Characterization of prostaglandin E2 generation through the cyclooxygenase (COX)-2 pathway in human neutrophils.
In the present study, we characterized the generation of prostaglandin (PG)E2 in human neutrophils. We found that the Ca2+-dependent type IV cytosolic phospholipase A2 (cPLA2) was pivotally involved in the COX-2-mediated generation of PGE2 in response to a calcium ionophore, as determined by the use of selected PLA2 inhibitors. PGE2 biosynthesis elicited by bacterial-derived peptides or by phagocytic stimuli acting on cell surface receptors also showed to be dependent on cPLA2 activity. We then assessed metabolism of unesterified arachidonic acid (AA), and observed that PGE2 production becomes favored over that of LTB4 with higher AA concentrations. Withdrawal of calcium prevented the generation of PGE2 in response to a calcium ionophore but did not affect the up-regulation of COX-2 or its capacity to convert AA, thus limiting its implication at the level of cPLA2 activation. Of the main eicosanoids produced by neutrophils, only LTB4 was able to up-regulate COX-2 expression. Finally, the only PGE synthase isoform found in neutrophils is microsomal PGE synthase-1; it co-localized with COX-2 and its expression appeared mainly constitutive. These results highlight key differences in regulatory processes of the 5-LO and COX pathways, and enhance our knowledge at several levels in the PGE2 biosynthesis in neutrophils.
St-Onge
Mireille
M
Centre de Recherche en Rhumatologie et Immunologie du CHUQ (CHUL), Sainte-Foy, and Department of Anatomy-Physiology, Faculty of Medicine, Laval University, Quebec, Canada, and Rheumatology Unit, Royal Adelaide Hospital, SA, Australia.
Flamand
Nicolas
N
Biarc
Jordane
J
Picard
Serge
S
Bouchard
Line
L
Dussault
Andrée-Anne
AA
Laflamme
Cynthia
C
James
Michael J
MJ
Caughey
Gillian E
GE
Cleland
Leslie G
LG
Borgeat
Pierre
P
Pouliot
Marc
M
D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D016718:Arachidonic Acid / Q000737:chemistry / Q000378:metabolism; D000001:Calcimycin / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D015232:Dinoprostone / Q000096:biosynthesis*; D004789:Enzyme Activation; D054513:Group IV Phospholipases A2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007476:Ionophores / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D007975:Leukotriene B4 / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D009000:Monocytes / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013928:Thromboxane A2 / Q000378:metabolism
D007476:Ionophores; D007527:Isoenzymes; D007975:Leukotriene B4; D016718:Arachidonic Acid; D000001:Calcimycin; D013928:Thromboxane A2; D001094:Arachidonate 5-Lipoxygenase; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D054513:Group IV Phospholipases A2; D015232:Dinoprostone; D002118:Calcium