Carrageenans from red algae may affect mice immune systems, finds study

05 Jan 2021 --- Carrageenans, biologically active polysaccharides isolated from red algae, have shown an express effect on the immune systems of mice.

Research conducted by Russian and Lithuanian scientists revealed that adding carrageenans to the diet of lab mice for one week reduced the activity of their congenital immunity cells and dropped their leukocyte count.

“Chemical substances isolated from marine algae are promising biologically active compounds, practically devoid of toxic properties,” study co-author Aleksandra Kalitnik from the School of Biomedicine, Far Eastern Federal University (FEFU), Vladivostok, Russia, tells NutritionInsight.

“We have been studying sulphated polysaccharides isolated from red algae for several years and we found a number of pronounced biological effects using different models in vitro as well as in vivo. This paper is a continuation of our previous research.”

Assessing the “surpressants”
It is still unclear whether the effect is good or bad, says Kalitnik. Although the research team has established carrageenans can suppress the activity of peritoneal phagocytes (abdominal immune cells) in mice, they cannot confirm carrageenans are immunosuppressants per se.

“Immunosuppressants are used to treat different disorders, such as allergies and autoimmune diseases, such as multiple sclerosis, systemic lupus erythematosus, rheumatoid arthritis, systemic scleroderma and dermatomyositis,” Kalitnik explains.

“Usually, these diseases are associated with the hyperactivation of some parts of the immune system or with the reduced production or functional activity of immunosuppressive cells.”

FEFU Center for Genomic and Regenerative Medicine (Credit: FEFU press office)Limited data on the mechanism of action
Because carrageenans of the red marine algae Chondrus armatus suppress phagocytotic activity of peritoneal macrophages, the researchers state this allows them to be viewed as pharmacologically active substances.

“The biological activity of high-molecular substances is largely determined by their structural features. Because of the high complexity of the macromolecular structure of these compounds, the data about the mechanism of their action are very limited,” Kalitnik explains.

Her research mirrors previous scientific findings suggesting that sulphated polysaccharides can interact with cell receptors on different cells directly.

“We also found in our previous research [the polysaccharides’] ability to bind receptors on phagocytic cells. Polysaccharides that are given orally manifest their immunological effects by acting receptors on immune cells located in the gastrointestinal (GI) tract.”

Testing the polysaccharides in mice
In a weeklong feeding experiment, the researchers demonstrated that, with an exception of one, all carrageenan samples at 100 μg/mL increased cellular motility and dose‐dependently decreased phagocytic activity.

The carrageenans did not affect the mice’s clinical appearance, body weight, liver weight, spleen or thymus or development of noticeable changes to their inner organs.

Moreover, all samples decreased murine peritoneal macrophages phagocytic activity, with λ‐samples possessing higher efficacy than their κ‐counterparts.

“Too soon” for carrageenans as drug
Carrageenans are used throughout the food industry as stabilizers, thickeners or jelly agents.

The polysaccharides are used in Roquette’s new pea starch technology Lycagel to create vegetarian capsules, but avoided in Ingredia’s Promilk B-Max functional protein to attract clean label-conscious consumers.

The microbial populations of the GI tracts of mice and humans are very different.When asked if the observed effects from the study mice could translate in human trials, Kalitnik explains that the microbial populations of the gastrointestinal (GI) tracts of mice and humans are very different.

“There is some data proving that carrageenan can be almost fully degraded in the GI tract of mice. But for the human organism, there are no enzymes in the human organism to digest these polysaccharides.”

According to Kalitnik, it is too soon to start thinking about developing a carrageenan-based immunosuppressive drug. The biological properties of carrageenans require further fundamental research that might take years.

The research team is planning to continue its research devoted to the pharmacological effects of carrageenans and their mechanisms once they secure additional funding.

“We would like to find out the way carrageenans influence cell receptors and signal paths that are involved in increasing and decreasing the leukocyte level,” she concludes.

“Such a study would help us better understand the potential of carrageenans as pharmacological substances or bio-additives that could reduce immune system hyperactivation.”

By Anni Schleicher

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