Danh C. Do

Cockroach allergen exposure and risk of asthma

Cockroach sensitization is an important risk factor for the development of asthma. However, its underlying immune mechanisms and the genetic etiology for differences in allergic responses remain unclear. Cockroach allergens identification and their expression as biologically active recombinant proteins have provided a basis for studying the mechanisms regarding cockroach allergen‐induced allergic sensitization and asthma. Glycans in allergens may play a crucial role in the immunogenicity of allergic diseases. Protease‐activated receptor (PAR)‐2, Toll‐like receptor (TLR), and C‐type lectin receptors have been suggested to be important for the penetration of cockroach allergens through epithelial cells to mediate allergen uptake, dendritic cell maturation, antigen‐presenting cell (APC) function in T‐cell polarization, and cytokine production. Environmental pollutants, which often coexist with the allergen, could synergistically elicit allergic inflammation, and aryl hydrocarbon receptor (AhR) activation and signaling may serve as a link between these two elements. Genetic factors may also play an important role in conferring the susceptibility to cockroach sensitization. Several genes have been associated with cockroach sensitization and asthma‐related phenotypes. In this review, we will discuss the epidemiological evidence for cockroach allergen‐induced asthma, cockroach allergens, the mechanisms regarding cockroach allergen‐induced innate immune responses, and the genetic basis for cockroach sensitization.

Aryl Hydrocarbon Receptor Protects Lungs from Cockroach Allergen–Induced Inflammation by Modulating Mesenchymal Stem Cells

Exposure to cockroach allergen leads to allergic sensitization and increased risk of developing asthma. Aryl hydrocarbon receptor (AhR), a receptor for many common environmental contaminants, can sense not only environmental pollutants but also microbial insults. Mesenchymal stem cells (MSCs) are multipotent progenitor cells with the capacity to modulate immune responses. In this study, we investigated whether AhR can sense cockroach allergens and modulate allergen-induced lung inflammation through MSCs. We found that cockroach allergen–treated AhR-deficient (AhR−/−) mice showed exacerbation of lung inflammation when compared with wild-type (WT) mice. In contrast, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an AhR agonist, significantly suppressed allergen-induced mouse lung inflammation. MSCs were significantly reduced in cockroach allergen–challenged AhR−/− mice as compared with WT mice, but increased in cockroach allergen–challenged WT mice when treated with TCDD. Moreover, MSCs express AhR, and AhR signaling can be activated by cockroach allergen with increased expression of its downstream genes cyp1a1 and cyp1b1. Furthermore, we tracked the migration of i.v.-injected GFP+ MSCs and found that cockroach allergen–challenged AhR−/− mice displayed less migration of MSCs to the lungs compared with WT. The AhR-mediated MSC migration was further verified by an in vitro Transwell migration assay. Epithelial conditioned medium prepared from cockroach extract–challenged epithelial cells significantly induced MSC migration, which was further enhanced by TCDD. The administration of MSCs significantly attenuated cockroach allergen–induced inflammation, which was abolished by TGF-β1–neutralizing Ab. These results suggest that AhR plays an important role in protecting lungs from allergen-induced inflammation by modulating MSC recruitment and their immune-suppressive activity.

Mannose receptor modulates macrophage polarization and allergic inflammation through miR-511-3p

