Caroline Sommereyns

IFN-Lambda (IFN-λ) Is Expressed in a Tissue-Dependent Fashion and Primarily Acts on Epithelial Cells In Vivo

Interferons (IFN) exert antiviral, immunomodulatory and cytostatic activities. IFN-α/β (type I IFN) and IFN-λ (type III IFN) bind distinct receptors, but regulate similar sets of genes and exhibit strikingly similar biological activities. We analyzed to what extent the IFN-α/β and IFN-λ systems overlap in vivo in terms of expression and response. We observed a certain degree of tissue specificity in the production of IFN-λ. In the brain, IFN-α/β was readily produced after infection with various RNA viruses, whereas expression of IFN-λ was low in this organ. In the liver, virus infection induced the expression of both IFN-α/β and IFN-λ genes. Plasmid electrotransfer-mediated in vivo expression of individual IFN genes allowed the tissue and cell specificities of the responses to systemic IFN-α/β and IFN-λ to be compared. The response to IFN-λ correlated with expression of the α subunit of the IFN-λ receptor (IL-28Rα). The IFN-λ response was prominent in the stomach, intestine and lungs, but very low in the central nervous system and spleen. At the cellular level, the response to IFN-λ in kidney and brain was restricted to epithelial cells. In contrast, the response to IFN-α/β was observed in various cell types in these organs, and was most prominent in endothelial cells. Thus, the IFN-λ system probably evolved to specifically protect epithelia. IFN-λ might contribute to the prevention of viral invasion through skin and mucosal surfaces.

IL-9 Promotes IL-13-Dependent Paneth Cell Hyperplasia and Up-Regulation of Innate Immunity Mediators in Intestinal Mucosa

IL-9 contributes to lung inflammatory processes such as asthma, by promoting mast cell differentiation, B cell activation, eosinophilia, and mucus production by lung epithelial cells. The observation that IL-9 overexpressing mice show increased mast cell numbers in the intestinal mucosa suggests that this cytokine might also play a role in intestinal inflammation. In colons from IL-9 transgenic mice, the expression of Muc2, a major intestinal mucin gene, was up-regulated, together with that of CLCA3 chloride channel and resistin like α, which are goblet cell-associated genes. Additional IL-9 up-regulated genes were identified and included innate immunity genes such as angiogenin 4 and the PLA2g2a phospholipase A2, which are typical Paneth cell markers. Histochemical staining of Paneth cells by phloxine/tartrazine showed that IL-9 induces Paneth cell hyperplasia in Lieberkühn glands of the small intestine, and in the colonic mucosa, where this cell type is normally absent. Expression of Paneth cell markers, including angiogenin 4, PLA2g2a, and cryptdins, was induced in the colon of wild-type mice after two to four daily administrations of IL-9. By crossing IL-9 transgenic mice with IL-13−/− mice, or by injecting IL-9 into IL-4R−/− mice, we showed that IL-13 was required for the up-regulation of these Paneth cell-specific genes by IL-9. Taken together, our data indicate that Paneth cell hyperplasia and expression of their various antimicrobial products contribute to the immune response driven by TH2 cytokines, such as IL-9 and IL-13 in the intestinal mucosa.

NADPH oxidase activation by hyperglycaemia in cardiomyocytes is independent of glucose metabolism but requires SGLT1

AIMS Exposure to high glucose (HG) stimulates reactive oxygen species (ROS) production by NADPH oxidase in cardiomyocytes, but the underlying mechanism remains elusive. In this study, we have dissected the link between glucose transport and metabolism and NADPH oxidase activation under hyperglycaemic conditions. METHODS AND RESULTS Primary cultures of adult rat cardiomyocytes were exposed to HG concentration (HG, 21 mM) and compared with the normal glucose level (LG, 5 mM). HG exposure activated Rac1GTP and induced p47phox translocation to the plasma membrane, resulting in NADPH oxidase (NOX2) activation, increased ROS production, insulin resistance, and eventually cell death. Comparison of the level of O-linked N-acetylglucosamine (O-GlcNAc) residues in LG- and HG-treated cells did not reveal any significant difference. Inhibition of the pentose phosphate pathway (PPP) by 6-aminonicotinamide counteracted ROS production in response to HG but did not prevent Rac-1 upregulation and p47phox translocation leading to NOX2 activation. Modulation of glucose uptake barely affected oxidative stress and toxicity induced by HG. More interestingly, non-metabolizable glucose analogues (i.e. 3-O-methyl-D-glucopyranoside and α-methyl-D-glucopyranoside) reproduced the toxic effect of HG. Inhibition of the sodium/glucose cotransporter SGLT1 by phlorizin counteracted HG-induced NOX2 activation and ROS production. CONCLUSION Increased glucose metabolism by itself does not trigger NADPH oxidase activation, although PPP is required to provide NOX2 with NADPH and to produce ROS. NOX2 activation results from glucose transport through SGLT1, suggesting that an extracellular metabolic signal transduces into an intracellular ionic signal.

