Synthetic and endogenous cannabinoids protect retinal neurons from AMPA excitotoxicity in vivo, via activation of CB1 receptors: Involvement of PI3K/Akt and MEK/ERK signaling pathways

The Metabolism of 2-arachidonoylglycerol in Rod Outer Segments Is Modulated by Proteins Involved in the Phototransduction Process

We previously reported that 2-arachidonoylglycerol (2-AG) synthesis by diacylglycerol lipase (DAGL) and lysophosphatidate phosphohydrolase (LPAP) and hydrolysis by monoacylglycerol lipase (MAGL) in rod outer segments (ROS) from bovine retina were differently modified by light applied to the retina. Based on these findings, the aim of the present research was to evaluate whether 2-AG metabolism could be modulated by proteins involved in the visual process. To this end, ROS kept in darkness (DROS) or obtained in darkness and then subjected to light (BROS) were treated with GTPγS and GDPβS, or with low and moderate ionic strength buffers for detaching soluble and peripheral proteins, or soluble proteins, respectively. Only DAGL activity was stimulated by the application of light to the ROS. GTPγS-stimulated DAGL activity in DROS reached similar values to that observed in BROS. The studies using different ionic strength show that (1) the highest decrease in DROS DAGL activity was observed when both phosphodiesterase (PDE) and transducin α (Tα) are totally membrane-associated; (2) the decrease in BROS DAGL activity does not depend on PDE association to membrane, and that (3) MAGL activity decreases, both in DROS and BROS, when PDE is not associated to the membrane. Our results indicate that the bioavailability of 2-AG under light conditions is favored by G protein-stimulated increase in DAGL activity and hindered principally by Tα/PDE association with the ROS membrane, which decreases DAGL activity.

Investigating the Effects of Exogenous and Endogenous 2-Arachidonoylglycerol on Retinal CB1 Cannabinoid Receptors and Reactive Microglia in Naive and Diseased Retina

The endocannabinoid system (ECS) is a new target for the development of retinal disease therapeutics, whose pathophysiology involves neurodegeneration and neuroinflammation. The endocannabinoid 2-arachidonoylglycerol (2-AG) affects neurons and microglia by activating CB1/CB2 cannabinoid receptors (Rs). The aim of this study was to investigate the effects of 2-AG on the CB1R expression/downregulation and retinal neurons/reactive microglia, when administered repeatedly (4 d), in three different paradigms. These involved the 2-AG exogenous administration (a) intraperitoneally (i.p.) and (b) topically and (c) by enhancing the 2-AG endogenous levels via the inhibition (AM11920, i.p.) of its metabolic enzymes (MAGL/ABHD6). Sprague Dawley rats were treated as mentioned above in the presence or absence of CB1/CB2R antagonists and the excitatory amino acid, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Immunohistochemistry, Western blot and a 2-AG level analyses were performed. The 2-AG repeated treatment (i.p.) induced the CB1R downregulation, abolishing its neuroprotective actions. However, 2-AG attenuated the AMPA-induced activation of microglia via the CB2R, as concurred by the AM630 antagonist effect. Topically administered 2-AG was efficacious as a neuroprotectant/antiapoptotic and anti-inflammatory agent. AM11920 increased the 2-AG levels providing neuroprotection against excitotoxicity and reduced microglial activation without affecting the CB1R expression. Our findings show that 2-AG, in the three paradigms studied, displays differential pharmacological profiles in terms of the downregulation of the CB1R and neuroprotection. All treatments, however, attenuated the activation of microglia via the CB2R activation, supporting the anti-inflammatory role of 2-AG in the retina.

A Cross Talk between the Endocannabinoid System and Different Systems Involved in the Pathogenesis of Hypertensive Retinopathy

The prognosis of hypertension leads to organ damage by causing nephropathy, stroke, retinopathy, and cardiomegaly. Retinopathy and blood pressure have been extensively discussed in relation to catecholamines of the autonomic nervous system (ANS) and angiotensin II of the renin–angiotensin aldosterone system (RAAS) but very little research has been conducted on the role of the ECS in the regulation of retinopathy and blood pressure. The endocannabinoid system (ECS) is a unique system in the body that can be considered as a master regulator of body functions. It encompasses the endogenous production of its cannabinoids, its degrading enzymes, and functional receptors which innervate and perform various functions in different organs of the body. Hypertensive retinopathy pathologies arise normally due to oxidative stress, ischemia, endothelium dysfunction, inflammation, and an activated renin–angiotensin system (RAS) and catecholamine which are vasoconstrictors in their biological nature. The question arises of which system or agent counterbalances the vasoconstrictors effect of noradrenaline and angiotensin II (Ang II) in normal individuals? In this review article, we discuss the role of the ECS and its contribution to the pathogenesis of hypertensive retinopathy. This review article will also examine the involvement of the RAS and the ANS in the pathogenesis of hypertensive retinopathy and the crosstalk between these three systems in hypertensive retinopathy. This review will also explain that the ECS, which is a vasodilator in its action, either independently counteracts the effect produced with the vasoconstriction of the ANS and Ang II or blocks some of the common pathways shared by the ECS, ANS, and Ang II in the regulation of eye functions and blood pressure. This article concludes that persistent control of blood pressure and normal functions of the eye are maintained either by decreasing systemic catecholamine, ang II, or by upregulation of the ECS which results in the regression of retinopathy induced by hypertension.

Blockade of CB1 or Activation of CB2 Cannabinoid Receptors Is Differentially Efficacious in the Treatment of the Early Pathological Events in Streptozotocin-Induced Diabetic Rats

Oxidative stress, neurodegeneration, neuroinflammation, and vascular leakage are believed to play a key role in the early stage of diabetic retinopathy (ESDR). The aim of this study was to investigate the blockade of cannabinoid receptor 1 (CB1R) and activation of cannabinoid receptor 2 (CB2R) as putative therapeutics for the treatment of the early toxic events in DR. Diabetic rats [streptozotocin (STZ)-induced] were treated topically (20 μL, 10 mg/mL), once daily for fourteen days (early stage DR model), with SR141716 (CB1R antagonist), AM1710 (CB2R agonist), and the dual treatment SR141716/AM1710. Immunohistochemical-histological, ELISA, and Evans-Blue analyses were performed to assess the neuroprotective and vasculoprotective properties of the pharmacological treatments on diabetes-induced retinal toxicity. Activation of CB2R or blockade of CB1R, as well as the dual treatment, attenuated the nitrative stress induced by diabetes. Both single treatments protected neural elements (e.g., RGC axons) and reduced vascular leakage. AM1710 alone reversed all toxic insults. These findings provide new knowledge regarding the differential efficacies of the cannabinoids, when administered topically, in the treatment of ESDR. Cannabinoid neuroprotection of the diabetic retina in ESDR may prove therapeutic in delaying the development of the advanced stage of the disease.

