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

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“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.

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.”

Endocannabinoids: A Promising Impact for Traumatic Brain Injury.

 

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“The endogenous cannabinoid (endocannabinoid) system regulates a diverse array of physiological processes and unsurprisingly possesses considerable potential targets for the potential treatment of numerous disease states, including two receptors (i.e., CB1 and CB2 receptors) and enzymes regulating their endogenous ligands N-arachidonoylethanolamine (anandamide) and 2-arachidonyl glycerol (2-AG).

Increases in brain levels of endocannabinoids to pathogenic events suggest this system plays a role in compensatory repair mechanisms.

Traumatic brain injury (TBI) pathology remains mostly refractory to currently available drugs, perhaps due to its heterogeneous nature in etiology, clinical presentation, and severity. Here, we review pre-clinical studies assessing the therapeutic potential of cannabinoids and manipulations of the endocannabinoid system to ameliorate TBI pathology.

Specifically, manipulations of endocannabinoid degradative enzymes (e.g., fatty acid amide hydrolase, monoacylglycerol lipase, and α/β-hydrolase domain-6), CB1and CB2 receptors, and their endogenous ligands have shown promise in modulating cellular and molecular hallmarks of TBI pathology such as; cell death, excitotoxicity, neuroinflammation, cerebrovascular breakdown, and cell structure and remodeling.

TBI-induced behavioral deficits, such as learning and memory, neurological motor impairments, post-traumatic convulsions or seizures, and anxiety also respond to manipulations of the endocannabinoid system.

As such, the endocannabinoid system possesses potential drugable receptor and enzyme targets for the treatment of diverse TBI pathology.

Yet, full characterization of TBI-induced changes in endocannabinoid ligands, enzymes, and receptor populations will be important to understand that role this system plays in TBI pathology.

Promising classes of compounds, such as the plant-derived phytocannabinoids, synthetic cannabinoids, and endocannabinoids, as well as their non-cannabinoid receptor targets, such as TRPV1 receptors, represent important areas of basic research and potential therapeutic interest to treat TBI.”

Co-localization of the cannabinoid type 1 receptor with corticotropin-releasing factor-containing afferents in the noradrenergic nucleus locus coeruleus: implications for the cognitive limb of the stress response.

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“The noradrenergic system has been shown to play a key role in the regulation of stress responses, arousal, mood, and emotional states. Corticotropin-releasing factor (CRF) is a primary mediator of stress-induced activation of noradrenergic neurons in the nucleus locus coeruleus (LC).

The endocannabinoid (eCB) system also plays a key role in modulating stress responses, acting as an “anti-stress” neuro-mediator.

In the present study, we investigated the cellular sites for interactions between the cannabinoid receptor type 1 (CB1r) and CRF in the LC.

Taken together, these results indicate that the eCB system is poised to directly modulate stress-integrative heterogeneous CRF afferents in the LC, some of which arise from limbic sources.”

CB2 cannabinoid receptors modulate HIF-1α and TIM-3 expression in a hypoxia-ischemia mouse model.

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“The role of CB2 cannabinoid receptors (CB2R) in global brain lesions induced by hypoxia-ischemia (HI) insult is still unresolved.

The aim of this study was to evaluate the involvement of CB2R in the behavioural and biochemical underpinnings related to brain damage induced by HI in adult mice, and the mechanisms involved.

Our results indicate that CB2R may have a crucial neuroprotective role following HI insult through the modulation of the inflammatory-related HIF-1α/TIM-3 signalling pathway in microglia.”

https://www.ncbi.nlm.nih.gov/pubmed/28253997

Endocannabinoid 2-arachidonoylglycerol protects inflammatory insults from sulfur dioxide inhalation via cannabinoid receptors in the brain.

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“Sulfur dioxide (SO2) pollution in the atmospheric environment causes brain inflammatory insult and inflammatory-related microvasculature dysfunction. However, there are currently no effective medications targeting the harmful outcomes from chemical inhalation.

Endocannabinoids (eCBs) are involved in neuronal protection against inflammation-induced neuronal injury. The 2-arachidonoylglycerol (2-AG), the most abundant eCBs and a full agonist for cannabinoid receptors (CB1 and CB2), is also capable of suppressing proinflammatory stimuli and improving microvasculature dysfunction.

Here, we indicated that endogenous 2-AG protected against neuroinflammation in response to SO2 inhalation by inhibiting the activation of microglia and astrocytes and attenuating the overexpression of inflammatory cytokines, including tumor necrosis factor alpha (TNF-a), interleukin (IL)-1β, and inducible nitric oxide synthase (iNOS).

In addition, endogenous 2-AG prevented cerebral vasculature dysfunction following SO2 inhalation by inhibiting endothelin 1 (ET-1), vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) expression, elevating endothelial nitric oxide synthase (eNOS) level, and restoring the imbalance between thromboxane A2 (TXA2) and prostaglandin I2 (PGI2).

In addition, the action of endogenous 2-AG on the suppression of inflammatory insult and inflammatory-related microvasculature dysfunction appeared to be mainly mediated by CB1 and CB2 receptors.

Our results provided a mechanistic basis for the development of new therapeutic approaches for protecting brain injuries from SO2 inhalation.”

https://www.ncbi.nlm.nih.gov/pubmed/28115138

Neuroimmmune interactions of cannabinoids in neurogenesis: focus on interleukin-1β (IL-1β) signalling.

Biochemical Society Transactions

“Neuroimmune networks and the brain endocannabinoid system contribute to the maintenance of neurogenesis.

