Isoliquiritigenin (ISL), a natural flavonoid derived from the root of liquorice, has been reported to possess anti-inflammatory and antioxidant activities. Previous studies have found that ISL plays a crucial role in anti-fibrosis of adipose tissue and renal tissue; however, its effect on pulmonary fibrogenesis has not been demonstrated. In this study, we aimed to explore the roles and the underlying mechanisms of ISL in TGF-β1-induced fibrogenesis using human lung fibroblast-derived MRC-5 cells. Cell proliferation and migration were determined by MTT and wound healing assay, respectively. The expression levels of alpha-smooth muscle actin (α-SMA), collagen type I alpha 1 (COLIA1) and fibronectin (FN), microtubule-associated protein light chain 3 (LC3) and related signaling molecules were detected by quantitative real-time PCR, western blot and immunofluorescence assay, correspondingly. EGFP-LC3 transfection was used for autophagy analysis. The results showed that ISL inhibited the TGF-β1-induced proliferation and migration, and down-regulated the expressions of α-SMA, COLIA1 and FN. ISL treatment led to up-regulation of LC3 in TGF-β1-treated MRC-5 cells, accompanied by significant decrease in the phosphorylation levels of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), and mammalian target of rapamycin (mTOR). In addition, the inhibitory effects of ISL on TGF-β1-induced fibrogenic features in MRC-5 cells were enhanced by pretreatment with autophagy activator Rapmycin and PI3K/AKT inhibitor LY294002 and reversed by autophagy inhibitor 3-methyladenine and PI3K/AKT activator IGF-1. Taken together, our results demonstrated that ISL could attenuate the fibrogenesis of TGF-β1-treated MRC-5 cells by activating autophagy via suppressing the PI3K/AKT/mTOR pathway. Therefore, ISL holds a great potential to be developed as a novel therapeutic agent for the treatment of pulmonary fibrosis.

中文翻译：

---

异黄体生成素可以通过PI3K / AKT / mTOR途径激活MRC-5细胞中的自噬来抑制TGF-β1诱导的纤维化。

据报道，异黄酮生成素（ISL）是一种从甘草根中提取的天然黄酮，具有抗炎和抗氧化的作用。先前的研究发现，ISL在脂肪组织和肾脏组织的抗纤维化中起着至关重要的作用。然而，尚未证明其对肺纤维化的作用。在这项研究中，我们旨在探讨人源成纤维细胞来源的MRC-5细胞在TGF-β1诱导的纤维化中ISL的作用和潜在机制。细胞增殖和迁移分别通过MTT和伤口愈合测定来确定。通过定量实时检测α-平滑肌肌动蛋白（α-SMA），I型胶原α1（COLIA1）和纤连蛋白（FN），微管相关蛋白轻链3（LC3）和相关信号分子的表达水平。 PCR，免疫印迹和免疫荧光测定。EGFP-LC3转染用于自噬分析。结果表明，ISL抑制TGF-β1诱导的增殖和迁移，并下调α-SMA，COLIA1和FN的表达。ISL处理导致TGF-β1处理的MRC-5细胞中LC3的上调，并伴随着磷脂酰肌醇3-激酶（PI3K），蛋白激酶B（AKT）和哺乳动物雷帕霉素靶标的磷酸化水平显着降低（ mTOR）。此外，自噬激活剂雷帕霉素和PI3K / AKT抑制剂LY294002预处理可增强ISL对MRC-5细胞中TGF-β1诱导的纤维化特征的抑制作用，而自噬抑制剂3-甲基腺嘌呤和PI3K / AKT激活剂IGF-则可逆转ISL的抑制作用。 1。在一起 我们的结果表明，ISL可以通过抑制PI3K / AKT / mTOR途径激活自噬来减轻TGF-β1处理的MRC-5细胞的纤维化。因此，ISL具有巨大的潜力，可以开发为治疗肺纤维化的新型治疗剂。