US researchers have found that electronic cigarettes, often targeted at youth and pregnant women, produce a stress response in brain stem cells.
Present throughout life, stem cells become specialised cells with more specific functions, such as brain cells, blood cells, or bone.
"Although originally introduced as safer, ECs, such as Vuse and JUUL, are not harmless," said researchers.
"Even short-term exposure can stress cells in a manner that may lead, with chronic use, to cell death or disease. Our observations are likely to pertain to any product containing nicotine."
Using cultured mouse neural stem cells, the researchers identified the mechanism underlying EC-induced stem cell toxicity as "stress-induced mitochondrial hyperfusion," or SIMH.
"SIMH is a protective, survival response," researchers added.
"Our data show that exposure of stem cells to e-liquids, aerosols, or nicotine produces a response that leads to SIMH," researchers said.
Electronic cigarettes, or ECs, are nicotine-delivery devices that aerosolize nicotine and flavour chemicals through heating.
The high levels of nicotine in ECs lead to a nicotine flooding of special receptors in the neural stem cell membrane," they said.
"Nicotine binds to these receptors, causing them to open up. Calcium and other ions begin to enter the cell. Eventually, a calcium overload follows," they said.
Researchers explained that too much calcium in the mitochondria is harmful. The mitochondria then swell, changing their morphology and function.
They can even rupture and leak molecules that lead to cell death, according to the study published in the journal iScience.
"If the nicotine stress persists, SIMH collapses, the neural stem cells get damaged and could eventually die," they said.
"If that happens, no more specialised cells – astrocytes and neurons, for example – can be produced from stem cells."
Damaged stem cell mitochondria could accelerate aging and lead to neurodegenerative diseases, they noted.