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More than 50 percent of asthma deaths occur at night, exposing a relationship between nocturnal asthma symptoms and asthma deaths.
A research group led by Kentaro Mizuta of the Tohoku University School of Dentistry (Japan), has discovered that Melatonin, a sleep hormone, makes asthma worse.
Patients with asthma often experience worsening of asthma symptoms at night in so-called "nocturnal asthma.". More than 50 percent of asthma deaths occur at night, exposing a link between nocturnal asthma symptoms and asthma deaths. Although several triggering factors have been proposed by some to explain the pathogenesis of nocturnal asthma, the precise mechanisms regulating this asthma phenotype remain obscure.
However, melatonin, which is often prescribed for insomnia, promotes a state of bronchoconstriction and weakens the relaxing effect of a bronchodilator by activating the MT2 melatonin receptor.
To elucidate this, the research group identified the expression of the melatonin receptor MT2 in the smooth muscle of the human airways. They observed that activation of the MT2 melatonin receptor with higher doses of melatonin or the melatonin receptor agonist ramelteon greatly enhanced bronchoconstriction. Besides, Melatonin attenuated the relaxing effects of the widely used B-adrenoceptor agonist bronchodilator.
"Although serum melatonin concentration did not significantly induce airway constriction, higher doses of melatonin, which is used clinically to treat insomnia, jet lag or cancer, worsened asthma symptoms and impaired the therapeutic effect of bronchodilators," explains Mizuta.
"Drug therapy that blocks the MT2 melatonin receptor could inhibit the harmful effects of melatonin in the airways," adds the first author of the work, Haruka Sasaki.
