Bronchial Fibroblasts Respond to House Dust Mite Challenge With Cytokine Secretion: Role in Allergic Airway Inflammation

Schematic of the early-stage characteristics of house dust mites-induced bronchial fibroblasts, which are characterized by suppressed extracellular matrix production alongside activated inflammatory signaling. Allergic asthma is characterized by airway inflammation and hyperresponsiveness, with house dust mites (HDM) being a major allergen [1]. Bronchial fibroblasts play a crucial role in tissue repair and airway remodeling and significantly regulate the inflammatory and immune microenvironment [2-4]. However, the role and mechanisms of HDM-induced bronchial fibroblasts in asthma-related airway inflammation remain unclear. In patients with allergic asthma, the cytokine C–C motif chemokine ligand 2 (CCL2) is highly expressed in airway mesenchymal cells (Figure 1A). Bronchial fibroblasts are important airway mesenchymal cells. Stimulation of primary human bronchial fibroblasts with HDM and gene expression profiling further revealed their role in asthma-related airway inflammation. Differentially expressed genes (DEG) were screened using the criteria of p < 0.05 and a fold change ≥ 1.5, identifying 271 significantly upregulated genes and 477 significantly downregulated genes (Figure 1B). Further analysis revealed the expression of multiple inflammation-related cytokines, including interleukin (IL)-6, IL-1β, TNF superfamily member 15 (TNFSF15), CCL2, chemokine (C-X-C motif) ligand 1 (CXCL1), CXCL2, CXCL3, CXCL5, and CXCL6 (Figure 1C). Among them, TNFSF15 and CCL2 were closely associated with eosinophils; and IL-6, IL-1β, CXCL1, CXCL2, CXCL3, CXCL5, and CXCL6 were linked to neutrophils [5, 6]. Fibrosis-related genes of collagen type I alpha-2 chain (COL1A2), collagen type III alpha-1 chain (COL3A1), collagen type IV alpha-3 chain (COL4A3), and actin alpha 2 (ACTA2) remained unchanged (Figure S1). Fibronectin, collagen type I alpha-1 chain (COL1A1), vimentin, and transforming growth factor beta 1 (TGFβ1) were downregulated, albeit with fold changes below 1.5 (Figure 1D). Gene ontology (GO) enrichment analysis indicated that these DEGs were closely associated with programmed cell death pathways, NF-κB and MAPK inflammatory signaling pathways, neutrophils, Th2 cells, and eosinophils (Figure 1E). These findings indicated that HDM-stimulated bronchial fibroblasts at the early stage are also involved in the development of asthma-related airway inflammation. Western blot analysis further revealed that HDM stimulation did not alter the expression of vimentin or α-smooth muscle actin (α-SMA) in bronchial fibroblasts, while fibronectin, COL1A1, and TGFβ1 levels were significantly reduced (Figure 2A). HDM stimulation activated the NF-κB signaling pathway and markedly increased inflammatory cytokines expression in bronchial fibroblasts (Figure 2B). The cell supernatant of HDM-stimulated bronchial fibroblasts was analyzed by ELISA to further assess cytokine secretion. The results showed elevated levels of IL-1β, IL-6, TNFSF15, CXCL1, CXCL2, CCL2, CCL5, and CCL20 in the supernatant of HDM-stimulated bronchial fibroblasts (Figure 2C). These findings suggested that HDM-induced bronchial fibroblasts contribute to the development of asthma-related airway inflammation. Zhang et al. [7] found that the pyroptosis of pulmonary fibroblasts through NLRC4 inflammasome leads to acute respiratory failure. Xie et al. [8] uncovered that IL-1β-induced fibroblast transdifferentiation promotes neutrophil recruitment in chronic rhinosinusitis with nasal polyps. Yi et al. [9] indicated that the upregulation of IL6-AS1 in fibroblasts enhances the interaction between the S100A9 protein and the AGER and TLR4 receptors on lung macrophages, thereby exacerbating pulmonary inflammation. Xu et al. [10] demonstrated that adventitial stromal cells and myofibroblasts recruit pro- and anti-inflammatory immune cells in allergic airway inflammation. A study showed that eosinophil trafficking in allergen-mediated pulmonary inflammation relies on IL-13 driven CCL-11 and CCL-24 production by tissue fibroblasts [11]. Fibroblasts can mediate interactions with epithelial cells and immune cells, such as eosinophils, through their phenotypic transformation. The significance of our study lies in identifying the early-stage characteristics of HDM-induced bronchial fibroblasts, which are characterized by suppressed extracellular matrix production and elevated inflammatory cytokine expression. These cytokines are closely linked to immune cells—such as neutrophils, Th2 cells, and eosinophils—in allergic airway inflammation. This study also has certain limitations. This study only confirmed the potential role of HDM-stimulated bronchial fibroblasts in the inflammatory microenvironment through in vitro experiments but did not validate their function in a mouse model. In addition, prolonged HDM stimulation can induce bronchial fibroblasts to adopt a fibrotic phenotype. The phenotypic transformation of bronchial fibroblasts is also influenced by their microenvironment. Therefore, further research into the underlying mechanisms is necessary to address challenges in clinical translation. In summary, these findings demonstrated that bronchial fibroblasts contribute critically to allergic airway inflammation by mediating inflammatory responses and recruiting immune cells. Dong Zhang conceived and conducted the study, wrote the original draft, and analyzed and interpreted the data. Wei Liu cultured and treated the bronchial fibroblasts and contributed to data analysis and interpretation. Qian Qi supervised the data analysis, analyzed partial mRNA data, and performed data proofreading. Tao Wang and Xiaozhi Wang participated in the conception and execution of parts of the study. All authors reviewed and approved the final manuscript for publication. This study was funded by the Noncommunicable Chronic Diseases—National Science and Technology Major Project (2024ZD0529700 and 2024ZD0529704), National Natural Science Foundation of China (81670078 and 82500047), Shandong Province Natural Science Foundation (ZR2024MH116 and ZR2024MH153), China Postdoctoral Science Foundation (2025M772384), Shandong Postdoctoral Science Foundation (SDBX2024057), and Doctoral Project Foundation of Binzhou Medical University Hospital. This study was conducted in accordance with the principles of the Helsinki Declaration and the Basel Declaration. Written informed consent was obtained from all participants, and all human-related procedures were performed following protocols approved by the Human Ethics Committee of Binzhou Medical University Hospital (Approval No. 2025-KYLL-020). All authors approved the final manuscript to be published. The authors declare no conflicts of interest. All supplementary data required to replicate or reanalyze the findings reported in this study are available from the corresponding author upon reasonable request. Supplementary Table 1: Baseline characteristics of asthmatic and the normal. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.