[Chrysin inhibited epithelial-mesenchymal transition of type Ⅱ alveolar epithelial cell by regulating NF-κB/Twist 1...

This study aimed to assess whether chrysin(ChR) can inhibit epithelial-mesenchymal transition(EMT) of type Ⅱ alveolar epithelial cell and produce anti-pulmonary fibrosis effect by regulating the NF-κB/Twist 1 signaling pathway. Sixty rats were randomly divided into the control group, the bleomycin(BLC) group, BLC+ChR(50 mg·kg~(-1)) group and BLC+ChR(100 mg·kg~(-1)) group, with 15 rats in each group. The pulmonary fibrosis model was induced by intratracheal injection of BLC(7 500 U·kg~(-1)). Rats were orally administered with different doses of ChR after BLC injection for 28 days. The cells were divided into control group, TGF-β1 group(5 ng·mL~(-1)), and TGF-β1+ChR(1, 10, 100 μmol·L~(-1)) groups. The type Ⅱ alveolar epithelial cells were treated with TGF-β1 for 24 h, and then treated with TGF-β1 for 48 h in the presence or absence of different doses of ChR(1, 10 and 100 μmol·L~(-1)). The morphological changes and collagen deposition in lung tissues were analyzed by HE staining, Masson staining and immunohistochemistry. The mRNA and protein expression levels of collagen Ⅰ, E-cadherin, zonula occludens-1(ZO-1), vimentin, alpha smooth muscle actin(α-SMA), inhibitor of nuclear factor kappa B alpha(IκBα), nuclear factor-kappa B p65(NF-κB p65), phospho-NF-κB p65(p-p65) and Twist 1 in lung tissues and cells were detected by qPCR and Western blot, respectively. The animal experiment results showed that as compared with the BLC group, after administration of ChR for 28 days, bleomycin-induced pulmonary fibrosis in rats was significantly relieved, collagen Ⅰ expression in lung tissues was significantly reduced(P<0.05 or P<0.01), and EMT of alveolar epithelial cells was obviously inhibited [the expression levels of E-cadherin and ZO-1 were increased and the expression levels of vimentin and α-SMA were decreased(P<0.05 or P<0.01)], concomitantly with significantly reduced IκBα and p65 phosphorylation level in cytoplasm and decreased NF-κB p65 and Twist 1 expression in nucleus(P<0.05 or P<0.01). The cell experiment results showed that different doses of ChR(1, 10 and 100 μmol·L~(-1)) significantly reduced TGF-β1-induced collagen Ⅰ expression(P<0.05 or P<0.01), significantly inhibited EMT of type Ⅱ alveolar epithelial cells[the expression levels of E-cadherin and ZO-1 were increased and the expression levels of vimentin and α-SMA were decreased(P<0.05 or P<0.01)], and inhibited IκBα and p65 phosphorylation in cytoplasm and down-regulated NF-κB p65 and Twist 1 expression in nucleus induced by TGF-β1(P<0.05 or P<0.01). The results suggest that ChR can reverse EMT of type Ⅱ alveolar epithelial cell and alleviate pulmonary fibrosis in rats, and its mechanism may be associated with reducing IκBα phosphorylation and inhibiting NF-κB p65 phosphorylation and nuclear transfer, thus down-regulating Twist 1 expression.