Phytic acid modulates in vitro IL-8 and IL-6 release from colonic epithelial cells stimulated with LPS and IL-1beta

Phytic acid (PA), a major fiber-associated component of wheat bran and legumes, is physiologically present in the human large gut. The aim of this study was to examine the role of PA in immunologic function of intestinal epithelial cells by analyzing its effect on interleukin (IL)-8 and IL-6 secretion by colonocytes and its role in the response of these cells to bacterial lipopolysaccharides (LPS) and IL-1beta. The human colon cell line Caco-2 was exposed to LPS isolated from two strains of Desulfovibrio desulfuricans, wild intestinal and type soil strains, as well as to LPS from E. coli. Cells were also treated with IL-1beta and with a combination of LPS and IL-1beta. PA had a suppressive effect on IL-8 basal release and it dose dependently reduced IL-8 secretion by colonocytes stimulated with LPS and IL-1beta. On the contrary, PA increased constitutive IL-6 secretion and exhibited differentiated effects on LPS responsiveness of cells depending on its concentration and LPS origin. PA was also an efficient down-regulator of IL-6 secretion stimulated by binary actions of LPS and IL-1beta. The ability of PA to modulate IL-8 and IL-6 release suggests that PA present in the intestinal milieu may exert immunoregulatory effects on colonic epithelium under physiological conditions or during microbe-induced infection/inflammation in order to maintain the colonic mucosa in a noninflammatory state or to counteract infection.