Like many other chronic diseases, women have a greater chance than men to have asthma, which may be due to the influence of sex hormones on lung cells. Thanks to the team of researchers led by Dr. Dawn Newcomb of Vanderbilt University, who revealed the significant role of testosterone for this gender difference.
Previous studies have revealed that prior to the puberty stage, boys have 1.5 times higher asthma rate than girls. However, the situation becomes reversed after adolescence, when women are twice as likely as men to develop asthma. Again, after menopause, the asthma rates begin to decline in women. Even though there are many other general factors behind asthma symptoms, this unique pattern of asthma linked to the menstrual cycle led the scientists to investigate the role of sex hormones behind this trend.
To carefully analyze the mechanisms behind the gender differences, Dr. Newcomb and her colleagues concentrated their study on a specific type of white blood cells in lungs, known as Group 2 innate lymphoid cells (ILC2 cells). When an allergen enters the lungs, these ILC2 cells produce proteins that result in mucus production and inflammation in the lungs, causing heavy breathing problems. Analysis of blood samples of individuals with and without asthma was carried out and the findings of the research team published in the Cell Reports journal revealed that people with asthma had higher levels of ILC2 cells than those without asthma. Moreover, women with asthma had almost twice the levels of ILC2 cells than men with the asthmatic condition.
The team carried out similar studies focusing on the ILC2 cells in the lungs of mice, where they found that the adult female mice had more ILC2 cells in their lungs than males. They carried out several experiments on these mouse cells to analyze the impact of hormones on ILC2 cells. They compared between mice which have sex hormones present in their bodies and those with their reproductive organs removed. It was observed that those mice without testosterone had more ILC2 expansion compared to those that had testosterone.
The researchers noted that the addition of ovarian hormones like estrogen and progesterone to ILC2 cells did not increase the protein production capacity of the cells. However, they found that testosterone was most important in preventing cell expansion and reducing protein production from ILC2 cells in lungs.
Sex hormones are just one of the many important mechanisms that influence asthma. This research by Dr. Newcomb and her colleagues was focused on Testosterone and the researchers are hopeful to conduct more studies to explore the impact of more sex hormones on asthma, which will provide new targets for medicine and will also influence the development of future clinical trials for asthma.
Newcomb et al. Testosterone attenuates group 2 innate lymphoid cell-mediated airway inflammation. Cell Reports 2017;21(9):2487-2499. DOI: 10.1016/j.celrep.2017.10.110