Hypoxia induces adrenomedullin from lung epithelia, stimulating ILC2 inflammation and immunity

Blocking the HIF-1α/glycolysis axis inhibits allergic airway inflammation by reducing ILC2 metabolism and function

BACKGROUND

The role of lung group 2 innate lymphoid cell (ILC2) activation in allergic asthma is increasingly established. However, the regulatory mechanisms underlying hypoxia-inducible factor-1α (HIF-1α)-mediated glycolysis in ILC2-mediated allergic airway inflammation remain unclear.

OBJECTIVE

To investigate the role of the HIF-1α/glycolysis axis in ILC2-mediated allergic airway inflammation.

METHODS

Glycolysis and HIF-1α inhibitors were used to identify their effect on the function and glucose metabolism of mouse and human ILC2s in vivo and vitro. Blocking glycolysis and HIF-1α in mice under interleukin-33 (IL-33) stimulation were performed to test ILC2 responses. Conditional HIF-1α-deficient mice were used to confirm the specific role of HIF-1α in ILC2-driven airway inflammation models. Transcriptomic, metabolic, and chromatin immunoprecipitation analyses were performed to elucidate the underlying mechanism.

RESULTS

HIF-1α is involved in ILC2 metabolism and is crucial in allergic airway inflammation. Single-cell sequencing data analysis and qPCR confirmation revealed a significant upregulation of glycolysis-related genes, particularly HIF-1α, in murine lung ILC2s after IL-33 intranasal administration or injection. Treatment with the glycolysis inhibitor 2-deoxy-D-glucose (2-DG) and the HIF-1α inhibitor 2-methoxyestradiol (2-ME) abrogated inflammation by suppressing ILC2s function. Conditional HIF-1α-deficient mice showed reduced ILC2 response and airway inflammation induced upon IL-33 or house dust mite (HDM) stimulation. Transcriptome and metabolic analyses revealed significantly impaired glycolysis in lung ILC2s in conditional HIF-1α knockout mice compared to that in their littermate controls. Chromatin immunoprecipitation results confirmed the transcriptional downregulation of glycolysis-related genes in HIF-1α-knockout and 2-DG-treated mice. Furthermore, impaired HIF-1α/glycolysis axis activation is correlated with downregulated ILC2 in patients with asthma.

CONCLUSION

The HIF-1α/glycolysis axis is critical for controlling ILC2 responses in allergic airway inflammation and has potential immunotherapeutic value in asthma.

Comparative Insights on IL-5 Targeting with Mepolizumab and Benralizumab: Enhancing EGPA Treatment Strategies

Eosinophilic granulomatosis with polyangiitis (EGPA) is a necrotizing vasculitis characterized by extravascular granulomas and eosinophilia in both blood and tissues. Eosinophils, which play a critical role in the pathophysiology of EGPA, require interleukin (IL)-5 for maturation in the bone marrow and migration to tissues. Glucocorticoids and immunosuppressants have been the cornerstone of treatment; however, their side effects have imposed a significant burden on many patients. Mepolizumab, an antibody that binds to and neutralizes IL-5, demonstrated efficacy in controlling disease activity in EGPA in the MIRRA trial conducted in 2017. In 2024, benralizumab, an IL-5 receptor alpha antagonist, was shown to be non-inferior to mepolizumab in efficacy against EGPA in the MANDARA trial. Both drugs were originally used for severe asthma and have benefited EGPA by reducing eosinophil counts. Due to differences in pharmacological structure and pharmacokinetics, the degree of eosinophil suppression varies between the two agents, and recent studies suggest that they may also affect inflammatory and homeostatic eosinophils differently. This review summarizes the latest insights into the pathophysiology of EGPA, highlights the similarities and differences between the two drugs, and discusses future treatment strategies for EGPA based on current clinical unmet needs, including drug selection.

