Macrophage Extracellular Traps Suppress Particulate Matter-Induced Airway Inflammation.

Accumulating evidence has substantiated the potential of ambient particulate matter (PM) to elicit detrimental health consequences in the respiratory system, notably airway inflammation. Macrophages, a pivotal component of the innate immune system, assume a crucial function in responding to exogenous agents. However, the roles and detailed mechanisms in regulating PM-induced airway inflammation remain unclear. The current study revealed that PM had the ability to stimulate the formation of macrophage extracellular traps (METs) both in vitro and in vivo. This effect was dependent on peptidylarginine deiminase type 4 (PAD4)-mediated histone citrullination. Additionally, reactive oxygen species were involved in the formation of PM-induced METs, in parallel with PAD4. Genetic deletion of PAD4 in macrophages resulted in an up-regulation of inflammatory cytokine expression. Moreover, mice with PAD4-specific knockout in myeloid cells exhibited exacerbated PM-induced airway inflammation. Mechanistically, inhibition of METs suppressed the phagocytic ability in macrophages, leading to airway epithelial injuries and an aggravated PM-induced airway inflammation. The present study demonstrates that METs play a crucial role in promoting the phagocytosis and clearance of PM by macrophages, thereby suppressing airway inflammation. Furthermore, it suggests that activation of METs may represent a novel therapeutic strategy for PM-related airway disorders.

Induction of ferroptosis-like cell death of eosinophils exerts synergistic effects with glucocorticoids in allergic airway inflammation.

INTRODUCTION: Eosinophils are critical in allergic disorders, and promoting eosinophil death effectively attenuates allergic airway inflammation. Ferroptosis is a recently described novel form of cell death; however, little is known about ferroptosis in eosinophils and related diseases. This study aimed to investigate the effects of ferroptosis-inducing agents (FINs) on eosinophil death and allergic airway inflammation, and to explore their potential synergistic effect with glucocorticoids (GCs). METHODS: Eosinophils isolated from the peripheral blood of humans or mice were incubated with FINs, and eosinophil ferroptosis was assessed. The in vivo effects of FINs alone or in combination with dexamethasone (DXMS) were examined in a mouse model of allergic airway inflammation. Bronchoalveolar lavage fluid and lung tissue were collected to examine airway inflammation. RESULTS: Treatment with FINs time and dose dependency induced cell death in human and mouse eosinophils. Interestingly, FINs induced non-canonical ferroptosis in eosinophils, which generated morphological characteristics unique to ferroptosis and was iron dependent but was independent of lipid peroxidation. The antioxidants glutathione and N-acetylcysteine significantly attenuated FIN-induced cell death. Treatment with FINs triggered eosinophil death in vivo and eventually relieved eosinophilic airway inflammation in mice. Furthermore, FINs exerted a synergistic effect with DXMS to induce eosinophil death in vitro and to alleviate allergic airway inflammation in vivo. CONCLUSIONS: FINs induced ferroptosis-like cell death of eosinophils, suggesting their use as a promising therapeutic strategy for eosinophilic airway inflammation, especially due to the advantage of their synergy with GCs in the treatment of allergic disorders.

Homeostatic and early-recruited CD101- eosinophils suppress endotoxin-induced acute lung injury.

INTRODUCTION: Acute lung injury (ALI) is a fatal but undertreated condition with severe neutrophilic inflammation, although little is known about the functions of eosinophils in the pathogenesis of ALI. Our objectives were to investigate the roles and molecular mechanisms of eosinophils in ALI. METHODS: Pulmonary eosinophils were identified by flow cytometry. Mice with abundant or deficient eosinophils were used. Cellularity of eosinophils and neutrophils in bronchoalveolar lavage fluid, inflammatory assessment, and survival rate were determined. Human samples were also used for validating experimental results. RESULTS: Blood eosinophils were increased in surviving patients with acute respiratory distress syndrome (ARDS) independent of corticosteroid usage. There existed homeostatic eosinophils in lung parenchyma in mice and these homeostatic eosinophils, originating from the bone marrow, were predominantly CD101-. More CD101- eosinophils could be recruited earlier than lipopolysaccharide (LPS)-initiated neutrophilic inflammation. Loss of eosinophils augmented LPS-induced pulmonary injury. Homeostatic CD101- eosinophils ameliorated, while allergic CD101+ eosinophils exacerbated, the neutrophilic inflammation induced by LPS. Likewise, CD101 expression in eosinophils from ARDS patients did not differ from healthy subjects. Mechanistically, CD101- eosinophils exhibited higher levels of Alox15 and Protectin D1. Administration of Protectin D1 isomer attenuated the neutrophilic inflammation. CONCLUSIONS: Collectively, our findings identify an uncovered function of native CD101- eosinophils in suppressing neutrophilic lung inflammation and suggest a potential therapeutic target for ALI.

