Cannabinoids and the eye

Retinal pharmacodynamic and pharmacokinetic profile of cannabidiol in an in vivo model of retinal excitotoxicity

Cannabidiol (CBD) is one of the principal constituents of Cannabis Sativa with no psychoactive properties. CBD is a promising neuroprotective compound bearing anti-inflammatory and antioxidant properties. However, considering its low solubility, CBD delivery to the retina represents an unresolved issue. The first aim was to investigate the potential neuroprotective effects of CBD in an in vivo model of retinal excitotoxicity induced by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Rats underwent intravitreal co-injection of AMPA (42 nmol) and CBD (10-4 M). The neuroprotective effect of CBD was investigated with histology and immunohistochemical evaluation of inflammatory and oxidative stress biomarkers. CBD reversed the AMPA-induced total retinal, inner nuclear layer and inner plexiform layer shrinkage and loss of amacrine cells. Moreover, CBD decreased the AMPA induced number of cleaved caspase-3, Iba-1 and nitrotyrosine (NT) positive cells. Based on this evidence, we developed a nanotechnological formulation of CBD to overcome critical issues related to its eye delivery. Particularly, nanostructured lipid carriers (NLC) loaded with CBD were prepared, optimized and characterized. Due to the optimal physicochemical characteristics, CBD-NLC3 has been selected and the in vitro release profile has been investigated. Additionally, CBD-NLC3 was topically administered to rats, and retinal CBD levels were determined. CBD-NLC3 formulation, after a single topical administration, efficiently delivered CBD in the retina (Cmax = 98 ± 25.9 ng/mg; Tmax = 60 min), showing a high translational value. In conclusion, these findings showed a good PD/PK profile of CBD warranting further pre-clinical and clinical evaluation of the new formulation for the treatment of retinal degenerative diseases.

Neuroprotective Actions of Cannabinoids in the Bovine Isolated Retina: Role of Hydrogen Sulfide

Both hydrogen sulfide and endocannabinoids can protect the neural retina from toxic insults under in vitro and in vivo conditions. Purpose: The aim of the present study was two-fold: (a) to examine the neuroprotective action of cannabinoids [methanandamide and 2-arachidonyl glycerol (2-AG)] against hydrogen peroxide (H2O2)-induced oxidative damage in the isolated bovine retina and (b) to evaluate the role of endogenously biosynthesized hydrogen sulfide (H2S) in the inhibitory actions of cannabinoids on the oxidative stress in the bovine retina. Methods: Isolated neural retinas from cows were exposed to oxidative damage using H2O2 (100 µM) for 10 min. When used, tissues were pretreated with methanandamide (1 nM-100 nM) and 2-AG (1-10 µM) for 30 min before a 10 min treatment with H2O2 (100 µM). In some experiments, retinas were pretreated with inhibitors of the biosynthesis of H2S [cystathionine β-synthase/cystathionine γ-lyase (CBS/CSE), aminooxyacetic acid, AOAA 30 µM, or 3-mercaptopyruvate sulfurtransferase (3MST), α-keto-butyric acid, KBA 1 mM] and the CB1-receptor antagonist, AM251 (100 nM) for 30 min before treatment with methanandamide (1 nM-100 µM). Enzyme immunoassay measurement of 8-epi PGF2α (8-isoprostane) levels was performed to assess lipid peroxidation in retinal tissues. Results: In the presence of H2O2 (100 µM), methanandamide (1 nM-100 µM) and 2-AG (1-10 µM) significantly (p < 0.001) blocked the H2O2-induced elevation in 8-isoprostane levels in the isolated bovine retina. In the presence of the CB1 antagonist AM251 (100 nM), the effect of methanandamide (1 nM) on the H2O2-induced 8-isoprostane production was significantly (p < 0.001) attenuated. While AOAA (30 µM) had no significant (p > 0.05) effect on the inhibition of H2O2-induced oxidative stress elicited by methanandamide, KBA (1 mM) reversed the neuroprotective action of methanandamide. Conclusions: The cannabinoids, methanandamide and 2-AG can prevent H2O2-induced oxidative stress in the isolated bovine retina. The neuroprotective actions of cannabinoids are partially dependent upon the activation of the CB1 receptors and endogenous production of H2S via the 3-MST/CAT pathway.