There's no place like home: How local tissue microenvironments shape the function of innate lymphoid cells

Innate lymphoid cells (ILC) have emerged as critical immune effectors with key roles in orchestrating the wider immune response. While ILC are relatively rare cells they are found enriched within discrete microenvironments, predominantly within barrier tissues. An emerging body of evidence implicates complex and multi-layered interactions between cell types, tissue structure and the external environment as key determinants of ILC function within these niches. In this review we will discuss the specific components that constitute ILC-associated microenvironments and consider how they act to determine health and disease. The development of holistic, integrated models of ILC function within complex tissue environments will inform new understanding of the contextual cues and mechanisms that determine the protective versus disease-causing roles of this immune cell family.

Single cell transcriptomic analysis reveals tumor immune infiltration by macrophage cells gene signature in lung adenocarcinoma

BACKGROUND

Tumor-associated macrophages (TAMs) play pivotal roles in innate immunity and contribute to the advancement of lung cancer. We aimed to identify novel TAM-related biomarkers and significance of macrophage infiltration in lung adenocarcinoma (LUAD) through an integrative analysis of single-cell RNA-sequencing (scRNA-seq) data. To describe the cell atlas and construct a novel prognostic signature in LUAD.

METHODS

The gene signature linked to TAMs was identified utilizing Scanpy from the scRNA-seq dataset GSE131907. Subsequent analysis involved evaluating the expression levels of these genes, their potential molecular mechanisms, and prognostic significance in LUAD using data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. We also constructed a risk score models through LASSO Cox regression for these genes. The underlying mechanism was further elucidated through the application of GSEA, ESTIMATE, TIDE, and other bioinformatic algorithms.

RESULTS

Single-cell atlas was described by analyze 29 scRNA-seq samples from 19 LUAD patients. The TAMs-related gene signature (TGS) was identified as an independent prognostic factor by LASSO Cox regression analysis using differential expression genes (DEGs) derived from pro- and anti-inflammatory macrophage cells. Risk score model including nine TAMs-related genes (FOSL1, ZNF697, ADM, UBE2S, TICAM1, S100P, BIRC3, TLE1, and DEFB1) were obtained for prognosis construction. Moreover, the risk model underwent additional validation in four external GEO cohorts: GSE31210, GSE72094, GSE26939, and GSE30219. Interestingly, TGS-high tumors revealed enrichments in TGF-β signaling and hypoxia pathways, which shown low immune infiltration and immunosuppression by ESTIMATE and TIDE algorithm. The TGS-high risk group exhibited lower richness and diversity in the T-cell receptor (TCR) repertoire.

CONCLUSION

This study introduces a novel TGS score developed through LASSO Cox regression analysis, utilizing DEGs in pro- and anti-inflammatory macrophage cells. High TGS tumors exhibited enrichment in TGF-β signaling and hypoxia pathways, suggesting their potential utility in predicting prognosis and immune responses in patients with LUAD. These results offer promising implications for the development of therapeutic strategies for LUAD.

Gasping for air: HIF2α in asthma

Despite protective roles in various type of infection and in would healing, T helper (Th)2 cells are drivers of inflammation in allergic asthma. In this issue of Immunity, Zou et al. demonstrate the crucial involvement of hypoxia inducible factor (HIF)2α in promoting the differentiation of inflammatory Th2 cells, suggesting HIF2α as a promising therapeutic target for the treatment of allergic asthma.

BNIP3+ fibroblasts associated with hypoxia and inflammation predict prognosis and immunotherapy response in pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most malignant tumors that lacks effective treatment options. Cancer-associated fibroblasts (CAFs), an important component of the tumor microenvironment, associated with tumor progression, prognosis, and treatment response. This work aimed to explore the novel CAFs-associated target to improve treatment strategies in PDAC.