Anti-IL-17A autovaccination prevents clinical and histological manifestations of experimental autoimmune encephalomyelitis.

Abstract:  Excessive or inappropriate production of IL‐17A has been reported in diseases such as rheumatoid arthritis, asthma, and multiple sclerosis. The potential clinical relevance of these correlations was suggested by the protective effects of anti‐IL‐17A monoclonal antibodies in various mouse disease models. However, the chronic nature of the corresponding human afflictions raises great challenges for Ab‐based therapies. An alternative to passive Ab therapy is autovaccination. Covalent association of self‐cytokines with foreign proteins has been reported to induce the production of antibodies capable of neutralizing the biological activity of the target cytokine. We recently reported that cross‐linking of IL‐17A to ovalbumin produced highly immunogenic complexes that induced long‐lasting IL‐17A‐neutralizing antibodies. Vaccinated SJL mice were completely protected against experimental autoimmune encephalomyelitis (EAE) induced by proteolipid protein peptide (PLP 139–151), and a monoclonal anti‐IL‐17A Ab (MM17F3), derived from C57Bl/6 mice vaccinated against IL‐17A‐OVA, also prevented disease development. Here we report that this Ab also protects C57Bl/6 mice from myelin oligdendrocyte glycoprotein (MOG)‐induced EAE. Histological analysis of brain sections of C57Bl/6 mice treated with MM17F3 showed a complete absence of inflammatory infiltrates and evidence for a marked inhibition of chemokine and cytokine messages in the spinal cord. These results further extend the analytical and therapeutic potential of the autovaccine procedure.

Connection between cardiac vascular permeability, myocardial edema, and inflammation during sepsis: role of the α1AMP-activated protein kinase isoform.

Objective:As adenosine monophosphate (AMP)-activated protein kinase both controls cytoskeleton organization in endothelial cells and exerts anti-inflammatory effects, we here postulated that it could influence vascular permeability and inflammation, thereby counteracting cardiac wall edema during sepsis. Design:Controlled animal study. Settings:University research laboratory. Subjects:C57BL/6J, &agr;1AMPK–/–, and &agr;1AMPK+/+ mice. Intervention:Sepsis was triggered in vivo using a sublethal injection of lipopolysaccharide (O55B5, 10 mg/kg), inducing systolic left ventricular dysfunction. Left ventricular function, edema, vascular permeability, and inflammation were assessed in vivo in both wild-type mice (&agr;1AMPK+/+) and &agr;1AMP-activated protein kinase–deficient mice (&agr;1AMPK–/–). The 5-aminoimidazole-4-carboxamide riboside served to study the impact of AMP-activated protein kinase activation on vascular permeability in vivo. The integrity of endothelial cell monolayers was also examined in vitro after lipopolysaccharide challenge in the presence of aminoimidazole-4-carboxamide riboside and/or after &agr;1AMP-activated protein kinase silencing. Measurements and Main Results:&agr;1AMP-activated protein kinase deficiency dramatically impaired tolerance to lipopolysaccharide challenge. Indeed, &agr;1AMPK–/– exhibited heightened cardiac vascular permeability after lipopolysaccharide challenge compared with &agr;1AMPK+/+. Consequently, an increase in left ventricular mass corresponding to exaggerated wall edema occurred in &agr;1AMPK–/–, without any further decrease in systolic function. Mechanistically, the lipopolysaccharide-induced &agr;1AMPK–/– cardiac phenotype could not be attributed to major changes in the systemic inflammatory response but was due to an increased disruption of interendothelial tight junctions. Accordingly, AMP-activated protein kinase activation by aminoimidazole-4-carboxamide riboside counteracted lipopolysaccharide-induced hyperpermeability in wild-type mice in vivo as well as in endothelial cells in vitro. This effect was associated with a potent protection of zonula occludens-1 linear border pattern in endothelial cells. Conclusions:Our results demonstrate for the first time the involvement of a signaling pathway in the control of left ventricular wall edema during sepsis. AMP-activated protein kinase exerts a protective action through the preservation of interendothelial tight junctions. Interestingly, exaggerated left ventricular wall edema was not coupled with aggravated systolic dysfunction. However, it could contribute to diastolic dysfunction in patients with sepsis.