Compartmentalized mitochondrial ferroptosis converges with optineurin-mediated mitophagy to impact airway epithelial cell phenotypes and asthma outcomes.

A stable mitochondrial pool is crucial for healthy cell function and survival. Altered redox biology can adversely affect mitochondria through induction of a variety of cell death and survival pathways, yet the understanding of mitochondria and their dysfunction in primary human cells and in specific disease states, including asthma, is modest. Ferroptosis is traditionally considered an iron dependent, hydroperoxy-phospholipid executed process, which induces cytosolic and mitochondrial damage to drive programmed cell death.

15LO1 dictates glutathione redox changes in asthmatic airway epithelium to worsen type 2 inflammation.

Altered redox biology challenges all cells, with compensatory responses often determining a cell's fate. When 15 lipoxygenase 1 (15LO1), a lipid-peroxidizing enzyme abundant in asthmatic human airway epithelial cells (HAECs), binds phosphatidylethanolamine-binding protein 1 (PEBP1), hydroperoxy-phospholipids, which drive ferroptotic cell death, are generated. Peroxidases, including glutathione peroxidase 4 (GPX4), metabolize hydroperoxy-phospholipids to hydroxy derivatives to prevent ferroptotic death, but consume reduced glutathione (GSH).

High-dimensional profiling clusters asthma severity by lymphoid and non-lymphoid status.

Clinical definitions of asthma fail to capture the heterogeneity of immune dysfunction in severe, treatment-refractory disease. Applying mass cytometry and machine learning to bronchoalveolar lavage (BAL) cells, we find that corticosteroid-resistant asthma patients cluster largely into two groups: one enriched in interleukin (IL)-4 innate immune cells and another dominated by interferon (IFN)-γ T cells, including tissue-resident memory cells. In contrast, BAL cells of a healthier population are enriched in IL-10 macrophages.

Ceramide in apoptosis and oxidative stress in allergic inflammation and asthma.

Background: Nothing is known about the mechanisms by which increased ceramide levels in the lung contribute to allergic responses and asthma severity.

Objective: We sought to investigate the functional role of ceramide in mouse models of allergic airway disease that recapitulate the cardinal clinical features of human allergic asthma.

Methods: Allergic airway disease was induced in mice by repeated intranasal administration of house dust mite or the fungal allergen Alternaria alternata.

PEBP1 acts as a rheostat between prosurvival autophagy and ferroptotic death in asthmatic epithelial cells.

Temporally harmonized elimination of damaged or unnecessary organelles and cells is a prerequisite of health. Under Type 2 inflammatory conditions, human airway epithelial cells (HAECs) generate proferroptotic hydroperoxy-arachidonoyl-phosphatidylethanolamines (HpETE-PEs) as proximate death signals. Production of 15-HpETE-PE depends on activation of 15-lipoxygenase-1 (15LO1) in complex with PE-binding protein-1 (PEBP1).

15-Lipoxygenase 1 in nasal polyps promotes CCL26/eotaxin 3 expression through extracellular signal-regulated kinase activation.

Background: 15-Lipoxygenase 1 (15LO1) is expressed in airway epithelial cells in patients with type 2-high asthma in association with eosinophilia. Chronic rhinosinusitis with nasal polyps (CRSwNP) is also associated with type 2 inflammation and eosinophilia. CCL26/eotaxin 3 has been reported to be regulated by 15LO1 in lower airway epithelial cells.

BAL Cell Gene Expression in Severe Asthma Reveals Mechanisms of Severe Disease and Influences of Medications.

Gene expression of BAL cells, which samples the cellular milieu within the lower respiratory tract, has not been well studied in severe asthma. To identify new biomolecular mechanisms underlying severe asthma by an unbiased, detailed interrogation of global gene expression. BAL cell expression was profiled in 154 asthma and control subjects.

Sialylation of MUC4β N-glycans by ST6GAL1 orchestrates human airway epithelial cell differentiation associated with type-2 inflammation.

Although type-2-induced (T2-induced) epithelial dysfunction is likely to profoundly alter epithelial differentiation and repair in asthma, the mechanisms for these effects are poorly understood. A role for specific mucins, heavily N-glycosylated epithelial glycoproteins, in orchestrating epithelial cell fate in response to T2 stimuli has not previously been investigated. Levels of a sialylated MUC4β isoform were found to be increased in airway specimens from asthmatic patients in association with T2 inflammation.

Dysfunctional ErbB2, an EGF receptor family member, hinders repair of airway epithelial cells from asthmatic patients.

