glyceryl-2-arachidonate and Brain-Edema

We reported earlier that closed head injury (CHI) in mice causes a sharp elevation of brain 2-arachidonoylglycerol (2-AG) levels, and that exogenous 2-AG reduces brain edema, infarct volume and hippocampal death and improved clinical recovery after CHI. The beneficial effect of 2-AG was attenuated by SR141716A, a CB1 cannabinoid receptor antagonist, albeit at relatively high doses. In the present study, we further explored the role of CB1 receptors in mediating 2-AG neuroprotection. CB1 receptor knockout mice (CB1-/-) showed minor spontaneous recovery at 24 h after CHI, in contrast to the significant improvement in neurobehavioral function seen in wild-type (WT) mice. Moreover, administration of 2-AG did not improve neurological performance and edema formation in the CB1-/- mice. In addition, 2-AG abolished the three- to four-fold increase of nuclear factor kappaB (NF-kappa B) transactivation, at 24 h after CHI in the WT mice, while it had no effect on NF-kappaB in the CB1-/- mice, which was as high as in the WT vehicle-treated mice. We thus propose that 2-AG exerts its neuroprotection after CHI, at least in part, via CB1 receptor-mediated mechanisms that involve inhibition of intracellular inflammatory signaling pathways.

Topics: Animals; Arachidonic Acids; Behavior, Animal; Brain Chemistry; Brain Edema; Cerebral Infarction; DNA; Electrophoretic Mobility Shift Assay; Endocannabinoids; Glycerides; Head Injuries, Closed; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuroprotective Agents; NF-kappa B; Receptor, Cannabinoid, CB1; Signal Transduction

Reactive oxygen species (ROS) were shown to play a role in altering blood-brain barrier (BBB) permeability and formation of brain edema induced by trauma and/or ischemia. 2-arachidonoyl glycerol (2-AG), a novel, potent vasodilatory and cytoprotective endocannabinoid has been implicated to act as an antioxidative agent. This study examines: 1) the possible 2-AG modulation of BBB injury and edema formation induced by closed head injury (CHI); and 2) comparable effects between 2-AG and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TPL), a known antioxidant nitroxide on endothelial Ca2+ and cytoskeletal responses to H2O2 (ROS). 2-AG treatment reduced the CHI-induced increase in BBB permeability and brain edema. The endothelial H2O2-stimulated Ca2+ mobilization and cytoskeleton (vimentin) rearrangement was modified by either 2-AG or TPL. These findings provide evidence of 2-AG antioxidant activity and are consistent with the involvement of ROS in the pathomechanism of CHI-induced BBB injury and brain edema.

Topics: Animals; Antioxidants; Arachidonic Acids; Blood-Brain Barrier; Brain Edema; Calcium; Cannabinoid Receptor Modulators; Capillary Permeability; Cyclic N-Oxides; Cytoskeleton; Endocannabinoids; Endothelium, Vascular; Free Radical Scavengers; Glycerides; Head Injuries, Closed; Hydrogen Peroxide; Male; Mice; Mice, Inbred Strains; Oxidants; Reactive Oxygen Species; Spin Labels; Vasomotor System

Traumatic brain injury triggers the accumulation of harmful mediators that may lead to secondary damage. Protective mechanisms to attenuate damage are also set in motion. 2-Arachidonoyl glycerol (2-AG) is an endogenous cannabinoid, identified both in the periphery and in the brain, but its physiological roles have been only partially clarified. Here we show that, after injury to the mouse brain, 2-AG may have a neuroprotective role in which the cannabinoid system is involved. After closed head injury (CHI) in mice, the level of endogenous 2-AG was significantly elevated. We administered synthetic 2-AG to mice after CHI and found significant reduction of brain oedema, better clinical recovery, reduced infarct volume and reduced hippocampal cell death compared with controls. When 2-AG was administered together with additional inactive 2-acyl-glycerols that are normally present in the brain, functional recovery was significantly enhanced. The beneficial effect of 2-AG was dose-dependently attenuated by SR-141761A, an antagonist of the CB1 cannabinoid receptor.

Topics: Animals; Arachidonic Acids; Body Temperature; Brain Edema; Brain Infarction; Brain Injuries; Cannabinoids; Cell Death; Disease Models, Animal; Endocannabinoids; Gas Chromatography-Mass Spectrometry; Glycerides; Head Injuries, Closed; Hippocampus; Male; Mice; Neuroprotective Agents; Receptors, Cannabinoid; Receptors, Drug

The endocannabinoid anandamide [N-arachidonoylethanolamine (AEA)] is thought to function as an endogenous protective factor of the brain against acute neuronal damage. However, this has never been tested in an in vivo model of acute brain injury. Here, we show in a longitudinal pharmacological magnetic resonance imaging study that exogenously administered AEA dose-dependently reduced neuronal damage in neonatal rats injected intracerebrally with the Na(+)/K(+)-ATPase inhibitor ouabain. At 15 min after injury, AEA (10 mg/kg) administered 30 min before ouabain injection reduced the volume of cytotoxic edema by 43 +/- 15% in a manner insensitive to the cannabinoid CB(1) receptor antagonist SR141716A. At 7 d after ouabain treatment, 64 +/- 24% less neuronal damage was observed in AEA-treated (10 mg/kg) rats compared with control animals. Coadministration of SR141716A prevented the neuroprotective actions of AEA at this end point. In addition, (1) no increase in AEA and 2-arachidonoylglycerol levels was detected at 2, 8, or 24 hr after ouabain injection; (2) application of SR141716A alone did not increase the lesion volume at days 0 and 7; and (3) the AEA-uptake inhibitor, VDM11, did not affect the lesion volume. These data indicate that there was no endogenous endocannabinoid tone controlling the acute neuronal damage induced by ouabain. Although our data seem to question a possible role of the endogenous cannabinoid system in establishing a brain defense system in our model, AEA may be used as a structural template to develop neuroprotective agents.

Topics: Animals; Animals, Newborn; Arachidonic Acids; Blotting, Western; Brain; Brain Edema; Brain Injuries; Cannabinoid Receptor Modulators; Cannabinoids; Disease Models, Animal; Dose-Response Relationship, Drug; Endocannabinoids; Enzyme Inhibitors; Glycerides; Longitudinal Studies; Magnetic Resonance Imaging; Microinjections; Neurons; Ouabain; Piperidines; Polyunsaturated Alkamides; Pyrazoles; Rats; Rats, Wistar; Receptors, Cannabinoid; Receptors, Drug; Rimonabant