Cyclooxygenase-2 expression inhibits trophic withdrawal apoptosis in nervegrowth factor-differentiated PC12 cells

Cyclooxygenase-2 (Cox-2), an enzyme responsible for catalyzing the committe d step in prostanoid biosynthesis, is the product of an immediate early gen e capable of being up-regulated by diverse stimuli. Significantly Cox-2 mRN A is absent from rat pheochromocytoma (PC12) cells, both basally and follow ing stimulation with a range of agonists, Using PC12 cells engineered to st ably express isopropyl-1-thio-beta-D-galactopyranoside-inducible Cox-2 (PCX II-4), we have investigated the putative effects of Cox-2 expression on dif ferentiation, proliferation, and trophic withdrawal apoptosis, Cox-2 bioact ivity had no effect on nerve growth factor-induced differentiation, epiderm al growth factor-induced proliferation, or aromatic L-amino acid decarboxyl ase expression, However, trophic withdrawal apoptosis, induced by the remov al of nerve growth factor following differentiation, was markedly reduced i n the PCXII-4 when compared with control cells, as assessed by annexin V st aining, DNA laddering, and Hoechst 33258 staining. The specificity of this effect was confirmed using two pharmacologically distinct nonsteroidal anti inflammatory drugs, indomethacin and NS398. Investigations showed that the activity of the pro-apoptotic protease caspase-3 was reduced in PCXII cells . This study demonstrates that Cox-2-derived prostaglandins exert cytoprote ctive effects in trophic factor withdrawal apoptosis and provides evidence that this is, at least in part, due to suppression of caspase-3 activity.