Xiao Na Ge

Transdifferentiation of pulmonary arteriolar endothelial cells into smooth muscle-like cells regulated by myocardin involved in hypoxia-induced pulmonary vascular remodelling.

Myocardin gene has been identified as a master regulator of smooth muscle cell differentiation. Smooth muscle cells play a critical role in the pathogenesis of hypoxia‐induced pulmonary hypertension (PH) and pulmonary vascular remodelling (PVR). The purpose of this study was to investigate the change of myocardin gene expression in the pulmonary vessels of hypoxia‐induced PH affected by Sildenafil treatment and the involvement of endothelial cells transdifferentiation into smooth muscle cells in the process of hypoxia‐induced PH and PVR. Myocardin and relative markers were investigated in animal models and cultured endothelial cells. Mean pulmonary artery pressure (mPAP) was measured. Immunohistochemistry and immunofluorescence were used to show the expression of smooth muscle α‐actin (SMA), in situ hybridization (ISH) and reverse transcription polymerase chain reaction (RT‐PCR) were performed respectively to detect the myocardin and SMA expression at mRNA levels. Small interfering RNA (siRNA) induced suppression of myocardin in cultured cells. We confirmed that hypoxia induced the PH and PVR in rats. Sildenafil could attenuate the hypoxia‐induced PH. We found that myocardin mRNA expression is upregulated significantly in the hypoxic pulmonary vessels and cultured cells but downregulated in PH with Sildenafil treatment. The porcine pulmonary artery endothelial cells (PAECs) transdifferentiate into smooth muscle‐like cells in hypoxic culture while the transdifferentiation did not occur when SiRNA of myocardin was applied. Our results suggest that myocardin gene, as a marker of smooth muscle cell differentiation, was expressed in the pulmonary vessels in hypoxia‐induced PH rats, which could be downregulated by Sildenafil treatment, as well as in hypoxic cultured endothelial cells. Hypoxia induced the transdifferentiation of endothelial cells of vessels into smooth muscle‐like cells which was regulated by myocardin.

Allergen-Induced Airway Remodeling Is Impaired in Galectin-3–Deficient Mice

The role played by the β-galactoside–binding lectin galectin-3 (Gal-3) in airway remodeling, a characteristic feature of asthma that leads to airway dysfunction and poor clinical outcome in humans, was investigated in a murine model of chronic allergic airway inflammation. Wild-type (WT) and Gal-3 knockout (KO) mice were subjected to repetitive allergen challenge with OVA up to 12 wk, and bronchoalveolar lavage fluid (BALF) and lung tissue collected after the last challenge were evaluated for cellular features associated with airway remodeling. Compared to WT mice, chronic OVA challenge in Gal-3 KO mice resulted in diminished remodeling of the airways with significantly reduced mucus secretion, subepithelial fibrosis, smooth muscle thickness, and peribronchial angiogenesis. The higher degree of airway remodeling in WT mice was associated with higher Gal-3 expression in the BALF as well as lung tissue. Cell counts in BALF and lung immunohistology demonstrated that eosinophil infiltration in OVA-challenged Gal-3 KO mice was significantly reduced compared with that WT mice. Evaluation of cellular mediators associated with eosinophil recruitment and airway remodeling revealed that levels of eotaxin-1, IL-5, IL-13, found in inflammatory zone 1, and TGF-β were substantially lower in Gal-3 KO mice. Finally, leukocytes from Gal-3 KO mice demonstrated decreased trafficking (rolling) on vascular endothelial adhesion molecules compared with that of WT cells. Overall, these studies demonstrate that Gal-3 is an important lectin that promotes airway remodeling via airway recruitment of inflammatory cells, specifically eosinophils, and the development of a Th2 phenotype as well as increased expression of eosinophil-specific chemokines and profibrogenic and angiogenic mediators.