Background: Genetic and genomic data increasingly point to the airway epithelium as critical to asthma pathogenesis. Epithelial growth factor (EGF) family members play a fundamental role in epithelial differentiation, proliferation, and repair. Although expression of erythroblastosis oncogene B2 (ErbB2) mRNA, an EGF family receptor, was reported to be lower in asthmatic patients, little is understood about its functional role.

IL-4 Induces IL17Rb Gene Transcription in Monocytic Cells with Coordinate Autocrine IL-25 Signaling.

IL-25 and IL-4 signaling in the setting of infection or allergic responses can drive Type 2 inflammation. IL-25 requires the IL-17 receptor B (IL-17Rb) to mediate signaling through nuclear factor κ B (NF-κB) transcriptional activation. Despite the known coexistence of these two cytokines in the Type 2 inflammatory environment, collaborative signaling between the IL-4 and IL-25 axes is poorly explored.

High IFN-γ and low SLPI mark severe asthma in mice and humans.

Severe asthma (SA) is a challenge to control, as patients are not responsive to high doses of systemic corticosteroids (CS). In contrast, mild-moderate asthma (MMA) is responsive to low doses of inhaled CS, indicating that Th2 cells, which are dominant in MMA, do not solely orchestrate SA development. Here, we analyzed broncholalveolar lavage cells isolated from MMA and SA patients and determined that IFN-γ (Th1) immune responses are exacerbated in the airways of individuals with SA, with reduced Th2 and IL-17 responses.

Brain-Derived Neurotrophic Factor Expression in Asthma. Association with Severity and Type 2 Inflammatory Processes.

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, exists in several isoforms, which differentially impacts neuronal and immune cell survival and differentiation. The role of BDNF and its isoforms in asthma remains unclear. The objectives of this study were to compare the BDNF protein isoforms and specific splice variant expression in sputum and bronchoscopic samples from healthy control subjects and participants with asthma, and to relate these changes to findings in IL-13-stimulated human airway epithelial cells.

IL-13 desensitizes β2-adrenergic receptors in human airway epithelial cells through a 15-lipoxygenase/G protein receptor kinase 2 mechanism.

Background: β2-Adrenergic receptor (β2AR) agonists are critical treatments for asthma. However, receptor desensitization can lead to loss of therapeutic effects. Although desensitization to repeated use of β2-agonists is well studied, type 2 inflammation could also affect β2AR function.

IL-27 and type 2 immunity in asthmatic patients: association with severity, CXCL9, and signal transducer and activator of transcription signaling.

Background: Severe asthma (SA) can involve both innate and type 2 cytokine-associated adaptive immunity. Although IL-27 has been reported to potentiate TH1 responses (including the chemokine CXCL9) and suppress TH2 responses, its function in asthmatic patients is unknown.

Objective: We sought to evaluate IL-27 expression in human asthma alone and in combination with type 2 immunity to determine the relationship to disease severity and CXCL9 expression.

Prostaglandin D₂ pathway upregulation: relation to asthma severity, control, and TH2 inflammation.

Background: Bronchoalveolar lavage (BAL) fluid prostaglandin D₂(PGD₂) levels are increased in patients with severe, poorly controlled asthma in association with epithelial mast cells (MCs). PGD₂, which is generated by hematopoietic prostaglandin D synthase (HPGDS), acts on 3 G protein-coupled receptors, including chemoattractant receptor-homologous molecule expressed on TH2 lymphocytes (CRTH2) and PGD₂ receptor 1 (DP1). However, much remains to be understood regarding the presence and activation of these pathway elements in asthmatic patients.

Epithelial eotaxin-2 and eotaxin-3 expression: relation to asthma severity, luminal eosinophilia and age at onset.

Background: Eosinophilic inflammation is implicated in asthma. Eotaxin 1-3 regulate eosinophil trafficking into the airways along with other chemotactic factors. However, the epithelial and bronchoalveolar lavage (BAL) cell expression of these chemokines in relation to asthma severity and eosinophilic phenotypes has not been addressed.

MAPK regulation of IL-4/IL-13 receptors contributes to the synergistic increase in CCL11/eotaxin-1 in response to TGF-β1 and IL-13 in human airway fibroblasts.

CCL11/eotaxin-1 is a potent eosinophilic CC chemokine expressed by primary human fibroblasts. The combination of TGF-β1 and IL-13 synergistically increases CCL11 expression, but the mechanisms behind the synergy are unclear. To address this, human airway fibroblast cultures from normal and asthmatic subjects were exposed to IL-13 alone or TGF-β1 plus IL-13.

