Studies Show Maternal Smoking Triggers Asthma in Grandchildren

Everyone knows that smoking cigarettes and other tobacco products is bad for your health... and for those around you. Now, there’s new evidence from studies with lab rats that the habit can cause asthma not only in smokers' children, but in their grandchildren, as well.

Researchers at Harbor-UCLA Medical Center in Los Angeles, California, have found evidence of a generational effect of tobacco-smoking on lung development. The scientists gave a group of pregnant rats injections of nicotine, the amount an average smoker would receive, exposing the animals' unborn pups to the chemical. Nicotine is one of more than 4,000 chemicals in tobacco smoke known to adversely affect lung development. As predicted, the injections caused changes in the fetal animals' upper and lower airway development consistent with asthma.

The chronic and potentially fatal respiratory condition, which afflicts growing numbers of people worldwide, causes fits of coughing, wheezing, gasping and chest tightness.  

After they were born, the rat pups were never again exposed to nicotine. Nor were their offspring. Nevertheless, researchers found that these second-generation rat pups showed the same physical signs of asthma.

“So even if they are not exposed to any smoke or nicotine in the second generation pregnancy or [even] third generation pregnancy, they still go on to have asthma,” said neurologist Verinder Rehan, who led the study.

The change in lung function in the second generation of rat pups NOT exposed to nicotine in the womb was caused, Rehan said, by so-called epigenetic factors - alterations in how DNA functions as a result of environmental factors, such as the first generation’s exposure to nicotine.

The researchers saw what turned out to be a significant generational ripple stemming from the initial nicotine exposure.

“We have for the first time developed this experimental model where we are showing these changes actually happening... and we are also providing a mechanism that is the epigenetic mechanism responsible for these changes," said Rehand. "And actually even more importantly we have shown if you can block these changes, you can block the transmission of asthma.”

To demonstrate this, Rehan's group gave a separate group of rat mothers that had been injected with nicotine a drug that normalized their lung function. That healing prevented lung damage in two subsequent generations of pups.

Rehan said his study shows that the effects of cigarette exposure can be both far-reaching and long-lasting - another reason pregnant women should avoid lighting up or exposing themselves to second-hand smoke.

An article on the generational effects of nicotine exposure in causing asthma is published in BioMed Central's open access journal BMC Medicine.