24% in the untreated group (P =.16). The colon epithelial cell proliferation index was significantly lower in treated patients than in untreated patients (P =.001). Following removal of the adenoma, the probability of recurrence was significantly lower in patients treated with UDCA than in controls (7% vs. 28% at 3 years, P =.04). In conclusion, this study suggests that, in patients with PBC, the prolonged administration of UDCA (1) is not associated with an increased prevalence of colorectal adenomas, and (2) significantly decreases the probability of colorectal adenoma recurrence following removal. These results are strengthened by the significant reduction in colon epithelial cell proliferation seen in patients treated with UDCA.

Adenoma↗
PubMed2003

The myofibroblastic conversion of peribiliary fibrogenic cells distinct from hepatic stellate cells is stimulated by platelet-derived growth factor during liver fibrogenesis.

The origin of myofibroblasts and the factors promoting their differentiation during liver fibrogenesis remain uncertain. During biliary-type fibrogenesis, the proliferation and chemoattraction of hepatic stellate cells (HSC) toward bile ducts is mediated by platelet-derived growth factor (PDGF), while myofibroblastic conversion of peribiliary cells distinct from HSC also occurs. We herein examined the phenotype of these peribiliary myofibroblasts as compared with myofibroblastic HSC and tested whether their differentiation was affected by PDGF. Biliary-type liver fibrogenesis was induced by common bile duct ligation in rats. After 48 hours, periductular fibrosis in portal tracts colocalized with smooth muscle alpha-actin-immunoreactive myofibroblasts, the majority of which were desmin negative. Simultaneously, in sinusoids, desmin immunoreactivity was induced in a large number of HSC, which were smooth muscle alpha-actin negative. Cultures of peribiliary myofibroblasts were expanded from isolated bile duct segments and compared with myofibroblastic HSC. Peribiliary myofibroblasts outgrowing from bile duct segments expressed smooth muscle alpha-actin, alpha1 (I) collagen mRNA, and PDGF receptor-beta subunit. Desmin immunoreactivity gradually decreased in cultured peribiliary myofibroblasts, contrasting with constant labeling of all myofibroblastic HSC. In addition, IL-6 expression in peribiliary myofibroblasts was up to 100-fold lower than in myofibroblastic HSC, whereas the expression of the complement-activating protease P100 in both cell types showed little difference and that of the extracellular matrix component fibulin 2 was similar. The expression of smooth muscle alpha-actin protein in cultured peribiliary myofibroblasts was stimulated by PDGF-BB and inhibited by STI571, a PDGF receptor tyrosine kinase inhibitor, whereas in bile duct-ligated rats, the administration of STI571 caused a significant decrease in peribiliary smooth muscle alpha-actin immunoreactivity, and to a lesser extent, a decrease in peribiliary fibrosis. These results indicate that peribiliary cells distinct from HSC undergo a PDGF-mediated conversion into myofibroblasts expressing IL-6 at lower levels than myofibroblastic HSC and contribute to the initial formation of biliary-type liver fibrosis.

Actins↗
PubMed2003

Percutaneous acetic acid injection for hepatocellular carcinoma: using CT fluoroscopy to evaluate distribution of acetic acid mixed with an iodinated contrast agent.

OBJECTIVE: The purpose of our study is to evaluate the distribution of acetic acid mixed with iodinated contrast agent during percutaneous acetic acid injection on CT fluoroscopy for hepatocellular carcinoma. CONCLUSION: Monitoring acetic acid distribution on CT fluoroscopy can detect extratumoral diffusion and may optimize the distribution of acetic acid in hepatocellular carcinoma.

Acetic Acid↗
PubMed2003

[Molecular mechanisms of bile formation and cholestatic diseases].