Ocular effects of synthetic cannabinoids: a case-control study

OBJECTIVE

To evaluate the ocular effects of "Bonzai", a synthetic cannabinoid (SC), in seropositive and seronegative users.

METHODS

Sixty eyes of 60 consecutive male patients with a history of "Bonzai" use and 30 eyes of 30 age-matched male healthy controls were enrolled in this case-control study. Patients with past "Bonzai" use were grouped as seropositive (n:30) and seronegative (n:30) according to urine toxicology tests. All groups were compared for blood pressures, intraocular pressure, foveal and parafoveal retinal thicknesses, subfoveal and parafoveal choroidal thicknesses, measurements of the peripapillary retinal nerve fibre layer (RNFL), and macular ganglion cell complex (GCC), subfoveal total choroidal, luminal and stromal areas, and choroidal vascularity index (CVI).

RESULTS

No differences were noted in blood pressures between the groups (p > 0.05). The mean intraocular pressure was significantly lower in the seropositive group than in the other groups (p < 0.001). Foveal and retinal thicknesses, RNFL, and GCC measurements did not differ between the groups (p > 0.05). Subfoveal and parafoveal choroidal thicknesses and areas were lower in the seropositive group than in the other groups (p < 0.001, for all). CVI increased in both groups with "Bonzai" use compared to the control group (p < 0.001, for all).

CONCLUSIONS

This study indicates that intraocular pressure may decrease, and choroidal changes may be observed in SC users. Further clinical studies with a larger sample size, especially using purified SC for therapeutic purposes, are needed to confirm the present findings, and further histopathologic studies are required to clarify the changes in the choroid despite SC seronegativity.

CLINICAL TRIAL ID

NCT06235346.

Adverse Ocular Impact and Emerging Therapeutic Potential of Cannabis and Cannabinoids: A Narrative Review

Cannabis is the most used drug worldwide with an estimated 219 million users. This narrative review aims to explore the adverse effects and therapeutic applications of cannabis and cannabinoids on the eye, given its growing clinical and non-clinical uses. The current literature reports several adverse ocular effects of cannabis and cannabinoids, including eyelid tremor, ptosis, reduced corneal endothelial cell density, dry eyes, red eyes, and neuro-retinal dysfunction. Cannabinoids may transiently impair night vision, depth perception, binocular and monocular contrast sensitivity, and dynamic visual acuity. Cannabinoids are not currently considered a first-line treatment option for any ocular conditions. Δ-9-tetrahydrocannabinol been shown to result in short-term intraocular pressure reduction, but insufficient evidence to support its use in treating glaucoma exists. Potential therapeutic applications of cannabinoids include their use as a second-line agent for treatment-refractory blepharospasm, for dry eye disease given corneal anti-inflammatory properties, and for suppression of pendular nystagmus in individuals with multiple sclerosis, which all necessitate further research for informed clinical practices.

The synthetic cannabinoids menace: a review of health risks and toxicity

Synthetic cannabinoids (SCs) are chemically classified as psychoactive substances that target the endocannabinoid system in many body organs. SCs can initiate pathophysiological changes in many tissues which can be severe enough to damage the normal functionality of our body systems. The majority of SCs-related side effects are mediated by activating Cannabinoid Receptor 1 (CB1R) and Cannabinoid Receptor 2 (CB2R). The activation of these receptors can enkindle many downstream signalling pathways, including oxidative stress, inflammation, and apoptosis that ultimately can produce deleterious changes in many organs. Besides activating the cannabinoid receptors, SCs can act on non-cannabinoid targets, such as the orphan G protein receptors GPR55 and GPR18, the Peroxisome Proliferator-activated Receptors (PPARs), and the Transient receptor potential vanilloid 1 (TRPV1), which are broadly expressed in the brain and the heart and their activation mediates many pharmacological effects of SCs. In this review, we shed light on the multisystem complications found in SCs abusers, particularly discussing their neurologic, cardiovascular, renal, and hepatic effects, as well as highlighting the mechanisms that intermediate SCs-related pharmacological and toxicological consequences to provide comprehensive understanding of their short and long-term systemic effects.

