The CB1 cannabinoid receptor mediates excitotoxicity-induced neural progenitor proliferation and neurogenesis

Neonatal dysregulation of 2-arachidonoylglycerol induces impaired brain function in adult mice

The endocannabinoid system (ECS) regulates neurotransmission linked to synaptic plasticity, cognition, and emotion. While it has been demonstrated that dysregulation of the ECS in adulthood is relevant not only to central nervous system (CNS) disorders such as autism spectrum disorder, cognitive dysfunction, and depression but also to brain function, there are few studies on how dysregulation of the ECS in the neonatal period affects the manifestation and pathophysiology of CNS disorders later in life. In this study, DO34, a diacylglycerol lipase alpha (DAGLα) inhibitor affecting endocannabinoid 2-AG production, was injected into C57BL/6N male mice from postnatal day (PND) 7 to PND 10, inducing dysregulation of the ECS in the neonatal period. Subsequently, we examined whether it affects neuronal function in adulthood through electrophysiological and behavioral evaluation. DO34-injected mice showed significantly decreased cognitive functions, attributed to impairment of hippocampal synaptic plasticity. The findings suggest that regulation of ECS activity in the neonatal period may induce enduring effects on adult brain function.

New insights into hypothalamic neurogenesis disruption after acute and intense stress: implications for microglia and inflammation

In recent years, the hypothalamus has emerged as a new neurogenic area, capable of generating new neurons after development. Neurogenesis-dependent neuroplasticity seems to be critical to continuously adapt to internal and environmental changes. Stress is a potent environmental factor that can produce potent and enduring effects on brain structure and function. Acute and chronic stress is known to cause alterations in neurogenesis and microglia in classical adult neurogenic regions such as the hippocampus. The hypothalamus is one of the major brain regions implicated in homeostatic stress and emotional stress systems, but little is known about the effect of stress on the hypothalamus. Here, we studied the impact of acute and intense stress (water immersion and restrain stress, WIRS), which may be considered as an inducer of an animal model of posttraumatic stress disorder, on neurogenesis and neuroinflammation in the hypothalamus of adult male mice, focusing on three nuclei: PVN, VMN and ARC, and also in the periventricular area. Our data revealed that a unique stressor was sufficient to provoke a significant impact on hypothalamic neurogenesis by inducing a reduction in the proliferation and number of immature neurons identified as DCX+ cells. These differences were accompanied by marked microglial activation in the VMN and ARC, together with a concomitant increase in IL-6 levels, indicating that WIRS induced an inflammatory response. To investigate the possible molecular mechanisms responsible for neuroplastic and inflammatory changes, we tried to identify proteomic changes. The data revealed that WIRS induced changes in the hypothalamic proteome, modifying the abundance of three and four proteins after 1 h or 24 h of stress application, respectively. These changes were also accompanied by slight changes in the weight and food intake of the animals. These results are the first to show that even a short-term environmental stimulus such as acute and intense stress can have neuroplastic, inflammatory, functional and metabolic consequences on the adult hypothalamus.

The Long-Term Neuroprotective Effect of the Endocannabinoid 2-AG and Modulation of the SGZ's Neurogenic Response after Neonatal Hypoxia-Ischemia

Neonatal hypoxia-ischemia (HI) often causes hypoxic-ischemic encephalopathy (HIE), a neurological condition that can lead to overall disability in newborns. The only treatment available for affected neonates is therapeutic hypothermia; however, cooling is not always effective to prevent the deleterious effects of HI, so compounds such as cannabinoids are currently under research as new therapies. Modulating the endocannabinoid system (ECS) may reduce brain damage and/or stimulate cell proliferation at the neurogenic niches. Further, the long-term effects of cannabinoid treatment are not so clear. Here, we studied the middle- and long-term effects of 2-AG, the most abundant endocannabinoid in the perinatal period after HI in neonatal rats. At middle-term (postnatal day 14), 2-AG reduced brain injury and increased SGZ's cell proliferation and the number of neuroblasts. At post-natal day 90, the treatment with the endocannabinoid showed global and local protection, suggesting long-lasting neuroprotective effects of 2-AG after neonatal HI in rats.

A Microbial-Based Approach to Mental Health: The Potential of Probiotics in the Treatment of Depression

Probiotics are currently the subject of intensive research pursuits and also represent a multi-billion-dollar global industry given their vast potential to improve human health. In addition, mental health represents a key domain of healthcare, which currently has limited, adverse-effect prone treatment options, and probiotics may hold the potential to be a novel, customizable treatment for depression. Clinical depression is a common, potentially debilitating condition that may be amenable to a precision psychiatry-based approach utilizing probiotics. Although our understanding has not yet reached a sufficient level, this could be a therapeutic approach that can be tailored for specific individuals with their own unique set of characteristics and health issues. Scientifically, the use of probiotics as a treatment for depression has a valid basis rooted in the microbiota-gut-brain axis (MGBA) mechanisms, which play a role in the pathophysiology of depression. In theory, probiotics appear to be ideal as adjunct therapeutics for major depressive disorder (MDD) and as stand-alone therapeutics for mild MDD and may potentially revolutionize the treatment of depressive disorders. Although there is a wide range of probiotics and an almost limitless range of therapeutic combinations, this review aims to narrow the focus to the most widely commercialized and studied strains, namely Lactobacillus and Bifidobacterium, and to bring together the arguments for their usage in patients with major depressive disorder (MDD). Clinicians, scientists, and industrialists are critical stakeholders in exploring this groundbreaking concept.

Congenital Gastrointestinal Anomalies in Europe 2010–2019: A Geo-Spatiotemporal and Causal Inferential Study of Epidemiological Patterns in Relationship to Cannabis- and Substance Exposure

Introduction: Congenital anomalies (CA’s) of most of the gastrointestinal tract have been linked causally with prenatal or community cannabis exposure. Therefore, we studied this relationship in Europe. Methods: CA data were from Eurocat. Drug-use data were sourced from the European Monitoring Centre for Drugs and Drug Addiction. Income data were taken from the World Bank. Results: When countries with increasing rates of daily cannabis use were compared with those which were not, the overall rate of gastrointestinal CA’s (GCA’s) was higher in the former group (p = 0.0032). The five anomalies which were related to the metrics of cannabis exposure on bivariate analysis were bile duct atresia, Hirschsprungs, digestive disorders, annular pancreas and anorectal stenosis or atresia. The following sequence of GCA’s was significantly linked with cannabis metrics at inverse-probability-weighted-panel modelling, as indicated: esophageal stenosis or atresia, bile duct atresia, small intestinal stenosis or atresia, anorectal stenosis or atresia, Hirschsprungs disease: p = 1.83 × 10−5, 0.0046, 3.55 × 10−12, 7.35 × 10−6 and 2.00 × 10−12, respectively. When this GCA series was considered in geospatial modelling, the GCA’s were significantly cannabis-related from p = 0.0003, N.S., 0.0086, 6.652 × 10−5, 0.0002, 71.4% of 35 E-value estimates and 54.3% minimum E-values (mEVv’s) > 9 (high zone) and 100% and 97.1% > 1.25 (causality threshold). The order of cannabis sensitivity by median mEVv was Hirschsprungs > esophageal atresia > small intestinal atresia > anorectal atresia > bile duct atresia. Conclusions: Seven of eight GCA’s were related to cannabis exposure and fulfilled the quantitative criteria for epidemiologically causal relationships. Penetration of cannabinoids into the community should be carefully scrutinized and controlled to protect against exponential and multigenerational genotoxicity ensuing from multiple cannabinoids.

Patterns of Cannabis- and Substance-Related Congenital General Anomalies in Europe: A Geospatiotemporal and Causal Inferential Study

INTRODUCTION

Recent series of congenital anomaly (CA) rates (CARs) have showed the close and epidemiologically causal relationship of cannabis exposure to many CARs. We investigated these trends in Europe where similar trends have occurred.

METHODS

CARs from EUROCAT. Drug use from European Monitoring Centre for Drugs and Drug Addiction. Income data from World Bank.

RESULTS

CARs were higher in countries with increasing daily use overall (p = 9.99 × 10-14, minimum E-value (mEV) = 2.09) and especially for maternal infections, situs inversus, teratogenic syndromes and VACTERL syndrome (p = 1.49 × 10-15, mEV = 3.04). In inverse probability weighted panel regression models the series of anomalies: all anomalies, VACTERL, foetal alcohol syndrome, situs inversus (SI), lateralization (L), and teratogenic syndromes (TS; AAVFASSILTS) had cannabis metric p-values from: p < 2.2 × 10-16, 1.52 × 10-12, 1.44 × 10-13, 1.88 × 10-7, 7.39 × 10-6 and <2.2 × 10-16. In a series of spatiotemporal models this anomaly series had cannabis metric p-values from: 8.96 × 10-6, 6.56 × 10-6, 0.0004, 0.0019, 0.0006, 5.65 × 10-5. Considering E-values, the cannabis effect size order was VACTERL > situs inversus > teratogenic syndromes > FAS > lateralization syndromes > all anomalies. 50/64 (78.1%) E-value estimates and 42/64 (65.6%) mEVs > 9. Daily cannabis use was the strongest predictor for all anomalies.

