Cannflavin A inhibits TLR4-induced chemokine and cytokine expression in human macrophages

Cannflavin A (CFL-A), a flavonoid present in the hemp plant Cannabis sativa L. (C. sativa), has anti-inflammatory and neuroprotective capacity. Research continues to elucidate the anti-inflammatory effects of components of C. sativa, with evidence that plant-derived cannabinoids and terpenes can mediate anti-inflammatory activity by targeting toll-like receptor (TLR) signalling, the sensors of pathogen-associated molecules. This study set out to determine if TLR-mediated inflammatory signalling is a CFL-A target using the endotoxin lipopolysaccharide (LPS) to induce TLR4 signalling in human THP-1-derived macrophages. TLR4 activation promoted the production of the chemokine CXCL10 and cytokines IL-1β and TNFα. Treatment with CFL-A dose-dependently attenuated TLR4-induced CXCL10 and IL-1β secretion, with our findings also indicating that the inhibitory effects of CFL-A on chemokine/cytokine secretion are in line with an NF-κB inhibitor. This study highlights TLR4 signalling as a cannflavin target in macrophages.

Toll-like receptor signalling as a cannabinoid target

Toll-like receptors (TLRs) have become a focus in biomedicine and biomedical research given the roles of this unique family of innate immune proteins in immune activation, infection, and autoimmunity. It is evident that TLR dysregulation, and subsequent alterations in TLR-mediated inflammatory signalling, can contribute to disease pathogenesis, and TLR targeted therapies are in development. This review highlights evidence that cannabinoids are key regulators of TLR signalling. Cannabinoids include component of the plant Cannabis sativa L. (C. sativa), synthetic and endogenous ligands, and overall represent a class of compounds whose therapeutic potential and mechanism of action continues to be elucidated. Cannabinoid-based medicines are in the clinic, and are furthermore under intense investigation for broad clinical development to manage symptoms of a range of disorders. In this review, we present an overview of research evidence that signalling linked to a range of TLRs is targeted by cannabinoids, and such cannabinoid mediated effects represent therapeutic avenues for further investigation. First, we provide an overview of TLRs, adaptors and key signalling events, alongside a summary of evidence that TLRs are linked to disease pathologies. Next, we discuss the cannabinoids system and the development of cannabinoid-based therapeutics. Finally, for the bulk of this review, we systematically outline the evidence that cannabinoids (plant-derived cannabinoids, synthetic cannabinoids, and endogenous cannabinoid ligands) can cross-talk with innate immune signalling governed by TLRs, focusing specifically on each member of the TLR family. Cannabinoids should be considered as key regulators of signalling controlled by TLRs, and such regulation should be a major focus in terms of the anti-inflammatory propensity of the cannabinoid system.

Animated teaching improves student learning of human gastrulation and neurulation

Human embryology is a complex topic that brings together core components of anatomy and physiology to describe the developmental process from fertilisation to birth. Embryonic development is a challenging topic of study that is core to the curricula for health science students. There are challenges ingrained in teaching and learning embryology, due to the three-dimensional dynamic processes that occur as the embryo develops. This study aimed to develop and assess two newly developed animations depicting key processes in embryology, namely gastrulation and neurulation, as supplemental learning aids for students. Indeed, animated teaching tools to enhance the learning of gastrulation and neurulation are not widely available. A multi-disciplinary team of physiologists, biochemists, anatomists, and a computer scientist developed the animation sets. A student cohort of 81 first-year health science students were enrolled in this study over a period of three academic years. Both animations are in line with the course content of the first-year health science students undertaking the Human Health and Disease BSc at Trinity College Dublin, who were the study participants. Participants were randomly assigned to a non-animation control group and an animation group. Each set of animated teaching aids was broken down into individual clips which were given identifiable headings to allow the user to interchange between clips to facilitate a more personal learning experience. The animation group had open access to the animations for a three-week period. Questionnaires were designed to assess participants' attitude to the animations and their knowledge of embryology, both at the start of the study and three weeks later following access to the animations. Data presented herein indicate that students incorporated the animated teaching aids into digital home study and that the use of the animations acted as a supplemental tool that increased student knowledge in key areas of human embryology. From a qualitative point of view, students described the animations as enjoyable and helpful in visualising complex processes. This study indicates that the development of gastrulation and neurulation animated learning tools allow for a more engaging learning experience, facilitating student's engagement with academically challenging concepts in human embryology.

Botanically-Derived Δ9-Tetrahydrocannabinol and Cannabidiol, and Their 1:1 Combination, Modulate Toll-like Receptor 3 and 4 Signalling in Immune Cells from People with Multiple Sclerosis

The innate immune response to bacterial and viral molecules involves the coordinated production of cytokines, chemokines, and type I interferons (IFNs), which is orchestrated by toll-like receptors (TLRs). TLRs, and their intracellular signalling intermediates, are closely associated with multiple sclerosis (MS) pathogenesis. Recent data from our laboratory reported that the plant-derived cannabinoids, Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD), regulate viral and bacterial inflammatory signalling pathways controlled by TLR3 and TLR4 in macrophages. The aim of this study was to assess the impact of THC and CBD, when delivered in isolation and in combination (1:1), on TLR3- and TLR4-dependent signalling in peripheral blood mononuclear cells (PBMCs) from people with MS (pwMS; n = 21) and healthy controls (HCs; n = 26). We employed the use of poly(I:C) and lipopolysaccharide (LPS) to induce viral TLR3 and bacterial TLR4 signalling, and PBMCs were pre-exposed to plant-derived highly purified THC (10 μM), CBD (10 μM), or a combination of both phytocannabinoids (1:1 ratio, 10:10 μM), prior to LPS/poly(I:C) exposure. TLR3 stimulation promoted the protein expression of the chemokine CXCL10 and the type I IFN-β in PBMCs from both cohorts. THC and CBD (delivered in 1:1 combination at 10 μM) attenuated TLR3-induced CXCL10 and IFN-β protein expression in PBMCs from pwMS and HCs, and this effect was not seen consistently when THC and CBD were delivered alone. In terms of LPS, TLR4 activation promoted TNF-α expression in PBMCs from both cohorts, and, interestingly, CBD when delivered alone at 10 μM, and in combination with THC (in 1:1 combination at 10 μM), exacerbated TLR4-induced TNF-α protein expression in PBMCs from pwMS and HCs. THC and CBD displayed no evidence of toxicity in primary PBMCs. No significant alteration in the relative expression of TLR3 and TLR4 mRNA, or components of the endocannabinoid system, including the cannabinoid receptor CB₁ (encoded by CNR1 gene) and CB₂ (encoded by CNR2 gene), and endocannabinoid metabolising enzymes, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGLL), was determined in PBMCs from pwMS versus HCs. Given their role in inflammation, TLRs are clinical targets, and data herein identify CBD and THC as TLR3 and TLR4 modulating drugs in primary immune cells in vitro. This offers insight on the cellular target(s) of phytocannabinoids in targeting inflammation in the context of MS.