Biliary function is a vital function of the liver which results from the vectorial transport of endogenous and exogenous substrates through three compartments sequentially: the vascular space, the cellular space and the biliary space. The biliary function is responsible for the homeostasis of lipid metabolism in particular of cholesterol metabolism, the elimination of toxic endo--and xenobiotics such as (bilirubin, lipid bacteria products (endotoxin)) and several inflammatory mediators. Bile elaborated in canaliculi, is modified by cholangiocytes through secretion and absorption. Bile is essential for the intestinal digestion and absorption of nutriments. The main determinant of bile formation is an osmotic filtration process resulting from active transport of bile acids and other osmotic solutes (glutathione). Most of the membrane transporters ensuring bile formation have now been identified. The expression of these membrane transporters is regulated through transcriptional and post-tranductional mechanisms. Transcriptional regulation is under the control of nuclear receptors activated by ligands such as bile acids, which act as endogenous steroids synthesized from cholesterol in hepatocytes. Cholestatic liver diseases comprise genetic diseases resulting from the complex interaction between genetic and environmental factors. Monogenic cholestatic diseases recently identified illustrate the key role of membrane transporters in biliary function. Bile acids and inflammatory mediators are potent modulators transporters and nuclear receptor genes and thus trigger an adaptative response to cholestasis. The extent of this adaptative response could explain the compelling phenotypic variability of cholestatic diseases in childhood and adults. The firstline medical treatment is currently ursodeoxycholic acid and in case of failure of this medical treatment, liver transplantation is required. Recent progress in the molecular pathogenesis of bile formation and cholestatic liver diseases is expected to provide the design of drugs targeted to the molecular abnormalities typical of cholestatic diseases.

Bile↗
PubMed2002

Bile salts potentiate adenylyl cyclase activity and cAMP-regulated secretion in human gallbladder epithelium.

Fluid and ion secretion in the gallbladder is mainly triggered by the intracellular second messenger cAMP. We examined the action of bile salts on the cAMP-dependent pathway in the gallbladder epithelium. Primary cultures of human gallbladder epithelial cells were exposed to agonists of the cAMP pathway and/or to bile salts. Taurochenodeoxycholate and tauroursodeoxycholate increased forskolin-induced cAMP accumulation to a similar extent, without affecting cAMP basal levels. This potentiating effect was abrogated after PKC inhibition, whereas both taurochenodeoxycholate and tauroursodeoxycholate induced PKC-alpha and -delta translocation to cell membranes. Consistent with a PKC-mediated stimulation of cAMP production, the expression of six adenylyl cyclase isoforms, including PKC-regulated isoforms 5 and 7, was identified in human gallbladder epithelial cells. cAMP-dependent chloride secretion induced by isoproterenol, a beta-adrenergic agonist, was significantly increased by taurochenodeoxycholate and by tauroursodeoxycholate. In conclusion, endogenous and therapeutic bile salts via PKC regulation of adenylyl cyclase activity potentiate cAMP production in the human gallbladder epithelium. Through this action, bile salts may increase fluid secretion in the gallbladder after feeding.

Adenylyl Cyclases↗
PubMed2002

Hepatocyte growth factor and c-Met inhibition by hepatic cell hypoxia: a potential mechanism for liver regeneration failure in experimental cirrhosis.

Hepatic resection in cirrhotic patients is associated with impaired liver regeneration and poor clinical outcome. Because experimental cirrhosis is associated with hepatic cell hypoxia, we herein investigated whether hypoxia might alter the mechanisms of liver regeneration in the cirrhotic liver. Cirrhosis was induced by diethylnitrosamine in rats. Immunohistochemistry was performed to assess hepatocellular hypoxia and proliferation 24 hours after a two-thirds partial hepatectomy (PH) in cirrhotic and control rats. Cultured hepatocytes and myofibroblastic hepatic stellate cells were submitted to hypoxia using anaerobic jars. Hepatocyte growth factor (HGF) and c-Met expressions were determined by reverse transcriptase-polymerase chain reaction, Northern blot, and Western blot. In control rats, hypoxia was restricted to perivenular hepatocytes, and PH induced a marked increase in hepatocyte proliferation and in liver HGF expression, whereas c-Met expression remained unchanged. In cirrhotic rats, hypoxia was detected virtually in all of the hepatocytes, and PH induced no significant change in hepatocyte proliferation and in liver HGF expression, whereas c-Met expression was decreased as compared to normal livers. In vitro, the expression of HGF in myofibroblastic hepatic stellate cells and of c-Met in hepatocytes underwent a dramatic decrease under hypoxia. Our results suggest that hepatocellular hypoxia causes inhibition of HGF (and of c-Met)-mediated proliferation and thereby might contribute to liver regeneration failure in cirrhotic liver.

