Asthma Diagnostic Detects Leaky Airways

Both asthma and chronic obstructive pulmonary disease (COPD) are airway disorders associated with elevated, uncontrolled inflammation in respiratory tissues. Spikes in inflammation culminate in several chronic, sometimes life-threatening symptoms, including wheezing, coughing, and shortness of breath. 

Over the last 25 years, researchers have been trying to piece together the pathophysiology of asthma to define the triggers and risk factors at play that give rise to these symptoms. In a recent study, a team of scientists at Rutgers University has brought forward another piece of the puzzle: a novel biomarker associated with asthma and COPD. 

The researchers, led by Reynold Panettieri, found that patients with chronic respiratory conditions have much higher levels of cyclic adenosine monophosphate (cAMP) circulating in their bloodstreams. This molecule is involved in a vast array of biological processes, most notably sensitizing cells to the effects of glucagon and adrenaline.

In the context of asthma, cAMP sends a message to the smooth muscle cells lining the lungs and airways to relax. In healthy individuals, the bands of smooth muscles circumventing airway passages are typically relaxed, allowing air to flow through easily. However, a cross-section of the asthmatic airway reveals that the lining of these tube-like structures is extremely inflamed and thickened. During an asthma attack, the bands of smooth muscles begin to spasm and contract, trapping air in the lungs' alveoli and blocking the passage of air in the airways. 

According to work by Panettieri, cAMP leaks out of the airways and into the bloodstream of asthmatics and COPD patients, where it loses the ability to relax smooth muscles. The researchers found that by blocking cAMP leakage, the protein remains localized in the lungs, allowing these patients to breathe easily once again. 

In addition, a simple blood test for cAMP can help improve the diagnosis of chronic airway conditions. At present, diagnosis requires a battery of tests to assess breathing in the patients, including the pulmonary function test and peak expiratory flow measurements. If positively diagnosed, patients are typically prescribed medications such as albuterol. 

"We determined that cAMP blood levels are higher in asthma patients," Panettieri said. "This knowledge allows for better diagnostics of the illness and forms the basis for new therapeutics that will plug the leak of cAMP in the protein."