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

Abstract

Summary 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, antiapoptotic 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 mitogenactivated protein kinase pathways.

Inhibitory effect of D1-like and D3dopamine receptors on norepinephrine-induced proliferation in vascular smooth muscle cells

“…In renal proximal tubule cells, the activation of D 1 -like receptor can stimulate ( and ) or inhibit (␦) new PKCs or translocate specific PKC isoforms from cytosol to membrane (␣, ␤, and ε) and membrane to cytosol (␦) (9,32,52,56). There are reports that PKC-␤1, PKC-␦, PKC-ε, PKC-, and PKC-have proliferative VSMC effects (1,56). In our studies, a Ca 2ϩ channel blocker has no effect on the ␣ 1 -adrenoceptor-mediated proliferation effect; therefore, it is possible that atypical and novel PKCs, and not conventional PKCs, are involved in this action.…”

Activation of the δ-opioid receptor inhibits serum deprivation-induced apoptosis of human liver cells via the activation of PKC and the mitochondrial pathway

“…We determined that the activation of the δ-opioid receptor enhances PKC expression. PKC stimulation inhibits the apoptosis of different types of cells (38)(39)(40). Meanwhile, PKC also participates in the protection against hepatic ischemia reperfusion injury and is involved in the processes of cellular proliferation and apoptosis (19,41).…”

Insulin-like growth factor-1 regulates platelet activation through PI3-Kα isoform

“…12 Activated PI3-K mediates Akt activation, which contributes to the survival signal of IGF-1. 14,15 ADP is an important agonist for platelet activation and causes platelets to change their shape, aggregate, and release contents of granules. ADP-induced platelet aggregation requires coactivation of the G q -coupled P2Y 1 and G i -coupled P2Y 12 receptors.…”