Animals↗
PubMed2002

Contribution of mrp2 in alterations of canalicular bile formation by the endothelin antagonist bosentan.

BACKGROUND/AIMS: Bosentan, a dual endothelin ET(A/B) receptor antagonist, may cause dose-dependent reversible cholestatic liver injury. We herein tested whether bosentan or metabolites, both eliminated in bile, induce alterations in bile secretion. METHODS: Bile flow and output of bile constituents were monitored in pentobarbital-anesthetized rats with biliary fistulas. Normal and TR(-) rats with a genetic defect in mrp2, received bosentan intravenous injections. RESULTS: Bosentan bolus intravenous injections of 0.1-10mg/kg triggered a dose-dependent increase in biliary bilirubin excretion. In addition, doses (> or =10mg/kg) caused a sustained increase in canalicular bile salt-independent bile flow, combined with significant increases in the concentration and output of glutathione and of bicarbonate in bile. In rats receiving bosentan (> or =10mg/kg), both under basal conditions and under intravenous taurocholate perfusion (2micromol/min/kg), phospholipid and cholesterol secretions were profoundly inhibited and uncoupled from bile salt secretion. In TR(-) rats, the choleretic effect of bosentan was reduced to non-significant levels. The stimulation of bilirubin secretion and the uncoupling of phospholipid from bile salt secretion were absent, whereas that of cholesterol was maintained. CONCLUSIONS: Bosentan alters canalicular bile formation in major part via mrp2-mediated mechanisms. Intermittent uncoupling of lipid from bile salt secretion may contribute to bosentan hepatic adverse reaction.

Animals↗
PubMed2002

Cystic fibrosis transmembrane conductance regulator (CFTR) gene defects in patients with primary sclerosing cholangitis.

BACKGROUND/AIMS: Because biliary tract lesions that resemble those of primary sclerosing cholangitis (PSC) may occur in cystic fibrosis (CF), we examined the prevalence and influence of CF transmembrane conductance regulator (CFTR) gene mutations in PSC patients. METHODS: Genomic DNA was analyzed in 29 consecutive PSC patients and in 115 healthy control individuals. A scanning method followed by direct DNA sequencing was used to scan the CFTR coding regions. RESULTS: Four patients (13.8%) were heterozygous for a CFTR mutation, including a new putative severe CF-causing mutation (N782K), and three mild defects (L997F, D1270N, and S1235R). The comparison of PSC patients with healthy controls showed no significant difference in the frequency of CFTR mutations (P=0.415). In addition, two patients (6.9%) were heterozygous for the IVS8-5T allele, which is not significantly different from the 5-6%-prevalence in the general population. Unusual clinical features including a severe outcome in childhood, with a lethal outcome at age 22, and biliary aspergillosis were recorded in patients with a CFTR mutation. CONCLUSIONS: The proportion of CF carriers is not significantly higher in PSC patients than in the general population. The possibility that CFTR mutations may contribute to a severe clinical course in PSC patients is worth further examining.

Adolescent↗
PubMed2002

Bone loss in primary biliary cirrhosis: absence of association with severity of liver disease.

