No abstract

Thrombospondin-1 (TSP-1) is an extracellular protein critical to normal lung homeostasis, and is reported to activate latent transforming growth factor-b (TGF-b). Because active TGF-b is causally involved in lung fibrosis after bleomycin challenge, alterations in TSP-1 may be relevant to pulmonary fibrosis. We sought to determine the effects of TSP-1 deficiency on the susceptibility to bleomycin-induced pulmonary fibrosis in a murine model. Agematched and sex-matched C57BL/6 wild-type (WT) and TSP-1-deficient mice were treated twice weekly for 4 weeks with intraperitoneal bleomycin (0.035 U/g) or PBS, and were allowed to rest 1 week before being killed. Their lungs were inflated with PBS, fixed in formalin, paraffin-embedded, and sectioned. A certified veterinary pathologist blindly scored each slide for inflammation and fibrosis. Lungs were homogenized to obtain RNA and protein for the real-time RT-PCR analysis of connective tissue growth factor (CTGF) and collagen I, and for Western blotting to detect phosphoSmad2, or total Smad2/3, respectively. In response to bleomycin treatment, measures of fibrosis and inflammation, along with CTGF and collagen I mRNA concentrations, were increased in TSP-1-deficient mice compared with WT mice. Notably, Smad 2/3 signaling was of equal strength in WT and TSP-1 knockout mice treated with bleomycin, suggesting that TSP-1 is not required for the activation of TGF-b. These results demonstrate that TSP-1 deficiency does not protect mice from systemic bleomycin challenge, and that TSP-1 deficiency is associated with increased expression of lung collagen and CTGF.

Latency Associated Peptide (LAP) binds TGF-β1, forming a latent complex. Currently, LAP is presumed to function only as a sequestering agent for active TGF-β1. Previous work shows that LAP can induce epithelial cell migration, but effects on leukocytes have not been reported. Because of the multiplicity of immunologic processes in which TGF-β1 plays a role, we hypothesized that LAP could function independently to modulate immune responses. In separate experiments we found that LAP promoted chemotaxis of human monocytes and blocked inflammation in vivo in a murine model of the delayed-type hypersensitivity response (DTHR). These effects did not involve TGF-β1 activity. Further studies revealed that disruption of specific LAP-thrombospondin-1 (TSP-1) interactions prevented LAP-induced responses. The effect of LAP on DTH inhibition depended on IL-10. These data support a novel role for LAP in regulating monocyte trafficking and immune modulation.

Background-Heat shock proteins (Hsps) are a family of evolutionary conserved proteins classified according to their size as small and large Hsps. They have a cytoprotective role and have been shown recently to be immunogenic molecules. In addition, self-reactivity to Hsps has been implicated in various autoimmune diseases and in the development of alloimmunity. The purpose of this study was to examine the relationship of large and small Hsps and anti-Hsp antibodies in recipients of lung transplantation (LTX) who have bronchiolitis obliterans syndrome (BOS).