Activation of cannabinoid receptors suppresses chronic inflammatory responses through the attenuation of pro-inflammatory mediators. Moreover, the endocannabinoid system directs cell fate specification of NSCs (neural stem cells) in the CNS (central nervous system).

The aim of our work is to understand better the relationship between the endocannabinoid and the IL-1β (interleukin-1β) associated signalling pathways and NSC biology, in order to develop therapeutical strategies on CNS diseases that may facilitate brain repair.

NSCs express functional CB1 and CB2 cannabinoid receptors, DAGLα (diacylglycerol lipase α) and the NSC markers SOX-2 and nestin. We have investigated the role of CB1 and CB2 cannabinoid receptors in the control of NSC proliferation and in the release of immunomodulators [IL-1β and IL-1Ra (IL-1 receptor antagonist)] that control NSC fate decisions. Pharmacological blockade of CB1 and/or CB2 cannabinoid receptors abolish or decrease NSC proliferation, indicating a critical role for both CB1 and CB2 receptors in the proliferation of NSC via IL-1 signalling pathways.

Thus the endocannabinoid system, which has neuroprotective and immunomodulatory actions mediated by IL-1 signalling cascades in the brain, could assist the process of proliferation and differentiation of embryonic or adult NSCs, and this may be of therapeutic interest in the emerging field of brain repair.

In summary, cannabinoids and IL-1β seem to play antagonistic roles in neurogenesis: although cannabinoids increase proliferation and induce formation and maturation of new neurons, IL-1β blocks proliferation and formation of new neurons, inducing a shift towards a glial fate. This may be important in situations such as in aging, neurodegenerative diseases, and lesions of the brain and spinal cord.”

Endogenous cannabinoid system alterations and their role in epileptogenesis after brain injury in rat.

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“Post-traumatic epilepsy (PTE) is one of the most common complications resulting from brain injury, however, antiepileptic drugs usually fail to prevent it.

Several lines of evidence have demonstrated that the endogenous cannabinoid system (ECS) plays a pivotal role during epileptogenesis in several animal models.

A recent study has shown that a cannabinoid type 1 (CB1) receptor antagonist could suppress long-term neuron hyperexcitability after brain injury, but the underlying mechanisms remain largely unknown.

In this study, we first analyzed the dynamic expression of different components of the ECS at various time points after brain injury in rats. Then, we conducted a 12-month-long session of behavioral monitoring after the brain injury, and based on the results, the rats were divided into a PTE group and a non-PTE group. Finally, the changes in the ECS between the two groups were compared.

We found that the ECS exhibited a biphasic alteration after brain injury; the expression of the CB1 receptor and 2-arachidonoylglycerol (2-AG) in the PTE group was significantly higher than that of the non-PTE group 12 months after traumatic brain injury.

Our preliminary results indicated that the ECS might be involved in post-traumatic epileptogenesis.”

https://www.ncbi.nlm.nih.gov/pubmed/27810514

Mild Traumatic Brain Injury Produces Neuron Loss That Can Be Rescued by Modulating Microglial Activation Using a CB2 Receptor Inverse Agonist.

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“We have previously reported that mild TBI created by focal left-side cranial blast in mice produces widespread axonal injury, microglial activation, and a variety of functional deficits.

We have also shown that these functional deficits are reduced by targeting microglia through their cannabinoid type-2 (CB2) receptors using 2-week daily administration of the CB2 inverse agonist SMM-189.

Overall, our findings indicate that SMM-189 rescues damaged neurons and thereby alleviates functional deficits resulting from TBI, apparently by selectively modulating microglia to the beneficial M2 state.

CB2 inverse agonists thus represent a promising therapeutic approach for mitigating neuroinflammation and neurodegeneration.”

Neuroprotective effects of the nonpsychoactive cannabinoid cannabidiol in hypoxic-ischemic newborn piglets.

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“To test the neuroprotective effects of the nonpsychoactive cannabinoid cannabidiol (CBD), piglets received i.v. CBD or vehicle after hypoxia-ischemia (HI: temporary occlusion of both carotid arteries plus hypoxia).

CBD administration was free from side effects; moreover, CBD administration was associated with cardiac, hemodynamic, and ventilatory beneficial effects.

In conclusion, administration of CBD after HI reduced short-term brain damage and was associated with extracerebral benefits.”

https://www.ncbi.nlm.nih.gov/pubmed/18679164

Cannabidiol reduces brain damage and improves functional recovery after acute hypoxia-ischemia in newborn pigs.

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“Newborn piglets exposed to acute hypoxia-ischemia (HI) received i.v. cannabidiol (HI + CBD) or vehicle (HI + VEH). In HI + VEH, 72 h post-HI brain activity as assessed by amplitude-integrated EEG (aEEG) had only recovered to 42 ± 9% of baseline, near-infrared spectroscopy (NIRS) parameters remained lower than normal, and neurobehavioral performance was abnormal (27.8 ± 2.3 points, normal 36). In the brain, there were fewer normal and more pyknotic neurons, while astrocytes were less numerous and swollen. Cerebrospinal fluid concentration of neuronal-specific enolase (NSE) and S100β protein and brain tissue percentage of TNFα(+) cells were all higher. In contrast, in HI + CBD, aEEG had recovered to 86 ± 5%, NIRS parameters increased, and the neurobehavioral score normalized (34.3 ± 1.4 points). HI induced histological changes, and NSE and S100β concentration and TNFα(+) cell increases were suppressed by CBD. In conclusion, post-HI administration of CBD protects neurons and astrocytes, leading to histological, functional, biochemical, and neurobehavioral improvements.”

https://www.ncbi.nlm.nih.gov/pubmed/21654550