Honokiol ameliorates silica-induced lung fibrosis by inhibiting macrophage pyroptosis via modulating cGAS/STING signaling

Silicosis is a life-threatening occupational disease because of inhaling silica dust, leading to chronic inflammation, pyroptosis, and fibrosis. Unfortunately, it is still lacking effective pharmacological intervention currently. Honokiol (HKL), a natural extract with biological activity from Magnolia bark, is known for its antioxidant and anti-inflammatory biological effects. The current work aimed to investigate the therapeutic potential of HKL in mitigating silica-induced lung fibrosis and pyroptosis, particularly focusing on the cGAS/STING signaling pathway. The pulmonary pathological results shown in H&E and Masson's trichrome staining images confirmed the protective effects of HKL on lung tissue structure. In addition, HKL significantly reduced lung inflammation, collagen deposition, and oxidative stress compared to mice in the silicosis group. HKL treatment also alleviated silica-induced pyroptosis by suppressing the activation of the cGAS/STING signaling pathway in lung tissues. Moreover, the in vitro experiments using J774A.1 macrophages demonstrated that HKL reduced pyroptosis and improved cell viability under exposure to silica combined lipopolysaccharide (LPS). These were attributed to HKL downregulating the activation of the cGAS/STING signaling pathway in pyroptotic J774A.1 cells induced by silica combined with LPS. Meanwhile, inhibition of STING signaling induced by DNase I significantly enhanced the protective effects of HKL on the inflammatory and pyroptotic processes induced by silica. Overall, HKL could attenuate silica-induced pyroptosis by modulating the cGAS/STING signaling pathway against pulmonary fibrosis. The current study offers a promising approach for treating silicosis and related inflammatory responses.