Preservation of spatial memory and neuroprotection by the fatty acid amide hydrolase inhibitor URB597 in a rat model of vascular dementia

Involvement of CB1 and CB2 receptors in neuroprotective effects of cannabinoids in experimental TDP-43 related frontotemporal dementia using male mice

BACKGROUND

The elevation of endocannabinoid levels through inhibiting their degradation afforded neuroprotection in CaMKIIα-TDP-43 mice, a conditional transgenic model of frontotemporal dementia. However, which cannabinoid receptors are mediating these benefits is still pending to be elucidated.

METHODS

We have investigated the involvement of the CB1 and the CB2 receptor using chronic treatments with selective ligands in CaMKIIα-TDP-43 mice, analysis of their cognitive deterioration with the Novel Object Recognition test, and immunostaining for neuronal and glial markers in two areas of interest in frontotemporal dementia.

RESULTS

Our results confirmed the therapeutic value of activating either the CB1 or the CB2 receptor, with improvements in the animal performance in the Novel Object Recognition test, preservation of pyramidal neurons, in particular in the medial prefrontal cortex, and attenuation of glial reactivity, in particular in the hippocampus. In addition, the activation of both CB1 and CB2 receptors reduced the elevated levels of TDP-43 in the medial prefrontal cortex of CaMKIIα-TDP-43 mice, an effect exerted by mechanisms that are currently under investigation.

CONCLUSIONS

These data reinforce the notion that the activation of CB1 and CB2 receptors may represent a promising therapy against TDP-43-induced neuropathology in frontotemporal dementia. Future studies will have to confirm these benefits, in particular with one of the selective CB2 agonists used here, which has been thoroughly characterized for clinical development.

Cannabinoids and endocannabinoids as therapeutics for nervous system disorders: preclinical models and clinical studies

Cannabinoids are lipophilic substances derived from Cannabis sativa that can exert a variety of effects in the human body. They have been studied in cellular and animal models as well as in human clinical trials for their therapeutic benefits in several human diseases. Some of these include central nervous system (CNS) diseases and dysfunctions such as forms of epilepsy, multiple sclerosis, Parkinson's disease, pain and neuropsychiatric disorders. In addition, the endogenously produced cannabinoid lipids, endocannabinoids, are critical for normal CNS function, and if controlled or modified, may represent an additional therapeutic avenue for CNS diseases. This review discusses in vitro cellular, ex vivo tissue and in vivo animal model studies on cannabinoids and their utility as therapeutics in multiple CNS pathologies. In addition, the review provides an overview on the use of cannabinoids in human clinical trials for a variety of CNS diseases. Cannabinoids and endocannabinoids hold promise for use as disease modifiers and therapeutic agents for the prevention or treatment of neurodegenerative diseases and neurological disorders.

Naringenin alleviates cognitive dysfunction in rats with cerebral ischemia/reperfusion injury through up-regulating hippocampal BDNF-TrkB signaling: involving suppression in neuroinflammation and oxidative stress

Cognitive dysfunction is one of the common complications of cerebral ischemia-reperfusion (CI/R) injury after ischemic stroke. Neuroinflammation and oxidative stress are the core pathological mechanism of CI/R injury. The activation of brain derived neurotrophic factor (BDNF)-tyrosine receptor kinase B (TrkB) signaling antagonize cognitive dysfunction in a series of neuropathy. Naringenin (NAR) improves cognitive function in many diseases, but the role of NAR in CI/R injury-induced cognitive dysfunction remains unexplored. The study aimed to explore the potential protective effects of NAR in CI/R injury-induced cognitive dysfunction and underlying mechanism. The rats were exposed to transient middle cerebral artery occlusion (MCAO) and then treated with distilled water or NAR (50 or 100 mg/kg/day, p.o.) for 30 days. The Y-maze test, Novel object recognition test and Morris water maze test were performed to assess cognitive function. The levels of oxidative stress and inflammatory cytokines were measured by ELISA. The expressions of BDNF/TrkB signaling were detected by Western blot. NAR prevented cognitive impairment in MCAO-induced CI/R injury rats. Moreover, NAR inhibited oxidative stress (reduced levels of malondialdehyde and 4-hydroxynonenal, increased activities of superoxide dismutase and Glutathione peroxidase) and inflammatory cytokines (reduced levels of tumor necrosis factor-α, Interleukin-1β and Interleukin-6), up-regulated the expressions of BDNF and p-TrkB in hippocampus of MCAO-induced CI/R rats. NAR ameliorated cognitive dysfunction of CI/R rats via inhibiting oxidative stress, reducing inflammatory response, and up-regulating BDNF/TrkB signaling pathways in the hippocampus.

