Italy called Limone sul Garda live approximately 40 carriers with a naturally occurring variant of apolipoprotein A-I known as ApoA-I Milano. Individuals with ApoA-I Milano are characterized by very low levels of highdensity lipoprotein cholesterol (HDL-C) (10-30 mg/dL [0.25-0.78 mmol/L]), apparent longevity, 1 and much less atherosclerosis than expected for their HDL-C levels. 2 The ApoA-I Milano protein differs from native ApoA-I in that cysteine is substituted at position 173 for arginine allowing disulfide-linked dimer formation. Recombinant ApoA-I Milano has been formulated in a complex with a naturally occurring phospho-lipid to mimic the properties of nascent HDL (ETC-216, Esperion Therapeutics, Ann Arbor, Mich). Studies in mice and rabbits with experimental ath-Author Affiliations and Financial Disclosures are listed at the end of this article.

Interleukin 17 (IL-17) plays a critical role in the pathogenesis of inflammatory and autoimmune diseases. Here we report that Act1, the key adaptor for IL-17R, forms a complex with IKKi upon IL-17 stimulation. Using IKKi-deficient mice, we show that IKKi was required for IL-17-induced inflammatory gene expression in primary airway epithelial cells, neutrophilia and pulmonary inflammation. IKKi deficiency abolished IL-17-induced Act1-TRAF2/5 complex formation, MAPK activation and mRNA stability, whereas the Act1-TRAF6-NFκB axis was retained. IKKi was required for IL-17-induced Act1 phosphorylation on serine 311, adjacent to a putative TRAF binding motif. S311A mutation impaired IL-17-mediated Act1-TRAF2/5 interaction and gene expression. Thus, IKKi is a novel kinase modulating IL-17 signaling through its impact on Act1 phosphorylation and consequent function.

Background-Receptor for advanced-glycation end products (RAGE) and its ligands AGEs and S100/calgranulins have been implicated in a range of disorders. However, the role of RAGE/ligand interaction in neointimal hyperplasia after vascular injury remains unclear. Methods and Results-We examined the expression of RAGE and its ligands after balloon injury of the carotid artery in both Zucker diabetic and nondiabetic rats. Using a soluble portion of the extracellular domain of RAGE, we determined the effects of suppressing RAGE/ligand interaction on vascular smooth muscle cell (VSMC) proliferation and neointimal formation after arterial injury. We demonstrate a significantly increased accumulation of AGE and immunoreactivities of RAGE and S100/calgranulins in response to balloon injury in diabetic compared with nondiabetic rats. Blockade of RAGE/ligand interaction significantly decreased S100-stimulated VSMC proliferation in vitro and bromodeoxyuridine (BrdU)-labeled proliferating VSMC in vivo, and suppressed neointimal formation and increased luminal area in both Zucker diabetic and nondiabetic rats. Conclusions-These

Hyaluronan matrices are ubiquitous in normal and pathological biological processes. This remarkable diversity is related to their unique mechanism of synthesis by hyaluronan synthases. These enzymes are normally activated in the plasma membrane and utilize cytosolic substrates directly to form these large polyanionic glycosaminoglycans, which are extruded directly into the extracellular space. The extracellular matrices that are formed interact with cell surface receptors, notably CD44, that often dictate the biological processes, as described in the accompanying minireviews of this series. This article focuses on the discovery in recent studies that many cell stress responses initiate the synthesis of a monocyte-adhesive hyaluronan extracellular matrix, which forms a central focus for subsequent inflammatory processes that are modulated by the dialogue between the matrix and the inflammatory cells. The mechanisms involve active hyaluronan synthases at the cell membrane when cell stresses occur at physiological levels of glucose. However, dividing cells at hyperglycemic levels of glucose initiate the synthesis of hyaluronan in intracellular compartments, which induces endoplasmic reticulum stress and autophagy, processes that probably contribute greatly to diabetic pathologies.

Asthma is a chronic inflammatory disease of the airways characterized by airway remodeling, which includes changes in the extracellular matrix (ECM). However the role of the ECM in mediating these changes is poorly understood. Hyaluronan (HA), a major component of the ECM, has been implicated in asthma as well as in many other biological processes. Our study investigates the processes involved in HA synthesis, deposition, localization and degradation during an acute and chronic murine model of ovalbumin (OVA)-induced allergic pulmonary inflammation. Mice were sensitized, challenged to OVA and sacrificed at various time points during an 8-week challenge protocol. Bronchoalveolar lavage (BAL) fluids, blood, and lung tissue were collected for study. RNA, HA, protein and histopathology were analyzed. Analyses of lung sections and BAL fluids revealed an early deposition and an increase in HA levels within 24 hours of antigen exposure. HA levels peaked at day 8 in BAL, while inflammatory cell recovery peaked at day 6. Hyaluronan synthase (HAS)1 and HAS2 on RNA levels peaked within 2 hours of antigen exposure, while hyaluronidase (HYAL)1 and HYAL2 on RNA levels decreased. Both inflammatory cell infiltrates and collagen deposition co-localized with HA deposition within the lungs. These data support a role for HA in the pathogenesis of inflammation and airway remodeling in a murine model of asthma. HA deposition appears largely due to up regulation of HAS1 and HAS2. In addition, HA appears to provide the scaffolding for inflammatory cell accumulation as well as for new collagen synthesis and deposition.

