l-glutamine regulates the expression of matrix proteins, pro-inflammatory cytokines and catabolic enzymes in interleukin-1beta-stimulated human chondrocytes

• l-glutamine (Gln) prevents the hypertrophic transformation and corrects proliferation rate of IL-1β-stimulated chondrocytes.
• Gln downregulates type I collagen, IL-1β, TNF-α, restores aggrecan and upregulates the TIMP-1 mRNA expressions in stimulated chondrocytes.
• Gln decreases IL-1β and improves TIMP-1 protein productions.
• Gln possesses anti-inflammatory and structure-protective properties.

Osteoarthritis (OA) of the knee is a major cause of mobility impairment. A number of studies demonstrated the therapeutic effect of l-glutamine (Gln) on different cells and tissues. However, little research has addressed the potential use of Gln on the treatment of OA. In this study, the regulation of Gln on OA-related mRNA expression and cytokine production in chondrocytes was evaluated. Human chondrocytes were stimulated with interleukin-1β (IL-1β) and subsequently cultured in Gln-supplemented medium. The results showed that Gln prevented the hypertrophic transformation and promoted the proliferation rate of IL-1β-stimulated chondrocytes. Gln also downregulated the mRNA expressions of type I collagen, IL-1β, and tumor necrosis factor-alpha (TNF-α) in stimulated cells. In addition, Gln restored the aggrecan and upregulated the TIMP-1 expressions. However, the matrix metalloproteinase-3 (MMP-3) and MMP-9 levels were highly expressed in IL-1β-stimulated chondrocytes and Gln treatment did not show any effects. Although Gln decreased the protein productions of IL-1β and TNF-α, the MMP-3 still highly produced. However, the production of tissue inhibitor of metalloproteinase-1 significantly increased. Our results suggest that Gln possesses anti-inflammatory and structure-protective properties in terms of preventing the hypertrophic transformation, regulating the productions of matrix proteins and catabolic enzymes in human chondrocytes.

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