Fruity vapes paralyse lung's immune system

A new study has found that berry-flavoured vapes can paralyse the action of immune cells that normal patrol the lungs and prevent infection. The study - which has just been published in the journal PNAS - and was conducted on experimental lab mice - is the work of Erika Penz at the University of Saskatchewan and Ajitha Thanabalasuriar at McGill University. Ajitha began by explaining how they ended up looking into this…

Ajitha - It really hit us in 2019 where there was this outbreak of e-cigarette related lung injury in teenagers. And one is the type of e-cigarette products that kids were drawn to. And that was marketed for them really, the fruity flavours and the candy flavours. And we thought, what specifically do these flavours do to our immune system?

Chris - What happened to those kids? What did they present with?

Ajitha - They presented with lung injury. So essentially they would go into the hospital and they looked like they had a flu infection, but when they did a test they came out negative for the influenza virus. And a large portion of these individuals who got sick, who got very sick or actually passed away, were in the US. And at the time there were a lot of studies done in the US and they kind of chalked it down to this one part of e-cigarettes called vitamin E acetate that was in their e-cigarette product. And since then they've banned vitamin E acetate from e-cigarettes and they've had fewer of these lung injuries and young kids. But the thing that was interesting is that vitamin E acetate was never allowed in e-cigarette products in Canada. And we also had those lung injury cases. And again, there were smaller proportions, but it still made us think there was something else to this story that we weren't catching yet.

Chris - So how did you pursue it?

Ajitha - My lab really focuses on something called intra vital microscopy we're actually able to image immune cells moving through the lungs of a live animal. And then Erika came in and she sort of suggested that we look at specific flavours that were really popular with kids. And so we focused on this like berry mixed flavour and we compared that to an unflavoured e-cigarette vape. And we looked to see how these mice responded to exposure to the e-cigarette products. And our outcome was this imaging technique where we were able to actually track these cells called macrophages, which are white blood cells in your airways, and we're able to see how they move around in the presence and absence of this flavoured e-cigarette product.

Chris - All I can see in my mind's eye at the moment is a mouse vaping. How do you do that?

Ajitha - So it's not exactly the same as humans. So humans can actually physically take in a puff from an e-cigarette device. Whereas with mice it's more of a passive treatment. So basically we put our animals into these little cages and then we expose them to an e-cigarette that's puffed through a machine and it just sort of blows it onto the animals and they inhale it passively. So it's more like secondhand smoke. And so what we did with the animals was that we exposed them to the e-cigarettes for one hour a day every day for three to 10 days. And we just really looked to see if there were subtle changes in our immune system.

Chris - So when you say you can see the cells, do you mean you can actually see the cells moving through blood vessels and tissues and then track what goes where?

Ajitha - Exactly. So our lungs have these spaces called alveolar spaces and they're essentially like these grape-like structures that are strung together and that's where our gas exchange occurs. And in those alveolar spaces we have these really important immune cells called alveolar macrophages. And what's interesting is that there are more alveolar spaces than alveolar macrophages and these macrophages are tasked with patrolling around each alveolar space and checking if there's anything that you inhale that's bad for you. The air we breathe is not sterile, it's filled with particulates, it's filled with bacteria and usually they are cleared by either inner nose, the mucus in our upper respiratory tract. But sometimes things do get down into our alveoli and these macrophages gobble them up. And their ability to do that relies on their ability to move and their ability to move around that alveolar space and between. And so we can actually visualise in a healthy mouse these alveolar macrophages moving around in alveolar space, and in between alveolar spaces.

Chris - Are you looking from outside the mouse then?

Ajitha - So it's a surgery that we put with a little window into the pleural surface of the lung. So we're not putting anything into the airways, we're actually looking from the outside in.

Chris - And what happens then when you compare animals that get this vape exposure with presumably equivalent mice that don't, how do they differ? What changes?

Ajitha - Alveolar macrophages stop moving when we expose them to specifically the berry vape. And really what we found was that the major movement that they were unable to do was to move from one alveolar space into the other, when we take in berry vape.

Chris - Do you think this is going to have functional consequences? In other words, were those mice to then be exposed to potentially infecting agents or other kinds of nasties from the environment that those macrophages would help to clear the fact they're paralysed or stuck in situ? Would that you think lead to these mice being much more susceptible to lung problems?

Ajitha - Oh yeah. So that's what we found. We gave them some bacteria and we found that the alveolar macrophages weren't able to get to bacteria that landed in an alveolar space that was next door that didn't have a macrophage in it. So this inability to squeeze to the next alveolar space, inhibited them from clearing that bacteria. And this resulted in more bacteria growing inside that berry mouse and the mouse not doing as well.

Chris - What do you think the mechanism of this is? What's the chemical that's doing it and can you recreate the effect by just providing the chemical in the vape in isolation? Can you paralyse macrophages that way to prove that it must be the chemical in the vapour? Or are there several things happening which culminate in these macrophages not doing their job properly?

Ajitha - You know, Chris, science is never black and white and so that's what we figured out. So we actually did all these fancy techniques and we took our berry e-cigarette vape and we figured out all the different chemicals in it and we isolated those chemicals and then we gave animals these individual chemicals. And it didn't have the same effect as the combination that blocked the alveolar macrophage function. So it really had to be all of these complex chemicals going in at the same time. And individually it didn't have an effect. And we actually tested one other flavour, because I didn't want to go down the garden path of testing every single flavour out there, but we kind of stuck to the chemical composition of different flavours. And we tested something that was very different from Berry, which was menthol, and it didn't inhibit alveolar macrophage behaviour.

Chris - What are the implications then in your view of what you've found?

Ajitha - I think that we've seen, and in many places including the province that I'm in right now in Canada, that flavours are probably not a good idea to have in e-cigarette products. And we need to be careful about the types of flavours that we're including in these products and they can have detrimental effects. And I think that's really the take home message, especially some of these vaping products are marketed for kids, like the way they're sold, the type of containers are sold in, it's very colourful and it's really attractive to children and this can be a really bad thing for our future. So I think that's really the take home message.