Activation of autophagy and Akt/CREB signaling play an equivalent role in the neuroprotective effect of rapamycin in neonatal hypoxia-ischemia.
We have previously shown that in neonatal rats subjected to hypoxia-ischemia (HI) rapamycin administration increases autophagy, decreases apoptosis and significantly reduces brain damage. After HI, when autophagy is blocked neuronal cells rapidly progress toward necrotic cell death. The present study was undertaken to assess the potential role of activation of autophagic and phosphatidylinositol 3-kinase (PI3K)/Akt kinase pathways in the neuroprotective effect of rapamycin. Rapamycin administration caused a significant reduction of 70 kDa S6 kinase (p70S6K) phosphorylation and a significant increase of the autophagic proteins Beclin 1 and microtubule-associated protein 1 light chain 3 (LC3), as of monodansylcadaverine (MDC) labeling in the lesioned side. The phosphorylation of Akt and cAMP response element binding protein (CREB) was increased in neuronal cells, and both p-Akt and p-CREB colocalized with Beclin 1. Wortmannin (WM) administration significantly reduced Akt and CREB phosphorylation as well as the neuroprotective effect of rapamycin but did not affect the phosphorylation of p70S6K, the expression of Beclin 1 and LC3, and MDC labeling. In contrast, 3-methyladenine (3MA) reduced the increased Beclin 1 expression, the MDC labeling and the neuroprotective effect of rapamycin without affecting Akt phosphorylation. However, both compounds significantly increased necrotic cell death. Taken together, these data indicate that in neonatal HI autophagy can be part of an integrated prosurvival signaling which includes the PI3K-Akt-mammalian target of rapamycin (mTOR) axis. When the autophagic or the PI3K-Akt-mTOR pathways are interrupted cells undergo necrotic cell death.
Carloni
Silvia
S
Department of Drug and Health Science, University of Urbino Carlo Bo, Urbino, Italy.
Girelli
Silvia
S
Scopa
Claudia
C
Buonocore
Giuseppe
G
Longini
Mariangela
M
Balduini
Walter
W
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects* / Q000502:physiology; D000071186:Beclin-1; D002545:Brain Ischemia / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D020123:Sirolimus / Q000494:pharmacology*; D000077191:Wortmannin
D000730:Androstadienes; D000903:Antibiotics, Antineoplastic; D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; D017362:Cyclic AMP Response Element-Binding Protein; D008869:Microtubule-Associated Proteins; D018696:Neuroprotective Agents; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D020123:Sirolimus; D000077191:Wortmannin; C512829:Becn1 protein, rat; C526109:Anxa3 protein, rat