Early recruited neutrophils promote asthmatic inflammation exacerbation by release of neutrophil elastase.

Neutrophils can regulate adaptive immune responses and contribute to chronic inflammation including asthma. However, the roles and mechanisms of neutrophils in initiating eosinophilic airway inflammation remain incompletely understood. Neutrophil elastase (NE) is a component of azurophilic granules and a serine protease with potent functions during inflammation. Here, we showed that neutrophils were early recruited at the onset of asthmatic inflammation by related chemokines. Furthermore, neutrophils could capture allergens and release NE to promote neutrophil aggregation at first. Then they prompt eosinophil infiltration and amplify type 2 immune responses in later phases. Also, this process can be rescued by administration of the NE inhibitor (GW311616). Our data collectively indicate that neutrophils could contribute to asthmatic inflammation by releasing NE.

TGF-ß signaling promotes eosinophil activation in inflammatory responses.

Eosinophils, traditionally associated with allergic phenomena, play a pivotal role in inflammatory responses. Despite accumulating evidence suggesting their pro-inflammatory function upon activation, the underlying mechanisms governing eosinophil activation remain incompletely characterized. In this study, we investigate the local activation of pulmonary and colon eosinophils within the inflammatory microenvironment. Leveraging transcriptional sequencing, we identify TGF-ß as a putative regulator of eosinophil activation, leading to the secretion of granule proteins, including peroxidase. Genetic deletion of TGF-ß receptors on eosinophils resulted in the inhibition of peroxidase synthesis, affirming the significance of TGF-ß signaling in eosinophil activation. Using models of HDM-induced asthma and DSS-induced colitis, we demonstrate the indispensability of TGF-ß-driven eosinophil activation in both disease contexts. Notably, while TGF-ß signaling did not significantly influence asthmatic inflammation, its knockout conferred protection against experimental colitis. This study delineates a distinct pattern of eosinophil activation within inflammatory responses, highlighting the pivotal role of TGF-ß signaling in regulating eosinophil behavior. These findings deepen our comprehension of eosinophil-related pathophysiology and may pave the way for targeted therapeutic approaches in allergic and inflammatory diseases.

Rapamycin Exacerbates Staphylococcus aureus Pneumonia by Inhibiting mTOR-RPS6 in Macrophages.

Purpose: This study aimed to explore the effect of Rapamycin (Rapa) in Staphylococcus aureus (S. aureus) pneumonia and clarify its possible mechanism. Methods: We investigated the effects of Rapa on S. aureus pneumonia in mouse models and in macrophages cultured in vitro. Two possible mechanisms were investigated: the mTOR-RPS6 pathway phosphorylation and phagocytosis. Furthermore, for the mechanism verification in vivo, mice with specific Mtor knockout in myeloid cells were constructed for pneumonia models. Results: Rapa exacerbated S. aureus pneumonia in mouse models, promoting chemokines secretion and inflammatory cells infiltration in lung. In vitro, Rapa upregulated the secretion of chemokines and cytokines in macrophages induced by S. aureus. Mechanistically, the mTOR-ribosomal protein S6 (RPS6) pathway in macrophages was phosphorylated in response to S. aureus infection, and the inhibition of RPS6 phosphorylation upregulated the inflammation level. However, Rapa did not increase the phagocytic activity. Accordingly, mice with specific Mtor knockout in myeloid cells experienced more severe S. aureus pneumonia. Conclusion: Rapa exacerbates S. aureus pneumonia by increasing the inflammatory levels of macrophages. Inhibition of mTOR-RPS6 pathway upregulates the expression of cytokines and chemokines in macrophages, thus increases inflammatory cells infiltration and exacerbates tissue damage.

The Scap-SREBP1-S1P/S2P lipogenesis signal orchestrates the homeostasis and spatiotemporal activation of NF-κB.

The nuclear factor κB (NF-κB) pathway plays essential roles in innate and adaptive immunity, but little is known how NF-κB signaling is compartmentalized and spatiotemporally activated in the cytoplasm. Here, we show that the lipogenesis signal cascade Scap-SREBP1-S1P/S2P orchestrates the homeostasis and spatiotemporal activation of NF-κB. SREBP cleavage-activating protein (Scap) and sterol regulatory element-binding protein 1 (SREBP1) form a super complex with inhibitors of NF-κB α (IκBα) to associate NF-κB close to the endoplasmic reticulum (ER). Upon lipopolysaccharide (LPS) stimulation, Scap transports the complex to the Golgi apparatus, where SREBP1 is cleaved by site-1 protease (S1P)/S2P, liberating IκBα for IκB kinase (Ikk)-mediated phosphorylation and subsequent activation of NF-κB. Loss of Scap or inhibition of S1P or S2P diminishes, while SREBP1 deficiency augments, LPS-induced NF-κB activation and subsequent inflammatory responses. Our results reveal the Scap-SREBP1 complex as an additional cytoplasmic checkpoint for NF-κB homeostasis and unveil the Golgi apparatus as the optimal cellular platform for NF-κB activation, providing insights into the crosstalk between lipogenesis signaling and immunity.