CONCLUSION

Data confirmed laboratory, preclinical and recent epidemiological studies from Canada, Australia, Hawaii, Colorado and USA for teratological links between cannabis exposure and AAVFASSILTS anomalies, fulfilled epidemiological criteria for causality and underscored importance of cannabis teratogenicity. VACTERL data are consistent with causation via cannabis-induced Sonic Hedgehog inhibition. TS data suggest cannabinoid contribution. SI&L data are consistent with results for cardiovascular CAs. Overall, these data show that cannabis is linked across space and time and in a manner which fulfills epidemiological criteria for causality not only with many CAs, but with several multiorgan teratologic syndromes. The major clinical implication of these results is that access to cannabinoids should be tightly restricted in the interests of safeguarding the community's genetic heritage to protect and preserve coming generations, as is done for all other major genotoxins.

Geospatiotemporal and Causal Inferential Study of European Epidemiological Patterns of Cannabis- and Substance-Related Congenital Orofacial Anomalies

INTRODUCTION

Since high rates of congenital anomalies (CAs), including facial CAs (FCAs), causally attributed to antenatal and community cannabis use have been reported in several recent series, it was of interest to examine this subject in detail in Europe.

METHODS

CA data were taken from the EUROCAT database. Drug exposure data were downloaded from the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA). Income was taken from the World Bank's online sources.

RESULTS

On the bivariate maps of both orofacial clefts and holoprosencephaly against resin, the Δ9-tetrahydrocannabinol concentration rates of both covariates increased together in France, Bulgaria, and the Netherlands. In the bivariate analysis, the anomalies could be ranked by the minimum E-value (mEV) as congenital glaucoma > congenital cataract > choanal atresia > cleft lip ± cleft palate > holoprosencephaly > orofacial clefts > ear, face, and neck anomalies. When nations with increasing daily use were compared to those without, the former had generally higher rates of FCAs (p = 0.0281). In the inverse probability weighted panel regression, the sequence of anomalies-orofacial clefts, anotia, congenital cataract, and holoprosencephaly-had positive and significant cannabis coefficients of p = 2.65 × 10^-5, 1.04 × 10^-8, 5.88 × 10^-16, and 3.21 × 10^-13, respectively. In the geospatial regression, the same series of FCAs had positive and significant regression terms for cannabis of p = 8.86 × 10^-9, 0.0011, 3.36 × 10^-8, and 0.0015, respectively. Some 25/28 (89.3%) E-value estimates and 14/28 (50%) mEVs were >9 (considered to be in the high range), and 100% of both were >1.25 (understood to be in the causal range).

CONCLUSION

Rising cannabis use is associated with all the FCAs and fulfils the epidemiological criteria for causality. The data indicate particular concerns relating to brain development and exponential genotoxic dose-responses, urging caution with regard to community cannabinoid penetration.

Effects of Prenatal Cannabinoids Exposure upon Placenta and Development of Respiratory Neural Circuits

Cannabis use has risen dangerously during pregnancy in the face of incipient therapeutic use and a growing perception of safety. The main psychoactive compound of the Cannabis sativa plant is the phytocannabinoid delta-9-tetrahydrocannabinol (A-9 THC), and its status as a teratogen is controversial. THC and its endogenous analogues, anandamide (AEA) and 2-AG, exert their actions through specific receptors (eCBr) that activate intracellular signaling pathways. CB1r and CB2r, also called classic cannabinoid receptors, together with their endogenous ligands and the enzymes that synthesize and degrade them, constitute the endocannabinoid system. This system is distributed ubiquitously in various central and peripheral tissues. Although the endocannabinoid system's most studied role is controlling the release of neurotransmitters in the central nervous system, the study of long-term exposure to cannabinoids on fetal development is not well known and is vital for understanding environmental or pathological embryo-fetal or postnatal conditions. Prenatal exposure to cannabinoids in animal models has induced changes in placental and embryo-fetal organs. Particularly, cannabinoids could influence both neural and nonneural tissues and induce embryo-fetal pathological conditions in critical processes such as neural respiratory control. This review aims at the acute and chronic effects of prenatal exposure to cannabinoids on placental function and the embryo-fetal neurodevelopment of the respiratory pattern. The information provided here will serve as a theoretical framework to critically evaluate the teratogen effects of the consumption of cannabis during pregnancy.

Role of integrating cannabinoids and the endocannabinoid system in neonatal hypoxic-ischaemic encephalopathy

Neonatal hypoxic-ischaemic events, which can result in long-term neurological impairments or even cell death, are among the most significant causes of brain injury during neurodevelopment. The complexity of neonatal hypoxic-ischaemic pathophysiology and cellular pathways make it difficult to treat brain damage; hence, the development of new neuroprotective medicines is of great interest. Recently, numerous neuroprotective medicines have been developed to treat brain injuries and improve long-term outcomes based on comprehensive knowledge of the mechanisms that underlie neuronal plasticity following hypoxic-ischaemic brain injury. In this context, understanding of the medicinal potential of cannabinoids and the endocannabinoid system has recently increased. The endocannabinoid system plays a vital neuromodulatory role in numerous brain regions, ensuring appropriate control of neuronal activity. Its natural neuroprotection against adult brain injury or acute brain injury also clearly demonstrate the role of endocannabinoid signalling in modulating neuronal activity in the adult brain. The goal of this review is to examine how cannabinoid-derived compounds can be used to treat neonatal hypoxic-ischaemic brain injury and to assess the critical function of the endocannabinoid system and its potential for use as a new neuroprotective treatment for neonatal hypoxic-ischaemic brain injury.

European Epidemiological Patterns of Cannabis- and Substance-Related Congenital Neurological Anomalies: Geospatiotemporal and Causal Inferential Study

Introduction. Of the many congenital anomalies (CAs) recently linked with community cannabis exposure, arguably the most concerning are neurological CAs (NCAs). We therefore conducted a detailed study of this in fourteen European nations. Methods. Congenital anomaly data were from Eurocat. Drug exposure data were from European Monitoring Centre for Drugs and Drug Addiction. Income from World bank. Results. The Netherlands, Spain, France and Bulgaria reported increasing rates of many NCAs. The NCA rate (NCAR) was higher in nations with increasing daily cannabis use when compared to those without (p = 0.0204, minimum E-value (mEV) = 1.35). At bivariate analysis, the mEVs of the following NCAs were significantly cannabis related: severe microcephaly 2.14 × 1013, craniosynostosis 5.27 × 1011, nervous system 4.87 × 1011, eye 2.73 × 107, microphthalmos 4.07 × 106, anencephalus 710.37, hydrocephalus 245.64, spina bifida 14.86 and neural tube defects 13.15. At inverse probability, weighted panel regression terms including cannabis were significantly related to the following series of anomalies: nervous system, anencephalus, severe microcephalus, microphthalmos, neural tube defect and spina bifida from p = 5.09 × 10−8, <2.2 × 10−16, <2.2 × 10−16, 4.84 × 10−11, <2.2 × 10−16 and 9.69 × 10−7. At geospatial regression, this same series of anomalies had terms including cannabis significant from p = 0.0027, 1.53 × 10−7, 3.65 × 10−6, 2.13 × 10−8, 0.0002 and 9.76 × 10−12. 88.0% of 50 E-value estimates and 72.0% of mEVs > 9. This analysis therefore demonstrates both close association of cannabis exposure with multiple NCAs across space-time and also fulfills the quantitative criteria of causal inferential analysis. Conclusions. Nine NCARs on bivariate and six NCARs on multivariable regression were cannabis related and fulfilled quantitative epidemiological criteria for causality and are consistent with other series. Particular concerns relate to exponential dose−response effects demonstrated in the laboratory and epidemiological studies. Great caution with community cannabinoid penetration is warranted. Data indicate that cannabis is a significant environmental teratogen and thus imply that cannabinoids should be regulated similarly to the manner in which all other important genotoxins are carefully controlled by communities for their self-sustaining longevity and the protection of generations yet to come.

The Endocannabinoid System as a Target for Neuroprotection/Neuroregeneration in Perinatal Hypoxic-Ischemic Brain Injury

The endocannabinoid (EC) system is a complex cell-signaling system that participates in a vast number of biological processes since the prenatal period, including the development of the nervous system, brain plasticity, and circuit repair. This neuromodulatory system is also involved in the response to endogenous and environmental insults, being of special relevance in the prevention and/or treatment of vascular disorders, such as stroke and neuroprotection after neonatal brain injury. Perinatal hypoxia-ischemia leading to neonatal encephalopathy is a devastating condition with no therapeutic approach apart from moderate hypothermia, which is effective only in some cases. This overview, therefore, gives a current description of the main components of the EC system (including cannabinoid receptors, ligands, and related enzymes), to later analyze the EC system as a target for neonatal neuroprotection with a special focus on its neurogenic potential after hypoxic-ischemic brain injury.

