COPD stands for chronic obstructive pulmonary disease, an illness that makes it difficult to breathe. It causes coughing with heavy mucus production, wheezing, shortness of breath, and chest tightness, among other symptoms. The disease is progressive and chronic, meaning it worsens over time as lung airways become more narrow, which increasingly blocks the flow of air. COPD is actually not one disease but several, for which airflow obstruction is the common symptom. The best-known of these diseases are chronic bronchitis (predominantly a disease of the airways) and emphysema (the destruction of lung tissue itself).
Smoking is the biggest risk factor for all types of COPD; ninety-nine percent of those diagnosed have a history of cigarette use. A smoker’s respiratory tract is bathed in toxins from cigarette smoke, which provokes a potent inflammatory reaction. The location of this reaction determines the type of COPD that develops.
The surprising statistic, however, is that only 10 to 20 percent of smokers get COPD. For the rest, their bodies somehow keep inflammatory reactions in check, allowing airways and lung tissue to recover. It could be that in those smokers who develop COPD, the genes involved in controlling inflammatory responses to toxins are not being properly expressed (turned “on” or “off”). The reactions are therefore greater, and the damage that occurs is not repaired.
No. In addition to exposure to indoor or outdoor pollutants, including secondhand smoke, other causes of COPD unrelated to smoking are certain genetic defects, including alpha-1-antitrypsin (A1AT) deficiency, or Alpha-1 for short. A1AT is a protein in the blood that blocks an enzyme called elastase, which white blood cells use to neutralize bacteria and tiny particles inhaled into the lungs. Without A1AT to stop elastase once its job is done, the enzyme can go on to destroy the normal air sacs of the lung. People who completely lack A1AT develop emphysema at a young age (in their 30 to 40s); those born with a less active form of A1AT and who also smoke are at extremely high risk of COPD. There may be other genes that contribute to susceptibility to COPD, something scientists hope to one day learn.
One of the LGRC’s goals is to thoroughly evaluate the genetics and the genomics of the human respiratory tract by comparing lung tissue samples from smokers who develop COPD with samples from smokers who don’t. We want to find out what causes COPD and how its incidence varies among individuals who have it. These first steps can lead researchers to design better therapies targeted at individual patients—in other words, to use a personalized medicine approach in treating COPD.
We’re also using the predictive power of genomic science to identify who might be at risk of developing COPD, before it happens. Genomic studies could also pave the way for new drugs that might reverse the disease early on, or even prevent it entirely. This is important because although current therapies can sometimes control COPD, there is currently no cure for the disease.
For more information, visit the National Heart, Lung, and Blood Institute’s page on COPD.