The adverse long-term effects of maternal smoking on the lungs of babies and children have long been recognised. Now, researchers from the Brigham and Women’s Hospital (BWH) in the United States have conducted a study to determine exactly what mechanisms are at work in damage to the lungs of fetuses in the womb.
Children whose mothers smoke whilst pregnant are not only at a higher risk of developing cancer, lung infections and respiratory diseases such as asthma, but also suffer a more rapid lung function decline if they begin to smoke themselves in later life.
The research paper, published in BioMed Central’s open access journal Respiratory Research
, gives details of the study into how retinoic acid (RA) signalling is affected by maternal smoking. Produced from vitamin A, retinoic acid is responsible for alveolar development as well as maintenance of lung function.
As well as affecting the number and average weight of mouse offspring, the development of the pups’ lungs was restricted and RA signalling disrupted.
"The pups were protected from breathing smoke themselves but were still affected by ‘second-hand’ smoke before birth and through their mother’s milk," explained Dr Kathleen Haley, lead author of the study. "Smoking affected the regulation of genes, controlled by RA, necessary for lung development, including surfactant apoprotein B."
"It is known that complete loss of surfactant apoprotein B is linked to severe respiratory failure in infants and down-regulation of this, and other genes regulated by RA, can have potentially serious consequences," Dr Haley added.
RA signalling was also affected in lung cells treated with cigarette smoke in vitro
in the laboratory. In the mouse pups, RA signalling and the expression of genes controlled by RA was most noticeable in the three to five day period after birth – the time during which development of the respiratory organs is at its fastest.
Although further research is needed, it seems likely that the same or similar effects are also at work in humans. The equivalent developmental stage in humans occurs while the fetus is still in the womb, receiving ‘second-hand’ cigarette smoke via the umbilical cord.