However, infection with TLR4-shRNA lentivirus inhibited TLR4 expression at the mRNA and protein levels (Figure 2C, 2D, Figure 3), downregulated the content of PICP in mouse BALF (Figure 2A) and hydroxyproline (Figure 2B), inhibited the expression of α-SMA and type I procollagen (Figure 2C, 2D, Figure 3), and therefore alleviated the degree of pulmonary fibrosis induced by LPS (Figure 1). Here, TLR4 is linked to pulmonary fibrosis.