Cannabinoid receptor 2 attenuates microglial accumulation and brain injury following germinal matrix hemorrhage via ERK dephosphorylation in vivo and in vitro

The role of cannabinoid-mediated signaling pathways and mechanisms in brain disorders

Cannabinoids play significant roles in the central nervous system (CNS), but cannabinoid-mediated physiopathological functions are not elaborated. Cannabinoid receptors (CBRs) mediate functions that include the regulation of neuroinflammation, oxidative stress, apoptosis, autophagy, and neurogenesis. Microglia are the primary immune cells responsible for mediating neuroinflammation in the CNS. Therefore, this article primarily focuses on microglia to summarize the inflammatory pathways mediated by cannabinoids in the CNS, including nuclear factor-κB (NF-κB), NOD-like receptor protein 3 (NLRP3) inflammasome, mitogen-activated protein kinase (MAPK), protein kinase B (Akt), and cAMP-dependent protein kinase (PKA) signaling pathways. Additionally, we provide a table summarizing the role of cannabinoids in various brain diseases. Medical use of cannabinoids has protective effects in preventing and treating brain diseases; however, excessive and repeated use can be detrimental to the CNS. We propose that cannabinoids hold significant potential for preventing and treating brain diseases, including ferroptosis, lactate metabolism, and mitophagy, providing new insights for further research on cannabinoids.

Pharmacological Strategies and Surgical Management of Posthemorrhagic Hydrocephalus Following Germinal Matrix-Intraventricular Hemorrhage in Preterm Infants

Germinal matrix-intraventricular hemorrhage (GM-IVH) is a detrimental neurological complication that occurs in preterm infants, especially in babies born before 32 weeks of gestation and in those with a very low birth weight. GM-IVH is defined as a rupture of the immature and fragile capillaries located in the subependymal germinal matrix zone of the preterm infant brain, and it can lead to detrimental neurological sequelae such as posthemorrhagic hydrocephalus (PHH), cerebral palsy, and other cognitive impairments. PHH following GM-IVH is difficult to treat in the clinic, and no levelone strategies have been recommended to pediatric neurosurgeons. Several cellular and molecular mechanisms of PHH following GM-IVH have been studied in animal models, but no effective pharmacological strategies have been used in the clinic. Thus, a comprehensive understanding of molecular mechanisms, potential pharmacological strategies, and surgical management of PHH is urgently needed. The present review presents a synopsis of the pathogenesis, diagnosis, and cellular and molecular mechanisms of PHH following GM-IVH and explores pharmacological strategies and surgical management.

Cannabinoid receptor 2 agonist AM1241 alleviates epileptic seizures and epilepsy-associated depression via inhibiting neuroinflammation in a pilocarpine-induced chronic epilepsy mouse model

Increasing evidence suggests that cannabinoid receptor 2 (CB2R) serves as a promising anti-inflammatory target. While inflammation is known to play crucial roles in the pathogenesis of epilepsy, the involvement of CB2R in epilepsy remains unclear. This study aimed to investigate the effects of a CB2R agonist, AM1241, on epileptic seizures and depressive-like behaviors in a mouse model of chronic epilepsy induced by pilocarpine. A chronic epilepsy mouse model was established by intraperitoneal administration of pilocarpine. The endogenous cannabinoid system (eCBs) in the hippocampus was examined after status epilepticus (SE). Animals were then treated with AM1241 and compared with a vehicle-treated control group. Additionally, the role of the AMPK/NLRP3 signaling pathway was explored using the selective AMPK inhibitor dorsomorphin. Following SE, CB2R expression increased significantly in hippocampal microglia. Administration of AM1241 significantly reduced seizure frequency, immobility time in the tail suspension test, and neuronal loss in the hippocampus. In addition, AM1241 treatment attenuated microglial activation, inhibited pro-inflammatory polarization of microglia, and suppressed NLRP3 inflammasome activation in the hippocampus after SE. Further, the therapeutic effects of AM1241 were abolished by the AMPK inhibitor dorsomorphin. Our findings suggest that CB2R agonist AM1241 may alleviate epileptic seizures and its associated depression by inhibiting neuroinflammation through the AMPK/NLRP3 signaling pathway. These results provide insight into a novel therapeutic approach for epilepsy.

