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A4479 - Resveratrol Suppresses Ly6C+ Subtype Macrophages in a Mouse Model with Acute Lung Injury
Author Block: Z. Jiang, L. Li, L. Zhu; Fudan University Zhongshan Hospital, Shanghai, China.
RATIONALE: Acute lung injury and acute respiratory distress symptom (ALI/ARDS) are life-threatening condition in critically ill patients, with diffuse lung inflammation and alveolar damage, influx of neutrophils and protein rich exudates in the alveolar spaces. Macrophages play important role in the pathogenesis of ALI/ARDS. Resveratrol (Res) is a natural polyphenol, secreted naturally by plants. Previous studies suggested that resveratrol has anti-inflammatory property by increasing SIRT1 expression and modulation of macrophage NLRP2 inflammasome, but whether resveratrol suppresses ALI/ARDS through modulation of macrophage phenotypes is still unknown. METHODS: In this study, we established a mouse model with ALI by intratracheal (i.t.) treatment with 5 mg/kg lipopolysaccharide (LPS). Then the mice were intraperitoneal (i.p.) treated with 30 mg/kg body weight resveratrol in 30% ethanol at 3 and 24 hours after LPS treatment, the mice that was i.p. received 30% ethanol were used as controls. Lung tissues, bronchoalveolar lavage (BAL) and blood were collected for analysis. RESULTS: There were significantly lower acute lung inflammation and amounts of Ly6G(high)F4/80(-) neutrophil infiltrates in the Res-treated mice 2 days after LPS treatment, as compared to the control mice. The beneficial effects were associated with significantly lower MCP-1, IL-6, IL-1beta and CXCL15 in BAL and lung tissues. More importantly, LPS significantly increased Ly6C+ population in F4/80(+)Ly6G(int) alveolar macrophages (AMs) and circulating monocytes, but the effects were effectively reversed by the Res-treatment in vivo. The Ly6C(+) phenotype macrophages share a similar property of classically activated macrophages or M1 cells, with expressing high levels of MCP-1, CCR2, CD80, iNOS and TNF-alpha. Supporting the results in vivo, treatment of bone marrow-derived macrophages (BMDMs) and RAW264.7 cells with 50 μM Res significantly reduced the macrophages expressing Ly6C, CCR2, CCL2, STAT3, HMGB1, TNF-alpha and iNOS1, but increased the expression of SIRT1, SOCS3, Arginase-1 and Mannose receptor (MR or CD206). In addition, we observed the reduced acetylation of STAT3 at Lys685 residue in the Res-treated BMDMs, suggesting the involvement of STAT3 activation and skew of macrophage differentiation from Ly6C+ or M1 phenotypes towards alternatively activated macrophage phenotypes (M2 cells) after Res treatment. Further adoptive transfer of the Res-treated BMDMs into LPS-induced ALI mouse model, significantly attenuated lung inflammation and neutrophil infiltration, in association with reduced PKH26 red fluorescence-labeled Ly6C+ BMDMs migration into the lung tissues. CONCLUSIONS: Resveratrol suppressed ALI through suppressing monocyte differentiation towards Ly6C(+) and M1 macrophage phenotypes and chemotaxis.