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Asthma is triggered by the overproduction by mast cells and other leukocytes of natural chemicals such as those called leukotrienes. Effective asthma drugs have been developed to block the production of leukotrienes.

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Asthma is a disease of inflammation caused by the actions of inflammatory cells such as mast cells, eosinophils, neutrophils, T- lymphocytes, epithelial cells, and macrophages. Inflammation of the airways produces the classic symptoms of asthma: coughing, wheezing, chest-tightening, and difficulty breathing.

Histamine release
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As with many other inflammatory reactions, the key molecules involved in causing asthma symptoms include histamine, leukotrienes, and various cytokines.

These molecules stimulate mucus production, which clog airways and make it hard to breathe. Inflammatory molecules also cause changes in blood vessel linings and in the structure of the smooth muscle of the airway vessels. In general, these inflammatory molecules appear to create "jittery" lungs that are too responsive and tend to overreact to various forms of stimuli.

Because of the prominent role of inflammation in asthma, medicines that block inflammation can be effective asthma treatments. Anti-inflammatory drugs used to treat asthma include certain forms of steroid molecules called inhaled corticosteroids and a relatively new class of drugs call leukotriene inhibitors (for example, Accolate® and Singulair®). As their name suggests, these drugs block the production of inflammatory leukotrienes, and help to minimize the biological effects of leukotrienes that attract eosinophils, crimping airway vessels, and producing excess mucus.