Cannabidiol ameliorates PTSD-like symptoms by inhibiting neuroinflammation through its action on CB2 receptors in the brain of male mice

Post-traumatic stress disorder (PTSD) is a debilitating mental health disease related to traumatic experience, and its treatment outcomes are unsatisfactory. Accumulating research has indicated that cannabidiol (CBD) exhibits anti-PTSD effects, however, the underlying mechanism of CBD remains inadequately investigated. Although many studies pertaining to PTSD have primarily focused on aberrations in neuronal functioning, the present study aimed to elucidate the involvement and functionality of microglia/macrophages in PTSD while also investigated the modulatory effects of CBD on neuroinflammation associated with this condition. We constructed a modified single-prolonged stress (SPS) mice PTSD model and verified the PTSD-related behaviors by various behavioral tests (contextual freezing test, elevated plus maze test, tail suspension test and novel object recognition test). We observed a significant upregulation of Iba-1 and alteration of microglial/macrophage morphology within the prefrontal cortex and hippocampus, but not the amygdala, two weeks after the PTSD-related stress, suggesting a persistent neuroinflammatory phenotype in the PTSD-modeled group. CBD (10 mg/kg, i.p.) inhibited all PTSD-related behaviors and reversed the alterations in both microglial/macrophage quantity and morphology when administered prior to behavioral assessments. We further found increased pro-inflammatory factors, decreased PSD95 expression, and impaired synaptic density in the hippocampus of the modeled group, all of which were also restored by CBD treatment. CBD dramatically increased the level of anandamide, one of the endocannabinoids, and cannabinoid type 2 receptors (CB2Rs) transcripts in the hippocampus compared with PTSD-modeled group. Importantly, we discovered the expression of CB2Rs mRNA in Arg-1-positive cells in vivo and found that the behavioral effects of CBD were diminished by CB2Rs antagonist AM630 (1 mg/kg, i.p.) and both the behavioral and molecular effects of CBD were abolished in CB2Rs knockout mice. These findings suggest that CBD would alleviate PTSD-like behaviors in mice by suppressing PTSD-related neuroinflammation and upregulation and activation of CB2Rs may serve as one of the underlying mechanisms for this therapeutic effect. The present study offers innovative experimental evidence supporting the utilization of CBD in PTSD treatment from the perspective of its regulation of neuroinflammation, and paves the way for leveraging the endocannabinoid system to regulate neuroinflammation as a potential therapeutic approach for psychiatric disorders.

The effect of cannabinoid type 2 receptor agonist on morphine tolerance

Pain highly impacts the quality of life of patients. Morphine is used for pain treatment; however, its side effects, especially morphine tolerance, limit its use in the clinic. The problem of morphine tolerance has plagued health workers and patients for years. Unfortunately, the exact mechanism of morphine tolerance has not been fully clarified. The mechanisms of morphine tolerance that are currently being studied may include μ-opioid receptor (MOR) desensitization and internalization, mitogen-activated protein kinase (MAPK) pathway activation and crosstalk, the effects of microglia and the increase in inflammatory factors. Morphine tolerance can be alleviated by improving the pathophysiological changes that lead to morphine tolerance. Previous studies have shown that a cannabinoid type 2 (CB2) receptor agonist could attenuate morphine tolerance in a variety of animal models. Many studies have shown an interaction between the cannabinoid system and the opioid system. The CB2 receptor may modulate the effect of morphine through a pathway that is common to the MOR, since both receptors are G protein-coupled receptors (GPCRs). This study introduces the potential mechanism of morphine tolerance and the effect of CB2 receptor agonists on reducing morphine tolerance, which can provide new ideas for researchers studying morphine and provide beneficial effects for patients suffering from morphine tolerance.

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

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

CB2 receptor in the CNS: from immune and neuronal modulation to behavior

Despite low levels of cannabinoid receptor type 2 (CB2R) expression in the central nervous system in human and rodents, a growing body of evidence shows CB2R involvement in many processes at the behavioral level, through both immune and neuronal modulations. Recent in vitro and in vivo evidence have highlighted the complex role of CB2R under physiological and inflammatory conditions. Under neuroinflammatory states, its activation seems to protect the brain and its functions, making it a promising target in a wide range of neurological disorders. Here, we provide a complete and updated overview of CB2R function in the central nervous system of rodents, spanning from modulation of immune function in microglia but also in other cell types, to behavior and neuronal activity, in both physiological and neuroinflammatory contexts.

Secukinumab attenuates neuroinflammation and neurobehavior defect via PKCβ/ERK/NF-κB pathway in a rat model of GMH

AIMS

Germinal matrix hemorrhage (GMH) is a disastrous clinical event for newborns. Neuroinflammation plays an important role in the development of neurological deficits after GMH. The purpose of this study is to investigate the anti-inflammatory role of secukinumab after GMH and its underlying mechanisms involving PKCβ/ERK/NF-κB signaling pathway.

METHODS

A total of 154 Sprague-Dawley P7 rat pups were used. GMH was induced by intraparenchymal injection of bacterial collagenase. Secukinumab was administered intranasally post-GMH. PKCβ activator PMA and p-ERK activator Ceramide C6 were administered intracerebroventricularly at 24 h prior to GMH induction, respectively. Neurobehavioral tests, western blot and immunohistochemistry were used to evaluate the efficacy of Secukinumab in both short-term and long-term studies.

RESULTS

Endogenous IL-17A, IL-17RA, PKCβ and p-ERK were increased after GMH. Secukinumab treatment improved short- and long-term neurological outcomes, reduced the synthesis of MPO and Iba-1 in the perihematoma area, and inhibited the synthesis of proinflammatory factors, such as NF-κB, IL-1β, TNF-α and IL-6. Additionally, PMA and ceramide C6 abolished the beneficial effects of Secukinumab.

