Abstract
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). The cystine transporter SLC7A11 critically restores/maintains intracellular GSH. We hypothesized that high 15LO1, PEBP1, and GPX4 activity drives abnormal asthmatic redox biology, evidenced by lower bronchoalveolar lavage (BAL) fluid and intraepithelial cell GSH:oxidized GSH (GSSG) ratios, to enhance type 2 (T2) inflammatory responses. GSH, GSSG (enzymatic assays), 15LO1, GPX4, SLC7A11, and T2 biomarkers (Western blot and RNA-Seq) were measured in asthmatic and healthy control (HC) cells and fluids, with siRNA knockdown as appropriate. GSSG was higher and GSH:GSSG lower in asthmatic compared with HC BAL fluid, while intracellular GSH was lower in asthma. In vitro, a T2 cytokine (IL-13) induced 15LO1 generation of hydroperoxy-phospholipids, which lowered intracellular GSH and increased extracellular GSSG. Lowering GSH further by inhibiting SLC7A11 enhanced T2 inflammatory protein expression and ferroptosis. Ex vivo, redox imbalances corresponded to 15LO1 and SLC7A11 expression, T2 biomarkers, and worsened clinical outcomes. Thus, 15LO1 pathway–induced redox biology perturbations worsen T2 inflammation and asthma control, supporting 15LO1 as a therapeutic target.
Highlights
Among all internal organs, the lung is most consistently exposed to exogenous oxidant threats
bronchoalveolar lavage (BAL) fluid samples were obtained from 23 healthy control (HC), 32 mild-moderate asthma (M/M), and 43 severe asthma (SA) subjects (Table 1) recruited through either the Severe Asthma Research Program 3 (SARP3) (HL-109152) or Immune Mechanisms of Severe Asthma (IMSA) (AI-06684)
While the patient groups did not differ by sex, M/M were of slightly lower age relative to both HC and SA and, unsurprisingly, higher fractional exhaled nitric oxide (FeNO) and lower FEV1 (% predicted) was observed across groups from HC to SA
Summary
The lung is most consistently exposed to exogenous oxidant threats. Reflect the generation of reactive hydroperoxy-phospholipids by the 15LO1-PEBP1 complex, and the compensatory levels and activity of GPX4, the availability of newly synthesized and regenerated GSH as well as extracellular transport. While failure of these compensatory mechanisms could cause ferroptotic cell death, more subtle changes in intracellular redox balance could enhance signaling pathways, including those associated with T2 inflammation [10]. These in vitro findings were recapitulated ex vivo in two distinct asthma populations and their clinical relationships to asthma severity and control determined
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