Targeting KDM4B attenuates IL-13-mediated fibrosis in bronchial fibroblasts of severe asthmatics

Background: Asthma is a heterogeneous disorder characterized by chronic inflammation and remodeling of the airways. Asthma is mainly driven by type 2 immune responses, where interleukin-13 (IL-13) plays a key role in asthma pathogenesis. KDM4B/JMJD2B is an IL-13-regulated epigenetic modifier in asthmatic airway fibroblasts. Therefore, this study aimed to target KDM4B to potentially alleviate IL-13-mediated fibrosis in asthma. Methods: Bronchial fibroblasts isolated from asthmatic individuals were stimulated with IL-13 and treated with JIB-04, a pan-selective inhibitor of histone demethylase(s). The expression of extracellular matrix (ECM) markers was assessed using quantitative real-time polymerase chain reaction, Western blotting, and matrix metalloproteinase (MMP) activity assay. Chromatin immunoprecipitation assay was used to determine the binding of KDM4B and H3K36me3 to promoter region of tissue inhibitor of metalloproteinase-2 (TIMP-2). KDM4B knockdown was performed to confirm its direct role on TIMP/MMP regulation. Results: JIB-04 inhibited KDM4B activity by reducing the demethylation of its downstream target, H3K36me3, in asthmatic fibroblasts. Inhibition of KDM4B significantly affected the viability of the bronchial fibroblasts at 48 h. KDM4B inhibition was further associated with the downregulation of ECM proteins such as MMP-2, MMP-9, collagen-1, and fibronectin, and upregulation of TIMP-2, at both the gene and protein levels. This was accompanied by the inhibition of IL-13-mediated fibrotic response. JIB-04 further prevented KDM4B association and enhanced H3K36 binding with promoter region of TIMP-2 leading to its increased transcription. KDM4B knockdown further resulted in inducing TIMP-2 expression and inhibited MMP-9 activation. Conclusion: Therapeutic targeting of KDM4B using JIB-04 is a promising candidate to alleviate IL-13-mediated responses in chronic disorders such as asthma.