Phytocannabinoid-dependent mTORC1 regulation is dependent upon inositol polyphosphate multikinase activity

BACKGROUND AND PURPOSE

Cannabidiol (CBD) has been shown to differentially regulate the mechanistic target of rapamycin complex 1 (mTORC1) in preclinical models of disease, where it reduces activity in models of epilepsies and cancer and increases it in models of multiple sclerosis (MS) and psychosis. Here, we investigate the effects of phytocannabinoids on mTORC1 and define a molecular mechanism.

EXPERIMENTAL APPROACH

A novel mechanism for phytocannabinoids was identified using the tractable model system, Dictyostelium discoideum. Using mouse embryonic fibroblasts, we further validate this new mechanism of action. We demonstrate clinical relevance using cells derived from healthy individuals and from people with MS (pwMS).

KEY RESULTS

Both CBD and the more abundant cannabigerol (CBG) enhance mTORC1 activity in D. discoideum. We identify a mechanism for this effect involving inositol polyphosphate multikinase (IPMK), where elevated IPMK expression reverses the response to phytocannabinoids, decreasing mTORC1 activity upon treatment, providing new insight on phytocannabinoids' actions. We further validated this mechanism using mouse embryonic fibroblasts. Clinical relevance of this effect was shown in primary human peripheral blood mononuclear cells, where CBD and CBG treatment increased mTORC1 activity in cells derived from healthy individuals and decreased mTORC1 activity in cells derived from pwMS.

CONCLUSION AND IMPLICATIONS

Our findings suggest that both CBD and the abundant CBG differentially regulate mTORC1 signalling through a mechanism dependent on the activity of the upstream IPMK signalling pathway, with potential relevance to the treatment of mTOR-related disorders, including MS.

MyD88-dependent and -independent signalling via TLR3 and TLR4 are differentially modulated by Δ9-tetrahydrocannabinol and cannabidiol in human macrophages

Toll-like receptors (TLRs) are sensors of pathogen-associated molecules that trigger inflammatory signalling in innate immune cells including macrophages. All TLRs, with the exception of TLR3, promote intracellular signalling via recruitment of the myeloid differentiation factor 88 (MyD88) adaptor, while TLR3 signals via Toll-Interleukin-1 Receptor (TIR)-domain-containing adaptor-inducing interferon (IFN)-β (TRIF) adaptor to induce MyD88-independent signalling. Furthermore, TLR4 can activate both MyD88-dependent and -independent signalling (via TRIF). The study aim was to decipher the impact of the highly purified plant-derived (phyto) cannabinoids Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD), when delivered in isolation and in combination (1:1), on MyD88-dependent and -independent signalling in macrophages. We employed the use of the viral dsRNA mimetic poly(I:C) and endotoxin lipopolysaccharide (LPS), to induce viral TLR3 and bacterial TLR4 signalling in human Tamm-Horsfall protein-1 (THP-1)-derived macrophages, respectively. TLR3/TLR4 stimulation promoted the activation of interferon (IFN) regulatory factor 3 (IRF3) and TLR4 promoted the activation of nuclear factor (NF)-κB signalling, with downstream production of the type I IFN-β, the chemokines CXCL10 and CXCL8, and cytokine TNF-α. THC and CBD (both at 10 μM) attenuated TLR3/4-induced IRF3 activation and induction of CXCL10/IFN-β, while both phytocannabinoids failed to impact TLR4-induced IκB-α degradation and TNF-α/CXCL8 expression. The role of CB₁, CB₂ and PPARγ receptors in mediating the effect of THC and CBD on MyD88-independent signalling was investigated. TLRs are attractive therapeutic targets given their role in inflammation and initiation of adaptive immunity, and data herein indicate that both CBD and THC preferentially modulate TLR3 and TLR4 signalling via MyD88-independent mechanisms in macrophages. This offers mechanistic insight into the role of phytocannabinoids in modulating cellular inflammation.

Anti-inflammatory Potential of Terpenes Present in Cannabis sativa L

Cannabis sativa L. (C. sativa) contains an array of plant-derived (phyto) cannabinoids and terpenes that are predominantly located in the trichome cavity of the plant. Terpenes, aromatic organic hydrocarbons characterized for their role in plant protection/pollination, are gaining attention for their potential as novel therapeutics in many areas of biomedicine. This Viewpoint will explore the exciting recent evidence that terpenes have anti-inflammatory/antioxidant propensity by targeting inflammatory signaling mechanisms relevant to human disease. Given their anti-inflammatory properties, terpenes may contribute to the effects of current cannabinoid-based therapies.

