Differential regulation of inducible and constitutive prostaglandin endoperoxide synthase in osteoblastic MC3T3-E1 cells.
Regulation of mRNA levels for the constitutive and inducible prostaglandin endoperoxide synthases, PGHS-1 and PGHS-2, was examined in murine osteoblastic MC3T3-E1 cells. Serum induction of PGHS-2 mRNA levels was rapid, transient, increased by cycloheximide, and inhibited 72% by cortisol. The cortisol inhibition was blocked by cycloheximide. Serum stimulation of PGHS-1 mRNA was slower, decreased by cycloheximide, and inhibited 28% by cortisol. Increased prostaglandin E2 (PGE2) production and induction of PGHS-2 immunoreactive protein paralleled changes in PGHS-2 mRNA. PGHS-2 mRNA was induced at 2 h in serum-free cells by transforming growth factor-beta (TGF-beta), phorbol 12-myristate 13-acetate, and, to a lesser extent, by forskolin. The combination of phorbol 12-myristate 13-acetate and forskolin was synergistic. TGF-beta induction was prolonged compared with serum, inhibited 67% by cortisol, and the inhibition was not blocked by cycloheximide. TGF-alpha had little effect on PGHS-2 mRNA at 2 h, but the combination of TGF-beta and TGF-alpha was synergistic for PGHS-1 and PGHS-2. PGE2 itself induced PGHS-2 mRNA, and inhibition of PGE2 production decreased the serum induction by 55%, suggesting an important role for autoamplification. The rapidity and amplitude of changes in PGHS-2 suggest that it may be involved in bone responses to acute stresses, such as mechanical strain, inflammation, and injury.
Pilbeam
C C
CC
University of Connectiut Health Center, Farmington 06030.
Kawaguchi
H
H
Hakeda
Y
Y
Voznesensky
O
O
Alander
C B
CB
Raisz
L G
LG
D000818:Animals; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D003470:Culture Media; D016895:Culture Media, Serum-Free; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism; D004790:Enzyme Induction; D006854:Hydrocortisone / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D003470:Culture Media; D016895:Culture Media, Serum-Free; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D003609:Dactinomycin; D005576:Colforsin; D004247:DNA; D003513:Cycloheximide; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate; D006854:Hydrocortisone