Methods: Eosinophils were enriched from tissue and peripheral blood obtained from control, aspirin-tolerant, and AERD subjects. mRNA was extracted and evaluated for expression of hematopoietic PGD synthase (hPGDS). Expression of hPGDS protein was confirmed with western blot and immunohistochemical staining. Cells were stimulated with aspirin and secretion of PGD2 quantified. Finally, CD34+ progenitor cells were isolated and matured into eosinophils in the presence or absence of IFN-γ and hPGDS mRNA and PGD2 release measured.
Results: Gene expression analysis revealed that eosinophils from AERD tissue and blood display increased levels of hPGDS compared with asthmatic and control samples. Western blot confirmed the increase in hPGDS gene expression translated to increased protein expression. Using immunofluorescence, mast cells and eosinophils from AERD and asthmatic subjects demonstrated hPGDS with higher levels in AERD eosinophils. Incubation of eosinophils from blood and tissue with aspirin stimulated PGD2 release. IFN-γ-matured eosinophil progenitors showed enhanced hPGDS expression and increased levels of PGD2 release at baseline and following stimulation with aspirin.
Conclusions: In addition to mast cells, eosinophils represent an important source of PGD2 in AERD at baseline and following exposure to aspirin.