Pretreatment with the monoacylglycerol lipase inhibitor URB602 protects from the long-term consequences of neonatal hypoxic-ischemic brain injury in rats.

BACKGROUND: The endocannabinoids are emerging as natural brain protective substances that exert potentially beneficial effects in several neurological disorders by virtue of their hypothermic, immunomodulatory, vascular, antioxidant, and antiapoptotic actions. This study was undertaken to assess whether preventing the deactivation of the endocannabinoid 2-arachidonoylglycerol (2-AG) with the monoacylglycerol lipase (MAGL) inhibitor URB602 can provide neuroprotective effects in hypoxia-ischemia (HI)-induced brain injury. METHODS: URB602 was administered into the right lateral ventricle 30 min before 7-day-old pup rats were subjected to HI. The neuroprotective effect was evaluated on postnatal day (PN) 14 or at adulthood (PN80) using behavioral and histological analyses. Activated caspase-3 expression and propidium iodide labeling were assessed as indexes of apoptotic and necrotic cell death, respectively. RESULTS: Pretreatment with URB602 reduced apoptotic and necrotic cell death, as well as the infarct volume measured at PN14. At adulthood, URB602-treated HI animals performed better at the T-maze and the Morris maze, and also showed a significant reduction of brain damage. CONCLUSION: These results demonstrate that a pretreatment with URB602 significantly reduces brain damage and improves functional outcome, indicating that endocannabinoid-degrading enzymes may represent an important target for neuroprotection in neonatal ischemic brain injury.

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.

Simvastatin acutely reduces ischemic brain damage in the immature rat via Akt and CREB activation.

We have previously shown that simvastatin (Sim) has long-lasting neuroprotective effects in a neonatal model of hypoxia-ischemia. Herein we evaluated the neuroprotective effect of different doses and duration of Sim treatment and further addressed its mechanism of action. Neonatal rats were subjected to occlusion of the right carotid artery followed by 2.5 h hypoxia (hypoxia-ischemia, HI). Sim was given at the dose of 10 or 5 mg/kg, s.c. from postnatal day 1 (PN1) to PN7, or at 20 mg/kg from PN4 to PN7, or at 20 mg/kg in a single administration 18 h before the onset of the ischemic procedure. Low-dose treatments or a single administration of the drug were effective in reducing HI-induced brain damage and its behavioural outcomes. Sim increased both Akt and CREB phosphorylation in neuronal cells and treatment with wortmannin completely blocked neuroprotection and p-Akt. These data demonstrate that even a single prophylactic Sim administration protects from hypoxic ischemic brain damage and that neuroprotection is in part obtained by preserving Akt and stimulating CREB phosphorylation in neuronal cells. Prophylactic Sim administration set in motion biochemical events that are known to increase brain tolerance to harmful factors, suggesting that the drug may exert neuroprotection by inducing pharmacological preconditioning.