Topical Remibrutinib Attenuates LL37-Induced Rosacea-Like Dermatitis by Inhibiting BTK Activation, NF-κB Signaling and Mast Cell Activation

Wangchao Li,1,2 Huiping Fan,1 Hua Liu,1,2 Qingsong Ma,1,2 Chengqi Liu,1 Dong Zhang,1,2 Weiyuan Ma1,21Department of Dermatology, Affiliated Hospital of Shandong Second Medical University, Weifang, Shandong, 261000, People’s Republic of China; 2School of Clinical Medicine, Shandong Second Medical University, Weifang, Shandong, 261000, People’s Republic of ChinaCorrespondence: Dong Zhang; Weiyuan Ma, Department of Dermatology, Affiliated Hospital of Shandong Second Medical University, School of Clinical Medicine, Shandong Second Medical University, No. 2428 Yuhe Road, Kuiwen District, Weifang, Shandong, People’s Republic of China, Email [email protected]; [email protected]: Rosacea is a chronic inflammatory skin disorder in which LL37-driven mast cell activation contributes to cutaneous inflammation. Bruton’s tyrosine kinase (BTK) is a key regulator of canonical IgE-dependent mast cell responses; however, its role in LL37-induced, IgE-independent mast cell activation remains unclear. This study investigated the involvement of BTK activation and nuclear factor-κB (NF-κB) signaling in LL37-induced mast cell activation and evaluated the therapeutic effects of topical remibrutinib in experimental rosacea-like dermatitis.Methods: Transcriptomic data from rosacea lesions (GSE65914) were analyzed to identify dysregulated inflammatory pathways. LL37-stimulated LUVA mast cells and an LL37-induced mouse model of rosacea-like dermatitis were used for in vitro and in vivo evaluation, respectively. Cell viability, mast cell degranulation, and inflammatory mediator production were assessed using the Cell Counting Kit-8 assay (CCK-8) and enzyme-linked immunosorbent assays (ELISA). Cutaneous inflammation and dermal mast cell accumulation were evaluated by histopathological examination and toluidine blue staining. BTK and NF-κB phosphorylation were examined by Western blotting and immunofluorescence.Results: Consistently, gene set enrichment analysis demonstrated enrichment of the NF-κB signaling pathway, with BTK included among the leading-edge genes contributing to this transcriptional signature. LL37 increased BTK and p65 phosphorylation in LUVA cells and mouse skin, accompanied by enhanced mast cell degranulation and inflammatory mediator release. Topical treatment with 1% remibrutinib reduced BTK and p65 phosphorylation, mast cell accumulation and degranulation, and inflammatory mediator levels. These changes were accompanied by reductions in erythema, epidermal thickening, and histopathological inflammation in mice.Conclusion: BTK and NF-κB are involved in LL37-induced, IgE-independent mast cell activation and rosacea-like inflammation. Topical remibrutinib attenuated experimental rosacea-like dermatitis by inhibiting BTK phosphorylation and NF-κB activation and mast cell activation, supporting topical BTK inhibition as a potential therapeutic strategy for rosacea.Keywords: rosacea, remibrutinib, bruton’s tyrosine kinase, p65, mast cell