Characterization of the neuroprotective effect of the cannabinoid agonist WIN-55212 in an in vitro model of hypoxic-ischemic brain damage in newborn rats

Novel neuroprotective 5,6-dihydropyrido[2',1':2,3]imidazo[4,5-c]quinoline derivatives acting through cholinesterase inhibition and CB2 signaling modulation

A novel group of 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines was prepared via a microwave assisted one-pot telescopic approach. The synthetic sequence involves the formation of an amine precursor of imidazo [1,2-a]pyridine via condensation and reduction under microwave irradiation. Subsequently, the Pictet-Spengler cyclisation reaction occurs with ketones (cyclic or acyclic) to obtain substituted 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines in excellent yields. The compounds were tested as neuroprotective agents. Observed protection of neuron-like cells, SH-SY5Y differentiated with ATRA, in Parkinson's and Huntington's disease models inspired further mechanistic studies of protective activity against damage induced by 1-methyl-4-phenylpyridinium (MPP+), a compound causing Parkinson's disease. The novel compounds exhibit similar or higher potency than ebselen, an established drug with antioxidant activity, in the cells against MPP + -induced total cellular superoxide production and cell death. However, they exhibit a significantly higher capacity to reduce mitochondrial superoxide and preserve mitochondrial membrane potential. We also observed marked differences between a selected derivative and ebselen in terms of normalizing MPP + -induced phosphorylation of Akt and ERK1/2. The cytoprotective activity was abrogated when signaling through cannabinoid receptor CB2 was blocked. The compounds also inhibit both acetylcholine and butyrylcholine esterases. Overall the data show that novel 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinoline have a broad cytoprotective activity which is mediated by several mechanisms including mitoprotection.

The potential neuroprotective effects of cannabinoids against paclitaxel-induced peripheral neuropathy: in vitro study on neurite outgrowth

Introduction: Chemotherapy-induced peripheral neuropathy (CIPN) is a shared burden for 68.1% of oncological patients undergoing chemotherapy with Paclitaxel (PTX). The symptoms are intense and troublesome, patients reporting paresthesia, loss of sensation, and dysesthetic pain. While current medications focus on decreasing the symptom intensity, often ineffective, no medication is yet recommended by the guidelines for the prevention of CIPN. Cannabinoids are an attractive option, as their neuroprotective features have already been demonstrated in neuropathies with other etiologies, by offering the peripheral neurons protection against toxic effects, which promotes analgesia. Methods: We aim to screen several new cannabinoids for their potential use as neuroprotective agents for CIPN by investigating the cellular toxicity profile and by assessing the potential neuroprotective features against PTX using a primary dorsal root ganglion neuronal culture. Results: Our study showed that synthetic cannabinoids JWH-007, AM-694 and MAB-CHMINACA and phytocannabinoids Cannabixir® Medium dried flowers (NC1) and Cannabixir® THC full extract (NC2) preserve the viability of fibroblasts and primary cultured neurons, in most of the tested dosages and time-points. The combination between the cannabinoids and PTX conducted to a cell viability of 70%-89% compared to 40% when PTX was administered alone for 48 h. When assessing the efficacy for neuroprotection, the combination between cannabinoids and PTX led to better preservation of neurite length at all tested time-points compared to controls, highly drug and exposure-time dependent. By comparison, the combination of the cannabinoids and PTX administered for 24 h conducted to axonal shortening between 23% and 44%, as opposed to PTX only, which shortened the axons by 63% compared to their baseline values. Discussion and Conclusion: Cannabinoids could be potential new candidates for the treatment of paclitaxel-induced peripheral neuropathy; however, our findings need to be followed by additional tests to understand the exact mechanism of action, which would support the translation of the cannabinoids in the oncological clinical practice.

Long-term Effects of Cannabidiol and/or Fentanyl Exposure in Rats Submitted to Neonatal Pain

The current study aimed to evaluate anxiety behavior, hippocampal ionized calcium-binding adaptor molecule 1 (Iba1) and cannabinoid receptor 1 (CB1) gene expression, and nociceptive response in adulthood after a combination of fentanyl and cannabidiol (CBD) for nociceptive stimuli induced during the first week of life in rats. Complete Freund's adjuvant-induced inflammatory nociceptive insult on postnatal day (PN) 1 and PN3. Both fentanyl and CBD were used alone or in combination from PN1 to PN7. Behavioral and nociceptive tests were performed at PN60 and PN62. The expression of the microglial calcium-binding proteins Iba1 and CB1 was detected in the hippocampus using reverse Quantitative polymerase chain reaction (qPCR) and immunohistochemistry. Our results suggest that the anxiety behavior response and immune activation in adult life depend on the CBD dose combined with fentanyl for the nociceptive stimuli induced during the first week of life. Treatment of neonatal nociceptive insult with CBD and opioids showed significant dose-dependent and male-female differences. The increased gene expression in the hippocampus of the analyzed cannabinoid gene supports this data. In addition, treatment with fentanyl led to an increase in CB1 protein expression. Moreover, the expression of Iba1 varied according to the administered dose of CBD and may or may not be associated with the opioid. A lower dose of CBD during the inflammatory period was associated with enhanced anxiety in adult life. PERSPECTIVE: The treatment of nociceptive stimuli with CBD and opioids during the first week of life demonstrated significant sex differences in adult life on anxiety behavior and supraspinal pain sensitivity.

Cytotoxicity associated with acute and chronic administration of synthetic cannabinoids “Strox” in the brain, liver, heart, and testes of male albino rats: histological and immunohistochemical study

Background

Synthetic cannabinoids are one of the largest groups of new psychoactive substances that invaded Egypt’s drug abuse market over the past few years.

Aim

Randomized controlled trial study to demonstrate the effects of acute and chronic toxicity by synthetic cannabinoid (Strox) on the brain, liver, heart, and testes in adult male albino rats through histopathological examination by light microscope and immunohistochemistry.

Methods

Total number of fifty male albino rats were divided into five different groups, two control and three treated groups. Negative and positive control groups received distilled water and dimethyl sulfoxide, respectively, acute group received LD50 (lethal dose 50) once and observed for 14 days, chronic group received 1/10 LD50 for 3 months, and finally chronic withdrawal groups received 1/10 LD50 for 3 months and then left 2 weeks without the substance to observe the withdrawal manifestations.

Results

The current study revealed various histopathological changes in all organs with increased expression of cannabinoid receptor 1. The most important findings observed by light microscope examination were shrinkage and degenerative changes in Purkinje cells in brain sections, abnormalities in blood sinusoids and architecture in liver section, disruption in cardiac muscle fiber in heart sections, and finally testes showed irregularities in seminiferous tubules and germinal cells. Immunohistochemical staining for caspase-3 in the brain, liver, and heart showed weak-positive reaction in acute group and a strong reaction with chronic groups. Additionally, increase in collagen fiber was observed in sections of the liver and heart of chronic group.

Conclusions

Synthetic cannabinoid sample (Strox) toxicity caused adverse effects on the brain, liver, heart, and testes as shown by increasing cannabinoid receptor 1 and caspase-3 expression.

