Early-life EV-A71 infection augments allergen-induced airway inflammation in asthma through trained macrophage immunity

Positive association between chlorinated paraffins and the risk of allergic diseases in children and adolescents

Contaminants may induce immune response polarization, leading to immune diseases, such as allergic diseases. Evidence concerning the effects of chlorinated paraffins (CPs), an emerging persistent organic pollutant, on immune system is scarce, particularly for epidemiological evidence. This study explores the association between CPs exposure and allergic diseases (allergic rhinitis, atopic eczema, and allergic conjunctivitis) in children and adolescents in the Pearl River Delta (PRD) in China. Herein, 131,304 children and adolescents from primary and secondary schools in the PRD were included and completed the questionnaire survey. The particulate matter (PM) samples were collected in the PRD and the PM2.5-bound CP concentrations were analyzed. In the multivarious adjustment mixed effect model (MEM), an IQR increase in ∑CPs was significantly associated with allergic diseases (rhinitis, eczema, and conjunctivitis) with the estimated odds ratios (ORs) for 1.11 (95% CI: 1.10, 1.13), 1.17 (95% CI: 1.15, 1.19), and 1.82 (95% CI: 1.76, 1.88), respectively. Interaction analysis indicated that overweight and obese individuals might have greater risk. Similar effect estimates were observed in several sensitivity analyses. This study provided epidemiological evidence on the immunotoxicity of CPs. More studies to confirm our findings and investigate mechanisms are needed.

Non-coding RNA regulation of macrophage function in asthma

As a chronic respiratory disease, asthma is related to airway inflammation and remodeling. Macrophages are regarded as main innate immune cells in the airway that exert various functions like antigen recognition and presentation, phagocytosis, and pathogen clearance, playing a crucial role in the pathogeneses of asthma. Non-coding RNAs (ncRNAs), mainly include microRNA, long non-coding RNA and circular RNA, have been extensively investigated on the regulation of pathological process in asthma. Recent studies have indicated that ncRNA-regulated macrophages affect macrophage polarization, airway inflammation, immune regulation and airway remodeling, which suggests that modulating macrophages by ncRNAs may be a promising strategy for the treatment of asthma. This review summarizes the effect of macrophages in asthma and the regulatory mechanisms of ncRNAs, as well as focuses on the role of ncRNAs-regulated macrophages in asthma, for the development of novel therapeutic strategies in this disease.

Moonlighting glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein of Lactobacillus gasseri attenuates allergic asthma via immunometabolic change in macrophages

BACKGROUND

The extra-intestinal effects of probiotics for preventing allergic diseases are well known. However, the probiotic components that interact with host target molecules and have a beneficial effect on allergic asthma remain unknown. Lactobacillus gasseri attenuates allergic airway inflammation through the activation of peroxisome proliferator- activated receptor γ (PPARγ) in dendritic cells. Therefore, we aimed to isolate and investigate the immunomodulatory effect of the PPARγ activation component from L. gasseri.

METHODS

Culture supernatants of L. gasseri were fractionated and screened for the active component for allergic asthma. The isolated component was subjected to in vitro functional assays and then cloned. The crystal structure of this component protein was determined using X-ray crystallography. Intrarectal inoculation of the active component-overexpressing Clear coli (lipopolysaccharide-free Escherichia coli) and intraperitoneal injection of recombinant component protein were used in a house dust mite (HDM)-induced allergic asthma mouse model to investigate the protective effect. Recombinant mutant component proteins were assayed, and their structures were superimposed to identify the detailed mechanism of alleviating allergic inflammation.

RESULTS

A moonlighting protein, glycolytic glyceraldehyde 3-phosphate dehydrogenase (GAPDH), LGp40, that has multifunctional effects was purified from cultured L. gasseri, and the crystal structure was determined. Both intrarectal inoculation of LGp40-overexpressing Clear coli and intraperitoneal administration of recombinant LGp40 protein attenuated allergic inflammation in a mouse model of allergic asthma. However, CDp40, GAPDH isolated from Clostridium difficile did not possess this anti-asthma effect. LGp40 redirected allergic M2 macrophages toward the M1 phenotype and impeded M2-prompted Th2 cell activation through glycolytic activity that induced immunometabolic changes. Recombinant mutant LGp40, without enzyme activity, showed no protective effect against HDM-induced airway inflammation.