Development and Assessment of a Three-Dimensional Tooth Morphology Quiz for Dental Students

Tooth morphology has a pivotal role in the dental curriculum and provides one of the important foundations of clinical practice. To supplement tooth morphology teaching a three-dimensional (3D) quiz application (app) was developed. The 3D resource enables students to study tooth morphology actively by selecting teeth from an interactive quiz, modify their viewpoint and level of zoom. Additionally, students are able to rotate the tooth to obtain a 3D spatial understanding of the different surfaces of the tooth. A cross-over study was designed to allow comparison of students' results after studying with the new application or traditionally with extracted/model teeth. Data show that the app provides an efficient learning tool and that students' scores improve with usage (18% increase over three weeks, P < 0.001). Data also show that student assessment scores were correlated with scores obtained while using the app but were not influenced by the teaching modality initially accessed (r²  = 0.175, P < 0.01). Comparison of the 2016 and 2017 class performance shows that the class that had access to the app performed significantly better on their final tooth morphology assessment (68.0% ±15.0 vs. 75.3% ±13.4, P < 0.01). Furthermore, students reported that the 3D application was intuitive, provided useful feedback, presented the key features of the teeth, and assisted in learning tooth morphology. The 3D tooth morphology app thus provides students with a useful adjunct teaching tool for learning dental anatomy. Anat Sci Educ 00: 000-000. © 2018 American Association of Anatomists.

A Survey of tooth morphology teaching methods employed in the United Kingdom and Ireland

BACKGROUND

Tooth morphology is a central component of the dental curriculum and is applicable to all dental specialities. Traditional teaching methods are being supplemented with innovative strategies to tailor teaching and accommodate the learning styles of the recent generation of students.

METHODS

An online survey was compiled and distributed to the staff involved in teaching tooth morphology in the United Kingdom and Ireland to assess the importance of tooth morphology in the dentistry curriculum and the methodologies employed in teaching.

RESULTS

The results of the survey show that tooth morphology constitutes a small module in the dental curriculum. It is taught in the first 2 years of the dental curriculum but is applicable in the clinical years and throughout the dental career. Traditional teaching methods, lecture and practical, are being augmented with innovative teaching including e-learning via virtual learning environment, tooth atlas and e-books leading to blended learning. The majority of the schools teach both normal dental anatomy and morphologic variations of dental anatomy and utilise plastic teeth for practical and examination purposes. Learning the 3D aspects of tooth morphology was deemed important by most of the respondents who also agreed that tooth morphology is a difficult topic for the students.

CONCLUSION

Despite being core to the dental curriculum, overall minimal time is dedicated to the delivery of tooth morphology, creating a reliance on the student to learn the material. New forms of delivery including computer-assisted learning tools should help sustain learning and previously acquired knowledge.

Evaluation of an animation tool developed to supplement dental student study of the cranial nerves

INTRODUCTION

The structure/function of the cranial nerves is a core topic for dental students. However, due to the perceived complexity of the subject, it is often difficult for students to develop a comprehensive understanding of key concepts using textbooks and models. It is accepted that the acquisition of anatomical knowledge can be facilitated by visualisation of structures. This study aimed to develop and assess a novel cranial nerve animation as a supplemental learning aid for dental students.

MATERIALS AND METHODS

A multidisciplinary team of anatomists, neuroscientists and a computer scientist developed a novel animation depicting the cranial nerves. The animation was viewed by newly enrolled first-year dental students, graduate entry dental students (year 1) and dental hygiene students (year 1). A simple life scenario employing the use of the cranial nerves was developed using a cartoon-type animation with a viewing time of 3.58 minutes. The animation was developed with emphasis on a life scenario. The animation was placed online for 2 weeks with open access or viewed once in a controlled laboratory setting. Questionnaires were designed to assess the participants' attitude towards the animation and their knowledge of the cranial nerves before and after visualisation. This study was performed before the delivery of core lectures on the cranial nerves.

RESULTS

Our findings indicate that the use of the animation can act as a supplemental tool to improve student knowledge of the cranial nerves. Indeed, data indicate that a single viewing of the animation, in addition to 2-week access to the animation, can act as a supplemental learning tool to assist student understanding of the structure and function of cranial nerves. The animation significantly enhanced the student's opinion that their cranial nerve knowledge had improved. From a qualitative point of view, the students described the animation as an enjoyable and useful supplement to reading material/lectures and indicated that the animation was a useful tool in understanding the cranial nerves.

CONCLUSION

Overall, these findings indicate that an animation demonstrating the cranial nerves in a simple, everyday functional scenario may act as a learning aid in the study of cranial nerves.

Impact of short-term cycle ergometer training on quality of life, cognition and depressive symptomatology in multiple sclerosis patients: a pilot study

In this pilot study, we investigate whether a routine cycle ergometry training programme has therapeutic potential in individuals with multiple sclerosis (MS) by improving quality of life (QOL) and depressive symptomatology, while ameliorating cognitive disturbances. Healthy volunteers and MS patients cycled for 30 min at 65-75% age-predicted maximal heart rate on a recumbent ergometer, with this session repeated twice a week for 8 weeks. QOL, depressive symptomatology and cognitive function were assessed pre- and post-exercise using the MS Quality of Life-54 (MSQOL-54) questionnaire, 16-item Quick Inventory of Depressive Symptomatology (QIDS-SR₁₆) questionnaire and the Cambridge Neuropsychological Test Automated Battery (CANTAB), respectively. We determined that QOL was lower in MS patients, compared to healthy subjects, with a reduction in physical and mental health summary scores observed. Exercise improved both physical and mental health scores in MS patients. In support of this, exercise was shown to reduce depressive symptomatology in MS patients. Exercise was also associated with an improvement in visual sustained attention, executive function/cognitive flexibility and hippocampal-dependent visuospatial memory in patients. Overall, this study identifies a short-term exercise programme that improves physical and mental health, while reducing depressive symptomatology and cognitive dysfunction in MS.