CONCLUSION

Secukinumab treatment suppressed neuroinflammation and attenuated neurological deficits after GMH, which was mediated through the downregulation of the PKCβ/ERK/NF-κB pathway. Secukinumab treatment may provide a promising therapeutic strategy for GMH patients.

Cannabidiol Inhibits Inflammation Induced by Cutibacterium acnes-Derived Extracellular Vesicles via Activation of CB2 Receptor in Keratinocytes

Background

Acne is a common inflammatory skin disease, while cannabidiol (CBD) is a representative non-psychoactive phytocannabinoid which has been proved to exert universal anti-inflammatory properties. This study aimed to explore the effect of CBD on acne inflammation induced by Cutibacterium acnes-derived extracellular vesicles (CEVs) in keratinocytes and reveal the underlying mechanisms.

Methods

Normal human epidermal keratinocytes (NHEKs) were stimulated by CEVs in the presence of CBD or vehicle. Interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α levels were examined by RT-PCR and ELISA. The expression of cannabinoid type-2 (CB2) receptor and transient receptor potential vanilloid type-1 (TRPV1) was detected by Western blotting. TNF-α levels in the presence of CB2 receptor antagonist (AM630) or TRPV1 antagonist (Capsazepine) were detected by RT-PCR. The activation of MAPK and NF-κB signaling pathways and the nuclear translocation of NF-κB p65 upon CBD treatment were analyzed by Western blotting and immunofluorescence assay, respectively.

Results

The expression of inflammatory cytokines (IL-6, IL-8 and TNF-α) in CEVs-stimulated NHEKs was suppressed by CBD. CB2 receptor expression was upregulated by CBD, whereas CEVs-promoted TRPV1 expression was downregulated by CBD. AM630 reversed TNF-α levels inhibited by CBD. Capsazepine exerted an inhibitory effect on CEVs-induced inflammation and had synergistic effect with CBD. The phosphorylation of ERK1/2 and NF-κB p65 and nuclear translocation of NF-κB p65 were induced by CEVs but reduced by CBD.

Conclusion

The results indicated that CBD could inhibit inflammation induced by CEVs in NHEKs, which was mediated by activation of CB2 receptor and enhanced by the TRPV1 antagonist, through inactivation of the MAPK and NF-κB signaling pathways. CBD might be a potential novel strategy for acne treatment in the future.

Adiponectin Ameliorates GMH-Induced Brain Injury by Regulating Microglia M1/M2 Polarization Via AdipoR1/APPL1/AMPK/PPARγ Signaling Pathway in Neonatal Rats

Adiponectin (APN), a fat-derived plasma hormone, is a classic anti-inflammatory agent. Multiple studies have demonstrated the beneficial role of APN in acute brain injury, but the effect of APN in germinal matrix hemorrhage (GMH) is unclear, and the underlying molecular mechanisms remain largely undefined. In the current study, we used a GMH rat model with rh-APN treatment, and we observed that APN demonstrated a protective effect on neurological function and an inhibitory effect on neuroinflammation after GMH. To further explore the underlying mechanisms of these effects, we found that the expression of Adiponectin receptor 1 (AdipoR1) primarily colocalized with microglia and neurons in the brain. Moreover, AdiopR1, but not AdipoR2, was largely increased in GMH rats. Meanwhile, further investigation showed that APN treatment promoted AdipoR1/APPL1-mediated AMPK phosphorylation, further increased peroxisome proliferator-activated receptor gamma (PPARγ) expression, and induced microglial M2 polarization to reduce the neuroinflammation and enhance hematoma resolution in GMH rats. Importantly, either knockdown of AdipoR1, APPL1, or LKB1, or specific inhibition of AMPK/PPARγ signaling in microglia abrogated the protective effect of APN after GMH in rats. In all, we propose that APN works as a potential therapeutic agent to ameliorate the inflammatory response following GMH by enhancing the M2 polarization of microglia via AdipoR1/APPL1/AMPK/PPARγ signaling pathway, ultimately attenuating inflammatory brain injury induced by hemorrhage.

Immunomodulatory Role of CB2 Receptors in Emotional and Cognitive Disorders

Emotional behavior, memory, and learning have been associated with alterations in the immune system in neuropsychiatric and neurodegenerative diseases. In recent years, several studies pointed out the involvement of the cannabinoid receptor 2 (CB2r) in the immune system and the regulation of inflammation. This receptor is widely distributed in different tissues and organs with higher expression in spleen and immune system cells. However, CB2r has also been detected in several brain areas and different brain cell types, such as neurons and glia. These findings suggest that CB2r may closely relate the immune system and the brain circuits regulating inflammation, mood, and cognitive functions. Therefore, we review the studies that may help elucidate the molecular bases of CB2r in regulating inflammation in different brain cells and its role in the pathophysiology of psychiatric and neurodegenerative disorders.

