Early release of mitochondrial cytochrome c and expression of mitochondrial epitope 7A6 with a porphyrin-derived photosensitizer: Bcl-2 and Bcl-X(L) overexpression do not prevent early mitochondrial events but still depress caspase activity

Christopher M. Carthy, David J. Granville, Huijun Jiang, Julia G. Levy, Charles M. Rudin, Craig B. Thompson, Bruce M. McManus, David W C Hunt

Research output: Contribution to journalArticle

Abstract

Certain nonmetallic porphyrins have potent antitumor activity upon visible light irradiation. Treatment of HeLa cells with nanomolar amounts of the photochemo therapeutic agent verteporfin and red light mobilized caspases 2, 3, 6, 7, 8, and 9, caused degradation of specific caspase substrates, and resulted in morphologic changes consistent with apoptosis. Caspase processing was detectable by 1 hour after light irradiation. The mitochondrial 7A6 epitope, recognized by monoclonal antibody APO2.7, became accessible, and cytochrome c was detectable within the cytosolic fraction of cells treated with verteporfin immediately after light irradiation. The general caspase inhibitor benzyloxycarboyl-Val-Ala-Asp-fluoromethylketone did not prevent 7A6 expression produced by photosensitization at peptide concentrations which completely prevented caspase activation and cleavage of caspase-specific substrates. Enforced overexpression of Bcl-2 or Bcl-x(L) prevented cytochrome c release and 7A6 expression produced by ultraviolet B light treatment, but did not prevent cytochrome c release or 7A6 expression elicited by verteporfin photosensitization. Bcl-2 or Bcl-x(L) overexpression delayed morphologic changes, depressed caspase activation, and limited substrate degradation, but did not protect against loss of viability after verteporfin photosensitization. This observation indicates that cells overexpressing Bcl- 2 or Bcl-x(L) exhibit resistance to caspase activation even after the appearance of cytochrome c in the cytosol. Porphyrin photosensitizers are effective chemotherapeutic agents that elicit primary proapoptotic mitochondrial events even in the setting of heightened Bcl-2 or Bcl-x(L) expression.

Original languageEnglish (US)
Pages (from-to)953-965
Number of pages13
JournalLaboratory Investigation
Volume79
Issue number8
StatePublished - Aug 1999
Externally publishedYes

Fingerprint

Photosensitizing Agents
Porphyrins
Caspases
Cytochromes c
Epitopes
Photosensitivity Disorders
Light
Caspase 2
Caspase Inhibitors
Ultraviolet Rays
HeLa Cells
Caspase 3
Cytosol
Monoclonal Antibodies
Apoptosis
Peptides
verteporfin

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

Cite this

Early release of mitochondrial cytochrome c and expression of mitochondrial epitope 7A6 with a porphyrin-derived photosensitizer : Bcl-2 and Bcl-X(L) overexpression do not prevent early mitochondrial events but still depress caspase activity. / Carthy, Christopher M.; Granville, David J.; Jiang, Huijun; Levy, Julia G.; Rudin, Charles M.; Thompson, Craig B.; McManus, Bruce M.; Hunt, David W C.

In: Laboratory Investigation, Vol. 79, No. 8, 08.1999, p. 953-965.

Research output: Contribution to journalArticle

Carthy, Christopher M. ; Granville, David J. ; Jiang, Huijun ; Levy, Julia G. ; Rudin, Charles M. ; Thompson, Craig B. ; McManus, Bruce M. ; Hunt, David W C. / Early release of mitochondrial cytochrome c and expression of mitochondrial epitope 7A6 with a porphyrin-derived photosensitizer : Bcl-2 and Bcl-X(L) overexpression do not prevent early mitochondrial events but still depress caspase activity. In: Laboratory Investigation. 1999 ; Vol. 79, No. 8. pp. 953-965.
@article{4ee19477ebeb4a5980046eb1e4f91cd6,
title = "Early release of mitochondrial cytochrome c and expression of mitochondrial epitope 7A6 with a porphyrin-derived photosensitizer: Bcl-2 and Bcl-X(L) overexpression do not prevent early mitochondrial events but still depress caspase activity",
abstract = "Certain nonmetallic porphyrins have potent antitumor activity upon visible light irradiation. Treatment of HeLa cells with nanomolar amounts of the photochemo therapeutic agent verteporfin and red light mobilized caspases 2, 3, 6, 7, 8, and 9, caused degradation of specific caspase substrates, and resulted in morphologic changes consistent with apoptosis. Caspase processing was detectable by 1 hour after light irradiation. The mitochondrial 7A6 epitope, recognized by monoclonal antibody APO2.7, became accessible, and cytochrome c was detectable within the cytosolic fraction of cells treated with verteporfin immediately after light irradiation. The general caspase inhibitor benzyloxycarboyl-Val-Ala-Asp-fluoromethylketone did not prevent 7A6 expression produced by photosensitization at peptide concentrations which completely prevented caspase activation and cleavage of caspase-specific substrates. Enforced overexpression of Bcl-2 or Bcl-x(L) prevented cytochrome c release and 7A6 expression produced by ultraviolet B light treatment, but did not prevent cytochrome c release or 7A6 expression elicited by verteporfin photosensitization. Bcl-2 or Bcl-x(L) overexpression delayed morphologic changes, depressed caspase activation, and limited substrate degradation, but did not protect against loss of viability after verteporfin photosensitization. This observation indicates that cells overexpressing Bcl- 2 or Bcl-x(L) exhibit resistance to caspase activation even after the appearance of cytochrome c in the cytosol. Porphyrin photosensitizers are effective chemotherapeutic agents that elicit primary proapoptotic mitochondrial events even in the setting of heightened Bcl-2 or Bcl-x(L) expression.",
author = "Carthy, {Christopher M.} and Granville, {David J.} and Huijun Jiang and Levy, {Julia G.} and Rudin, {Charles M.} and Thompson, {Craig B.} and McManus, {Bruce M.} and Hunt, {David W C}",
year = "1999",
month = "8",
language = "English (US)",
volume = "79",
pages = "953--965",
journal = "Laboratory Investigation",
issn = "0023-6837",
publisher = "Nature Publishing Group",
number = "8",

