Molecules in cruciferous vegetables, such as broccoli, can help to maintain a healthy barrier in the lung, which can ease infection, British researchers reported last night.
In mouse model studies, published today in Nature, the protein AHR – aryl hydrocarbon receptor – was found to be highly active in endothelial cells lining blood vessels in the lung.
AHR is found at barrier sites like the gut and the lung and natural molecules in cruciferous vegetables, such as kale, cauliflower, broccoli, or cabbage, are dietary ligands for AHR.
Researchers at the Francis Crick Institute, UK, conducted a series of experiments in mice to show how AHR impacts lung barriers.
When mice were infected with the flu virus, blood was found in the airspaces in the lungs, as it had leaked across the damaged barrier. But AHR could prevent the barrier from becoming leaky and when AHR was overactivated, the researchers observed less blood in the lung spaces.
They also found that mice with enhanced AHR activity lost less weight when infected with flu and could fight off a bacterial infection on top of the original virus more effectively.
When AHR was prevented from being expressed in the lung endothelial cells of infected mice, more blood and immune cells were seen in the air spaces, showing greater damage to the barrier.
Flu infection caused a decrease in protective lung AHR activity, but only in mice fed AHR ligands in their diet before the illness.
The researchers say these findings link food consumption to AHR activity and outcome in viral infection.
Despite the infection-driven reduction of AHR activity, it was beneficial for mice to be on an AHR ligand-rich diet because they had better barrier integrity and less lung damage during infection than mice on the control diet.
Andreas Wack, group leader of the institute’s immunoregulation laboratory, said: “Until recently, we’ve mainly looked at barrier protection through the lens of immune cells. Now we’ve shown that AHR is important for maintaining a strong barrier in the lungs through the endothelial cell layer, which is disrupted during infection.
“People may be less likely to maintain a good diet when they’re ill, so aren’t taking in the molecules from vegetables which make this system work. It’s a good idea to eat lots of cruciferous vegetables anyway, but this shows it’s even more important to continue eating them when you’re ill.”
First author Dr Jack Major added: “What we’ve identified is a gut-lung axis – linking diet to protection against lung infection via endothelial cells. We looked at flu in this research, but other research has shown that COVID-19 may also reduce AHR activity in the lung.
“It will be interesting to investigate the impact of other respiratory viruses on AHR, and also whether different molecules in our diet use other pathways than AHR to affect lung function via endothelial cells.”
In a second study published in Nature, authors say AHR may be important in endothelial cells in other barrier organs. A team at the Medical Research Council and Imperial College London, report dietary factors activate AHR in the gut endothelial cells, preventing excessive cell reproduction and inflammation. They show gut endothelial AHR is important in protection against gut infection.
Major J et al. Endothelial AHR activity prevents lung barrier disruption in viral infection. Nature 16 August; doi: 10.1038/s41586-023-06287-y
Wiggins B et al. Endothelial sensing of AHR ligands regulates intestinal homeostasis. Nature 16 August 2023; doi: 10.1038/s41586-023-06508-4.
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