Evidence that insulin-like growth factor-1 requires protein kinase C-ε, PI3-kinase and mitogen-activated protein kinase pathways to protect human vascular smooth muscle cells from apoptosis

Todd R. Allen, Kristopher D. Krueger, William J. Hunter, Devendra K. Agrawal

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Abstract

Insulin-like growth factor (IGF)-1 has been implicated in the development of occlusive vascular lesions. Although its role in vascular smooth muscle cell (VSMC) growth and migration are fairly well characterized, anti-apoptotic signals of IGF-1 in human VSMC remain largely unknown. In this study, we examined IGF-1 signals that protect human and rat VSMC from staurosporine (STAU)- and c-myc- induced apoptosis, respectively. Treatment with STAU resulted in apoptotic DNA fragmentation, phosphatidylserine externalization and cell shrinkage, but only occasional VSMC 'blebbing'. STAU-induced death and IGF-1-mediated survival were concentration dependent, while time-lapse video microscopy showed that IGF-1 inhibited c-myc-induced apoptosis by 90%. Pretreatment with mitogen-activated protein kinase/extracellular signal regulated kinase kinase (MEK) inhibitors UO126 and PD098059, or with the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin, reversed IGF-1-mediated human VSMC survival by 25-27% and 66%, respectively. Translocation studies showed that IGF-1 activated protein kinase C (PKC)-ε, but not PKC-α or PKC-δ, even in the presence of STAU, while pharmacological PKC inhibition (Ro-318220 or Go6976) implicated PKC-ζ or a novel PKC isozyme in IGF-1-mediated survival. Transient expression of activated PKC-ε but not activated PKC-ζ decreased myc-induced apoptosis in rat VSMC. In human VSMC, antisense oligodeoxynucleotides to PKC-ε partially reversed IGF-1-induced survival. In addition, IGF-1 elicited a mild but sustained activation of extracellular signal regulated kinase (ERK)1/2 in human VSMC that was abolished after 1 h in the presence of STAU. PKC downregulation reversed both IGF-1- and PMA-induced ERK activity, but platelet-derived growth factor (PDGF)-induced activity was unchanged. These results indicate for the first time that IGF-1 can protect human VSMC via multiple signals, including PKC-ε, PI3-K and mitogen-activated protein kinase pathways.

Original languageEnglish
Pages (from-to)651-667
Number of pages17
JournalImmunology and Cell Biology
Volume83
Issue number6
DOIs
StatePublished - Dec 2005

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Somatomedins
Mitogen-Activated Protein Kinases
Phosphatidylinositol 3-Kinases
Vascular Smooth Muscle
Protein Kinase C
Smooth Muscle Myocytes
Muscle
Cells
Apoptosis
Staurosporine
Phosphatidylinositol 3-Kinase
Extracellular Signal-Regulated MAP Kinases
Survival
protein kinase C kinase
Rats
MAP Kinase Kinase Kinases
Video Microscopy
Mitogen-Activated Protein Kinase 3
Oligodeoxyribonucleotides
Mitogen-Activated Protein Kinase 1

All Science Journal Classification (ASJC) codes

  • Immunology
  • Clinical Biochemistry
  • Cell Biology

Cite this

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title = "Evidence that insulin-like growth factor-1 requires protein kinase C-ε, PI3-kinase and mitogen-activated protein kinase pathways to protect human vascular smooth muscle cells from apoptosis",
abstract = "Insulin-like growth factor (IGF)-1 has been implicated in the development of occlusive vascular lesions. Although its role in vascular smooth muscle cell (VSMC) growth and migration are fairly well characterized, anti-apoptotic signals of IGF-1 in human VSMC remain largely unknown. In this study, we examined IGF-1 signals that protect human and rat VSMC from staurosporine (STAU)- and c-myc- induced apoptosis, respectively. Treatment with STAU resulted in apoptotic DNA fragmentation, phosphatidylserine externalization and cell shrinkage, but only occasional VSMC 'blebbing'. STAU-induced death and IGF-1-mediated survival were concentration dependent, while time-lapse video microscopy showed that IGF-1 inhibited c-myc-induced apoptosis by 90{\%}. Pretreatment with mitogen-activated protein kinase/extracellular signal regulated kinase kinase (MEK) inhibitors UO126 and PD098059, or with the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin, reversed IGF-1-mediated human VSMC survival by 25-27{\%} and 66{\%}, respectively. Translocation studies showed that IGF-1 activated protein kinase C (PKC)-ε, but not PKC-α or PKC-δ, even in the presence of STAU, while pharmacological PKC inhibition (Ro-318220 or Go6976) implicated PKC-ζ or a novel PKC isozyme in IGF-1-mediated survival. Transient expression of activated PKC-ε but not activated PKC-ζ decreased myc-induced apoptosis in rat VSMC. In human VSMC, antisense oligodeoxynucleotides to PKC-ε partially reversed IGF-1-induced survival. In addition, IGF-1 elicited a mild but sustained activation of extracellular signal regulated kinase (ERK)1/2 in human VSMC that was abolished after 1 h in the presence of STAU. PKC downregulation reversed both IGF-1- and PMA-induced ERK activity, but platelet-derived growth factor (PDGF)-induced activity was unchanged. These results indicate for the first time that IGF-1 can protect human VSMC via multiple signals, including PKC-ε, PI3-K and mitogen-activated protein kinase pathways.",
author = "Allen, {Todd R.} and Krueger, {Kristopher D.} and Hunter, {William J.} and Agrawal, {Devendra K.}",
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T1 - Evidence that insulin-like growth factor-1 requires protein kinase C-ε, PI3-kinase and mitogen-activated protein kinase pathways to protect human vascular smooth muscle cells from apoptosis

