Asthma Pathophysiology: A Complex Interplay of Immunity and Inflammation
Asthma is a chronic inflammatory disorder of the respiratory system, characterized by reversible airway obstruction, airway hyperresponsiveness, and persistent inflammation. Clinical symptoms include wheezing, coughing, chest tightness, and shortness of breath. Globally, asthma incidence continues to rise, placing a growing burden on healthcare systems.
The pathogenesis of asthma involves a multifactorial interaction between genetic susceptibility, environmental exposure, and immune system dysfunction. Asthma is often categorized into subtypes, notably eosinophilic, neutrophilic, and mixed inflammatory phenotypes. Among these, eosinophilic asthma is considered more severe and is associated with elevated levels of eosinophils and type 2 cytokines such as IL-4, IL-5, and IL-13. These mediators facilitate immune cell recruitment, mucus production, and tissue remodeling.
Conventional treatment strategies focus on inhaled corticosteroids and bronchodilators. However, biologic therapies have emerged as targeted options for severe asthma cases, addressing specific immune pathways (e.g., IL-5 and IgE). While these therapies offer benefits, a more comprehensive understanding of the disease’s molecular mechanisms is necessary for identifying new therapeutic targets.
Ferroptosis as a Contributor to Asthma Pathogenesis
Ferroptosis is an iron-dependent form of regulated cell death, characterized by lipid peroxidation and oxidative stress. It differs fundamentally from apoptosis and necrosis and is increasingly linked to the pathology of chronic lung diseases, including asthma.
In the context of asthma, studies have reported increased iron accumulation in airway cells such as smooth muscle cells and fibroblasts. This promotes the release of pro-inflammatory cytokines and contributes to airway remodeling. In vivo experiments suggest that iron dysregulation exacerbates hallmark asthma features, including hyperreactivity, fibrosis, and type 2 inflammation. Inhibitors of ferroptosis, such as ferrostatin-1, have shown therapeutic potential in preclinical asthma models.
Bioinformatics Reveals Ferroptosis-Related Signaling in Asthma
In this study, the authors used data from the GSE134544 dataset (GEO database), which includes transcriptomic profiles from 20 control and 41 asthma patient samples. They identified 1,698 differentially expressed genes (DEGs), including 777 upregulated and 921 downregulated genes.
Pathway analysis revealed that upregulated genes were enriched in TNF, HIF-1, and NOD-like receptor signaling pathways. Downregulated genes were linked to T cell receptor signaling and cellular senescence. Notably, immune response and inflammation-related biological processes were among the top enriched categories, supporting their central role in asthma.
Using Weighted Gene Co-expression Network Analysis (WGCNA), a blue module of genes was identified as highly correlated with asthma. By intersecting these module genes with ferroptosis-related genes from the FerrDb database, the researchers identified 24 overlapping genes. A protein–protein interaction (PPI) network constructed from these genes highlighted five hub genes: EPAS1, STAT3, CYBB, G6PD, and CBS.
Diagnostic Potential and Immune Associations of Key Genes
Receiver Operating Characteristic (ROC) curve analysis showed that EPAS1, STAT3, CYBB, G6PD, and CBS each had high diagnostic accuracy for asthma (AUC > 0.8). Gene set enrichment analysis (GSEA) further revealed that these genes are involved in processes such as Fc receptor signaling, oxidative phosphorylation, and ribosomal activity.
Immune cell profiling using ImmuneCellAI revealed altered immune infiltration in asthma samples. Thirteen of 24 immune cell types were significantly different between asthma and control groups. Notably, asthma patients showed increased monocytes, macrophages, and neutrophils, while controls had more NK cells and T cell subtypes, including CD4+, CD8+, and Tregs.
Correlation analysis showed that EPAS1 was negatively associated with cytotoxic immune cells (e.g., CD8+ T cells, NK cells), suggesting a potential role in modulating immune suppression in asthma. STAT3 and CYBB were positively correlated with inflammatory cells such as macrophages and neutrophils, linking them directly to asthma-associated inflammation.
