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Published online before print July 26, 2005
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Article |
,
,
,
,
Departments of *Experimental Pharmacology and
Biology and Cellular and Molecular Pathology "L. Califano," University of Naples Federico II, Italy; and
Department of Clinical and Experimental Medicine and Pharmacology, University of Messina, Italy
@ To whom correspondence should be addressed. E-mail: sautebin{at}unina.it.
| Abstract |
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Leukotrienes (LT) and prostaglandins (PG) are proinflammatory mediators generated by the conversion of arachidonic acid via 5-lipoxygenase (5-LO) and cyclooxygenase (COX) pathways. It has long been proposed that the inhibition of the 5-LO could enhance the COX pathway leading to an increased PG generation. We have found that in in vitro models of inflammation, such as mice-elicited peritoneal macrophages activated with lipopolysaccharide (LPS)/interferon-
(IFN-
), the deletion of the gene encoding for 5-LO or the enzyme activity inhibition corresponded to a negative modulation of the COX pathway. Moreover, exogenously added LTC4, but not LTD4, LTE4, and LTB4, was able to increase PG production in stimulated cells from 5-LO wild-type and knockout mice. LTC4 was not able to induce COX-2 expression by itself but rather potentiated the action of LPS/IFN-
through the extracellular signal-regulated kinase-1/2 activation, as demonstrated by the use of a specific mitogen-activated protein kinase (MAPK) kinase inhibitor. The LT-induced increase in PG generation, as well as MAPK activation, was dependent by a specific ligand-receptor interaction, as demonstrated by the use of a cys-LT1 receptor antagonist, although also, a direct action of the antagonist used on PG generation cannot be excluded. Thus, the balance between COX and 5-LO metabolites could be of great importance in controlling macrophage functions and consequently, inflammation and tumor promotion.
Key Words: eicosanoids cyclooxygenase 2 5-lipoxygenase mitogen-activated protein kinase
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