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J Allergy Clin Immunol. 2008 May;121(5):1232-7. doi: 10.1016/j.jaci.2008.02.007. Epub 2008 Mar 19.

Corticosteroids as inhibitors of cysteinyl leukotriene metabolic and signaling pathways.

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1
Asthma and Allergic Disease Center, Beirne Carter Center for Immunology Research, Department of Medicine, University of Virginia Health System, Charlottesville, Va.

Abstract

BACKGROUND:

Corticosteroids (CCSs) do not influence secretion of cysteinyl leukotrienes (CysLTs) that occurs on cellular activation during allergic reactions nor do they modulate bronchospastic responses to inhalation challenges with leukotrienes (LTs).

OBJECTIVES:

We speculated that CCSs might modulate pathways responsible for CysLT production and diminish the ability of cellular activation to cause their release. Similarly, CCSs could reduce expression of CysLT receptor 1 (CysLTR1) and CysLT receptor 2 (CysLT2R) and modulate their responsiveness.

METHODS:

We investigated influences of fluticasone on expression of mRNA for LTC(4) synthase (LTC(4)S), CysLT1R, and CysLT2R within T lymphocytes, monocytes, and eosinophils by means of quantitative PCR. Effects on receptor protein expression were evaluated by means of flow cytometry.

RESULTS:

Circulating immune cells (T cells, monocytes, and eosinophils) express low levels of LTC(4)S mRNA, and this was not influenced by CCSs. However, IL-4 induced transcripts in T lymphocytes, and this was prevented by fluticasone. Paradoxically, CCSs synergized with IL-4 to increase LTC(4)S expression in monocytes. Although not influencing basal or IL-4-stimulated CysLT1R expression, fluticasone inhibited basal CysLT2R transcript expression on monocytes and IL-4-induced expression in all 3 cell types.

CONCLUSIONS:

In addition to not blocking the acute release of CysLTs on cellular activation, CCSs do not diminish the capacity of cells to synthesize these compounds. CCSs do not diminish CysLT1R expression, consistent with their lack of influence on bronchospasm, which is mediated through this receptor.

PMID:
18355910
DOI:
10.1016/j.jaci.2008.02.007
[Indexed for MEDLINE]
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