BACKGROUND AND PURPOSEEndogenous glucocorticoids are pro-resolving mediators, an example of which is the endogenous glucocorticoid-regulated protein annexin A1 (ANXA1). Because silicosis is an occupational lung disease characterized by unabated inflammation and fibrosis, in this study we tested the therapeutic properties of the N-terminal ANXA1-derived peptide annexin 1-(2-26) (Ac2-26) on experimental silicosis. EXPERIMENTAL APPROACHSwiss-Webster mice were administered silica particles intranasally and were subsequently treated with intranasal peptide Ac2-26 (200 μg per mouse) or dexamethasone (25 μg per mouse) for 7 days, starting 6 h post-challenge. Ac2-26 abolished the leukocyte infiltration, collagen deposition, granuloma formation and generation of pro-inflammatory cytokines evoked by silica; these variables were only partially inhibited by dexamethasone. KEY RESULTSA clear exacerbation of the silica-induced pathological changes was observed in ANXA1 knockout mice as compared with their wild-type (WT) littermate controls. Incubation of lung fibroblasts from WT mice with Ac2-26 in vitro reduced IL-13 or TGF-β-induced production of CCL2 (MCP-1) and collagen, but this peptide did not affect the production of CCL2 (MCP-1) by stimulated fibroblasts from formyl peptide receptor type 1 (FPR1) knockout mice. Ac2-26 also inhibited the production of CCL2 (MCP-1) from fibroblasts of FPR2 knockout mice. CONCLUSIONS AND IMPLICATIONSCollectively, our findings reveal novel protective properties of the ANXA1 derived peptide Ac2-26 on the inflammatory and fibrotic responses induced by silica, and suggest that ANXA1 mimetic agents might be a promising strategy as innovative anti-fibrotic approaches for the treatment of silicosis. IntroductionSilicosis is a lung occupational disease caused by inhalation of free crystalline silica particles over a prolonged period of time. This disease mainly affects workers in the ceramic industry, glass manufacturing, sandblasting, mining, quarrying and civil construction (Leung et al., 2012;Singer et al., 2012). Silicosis is a problem worldwide, but it is prevalent in countries of low and middle income. China had more than 500 000 cases recorded between 1991 and 1995, and 6000 new cases and more than 24 000 deaths are reported annually (Leung et al., 2012). In Brazil more than 4500 workers were reported to have silicosis between 1978 and 1998, especially in the gold-mining area in Minas Gerais (Carneiro et al., 2006). The irritative action of silica in the lungs results in the formation of nodular lesions, which may coalesce resulting in massive areas of fibrous tissue and reduction of lung elasticity (Davis, 1986). Because of its surface properties, crystalline silica leads to activation of alveolar macrophages [acting on 'scavenger' receptors such as the MARCO (macrophage receptor with collagenous structure)], epithelial cells and fibroblasts (Mossman and Churg, 1998;Fubini and Hubbard, 2003;Huaux, 2007). The granulomatous inflammation induced by silica is characterized by the accumulati...

Instillation of silica into the lungs of rodents results in pathological changes that strongly mimic human silicosis, an occupational lung disease marked by restrictive airway obstruction, inflammation, and fibrosis. Because IL-13 is a pivotal proinflammatory and fibrogenic cytokine, we examined whether a recombinant immunotoxin comprised of human IL-13 and a mutated form of Pseudomonas exotoxin (IL-13–PE) might affect pathological features of experimental silicosis. Mice received a single intranasal instillation of silica particles and were treated with intranasal IL-13–PE every other day from days 21 to 27 postsilica. The sensitivity of putative cell targets to IL-13–PE was also assessed in in vitro settings. Upregulation of IL-13, its receptor subunits IL-13Rα1 and IL-13Rα2, and shared receptor IL-4Rα were associated with development of granulomatous lung inflammation triggered by silica. IL-13–PE inhibited silica-induced granuloma and fibrotic responses noted at 24 h and 15 d after the last treatment. Upregulation of TNF-α, TGF-β, and chemokines, as well as increased collagen deposition and airway hyperreactivity to methacholine were all clearly sensitive to IL-13–PE. In addition, IL-13–PE inhibited both IL-13–induced proliferation of cultured lung fibroblasts from silicotic mice and silica-induced IL-8 generation from A549 cells. In conclusion, our findings show that therapeutic treatment with IL-13–PE can reverse important pathological features caused by inhalation of silica particles, suggesting that this recombinant immunotoxin is a promising molecular template in drug discovery for the treatment of silicosis.

The receptors underlying the endothelin-dependent component of lung plasma extravasation and leucocyte infiltration induced by oleic acid were assessed in mice. Oleic acid (1 mg.kg(-1) intravenously), but not endothelin-1 (up to 1 nmol.kg(-1) intravenously), increased accumulation of Evans blue in the lungs (excluding the trachea and main bronchi) from 11.8+/-3.9 to 98.6+/-10.7 microg 1 h after injection. Bosentan, the antagonist of endothelin receptors (ET(A) and ET(B)) or the selective ET(B) receptor antagonists Ro 46-8443 or A-192621 (administered 1 h before oleic acid at doses of 30, 10 and 30 mg x kg(-1) respectively) reduced the effect of oleic acid by 71%, 58% and 79% respectively. However, the selective ET(A) receptor antagonist A-127722.5 (10 mg x kg(-1)) was inactive. Oleic acid (2 mg xkg(-1), intravenously) raised the number of total leucocytes, mononuclear cells and neutrophils in broncho-alveolar lavage fluid 4 h after injection. Bosentan and Ro 46-8443 (at doses of 30 and 10 mg x kg(-1) respectively) inhibited the neutrophil infiltration induced by oleic acid by approx. 80%. None of the antagonists modified control (basal) pulmonary microvascular permeability or total and differential cell counts. Thus, endogenous endothelins, acting via ET(B) receptor-dependent mechanisms, play a major role in oleic acid-induced lung injury in the mouse by promoting infiltration of circulating neutrophils and enhancement of pulmonary microvascular plasma extravasation. These findings suggest that either ET(B) or mixed ET(A)/ET(B) receptor antagonists might be beneficial in the treatment of the adult respiratory distress syndrome.

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