Abstract
Ischemic stress causes neuronal death and functional impairment. Evidence has suggested that cells in the ischemic core first lose viability due to the decline in blood flow and cellular energy metabolism and then die by necrosis. Although inhibition of necrosis could be a potent therapeutic target for brain ischemia, known neurotrophic factors are ineffective for neuronal necrosis. We previously reported that insulin, but not brain-derived neurotrophic factor or insulin like-growth factor-1, inhibited neuronal necrosis under serum-free starvation stress. Although insulin receptors are abundant in the central nervous system as well as in peripheral tissues, neurons are not dependent upon insulin for their glucose supply, indicating that insulin receptors have other roles in the central nervous system. In the present study, by using hypoxia-reperfusion stress, we showed that cortical neurons rapidly died by necrosis as evaluated by propidium iodide staining and transmission electron microscopic analysis. As expected, insulin treatment significantly inhibited neuronal necrosis, although this effect was blocked by pretreatment with an antisense oligonucleotide for the insulin receptor. Furthermore, an inhibitor of protein kinase C (PKC) eliminated the insulin-induced antinecrotic effect. The addition of insulin induced significant translocation of only the PKC-γ isoform, whereas antisense oligonucleotide treatment for this isoform abolished the insulin-induced inhibition of necrosis. Together, these results suggest that insulin mediates inhibition of neuronal necrosis through a novel mechanism involving PKC-γ activation.
Footnotes
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Parts of this study were supported by grants-in-aid and special coordination funds from the Ministry of Education, Culture, Sports, Science and Technology.
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doi:10.1124/jpet.104.082735.
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ABBREVIATIONS: IR, insulin receptor; PBS, phosphate-buffered saline; HS, horse serum; FBS, fetal bovine serum; WST-8, 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt; Ara-C, cytosine β-d-arabinofranoside; BSS, balanced salt solution; PI, propidium iodide; PFA, paraformaldehyde; BSA, bovine serum albumin; FITC, fluorescein isothiocyanate; ChAT, choline acetyltransferase; VGLUT2, vesicular glutamate transporter 2; PKC, protein kinase C; AS-ODN, antisense oligonucleotide; MS-ODN, missense oligonucleotide; PAGE, polyacrylamide gel electrophoresis; TEM, transmission electron microscopy; HBDDE, 2,2′,3,3′,4,4′-hexahydroxy-1,1′-biphenyl-6,6′-dimethanol dimethyl ether; Gö6976, 12-(2-cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-c)-carbazole; PI3-K, phosphatidyl inositol-3-OH-kinase; MEK, mitogen-activated protein kinase kinase; PD98059, 2′-amino-3′-methoxyflavone.
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↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
- Received December 21, 2004.
- Accepted February 8, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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