Hsueh MF, et al. - In the present study, the anti-inflammatory impacts of clinically relevant naproxen sodium (Nx) concentrations on human monocyte-derived macrophages in a controlled in vitro system and human primary synovial fluid (SF) cells were examined. Researchers differentiated THP-1 human monocytic cells into mature monocyte-derived macrophages in vitro then treated with Nx pre- or post-activating an inflammatory response with lipopolysaccharide (LPS) and hyaluronan (HA) fragments (n=8/group) using phorbol 12-myristate 13-acetate. The study analyzed cell culture supernatants for NF-κB activity and prostaglandin E2 (PGE2), indicating cyclooxygenase enzyme activity. Inflammation of THP-1 monocytic and primary human SF cells was produced by LPS/HA. The results showed that low dose Nx both prevented and decreased inflammatory responses of a human monocytic cell line and decreased IL-1β production by primary human SF monocytes and macrophages.