Topical application of magnolol ameliorates psoriasis-like dermatitis by inhibiting NLRP3/Caspase-1 pathway and regulating tryptophan metabolism.

Psoriasis (PSO) is a common inflammatory skin disease caused by multiple factors. Magnolia officinalis is an important medicinal plant in China, with various values such as ecology, medicine, food, and daily chemicals. However, its diverse application potential has not been fully explored. Magnolol (MGO) is the main active compound of Magnolia officinalis with significant anti-inflammatory effect. To investigate the application potential of MGO in inflammatory skin disease, the effects and underlying mechanisms of topical MGO treating psoriasis were explored in this study. Network pharmacology and molecular docking firstly predicted that topical MGO may treat psoriasis by regulating pyroptosis pathway and acting on caspase-1 (CASP1). In vitro experiments then demonstrated that MGO could inhibit the level of inflammatory cytokines and the key protein expression of NOD-like receptor protein 3 (NLRP3)/Caspase-1 pathway in lipopolysaccharide (LPS)-stimulated phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 cells. Meanwhile, MGO could inhibit CuSO-induced neutrophils migration in Tg (mpx:EGFP) zebrafish by suppressing inflammation and pyroptosis. This study further indicated that topical application of MGO ameliorated imiquimod (IMQ)-induced psoriasis-like dermatitis by reducing the release of inflammatory factors and decreasing the key protein expression of pyroptosis-related NLRP3/Caspase-1 pathway. Metabolomics analysis revealed that topical application of MGO could significantly regulate tryptophan metabolism and affect the level of tryptophan in skin lesions. Tryptophan could also regulate inflammation-related genes and inhibit pyroptosis-related NLRP3/Caspase-1 pathway in LPS-stimulated PMA-differentiated THP-1 cells. In conclusion, this study suggested that topical MGO may ameliorate psoriasis-like dermatitis by inhibiting NLRP3/Caspase-1 pathway and regulating tryptophan metabolism.