New insights on the possible role of mast cells in aspirin-induced asthma.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are major drugs used in the treatment of inflammation and pain in a wide variety of disorders. The best-known mechanism of action of NSAIDs is the inhibition of prostaglandin synthesis as a result of their action on cyclooxygenase (COX) enzymes. However, data have been accumulating through the years indicating that NSAIDs also act on other targets in cell signaling. It has been established that NSAIDs induce anti-inflammatory effects independent of COX. Acetylsalicylic acid (ASA) and other inhibitors of COX induce severe bronchospasms and asthmatic attacks in a significant population of asthmatic patients. The etiology of ASA induced asthma is complex and not fully understood, but most evidence points towards an abnormality of arachidonic acid (AA) metabolism. Since doses of ASA necessary to treat chronic inflammatory diseases appeared much higher than those required to inhibit PG synthesis, COX-independent mechanisms of NSAIDs were postulated. Recently, we have shown that NSAIDs induced expression of heat shock proteins specially HSP70. Heat shock proteins (HSPs) are normal intracellular proteins that are produced in greater amounts when cells are subjected to stress or injury. Interestingly, a potential pathogenic role for heat shock proteins in diseases such as autoimmune disease, vascular disease has been reported. Because mast cells have been reported to play a role in the pathogenesis of ASA induced asthma, a link between heat shock proteins and this disease could postulated. In this review, an overview is given on aspirin-induced asthma and the cells and mediators that may play a role therein. Mast cell signaling with regard to interaction with NSAIDs and heat shock proteins (HSPs) and toll-like receptors (TLRs) is further highlighted.