STAT3 and EPAS1 Mediate IL-13-Induced Ferroptosis
Functional experiments in 16HBE human bronchial epithelial cells demonstrated that IL-13 exposure suppressed cell proliferation and elevated inflammatory cytokines (IL-1β, IL-6, and IL-18). It also increased ferroptosis markers, including malondialdehyde (MDA) and reactive oxygen species (ROS), while reducing antioxidant defenses (SOD, GSH). Iron measurements showed an increase in Fe²⁺ and a decrease in Fe³⁺, and expression of the ferroptosis inhibitor GPX4 was downregulated.
IL-13 treatment also increased the expression of JAK2, STAT3, and phosphorylated STAT3. Overexpression of STAT3 enhanced inflammation and ferroptosis markers, whereas STAT3 knockdown reversed these effects. Transmission electron microscopy (TEM) confirmed mitochondrial abnormalities consistent with ferroptosis, such as outer membrane rupture and cristae reduction.
EPAS1 Functions Downstream of STAT3 in Asthma Models
Further investigation showed that IL-13 also upregulated EPAS1 expression. STAT3 overexpression increased EPAS1 levels, while STAT3 knockdown reduced them, indicating that EPAS1 acts downstream of STAT3. Overexpression of EPAS1 in STAT3-silenced cells partially restored IL-13-induced inflammatory and ferroptotic responses. These included increased levels of IL-6, IL-1β, and IL-18, along with elevated ROS and lipid peroxidation.
Western blot and qRT-PCR analyses confirmed that manipulating STAT3 levels had no effect on JAK2 expression, and altering EPAS1 levels did not affect STAT3 phosphorylation. This supports the conclusion that JAK2 activates STAT3, which in turn promotes EPAS1 expression, leading to enhanced ferroptosis and inflammation in asthma.
Conclusion: JAK2/STAT3/EPAS1 Axis as a Therapeutic Target
This study provides strong evidence that the JAK2/STAT3/EPAS1 signaling axis plays a pivotal role in asthma pathogenesis by regulating ferroptosis and inflammatory responses. The identification of EPAS1 as a downstream effector and potential biomarker adds a new layer of insight into the molecular mechanisms of asthma.
The findings suggest that targeting ferroptosis through this axis may offer novel therapeutic opportunities, particularly for patients with severe or treatment-resistant asthma. The study also demonstrates how integrated bioinformatics and experimental validation can uncover critical pathways in complex diseases like asthma.
