Regarding comments by Persson et al. (Airway, apoptosis, and asthma) to J. L. Simpson, P. G. Gibson, I. A. Yang, J. Upham, A. James, P. N. Reynolds, S. Hodge and AMAZES Study Research. Impaired macrophage phagocytosis in noneosinophilic asthma. Clin Exp Allergy 2013; 43:29-35

Apigenin ameliorates non-eosinophilic inflammation, dysregulated immune homeostasis and mitochondria-mediated airway epithelial cell apoptosis in chronic obese asthma via the ROS-ASK1-MAPK pathway

BACKGROUND

Obese asthma is one of the important asthma phenotypes that have received wide attention in recent years. Excessive oxidative stress and different inflammatory endotypes may be important reasons for the complex symptoms, frequent aggravation, and resistance to traditional treatments of obese asthma. Apigenin (API), is a flavonoid natural small molecule compound with good anti-inflammatory and antioxidant activity in various diseases and proved to have the potential efficacy to combat obese asthma.

METHODS

In vivo, this study fed C57BL/6 J mice with high-fat diets(HFD)for 12 weeks and then stimulated them with OVA for 6 weeks to establish a model of chronic obese asthma, while different doses of oral API or dexamethasone were used for therapeutic interventions. In vitro, this study used HDM to stimulate human bronchial cells (HBEs) to establish the model and intervened with API or Selonsertib (SEL).

RESULTS

This study clarified that OVAinduced a type of mixed granulocytic asthma with elevated neutrophils and eosinophils in obese male mice fed with long-term HFD, which also exhibited mixed TH17/TH1/TH2 inflammation. Apigenin effectively suppressed this complex inflammation and acted as a regulator of immune homeostasis. Meanwhile, apigenin reduced AHR, inflammatory cell infiltration, airway epithelial cell apoptosis, airway collagen deposition, and lung oxidative stress via the ROS-ASK1-MAPK pathway in an obese asthma mouse model. In vitro, this study found that apigenin altered the binding status of TRAF6 to ASK1, inhibited ASK1 phosphorylation, and protected against ubiquitin-dependent degradation of ASK1, suggesting that ROS-activated ASK1 may be an important target for apigenin to exert anti-inflammatory and anti-apoptotic effects. To further verify the intervention mechanism, this study clarified that apigenin improved cell viability and mitochondrial function and inhibited apoptosis by interfering with the ROS-ASK1-MAPK pathway.

CONCLUSIONS

This study demonstrates for the first time the therapeutic effect of apigenin in chronic obese asthma and further clarifies its potential therapeutic targets. In addition, this study clarifies the specificity of chronic obese asthma and provides new options for its treatment.

Disrupted epithelial/macrophage crosstalk via Spinster homologue 2-mediated S1P signaling may drive defective macrophage phagocytic function in COPD

INTRODUCTION

We have previously established a link between impaired phagocytic capacity and deregulated S1P signaling in alveolar macrophages from COPD subjects. We hypothesize that this defect may include a disruption of epithelial-macrophage crosstalk via Spns2-mediated intercellular S1P signaling.

METHODS

Primary alveolar macrophages and bronchial epithelial cells from COPD subjects and controls, cell lines, and a mouse model of chronic cigarette smoke exposure were studied. Cells were exposed to 10% cigarette smoke extract, or vehicle control. Spns2 expression and subcellular localization was studied by immunofluorescence, confocal microscopy and RT-PCR. Phagocytosis was assessed by flow-cytometry. Levels of intra- and extracellular S1P were measured by S1P [3H]-labeling.

RESULTS

Spns2 expression was significantly increased (p<0.05) in alveolar macrophages from current-smokers/COPD patients (n = 5) compared to healthy nonsmokers (n = 8) and non-smoker lung transplant patients (n = 4). Consistent with this finding, cigarette smoke induced a significant increase in Spns2 expression in both human alveolar and THP-1 macrophages. In contrast, a remarkable Spns2 down-regulation was noted in response to cigarette smoke in 16HBE14o- cell line (p<0.001 in 3 experiments), primary nasal epithelial cells (p<0.01 in 2 experiments), and in smoke-exposed mice (p<0.001, n = 6 animals per group). Spns2 was localized to cilia in primary bronchial epithelial cells. In both macrophage and epithelial cell types, Spns2 was also found localized to cytoplasm and the nucleus, in line with a predicted bipartile Nuclear Localization Signal at the position aa282 of the human Spns2 sequence. In smoke-exposed mice, alveolar macrophage phagocytic function positively correlated with Spns2 protein expression in bronchial epithelial cells.

CONCLUSION

Our data suggest that the epithelium may be the major source for extracellular S1P in the airway and that there is a possible disruption of epithelial/macrophage cross talk via Spns2-mediated S1P signaling in COPD and in response to cigarette smoke exposure.