AB0072 Evaluation of anti-inflammatory effects of naproxen sodium on human osteoarthritis synovial cells

Background Inflammation is increasingly recognised as an essential factor in the pathogenesis and progression of osteoarthritis (OA). Etarfolatide imaging for activated macrophage quantification in knee joints confirms a high prevalence (~70%–80%) of joint inflammation in association with OA1. Naproxen sodium is a non-steroidal anti-inflammatory drug that is widely available over-the-counter (OTC) and has been shown to be effective in different pain models including OA2, 3. Naproxen pre-treatment reduces inflammatory responses of chondrocytes. However, the effects of naproxen sodium on human OA synovial cells are not well known. Objectives Evaluate the ability of naproxen sodium to block the inflammatory responses and to reduce the activated inflammatory responses of a human monocyte cell line and primary human synovial fluid (SF) cells in vitro. Methods The immortalised human monocytic cell line, THP-1, was grown and differentiated into mature macrophages using phorbol 12-myristate 13-acetate as described previously4. Mature macrophages were treated with various concentrations of naproxen sodium two hours before or 24 hours after inducing an inflammatory reaction using lipopolysaccharide (LPS) and hyaluronan (HA) fragments (n=8/group). After a further 24 hours, the cell culture supernatants were assessed for NF-κB activity, pro-inflammatory cytokines (IL-1β, IL-6, IFN-γ, and TNF-α), and prostaglandin E2 (PGE2). Cell viability was assessed using PrestoBlue reagent. Primary human SF cells were collected at the time of knee joint replacement for OA and treated 24 hours with naproxen sodium with and without the addition of LPS/HA (n=2/group). All results were expressed as fold change from the negative control (media only) after normalisation for cell viability. One-way ANOVA with Dunnett’s post-hoc tests were done using GraphPad Prism. Results Compared to the placebo group, NF-κB activity of THP-1 cells was significantly reduced by as little as 28.9 mg/L naproxen sodium (corresponding to a trough plasma concentration achieved by a daily oral dose of 55 mg naproxen sodium) when added before or after the activation by LPS/HA (84% and 78% NF-κB activity reduction, respectively) (Fig1). When cells were treated before the activation with 33 mg/L naproxen sodium (corresponding to the concentration achieved by a 220 mg daily OTC dose), NF-κB activity was reduced 79% and IL-6 secretion was reduced by 77%. Cyclooxygenase enzyme activity, represented by PGE2 production, was reduced to basal levels by as little as 28.2 mg/L naproxen sodium (p *p *p Conclusions Naproxen sodium at low dose can both prevent and reduce inflammatory responses of a human monocytic cell line and primary human SF cells in vitro. These results highlight the potent activity of the OTC dose of naproxen sodium to dramatically reduce PGE2, NF-κB activity and cytokine production. References [1] Kraus VB. Osteoarthritis Cartilage2016;24(9):1613–21. [2] Golden HE. Am J Ther2004;11(2):85–94. [3] Schiff M. J Rheumatol2004;31(7):1373–83. [4] Stabler TV. Osteoarthritis Cartilage2017;25(1):166–174. Disclosure of Interest M.-F. Hsueh Grant/research support from: Bayer HealthCare, V. Kraus Grant/research support from: Bayer HealthCare