&NA; Figure. No caption available. Background: Mannose receptor (MRC1/CD206) has been suggested to mediate allergic sensitization and asthma to multiple glycoallergens, including cockroach allergens. Objective: We sought to determine the existence of a protective mechanism through which MRC1 limits allergic inflammation through its intronic miR‐511‐3p. Methods: We examined MRC1‐mediated cockroach allergen uptake by lung macrophages and lung inflammation using C57BL/6 wild‐type (WT) and Mrc1−/− mice. The role of miR‐511‐3p in macrophage polarization and cockroach allergen–induced lung inflammation in mice transfected with adeno‐associated virus (AAV)–miR‐511‐3p (AAV–cytomegalovirus–miR‐511‐3p–enhanced green fluorescent protein) was analyzed. Gene profiling of macrophages with or without miR‐511‐3p overexpression was also performed. Results: Mrc1−/− lung macrophages showed a significant reduction in cockroach allergen uptake compared with WT mice, and Mrc1−/− mice had an exacerbated lung inflammation with increased levels of cockroach allergen–specific IgE and TH2/TH17 cytokines in a cockroach allergen–induced mouse model compared with WT mice. Macrophages from Mrc1−/− mice showed significantly reduced levels of miR‐511‐3 and an M1 phenotype, whereas overexpression of miR‐511‐3p rendered macrophages to exhibit a M2 phenotype. Furthermore, mice transfected with AAV–miR‐511‐3p showed a significant reduction in cockroach allergen–induced inflammation. Profiling of macrophages with or without miR‐511‐3p overexpression identified 729 differentially expressed genes, wherein expression of prostaglandin D2 synthase (Ptgds) and its product PGD2 were significantly downregulated by miR‐511‐3p. Ptgds showed a robust binding to miR‐511‐3p, which might contribute to the protective effect of miR‐511‐3p. Plasma levels of miR‐511‐3p were significantly lower in human asthmatic patients compared with nonasthmatic subjects. Conclusion: These studies support a critical but previously unrecognized role of MRC1 and miR‐511‐3p in protection against allergen‐induced lung inflammation.

Macrophage polarization and allergic asthma

&NA; Allergic asthma is associated with airway inflammation and airway hyperresponsiveness. Macrophage polarization has been shown to have a profound impact on asthma pathogenesis. On exposure to local microenvironments, recruited macrophages can be polarized into either classically activated (or M1) or alternatively activated (or M2) phenotypes. Macrophage polarization has been heavily associated with development of asthma. The process of regulation of macrophage polarization involves an intricate interplay between various cytokines, chemokines, transcriptional factors, and immune‐regulatory cells. Different signals from the microenvironment are controlled by different receptors on the macrophages to initiate various macrophage polarization pathways. Most importantly, there is an increased attention on the epigenetic changes (eg, microRNAs, DNA methylation, and histone modification) that impact macrophage functional responses and M1/M2 polarization through modulating cellular signaling and signature gene expression. Thus, modulation of macrophage phenotypes through molecular intervention by targeting some of those potential macrophage regulators may have therapeutic potential in the treatment of allergic asthma and other allergic diseases. In this review, we will discuss the origin of macrophages, characterization of macrophages, macrophage polarization in asthma, and the underlying mechanisms regarding allergen‐induced macrophage polarization with emphasis on the regulation of epigenetics, which will provide new insights into the therapeutic strategy for asthma. Abbreviations: AhR: aryl hydrocarbon receptor; DMR: differentially methylated region; DNMT: DNA methyltransferases; HAT: histone acetyltransferase; HDAC: deacetylation occurs by histone deacetylase; HDM: house dust mite; ILC2: innate lymphoid cells; IM: interstitial macrophages; M1: classically activated macrophage; M2: alternatively activated macrophage; miRNA: microRNA; Mo‐AMs: monocyte‐derived alveolar macrophages; MSC: mesenchymal stem cells; RES: reticulo‐endothelial system; TR‐AMs: tissue‐resident alveolar macrophages.

Oxidized CaMKII promotes asthma through the activation of mast cells.

