瘦素通过上调 LOXL3 在骨关节炎发病机制中诱导软骨细胞凋亡激活和自噬抑制。

BACKGROUND: Osteoarthritis is one of the usual chronic musculoskeletal dysfunctions. It is one of the primary leading causes which leads to limitation of movement and absenteeism in the working adult population. Chondrocytes are the singlecellular-based component found in the cartilage which has an important role in the degradation of the cartilage. In recent studies, autophagy is observed to protect the human chondrocytes from stress.Leptin an adipokine managing food consumption and energy outlay. Chondrocytes indicate prolonged isoform of the leptin receptor where inside these cells theleptin signals individually or combine with the remaining molecules and promptthe indication of the pro-inflammatory molecules and cartilage disintegration enzymes. MATERIALS AND METHODS: mRNA expressions of Lysyl oxidase-like 3 in tissues of cartilage and concentration of leptin from synovial fluidwere measured from all samples from disease-induced groups, sham group, and RAPA-treated groups via RT-PCR and immunoassays. Histopathological analysis was also performed post-induction of the rat osteoarthritis model by the anterior cruciate ligament transection method. Western blot analysis was done, and expressions were analyzed by autophagy and apoptosis regulatory markers. Cell apoptosis and cell survival were evaluated with the help of flow cytometry, respectively, in all groups. RESULT: mRNA of LOXL3 was increased in osteoarthritis models which were directly related to leptin concentration in SF. ACLT surgery caused an increase in cleaved caspase 3 protein levels, while a significant reduction in Bcl-2, Beclin1, and LC3 I was noted (figure 4,5). When LOXL3 was silenced in the ACLT group and leptin-treated group apoptosis was inhibited and autophagy, cell proliferation was promoted in primary chondrocytes. A significant increase in LOXL3 caused inhibition of autophagy in chondrocytes. CONCLUSION: LOXL3 has stimulated apoptosis while inhibited autophagy in chondrocytes; hence LOXL3 is a prominent target for treating osteoarthritis. Keywords:chondrocytes, LOXL3, Leptin, osteoarthritis, qRT-PCR, ACLT, mRNA.

背景：骨关节炎是常见的慢性肌肉骨骼功能障碍之一。它是导致成年劳动力运动受限和缺勤的主要原因之一。软骨细胞是软骨中发现的单细胞成分，在软骨降解中起着重要作用。最近的研究表明，自噬可保护人软骨细胞免受应激。瘦素是一种调节食物摄入和能量消耗的脂肪细胞因子。软骨细胞显示出瘦素受体的延长异构体，在这些细胞内，瘦素信号单独或与其他分子结合，提示促炎分子和软骨分解酶的表达。

材料和方法：通过 RT-PCR 和免疫测定法测量所有疾病诱导组、假手术组和 RAPA 处理组的软骨组织中赖氨酰氧化酶样 3（Lysyl oxidase-like 3，LOXL3）的 mRNA 表达和滑液中瘦素的浓度。通过前交叉韧带横断法诱导大鼠骨关节炎模型后还进行了组织病理学分析。通过 Western blot 分析和自噬和凋亡调节标志物分析，分别分析了各组的表达。通过流式细胞术分别评估了各组的细胞凋亡和细胞存活。

结果：LOXL3 的 mRNA 在骨关节炎模型中增加，这与 SF 中的瘦素浓度直接相关。ACL 手术导致 cleaved caspase 3 蛋白水平升高，而 Bcl-2、Beclin1 和 LC3 I 显著降低（图 4，5）。当 LOXL3 在 ACLT 组和瘦素处理组中沉默时，细胞凋亡受到抑制，原代软骨细胞中的自噬、细胞增殖得到促进。LOXL3 的显著增加导致软骨细胞中的自噬受到抑制。

结论：LOXL3 刺激软骨细胞中的凋亡，同时抑制自噬；因此，LOXL3 是治疗骨关节炎的一个重要靶点。关键词：软骨细胞、LOXL3、瘦素、骨关节炎、qRT-PCR、ACL、mRNA。