Alleviating CB2-Dependent ER Stress and Mitochondrial Dysfunction Improves Chronic Cerebral Hypoperfusion-Induced Cognitive Impairment

Augmentation of endoplasmic reticulum (ER) stress may trigger excessive oxidative stress, which induces mitochondrial dysfunction. The fatty acid amide hydrolase inhibitor, URB597, shows anti-oxidation characteristics in multiple neurological disorders. The present study aimed to determine whether inhibition of ER stress was involved in the protective effects of URB597 against chronic cerebral hypoperfusion (CCH)-induced cognitive impairment. Hippocampal HT-22 cells were exposed to oxygen-glucose deprivation. The cell viability, apoptosis, ER stress, mitochondrial ATP, and oxidative stress levels were assessed following treatment with URB597, benzenebutyric acid (4-PBA), and thapsigargin (TG). Furthermore, the effects of URB597 on ER stress and related pathways were investigated in the CCH animal model, including Morris water maze testing of cognition, western blotting analysis of ER stress signaling, and transmission electron microscopy of mitochondrial and ER ultrastructure changes. The results suggested that cerebral ischemia caused ER stress with upregulation of ER stress signaling-related proteins, mitochondrial dysfunction, neuronal apoptosis, ultrastructural injuries of mitochondria-associated ER membranes, and cognitive decline. Co-immunoprecipitation experiments confirmed the interaction between CB2 and β-Arrestin1. Inhibiting ER stress by URB597 improved these changes by activating CB2/β-Arrestin1 signaling, which was reversed by the CB2 antagonist, AM630. Together, the results identified a novel mechanism of URB597, involving CCH-induced cognitive impairment alleviation of CB2-dependent ER stress and mitochondrial dysfunction. Furthermore, this study identified CB2 as a potential target for therapy of ischemic cerebrovascular diseases.

Anxiogenic doses of rapamycin prevent URB597-induced anti-stress effects in socially defeated mice

Repeated exposure to psychosocial stress modulates the endocannabinoid system, particularly anandamide (AEA) signaling in brain regions associated with emotional distress. The mTOR protein regulates various neuroplastic processes in the brain disrupted by stress, including adult hippocampal neurogenesis. This kinase has been implicated in multiple effects of cannabinoid drugs and the anti-stress behavioral effects of psychoactive drugs. Therefore, our hypothesis is that enhancing AEA signaling via pharmacological inhibition of the fatty acid amide hydrolase (FAAH) enzyme induces an anti-stress behavioral effect through an mTOR-dependent mechanism. To test this hypothesis, male C57Bl6 mice were exposed to social defeat stress (SDS) for 7 days and received daily treatment with either vehicle or different doses of the FAAH inhibitor, URB597 (0.1; 0.3; 1 mg/Kg), alone or combined with rapamycin. The results suggested that URB597 induced an inverted U-shaped dose-response curve in mice subjected to SDS (with the intermediate dose of 0.3 mg/kg being anxiolytic, and the higher tested dose of 1 mg/Kg being anxiogenic). In a second independent experiment, rapamycin treatment induced an anxiogenic-like response in control mice. However, in the presence of rapamycin, the anxiolytic dose of URB597 treatment failed to reduce stress-induced anxiety behaviors in mice. SDS exposure altered the hippocampal expression of the mTOR scaffold protein Raptor. Furthermore, the anxiogenic dose of URB597 decreased the absolute number of migrating doublecortin (DCX)-positive cells in the dentate gyrus, suggesting an anti-anxiety effect independent of newly generated/immature neurons. Therefore, our results indicate that in mice exposed to repeated psychosocial stress, URB597 fails to counteract the anxiogenic-like response induced by the pharmacological dampening of mTOR signaling.

