Acrylamide, an air pollutant, enhances allergen-induced eosinophilic lung inflammation via group 2 innate lymphoid cells.

Air pollution significantly impacts the aggravation of asthma. Exposure to acrylamide, a volatile organic compound in tobacco smoke, is associated with elevated risks of allergy-related outcomes among active smokers. As group 2 innate lymphoid cells (ILC2s) can act as an environmental sensor and significantly contribute to protease allergen-induced lung inflammation, we aimed to elucidate the causal relationship and how inhaled acrylamide worsens allergic lung inflammation via ILC2s. Intranasal acrylamide exposure at nanomolar levels significantly enhanced allergen-induced or recombinant mouse interleukin-33-induced lung inflammation in C57BL/6 mice or Rag1-/- mice, respectively. The cardinal features of lung inflammation included accumulated infiltration of ILC2s and eosinophils. Transcriptomic analysis revealed a gene expression pattern associated with proliferation-related pathways in acrylamide-treated ILC2s. Western blotting revealed significantly higher expression of Ras and phospho-Erk in acrylamide-treated ILC2s than the control, suggesting Ras-Erk signaling pathway involvement. Ex vivo and in vitro analysis showed that acrylamide treatment mainly increased Ki-67+ ILC2s and the cell number of ILC2s whereas PD98059, a highly selective Erk inhibitor, effectively counteracted the acrylamide effect. Intratracheal administration of acrylamide-treated ILC2s significantly enhanced eosinophil infiltration in Rag1-/- mice. This study suggests that airborne acrylamide may enhance the severity of allergen-induced airway eosinophilic inflammation, partly via altering ILC2 proliferative activity.

Di-(2-ethylhexyl) Phthalate Promotes Allergic Lung Inflammation by Modulating CD8α+ Dendritic Cell Differentiation via Metabolite MEHP-PPARγ Axis.

Di-(2-ethylhexyl) phthalate (DEHP), a common plasticizer, is a ubiquitous environmental pollutant that can disrupt endocrine function. Epidemiological studies suggest that chronic exposure to DEHP in the environment is associated with the prevalence of childhood allergic diseases; however, the underlying causal relationship and immunological mechanism remain unclear. This study explored the immunomodulatory effect of DEHP on allergic lung inflammation, while particularly focusing on the impact of DEHP and its metabolite on dendritic cell differentiation and activity of peroxisome proliferator-activated receptor gamma (PPARγ). The results showed that exposure to DEHP at a human tolerable daily intake dose exacerbated allergic lung inflammation in mice. Ex vivo flow cytometric analysis revealed that DEHP-exposed mice displayed a significantly decreased number of CD8α+ dendritic cells (DCs) in spleens and DC progenitors in the bone marrow, as well as, less interleukin-12 production in splenic DCs and increased T helper 2 polarization. Pharmacological experiments showed that mono-(2-ethylhexyl) phthalate (MEHP), the main metabolite of DEHP, significantly hampered the differentiation of CD8α+ DCs from Fms-like tyrosine kinase 3 ligand-differentiated bone marrow culture, by modulating PPARγ activity. These results suggested that chronic exposure to DEHP at environmentally relevant levels, promotes allergic lung inflammation, at least in part, by altering DC differentiation through the MEHP-PPARγ axis. This study has crucial implications for the interaction(s) between environmental pollutants and innate immunity, with respect to the development of allergic asthma.

Fibrinogen-Like Protein 1 Serves as an Anti-Inflammatory Agent for Collagen-Induced Arthritis Therapy in Mice.

