Yufeng Zhou

Aryl hydrocarbon receptor controls murine mast cell homeostasis

We propose that the aryl hydrocarbon receptor (AhR), a unique chemical sensor, is critical in controlling mast cell differentiation, growth, and function in vitro and in vivo. In antigen-stimulated mast cells, exposure to AhR ligands resulted in a calcium- and reactive oxygen species (ROS)-dependent increase of reversible oxidation in and reduced activity of SHP-2 phosphatase, leading to enhanced mast cell signaling, degranulation, and mediator and cytokine release, as well as the in vivo anaphylactic response. Surprisingly, significant mast cell deficiency was noted in AhR-null mice due to defective calcium signaling and mitochondrial function, concomitant with reduced expression of c-kit and cytosolic STAT proteins, as well as enhanced intracellular ROS and apoptosis. Consequently, AhR-null mast cells responded poorly to stimulation, demonstrating a critical role of AhR signaling in maintaining mast cell homeostasis.

Functional Effects of TGF-β1 on Mesenchymal Stem Cell Mobilization in Cockroach Allergen–Induced Asthma

Mesenchymal stem cells (MSCs) have been suggested to participate in immune regulation and airway repair/remodeling. TGF-β1 is critical in the recruitment of stem/progenitor cells for tissue repair, remodeling, and cell differentiation. In this study, we sought to investigate the role of TGF-β1 in MSC migration in allergic asthma. We examined nestin expression (a marker for MSCs) and TGF-β1 signaling activation in airways in cockroach allergen extract (CRE)–induced mouse models. Compared with control mice, there were increased nestin+ cells in airways and higher levels of active TGF-β1 in serum and p-Smad2/3 expression in lungs of CRE-treated mice. Increased activation of TGF-β1 signaling was also found in CRE-treated MSCs. We then assessed MSC migration induced by conditioned medium from CRE-challenged human epithelium in air/liquid interface culture in Transwell assays. MSC migration was stimulated by epithelial-conditioned medium, but was significantly inhibited by either TGF-β1–neutralizing Ab or TβR1 inhibitor. Intriguingly, increased migration of MSCs from blood and bone marrow to the airway was also observed after systemic injection of GFP+ MSCs and from bone marrow of Nes-GFP mice following CRE challenge. Furthermore, TGF-β1–neutralizing Ab inhibited the CRE-induced MSC recruitment, but promoted airway inflammation. Finally, we investigated the role of MSCs in modulating CRE-induced T cell response and found that MSCs significantly inhibited CRE-induced inflammatory cytokine secretion (IL-4, IL-13, IL-17, and IFN-γ) by CD4+ T cells. These results suggest that TGF-β1 may be a key promigratory factor in recruiting MSCs to the airways in mouse models of asthma.

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.

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.