Synthetic cannabinoids reduce the inflammatory activity of microglia and subsequently improve neuronal survival in vitro

Microglia are resident immune cells of the brain that survey the microenvironment, provide trophic support to neurons, and clear debris to maintain homeostasis and healthy brain function. Microglia are also drivers of neuroinflammation in several neurodegenerative diseases. Microglia produce endocannabinoids and express both cannabinoid receptor subtypes suggesting that this system is a target to suppress neuroinflammation. We tested whether cannabinoid type 1 (CB₁) or type 2 (CB₂) receptors could be targeted selectively or in combination to dampen the pro-inflammatory behavior of microglia, and whether this would have functional relevance to decrease secondary neuronal damage. We determined that components of the endocannabinoid system were altered when microglia are treated with lipopolysaccharide and interferon-gamma and shift to a pro-inflammatory phenotype. Furthermore, pro-inflammatory microglia released cytotoxic factors that induced cell death in cultured STHdh^Q7/Q7 neurons. Treatment with synthetic cannabinoids that were selective for CB₁ receptors (ACEA) or CB₂ receptors (HU-308) dampened the release of nitric oxide (NO) and pro-inflammatory cytokines and decreased levels of mRNA for several pro-inflammatory markers. A nonselective agonist (CP 55,940) exhibited similar influence over NO release but to a lesser extent relative to ACEA or HU-308. All three classes of synthetic cannabinoids ultimately reduced the secondary damage to the cultured neurons. The mechanism for the observed neuroprotective effects appeared to be related to cannabinoid-mediated suppression of MAPK signaling in microglia. Taken together, the data indicate that activation of CB₁ or CB₂ receptors interfered with the pro-inflammatory activity of microglia in a manner that also reduced secondary damage to neurons.

Intertwined associations between oxidative and nitrosative stress and endocannabinoid system pathways: Relevance for neuropsychiatric disorders

The endocannabinoid system (ECS) appears to regulate metabolic, cardiovascular, immune, gastrointestinal, lung, and reproductive system functions, as well as the central nervous system. There is also evidence that neuropsychiatric disorders are associated with ECS abnormalities as well as oxidative and nitrosative stress pathways. The goal of this mechanistic review is to investigate the mechanisms underlying the ECS's regulation of redox signalling, as well as the mechanisms by which activated oxidative and nitrosative stress pathways may impair ECS-mediated signalling. Cannabinoid receptor (CB)1 activation and upregulation of brain CB2 receptors reduce oxidative stress in the brain, resulting in less tissue damage and less neuroinflammation. Chronically high levels of oxidative stress may impair CB1 and CB2 receptor activity. CB1 activation in peripheral cells increases nitrosative stress and inducible nitric oxide (iNOS) activity, reducing mitochondrial activity. Upregulation of CB2 in the peripheral and central nervous systems may reduce iNOS, nitrosative stress, and neuroinflammation. Nitrosative stress may have an impact on CB1 and CB2-mediated signalling. Peripheral immune activation, which frequently occurs in response to nitro-oxidative stress, may result in increased expression of CB2 receptors on T and B lymphocytes, dendritic cells, and macrophages, reducing the production of inflammatory products and limiting the duration and intensity of the immune and oxidative stress response. In conclusion, high levels of oxidative and nitrosative stress may compromise or even abolish ECS-mediated redox pathway regulation. Future research in neuropsychiatric disorders like mood disorders and deficit schizophrenia should explore abnormalities in these intertwined signalling pathways.

GPR18 drives FAAH inhibition-induced neuroprotection against HIV-1 Tat-induced neurodegeneration

Human immunodeficiency virus type 1 (HIV-1) is known to provoke microglial immune responses which likely play a paramount role in the development of chronic neuroinflammatory conditions and neuronal damage related to HIV-1 associated neurocognitive disorders (HAND). In particular, HIV-1 Tat protein is a proinflammatory neurotoxin which predisposes neurons to synaptodendritic injury. Drugs targeting the degradative enzymes of endogenous cannabinoids have shown promise in reducing inflammation with minimal side effects in rodent models. Considering that markers of neuroinflammation can predict the extent of neuronal injury in HAND patients, we evaluated the neurotoxic effect of HIV-1 Tat-exposed microglia following blockade of fatty acid amid hydrolyze (FAAH), a catabolic enzyme responsible for degradation of endocannabinoids, e.g. anandamide (AEA). In the present study, cultured murine microglia were incubated with Tat and/or a FAAH inhibitor (PF3845). After 24 h, cells were imaged for morphological analysis and microglial conditioned media (MCM) was collected. Frontal cortex neuron cultures (DIV 7–11) were then exposed to MCM, and neurotoxicity was assessed via live cell calcium imaging and staining of actin positive dendritic structures. Results demonstrate a strong attenuation of microglial responses to Tat by PF3845 pretreatment, which is indicated by 1) microglial changes in morphology to a less proinflammatory phenotype using fractal analysis, 2) a decrease in release of neurotoxic cytokines/chemokines (MCP-1/CCL2) and matrix metalloproteinases (MMPs; MMP-9) using ELISA/multiplex assays, and 3) enhanced production of endocannabinoids (AEA) using LC/MS/MS. Additionally, PF3845’s effects on Tat-induced microglial-mediated neurotoxicity, decreased dysregulation of neuronal intracellular calcium and prevented the loss of actin-positive staining and punctate structure in frontal cortex neuron cultures. Interestingly, these observed neuroprotective effects appeared to be independent of cannabinoid receptor activity (CB₁R & CB₂R). We found that a purported GPR18 antagonist, CID-85469571, blocked the neuroprotective effects of PF3845 in all experiments. Collectively, these experiments increase understanding of the role of FAAH inhibition and Tat in mediating microglial neurotoxicity in the HAND condition.

Cannabinoid CB2 Receptor Activation Attenuates Fentanyl-Induced Respiratory Depression

Introduction: Overdose fatalities associated with the opioid epidemic are predictably attributable to drug-induced respiratory depression. In terms of illicit opioid abuse, fentanyl is the synthetic opioid responsible for the largest number of overdose deaths. There is, therefore, an urgent need to identify safe and effective therapeutics that can attenuate fentanyl-induced respiratory depression. Identification of effective alternate analgesic strategies that lessen the respiratory depression associated with narcotics would also help improve current strategies for pain management. Our laboratory recently reported that the G protein-biased CB₂ cannabinoid receptor agonist LY2828360 suppressed chemotherapy-induced neuropathic nociception and attenuated both morphine tolerance and physical dependence in paclitaxel-treated mice. However, the impact of LY2828360 on other undesirable side effects of opioids, such as opioid-induced respiratory depression, remains unknown. Materials and Methods: We used whole-body plethysmography to assess the impact of the CB₂ cannabinoid agonist LY2828360 on fentanyl-induced respiratory depression using wild-type (WT) and CB₂ knockout (CB₂KO) mice. Results: Fentanyl reduced minute ventilation and respiratory frequency without altering tidal volume in both WT and CB₂KO mice. In WT mice, the high dose of fentanyl (0.2 mg/kg intraperitoneal [i.p.]) produced a greater suppression of respiratory parameters compared with the low dose of fentanyl (0.1 mg/kg i.p.). Coadministration of a behaviorally active dose of LY2828360 (3 mg/kg i.p.) with fentanyl (0.2 mg/kg i.p.) attenuated fentanyl-induced respiratory depression in WT mice. Notably, LY2828360 (3 mg/kg i.p.) did not attenuate fentanyl-induced respiratory depression in CB₂KO mice, consistent with mediation by CB₂ receptors. Moreover, LY2828360 (3 mg/kg i.p.) alone lacked intrinsic effects on respiratory parameters in either WT or CB₂KO mice. Conclusion: The combination of a CB₂ agonist with fentanyl may represent a safer adjunctive therapeutic strategy compared with a narcotic analgesic alone by attenuating the development of opioid-induced respiratory depression. Moreover, the CB₂ agonist, administered alone, did not alter respiration. Our findings suggest that the CB₂ cannabinoid agonist LY2828360 may provide CB₂-mediated protection against fentanyl-induced respiratory depression, a detrimental and unwanted side effect of opioid use and abuse.