Assessment of Thiel-Embalmed Cadavers as a Teaching Tool for Oral Anatomy and Local Anesthesia

The aim of this study was to determine whether Thiel-embalmed cadavers would provide a useful anatomy teaching tool for topics that cannot be approached using formalin-fixed cadavers such as oral cavity examination and maxillary anesthesia. The suitability of Thiel-embalmed bodies for performing oral examinations was assessed by asking first-year dental and dental hygiene students at a dental school in Ireland to identify oral structures on a classmate and on a Thiel-embalmed body. The study was conducted in 2016. The ease of location was compared in the two settings, and their quality was assessed on the cadavers. The suitability of Thiel-embalmed cadavers to teach maxillary anesthesia was assessed by students' performing mock injections at five adjacent sites daily for five consecutive days, followed by inspection of the gingival surface by experienced anatomists and dentists. Data were obtained from 57 students, but only the 54 forms that were fully completed were analyzed, for an overall response rate of 85.7%. The results showed that most oral structures were more difficult to locate on cadavers. The texture and appearance of features in the cadavers were rated at a midpoint between realistic and unrealistic. The relative inexperience of the participants, the accumulation of fixative in the oral cavity, and discoloration were mentioned as potential confounding factors. Visual analysis of images obtained following repeated injections revealed no deterioration of the tissue. Importantly, the puncture marks appeared to reduce over time, suggesting that the gingival tissue maintains some elasticity following Thiel fixation. These findings suggest that Thiel-embalmed cadavers may be a useful tool to provide students more time to localize and study aspects of the oral cavity. Likewise, the recoiling capacity of gingival tissue suggests that Thiel-embalmed cadavers may provide an ideal tool for teaching injection technique of local anesthetics.

Impact of Exercise on Innate Immunity in Multiple Sclerosis Progression and Symptomatology

Multiple Sclerosis (MS), an idiopathic progressive immune-mediated neurological disorder of the central nervous system (CNS), is characterized by recurrent episodes of inflammatory demyelination and consequent axonal deterioration. It accounts for functional deterioration and lasting disability among young adults. A body of literature demonstrates that physical activity counteracts fatigue and depression and may improve overall quality of life in MS patients. Furthermore, much data indicates that exercise ameliorates chronic neuroinflammation and its related pathologies by tipping cytokine profiles toward an anti-inflammatory signature. Recent data has focused on the direct impact of exercise training on the innate immune system by targeting toll-like receptors (TLRs), signaling pattern recognition receptors that govern the innate immune response, shedding light on the physiological role of TLRs in health and disease. Indeed, TLRs continue to emerge as players in the neuroinflammatory processes underpinning MS. This review will highlight evidence that physical activity and exercise are potential immunomodulatory therapies, targeting innate signaling mechanism(s) to modulate MS symptom development and progression.

Inhibiting neuroinflammation: The role and therapeutic potential of GABA in neuro-immune interactions

The central nervous system, once thought to be a site of immunological privilege, has since been found to harbour immunocompetent cells and to communicate with the peripheral nervous system. In the central nervous system (CNS), glial cells display immunological responses to pathological and physiological stimuli through pro- and anti-inflammatory cytokine and chemokine signalling, antigen presentation and the clearing of cellular debris through phagocytosis. While this neuroinflammatory signalling can act to reduce neuronal damage and comprises a key facet of CNS homeostasis, persistent inflammation or auto-antigen-mediated immunoreactivity can induce a positive feedback cycle of neuroinflammation that ultimately results in necrosis of glia and neurons. Persistent neuroinflammation has been recognised as a major pathological component of virtually all neurodegenerative diseases and has also been a focus of research into the pathology underlying psychiatric disorders. Thus, pharmacological strategies to curb the pathological effects of persistent neuroinflammation are of interest for many disorders of the CNS. Accumulating evidence suggests that GABAergic activities are closely bound to immune processes and signals, and thus the GABAergic neurotransmitter system might represent an important therapeutic target in modulating neuroinflammation. Here, we review evidence that inflammation induces changes in the GABA neurotransmitter system in the CNS and that GABAergic signalling exerts a reciprocal influence over neuroinflammatory processes. Together, the data support the hypothesis that the GABA system is a potential therapeutic target in the modulation of central inflammation.

Toll-like receptor signalling as a cannabinoid target in Multiple Sclerosis

Toll-like receptors (TLRs) are the sensors of pathogen-associated molecules that trigger tailored innate immune intracellular signalling responses to initiate innate immune reactions. Data from the experimental autoimmune encephalomyelitis (EAE) model indicates that TLR signalling machinery is a pivotal player in the development of murine EAE. To compound this, data from human studies indicate that complex interplay exists between TLR signalling and Multiple Sclerosis (MS) pathogenesis. Cannabis-based therapies are in clinical development for the management of a variety of medical conditions, including MS. In particular Sativex^®, a combination of plant-derived cannabinoids, is an oromucosal spray with efficacy in MS patients, particularly those with neuropathic pain and spasticity. Despite this, the precise cellular and molecular mechanisms of action of Sativex^® in MS patients remains unclear. This review will highlight evidence that novel interplay exists between the TLR and cannabinoid systems, both centrally and peripherally, with relevance to the pathogenesis of MS. This article is part of the Special Issue entitled 'Lipid Sensing G Protein-Coupled Receptors in the CNS'.

Delineating the Role of Toll-Like Receptors in the Neuro-inflammation Model EAE

Experimental autoimmune encephalomyelitis (EAE) is the most relevant and commonly used animal model to study autoimmune demyelinating diseases like Multiple Sclerosis (MS). In EAE, the activation of CD4+ T-cells is considered to be the main trigger leading to inflammation and central nervous system (CNS) demyelination. Toll-like receptors (TLRs) are the most important and first class of pattern recognition receptors (PRRs) in innate immune system and play critical roles in initiating inflammatory responses and promoting adaptive immune responses due to their ability to recognize a wide range of pathogen associated molecular patterns (PAMPs) and being expressed in a wide range of cell types both in the innate and adaptive immune systems. Upon TLR stimulation by appropriate ligand, innate immune cells produce pro-inflammatory cytokines and can serve as antigen-presenting cells (APCs) to prime naïve T cells to recognize antigens. Thus, TLRs play an important role in linking the innate to the adaptive immune response. To date, large numbers of studies have been done to investigate the role of adaptive immunity in both EAE and MS but delineating the role of innate immunity in EAE received very little focus and appreciation taking into account that it might contribute to both the initiation and progression of the disease. Moreover, EAE is not only a model to study inflammatory demyelination in the CNS; it is in general a model to study cell-mediated organ-specific autoimmune conditions. Roles of different TLRs were studied in relation to EAE and MS. More recently, some studies demonstrated the immune adjuvant properties of certain TLR ligands including TLR2, TLR4, and TLR9 in EAE. This chapter outlines different methods employed in our labs to investigate the role of TLRs in EAE model.