15-Lipoxygenase 1 interacts with phosphatidylethanolamine-binding protein to regulate MAPK signaling in human airway epithelial cells.

Epithelial 15-lipoxygenase 1 (15LO1) and activated ERK are increased in asthma despite modest elevations in IL-13. MAPK kinase (MEK)/ERK activation is regulated by interactions of Raf-1 with phosphatidylethanolamine-binding protein 1 (PEBP1). Epithelial 15LO1 generates intracellular 15-hydroxyeicosatetraenoic acid (15HETE) conjugated to phosphatidylethanolamine (PE) (15HETE-PE).

Interleukin-13-induced MUC5AC is regulated by 15-lipoxygenase 1 pathway in human bronchial epithelial cells.

Rationale: 15-Lipoxygenase-1 (15LO1) and MUC5AC are highly expressed in asthmatic epithelial cells. IL-13 is known to induce 15LO1 and MUC5AC in human airway epithelial cells in vitro. Whether 15LO1 and/or its product 15-HETE modulate MUC5AC expression is unknown.

Mechanisms of tissue inhibitor of metalloproteinase 1 augmentation by IL-13 on TGF-beta 1-stimulated primary human fibroblasts.

Background: TGF-beta induces expression of tissue inhibitor of metalloproteinase 1 (TIMP-1), a potent inhibitor of matrix metalloproteinases that controls extracellular matrix metabolism and deposition. IL-13 alone does not induce TIMP-1, but in combination with TGF-beta it augments TIMP-1 expression. Although these interactions have implications for remodeling in asthma, little is understood regarding the mechanisms controlling TIMP-1 product.

Selective downregulation of prostaglandin E2-related pathways by the Th2 cytokine IL-13.

Background: Levels of COX-2 and downstream products, such as prostaglandin (PG) E2, are increased in inflammatory settings after stimulation by IL-1beta, LPS, and other innate factors. Although the TH2 cytokines IL-4 and IL-13 have been reported to decrease COX-2 levels in some cell types, neither the effect of these cytokines on other PGE2-related pathways nor their effect in primary human airway epithelial cells has been evaluated.

Objective: To determine the impact of IL-13 on PGE2 pathways in primary human airway epithelial cells.

Regional fibroblast heterogeneity in the lung: implications for remodeling.

Rationale: Excessive deposition of extracellular matrix occurs in proximal airways of individuals with asthma, but fibrosis in distal lung has not been observed. Whether differing fibrotic capacities of fibroblasts from these two regions contribute to this variability is unknown.

Objectives: We compared morphologic and functional characteristics of fibroblasts isolated from proximal airways and distal lung parenchyma to determine phenotypic differences.

Increased TGF-beta2 in severe asthma with eosinophilia.

Background: Airway eosinophilia and thickened subepithelial basement membrane have previously been reported to increase with increases in TGF-beta expression. However, little is known regarding the expression of specific TGF-beta isoforms (TGF-beta1, TGF-beta2, and TGF-beta3) in asthma, despite recent evidence suggesting that isoforms may have differing biologic activities.

Objective: This study examined airway tissue expression of the 3 TGF-beta isoforms and several downstream pathway elements in 48 patients with severe asthma with or without persistent eosinophilia, 14 patients with mild asthma, and 21 normal subjects.

Transforming growth factor-beta2 induces bronchial epithelial mucin expression in asthma.

The transforming growth factor (TGF)-beta family is important for tissue repair in pathological conditions including asthma. However, little is known about the impact of either TGF-beta1 or TGF-beta2 on asthmatic airway epithelial mucin expression. We evaluated bronchial epithelial TGF-beta1 and TGF-beta2 expression and their effects on mucin expression, and the role of TGF-beta1 or TGF-beta2 in interleukin (IL)-13-induced mucin expression.

Interleukin-13 augments transforming growth factor-beta1-induced tissue inhibitor of metalloproteinase-1 expression in primary human airway fibroblasts.

Tissue inhibitor of metalloproteinase (TIMP)-1 is a potent inhibitor of activated matrix metalloproteinases (MMPs) such as gelatinases and collagenases. TIMP-1 is induced by transforming growth factor-beta1 (TGF-beta1), but details regarding signaling pathways remain unclear. T-helper-2 cytokines also have profibrotic properties and can interact with TGF-beta.