Oxidation of calmodulin-dependent protein kinase II (ox-CaMKII) by ROS has been associated with asthma. However, the contribution of ox-CaMKII to the development of asthma remains to be fully characterized. Here, we tested the effect of ox-CaMKII on IgE-mediated mast cell activation in an allergen-induced mouse model of asthma using oxidant-resistant CaMKII MMVVδ knockin (MMVVδ) mice. Compared with WT mice, the allergen-challenged MMVVδ mice displayed less airway hyperresponsiveness (AHR) and inflammation. These MMVVδ mice exhibited reduced levels of ROS and diminished recruitment of mast cells to the lungs. OVA-activated bone marrow-derived mast cells (BMMCs) from MMVVδ mice showed a significant inhibition of ROS and ox-CaMKII expression. ROS generation was dependent on intracellular Ca2+ concentration in BMMCs. Importantly, OVA-activated MMVVδ BMMCs had suppressed degranulation, histamine release, leukotriene C4, and IL-13 expression. Adoptive transfer of WT, but not MMVVδ, BMMCs, reversed the alleviated AHR and inflammation in allergen-challenged MMVVδ mice. The CaMKII inhibitor KN-93 significantly suppressed IgE-mediated mast cell activation and asthma. These studies support a critical but previously unrecognized role of ox-CaMKII in mast cells that promotes asthma and suggest that therapies to reduce ox-CaMKII may be a novel approach for asthma.

Functional role of kynurenine and aryl hydrocarbon receptor axis in chronic rhinosinusitis with nasal polyps

Background: Chronic rhinosinusitis with nasal polyps (CRSwNP) is associated with mast cell–mediated inflammation and heightened oxidant stress. Kynurenine (KYN), an endogenous tryptophan metabolite, can promote allergen‐induced mast cell activation through the aryl hydrocarbon receptor (AhR). Objectives: We sought to determine the role of the KYN/AhR axis and oxidant stress in mast cell activation and the development of CRSwNP. Methods: We measured the expression of indoleamine 2,3‐dioxygenase 1, tryptophan 2,3‐dioxygenase, KYN, and oxidized calmodulin‐dependent protein kinase II (ox‐CaMKII) in nasal polyps and controls. KYN‐potentiated ovalbumin (OVA)‐induced ROS generation, cell activation, and ox‐CaMKII expression were investigated in wild‐type and AhR‐deficient (AhR−/−) mast cells. The role of ox‐CaMKII in mast cell activation was further investigated. Results: Nasal polyps in CRSwNP showed an increased expression of indoleamine 2,3‐dioxygenase 1, tryptophan2,3‐dioxygenase, and KYN compared with controls. AhR was predominantly expressed in mast cells in nasal polyps. Activated mast cells and local IgE levels were substantially increased in eosinophilic polyps compared with noneosinophilic polyps and controls. Furthermore, KYN potentiated OVA‐induced ROS generation, intracellular Ca2+ levels, cell activation, and expression of ox‐CaMKII in wild‐type, but not in AhR−/− mast cells. Compared with noneosinophilic polyps and controls, eosinophilic polyps showed increased expression of ox‐CaMKII in mast cells. Mast cells from ROS‐resistant CaMKII MMVV&dgr; mice or pretreated with CaMKII inhibitor showed protection against KYN‐promoted OVA‐induced mast cell activation. Conclusions: These studies support a potentially critical but previously unidentified function of the KYN/AhR axis in regulating IgE‐mediated mast cell activation through ROS and ox‐CaMKII in CRSwNP.

miR-155 Modulates Cockroach Allergen– and Oxidative Stress–Induced Cyclooxygenase-2 in Asthma

