Sulfated Polysaccharide From Brown Algae Dictyota Caribaea Stimulates Macrophages To An Antitumoral Phenotype

Fucoidans are sulfated polysaccharides capable of exerting biological activities such as antitumor and immunomodulatory effects. Previous studies demonstrated the antitumor activity of non-cytotoxic fucoidan from the seaweed Dictyota caribaea (Dc-SP) in vivo. Macrophages (M{varphi}) are innate immune cells capable of promoting or inhibiting tumor growth depending on the stimulus. This study aimed to evaluate the immunostimulant activity of Dc-SP on murine M{varphi} (RAW264.7) in vitro. Dc-SP was assessed for its ability to modify cell viability and stimulate the production of antitumor markers on RAW264.7 cells. Dc-SP induced an increase (p<0.05) in the production of NO and cytokines TNF-, IL-1{beta}, and IL-10. The exposure of M{varphi} to Dc-SP also increased (p<0.05) the expression of M1 macrophage markers such as iNOS, CD86, and MHC II. The antiproliferative activity of RAW264.7 cells stimulated with DC-SP on melanoma cells (B16-F10) in vitro. Dc-SP did not exhibit direct cytotoxicity on B16-F10, however, the conditioned medium (CM) of RAW264.7 previously stimulated with Dc-SP (CM-Dc-SP) showed antiproliferative activity on tumor cells. B16-F10 incubated with CM-Dc-SP showed a cytostatic profile, tumor cells did not alter membrane integrity, however, suffered morphological changes such as cell shrinkage and high granularity. In conclusion, Dc-SP stimulated M{varphi} to an antitumor phenotype.