Effect of red seaweed sulfated galactans on initial steps of complement activation in vitro.

The research described here presents data on the effect of galactans of red algae, carrageenans (λ/µ/ν-, κ-, κ/ß-, and ι/κ-types), and agar on complement system activation in normal human serum. The experiments were based on well surfaces coated with triggering agents for binding initiating complement components -C3 and C4. The sulfated galactans inhibited C3 binding to lipopolysaccharide with direct dependence on the sulfation degree of polysaccharides. Sulfation degree was also important in carrageenans' capacity to reduce C4 binding to mannan. However, C4 binding to antibodies was considerably activated by carrageenans, especially with 3,6-anhydrogalactose. The gelling carrageenans were able to block antigen binding centers of total serum IgM and with more intensity than non-gelling. No structural characteristics mattered in ameliorating C5 cleavage by plasmin in extrinsic protease complement activation, but λ/µ/ν- and κ/ß-carrageenans almost completely inhibited C5 cleavage. Thus, galactans participated in cell surface biology by imitating surface glycans in inhibition of C3 binding and mannose binding lectin, but as to the tthe heclassical pathway these substances stimulated complement, probably due to their structure based on carrabiose.

Effect of carrageenans on some lipid metabolism components in vitro.

The research described here focused on the effect of sulfated red algal polysaccharides (κ-, κ/ß-, ι/κ-carrageenan) individually and in combination with lipopolysaccharide (LPS) on the synthesis of prostaglandin E2 (PGE2) and cytokines (interleukin [IL]-1ß and IL-6) in whole blood model in vitro. The results demonstrated that, at high concentrations, carrageenans have substantial ability to modulate PGE2 synthesis and stimulate IL-1ß and IL-6 synthesis. A low degree of sulfate and high molecular weight were a prerequisite for the ability of carrageenans to modulate PGE2 synthesis. Further, we investigated the ability of the carrageenans alone and in combination with casein to affect bile salt permeability through an artificial membrane imitating the gastrointestinal barrier. The least sulfated κ/ß-carrageenan could retain bile salt permeation the most but less efficiently than cholestyramine. The polysaccharides did not affect pancreatic lipase activity. Our data confirm a possible mechanism of the cholesterol-reducing properties of carrageenan.

Influence of carrageenan on cytokine production and cellular activity of mouse peritoneal macrophages and its effect on experimental endotoxemia.

The in vivo effect of κ/ß-carrageenan isolated from the red alga Tichocarpus crinitus on cytokine synthesis and cellular activity of murine peritoneal macrophages and also the protective effect of polysaccharides in LPS-induced endotoxemia in mice was studied. It was established that κ/ß-carrageenan given orally at a dose of 100 mg/kg stimulates the induction of anti-inflammatory cytokines (IL-10) in mouse blood cells by more than 2.5-fold compared with control, with no effect on pro-inflammatory cytokine (TNF-α) production. Pretreating mice with carrageenan once a day before injecting LPS increased the levels of IL-10 by 2.5-fold and reduced TNF-α production by 2-fold compared with control. So, κ/ß-carrageenan alone and in combination with LPS enhanced the cellular activity and mobility of peritoneal macrophages by increasing cell adhesion and migration compared with control. LPS activated cells intensively, sometimes resulting in their destruction by necrosis; carrageenan pretreatment reduced the excessive inflammatory cell activation caused by LPS. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1549-1557, 2017.