It is now clear from pharmacologic studies with COX inhibitors and from studies with COX-1 and COX-2 knockout mice that inhibition of PG production exacerbates allergic airway responses. We demonstrated that PAH and DEP extracts dramatically inhibit PG production in macrophages, mast cells and fibroblasts. We suggest that DEP components may exacerbate allergic airway inflammation either by suppressing production of ameliorating PGs and/or by increasing production of bronchoconstrictive leukotrienes. We will clarify the molecular and cellular mechanisms by which DEP components reduce PG production and determine whether leukotrienes are elevated, as a consequence of DEP inhibition of PG production in macrophages and mast cells. With Drs. Nel and Diaz-Sanchez, we will determine if inhibition of PG production and elevation of leukotriene synthesis contribute to DEP exacerbation of allergic airway inflammation in the murine ovalbumin airway challenge model. With Dr. Nel and the Fractionation Core, we will determine if DEP components most active in the exacerbation of allergic airway inflammation are also the most potent inhibitors of PG production. With Dr. Saxon, we will determine whether DEP alteration of eicosanoid metabolism plays a role in exacerbation of allergen-induced airway inflammation in human subjects. Like the COXs, the phospholipases (PLAs) play key roles in eicosanoid production and, consequently, in allergic airway inflammation. We and others have shown pharmacologically that group V secretary PLA(2) mediates specific aspects of eicosanoid production. By creating a group V secretory (sPLA[2]) knockout mouse and analyzing its responsiveness in the murine ovalbumin challenge model with Drs. Diaz-Sanchez and Nel, we hope to identify additional targets to ameliorate DEP exacerbation of allergic airway inflammation. The efficacy of COX-2 specific inhibitors such as Vioxx and Celebrex depends on the cellular sequestration of arachidonic acid, preventing its accessibility to COX-1. By using a series of mutational analyses of COX-1 and COX-2, we will determine the molecular basis for arachidonic acid sequestration. These studies should provide potential new approaches to pharmacologic manipulation of PG and leukotriene synthesis. PGs produced by different cell types modulate allergic airway inflammation in distinct ways. COX-2 inhibitors are not cell-type specific, however; they inhibit COX-2 in all cell types. We find that the signaling pathways activating COX-2 expression differ in activated mast cells and stimulated macrophages, two important cell types in allergic airway inflammation. We will explore these pathways, with the possibility that methods for cell-type specific manipulation of PG synthesis in vivo might be identified.