Laure Americh

Bio: Laure Americh is an academic researcher. The author has contributed to research in topics: Endothelial stem cell & Cell adhesion molecule. The author has an hindex of 3, co-authored 3 publications receiving 1020 citations.

IL-33, the IL-1-like cytokine ligand for ST2 receptor, is a chromatin-associated nuclear factor in vivo

Abstract: Recent studies indicate that IL-1alpha functions intracellularly in pathways independent of its cell surface receptors by translocating to the nucleus and regulating transcription. Similarly, the chromatin-associated protein HMGB1 acts as both a nuclear factor and a secreted proinflammatory cytokine. Here, we show that IL-33, an IL-1-like cytokine that signals via the IL-1 receptor-related protein ST2 and induces T helper type 2-associated cytokines, is an endothelium-derived, chromatin-associated nuclear factor with transcriptional repressor properties. We found that IL-33 is identical to NF-HEV, a nuclear factor preferentially expressed in high endothelial venules (HEV), that we previously characterized. Accordingly, in situ hybridization demonstrated that endothelial cells constitute a major source of IL-33 mRNA in chronically inflamed tissues from patients with rheumatoid arthritis and Crohn's disease. Immunostaining with three distinct antisera, directed against the N-terminal part and IL-1-like C-terminal domain, revealed that IL-33 is a heterochromatin-associated nuclear factor in HEV endothelial cells in vivo. Association of IL-33 with heterochromatin was also observed in human and mouse cells under living conditions. In addition, colocalization of IL-33 with mitotic chromatin was noted. Nuclear localization, heterochromatin-association, and targeting to mitotic chromosomes were all found to be mediated by an evolutionarily conserved homeodomain-like helix-turn-helix motif within the IL-33 N-terminal part. Finally, IL-33 was found to possess transcriptional repressor properties, associated with the homeodomain-like helix-turn-helix motif. Together, these data suggest that, similarly to IL1alpha and HMGB1, IL-33 is a dual function protein that may function as both a proinflammatory cytokine and an intracellular nuclear factor with transcriptional regulatory properties.

A comparative study of endothelial cell markers expressed in chronically inflamed human tissues: MECA‐79, Duffy antigen receptor for chemokines, von Willebrand factor, CD31, CD34, CD105 and CD146

Abstract: Endothelial cells play a central role in chronic inflammation: for example, they express adhesion molecules and present chemokines leading to enhanced leukocyte recruitment into tissues. Numerous markers of endothelial cells have been reported but there has been a lack of comparative data on their specificity. The present study compared the specificity of seven endothelial cell markers in the rheumatoid synovium and the colon of patients with Crohn's disease. These markers were: the sulphated epitope MECA-79, the Duffy antigen receptor for chemokines (DARC), von Willebrand factor, CD31 (PECAM-1), CD34, CD105 (endoglin) and CD146. MECA-79, DARC and von Willebrand factor showed a specific endothelial cell distribution. MECA-79, which recognizes sulphated ligands for leukocyte adhesion receptor L-selectin (CD62L), was selective for a subset of venules in highly inflamed tissue and was present in rheumatoid but not control osteoarthritic synovia. DARC was also specific for venules but had a more widespread distribution than MECA-79, and was present in rheumatoid and control synovia. The other markers all labelled endothelial cells in venules, arterioles and capillaries. However, they also localized to other cell types. For example, CD34 stained fibroblasts, CD146 was expressed by the pericytes and smooth muscle cells of vessel walls and CD31 and CD105 labelled a broad range of cell types.

