GALACTO-OLIGOSACCHARIDES, ANTAGONIZE TOXIC EFFECTS OF ENTEROHAEMORRHAGIC ESCHERICHIA COLI ON CULTURED CELLS AND BRINE SHRIMP MODEL.

HUGO, A. A.; BUGALLO, AIXA; RAMOS, VICTORIA; PALERMO, MARINA

Mar del Plata

Congreso; Reunión Anual de Sociedades de Sociedades de Biociencias; 2022

Enterohaemorrhagic Escherichia coli (EHEC) is a food-borne zoonotic pathogen, responsible for bloody diarrhea, enterocolitis and hemolytic uremic syndrome. The main virulence factors responsible for disease development are Shiga toxins. Galacto oligosaccharides (GOS) are prebiotic compounds, with capacity to increase the number of beneficial microbes in the intestinal tract. They are composed of a variable number of galactose units linked to a glucose unit, forming di, tri tetra or pentasacharides.The aim of this work is to evaluate the inhibitory capacity of different GOS formulations against toxic effect of Shiga toxin using in vitro models of Vero cells and Artemia salina. Biological activity of Shiga toxin (recombinant Stx2) was tested, in the presence or not of GOS, using Vero cells (LDH assay and crystal violet staining) and brine shrimp (lethality test). In Vero cells, GOS formulations exhibited a protection between 30% and 50% when GOS were added at a concentration ranging from 4% to 2%. Inhibitory effect was assayed with different GOS concentrations and fitted to a dose response curve. Formulations with higher percentage of GOS showed the highest protection. In the brine shrimp assay, nauplii decreased their viability in the presence of Shiga toxin, and the incubation with GOS at 4% and 2% GOS significantly reduced their mortality. Results revealed the capacity of GOS to antagonize the biological effect of Shiga toxin on Vero cells and the brine shrimp model. This protective effect could be ascribed to the interaction of the galactose units of GOS with the Shiga toxin. In fact, the globotriaosylceramide-3 (Gb3) receptor of the Shiga toxin is a ceramide trihexose formed by the alpha linkage of galactose to lactosyl-ceramide. The galactose units of GOS may bind to the toxin thus acting as a competitive inhibitor avoiding binding to receptors on the surface of eukaryotic cells. Our findings suggest the potentiality of GOS for antagonizing biological activity of bacterial toxins by competition with Gb3 receptors.