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Increasing the endogenous NO level causes catalase inactivation and reactivation of intercellular apoptosis signaling specifically in tumor cells.

Bauer G - Redox Biol (2015)

Bottom Line: Finally, singlet oxygen is generated at sufficiently high concentration to inactivate protective catalase and to reactivate intercellular apoptosis-inducing ROS signaling.This regulatory network allows to establish several pathways for synergistic interactions, like the combination of modulators of NO metabolism with enhancers of superoxide anion generation, modulators of NO metabolism that act at different targets and between modulators of NO metabolism and direct catalase inhibitors.It is also shown that hybrid molecules like NO-aspirin utilize this synergistic potential.

View Article: PubMed Central - PubMed

Affiliation: Institute of Virology, Department of Medical Microbiology and Hygiene, University Medical Center Freiburg, Hermann-Herder Strasse 11, D-79104 Freiburg, Germany. Electronic address: georg.bauer@uniklinik-freiburg.de.

No MeSH data available.


Related in: MedlinePlus

Synergistic effect between the NOD inhibitor malvidin and low dose gamma radiation-enhanced superoxide anion generation (A) 12,500 MKN-45 cells per assay received no inhibitor (control) or 25 µM caspase-8 inhibitor (CASP-8 INH) either 15 min before or 20 min after the addition of the indicated concentrations of malvidin. The percentages of apoptotic cells were determined after 12 h. B. MKN-45 cells were irradiated at a density of 200,000 cells/ml with 75 mGy gamma radiation and incubated for 1 h. The cells were seeded at a density of 12,500 cells per assay and received no inhibitor (control) or 25 µM caspase-8 inhibitor (CASP-8 INH) either 15 before or 20 min after the addition of the indicated concentrations of malvidin. The percentages of apoptotic cells were determined after 12 h. Statistical analysis:A: Apoptosis induction by 4 ng/ml and 1000 ng/ml was significant (p<0.01), apoptosis induction by 12–330 ng/ml was highly significant (p<0.001). Inhibition by caspase-8 inhibitor added 15 min before cyanidin was highly significant (p<0.001), whereas caspase-8 inhibitor added 25 min after cyanidin only caused highly significant inhibition (p<0.001) at 110 ng/ml cyanidin. B: The low dose irradiation-dependent shift of the curve compared to A was highly significant (p<0.001). There was no significant inhibition by caspase-8 inhibitor.
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f0055: Synergistic effect between the NOD inhibitor malvidin and low dose gamma radiation-enhanced superoxide anion generation (A) 12,500 MKN-45 cells per assay received no inhibitor (control) or 25 µM caspase-8 inhibitor (CASP-8 INH) either 15 min before or 20 min after the addition of the indicated concentrations of malvidin. The percentages of apoptotic cells were determined after 12 h. B. MKN-45 cells were irradiated at a density of 200,000 cells/ml with 75 mGy gamma radiation and incubated for 1 h. The cells were seeded at a density of 12,500 cells per assay and received no inhibitor (control) or 25 µM caspase-8 inhibitor (CASP-8 INH) either 15 before or 20 min after the addition of the indicated concentrations of malvidin. The percentages of apoptotic cells were determined after 12 h. Statistical analysis:A: Apoptosis induction by 4 ng/ml and 1000 ng/ml was significant (p<0.01), apoptosis induction by 12–330 ng/ml was highly significant (p<0.001). Inhibition by caspase-8 inhibitor added 15 min before cyanidin was highly significant (p<0.001), whereas caspase-8 inhibitor added 25 min after cyanidin only caused highly significant inhibition (p<0.001) at 110 ng/ml cyanidin. B: The low dose irradiation-dependent shift of the curve compared to A was highly significant (p<0.001). There was no significant inhibition by caspase-8 inhibitor.

Mentions: The reaction scheme shown in Fig. 4B allowed to predict that the combination of compounds that affect different targets within the biochemical network described might establish useful synergistic effects. As shown in Fig. 11A, the NOD inhibitor malvidin caused apoptosis induction in tumor cells in a concentration-dependent mode. The reaction required an early caspase-8-dependent step. When the cells had been pretreated with low dose gamma irradiation (75 mGy) and allowed to establish bystander-mediated enhancement of NOX1-dependent superoxide anion production [132] before malividin was added, a remarkable synergistic effect was seen (Fig. 11B). Apoptosis induction by the synergistically acting effectors was independent of caspase-8. This confirms our previous finding that the caspase-8-dependent reaction during singlet oxygen-mediated catalase inactivation was dispensable when the superoxide anion concentration was increased [52,85]. This finding also confirmed that in the context of these experiments caspase-8, was not involved in the execution of cell death, but that its action was rather restricted to the modulation of singlet oxygen generation. If this conclusion was correct, caspase-8-deficient tumor cells should not show apoptosis induction by malvidin applied alone, but should die by apoptosis after stimulation of NOX1 activity by low dose radiation, which compensated for the specific modulatory function of caspase-8.


