Increased dietary salt intake can induce a group of aggressive immune cells that are involved in triggering and sustaining autoimmune diseases, say an international team of researchers.
There has been a steady rise in the incidence of autoimmune diseases in the Western world and one hypothesis is that the increase is linked to environmental factors. Among the suspected culprits are changes in lifestyle and dietary habits in developed countries, where highly processed food and fast food are consumed daily. These foods tend to have substantially higher salt content and the researchers think this may be one of the factors driving the increased incidence of autoimmune diseases.
Previous research has shown that excess dietary salt can affect the immune system's macrophages (scavenger cells) and T helper cells. The researchers decided to investigate the effects on a specific subset of T helper cells that produce the cytokine interleukin 17 (Th17). Evidence is mounting that Th17 cells, apart from fighting infections, play a pivotal role in autoimmune diseases.
In cell culture experiments, the researchers showed that increased salt can lead to a dramatic induction of Th17 cells. "In the presence of elevated salt concentrations this increase can be ten times higher than under usual conditions," said Yale researcher Markus Kleinewietfeld. "Under the new high salt conditions, the cells undergo further changes in their cytokine profile, resulting in particularly aggressive Th17 cells."
The study, appearing in the journal Nature, showed that the high salt diet accelerated the development of helper T cells into pathogenic Th17 cells. The researchers also conducted a closer examination of these effects in cell culture experiments and showed that the increased induction of aggressive Th17 cells is regulated by salt on the molecular level.
"These findings are an important contribution to the understanding of multiple sclerosis and may offer new targets for a better treatment of the disease, for which at present there is no known cure," said co-researcher Ralf Linker, at University Hospital, Erlangen, Germany.
Besides multiple sclerosis, the researchers want to study psoriasis, another autoimmune disease related to Th17. Linker says the skin plays a key role in salt storage and also affects the immune system. "It would be interesting to find out if patients with psoriasis can alleviate their symptoms by reducing their salt intake," he concluded.
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Source: Helmholtz Association of German Research Centres