Efeito antiproliferativo in vitro de macrófagos murinos (raw264.7) ativados por polissacarídeos sulfatados obtidos das algas marinhas vermelhas Gracilaria cornea J. Agardh e Solieria filiformis (Kützing) P.W. Gabrielson

Abstract

Marine seaweeds are sources of compounds with several biological activities described in the literature. Among these compounds, the most prominent are Sulfated Polysaccharides (SP). Studies with SP from red seaweeds Gracilaria cornea, Gracilaria birdiae and Solieria filiformis have demonstrated antinociceptive, anti inflammatory, antioxidant, antiviral and other activities. However, there are no studies investigating the stimulating potential of these SP in cells of the immune system to promote inhibition of tumor growth in vitro. Although cancer is characterized by the uncontrolled proliferation of transformed cells, malignant tumors are formed by a complex system of different cells (tumor and non-tumoral) that interact with each other to form a tumor microenvironment (MAT), which allows the growth and development of malignant cells. Among the non- tumor cells present in the MAT, the macrophages are highlighted. Tumor-associated macrophages (TAMs) have high phenotypic plasticity and may exhibit an antitumor (M1 - like) or pro-tumor (M2-like) profile. The activation of TAMs for M1-like phenotypes is a strategy that aims to assist in the treatment of malignant tumors. In this context, the SP of seaweeds can act as modifiers of the biological response potentiating the immune response against tumor cells. The aims of this work was to evaluate the stimulating effect of SP from G. cornea (Gco-SP), G. birdiae (Gbi-SP) and S. filiformis (Sfi-SP) on a murine macrophages strain RAW264.7, through the Griess assay, and investigate the in vitro antiproliferative potential of SP-stimulated macrophages supernatants against a murine metastatic melanoma (B16-F10) line by the SRB assay. Except for Gbi-SP, all samples were able to activate RAW264.7 (evidenced by increased nitrite production), and the SP- stimulated macrophages supernatants were able to inhibit the proliferation of B16 -F10. In addition, an increase of TNF-α, a proinflammatory cytokine associated with antitumor macrophage phenotypes, was detected in RAW264.7 supernatants when compared with negative control. Analysis of the antiproliferative effect by flow cytometry showed a decrease in the B16-F10 count, as well as a reduction of the percentage of these cells in the G2/M of the cell cycle phase, when compared with negative control. Changes in morphology (elevation of the cell populations with reduced size and with increased granularity) of B16-F10 were also observed, however, without compromising plasma membrane integrity. In this way, we conclude that the SP from red seaweeds G. cornea and S. filiformis showed macrophages stimulating effect in vitro presenting potential to act on TAMs activating them for antitumor phenotypes. Further studies are needed to understand the mechanisms of action involved in the activation of macrophages by SP and in the antiproliferative effect of SP-stimulated macrophages supernatants against B16-F10 cells.