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

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.

Multifaceted Roles of Ferroptosis in Lung Diseases

“…The ferroptosis inducer Ras-selective lethal small molecule 3 (RSL3) significantly promotes the occurrence of lipid peroxidation and ferroptosis in IL-13-treated human airway epithelial cells (Zhao et al, 2009;Zhao et al, 2011;Wenzel et al, 2017;Zhao et al, 2020a;Nagasaki et al, 2022). In an experimental model of house dust mite-induced asthma, an association between elevated lung iron levels in airway tissue, increased ROS and lipid peroxidation and decreased GSH levels in the lungs was observed (Tang et al, 2021b), suggesting the involvement of ferroptosis in the pathogenesis of allergic asthma.…”

The role of 15 lipoxygenase 1 in asthma comes into focus

“…In this issue of the JCI , Nagasaki and colleagues provide direct evidence that 15LO1-derived 15-HpETE-PE plays a role in controlling redox balance in the airway of patients with asthma, with potential pathophysiologic consequences ( 22 ). Using measures of redox balance in BAL fluids and freshly harvested bronchial epithelial cells from subjects with asthma who were enrolled in two cohort studies, the investigators found higher glutathione disulfide (GSSH) (reflecting the consumption of GSH) and lower GSH/GSSH ratios in BAL fluids from subjects with severe asthma than those with mild/moderate disease and healthy controls.…”

“…Based on studies using small interfering RNA knockdown and pharmacologic inhibition of 15LO1 in IL-13–stimulated epithelial cells, the changes involved 15LO1. Intracellular GSH levels and GSH/GSSH ratios in freshly obtained bronchial epithelial cells correlated inversely with 15LO1 expression levels but positively with the SLC7A11/15LO1 expression ratio ( 22 ). Treatment of the IL-13–stimulated epithelial cells with erastin, an inhibitor of SLC7A11 that depletes intracellular levels of GSH, induced cell death while modestly increasing expression and secretion of CCL26, periostin, and MUC5AC, each of which had previously been linked to 15LO1 activity based on ex vivo studies ( 18 , 22 , 23 , 24 ).…”

“…Intracellular GSH levels and GSH/GSSH ratios in freshly obtained bronchial epithelial cells correlated inversely with 15LO1 expression levels but positively with the SLC7A11/15LO1 expression ratio ( 22 ). Treatment of the IL-13–stimulated epithelial cells with erastin, an inhibitor of SLC7A11 that depletes intracellular levels of GSH, induced cell death while modestly increasing expression and secretion of CCL26, periostin, and MUC5AC, each of which had previously been linked to 15LO1 activity based on ex vivo studies ( 18 , 22 , 23 , 24 ). Thus, perturbations in redox homeostasis may substantially influence the physiological consequences of induced 15LO1 expression in asthma, CRSwNP, and other diseases associated with T2 inflammation.…”

“…The study by Nagasaki et al ( 22 ) directly implicates altered redox balance in severe asthma, and links this altered balance to the induced expression and function of 15LO1. Although the authors do not directly demonstrate 15LO1-mediated ferroptosis in vivo, it is tempting to speculate that the altered barrier integrity observed in both asthma and CRSwNP may at least partly reflect this process.…”