The synthetic cannabinoid JWH-018 modulates Saccharomyces cerevisiae energetic metabolism

Synthetic cannabinoids are a group of novel psychoactive substances with similar properties to Δ9-THC. Among the vast number of synthetic cannabinoids, designed to be tested in clinical trials, JWH-018 was the first novel psychoactive substance found in the recreational drug marketplace. The consumption of JWH-018 shows typical effects of CB1 agonists including sedation, cognitive dysfunction, tachycardia, postural hypotension, dry mouth, ataxia and psychotropic effects, but appeared to be more potent than Δ9-THC. However, studies on human cells have shown that JWH-018 toxicity depends on the cellular line used. Despite these studies, the underlying molecular mechanisms to JWH-018 action has not been clarified yet. To understand the impact of JWH-018 at molecular and cellular level, we used Saccharomyces cerevisiae as a model. The results showed an increase in yeast growth rate in the presence of this synthetic cannabinoid due to an enhancement in the glycolytic flux at expense of a decrease in pentose phosphate pathway, judging by 2D-Gel proteomic analysis, qRT-PCR experiments and ATP measurements. Overall, our results provide insights into molecular mechanisms of JWH-018 action, also indicating that Saccharomyces cerevisiae is a good model to study synthetic cannabinoids.

Differential mechanisms of tolerance induced by NMDA and 3,5-dihydroxyphenylglycine (DHPG) preconditioning

We investigated the molecular events triggered by NMDA and 3,5-dihydroxyphenylglycine (DHPG) preconditioning, that lead to neuroprotection against excitotoxic insults (AMPA or oxygen and glucose deprivation) in rat organotypic hippocampal slices, with particular attention on glutamate receptors and on cannabinoid system. We firstly evaluated the protein expression of NMDA and AMPA receptor subunits after preconditioning using western blot analysis performed in post-synaptic densities. We observed that following NMDA, but not DHPG preconditioning, the expression of GluA1 was significantly reduced and this reduction appeared to be associated with the internalization of AMPA receptors. Whole-cell voltage clamp recordings on CA1 pyramidal neurons of organotypic slices show that 24 hr after exposure to NMDA and DHPG preconditioning, AMPA-induced currents were significantly reduced. To clarify the mechanisms induced by DHPG preconditioning, we then investigated the involvement of the endocannabinoid system. Exposure of slices to the CB1 antagonist AM251 prevented the development of tolerance to AMPA toxicity induced by DHPG but not NMDA. Accordingly, the MAG-lipase inhibitor URB602, that increases arachidonoylglycerol (2-AG) content, but not the FAAH inhibitor URB597, that limits the degradation of anandamide, was also able to induce tolerance versus AMPA and OGD toxicity, suggesting that 2-AG is responsible for the DHPG-induced tolerance. In conclusion, preconditioning with NMDA or DHPG promotes differential neuroprotective mechanisms: NMDA by internalization of GluA1-AMPA receptors, DHPG by producing the endocannabinoid 2-AG.

Cannabinoid-mediated Modulation of Oxidative Stress and Early Inflammatory Response after Hypoxia-Ischemia

In the process of neonatal encephalopathy, oxidative stress and neuroinflammation have a prominent role after perinatal asphyxia. With the exception of therapeutic hypothermia, no therapeutic interventions are available in the clinical setting to target either the oxidative stress or inflammation, despite the high prevalence of neurological sequelae of this devastating condition. The endocannabinoid system (ECS), recently recognized as a widespread neuromodulatory system, plays an important role in the development of the central nervous system (CNS). This study aims to evaluate the potential effect of the cannabinoid (CB) agonist WIN 55,212-2 (WIN) on reactive oxygen species (ROS) and early inflammatory cytokine production after hypoxia–ischemia (HI) in fetal lambs. Hypoxic–ischemic animals were subjected to 60 min of HI by partial occlusion of the umbilical cord. A group of lambs received a single dose of 0.01 μg/kg WIN, whereas non-asphyctic animals served as controls. WIN reduced the widespread and notorious increase in inflammatory markers tumor necrosis factor (TNF)-α and interleukin (IL)-1β and IL-6 induced by HI, a modulatory effect not observed for oxidative stress. Our study suggests that treatment with a low dose of WIN can alter the profile of pro-inflammatory cytokines 3 h after HI.

Cannabinoid signalling in embryonic and adult neurogenesis: possible implications for psychiatric and neurological disorders

Cannabinoid signalling modulates several aspects of brain function, including the generation and survival of neurons during embryonic and adult periods. The present review intended to summarise evidence supporting a role for the endocannabinoid system on the control of neurogenesis and neurogenesis-dependent functions. Studies reporting participation of cannabinoids on the regulation of any step of neurogenesis and the effects of cannabinoid compounds on animal models possessing neurogenesis-dependent features were selected from Medline. Qualitative evaluation of the selected studies indicated that activation of cannabinoid receptors may change neurogenesis in embryonic or adult nervous systems alongside rescue of phenotypes in animal models of different psychiatric and neurological disorders. The text offers an overview on the effects of cannabinoids on central nervous system development and the possible links with psychiatric and neurological disorders such as anxiety, depression, schizophrenia, brain ischaemia/stroke and Alzheimer's disease. An understanding of the mechanisms by which cannabinoid signalling influences developmental and adult neurogenesis will help foster the development of new therapeutic strategies for neurodevelopmental, psychiatric and neurological disorders.

Cannabinoid Receptor Type 1 Agonist ACEA Improves Cognitive Deficit on STZ-Induced Neurotoxicity Through Apoptosis Pathway and NO Modulation

The cannabinoid system has the ability to modulate cellular and molecular mechanisms, including excitotoxicity, oxidative stress, apoptosis, and inflammation, acting as a neuroprotective agent, by its relationship with signaling pathways associated to the control of cell proliferation, differentiation, and survival. Recent reports have raised new perspectives on the possible role of cannabinoid system in neurodegenerative diseases like Alzheimer disease's (AD). AD is a neurodegenerative disorder characterized by the presence of amyloid plaques, neurofibrillary tangles, neuronal death, and progressive cognitive loss, which could be caused by energy metabolism impairment, changes in insulin signaling, chronic oxidative stress, neuroinflammation, Tau hyperphosphorylation, and Aβ deposition in the brain. Thus, we investigated the presumptive protective effect of the cannabinoid type 1 (CB1)-selective receptor agonist arachidonyl-2'-chloroethylamide (ACEA) against streptozotocin (STZ) exposure stimuli in an in vitro neuronal model (Neuro-2a neuroblastoma cells) and in vivo model (intracerebroventricular STZ injection), experimental models of sporadic AD. Our results demonstrated that ACEA treatment reversed cognitive impairment and increased activity of Akt and ERK triggered by STZ, and increased IR expression and increased the anti-apoptotic proteins levels, Bcl-2. In the in vitro model, ACEA was able to rescue cells from STZ-triggered death and modulated the NO release by STZ. Our study has demonstrated a participation of the cannabinoid system in cellular survival, involving the CB1 receptor, which occurs by positive regulation of the anti-apoptotic proteins, suggesting the participation of this system in neurodegenerative processes. Our data suggest that the cannabinoid system is an interesting therapeutic target for the treatment of neurodegenerative diseases.

