Estrogen may reduce airway constriction in asthmatic women

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Washington, May 17 (ANI): A new Mayo Clinic research suggests that female sex hormones may work with beta-agonists in reducing airway constriction in women patients with asthma.

After puberty, women tend to have worse asthma symptoms and exacerbations than men. Women also experience changes in airway reactivity throughout their menstrual cycle, with pregnancy, and at the onset of menopause.

"Given these clinical observations, it is of interest to determine whether sex steroids (estrogen, progesterone) play a role in modulating airway tone," said lead student researcher, Elizabeth A. Townsend, of the Mayo Clinic Department of Physiology and Biomedical Engineering.

"Increased bronchoconstriction, as in asthma, is directly influenced by the amount of intracellular calcium in airway smooth muscle. Therefore, we set out to explore the effect of estrogens on calcium regulation in airway smooth muscle. Calcium regulation is a key factor in determining bronchoconstriction.

"Since asthma symptoms have been documented to be worst when estrogen levels are lowest in the late luteal phase, we hypothesized that estrogens facilitate bronchodilation, rather than constriction," said Townsend.

To test her theory, Townsend and colleagues exposed human airway smooth muscle tissue and cells isolated from surgical lung samples to small doses of estradiol comparable to physiologic levels found in women.

They found that the exposure decreased intracellular calcium in airway smooth muscle cells.

Townsend and colleagues then asked whether estrogens could produce bronchodilation, and whether the combination of commonly used bronchodilators (2 agonists) and estrogens be used to produce even greater bronchodilation.

They found that combined treatment with estradiol and the agonist, isoproterenol (which non-selectively activates both 1 and 2 adrenergic receptors), had a synergistic effect on decreasing intracellular calcium and force more than either estradiol or isoproterenol alone.

"These novel data suggest that estradiol has bronchodilatory properties, and may potentiate 2-agonist effects. The finding that estrogens interact synergistically with adrenoceptor signaling (perhaps using common pathways) to facilitate bronchodilation was exciting, and lends itself to further studies on interactions between sex steroids and 2-agonists," said Townsend.

But she and her team also cautioned that there is still considerable research necessary to fully understand the association between sex steroids and factors that contribute to asthma, before the information can be used clinically in patients to relieve asthma symptoms.

The findings will be presented at the ATS 2010 International Conference in New Orleans. (ANI)

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