Exposure to cockroach allergen is a strong risk factor for developing asthma. Asthma has been associated with allergen-induced airway epithelial damage and heightened oxidant stress. In this study, we investigated cockroach allergen–induced oxidative stress in airway epithelium and its underlying mechanisms. We found that cockroach extract (CRE) could induce reactive oxygen species (ROS) production, particularly mitochondrial-derived ROS, in human bronchial epithelial cells. We then used the RT2 Profiler PCR array and identified that cyclooxygenase-2 (COX-2) was the most significantly upregulated gene related to CRE-induced oxidative stress. miR-155, predicted to target COX-2, was increased in CRE-treated human bronchial epithelial cells, and was showed to regulate COX-2 expression. Moreover, miR-155 can bind COX-2, induce COX-2 reporter activity, and maintain mRNA stability. Furthermore, CRE-treated miR-155−/− mice showed reduced levels of ROS and COX-2 expression in lung tissues and PGE2 in bronchoalveolar lavage fluid compared with wild-type mice. These miR-155−/− mice also showed reduced lung inflammation and Th2/Th17 cytokines. In contrast, when miR-155−/− mice were transfected with adeno-associated virus carrying miR-155, the phenotypic changes in CRE-treated miR-155−/− mice were remarkably reversed, including ROS, COX-2 expression, lung inflammation, and Th2/Th17 cytokines. Importantly, plasma miR-155 levels were elevated in severe asthmatics when compared with nonasthmatics or mild-to-moderate asthmatics. These increased plasma miR-155 levels were also observed in asthmatics with cockroach allergy compared with those without cockroach allergy. Collectively, these findings suggest that COX-2 is a major gene related to cockroach allergen–induced oxidative stress and highlight a novel role of miR-155 in regulating the ROS–COX-2 axis in asthma.

N-glycan in cockroach allergen regulates human basophil function: N-glycan and basophil function

Cockroach allergen exposure elicits cockroach sensitization and poses an increased risk for asthma. However, the major components in cockroach allergen and the mechanisms underlying the induction of cockroach allergen‐induced allergy and asthma remain largely elusive. We sought to examine the role of cockroach‐associated glycan in regulating human basophil function.

Ras homolog family member A/Rho-associated protein kinase 1 signaling modulates lineage commitment of mesenchymal stem cells in asthmatic patients through lymphoid enhancer–binding factor 1

Background Numbers of mesenchymal stem cells (MSCs) are increased in the airways after allergen challenge. Ras homolog family member A (RhoA)/Rho‐associated protein kinase 1 (ROCK) signaling is critical in determining the lineage fate of MSCs in tissue repair/remodeling. Objectives We sought to investigate the role of RhoA/ROCK signaling in lineage commitment of MSCs during allergen‐induced airway remodeling and delineate the underlying mechanisms. Methods Active RhoA expression in lung tissues of asthmatic patients and its role in cockroach allergen–induced airway inflammation and remodeling were investigated. RhoA/ROCK signaling–mediated MSC lineage commitment was assessed in an asthma mouse model by using MSC lineage tracing mice (nestin‐Cre; ROSA26‐EYFP). The role of RhoA/ROCK in MSC lineage commitment was also examined by using MSCs expressing constitutively active RhoA (RhoA‐L63) or dominant negative RhoA (RhoA‐N19). Downstream RhoA‐regulated genes were identified by using the Stem Cell Signaling Array. Results Lung tissues from asthmatic mice showed increased expression of active RhoA when compared with those from control mice. Inhibition of RhoA/ROCK signaling with fasudil, a RhoA/ROCK inhibitor, reversed established cockroach allergen–induced airway inflammation and remodeling, as assessed based on greater collagen deposition/fibrosis. Furthermore, fasudil inhibited MSC differentiation into fibroblasts/myofibroblasts but promoted MSC differentiation into epithelial cells in asthmatic nestin‐Cre; ROSA26‐EYFP mice. Consistently, expression of RhoA‐L63 facilitated differentiation of MSCs into fibroblasts/myofibroblasts, whereas expression of RhoA‐19 switched the differentiation toward epithelial cells. The gene array identified the Wnt signaling effector lymphoid enhancer–binding factor 1 (Lef1) as the most upregulated gene in RhoA‐L63–transfected MSCs. Knockdown of Lef1 induced MSC differentiation away from fibroblasts/myofibroblasts but toward epithelial cells. Conclusions These findings uncover a previously unrecognized role of RhoA/ROCK signaling in MSC‐involved airway repair/remodeling in the setting of asthma.