METHODS

The PDAC single-cell sequencing data (CRA001160, n = 35) were downloaded and integrated based on GSA databases to classify fibroblasts into fine subtypes. Functional enrichment analysis and coexpression regulatory network analysis were used to identify the functional phenotypes and biological properties of the different fibroblast subtypes. Fibroblast differentiation trajectories were constructed using pseudochronological analysis to identify initial and terminally differentiated subtypes of fibroblasts. The changes in the proportions of different fibroblast subtypes before and after PDAC immunotherapy were compared in responsive and nonresponding patients, and the relationships between fibroblast subtypes and PDAC immunotherapy responsiveness were determined based on GSA and GEO database. Using molecular biology methods to confirm the effects of BNIP3 on hypoxia and inflammation in CAFs. CAFs were co cultured with pancreatic cancer cells to detect their effects on migration and invasion of pancreatic cancer.

RESULTS

Single-cell data analysis divided fibroblasts into six subtypes. The differentiation trajectory suggested that BNIP3+ Fibro subtype exhibited terminal differentiation, and the expression of genes related to hypoxia and the inflammatory response increased gradually with differentiation time. The specific overexpressed genes in the BNIP3+ Fibro subtype were significantly associated with overall and disease progression-free survival in the patients with PDAC. Interestingly, the greater the proportion of the BNIP3+ Fibro subtype was, the worse the response of PDAC patients to immunotherapy, and the CRTL treatment regimen effectively reduced the proportion of the BNIP3+ Fibro subtype. After knocking out BNIP3, the hypoxia markers and inflammatory factors of CAFs were inhibited. Co-culture of CAFs with pancreatic cancer cells can increase the migration and invasion of pancreatic cancer, but this could be reversed by knocking out BNIP3.

CONCLUSIONS

This study revealed the BNIP3+ Fibro subtype associated with hypoxia and inflammatory responses, which was closely related to the poor prognosis of patients with PDAC, and identified signature genes that predict the immunotherapy response in PDAC.

Adrenomedullin improved endothelial dysfunction via receptor-Akt pathway in rats with obesity-related hypertension

Obesity-related hypertension (OH) is accompanied by obvious endothelial dysfunction, which contributes to increased peripheral vascular resistance and hypertension. Adrenomedullin (ADM), a multifunctional active peptide, is elevated in obese humans. The OH rats induced by high fat diet (HFD) for 28 weeks and the human umbilical vein endothelial cells (HUVECs)-treated by palmitic acid (PA) were used to investigate the effects of ADM on endothelial dysfunction and the underlying mechanisms. Vascular reactivity was assessed using mesenteric arteriole rings, and the protein expression levels were examined by Western blot analysis. Compared with the control rats, OH rats exhibited hypertension and endothelial dysfunction, along with reduced eNOS protein expression and Akt activation, and increased protein expression of proinflammatory cytokines and ROS levels. Four-week ADM administration improved hypertension and endothelial function, increased eNOS protein expression and Akt activation, and attenuated endothelial inflammation and oxidative stress in OH rats. In vitro experiment, the antagonism of ADM receptors with ADM22-52 and the suppression of Akt signaling with A6730 significantly blocked ADM-caused increase of NO content and activation of eNOS and Akt, and inhibited the anti-inflammatory and anti-oxidant effect of ADM in PA-stimulated HUVECs. These data indicate that endothelial dysfunction in OH rats is partially attributable to the decreased NO level, and the increased inflammation and oxidative stress. ADM improves endothelial function and exerts hypotensive effect depending on the increase of NO, and its anti-inflammatory and anti-oxidant effect via receptor-Akt pathway.

Lysophospholipid acyltransferase-mediated formation of saturated glycerophospholipids maintained cell membrane integrity for hypoxic adaptation