Recent Insights into the Etiopathogenesis of Diabetic Retinopathy and Its Management

Purpose: Diabetic retinopathy (DR) is a microvascular retinal disease associated with chronic diabetes mellitus, characterized by the damage of blood vessels in the eye. It is projected to become the leading cause of blindness, given the increasing burden of the diabetic population worldwide. The diagnosis and management of DR pose significant challenges for physicians because of the involvement of multiple biochemical pathways and the complexity of ocular tissues. This review aims to provide a comprehensive understanding of the molecular pathways implicated in the pathogenesis of DR, including the polyo pathway, hexosamine pathway, protein kinase C (PKC), JAK/STAT signaling pathways, and the renin-angiotensin system (RAS). Methods: Academic databases such as PubMed, Scopus, Google Scholar and Web of Science was systematically searched using a carefully constructed search strategy incorporating keywords like "Diabetic Retinopathy," "Molecular Pathways," "Pharmacological Treatments," and "Clinical Trials" to identify relevant literature for the comprehensive review. Results: In addition to activating other inflammatory cascades, these pathways contribute to the generation of oxidative stress within the retina. Furthermore, it aims to explore the existing pharmacotherapy options available for the treatment of DR. In addition to conventional pharmacological therapies such as corticosteroids, antivascular endothelial growth factors, and nonsteroidal anti-inflammatory drugs (NSAIDs), this review highlights the potential of repurposed drugs, phyto-pharmaceuticals, and novel pipeline drugs currently undergoing various stages of clinical trials. Conclusion: Overall, this review serves as a technical exploration of the complex nature of DR, highlighting both established and emerging molecular pathways implicated in its pathogenesis. Furthermore, it delves into the available pharmacological treatments, as well as the promising repurposed drugs, phyto-pharmaceuticals, and novel drugs currently being evaluated in clinical trials, with a focus on their specific mechanisms of action.

Cannabinoids for the Treatment of Glaucoma: A Review

BACKGROUND

Glaucoma is an ocular disease with significant health burden. Despite the availability of many antiglaucoma drugs, a significant proportion of patients may experience worsening of the disease. Hence, there is a need for newer antiglaucoma drugs.

SUMMARY

Natural and synthetic derivatives of cannabis plants have been studied in the treatment of glaucoma since the 1970s. This review describes the potential mechanisms of the cannabinoids in the treatment of glaucoma, summarizes the findings of clinical studies describing the efficacy of these compounds, and describes the adverse effects observed with the various cannabinoid formulations evaluated in clinical studies of glaucoma in healthy volunteers and patients. The implications of these findings in terms of the potential clinical status of cannabinoids in the treatment of glaucoma and the challenges involved have also been described.

KEY MESSAGES

Cannabinoids lower intraocular pressure. However, the effect is short-lived. There is also a lack of well-formulated ocular delivery system. The available evidence is inadequate to recommend the use of cannabinoids for the routine treatment of glaucoma.

Cannabidiol nanoemulsion for eye treatment - Anti-inflammatory, wound healing activity and its bioavailability using in vitro human corneal substitute

Cannabidiol (CBD) is the non-psychoactive component of the plant Cannabis sativa (L.) that has great anti-inflammatory benefits and wound healing effects. However, its high lipophilicity, chemical instability, and extensive metabolism impair its bioavailability and clinical use. Here, we report on the preparation of a human cornea substitute in vitro and validate this substitute for the evaluation of drug penetration. CBD nanoemulsion was developed and evaluated for stability and biological activity. The physicochemical properties of CBD nanoemulsion were maintained during storage for 90 days under room conditions. In the scratch assay, nanoformulation showed significantly ameliorated wound closure rates compared to the control and pure CBD. Due to the lower cytotoxicity of nanoformulated CBD, a higher anti-inflammatory activity was demonstrated. Neither nanoemulsion nor pure CBD can penetrate the cornea after the four-hour apical treatment. For nanoemulsion, 94 % of the initial amount of CBD remained in the apical compartment while only 54 % of the original amount of pure CBD was detected in the apical medium, and 7 % in the cornea, the rest was most likely metabolized. In summary, the nanoemulsion developed in this study enhanced the stability and biological activity of CBD.

