Have you ever wondered why some people can smoke all their lives and barely get sick while others more easily fall prey to the chronic and deadly illnesses caused by cigarettes?
Around 124,000 Australians are currently living with the chronic lung disease emphysema with a further 567,000 Australians suffering chronic bronchitis, a total of 665,000 Australians with emphysema and/or chronic bronchitis, collectively known as chronic obstructive pulmonary disease.
COPD is the fourth largest killer of Australians and smoking is the most important risk factor for COPD.
As for why some people get sick and others don’t, well, today we know more about the link between smoking and emphysema – and it’s basically genetic.
A molecule expressed in response to smoking has been identified as a critical regulator of emphysema.
A new study published online in Nature Immunology found that smoking-induced expression of the regulatory RNA miR-22 can drive expression of inflammatory mediators that can lead to emphysema.
David Corry, Farrah Kheradmand and colleagues found that miR-22 is expressed more in the lungs of smokers than in those of non-smokers and that mice exposed to cigarette smoke or carbon black nanoparticles, which mimic soot, also increase their expression of miR-22.
Their research shows that in lung immune cells, miR-22 inhibits the expression of a specific enzyme in response to smoke.
This enzyme prevents expression of mediators that recruit T cells and other inflammatory cells to the lung, where their activation contributes to the progressive loss of lung elasticity and function associated with emphysema.
Genetically modified mice that cannot express miR-22 fail to develop disease after exposure to smoke or carbon black, revealing a link between this RNA and disease development.
The researchers conclude that selectively inhibiting miR-22 might represent a future therapy for inflammatory diseases.
While it had been known that smoking-related emphysema is driven by T cells, the underlying mechanisms that act on a molecular level were not known before these latest findings.
The risk of emphysema is only one more reason to stop smoking.
Were you a smoker? What did you find was the best way to quit?