Modulatory Activity of the Endocannabinoid System in the Development and Proliferation of Cells in the CNS

The Endocannabinoid System (ECS, also known as Endocannabinoidome) plays a key role in the function of the Central Nervous System, though the participation of this system on the early development - specifically in neuroprotection and proliferation of nerve cells - has been poorly studied. Here, we collect and describe evidence regarding how cannabinoid receptors CB1R and CB2R regulate several cell markers related to proliferation. While CB1R participates in the modulation of neuronal and glial proliferation, CB2R is involved in the proliferation of glial cells. The endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) exert significant effects on nerve cell proliferation. AEA generated during embryogenesis induces major effects on the differentiation of neuronal progenitor cells, whereas 2-AG participates in modulating cell migration events rather than affecting the neural proliferation rate. However, although the ECS has been demonstrated to participate in neuroprotection, more characterization on its role in neuronal and glial proliferation and differentiation is needed, especially in brain areas with recognized high neurogenesis rates. This has encouraged scientists to elucidate and propose specific mechanisms related with these cell proliferation mechanisms to better understand some neurodegenerative disorders such as Parkinson, Huntington and Alzheimer diseases, in which neuronal loss and poor neurogenesis are crucial factors for their onset and progression. In this review, we collect and present recent evidence published pointing to an active role of the ECS in the development and proliferation of nerve cells.

Endocannabinoids and related compounds as modulators of angiogenesis: Concepts and clinical significance

Vasculogenesis (the process of differentiation of angioblasts toward endothelial cells and de novo formation of crude vascular networks) and angiogenesis (the process of harmonized sprouting and dispersal of new capillaries from previously existing ones) are two fundamentally complementary processes, obligatory for maintaining physiological functioning of vascular system. In clinical practice, however, the later one is of more importance as it guarantees correct embryonic nourishment, accelerates wound healing processes, prevents uncontrolled cell growth and tumorigenesis, contributes in supplying nutritional demand following occlusion of coronary vessels and is in direct relation with development of diabetic retinopathy. Hence, discovery of novel molecules capable of modulating angiogenic events are of great clinical importance. Recent studies have demonstrated multiple angio-regulatory activities for endocannabinoid system modulators and endocannabinoid-like molecules, as well as their metabolizing enzymes. Hence, in present article, we reviewed the regulatory roles of these molecules on angiogenesis and described molecular mechanisms underlying them.

Epidemiological Patterns of Cannabis- and Substance- Related Congenital Uronephrological Anomalies in Europe: Geospatiotemporal and Causal Inferential Study

INTRODUCTION

Recent reports linking prenatal and community cannabis exposure to elevated uronephrological congenital anomaly (UCA) rates (UCAR's) raise the question of its European epidemiology given recent increases in community cannabinoid penetration there.

METHODS

UCAR data from Eurocat. Drug use data from European Monitoring Centre for Drugs and Drug Addiction. Income from World bank.

RESULTS

UCAR increased across Spain, Netherlands, Poland and France. UCAR's and cannabis resin THC increased simultaneously in France, Spain, Netherlands and Bulgaria. At bivariate analysis all UCA's were related to cannabis herb and resin THC concentrations. All UCAR's were bivariately related to cannabis metrics ordered by median minimum E-value (mEV) as hypospadias > multicystic renal disease > bilateral renal agenesis > UCA's > hydronephrosis > posterior urethral valve > bladder exstrophy/epispadias. At inverse probability weighted multivariable analysis terms including cannabis were significant for the following series of anomalies: UCA's, multicystic renal disease, bilateral renal agenesis, hydronephrosis, congenital posterior urethral valves from P = 1.91 × 10-5, 2.61 × 10-8, 4.60 × 10-15, 4.60 × 10-15 and 2.66 × 10-10. At geospatial analysis the same series of UCA's were significantly related to cannabis from P = 7.84 × 10-15, 7.72 × 10-5, 0.0023, 6.95 × 10-5, and 8.82 × 10-5. 45/51 (88.2%) of E-value estimates and 31/51 (60.8%) of mEV's >9.

CONCLUSION

Analysis confirms a close relationship between cannabis metrics and all seven UCA's and fulfill formal criteria for quantitative causal inference. Given the exponential cannabinoid genotoxicity dose-response relationship results provide a powerful stimulus to constrain community cannabinoid exposure including protection of the food chain to preserve the genome and epigenome of coming generations.

The Therapeutic Potential of the Endocannabinoid System in Age-Related Diseases

The endocannabinoid system (ECS) dynamically regulates many aspects of mammalian physiology. ECS has gained substantial interest since growing evidence suggests that it also plays a major role in several pathophysiological conditions due to its ability to modulate various underlying mechanisms. Furthermore, cannabinoids, as components of the cannabinoid system (CS), have proven beneficial effects such as anti-inflammatory, immunomodulatory, neuromodulatory, antioxidative, and cardioprotective effects. In this comprehensive review, we aimed to describe the complex interaction between CS and most common age-related diseases such as neuro-degenerative, oncological, skeletal, and cardiovascular disorders, together with the potential of various cannabinoids to ameliorate the progression of these disorders. Since chronic inflammation is postulated as the pillar of all the above-mentioned medical conditions, we also discuss in this paper the potential of CS to ameliorate aging-associated immune system dysregulation.

European Epidemiological Patterns of Cannabis- and Substance-Related Body Wall Congenital Anomalies: Geospatiotemporal and Causal Inferential Study

As body wall congenital anomalies (BWCAs) have a long history of being associated with prenatal or community cannabis exposure (CCE), it was of interest to investigate these epidemiological relationships in Europe given the recent increases in cannabis use prevalence, daily intensity, and Δ9-tetrahydrocannabinol (THC) potency. Methods: This study makes use of BWCA data from Eurocat, drug exposure data from the European Monitoring Centre for Drugs and Drug Addiction, and income from the World Bank. Results: The mapping analysis showed that BWCARs increased in France, Spain, and the Netherlands. The bivariate mapping analysis showed that the BWCA rates (BWCAR) and the cannabis resin THC concentration rose simultaneously in France, the Netherlands, Bulgaria, Sweden, and Norway. The bivariate ranking of the BWCARs by median minimum E-value (mEV) was omphalocele > diaphragmatic hernia > abdominal wall defects > gastroschisis. With inverse probability weighted multivariable panel regression, the series of BWCAs, including gastroschisis, omphalocele, and diaphragmatic hernia, was positively related to various metrics of cannabis use from p = 2.45 × 10−14, 4.77 × 10−7 and <2.2 × 10−16. With geospatial regression, the same series of BWCAs was related to cannabis metrics from p = 0.0016, 5.28 × 10−6 and 4.88 × 10−9. Seventeen out of twenty-eight (60.7%) of the E-value estimates were >9 (high range), as were 14/28 (50.0%) of the mEVs. Conclusion: The data confirm the close relationship of the BWCARs with the metrics of CCE, fulfill the quantitative criteria of causal inference, and underscore the salience of the public health impacts of cannabinoid teratogenicity. Of major concern is the rising CCE impacting exponential cannabinoid genotoxic dose-response relationships. CCE should be carefully restricted to protect the food chain, the genome, and the epigenome of coming generations.

Geotemporospatial and causal inferential epidemiological overview and survey of USA cannabis, cannabidiol and cannabinoid genotoxicity expressed in cancer incidence 2003-2017: part 2 - categorical bivariate analysis and attributable fractions

BACKGROUND

As the cannabis-cancer relationship remains an important open question epidemiological investigation is warranted to calculate key metrics including Rate Ratios (RR), Attributable Fractions in the Exposed (AFE) and Population Attributable Risks (PAR) to directly compare the implicated case burden between emerging cannabinoids and the established carcinogen tobacco.

METHODS

SEER*Stat software from Centres for Disease Control was used to access age-standardized state census incidence of 28 cancer types (including "All (non-skin) Cancer") from National Cancer Institute in US states 2001-2017. Drug exposures taken from the National Survey of Drug Use and Health 2003-2017, response rate 74.1%. Federal seizure data provided cannabinoid exposure. US Census Bureau furnished income and ethnicity. Exposure dichotomized as highest v. lowest exposure quintiles. Data processed in R.

RESULTS

Nineteen thousand eight hundred seventy-seven age-standardized cancer rates were returned. Based on these rates and state populations this equated to 51,623,922 cancer cases over an aggregated population 2003-2017 of 124,896,418,350. Fifteen cancers displayed elevated E-Values in the highest compared to the lowest quintiles of cannabidiol exposure, namely (in order): prostate, melanoma, Kaposi sarcoma, ovarian, bladder, colorectal, stomach, Hodgkins, esophagus, Non-Hodgkins lymphoma, All cancer, brain, lung, CLL and breast. Eleven cancers were elevated in the highest THC exposure quintile: melanoma, thyroid, liver, AML, ALL, pancreas, myeloma, CML, breast, oropharynx and stomach. Twelve cancers were elevated in the highest tobacco quintile confirming extant knowledge and study methodology. For cannabidiol RR declined from 1.397 (95%C.I. 1.392, 1.402), AFE declined from 28.40% (28.14, 28.66%), PAR declined from 15.3% (15.1, 15.5%) and minimum E-Values declined from 2.13. For THC RR declined from 2.166 (95%C.I. 2.153, 2.180), AFE declined from 53.8% (53.5, 54.1%); PAR declined from 36.1% (35.9, 36.4%) and minimum E-Values declined from 3.72. For tobacco, THC and cannabidiol based on AFE this implies an excess of 93,860, 91,677 and 48,510 cases; based on PAR data imply an excess of 36,450, 55,780 and 14,819 cases.

CONCLUSION

Data implicate 23/28 cancers as being linked with THC or cannabidiol exposure with epidemiologically-causal relationships comparable to those for tobacco. AFE-attributable cases for cannabinoids (91,677 and 48,510) compare with PAR-attributable cases for tobacco (36,450). Cannabinoids constitute an important multivalent community carcinogen.

