title: Cyclic-AMP inhibits nitric oxide-induced apoptosis in human osteoblast: the regulation of caspase-3, -6, -9 and the release of cytochrome c in nitric oxide-induced apoptosis by cAMP.
abstract: Nitric oxide (NO) induces apoptotic cell death and cAMP has a significantly protective effect on NO-induced cytotoxicity in human osteoblasts, MG-63 cells. Treatment with S-nitroso-N-acetylpenicillamine (SNAP) (0.6 mM) resulted in genomic DNA fragmentation, characteristic of apoptosis. However, concomitant incubation of the cells with either DBcAMP or forskolin markedly inhibited SNAP-induced apoptosis in a dose-dependent manner. Furthermore, pretreatment of MG-63 cells with H-89 or KT5720, which is known to inhibit cAMP-dependent protein kinase (PKA), abolished the protective effect of DBcAMP and forskolin on SNAP-induced apoptosis. In this study, we explored the involvement of caspases in the regulatory mechanism of SNAP-induced apoptosis by cAMP. Our data show that DBcAMP or forskolin blocked SNAP-induced caspase-3-like cysteine protease activation and that H-89, a PKA inhibitor, reversed the cAMP-induced regulatory effect of caspase-3 like protease. Consistent with the results, cAMP inhibited the proteolytic cleavage of caspase-3, -6, -9 and cytochrome c release to cytoplasm. The inhibition of caspase-3 activation did not block SNAP-induced cytochrome c release to cytoplasm, suggesting that caspase-3 activation may occur downstream of cytochrome c release. In summary, these findings show that the exposure of MG-63 cells to cAMP analogs renders them more resistant to NO-induced damage and suggests the presence of regulatory mechanisms of the cell death pathway by cAMP in which caspase-3, -6, and -9 and cytochrome c release serves to mediate NO-induced apoptosis.
authors.affiliation: Department of Dental Pharmacology and Wonkwang Dental Research Institute, School of Dentistry, Chonbuk, South Korea.
authors.forename: H J
authors.initials: HJ
authors.lastname: Chae
authors.forename: S W
authors.initials: SW
authors.lastname: Chae
authors.forename: N H
authors.initials: NH
authors.lastname: An
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.forename: C W
authors.initials: CW
authors.lastname: Kim
authors.forename: S K
authors.initials: SK
authors.lastname: Yoo
authors.forename: H H
authors.initials: HH
authors.lastname: Kim
authors.forename: Z H
authors.initials: ZH
authors.lastname: Lee
authors.forename: H R
authors.initials: HR
authors.lastname: Kim
mesh_terms: D017209:Apoptosis; D053148:Caspase 3; D053178:Caspase 6; D053453:Caspase 9; D020169:Caspases / Q000502:physiology*; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D003574:Cytochrome c Group / Q000378:metabolism*; D006801:Humans; D009569:Nitric Oxide / Q000502:physiology*; D010006:Osteoblasts / Q000201:enzymology / Q000502:physiology*; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D003574:Cytochrome c Group; C110881:S-nitro-N-acetylpenicillamine; D005576:Colforsin; D009569:Nitric Oxide; D000242:Cyclic AMP; C505407:CASP3 protein, human; C505514:CASP6 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053178:Caspase 6; D053453:Caspase 9; D020169:Caspases; D010396:Penicillamine