Involvement of Gas6 protein in mouse model of lipopolysaccharide-induced lung inflammation

Background: Gas6 is a product of growth arrest-specific gene 6 and is mostly expressed by the growth-arrested organs and is implicated in thrombosis, various inflammation, and age-related diseases. However, its role in chronic obstructive pulmonary disease has not been investigated yet. Methods: We developed lipopolysaccharide-induced mouse model of chronic lung inflammation to study its involvement. Therefore, male C57BL/6 mice (20–25 g) were grouped into control and LPS group; each group having 15 animals each. LPS group was nebulized with LPS (1 mg/ml) for 45 min, once a week for 8 weeks to induce chronic inflammatory conditions in the lungs by use of nebulizer. The mice model was validated by assessing infiltration of various immune cells (T-cells, B-cells, and neutrophils) into the lungs and pro-inflammatory and anti-inflammatory cytokine profile by cytokine bead array kit by flow cytometry. Lung deterioration was assessed by lung histology. The level of gas6 protein from the lung homogenate was measured by quantikine enzyme-linked immunosorbent assay kit. Furthermore, lung homogenate was analyzed by Western blotting for expression profile of gas6 protein. Results: There was significant increase in the level of T-cells (19±8% vs 65±11%), B-cells (24±7% vs 64±10%), and neutrophils (22±9% vs 57±10%) and significant increase in the level of tumor necrosis factor (200 ± 17 pg/ml vs. 1222 ± 152 pg/ml) and IL-6 (106 ± 13 pg/ml vs. 448 ± 122 pg/ml). Lung deterioration was observed in LPS group. We observed significant increase in the level of gas6 protein in lung homogenate in LPS group (0.16 ± 0.1 ng/ml vs. 4.2 ± 0.1 ng/ml). Furthermore, we found significant increase in gas6 protein in the lung homogenate of LPS-treated group by Western blotting. Conclusion: The current study establishes the involvement gas6 protein in lung inflammation.