Glibenclamide Attenuates Neuroinflammation and Promotes Neurological Recovery After Intracerebral Hemorrhage in Aged Rats

Intracerebral hemorrhage (ICH) is a common disease in the elderly population. Inflammation following ICH plays a detrimental role in secondary brain injury, which is associated with a poor prognosis of patients with ICH, and no efficient pharmacological preventions are available. Here, we investigated the effects of glibenclamide (GLC) on neuroinflammation in an autoblood-induced aged rat (18 months old) model of ICH. Rats were randomized into the sham, vehicle, and GLC groups. First, we investigated the expression level of sulfonylurea receptor 1 (Sur1) surrounding the hematoma after ICH. Then, neurological scores were calculated, and water maze tests, brain water content analysis, western blotting, and immunofluorescence assays were implemented to detect the neuroprotective effect of GLC. The expression of the Sur1-Trpm4 channel was significantly increased in the perihematomal tissue following ICH in aged rats. The GLC administration effectively reduced brain edema and improved neurofunction deficits following ICH. In addition, GLC increased the expression of brain-derived neurotrophic factors and decreased the expression of proinflammatory factors [tumor necrosis factor (TNF)-α,interleukin (IL)-1, and IL-6]. Moreover, GLC markedly reduced Ikappa-B (IκB) kinase (IKK) expression in microglia and nuclear factor (NF)-κB-P65 levels in perihematomal tissue. GLC ameliorated ICH-induced neuroinflammation and improved neurological outcomes in aged rats. In part, GLC may exert these effects by regulating the NF-κB signaling pathway through the Sur1-Trpm4 channel.

Cannabinoid Type-2 Receptor Agonist, JWH133 May Be a Possible Candidate for Targeting Infection, Inflammation, and Immunity in COVID-19

The COVID-19 pandemic, caused by SARS-CoV-2, is a deadly disease affecting millions due to the non-availability of drugs and vaccines. The majority of COVID-19 drugs have been repurposed based on antiviral, immunomodulatory, and antibiotic potential. The pathogenesis and advanced complications with infection involve the immune-inflammatory cascade. Therefore, a therapeutic strategy could reduce infectivity, inflammation, and immune modulation. In recent years, modulating the endocannabinoid system, particularly activation of the cannabinoid type 2 (CB2) receptor is a promising therapeutic target for modulation of immune-inflammatory responses. JWH133, a selective, full functional agonist of the CB2 receptor, has been extensively studied for its potent anti-inflammatory, antiviral, and immunomodulatory properties. JWH133 modulates numerous signaling pathways and inhibits inflammatory mediators, including cytokines, chemokines, adhesion molecules, prostanoids, and eicosanoids. In this study, we propose that JWH133 could be a promising candidate for targeting infection, immunity, and inflammation in COVID-19, due to its pharmacological and molecular mechanisms in numerous preclinical efficacy and safety studies, along with its immunomodulatory, anti-inflammatory, organoprotective, and antiviral properties. Thus, JWH133 should be investigated in preclinical and clinical studies for its potential as an agent or adjuvant with other agents for its effect on viremia, infectivity, immune modulation, resolution of inflammation, reduction in severity, and progression of complications in COVID-19. JWH133 is devoid of psychotropic effects due to CB2 receptor selectivity, has negligible toxicity, good bioavailability and druggable properties, including pharmacokinetic and physicochemical effects. We believe that JWH133 could be a promising drug and may inspire further studies for an evidence-based approach against COVID-19.

Pharmacological potential of JWH133, a cannabinoid type 2 receptor agonist in neurodegenerative, neurodevelopmental and neuropsychiatric diseases

The pharmacological activation of cannabinoid type 2 receptors (CB2R) gained attention due to its ability to mitigate neuroinflammatory events without eliciting psychotropic actions, a limiting factor for the drugs targeting cannabinoid type 1 receptors (CB1R). Therefore, ligands activating CB2R are receiving enormous importance for therapeutic targeting in numerous neurological diseases including neurodegenerative, neuropsychiatric and neurodevelopmental disorders as well as traumatic injuries and neuropathic pain where neuroinflammation is a common accompaniment. Since the characterization of CB2R, many CB2R selective synthetic ligands have been developed with high selectivity and functional activity. Among numerous ligands, JWH133 has been found one of the compounds with high selectivity for CB2R. JWH133 has been reported to exhibit numerous pharmacological activities including antioxidant, anti-inflammatory, anticancer, cardioprotective, hepatoprotective, gastroprotective, nephroprotective, and immunomodulatory. Recent studies have shown that JWH133 possesses potent neuroprotective properties in several neurological disorders, including neuropathic pain, anxiety, epilepsy, depression, alcoholism, psychosis, stroke, and neurodegeneration. Additionally, JWH133 showed to protect neurons from oxidative damage and inflammation, promote neuronal survival and neurogenesis, and serve as an immunomodulatory agent. The present review comprehensively examined neuropharmacological activities of JWH133 in neurological disorders including neurodegenerative, neurodevelopmental and neuropsychiatric using synoptic tables and elucidated pharmacological mechanisms based on reported observations. Considering the cumulative data, JWH133 appears to be a promising CB2R agonist molecule for further evaluation and it can be a prototype agent in drug discovery and development for a unique class of agents in neurotherapeutics. Further, regulatory toxicology and pharmacokinetic studies are required to determine safety and proceed for clinical evaluation.