ORMDL3 promotes eosinophil trafficking and activation via regulation of integrins and CD48

ORM (yeast)-Like protein isoform 3 (ORMDL3) has recently been identified as a candidate gene for susceptibility to asthma; however the mechanisms by which it contributes to asthma pathogenesis are not well understood. Here we demonstrate a functional role for ORMDL3 in eosinophils in the context of allergic inflammation. Eosinophils recruited to the airways of allergen-challenged mice express ORMDL3. ORMDL3 expression in bone marrow eosinophils is localized in the endoplasmic reticulum and is induced by IL-3 and eotaxin-1. Over-expression of ORMDL3 in eosinophils causes increased rolling, distinct cytoskeletal rearrangement, ERK (1/2) phosphorylation and nuclear translocation of NF-κB. Knock-down of ORMDL3 significantly inhibits activation-induced cell shape changes, adhesion and recruitment to sites of inflammation in vivo, combined with reduced expression of CD49d and CD18. Additionally, ORMDL3 regulates IL-3-induced expression of CD48 and CD48-mediated eosinophil degranulation. These studies show that ORMDL3 regulates eosinophil trafficking, recruitment and degranulation, further elucidating a role for this molecule in allergic asthma and potentially other eosinophilic disorders.

Deficiency of Endothelial Heparan Sulfates Attenuates Allergic Airway Inflammation

The effect of targeted inactivation of the gene encoding N-deacetylase/N-sulfotransferase-1 (Ndst1), a key enzyme involved in the biosynthesis of heparan sulfate (HS) chains, on the inflammatory response associated with allergic inflammation in a murine model of OVA-induced acute airway inflammation was investigated. OVA-exposed Ndst1f/fTekCre+ (mutant) mice deficient in endothelial and leukocyte Ndst1 demonstrated significantly decreased allergen-induced airway hyperresponsiveness and inflammation characterized by a significant reduction in airway recruitment of inflammatory cells (eosinophils, macrophages, neutrophils, and lymphocytes), diminished IL-5, IL-2, TGF-β1, and eotaxin levels, as well as decreased expression of TGF-β1 and the angiogenic protein FIZZ1 (found in inflammatory zone 1) in lung tissue compared with OVA-exposed Ndst1f/fTekCre− wild-type littermates. Furthermore, murine eosinophils demonstrated significantly decreased rolling on lung endothelial cells (ECs) from mutant mice compared with wild-type ECs under conditions of flow in vitro. Treatment of wild-type ECs, but not eosinophils, with anti-HS Abs significantly inhibited eosinophil rolling, mimicking that observed with Ndst1-deficient ECs. In vivo, trafficking of circulating leukocytes in lung microvessels of allergen-challenged Ndst1-deficient mice was significantly lower than that observed in corresponding WT littermates. Endothelial-expressed HS plays an important role in allergic airway inflammation through the regulation of recruitment of inflammatory cells to the airways by mediating interaction of leukocytes with the vascular endothelium. Furthermore, HS may also participate by sequestering and modulating the activity of allergic asthma-relevant mediators such as IL-5, IL-2, and TGF-β1.

Regulation of Eosinophil Trafficking by SWAP-70 and Its Role in Allergic Airway Inflammation

Eosinophils are the predominant inflammatory cells recruited to allergic airways. In this article, we show that human and murine eosinophils express SWAP-70, an intracellular RAC-binding signaling protein, and examine its role in mediating eosinophil trafficking and pulmonary recruitment in a murine model of allergic airway inflammation. Compared with wild-type eosinophils, SWAP-70–deficient (Swap-70−/−) eosinophils revealed altered adhesive interactions within inflamed postcapillary venules under conditions of blood flow by intravital microscopy, exhibiting enhanced slow rolling but decreased firm adhesion. In static adhesion assays, Swap-70−/− eosinophils adhered poorly to VCAM-1 and ICAM-1 and exhibited inefficient leading edge and uropod formation. Adherent Swap-70−/− eosinophils failed to translocate RAC1 to leading edges and displayed aberrant cell surface localization/distribution of α4 and Mac-1. Chemokine-induced migration of Swap-70−/− eosinophils was significantly decreased, correlating with reduced intracellular calcium levels, defective actin polymerization/depolymerization, and altered cytoskeletal rearrangement. In vivo, recruitment of eosinophils to the lungs of allergen-challenged Swap-70−/− mice, compared with wild-type mice, was significantly reduced, along with considerable attenuation of airway inflammation, indicated by diminished IL-5, IL-13, and TNF-α levels; reduced mucus secretion; and improved airway function. These findings suggest that regulation of eosinophil trafficking and migration by SWAP-70 is important for the development of eosinophilic inflammation after allergen exposure.