Investigation on the neuroprotective effect of a cannabidiol-enriched non-psychotropic Cannabis sativa L. extract in an in vitro model of excitotoxicity

The purpose of this study was to evaluate the neuroprotective effect of a cannabidiol-enriched non-psychotropic Cannabis sativa L. extract (CSE) and its main constituents, cannabidiol and β-caryophyllene. An in vitro model of glutamate-induced neuronal excitotoxicity using SH-SY5Y cells was optimized. The impact of CSE on glutamate-impaired cell viability, brain-derived neurotrophic factor release, CB1 protein expression, and ERK levels was evaluated. The involvement of CB1 modulation was verified by the cotreatment with the CB1 antagonist AM4113. CSE was able to significantly protect SH-SY5Y from glutamate-impaired cell viability, and to counteract the changes in brain-derived neurotrophic factor levels, with a mechanism of action involving ERK modulation. Moreover, CSE completely reversed the reduction of CB1 receptor expression induced by glutamate, and the presence of the CB1 antagonist AM4113 reduced CSE effectiveness, suggesting that CBr play a role in the modulation of neuronal excitotoxicity. This work demonstrated the in vitro effectiveness of CSE as a neuroprotective agent, proposing the whole cannabis phytocomplex as a more effective strategy, compared to its main constituents alone, and suggested further investigations by using more complex cell models before moving to in vivo studies.

CB1R, CB2R and TRPV1 expression and modulation in in vivo, animal glaucoma models: A systematic review

BACKGROUND

The endocannabinoid system (ECS) is a complex biological regulatory system. Its expression and functionality have been widely investigated in ocular tissues. Recent data have reported its modulation to be valid in determining an ocular hypotensive and a neuroprotective effect in preclinical animal models of glaucoma.

AIM

This study aimed to explore the available literature on cannabinoid receptor 1 (CB₁R), cannabinoid receptor 2 (CB₂R), and transient receptor potential vanilloid 1 (TRPV1) expression in the trabecular meshwork (TM), ciliary body (CB), and retina as well as their ocular hypotensive and neuroprotective effects in preclinical, in vivo, animal glaucoma models.

MATERIALS AND METHODS

The study adhered to both PRISMA and SYRCLE guidelines. Sixty-nine full-length articles were included in the final analysis.

RESULTS

Preclinical studies indicated a widespread distribution of CB₁R, CB₂R, and TRPV1 in the TM, CB, and retina, although receptor-, age-, and species-dependent differences were observed. CB₁R and CB₂R modulation have been shown to exert ocular hypotensive effects in preclinical models via the regulation of inflow and outflow pathways. Retinal cell neuroprotection has been achieved in several experimental models, mediated by agonists and antagonists of CB₁R, CB₂R, and TRPV1.

DISCUSSION

Despite the growing body of preclinical data regarding the expression and modulation of ECS in ocular tissues, the mechanisms responsible for the hypotensive and neuroprotective efficacy exerted by this system remain largely elusive. Research on this topic is advocated to further substantiate the hypothesis that the ECS is a new potential therapeutic target in the context of glaucoma.

The Role of the Possible Receptors and Intracellular Pathways in Protective Effect of Exogenous Anandamide in Kindling Model of Epilepsy

In this research, the involvement of CB1 and TRPV1 receptors in the possible protective effects of anandamide were investigated in the kindling model of epilepsy. The basolateral amygdala of the rat brain was chosen to put stimulating electrodes. Semi-rapid kindling was induced by a repetitive sub-threshold stimulation for 5-9 consecutive days. There were seven groups, six of which were kindled and used for drug testing by intracerebroventricular (i.c.v.) microinjection. (i) Sham, (ii) control group received vehicles, (iii) anandamide (AEA; 100 ng/rat), (iv) capsazepine (TRPV1 antagonist; 100 ng/rat), (v) AM251 (CB1 antagonist; 100 ng/rat), (vi) AM251 + anandamide, and (vii) capsazepine + anandamide. The after-discharge duration, seizure duration, and stage five duration were measured in rats. Moreover, the expressions of the extracellular signal-regulated kinase (ERK) and the cAMP responsive element binding (CREB) proteins in the hippocampus were also studied. The anandamide-treated group showed a significant decrease in seizure scores, while no change was shown in seizure scores in the capsazepine- and AM251-treated groups compared with the control group. Co-administrations of either capsazepine + AEA or AM251 + AEA attenuated the protective effect of AEA against seizure. Furthermore, the group received AEA showed a decrease in the expressions of CREB and p-CREB possibly through the activation of the CB1 and TRPV1 receptors. Activation of CB1 and TRPV1 receptors might be involved in AEA anticonvulsant effect in kindling model of epilepsy. This effect could be due to suppression of CREB phosphorylation in hippocampal neurons.

The Vertical and Horizontal Pathways in the Monkey Retina Are Modulated by Typical and Atypical Cannabinoid Receptors

The endocannabinoid (eCB) system has been found in all visual parts of the central ner-vous system and plays a role in the processing of visual information in many species, including monkeys and humans. Using anatomical methods, cannabinoid receptors are present in the monkey retina, particularly in the vertical glutamatergic pathway, and also in the horizontal GABAergic pathway. Modulating the eCB system regulates normal retinal function as demonstrated by electrophysiological recordings. The characterization of the expression patterns of all types of cannabinoid receptors in the retina is progressing, and further research is needed to elucidate their exact role in processing visual information. Typical cannabinoid receptors include G-protein coupled receptor CB1R and CB2R, and atypical cannabinoid receptors include the G-protein coupled receptor 55 (GPR55) and the ion channel transient receptor potential vanilloid 1 (TRPV1). This review focuses on the expression and localization studies carried out in monkeys, but some data on other animal species and humans will also be reported. Furthermore, the role of the endogenous cannabinoid receptors in retinal function will also be presented using intraocular injections of known modulators (agonists and antagonists) on electroretinographic patterns in monkeys. The effects of the natural bioactive lipid lysophosphatidylglucoside and synthetic FAAH inhibitor URB597 on retinal function, will also be described. Finally, the potential of typical and atypical cannabinoid receptor acti-vity regulation in retinal diseases, such as age-related macular degeneration, diabetic retinopathy, glaucoma, and retinitis pigmentosa will be briefly explored.

