Boston, Mass. — Atmospheric dryness associated with heatwaves may increase cough hypersensitivity by dehydrating airway mucus, while inhaled magnesium salt aerosols could help reverse the effect, according to a new study involving SC Therapeutics, the University of North Carolina, Imperial College London and Boston University.
The study, published in Nature Scientific Reports, found that dry atmospheric conditions can cause mucus in human airways to collapse onto cilia, a process also seen in chronic respiratory diseases such as cystic fibrosis and asthma.
Researchers reported that alkaline aerosols containing magnesium salts helped reverse the mucus collapse for several hours. In a randomized, double-blind, placebo-controlled study involving 10 patients with refractory chronic cough, the treatment was associated with a placebo-adjusted 59% reduction in daily cough bout rate. Researchers also reported that suppression of coughing persisted for one to three weeks after treatment.
“Paris recorded 5,764 excess deaths between 17 June and 2 July, a period of time during which we report atmospheric aridity in the city increased approximately 3-fold relative to the 35 year average for this same period,” said Dr. Kian Fan Chung, Professor of Respiratory Medicine at Imperial College London. “Hospitalization and deaths during heatwaves are especially great among the elderly, with a high prevalence of respiratory complications, including chronic cough.”
Dr. David A. Edwards, founder of SC Therapeutics, Adjunct Professor of Medicine at Johns Hopkins University and Distinguished Visiting Scientist at Imperial College London, said exposure to dry air is becoming increasingly common because of urbanization, indoor living and more frequent heatwaves.
“Unlike dirty air, which provokes inflammation by exposure to toxic particles and gases, atmospheric aridity inflames human airways by rapid water loss, making anti-inflammatory relief possible by prolonged rehydration, as demonstrated in this study,” Edwards said.
Dr. Brian Button, Professor of Biochemistry and Biophysics at the University of North Carolina, said hypertonic salts have long been used to treat cystic fibrosis, which is characterized by dehydrated airways.
“This study gives evidence that new kinds of hypertonic salts, longer acting and rendered therapeutic by optimization of rehydration processes within mucus we are only beginning to discover, might provide prophylaxis and treatment options for a human population previously spared the damages of mucosal dehydration,” Button said.
Refractory chronic cough affects patients who continue to experience persistent coughing despite standard treatment. The condition is associated with cough hypersensitivity, in which the threshold that triggers the cough reflex is abnormally lowered, potentially causing persistent symptoms that can significantly affect quality of life.
Researchers said mechanosensitive ion channels have emerged as a potential therapeutic target because of their role in transmitting mechanical signals that can trigger the hypersensitive cough reflex.