Endocannabinoid Modulation of Microglial Phenotypes in Neuropathology

Microglia, the resident immune cells of the central nervous system, mediate brain homeostasis by controlling neuronal proliferation/differentiation and synaptic activity. In response to external signals from neuropathological conditions, homeostatic (M0) microglia can adopt one of two activation states: the classical (M1) activation state, which secretes mediators of the proinflammatory response, and the alternative (M2) activation state, which presumably mediates the resolution of neuroinflammation and tissue repair/remodeling. Since chronic inflammatory activation of microglia is correlated with several neurodegenerative diseases, functional modulation of microglial phenotypes has been considered as a potential therapeutic strategy. The endocannabinoid (eCB) system, composed of cannabinoid receptors and ligands and their metabolic/biosynthetic enzymes, has been shown to activate anti-inflammatory signaling pathways that modulate immune cell functions. Growing evidence has demonstrated that endogenous, synthetic, and plant-derived eCB agonists possess therapeutic effects on several neuropathologies; however, the molecular mechanisms that mediate the anti-inflammatory effects have not yet been identified. Over the last decade, it has been revealed that the eCB system modulates microglial activation and population. In this review, we thoroughly examine recent studies on microglial phenotype modulation by eCB in neuroinflammatory and neurodegenerative disease conditions. We hypothesize that cannabinoid 2 receptor (CB2R) signaling shifts the balance of expression between neuroinflammatory (M1-type) genes, neuroprotective (M2-type) genes, and homeostatic (M0-type) genes toward the latter two gene expressions, by which microglia acquire therapeutic functionality.

Posthemorrhagic hydrocephalus development after germinal matrix hemorrhage: Established mechanisms and proposed pathways

In addition to being the leading cause of morbidity and mortality in premature infants, germinal matrix hemorrhage (GMH) is also the leading cause of acquired infantile hydrocephalus. The pathophysiology of posthemorrhagic hydrocephalus (PHH) development after GMH is complex and vaguely understood, although evidence suggests fibrosis and gliosis in the periventricular and subarachnoid spaces disrupts normal cerebrospinal fluid (CSF) dynamics. Theories explaining general hydrocephalus etiology have substantially evolved from the original bulk flow theory developed by Dr. Dandy over a century ago. Current clinical and experimental evidence supports a new hydrodynamic theory for hydrocephalus development involving redistribution of vascular pulsations and disruption of Starling forces in the brain microcirculation. In this review, we discuss CSF flow dynamics, history and development of theoretical hydrocephalus pathophysiology, and GMH epidemiology and etiology as it relates to PHH development. We highlight known mechanisms and propose new avenues that will further elucidate GMH pathophysiology, specifically related to hydrocephalus.

Intraperitoneal cannabidiol attenuates neonatal germinal matrix hemorrhage-induced neuroinflamation and perilesional apoptosis

Background. As the survival of preterm infants has increased significantly, germinal matrix hemorrhage (GMH) has become an important public health issue. Nevertheless, treatment strategies for the direct neuronal injury are still scarce. The present study aims to analyze the neuroprotective properties of cannabidiol in germinal matrix hemorrhage. Methods. 112 Wistar rat pups (P7) were submitted to an experimental collagenase induced model of GMH. Inflammatory response and neuronal death were analyzed both at the perilesional area as at the distant ipsilateral CA1 hippocampal area. Immunohistochemistry for GFAP and caspase 3 was used. The ipsilateral free water content was assessed for stimation of cerebral edema, and neurodevelopment and neurofunctional tests were conducted. Results. Reduction of reactive astrocytosis was observed both in the perilesional area 24 hours and 14 days after the hemorrhage lesion (p < 0.001) and in the Stratum oriens of the ipsilateral hippocampal CA1 14 days after the hemorrhage lesion (p < 0.05) in the treated groups. Similarly, there was a reduction in the number of Caspase 3-positive astrocytes in the perilesional area in the treated groups 24 hours after the hemorrhage lesion (p < 0.001). Finally, we found a significant increase in the weight of the rats treated with cannabidiol. Conclusion. The treatment of GMH with cannabidiol significantly reduced the number of apoptotic cells and reactive astrocytes in the perilesional area and the ipsilateral hippocampus. In addition, this response was sustained 14 days after the hemorrhage. These results corroborate our hypothesis that cannabidiol is a potential neuroprotective agent in the treatment of germinal matrix hemorrhage.

