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Levels of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, are increased in lung, sputum, exhaled breath condensate and plasma samples from asthma patients. ADMA is metabolized primarily by dimethylarginine dimethylaminohydrolase 1 (DDAH1) and DDAH2. We determined the effect of DDAH1 overexpression on development of allergic inflammation in a mouse model of asthma. The expression of DDAH1 and DDAH2 in mouse lungs was determined by RT-quantitative PCR (qPCR). ADMA levels in bronchoalveolar lavage fluid (BALF) and serum samples were determined by mass spectrometry. Wild type and DDAH1-transgenic mice were intratracheally challenged with PBS or house dust mite (HDM). Airway inflammation was assessed by bronchoalveolar lavage (BAL) total and differential cell counts. The levels of IgE and IgG1 in BALF and serum samples were determined by ELISA. Gene expression in lungs was determined by RNA-Seq and RT-qPCR. Our data showed that the expression of DDAH1 and DDAH2 was decreased in the lungs of mice following HDM exposure, which correlated with increased ADMA levels in BALF and serum. Transgenic overexpression of DDAH1 resulted in decreased BAL total cell and eosinophil numbers following HDM exposure. Total IgE levels in BALF and serum were decreased in HDM-exposed DDAH1-transgenic mice compared to HDM-exposed wild type mice. RNA-Seq results showed downregulation of genes in the inducible nitric oxide synthase (iNOS) signaling pathway in PBS-treated DDAH1-transgenic mice versus PBS-treated wild type mice and downregulation of genes in IL-13/FOXA2 signaling pathway in HDM-treated DDAH1-transgenic mice versus HDM-treated wild type mice. Our findings suggest that decreased expression of DDAH1 and DDAH2 in the lungs may contribute to allergic asthma and overexpression of DDAH1 attenuates allergen-induced airway inflammation through modulation of Th2 responses. [ABSTRACT FROM AUTHOR]

Despite its presence on resident skin cells, the role of TLR4 in skin diseases remains poorly understood. This is highly significant because the skin biome is rich with potential TLR4 agonists. We aimed to establish the contribution of TLR4 to atopic dermatitis and determine the mechanism by which TLR4 acts in an experimental model of atopic dermatitis. MyD88, TLR4, or Toll-IL-1R domain-containing adapter-inducing IFN-β (TRIF)-deficient and wild-type mice were epicutaneously exposed to Aspergillus fumigatus allergen over 3 wk. Impaired skin barrier function was assessed by measuring transepidermal water loss (TEWL). Skin levels of innate and adaptive genes were quantified. In an experimental model of atopic dermatitis, TEWL, allergic sensitization, and epidermal thickness were increased following cutaneous allergen exposure, and these were further enhanced in the absence of TLR4. Increased allergen-induced skin levels of innate (S100A8/A9, IL-1β, TNF-α, and CXCL2) and Th17 genes (IL-17A and IL-17F) were observed in TLR4-deficient mice compared with wild-type mice. The absence of MyD88 alleviated disease (decreased TEWL, skin thickness, proinflammatory cytokines), whereas TRIF deficiency exacerbated disease. In conclusion, signaling through the TLR4 and TRIF pathways limits skin barrier dysfunction, cutaneous allergic sensitization, and proinflammatory cytokine production. [ABSTRACT FROM AUTHOR]

There is considerable evidence supporting a role for mold exposure in the pathogenesis and expression of childhood asthma. Aspergillus versicolor and Cladosporium cladosporioides are common molds that have been implicated in asthma. In a model of mold-induced asthma, mice were repeatedly exposed to either A. versicolor or C. cladosporioides spores. The two molds induced distinct phenotypes, and this effect was observed in both BALB/c and C57BL/6 strains. C. cladosporioides induced robust airway hyperresponsiveness (AHR), eosinophilia, and a predominately Th2 response, whereas A. versicolor induced a strong Thl7 response and neutrophilic inflammation, but very mild AHR. Neutralization of IL-17A resulted in strong AHR and eosinophilic inflammation following A. versicolor exposure. In Dectin-l-deficient mice, A. versicolor exposure resulted in markedly attenuated IL-17A and robust AHR compared with wild-type mice. In contrast, C. cladosporioides induced AHR and eosinophilic inflam-mation independent of IL-17A and Dectin-1. A. versicolor, but not C. cladosporioides, spores had increased exposure of (i-glucans on their surface and were able to bind Dectin-1. Thus, the host response to C. cladosporioides was IL-17A- and Dectin-1-independent, whereas Dectin-1- and IL-17A-dependent pathways were protective against the development of asthma after exposure to A. versicolor. [ABSTRACT FROM AUTHOR]

Despite the important role for epidermal growth factor (EGF) in epithelial homeostasis and wound healing, it has not been investigated in atopic dermatitis (AD). We used AD animal models to explore the role of EGF in AD. In an acute AD model, skin transepidermal water loss was significantly attenuated in EGF-treated mice. Blockade of EGFR signaling genetically or pharmacologically confirms a protective role for EGFR signaling in AD. In a chronic/relapsing AD model, EGF treatment of mice with established AD resulted in an attenuation of AD exacerbation (skin epithelial thickness, cutaneous inflammation, and total and allergen specific IgE) following cutaneous allergen rechallenge. EGF treatment did not alter expression of skin barrier junction proteins or antimicrobial peptides in the AD model. However, EGF treatment attenuated allergen-induced expression of IL-17A, CXCL1, and CXCL2 and neutrophil accumulation in AD skin following cutaneous allergen exposure. IL-17A production was decreased in the in vitro restimulated skindraining lymph node cells from the EGF-treated mice. Similarly, IL-17A was increased in waved-2 mice skin following allergen exposure. Whereas IL-6 and IL-1β expression was attenuated in the skin of EGF-treated mice, EGF treatment also suppressed allergen-induced IL-6 production by kératinocytes. Given the central role of IL-6 in priming Thl7 differentiation in the skin, this effect of EGF on kératinocytes may contribute to the protective roles for EGFR in AD pathogenesis. In conclusion, our study provides evidence for a previously unrecognized protective role for EGF in AD and a new role for EGF in modulating IL-17 responses in the skin. [ABSTRACT FROM AUTHOR]