Modulation of TLR3/TLR4 inflammatory signaling by the GABAB receptor agonist baclofen in glia and immune cells: relevance to therapeutic effects in multiple sclerosis

The GABAB receptor agonist, baclofen, is used to treat muscle tightness and cramping caused by spasticity in a number of disorders including multiple sclerosis (MS), but its precise mechanism of action is unknown. Neuroinflammation drives the central pathology in MS and is mediated by both immunoreactive glial cells and invading lymphocytes. Furthermore, a body of data indicates that the Toll-like receptor (TLR) family of innate immune receptors is implicated in MS progression. In the present study we investigated whether modulation of GABAB receptors using baclofen can exert anti-inflammatory effects by targeting TLR3 and(or) TLR4-induced inflammatory signaling in murine glial cells and human peripheral blood mononuclear cells (PBMCs) isolated from healthy control individuals and patients with the relapse-remitting (RR) form of MS. TLR3 and TLR4 stimulation promoted the nuclear sequestration of NF-κB and pro-inflammatory cytokine expression in murine glia, while TLR4, but not TLR3, promoted pro-inflammatory cytokine expression in PBMCs isolated from both healthy donors and RR-MS patients. Importantly, this effect was exacerbated in RR-MS patient immune cells. We present further evidence that baclofen dose-dependently attenuated TLR3- and TLR4-induced inflammatory signaling in primary glial cells. Pre-exposure of PBMCs isolated from healthy donors to baclofen attenuated TLR4-induced TNF-α expression, but did not affect TLR4-induced TNF-α expression in RR-MS patient PBMCs. Interestingly, mRNA expression of the GABAB receptor was reduced in PBMCs from RR-MS donors when compared to healthy controls, an effect that might contribute to the differential sensitivity to baclofen seen in healthy and RR-MS patient cells. Overall these findings indicate that baclofen differentially regulates TLR3 and TLR4 signaling in glia and immune cells, and offers insight on the role of baclofen in the treatment of neuroinflammatory disease states including MS.

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.

High hopes for CB(2) receptors in neurogenesis

During life, new neurons are continually added to hippocampal circuitry, with evidence suggesting that these adult-born neurons are functionally linked to cognition and emotion. The mammalian brain contains actively dividing neural stem cells in discrete regions, including the subventricular zone of the lateral ventricles and the subgranular zone of the dentate gyrus. Once mature, these neurons integrate into neuronal networks, forming synaptic connections with interneurons, mossy cells and CA3 pyramidal cells

LINKED ARTICLE

This article is a commentary on Avraham et al., pp. 468-479 of volume 171 issue 2. To view this paper visit http://dx.doi.org/10.1111/bph.12478.

Neuropathic orofacial pain: cannabinoids as a therapeutic avenue

Neuropathic orofacial pain (NOP) exists in several forms including pathologies such as burning mouth syndrome (BMS), persistent idiopathic facial pain (PIFP), trigeminal neuralgia (TN) and postherpetic neuralgia (PHN). BMS and PIFP are classically diagnosed by excluding other facial pain syndromes. TN and PHN are most often diagnosed based on a typical history and presenting pain characteristics. The pathophysiology of some of these conditions is still unclear and hence treatment options tend to vary and include a wide variety of treatments including cognitive behaviour therapy, anti-depressants, anti-convulsants and opioids; however such treatments often have limited efficacy with a great amount of inter-patient variability and poorly tolerated side effects. Analgesia is one the principal therapeutic targets of the cannabinoid system and many studies have demonstrated the efficacy of cannabinoid compounds in the treatment of neuropathic pain. This review will investigate the potential use of cannabinoids in the treatment of symptoms associated with NOP.

Mitogen-Activated Protein Kinase Phosphatase (MKP)-1 in Nervous System Development and Disease

Mitogen-activated protein kinase phosphatase (MKP)-1 provides a negative feedback mechanism for regulating mitogen-activated protein kinase (MAPK) activity and thus a variety of cellular processes such as proliferation, differentiation, growth and apoptosis. MKP-1 is established as a central regulator of a variety of functions in the immune, metabolic and cardiovascular systems, and it is now increasingly acknowledged as having a role to play in the nervous system. It has been implicated in regulating processes of neuronal cell development and death as well as in glial cell function. Reduced MKP-1 levels have been observed in models of neurological conditions including Huntington's disease, multiple sclerosis, ischemia and cerebral hypoxia. It has also been suggested to have a role to play in psychiatric disorders such as major depressive disorder. Here, we discuss the role of MKP-1 in nervous system development and disease and examine current evidence providing insight into MKP-1 as a potential therapeutic target for various diseases of the central nervous system.

Identifying early inflammatory changes in monocyte-derived macrophages from a population with IQ-discrepant episodic memory

Background

Cells of the innate immune system including monocytes and macrophages are the first line of defence against infections and are critical regulators of the inflammatory response. These cells express toll-like receptors (TLRs), innate immune receptors which govern tailored inflammatory gene expression patterns. Monocytes, which produce pro-inflammatory mediators, are readily recruited to the central nervous system (CNS) in neurodegenerative diseases.

Methods

This study explored the expression of receptors (CD11b, TLR2 and TLR4) on circulating monocyte-derived macrophages (MDMs) and peripheral blood mononuclear cells (PBMCs) isolated from healthy elderly adults who we classified as either IQ memory-consistent (high-performing, HP) or IQ memory-discrepant (low-performing, LP).

Results

The expression of CD11b, TLR4 and TLR2 was increased in MDMs from the LP group when compared to HP cohort. MDMs from both groups responded robustly to treatment with the TLR4 activator, lipopolysaccharide (LPS), in terms of cytokine production. Significantly, MDMs from the LP group displayed hypersensitivity to LPS exposure.

