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Abstract
BackgroundRecent studies have revealed that cyclooxygenase-2 (COX-2) expression is down-regulated in aspirin-induced asthma (AIA). Various signal pathways (MAPKs, NF-κB and C/EBP) are involved in COX-2 regulation.ObjectiveTo investigate the regulation of COX-2 expression through MAP-kinase pathway activation and nuclear factor translocation in aspirin-induced asthma (AIA).MethodsFibroblasts were isolated from specimens of nasal mucosa (NM, N = 5) and nasal polyps (NP, N = 5). After IL-1β (1 ng/ml) incubation, COX-2 and phosphorylated forms of ERK, JNK and p38 MAPK were measured by Western blot. MAPK’s role in IL-1β-induced COX-2 expression was assessed by treating cells with ERK (PD98059), JNK (SP600125) and p38 MAPK (SB203580) inhibitors (0.1–10 µM) prior to IL-1β exposure. NF-κB and C/EBP nuclear translocation was measured by Western blot and TransAM® after IL-1β (10 ng/ml) exposure.ResultsNo differences were observed in the MAPK phosphorylation time-course between NM and NP-AIA fibroblasts. The p38 MAPK inhibitor at 10 µM significantly reduced IL-1β-induced COX-2 expression in NM fibroblasts (85%). In NP-AIA fibroblasts the COX-2 inhibition (65%) at 1 and 10 µM was not statistically significant compared to non-treated cells. ERK and JNK inhibitors had no significant effect in either the NM or NP-AIA cultures. The effect of IL-1β on NF-κB and C/EBP subunits’ nuclear translocation was similar between NM and NP-AIA fibroblasts.ConclusionsThese results suggest that p38 MAPK is the only MAPK involved in IL-1β-induced COX-2 expression. NM and NP-AIA fibroblasts have similar MAPK phosphorylation dynamics and nuclear factor translocation (NF-κB and C/EBP). COX-2 downregulation observed in AIA patients appears not to be caused by differences in MAPK dynamics or transcription factor translocation.
Highlights
Aspirin-induced asthma (AIA) is a syndrome clinically characterized by chronic rhinosinusitis with nasal polyposis (CRSwNP), asthma and bronchoconstriction episodes triggered by the intake of non-steroidal-anti-inflammatory drugs (NSAIDs) [1]
These results suggest that p38 mitogen-activated protein kinases (MAPKs) is the only MAPK involved in IL-1b-induced COX-2 expression
COX-2 downregulation observed in aspirin-induced asthma (AIA) patients appears not to be caused by differences in MAPK dynamics or transcription factor translocation
Summary
Aspirin-induced asthma (AIA) is a syndrome clinically characterized by chronic rhinosinusitis with nasal polyposis (CRSwNP), asthma and bronchoconstriction episodes triggered by the intake of non-steroidal-anti-inflammatory drugs (NSAIDs) [1]. The pathogenesis of AIA remains poorly understood but accumulated evidence suggests that abnormalities in arachidonic acid metabolism may play a role [2,3] Both an overactive 5lipoxygenase pathway (5-LO) and reduced COX expression have been demonstrated, resulting in increased cysteinyl leukotriene production and reduced PGE2 release in AIA [1,4,5,6,7]. There are two well-characterized COX enzymes: COX-1, considered a constitutive form involved in cell homeostasis [8], and COX-2, an inducible form activated by pro-inflammatory mediators, growth factors and cytokines These alterations in AIA patients seem to be present in both the lower [6] and upper airways [4]. Various signal pathways (MAPKs, NF-kB and C/EBP) are involved in COX-2 regulation
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