IntroductionEosinophils 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).MethodsEosinophils 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.ResultsTreatment 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.ConclusionsFINs 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.
Background and objective: Some types of T lymphocytes, especially cytotoxic T-cells (Tc1) and T-helper (Th17) cells, play a pivotal role in cigarette smokeinduced lung diseases. However, whether Tc17 cells are involved remains largely unknown.We investigated Tc17 involvement using a cigarette smoke-exposure model. Methods: Groups of mice were exposed to cigarette smoke or filtered air. At weeks 2, 8, 12 and 24, mice were sacrificed to observe histological changes by HE stain and/or immunohistochemical staining.The frequency of T cell subsets in the lung and spleen were detected by flow cytometry. In addition, the expression levels of T cellrelated factors were measured by real-time polymerase chain reaction or enzyme-linked immunosorbent assay. Results: Cigarette smoke caused substantial inflammatory cell infiltration and led to emphysema. Cigarette smoke exposure promoted the expression of interferon-gamma (IFN)-γ and interleukin (IL)-17A at the messenger ribonucleic acid and protein levels. In addition to Tc1 and Th17 cells, pulmonary and splenic Tc17 cells increased, which was accompanied by the upregulation of cytokines IL-6, transforming growth factor beta (TGF)-β) and transcriptional factors Stat3 and RAR-related orphan receptor gamma. Compared with untreated mice, γH2AX-positive cells were more frequently observed in mice exposed to cigarette smoke. Conclusions: Long-term cigarette smoke exposure induced Tc17 cell expansion both locally and distally, which was associated with emphysema and deoxyribonucleic acid damage. As an important source of IL-17A, this T cell subset may be a potential target for chronic obstructive pulmonary disease therapy.
Ozone is a common environmental air pollutant leading to respiratory illness. The mechanisms regulating ozone-induced airway inflammation remain poorly understood. We hypothesize that ozone-triggered inflammasome activation and interleukin (IL)-1 production regulate neutrophilic airway inflammation through IL-17A. Pulmonary neutrophilic inflammation was induced by extended (72 h) low-dose (0.7 ppm) exposure to ozone. IL-1 receptor 1 (Il1r1)−/−, Il17a−/− mice and the caspase-1 inhibitor acetyl-YVAD-chloromethylketone (Ac-YVAD-cmk) were used for in vivo studies. Cellular inflammation and protein levels in bronchial alveolar lavage fluid (BALF), cytokines, and IL-17A-producing γδT-cells, as well as mitochondrial reactive oxygen species (ROS), mitochondrial DNA (mtDNA) release, and inflammasome activation in lung macrophages were analyzed. Ozone-induced neutrophilic airway inflammation, accompanied an increased production of IL-1β, IL-18, IL-17A, Granulocyte-colony stimulating factor (G-CSF), Interferon-γ inducible protein 10 (IP-10) and BALF protein in the lung. Ozone-induced IL-17A production was predominantly in γδT-cells, and Il17a-knockout mice exhibited reduced airway inflammation. Lung macrophages from ozone-exposed mice exhibited higher levels of mitochondrial ROS, enhanced cytosolic mtDNA, increased caspase-1 activation, and higher production of IL-1β. Il1r1-knockout mice or treatment with Ac-YVAD-cmk decreased the IL-17A production and subsequent airway inflammation. Taken together, we demonstrate that ozone-induced IL-17A and neutrophilic airway inflammation is orchestrated by the caspase-1-IL-1 cascade.
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