Therapeutic Potential of Cannabinoids in Glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide. To date, intraocular pressure (IOP) is the only modifiable risk factor in glaucoma treatment, but even in treated patients, the disease can progress. Cannabinoids, which have been known to lower IOP since the 1970s, have been shown to have beneficial effects in glaucoma patients beyond their IOP-lowering properties. In addition to the classical cannabinoid receptors CB1 and CB2, knowledge of non-classical cannabinoid receptors and the endocannabinoid system has increased in recent years. In particular, the CB2 receptor has been shown to mediate anti-inflammatory, anti-apoptotic, and neuroprotective properties, which may represent a promising therapeutic target for neuroprotection in glaucoma patients. Due to their vasodilatory effects, cannabinoids improve blood flow to the optic nerve head, which may suggest a vasoprotective potential and counteract the altered blood flow observed in glaucoma patients. The aim of this review was to assess the available evidence on the effects and therapeutic potential of cannabinoids in glaucoma patients. The pharmacological mechanisms underlying the effects of cannabinoids on IOP, neuroprotection, and ocular hemodynamics have been discussed.

The therapeutic potential of purified cannabidiol

The use of cannabidiol (CBD) for therapeutic purposes is receiving considerable attention, with speculation that CBD can be useful in a wide range of conditions. Only one product, a purified form of plant-derived CBD in solution (Epidiolex), is approved for the treatment of seizures in patients with Lennox-Gastaut syndrome, Dravet syndrome, or tuberous sclerosis complex. Appraisal of the therapeutic evidence base for CBD is complicated by the fact that CBD products sometimes have additional phytochemicals (like tetrahydrocannabinol (THC)) present, which can make the identification of the active pharmaceutical ingredient (API) in positive studies difficult. The aim of the present review is to critically review clinical studies using purified CBD products only, in order to establish the upcoming indications for which purified CBD might be beneficial. The areas in which there is the most clinical evidence to support the use of CBD are in the treatment of anxiety (positive data in 7 uncontrolled studies and 17 randomised controlled trials (RCTs)), psychosis and schizophrenia (positive data in 1 uncontrolled study and 8 RCTs), PTSD (positive data in 2 uncontrolled studies and 4 RCTs) and substance abuse (positive data in 2 uncontrolled studies and 3 RCTs). Seven uncontrolled studies support the use of CBD to improve sleep quality, but this has only been verified in one small RCT. Limited evidence supports the use of CBD for the treatment of Parkinson's (3 positive uncontrolled studies and 2 positive RCTs), autism (3 positive RCTs), smoking cessation (2 positive RCTs), graft-versus-host disease and intestinal permeability (1 positive RCT each). Current RCT evidence does not support the use of purified oral CBD in pain (at least as an acute analgesic) or for the treatment of COVID symptoms, cancer, Huntington's or type 2 diabetes. In conclusion, published clinical evidence does support the use of purified CBD in multiple indications beyond epilepsy. However, the evidence base is limited by the number of trials only investigating the acute effects of CBD, testing CBD in healthy volunteers, or in very small patient numbers. Large confirmatory phase 3 trials are required in all indications.

Green Smoke, Red Flag: Cannabis and the Risk of Orbitopathy and Dermopathy in Thyrotoxicosis

Background The use of cannabis has been associated with an array of multi-systemic physiological effects. However, the medical literature on the potential role of cannabinoids in the management and outcomes of thyrotoxicosis remains scarce. We studied the association between cannabis use and orbitopathy, dermopathy, and the length of hospital stay for thyrotoxicosis admissions. Methods A thorough analysis was conducted on adult hospitalizations in 2020 with a primary discharge diagnosis of thyrotoxicosis, using data from the Nationwide Inpatient Sample (NIS). To ensure data completeness and consistency, hospitalizations with missing or incomplete information, as well as those involving patients under 18 years of age, were excluded from the study. The remaining study sample was categorized into two groups based on the presence or absence of cannabis use, as determined by ICD-10-CM/PCS codes. Subtypes of orbitopathy, dermopathy, and potential confounding factors were identified based on previous literature and defined using validated ICD-10-CM/PCS codes. The association between cannabis use and the outcomes was evaluated using multivariate regression analysis. The primary focus was on thyroid orbitopathy, while dermopathy and the average length of hospital stay were considered as secondary outcomes. Results A total of 7,210 hospitalizations for thyrotoxicosis were included in the analysis. Among them, 404 (5.6%) were associated with cannabis use, while 6,806 (94.4%) were non-users serving as controls. Cannabis users were predominantly female (227, 56.3%), which was similar to the control group (5,263, 73%), and they were primarily of Black descent. Notably, the cohort of cannabis users was significantly younger than the control group (37.7 ± 1.3 vs. 63.6 ± 0.3). Upon conducting multivariate regression analysis, it was found that cannabis use was linked to a significant increase in the odds of orbitopathy among patients with thyrotoxicosis (AOR: 2.36; 95% CI: 1.12-4.94; P = 0.02). Additionally, a history of tobacco smoking was also correlated with higher odds of orbitopathy in the study (AOR: 1.21; 95% CI: 0.76-1.93; p = 0.04). However, no significant association was observed between cannabis use and the odds of dermopathy (AOR: 0.88; 95% CI: 0.51-1.54; p = 0.65) or the average length of hospital stay (IRR: 0.44; 95% CI: 0.58-1.46; p = 0.40). Conclusion The study identified a significant association between cannabis use and increased odds of orbitopathy in patients with thyrotoxicosis. Additionally, a history of tobacco smoking was also found to be correlated with augmented odds of orbitopathy.

