Lin Yi-Cheng, Liang Yu-Chih, Sheu Ming-Thau, Lin Yu-Chen, Hsieh Ming-Shium, Chen Tzeng-Fu, Chen Chien-Ho
Department of Orthopedics, Mackay Memorial Hospital, Taipei, Taiwan, ROC.
Rheumatol Int. 2008 Aug;28(10):1009-16. doi: 10.1007/s00296-008-0561-4. Epub 2008 Mar 14.
The purpose of the present study was to elucidate the possible signal transduction pathway involved in the underlying mechanism of glucosamine (GLN)'s influence on the gene expression of matrix metalloproteinases (MMPs) in chondrocytes stimulated with IL-1beta. Using chondrosarcoma cells stimulated with IL-1beta, the effects of GLN on the mRNA and protein levels of MMP-3, the activation of JNK, ERK, p38, NF-kappaB, and AP-1, the nuclear translocation of NF-kappaB/Rel family members, and PI3-kinase/Akt activation were studied. GLN inhibited the expression and the synthesis of MMP-3 induced by IL-1beta, and that inhibition was mediated at the level of transcription involving both the NF-kappaB and AP-1 transcription factors. Translocation of NF-kappaB was reduced by GLN as a result of the inhibition of IkappaB degradation. A slightly synergistic effect on the activation of AP-1 induced by IL-1beta was shown in the presence of GLN. Among MAPK pathways involved in the transcriptional regulation of AP-1, phosphorylation of JNK and ERK was found to increase with the presence of GLN under IL-1beta treatment, while that for p38 decreased. It was also found that GLN alone, but also synergistically with IL-1beta, was able to activate the Akt pathway. The requirements of NF-kappaB translocation and p38 activity are indispensably involved in the induction of MMP-3 expression in chondrosarcoma cells stimulated by IL-1beta. Inhibition of the p38 pathway in the presence of GLN substantially explains the chondroprotective effect of GLN on chondrocytes that regulate COX-2 expression, PGE(2) synthesis, and NO expression and synthesis. The chondroprotective effect of GLN through the decrease in MMP-3 production and stimulation of proteoglycan synthesis may follow another potential signaling pathway of Akt.
本研究的目的是阐明氨基葡萄糖（GLN）影响白细胞介素-1β（IL-1β）刺激的软骨细胞中基质金属蛋白酶（MMPs）基因表达的潜在机制所涉及的信号转导途径。使用IL-1β刺激的软骨肉瘤细胞，研究了GLN对MMP-3的mRNA和蛋白水平、JNK、ERK、p38、核因子κB（NF-κB）和活化蛋白-1（AP-1）的激活、NF-κB/Rel家族成员的核转位以及磷脂酰肌醇-3激酶（PI3-激酶）/蛋白激酶B（Akt）激活的影响。GLN抑制IL-1β诱导的MMP-3的表达和合成，且该抑制作用在转录水平上介导，涉及NF-κB和AP-1转录因子。由于抑制了IκB降解，GLN降低了NF-κB的转位。在有GLN存在的情况下，显示出对IL-1β诱导的AP-1激活有轻微的协同作用。在参与AP-1转录调控的丝裂原活化蛋白激酶（MAPK）途径中，发现在IL-1β处理下有GLN存在时，JNK和ERK的磷酸化增加，而p38的磷酸化减少。还发现GLN单独以及与IL-1β协同均能够激活Akt途径。NF-κB转位和p38活性的需求不可避免地参与了IL-1β刺激的软骨肉瘤细胞中MMP-3表达的诱导。在有GLN存在的情况下抑制p38途径基本上解释了GLN对调节环氧合酶-2（COX-2）表达、前列腺素E2（PGE2）合成以及一氧化氮（NO）表达和合成的软骨细胞的软骨保护作用。GLN通过减少MMP-3产生和刺激蛋白聚糖合成的软骨保护作用可能遵循Akt的另一条潜在信号途径。