AU - Allen, Todd R.

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AU - Hunter, William J.

AU - Agrawal, Devendra K.

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N2 - Insulin-like growth factor (IGF)-1 has been implicated in the development of occlusive vascular lesions. Although its role in vascular smooth muscle cell (VSMC) growth and migration are fairly well characterized, anti-apoptotic signals of IGF-1 in human VSMC remain largely unknown. In this study, we examined IGF-1 signals that protect human and rat VSMC from staurosporine (STAU)- and c-myc- induced apoptosis, respectively. Treatment with STAU resulted in apoptotic DNA fragmentation, phosphatidylserine externalization and cell shrinkage, but only occasional VSMC 'blebbing'. STAU-induced death and IGF-1-mediated survival were concentration dependent, while time-lapse video microscopy showed that IGF-1 inhibited c-myc-induced apoptosis by 90%. Pretreatment with mitogen-activated protein kinase/extracellular signal regulated kinase kinase (MEK) inhibitors UO126 and PD098059, or with the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin, reversed IGF-1-mediated human VSMC survival by 25-27% and 66%, respectively. Translocation studies showed that IGF-1 activated protein kinase C (PKC)-ε, but not PKC-α or PKC-δ, even in the presence of STAU, while pharmacological PKC inhibition (Ro-318220 or Go6976) implicated PKC-ζ or a novel PKC isozyme in IGF-1-mediated survival. Transient expression of activated PKC-ε but not activated PKC-ζ decreased myc-induced apoptosis in rat VSMC. In human VSMC, antisense oligodeoxynucleotides to PKC-ε partially reversed IGF-1-induced survival. In addition, IGF-1 elicited a mild but sustained activation of extracellular signal regulated kinase (ERK)1/2 in human VSMC that was abolished after 1 h in the presence of STAU. PKC downregulation reversed both IGF-1- and PMA-induced ERK activity, but platelet-derived growth factor (PDGF)-induced activity was unchanged. These results indicate for the first time that IGF-1 can protect human VSMC via multiple signals, including PKC-ε, PI3-K and mitogen-activated protein kinase pathways.

AB - Insulin-like growth factor (IGF)-1 has been implicated in the development of occlusive vascular lesions. Although its role in vascular smooth muscle cell (VSMC) growth and migration are fairly well characterized, anti-apoptotic signals of IGF-1 in human VSMC remain largely unknown. In this study, we examined IGF-1 signals that protect human and rat VSMC from staurosporine (STAU)- and c-myc- induced apoptosis, respectively. Treatment with STAU resulted in apoptotic DNA fragmentation, phosphatidylserine externalization and cell shrinkage, but only occasional VSMC 'blebbing'. STAU-induced death and IGF-1-mediated survival were concentration dependent, while time-lapse video microscopy showed that IGF-1 inhibited c-myc-induced apoptosis by 90%. Pretreatment with mitogen-activated protein kinase/extracellular signal regulated kinase kinase (MEK) inhibitors UO126 and PD098059, or with the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin, reversed IGF-1-mediated human VSMC survival by 25-27% and 66%, respectively. Translocation studies showed that IGF-1 activated protein kinase C (PKC)-ε, but not PKC-α or PKC-δ, even in the presence of STAU, while pharmacological PKC inhibition (Ro-318220 or Go6976) implicated PKC-ζ or a novel PKC isozyme in IGF-1-mediated survival. Transient expression of activated PKC-ε but not activated PKC-ζ decreased myc-induced apoptosis in rat VSMC. In human VSMC, antisense oligodeoxynucleotides to PKC-ε partially reversed IGF-1-induced survival. In addition, IGF-1 elicited a mild but sustained activation of extracellular signal regulated kinase (ERK)1/2 in human VSMC that was abolished after 1 h in the presence of STAU. PKC downregulation reversed both IGF-1- and PMA-induced ERK activity, but platelet-derived growth factor (PDGF)-induced activity was unchanged. These results indicate for the first time that IGF-1 can protect human VSMC via multiple signals, including PKC-ε, PI3-K and mitogen-activated protein kinase pathways.

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