l-Glutathione enhances antioxidant capacity of hyaluronic acid and modulates expression of pro-inflammatory cytokines in human fibroblast-like synoviocytes.

Intra-articular injection of hyaluronic acid (HA) has been widely accepted for the treatment of osteoarthritis (OA) in early stage. l-Glutathione (GSH), an antioxidant, has an anti-inflammatory effect on protecting cells from reactive oxygen species and reactive nitrogen species (ROS/RNS). In this study, the therapeutic effects of HA (0.1%) supplemented with GSH (0, 5, 10, and 20% in weight ratios to HA) on human fibroblast-like synoviocytes (FLSs) were evaluated. The results showed that cell morphology and glycosaminoglycan production of FLSs were not changed under treatments. However, the addition of HA + 20% GSH significantly decreased cell survival (p < 0.001) relative to other groups. Relative to un-stimulated FLSs, interleukin-1 beta (IL-1β) stimulation significantly decreased the total antioxidant capacity (p < 0.001) of cells. The antioxidant capacity was restored and the intracellular ROS/RNS was decreased in HA or HA + GSH-treated FLSs. Real-time PCR analysis revealed the mRNA levels of IL-1β, tumor necrosis factor-alpha, and matrix metalloproteinase-3 were down-regulated significantly (all p < 0.05) when FLSs cultured in HA or HA + GSH. IL-6 mRNA expressions were down-regulated significantly in HA and HA + 5% GSH groups (both p < 0.05) but up-regulated when HA supplemented with 10% and 20% GSH (both p < 0.01). In addition, the protein levels of IL-1β were further decreased with significant differences (both p < 0.05) in the HA + 10% GSH and HA + 20% GSH groups when compared to FLSs cultured in normal medium. In conclusion, HA supplemented with GSH improves antioxidant capacity and modulates pro-inflammatory cytokines expressions in FLSs. GSH has the potential to augment the effect of viscosupplementation using HA on OA patients.