Annie-France Bringuier

The plasma membrane polarity of human biliary epithelial cells: In situ immunohistochemical analysis and functional implications

BACKGROUND/AIMSnIn transporting epithelia, like the biliary epithelium, most plasma membrane proteins present a polarized distribution, essential for the maintenance of the structural and functional properties of the epithelium. We therefore analyzed the expression of polarized plasma membrane proteins by human biliary epithelial cells in order to compare them with other transporting epithelial cells and to search for differences in plasma membrane protein expression between their different anatomical subsets.nnnMETHODSnWe designed an in situ immunohistochemical study of the various anatomical compartments of the human biliary tract in order to assess the pattern of expression of selected polarized plasma membrane proteins, including integrin receptors, ectopeptidases, membrane transporters and GPI-linked proteins.nnnRESULTSnAll biliary epithelial cells expressed the same repertoire of integrins, except for integrin chain alpha5, restricted to the intra-hepatic compartments. All biliary epithelial cells expressed the following apical ectopeptidases: aminopeptidase-N, neutral-endopeptidase, dipeptidyl-peptidase IV. All biliary epithelial cells expressed the membrane transporter Na+ K+-ATPase, restricted to the basolateral domain, and the apical transporters CFTR and MDR-1. The apical AE2 anion exchanger was restricted to the small intra-hepatic bile ducts and the gallbladder. The GPI-linked protein protectin was basolateral in the intrahepatic bile ducts and apical in the gallbladder.nnnCONCLUSIONSnThe structural organization of the plasma membrane of biliary epithelial cells is very similar to that of other simple epithelia and exhibits a limited degree of heterogeneity.

Cadmium induces mitochondria-dependent apoptosis of normal human hepatocytes

The heavy metal cadmium, an environmental pollutant, has been widely demonstrated to be toxic, in particular for liver. In murines, cadmium induces apoptosis of hepatocytes and hepatomas. In human cells, apoptosis induced by cadmium has been exclusively demonstrated in tumoral cell lines. Nothing was known in normal liver, in vitro or in vivo. In the present study, we examined the effects of cadmium in nonmalignant human hepatocytes. For that purpose, we investigated whether cadmium was able to induce apoptosis of normal human hepatocytes (NHH) in primary culture and of a SV40-immortalized human hepatocyte (IHH) cell line. Treatment of IHH and NHH with cadmium induced the presence of a sub-G1 population at 10 and 100xa0μmol/L, respectively. DAPI staining of both cell types treated with cadmium 100xa0μmol/L revealed the induction of nuclear apoptotic bodies, supporting the hypothesis of apoptosis. In IHH and NHH, cadmium 100xa0μmol/L induced PARP cleavage into a 85xa0kDa fragment. In order to investigate the involvement of mitochondria in cadmium-induced apoptosis, we measured the mitochondrial membrane potential (ΔΨm). We observed that in IHH and NHH, cadmium 100xa0μmol/L induced a decrease of ΔΨm. As expected, cadmium under the same conditions enhanced caspase-9 and caspase-3 activities. In addition, cadmium from 1 to 100xa0μmol/L induced the expression of p53 and phosphorylation of its Ser15 in IHH and NHH. In conclusion, we showed in this study that human hepatocytes were sensitive to cadmium and apoptosis induced at concentrations suggested in the literature to inhibit p53 DNA-binding and DNA repair.

Protein kinase PKC delta and c-Abl are required for mitochondrial apoptosis induction by genotoxic stress in the absence of p53, p73 and Fas receptor

Doxorubicin, cis‐diamminedichloroplatinum (II) and 5‐fluorouracil used in chemotherapy induce apoptosis in Hep3B cells in the absence of p53, p73, and functional Fas. Since mediators remain unknown, the requirement of PKC delta (PKCδ) and c‐Abl was investigated. Suppression of c‐Abl or PKCδ expression using SiRNAs impaired PARP cleavage, Gleevec® and/or rottlerin inhibited the induction of the subG1 phase and the increase of reactive oxygen species level. Co‐precipitations and phosphorylations to mitochondria of c‐Abl, PKCδ and Bcl‐XL/s were induced. A depolarization of the mitochondrial membrane and activations of caspase‐2 and ‐9 were observed. We propose that, in the absence of p53, p73 and Fas, genotoxic drugs could require both PKCδ and c‐Abl to induce apoptosis through the mitochondrial pathway.

Study of the effects of interferon a on several human hepatoma cell lines: analysis of the signalling pathway of the cytokine and of its effects on apoptosis and cell proliferation

Background: Interferon α (IFNα), currently used for the treatment of chronic viral hepatitis, is also known to prevent the development of hepatocellular carcinoma (HCC), the mechanism of this action being still debatable.

Soluble intercellular adhesion molecule 1 in umbilical cord serum: Potential for the diagnosis of neonatal infections

Objective: To evaluate the diagnostic relevance to neonatal infections of the soluble intercellular adhesion molecule 1 (sICAM-1) cord serum level. Methods: The case-control study included 66 term newborn infants with and without risk factors for neonatal infections. Cord blood serum determinations of white blood cell count, C-reactive protein, fibrinogen, and sICAM-1 were systematically performed associated with bacterial cultures from placenta, ears, and gastric fluids. Results: 6 of 33 infants (18.2%) with risk factors were infected, and 13 (39.4%) were colonized. Two infants included in the group without infection risk factors (n = 33) were colonized. No difference in sICAM-1 cord serum levels was found according to the presence of premature rupture of membrane, fetal tachycardia >160 bpm, meconial amniotic fluid, and duration of labour >10 h. No difference in sICAM-1 was noted between infected and non-infected infants. The cord serum levels of sICAM-1 were significantly higher in infants after forceps extraction (p = 0.01). A correlation was observed between sICAM-1 and C-reactive protein cord serum levels (p = 0.004, r = 0.371) and between sICAM-1 level and neutrophil count (p = 0.01, r = 0.489). Conclusions: Our results suggest that cord serum sICAM-1 determinations have no diagnostic relevance to neonatal infection. The increase of sICAM-1 cord serum levels in infants after forceps extraction suggests its potential to evaluate cerebral trauma or hypoxia.