Roles of the Cannabinoid System in the Basal Ganglia in Parkinson’s Disease

Parkinson’s disease (PD) is a neurodegenerative disease usually caused by neuroinflammation, oxidative stress and other etiologies. Recent studies have found that the cannabinoid system present in the basal ganglia has a strong influence on the progression of PD. Altering the cannabinoid receptor activation status by modulating endogenous cannabinoid (eCB) levels can exert an anti-movement disorder effect. Therefore, the development of drugs that modulate the endocannabinoid system may be a novel strategy for the treatment of PD. However, eCB regulation is complex, with diverse cannabinoid receptor functions and the presence of dopaminergic, glutamatergic, and γ-aminobutyric signals interacting with cannabinoid signaling in the basal ganglia region. Therefore, the study of eCB is challenging. Here, we have described the function of the cannabinoid system in the basal ganglia and its association with PD in three parts (eCBs, cannabinoid receptors, and factors regulating the cannabinoid metabolism) and summarized the mechanisms of action related to the cannabinoid analogs currently aimed at treating PD. The shortcomings identified from previous studies and the directions that should be explored in the future will provide insights into new approaches and ideas for the future development of cannabinoid-based drugs and the treatment of PD.

Brain-derived neurotrophic factor in Alzheimer's disease and its pharmaceutical potential

Synaptic abnormalities are a cardinal feature of Alzheimer's disease (AD) that are known to arise as the disease progresses. A growing body of evidence suggests that pathological alterations to neuronal circuits and synapses may provide a mechanistic link between amyloid β (Aβ) and tau pathology and thus may serve as an obligatory relay of the cognitive impairment in AD. Brain-derived neurotrophic factors (BDNFs) play an important role in maintaining synaptic plasticity in learning and memory. Considering AD as a synaptic disorder, BDNF has attracted increasing attention as a potential diagnostic biomarker and a therapeutical molecule for AD. Although depletion of BDNF has been linked with Aβ accumulation, tau phosphorylation, neuroinflammation and neuronal apoptosis, the exact mechanisms underlying the effect of impaired BDNF signaling on AD are still unknown. Here, we present an overview of how BDNF genomic structure is connected to factors that regulate BDNF signaling. We then discuss the role of BDNF in AD and the potential of BDNF-targeting therapeutics for AD.

Spontaneous Activity of CB2 Receptors Attenuates Stress-Induced Behavioral and Neuroplastic Deficits in Male Mice

The monoaminergic theory of depression/anxiety disorders cannot fully explain the behavioral and neuroplastic changes observed after ADs chronic treatment. Endocannabinoid system, which comprises CB2 receptors, has been associated with the chronic effects of these drugs, especially in stressed mice. CB2-KO mice display more vulnerability to stressful stimuli. In the present study, we hypothesized that the behavioral and neuroplastic effects observed after repeated treatment with the AD escitalopram (Esc) in chronically stressed mice depend on CB2 receptor signaling. Male mice submitted to chronic unpredictable stress (CUS) paradigm (21 days) were treated daily with AM630 (0.01; 0.03 or 0.3 mg/kg, i.p) a CB2 receptor antagonist/inverse agonist. At e 19th day of the CUS protocol, mice were submitted to Open field test and Tail-suspension test to evaluate antidepressant-like behavior. At the end of the stress protocol, mice were submitted to Novel Suppressed Feeding test (day 22nd) to evaluate anxiety-like behavior. In a second series of experiments, male mice treated with Esc (10 mg/kg, daily, 21 days) in the presence or not of AM630 (0.30 mg/kg) were submitted to the same round of behavioral tests in the same conditions as performed in the dose-response curve protocol. Animals were then euthanized under deep anesthesia, and their brains/hippocampi removed for immunohistochemistry (Doublecortin-DCX) or Western Blot assay. Our results demonstrated that chronic treatment with AM630, a CB2 antagonist/inverse agonist, induces anxiolytic-like effects in stressed mice. Moreover, chronic reduction of CB2 receptor endogenous activity by AM630 attenuated the neuroplastic (potentiating stress-induced decreased expression of pro-BDNF, but enhanced pmTOR and DAGL expression in the hippocampus reduced in stressed mice), the antidepressant- but not the anxiolytic-like effects of Esc. AM630 alone or in combination with Esc decreased the expression of DCX + cell in both the subgranular and granular layers of the dentate gyrus (DG), indicating a general reduction of DCX + neuroblasts and a decrease in their migration through the DG layers. We suggest that the antidepressant-like behavior and the pro-neurogenic effect, but not the anxiolytic like behavior, promoted by Esc in stressed mice are, at least in part, mediated by CB2 receptors.

Geotemporospatial and causal inference epidemiological analysis of US survey and overview of cannabis, cannabidiol and cannabinoid genotoxicity in relation to congenital anomalies 2001–2015

Background

Cannabinoids including cannabidiol have recognized genotoxic activities but their significance has not been studied broadly epidemiologically across the teratological spectrum. We examined these issues including contextual space-time relationships and formal causal inferential analysis in USA.

Methods

State congenital anomaly (CA) rate (CAR) data was taken from the annual reports of the National Birth Defects Prevention Network 2001–2005 to 2011–2015. Substance abuse rates were from the National Survey of Drug Use and Health a nationally representative longitudinal survey of the non-institutionalized US population with 74.1% response rate. Drugs examined were cigarettes, monthly and binge alcohol, monthly cannabis and analgesic and cocaine abuse. Early termination of pregnancy for abortion (ETOPFA) rates were taken from the published literature. Cannabinoid concentrations were from Drug Enforcement Agency. Ethnicity and income data were from the US Census Bureau. Inverse probability weighted (IPW) regressions and geotemporospatial regressions conducted for selected CAs.

Results

Data on 18,328,529 births from an aggregated population of 2,377,483,589 for mid-year analyses 2005–2013 comprehending 12,611 CARs for 62 CAs was assembled and ETOPFA-corrected (ETOPFACAR) where appropriate. E-Values for ETOPFACARs by substance trends were elevated for THC (40 CAs), cannabis (35 CAs), tobacco (11 CAs), cannabidiol (8 CAs), monthly alcohol (5 CAs) and binge alcohol (2 CAs) with minimum E-Values descending from 16.55, 1.55x107, 555.10, 7.53x1019, 9.30 and 32.98. Cardiovascular, gastrointestinal, chromosomal, limb reductions, urinary, face and body wall CAs particularly affected. Highest v. lowest substance use quintile CAR prevalence ratios 2.84 (95%C.I. 2.44, 3.31), 4.85 (4.08, 5.77) and 1.92 (1.63, 2.27) and attributable fraction in exposed 0.28 (0.27, 0.28), 0.57 (0.51, 0.62) and 0.47 (0.38, 0.55) for tobacco, cannabis and cannabidiol. Small intestinal stenosis or atresia and obstructive genitourinary defect were studied in detail in lagged IPW pseudo-randomized causal regressions and spatiotemporal models confirmed the causal role of cannabinoids. Spatiotemporal predictive modelling demonstrated strongly sigmoidal non-linear cannabidiol dose-response power-function relationships (P = 2.83x10−60 and 1.61x10−71 respectively).

Conclusions

Data implicate cannabinoids including cannabidiol in a diverse spectrum of heritable CAs. Sigmoidal non-linear dose-response relationships are of grave concern.

These transgenerational genotoxic, epigenotoxic, chromosomal-toxic putatively causal teratogenic effects strongly indicate tight restrictions on community cannabinoid penetration.

Effects of cannabis on congenital limb anomalies in 14 European nations: A geospatiotemporal and causal inferential study

Cannabinoid exposure is increasing in some European nations. Europe therefore provides an interesting test environment for the recently reported link between cannabis exposure and congenital limb anomaly (CLA) rates (CLARs). Exponential genotoxic dose-response relationships make this investigation both intriguing and imperative. Annual CLAR in 14 nations were from Epidemiological Surveillance of Congenital Anomalies. Drug use rates were from European Monitoring Centre for Drugs and Drug Dependency. Median household income was from the World Bank. E-values provide a quantitative measure of robustness of results to confounding by extraneous covariates. Inverse probability weighting is an important technique for equalizing exposures across countries and removing sources of bias. Rates of CLA, hip dysplasia and the whole group of limb anomalies were higher in countries with increasing daily cannabis use (P = 1.81 × 10^-16, 0.0005 and 2.53 × 10^-6, respectively). In additive inverse-probability-weighted panel models, the limb reduction-resin Δ9-tetrahydrocannabinol (THC) concentration E-value estimate was 519.93 [95% lower bound (mEV) 49.56], order Resin > Herb ≫ Tobacco > Alcohol. Elevations were noted in 86% E-value estimates and 70.2% of mEVs from 57 E-value pairs from inverse-probability-weighted panel models and from spatial models. As judged by the mEV the degree of association with metrics of cannabis exposure was hip dysplasia > polydactyly > syndactyly > limb anomalies > limb reductions with median E-value estimates from 3.40 × 10⁶⁵ to 7.06 and median mEVs from 6.14 × 10³³ to 3.41. Daily cannabis use interpolated was a more powerful metric of cannabis exposure than herb or resin THC exposure. Data indicate that metrics of cannabis exposure are closely linked with CLAR and satisfy epidemiological criteria for causality. Along with Hawaii and the USA, Europe now forms the third international population in which this causal link has been demonstrated. Cannabis as a predictor of limb anomalies was more potent than tobacco or alcohol. Cannabinoid access should be restricted to protect public health and the community genome/epigenome transgenerationally.