The p110δ subunit of PI3K regulates bone marrow-derived eosinophil trafficking and airway eosinophilia in allergen-challenged mice

Trafficking and recruitment of eosinophils during allergic airway inflammation is mediated by the phosphatidylinositol 3-kinase (PI3K) family of signaling molecules. The role played by the p110δ subunit of PI3K (PI3K p110δ) in regulating eosinophil trafficking and recruitment was investigated using a selective pharmacological inhibitor (IC87114). Treatment with the PI3K p110δ inhibitor significantly reduced murine bone marrow-derived eosinophil (BM-Eos) adhesion to VCAM-1 as well as ICAM-1 and inhibited activation-induced changes in cell morphology associated with reduced Mac-1 expression and aberrant cell surface localization/distribution of Mac-1 and α4. Infused BM-Eos demonstrated significantly decreased rolling and adhesion in inflamed cremaster muscle microvessels of mice treated with IC87114 compared with vehicle-treated mice. Furthermore, inhibition of PI3K p110δ significantly attenuated eotaxin-1-induced BM-Eos migration and prevented eotaxin-1-induced changes in the cytoskeleton and cell morphology. Knockdown of PI3K p110δ with siRNA in BM-Eos resulted in reduced rolling, adhesion, and migration, as well as inhibition of activation-induced changes in cell morphology, validating its role in regulating trafficking and migration. Finally, in a mouse model of cockroach antigen-induced allergic airway inflammation, oral administration of the PI3K p110δ inhibitor significantly inhibited airway eosinophil recruitment, resulting in attenuation of airway hyperresponsiveness in response to methacholine, reduced mucus secretion, and expression of proinflammatory molecules (found in inflammatory zone-1 and intelectin-1). Overall, these findings indicate the important role played by PI3K p110δ in mediating BM-Eos trafficking and migration by regulating adhesion molecule expression and localization/distribution as well as promoting changes in cell morphology that favor recruitment during inflammation.

Regulation of eosinophilia and allergic airway inflammation by the glycan-binding protein galectin-1

