Altered arachidonic acid metabolism during differentiation of the human monoblastoid cell line U937.
The human cell line U937 was used as a model for differentiation along the mononuclear phagocyte lineage. Following treatment with the phorbol ester TPA, PGE2 and TxB2 secretion was induced 50-100-fold, and both PGF2 alpha and PGI2 levels became detectable in the supernatant of TPA-differentiated U937 cells. The content of the prostaglandin precursor, arachidonic acid, remained unchanged in the cellular phospholipids of undifferentiated and TPA-differentiated U937 cells. Of the enzymes involved in the availability and metabolism of arachidonic acid, phospholipase A2 activity was increased 2-fold in the membranes of TPA-differentiated U937 cells, whereas lysophosphatide acyltransferase activity remained unaltered. Cyclooxygenase activity, however, was enhanced 5-10-fold, which was due to enhanced expression of the enzyme as demonstrated by dot-blot analysis. The data suggest that the capacity to secrete prostaglandins is acquired during differentiation with TPA and results mainly from an increased cyclooxygenase activity. Despite the capacity of TPA-differentiated U937 cells to synthesize prostaglandins, none of the known monocytic stimuli further stimulated prostaglandin secretion in TPA-differentiated U937 cells. Generation of leukotrienes appears to represent a later state in the differentiation along the monocyte-macrophage lineage, since neither LTB4 nor cysteinyl-leukotrienes were detectable in the supernatants of either undifferentiated or TPA-differentiated U937 cells.
Koehler
L
L
Department of Pharmacology and Toxicology, Medical School Hannover, F.R.G.
Hass
R
R
Wessel
K
K
DeWitt
D L
DL
Kaever
V
V
Resch
K
K
Goppelt-Struebe
M
M
D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D005227:Fatty Acids / Q000032:analysis; D006801:Humans; D019746:Intramolecular Oxidoreductases; D007535:Isomerases / Q000032:analysis; D015289:Leukotrienes / Q000096:biosynthesis; D008084:Lipoxygenase / Q000032:analysis; D008954:Models, Biological; D009000:Monocytes / Q000187:drug effects / Q000201:enzymology*; D010741:Phospholipases A / Q000032:analysis; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism; D000071876:Prostaglandin-E Synthases; D011453:Prostaglandins / Q000096:biosynthesis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001095:Arachidonic Acids; D005227:Fatty Acids; D015289:Leukotrienes; D010743:Phospholipids; D011453:Prostaglandins; D016718:Arachidonic Acid; D008084:Lipoxygenase; D010741:Phospholipases A; D054467:Phospholipases A2; D007535:Isomerases; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases; D013755:Tetradecanoylphorbol Acetate