Oleoylethanolamide and Palmitoylethanolamide Protect Cultured Cortical Neurons Against Hypoxia

Introduction: Perinatal hypoxic-ischemic (HI) encephalopathy is defined as a neurological syndrome where the newborn suffers from acute ischemia and hypoxia during the perinatal period. New therapies are needed. The acylethanolamides, oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), possess neuroprotective properties, and they could be effective against perinatal HI. These lipid mediators act through peroxisome proliferator-activated receptors subtype α (PPARα), or transient receptor potential vanilloid (TRPV), such as TRPV subtype 1 and 4. Materials and Methods: The objectives of this study were to discern: (1) the neuroprotective role of OEA and PEA in parietotemporal cortical neurons of newborn rats and mice subjected to hypoxia, and (2) the role of the receptors, PPARα, TRPV1, and TRPV4, in neuroprotective effects. Cell culture of cortical neurons and the lactate dehydrogenase assay was carried out. The role of receptors was discerned by using selective antagonist and agonist ligands, as well as knockout (KO) PPARα mice. Results: The findings indicate that OEA and PEA exert neuroprotective effects on cultured cortical neurons subjected to a hypoxic episode. These protective effects are not mediated by the receptors, PPARα, TRPV1, or TRPV4, because neither PPARα KO mice nor receptor ligands significantly modify OEA and PEA-induced effects. Blocking TRPV4 with RN1734 is neuroprotective per se, and cotreatment with OEA and PEA is able to enhance neuroprotective effects of the acylethanolamides. Since stimulating TRPV4 was devoid of effects on OEA and PEA-induced protective effects, effects of RN1734 cotreatment seem to be a consequence of additive actions. Conclusion: The lipid mediators, OEA and PEA, exert neuroprotective effects on cultured cortical neurons subjected to hypoxia. Coadministration of OEA or PEA, and the TRPV4 antagonist RN1734 is able to enhance neuroprotective effects. These in vitro results could be of utility for developing new therapeutic tools against perinatal HI.

Current and Emerging Therapies in the Management of Hypoxic Ischemic Encephalopathy in Neonates

Neonatal hypoxic ischemic encephalopathy (HIE) presents a significant clinical burden with its high mortality and morbidity rates globally. Therapeutic hypothermia (TH) is now standard of care for infants with moderate to severe HIE, but has not definitively changed outcomes in severe HIE. In this review, we discuss newer promising markers that may help the clinician identify severity of HIE. Therapies that are beneficial and agents that hold promise for neuroprotection are described, both for use either alone or as adjuncts to TH. These include endogenous pathway modifiers such as erythropoietin and analogues, melatonin, and remote ischemic post conditioning. Stem cells have therapeutic potential in this condition, as in many other neonatal conditions. Of the agents listed, only erythropoietin and analogues are currently being evaluated in large randomized controlled trials (RCTs). Exogenous therapies such as argon and xenon, allopurinol, monosialogangliosides, and magnesium sulfate continue to be investigated. The recognition of tertiary mechanisms of brain damage has opened up new research into therapies not only to attenuate brain damage but also to promote cell repair and regeneration in a developmentally disorganized brain long after the perinatal insult. These alternative modalities may be especially important in mild HIE and in areas of the world where there is limited access to expensive hypothermia equipment and services.

Inhibition of interleukin-1β-induced endothelial tissue factor expression by the synthetic cannabinoid WIN 55,212-2

The role of cannabinoids in thrombosis remains controversial. In view of the primary importance of tissue factor (TF) in blood coagulation and its involvement in the pathology of several cardiovascular, inflammatory and neoplastic diseases, a regulation of this initial procoagulant signal seems to be of particular interest. Using human umbilical vein endothelial cells (HUVEC) the present study investigated the impact of the synthetic cannabinoid WIN 55,212-2 on interleukin (IL)-1β-induced TF expression and activity. WIN 55,212-2 caused a time- and concentration-dependent suppression of IL-1β-induced TF protein accompanied by decreases in TF mRNA and activity. Inhibition of TF protein expression by WIN 55,212-2 was mimicked by its cannabinoid receptor-inactive enantiomer WIN 55,212-3 but not by structurally unrelated phyto-, endo- and synthetic cannabinoids. In addition, the inhibitory effect of WIN 55,212-2 was not reversed by antagonists to cannabinoid receptors (CB₁, CB₂) or transient receptor potential vanilloid 1. Mechanistic approaches revealed WIN 55,212-2 to suppress IL-1β-induced TF expression via inhibition of ceramide formation and via decreased phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinases. Further inhibitor experiments demonstrated neutral sphingomyelinase (nSMase) to confer ceramide generation upon IL-1β treatment with the parallel IL-1β-mediated activation of MAPKs occurring via an nSMase-independent pathway. Finally, a receptor-independent inhibition of IL-1β-induced TF protein by WIN 55,212-2 was confirmed in human blood monocytes. Collectively, this data provide a hitherto unknown receptor-independent anticoagulatory action of the cannabinoid WIN 55,212-2.

Genetic or pharmacological depletion of cannabinoid CB1 receptor protects against dopaminergic neurotoxicity induced by methamphetamine in mice

Accumulating evidence suggests that cannabinoid ligands play delicate roles in cell survival and apoptosis decisions, and that cannabinoid CB1 receptors (CB1R) modulate dopaminergic function. However, the role of CB1R in methamphetamine (MA)-induced dopaminergic neurotoxicity in vivo remains elusive. Multiple high doses of MA increased phospho-ERK and CB1R mRNA expressions in the striatum of CB1R (+/+) mice. These increases were attenuated by CB1R antagonists (i.e., AM251 and rimonabant), an ERK inhibitor (U0126), or dopamine D2R antagonist (sulpiride). In addition, treatment with MA resulted in dopaminergic impairments, which were attenuated by CB1R knockout or CB1R antagonists (i.e., AM251 and rimonabant). Consistently, MA-induced oxidative stresses (i.e., protein oxidation, lipid peroxidation and reactive oxygen species) and pro-apoptotic changes (i.e., increases in Bax, cleaved PKCδ- and cleaved caspase 3-expression and decrease in Bcl-2 expression) were observed in the striatum of CB1R (+/+) mice. These toxic effects were attenuated by CB1R knockout or CB1R antagonists. Consistently, treatment with four high doses of CB1R agonists (i.e., WIN 55,212-2 36mg/kg and ACEA 16mg/kg) also resulted in significant oxidative stresses, pro-apoptotic changes, and dopaminergic impairments. Since CB1R co-immunoprecipitates PKCδ in the presence of MA or CB1R agonists, we applied PKCδ knockout mice to clarify the role of PKCδ in the neurotoxicity elicited by CB1Rs. CB1R agonist-induced toxic effects were significantly attenuated by CB1R knockout, CB1R antagonists or PKCδ knockout. Therefore, our results suggest that interaction between D2R, ERK and CB1R is critical for MA-induced dopaminergic neurotoxicity and that PKCδ mediates dopaminergic damage induced by high-doses of CB1R agonist.

