TLR4 and pulmonary fibrosis: Studies have shown that 4 weeks of moderate-intensity aerobic exercise suppresses the expression of TGF-β1 and inflammatory pathways TLR4/TNF-α and SRB/NLPR3, which, in turn, suppresses the expression of macrophage-derived IL-17A, thereby ameliorating silica-induced pulmonary fibrosis [6].