Progress in brain cannabinoid CB2 receptor research: From genes to behavior

The type 2 cannabinoid receptor (CB2R) was initially regarded as a peripheral cannabinoid receptor. However, recent technological advances in gene detection, alongside the availability of transgenic mouse lines, indicate that CB2Rs are expressed in both neurons and glial cells in the brain under physiological and pathological conditions, and are involved in multiple functions at cellular and behavioral levels. Brain CB2Rs are inducible and neuroprotective via up-regulation in response to various insults, but display species differences in gene and receptor structures, CB2R expression, and receptor responses to various CB2R ligands. CB2R transcripts also differ between the brain and spleen. In the brain, CB2A is the major transcript isoform, while CB2A and CB2B transcripts are present at higher levels in the spleen. These new findings regarding brain versus spleen CB2R isoforms may in part explain why early studies failed to detect brain CB2R gene expression. Here, we review evidence supporting the expression and function of brain CB2R from gene and receptor levels to cellular functioning, neural circuitry, and animal behavior.

Anti-inflammation conferred by stimulation of CD200R1 via Dok1 pathway in rat microglia after germinal matrix hemorrhage

CD200 has been reported to be neuroprotective in neurodegenerative diseases. However, the potential protective effects of CD200 in germinal matrix hemorrhage (GMH) have not been investigated. We examined the anti-inflammatory mechanisms of CD200 after GMH. A total of 167 seven-day-old rat pups were used. The time-dependent effect of GMH on the levels of CD200 and CD200 Receptor 1 (CD200R1) was evaluated by western blot. CD200R1 was localized by immunohistochemistry. The short-term (24 h) and long-term (28 days) outcomes were evaluated after CD200 fusion protein (CD200Fc) treatment by neurobehavioral assessment. CD200 small interfering RNA (siRNA) and downstream of tyrosine kinase 1 (Dok1) siRNA were injected intracerebroventricularly. Western blot was employed to study the mechanisms of CD200 and CD200R1. GMH induced significant developmental delay and caused impairment in both cognitive and motor functions in rat pups. CD200Fc ameliorated GMH-induced damage. CD200Fc increased expression of Dok1 and decreased IL-1beta and TNF-alpha levels. CD200R1 siRNA and Dok1 siRNA abolished the beneficial effects of CD200Fc, as demonstrated by enhanced expression levels of IL-1beta and TNF-alpha. CD200Fc inhibited GMH-induced inflammation and this effect may be mediated by CD200R1/Dok1 pathway. Thus, CD200Fc may serve as a potential treatment to ameliorate brain injury for GMH patients.

Research Advances of Germinal Matrix Hemorrhage: An Update Review

Germinal matrix hemorrhage (GMH) refers to bleeding that derives from the subependymal (or periventricular) germinal region of the premature brain. GMH can induce severe and irreversible damage attributing to the vulnerable structure of germinal matrix and deleterious circumstances. Molecular mechanisms remain obscure so far. In this review, we summarized the newest preclinical discoveries recent years about GMH to distill a deeper understanding of the neuropathology, and then discuss the potential diagnostic or therapeutic targets among these pathways. GMH studies mostly in recent 5 years were sorted out and the authors generalized the newest discoveries and ideas into four parts of this essay. Intrinsic fragile structure of preterm germinal matrix is the fundamental cause leading to GMH. Many molecules have been found effective in the pathophysiological courses. Some of these molecules like minocycline are suggested active to reduce the damage in animal GMH model. However, researchers are still trying to find efficient diagnostic methods and remedies that are available in preterm infants to rehabilitate or cure the sequent injury. Merits have been obtained in the last several years on molecular pathways of GMH, but more work is required to further unravel the whole pathophysiology.

Clinical studies and anti-inflammatory mechanisms of treatments

In this exciting era, we are coming closer and closer to bringing an anti-inflammatory therapy to the clinic for the purpose of seizure prevention, modification, and/or suppression. At present, it is unclear what this approach might entail, and what form it will take. Irrespective of the therapy that ultimately reaches the clinic, there will be some commonalities with regard to clinical trials. A number of animal models have now been used to identify inflammation as a major underlying mechanism of both chronic seizures and the epileptogenic process. These models have demonstrated that specific anti-inflammatory treatments can be effective at both suppressing chronic seizures and interfering with the process of epileptogenesis. Some of these have already been evaluated in early phase clinical trials. It can be expected that there will soon be more clinical trials of both "conventional, broad spectrum" anti-inflammatory agents and novel new approaches to utilizing specific anti-inflammatory therapies with drugs or other therapeutic interventions. A summary of some of those approaches appears below, as well as a discussion of the issues facing clinical trials in this new domain.