Significance Allergic asthma is a chronic airway disease, and the number of individuals with asthma continues to grow. Eosinophils recruited to allergic airways contribute significantly to airway inflammation via release of proinflammatory mediators that cause epithelial tissue damage, bronchoconstriction, and airway remodeling. Here we show that galectin-1 (Gal-1), an endogenous immunoregulatory lectin, binds to eosinophil-expressed surface glycans to inhibit cell migration and induce apoptosis. Using a mouse model of allergic asthma, we show that mice lacking Gal-1 exhibit increased airway eosinophils and airway hyperresponsiveness compared with wild-type mice. Because Gal-1 plays an important role in regulating airway inflammation, identifying pathways to induce Gal-1 synthesis and/or favor its biological activity might enable exploitation of its proresolving function to suppress allergic asthma. Galectin-1 (Gal-1), a glycan-binding protein with broad antiinflammatory activities, functions as a proresolving mediator in autoimmune and chronic inflammatory disorders. However, its role in allergic airway inflammation has not yet been elucidated. We evaluated the effects of Gal-1 on eosinophil function and its role in a mouse model of allergic asthma. Allergen exposure resulted in airway recruitment of Gal-1–expressing inflammatory cells, including eosinophils, as well as increased Gal-1 in extracellular spaces in the lungs. In vitro, extracellular Gal-1 exerted divergent effects on eosinophils that were N-glycan– and dose-dependent. At concentrations ≤0.25 µM, Gal-1 increased eosinophil adhesion to vascular cell adhesion molecule-1, caused redistribution of integrin CD49d to the periphery and cell clustering, but inhibited ERK(1/2) activation and eotaxin-1–induced migration. Exposure to concentrations ≥1 µM resulted in ERK(1/2)-dependent apoptosis and disruption of the F-actin cytoskeleton. At lower concentrations, Gal-1 did not alter expression of adhesion molecules (CD49d, CD18, CD11a, CD11b, L-selectin) or of the chemokine receptor CCR3, but decreased CD49d and CCR3 was observed in eosinophils treated with higher concentrations of this lectin. In vivo, allergen-challenged Gal-1–deficient mice exhibited increased recruitment of eosinophils and CD3+ T lymphocytes in the airways as well as elevated peripheral blood and bone marrow eosinophils relative to corresponding WT mice. Further, these mice had an increased propensity to develop airway hyperresponsiveness and displayed significantly elevated levels of TNF-α in lung tissue. This study suggests that Gal-1 can limit eosinophil recruitment to allergic airways and suppresses airway inflammation by inhibiting cell migration and promoting eosinophil apoptosis.

N-Glycans Differentially Regulate Eosinophil and Neutrophil Recruitment during Allergic Airway Inflammation

Background: Cell surface-expressed glycans play a role in leukocyte trafficking and recruitment. Results: Deficiency of MGAT5 causes attenuation of allergen-induced eosinophilia and Th2 cytokines but increases neutrophilic inflammation and airway hyperreactivity. Conclusion: Recruitment of eosinophils and neutrophils is differentially regulated by MGAT5-modified N-glycans during airway inflammation. Significance: This study demonstrates a significant role for N-glycans in the development of allergic airway inflammation and asthma. Allergic airway inflammation, including asthma, is usually characterized by the predominant recruitment of eosinophils. However, neutrophilia is also prominent during severe exacerbations. Cell surface-expressed glycans play a role in leukocyte trafficking and recruitment during inflammation. Here, the involvement of UDP-N-acetylglucosamine:α-6-d-mannoside β1,6-N-acetylglucosaminyltransferase V (MGAT5)-modified N-glycans in eosinophil and neutrophil recruitment during allergic airway inflammation was investigated. Allergen-challenged Mgat5-deficient (Mgat5−/−) mice exhibited significantly attenuated airway eosinophilia and inflammation (decreased Th2 cytokines, mucus production) compared with WT counterparts, attributable to decreased rolling, adhesion, and survival of Mgat5−/− eosinophils. Interestingly, allergen-challenged Mgat5−/− mice developed airway neutrophilia and increased airway reactivity with persistent elevated levels of proinflammatory cytokines (IL-17A, TNFα, IFNγ)). This increased neutrophil recruitment was also observed in LPS- and thioglycollate (TG)-induced inflammation in Mgat5−/− mice. Furthermore, there was significantly increased recruitment of infused Mgat5−/− neutrophils compared with WT neutrophils in the peritoneal cavity of TG-exposed WT mice. Mgat5−/− neutrophils demonstrated enhanced adhesion to P-selectin as well as increased migration toward keratinocyte-derived chemokine compared with WT neutrophils in vitro along with increased calcium mobilization upon activation and expression of elevated levels of CXCR2, which may contribute to the increased neutrophil recruitment. These data indicate an important role for MGAT5-modified N-glycans in differential regulation of eosinophil and neutrophil recruitment during allergic airway inflammation.