Interpretation

Overall these findings define differential receptor expression and cytokine profiles that occur in MDMs derived from a cohort of IQ memory-discrepant individuals. These changes are indicative of inflammation and may be involved in the prodromal processes leading to the development of neurodegenerative disease.

The synthetic cannabinoid R(+)WIN55,212-2 augments interferon-β expression via peroxisome proliferator-activated receptor-α

We have demonstrated that R(+)WIN55,212-2, a synthetic cannabinoid that possesses cannabimimetic properties, acts as a novel regulator of Toll-like receptor 3 (TLR3) signaling to interferon (IFN) regulatory factor 3 (IRF3) activation and IFN-β expression, and this is critical for manifesting its protective effects in a murine multiple sclerosis model. Here we investigated the role of peroxisome proliferator-activated receptor-α (PPARα) in mediating the effects of R(+)WIN55,212-2 on this pathway. Data herein demonstrate that the TLR3 agonist poly(I:C) promotes IFN-β expression and R(+)WIN55,212-2 enhances TLR3-induced IFN-β expression in a stereoselective manner via PPARα. R(+)WIN55,212-2 promotes increased transactivation and expression of PPARα. Using the PPARα antagonist GW6471, we demonstrate that R(+)WIN55,212-2 acts via PPARα to activate JNK, activator protein-1, and positive regulatory domain IV to transcriptionally regulate the IFN-β promoter. Furthermore, GW6471 ameliorated the protective effects of R(+)WIN55,212-2 during the initial phase of experimental autoimmune encephalomyelitis. Overall, these findings define PPARα as an important mediator in manifesting the effects of R(+)WIN55,212-2 on the signaling cascade regulating IFN-β expression. The study adds to our molecular appreciation of potential therapeutic effects of R(+)WIN55,212-2 in multiple sclerosis.

Dok2 mediates the CD200Fc attenuation of Aβ-induced changes in glia

Background

The interaction between the membrane glycoprotein, CD200 and its cognate receptor CD200 receptor (CD200R), has been shown to play a role in maintaining microglia in a quiescent state. There is evidence of increased activation under resting and stimulated conditions in microglia prepared from CD200-deficient mice compared with wild-type mice, whereas activation of the receptor by CD200 fusion protein (CD200Fc) ameliorates inflammatory changes which are evident in the central nervous system (CNS) of the mouse model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE) and also in the hippocampus of aged rats. Additionally, an inverse relationship between microglial activation and expression of CD200 has been observed in animals treated with lipopolysaccharide (LPS) or amyloid-β (Aβ).

Methods

We assessed the effect of CD200R activation by CD200Fc on Aβ-induced production of the pro-inflammatory cytokines, interleukin-1β (IL-1β) and tumor necrosis factor-α (TNFα) and the expression of microglial activation markers, CD68 and CD40 in cultured glia. The role played by downstream of tyrosine kinase 2 (Dok2) phosphorylation in mediating the effects of CD200R activation was evaluated by siRNA knockdown of Dok2. To further examine the impact of inflammatory changes on synaptic plasticity, the effect of CD200Fc on Aβ-induced impairment of long-term potentiation (LTP) in the CA1 region of hippocampal slices was also investigated.

Results

We demonstrate that Aβ-induced increases in IL-1β, TNFα, CD68 and CD40 were inhibited by CD200Fc. The evidence suggests that Dok2 phosphorylation is a key factor in mediating the effect of CD200Fc, since Dok2 knockdown by siRNA abrogated its effects on microglial activation and inflammatory cytokine production. Consistent with evidence that inflammatory changes negatively impact on LTP, we show that the Aβ-induced impairment of LTP was attenuated by CD200Fc.

Conclusions

The findings suggest that activation of CD200R and Dok2 is a valuable strategy for modulating microglial activation and may have therapeutic potential in neurodegenerative conditions.

Cannabinoids and innate immunity: taking a toll on neuroinflammation

The biologically active components of cannabis have therapeutic potential in neuroinflammatory disorders due to their anti-inflammatory propensity. Cannabinoids influence immune function in both the peripheral and the central nervous system (CNS), and the components of the cannabinoid system, the cannabinoid receptors and their endogenous ligands (endocannabinoids), have been detected on immune cells as well as in brain glia. Neuroinflammation is the complex innate immune response of neural tissue to control infection and eliminate pathogens, and Toll-like receptors (TLRs), a major family of pattern recognition receptors (PRRs) that mediate innate immunity, have emerged as players in the neuroinflammatory processes underpinning various CNS diseases. This review will highlight evidence that cannabinoids interact with the immune system by impacting TLR-mediated signaling events, which may provide cues for devising novel therapeutic approaches for cannabinoid ligands.

Identification of the synthetic cannabinoid R(+)WIN55,212-2 as a novel regulator of IFN regulatory factor 3 activation and IFN-beta expression: relevance to therapeutic effects in models of multiple sclerosis

β-Interferons (IFN-βs) represent one of the first line treatments for relapsing-remitting multiple sclerosis, slowing disease progression while reducing the frequency of relapses. Despite this, more effective, well tolerated therapeutic strategies are needed. Cannabinoids palliate experimental autoimmune encephalomyelitis (EAE) symptoms and have therapeutic potential in MS patients although the precise molecular mechanism for these effects is not understood. Toll-like receptor (TLR) signaling controls innate immune responses and TLRs are implicated in MS. Here we demonstrate that the synthetic cannabinoid R(+)WIN55,212-2 is a novel regulator of TLR3 and TLR4 signaling by inhibiting the pro-inflammatory signaling axis triggered by TLR3 and TLR4, whereas selectively augmenting TLR3-induced activation of IFN regulatory factor 3 (IRF3) and expression of IFN-β. We present evidence that R(+)WIN55,212-2 strongly promotes the nuclear localization of IRF3. The potentiation of IFN-β expression by R(+)WIN55,212-2 is critical for manifesting its protective effects in the murine MS model EAE as evidenced by its reduced therapeutic efficacy in the presence of an anti-IFN-β antibody. R(+)WIN55,212-2 also induces IFN-β expression in MS patient peripheral blood mononuclear cells, whereas down-regulating inflammatory signaling in these cells. These findings identify R(+)WIN55,212-2 as a novel regulator of TLR3 signaling to IRF3 activation and IFN-β expression and highlights a new mechanism that may be open to exploitation in the development of new therapeutics for the treatment of MS.

