Abstract
The aim of this study was to determine the effects of glucosamine on matrix metalloprotease (MMP) production, on mitogen-activated protein kinase (MAPK) phosphorylation, and on activator protein (AP)-1 transcription factor activation in human chondrocytes. The human immortalized cell line lbpva55 and healthy human chondrocytes (obtained from healthy donors) were subjected to challenge with 10 ng/ml IL-1β after pretreatment with 2.5 or 10 mmol/l glucosamine. MMP mRNA expression levels were evaluated using quantitative real-time PCR, and MMP protein production levels were evaluated in the culture supernatant using ELISA. MAPK phosphorylation was evaluated using Western blotting. AP-1 transcription factor activation was evaluated by measuring AP-1 DNA-binding activity. After IL-1β stimulation, levels of MMP-1, MMP-3 and MMP-13 production were markedly increased. Treatment with 2.5 and 10 mmol/l glucosamine reduced expression of these metalloproteases. MMP expression is regulated by transcription factors such as the AP-1 complex, which is activated by phosphorylated MAPKs. IL-1β stimulated phosphorylation of c-jun amino-terminal kinase, p38 MAPK and extracellular signal-regulated kinase-1/2. Glucosamine inhibited c-jun amino-terminal kinase and p38 phosphorylation, and consequently c-jun binding activity. These findings demonstrate, for the first time, that glucosamine inhibits IL-1β-stimulated MMP production in human chondrocytes by affecting MAPK phosphorylation.
Highlights
The pharmacological treatment of osteoarthritis (OA), a joint disorder characterized by slow, progressive degradation of the cartilage, includes analgesic agents and nonsteroidal antinflammatory drugs
To address whether glucosamine can inhibit production of matrix metalloprotease (MMP) by affecting IL-1β-induced mitogen-activated protein kinase (MAPK) activation, we investigated the phosphorylation of c-jun amino-terminal kinase (JNK), p38 and extracellular signal-regulated kinase (ERK)1/2 after pretreatment with glucosamine and stimulation with IL1β
Consistent with quantitative realtime PCR findings, the ELISA assay demonstrated that levels of MMP-1 and MMP-13 protein secreted into the media were significantly decreased by 10 mmol/l glucosamine (P < 0.05; Figure 1c,d)
Summary
The pharmacological treatment of osteoarthritis (OA), a joint disorder characterized by slow, progressive degradation of the cartilage, includes analgesic agents and nonsteroidal antinflammatory drugs. Glucosamine was found to be effective in reducing joint space narrowing compared with placebo in clinical trials conducted over a period of 3 years [1,2,3,4]. Cartilage degradation in OA is due to an imbalance between synthesis and degradation of extracellular matrix components Proinflammatory cytokines, such as IL-1β, which are produced in OA, trigger several biological effects by stimulating mitogenactivated protein kinase (MAPK) phosphorylation. The latter results in activation of transcription factors [8,9,10], which in turn upregulate the production of several molecules such as matrix metalloproteases (MMPs) and aggrecanases. Increased enzymatic activity of MMPs and aggrecanases is the major factor responsible for matrix degradation [11,12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