Endothelial cell phenotypes in the rheumatoid synovium: activated, angiogenic, apoptotic and leaky

Abstract: Endothelial cells are active participants in chronic inflammatory diseases. These cells undergo phenotypic changes that can be characterised as activated, angiogenic, apoptotic and leaky. In the present review, these phenotypes are described in the context of human rheumatoid arthritis as the disease example. Endothelial cells become activated in rheumatoid arthritis pathophysiology, expressing adhesion molecules and presenting chemokines, leading to leukocyte migration from the blood into the tissue. Endothelial cell permeability increases, leading to oedema formation and swelling of the joints. These cells proliferate as part of the angiogenic response and there is also a net increase in the turnover of endothelial cells since the number of apoptotic endothelial cells increases. The endothelium expresses various cytokines, cytokine receptors and proteases that are involved in angiogenesis, proliferation and tissue degradation. Associated with these mechanisms is a change in the spectrum of genes expressed, some of which are relatively endothelial specific and others are widely expressed by other cells in the synovium. Better knowledge of molecular and functional changes occurring in endothelial cells during chronic inflammation may lead to the development of endothelium-targeted therapies for rheumatoid arthritis and other chronic inflammatory diseases.

Immunological and Inflammatory Functions of the Interleukin-1 Family

Abstract: More than any other cytokine family, the interleukin (IL)-1 family is closely linked to the innate immune response. This linkage became evident upon the discovery that the cytoplasmic domain of the IL-1 receptor type I is highly homologous to the cytoplasmic domains of all Toll-like receptors (TLRs). Thus, fundamental inflammatory responses such as the induction of cyclooxygenase type 2, increased expression of adhesion molecules, or synthesis of nitric oxide are indistinguishable responses of both IL-1 and TLR ligands. Both families nonspecifically affect antigen recognition and lymphocyte function. IL-1β is the most studied member of the IL-1 family because of its role in mediating autoinflammatory diseases. Although the TLR and IL-1 families evolved to assist in host defense against infection, unlike the TLR family, the IL-1 family also includes members that suppress inflammation, both specifically within the IL-1 family but also nonspecifically for TLR ligands and the innate immune response.

Sterile inflammation: sensing and reacting to damage

Abstract: Over the past several decades, much has been revealed about the nature of the host innate immune response to microorganisms, with the identification of pattern recognition receptors (PRRs) and pathogen-associated molecular patterns, which are the conserved microbial motifs sensed by these receptors. It is now apparent that these same PRRs can also be activated by non-microbial signals, many of which are considered as damage-associated molecular patterns. The sterile inflammation that ensues either resolves the initial insult or leads to disease. Here, we review the triggers and receptor pathways that result in sterile inflammation and its impact on human health.

A large-scale, consortium-based genomewide association study of asthma.

Abstract: A b s t r ac t Background Susceptibility to asthma is influenced by genes and environment; implicated genes may indicate pathways for therapeutic intervention. Genetic risk factors may be useful in identifying subtypes of asthma and determining whether intermediate phenotypes, such as elevation of the total serum IgE level, are causally linked to disease. Methods We carried out a genomewide association study by genotyping 10,365 persons with physician-diagnosed asthma and 16,110 unaffected persons, all of whom were matched for ancestry. We used random-effects pooled analysis to test for association in the overall study population and in subgroups of subjects with childhood-onset asthma (defined as asthma developing before 16 years of age), later-onset asthma, severe asthma, and occupational asthma. Results We observed associations of genomewide significance between asthma and the following single-nucleotide polymorphisms: rs3771166 on chromosome 2, implicating IL1RL1/IL18R1 (P =3×10 −9 ); rs9273349 on chromosome 6, implicating HLA-DQ (P = 7×10 −14 ); rs1342326 on chromosome 9, flanking IL33 (P = 9×10 −10 ); rs744910 on chromosome 15 in SMAD3 (P = 4×10 −9 ); and rs2284033 on chromosome 22 in IL2RB (P = 1.1×10 −8 ). Association with the ORMDL3/GSDMB locus on chromosome 17q21 was specific to childhood-onset disease (rs2305480, P = 6×10 −23 ). Only HLA-DR showed a significant genomewide association with the total serum IgE concentration, and loci strongly associated with IgE levels were not associated with asthma. Conclusions Asthma is genetically heterogeneous. A few common alleles are associated with disease risk at all ages. Implicated genes suggest a role for communication of epithelial damage to the adaptive immune system and activation of airway inflammation. Variants at the ORMDL3/GSDMB locus are associated only with childhood-onset disease. Elevation of total serum IgE levels has a minor role in the development of asthma. (Funded by the European Commission and others.)