Asthma Gene Change Linked to Air Pollution

in Asthma
Published: March 12, 2013
Air pollution seen over Shanghai's Puxi District buildings at dusk, China
Photo: Getty

Researchers have found a link between certain air pollutants and a change to our DNA that worsens asthma symptoms. It could even lead to new cases of the disease.

“We’ve shown that the gene being changed is directly associated with asthma and severity of the asthma,” says Dr. Kari Nadeau of Stanford University, the senior study author.

The study showed that exposure to polycyclic aromatic hydrocarbons (PAHs) in the air directly led to a change in a gene known as FOXP3. This gene exists inside regulatory T-cells, whose job is to suppress inappropriate immune responses, such as the airway inflammation associated with asthma.

This alteration in the gene makes it harder for the T-regulatory cells to do their job, leading to worsened asthma symptoms.

The study also associated PAH exposure with higher overall levels of IgE antibodies, which play a major role in any allergic response.

How Asthma and Genes Studied

For the study, researchers observed a group of children and teens at two sites in California. The first was Fresno, which is known for heavy air pollution and a high rate of asthma (about 22 percent). Stanford, a lower-pollution area, was the second site and used as a control group.

The PAH levels in the air were measured. As well, the children underwent lung function tests, and they also gave blood and urine samples.

The children who had been exposed to PAHs for three months before the testing were more likely to have altered FOXP3 genes, decreased T-regulatory cell function and high levels of IgE antibodies. All three differences make asthma more likely, and its impact more severe.

“Exposure to high PAH quantities may be having an effect at the molecular level, possibly leading to new cases of asthma,” said Nadeau. This altered version of FOXP3 was even found in individuals from the area who didn’t have asthma – and it is unknown whether this change is reversible.

More than 100 chemicals are classified as PAHs, which form when an organic substance is burned incompletely. Sources include oil, gas, coal, tobacco, or even meat from a barbecue. (The latter occurs when drippings fall onto the flames. PAHs are formed and then adhere to the meat).

Man-made PAHs can also be found – in tars as well as some plastics, dyes and pesticides.

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