Cannabinoid and substance relationships of European congenital anomaly patterns: a space-time panel regression and causal inferential study

With reports from Australia, Canada, USA, Hawaii and Colorado documenting a link between cannabis and congenital anomalies (CAs), this relationship was investigated in Europe. Data on 90 CAs were accessed from Eurocat. Tobacco and alcohol consumption and median household income data were from the World Bank. Amphetamine, cocaine and last month and daily use of cannabis from the European Monitoring Centre for Drugs and Drug Addiction. Cannabis herb and resin Δ9-tetrahydrocannabinol concentrations were from published reports. Data were processed in R. Twelve thousand three hundred sixty CA rates were sourced across 16 nations of Europe. Nations with a higher or increasing rate of daily cannabis use had a 71.77% higher median CA rates than others [median ± interquartile range 2.13 (0.59, 6.30) v. 1.24 (0.15, 5.14)/10 000 live births (P = 4.74 × 10^-17; minimum E-value (mEV) = 1.52]. Eighty-nine out of 90 CAs in bivariate association and 74/90 CAs in additive panel inverse probability weighted space-time regression were cannabis related. In inverse probability weighted interactive panel models lagged to zero, two, four and six years, 76, 31, 50 and 29 CAs had elevated mEVs (< 2.46 × 10³⁹) for cannabis metrics. Cardiovascular, central nervous, gastrointestinal, genital, uronephrology, limb, face and chromosomalgenetic systems along with the multisystem VACTERL syndrome were particularly vulnerable targets. Data reveal that cannabis is related to many CAs and fulfil epidemiological criteria of causality. The triple convergence of rising cannabis use prevalence, intensity of daily use and Δ9-tetrahydrocannabinol concentration in herb and resin is powerfully implicated as a primary driver of European teratogenicity, confirming results from elsewhere.

Orexin-A and endocannabinoids are involved in obesity-associated alteration of hippocampal neurogenesis, plasticity, and episodic memory in mice

The mammalian brain stores and distinguishes among episodic memories, i.e. memories formed during the personal experience, through a mechanism of pattern separation computed in the hippocampal dentate gyrus. Decision-making for food-related behaviors, such as the choice and intake of food, might be affected in obese subjects by alterations in the retrieval of episodic memories. Adult neurogenesis in the dentate gyrus regulates the pattern separation. Several molecular factors affect adult neurogenesis and exert a critical role in the development and plasticity of newborn neurons. Orexin-A/hypocretin-1 and downstream endocannabinoid 2-arachidonoylglycerol signaling are altered in obese mice. Here, we show that excessive orexin-A/2-arachidonoylglycerol/cannabinoid receptor type-1 signaling leads to the dysfunction of adult hippocampal neurogenesis and the subsequent inhibition of plasticity and impairment of pattern separation. By inhibiting orexin-A action at orexin-1 receptors we rescued both plasticity and pattern separation impairment in obese mice, thus providing a molecular and functional mechanism to explain alterations in episodic memory in obesity.

The authors show that adult hippocampal neurogenesis is altered in the dentate gyrus of obese mice with subsequent inhibition of long-term potentiation and impairment of pattern separation. Inhibition of orexin-A action at orexin-1 receptors rescued both impairments in obese mice.

Anti-LINGO-1 antibody ameliorates cognitive impairment, promotes adult hippocampal neurogenesis, and increases the abundance of CB1R-rich CCK-GABAergic interneurons in AD mice

In view of the negative regulatory effect of leucine-rich repeat and immunoglobulin-like domain-containing nogo receptor-interacting protein 1 (LINGO-1) on neurons, an antibody against LINGO-1 (anti-LINGO-1 antibody) was herein administered to 10-month-old APP/PS1 transgenic Alzheimer's disease (AD) mice for 2 months as an experimental intervention. Behavioral, stereology, immunohistochemistry and immunofluorescence analyses revealed that the anti-LINGO-1 antibody significantly improved the cognitive abilities, promoted adult hippocampal neurogenesis (AHN), decreased the amyloid beta (Aβ) deposition, enlarged the hippocampal volume, and increased the numbers of total neurons and GABAergic interneurons, including GABAergic and CCK-GABAergic interneurons rich in cannabinoid type 1 receptor (CB1R), in the hippocampus of AD mice. In contrast, this intervention significantly reduced the number of GABAergic interneurons expressing LINGO-1 and CB1R in the hippocampus of AD mice. More importantly, we also found a negative correlation between LINGO-1 and CB1R on GABAergic interneurons in the hippocampus of AD mice, while the anti-LINGO-1 antibody reversed this relationship. These results indicated that LINGO-1 plays an important role in the process of hippocampal neuron loss in AD mice and that antagonizing LINGO-1 can effectively prevent hippocampal neuron loss and promote AHN. The improvement in cognitive abilities may be attributed to the improvement in AHN, and in the numbers of GABAergic interneurons and CCK-GABAergic interneurons rich in CB1Rs in the hippocampus of AD mice induced by the anti-LINGO-1 antibody. Collectively, the double target effect (LINGO-1 and CB1R) initiated by the anti-LINGO-1 antibody may provide an important basis for the study of drugs for the prevention and treatment of AD in the future.

Chronic Inhibition of FAAH Reduces Depressive-Like Behavior and Improves Dentate Gyrus Proliferation after Chronic Unpredictable Stress Exposure

Symptoms of depressive disorders such as anhedonia and despair can be a product of an aberrant adaptation to stress conditions. Chronic unpredictable stress model (CUS) can generate an increase in the activity of the hypothalamic-pituitary-adrenal axis (HPA) and induce a reduction of neurotrophin signaling and the proliferation of neural progenitors in the adult dentate gyrus, together with increased oxidative stress. Levels of the endocannabinoid anandamide (AEA) seem to affect these depression-by-stress-related features and could be modulated by fatty acid amide hydrolase (FAAH). We aimed to evaluate the effects of FAAH inhibitor, URB597, on depressive-like behavior and neural proliferation of mice subjected to a model of CUS. URB597 was administered intraperitoneally at a dose of 0.2 mg/kg for 14 days after CUS. Depressive-like behaviors, anhedonia, and despair were evaluated in the splash and forced swimming tests, respectively. Alterations at the HPA axis level were analyzed using the relative weight of adrenal glands and serum corticosterone levels. Oxidative stress and brain-derived neurotrophic factor (BDNF) were also evaluated. Fluorescence immunohistochemistry tests were performed for the immunoreactivity of BrdU and Sox2 colabeling for comparison of neural precursors. The administration of URB597 was able to reverse the depressive-like behavior generated in mice after the model. Likewise, other physiological responses associated with CUS were reduced in the treated group, among them, increase in the relative weight of the adrenal glands, increased oxidative stress, and decreased BDNF and number of neural precursors. Most of these auspicious responses to enzyme inhibitor administration were blocked by employing a cannabinoid receptor antagonist. In conclusion, the chronic inhibition of FAAH generated an antidepressant effect, promoting neural progenitor proliferation and BDNF expression, while reducing adrenal gland weight and oxidative stress in mice under the CUS model.

Effect of gut microbiota on depressive-like behaviors in mice is mediated by the endocannabinoid system

Depression is the leading cause of disability worldwide. Recent observations have revealed an association between mood disorders and alterations of the intestinal microbiota. Here, using unpredictable chronic mild stress (UCMS) as a mouse model of depression, we show that UCMS mice display phenotypic alterations, which could be transferred from UCMS donors to naïve recipient mice by fecal microbiota transplantation. The cellular and behavioral alterations observed in recipient mice were accompanied by a decrease in the endocannabinoid (eCB) signaling due to lower peripheral levels of fatty acid precursors of eCB ligands. The adverse effects of UCMS-transferred microbiota were alleviated by selectively enhancing the central eCB or by complementation with a strain of the Lactobacilli genus. Our findings provide a mechanistic scenario for how chronic stress, diet and gut microbiota generate a pathological feed-forward loop that contributes to despair behavior via the central eCB system.

The Pro-neurogenic Effects of Cannabidiol and Its Potential Therapeutic Implications in Psychiatric Disorders

During the last decades, researchers have investigated the functional relevance of adult hippocampal neurogenesis in normal brain function as well as in the pathogenesis of diverse psychiatric conditions. Although the underlying mechanisms of newborn neuron differentiation and circuit integration have yet to be fully elucidated, considerable evidence suggests that the endocannabinoid system plays a pivotal role throughout the processes of adult neurogenesis. Thus, synthetic, and natural cannabinoid compounds targeting the endocannabinoid system have been utilized to modulate the proliferation and survival of neural progenitor cells and immature neurons. Cannabidiol (CBD), a constituent of the Cannabis Sativa plant, interacts with the endocannabinoid system by inhibiting fatty acid amide hydrolase (FAAH) activity (the rate-limiting enzyme for anandamide hydrolysis), allosterically modulating CB1 and CB2 receptors, and activating components of the "extended endocannabinoid system." Congruently, CBD has shown prominent pro-neurogenic effects, and, unlike Δ9-tetrahydrocannabinol, it has the advantage of being devoid of psychotomimetic effects. Here, we first review pre-clinical studies supporting the facilitating effects of CBD on adult hippocampal neurogenesis and available data disclosing cannabinoid mechanisms by which CBD can induce neural proliferation and differentiation. We then review the respective implications for its neuroprotective, anxiolytic, anti-depressant, and anti-reward actions. In conclusion, accumulating evidence reveals that, in rodents, adult neurogenesis is key to understand the behavioral manifestation of symptomatology related to different mental disorders. Hence, understanding how CBD promotes adult neurogenesis in rodents could shed light upon translational therapeutic strategies aimed to ameliorate psychiatric symptomatology dependent on hippocampal function in humans.