}

TY - JOUR

T1 - Early release of mitochondrial cytochrome c and expression of mitochondrial epitope 7A6 with a porphyrin-derived photosensitizer

T2 - Bcl-2 and Bcl-X(L) overexpression do not prevent early mitochondrial events but still depress caspase activity

AU - Carthy, Christopher M.

AU - Granville, David J.

AU - Jiang, Huijun

AU - Levy, Julia G.

AU - Rudin, Charles M.

AU - Thompson, Craig B.

AU - McManus, Bruce M.

AU - Hunt, David W C

PY - 1999/8

Y1 - 1999/8

N2 - Certain nonmetallic porphyrins have potent antitumor activity upon visible light irradiation. Treatment of HeLa cells with nanomolar amounts of the photochemo therapeutic agent verteporfin and red light mobilized caspases 2, 3, 6, 7, 8, and 9, caused degradation of specific caspase substrates, and resulted in morphologic changes consistent with apoptosis. Caspase processing was detectable by 1 hour after light irradiation. The mitochondrial 7A6 epitope, recognized by monoclonal antibody APO2.7, became accessible, and cytochrome c was detectable within the cytosolic fraction of cells treated with verteporfin immediately after light irradiation. The general caspase inhibitor benzyloxycarboyl-Val-Ala-Asp-fluoromethylketone did not prevent 7A6 expression produced by photosensitization at peptide concentrations which completely prevented caspase activation and cleavage of caspase-specific substrates. Enforced overexpression of Bcl-2 or Bcl-x(L) prevented cytochrome c release and 7A6 expression produced by ultraviolet B light treatment, but did not prevent cytochrome c release or 7A6 expression elicited by verteporfin photosensitization. Bcl-2 or Bcl-x(L) overexpression delayed morphologic changes, depressed caspase activation, and limited substrate degradation, but did not protect against loss of viability after verteporfin photosensitization. This observation indicates that cells overexpressing Bcl- 2 or Bcl-x(L) exhibit resistance to caspase activation even after the appearance of cytochrome c in the cytosol. Porphyrin photosensitizers are effective chemotherapeutic agents that elicit primary proapoptotic mitochondrial events even in the setting of heightened Bcl-2 or Bcl-x(L) expression.

AB - Certain nonmetallic porphyrins have potent antitumor activity upon visible light irradiation. Treatment of HeLa cells with nanomolar amounts of the photochemo therapeutic agent verteporfin and red light mobilized caspases 2, 3, 6, 7, 8, and 9, caused degradation of specific caspase substrates, and resulted in morphologic changes consistent with apoptosis. Caspase processing was detectable by 1 hour after light irradiation. The mitochondrial 7A6 epitope, recognized by monoclonal antibody APO2.7, became accessible, and cytochrome c was detectable within the cytosolic fraction of cells treated with verteporfin immediately after light irradiation. The general caspase inhibitor benzyloxycarboyl-Val-Ala-Asp-fluoromethylketone did not prevent 7A6 expression produced by photosensitization at peptide concentrations which completely prevented caspase activation and cleavage of caspase-specific substrates. Enforced overexpression of Bcl-2 or Bcl-x(L) prevented cytochrome c release and 7A6 expression produced by ultraviolet B light treatment, but did not prevent cytochrome c release or 7A6 expression elicited by verteporfin photosensitization. Bcl-2 or Bcl-x(L) overexpression delayed morphologic changes, depressed caspase activation, and limited substrate degradation, but did not protect against loss of viability after verteporfin photosensitization. This observation indicates that cells overexpressing Bcl- 2 or Bcl-x(L) exhibit resistance to caspase activation even after the appearance of cytochrome c in the cytosol. Porphyrin photosensitizers are effective chemotherapeutic agents that elicit primary proapoptotic mitochondrial events even in the setting of heightened Bcl-2 or Bcl-x(L) expression.

UR - http://www.scopus.com/inward/record.url?scp=0032773849&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0032773849&partnerID=8YFLogxK

M3 - Article

C2 - 10462033

AN - SCOPUS:0032773849

VL - 79

SP - 953

EP - 965

JO - Laboratory Investigation

JF - Laboratory Investigation

SN - 0023-6837

IS - 8

ER -