The endocannabinoid 2-arachidonoylglycerol and dual ABHD6/MAGL enzyme inhibitors display neuroprotective and anti-inflammatory actions in the in vivo retinal model of AMPA excitotoxicity

The endocannabinoid system has been shown to be a putative therapeutic target for retinal disease. Here, we aimed to investigate the ability of the endocannabinoid 2-arachidonoylglycerol (2-AG) and novel inhibitors of its metabolic enzymes, α/β-hydrolase domain-containing 6 (ABHD6) and monoacylglycerol lipase (MAGL), a) to protect the retina against excitotoxicity and b) the mechanisms involved in the neuroprotection. Sprague-Dawley rats, wild type and Akt2^-/- C57BL/6 mice were intravitreally administered with phosphate-buffered saline or (RS)-α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid hydrobromide (AMPA). 2-AG was intravitreally co-administered with AMPA in the absence and presence of AM251 or AM630 (cannabinoid 1 and 2 receptor antagonists, respectively) or Wortmannin [Phosphoinositide 3-Kinase (PI3K)/Akt inhibitor]. Inhibitors of ABHD6 and dual ABHD6/MAGL (AM12100 and AM11920, respectively) were co-administered with AMPA intravitreally in rats. Immunohistochemistry was performed using antibodies raised against retinal neuronal markers (bNOS), microglia (Iba1) and macroglia (GFAP). TUNEL assay and real-time PCR were also employed. The CB2 receptor was expressed in rat retina (approx. 62% of CB1 expression). 2-AG attenuated the AMPA-induced increase in TUNEL⁺ cells. 2-AG activation of both CB1 and CB2 receptors and the PI3K/Akt downstream signaling pathway, as substantiated by the use of Akt2^-/- mice, afforded neuroprotection against AMPA excitotoxicity. AM12100 and AM11920 attenuated the AMPA-induced glia activation and produced a dose-dependent partial neuroprotection, with the dual inhibitor AM11920 being more efficacious. These results show that 2-AG has the pharmacological profile of a putative therapeutic for retinal diseases characterized by neurodegeneration and neuroinflammation, when administered exogenously or by the inhibition of its metabolic enzymes.

Effect of acute and subchronic administration of (R)-WIN55,212-2 induced neuroprotection and anti inflammatory actions in rat retina: CB1 and CB2 receptor involvement

Cannabinoids have been shown to protect the retina from ischemic/excitotoxic insults. The aim of the present study was to investigate the neuroprotective and anti-inflammatory properties of the synthetic cannabinoid (R)-WIN55,212-2 (CB1/CB2 receptor agonist) when administered acutely or subchronically in control and AMPA treated retinas. Sprague-Dawley rats were intravitreally administered (acutely) with vehicle or AMPA, in the absence or presence of (R)-WIN55,212-2 (10^-7-10^-4M) alone or in combination with AM251 [CB1 receptor antagonist/inverse agonist,10^-4M] and AM630 (CB2 receptor antagonist,10^-4M). In addition, AMPA was co-administered with the racemic (R,S)-WIN55,212 (10^-4Μ). (R)-WIN55,212-2 was also administered subchronically (25,100 μg/kg,i.p.,4d) in control and AMPA treated rats. Immunohistochemical studies were performed using antibodies against the CB1R, and retinal markers for retinal neurons (brain nitric oxide synthetase, bNOS) and microglia (ionized calcium binding adaptor molecule 1, Iba1). ELISA assay was employed to assess TNFα levels in AMPA treated retinas. Intravitreal administration of (R)-WIN55,212-2 reversed the AMPA induced loss of bNOS expressing amacrine cells, an effect that was blocked by both AM251 and AM630. (R,S)WIN55,212 had no effect. (R)-WIN55,212-2 also reduced a) the AMPA induced activation of microglia, by activating CB2 receptors that were shown to be colocalized with Iba1⁺ reactive microglial cells, and b) TNFα levels in retina. (R)-WIN55,212-2 administered subchronically led to the downregulation of CB1 receptors at the high dose of 100 μg/kg(i.p.), and to the attenuation of the WIN55,212-2 induced neuroprotection of amacrine cells. At the same dose, (R)-WIN55,212-2 did not attenuate the AMPA induced increase in the number of reactive microglia cells, suggesting CB2 receptor downregulation under subchronic conditions. This study provides new findings regarding the role of CB1 and CB2 receptor activation by the synthetic cannabinoid (R)-WIN55,212-2, administered acutely or sub-chronically, on neuron viability and microglia activation in healthy and diseased retina.

The Effect of Orally Administered Dronabinol on Optic Nerve Head Blood Flow in Healthy Subjects-A Randomized Clinical Trial

It has been hypothesized that besides its intraocular pressure (IOP) lowering potential, tetrahydrocannabinol (THC) may also improve ocular hemodynamics. The aim of the present study was to investigate whether single oral administration of dronabinol, a synthetic THC, alters optic nerve head blood flow (ONHBF) and its regulation in healthy subjects. The study was carried out in a randomized, placebo-controlled, double-masked, two-way crossover design in 24 healthy subjects. For each study participant, 2 study days were scheduled, on which they either received capsules containing 5 mg dronabinol or placebo. ONHBF was measured with laser Doppler flowmetry at rest and while the study participants performed isometric exercise for 6 minutes to increase mean arterial blood pressure (MAP). This was repeated 1 hour after drug intake. Ocular perfusion pressure (OPP) was calculated as 2/3MAP-IOP. Dronabinol was well tolerated and no cannabinoid-related psychoactive effects were reported. Neither administration of dronabinol nor placebo had an effect on IOP, MAP, or OPP. In contrast, dronabinol significantly increased ONHBF at rest by 9.5 ± 8.1%, whereas placebo did not show a change in ONHBF (0.3 ± 7.4% vs. baseline, P < 0.001 between study days). Dronabinol did not alter the autoregulatory response of ONHBF to isometric exercise. In conclusion, the present data indicate that low-dose dronabinol increases ONHBF in healthy subjects without affecting IOP, OPP, or inducing psychoactive side effects. In addition, dronabinol does not alter the autoregulatory response of ONHBF to an experimental increase in OPP. Further studies are needed to investigate whether this effect can also be observed in patients with glaucoma.

Retinal Cell Protection in Ocular Excitotoxicity Diseases. Possible Alternatives Offered by Microparticulate Drug Delivery Systems and Future Prospects

Excitotoxicity seems to play a critical role in ocular neurodegeneration. Excess-glutamate-mediated retinal ganglion cells death is the principal cause of cell loss. Uncontrolled glutamate in the synapsis has significant implications in the pathogenesis of neurodegenerative disorders. The exploitation of various approaches of controlled release systems enhances the pharmacokinetic and pharmacodynamic activity of drugs. In particular, microparticles are secure, can maintain therapeutic drug concentrations in the eye for prolonged periods, and make intimate contact by improving drug bioavailability. According to the promising results reported, possible new investigations will focus intense attention on microparticulate formulations and can be expected to open the field to new alternatives for doctors, as currently required by patients.