The therapeutic role of cannabinoid receptors and its agonists or antagonists in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease and its characteristic is the progressive degeneration of dopaminergic neurons within the substantia nigra (SN) of the midbrain. There is hardly any clinically proven efficient therapeutics for its cure in several recent preclinical advances proposed to treat PD. Recent studies have found that the endocannabinoid signaling system in particular the comprised two receptors, CB1 and CB2 receptors, has a significant regulatory function in basal ganglia and is involved in the pathogenesis of PD. Therefore, adding new insights into the biochemical interactions between cannabinoids and other signaling pathways may help develop new pharmacological strategies. Factors of the endocannabinoid system (ECS) are abundantly expressed in the neural circuits of basal ganglia, where they interact interactively with glutamatergic, γ-aminobutyric acid-ergic (GABAergic), and dopaminergic signaling systems. Although preclinical studies on PD are promising, the use of cannabinoids at the clinical level has not been thoroughly studied. In this review, we evaluated the available evidence and reviewed the involvement of ECS in etiologies, symptoms and treatments related to PD. Since CB1 and CB2 receptors are the two main receptors of endocannabinoids, we primarily put the focus on the therapeutic role of CB1 and CB2 receptors in PD. We will try to determine future research clues that will help understand the potential therapeutic benefits of the ECS in the treatment of PD, aiming to open up new strategies and ideas for the treatment of PD.

The Acute Activation of the CB1 Receptor in the Hippocampus Decreases Neurotoxicity and Prevents Spatial Memory Impairment in Rats Lesioned with β-Amyloid 25-35

Given their anti-inflammatory properties, cannabinoids have been shown to be neuroprotective agents and to reduce excitotoxicity, through the activation of the Cannabinoid receptor type 1 (CB1r). These properties have led to CB1r being proposed as pharmacological targets for the treatment of various neurodegenerative diseases. Amyloid-β 25-35 (Aβ_25-35) induces the expression of inducible nitric oxide synthase (iNOS) and increases nitric oxide (NO●) levels. It has been observed that increased NO● concentrations trigger biochemical pathways that contribute to neuronal death and cognitive damage. This study aimed to evaluate the neuroprotective effect of an acute activation of CB1r on spatial memory and its impact on iNOS protein expression, NO● levels, gliosis and the neurodegenerative process induced by the injection of Aβ_(25-35) into the CA1 subfield of the hippocampus. ACEA [1 μM/1 μL] and Aβ_(25-35) [100 μM/1 μL] and their respective vehicle groups were injected into the CA1 subfield of the hippocampus. The animals were tested for spatial learning and memory in the eight-arm radial maze, with the results revealing that the administration of ACEA plus Aβ_(25-35) improves learning and memory processes, in contrast with the Aβ_(25-35) group. Moreover, ACEA plus Aβ_(25-35) prevented both the increase in iNOS protein and NO● levels and the reactive gliosis induced by Aβ_(25-35). Importantly, neurodegeneration was significantly reduced by the administration of ACEA plus Aβ_(25-35) in the CA1 subfield of the hippocampus. The data obtained in the present research suggest that the acute early activation of CB1r is crucial for neuroprotection.

Cannabinoid Actions on Neural Stem Cells: Implications for Pathophysiology

With the increase of life expectancy, neurodegenerative disorders are becoming not only a health but also a social burden worldwide. However, due to the multitude of pathophysiological disease states, current treatments fail to meet the desired outcomes. Therefore, there is a need for new therapeutic strategies focusing on more integrated, personalized and effective approaches. The prospect of using neural stem cells (NSC) as regenerative therapies is very promising, however several issues still need to be addressed. In particular, the potential actions of pharmacological agents used to modulate NSC activity are highly relevant. With the ongoing discussion of cannabinoid usage for medical purposes and reports drawing attention to the effects of cannabinoids on NSC regulation, there is an enormous, and yet, uncovered potential for cannabinoids as treatment options for several neurological disorders, specifically when combined with stem cell therapy. In this manuscript, we review in detail how cannabinoids act as potent regulators of NSC biology and their potential to modulate several neurogenic features in the context of pathophysiology.

Psychopharmacology of chronic pain

Chronic pain is a frequent condition that affects an estimated 20% of people worldwide, accounting for 15%-20% of doctors' appointments (Treede et al., 2015). It lacks the acute warning function of physiologic nociception, and instead involves the activation of multiple neurophysiologic mechanisms in the somatosensory system, a complex neuronal network under the control of powerful autoregulatory loops and able to undergo rapid neuroplastic alteration (Verdu et al., 2008). There is a growing body of research suggesting that some such pathways are shared by major psychologic disorders such as depression and anxiety, opening new avenues in co-treatment strategies. In particular, besides anticonvulsants, which are today used as analgesics, other psychopharmaceuticals, such as the tricyclic antidepressants, are displaying efficacy in the treatment of neuropathic and nociceptive chronic pain. The state of the art regarding the mechanisms of nociception and the pharmacology of both the neurotransmitters involved and the wide range of psychoactive compounds that may be useful in the treatment of chronic pain are discussed.

Brain-Derived Neurotrophic Factor (BDNF) Role in Cannabinoid-Mediated Neurogenesis

The adult mammalian brain can produce new neurons in a process called adult neurogenesis, which occurs mainly in the subventricular zone (SVZ) and in the hippocampal dentate gyrus (DG). Brain-derived neurotrophic factor (BDNF) signaling and cannabinoid type 1 and 2 receptors (CB1R and CB2R) have been shown to independently modulate neurogenesis, but how they may interact is unknown. We now used SVZ and DG neurosphere cultures from early (P1-3) postnatal rats to study the CB1R and CB2R crosstalk with BDNF in modulating neurogenesis. BDNF promoted an increase in SVZ and DG stemness and cell proliferation, an effect blocked by a CB2R selective antagonist. CB2R selective activation promoted an increase in DG multipotency, which was inhibited by the presence of a BDNF scavenger. CB1R activation induced an increase in SVZ and DG cell proliferation, being both effects dependent on BDNF. Furthermore, SVZ and DG neuronal differentiation was facilitated by CB1R and/or CB2R activation and this effect was blocked by sequestering endogenous BDNF. Conversely, BDNF promoted neuronal differentiation, an effect abrogated in SVZ cells by CB1R or CB2R blockade while in DG cells was inhibited by CB2R blockade. We conclude that endogenous BDNF is crucial for the cannabinoid-mediated effects on SVZ and DG neurogenesis. On the other hand, cannabinoid receptor signaling is also determinant for BDNF actions upon neurogenesis. These findings provide support for an interaction between BDNF and endocannabinoid signaling to control neurogenesis at distinct levels, further contributing to highlight novel mechanisms in the emerging field of brain repair.

Long-Term Stress and Concomitant Marijuana Smoke Exposure Affect Physiology, Behavior and Adult Hippocampal Neurogenesis

Marijuana is a widely used recreational drug with increasing legalization worldwide for medical purposes. Most experimental studies use either synthetic or plant-derived cannabinoids to investigate the effect of cannabinoids on anxiety and cognitive functions. The aim of this study was to mimic real life situations where young people smoke cannabis regularly to relax from everyday stress. Therefore, we exposed young adult male NMRI mice to daily stress and concomitant marijuana smoke for 2 months and investigated the consequences on physiology, behavior and adult hippocampal neurogenesis. Animals were restrained for 6-h/day for 5-days a week. During the stress, mice were exposed to cannabis smoke for 2 × 30 min/day. We burned 2 “joints” (2 × 0.8 g marijuana) per occasion in a whole body smoking chamber. Cannabinoid content of the smoke and urine samples was measured by HPLC and SFC-MS/MS. Body weight gain was recorded daily and we did unrestrained, whole body plethysmography to investigate pulmonary functions. The cognitive performance of the animals was evaluated by the novel object recognition and Y maze tests. Anxietyrelated spontaneous locomotor activity and self-grooming were assessed in the open field test (OFT). Adult neurogenesis was quantified post mortem in the hippocampal dentate gyrus. The proliferative activity of the precursor cells was detected by the use of the exogenous marker 5-bromo-20-deoxyuridine. Treatment effects on maturing neurons were studied by the examination of doublecortin-positive neurons. Both stress and cannabis exposure significantly reduced body weight gain. Cannabis smoke had no effect on pulmonary functions, but stress delayed the maturation of several lung functions. Neither stress, nor cannabis smoke affected the cognitive functioning of the animals. Results of the OFT revealed that cannabis had a mild anxiolytic effect and markedly increased self-grooming behavior. Stress blocked cell proliferation in the dentate gyrus, but cannabis had no effect on this parameter. Marijuana smoke however had a pronounced impact on doublecortin-positive neurons influencing their number, morphology and migration. In summary, we report here that long-term stress in combination with cannabis smoke exposure can alter several health-related measures, but the present experimental design could not reveal any interaction between these two treatment factors except for body weight gain.