TFOS Lifestyle: Impact of lifestyle challenges on the ocular surface

Many factors in the domains of mental, physical, and social health have been associated with various ocular surface diseases, with most of the focus centered on aspects of dry eye disease (DED). Regarding mental health factors, several cross-sectional studies have noted associations between depression and anxiety, and medications used to treat these disorders, and DED symptoms. Sleep disorders (both involving quality and quantity of sleep) have also been associated with DED symptoms. Under the domain of physical health, several factors have been linked to meibomian gland abnormalities, including obesity and face mask wear. Cross-sectional studies have also linked chronic pain conditions, specifically migraine, chronic pain syndrome and fibromyalgia, to DED, principally focusing on DED symptoms. A systematic review and meta-analysis reviewed available data and concluded that various chronic pain conditions increased the risk of DED (variably defined), with odds ratios ranging from 1.60 to 2.16. However, heterogeneity was noted, highlighting the need for additional studies examining the impact of chronic pain on DED signs and subtype (evaporative versus aqueous deficient). With respect to societal factors, tobacco use has been most closely linked to tear instability, cocaine to decreased corneal sensitivity, and alcohol to tear film disturbances and DED symptoms.

Cannabinoid-Based Ocular Therapies and Formulations

The interest in the pharmacological applications of cannabinoids is largely increasing in a wide range of medical areas. Recently, research on its potential role in eye conditions, many of which are chronic and/or disabling and in need of new alternative treatments, has intensified. However, due to cannabinoids’ unfavorable physicochemical properties and adverse systemic effects, along with ocular biological barriers to local drug administration, drug delivery systems are needed. Hence, this review focused on the following: (i) identifying eye disease conditions potentially subject to treatment with cannabinoids and their pharmacological role, with emphasis on glaucoma, uveitis, diabetic retinopathy, keratitis and the prevention of Pseudomonas aeruginosa infections; (ii) reviewing the physicochemical properties of formulations that must be controlled and/or optimized for successful ocular administration; (iii) analyzing works evaluating cannabinoid-based formulations for ocular administration, with emphasis on results and limitations; and (iv) identifying alternative cannabinoid-based formulations that could potentially be useful for ocular administration strategies. Finally, an overview of the current advances and limitations in the field, the technological challenges to overcome and the prospective further developments, is provided.

A review of cannabis allergy in the early days of legalization

Cannabis allergy is a burgeoning field; consequently, research is still in its infancy and allergists' knowledge surrounding this topic is limited. As cannabis legalization expands across the world, it is anticipated that there will be an increase in cannabis use. Thus, we hypothesize that a concomitant rise in the incidence of allergy to this plant can be expected. Initiatives aimed at properly educating health care professionals are therefore necessary. This review presents the most up-to-date information on a broad range of topics related to cannabis allergy. Although the clinical features of cannabis allergy are becoming more well described and recognized, the tools available to make a correct diagnosis are meager and often poorly accessible. In addition, research on cannabis allergy is still taking its first steps, and new and potentially groundbreaking findings in this field are expected to occur in the next few years. Finally, although therapeutic approaches are being developed, patient and physician education regarding cannabis allergy is certainly needed.