Preclinical investigation in FAAH inhibition as a neuroprotective therapy for frontotemporal dementia using TDP-43 transgenic male mice

BACKGROUND

Frontotemporal dementia (FTD) is a heterogeneous group of early onset and progressive neurodegenerative disorders, characterized by degeneration in the frontal and temporal lobes, which causes deterioration in cognition, personality, social behavior and language. Around 45% of the cases are characterized by the presence of aggregates of the RNA-binding protein TDP-43.

METHODS

In this study, we have used a murine model of FTD that overexpresses this protein exclusively in the forebrain (under the control of the CaMKIIα promoter) for several biochemical, histological and pharmacological studies focused on the endocannabinoid system.

RESULTS

These mice exhibited at postnatal day 90 (PND90) important cognitive deficits, signs of emotional impairment and disinhibited social behaviour, which were, in most of cases, maintained during the first year of life of these animals. Motor activity was apparently normal, but FTD mice exhibited higher mortality. Their MRI imaging analysis and their ex-vivo histopathological evaluation proved changes compatible with atrophy (loss of specific groups of pyramidal neurons: Ctip2- and NeuN-positive cells) and inflammatory events (astroglial and microglial reactivities) in both cortical (medial prefrontal cortex) and subcortical (hippocampus) structures at PND90 and also at PND365. The analysis of the endocannabinoid system in these mice proved a decrease in the hydrolysing enzyme FAAH in the prefrontal cortex and the hippocampus, with an increase in the synthesizing enzyme NAPE-PLD only in the hippocampus, responses that were accompanied by modest elevations in anandamide and related N-acylethanolamines. The potentiation of these elevated levels of anandamide after the pharmacological inactivation of FAAH with URB597 resulted in a general improvement in behaviour, in particular in cognitive deterioration, associated with the preservation of pyramidal neurons of the medial prefrontal cortex and the CA1 layer of the hippocampus, and with the reduction of gliosis in both structures.

CONCLUSIONS

Our data confirmed the potential of elevating the endocannabinoid tone as a therapy against TDP-43-induced neuropathology in FTD, limiting glial reactivity, preserving neuronal integrity and improving cognitive, emotional and social deficits.

Experimental Animal Models for Moyamoya Disease: A Species-Oriented Scoping Review

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by progressive stenosis of large intracranial arteries and a hazy network of basal collaterals called moyamoya vessels. The etiology and pathogenesis of MMD are still obscure. The biggest obstacles in the basic research of MMD are difficulty in obtaining specimens and the lack of an animal model. It is necessary to use appropriate and rationally designed animal models for the correct evaluation. Several animal models and methods have been developed to produce an effective MMD model, such as zebrafish, mice and rats, rabbits, primates, felines, canines, and peripheral blood cells, each with advantages and disadvantages. There are three mechanisms for developing animal models, including genetic, immunological/inflammatory, and ischemic animal models. This review aims to analyze the characteristics of currently available models, providing an overview of the animal models framework and the convenience of selecting model types for MMD research. It will be a great benefit to identify strategies for future model generations.

Targeting Endocannabinoid System in Epilepsy: For Good or for Bad

Epilepsy is a neurological disorder with a high prevalence worldwide. Several studies carried out during the last decades indicate that the administration of cannabinoids as well as the activation of the endocannabinoid system (ECS) represent a therapeutic strategy to control epilepsy. However, there are controversial studies indicating that activation of ECS results in cell damage, inflammation and neurotoxicity, conditions that facilitate the seizure activity. The present review is focused to present findings supporting this issue. According to the current discrepancies, it is relevant to elucidate the different effects induced by the activation of ECS and determine the conditions under which it facilitates the seizure activity.