Δ9-tetrahydrocannabinol and 2-AG decreases neurite outgrowth and differentially affects ERK1/2 and Akt signaling in hiPSC-derived cortical neurons

Endocannabinoids regulate different aspects of neurodevelopment. In utero exposure to the exogenous psychoactive cannabinoid Δ⁹-tetrahydrocannabinol (Δ⁹-THC), has been linked with abnormal cortical development in animal models. However, much less is known about the actions of endocannabinoids in human neurons. Here we investigated the effect of the endocannabinoid 2-arachidonoyl glycerol (2AG) and Δ⁹-THC on the development of neuronal morphology and activation of signaling kinases, in cortical neurons derived from human induced pluripotent stem cells (hiPSCs). Our data indicate that the cannabinoid type 1 receptor (CB1R), but not the cannabinoid 2 receptor (CB2R), GPR55 or TRPV1 receptors, is expressed in young, immature hiPSC-derived cortical neurons. Consistent with previous reports, 2AG and Δ⁹-THC negatively regulated neurite outgrowth. Interestingly, acute exposure to both 2AG and Δ⁹-THC inhibited phosphorylation of serine/threonine kinase extracellular signal-regulated protein kinases (ERK1/2), whereas Δ⁹-THC also reduced phosphorylation of Akt (aka PKB). Moreover, the CB1R inverse agonist SR 141716A attenuated the decrease in neurite outgrowth and ERK1/2 phosphorylation induced by 2AG and Δ⁹-THC. Taken together, our data suggest that hiPSC-derived cortical neurons express CB1Rs and are responsive to exogenous cannabinoids. Thus, hiPSC-neurons may represent a good cellular model for investigating the role of the endocannabinoid system in regulating cellular processes in developing human neurons.

SIRT1 is required for the neuroprotection of resveratrol on retinal ganglion cells after retinal ischemia-reperfusion injury in mice

PURPOSE

Retinal ganglion cells (RGCs) loss is closely related to visual impairment in glaucoma, so the neuroprotection on RGCs is important and novel for glaucoma research. SIRT1, a family member of sirtuins, is implicated in many crucial processes of eye diseases. The purpose of this study is to determine the neuroprotection of SIRT1 on RGCs and to investigate the underlying mechanisms of these effects in an experimental model for acute glaucoma.

METHODS

Retinal ischemia-reperfusion (IR) injury was induced in C57BL/6J mice. Resveratrol (RSV, activator of SIRT1) and sirtinol (inhibitor of SIRT1) were injected intravitreally 1 day before IR injury. RGCs survival rate was quantified by immunofluorescence staining. RGCs apoptosis was evaluated by the staining of TUNEL and cleaved caspase-3, and SIRT1 level was detected by western blot. Expressions of phospho-Akt, Akt, Bax, and Bcl-2 were further determined by western blot to investigate the neuroprotective mechanisms of SIRT1.

RESULTS

RGCs survival rates and SIRT1 levels were decreased over time after IR injury. Intravitreal injection of RSV remarkably attenuated RGCs loss in a dose-dependent manner, and the most effective concentration of RSV was 100 μM. Up-regulation of SIRT1 by RSV significantly inhibited RGCs apoptosis, increased p-Akt level, decreased Bax and cleaved caspase-3 expressions, and all these effects were diminished by 100 μM sirtinol. Moreover, there were no significant changes in total Akt and Bcl-2 levels.

CONCLUSION

SIRT1 activation by RSV confers neuroprotection on RGCs in retinal IR injury through the activation of Akt pathway and subsequent suppression of mitochondrial apoptotic pathway. Determination of the effective concentration of intravitreal injection of RSV also provides a theoretical basis for the clinical application of RSV.

Cisplatin-induced ototoxicity involves interaction of PRMT3 and cannabinoid system

This study investigated whether protein arginine methyltransferase (PRMT) and the cannabinoid system are involved in cisplatin-induced ototoxicity. Cisplatin increased cytosine-cytosine-adenosine-adenosine-thymidine-enhancer-binding protein homologous protein expression. This effect is indicative of an increase in endoplasmic reticulum (ER) stress, and apoptosis signaling including cleavage of caspase-3, caspase-9, poly-adenosine diphosphate-ribose polymerase, and phospho-p53, as well as expression of PRMT3, PRMT4 and fatty acid amide hydrolase (FAAH)1 in House Ear Institute-Organ of Corti 1 (HEI-OC1) cells. In addition, overexpression of PRMT3 or PRMT4 increased the expression of FAAH1 expression, apoptosis, and ER stress signaling in HEI-OC1 cells, whereas PRMT3 or PRMT4 knockdown had the opposite effect. Furthermore, overexpression of FAAH1 increased apoptosis and ER stress, but expression of the PRMTs was unchanged. In addition, a cannabinoid 1 receptor agonist and FAAH inhibitor attenuated apoptosis and ER stress, while cisplatin increased the binding of PRMT3 with FAAH1. In the in vivo experiments, cisplatin was injected intraperitoneally at 6 mg/kg/day into C57BL/6 mice, and 7 days later, this study confirmed that PRMT3 and PRMT4 were upregulated in the organ of Corti of the mice. These results indicate that cisplatin-induced ototoxicity was correlated with PRMT3, PRMT4 and the cannabinoid system, and PRMT3 binding with FAAH1 was increased by cisplatin in HEI-OC1 cells. Therefore, this study suggests that PRMT3 mediates cisplatin-induced ototoxicity via interaction with FAAH1 in vitro and in vivo.

Neuroprotective Effects of Low Dose Anandamide in Pentylenetetrazole-Induced Kindling in Rats

Anandamide (N-arachidonoylethanolamine) is an endogenous cannabinoid receptor CB1 ligand that exhibits neuroprotective effects in the brain. In this study, the effect of exogenously given anandamide on pentylenetetrazole (PTZ)-induced chemical kindling oxidative stress and brain damage in rats was studied. Rats were intraperitoneally (i.p.) injected with 35 mg/kg PTZ once every 48 hours for 12 times to induce seizures. Anandamide was i.p. given. 30 min prior to PTZ injection at 100 or 200 mg/kg. Injections of PTZ induced significant increase in brain lipid peroxidation (malondialdehyde: MDA), and nitric oxide associated with marked decrease in brain reduced glutathione (GSH). There were also significant decrements in acetylcholinesterase (AChE) concentration, butyrylcholinesterase (BChE) and paraoxonase-1 (PON-1) activities in brain tissue of PTZ injected rats. Meanwhile, there was no significant effect for PTZ on the concentration of brain neutrophil elastase. Anandamide administered at 100 and 200 mg/kg significantly decreased MDA and increased GSH contents and at 200 mg/kg significantly decreased nitric oxide in brain of PTZ-treated rats. The drug also caused significant increments in AChE concentration and PON-1 activity but had no significant effect on BChE or neutrophil elastase in rats treated with PTZ. Anandamide given at the dose of 200mg/kg significantly decreased the mean seizure scores over the study period by 22.3% and the frequency of myoclonic jerks and rearing (stage 3) by 56.7% compared with the vehicle-treated group. Anandamide given at 100 and 200 mg/kg completely inhibited the development of generalized tonic-clonic seizures (stage 5). It is concluded that in the PTZ-induced seizures, the cannabinoid receptor CB1 agonist anandamide decreases brain oxidative stress, neuronal injury, and exerts an antiepileptic activity.