Fibrinogen-like protein 1 (FGL1) was recently identified as a major ligand of lymphocyte-activation gene-3 (LAG-3) on activated T cells and serves as an immune suppressive molecule for regulation of immune homeostasis. However, whether FGL1 has therapeutic potential for use in the T cell-induced the autoimmune disease, rheumatoid arthritis (RA), is still unknown. Here, we attempted to evaluate the effect of FGL1 protein on arthritis progression. We also evaluated potential adverse events in a collagen-induced arthritis (CIA) mouse model. We first confirmed that soluble Fgl1 protein could specifically bind to surface Lag-3 receptor on 3T3-Lag-3 cells and further inhibit interleukin (IL-2) and interferon gamma (IFNγ) secretion from activated primary mouse T cells by 95% and 43%, respectively. Intraperitoneal administration of Fgl1 protein significantly decreased the inflammatory cytokine level (i.e., IL-1ß and IL-6) in local paw tissue, and prevented joint inflammation, cellular infiltration, bone deformation and attenuated collagen-induced arthritis progression in vivo. We further demonstrated that exogenous Fgl1 does not cause obvious adverse events during treatment by monitoring body weight and liver weight, and assessing the morphology of several organs (i.e., heart, liver, spleen, lung and kidney) by pathological studies. We expect that Fgl1 protein may be suitable to serve as a potential therapeutic agent for treatment of RA or even other types of T cell-induced autoimmune or inflammatory diseases in the future.

Stimulatory effect of gastroesophageal reflux disease (GERD) on pulmonary fibroblast differentiation.

Epidemiological studies indicate that prolonged micro-aspiration of gastric fluid is associated in gastroesophageal reflux disease with the development of chronic respiratory diseases, possibly caused by inflammation-related immunomodulation. Therefore, we sought to ascertain the effect of gastric fluid exposure on pulmonary residential cells. The expression of α-smooth muscle actin as a fibrotic marker was increased in both normal human pulmonary fibroblast cells and mouse macrophages. Gastric fluid enhanced the proliferation and migration of HFL-1 cells and stimulated the expression of inflammatory cytokines in an antibody assay. Elevated expression of the Rho signaling pathway was noted in fibroblast cells stimulated with gastric fluid or conditioned media. These results indicate that gastric fluid alone, or the mixture of proinflammatory mediators induced by gastric fluid in the pulmonary context, can stimulate pulmonary fibroblast cell inflammation, migration, and differentiation, suggesting that a wound healing process is initiated. Subsequent aberrant repair in pulmonary residential cells may lead to pulmonary fibroblast differentiation and fibrotic progression. The results point to a stimulatory effect of chronic GERD on pulmonary fibroblast differentiation, and this may promote the development of chronic pulmonary diseases in the long term.

Aryl hydrocarbon receptor signaling promotes ORMDL3-dependent generation of sphingosine-1-phosphate by inhibiting sphingosine-1-phosphate lyase.

Aryl hydrocarbon receptor (AhR), a cellular chemical sensor, controls cellular homeostasis, and sphingosine-1-phosphate (S1P), a bioactive intermediate of sphingolipid metabolism, is believed to have a role in immunity and inflammation, but their potential crosstalk is currently unknown. We aimed to determine whether there is a functional linkage between AhR signaling and sphingolipid metabolism. We showed that AhR ligands, including an environmental polycyclic aromatic hydrocarbon (PAH), induced S1P generation, and inhibited S1P lyase (S1PL) activity in resting cells, antigen/IgE-activated mast cells, and mouse lungs exposed to the AhR ligand alone or in combination with antigen challenge. The reduction of S1PL activity was due to AhR-mediated oxidation of S1PL at residue 317, which was reversible by the addition of an antioxidant or in cells with knockdown of the ORMDL3 gene encoding an ER transmembrane protein, whereas C317A S1PL mutant-transfected cells were resistant to the AhR-mediated effect. Furthermore, analysis of AhR ligand-treated cells showed a time-dependent increase of the ORMDL3-S1PL complex, which was confirmed by FRET analysis. This change increased the S1P levels, which in turn, induced mast cell degranulation via S1PR2 signaling. In addition, elevated levels of plasma S1P were found in children with asthma compared to non-asthmatic subjects. These results suggest a new regulatory pathway whereby the AhR-ligand axis induces ORMDL3-dependent S1P generation by inhibiting S1PL, which may contribute to the expression of allergic diseases.

