Vape Smoke Linked to Brain Inflammation

Substances in popular vapes provoke inflammatory changes in multiple organs...
02 August 2022

Interview with 

Laura Crotty-Alexander, University of California, San Diego


The chemicals in vape smoke move into the bloodstream - that’s of course how the nicotine users crave gets in. But those other chemicals also make it into the nervous system and other organs, including the heart. So what effects do they exert there, if any? Laura Crotty-Alexander’s been trying to answer this question at the University of California San Diego, using laboratory mice…

Laura - Cigarette smoke contains about 7,000 chemicals, and that use of cigarettes leads to damage across the body - everywhere from your lips, where it first makes contact, all the way down to the GI tract and out to the skin and to the brain. And what we sought to find was whether e-cigarette aerosols could also impact all these different organs across the body. So we have this special setup where we take the mice and we put them in a little pie-shaped wedge container where they can move around. And then we use e-cigarettes that we have bought on regular websites and we give them a puff of e-cigarette aerosol and then regular air. And we have them breathe that in for 30 minutes, three times a day.

Chris - And is the mouse dose equivalent to what a human consuming these products would get? Or are the mice getting a much bigger impact and a bigger dose? Because obviously a human breath would be massive for a mouse...

Laura - We do try our best to design these mouse models to mimic human use, which is why we expose the mice multiple times a day, because a lot of humans use e-cigarettes throughout the day. And when we take one puff that's more human-sized, we actually put it into a large chamber where it diffuses. So 16 mice are breathing in that aerosol.

Chris - And how do you then marry up what that intake is doing in different parts of the body?

Laura - We actually harvest the mice and then we take all the different body parts. And we look at them using special tools that look at gene expression or levels of protein. And we actually even look at organ function. And so we use these different measures to try and determine whether inhaling these e-cigarette aerosols over months leads to changes in these organs.

Chris - And what crops up when you do this? Do you see systemic effects?

Laura - Yes. So I was very surprised that we found profound changes in the brain in particular of these mice that inhaled JUUL mint and JUUL mango, which are two flavours that were very popular at the time we started this study. And both of those aerosols led to inflammation in the brain, which is shocking because the brain is a protected compartment. So it was very worrisome that inhaling the e-cigarette aerosols for just a month led to very impressive levels of inflammation in a part of the brain that controls mood and behaviour and memory.

Chris - Are you saying that it's specifically the flavours that are doing that? So this is an effect beyond the addictive qualities of the nicotine and so on?

Laura - In the brain, the fact that we saw similar changes in both flavours indicated more that it was the nicotine and the other substances at the core of these e-liquids that were driving the changes. But, for example, in the heart, we found that the mint flavour really changed and drove inflammation, whereas the mango flavour did not. And so that comparison helped us to understand that maybe the heart effects are maybe particularly driven by the mint flavour and not the nicotine and other components.

Chris - We'll come on in a second to what the impact of that might be, but just considering for a minute the fact you've got this effect, how does it compare in scale with if the mice were just (if mice could) smoking normal cigarettes?

Laura - If I were to look back at the historic data, I would say that the neurologic effects are of a scale that appears to be either equal to, or greater than, what is seen in conventional tobacco, and that the effects are different.

Chris - We believe that chronic inflammation might be linked to at least the progression, if not in some cases the cause, of certain neurodegenerative conditions and probably also degeneration in other organs. So do you think then that this is indicative of the fact that people doing this could be speeding up the ageing process of their brain? They're effectively bringing forward the age at which they may well succumb to degenerative conditions of the nervous system?

Laura - I absolutely agree that that is a concern. And, in addition, the changes in these parts of the brain suggest that people who are using e-cigarettes may have more anxiety and depression and might have sort of permanent changes to their behaviour patterns.


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