Prenatal and postnatal exposure to Bisphenol A and Asthma: a systemic review and meta-analysis.

BACKGROUND: Bisphenol A (BPA) is a plasticizer with high production and ubiquitous usage in polycarbonate plastics and epoxy resins. The association between prenatal or postnatal exposure to BPA and childhood wheeze/asthma has not been well established. Our study aimed to provide further justification for the current studies. METHODS: Studies were searched from PubMed, Web of Science, Scopus and Embase from inception until Sep 15, 2020. Meta-analysis was performed to calculate pooled adjusted odds ratios (aOR). The methodological quality of included studies was assessed by using the Newcastle Ottawa Scale (NOS). RESULTS: Of 2,814 screened articles, 9 studies with 3,885 participants were included in the final analysis. When all studies were pooled, postnatal exposure to BPA was associated with a higher risk of childhood asthma (aOR =1.43; 95% CI: 1.28-1.59) or childhood wheeze (aOR =1.38; 95% CI: 1.18-1.62). Prenatal exposure to BPA had a small but significant increased risk of childhood asthma (aOR =1.17; 95% CI: 1.01-1.34). An increased risk of childhood wheeze was related to prenatal exposure to BPA at 16 weeks' gestation (aOR =1.29; 95% CI: 1.07-1.55), but not at 26 weeks' gestation (aOR =1.07; 95% CI: 0.88-1.29) nor at random-time gestation (aOR =1.02; 95% CI: 0.89-1.16). CONCLUSIONS: Prenatal and postnatal exposure to BPA was related to an increased risk of childhood asthma. However, only postnatal and early gestational exposure (at 16 weeks) to BPA could induce the risk of childhood wheeze, but not late gestational exposure (at 26 weeks).

SETD8C302R Mutation Revealed from Myofibroblastoma-Discordant Monozygotic Twins Leads to p53/p21 Deficit and WEE1 Inhibitor Sensitivity.

High-throughput gene sequencing has identified various genetic variants as the culprits for some common hereditary cancers. However, the heritability of a substantial proportion of cancers remains unexplained, which may result from rare deleterious mutations hidden in a myriad of nonsense genetic variations. This poses a great challenge to the understanding of the pathology and thus the rational design of effective treatments for affected patients. Here, whole genome sequencing is employed in a representative case in which one monozygotic twin is discordant for lung inflammatory myofibroblastoma to disclose rare tumor-related mutations. A missense single nucleotide variation rs61955126 T>C in the lysine methyltransferase SETD8 (accession: NM_020382, SETD8C302R ) is exposed. It is shown that SETD8 is vital for genomic integrity by promoting faithful DNA replication, and its C302R mutation downregulates the p53/p21 pathway. Importantly, the SETD8C302R mutation significantly increases the sensitivity of cancer cells to WEE1 inhibition. Given that WEE1 inhibitors have shown great promise for clinical approval, these results impart a potential therapeutic approach using WEE1 inhibitor for cancer patients carrying the same mutation, and indicate that genome sequencing and genetic functional studies can be integrated into individualized therapies.

mTOR complexes differentially orchestrates eosinophil development in allergy.

Eosinophil infiltration is considered a hallmark in allergic airway inflammation, and the blockade of eosinophil differentiation may be an effective approach for treating eosinophil-related disorders. Mammalian target of rapamycin (mTOR) is a vital modulator in cell growth control and related diseases, and we have recently demonstrated that rapamycin can suppress eosinophil differentiation in allergic airway inflammation. Considering its critical role in haematopoiesis, we further investigated the role of mTOR in eosinophil differentiation in the context of asthmatic pathogenesis. Intriguingly, the inhibition of mTOR, either by genetic deletion or by another pharmacological inhibitor torin-1, accelerated the eosinophil development in the presence of IL-5. However, this was not observed to have any considerable effect on eosinophil apoptosis. The effect of mTOR in eosinophil differentiation was mediated by Erk signalling. Moreover, myeloid specific knockout of mTOR or Rheb further augmented allergic airway inflammation in mice after allergen exposure. Ablation of mTOR in myeloid cells also resulted in an increased number of eosinophil lineage-committed progenitors (Eops) in allergic mice. Collectively, our data uncovered the differential effects of mTOR in the regulation of eosinophil development, likely due to the distinct functions of mTOR complex 1 or 2, which thus exerts a pivotal implication in eosinophil-associated diseases.