Laboratory for Experimental Orthopaedics, Department of Orthopaedics, Justus Liebig University Giessen, Germany.
Department of Clinical Chemistry and Laboratory Medicine, University Hospital Regensburg, Germany.
Osteoarthritis Cartilage. 2017 Nov;25(11):1890-1899. doi: 10.1016/j.joca.2017.07.011. Epub 2017 Jul 20.
Phospholipids (PLs), together with hyaluronan and lubricin, are involved in boundary lubrication within human articular joints. Levels of lubricants in synovial fluid (SF) have been found to be associated with the health status of the joint. However, the biosynthesis and release of PLs within human joints remains poorly understood. This study contributes to our understanding of the effects of cytokines on the biosynthesis of PLs using cultured fibroblast-like synoviocytes (FLS) from human osteoarthritic knee joints.
Cultured FLS were stimulated with IL-1β, TNFα, IL-6, or inhibitors of cell signaling pathways such as QNZ, SB203580 and SP600125 in the presence of stable isotope-labeled precursors of PLs. Lipids were extracted and quantified using electrospray ionization tandem mass spectrometry (ESI-MS/MS).
Our analyses provide for the first time a detailed overview of PL species being synthesized by FLS. IL-1β increased the biosynthesis of both phosphatidylethanolamine (PE) and PE-based plasmalogens. We show here that the NF-κB, p38 MAPK and JNK signaling pathways are all involved in IL-1β-induced PL biosynthesis. IL-6 had no impact on PLs, whereas TNFα increased the biosynthesis of all PL classes.
The biosynthesis of various PLs is controlled by IL-1β and TNFα. Our detailed PL species analysis revealed that FLS can partly contribute to the elevated PL levels found in human osteoarthritis (OA) SF. IL-1β in particular stimulates PE and PE-based plasmalogens which can act as cell-protective antioxidants. These results suggest that during OA progression, FLS undergo alterations in their PL composition to adapt to the new diseased environment.
磷脂（PLs）与透明质酸和润滑素一起参与了人体关节的边界润滑。人们发现滑液（SF）中的润滑剂水平与关节的健康状况有关。然而，人们对人体关节中 PLs 的生物合成和释放仍知之甚少。本研究使用来自人类骨关节炎膝关节的培养成纤维样滑膜细胞（FLS），探讨了细胞因子对 PL 生物合成的影响，有助于我们加深对这一过程的理解。
在存在 PL 稳定同位素标记前体的情况下，用白细胞介素 1β（IL-1β）、肿瘤坏死因子-α（TNFα）、白细胞介素 6（IL-6）或细胞信号通路抑制剂（如 QNZ、SB203580 和 SP600125）刺激培养的 FLS。采用电喷雾串联质谱（ESI-MS/MS）法提取和定量分析脂质。
我们的分析首次详细概述了 FLS 合成的 PL 种类。IL-1β增加了磷脂酰乙醇胺（PE）和基于 PE 的血小板质的生物合成。我们在这里表明，NF-κB、p38MAPK 和 JNK 信号通路均参与了 IL-1β诱导的 PL 生物合成。IL-6 对 PL 没有影响，而 TNFα 增加了所有 PL 类别的生物合成。
各种 PL 的生物合成受 IL-1β 和 TNFα 的控制。我们详细的 PL 种类分析表明，FLS 可部分导致人骨关节炎（OA）SF 中发现的 PL 水平升高。特别是 IL-1β刺激 PE 和基于 PE 的血小板质，它们可以作为细胞保护抗氧化剂。这些结果表明，在 OA 进展过程中，FLS 的 PL 组成发生改变，以适应新的疾病环境。