OBJECTIVES: The aim of the study was to measure the lumbar bone mineral density in women with primary biliary cirrhosis and to evaluate whether bone mineral density was related to the liver disease, hormonal status and corticosteroid use in these women. METHODS: Bone mineral density of the lumbar spine (L2-L4) was assessed by dual emission X-ray absorptiometry in 40 women with primary biliary cirrhosis. Hormonal, bone and liver status were compared with bone mineral density and analyzed by nonparametric statistical tests. RESULTS: Bone loss was evidenced in women with primary biliary cirrhosis compared with control age-matched women (Z-score: -0.9 SD), 32.5% had osteoporosis and 32.5% had osteopenia. The main risk factor of bone loss was the hormonal status: T-score was -1 SD in premenopausal women, -1.1 SD in postmenopausal women receiving an hormonal replacementtherapy and - 2.7SD in postmenopausal untreated women. There was no statistically significant relationship between bone mineral density and biological and histological liver characteristics. CONCLUSION: Primary biliary cirrhosis-associated bone loss was significantly related to postmenopausal estrogen deficiency, and efficiently prevented by hormonal replacement therapy. Interestingly, the severity of primary biliary cirrhosis was not a determinant factor for bone loss in these women.

Absorptiometry, Photon↗
PubMed2002

Primary biliary cirrhosis: incidence and predictive factors of cirrhosis development in ursodiol-treated patients.

BACKGROUND & AIMS: Ursodeoxycholic acid (UDCA) slows the progression of primary biliary cirrhosis (PBC). However, some UDCA-treated patients escape and progress toward cirrhosis and end-stage disease. This study aimed to assess the incidence of cirrhosis in UDCA-treated patients with PBC and to determine the predictive factors of cirrhosis development under this treatment. METHODS: A Markov model was used to describe the progression toward cirrhosis in 183 UDCA-treated patients with PBC. A total of 254 pairs of liver biopsy specimens collected during 655 patient-years were studied. RESULTS: The incidence of cirrhosis after 5 years of UDCA treatment was 4%, 12%, and 59% among patients followed-up from stages I, II, and III, respectively. At 10 years, the incidence was 17%, 27%, and 76%, respectively. The median time for developing cirrhosis from stages I, II, and III was 25 years, 20 years, and 4 years, respectively. The independent predictive factors of cirrhosis development were serum bilirubin greater than 17 mumol/L, serum albumin less than 38 g/L, and moderate to severe lymphocytic piecemeal necrosis. CONCLUSIONS: This study provides new data about the time course of PBC under UDCA and constitutes a rationale for the design and evaluation of clinical trials aimed to assess the efficacy of drugs associated with UDCA.

Bilirubin↗
PubMed2002

Hypoxia-induced VEGF and collagen I expressions are associated with angiogenesis and fibrogenesis in experimental cirrhosis.

Cirrhosis consists of hepatocyte nodules surrounded by a highly vascularized fibrous tissue. We previously showed that the development of biliary cirrhosis in the rat is associated with the occurrence of hepatocellular hypoxia and the induction of hepatic angiogenesis. We herein examined the occurrence of hypoxia in an experimental model of diethylnitrosamine (DEN)-induced cirrhosis. We also determined whether hypoxia directly affects the expression of vascular endothelial growth factor (VEGF), of VEGF receptors (Flt-1, Flk-1), and of type I and type IV collagens in activated hepatic stellate cells (HSCs) and the expression of VEGF in hepatocytes. Our results show that in DEN-treated rats, although the progression of liver fibrosis is associated with hepatocellular hypoxia and angiogenesis, VEGF and Flt-1 expressions in the liver are increased and correlated with the density of microvessels. In vitro, hypoxia induces the expression of VEGF, Flt-1, and type I collagen in activated HSCs and that of VEGF in hepatocytes. In addition, we show that hypoxia-induced type I collagen expression in HSCs may occur independently of transforming growth factor beta1 (TGF-beta1) overexpression. In conclusion, the present study provides further evidence that hepatocellular hypoxia and angiogenesis progress together with fibrogenesis after liver injury and that hypoxia directly contributes to the progression of liver fibrosis.

Alkylating Agents↗
PubMed2002

Effect of interferon alpha-ribavirin bitherapy on cytochrome P450 1A2 and 2D6 and N-acetyltransferase-2 activities in patients with chronic active hepatitis C.

