Trinity researchers have discovered how lung cell exhaustion, caused by cigarette smoking, can lead to tuberculosis (TB), and have published their findings in the American Journal of Respirator Cell and Molecular Biology.
The researchers compared the lung cells of smokers to non-smokers and have found that lung macrophages, responsible for engulfing and destroying pathogens, can turn on helpful pathways of energy production after infection with the tuberculosis bacteria. They demonstrated that these energetic pathways can be recruited in the lung after bacterial infection. This can effectively control the bacteria after it has been inhaled from an infectious person with TB. The ability to switch metabolism appears to be a crucial process in host defence.
However, macrophages are not able to function properly in a smoker’s lung due to exhaustion. Looking at lung macrophages from smokers, the scientists noted that the cells had markedly reduced metabolic activity and had no metabolic reserves to respond to the infection. The observation marks a first description of smoker’s lung cells as an exhausted macrophage. The researchers are now aiming to restore these helpful pathways to fortify immunity in smokers and prevent infectious diseases such as tuberculosis
Dr Laura Gleeson commented on the importance of volunteers’ contributions in the finding, saying: “Because volunteers attend St James’s and partake in medical research, we were able to tightly compare smokers to non-smokers – to understand better how lung immunity against tuberculosis works. Our new description of macrophage exhaustion in the lung might also lead to treatments that could be applied to other TB susceptible groups. These include persons who suffer from immunosuppressive conditions such as diabetes, HIV, and those taking immunosuppressive drugs.”
Dr Fred Sheedy, co-author of the paper also commented on the significance of the finding: “By better understanding the immunological processes which are damaged in the lungs of the smoker, we might also uncover ways to support the health of people who smoke to avoid not just infections but also lung cancer”.