Mobasheri A, Richardson S, Mobasheri R, Shakibaei M, Hoyland J A
Molecular Pathogenesis and Connective Tissue Research Groups, Faculty of Veterinary Science, University of Liverpool, UK.
Histol Histopathol. 2005 Oct;20(4):1327-38. doi: 10.14670/HH-20.1327.
Articular cartilage is an avascular connective tissue in which the availability of oxygen and glucose is significantly lower than synovial fluid and plasma. Glucose is an important metabolic fuel and structural precursor that plays a key role in the synthesis of extracellular matrix macromolecules in articular cartilage. However, glucose concentrations in cartilage can fluctuate depending on age, physical activity and endocrine status. Chondrocytes are glycolytic cells and must be able to sense the quantities of oxygen and glucose available to them in the extracellular matrix and respond appropriately by adjusting cellular metabolism. Consequently chondrocytes must have the capacity to survive in an extracellular matrix with limited nutrients and low oxygen tensions. The molecular mechanisms responsible for allowing chondrocytes to adapt to these harsh environmental conditions are poorly understood. In this article we present a novel "dual" model of oxygen and glucose sensing in chondrocytes based on recent experimental data. This model incorporates the hypoxia-inducible factor alpha (HIF-1alpha) as an oxygen sensor and the hypoxia responsive facilitative glucose transporters, GLUT1 and GLUT3 as putative components of the glucose sensing apparatus in chondrocytes. Recent studies have shown that GLUT1 and GLUT3 are both expressed in chondrocytes and their HIF-1alpha-mediated transcription may be dually stimulated in response to hypoxia and low glucose conditions which in turn promote anaerobic glycolysis in favor of oxidative phosphorylation. This working model provides, for the first time, a unifying hypothesis to explain how chondrocytes might sense and respond to low oxygen tensions and alterations in extracellular glucose.
关节软骨是一种无血管的结缔组织,其中氧气和葡萄糖的可利用性显著低于滑液和血浆。葡萄糖是一种重要的代谢燃料和结构前体,在关节软骨细胞外基质大分子的合成中起关键作用。然而,软骨中的葡萄糖浓度会因年龄、身体活动和内分泌状态而波动。软骨细胞是糖酵解细胞,必须能够感知细胞外基质中可利用的氧气和葡萄糖量,并通过调节细胞代谢做出适当反应。因此,软骨细胞必须有能力在营养有限和低氧张力的细胞外基质中存活。目前对软骨细胞适应这些恶劣环境条件的分子机制了解甚少。在本文中,我们根据最近的实验数据提出了一种新的软骨细胞氧气和葡萄糖感知“双重”模型。该模型将缺氧诱导因子α(HIF-1α)作为氧气传感器,将缺氧反应性易化葡萄糖转运蛋白GLUT1和GLUT3作为软骨细胞葡萄糖传感装置的假定组成部分。最近的研究表明,GLUT1和GLUT3均在软骨细胞中表达,它们的HIF-1α介导的转录可能在缺氧和低糖条件下受到双重刺激,进而促进无氧糖酵解以利于氧化磷酸化。这个工作模型首次提供了一个统一的假设,来解释软骨细胞如何感知并应对低氧张力和细胞外葡萄糖的变化。