Reactive oxygen species mediate cyclooxygenase-2 induction during monocyte to macrophage differentiation: critical role of NADPH oxidase.
OBJECTIVE
The objective of this study was to explore the relationship between monocyte differentiation into macrophages and cyclooxygenase-2 (Cox-2) expression, based upon the observation that high amounts of this enzyme, colocalizing mainly with macrophages, have been found in human atherosclerotic lesions. Moreover, the hypothesis that reactive oxygen species (ROS) could be important as mediators of Cox-2 expression during monocyte differentiation was verified. Although ROS are known as modulators of gene expression profile, their involvement in monocyte differentiation has not been explored previously.


METHODS
Human adherent monocytes and the promonocytic cell line U937 were differentiated into macrophages by phorbol ester (PMA). Cox-2 was evaluated in terms of protein, mRNA and activity. Intracellular ROS formation was measured by the oxidant sensitive dye 2',7'-dichlorofluorescein diacetate. NADPH oxidase subunit p47(phox) was evaluated by Western blot analysis.


RESULTS
Functionally active Cox-2 is expressed during PMA-induced monocyte transition into macrophages and ROS driven by the NADPH oxidase play a critical role in this event.


CONCLUSIONS
Monocyte differentiation into macrophages, possibly triggered by unquenched ROS, may contribute to the increased inflammatory response within atheromata.
Barbieri
Silvia Stella
SS
E. Grossi Paoletti Center, Department of Pharmacological Sciences, University of Milan, Via Balzaretti 9, 20133, Milan, Italy. susanna.colli@unimi.it
Eligini
Sonia
S
Brambilla
Marta
M
Tremoli
Elena
E
Colli
Susanna
S
D000199:Actins / Q000032:analysis / Q000378:metabolism; D000704:Analysis of Variance; D001161:Arteriosclerosis / Q000201:enzymology* / Q000276:immunology*; D015153:Blotting, Western; D002454:Cell Differentiation; D051546:Cyclooxygenase 2; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation; D005434:Flow Cytometry; D006801:Humans; D007527:Isoenzymes / Q000032:analysis* / Q000235:genetics; D008264:Macrophages / Q000201:enzymology*; D008565:Membrane Proteins; D019255:NADPH Oxidases / Q000032:analysis / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000032:analysis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020298:U937 Cells
D000199:Actins; D007527:Isoenzymes; D008565:Membrane Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D019255:NADPH Oxidases