Cannabinoid CB1 and CB2 receptors differentially modulate L- and T-type Ca2+ channels in rat retinal ganglion cells

Endocannabinoid signaling system is involved in regulating multiple neuronal functions in the central nervous system by activating G-protein coupled cannabinoid CB1 and CB2 receptors (CB1Rs and CB2Rs). Growing evidence has shown that CB1Rs and CB2Rs are extensively expressed in retinal ganglion cells (RGCs). Here, modulation of L- and T-types Ca²⁺ channels by activating CB1Rs and CB2Rs in RGCs was investigated. Triple immunofluorescent staining showed that L-type subunit Ca_V1.2 was co-localized with T-type subunits (Ca_V3.1, Ca_V3.2 and Ca_V3.3) in rat RGCs. In acutely isolated rat RGCs, the CB1R agonist WIN55212-2 suppressed both peak and steady-state Ca²⁺ currents in a dose-dependent manner, with IC₅₀ being 9.6 μM and 8.4 μM, respectively. It was further shown that activation of CB1Rs by WIN55212-2 or ACEA, another CB1R agonist, significantly suppressed both L- and T-type Ca²⁺ currents, and shifted inactivation curve of T-type one toward hyperpolarization direction. While the effect on L-type Ca²⁺ channels was mediated by intracellular cAMP/protein kinase A (PKA), mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and calcium/calmodulin-dependent protein kinase II (CaMKII) signaling pathways, only CaMKII signaling pathway was involved in the effect on T-type Ca²⁺ channels. Furthermore, CB65 and HU308, two specific CB2R agonists, significantly suppressed T-type Ca²⁺ channels, which was mediated by intracellular cAMP/PKA and CaMKII signaling pathways, but had no effect on L-type channels. These results imply that endogenous cannabinoids may modulate the excitability and the output of RGCs by differentially suppressing the activity of L- and T-type Ca²⁺ channels through activation of CB1Rs and CB2Rs. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Inflammatory Regulation by Driving Microglial M2 Polarization: Neuroprotective Effects of Cannabinoid Receptor-2 Activation in Intracerebral Hemorrhage

The cannabinoid receptor-2 (CB2R) was initially thought to be the “peripheral cannabinoid receptor.” Recent studies, however, have documented CB2R expression in the brain in both glial and neuronal cells, and increasing evidence suggests an important role for CB2R in the central nervous system inflammatory response. Intracerebral hemorrhage (ICH), which occurs when a diseased cerebral vessel ruptures, accounts for 10–15% of all strokes. Although surgical techniques have significantly advanced in the past two decades, ICH continues to have a high mortality rate. The aim of this study was to investigate the therapeutic effects of CB2R stimulation in acute phase after experimental ICH in rats and its related mechanisms. Data showed that stimulation of CB2R using a selective agonist, JWH133, ameliorated brain edema, brain damage, and neuron death and improved neurobehavioral outcomes in acute phase after ICH. The neuroprotective effects were prevented by SR144528, a selective CB2R inhibitor. Additionally, JWH133 suppressed neuroinflammation and upregulated the expression of microglial M2-associated marker in both gene and protein level. Furthermore, the expression of phosphorylated cAMP-dependent protein kinase (pPKA) and its downstream effector, cAMP-response element binding protein (CREB), were facilitated. Knockdown of CREB significantly inversed the increase of M2 polarization in microglia, indicating that the JWH133-mediated anti-inflammatory effects are closely associated with PKA/CREB signaling pathway. These findings demonstrated that CB2R stimulation significantly protected the brain damage and suppressed neuroinflammation by promoting the acquisition of microglial M2 phenotype in acute stage after ICH. Taken together, this study provided mechanism insight into neuroprotective effects by CB2R stimulation after ICH.

Intraventricular administration of urokinase as a novel therapeutic approach for communicating hydrocephalus

Fibrosis of the subarachnoid space (SAS) after infection, inflammation, or hemorrhage can impair cerebrospinal fluid absorption and circulation, causing diffuse ventricular dilatation. In the present study, we tested the hypothesis that urokinase (also known as urokinase-type plasminogen activator [uPA]), a fibrinolytic agent, attenuates fibrosis and ventriculomegaly in a rat model of kaolin-induced communicating hydrocephalus and thus may have potential as a therapy for these conditions. Thirty microliters of sterile 25% kaolin suspension was injected into the basal cisterns of adult Sprague-Dawley rats to induce hydrocephalus, and 2 intraventricular injections of either uPA or vehicle (saline) were administered immediately and 3 days thereafter. Ventricular volumes were measured by magnetic resonance imaging (MRI) on days 3, 14, and 28 after kaolin injection. Fibrosis and reactive astrogliosis were evaluated on day 28 by immunofluorescence and Western blotting. Neurocognitive features were tested using the Morris water maze from days 23 to 28. MRI analysis demonstrated that kaolin administration successfully induced hydrocephalus in rats and that uPA treatment significantly attenuated ventricular enlargement. In addition, uPA inhibited the deposition of laminin and fibronectin, extracellular matrix molecules, in the SAS, attenuated gliosis, and improved learning and memory in kaolin-treated rats. Therefore, we concluded that uPA prevents the development of kaolin-induced communicating hydrocephalus by preventing the development of subarachnoid fibrosis and by eliciting improvements in neurocognition. The results of this study indicate that uPA may be a novel clinical therapy for communicating hydrocephalus.

