New insights into how too much salt disrupts immune cell function
A new study is offering novel insights into the effects of too much salt on certain immune cells. The research reveals how salt can dampen mitochondrial functions, disrupting normal immune cell activity and potentially promoting inflammation.
The relationship between salt and cardiovascular disease is well-known. It’s clear how a high-salt diet can lead to hypertension but recently researchers have started to investigate how salt influences immune system function.
A few years ago researchers discovered that elevated levels of sodium in the blood disrupted the normal functions of monocytes, a type of immune cells that circulates in the body before migrating into tissues and transforming into a more complex immune cell. This new study set out to understand exactly how salt was altering this process.
The new research found excessive salt levels can dampen mitochondrial activities in our immune cells. Mitochrondia are present in almost all cells in the human body and are a little like tiny power plants. One of their main functions is to produce a molecule called adenosine triphosphate (ATP), through a series of chemical reactions called the respiratory chain.
ATP is the body’s universal fuel source. When it is not effectively produced within monocytes, these vital immune cells do not mature normally. And it is through disrupting this mechanism that salt can cause alterations to normal immune system functions.
“The fundamental finding of our study is that a molecule as small as the sodium ion can be extremely efficient at inhibiting an enzyme that plays a crucial role in the respiratory chain,” says Kempa. “When these ions flood into the mitochondria – and they do this under a variety of physiological conditions – they regulate the central part of the electron transport chain.”
Alongside these in vitro experiments the researchers set out to study this mechanism in human subjects. One experiment involved healthy subjects eating a pizza containing 10 grams of salt. Blood was taken from the subjects three and eight hours after eating.
Studying monocytes in the blood samples the researchers found mitochondrial activity was dampened three hours after eating the mean high in salt. But interestingly, the mitochondria largely returned to normal by the eight-hour mark.
“That’s a good thing,” notes Dominik Muller, another author on the new study. “If it had been a prolonged disturbance, we’d be worried about the cells not getting enough energy for a long time.”
What this suggests is that excessive salt intake may acutely influence mitochondrial activity, but only temporarily. So any long-term disruption to immune function may only become apparent through chronic high salt consumption.
Markus Kleinewietfeld, another researcher working on the study, says the next step is to investigate whether this mitochondrial mechanism is altered by salt in types of cells other than immune cells. He believes it is highly likely excessive salt intake influences all cells in this way and this new research is a confirmation that too much salt is certainly bad for our health.
“Of course the first thing you think of is the cardiovascular risk,” says Kleinewietfeld. “But multiple studies have shown that salt can affect immune cells in a variety of ways. If such an important cellular mechanism is disrupted for a long period, it could have a negative impact – and could potentially drive inflammatory diseases of the blood vessels or joints, or autoimmune diseases.”
The new research is published in the journal Circulation.