Phytocannabinoids, CNS cells and development: a dead issue?

ISSUES

Marijuana and hashish consist of at least 66 distinctive plant-derived (phyto-) cannabinoid compounds, with tetrahydrocannabinoids proving the most effective phytocannabinoid psychotropically. Despite the known pharmacological effects of phytocannabinoids, their role in controlling the cell survival/death decision in cells of the CNS continues to be unravelled.

APPROACH

In this review, we examine the influence of phytocannabinoids on neural cell fate, with particular emphasis on how the time of marijuana exposure (neonatal vs. pubertal vs. adult) might influence the neurotoxic activities of phytocannabinoid compounds.

KEY FINDINGS

Evidence in the literature indicates that exposure to phytocannabinoids during the prenatal period, in addition to the adolescent period, can alter the temporally ordered sequence of events that occur during neurotransmitter development, in addition to negatively impacting neural cell survival and maturation. Regarding the effect of marijuana consumption on brain composition in adults the evidence is contradictory.

IMPLICATIONS

Exposure to marijuana during pregnancy might impact negatively on brain structure in the first years of postnatal life. Furthermore, early-onset (before age 17) marijuana use might also have damaging effects on brain composition.

CONCLUSION

The neonatal and immature CNS is more susceptible to phytocannabinoid damage. In the adult CNS the data are conflicting and the continued development of methods to assess whether marijuana consumption results in brain atrophy or morphometric changes will determine if structural changes are occurring.

Decreased neuronal CD200 expression in IL-4-deficient mice results in increased neuroinflammation in response to lipopolysaccharide

Maintenance of the balance between pro- and anti-inflammatory cytokines in the brain, which is affected by the activation state of microglia, is important for maintenance of neuronal function. Evidence has suggested that IL-4 plays an important neuromodulatory role and has the ability to decrease lipopolysaccharide-induced microglial activation and the production of IL-1beta. We have also demonstrated that CD200-CD200R interaction is involved in immune homeostasis in the brain. Here, we investigated the anti-inflammatory role of IL-4 and, using in vitro and in vivo analysis, established that the effect of lipopolysaccharide was more profound in IL-4(-/-), compared with wildtype, mice. Intraperitoneal injection of lipopolysaccharide exerted a greater inhibitory effect on exploratory behaviour in IL-4(-/-), compared with wildtype, mice and this was associated with evidence of microglial activation. We demonstrate that the increase in microglial activation is inversely related to CD200 expression. Furthermore, CD200 was decreased in neurons prepared from IL-4(-/-) mice, whereas stimulation with IL-4 enhanced CD200 expression. Importantly, neurons prepared from wildtype, but not from IL-4(-/-), mice attenuated the lipopolysaccharide-induced increase in pro-inflammatory cytokine production by glia. These findings suggest that the neuromodulatory effect of IL-4, and in particular its capacity to maintain microglia in a quiescent state, may result from its ability to upregulate CD200 expression on neurons.

Fractalkine-induced activation of the phosphatidylinositol-3 kinase pathway attentuates microglial activation in vivo and in vitro

Several neurodegenerative disorders are associated with evidence of inflammation, one feature of which is increased activation of microglia, the most likely cellular source of inflammatory cytokines like interleukin-1beta. It is now recognized that interaction of microglia with other cells contributes to maintenance of microglia in a quiescent state and the complementary distribution of the chemokine, fractalkine (CX(3)CL1) on neurons and its receptor (CX(3)CR1) on microglia, suggests that this interaction may play a role in modulating microglial activation. Here we demonstrate that both soluble and membrane-bound fractalkine attenuate lipopolysaccharide-induced microglial activation in vitro. We also show that fractalkine expression is reduced in the brain of aged rats and this is accompanied by an age-related increase in microglial activation. Treatment of aged rats with fractalkine attenuates the age-related increase in microglial activation and the evidence indicates that fractalkine-induced activation of the phosphatidylinositol-3 kinase pathway is required to maintain microglia in a quiescent state both in vivo and in vitro.

A comparison of the apoptotic effect of Δ9-tetrahydrocannabinol in the neonatal and adult rat cerebral cortex

The maternal use of cannabis during pregnancy results in a number of cognitive deficits in the offspring that persist into adulthood. The endocannabinoid system has a role to play in neurodevelopmental processes such as neurogenesis, migration and synaptogenesis. However, exposure to phytocannabinoids, such as Delta(9)-tetrahydrocannabinol, during gestation may interfere with these events to cause abnormal patterns of neuronal wiring and subsequent cognitive impairments. Aberrant cell death evoked by Delta(9)-tetrahydrocannabinol may also contribute to cognitive deficits and in cultured neurones Delta(9)-tetrahydrocannabinol induces apoptosis via the CB(1) cannabinoid receptor. In this study we report that Delta(9)-tetrahydrocannabinol (5-50 microM) activates the stress-activated protein kinase, c-jun N-terminal kinase, and the pro-apoptotic protease, caspase-3, in in vitro cerebral cortical slices obtained from the neonatal rat brain. The proclivity of Delta(9)-tetrahydrocannabinol to impact on these pro-apoptotic signalling molecules was not observed in in vitro cortical slices obtained from the adult rat brain. In vivo, subcutaneous administration of Delta(9)-tetrahydrocannabinol (1-30 mg/kg) activated c-jun N-terminal kinase, caspase-3 and cathepsin-D, and induced DNA fragmentation in the cerebral cortex of neonatal rats. In contrast, in vivo administration of Delta(9)-tetrahydrocannabinol to adult rats was not associated with the apoptotic pathway in the cerebral cortex. The data provide evidence which supports the hypothesis that the neonatal rat brain is more vulnerable to the neurotoxic influence of Delta(9)-tetrahydrocannabinol, suggesting that the cognitive deficits that are observed in humans exposed to marijuana during gestation may be due, in part, to abnormal engagement of the apoptotic cascade during brain development.