Adaptation to hypoxia has attracted much public interest because of its clinical significance. However, hypoxic adaptation in the body is complicated and difficult to fully explore. To explore previously unknown conserved mechanisms and key proteins involved in hypoxic adaptation in different species, we first used a yeast model for mechanistic screening. Further multi-omics analyses in multiple species including yeast, zebrafish and mice revealed that glycerophospholipid metabolism was significantly involved in hypoxic adaptation with up-regulation of lysophospholipid acyltransferase (ALE1) in yeast, a key protein for the formation of dipalmitoyl phosphatidylcholine [DPPC (16:0/16:0)], which is a saturated phosphatidylcholine. Importantly, a mammalian homolog of ALE1, lysophosphatidylcholine acyltransferase 1 (LPCAT1), enhanced DPPC levels at the cell membrane and exhibited the same protective effect in mammalian cells under hypoxic conditions. DPPC supplementation effectively attenuated growth restriction, maintained cell membrane integrity and increased the expression of epidermal growth factor receptor under hypoxic conditions, but unsaturated phosphatidylcholine did not. In agreement with these findings, DPPC treatment could also repair hypoxic injury of intestinal mucosa in mice. Taken together, ALE1/LPCAT1-mediated DPPC formation, a key pathway of glycerophospholipid metabolism, is crucial for cell viability under hypoxic conditions. Moreover, we found that ALE1 was also involved in glycolysis to maintain sufficient survival conditions for yeast. The present study offers a novel approach to understanding lipid metabolism under hypoxia and provides new insights into treating hypoxia-related diseases.

Grimm S, Coarfa C, Theis F, Simon LM, Shivanna B. Leveraging Integrated RNA Sequencing to Decipher Adrenomedullin's Protective Mechanisms in Experimental Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease commonly affecting premature infants, with limited therapeutic options and increased long-term consequences. Adrenomedullin (Adm), a proangiogenic peptide hormone, has been found to protect rodents against experimental BPD. This study aims to elucidate the molecular and cellular mechanisms through which Adm influences BPD pathogenesis using a lipopolysaccharide (LPS)-induced model of experimental BPD in mice. Bulk RNA sequencing of Adm-sufficient (wild-type or Adm+/+) and Adm-haplodeficient (Adm+/-) mice lungs, integrated with single-cell RNA sequencing data, revealed distinct gene expression patterns and cell type alterations associated with Adm deficiency and LPS exposure. Notably, computational integration with cell atlas data revealed that Adm-haplodeficient mouse lungs exhibited gene expression signatures characteristic of increased inflammation, natural killer (NK) cell frequency, and decreased endothelial cell and type II pneumocyte frequency. Furthermore, in silico human BPD patient data analysis supported our cell type frequency finding, highlighting elevated NK cells in BPD infants. These results underscore the protective role of Adm in experimental BPD and emphasize that it is a potential therapeutic target for BPD infants with an inflammatory phenotype.

Mineralised collagen regulated the secretion of adrenomedullin by macrophages to activate the PI3K/AKT signalling pathway to promote bone defect repair

Biomaterials can affect the osteogenic process by regulating the function of macrophages and transforming the bone immune microenvironment. Mineralised collagen (MC) is an artificial bone that is highly consistent to the microstructure of the native osseous matrix. The studies have confirmed that MC can achieve effective regeneration of bone defects, but the potential mechanism of MC regulating osteogenesis is still unclear. This study confirmed that MC regulate the high expression of adrenomedullin (ADM) in macrophages and promote the osteogenic differentiation, proliferation and migration of BMSCs. Moreover, ADM activated the PI3K/Akt pathway, while the inhibition of PI3K/Akt hindered the proliferation, migration and osteogenic differentiation of BMSCs promoted by ADM. Additionally, the rat mandibular defect model confirmed that ADM promote the repair of mandibular defects, and the inhibition of PI3K/Akt pathway hinders the osteogenic effect of ADM. Our study suggests that MC regulates ADM secretion by macrophages, creates an ideal bone immune microenvironment, activates the PI3K/AKT signalling pathway, and promotes osteogenesis.

Network pharmacology prediction, molecular docking and in vitro experiment explored the potential mechanism of Gaoyuan'an capsule in improving hypoxia tolerance

BACKGROUND

Tibetan medicine Gaoyuan'an capsule (GYAC) is widely used to prevent pulmonary edema at high altitude, but the specific mechanism has not been explored. In this study, we analyzed the mechanism of GYAC in hypoxia tolerance, and provided a new idea for the prevention and treatment of altitude disease.