The cell and its glycosaminoglycan-rich pericellular matrix (PCM) comprise a functional unit. Because modification of PCM influences cell behavior, we investigated molecular mechanisms that regulate PCM volume and composition. In fibroblasts and other cells, aggregates of hyaluronan and versican are found in the PCM. Dermal fibroblasts from Adamts5 ؊/؊ mice, which lack a versican-degrading protease, ADAMTS5, had reduced versican proteolysis, increased PCM, altered cell shape, enhanced ␣-smooth muscle actin (SMA) expression and increased contractility within three-dimensional collagen gels. The myofibroblast-like phenotype was associated with activation of TGF␤ signaling. We tested the hypothesis that fibroblast-myofibroblast transition in Adamts5 ؊/؊ cells resulted from versican accumulation in PCM. First, we noted that versican overexpression in human dermal fibroblasts led to increased SMA expression, enhanced contractility, and increased Smad2 phosphorylation. In contrast, dermal fibroblasts from Vcan haploinsufficient (Vcan hdf/؉ ) mice had reduced contractility relative to wild type fibroblasts. Using a genetic approach to directly test if myofibroblast transition in Adamts5 ؊/؊ cells resulted from increased PCM versican content, we generated Adamts5 ؊/؊ ;Vcan hdf/؉ mice and isolated their dermal fibroblasts for comparison with dermal fibroblasts from Adamts5 ؊/؊ mice. In Adamts5 ؊/؊ fibroblasts, Vcan haploinsufficiency or exogenous ADAMTS5 restored normal fibroblast contractility. These findings demonstrate that altering PCM versican content through proteolytic activity of ADAMTS5 profoundly influenced the dermal fibroblast phenotype and may regulate a phenotypic continuum between the fibroblast and its alter ego, the myofibroblast. We propose that a physiological function of ADAMTS5 in dermal fibroblasts is to maintain optimal versican content and PCM volume by continually trimming versican in hyaluronan-versican aggregates.In addition to the role of cells in building specialized structural extracellular matrix, they maintain a pericellular matrix (PCM) 2 that is dynamic, provisional, and intimately associated with the cell surface (1, 2). Thus, it is appropriate to view a cell and its PCM as a functional unit. Processes that could potentially be regulated by PCM include macromolecular assembly (e.g. assembly of collagen, fibronectin fibrils, or fibrillin microfibrils), cell surface receptor-ligand interactions, binding of pathogens, and cell-matrix and cell-cell adhesion. PCM is sometimes referred to as the glycocalyx because of its abundant carbohydrate content (3). The PCM in many cell types such as chondrocytes, ova, neurons (in which PCM is also termed the perineuronal net), vascular smooth muscle cells, and fibroblasts contains aggregates of hyaluronan (HA) with chondroitin sulfate proteoglycans (CSPG) (4 -7). These aggregates are formed from non-covalent association of HA with large CSPGs such as aggrecan, versican, brevican, and neurocan. In contrast to the aforementioned cell types, heparan sulfa...

Tumor necrosis factor (TNF)-stimulated gene-6 (TSG-6) binds to hyaluronan and can reorganize/stabilize its structure, also enhancing the binding of this glycosaminoglycan to its cell surface receptor, CD44. TSG-6 is rapidly up-regulated in response to inflammatory cytokines protecting tissues from the damaging effects of inflammation. Despite TSG-6 treatment having been shown to improve outcomes in an experimental model of traumatic brain injury, TSG-6 expression has not been extensively studied in the central nervous system (CNS). We hereby analyzed the expression profile of TSG-6 in the developing CNS and following injury. We show that TSG-6 is expressed in the rat CNS by GFAP ؉ and CD44 ؉ astrocytes, solely in the mature brain and spinal cord, and is not present during the development of the CNS. TSG-6 ؊/؊ mice present a reduced number of GFAP ؉ astrocytes when compared with the littermate TSG-6 ؉/؊ mice. TSG-6 expression is drastically up-regulated after injury, and the TSG-6 protein is present within the glial scar, potentially coordinating and stabilizing the formation of this hyaluronan-rich matrix. This study shows that TSG-6 is expressed in the CNS, suggesting a role for TSG-6 in astrocyte activation and tissue repair. We hypothesize that within this context TSG-6 could participate in the formation of the glial scar and confer anti-inflammatory properties. Further studies are required to elucidate the therapeutic potential of targeting TSG-6 after CNS injury to promote its protective effects while reducing the inhibitory properties of the glial scar in axon regeneration.

Background: TSG-6 is important in the organization of hyaluronan (HA). Results: Lack of TSG-6 results in diminished HA accumulation, inflammation, and airway hyperresponsiveness. Conclusion: TSG-6 is essential for the pathological manifestations in a murine model of asthma. Significance: TSG-6 is likely to contribute to the pathogenesis of asthma.