Researchers: Air Pollutant is Likely Contributor to Most Severe Asthma Species
Asthma affects more than 300 million people worldwide. The most severe manifestation, known as non-Th2 or non-atopic asthma in children, represents the majority of cases, greater than 85%, especially in low-income countries Hyunok Choi, an associate professor at the Lehigh University College of Health. However, it is unknown whether non-Th2 is a particular disease (or endotype) or simply a distinct set of symptoms (or phenotypes).
“Non-Th2 asthma is linked to a very poor prognosis in children and great lifelong suffering because there are no effective therapies,” says Choi. “There is an urgent need to better understand its mechanistic origin in order to allow early diagnosis and stop the disease from progressing before it becomes severe.”
Studies show that nearly 50% of children whose asthma is poorly controlled will develop as severe cases in adults. However, a unified approach to treatment that is currently the norm for asthma is ineffective and, as Choi says, partially responsible for the growing economic burden of asthma.
“The main reason for the lack of therapeutic and preventive measures is that an etiological or causal driver for the non-Th2 asthma has never been identified,” says Choi.
Now, for the first time, an epidemiological study led by Choi has shown that not only is non-Th2 a disease in itself, but it is also likely to be an early childhood airborne exposure Benzo[a]Pyrene, a by-product of fossil fuel burning. Choi and her colleagues are the first to identify air pollution as a driver of the most difficult type of asthma, the severe subtype that is unresponsive to current therapies.
The team describes their results in an article recently online in the Environmental Health Journal with the title “Benzo in the air[a]Pyrene can contribute to different pheno-endotypes in children. ”(Other authors: Miroslav Dostal, Anna Pastorkova, Pavel Rossner Jr. and Radim J. Sram from the Department of Genotoxicology and Nanotoxicology, Institute of Experimental Medicine, Czech Academy of Sciences, Prague, Czech Republic.)
What is known as asthma is an umbrella term for several diseases with common symptoms. Asthma has been broadly classified as two main symptoms: T helper cells high (Th2 high) and T helper cells low (non-Th2). Th2-high is associated with early childhood allergies to common pollutants such as dander, tree pollen or mold. In contrast, non-TH2 is not associated with an allergic reaction. The non-Th2 type, which is explicitly labeled as non-allergy related, is far less well known than the TH-2 type and could turn into a severe or difficult-to-treat type.
“The identification of non-Th2 asthma as a disease in its own right with early exposure to benzo[a]Pyrene as a driver can hit tens of millions of people, as this would allow action to be taken before irreversible respiratory tract injuries occur, ”says Choi.
The team tested two comparable groups of children from an industrial city, Ostrava, and the surrounding semi-rural area of South Bohemia in the Czech Republic: 194 children with asthma and a control group consisting of 191 children. According to the study, Ostrava is an industrial city with a high level of coal mining, coal processing and metallurgical refining. The district-level environmental agent for Benzo[a]At the time of their investigation (November 2008), Pyrene was eleven times higher than the recommended indoor and outdoor air quality standard.
It wasn’t just increased exposure to benzo[a]Pyrene was associated with correspondingly increased chances of non-Th2 asthma; it was also associated with decreased systemic oxidant levels.
“Contrary to current evidence showing the incidence of non-atopic asthma in adults, our data suggest for the first time that pulmonary function deficit and suppressed oxidative stress during early childhood are critical sentinel events prior to non-atopic asthma “says Choi.