Advances in mechanisms of allergic disease in 2017

Exposure to Heavy Metals and Allergic Outcomes in Children: a Systematic Review and Meta-analysis

It has been reported that heavy metals have adverse effects on the immune system. However, the relationship between heavy metal exposure and allergic outcomes remains unclear. This systematic review was conducted to examine whether heavy metal exposure is associated with allergic outcomes during childhood. We performed a systematic search of all relevant articles in Web of Science, EMBASE, and PubMed, from inception through to November 2020. We used odds ratio (OR) and the standard mean differences (SMDs) with 95% confidence intervals (CIs) to present estimates from individual studies. In addition, random-effects meta-analysis was used to pool the data. We also conducted the meta-regression and subgroup analysis to explore potential sources of heterogeneity. After duplicate removal, we finally included 35 articles in the systematic review and meta-analysis from an initial 11,181 articles. The overall results showed that copper (Cu) was associated with asthma (pooled SMD = 1.50, 95% CI = 0.13-2.86); in the subgroup analysis, the results indicated that lead (Pb) was associated with asthma (pooled OR = 6.27, 95% CI = 2.24-17.56), and Cu and Pb were connected with atopic dermatitis (SMD =  - 1.05, 95% CI =  - 1.45 to - 0.65; SMD = 5.68, 95% CI = 5.05-6.32), respectively. Mercury (Hg) was associated with atopic dermatitis (pooled OR = 1.13, 95% CI = 1.04-1.22) and wheeze (OR = 1.20, 95% CI = 1.05-1.37). The meta-analysis results indicate that Cu might be connected with childhood asthma, but not with other allergic diseases; Hg and Pb may have no association with allergic diseases during childhood. Given some limits observed in the current studies, more prospective cohort studies are still needed to verify our findings. Review registration: PROSPERO CRD42020222167.

Follistatin-Like 1 Induces the Activation of Type 2 Innate Lymphoid Cells to Promote Airway Inflammation in Asthma

Asthma is a chronic disease closely related to airway inflammation. It has been proven that type 2 innate lymphoid cells (ILC2s) play an essential role in airway inflammation in asthma. Furthermore, there is growing evidence that Follistatin-like 1 (FSTL1) can participate in various inflammatory reactions mediated by the JAK/STAT signaling pathway, among others. Therefore, we put forward a new hypothesis: FSTL1 promotes asthmatic airway inflammation by activating ILC2. This study generated an ovalbumin-sensitized asthma model in C57BL/6 and Fstl1^+/- mice. The results showed that the absolute number and the proportion of ILC2 in the ovalbumin-challenged Fstl1^+/- group were lower than in the ovalbumin-challenged wild-type group. We also measured the levels of Th2-type cytokines in the serum and bronchoalveolar lavage fluid (BALF) of mice and found that the corresponding cytokines in the Fstl1^+/- were lower than in the wild-type groups. Finally, we tested whether MEK-JAK-STAT-GATA3 is the specific pathway for FSTL1 to activate ILC2, and further tested our working hypothesis by adding various inhibitors of proteins from this pathway. Overall, these findings reveal that FSTL1 can activate ILC2 through MEK-JAK-STAT-GATA3 to promote airway inflammation and participate in the pathogenesis of asthma.

Identification of oral symptoms associated with atopic dermatitis in adolescents: Results from the Korea national representative survey 2009-2017

