NLRP3 Inflammasome Inhibition by Xuanfei Baidu Decoction Attenuates Pulmonary Inflammation and Collagen Deposition in...

Background/Objectives: Silicosis is a chronic disease caused by long-term exposure to high levels of silica dust, which leads to extensive nodular fibrosis in the lungs. The disease is currently a serious occupational health hazard globally. Xuanfei Baidu decoction (XFBD) is a mature Chinese herbal medicine in China that has shown anti-inflammatory and anti-fibrotic effects in mouse experiments, making it a promising candidate for addressing the persistent inflammation and fibrosis in silicosis. Methods: Silicosis was induced in male C57BL/6J mice using crystalline silica (CS). XFBD's early anti-inflammatory role was verified in vitro in peritoneal macrophages (PMs) and in vivo in silicosis mice, while its late anti-collagen deposition and anti-fibrotic activities were further investigated. Results: In vitro, XFBD effectively inhibits the activation of the NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) inflammasome in CS-induced lipopolysaccharide (LPS)-primed PMs, decreases the release of inflammatory cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α), and modulates the phenotypic transition of macrophages from the M2 to the M1 phenotype. In vivo studies further validated that XFBD significantly downregulates the expression of NLRP3 and Cleaved-Caspase-1 proteins in the lung tissues of mice afflicted with silicosis. Additionally, XFBD enhanced pulmonary function, inhibited collagen deposition and pulmonary fibrosis in silicosis mice, and reversed epithelial-mesenchymal transition (EMT) by regulating key EMT-related proteins to slow fibrosis. Conclusions: The beneficial effects of XFBD on CS-induced pulmonary fibrosis can be attributed to the induction of macrophage polarization-mediated anti-inflammatory responses during the early stage of fibrotic development, as well as its anti-collagen deposition and anti-fibrotic activities during the intermediate stage of fibrotic development. This study provides preclinical evidence supporting XFBD as a promising candidate for prevention or adjunctive therapy, and its multi-target, time-phase mechanism offers a novel rationale and theoretical foundation for the development of new strategies against silicosis.