Intestinal uptake and immunological effects of carrageenan—current concepts

Abstract

Carrageenans are a group of high molecular weight sulphated polygalactans which find extensive use in the food industry as thickening, gelling and protein-suspending agents. Although there is no evidence to suggest that the persorption of small amounts of carrageenans across the intestinal barrier poses an acute toxic hazard, they are known to be biologically active in a number of physiological systems and extended oral administration in laboratory animals has been shown to modify both in vivo and in vitro immune competence. Whereas this effect could be attributed to carrageenan having a selective toxic effect on antigen-processing macrophages, additional studies suggest that macrophages can also influence immune responses by the timed release of immunoregulatory mediators. Evidence in support of this comes from in vitro studies which demonstrate that carrageenan-treated macrophages can, depending on conditions and time of administration, release either stimulatory or inhibitory factors. The former is known to be the immunostimulatory agent interleukin 1 (IL-1). The inhibitory factor, which is produced at an early stage following exposure to non-toxic doses of carrageenans, has yet to be formally identified but it is believed to be a prostaglandin because of its specific mode of action and short biological half-life. At present it is impossible to relate these studies to the human situation. Although it is established that carrageenans can cross the intestinal barrier of experimental animals, there is no evidence to suggest that the limited uptake that may occur in man in any way interferes with normal immune competence. Nevertheless, increased exposure may occur in the neonate during weaning, and adults and children following allergic reactions and episodes of gastrointestinal disease. Further studies under such conditions now seem warranted in order to elucidate the possible immunological consequences which may be associated with enhanced uptake of carrageenans in vulnerable groups.

Histological and Ultrastructural Changes of Cardiomyocytes in Experimental Rats with Tail Thrombosis following Subplantar Application of Carrageenin

“…Although the European Commission of Scientific Committee on Food stated that food-grade carrageenin is safe to use [2,3] , some earlier evidence from animal studies has demonstrated that degraded carrageenin, with a molecular weight of ^ 30,000, causes ulcerations and malignancies in the gastrointestinal tract [4] and affects incidence of mammary carcinoma [5] . Carrageenin, which can in limited amounts pass through intestinal barrier in experimental animals, may be harmless in healthy organisms, but it may become toxic in groups with disorders of the gastrointestinal tract [1] . The adverse effects of poligeenan (a product of acid hydrolysis in stomach) are ulcerations of intestinal mucosa [6][7][8] , or stimulating neoplastic effect [9] .…”

Toxicological properties of carrageenan

“…The tight junctions between the intestinal epithelial cells provide an efficient barrier to absorption of macromolecules, including food-grade carrageenans [13]. Uptake of macromolecules can occur via the macrophages of the gut-associated lymphoid tissue [13,21]. The presence of carrageenan in the macrophages or epithelial cells of the gut-associated lymphoid tissue is consistent with the normal process of antigen sampling by the gastrointestinal tract [11,21].…”

“…Some of the effects of systemic administration include acronecrosis, nephrotoxicity, hepatotoxicity, increased spleen weight, hematological changes and storage of carrageenan in the liver, kidney and macrophages (see 2,33,34). Intraperitoneal administration of carrageenan to laboratory animals at sufficient doses may produce reduced primary antibody responses to T-cell dependent antigens (see 21). Whether carrageenan administered orally has effects on the immune system is the subject of intense research.…”

Protective Effect of Carrageenan against Murine Cytomegalovirus Infection in Mice

“…Carrageenan (CAR) is a sulphated polygalactose extracted from red seaweeds, Chrondrus crispus, Gigartina stellata and various Euchema species (Nicklin and Miller, 1989). Currently, CAR is widely used in the food industry as a thickening, gelling, stabilizing and/or proteinsuspending agent.…”

“…Those include suppression of antibody production, cellular immunity, and delayed-type hypersensitivity and elongation of graft survival (Thomson and Fowler, 1981;Kolb et al, 1981). Additionally, CARtreatment led macrophages to release two contradictory immunoregulat ory mediators in vitro, interleukin-1 and prostaglandin (Nicklin and Miller, 1989).…”