Cannabinoid Receptor Type 1 Agonist ACEA Improves Cognitive Deficit on STZ-Induced Neurotoxicity Through Apoptosis Pathway and NO Modulation

The cannabinoid system has the ability to modulate cellular and molecular mechanisms, including excitotoxicity, oxidative stress, apoptosis, and inflammation, acting as a neuroprotective agent, by its relationship with signaling pathways associated to the control of cell proliferation, differentiation, and survival. Recent reports have raised new perspectives on the possible role of cannabinoid system in neurodegenerative diseases like Alzheimer disease's (AD). AD is a neurodegenerative disorder characterized by the presence of amyloid plaques, neurofibrillary tangles, neuronal death, and progressive cognitive loss, which could be caused by energy metabolism impairment, changes in insulin signaling, chronic oxidative stress, neuroinflammation, Tau hyperphosphorylation, and Aβ deposition in the brain. Thus, we investigated the presumptive protective effect of the cannabinoid type 1 (CB1)-selective receptor agonist arachidonyl-2'-chloroethylamide (ACEA) against streptozotocin (STZ) exposure stimuli in an in vitro neuronal model (Neuro-2a neuroblastoma cells) and in vivo model (intracerebroventricular STZ injection), experimental models of sporadic AD. Our results demonstrated that ACEA treatment reversed cognitive impairment and increased activity of Akt and ERK triggered by STZ, and increased IR expression and increased the anti-apoptotic proteins levels, Bcl-2. In the in vitro model, ACEA was able to rescue cells from STZ-triggered death and modulated the NO release by STZ. Our study has demonstrated a participation of the cannabinoid system in cellular survival, involving the CB1 receptor, which occurs by positive regulation of the anti-apoptotic proteins, suggesting the participation of this system in neurodegenerative processes. Our data suggest that the cannabinoid system is an interesting therapeutic target for the treatment of neurodegenerative diseases.

Effect of apigenin on apoptosis induced by renal ischemia/reperfusion injury in vivo and in vitro

Objectives: This study aims to investigate the effects and molecular mechanisms of apigenin (ApI) on renal ischemia/reperfusion (I/R) injury in vivo and in vitro.

Methods:In vivo, the left renal artery was clamped for 45 min and the right kidney was removed to study renal I/R injury on Sprague-Dawley (SD) rats. ApI was injected at 60 min before renal ischemia. In vitro, renal tubular epithelial cells (HK-2) were pretreated with or without ApI (20 uM) for 60 min and then treated with hypoxia/reoxygenation (H/R). Renal function, histology, cells apoptosis, and cell viability were tested. Furthermore, the potential molecular mechanisms were assessed.

Results: ApI pretreatment could significantly alleviated the renal function and the pathological damage as well as cells apoptosis after I/R injury. Meanwhile, ApI treatment protects H/R induced HK-2 cell apoptosis in vitro. The results of Western blot showed that ApI significantly increased the expressions of B-cell lymphoma 2 (Bcl-2) and phosphor-AKt (p-AKt), Phosphoinositide 3-kinase (PI3K), while down-regulated the expressions of Caspase3 and Bax induced by H/R injury.

Conclusions: ApI pretreatment can protect renal function against I/R injury and prevent renal tubular cells from apoptosis in vivo and in vitro which might through PI3K/Akt mediated mitochondria-dependent apoptosis signaling pathway.

Therapeutic applications of cannabinoids

The psychoactive property of cannabinoids is well known and there has been a continuous controversy regarding the usage of these compounds for therapeutic purposes all over the world. Their use for medical and research purposes are restricted in various countries. However, their utility as medications should not be overshadowed by its negative physiological activities. This review article is focused on the therapeutic potential and applications of phytocannabinoids and endocannabinoids. We further highlights their mode of action, overall effects on physiology, various in vitro and in vivo studies that have been done so far and the extent to which these compounds can be useful in different disease conditions such as cancer, Alzheimer's disease, multiple sclerosis, pain, inflammation, glaucoma and many others. Thus, this work is an attempt to make the readers understand the positive implications of these compounds and indicates the significant developments of utilizing cannabinoids as therapeutic agents.

Neuroprotection by (endo)Cannabinoids in Glaucoma and Retinal Neurodegenerative Diseases

BACKGROUND

Emerging neuroprotective strategies are being explored to preserve the retina from degeneration, that occurs in eye pathologies like glaucoma, diabetic retinopathy, age-related macular degeneration, and retinitis pigmentosa. Incidentally, neuroprotection of retina is a defending mechanism designed to prevent or delay neuronal cell death, and to maintain neural function following an initial insult, thus avoiding loss of vision.

METHODS

Numerous studies have investigated potential neuroprotective properties of plant-derived phytocannabinoids, as well as of their endogenous counterparts collectively termed endocannabinoids (eCBs), in several degenerative diseases of the retina. eCBs are a group of neuromodulators that, mainly by activating G protein-coupled type-1 and type-2 cannabinoid (CB1 and CB2) receptors, trigger multiple signal transduction cascades that modulate central and peripheral cell functions. A fine balance between biosynthetic and degrading enzymes that control the right concentration of eCBs has been shown to provide neuroprotection in traumatic, ischemic, inflammatory and neurotoxic damage of the brain.

RESULTS

Since the existence of eCBs and their binding receptors was documented in the retina of numerous species (from fishes to primates), their involvement in the visual processing has been demonstrated, more recently with a focus on retinal neurodegeneration and neuroprotection.

CONCLUSION

The aim of this review is to present a modern view of the endocannabinoid system, in order to discuss in a better perspective available data from preclinical studies on the use of eCBs as new neuroprotective agents, potentially useful to prevent glaucoma and retinal neurodegenerative diseases.