Urokinase, a promising candidate for fibrinolytic therapy for intracerebral hemorrhage

OBJECTIVE Intracerebral hemorrhage (ICH) is associated with a high rate of mortality and severe disability, while fibrinolysis for ICH evacuation is a possible treatment. However, reported adverse effects can counteract the benefits of fibrinolysis and limit the use of tissue-type plasminogen activator (tPA). Identifying appropriate fibrinolytics is still needed. Therefore, the authors here compared the use of urokinase-type plasminogen activator (uPA), an alternate thrombolytic, with that of tPA in a preclinical study. METHODS Intracerebral hemorrhage was induced in adult male Sprague-Dawley rats by injecting autologous blood into the caudate, followed by intraclot fibrinolysis without drainage. Rats were randomized to receive uPA, tPA, or saline within the clot. Hematoma and perihematomal edema, brain water content, Evans blue fluorescence and neurological scores, matrix metalloproteinases (MMPs), MMP mRNA, blood-brain barrier (BBB) tight junction proteins, and nuclear factor-κB (NF-κB) activation were measured to evaluate the effects of these 2 drugs in ICH. RESULTS In comparison with tPA, uPA better ameliorated brain edema and promoted an improved outcome after ICH. In addition, uPA therapy more effectively upregulated BBB tight junction protein expression, which was partly attributed to the different effects of uPA and tPA on the regulation of MMPs and its related mRNA expression following ICH. CONCLUSIONS This study provided evidence supporting the use of uPA for fibrinolytic therapy after ICH. Large animal experiments and clinical trials are required to further explore the efficacy and safety of uPA in ICH fibrinolysis.

Cannabinoid receptor-2 stimulation suppresses neuroinflammation by regulating microglial M1/M2 polarization through the cAMP/PKA pathway in an experimental GMH rat model

Excessive inflammatory responses are involved in secondary brain injury during germinal matrix hemorrhage (GMH). The process of microglial polarization to the pro-inflammatory M1 or anti-inflammatory M2 phenotypes is considered to occur in a major immunomodulatory manner during brain inflammation. We previously found that cannabinoid receptor-2 (CB2R) stimulation attenuated microglial accumulation and brain injury following experimental GMH. However, whether CB2R has effects on microglial polarization after GMH remains unclear. Herein, we investigated the effects of CB2R stimulation on neuroinflammation after experimental GMH and the potential mechanisms that mediate M1/M2 microglial phenotype regulation. The results indicated that during the GMH acute phase, microglia primarily polarized to the M1 phenotype and induced an overwhelming release of pro-inflammatory cytokines. However, JWH133, a selective CB2R agonist, significantly prevented the pro-inflammatory cytokine release while promoting an M1 to M2 phenotype transformation in microglia, resulting in an increased anti-inflammatory cytokine release. Moreover, in thrombin-induced rat primary microglial cells, JWH133 reduced the pro-inflammatory cytokine levels and M1 phenotype by enhancing the acquisition of the M2 phenotype. Additionally, JWH133 facilitated synthesis of cyclic AMP (cAMP) and its downstream effectors, phosphorylated cAMP-dependent protein kinase (p-PKA) and exchange protein activated by cyclic-AMP 1 (Epac1). The promoting effects of JWH133 on M2 polarization were attenuated with a specific PKA inhibitor but not with an Epac inhibitor, indicating that the cAMP/PKA signaling pathway was involved in the JWH133 effects. This is the first study to propose that promotion of microglial M2 polarization through the cAMP/PKA pathway participates in the CB2R-mediated anti-inflammatory effects after GMH induction. The results will help to further understand the mechanisms that underlie neuroprotection by CB2R in GMH and promote clinical translational research for CB2R agonists.

Pharmacological Preventions of Brain Injury Following Experimental Germinal Matrix Hemorrhage: an Up-to-Date Review

Germinal matrix hemorrhage (GMH) is defined as the rupture of immature blood vessels in the subependymal zone of premature infants with significant mortality and morbidity. Considering the notable social and ecological stress brought by GMH-induced brain injury and sequelae, safe and efficient pharmacological preventions are badly needed. Currently, several appropriate animal models are available to mimic the clinical outcomes of GMH in human patients. In the long run, hemorrhagic strokes are the research target. Previously, we found that minocycline was efficient to alleviate GMH-induced brain edema and posthemorrhagic hydrocephalus (PHH) in rats, which may be closely related to the activation of cannabinoid receptor 2 (CB2R). However, how the two molecules correlate and the underlined molecular pathway remain unknown. To extensively understand current experimental GMH treatment, this literature review critically evaluates existing therapeutic strategies, potential treatments, and potentially involved molecular mechanisms. Each strategy has its own advantages and disadvantages. Some of the mechanisms are still controversial, requiring an increasing number of animal experiments before the therapeutic strategy would be widely accepted.