角蛋白 15 通过 MMP-9 保护上皮细胞免受香烟烟雾诱导的上皮间质转化。

BACKGROUND: Chronic obstructive pulmonary disease (COPD), a chronic inflammatory lung disease, is a leading cause of morbidity and mortality worldwide. Prolonged cigarette smoking (CS) that causes irreversible airway remodeling and significantly reduces lung function is a major risk factor for COPD. Keratin15 (Krt15) cells with the potential of self-renewal and differentiation properties have been implicated in the maintenance, proliferation, and differentiation of airway basal cells; however, the role of Krt15 in COPD is not clear. METHODS: Krt15 knockout (Krt15) and wild-type (WT) mice of C57BL/6 background were exposed to CS for six months to establish COPD models. Krt15-CrePGR;Rosa26-LSL-tdTomato mice were used to trace the fate of the Krt15 cells. Hematoxylin and eosin (H&E) and Masson stainings were performed to assess histopathology and fibrosis, respectively. Furthermore, lentivirus-delivered short hairpin RNA (shRNA) was used to knock down KRT15 in human bronchial epithelial (HBE) cells stimulated with cigarette smoke extract (CSE). The protein expression was assessed using western blot, immunohistochemistry, and enzyme-linked immunosorbent assay. RESULTS: Krt15 CS mice developed severe inflammatory cell infiltration, airway remodeling, and emphysema. Moreover, Krt15 knockout aggravated CS-induced secretion of matrix metalloproteinase-9 (MMP-9) and epithelial-mesenchymal transformation (EMT), which was reversed by SB-3CT, an MMP-9 inhibitor. Consistent with this finding, KRT15 knockdown promoted MMP-9 expression and EMT progression in vitro. Furthermore, Krt15 cells gradually increased in the bronchial epithelial cells and were transformed into alveolar type II (AT2) cells. CONCLUSION: Krt15 regulates the EMT process by promoting MMP-9 expression and protects the lung tissue from CS-induced injury, inflammatory infiltration, and apoptosis. Furthermore, Krt15 cells transformed into AT2 cells to protect alveoli. These results suggest Krt15 as a potential therapeutic target for COPD.

背景：慢性阻塞性肺疾病（COPD）是一种慢性炎症性肺部疾病，是全球发病率和死亡率的主要原因。导致气道重塑不可逆转并显著降低肺功能的长期吸烟（CS）是 COPD 的主要危险因素。具有自我更新和分化特性的角蛋白 15（Krt15）细胞已被牵涉到气道基底细胞的维持、增殖和分化中；然而，Krt15 在 COPD 中的作用尚不清楚。

方法：使用 C57BL/6 背景的 Krt15 敲除（Krt15）和野生型（WT）小鼠暴露于 CS 六个月以建立 COPD 模型。使用 Krt15-CrePGR；Rosa26-LSL-tdTomato 小鼠来追踪 Krt15 细胞的命运。进行苏木精和伊红（H&E）和 Masson 染色分别评估组织病理学和纤维化。此外，使用慢病毒传递的短发夹 RNA（shRNA）敲低香烟烟雾提取物（CSE）刺激的人支气管上皮（HBE）细胞中的 KRT15。使用蛋白质印迹、免疫组织化学和酶联免疫吸附测定评估蛋白质表达。

结果：Krt15 CS 小鼠发生严重的炎症细胞浸润、气道重塑和肺气肿。此外，Krt15 敲除加重了 CS 诱导的基质金属蛋白酶-9（MMP-9）和上皮间质转化（EMT）的分泌，这一过程可被 MMP-9 抑制剂 SB-3CT 逆转。与此发现一致，KRT15 敲低促进了体外 MMP-9 表达和 EMT 进展。此外，Krt15 细胞逐渐增加在支气管上皮细胞中，并转化为肺泡型 II（AT2）细胞。

结论：Krt15 通过促进 MMP-9 表达调节 EMT 过程，并保护肺组织免受 CS 诱导的损伤、炎症浸润和细胞凋亡。此外，Krt15 细胞转化为 AT2 细胞以保护肺泡。这些结果表明 Krt15 是 COPD 的潜在治疗靶点。