The endocannabinoid system: 'NO' longer anonymous in the control of nitrergic signalling?

The endocannabinoid system (ECS) is a key cellular signalling system that has been implicated in the regulation of diverse cellular functions. Importantly, growing evidence suggests that the biological actions of the ECS may, in part, be mediated through its ability to regulate the production and/or release of nitric oxide, a ubiquitous bioactive molecule, which functions as a versatile signalling intermediate. Herein, we review and discuss evidence pertaining to ECS-mediated regulation of nitric oxide production, as well as the involvement of reactive nitrogen species in regulating ECS-induced signal transduction by highlighting emerging work supporting nitrergic modulation of ECS function. Importantly, the studies outlined reveal that interactions between the ECS and nitrergic signalling systems can be both stimulatory and inhibitory in nature, depending on cellular context. Moreover, such crosstalk may act to maintain proper cell function, whereas abnormalities in either system can undermine cellular homoeostasis and contribute to various pathologies associated with their dysregulation. Consequently, future studies targeting these signalling systems may provide new insights into the potential role of the ECS–nitric oxide signalling axis in disease development and/or lead to the identification of novel therapeutic targets for the treatment of nitrosative stress-related neurological, cardiovascular, and metabolic disorders.

The endocannabinoid system, a novel and key participant in acupuncture's multiple beneficial effects

Acupuncture and its modified forms have been used to treat multiple medical conditions, but whether the diverse effects of acupuncture are intrinsically linked at the cellular and molecular level and how they might be connected have yet to be determined. Recently, an emerging role for the endocannabinoid system (ECS) in the regulation of a variety of physiological/pathological conditions has been identified. Overlap between the biological and therapeutic effects induced by ECS activation and acupuncture has facilitated investigations into the participation of ECS in the acupuncture-induced beneficial effects, which have shed light on the idea that the ECS may be a primary mediator and regulatory factor of acupuncture's beneficial effects. This review seeks to provide a comprehensive summary of the existing literature concerning the role of endocannabinoid signaling in the various effects of acupuncture, and suggests a novel notion that acupuncture may restore homeostasis under different pathological conditions by regulating similar networks of signaling pathways, resulting in the activation of different reaction cascades in specific tissues in response to pathological insults.

Regulation of divalent metal transporter-1 by serine phosphorylation

Divalent metal transporter-1 (DMT1) mediates dietary iron uptake across the intestinal mucosa and facilitates peripheral delivery of iron released by transferrin in the endosome. Here, we report that classical cannabinoids (Δ⁹-tetrahydrocannabinol, Δ⁹-THC), nonclassical cannabinoids (CP 55,940), aminoalkylindoles (WIN 55,212-2) and endocannabinoids (anandamide) reduce ⁵⁵Fe and ⁵⁴Mn uptake by HEK293T(DMT1) cells stably expressing the transporter. siRNA knockdown of cannabinoid receptor type 2 (CB2) abrogated inhibition. CB2 is a G-protein (GTP-binding protein)-coupled receptor that negatively regulates signal transduction cascades involving serine/threonine kinases. Immunoprecipitation experiments showed that DMT1 is serine-phosphorylated under basal conditions, but that treatment with Δ⁹-THC reduced phosphorylation. Site-directed mutation of predicted DMT1 phosphosites further showed that substitution of serine with alanine at N-terminal position 43 (S⁴³A) abolished basal phosphorylation. Concordantly, both the rate and extent of ⁵⁵Fe uptake in cells expressing DMT1(S⁴³A) was reduced compared with those expressing wild-type DMT1. Among kinase inhibitors that affected DMT1-mediated iron uptake, staurosporine also reduced DMT1 phosphorylation confirming a role for serine phosphorylation in iron transport regulation. These combined data indicate that phosphorylation at serine 43 of DMT1 promotes transport activity, whereas dephosphorylation is associated with loss of iron uptake. Since anti-inflammatory actions mediated through CB2 would be associated with reduced DMT1 phosphorylation, we postulate that this pathway provides a means to reduce oxidative stress by limiting iron uptake.

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

Cannabinoids form a singular family of plant-derived compounds (phytocannabinoids), endogenous signaling lipids (endocannabinoids), and synthetic derivatives with multiple biological effects and therapeutic applications in the central and peripheral nervous systems. One of these properties is the regulation of neuronal homeostasis and survival, which is the result of the combination of a myriad of effects addressed to preserve, rescue, repair, and/or replace neurons, and also glial cells against multiple insults that may potentially damage these cells. These effects are facilitated by the location of specific targets for the action of these compounds (e.g., cannabinoid type 1 and 2 receptors, endocannabinoid inactivating enzymes, and nonendocannabinoid targets) in key cellular substrates (e.g., neurons, glial cells, and neural progenitor cells). This potential is promising for acute and chronic neurodegenerative pathological conditions. In this review, we will collect all experimental evidence, mainly obtained at the preclinical level, supporting that different cannabinoid compounds may be neuroprotective in adult and neonatal ischemia, brain trauma, Alzheimer's disease, Parkinson's disease, Huntington's chorea, and amyotrophic lateral sclerosis. This increasing experimental evidence demands a prompt clinical validation of cannabinoid-based medicines for the treatment of all these disorders, which, at present, lack efficacious treatments for delaying/arresting disease progression, despite the fact that the few clinical trials conducted so far with these medicines have failed to demonstrate beneficial effects.

Pathophysiology and neuroprotection of global and focal perinatal brain injury: lessons from animal models

BACKGROUND

Arterial ischemic stroke occurs more frequently in term newborns than in the elderly, and brain immaturity affects mechanisms of ischemic injury and recovery. The susceptibility to injury of the brain was assumed to be lower in the perinatal period as compared with childhood. This concept was recently challenged by clinical studies showing marked motor disabilities after stroke in neonates, with the severity of motor and cortical sensory deficits similar in both perinatal and childhood ischemic stroke. Our understanding of the triggers and the pathophysiological mechanisms of perinatal stroke has greatly improved in recent years, but many factors remain incompletely understood.

METHODS

In this review, we focus on the pathophysiology of perinatal stroke and on therapeutic strategies that can protect the immature brain from the consequences of stroke by targeting inflammation and brain microenvironment.

RESULTS

Studies in neonatal rodent models of cerebral ischemia have suggested a potential role for soluble inflammatory molecules as important modulators of injury and recovery. A great effort is underway to investigate neuroprotective molecules based on our increasing understanding of the pathophysiology.

CONCLUSION

In this review, we provide a comprehensive summary of new insights concerning pathophysiology of focal and global perinatal brain injury and their implications for new therapeutic approaches.

Pretreatment with scutellaria baicalensis stem-leaf total flavonoid protects against cerebral ischemia/reperfusion injury in hippocampal neurons

Previous experimental studies have shown that cerebral infarction can be effectively reduced following treatment with scutellaria baicalensis stem-leaf total flavonoid (SSTF). However, the mechanism of action of SSTF as a preventive drug to treat cerebral infarction remains unclear. In this study, Sprague-Dawley rats were pretreated with 50, 100, 200 mg/kg SSTF via intragastric administration for 1 week prior to the establishment of focal cerebral ischemia/reperfusion injury. The results showed that pretreatment with SSTF effectively improved neurological function, reduced brain water content and the permeability of blood vessels, ameliorated ischemia-induced morphology changes in hippocampal microvessels, down-regulated Fas and FasL protein expression, elevated the activity of superoxide dismutase and glutathione peroxidase, and decreased malondialdehyde content. In contrast to low-dose SSTF pretreatment, the above changes were most obvious after pretreatment with moderate- and high-doses of SSTF. Experimental findings indicate that SSTF pretreatment can exert protective effects on the brain against cerebral ischemia/reperfusion injury. The underlying mechanisms may involve reducing brain water content, increasing microvascular recanalization, inhibiting the apoptosis of hippocampal neurons, and attenuating free radical damage.

