Background: The pathogenesis of asthma and airway obstruction is the result of an abnormal response to different environmental exposures. The scientific premise of our study was based on the finding that FoxO1 expression is increased in lung macrophages of mice after allergen exposure and human asthmatic patients. Macrophages are capable of switching from one functional phenotype to another, and it is important to understand the mechanisms involved in the transformation of macrophages and how their cellular function affects the peribronchial stromal microenvironment. Methods:We employed a murine asthma model, in which mice were treated by intranasal insufflation with allergens for 2-8 weeks. We used both a pharmacologic approach using a highly specific FoxO1 inhibitor and genetic approaches using FoxO1 knockout mice (FoxO1 fl/fl LysMcre). Cytokine level in biological fluids was measured by ELISA and the expression of encoding molecules by NanoString assay and qRT-PCR.Results: We show that the levels of FoxO1 gene are significantly elevated in the airway macrophages of patients with mild asthma in response to subsegmental bronchial allergen challenge. Transcription factor FoxO1 regulates a pro-asthmatic phenotype of lung macrophages that is involved in the development and progression of chronic allergic airway disease. We have shown that inhibition of FoxO1 induced phenotypic conversion of lung macrophages and downregulates pro-asthmatic and pro-fibrotic gene expression by macrophages, which contribute to airway inflammation and airway remodeling in allergic asthma.Conclusion: Targeting FoxO1 with its downstream regulator IRF4 is a novel therapeutic target for controlling allergic inflammation and potentially reversing fibrotic airway remodeling.

Lysophosphatidylcholine (LPC), a derivative of phosphatidylcholine, is generated through the hydrolytic action of phospholipase A 2 at the sn-2 position of phosphatidylcholine. In vivo, LPC is claimed to be the major effective component of oxidized low-density lipoprotein [1,2], and is found in high concentrations Lysophosphatidylcholine induces expression of adhesion molecules; however, the underlying molecular mechanisms of this are not well elucidated. In this study, the intracellular signaling by which lysophosphatidylcholine upregulates vascular cell adhesion molecule-1 and P-selectin was delineated using YPEN-1 and HEK293T cells. The results showed that lysophosphatidylcholine dose-dependently induced expression of vascular cell adhesion molecule-1 and P-selectin, accompanied by the activation of transcription factor nuclear factor jB. However, the nuclear factor jB inhibitor caffeic acid phenethyl ester (CAPE) and the antioxidant N-acetylcysteine only partially blocked lysophosphatidylcholine-induced adhesion molecules. Subsequently, we found that the lysophosphatidylcholine receptor G protein-coupled receptor 4 (GPK4) was expressed in YPEN-1 cells and triggered the cAMP ⁄ protein kinase A ⁄ cAMP response element-binding protein pathway, resulting in upregulation of adhesion molecules. Further evidence showed that overexpression of human GPK4 enhanced lysophosphatidylcholine-induced expression of adhesion molecules in YPEN-1 cells, and enabled HEK293T cells to express adhesion molecules in response to lysophosphatidylcholine. In conclusion, the current study suggested two pathways by which lysophosphatidylcholine regulates the expression of adhesion molecules, the lysophosphatidylcholine ⁄ nuclear factor-jB ⁄ adhesion molecule and lysophosphatidylcholine ⁄ GPK4 ⁄ cAMP ⁄ protein kinase A ⁄ cAMP response element-binding protein ⁄ adhesion molecule pathways, emphasizing the importance of the lysophosphatidylcholine receptor in regulating endothelial cell function.Abbreviations AC, adenylyl cyclase; ACREB, dominant-negative mutant CREB protein; AM, adhesion molecule; CAPE, caffeic acid phenethyl ester; CRE, cAMP response element; CREB, cAMP response element-binding protein; EC, endothelial cell; ERK, extracellular signal-related kinase; FSK, forskolin; G2A, G2 accumulation protein; GPR4, G protein-coupled receptor 4; GPR119, G protein-coupled receptor 119; hGPR4, human GPR4 expression vector; LPC, lysophosphatidylcholine; MDL, MDL12330A; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide; NAC, N-acetylcysteine; NF-jB, nuclear factor-kappaB; PKA, protein kinase A; PKC, protein kinase C; TNF-a, tumor necrosis factor-a; VCAM-1, vascular cell adhesion molecule-1.