Aspirin induces IL-4 production: augmented IL-4 production in aspirin-exacerbated respiratory disease

Aspirin hypersensitivity is a hallmark of aspirin-exacerbated respiratory disease (AERD), a clinical syndrome characterized by the severe inflammation of the respiratory tract after ingestion of cyclooxygenase-1 inhibitors. We investigated the capacity of aspirin to induce interleukin-4 (IL-4) production in inflammatory cells relevant to AERD pathogenesis and examined the associated biochemical and molecular pathways. We also compared IL-4 production in peripheral blood mononuclear cells (PBMCs) from patients with AERD vs aspirin-tolerant asthma (ATA) upon exposure to aspirin. Aspirin induced IL-4 expression and activated the IL-4 promoter in a report assay. The capacity of aspirin to induce IL-4 expression correlated with its activity to activate mitogen-activated protein kinases, to form DNA-protein complexes on P elements in the IL-4 promoter and to synthesize nuclear factor of activated T cells, critical transcription factors for IL-4 transcription. Of clinical importance, aspirin upregulated IL-4 production twice as much in PBMCs from patients with AERD compared with PBMCs from patients with ATA. Our results suggest that IL-4 is an inflammatory component mediating intolerance reactions to aspirin, and thus is crucial for AERD pathogenesis.

Roles of RUNX1 and PU.1 in CCR3 Transcription

CCR3 is a chemokine receptor that mediates the accumulation of allergic inflammatory cells, including eosinophils and Th2 cells, at inflamed sites. The regulatory sequence of the CCR3 gene, contains two Runt-related transcription factor (RUNX) 1 sites and two PU.1 sites, in addition to a functional GATA site for transactivation of the CCR3 gene. In the present study, we examined the effects of the cis-acting elements of RUNX1 and PU.1 on transcription of the gene in EoL-1 eosinophilic cells and Jurkat T cells, both of which expressed functional surface CCR3 and these two transcription factors. Introduction of RUNX1 siRNA or PU.1 siRNA resulted in a modest decrease in CCR3 reporter activity in both cell types, compared with transfection of GATA-1 siRNA. Cotransfection of the two siRNAs led to inhibition in an additive manner. EMSA analysis showed that RUNX1, in particular, bound to its binding motifs. Mutagenesis analysis revealed that all point mutants lacking RUNX1- and PU.1-binding sites exhibited reduced reporter activities. These results suggest that RUNX1 and PU.1 participate in transcriptional regulation of the CCR3 gene.