The cannabinoid CB2 receptor agonist GW405833 does not ameliorate brain damage induced by hypoxia-ischemia in rats

The cannabinoid CB2 receptor has been under investigation as a potential target for neuroprotection with the suppression of neuroinflammation as the proposed mechanism of action. Several studies have now reported that CB2 agonists are neuroprotective in models of cerebral ischemia. However, these studies have tended to measure brain infarctions in rodents 1-3 days after drug administration and have not assessed behavioral outcomes. As it has been shown that apparent protection soon after injury is not necessarily correlated with improved outcome after several weeks, we tested the CB2 selective agonist GW405833 in a model of cerebral hypoxia-ischemia, and assessed histological and behavioral outcomes 15 days after injury. Many putatively neuroprotective drugs have failed to translate from promising preclinical results to clinical success. We designed our experiments to not only stringently test CB2 mediated neuroprotection, but also to test several drug administration regimens to maximize the chance of detecting any therapeutic effect. However, GW405833 failed to provide neuroprotection in any of our experiments. These results challenge how far the results of earlier studies into CB2 mediated neuroprotection as measured at early time points may be extrapolated to later time points or to other models.

Improved cardiac and neurologic outcomes with postresuscitation infusion of cannabinoid receptor agonist WIN55, 212-2 depend on hypothermia in a rat model of cardiac arrest

OBJECTIVES

To investigate the mechanisms of improved myocardial and neurological function and survival following i.v. administration of cannabinoid receptor agonist, WIN55, 212-2 in a rat model of cardiac arrest.

DESIGN

Prospective randomized controlled experimental study.

SETTING

University-affiliated research institute.

SUBJECTS

Thirty male Sprague-Dawley rats.

INTERVENTIONS

Ventricular fibrillation was electrically induced in 30 male Sprague-Dawley rats weighing between 450 and 550 g. Cardiopulmonary resuscitation was initiated after 6 minutes of untreated ventricular fibrillation. The precordial compression was performed with a pneumatically driven mechanical chest compressor. No pharmacological agent was used during cardiopulmonary resuscitation. After 8 minutes of cardiopulmonary resuscitation, up to three 2-J defibrillations were attempted. The animals were then randomized into three groups: 1) WIN55, 212-2 hypothermia, 2) WIN55, 212-2 with normal body temperature, and 3) placebo control. Either WIN55, 212-2 (1.0 mg/kg/hr) or saline placebo was continuously infused for 2 hours. Except for the WIN55, 212-2 hypothermia group, the body temperature in the other two groups was maintained at 37.0 ± 0.2°C using an external heating lamp. Postresuscitation myocardial function was measured by echocardiogram. Neurological deficit scores and survival time were observed for up to 72 hours.

MEASUREMENTS AND MAIN RESULTS

Blood temperatures decreased from 37°C to 33°C in 4 hours in animals in WIN55, 212-2 hypothermia group. Myocardial function, as measured by cardiac output, ejection fraction, and myocardial performance index, was significantly impaired in all animals after successful resuscitation when compared with the baseline values. There was a significant improvement in myocardial function in the animals treated with WIN55, 212-2 hypothermia beginning at 1 hour after start of infusion. However, no improvement was observed in the groups of WIN55, 212-2 with normal body temperature and placebo control. WIN55, 212-2 hypothermia group was associated with significantly improved neurologic deficit scores and survival time when compared with placebo control group and WIN55, 212-2 with normal body temperature group.

CONCLUSIONS

In a rat model of cardiac arrest, better postresuscitation myocardial function, neurological deficit scores, and longer duration of survival were observed by the pharmacologically induced hypothermia with WIN55, 212-2. The improved outcomes of cardiopulmonary resuscitation following administration of WIN55, 212-2 appeared to be the results from its temperature reduction effects.

Cannabinoids: well-suited candidates for the treatment of perinatal brain injury

Perinatal brain injury can be induced by a number of different damaging events occurring during or shortly after birth, including neonatal asphyxia, neonatal hypoxia-ischemia and stroke-induced focal ischemia. Typical manifestations of these conditions are the presence of glutamate excitoxicity, neuroinflammation and oxidative stress, the combination of which can potentially result in apoptotic-necrotic cell death, generation of brain lesions and long-lasting functional impairment. In spite of the high incidence of perinatal brain injury, the number of clinical interventions available for the treatment of the affected newborn babies is extremely limited. Hence, there is a dramatic need to develop new effective therapies aimed to prevent acute brain damage and enhance the endogenous mechanisms of long-term brain repair. The endocannabinoid system is an endogenous neuromodulatory system involved in the control of multiple central and peripheral functions. An early responder to neuronal injury, the endocannabinoid system has been described as an endogenous neuroprotective system that once activated can prevent glutamate excitotoxicity, intracellular calcium accumulation, activation of cell death pathways, microglia activation, neurovascular reactivity and infiltration of circulating leukocytes across the blood-brain barrier. The modulation of the endocannabinoid system has proven to be an effective neuroprotective strategy to prevent and reduce neonatal brain injury in different animal models and species. Also, the beneficial role of the endocannabinoid system on the control of the endogenous repairing responses (neurogenesis and white matter restoration) to neonatal brain injury has been described in independent studies. This review addresses the particular effects of several drugs that modulate the activity of the endocannabinoid system on the progression of different manifestations of perinatal brain injury during both the acute and chronic recovery phases using rodent and non-rodent animal models, and will provide a complete description of the known mechanisms that mediate such effects.

Cannabinoid receptor 2: potential role in immunomodulation and neuroinflammation

An accumulating body of evidence suggests that endocannabinoids and cannabinoid receptors type 1 and 2 (CB(1), CB(2)) play a significant role in physiologic and pathologic processes, including cognitive and immune functions. While the addictive properties of marijuana, an extract from the Cannabis plant, are well recognized, there is growing appreciation of the therapeutic potential of cannabinoids in multiple pathologic conditions involving chronic inflammation (inflammatory bowel disease, arthritis, autoimmune disorders, multiple sclerosis, HIV-1 infection, stroke, Alzheimer's disease to name a few), mainly mediated by CB(2) activation. Development of CB(2) agonists as therapeutic agents has been hampered by the complexity of their intracellular signaling, relative paucity of highly selective compounds and insufficient data regarding end effects in the target cells and organs. This review attempts to summarize recent advances in studies of CB(2) activation in the setting of neuroinflammation, immunomodulation and HIV-1 infection.

