In the UK asthma is the commonest chronic illness of children, but attempts to prevent childhood asthma have been largely unsuccessful. Epidemiological studies have suggested that exposure of a child before and after birth to tobacco smoke and air pollution increases their risk of developing asthma. A low consumption of fruit and vegetables and antioxidant vitamins (vitamins C, E and A) early in life may also increase risk. In the ALSPAC study we recently discovered that children with particular types of a gene called TRPA1 were more likely than children with other types of the gene to develop asthma. The TRPA1 gene controls a protein which is thought to increase inflammation of the airways in asthma, and the action of this protein is increased by harmful substances in the environment, such as tobacco smoke and air pollution.
We believe that children with ‘risky’ forms of the TRPA1 gene may be more likely than other children to develop asthma when they are exposed early in life to tobacco smoke and air pollution, or if their intake of protective antioxidants (from fruit, vegetables and vitamins) is low. We plan to test this hypothesis by analysing existing data in ALSPAC. In a subset of ALSPAC mothers and children we will also explore whether the risk of developing asthma partly depends on whether the TRPA1 gene is turned on or off. We will do this by measuring how much the DNA in the TRPA1 gene is chemically altered by a process called 'methylation'. Exposure to pollutants can alter the level of DNA methylation and this, in turn, can influence the extent to which a gene is turned on or off.
If we can confirm that infants who carry ‘risky’ forms of the TRPA1 gene are more likely to develop later asthma when exposed to harmful pollutants or a poor diet, this could help us to find ways to prevent childhood asthma from developing in the first place in these vulnerable individuals. For example, infants who are genetically susceptible in this way might particularly benefit from taking antioxidant vitamin supplements or from strategies designed to reduce their exposure to air pollution.