Dual role of dextran sulfate 5000 Da as anti-apoptotic and pro-autophagy agent

Dextran sulfate 5,000 Da (DS), a sulfated polysaccharide, has been used in recombinant mammalian cell cultures to prevent cell aggregation, thereby increasing cell viability. Previous studies using Chinese hamster ovary (CHO) suspension cultures had shown that low concentrations of DS are related to an inhibition of apoptosis. In this study, DS was used on anchorage-dependent CHO cells producing erythropoietin (EPO), in order to investigate the effect of this molecule on anti-apoptotic and pro-survival cellular pathways. DS 5,000 Da treatment was shown to prolong the life of cells and increase productivity of EPO by 1.8-fold comparing with controls, in standard batch conditions. At a molecular level, we show that DS inhibits apoptosis by DNA fragmentation delay and decrease of annexin V-labeled cells, causes a G0/G1 cell cycle arrest, decreases p53 expression and increases the pro-survival factor Hsc70 expression. DS treatment also resulted in an enhanced LC3-I to LC3-II conversion and increased autophagosomes formation employing tagged-LC3. Our data show, for the first time, that low doses of DS may promote autophagy in different cell lines. These findings suggest that a better understanding and manipulation of phenomenon of autophagy could be of crucial importance in the bio-pharmaceutical industry, in particular in the field of protein production.