Neuroprotective effect of cannabinoid receptor 1 antagonist in the MNU-induced retinal degeneration model

Endocannabinoid system involves in neuroprotective effects on the central neural system. The cannabinoid receptor 1 (CB1R) is widely expressed in the mouse retina. However, the role of cannabinoid receptors in the retina remains unclear. In this work, we established a photoreceptor degeneration mouse model via N-methyl-N-nitrosourea (MNU) administration to identify the neuroprotective effects of cannabinoid receptors. The MNU-induced retinal degeneration behaves similarly to that in the human retinitis pigmentosa (RP). Administration of the CB1R antagonist SR141716A distinctly recovered the photoreceptor loss, decreased glial reactivity and reduced abnormal vascular complexes in an MNU-induced mouse model. The BC dendrites were shrunk in the MNU-treated retina with eliminated ON-BCs responses and partially diminished OFF-BCs responses in patch-clamp recordings. In the MNU + SR1 group, both the function and structure of ON-BCs recovered. Taken together, our study showed that the inhibition of CB1R can effectively prevent MNU-induced retinal degeneration, suggesting a potential therapeutic effect of the CB1R antagonist SR1 in retinal degeneration diseases.

Endocannabinoids exert CB1 receptor-mediated neuroprotective effects in models of neuronal damage induced by HIV-1 Tat protein

In the era of combined antiretroviral therapy (cART), human immunodeficiency virus type 1 (HIV-1) is considered a chronic disease that specifically targets the brain and causes HIV-1-associated neurocognitive disorders (HAND). Endocannabinoids (eCBs) elicit neuroprotective and anti-inflammatory actions in several central nervous system (CNS) disease models, but their effects in HAND remain unknown. HIV-1 does not infect neurons, but produces viral toxins, such as transactivator of transcription (Tat), that disrupt neuronal calcium equilibrium and give rise to synaptodendritic injuries and cell death, the former being highly correlated with HAND. Consequently, we tested whether the eCBs N-arachidonoylethanolamine (anandamide/AEA) and 2-arachidonoyl-glycerol (2-AG) offer neuroprotective actions in a neuronal culture model. Specifically, we examined the neuroprotective actions of these eCBs on Tat excitotoxicity in primary cultures of prefrontal cortex neurons (PFC), and whether cannabinoid receptors mediate this neuroprotection. Tat-induced excitotoxicity was reflected by increased intracellular calcium levels, synaptodendritic damage, neuronal excitability, and neuronal death. Further, upregulation of cannabinoid 1 receptor (CB₁R) protein levels was noted in the presence of HIV-1 Tat. The direct application of AEA and 2-AG reduced excitotoxic levels of intracellular calcium and promoted neuronal survival following Tat exposure, which was prevented by the CB₁R antagonist rimonabant, but not by the CB₂R antagonist AM630. Overall, our findings indicate that eCBs protect PFC neurons from Tat excitotoxicity in vitro via a CB₁R-related mechanism. Thus, the eCB system possesses promising targets for treatment of neurodegenerative disorders associated with HIV-1 infection.

N-stearoyltyrosine protects primary cortical neurons against oxygen-glucose deprivation-induced apoptosis through inhibiting anandamide inactivation system

N-stearoylthrosine (NST), a synthesized anandamide (AEA) analogue, plays a neuroprotective role in neurodegenerative diseases and cerebrovascular diseases. Several studies have demonstrated that the endocannabinoids systems (ECS) are involved in the neuroprotective effects against cerebral ischemic injury. Oxygen-glucose deprivation (OGD)-induced neuronal injury elevated the levels of endocannabinoids and activated ECS. This research was conducted to investigate the neuroprotective effect of NST against OGD-induced neuronal injury in cultured primary cortical neurons and the potential mechanism involved. Cortical neurons were treated with NST at indicate concentrations for 30min prior to injury and OGD injured neurons were incubated with normal conditions for 0-24h. The best neuroprotective effect of NST against OGD-induced injury occurred at 10μM. All data indicated that the neuroprotective effect of NST against OGD-induced injury resulted from blocking anandamide membrane transporter (AMT) (IC₅₀=11.74nM) and inhibiting fatty acid amide hydrolase activity (FAAH) (IC₅₀=16.54nM). Our findings demonstrated that NST has an important role in cerebral ischemic injury pathological progression through activating cannabinoid receptors by inhibiting AEA inactivation system. These data suggested a potential role for NST in the therapeutic consideration of cerebral ischemic injury. However, inhibition of AEA inactivation system may provide a neuroprotective effect during cerebral ischemic injury.

Neuroprotective effects of a novel peptide, FK18, under oxygen-glucose deprivation in SH-SY5Y cells and retinal ischemia in rats via the Akt pathway

Ischemic neuronal injury is associated with several life- and vision-threatening diseases. Neuroprotection is essential in the treatment of these diseases. Here, we identified and characterized a novel peptide, FK18, from basic fibroblast growth factor (bFGF). We further assessed the neuroprotective effects of this peptide and its potential mechanisms using the in vitro oxygen-glucose deprivation (OGD) model in SH-SY5Y cells and the in vivo retinal ischemia-reperfusion (I/R) injury model to mimic ischemic neuronal injury. Our results suggested that FK18 significantly increased the viability of and attenuated the apoptosis of SH-SY5Y cells. It also markedly alleviated I/R-induced retinal neuronal apoptosis, damage to retinal ganglion cells (RGCs), and morphological and functional damage to the retina. Moreover, FK18 increased Akt phosphorylation under both normoxic and OGD conditions, attenuated mitochondrial translocation of the proapoptotic protein Bad, up-regulated the expression of Bcl-2/Bax, and inhibited the release of cytochrome c from the mitochondria into the cytoplasm. These results suggested that FK18 is a novel neuroprotective agent that may serve as a prototype for neuroprotective drug development.

A Pulsed Electromagnetic Field Protects against Glutamate-Induced Excitotoxicity by Modulating the Endocannabinoid System in HT22 Cells

Glutamate-induced excitotoxicity is common in the pathogenesis of many neurological diseases. A pulsed electromagnetic field (PEMF) exerts therapeutic effects on the nervous system, but its specific mechanism associated with excitotoxicity is still unknown. We investigated the role of PEMF exposure in regulating glutamate-induced excitotoxicity through the endocannabinoid (eCB) system. PEMF exposure improved viability of HT22 cells after excitotoxicity and reduced lactate dehydrogenase release and cell death. An eCB receptor 1 (CB1R) specific inhibitor suppressed the protective effects of PEMF exposure, even though changes in CB1R expression were not observed. Elevation of N-arachidonylethanolamide (AEA) and 2-arachidonylglycerol (2-AG) following PEMF exposure indicated that the neuroprotective effects of PEMF were related to modulation of the eCB metabolic system. Furthermore, CB1R/ERK signaling was shown to be an important downstream pathway of PEMF in regulating excitotoxicity. These results suggest that PEMF exposure leads to neuroprotective effects against excitotoxicity by facilitating the eCB/CB1R/ERK signaling pathway. Therefore, PEMF may be a potential physical therapeutic technique for preventing and treating neurological diseases.

