The Cannabinoid Agonist Win55212 Reduces Brain Damage in an In Vivo Model of Hypoxic-Ischemic Encephalopathy in Newborn Rats

Abstract

Neonatal hypoxic-ischemic encephalopathy (NHIE) is a devastating condition for which effective therapeutic treatments are still unavailable. Cannabinoids emerge as neuroprotective substances in adult animal studies; therefore, we aimed herein to test whether cannabinoids might reduce brain damage induced by hypoxiaischemia (HI) in newborn rats. Thus, 7-d-old Wistar rats (P7) were exposed to 8% O 2 for 120 min after left carotid artery ligature, then received s.c. vehicle (VEH) (HIϩVEH), the cannabinoid agonist WIN55212 (WIN) (0.1 mg/kg), or WIN with the CB 1 or CB 2 receptor antagonist SR141617 (SR1) (3 mg/kg) or SR141588 (SR2) (2 mg/kg). Brain damage was assessed by magnetic resonance imaging (MRI) at 1, 3, and 7 d after the insult. At the end of the experiment, MRI findings were corroborated by histology (Nissl staining). HIϩVEH showed an area of cytotoxic and vasogenic edema at 24 h after the insult, then evolving to necrosis. HIϩWIN showed a similar damaged area at 24 h after the insult, but the final necrotic area was reduced by 66%. Coadministration of either SR1 or SR2 reversed the effects of WIN. N HIE remains as a prevalent condition, inducing devastating brain injury leading to death or long-lasting sequelae (1,2). Despite recent progress in neonatology, the incidence of NHIE is not decreasing, likely because the complex pathophysiology of NHIE demands combined therapies or the use of treatments acting at different levels, as hypothermia (1,(3)(4)(5). In addition, due to the current inability to predict accurately perinatal asphyxia, only a posteriori treatments are feasible (1,2).Cannabinoids and their receptors constitute an endogenous system involved, for instance, in the control of synaptic transmission, memory modulation, motivation, movement, nociception, appetite, and thermoregulation (6,7). Two cannabinoid receptors present in the brain have been cloned so far: CB 1 receptors are expressed primarily by neurons but can also be found in glial cells; CB 1 receptors are Gi/o proteincoupled receptors that modulate the activity of several plasma membrane proteins and intracellular signaling pathways (7,8). CB 2 receptors are also Gi/o protein-coupled receptors; although it is accepted that CB 2 receptors are not expressed in forebrain neurons, they have been described in activated glia (8 -10). Lately, cannabinoids are emerging as valuable neuroprotective agents in models of acute and chronic neurodegenerative conditions (6,7,11-15), which may also affect the immature rat brain (16).Due to this evidence, we decided to test whether cannabinoids might be useful for decreasing brain damage in NHIE. For this purpose, we used the Rice-Vannucci model (17), an in vivo model that closely mimics actual NHIE conditions. Importantly, we assessed the effect of WIN when administered after the onset of the HI insult. To evaluate brain damage, we used MRI, an approach with several advantages: (1) MRI allows the development of imaging-based longitudinal studies, providing important data on the response tim...

Endocannabinoid-Mediated Control of Synaptic Transmission

“…In a rat model of neonatal hypoxic-ischemic encephalopathy, administration of WIN55,212-2 (0.1 mg/kg) after the hypoxia-ischemia procedure reduced the final necrotic area. This protective effect was reversed by coadministration of either the CB 1 antagonist SR141716A (3 mg/kg) or the CB 2 antagonist SR141588 (2 mg/kg) (155). In closed head injury of mice, exogenously applied 2-AG (0.1-10 mg/kg) reduced brain edema, infarct volume, and hippocampal death and improved clinical recovery (412).…”

Cannabinoids in Neurodegenerative Disorders and Stroke/Brain Trauma: From Preclinical Models to Clinical Applications

“…This evidence derives from studies that were initiated >10 years ago using newborn rat forebrain slices subjected to oxygen glucose deprivation and exposed to the CB 1 R/CB 2 R agonist WIN55212-2, which reduced cell death, decreasing glutamate and cytokine release, as well as inducible nitric oxide synthase expression, effects that were abolished by either CB 1 R or CB 2 R antagonists [65]. In newborn rats exposed to severe anoxia or to acute hypoxiaischemia [66,67], postinsult administration of WIN55212-2 afforded a strong neuroprotective effect, abolished by either CB 1 R or CB 2 R antagonists, too, as well as increasing neuronal and oligodendroglial cell proliferation in the subventricular zone 7 days after neonatal HI in rats [68]. In term fetal lambs exposed to HI damage by umbilical cord occlusion, postinsult administration of WIN55212-2 improved cerebral blood flow and reduced astrocytic, as well as apoptotic neuronal, death-those effects relying on the preservation of mitochondrial integrity and functionality [69].…”

Neuroprotective Effects of the Nonpsychoactive Cannabinoid Cannabidiol in Hypoxic-Ischemic Newborn Piglets

“…Lately, our group has demonstrated that the cannabinoid receptor agonist WIN55212-2 induces signs of neuroprotection in both in vitro and in vivo models of neonatal hypoxic-ischemic encephalopathy (NHIE) in rats (3,4). Because the production of psychoactive effects is likely to limit the therapeutic value of compounds such as WIN55212-2, we have now also performed experiments with cannabidiol (CBD), a major nonpsychoactive constituent of cannabis.…”