CD200 ligand receptor interaction modulates microglial activation in vivo and in vitro: a role for IL-4

Deficits in cognitive function are associated with neuroinflammatory changes, typified by activation of glial cells and an alteration of the pro- and anti-inflammatory cytokine balance in the brain. Although there is evidence to suggest that activation of microglia is regulated by interaction with other cell types in the brain, the mechanism(s) involved is poorly understood. Here, we provide evidence that interaction between CD200 and its receptor plays a role in modulating microglial activation under conditions of chronic and acute inflammation of the brain. We report that interleukin-4 (IL-4) plays a central role in modulating expression of CD200 and identify a mechanism by which IL-4 directly controls microglial cell activation. Our findings provide the first demonstration of a role for IL-4 in modulating CD200 expression and suggest a mechanism for regulation of microglial activation in the intact CNS under inflammatory conditions.

The tumour suppressor protein, p53, is involved in the activation of the apoptotic cascade by Delta9-tetrahydrocannabinol in cultured cortical neurons

Cannabis is the most commonly used illegal drug of abuse in Western society. Delta(9)-tetrahydrocannabinol, the psychoactive ingredient of marijuana, regulates a variety of neuronal processes including neurotransmitter release and synaptic transmission. An increasing body of evidence suggests that cannabinoids play a key role in the regulation of neuronal viability. In cortical neurons tetrahydrocannabinol has a neurodegenerative effect, the mechanisms of which are poorly understood, but involve the cannabinoid receptor subtype, CB(1). In this study we report that tetrahydrocannabinol (5 muM) evokes a rapid phosphorylation, and thus activation, of the tumour suppressor protein, p53, in a manner involving the cannabinoid CB(1) receptor, and the stress-activated protein kinase, c-jun N-terminal kinase, in cultured cortical neurons. Tetrahydrocannabinol increased expression of the p53-transcriptional target, Bax and promoted Bcl phosphorylation. These events were abolished by the p53 inhibitor, pifithrin-alpha (100 nM). The tetrahydrocannabinol-induced activation of the pro-apoptotic cysteine protease, caspase-3, and DNA fragmentation was also blocked by pifithrin-alpha. A siRNA knockdown of p53 further verified the role of p53 in tetrahydrocannabinol-induced apoptosis. This study demonstrates a novel cannabinoid signalling pathway involving p53 that culminates in neuronal apoptosis.

Tetrahydrocannabinol-induced neurotoxicity depends on CB1 receptor-mediated c-Jun N-terminal kinase activation in cultured cortical neurons

Delta9-Tetrahydrocannabinol (THC), the main psychoactive ingredient of marijuana, induces apoptosis in cultured cortical neurons. THC exerts its apoptotic effects in cortical neurons by binding to the CB1 cannabinoid receptor. The CB1 receptor has been shown to couple to the stress-activated protein kinase, c-Jun N-terminal kinase (JNK). However, the involvement of specific JNK isoforms in the neurotoxic properties of THC remains to be established. The present study involved treatment of rat cultured cortical neurons with THC (0.005-50 microM), and combinations of THC with the CB1 receptor antagonist, AM 251 (10 microM) and pertussis toxin (PTX; 200 ng ml-1). Antisense oligonucleotides (AS) were used to deplete neurons of JNK1 and JNK2 in order to elucidate their respective roles in THC signalling. Here we report that THC induces the activation of JNK via the CB1 receptor and its associated G-protein, Gi/o. Treatment of cultured cortical neurons with THC resulted in a differential timeframe of activation of the JNK1 and JNK2 isoforms. Use of specific JNK1 and JNK2 AS identified activation of caspase-3 and DNA fragmentation as downstream consequences of JNK1 and JNK2 activation. The results from this study demonstrate that activation of the CB1 receptor induces JNK and caspase-3 activation, an increase in Bax expression and DNA fragmentation. The data demonstrate that the activation of both JNK1 and JNK2 isoforms is central to the THC-induced activation of the apoptotic pathway in cortical neurons.

A role for c-Jun N-terminal kinase 1 (JNK1), but not JNK2, in the beta-amyloid-mediated stabilization of protein p53 and induction of the apoptotic cascade in cultured cortical neurons

beta-Amyloid (A beta) peptide has been shown to induce neuronal apoptosis; however, the mechanisms underlying A beta-induced neuronal cell death remain to be fully elucidated. The stress-activated protein kinase, c-Jun N-terminal kinase (JNK), is activated in response to cellular stress and has been identified as a proximal mediator of cell death. In the present study, expression of active JNK was increased in the nucleus and cytoplasm of A beta-treated cells. Evaluation of the nature of the JNK isoforms activated by A beta revealed a transient increase in JNK1 activity that reached its peak at 1 h and a later activation (at 24 h) of JNK2. The tumour suppressor protein, p53, is a substrate for JNK and can serve as a signalling molecule in apoptosis. In cultured cortical neurons, we found that A beta increased p53 protein expression and phosphorylation of p53 at Ser(15). Thus it appears that A beta increases p53 expression via phosphorylation-mediated stabilization of the protein. Given the lack of availability of a JNK inhibitor that can distinguish between JNK1- and JNK2-mediated effects, we employed antisense technology to deplete cells of JNK1 or JNK2 selectively. Using this strategy, the respective roles of JNK1 and JNK2 on the A beta-mediated activation of the apoptotic cascade (i.e. p53 stabilization, caspase 3 activation and DNA fragmentation) were examined. The results obtained demonstrate a role for JNK1 in the A beta-induced stabilization of p53, activation of caspase 3 and DNA fragmentation. In contrast, depletion of JNK2 had no effect on the proclivity of A beta to activate capase 3 or induce DNA fragmentation. These results demonstrate a significant role for JNK1 in A beta-mediated induction of the apoptotic cascade in cultured cortical neurons.