Experimental animal models for moyamoya disease and treatment: a pathogenesis-oriented scoping review

OBJECTIVE

Moyamoya disease (MMD) is an intracranial steno-occlusive pathology characterized by progressive narrowing of proximal large vessels, including the terminal internal carotid arteries (ICAs), middle cerebral arteries, or anterior cerebral arteries. Named for the "puff of smoke" appearance of the anomalous vascularization visualized on cerebral angiography, MMD lacks a well-defined etiology, although significant insights have been made, including the identification of a susceptibility gene, RNF213, in humans with the disease. A limitation to advancing the understanding and treatment of MMD has been the lack of experimental animal models that authentically reflect the clinical pathogenesis. In an effort to analyze characteristics of currently available models and identify strategies for future model generation, the authors performed a scoping review of experimental animal models that have been used to study MMD.

METHODS

A systematic search of PubMed, Web of Science, and Scopus was performed to identify articles describing animal models used to study MMD. Additional articles were identified via citation searching. Study selection and data extraction were performed by two independent reviewers based on defined inclusion and exclusion criteria.

RESULTS

A total of 44 articles were included for full-text review. The methods used to generate these animal models were broadly classified as surgical (n = 25, 56.8%), immunological (n = 7, 15.9%), genetic (n = 6, 13.6%), or a combination (n = 6, 13.6%). Surgical models typically involved permanent ligation of one or both of the common carotid arteries or ICAs to produce chronic cerebral hypoperfusion. Genetic models utilized known MMD or cerebrovascular disease-related genes, such as RNF213 or ACTA2, to induce heritable cerebral vasculopathy. Finally, immunological models attempted to induce vasculitis-type pathology by recapitulating the inflammatory milieu thought to underlie MMD.

CONCLUSIONS

Models generated for MMD have involved three general approaches: surgical, immunological, and genetic. Although each reflects a key aspect of MMD pathogenesis, the failure of any individual model to recapitulate the development, progression, and consequences of the disease underscores the importance of future work in developing a multietiology model.

Neuroprotective Effects of VEGF-A Nanofiber Membrane and FAAH Inhibitor URB597 Against Oxygen-Glucose Deprivation-Induced Ischemic Neuronal Injury

INTRODUCTION

Brain ischemia is a common neurological disorder worldwide that activates a cascade of pathophysiological events involving decreases in oxygen and glucose levels. Despite substantial efforts to explore its pathogenesis, the management of ischemic neuronal injury remains an enormous challenge. Accumulating evidence suggests that VEGF modified nanofiber (NF) materials and the fatty-acid amide hydrolase (FAAH) inhibitor URB597 exert an influence on alleviating ischemic brain damage. We aimed to further investigate their effects on primary hippocampal neurons, as well as the underlying mechanisms following oxygen-glucose deprivation (OGD).

METHODS

Different layers of VEGF-A loaded polycaprolactone (PCL) nanofibrous membranes were first synthesized by using layer-by-layer (LBL) self-assembly of electrospinning methods. The physicochemical and biological properties of VEGF-A NF membranes, and their morphology, hydrophilicity, and controlled-release of VEGF-A were then estimated. Furthermore, the effects of VEGF-A NF and URB597 on OGD-induced mitochondrial oxidative stress, inflammatory responses, neuronal apoptosis, and endocannabinoid signaling components were assessed.

RESULTS

The VEGF-A NF membrane and URB597 can not only promote hippocampal neuron adhesion and viability following OGD but also exhibited antioxidant/anti-inflammatory and mitochondrial membrane potential protection. The VEGF-A NF membrane and URB597 also inhibited OGD-induced cellular apoptosis through activating CB1R signaling. These results indicate that VEGF-A could be controlled-released by LBL self-assembled NF membranes.

DISCUSSION

The VEGF-A NF membrane and URB597 displayed positive synergistic neuroprotective effects through the inhibition of mitochondrial oxidative stress and activation of CB1R/PI3K/AKT/BDNF signaling, suggesting that a VEGF-A loaded NF membrane and the FAAH inhibitor URB597 could be of therapeutic value in ischemic cerebrovascular diseases.