Background Chondroitin sulfate (CS), an interesting candidate for the therapeutic treatment of osteoarthritis (OA), has been shown in clinical trials to reduce swelling and effusion in knee OA.

Objectives We thus aimed to further investigate the effect of CS alone or in combination with glucosamine sulfate (GS), an anti-COX-2 (celecoxib), or acetaminophen on some synovial membrane anti-angiogenic and inflammatory factors.

Methods Treatment with CS (200 μg/ml; CSbBio-Active®, Bioibérica, Spain), GS (5 mM),celecoxib or acetaminophenalone, and CS in combination with the other mentioned products was investigated on human OA synovial fibroblasts in the presence or absence of IL-1β at 10 and 100 pg/ml. To determine whether CS has an additional effect with celecoxib or acetaminophen, preliminary experiments were performed to find concentrations of these products that induced about a 50% reduction in prostaglandin E₂ production under IL-1β at 100 pg/ml. A concentration of 10 nM was found for celecoxib and 25 μM for acetaminophen.The expression levels (real time PCR) and/or protein production of vascular endothelial growth inhibitor (VEGI),thrombospondin-1 (TSP-1),hyaluronic acid (HA), secreted phospholipase A2 (sPLA2), and cytosolic phospholipase A2 (cPLA2) were determined using specific primers (expression) and ELISAs (protein).

Results On the anti-angiogenic factors VEGI and TSP-1, IL-1β dose-dependently decreased their levels. On cells under basal conditions or treated with IL-1β, CS significantly induced the levels of VEGI expression and TSP-1 production. All the other products tested (GS, celecoxib, and acetaminophen) alone had no effect or decreased these anti-angiogenic factors, but in conjunction with CS their levels were significantly increased. HA production was slightly but significantly increased by IL-1β at 10 pg/ml and a heightened induction was found at 100 pg/ml. CS significantly increased HA under basal conditions and in the presence of IL-1β at 10 pg/ml. GS had no effect and celecoxib and acetaminophen significantly decreased it. Concomitant incubation of CS with GS, celecoxib, or acetaminophen significantly increased HA production. Interestingly, sPLA2, which is considered an anti-inflammatory (resolving) factor, demonstrated a significant decrease under IL-1β. Incubation with CS alone and in conjunction with celecoxib or acetaminophen significantly increased its level. The inflammatory factor cPLA2 showed significantly decreased expression levels by CS, GS, and the combination of CS and GS. IL-1β markedly and significantly increased it at both concentrations and under IL-1β, CS alone had no effect, but in combination with GS, its level was significantly reduced.

Conclusions The anti-inflammatory effect of CS appears to occur through a number of mechanisms including the increased level of the anti-angiogenic factors TSP-1 and VEGI as well as sPLA2, a factor associated with an anti-inflammatory effect, and through increasing HA production and decreasing cPLA2. Importantly, these effects of CS occurred in the presence of other products, even though those products alone had no or a reverse effect.

Disclosure of Interest None Declared