CONCLUSIONS

We found a novel mechanism of moonlighting LGp40 in the reversal of M2-prompted Th2 cell activation through glycolytic activity, which has an important immunoregulatory role in preventing allergic asthma. Our results provide a new strategy for probiotics application in alleviating allergic asthma.

β-glucan-coupled superparamagnetic iron oxide nanoparticles induce trained immunity to protect mice against sepsis

Background: Innate immune memory, also termed “trained immunity”, is thought to protect against experimental models of infection, including sepsis. Trained immunity via reprogramming monocytes/macrophages has been reported to result in enhanced inflammatory status and antimicrobial activity against infection in sepsis. However, a safe and efficient way to induce trained immunity remains unclear.

Methods: β-glucan is a prototypical agonist for inducing trained immunity. Ferumoxytol, superparamagnetic iron oxide (SPIO) with low cytotoxicity, has been approved by FDA for clinical use. We synthesized novel nanoparticles BSNPs by coupling β-glucan with SPIO. BSNPs were further conjugated with fluorescein for quantitative analysis and trace detection of β-glucan on BSNPs. Inflammatory cytokine levels were measured by ELISA and qRT-PCR, and the phagocytosis of macrophages was detected by flow cytometry and confocal microscopy. The therapeutic effect of BSNPs was evaluated on the well-established sepsis mouse model induced by both clinical Escherichia coli (E. coli) and cecal ligation and puncture (CLP).

Results: BSNPs were synthesized successfully with a 3:20 mass ratio of β-glucan and SPIO on BSNPs, which were mainly internalized by macrophages and accumulated in the lungs and livers of mice. BSNPs effectively reprogrammed macrophages to enhance the production of trained immunity markers and phagocytosis toward bacteria. BSNP-induced trained immunity protected mice against sepsis caused by E. coli and CLP and also against secondary infection. We found that BSNP treatment elevated Akt, S6, and 4EBP phosphorylation, while mTOR inhibitors decreased the trained immunity markers and phagocytosis enhanced by BSNPs. Furthermore, the PCR Array analysis revealed Igf1, Sesn1, Vegfa, and Rps6ka5 as possible key regulators of mTOR signaling during trained immunity. BSNP-induced trained immunity mainly regulated cellular signal transduction, protein modification, and cell cycle by modulating ATP binding and the kinase activity. Our results indicated that BSNPs induced trained immunity in an mTOR-dependent manner.

Conclusion: Our data highlight that the trained immunity of macrophages is an effective strategy against sepsis and suggest that BSNPs are a powerful tool for inducing trained immunity to prevent and treat sepsis and secondary infections.

Macrophages acquire a TNF-dependent inflammatory memory in allergic asthma

BACKGROUND

Infectious agents can reprogram or "train" macrophages and their progenitors to respond more readily to subsequent insults. However, whether such an inflammatory memory exists in type-2 inflammatory conditions such as allergic asthma was not known.

OBJECTIVE

To decipher macrophage trained immunity in allergic asthma.

METHODS

We used a combination of clinical sampling of house dust mite (HDM)-allergic patients, HDM-induced allergic airway inflammation (AAI) in mice and an in vitro training set-up to analyze persistent changes in macrophage eicosanoid-, cytokine- and chemokine production as well as underlying metabolic and epigenetic mechanisms. Transcriptional and metabolic profiles of patient-derived and in vitro trained macrophages were assessed by RNA sequencing or Seahorse and LC-MS/MS analysis, respectively.

RESULTS

We found that macrophages differentiated from bone marrow- or blood monocyte- progenitors of HDM-allergic mice or asthma patients show inflammatory transcriptional reprogramming and excessive mediator (TNF-α, CCL17, leukotriene, PGE₂, IL-6) responses upon stimulation. Macrophages from HDM-allergic mice initially exhibited a type-2 imprint, which shifted towards a classical inflammatory training over time. HDM-induced AAI elicited a metabolically activated macrophage phenotype, producing high amounts of 2-hydroxyglutarate (2-HG). HDM-induced macrophage training in vitro was mediated by a formyl-peptide receptor 2 (FPR2)-TNF-2-HG-PGE₂/EP2-axis, resulting in an M2-like macrophage phenotype with high CCL17 production. TNF blockade by etanercept or genetic ablation of Tnf in myeloid cells prevented the inflammatory imprinting of bone marrow-derived macrophages from HDM-allergic mice.

CONCLUSION

Allergen-triggered inflammation drives a TNF-dependent innate memory, which may perpetuate and exacerbate chronic type-2 airway inflammation and thus represents a target for asthma therapy.