Insulin inhibits AMPA-induced neuronal damage via stimulation of protein kinase B (Akt).
We designed a series of experiments to explore the neuroprotective effects of insulin. Insulin significantly inhibited the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-induced neuronal cell damage as evidenced by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) assay. However, insulin had little affect on the AMPA-induced glial cell damage. To determine whether insulin inhibits AMPA-induced excitotoxicity, we performed grease-gap recording assays using rat brain slices. In these experiments, insulin also significantly inhibited AMPA-induced depolarization. Flow cytometry and DNA fragmentation assays showed that insulin inhibits AMPA-induced apoptosis and DNA fragmentation, respectively. Insulin stimulated protein kinase B (Akt) activity, whereas AMPA pretreatment did not alter the insulin-stimulated Akt activity. On the contrary, insulin blocked induction of SAPK/JNK, which AMPA stimulated. Taken together, these results suggest that insulin exerts neuroprotective effects by inhibiting AMPA-induced excitotoxicity and apoptosis, possibly by activating Akt and blocking SAPK/JNK.
Kim
S-J
SJ
Department of Pharmacology, School of Dentistry, Kyung Hee University, Seoul, Korea. kimsj@khu.ac.kr
Han
Y
Y
D000818:Animals; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D009410:Nerve Degeneration / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism* / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000037:antagonists & inhibitors* / Q000633:toxicity*
D007328:Insulin; D018696:Neuroprotective Agents; D011518:Proto-Oncogene Proteins; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt