Zhongshan Hospital, Xiamen University, Xiamen, Fujian, China.
School of Medicine, Xiamen University, Xiamen, Fujian, China.
J Cell Mol Med. 2019 Apr;23(4):2782-2793. doi: 10.1111/jcmm.14184. Epub 2019 Feb 7.
Autophagy maintains cellular homoeostasis. The enhancement of autophagy in chondrocytes could prevent osteoarthritis (OA) progression in articular cartilage. Peroxisome proliferator-activated receptor α (PPARα) activation may also protect articular chondrocytes against cartilage degradation in OA. However, whether the protective effect of activated PPARα is associated with autophagy induction in chondrocytes is not determined. In this study, we investigated the effect of PPARα activation by its agonist, WY14643, on the protein expression level of Aggrecan and ADAMTS5, and the protein expression level of autophagy biomarkers, including LC3B and P62, using Western blotting analysis in isolated mouse chondrocytes pre-treated with lipopolysaccharides (LPS, mimicking OA chondrocytes) with or without the autophagy inhibitor chloroquine diphosphate salt. Furthermore, Akt and ERK phosphorylation was detected in LPS-treated chondrocytes in response to WY14643. In addition, the effect of intra-articularly injected WY14643 on articular cartilage in a mouse OA model established by the destabilization of the medial meniscus was assessed using the Osteoarthritis Research Society International (OARSI) histopathology assessment system, along with the detection of Aggrecan, ADAMTS5, LC3B and P62 protein levels using immunohistochemistry assay. The results indicated that PPARα activation by WY14643 promoted proteoglycan synthesis by autophagy enhancement in OA chondrocytes in vivo and in vitro concomitant with the elevation of Akt and ERK phosphorylation. Therefore, autophagy could contribute to the chondroprotection of PPARα activation by WY14643, with the implication that PPARα activation by WY14643 may be a potential approach for OA therapy.
自噬维持细胞内稳态。软骨细胞中自噬的增强可以防止关节软骨中的骨关节炎（OA）进展。过氧化物酶体增殖物激活受体α（PPARα）的激活也可能保护关节软骨免受 OA 中软骨降解的影响。然而，激活的 PPARα 的保护作用是否与软骨细胞中的自噬诱导有关尚不确定。在这项研究中，我们通过其激动剂 WY14643 研究了 PPARα 激活对分离的小鼠软骨细胞中 Aggrecan 和 ADAMTS5 蛋白表达水平的影响，并用 Western blot 分析检测了自噬生物标志物 LC3B 和 P62 的蛋白表达水平，这些软骨细胞先用脂多糖（LPS，模拟 OA 软骨细胞）预处理，然后用自噬抑制剂氯喹二磷酸盐处理或不处理。此外，还检测了 LPS 处理的软骨细胞中 Akt 和 ERK 磷酸化对 WY14643 的反应。此外，还通过软骨内注射 WY14643 来评估其对内侧半月板不稳定建立的小鼠 OA 模型关节软骨的影响，使用骨关节炎研究协会国际（OARSI）组织病理学评估系统，以及使用免疫组织化学检测 Aggrecan、ADAMTS5、LC3B 和 P62 蛋白水平。结果表明，WY14643 通过激活 PPARα 促进 OA 软骨细胞中的蛋白聚糖合成，通过自噬增强，同时提高 Akt 和 ERK 磷酸化。因此，自噬可能有助于 WY14643 激活的 PPARα 的软骨保护作用，这表明 WY14643 激活的 PPARα 可能是 OA 治疗的一种潜在方法。
