Department of Occupational Health and Occupational Disease, College of Public Health, Zhengzhou University, Zhengzhou, Henan, PR China.
Department of Occupational Health and Occupational Disease, College of Public Health, Zhengzhou University, Zhengzhou, Henan, PR China.
Int Immunopharmacol. 2024 Dec 5;142(Pt B):113186. doi: 10.1016/j.intimp.2024.113186. Epub 2024 Sep 18.
Silicosis is a progressive interstitial lung disease characterized by diffuse pulmonary fibrosis. The transdifferentiation of lung fibroblasts into myofibroblasts is a key cellular event driving the progression of silicosis fibrosis. Recent studies have shown that PD-L1 expression is significantly upregulated in activated fibroblasts, and PD-L1 plays a crucial role in mediating fibroblast transdifferentiation. This study aims to elucidate the molecular mechanisms regulating PD-L1 expression in fibroblasts and analyze the functional significance of PD-L1 upregulation in fibroblast activity and silicosis fibrosis. In this research, an in vitro model of TGF-β1-induced NIH-3 T3 fibroblast transdifferentiation was established. Small molecule inhibitors, siRNA, and plasmids were used to interfere with the PI3K/AKT/mTOR signaling pathway and PD-L1 expression. It was found that TGF-β1 stimulation increased PD-L1 expression in fibroblasts, while blocking the PI3K/AKT/mTOR pathway inhibited this upregulation. Knockdown of PD-L1 significantly inhibited fibroblast transdifferentiation and impeded TGF-β1-induced activation of the PI3K/AKT/mTOR pathway, whereas PD-L1 overexpression had the opposite effect. Additionally, PD-L1 protein in fibroblasts undergoes ubiquitin-proteasome-mediated degradation, negatively regulating PD-L1 upregulation. In vivo, adeno-associated virus was used to specifically knockdown PD-L1 in mouse lung fibroblasts, resulting in significantly reduced lung tissue damage and fibrosis in silicosis mice. This effect was associated with the involvement of the PI3K/AKT/mTOR pathway. In summary, PD-L1 expression in fibroblasts is upregulated during transdifferentiation, a process regulated by the PI3K/AKT/mTOR pathway. Upregulated PD-L1 enhances PI3K/AKT/mTOR signaling through positive feedback, sustaining fibroblast activation. Ubiquitin-proteasome-mediated protein degradation may serve as a negative feedback mechanism maintaining PD-L1 homeostasis.
矽肺是一种进行性间质性肺疾病，其特征为弥漫性肺纤维化。肺成纤维细胞向肌成纤维细胞的转分化是驱动矽肺纤维化进展的关键细胞事件。最近的研究表明，PD-L1 在激活的成纤维细胞中表达显著上调，PD-L1 在介导成纤维细胞转分化中发挥关键作用。本研究旨在阐明调节成纤维细胞中 PD-L1 表达的分子机制，并分析 PD-L1 上调在成纤维细胞活性和矽肺纤维化中的功能意义。在这项研究中，建立了 TGF-β1 诱导的 NIH-3T3 成纤维细胞转分化的体外模型。使用小分子抑制剂、siRNA 和质粒干扰 PI3K/AKT/mTOR 信号通路和 PD-L1 表达。结果发现，TGF-β1 刺激增加了成纤维细胞中 PD-L1 的表达，而阻断 PI3K/AKT/mTOR 通路抑制了这种上调。PD-L1 敲低显著抑制成纤维细胞转分化，并阻碍 TGF-β1 诱导的 PI3K/AKT/mTOR 通路的激活，而 PD-L1 过表达则产生相反的效果。此外，成纤维细胞中的 PD-L1 蛋白经历泛素-蛋白酶体介导的降解，负调控 PD-L1 的上调。在体内，腺相关病毒被用于特异性敲低小鼠肺成纤维细胞中的 PD-L1，导致矽肺小鼠的肺组织损伤和纤维化显著减少。这种效果与 PI3K/AKT/mTOR 通路的参与有关。总之，成纤维细胞在转分化过程中 PD-L1 的表达上调，该过程受 PI3K/AKT/mTOR 通路调节。上调的 PD-L1 通过正反馈增强 PI3K/AKT/mTOR 信号，维持成纤维细胞的激活。泛素-蛋白酶体介导的蛋白降解可能是维持 PD-L1 内稳态的负反馈机制。
