Extraction, characterization and biological effects of polysaccharides from marine (micro)algae

Abstract

Resumo: Polissacarídeos purificados de algas marinhas possuem alto valor biotecnológico e apresentam diversas ações biológicas, incluindo atividade citotóxica, antiviral, anticoagulante, entre outras. Nesta tese, vários polissacarídeos foram isolados de algas e microalgas marinhas, caracterizados e quimicamente modificados para melhorar seus potenciais efeitos biológicos. O objetivo principal da tese foi caracterizar suas estruturas químicas e vinculá-las a potenciais efeitos biológicos. A B-D-glucana purificada de Conticribra weissflogii aumentou a atividade fagocítica de macrófagos. Vários polissacarídeos purificados de Isochrysis galbana induziram uma redução do metabolismo mitocondrial ao nível da glicólise, ciclo cítrico, aminoácidos e oxidação de ácidos graxos e reduziram a atividade metabólica geral das células de glioblastoma U251. Dados recentes mostraram um efeito citotóxico de células U87MG em resposta a polissacarídeos e correspondente heterorhammana purificada, oversulfatada de Gayralia brasiliensis. Nesta tese, foi investigado os efeitos desses polissacarídeos nas funções mitocondriais. Foi observada a polarização da membrana mitocondrial e o aumento da produção de ROS mitocondrial em resposta à aplicação desses polissacarídeos. Em conclusão, os polissacarídeos exercem vários efeitos biológicos nas células tumorais, e esses efeitos variam desde a morte celular até o metabolismo mitocondrial dependendo do modelo biológico, da estrutura química nativa ou da modificação estrutural induzida. Para estudos futuros, sugere-se investigar as vias moleculares dos polissacarídeos em relação a ligação a receptores e a regulação a proteínas.

Abstract: Polysaccharides purified from marine algae have high biotechnological value and exhibit various biological actions including cytotoxic activity, antiviral, and anticoagulant, among others. In this thesis, various polysaccharides were isolated from marine algae and microalgae, characterized and chemically modified to improve their potential biological effects. The main aim of the thesis was to characterize their chemical structures and link them to potential biological effects. B-D-glucan purified from Conticribra weissflogii enhanced phagocytic activity of macrophages. Several polysaccharides purified from Isochrysis galbana induced a reduction of the mitochondrial metabolism at the level of glycolysis, the citric cycle, amino acid, and fatty acid oxidation and reduced the overall metabolic activity of U251 glioblastoma cells. Recent data showed a cytotoxic effect of U87MG cells in response to polysaccharides and corresponding oversulfated heterorhamman purified from Gayralia brasiliensis. In this thesis, we further investigated the effects of these polysaccharides on the mitochondrial functions. We observed mitochondrial membrane polarization and increased mitochondrial ROS production in response to these polysaccharides application. In conclusion, polysaccharides exert various biological effects in tumor cells, and these effects vary from cell death to mitochondrial metabolism depending on the biological model, the chemical native structure or induced structural modification. For further studies, it would be worth investigating the molecular pathways of polysaccharides in relation to receptor binding and downstream protein regulation.

Samenvatting: Algen en microalgen hebben hoge biotechnologische waarde. Polysachariden hebben meerdere biologische effecten, zoals onder andere cytotoxische, antivirale en antistolling activiteit. Het doel van dit werk is om polysachariden uit algen en microalgen te isoleren, karakteriseren en chemisch te modificeren en hun immunostimulerende effect op macrofagen (RAW 269.7) en cytotoxische activiteit tegen glioblastoom cellen (U87MG en U251) te onderzoeken. De bestudeerde stammen waren: Conticribra weissflogii, Isocrysis galbana, en de zee-algen stam Gayralia brasiliensis. Chemische en spectroscopische analyse toonde dat microalgen stammen verschillende typen B-D-glucans hadden. Gayralia brasiliensis had een heterorhamman, en deze werd overgesulfateerd om de biologische activiteit te verhogen. Biologisch onderzoek gepresenteerd in deze thesis toonde dat B-D-glucan van Conticribra weissflogii een verhoogde fagocytotische activiteit van macrofagen van gist induceerde. Een interventie met Isochrysis galbana in mitochondrieel metabolisme op het niveau van glycolyse, de citroenzuurcyclus, aminozuren en B-oxidatie verlaagde de metabolische activiteit van U251 glioblastoom cellen. Eerdere data toonde dat Gayralia brasiliensis heterorhamman een cytotoxisch effect heeft op U87MG cellen. Verder onderzoek werd uitgevoerd om de effecten op de mitochondrien te bestuderen. Dit polysacharide kan de mitochondriele membraanpolarisatie en de mitochondriele ROS-productie bei'nvloeden, wat mogelijk de levensvatbaarheid van de cellen bei'nvloedt. In conclusie, polysachariden toonden verschillende biologische effecten op cellen, afhankelijk van het biologische model, de structuur van het natuurlijke polysacharide of de gemodificeerde structuur. Voor toekomstige studies is het interessant om te richten op moleculaire interacties tussen polysachariden en cellen.