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Immunocytochemical localization of cyclo-oxygenase isoforms in cultured human airway structural cells

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Abstract:

Background

Cyclo-oxygenase (COX) exists as two isoforms, COX-1, the constitutive isoform, and COX-2, which is inducible by cytokines or inflammatory stimuli and may participate in airway inflammation. Objective

To determine the basal distribution of COX isoforms, and their regulation by interleukin-1 beta (IL-1β), bradykinin (BK) and dexamethasone (Dex) in cultured airway structural cells. Methods

We measured COX-1 and COX-2 in cultured human airway smooth muscle (HASM) cells, MRC5 fibroblasts and normal human epithelial cells (NHBE) using immunocytochemical analysis. Results

The majority of all types of untreated cultured cells expressed COX-1 (75% of HASM, 75% of MRC5 fibroblasts and 72% of NHBE cells). Fibroblasts and smooth muscle cells showed low constitutive COX-2 expression (2 and 8%, respectively) but this was higher in NHBE cells (28%). IL-1β (24 h incubation) or BK (4 h incubation) had no effect on COX-1 expression in any of the cells studied. In contrast, there was a two- and 1.5-fold rise in the percentage of NHBE cells expressing COX-2; a 7.5- and sixfold rise in the percentage of HASM cells expressing COX-2 and a 33.5- and 20.5-fold increase in the percentage of fibroblasts expressing COX-2 after IL-1β or BK treatment, respectively. Pretreatment with dexamethasone abolished IL-1β- and BK-stimulated COX-2 induction in all cells studied. Conclusion

COX-1 is expressed constitutively in human airway fibroblasts, smooth muscle and epithelial cells but epithelial cells also show constitutive expression of COX-2. Both IL-1β and BK induced COX-2 expression in all cells studied and this induction was blocked by dexamethasone. Immunocytochemical techniques can be successfully used to detect the distribution of COX isoforms in cell cultures.

Keywords: bradykinin; cyclo-oxygenase; dexamethasone; epithelial cells; fibroblasts; immunocytochemistry; interleukin 1 beta; smooth muscle cells

Document Type: Research Article

DOI: http://dx.doi.org/10.1046/j.1365-2222.1999.00573.x

Affiliations: Respiratory Medicine Unit, City Hospital, Nottingham, UK

Publication date: July 1, 1999

bsc/cea/1999/00000029/00000007/art00014
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