Department of Orthopedics, Zhongshan Hospital, Shanghai, China.
Cartilage. 2021 Dec;13(2_suppl):1030S-1040S. doi: 10.1177/19476035211035434. Epub 2021 Aug 28.
To investigate the relationship between hypoxia inducible factor-1α (HIF-1α) and the autophagic response in osteoarthritic chondrocytes (OA), under inflammatory insult as represented by OA model.
Human chondrocyte cell line C28/I2 was cultured in both normoxic and hypoxic conditions and treated with interleukin-1β (IL1β) to emulate OA inflammatory insult . Cellular HIF-1α expression was silenced using siRNA transfection and cellular autophagic (P62/LC3II) response and OA chondrocyte damage (COL2A1/MMP13) related proteins were examined using western blotting. Cellular mitophagic (BNIP3/PINK1/Parkin) and apoptotic (Caspase/Cleaved Caspase 3) were also evaluated to assess mitophagy-mediated cell death due to HIF-1α silencing.
Chondrocyte basal autophagy levels were higher in a HIF-1α elevated environment and was more resistant to IL1β-induced inflammatory insult. Increase in autophagic proteins showed better chondrocyte repair, which resulted a lower level of reactive oxygen species production, and lesser damage to chondrocyte integrity. Silencing HIF-1α activates cellular PINK1/Parkin and BNIP3 mitophagic proteins, which leads to the activation of Caspase/Cleaved Caspase 3 apoptotic cascade.
Our results show that chondrocyte autophagy is dependent on HIF-1α expression, showing the importance of HIF-1α in hypoxic chondrocyte function in OA. Dysregulation of HIF-1α expression results in the activation of mitophagy-mediated apoptosis.
在骨关节炎软骨细胞（OA）炎症损伤模型下，研究缺氧诱导因子-1α（HIF-1α）与自噬反应的关系。
在常氧和缺氧条件下培养人软骨细胞系 C28/I2，并使用白细胞介素-1β（IL1β）模拟 OA 炎症损伤。使用 siRNA 转染沉默细胞 HIF-1α 表达，并用 Western blot 检测细胞自噬（P62/LC3II）反应和 OA 软骨细胞损伤（COL2A1/MMP13）相关蛋白。还评估了细胞 mitophagy（BNIP3/PINK1/Parkin）和细胞凋亡（Caspase/Cleaved Caspase 3），以评估由于 HIF-1α 沉默导致的 mitophagy 介导的细胞死亡。
在 HIF-1α 升高的环境中，软骨细胞的基础自噬水平较高，对 IL1β 诱导的炎症损伤更具抵抗力。自噬蛋白的增加显示出更好的软骨细胞修复，从而产生较低水平的活性氧，对软骨细胞完整性的损伤较小。沉默 HIF-1α 激活细胞 PINK1/Parkin 和 BNIP3 mitophagy 蛋白，导致 Caspase/Cleaved Caspase 3 凋亡级联的激活。
我们的结果表明，软骨细胞自噬依赖于 HIF-1α 的表达，表明 HIF-1α 在 OA 缺氧软骨细胞功能中的重要性。HIF-1α 表达的失调导致 mitophagy 介导的细胞凋亡的激活。