Using the endocannabinoid system as a neuroprotective strategy in perinatal hypoxic-ischemic brain injury

One of the most important causes of brain injury in the neonatal period is a perinatal hypoxic-ischemic event. This devastating condition can lead to long-term neurological deficits or even death. After hypoxic-ischemic brain injury, a variety of specific cellular mechanisms are set in motion, triggering cell damage and finally producing cell death. Effective therapeutic treatments against this phenomenon are still unavailable because of complex molecular mechanisms underlying hypoxic-ischemic brain injury. After a thorough understanding of the mechanism underlying neural plasticity following hypoxic-ischemic brain injury, various neuroprotective therapies have been developed for alleviating brain injury and improving long-term outcomes. Among them, the endocannabinoid system emerges as a natural system of neuroprotection. The endocannabinoid system modulates a wide range of physiological processes in mammals and has demonstrated neuroprotective effects in different paradigms of acute brain injury, acting as a natural neuroprotectant. The aim of this review is to study the use of different therapies to induce long-term therapeutic effects after hypoxic-ischemic brain injury, and analyze the important role of the endocannabinoid system as a new neuroprotective strategy against perinatal hypoxic-ischemic brain injury.

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 the CB2 receptor system reverses amyloid-induced memory deficiency

Cannabinoid type 2 (CB(2)) agonists are neuroprotective and appear to play modulatory roles in neurodegenerative processes in Alzheimer's disease. We have studied the effect of 1-((3-benzyl-3-methyl-2,3-dihydro-1-benzofuran-6-yl) carbonyl) piperidine (MDA7)-a novel selective CB(2) agonist that lacks psychoactivity-on ameliorating the neuroinflammatory process, synaptic dysfunction, and cognitive impairment induced by bilateral microinjection of amyloid-β (Aβ)(1-40) fibrils into the hippocampal CA1 area of rats. In rats injected with Aβ(1-40) fibrils, compared with the administration of intraperitoneal saline for 14 days, treatment with 15 mg/kg of intraperitoneal MDA7 daily for 14 days (1) ameliorated the expression of CD11b (microglia marker) and glial fibrillary acidic protein (astrocyte marker), (2) decreased the secretion of interleukin-1β, (3) decreased the upsurge of CB(2) receptors, (4) promoted Aβ clearance, and (5) restored synaptic plasticity, cognition, and memory. Our findings suggest that MDA7 is an innovative therapeutic approach for the treatment of Alzheimer's disease.

Cannabinoid 1 (CB1) receptor mediates WIN55, 212-2 induced hypothermia and improved survival in a rat post-cardiac arrest model

AIM

The nonselective Cannabinoid (CB) receptor agonist, WIN55, 212-2, was demonstrated to induce hypothermia and improve post-resuscitation outcomes in a rat post-cardiac arrest model. The present study was to explore the potential mechanisms of WIN55, 212-2 on thermoregulation following resuscitation and to investigate which class of CB receptors was involved in WIN55, 212-2-induced hypothermia.

METHODS

Ventricular fibrillation (VF) was induced and untreated for 6 min in 20 male Sprague-Dawley rats. Defibrillation was attempted after 8min of Cardiopulmonary resuscitation (CPR). Five min post-resuscitation, resuscitated animals were randomized to receive an intramuscular injection of selective CB1 receptors antagonist, SR141716A (5 mg kg(-1)); selective CB2 receptors antagonist SR144528 (5 mg kg(-1)); or placebo. Thirty min after injection, animals received continuous intravenous infusion of WIN55, 212-2 (1.0 mgkg(-1) h(-1)) for 4h while control animals received placebo. The identical temperature environment was maintained in all animals.

RESULTS

In animals treated with WIN55, 212-2, blood temperatures decreased progressively from 37 °C to 34 °C within 4h. This hypothermic effect was completely blocked by CB1 but not CB2 antagonist. Accordingly, significantly better cardiac output, ejection fraction and myocardial performance index, reduced neurological deficit scores, improved microcirculation and longer duration of survival were observed in WIN55, 212-2-treated animals, which were also completely abolished by pretreatment with CB1 antagonist.

CONCLUSIONS

Pharmacologically induced hypothermia with WIN55, 212-2 improved post-resuscitation myocardial and cerebral function, associated with a significantly increased duration of survival in a rat post-cardiac arrest model. The hypothermic and resulted beneficial effects of WIN55, 212-2 were mediated through CB1 receptors.

Reduced infarct size and accumulation of microglia in rats treated with WIN 55,212-2 after neonatal stroke

Cannabinoids have emerged as brain protective agents under neurodegenerative conditions. Many neuroprotective actions of cannabinoids depend on the activation of specific receptors, cannabinoid receptor type 1 (CB1R) and type 2 (CB2R). The aim of the present study was to determine whether the CB2R and CB1R agonist WIN 55,212-2 (WIN) protects neonatal brain against focal cerebral ischemia-reperfusion and whether anti-inflammatory mechanisms play a role in protection. Seven-day-old rats were subjected to 90-min middle cerebral artery occlusion (MCAO), and injured rats were identified by diffusion-weighted MRI during the occlusion. After reperfusion, rats were subcutaneously administered 1 mg/kg of WIN or vehicle twice daily until sacrifice. MCAO led to increased mRNA expression of CB2R (but not CB1R), chemokine receptors (CCR2 and CX3CR1), and cytokines (IL-1β and TNFα), as well as increased protein expression of chemokines MCP-1 and MIP-1α and microglial activation 24 h after MCAO. WIN administration significantly reduced microglial activation at this point and attenuated infarct volume and microglial accumulation and proliferation in the injured cortex 72 h after MCAO. Cumulatively, our results show that the cannabinoid agonist WIN protects against neonatal focal stroke in part due to inhibitory effects on microglia.

Cannabinoid as a neuroprotective strategy in perinatal hypoxic-ischemic injury

Perinatal hypoxia-ischemia remains the single most important cause of brain injury in the newborn, leading to death or lifelong sequelae. Because of the fact that there is still no specific treatment for perinatal brain lesions due to the complexity of neonatal hypoxic-ischemic pathophysiology, the search of new neuroprotective therapies is of great interest. In this regard, therapeutic possibilities of the endocannabinoid system have grown lately. The endocannabinoid system modulates a wide range of physiological processes in mammals and has demonstrated neuroprotective effects in different paradigms of acute brain injury, acting as a natural neuroprotectant. Concerning perinatal asphyxia, the neuroprotective role of this endogenous system is emerging these years. The present review mainly focused on the current knowledge of the cannabinoids as a new neuroprotective strategy against perinatal hypoxic-ischemic brain injury.

Pharmacological activation/inhibition of the cannabinoid system affects alcohol withdrawal-induced neuronal hypersensitivity to excitotoxic insults

Cessation of chronic ethanol consumption can increase the sensitivity of the brain to excitotoxic damages. Cannabinoids have been proposed as neuroprotectants in different models of neuronal injury, but their effect have never been investigated in a context of excitotoxicity after alcohol cessation. Here we examined the effects of the pharmacological activation/inhibition of the endocannabinoid system in an in vitro model of chronic ethanol exposure and withdrawal followed by an excitotoxic challenge. Ethanol withdrawal increased N-methyl-D-aspartate (NMDA)-evoked neuronal death, probably by altering the ratio between GluN2A and GluN2B NMDA receptor subunits. The stimulation of the endocannabinoid system with the cannabinoid agonist HU-210 decreased NMDA-induced neuronal death exclusively in ethanol-withdrawn neurons. This neuroprotection could be explained by a decrease in NMDA-stimulated calcium influx after the administration of HU-210, found exclusively in ethanol-withdrawn neurons. By contrast, the inhibition of the cannabinoid system with the CB1 receptor antagonist rimonabant (SR141716) during ethanol withdrawal increased death of ethanol-withdrawn neurons without any modification of NMDA-stimulated calcium influx. Moreover, chronic administration of rimonabant increased NMDA-stimulated toxicity not only in withdrawn neurons, but also in control neurons. In summary, we show for the first time that the stimulation of the endocannabinoid system is protective against the hyperexcitability developed during alcohol withdrawal. By contrast, the blockade of the endocannabinoid system is highly counterproductive during alcohol withdrawal.