Regulation of Serotonin-Induced Trafficking and Migration of Eosinophils

Association of the neurotransmitter serotonin (5-HT) with the pathogenesis of allergic asthma is well recognized and its role as a chemoattractant for eosinophils (Eos) in vitro and in vivo has been previously demonstrated. Here we have examined the regulation of 5-HT-induced human and murine Eos trafficking and migration at a cellular and molecular level. Eos from allergic donors and bone marrow-derived murine Eos (BM-Eos) were found to predominantly express the 5-HT2A receptor. Exposure to 5-HT or 2,5-dimethoxy-4-iodoamphetamine (DOI), a 5-HT2A/C selective agonist, induced rolling of human Eos and AML14.3D10 human Eos-like cells on vascular cell adhesion molecule (VCAM)-1 under conditions of flow in vitro coupled with distinct cytoskeletal and cell shape changes as well as phosphorylation of MAPK. Blockade of 5-HT2A or of ROCK MAPK, PI3K, PKC and calmodulin, but not Gαi-proteins, with specific inhibitors inhibited DOI-induced rolling, actin polymerization and changes in morphology of VCAM-1-adherent AML14.3D10 cells. More extensive studies with murine BM-Eos demonstrated the role of 5-HT in promoting rolling in vivo within inflamed post-capillary venules of the mouse cremaster microcirculation and confirmed that down-stream signaling of 5-HT2A activation involves ROCK, MAPK, PI3K, PKC and calmodulin similar to AML14.3D10 cells. DOI-induced migration of BM-Eos is also dependent on these signaling molecules and requires Ca2+. Further, activation of 5-HT2A with DOI led to an increase in intracellular Ca2+ levels in murine BM-Eos. Overall, these data demonstrate that 5-HT (or DOI)/5-HT2A interaction regulates Eos trafficking and migration by promoting actin polymerization associated with changes in cell shape/morphology that favor cellular trafficking and recruitment via activation of specific intracellular signaling molecules (ROCK, MAPK, PI3K and the PKC-calmodulin pathway).

Eosinophil-expressed galectin-3 regulates cell trafficking and migration.

Galectin-3 (Gal-3), a β galactoside-binding lectin, is implicated in the pathogenesis of allergic airway inflammation and allergen-challenged mice deficient in Gal-3 (Gal-3-/-) exhibit decreased airway recruitment of eosinophils (Eos). Gal-3 is expressed and secreted by several cell types and can thus function extracellularly and intracellularly to regulate a variety of cellular responses. We sought to determine the role of Eos-expressed Gal-3 in promoting Eos trafficking and migration in the context of allergic airway inflammation using bone marrow (BM)-derived Eos from wild-type (WT) and Gal-3-/- mice. Airway recruitment of Eos in acute (4 weeks) and chronic (8–12 weeks) allergen-challenged WT mice correlated with Gal-3 expression in the lungs. BM-derived Eos were found to express Gal-3 on the cell surface and secrete soluble Gal-3 when exposed to eotaxin-1. Compared to WT Eos, Gal-3-/- Eos exhibited significantly reduced rolling on vascular cell adhesion molecule 1 (VCAM-1) and decreased stable adhesion on intercellular adhesion molecule 1 (ICAM-1) under conditions of flow in vitro. Evaluation of cytoskeletal rearrangement demonstrated that relatively fewer adherent Gal-3-/- Eos undergo cell spreading and formation of membrane protrusions. In addition, cell surface expression of integrin receptor αM (CD11b) was lower in Gal-3-/- Eos, which is likely to account for their altered adhesive interactions with VCAM-1 and ICAM-1. Gal-3-/- Eos also exhibited significantly decreased migration toward eotaxin-1 compared to WT Eos irrespective of similar levels of CCR3 expression. Further, eotaxin-induced migration of WT Eos remained unaffected in the presence of lactose, suggesting a role for intracellular Gal-3 in regulating Eos migration. Overall, our findings indicate that Gal-3 expression in the lungs correlates with Eos mobilization during allergic airway inflammation and signaling involving intracellular Gal-3 and/or secreted Gal-3 bound to the cell surface of Eos appears to be essential for Eos trafficking under flow as well as for migration.