Differential regulation of inducible and constitutive prostaglandin endoperoxide synthase in osteoblastic MC3T3-E1 cells

• Published in: The Journal of biological chemistry 1993-12, Vol.268 (34), p.25643-25649
• Main Authors: Pilbeam, C C, Kawaguchi, H, Hakeda, Y, Voznesensky, O, Alander, C B, Raisz, L G
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Cell Line; Colforsin - pharmacology; Culture Media; Culture Media, Serum-Free; Cycloheximide - pharmacology; Dactinomycin - pharmacology; Dinoprostone - metabolism; DNA - metabolism; Enzyme Induction; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydrocortisone - pharmacology; Kinetics; Mice; Osteoblasts - drug effects; Osteoblasts - enzymology; Oxidoreductases; Prostaglandin-Endoperoxide Synthases - biosynthesis; Prostaglandin-Endoperoxide Synthases - metabolism; RNA, Messenger - biosynthesis; RNA, Messenger - metabolism; Tetradecanoylphorbol Acetate - pharmacology; Time Factors; Transforming Growth Factor beta - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)74438-X

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.