HIV-1 infection and alcohol abuse: neurocognitive impairment, mechanisms of neurodegeneration and therapeutic interventions

Clinical studies indicate that alcohol dependence has an additive effect on cognitive deficits associated with HIV-1 infection. Findings in humans and animal models suggest that alcohol, similar to HIV-1, induces inflammatory processes in the brain leading to neurodegeneration. The causes of HIV-1-associated neurotoxicity are comparable to those mediating alcohol-induced neuronal injury. This review aims to present the mechanisms of the combined effects of HIV-1 and alcohol abuse in the brain and to discuss neuroprotective therapies. Oxidative stress, overproduction of pro-inflammatory factors, impairment of blood-brain barrier and glutamate associated neurotoxicity appear to play important roles in alcohol driven neurodegeneration. Diminution of neuroinflammation constitutes a logical approach for prevention of HIV-1 and alcohol mediated neurodegeneration. Agonists of cannabinoid receptor 2 (CB₂) possess potent anti-inflammatory and neuroprotective properties. We address multifaceted beneficial effects of CB₂ activation in the setting of HIV-1 brain infection and alcohol abuse.

Cannabinoid/agonist WIN 55,212-2 reduces cardiac ischaemia–reperfusion injury in Zucker diabetic fatty rats: role of CB2 receptors and iNOS/eNOS

BACKGROUND

Diabetes increases cardiac damage after myocardial ischaemia. Cannabinoids can protect against myocardial ischaemia/reperfusion injury. The aim of this study was to examine the cardioprotective effect of the cannabinoid agonist WIN 55,212-2 (WIN) against ischaemia/reperfusion injury in an experimental model of type 2 diabetes. We performed these experiments in the Zucker diabetic fatty rat, and focused on the role of cannabinoid receptors in modulation of cardiac inducible nitric oxide synthase (iNOS)/endothelial-type nitric oxide synthase (eNOS) expression.

METHODS

Male 20-week-old Zucker diabetic fatty rats were treated with vehicle, WIN, the selective CB1 or CB2 receptor antagonists AM251 and AM630, respectively, AM251 + WIN or AM630 + WIN. Hearts were isolated from these rats, and the cardiac functional response to ischaemia/reperfusion injury was evaluated. In addition, cardiac iNOS and eNOS expression were determined by western blot.

RESULTS

WIN significantly improved cardiac recovery after ischaemia/ reperfusion in the hearts from Zucker diabetic fatty rats by restoring coronary perfusion pressure and heart rate to preischaemic levels. Additionally, WIN decreased cardiac iNOS expression and increased eNOS expression after ischaemia/reperfusion in diabetic hearts. WIN-induced cardiac functional recovery was completely blocked by the CB2 antagonist AM630. However, changes in NOS isoenzyme expression were not affected by the CB antagonists.

CONCLUSIONS

This study shows a cardioprotective effect of a cannabinoid agonist on ischaemia/reperfusion injury in an experimental model of a metabolic disorder. The activation mainly of CB2 receptors and the restoration of iNOS/eNOS cardiac equilibrium are mechanisms involved in this protective effect. These initial studies have provided the basis for future research in this field.

Regulatory role of cannabinoid receptor 1 in stress-induced excitotoxicity and neuroinflammation

Exposure to stress elicits excitoxicity and neuroinflammation in the brain, contributing to cell death and damage in stress-related neurological and neuropsychiatric diseases. The endocannabinoid system is present in stress-responsive neural circuits and has been proposed as an endogenous neuroprotective system activated in some neuropathological scenarios to restore homeostasis. To elucidate the possible regulatory role of cannabinoid receptor 1 (CB1) in stress-induced excitotoxicity and neuroinflammation, both genetic and pharmacological approaches were used alternatively: (1) wild-type (WT) and CB1 knockout mice (CB1-KO) were exposed to immobilization/acoustic stress (2 h/day for 4 days) and (2) to specifically activate CB1, the selective CB1 agonist Arachidonyl-2'-chloroethylamide (ACEA) (2.5 mg/kg) was intraperitoneally administered daily to some groups of animals. Stress exposure increased CB1 mRNA and protein expression in the prefrontal cortex of WT mice in a mechanism related to N-methyl-D-aspartate glutamate receptor activation. Daily ACEA pretreatment prevented stress-induced: (1) upregulation of CB1 mRNA and protein, (2) decrease in glutamate uptake and glutamate astroglial transporter excitatory amino acid transporter 2 expression, (3) increase in consecutive proinflammatory molecules, such as cytokines (tumor necrosis factor-α and MCP-1), nuclear factor kappa B, and enzymatic sources, such as inducible nitric oxide synthase (NOS-2) and cyclooxygenase-2 (COX-2), (4) increase in lipid peroxidation; although having no effect on plasma corticosterone. Interestingly, a possible related mechanism could be the positive ACEA modulation of the antiinflammatory pathway deoxyprostaglandin/peroxisome proliferator-activated receptor γ (15d-PGJ(2)/PPARγ). Conversely, KO animal experiments indicated that a lack of CB1 produces hypothalamic/pituitary/adrenal (HPA) axis dysregulation and exacerbates stress-induced excitotoxic/neuroinflammatory responses. These multifaceted neuroprotective effects suggest that CB1 activation could be a new therapeutic strategy against neurological/neuropsychiatric pathologies with HPA axis dysregulation and an excitotoxic/neuroinflammatory component in their pathophysiology.

CB1 receptors and post-ischemic brain damage: studies on the toxic and neuroprotective effects of cannabinoids in rat organotypic hippocampal slices

Cannabinoids (CBs) are implicated in a number of physiological and pathological mechanisms in the central nervous system, but their exact role in post-ischemic brain injury is unclear. The toxic and neuroprotective effects of synthetic and endogenous CBs were evaluated in rat organotypic hippocampal slices exposed to 20 min oxygen-glucose deprivation (OGD) and in gerbils subjected to bilateral carotid occlusion for 5 min. When present in the incubation medium, the synthetic CB agonists WIN 55212-2 and CP 55940 (1-30 μM) and the CB1 agonist ACEA exacerbated CA1 injury induced by OGD, whereas the CB1 receptor antagonists AM 251 and LY 320135 were neuroprotective with maximal activity at 1 μM. AM 251 (at 3 mg/kg, i.p.) also attenuated CA1 pyramidal cell death in gerbils in vivo. The endocannabinoid 2-arachidonoylglycerol (2-AG) reduced OGD injury in hippocampal slices at 0.1-1 μM, whereas anandamide (AEA) was neurotoxic at the same concentrations. The effects of WIN 55212-2, AEA and 2-AG in slices were all dependent on the activation of CB1 but not CB2 receptors, except for the toxic effects of AEA that were also dependent on vanilloid TRPV1 receptors. Our results suggest that exogenous administration of CB1 agonists and the production of endocannabinoids "on demand" may produce different, if not opposite, effects on the fate of neurons following cerebral ischemia.