Tumor-promoting effects of cannabinoid receptor type 1 in human melanoma cells

The role of endocannabinoid system in melanoma development and progression is actually not fully understood. This study was aimed at clarifying whether cannabinoid-type 1 (CB1) receptor may function as tumor-promoting or -suppressing signal in human cutaneous melanoma. CB1 receptor expression was measured in human melanoma cell lines by real-time PCR. A genetic deletion of CB1 receptors in selected melanoma cells was carried out by using three different short hairpin RNAs (shRNAs). Performance of target gene silencing was verified by real-time PCR and Western blot. The effects of CB1 receptor silencing on cell growth, clonogenicity, migration capability, cell cycle progression, and activation of mitogenic signals was tested. Lentiviral shRNAs vectors targeting different regions of the human CB1 gene led to a significant reduction in CB1 receptor mRNA and a near complete loss of CB1 receptor protein, compared to control vector (LV-c). The number of viable cells, the colony-forming ability and cell migration were significantly reduced in cells transduced with CB1 lentiviral shRNAs compared to LV-c. Cell cycle analyses showed arrest at G1/S phase. p-Akt and p-ERK expression were decreased in transduced versus control cells. Findings of this study suggest that CB1 receptor might function as tumor-promoting signal in human cutaneous melanoma.

Cannabinoid receptors and TRPA1 on neuroprotection in a model of retinal ischemia

Retinal ischemia is a pathological event present in several retinopathies such as diabetic retinopathy and glaucoma, leading to partial or full blindness with no effective treatment available. Since synthetic and endogenous cannabinoids have been studied as modulators of ischemic events in the central nervous system (CNS), the present study aimed to investigate the involvement of cannabinoid system in the cell death induced by ischemia in an avascular (chick) retina. We observed that chick retinal treatment with a combination of WIN 55212-2 and cannabinoid receptor antagonists (either AM251/O-2050 or AM630) decreased the release of lactate dehydrogenase (LDH) induced by retinal ischemia in an oxygen and glucose deprivation (OGD) model. Further, the increased availability of endocannabinoids together with cannabinoid receptor antagonists also had a neuroprotective effect. Surprisingly, retinal exposure to any of these drugs alone did not prevent the release of LDH stimulated by OGD. Since cannabinoids may also activate transient receptor potential (TRP) channels, we investigated the involvement of TRPA1 receptors (TRPA1) in retinal cell death induced by ischemic events. We demonstrated the presence of TRPA1 in the chick retina, and observed an increase in TRPA1 content after OGD, both by western blot and immunohistochemistry. In addition, the selective activation of TRPA1 by mustard oil (MO) did not worsen retinal LDH release induced by OGD, whereas the blockage of TRPA1 completely prevented the extravasation of cellular LDH in ischemic condition. Hence, these results show that during the ischemic event there is an augment of TRPA1, and activation of this receptor is important in cell death induction. The data also indicate that metabotropic cannabinoid receptors, both type 1 and 2, are not involved with the cell death found in the early stages of ischemia. Therefore, the study points to a potential role of TRPA1 as a target for neuroprotective approaches in retinal ischemia.

Somatostatin receptor 5 is a prominent regulator of signaling pathways in cells with coexpression of Cannabinoid receptors 1

Endocannabinoids and somatostatin (SST) play critical roles in several pathophysiological conditions via binding to different receptor subtypes. Cannabinoid receptor 1 (CB1R) and somatostatin receptors (SSTRs) are expressed in several brain regions and share overlapping functions. Whether these two prominent members of G-protein-coupled receptor (GPCR) family interact with each other and constitute a functional receptor complex is not known. In the present study, we investigated the colocalization of CB1R and SSTR5 in rat brain, and studied receptor internalization, interaction and signal transduction pathways in HEK-293 cells cotransfected with human cannabinoid receptor 1 (hCB1R) and hSSTR5. Our results showed that CB1R and SSTR5 colocalized in rat brain cortex, striatum, and hippocampus. CB1R was expressed in SSTR5 immunoprecipitate prepared from the brain tissue lysate, indicating their association in a system where these receptors are endogenously expressed. In cotransfected HEK-293 cells, SSTR5 and CB1R existed in a constitutive heteromeric complex under basal condition, which was disrupted upon agonist treatments. Furthermore, concurrent receptor activation led to preferential formation of SSTR5 homodimer and dissociation of CB1R homodimer. We also discovered that second messenger cyclic adenosine monophosphate and downstream signaling pathways were modulated in a SSTR5-dominant and concentration-dependent manner in the presence of receptor-specific agonist. In conclusion, with predominant role of SSTR5, the functional consequences of crosstalk between SSTR5 and CB1R resulting in the regulation of receptor trafficking and signal transduction pathways open new therapeutic avenue in cancer biology and excitotoxicity.

Antidepressant effects of curcumin and HU-211 coencapsulated solid lipid nanoparticles against corticosterone-induced cellular and animal models of major depression

Major depression is a complex neuropsychiatric disorder with few treatment approaches. The use of nontargeted antidepressants induced many side effects with their low efficacy. A more precise targeting strategy is to develop nanotechnology-based drug delivery systems; hence, we employed solid lipid nanoparticles (SLNs) to encapsulate HU-211 and curcumin (Cur). The antidepressant effects of the dual-drug nanoparticles (Cur/SLNs-HU-211) for major depression treatment were investigated in corticosterone-induced cellular and animal models of major depression. Cur/SLNs-HU-211 can effectively protect PC12 cells from corticosterone-induced apoptosis and can release more dopamine, which may be associated with the higher uptake of Cur/SLNs-HU-211 shown by cellular uptake behavior analysis. Additionally, Cur/SLNs-HU-211 significantly reduced the immobility time in forced swim test, enhanced fall latency in rotarod test, and improved the level of dopamine in mice blood. Cur/SLNs-HU-211 can deliver more Cur to the brain and thus produce a significant increase in neurotransmitters level in brain tissue, especially in the hippocampus and striatum. The results of Western blot and immunofluorescence revealed that Cur/SLNs-HU-211 can significantly enhance the expression of CB1, p-MEK1, and p-ERK1/2. Our study suggests that Cur/SLNs-HU-211 may have great potential for major depression treatment.

