Silibinin alleviates house dust mite induced allergic airway inflammation by inhibiting NLRC4 inflammasome and MMP-9 expression

Abstract

Silibinin, a major compound of silymarin, has been reported to alleviate respiratory diseases including acute lung injury, asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis through its antifibrotic, anti-inflammatory, and antioxidant properties. However, the specific mechanisms underlying its therapeutic effects, particularly in allergic asthma, are not fully understood. With the increasing prevalence and impact of allergic asthma, there is a need to elucidate the exact underlying mechanisms of its potential treatment effects. Herein, we investigated the therapeutic effects of silibinin on allergic asthma using house dust mite (HDM)-exposed mice and an HDM-stimulated human bronchial epithelium cell line, focusing on the roles of the NLR family CARD domain containing 4 (NLRC4) inflammasome and matrix metalloproteinase-9 (MMP-9). To induce airway inflammation, HDM extracts were instilled intranasally on days 0, 4, 8, and 12 to mice. Silibinin (20 and 40 mg/kg) was orally administered daily from days 0–12. The results showed that silibinin treatment attenuated allergic immune responses induced by HDM exposure, as evidenced by decreased airway hyperresponsiveness, reduced inflammatory cells and cytokines, lower immunoglobulin E levls, and decreased mucus production. Furthermore, silibinin treatment suppressed NLRC4 inflammasome activation and downregulated MMP-9 expression in the lungs. In HDM-stimulated cells, silibinin treatment decreased inflammatory cytokine levels and the expression of NLRC4 and interleukin-1β, indicating inhibition of NLRC4 inflammasome activation. Overall, our data demonstrated that silibinin alleviated allergic responses in HDM-induced asthmatic mice by inhibiting NLRC4 inflammasome activation and MMP-9 expression, underscoring its therapeutic potential in the treatment of asthma.