This project tests the hypotheses that deficient EP2 receptor expression and function in platelets and leukocytes alters homeostasis of the adenylyl cyclase/cyclic adenosine monophosphate (cAMP) pathway as a disease-causing mechanism in aspirin exacerbated respiratory disease (AERD). Platelets are required for granulocyte recruitment in animal models of pulmonary inflammation, binding to leukocytes via P-selectin (CD62P) and facilitating integrin avidity. When bound to neutrophils, platelets can also form leukotriene (LT)C4 (the parent of the cysteinly leukotrienes (cys-LTs)) from neutrophil-derived LTA4. We have discovered that platelets from subjects with aspirin exacerbated respiratory disease (AERD) are markedly deficient in expression of the Gs-linked EP2 receptor for PGE2 relative to platelets from normal and aspirin-tolerant asthmatic (ATA) controls. As a result, neither exogenous PGE2 nor a selective EP2 agonist can block activation of platelets from individuals with AERD in vitro, or the formation of platelet-leukocyte aggregates. Moreover, peripheral blood samples from individuals with AERD contain several fold higher frequencies of platelet-leukocyte aggregates than do samples from normal and aspirin-tolerant ATA controls, suggesting a functional result of diminished EP2 signaling in vivo that could enhance both tissue inflammation and the generation of cys-LTs. Furthermore, the defect in EP2 receptor expression extends to peripheral blood leukocytes from individuals with AERD, accompanied by concomitantly defective expression of mRNA encoding EP4 receptors;both defects are reversed by aspirin treatment.
Aim 1 is to determine the consequences of defects in the function of the EP2 subtype of prostaglandin E2 receptor on platelets in the pathophysiology of AERD.
Aim 2 is to determine the consequences of deficient of EP2 and EP4 receptor signaling on 5-lipoxygenase (5-LO) pathway activity in peripheral blood leukocytes and whether the deficiency is corrected by treatment with aspirin.
Aim 3 is to characterize the extent of epigenetic variation in EP receptors, classical and novel CysLTRs, and associated candidate effectors in AERD.

Public Health Relevance

Aspirin exacerbated respiratory disease (AERD) is a severe form of asthma. This project seeks to determine the reason why individuals with AERD lack a protein called EP2, and to determine whether the lack of EP2 is a causitive feature of the disease. The studies will point the way toward expaining why people develop AERD, and what can be done to treat or prevent it.

National Institute of Health (NIH)
Research Program--Cooperative Agreements (U19)
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Special Emphasis Panel (ZAI1)
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Brigham and Women's Hospital
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