Cannabinoids as New Drug Candidates for the Treatment of Glaucoma

Glaucoma is a blinding eye disease that affects about 70 million patients globally today. The cannabinoid receptors and the endocannabinoid system have found attention for new drug concepts. This review will analyze the potential of cannabinoids, primarily tetrahydrocannabinol, THCVS, and cannabinol, as drug candidates and the role of CB1/CB2 receptors with regard to the pathophysiology of glaucoma. The mode of action of cannabinoids as innovative drug candidates and recent formulations for topical delivery will be discussed. Cannabinoid receptors with associated TRPV channels will be evaluated for their potential as drug targets. Especially the role of the endocannabinoid system (fatty acid amide hydrolase, monoacylglycerol lipase) impacting the prostaglandin network (cyclooxygenase, PGE, PGF) and neuroprotection by inhibition of nitric oxide radical formation is in the focus of this review. Delivery systems, including recent clinical trials, will be analyzed to evaluate the potential for innovative future ophthalmological drugs.

Cannabis smoking and age-related macular degeneration in the UK Biobank cohort

BACKGROUND

A major cause of blindness in older persons is age-related macular degeneration (AMD). Cigarette smoking is one of the major risk factors for AMD. In the present study, we analyzed UK Biobank data to determine whether smoking cannabis, like cigarettes, might be related to AMD.

METHODS

Our UK Biobank application was approved as UKB project 57245 (S.L., P.H.R.). Our analysis included all subjects with AMD and cannabis smoking information. The diagnosis of AMD was ascertained based on the 10th Revision of the International Classification of Diseases (ICD10), H35.3. Age at time of diagnosis of AMD was obtained from data field 5923. Cannabis information was recorded in UKB category 143, data field 20453, ever taken cannabis. A touch screen posed the question, "Have you taken CANNABIS (cannabis, grass, hash, ganja, blow, draw, skunk, weed, spliff, dope), even if it was a long time ago?" Possible answers were no, yes, 1-2 times, yes 3-10 times, yes, 11-100 times, yes, more than 100 times.

RESULTS

Subjects who had used marijuana more than 100 times had a significantly reduced risk of AMD, compared to subjects who had never used marijuana, and use of marijuana every day was associated with less AMD than use of marijuana less than once a month. But subjects who used cannabis 100 times or more were significantly younger (8years) when they developed AMD than subjects who never used cannabis.

CONCLUSION

Drusen, deposits of lipids, proteins, and cellular debris, accumulate in Bruch's membrane, limiting transport between the retinal pigment epithelium and the vasculature, triggering an inflammatory reaction. Marijuana can retard the inflammatory process because it is a powerful anti-inflammatory agent. Therefore, marijuana could reduce the risk of AMD. At the same time, blood vessels in the choriocapillaris below Bruch's membrane become more sparse with age. This phenomenon is believed to be a starting point for AMD. Marijuana can accelerate the loss of blood vessels due to its anti-angiogenic properties. Therefore, marijuana use might cause AMD to develop sooner in younger people.

MAGL inhibitor NanoMicellar formulation (MAGL-NanoMicellar) for the development of an antiglaucoma eye drop

The ocular endocannabinoid system (ECS) including enzymes and CB1/CB2 receptors determines various substantial effects, such as anti-inflammatory activity and reduction of the intraocular pressure (IOP). The modulation of 2-arachidonoylglycerol (2-AG) levels obtained via MAGL inhibition is considered as a promising pharmacological strategy to activate the ECS. Within the scope of this study, the effect of a selective monoacylglycerol lipase (MAGL) inhibitor (MAGL17b) was investigated by measuring the IOP reduction in normotensive rabbits after performing a solubilisation process of the molecule with non-ionic surfactants, to produce suitable eye drops containing the highest possible concentration of the drug. Furthermore, the study involved the evaluation of cytotoxicity and of in vitro/ex vivo corneal permeation of MAG17b of selected formulations based on polyoxyl(35)castor oil (C-EL) and polyethylene glycol (80) sorbitan monolaurate (TW80). The solubilisation of 0.5 mM MAGL17b with 3% w/w TW80 (TW80/3-17b), through the formation of NanoMicellar structures (diameter of 12.3 nm), determined a significant permeation of MAGL17b, both through excised rabbits corneas and reconstituted corneal epithelium, with a limited corneal epithelial cells death. The blockade of MAGL activity induced a IOP reduction up to 4 mmHg in albino and pigmented rabbits after topical instillation, thus confirming the potential efficacy of the MAGL inhibition approach in the treatment of ocular pathologies.

