Lysophosphatidylserine Induces MUC5AC Production via the Feedforward Regulation of the TACE-EGFR-ERK Pathway in Airway Epithelial Cells in a Receptor-Independent Manner

Possible Involvement of Lysophospholipids in Severe Asthma as Novel Lipid Mediators

In severe asthma, symptoms are unstable despite intensive treatment based on high doses of inhaled corticosteroids and on-demand use of oral corticosteroids. Although, recently, various biological agents related to Th2 cytokines have been added to intensive controller medications for severe asthma, a significant progress has not been observed in the management for symptoms (dyspnea, wheezing and cough). Medical treatment focused on Type 2 inflammation is probably insufficient to maintain good long-term management for severe asthma. Airway eosinophilia and decreased reversibility in forced expiratory volume in 1 second (FEV1) are listed as major predictors for exacerbation-prone asthma. However, it is generally considered that asthma is complex and heterogeneous. It is necessary to establish precision medicine using treatable traits based on a multidimensional approach related to asthma. Since phospholipids generate lysophospholipids and arachidonic acid by phospholipases, lysophospholipids can be associated with the pathogenesis of this disease via action on smooth muscle, endothelium, and epithelium in the airways. Lysophosphatidic acid (LPA), lysophosphatidylcholine (LPC), and sphingosine 1-phosphate (S1P) are increased in bronchoalveolar fluid after allergen challenge. LPA, LPC, and S1P recruit eosinophils to the lungs and cause β2-adrenergic desensitization. LAP and S1P cause contraction and hyperresponsiveness in airway smooth muscle. Moreover, lysophosphatidylserine and S1P are associated with the allergic reaction related to IgE/FcεRI in mast cells. Lysophospholipid action is probably comprised of corticosteroid resistance and is independent of Type 2 inflammation, and may be corelated with oxidative stress. Lysophospholipids may be a novel molecular target in advancing the management and treatment of asthma. This review discusses the clinical relevance of lysophospholipids in asthma.

(-)-Epigallocatechin-3-gallate (EGCG) ameliorates ovalbumin-induced asthma by inhibiting inflammation via the TNF-α/TNF-R1/NLRP3 signaling pathway

(-)-Epigallocatechin-3-gallate (EGCG) is a polyphenol in green tea with potential lung-protective effects. However, the effects of EGCG on airway inflammation in asthma remain unclear. The aim of this study was to investigate the effect and mechanism of EGCG on asthmatic airway inflammation. In this study, the therapeutic effects of EGCG on ovalbumin (OVA)-induced asthmatic mice were tested first. Second, the effects of EGCG on airway inflammation, airway hyperresponsiveness (AHR), airway mucus hypersecretion, cell apoptosis and differential genes were investigated. Finally, the relationships between the effects of EGCG on airway inflammation and the TNF-α/TNF-R1/NLRP3 signaling pathway in asthmatic mice were explored. The results showed that EGCG could attenuate AHR, alleviate the symptoms of alveolar wall thickening and inflammatory cell infiltration, decrease the levels of inflammatory cytokines and airway mucus markers, reduce apoptosis and reactive oxygen species (ROS) and increase the mitochondrial membrane potential (MMP) in primary lung cells in asthmatic mice. Additionally, EGCG significantly inhibited the activation of the TNF-α/TNF-R1/NLRP3 signaling pathway in the lung tissues of asthmatic mice. The lowest binding free energies of EGCG with TNF-α, TNF-R1 and NLRP3 were -11.6, -11.6 and -8.2 kcal/mol, respectively. Moreover, the equilibrium dissociation constant (KD) of EGCG and TNF-R1was 26.05 μmol/L. EGCG-mediated inhibition of TNF-α/TNF-R1/NLRP3 signaling pathway activation was blocked in LPS-induced BEAS-2B and RAW264.7 cells overexpressing TNF-α. Consequently, EGCG effectively attenuated AHR and inhibited airway inflammation and airway mucus hypersecretion in asthmatic mice, and these effects may be closely related to the TNF-α/TNF-R1/NLRP3 signaling pathway.

Understanding the modulations of glycero-lysophospholipids in an elastase-induced murine emphysema model

BACKGROUND

Increasing evidence indicates that bioactive lipid mediators are involved in chronic obstructive pulmonary disease (COPD) pathogenesis. Recently, glycero-lysophospholipids, such as lysophosphatidic acid (LysoPA) and lysophosphatidylserine (LysoPS), have been recognized as significant inflammation-related lipid mediators. However, their association with COPD remains unclear.

METHODS

We used an elastase-induced murine emphysema model to analyze the levels of lysophospholipids and diacyl-phospholipids in the lungs. Additionally, we assessed the expression of LysoPS-related genes and published data on smokers.

RESULTS

In the early phase of an elastase-induced murine emphysema model, the levels of LysoPS and its precursor (phosphatidylserine [PS]) were significantly reduced, without significant modulations in other glycero-lysophospholipids. Additionally, there was an upregulation in the expression of lysoPS receptors, specifically GPR34, observed in the lungs of a cigarette smoke-exposed mouse model and the alveolar macrophages of human smokers. Elastase stimulation induces GPR34 expression in a human macrophage cell line in vitro.

CONCLUSIONS

Elastase-induced lung emphysema affects the LysoPS/PS-GPR34 axis, and cigarette smoking or elastase upregulates GPR34 expression in alveolar macrophages. This novel association may serve as a potential pharmacological target for COPD treatment.

Lung Lipidomic Alterations in Beagle Dogs Infected with Toxocara canis

Toxocariasis, mainly caused by Toxocara canis, and to a lesser extent, Toxocara cati, is a neglected parasitic zoonosis. The mechanisms that underlie the changes in lipid metabolism of T. canis infection in Beagle dogs' lungs remain unclear. Lipidomics is a rapidly emerging approach that enables the global profiling of lipid composition by mass spectrometry. In this study, we performed a non-targeted lipidomic analysis of the lungs of Beagle dogs infected with the roundworm T. canis using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 1197 lipid species were identified, of which 63, 88, and 157 lipid species were significantly altered at 24 h post-infection (hpi), 96 hpi, and 36 days post-infection (dpi), respectively. This global lipidomic profiling identified infection-specific lipid signatures for lung toxocariasis, and represented a comprehensive comparison between the lipid composition of dogs' lungs in the presence and absence of T. canis infection. The potential roles of the identified lipid species in the pathogenesis of T. canis are discussed, which has important implications for better understanding the interaction mechanism between T. canis and the host lung.