Christiane Chéreau

Pivotal role of superoxide anion and beneficial effect of antioxidant molecules in murine steatohepatitis

Nonalcoholic fatty liver disease, frequently associated with obesity, can lead to nonalcoholic steatohepatitis (NASH) and cirrhosis. The pathophysiology of NASH is poorly understood, and no effective treatment is available. In view of a potential deleterious role for reactive oxygen species (ROS), we investigated the origin of ROS overproduction in NASH. Mitochondrial production of ROS and its alterations in the presence of antioxidant molecules were studied in livers from ob/ob mice that bear a mutation of the leptin gene and develop experimental NASH. N‐acetyl‐cysteine and the superoxide dismutase (SOD) mimics ambroxol, manganese [III] tetrakis (5,10,15,20 benzoic acid) (MnTBAP), and copper [II] diisopropyl salicylate (CuDIPS) were used to target different checkpoints of the oxidative cascade to determine the pathways involved in ROS production. Liver mitochondria from ob/ob mice generated more O2°− than those of lean littermates (P < .01). Ex vivo, all three SOD mimics decreased O2°− generation (P < .001) and totally inhibited lipid peroxidation (P < .001) versus untreated ob/ob mice. Those modifications were associated with in vivo improvements: MnTBAP and CuDIPS reduced weight (P < .02) and limited the extension of histological liver steatosis by 30% and 52%, respectively, versus untreated ob/ob mice. In conclusion, these data demonstrate deleterious effects of superoxide anions in NASH and point at the potential interest of nonpeptidyl mimics of SOD in the treatment of NASH in humans. (HEPATOLOGY 2004;39:1277–1285.)

Association of the 5′ HS4 sequence of the chicken β‐globin locus control region with human EF1α gene promoter induces ubiquitous and high expression of human CD55 and CD59 cDNAs in transgenic rabbits

Whatever its field of application, animal transgenesis aims at a high level of reproducible and stable transgene expression. In the case of xenotransplantation, prevention of hyperacute rejection of grafts of animal origin requires the use of organs expressing human inhibitors of complement activation such as CD55 (DAF) and CD59. Pigs transgenic for these molecules have been produced, but with low and variable levels of expression. In order to improve cDNA expression, a vector containing the 5′HS4 region from the LCR of the chicken β‐globin locus and the promoter and the first intron from the human EF1α gene, was used to co‐express human CD55 and CD59 cDNAs in transgenic rabbits. The transgenic lines with the 5′HS4 region displayed dramatically enhanced CD55 and CD59 mRNA concentrations in brain, heart, kidney, liver, lung, muscle, spleen and aortic endothelial cells in comparison with the transgenic lines without the 5′HS4 region. In the absence of the 5′HS4 region, only some of the transgenic lines displayed specific mRNAs and at low levels. Human CD55 and CD59 proteins were detectable in mononuclear cells from transgenic rabbits although at a lower level than in human mononuclear cells. On the other hand, primary aortic endothelial cells from a bi‐transgenic line were very efficiently protected in vitro against human complement‐dependent lysis. Transgenic rabbits harbouring the two human inhibitors of complement activation, CD55 and CD59, can therefore be used as new models in xenotransplantation. Moreover, the vector containing the 5′HS4 region from the LCR of the chicken β‐globin locus seems appropriate not only for xenotransplantation but also for any other studies involving transgenic animals in which cDNAs have to be expressed at a high level in all cell types.

Hypodermin A, a new inhibitor of human complement for the prevention of xenogeneic hyperacute rejection

Abstract:u2002Background: Hyperacute rejection (HAR) of discordant xenografts in the pig‐to‐human combination can be prevented using tranplants expressing transgenic molecules that inhibit human complement. Hypodermin A (HA), a serine esterase that degrades C3, was tested in the guinea‐pig‐to‐rat and in the pig‐to‐human combinations.

Effects of bile salts and aliphatic ionic surfactants on human lymphocyte proliferation

Background The molecular mechanisms involved in the immunosuppressive properties of bile salts are partly unknown.

Human preformed IgG combining with membrane-bound porcine serotransferrin lyse porcine endothelial cells through antibody-dependent cellular cytotoxicity

Preformed antibodies are involved in xenograft rejection. The purpose of this work was to characterize porcine xenoantigens recognized by human preformed IgG (hpIgG), and to investigate the role of hpIgG in xenogeneic rejection. IgG eluted from porcine livers perfused with human plasma, human sera and total human IgG were immunoblotted on porcine aortic endothelial cell extracts. The amino acid sequence of a 76‐kDa antigen constantly revealed was 100u2009% homologous with porcine serotransferrin (psTf). hpIgG from human sera, human IgG1 and IgG2 and F(abu2009′u2009)2u2009γ specifically bound to psTf. Neutralization by psTf abolished that binding. Although α1,u20093‐linked galactose residues (Galα1,3Gal) is the dominant epitope recognized by preformed antibodies in the swine‐to‐human combination, the analysis of carbohydrate composition of psTf showed that the molecule was devoid of Galα1,3Gal moieties and that preformed anti‐psTf IgG bound to epitopes localized on the peptide core of the molecule. Purified human anti‐psTf IgG antibodies were able to bind to psTf linked to its receptor on porcine endothelial cells, and to kill those cells through antibody‐dependent cellular cytotoxicity.