Using cell models, the team specifically showed that respiratory syncytial virus (RSV) infection increases the number of a type of receptor called Toll-4 on the airway cells. This Toll-4 receptor can provide a foothold for inhaled endotoxin, a naturally occurring environmental contaminant that comes from bacteria and is found in household dust, grain dust and objects such as pillows. The presence of receptors for endotoxin would lead to interaction between the epithelial cell and the endotoxin and potentially cause inflammation. The study appeared in the December 26, 2003, issue of the Journal of Biological Chemistry.
"The big picture here is that viral infections may upregulate, or increase, one or more receptors on the airway cells and make them more sensitive to environmental exposures. This could explain the viral-induced asthma exacerbations seen in people with asthma," said Martha Monick, senior research assistant in the Division of Pulmonary, Critical Care and Occupational Medicine in the UI Department of Internal Medicine and the study's co-lead author.
Monick said the inspiration for the study came when the team put endotoxin on normal airway epithelial cells and noticed there was no inflammatory response.
"This puzzled us, so we started thinking about receptors on lung cells," Monick said. "When we looked in normal lung cells for
Contact: Becky Soglin
University of Iowa