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.

Medical therapy for glaucoma: A review

A number of pharmacological targets are exploited to modify the parameters in the Goldmann equation and reduce the intraocular pressure (IOP). This strategy constitutes the foundation for the medical management of glaucoma, the evolution of which, until only recently, has been in relative stagnation. A burst of innovation has produced new ocular hypotensive drugs and long-acting delivery methods, including intracameral delivery, which are expanding the clinician's medical armamentarium. A number of IOP-independent neuroprotection strategies have shown strong potential in animal models of glaucoma, but translational attempts have been surprisingly limited. However, while pharmacological options are expanding, the traditional role of topical medical therapy is being challenged by selective laser trabeculoplasty, micro-invasive glaucoma surgery, and sustained delivery methods. A scientifically rigorous assessment of new treatments will be critical to empower clinicians with evidence-based information to optimise vision preservation and quality of life outcomes for their patients.

Recent developments of neuroprotective agents for degenerative retinal disorders

Retinal degeneration is a debilitating ocular complication characterized by the progressive loss of photoreceptors and other retinal neurons, which are caused by a group of retinal diseases affecting various age groups, and increasingly prevalent in the elderly. Age-related macular degeneration, diabetic retinopathy and glaucoma are among the most common complex degenerative retinal disorders, posing significant public health problems worldwide largely due to the aging society and the lack of effective therapeutics. Whilst pathoetiologies vary, if left untreated, loss of retinal neurons can result in an acquired degeneration and ultimately severe visual impairment. Irrespective of underlined etiology, loss of neurons and supporting cells including retinal pigment epithelium, microvascular endothelium, and glia, converges as the common endpoint of retinal degeneration and therefore discovery or repurposing of therapies to protect retinal neurons directly or indirectly are under intensive investigation. This review overviews recent developments of potential neuroprotectants including neuropeptides, exosomes, mitochondrial-derived peptides, complement inhibitors, senolytics, autophagy enhancers and antioxidants either still experimentally or in clinical trials. Effective treatments that possess direct or indirect neuroprotective properties would significantly lift the burden of visual handicap.

Cannabinoid Formulations and Delivery Systems: Current and Future Options to Treat Pain

The field of Cannabis sativa L. research for medical purposes has been rapidly advancing in recent decades and a growing body of evidence suggests that phytocannabinoids are beneficial for a range of conditions. At the same time impressing development has been observed for formulations and delivery systems expanding the potential use of cannabinoids as an effective medical therapy. The objective of this review is to present the most recent results from pharmaceutical companies and research groups investigating methods to improve cannabinoid bioavailability and to clearly establish its therapeutic efficacy, dose ranges, safety and also improve the patient compliance. Particular focus is the application of cannabinoids in pain treatment, describing the principal cannabinoids employed, the most promising delivery systems for each administration routes and updating the clinical evaluations. To offer the reader a wider view, this review discusses the formulation starting from galenic preparation up to nanotechnology approaches, showing advantages, limits, requirements needed. Furthermore, the most recent clinical data and meta-analysis for cannabinoids used in different pain management are summarized, evaluating their real effectiveness, in order also to spare opioids and improve patients' quality of life. Promising evidence for pain treatments and for other important pathologies are also reviewed as likely future directions for cannabinoids formulations.

Effects of acute stress, general anesthetics, tonometry, and temperature on intraocular pressure in rats

