Versican is produced by Trif- and type I interferon-dependent signaling in macrophages and contributes to fine control of innate immunity in lungs

Growing evidence suggests that versican is important in the innate immune response to lung infection. Our goal was to understand the regulation of macrophage-derived versican and the role it plays in innate immunity. We first defined the signaling events that regulate versican expression, using bone marrow-derived macrophages (BMDMs) from mice lacking specific Toll-like receptors (TLRs), TLR adaptor molecules, or the type I interferon receptor (IFNAR1). We show that LPS and polyinosinic-polycytidylic acid [poly(I:C)] trigger a signaling cascade involving TLR3 or TLR4, the Trif adaptor, type I interferons, and IFNAR1, leading to increased expression of versican by macrophages and implicating versican as an interferon-stimulated gene. The signaling events regulating versican are distinct from those for hyaluronan synthase 1 (HAS1) and syndecan-4 in macrophages. HAS1 expression requires TLR2 and MyD88. Syndecan-4 requires TLR2, TLR3, or TLR4 and both MyD88 and Trif. Neither HAS1 nor syndecan-4 is dependent on type I interferons. The importance of macrophage-derived versican in lungs was determined with LysM/Vcan-/- mice. These studies show increased recovery of inflammatory cells in the bronchoalveolar lavage fluid of poly(I:C)-treated LysM/Vcan-/- mice compared with control mice. IFN-β and IL-10, two important anti-inflammatory molecules, are significantly decreased in both poly(I:C)-treated BMDMs from LysM/Vcan-/- mice and bronchoalveolar lavage fluid from poly(I:C)-treated LysM/Vcan-/- mice compared with control mice. In short, type I interferon signaling regulates versican expression, and versican is necessary for type I interferon production. These findings suggest that macrophage-derived versican is an immunomodulatory molecule with anti-inflammatory properties in acute pulmonary inflammation.

Versican, a major hyaluronan-binding component in the dermis, loses its hyaluronan-binding ability in solar elastosis

Versican interacts with hyaluronan (HA) at its N-terminus and with fibrillin-1 at its C terminus. As versican in the dermis connects microfibrils to the HA-rich matrix for viscoelasticity, dermal diseases may involve destruction of these complexes. A recombinant versican protein, rVN, covering the HA binding region (HABR) of human versican and a polyclonal antibody, 6084, against rVN were prepared and characterized. Blotting analyses of skin extracts with 6084 and biotin-conjugated HA revealed that versican was a major HA-binding component in the dermis. Matrix metalloprotease-12, which is expressed in areas of solar elastosis, degraded versican and abrogated its HA-binding ability. Immunohistochemical analyses revealed that the elastic materials in solar elastosis lesions were negative for 6084, but positive for 2B1, an antibody recognizing the C-terminus of versican, indicating loss of the HABR in the aggregated elastic fibers. This loss of the HA-binding ability of versican followed by HA exclusion may be responsible for the pathological and phenotypical changes observed in solar elastosis.

Type I Interferon Signaling Increases Versican Expression and Synthesis in Lung Stromal Cells During Influenza Infection

Versican, a chondroitin sulfate proteoglycan, is an essential component of the extracellular matrix (ECM) in inflammatory lung disease. Versican's potential as an immunomodulatory molecule makes it a promising therapeutic target for controlling host immune responses in the lungs. To establish changes to versican expression and accumulation during influenza A viral pneumonia, we document the temporal and spatial changes to versican mRNA and protein in concert with pulmonary inflammatory cell infiltration. These studies were performed in the lungs of wild-type C57BL6/J mice on days 3, 6, 9, and 12 post-infection with influenza A virus using immunohistochemistry, in situ hybridization, and quantitative digital pathology. Using duplex in situ hybridization, we demonstrate that type I interferon signaling contributes significantly to versican expression in lung stromal cells. Our findings show that versican is a type I interferon-stimulated gene in pulmonary fibroblasts and pericytes in the context of viral pneumonia. These data also provide a guide for future studies to determine the role of versican in the pulmonary immune response to influenza infection.