BACKGROUND: Interferon alpha (IFN-alpha) is thought to be responsible for cytochrome P450 (CYP)-dependent drug interactions mediated by a decrease in CYP activities. OBJECTIVES: The objectives are to determine whether IFN-alpha and ribavirin can alter pretreatment CYP1A2, CYP2D6, CYP3A4 and N-acetyltransferase-2 activities after 1 month of treatment. METHODS: Enzymatic activities were determined among 14 patients with chronic active hepatitis C before IFN-alpha (3. 10(6) U, 3 times a week) and ribavirin introduction and after 1 month of treatment. During both study periods, subjects received 80 mg dextromethorphan and 140 mg caffeine (1,3,7-trimethylxanthine [137X]). CYP3A4, CYP2D6, and NAT2 activities were assessed by use of urinary metabolic ratios of 3-methoxymorphinan/dextromethorphan, dextrorphan/dextromethorphan, and 5-acetylamino-6-formylamino-3-methyluracil (AFMU)/1-methylxanthine(1X). The plasma paraxanthine/caffeine ratio was used to measure CYP1A2 activity. RESULTS: CYP3A4 and CYP2D6 activities tended to increase after 1 month of antiviral therapy, but the change did not reach statistical significance. CYP1A2 and NAT2 activities were not significantly modified after 1 month of antiviral treatment. Pretreatment activities were significantly lower than those previously observed in healthy volunteers for CYP2D6 (mean +/- SD, 148 +/- 139 versus 759 +/- 692; P =.0008) and CYP3A4 (0.18 +/- 0.06 versus 0.52 +/- 0.72; P =.0006). This difference was no longer statistically significant after 1 month of treatment, because CYP2D6 and CYP3A4 activities improved in 7 patients. CONCLUSION: In patients with chronic hepatitis C, pretreatment CYP3A4 and CYP2D6 activities were significantly lower than those observed in healthy volunteers. These differences disappeared after 1 month of antiviral treatment because of the restoration of these CYP activities in about half of the patients.

Acute Disease↗
PubMed2002

Effect of the interaction between steatosis and alcohol intake on liver fibrosis progression in chronic hepatitis C.

OBJECTIVES: Liver steatosis is a common histopathological finding in patients infected with hepatitis C virus. Patients with chronic hepatitis C having both steatosis and factors causing oxidative stress may be at a higher risk of fibrogenesis. In a subset of patients with a definite date of contamination, our study aimed to assess the potential synergistic interaction between steatosis and factors likely to induce oxidative stress-namely, alcohol intake, iron overload, and drugs. METHODS: Out of 700 anti-HCV-positive screened patients, 142 untreated patients with liver biopsy and with one known risk factor were selected. Liver fibrosis, inflammation, and necrosis were graded according to the Knodell score, and steatosis as moderate to severe if more than 30% of hepatocytes were affected. Drinkers were defined as having daily mean alcohol intakes of more than 30 g in men and 20 g in women. RESULTS: In multivariate analysis, two factors were independently associated with extensive fibrosis: the degree of severity of piecemeal necrosis (OR = 3.27, CI = 1 .17-9.16) and a combination of moderate to severe steatosis and alcohol intake (OR = 7.02, CI = 1.12-44). The median progression rate of fibrosis was about twice as high among drinkers with steatosis than among drinkers without steatosis or nondrinkers with or without steatosis (0.25 vs 0. I vs 0.13 vs 0.08, respectively; p = 0.02). Independent parameters significantly associated with moderate to severe steatosis were body mass index (OR = 1.13, CI = 1.02-1.26) and infection with genotype 3 (OR = 5.5, CI = 1.88-16), but not alcohol consumption. CONCLUSIONS: As well as the key role of the severity of piecemeal necrosis, the study underlines the synergistic interaction between steatosis and even low alcohol consumption as a contributory factor in extensive liver fibrosis.

Adult↗