Increasing the endogenous NO level causes catalase inactivation and reactivation of intercellular apoptosis signaling specifically in tumor cells.

Bauer G - Redox Biol (2015)

Synergistic effect between the NOD inhibitor malvidin and low dose gamma radiation-enhanced superoxide anion generation (A) 12,500 MKN-45 cells per assay received no inhibitor (control) or 25 µM caspase-8 inhibitor (CASP-8 INH) either 15 min before or 20 min after the addition of the indicated concentrations of malvidin. The percentages of apoptotic cells were determined after 12 h. B. MKN-45 cells were irradiated at a density of 200,000 cells/ml with 75 mGy gamma radiation and incubated for 1 h. The cells were seeded at a density of 12,500 cells per assay and received no inhibitor (control) or 25 µM caspase-8 inhibitor (CASP-8 INH) either 15 before or 20 min after the addition of the indicated concentrations of malvidin. The percentages of apoptotic cells were determined after 12 h. Statistical analysis:A: Apoptosis induction by 4 ng/ml and 1000 ng/ml was significant (p<0.01), apoptosis induction by 12–330 ng/ml was highly significant (p<0.001). Inhibition by caspase-8 inhibitor added 15 min before cyanidin was highly significant (p<0.001), whereas caspase-8 inhibitor added 25 min after cyanidin only caused highly significant inhibition (p<0.001) at 110 ng/ml cyanidin. B: The low dose irradiation-dependent shift of the curve compared to A was highly significant (p<0.001). There was no significant inhibition by caspase-8 inhibitor.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4564397&req=5

f0055: Synergistic effect between the NOD inhibitor malvidin and low dose gamma radiation-enhanced superoxide anion generation (A) 12,500 MKN-45 cells per assay received no inhibitor (control) or 25 µM caspase-8 inhibitor (CASP-8 INH) either 15 min before or 20 min after the addition of the indicated concentrations of malvidin. The percentages of apoptotic cells were determined after 12 h. B. MKN-45 cells were irradiated at a density of 200,000 cells/ml with 75 mGy gamma radiation and incubated for 1 h. The cells were seeded at a density of 12,500 cells per assay and received no inhibitor (control) or 25 µM caspase-8 inhibitor (CASP-8 INH) either 15 before or 20 min after the addition of the indicated concentrations of malvidin. The percentages of apoptotic cells were determined after 12 h. Statistical analysis:A: Apoptosis induction by 4 ng/ml and 1000 ng/ml was significant (p<0.01), apoptosis induction by 12–330 ng/ml was highly significant (p<0.001). Inhibition by caspase-8 inhibitor added 15 min before cyanidin was highly significant (p<0.001), whereas caspase-8 inhibitor added 25 min after cyanidin only caused highly significant inhibition (p<0.001) at 110 ng/ml cyanidin. B: The low dose irradiation-dependent shift of the curve compared to A was highly significant (p<0.001). There was no significant inhibition by caspase-8 inhibitor.
Mentions: The reaction scheme shown in Fig. 4B allowed to predict that the combination of compounds that affect different targets within the biochemical network described might establish useful synergistic effects. As shown in Fig. 11A, the NOD inhibitor malvidin caused apoptosis induction in tumor cells in a concentration-dependent mode. The reaction required an early caspase-8-dependent step. When the cells had been pretreated with low dose gamma irradiation (75 mGy) and allowed to establish bystander-mediated enhancement of NOX1-dependent superoxide anion production [132] before malividin was added, a remarkable synergistic effect was seen (Fig. 11B). Apoptosis induction by the synergistically acting effectors was independent of caspase-8. This confirms our previous finding that the caspase-8-dependent reaction during singlet oxygen-mediated catalase inactivation was dispensable when the superoxide anion concentration was increased [52,85]. This finding also confirmed that in the context of these experiments caspase-8, was not involved in the execution of cell death, but that its action was rather restricted to the modulation of singlet oxygen generation. If this conclusion was correct, caspase-8-deficient tumor cells should not show apoptosis induction by malvidin applied alone, but should die by apoptosis after stimulation of NOX1 activity by low dose radiation, which compensated for the specific modulatory function of caspase-8.

Bottom Line: Finally, singlet oxygen is generated at sufficiently high concentration to inactivate protective catalase and to reactivate intercellular apoptosis-inducing ROS signaling.This regulatory network allows to establish several pathways for synergistic interactions, like the combination of modulators of NO metabolism with enhancers of superoxide anion generation, modulators of NO metabolism that act at different targets and between modulators of NO metabolism and direct catalase inhibitors.It is also shown that hybrid molecules like NO-aspirin utilize this synergistic potential.

View Article: PubMed Central - PubMed

Affiliation: Institute of Virology, Department of Medical Microbiology and Hygiene, University Medical Center Freiburg, Hermann-Herder Strasse 11, D-79104 Freiburg, Germany. Electronic address: georg.bauer@uniklinik-freiburg.de.

No MeSH data available.


Related in: MedlinePlus