Adult Cellular Neuroadaptations Induced by Adolescent THC Exposure in Female Rats Are Rescued by Enhancing Anandamide Signaling

BACKGROUND

In rodent models, chronic exposure to cannabis' psychoactive ingredient, Δ9-tetrahydrocannabinol, during adolescence leads to abnormal behavior in adulthood. In female rats, this maladaptive behavior is characterized by endophenotypes for depressive-like and psychotic-like disorders as well as cognitive deficits. We recently reported that most depressive-like behaviors triggered by adolescent Δ9-tetrahydrocannabinol exposure can be rescued by manipulating endocannabinoid signaling in adulthood with the anandamide-inactivating enzyme FAAH inhibitor, URB597. However, the molecular mechanisms underlying URB597's antidepressant-like properties remain to be established.

METHODS

Here we examined the impact of adult URB597 treatment on the cellular and functional neuroadaptations that occurred in the prefrontal cortex and dentate gyrus of the hippocampus upon Δ9-tetrahydrocannabinol during adolescence through biochemical, morphofunctional, and electrophysiological studies.

RESULTS

We found that the positive action of URB597 is associated with the rescue of Δ9-tetrahydrocannabinol-induced deficits in endocannabinoid-mediated signaling and synaptic plasticity in the prefrontal cortex and the recovery of functional neurogenesis in the dentate gyrus of the hippocampus. Moreover, the rescue property of URB597 on depressive-like behavior requires the activity of the CB1 cannabinoid receptor.

CONCLUSIONS

By providing novel insights into the cellular and molecular mechanisms of URB597 at defined cortical and hippocampal circuits, our results highlight that positive modulation of endocannabinoid-signaling could be a strategy for treating mood alterations secondary to adolescent cannabis use.

Opposing Effects of CREBBP Mutations Govern the Phenotype of Rubinstein-Taybi Syndrome and Adult SHH Medulloblastoma

Recurrent mutations in chromatin modifiers are specifically prevalent in adolescent or adult patients with Sonic hedgehog-associated medulloblastoma (SHH MB). Here, we report that mutations in the acetyltransferase CREBBP have opposing effects during the development of the cerebellum, the primary site of origin of SHH MB. Our data reveal that loss of Crebbp in cerebellar granule neuron progenitors (GNPs) during embryonic development of mice compromises GNP development, in part by downregulation of brain-derived neurotrophic factor (Bdnf). Interestingly, concomitant cerebellar hypoplasia was also observed in patients with Rubinstein-Taybi syndrome, a congenital disorder caused by germline mutations of CREBBP. By contrast, loss of Crebbp in GNPs during postnatal development synergizes with oncogenic activation of SHH signaling to drive MB growth, thereby explaining the enrichment of somatic CREBBP mutations in SHH MB of adult patients. Together, our data provide insights into time-sensitive consequences of CREBBP mutations and corresponding associations with human diseases.

Cannabinoid Modulation of the Stressed Hippocampus

Exposure to stressful situations is one of the risk factors for the precipitation of several psychiatric disorders, including Major Depressive Disorder, Posttraumatic Stress Disorder and Schizophrenia. The hippocampal formation is a forebrain structure highly associated with emotional, learning and memory processes; being particularly vulnerable to stress. Exposure to stressful stimuli leads to neuroplastic changes and imbalance between inhibitory/excitatory networks. These changes have been associated with an impaired hippocampal function. Endocannabinoids (eCB) are one of the main systems controlling both excitatory and inhibitory neurotransmission, as well as neuroplasticity within the hippocampus. Cannabinoids receptors are highly expressed in the hippocampus, and several lines of evidence suggest that facilitation of cannabinoid signaling within this brain region prevents stress-induced behavioral changes. Also, chronic stress modulates hippocampal CB₁ receptors expression and endocannabinoid levels. Moreover, cannabinoids participate in mechanisms related to synaptic plasticity and adult neurogenesis. Here, we discussed the main findings supporting the involvement of hippocampal cannabinoid neurotransmission in stress-induced behavioral and neuroplastic changes.

Fatty acid amide hydrolase inhibitor URB597 may protect against kainic acid-induced damage to hippocampal neurons: Dependence on the degree of injury

OBJECTIVE

Status epilepticus (SE) provokes changes, which lead to neuronal alterations. Endocannabinoids (eCBs) can affect the neuronal survival during excitotoxicity and brain damage. Using a kainic acid (KA)-induced experimental SE model, we investigated whether cellular changes entail damage to endoplasmic reticulum (ER), mitochondria, and nuclei in hippocampal cells (CA1 field), and whether these alterations can be diminished by treatment with URB597, an inhibitor of eCB enzymatic degradation.

MATERIAL AND METHODS

SE was induced in Wistar rats by the microinjection of KA into the lateral ventricle. URB597 or a vehicle (10% DMSO) were injected in the same way into the brain of animals 24h after the KA infusion and then daily for the next nine days. The behavior of animals was controlled visually and recorded with a video system. The intensity of SE significantly varied in different animals. Convulsive (stages 3-5 according to the Racine scale) and nonconvulsive seizures (mainly stages 1, 2 and rarely 3, 4) were recognized.

RESULTS

Two weeks after SE, a significant loss of hippocampal cells occurred in animals with KA injections. In survived cells, ultrastructural alterations in ER, mitochondria, and nuclei of hippocampal neurons were observed. The degree of cell injury depended on the severity of SE. Alterations evoked by moderate seizures were prevented or diminished by URB597, but strong seizures induced mostly irreversible damage.

CONCLUSIONS

The beneficial impact of the FAAH inhibitor URB597 can give impetus to the development of novel neuroprotective strategies.

Interaction between Cannabinoid Type 1 and Type 2 Receptors in the Modulation of Subventricular Zone and Dentate Gyrus Neurogenesis

Neurogenesis in the adult mammalian brain occurs mainly in two neurogenic niches, the subventricular zone (SVZ) and the subgranular zone (SGZ) of the dentate gyrus (DG). Cannabinoid type 1 and 2 receptors (CB₁R and CB₂R) have been shown to differently modulate neurogenesis. However, low attention has been given to the interaction between CB₁R and CB₂R in modulating postnatal neurogenesis (proliferation, neuronal differentiation and maturation). We focused on a putative crosstalk between CB₁R and CB₂R to modulate neurogenesis and cultured SVZ and DG stem/progenitor cells from early postnatal (P1-3) Sprague-Dawley rats. Data showed that the non-selective cannabinoid receptor agonist WIN55,212-2 promotes DG cell proliferation (measured by BrdU staining), an effect blocked by either CB₁R or CB₂R selective antagonists. Experiments with selective agonists showed that facilitation of DG cell proliferation requires co-activation of both CB₁R and CB₂R. Cell proliferation in the SVZ was not affected by the non-selective receptor agonist, but it was enhanced by CB₁R selective activation. However, either CB₁R or CB₂R selective antagonists abolished the effect of the CB₁R agonist in SVZ cell proliferation. Neuronal differentiation (measured by immunocytochemistry against neuronal markers of different stages and calcium imaging) was facilitated by WIN55,212-2 at both SVZ and DG. This effect was mimicked by either CB₁R or CB₂R selective agonists and blocked by either CB₁R or CB₂R selective antagonists, cross-antagonism being evident. In summary, our findings indicate a tight interaction between CB₁R and CB₂R to modulate neurogenesis in the two major neurogenic niches, thus contributing to further unraveling the mechanisms behind the action of endocannabinoids in the brain.

BDNF-induced endocannabinoid release modulates neocortical glutamatergic neurotransmission

Endocannabinoids (eCBs) and neurotrophins, particularly brain-derived neurotrophic factor (BDNF), are potent neuromodulators found throughout the mammalian neocortex. Both eCBs and BDNF play critical roles in many behavioral and neurophysiological processes and are targets for the development of novel therapeutics. The effects of eCBs and BDNF are primarily mediated by the type 1 cannabinoid (CB1) receptor and the trkB tyrosine kinase receptor, respectively. Our laboratory and others have previously established that BDNF potentiates excitatory transmission by enhancing presynaptic glutamate release and modulating NMDA receptors. In contrast, we have shown that BDNF attenuates inhibitory transmission by inducing postsynaptic release of eCBs that act retrogradely to suppress GABA release in layer 2/3 of somatosensory cortex. Here, we hypothesized that BDNF also induces release of eCBs at excitatory synapses, which could have a mitigating or opposing effect on the direct presynaptic effects of BDNF. We found the highest levels of expression of CB1 and trkB and receptors in layers 2/3 and 5. Surprisingly, BDNF did not increase the frequency of spontaneous miniature excitatory postsynaptic currents (mEPSCs) onto layer 5 pyramidal neurons in somatosensory cortex, in contrast to its effects in the hippocampus and visual cortex. However, the effect of BDNF on mEPSC frequency in somatosensory cortex was unmasked by blocking CB1 receptors or disrupting eCB release. Thus, BDNF-trKB signaling regulates glutamate release in the somatosensory cortex via opposing effects, a direct presynaptic enhancement of release probability, and simultaneous postsynaptically-induced eCB release that decreases release probability via presynaptic CB1 receptors.

