AB0072 Evaluation of anti-inflammatory effects of naproxen sodium on human osteoarthritis synovial cells
Authors: M.-F. Hsueh, V.B. Kraus
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> 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 OA<sup>1</sup>. 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 OA<sup>2, 3</sup>. Naproxen pre-treatment reduces inflammatory responses of chondrocytes. However, the effects of naproxen sodium on human OA synovial cells are not well known. <h3>Objectives</h3> 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 <i>in vitro</i>. <h3>Methods</h3> The immortalised human monocytic cell line, THP-1, was grown and differentiated into mature macrophages using phorbol 12-myristate 13-acetate as described previously<sup>4</sup>. 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 E<sub>2</sub> (PGE<sub>2</sub>). 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. <h3>Results</h3> 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 PGE<sub>2</sub> production, was reduced to basal levels by as little as 28.2 mg/L naproxen sodium (p&lt;0.05) when cells were treated either before or after the activation. Primary human SF cells treated with LPS/HA showed a striking increase in cytokine secretion ranging from 50-fold (IL-8) to 600-fold (IL-6). Cytokine production was reduced by naproxen sodium but a rebound phenomenon was observed for the highest concentration of 55/mg/L, which may indicate the cell stress response. *p&lt;0.05 for post-hoc test using placebo as control. *p&lt;0.05 for post-hoc test using placebo as control. <h3>Conclusions</h3> Naproxen sodium at low dose can both prevent and reduce inflammatory responses of a human monocytic cell line and primary human SF cells <i>in vitro</i>. These results highlight the potent activity of the OTC dose of naproxen sodium to dramatically reduce PGE<sub>2</sub>, NF-κB activity and cytokine production. <h3>References</h3> [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. <h3>Disclosure of Interest</h3> M.-F. Hsueh Grant/research support from: Bayer HealthCare, V. Kraus Grant/research support from: Bayer HealthCare