The relationship between oral health and atopic dermatitis (AD) remains unclear. Here we investigated the association between oral health status and AD using data from 634,299 subjects in the Korean Youth Risk Behavior Survey (KYRBS). Participants with oral symptoms were defined as those with any of following: sensitive teeth, toothache, bleeding gums or gum pain, and dry mouth. Current AD was determined by the question if participant had been diagnosed with AD from doctor within the past 12 months. We estimated the odds ratio (OR) for AD diagnosis according to the presence of oral symptoms. The OR for current AD, which is a dependent variable, was significantly increased in participants with oral symptoms, which are independent variables, in an adjusted model (OR, 1.27; 95% confidence interval [CI], 1.26–1.29; P < 0.001). In detailed analyses, all four oral symptoms were significantly associated with AD diagnosis: sensitive teeth (OR, 1.21; CI, 1.19–1.23; P < 0.001), bad breath (OR, 1.18; CI, 1.17–1.20; P < 0.001), toothache (OR, 1.18; CI, 1.16–1.20; P < 0.001), and bleeding gums (OR, 1.14; CI, 1.12–1.16; P < 0.001). In the presence of oral symptoms, the ORs for having two or more allergic diseases (AD, allergic rhinitis, and/or asthma) were higher than that of AD alone. In this study, oral symptoms appeared to be associated with AD in Korean adolescences.

Streptococcus pneumoniae aminopeptidase N regulates dendritic cells that attenuates type-2 airway inflammation in murine allergic asthma

BACKGROUND AND PURPOSE

Epidemiological and experimental studies suggest that microbial exposure in early childhood is linked with reduced risk to suffer asthma. Thus microbial components with immunoregulatory capabilities might serve as a preventive strategy for allergic asthma. Recently, it was identified that Streptococcus pneumoniae aminopeptidase N (PepN) could suppress T cell effector function. We sought to investigate the effect of PepN on murine allergic asthma and elucidate the underlying mechanism.

EXPERIMENTAL APPROACH

The effects of intranasal administration of PepN during or before sensitization were examined in ovalbumin (OVA)-induced murine allergic asthma. The roles of CD11b⁺ dendritic cells in PepN treated OVA-induced allergic asthma were evaluated by flow cytometry, cytokines detection and adoptive transfer. Moreover, the numbers of lung type 2 innate lymphoid cells (ILC2s) were also detected.

KEY RESULTS

Administration of PepN during or before sensitization attenuated type-2 airway inflammation (eosinophilia, mucus hypersecretion, Th2 cytokines production and IgE production) in allergic asthma mice. PepN reduced lung accumulation of CD11b⁺ dendritic cells, which was accompanied by diminished dendritic cell-attracting chemokine CCL20 production as well as CCL17 and CCL22, which are Th2-cell chemokines predominantly produced by CD11b⁺ dendritic cells. Adoptive transfer of BM-derived CD11b⁺ dendritic cells abolished the inhibitory effect of PepN on OVA-induced type-2 airway inflammation. The numbers of lung ILC2s were decreased in asthmatic mice receiving PepN.

CONCLUSION AND IMPLICATIONS

PepN alleviated type-2 inflammation in OVA-induced allergic asthma mice, which was mediated by regulation of lung CD11b⁺ dendritic cells. Our study provides a novel strategy for the prevention of allergic asthma.

PD-1 pathway regulates ILC2 metabolism and PD-1 agonist treatment ameliorates airway hyperreactivity

Allergic asthma is a leading chronic disease associated with airway hyperreactivity (AHR). Type-2 innate lymphoid cells (ILC2s) are a potent source of T-helper 2 (Th2) cytokines that promote AHR and lung inflammation. As the programmed cell death protein-1 (PD-1) inhibitory axis regulates a variety of immune responses, here we investigate PD-1 function in pulmonary ILC2s during IL-33-induced airway inflammation. PD-1 limits the viability of ILC2s and downregulates their effector functions. Additionally, PD-1 deficiency shifts ILC2 metabolism toward glycolysis, glutaminolysis and methionine catabolism. PD-1 thus acts as a metabolic checkpoint in ILC2s, affecting cellular activation and proliferation. As the blockade of PD-1 exacerbates AHR, we also develop a human PD-1 agonist and show that it can ameliorate AHR and suppresses lung inflammation in a humanized mouse model. Together, these results highlight the importance of PD-1 agonistic treatment in allergic asthma and underscore its therapeutic potential.