Correction to: Aryl hydrocarbon receptor signaling promotes ORMDL3-dependent generation of sphingosine-1-phosphate by inhibiting sphingosine-1-phosphate lyase.

In this article, published online 23 March 2018, the affiliation 10 of Zhou Y was incorrect. The affiliation should be "Children's Hospital and Institute of Biomedical Sciences, Fudan University. Key Laboratory of Neonatal Disease, Ministry of Health, 201102, Shanghai, China." The authors regret the errors.

A prominent air pollutant, Indeno[1,2,3-cd]pyrene, enhances allergic lung inflammation via aryl hydrocarbon receptor.

Chronic exposure to ambient polycyclic aromatic hydrocarbons (PAHs) is associated with asthma, but its regulatory mechanisms remain incompletely defined. We report herein that elevated levels of urinary 1-hydroxypyrene, a biomarker of PAH exposure, were found in asthmatic subjects (n = 39) as compared to those in healthy subjects (n = 43) living in an industrial city of Taiwan, where indeno[1,2,3-cd]pyrene (IP) was found to be a prominent PAH associated with ambient PM2.5. In a mouse model, intranasal exposure of mice with varying doses of IP significantly enhanced antigen-induced allergic inflammation, including increased airway eosinophilia, Th2 cytokines, including IL-4 and IL-5, as well as antigen-specific IgE level, which was absent in dendritic cell (DC)-specific aryl hydrocarbon receptor (AhR)-null mice. Mechanistically, IP treatment significantly altered DC's function, including increased level of pro-inflammatory IL-6 and decreased generation of anti-inflammatory IL-10. The IP's effect was lost in DCs from mice carrying an AhR-mutant allele. Taken together, these results suggest that chronic exposure to environmental PAHs may pose a significant risk for asthma, in which IP, a prominent ambient PAH in Taiwan, was shown to enhance the severity of allergic lung inflammation in mice through, at least in part, its ability in modulating DC's function in an AhR-dependent manner.

Aryl hydrocarbon receptor-ligand axis mediates pulmonary fibroblast migration and differentiation through increased arachidonic acid metabolism.

Pulmonary fibroblast migration and differentiation are critical events in fibrogenesis; meanwhile, fibrosis characterizes the pathology of many respiratory diseases. The role of aryl hydrocarbon receptor (AhR), a unique cellular chemical sensor, has been suggested in tissue fibrosis, but the mechanisms through which the AhR-ligand axis influences the fibrotic process remain undefined. In this study, the potential impact of the AhR-ligand axis on pulmonary fibroblast migration and differentiation was analyzed using human primary lung fibroblasts HFL-1 and CCL-202 cells. Boyden chamber-based cell migration assay showed that activated AhR in HFL-1cells significantly enhanced cell migration in response to 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), and a known AhR antagonist, CH223191, inhibited its migratory activity. Furthermore, the calcium mobilization and subsequent upregulated expression of arachidonic acid metabolizing enzymes, including cyclooxygenase2 (COX-2) and 5-lipoxygenase (5-LOX), were observed in TCDD-treated HFL-1 cells, concomitant with elevated levels of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) secretion. Also, significantly increased expression of α-smooth muscle actin α-SMA), a fibroblast differentiation marker, was also noted in TCDD-treated HFL-1 cells (p<0.05), resulting in a dynamic change in cytoskeleton protein levels and an increase in the nuclear translocation of the myocardin-related transcription factor. Moreover, the enhanced levels of α-SMA expression and fibroblast migration induced by TCDD, PGE2 and LTB4 were abrogated by selective inhibitors for COX-2 and 5-LOX. Knockdown of AhR by siRNA completely diminished intracellular calcium uptake and reduced α-SMA protein verified by promoter-reporter assays and chromatin immunoprecipitation. Taken together, our results suggested the importance of the AhR-ligand axis in fibroblast migration and differentiation through its capacity in enhancing arachidonic acid metabolism.