Neurogenic Traditional Chinese Medicine as a Promising Strategy for the Treatment of Alzheimer's Disease

Hippocampal neurogenesis plays a critical role in the formation of new neurons during learning and memory development. Attenuation of neurogenesis in the brain is one of the primary causes of dementia in Alzheimer’s disease (AD), and, conversely, modulating the process of hippocampal neurogenesis benefit patients with AD. Traditional Chinese medicine (TCM), particularly herbal medicine, has been in use for thousands of years in Asia and many regions of the world for the treatment of cancer, cardiovascular diseases and neurodegenerative diseases. In this review, we summarize the role of neurotrophic factors, signal transducing factors, epigenetic modulators and neurotransmitters in neurogenesis, and we also discuss the functions of several Chinese herbs and their active molecules in activating multiple pathways involved in neurogenesis. TCM herbs target pathways such as Notch, Wnt, Sonic Hedgehog and receptor tyrosine kinase pathway, leading to activation of a signaling cascade that ultimately enhances the transcription of several important genes necessary for neurogenesis. Given these pathway activating effects, the use of TCM herbs could be an effective therapeutic strategy for the treatment of AD.

Cannabis, Cannabinoids, and Cerebral Metabolism: Potential Applications in Stroke and Disorders of the Central Nervous System

No compound has generated more attention in both the scientific and recently in the political arena as much as cannabinoids. These diverse groups of compounds referred collectively as cannabinoids have both been vilified due to its dramatic and potentially harmful psychotropic effects and glorified due to its equally dramatic and potential application in a number of acute and chronic neurological conditions. Previously illegal to possess, cannabis, the plant where natural form of cannabinoids are derived, is now accepted in a growing number of states for medicinal purpose, and some even for recreational use, increasing opportunities for more scientific experimentation. The purpose of this review is to summarize the growing body of literature on cannabinoids and to present an overview of our current state of knowledge of the human endocannabinoid system in the hope of defining the future of cannabinoids and its potential applications in disorders of the central nervous system, focusing on stroke.

Expression of the Endocannabinoid Receptor 1 in Human Stroke: An Autoptic Study

OBJECTIVE

Stroke is one of the leading causes of disability and death in the world. The endocannabinoid (eCB) system is upregulated in several neurological diseases including stroke. A previous animal study demonstrated an increased expression of the endocannabinoid receptor 1 (CB1R) in the penumbra area surrounding the ischemic core, suggesting a crucial role in inflammation/reperfusion after stroke. Regarding the localization of CB1/CB2 receptors, animal studies showed that cortical neurons, activated microglia, and astroglia are involved. Our aim was to evaluate the cerebral expression of CB1R in the ischemic brain areas of 9 patients who died due to acute cerebral infarction in the middle cerebral artery territory.

METHODS

The cerebral autoptic tissue was collected within 48 hours since death. Ischemic and contralateral normal-appearing areas were identified. After tissue preprocessing, 4-µm-thick cerebral sections were incubated with the primary CB1R antibodies (Cayman Chemical Company, Ann Arbor, MI). Thereafter, all cerebral sections were hematoxylin treated. In each section, the total cell number and CB1R-positive cells were counted and the CB1R-positive cell count ratio was calculated. For statistical analysis, Student's t-test was used.

RESULTS

In normal tissue, CB1R-positive neurons were the majority; a few non-neuronal cells expressed CB1R. In the ischemic areas, a few neurons were detectable. A significant increase in total CB1R staining was found in the ischemic regions compared to contralateral areas.

CONCLUSIONS

We found an increase in CB1R expression in the ischemic region (neuronal and non-neuronal cell staining), suggesting the inflammatory reaction to the ischemic insult. Whether such response might mediate neuroprotective actions or excitotoxicity-related detrimental effects is still unclear.

Dissecting the Signaling Pathways Involved in the Crosstalk between Metabotropic Glutamate 5 and Cannabinoid Type 1 Receptors

The metabotropic glutamate 5 receptor and the cannabinoid type 1 receptor are G protein-coupled receptors that are widely expressed in the central nervous system. Metabotropic glutamate 5 receptors, present at the postsynaptic site, are coupled to Gα_q/11 proteins and display an excitatory response upon activation, whereas the cannabinoid type 1 receptor, mainly present at presynaptic terminals, is coupled to the G_i/o protein and triggers an inhibitory response. Recent studies suggest that the glutamatergic and endocannabinoid systems exhibit a functional interaction to modulate several neural processes. In this review, we discuss possible mechanisms involved in this crosstalk and its relationship with physiologic and pathologic conditions, including nociception, addiction, and fragile X syndrome.

Anandamide drives cell cycle progression through CB1 receptors in a rat model of synchronized liver regeneration

The endocannabinoid system, through cannabinoid receptor signaling by endocannabinoids, is involved in a wide range of functions and physiopathological conditions. To date, very little is known concerning the role of the endocannabinoids in the control and regulation of cell proliferation. An anti-proliferative action of CB1 signaling blockade in neurogenesis and angiogenesis argues in favor of proliferation-promoting functions of endocannabinoids through CB1 receptors when pro-growth signals are present. Furthermore, liver regeneration, a useful in vivo model of synchronized cell proliferation, is characterized by a peak of anandamide that elicits through CB1 receptor, the expression of critical mitosis genes. The aim of this study was to focus on the timing of endocannabinoid signaling changes during the different phases of the cell cycle, exploiting the rat liver regeneration model following partial hepatectomy, the most useful to study synchronized cell cycle in vivo. Hepatic regeneration led to increased levels of anandamide and endocannabinoid-like molecules oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) in the G1 phase of the cell cycle, with a concomitant increase in CB1 mRNA levels, whose protein expression peaked later during the S phase. Blocking of CB1 receptor with a low dose of the selective antagonist/inverse agonist SR141716 (0.7 mg/kg/dose) affected cell cycle progression reducing the expression of PCNA, and through the inhibition of pERK and pSTAT3 pathways. These results support the notion that the signaling mediated by anandamide through CB1 receptor may be important for the entry and progression of cells into the cell cycle and hence for their proliferation under mitogenic signals.

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.

Impaired neurogenesis by HIV-1-Gp120 is rescued by genetic deletion of fatty acid amide hydrolase enzyme

Background and Purpose

The HIV-envelope glycoprotein Gp120 is involved in neuronal injury and is associated with neuro-AIDS pathogenesis in the brain. Endocannabinoids are important lipid ligands in the CNS regulating neural functions, and their degeneration is controlled by hydrolysing enzymes such as the fatty acid amide hydrolase (FAAH). Here, we examined whether in vivo genetic deletion of Faah gene prevents HIV-1 Gp120-mediated effects on neurogenesis.

Experimental Approach

We generated new GFAP/Gp120 transgenic (Tg) mice that have genetic deletion of Faah gene by mating glial fribillary acidic protein (GFAP)/Gp120 Tg mice with Faah−/− mice. Neurogenesis and cell death were assessed by immunocytochemical analysis.

Key Results

Endocannabinoid levels in the brain of the double GFAP/Gp120//Faah−/− mice were similar to those observed in Faah−/− mice. However, unlike the impaired neurogenesis observed in GFAP/Gp120 Tg mice and Faah−/− mice, these GFAP/Gp120//Faah-/ mice showed significantly improved neurogenesis in the hippocampus, indicated by a significant increase in neuroblasts and neuronal cells, an increase in BrdU⁺ cells and doublecortin positive cells (DCX⁺), and an increase in the number of PCNA. Furthermore, a significant decrease in astrogliosis and gliogenesis was observed in GFAP/Gp120//Faah−/−mice and neurogenesis was stimulated by neural progenitor cells (NPCs) and/or the newly formed NPC niches characterized by increased COX-2 expression and elevated levels of PGE₂.

Conclusions and Implications

In vivo genetic ablation of Faah, resulted in enhanced neurogenesis through modulation of the newly generated NPC niches in GFAP/Gp120//Faah−/− mice. This suggests a novel approach of using FAAH inhibitors to enhance neurogenesis in HIV-1 infected brain.

The role of cannabinoids in adult neurogenesis

The processes underpinning post-developmental neurogenesis in the mammalian brain continue to be defined. Such processes involve the proliferation of neural stem cells and neural progenitor cells (NPCs), neuronal migration, differentiation and integration into a network of functional synapses within the brain. Both intrinsic (cell signalling cascades) and extrinsic (neurotrophins, neurotransmitters, cytokines, hormones) signalling molecules are intimately associated with adult neurogenesis and largely dictate the proliferative activity and differentiation capacity of neural cells. Cannabinoids are a unique class of chemical compounds incorporating plant-derived cannabinoids (the active components of Cannabis sativa), the endogenous cannabinoids and synthetic cannabinoid ligands, and these compounds are becoming increasingly recognized for their roles in neural developmental processes. Indeed, cannabinoids have clear modulatory roles in adult neurogenesis, probably through activation of both CB1 and CB2 receptors. In recent years, a large body of literature has deciphered the signalling networks involved in cannabinoid-mediated regulation of neurogenesis. This timely review summarizes the evidence that the cannabinoid system is intricately associated with neuronal differentiation and maturation of NPCs and highlights intrinsic/extrinsic signalling mechanisms that are cannabinoid targets. Overall, these findings identify the central role of the cannabinoid system in adult neurogenesis in the hippocampus and the lateral ventricles and hence provide insight into the processes underlying post-developmental neurogenesis in the mammalian brain.