The Timing of Raf/ERK and AKT Activation in Protecting PC12 Cells against Oxidative Stress

Acute brain injuries such as ischemic stroke or traumatic brain injury often cause massive neural death and irreversible brain damage with grave consequences. Previous studies have established that a key participant in the events leading to neural death is the excessive production of reactive oxygen species. Protecting neuronal cells by activating their endogenous defense mechanisms is an attractive treatment strategy for acute brain injuries. In this work, we investigate how the precise timing of the Raf/ERK and the AKT pathway activation affects their protective effects against oxidative stress. For this purpose, we employed optogenetic systems that use light to precisely and reversibly activate either the Raf/ERK or the AKT pathway. We find that preconditioning activation of the Raf/ERK or the AKT pathway immediately before oxidant exposure provides significant protection to cells. Notably, a 15-minute transient activation of the Raf/ERK pathway is able to protect PC12 cells against oxidant strike that is applied 12 hours later, while the transient activation of the AKT pathway fails to protect PC12 cells in such a scenario. On the other hand, if the pathways are activated after the oxidative insult, i.e. postconditioning, the AKT pathway conveys greater protective effect than the Raf/ERK pathway. We find that postconditioning AKT activation has an optimal delay period of 2 hours. When the AKT pathway is activated 30min after the oxidative insult, it exhibits very little protective effect. Therefore, the precise timing of the pathway activation is crucial in determining its protective effect against oxidative injury. The optogenetic platform, with its precise temporal control and its ability to activate specific pathways, is ideal for the mechanistic dissection of intracellular pathways in protection against oxidative stress.

Cannabinoids Occlude the HIV-1 Tat-Induced Decrease in GABAergic Neurotransmission in Prefrontal Cortex Slices

In the era of combined antiretroviral therapy (cART), human immunodeficiency virus type 1 (HIV-1) is now considered a chronic disease that specifically targets the brain and causes HIV-1-associated neurocognitive disorders (HAND). Endocannabinoids exhibit neuroprotective and anti-inflammatory properties in several central nervous system (CNS) disease models, but their effects in HAND are poorly understood. To address this issue, whole-cell recordings were performed on young (14-24 day old) C57BL/6J mice. We investigated the actions of the synthetic cannabinoid WIN55,212-2 (1 μM) and the endocannabinoid N-arachidonoyl ethanolamine (anandamide; AEA, 1 μM) in the presence of HIV-1 Tat on GABAergic neurotransmission in mouse prefrontal cortex (PFC) slices. We found a Tat concentration-dependent (5-50 nM) decrease in the frequency and amplitude of miniature inhibitory postsynaptic currents (mIPSCs). The cannabinoid 1 receptor (CB1R) antagonist rimonabant (1 μM) and zero extracellular calcium prevented the significant Tat-induced decrease in mIPSCs. Further, bath-applied WIN55,212-2 or AEA by itself, significantly decreased the frequency, but not amplitude of mIPSCs and/or spontaneous IPSCs (sIPSCs), and occluded a further downregulation of IPSCs by Tat. Pretreatment with rimonabant but not the CB2R antagonist AM630 (1 μM) prevented the WIN55,212-2- and AEA-induced decrease in IPSCs frequency without any further Tat effect. Results indicated a Tat-induced decrease in GABAergic neurotransmission, which was occluded by cannabinoids via a CB1R-related mechanism. Understanding the relationship between Tat toxicity and endocannabinoid signaling has the potential to identify novel therapeutic interventions to benefit individuals suffering from HAND and other cognitive impairments.

Endogenous and Synthetic Cannabinoids as Therapeutics in Retinal Disease

The functional significance of cannabinoids in ocular physiology and disease has been reported some decades ago. In the early 1970s, subjects who smoked Cannabis sativa developed lower intraocular pressure (IOP). This led to the isolation of phytocannabinoids from this plant and the study of their therapeutic effects in glaucoma. The main treatment of this disease to date involves the administration of drugs mediating either the decrease of aqueous humour synthesis or the increase of its outflow and thus reduces IOP. However, the reduction of IOP is not sufficient to prevent visual field loss. Retinal diseases, such as glaucoma and diabetic retinopathy, have been defined as neurodegenerative diseases and characterized by ischemia-induced excitotoxicity and loss of retinal neurons. Therefore, new therapeutic strategies must be applied in order to target retinal cell death, reduction of visual acuity, and blindness. The aim of the present review is to address the neuroprotective and therapeutic potential of cannabinoids in retinal disease.

Expression and Function of the Endocannabinoid System in the Retina and the Visual Brain

Endocannabinoids are important retrograde modulators of synaptic transmission throughout the nervous system. Cannabinoid receptors are seven transmembrane G-protein coupled receptors favoring G_i/o protein. They are known to play an important role in various processes, including metabolic regulation, craving, pain, anxiety, and immune function. In the last decade, there has been a growing interest for endocannabinoids in the retina and their role in visual processing. The purpose of this review is to characterize the expression and physiological functions of the endocannabinoid system in the visual system, from the retina to the primary visual cortex, with a main interest regarding the retina, which is the best-described area in this system so far. It will show that the endocannabinoid system is widely present in the retina, mostly in the through pathway where it can modulate neurotransmitter release and ion channel activity, although some evidence also indicates possible mechanisms via amacrine, horizontal, and Müller cells. The presence of multiple endocannabinoid ligands, synthesizing and catabolizing enzymes, and receptors highlights various pharmacological targets for novel therapeutic application to retinal diseases.

N-Oleoyl glycine, a lipoamino acid, stimulates adipogenesis associated with activation of CB1 receptor and Akt signaling pathway in 3T3-L1 adipocyte

Adipose tissue plays a vital role in the development of obesity and related diseases. The aim of the present study was to investigate the effects of N-Oleoyl glycine (OLGly), a lipoamino acid, on 3T3-L1 adipogenesis and to explore the likely mechanisms underlying this process. Lipid accumulation were evaluated using Oil Red O staining and triglyceride content assay. The mRNA expressions of cannabinoid receptors and the protein expressions of adipogenic genes and intracellular signaling pathway were determined by real-time quantitative PCR and western blot, respectively. The results indicated that OLGly itself, but not its degradation products, stimulated lipid accumulation and significantly increased adipogenic genes (PPARγ and aP2), in a dose- and time-dependent manner. Additionally, OLGly markedly increased the mRNA expression of CB1 receptor (CB1R) and the inhibition of CB1R by its antagonist SR141716 abolished the promotive effects of OLGly on lipid accumulation and the protein expression of PPARγ and aP2. Furthermore, OLGly increased the ratio of p-Akt/Akt and p-FoxO1/FoxO1, which could be reversed by SR141716. Moreover, OLGly-induced enhancement of adipogenesis, activation of insulin-mediated Akt signaling pathway and inactivation of FoxO1 were effectively blocked by Wortmannin, a specific PI3K/Akt inhibitor, indicating the essential role of Akt signaling pathway in the process of OLGly-stimulated 3T3-L1 adipogenesis. In conclusion, OLGly, a lipoamino acid, was able to promote 3T3-L1 adipogenesis through the activation of CB1 receptor and the enhancement of insulin-mediated Akt signaling pathway. These findings suggested the potential role of OLGly in increasing insulin sensitivity and suppressing obesity and diabetes.