Hyaluronan-induced signaling and gene regulation

描述（由申请人提供）：慢性炎症和组织纤维化的特征是炎症细胞的涌入，炎症介质的积累以及细胞外基质（ECM）的周转和生产增加。在完整的肺中，高分子量的ECM成分，如透明质酸（HA），在维持构象完整性和水稳态方面起着关键作用，但被认为是生物惰性的。然而，在炎症的情况下，HA被降解成低分子量的片段，刺激巨噬细胞产生重要的组织损伤和修复介质。虽然已知HA片段诱导NF-kappaB活化，但HA诱导基因表达的受体和信号通路尚未阐明。本研究的目的是表征HA片段诱导基因表达的信号转导途径，以及ifn - γ在体外和体内对HA诱导的肺泡巨噬细胞趋化因子表达的差异调节的分子机制。我们假设HA片段通过蛋白激酶C和nf - κ b途径通过toll样受体（TLR）诱导趋化因子基因表达，此外，ifn - γ通过ECM选择性地改变巨噬细胞来源的趋化因子表达来发挥其抗纤维化作用。这将通过确定：(1)MyD88在巨噬细胞中介导HA诱导基因的机制，负责HA信号传导的toll样受体，以及MyD88缺乏对博莱霉素诱导的肺损伤的影响。(2) HA激活蛋白激酶C的机制，蛋白激酶C调控HA诱导基因的机制，以及蛋白激酶C对博莱霉素诱导肺损伤的药理抑制作用。(3)共激活在介导HA与ifn - γ协同诱导的MIG表达中的作用，共抑制在介导ifn - γ抑制HA诱导的mip -1 α表达中的作用，NF-kappaB p50缺乏对博莱霉素诱导的肺损伤的影响。因此，在炎症的情况下，ECM不仅是炎症的目标，而且其分解产物调节免疫反应的大小和质量。阐明ECM在炎症中的作用可能有助于更好地理解纤维化过程，并为新的治疗策略提供新的靶点。

DESCRIPTION (provided by applicant): The hallmarks of chronic inflammation and tissue fibrosis are the influx of inflammatory cells, accumulation of inflammatory mediators and increased turnover and production of the extracellular matrix (ECM). In intact lungs, high molecular weight ECM components, such as hyaluronan (HA), play a critical role in maintaining conformational integrity and water homeostasis but are considered biologically inert. However, in the setting of inflammation, the HA is degraded into lower molecular weight fragments that stimulate macrophages to produce important mediators of tissue injury and repair. Although it is known that HA fragments induce the activation of NF-kappaB, the receptor and signaling pathways responsible for HA induced gene expression have yet to be elucidated. The aim of this proposal is to characterize the signal transduction pathways involved in HA fragment induced gene expression as well as the molecular mechanisms by which IFN-gamma differentially regulates HA-induced chemokine expression in alveolar macrophages both in vitro and in vivo. We hypothesize that HA, fragments induce chemokine gene expression through toll-like receptors (TLR) via Protein Kinase C and NF-kappaB pathways, and furthermore that IFN-gamma exerts its anti-fibrotic effects by selectively altering macrophage-derived chemokine expression by ECM. This will be pursued by determining: (1) the mechanism by which MyD88 mediates HA-induced genes in macrophages, the toll-like receptor responsible for HA signaling and the effect of MyD88 deficiency on bleomycin-induced lung injury. (2) The mechanism by which HA activates Protein Kinase C as well as the mechanism by which Protein Kinase C regulates HA-induced genes and the effect of pharmacologic inhibition of Protein Kinase C on bleomycin-induced lung injury. (3) The role of co-activation in mediating the synergy between HA and IFN-gamma induced MIG expression, the role of co-repression in mediating the inhibition of HA-induced MIP-1alpha expression by IFN-gamma, and the effect of NF-kappaB p50 deficiency on bleomycin-induced lung injury. Thus, in the setting of inflammation, the ECM is not only the target of inflammation, but its breakdown products modulate the magnitude and quality of an immune response. The elucidation of the role of ECM in inflammation may lead to a better understanding of the process of fibrosis as well as to new targets for novel treatment strategies.