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Too Much Salt May Trigger Autoimmune Diseases
For the past few decades, health officials have been reporting increases in the incidence of autoimmune diseases, such as multiple sclerosis (MS). Now researchers at Yale Medical School, Harvard Medical School, and the Broad Institute have identified a prime suspect in the mystery — dietary salt.
In the March 6 issue of Nature, Yale researchers showed that salt can induce and worsen responses of the pathogenic immune system in mice and that these responses are regulated by genes already implicated in a variety of autoimmune diseases.
In accompanying papers in the same issue of Nature, researchers at Brigham and Women’s Hospital and at Harvard Medical School identified the key molecular pathway involved in the response to salt, and the investigators at Broad Institute sketched out the regulatory network of genes that governs this autoimmune response.
“These are not diseases of bad genes alone or diseases caused by the environment, but diseases of a bad interaction between genes and the environment,” said Dr. David Hafler, senior author of the Yale paper.
The research was inspired, in part, by an observation that eating at fast-food restaurants tended to trigger an increase in the production of inflammatory cells, which are mobilized by the immune system to respond to injury or pathogens but which, in autoimmune diseases, attack healthy tissue. Researchers at Yale and colleagues in Germany wanted to know whether a high salt content in the diet might induce the destructive immune system response that is the hallmark of autoimmunity.
They found that adding salt to the diet of mice induced the production of a type of T cell previously associated with autoimmune diseases and that mice on high-salt diets developed a more severe form of an animal model of MS — experimental autoimmune encephalomyelitis.
The new research expands the understanding of how one type of immune cell — known as a T-helper 17 (Th17) cell — develops, and how its growth influences the development of other cells involved in the immune system. Reconstruction of this molecular circuitry confirmed the surprising role of salt, said the researchers.
Hafler noted that all test-tube cell biology is performed based on the salt levels found in blood and not in the tissues where immune cells ultimately travel to fight infections. That may have been a reason why salt’s role in autoimmunity has gone undetected.
Source: Yale University; March 6, 2013.