Phosphatidylinositol 3-kinase-mediated regulation of neuronal apoptosis and necrosis by insulin and IGF-I

✍ Scribed by Ryu, Bo Rum ;Ko, Hyuk Wan ;Jou, Ilo ;Noh, Jai Sung ;Gwag, Byoung Joo

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 206 KB
• Volume: 39
• Category: Article
• ISSN: 0022-3034
• DOI: 10.1002/(sici)1097-4695(19990615)39:4<536::aid-neu7>3.0.co;2-j

✦ Synopsis

We examined effects of two insulinlike growth factors, insulin and insulin-like growth factor-I (IGF-I), against apoptosis, excitotoxicity, and free radical neurotoxicity in cortical cell cultures. Like IGF-I, insulin attenuated serum deprivation-induced neuronal apoptosis in a dose-dependent manner at 10 -100 ng/mL. The anti-apoptosis effect of insulin against serum deprivation disappeared by addition of a broad protein kinase inhibitor, staurosporine, but not by calphostin C, a selective protein kinase C inhibitor. Addition of PD98059, a mitogen-activated protein kinase kinase (MAPKK) inhibitor, blocked insulin-induced activation of extracellular signal-regulated protein kinases (ERK1/2) without altering the neuroprotective effect of insulin. Cortical neurons underwent activation of phosphatidylinositol (PI) 3-kinase as early as 1 min after exposure to insulin. Inclusion of wortmannin or LY294002, selective inhibitors of PI 3-K, reversed the insulin effect against apoptosis. In contrast to the antiapoptosis effect, neither insulin nor IGF-I protected excitotoxic neuronal necrosis following continuous exposure to 15 M N-methyl-D-aspartate or 40 M kainate for 24 h. Surprisingly, concurrent inclusion of 50 ng/mL insulin or IGF-I aggravated free radical-induced neuronal necrosis over 24 h following continuous exposure to 10 M Fe 2؉ or 100 M buthionine sulfoximine. Wortmannin or LY294002 also reversed this potentiation effect of insulin. These results suggest that insulinlike growth factors act as anti-apoptosis factor and pro-oxidant depending uon the activation of PI 3-kinase.