[MOL] Beta-adrenergic Agonists May promote Lung Cancers..... [02346] Medicine On Line

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[MOL] Beta-adrenergic Agonists May promote Lung Cancers.....


Beta-adrenergic Agonists May Promote Lung Cancers
by Sheila Stavish

Inhaled and oral beta-adrenergic agonists, a mainstay of symptom control for asthma and chronic obstructive pulmonary disease (emphysema and bronchitis), may promote lung cancers, according to studies in animal models and human cell lines.

Hildegard M. Schuller and colleagues at the University of Tennessee in Knoxville found that two human lung adenocarcinoma cell lines expressed mRNA for beta 1- and -2 adrenergic receptors -- whose ligands are epinephrine and other catecholamines. What’s more, the levels of arachadonic acid rose correspondingly when they added a nitrosamine,( 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone).

Rodents are already known to develop lung carcinomas when they’re dosed with NNK. Along with churning out more arachadonic acid, the cell line revved up DNA synthesis and cell growth.

Each of the cell lines’ surprising responses to the NNK – beta-adrenergic receptor expression, proliferation of arachadonic acid, DNA replication and cell growth -- was prevented by adding beta-adrenergic antagonists – the familiar prescription drugs, beta blockers.

Schuller and colleagues’ experiments have traced out a previously unknown pathway to lung cancer.

Considering the protective effect of beta-blockers in cardiovascular disease, the researchers wonder whether NNK may be involved in the increased risk for cardiovascular disease that smoking causes.

Schuller remarked in an interview on the increase in adenocarcinoma of the lung over the same time period that beta-agonists have been increasingly used. These drugs get catecholamines to the respiratory tract, to temporarily counter the bronchospasm of asthma.

Twenty years ago, adenocarcinomas constituted 5 percent of lung cancers; now they account for 75 percent. Schuller credited Randy Harris, the Ohio State University epidemiologist, for making that connection.

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