Cyclo-oxygenase (COX), also known as prostaglandin H synthase (PGHS), is the rate limiting enzyme for the conversion of arachidonic acid to prostanoids and exists in two isoforms. COX-1 is constitutively expressed and is responsible for the basal production of prostanoids, whereas COX-2 is highly inducible by a number of stimuli including cytokines and is associated with inflammation. Accumulating evidence suggests that the induction and regulation of COX-2 may be key elements in the pathophysiological process of a number of inflammatory disorders and may play an important role in the pathogenesis of asthma.1

Bronchoalveolar lavage fluid from patients with symptomatic asthma contains significantly increased levels of a number of proinflammatory cytokines including interleukin 1β and tumour necrosis factor α.2 ,3 It has recently been shown that these proinflammatory cytokines are capable of inducing COX-2 in a number of cultured airway cells including airway epithelial cells,4 ,5 airway smooth muscle cells,6 ,7and airway fibroblasts.8 In addition, we have shown that transforming growth factor β_{1 …}