The translation of the preceding English text in Chinese:
哮喘的发病机制：免疫与炎症的复杂相互作用
哮喘是一种慢性炎症性呼吸系统疾病，特点是可逆性气道阻塞、气道高反应性和持续性炎症。临床表现包括喘息、咳嗽、胸闷和呼吸困难。全球哮喘发病率持续上升，给医疗系统带来越来越大的负担。
哮喘的发病机制涉及遗传易感性、环境暴露和免疫系统功能障碍之间的多因素相互作用。哮喘常被分为不同的炎症表型，如嗜酸性型、中性粒细胞型和混合型。其中，嗜酸性哮喘通常更为严重，并伴有嗜酸性粒细胞和2型细胞因子（如IL-4、IL-5和IL-13）水平升高。这些因子促进免疫细胞募集、黏液产生和组织重塑。
常规治疗策略包括吸入性糖皮质激素和支气管扩张剂。然而，针对严重哮喘的生物制剂治疗已成为新选择，靶向特定的免疫通路（如IL-5和IgE）。尽管这些疗法有效，但对哮喘分子机制更深入的理解仍是发现新靶点的关键。
铁死亡与哮喘发病机制的关联
铁死亡是一种依赖铁的程序性细胞死亡形式，特征为脂质过氧化和氧化应激。其机制与细胞凋亡和坏死显著不同，且越来越多地被认为与包括哮喘在内的慢性肺病相关。
在哮喘中，研究发现气道平滑肌细胞和成纤维细胞中铁积聚增多，促进促炎细胞因子的释放，导致气道重塑。动物实验表明，铁稳态失调加剧了哮喘的典型特征，如气道高反应性、纤维化和2型炎症。铁死亡抑制剂如ferrostatin-1在动物哮喘模型中展现出治疗潜力。
生物信息学揭示哮喘中的铁死亡相关信号通路
本研究利用GEO数据库中的GSE134544转录组数据，分析了20例对照组和41例哮喘患者样本，鉴定出1698个差异表达基因（DEGs），其中上调777个，下调921个。
通路富集分析显示，上调基因集中在TNF、HIF-1和NOD样受体信号通路；下调基因则关联T细胞受体信号传导和细胞衰老过程。与免疫和炎症相关的生物过程位居前列，强调其在哮喘中的关键作用。
通过加权基因共表达网络分析（WGCNA），研究者鉴定出一个与哮喘高度相关的蓝色模块。将该模块中的基因与FerrDb数据库中的铁死亡基因交集分析，发现了24个重叠基因。基于这些基因构建的蛋白互作（PPI）网络中，筛选出5个核心基因：EPAS1、STAT3、CYBB、G6PD 和 CBS。
关键基因的诊断潜力及其免疫学关联
ROC曲线分析显示，EPAS1、STAT3、CYBB、G6PD 和 CBS 对哮喘的诊断准确性较高（AUC > 0.8）。基因集富集分析（GSEA）表明，这些基因涉及Fc受体信号通路、氧化磷酸化和核糖体活性等过程。
免疫细胞分析（ImmuneCellAI）显示，哮喘组中13种免疫细胞类型与对照组有显著差异。哮喘患者中单核细胞、巨噬细胞和中性粒细胞比例升高，而对照组则含有更多的NK细胞和T细胞亚群，包括CD4+、CD8+和Tregs。
相关性分析发现，EPAS1与CD8+ T细胞和NK细胞等细胞毒性免疫细胞呈负相关，提示其可能在哮喘免疫抑制中起调控作用。STAT3和CYBB则与促炎细胞（如巨噬细胞和中性粒细胞）呈正相关，进一步证实其在哮喘炎症反应中的角色。
STAT3和EPAS1介导IL-13诱导的铁死亡
在人支气管上皮细胞（16HBE）中进行的功能实验表明，IL-13处理可抑制细胞增殖，升高炎症因子（IL-1β、IL-6和IL-18）水平，同时增加铁死亡相关标志物（MDA和ROS），并降低抗氧化物（SOD和GSH）含量。铁含量检测显示Fe²⁺增加而Fe³⁺减少，铁死亡抑制因子GPX4表达下调。
IL-13还可上调JAK2、STAT3及其磷酸化形式。STAT3过表达增强了炎症和铁死亡标志物，而敲除STAT3则逆转上述效应。透射电镜显示线粒体外膜破裂、嵴减少等铁死亡特征。
EPAS1作为STAT3下游因子在哮喘模型中的作用
进一步研究显示，IL-13可上调EPAS1表达。STAT3过表达促进EPAS1表达，而STAT3敲除则抑制该表达，说明EPAS1是STAT3的下游靶点。在STAT3被敲除的细胞中过表达EPAS1，能够部分恢复IL-13诱导的炎症和铁死亡反应，如IL-6、IL-1β、IL-18水平升高，以及ROS和脂质过氧化增强。
Western blot和qRT-PCR分析表明，调控STAT3水平不影响JAK2表达，而调控EPAS1水平也不影响STAT3磷酸化状态，说明JAK2激活STAT3，后者调控EPAS1，从而增强哮喘中的铁死亡和炎症反应。
结论：JAK2/STAT3/EPAS1轴是潜在的治疗靶点
本研究强有力地证实了JAK2/STAT3/EPAS1信号轴在哮喘发病机制中的关键作用，主要通过调控铁死亡和炎症过程。EPAS1作为下游效应因子和潜在生物标志物，为深入理解哮喘的分子机制提供了新视角。
研究结果提示，针对该信号轴调控铁死亡可能成为治疗重度或难治性哮喘的新策略。此外，本研究也展示了生物信息学与实验验证联合应用在揭示复杂疾病机制中的巨大潜力。
Reference:
Lili Liu, Cheng Yang, Yan Li, Hao Zhou, Mei Shi, Tiantian Shi, Weibing Shi
EPAS1 amplifies asthma pathogenesis through JAK2/STAT3-mediated ferroptosis and inflammation.
Biomol Biomed [Internet]. 2025 Mar. 27 [cited 2025 Jun. 12];
Available from: https://www.bjbms.org/ojs/index.php/bjbms/article/view/11334
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