Objective: Rosacea is a common chronic inflammatory skin disease with unclear pathogenesis and limited treatment options. Our preliminary studies have demonstrated the potential therapeutic efficacy of Tranilast (TR) against rosacea. However, the molecular mechanisms underlying this effect remain to be elucidated. Given that TR is known to suppress macrophage-mediated inflammation, this study aimed to investigate whether this pathway is involved in the anti-rosacea action of TR. Methods: J774A.1 cells were used for in vitro experiments, whereas an LL-37-induced rosacea-like dermatitis model was established for in vivo studies; all animals were randomly allocated to groups. On the final intervention day, areas of erythema on mouse skin lesions were compared. Pathological changes were assessed via haematoxylin–eosin staining. Expression patterns of key proteins in Toll-like receptor (TLR) 4–tumour necrosis factor (TNF)-α and NOD-, LRR- and pyrin domain-containing protein (NLRP) 3 –interleukin (IL) -1β pathways were evaluated by immunofluorescence staining and Western blotting. Immunohistochemical staining was conducted to assess F4/80 expression, and Western blotting was utilized to quantify protein expression levels of cathelicidin antimicrobial peptide (CAMP), vascular endothelial growth factor (VEGF). Data from multiple groups were compared using one-way ANOVA. Results: TR alleviated symptoms of rosacea-like inflammation in mice, as demonstrated by the following findings: The area of erythema decreased from 20.26 ± 1.44 mm 2 to 9.10 ± 1.21 mm 2 ( P < 0.001), and nuclear counting of HE-stained sections revealed a significant reduction in dermal inflammatory cell infiltration (342.20 ± 35.17 vs . 130.20 ± 19.92, P < 0.001). Western blotting showed pronounced downregulation of vascular markers CAMP and VEGF; immunofluorescence staining indicated that TR effectively reduced the expression levels of TLR4, TNF-α, and NLRP3. Western blotting further demonstrated reduced protein expression of TLR4, MyD88, p-p65, TNF-α, NLRP3, and IL-1β, whereas immunohistochemical staining showed a significant decrease in F4/80+ macrophage infiltration (13.20 ± 1.48 vs. 1.60 ± 0.55, P < 0.001). TR decreased the expression of key proteins in the TLR4–TNF-α and NLRP3–IL-1β pathways in J774A.1 cells. Additionally, the TLR4 inhibitor TLR4-C34 suppressed LL-37-induced NLRP3 expression in macrophages. Finally, TR reduced the expression of TLR4, MyD88, p-p65, TNF-α, NLRP3, and IL-1β in J774A.1 cells with lipopolysaccharide-induced inflammation. Conclusion: These findings demonstrate that TR ameliorates rosacea-like inflammation in mice, possibly via regulation of TLR4-mediated MyD88–NF-κB signalling and NLRP3-mediated macrophage inflammatory responses, suggesting its therapeutic potential for rosacea and warranting future studies.
Jin et al. (Wed,) studied this question.