METHODS

The effective components and corresponding targets of GYAC were screened out by the Chinese herbal medicine network database, and the key targets of hypoxia tolerance were retrieved by Genecards, OMIM and PubMed database. Cytoscape 3.7.2 was used to construct GYAC ingredient-target-hypoxia tolerance-related target network. GO function annotation and KEGG enrichment analysis were performed to predict the pathways in which target genes may be involved, and molecular docking was used to verify the binding ability of the compound to target genes. In vitro, the above results were further verified by molecular experiment.

RESULTS

We found that GYAC can improve hypoxia tolerance by regulating various target genes, including IL6, IFNG, etc. The main regulatory pathways were HIF-1 signaling pathway. Molecular docking showed that the affinity between luteolin and target genes (IL6, IFNG) were better. In vitro, we observed that hypoxia can inhibit cell viability and promote apoptosis of H9C2 cell. And hypoxia can promote the expression of LDH. After the addition of luteolin, the decrease of cell viability, the increase of cell apoptosis, LDH release and the decrease of mitochondrial membrane potential were inhibited. Besides, inflammatory related factors (IL-6, IL-10, IL-2, IFNG and VEGFA) expression were also inhibited hypoxic cell models.

CONCLUSIONS

The results of network pharmacology and molecular docking showed that luteolin, a monomeric component of GYAC, played a role in hypoxia tolerance through a variety of target genes, such as IL6, IFNG. What's more, we have discovered that luteolin can reduce the inflammatory response in cardiac myocytes, thereby alleviating mitochondrial damage, and ultimately enhancing the hypoxia tolerance of H9C2 cardiomyocytes.

Communication between Mast Cells and Group 2 Innate Lymphoid Cells in the Skin

The skin is a dynamic organ with a complex immune network critical for maintaining balance and defending against various pathogens. Different types of cells in the skin, such as mast cells (MCs) and group 2 innate lymphoid cells (ILC2s), contribute to immune regulation and play essential roles in the early immune response to various triggers, including allergens. It is beneficial to dissect cell-to-cell interactions in the skin to elucidate the mechanisms underlying skin immunity. The current manuscript concentrates explicitly on the communication pathways between MCs and ILC2s in the skin, highlighting their ability to regulate immune responses, inflammation, and tissue repair. Furthermore, it discusses how the interactions between MCs and ILC2s play a crucial role in various skin conditions, such as autoimmune diseases, dermatological disorders, and allergic reactions. Understanding the complex interactions between MCs and ILC2s in different skin conditions is crucial to developing targeted treatments for related disorders. The discovery of shared pathways could pave the way for novel therapeutic interventions to restore immunological balance in diseased skin tissues.

The role of hormones in ILC2-driven allergic airway inflammation

Group 2 innate lymphoid cells (ILC2s) are a type of innate immune cells that produce a large amount of IL-5 and IL-13 and two cytokines that are crucial for various processes such as allergic airway inflammation, tissue repair and tissue homeostasis. It is known that damaged epithelial-derived alarmins, such as IL-33, IL-25 and thymic stromal lymphopoietin (TSLP), are the predominant ILC2 activators that mediate the production of type 2 cytokines. In recent years, abundant studies have found that many factors can regulate ILC2 development and function. Hormones synthesized by the body's endocrine glands or cells play an important role in immune response. Notably, ILC2s express hormone receptors and their proliferation and function can be modulated by multiple hormones during allergic airway inflammation. Here, we summarize the effects of multiple hormones on ILC2-driven allergic airway inflammation and discuss the underlying mechanisms and potential therapeutic significance.

