Fibrosis, the hallmark of scleroderma, represents the transformation of normal wound-healing into a deregulated self-sustaining process that contributes to the high morbidity and mortality of this disease. While multiple intracellular signaling pathways are known to be implicated in TGF-beta-mediated fibrotic responses, the nature of their persistent deregulation in pathological inflammation and fibrosis remain poorly understood. Elucidation of the mechanism underlying the switch from self-limited repair to intractable scar is essential for the design of rational therapies to interrupt the process in scleroderma. Recent results from the parent R01 grant indicate that an immune signaling receptor toll-like receptor4 (TLR4) and its endogenous ligands such as fibrovection - EDA are markedly elevated in skin and lungs from patients with scleroderma. Stimulation of TLR4 in fibroblasts was associated with the induction of extracellular matrix remodeling and tissue repair programs as well as synergistic enhancement of TGF-beta-mediated fibrotic responses. Thus, in a fibrogenic milieu enriched with TGF-beta and endogenous TLR4 ligands, fibroblasts expressing elevated TLR4 engage in uncontrolled collagen synthesis and myofibroblast differentiation contributing to progression of fibrosis. These observations suggest a novel paradigm for fibrosis linking recurrent injury, accumulation of endogenous ligands and fibrogenesis in scleroderma. Disrupting persistent TLR4 signaling with small molecule TLR4 inhibitors represent potential strategies for breaking the vicious cycle of progressive fibrosis in scleroderma. In this new interdisciplinary research collaboration, we will first optimize novel small-molecule TLR4 inhibitors for anti-fibrotic efficacy (University of Colorado), and study the two lead candidates in vivo in complementary mouse models of scleroderma using both prevention and regression approaches (Northwestern University). These results might have significant implications for the development of effective agents to treat scleroderma.