Anti-inflammatory effect of a sulphated polysaccharide fraction extracted from the red algae Hypnea musciformis via the suppression of neutrophil migration by the nitric oxide signalling pathway

Objectives The aim of this study was to evaluate the anti‐inflammatory effect of a sulphated polysaccharide fraction (PLS) extracted from the alga Hypnea musciformis and investigate the possible involvement of the nitric oxide (NO) pathway in this effect. Methods The anti‐inflammatory activity of PLS was evaluated using inflammatory agents (carrageenan and dextran) to induce paw oedema and peritonitis in Swiss mice. Samples of paw tissue and peritoneal fluid were removed to determine myeloperoxidase (MPO) activity, NO3/NO2 levels, and interleukin‐1β (IL‐1β) level. The involvement of NO in the modulation of neutrophil migration in carrageenan‐induced paw oedema or peritonitis was also investigated. Key findings Compared with vehicle‐treated mice, mice pretreated with PLS (10 mg/kg) inhibited carrageenan‐induced and dextran‐induced oedema; it also inhibited total and differential peritoneal leucocyte counts in a model of peritonitis. These PLS effects were reversed by l‐arginine treatment and recovered with the administration of a NO synthase blocker (aminoguanidine). Furthermore, PLS reduced the MPO activity, decreased IL‐1β levels, and increased NO3/NO2 levels in the peritoneal cavity. Conclusions PLS reduced the inflammatory response by modulating neutrophil migration, which appeared to be dependent on the NO pathway.