Toxicity of Metal Oxide Nanoparticles: Looking through the Lens of Toxicogenomics

The impact of solubility on the toxicity of metal oxide nanoparticles (MONPs) requires further exploration to ascertain the impact of the dissolved and particulate species on response. In this study, FE1 mouse lung epithelial cells were exposed for 2-48 h to 4 MONPs of varying solubility: zinc oxide, nickel oxide, aluminum oxide, and titanium dioxide, in addition to microparticle analogues and metal chloride equivalents. Previously published data from FE1 cells exposed for 2-48 h to copper oxide and copper chloride were examined in the context of exposures in the present study. Viability was assessed using Trypan Blue staining and transcriptomic responses via microarray analysis. Results indicate material solubility is not the sole property governing MONP toxicity. Transcriptional signaling through the 'HIF-1α Signaling' pathway describes the response to hypoxia, which also includes genes associated with processes such as oxidative stress and unfolded protein responses and represents a conserved response across all MONPs tested. The number of differentially expressed genes (DEGs) in this pathway correlated with apical toxicity, and a panel of the top ten ranked DEGs was constructed (Hmox1, Hspa1a, Hspa1b, Mmp10, Adm, Serpine1, Slc2a1, Egln1, Rasd1, Hk2), highlighting mechanistic differences among tested MONPs. The HIF-1α pathway is proposed as a biomarker of MONP exposure and toxicity that can help prioritize MONPs for further evaluation and guide specific testing strategies.

The modulation of pulmonary group 2 innate lymphoid cell function in asthma: from inflammatory mediators to environmental and metabolic factors

A dysregulated type 2 immune response is one of the fundamental causes of allergic asthma. Although Th2 cells are undoubtedly central to the pathogenesis of allergic asthma, the discovery of group 2 innate lymphoid cells (ILC2s) has added another layer of complexity to the etiology of this chronic disease. Through their inherent innate type 2 responses, ILC2s not only contribute to the initiation of airway inflammation but also orchestrate the recruitment and activation of other members of innate and adaptive immunity, further amplifying the inflammatory response. Moreover, ILC2s exhibit substantial cytokine plasticity, as evidenced by their ability to produce type 1- or type 17-associated cytokines under appropriate conditions, underscoring their potential contribution to nonallergic, neutrophilic asthma. Thus, understanding the mechanisms of ILC2 functions is pertinent. In this review, we present an overview of the current knowledge on ILC2s in asthma and the regulatory factors that modulate lung ILC2 functions in various experimental mouse models of asthma and in humans.

CD90 is not constitutively expressed in functional innate lymphoid cells

Huge progress has been made in understanding the biology of innate lymphoid cells (ILC) by adopting several well-known concepts in T cell biology. As such, flow cytometry gating strategies and markers, such as CD90, have been applied to indentify ILC. Here, we report that most non-NK intestinal ILC have a high expression of CD90 as expected, but surprisingly a sub-population of cells exhibit low or even no expression of this marker. CD90-negative and CD90-low CD127+ ILC were present amongst all ILC subsets in the gut. The frequency of CD90-negative and CD90-low CD127+ ILC was dependent on stimulatory cues in vitro and enhanced by dysbiosis in vivo. CD90-negative and CD90-low CD127+ ILC were a potential source of IL-13, IFNγ and IL-17A at steady state and upon dysbiosis- and dextran sulphate sodium-elicited colitis. Hence, this study reveals that, contrary to expectations, CD90 is not constitutively expressed by functional ILC in the gut.

Modes of type 2 immune response initiation

Type 2 immunity defends against macro-parasites and can cause allergic diseases. Our understanding of the mechanisms governing the initiation of type 2 immunity is limited, whereas we know more about type 1 immune responses. Type 2 immunity can be triggered by a wide array of inducers that do not share common features and via diverse pathways and mechanisms. To address the complexity of the type 2 initiation pathways, we suggest a framework that conceptualizes different modes of induction of type 2 immunity. We discuss categories of type 2 inducers and their immunogenicity, types of tissue perturbations that are caused by these inducers, sensing strategies for the initiation of Th2 immune responses, and categorization of the signals that are produced in response to type 2 challenges. We describe tissue-specific examples of functional disruption that could lead to type 2 inflammation and propose that different sensing strategies that operate at the tissue level converge on the initiation of type 2 immune responses.