Pulmonary fibrosis is a growing clinical problem that develops as a result of abnormal wound healing, leading to breathlessness, pulmonary dysfunction and ultimately death. However, therapeutic options for pulmonary fibrosis are limited because the underlying pathogenesis remains incompletely understood. Circular RNAs, as key regulators in various diseases, remain poorly understood in pulmonary fibrosis induced by silica. We performed studies with fibroblast cell lines and silica-induced mouse pulmonary fibrosis models. The expression of circZNF609, miR-145-5p, and KLF4 was determined by quantitative real-time polymerase chain reaction (qRT-PCR) analysis. RNA immunoprecipitation (RIP) assays and m6A RNA immunoprecipitation assays (MeRIP), Western blotting, immunofluorescence assays, and CCK8 were performed to investigate the role of the circZNF609/miR-145-5p/KLF4 axis and circZNF609-encoded peptides in fibroblast activation. Our data showed that circZNF609 was downregulated in activated fibroblasts and silica-induced fibrotic mouse lung tissues. Overexpression of circZNF609 could inhibit fibroblast activation induced by transforming growth factor-β1 (TGF-β1). Mechanically, we revealed that circZNF609 regulates pulmonary fibrosis via miR-145-5p/KLF4 axis and circZNF609-encoded peptides. Furthermore, circZNF609 was highly methylated and its expression was controlled by N6-methyladenosine (m6A) modification. Lastly, in vivo studies revealed that overexpression of circZNF609 attenuates silica-induced lung fibrosis in mice. Our data indicate that circZNF609 is a critical regulator of fibroblast activation and silica-induced lung fibrosis. The circZNF609 and its derived peptides may represent novel promising targets for the treatment of pulmonary fibrosis.

中文翻译：

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CircZNF609通过miR-145-5p/KLF4轴及其翻译功能调节肺纤维化

肺纤维化是一个日益严重的临床问题，由伤口愈合异常引起，导致呼吸困难、肺功能障碍并最终死亡。然而，肺纤维化的治疗选择有限，因为潜在的发病机制仍未完全了解。环状RNA作为各种疾病的关键调节因子，在二氧化硅诱导的肺纤维化中仍然知之甚少。我们对成纤维细胞系和二氧化硅诱导的小鼠肺纤维化模型进行了研究。通过定量实时聚合酶链反应 (qRT-PCR) 分析确定 circZNF609、miR-145-5p 和 KLF4 的表达。进行 RNA 免疫沉淀 (RIP) 测定和 m6A RNA 免疫沉淀测定 (MeRIP)、蛋白质印迹、免疫荧光测定和 CCK8，以研究 circZNF609/miR-145-5p/KLF4 轴和 circZNF609 编码肽在成纤维细胞激活中的作用。我们的数据表明，circZNF609 在活化的成纤维细胞和二氧化硅诱导的纤维化小鼠肺组织中下调。 circZNF609 的过表达可以抑制转化生长因子-β1 (TGF-β1) 诱导的成纤维细胞活化。从机制上讲，我们揭示了 circZNF609 通过 miR-145-5p/KLF4 轴和 circZNF609 编码的肽调节肺纤维化。此外，circZNF609 高度甲基化，其表达受 N6-甲基腺苷 (m6A) 修饰控制。最后，体内研究表明，circZNF609 的过度表达可减轻二氧化硅诱导的小鼠肺纤维化。我们的数据表明，circZNF609 是成纤维细胞活化和二氧化硅诱导的肺纤维化的关键调节因子。 circZNF609 及其衍生肽可能代表治疗肺纤维化的新的有希望的靶标。