Intraocular pressure (IOP) is important for eye health as abnormal levels can led to ocular tissue damage. IOP is typically estimated by tonometry, which only provides snapshots of pressure history. Tonometry also requires subject cooperation and corneal contact that may influence IOP readings. The aim of this research was to investigate IOP dynamics of conscious animals in response to stressors, common anesthetics, tonometry, and temperature manipulations. An eye of male Brown-Norway rats was implanted with a fluid-filled cannula connected to a wireless telemetry system that records IOP continuously. Stress effects were examined by restricting animal movements. Anesthetic effects were examined by varying isoflurane concentration or injecting a bolus of ketamine. Tonometry effects were examined using applanation and rebound tonometers. Temperature effects were examined by exposing anesthetized and conscious animals to warm or cool surfaces. Telemetry recordings revealed that IOP fluctuates spontaneously by several mmHg, even in idle and anesthetized animals. Environmental disturbances also caused transient IOP fluctuations that were synchronous in recorded animals and could last over a half hour. Animal immobilization produced a rapid sustained elevation of IOP that was blocked by anesthetics, whereas little-to-no IOP change was detected in isoflurane- or ketamine-anesthetized animals if body temperature (BT) was maintained. IOP and BT decreased precipitously when heat support was not provided and were highly correlated during surface temperature manipulations. Surface temperature had no impact on IOP of conscious animals. IOP increased slightly during applanation tonometry but not rebound tonometry. The results show that IOP is dynamically modulated by internal and external factors that can activate rapidly and last long beyond the initiating event. Wireless telemetry indicates that animal interaction induces startle and stress responses that raise IOP. Anesthesia blocks these responses, which allows for better tonometry estimates of resting IOP provided that BT is controlled.

Lasting effects of prenatal exposure to Cannabis in the retina of the offspring: an experimental study in mice

Background

Prenatal exposure to Cannabis is a worldwide growing problem. Although retina is part of the central nervous system, the impact of maternal Cannabis use on the retinal development and its postnatal consequences remains unknown. As the prenatal period is potentially sensitive in the normal development of the retina, we hypothesized that recreational use of Cannabis during pregnancy may alter retina structure in the offspring. To test this, we developed a murine model that mimics human exposure in terms of dose and use.

Methods

Pregnant BalbC mice were exposed daily for 5 min to Cannabis smoke (0.2 g of Cannabis) or filtered air, from gestational day 5 to 18 (N = 10/group). After weaning period, pups were separated and examined weekly. On days 60, 120, 200, and 360 after birth, 10 pups from each group were randomly selected for Spectral Domain Optical Coherence Tomography (SD-OCT) analysis of the retina. All retina layers were measured and inner, outer, and total retina thickness were calculated. Other 37 mice from both groups were sacrificed on days 20, 60, and 360 for retinal stereology (total volume of the retina and volume fraction of each retinal layer) and light microscopy. Means and standard deviations were calculated and MANOVA was performed.

Results

The retina of animals which mother was exposed to Cannabis during gestation was 17% thinner on day 120 (young adult) than controls (P = 0.003) due to 21% thinning of the outer retina (P = 0.001). The offspring of mice from the exposed group presented thickening of the IS/OS in comparison to controls on day 200 (P < 0.001). In the volumetric analyzes by retinal stereology, the exposed mice presented transitory increase of the IS/OS total volume and volume fraction on day 60 (young adult) compared to controls (P = 0.008 and P = 0.035, respectively). On light microscopy, exposed mice presented thickening of the IS/OS on day 360 (adult) compared to controls (P = 0.03).

Conclusion

Gestational exposure to Cannabis smoke may cause structural changes in the retina of the offspring that return to normal on mice adulthood. These experimental evidences suggest that children and young adults whose mothers smoked Cannabis during pregnancy may require earlier and more frequent clinical care than the non-exposed population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40942-021-00314-8.

Change in Refractive Error Associated With the Use of Cannabidiol Oil

Cannabinoid (CBD) products have gained popularity since their legalization in 2018, causing a plethora of unregulated CBD products to be sold in the United States. These products are available in various combinations for topical and oral consumption, claiming credit for potentially improving various diseases. In this report, we present a newfound case reporting a shift in refraction that may be associated with the regular use of CBD oil supplements.

A 57-year-old woman with a history of diabetes mellitus type 2, hyperlipidemia, obstructive sleep apnea, with no change in medications, diet, or lifestyle was found to have a hyperopic shift in vision with the recent daily addition of CBD oil intake.

This case report highlights the possible association of CBD oil and vision changes after regular consumption of CBD oil in an otherwise stable patient. Further study is required to understand the mechanisms of CBD oil-associated shift in refractive error. Because the patient is diabetic and the refraction shift was hyperopic, other etiologies, such as un-noted lenticular change, cannot be ruled out. CBD products are unregulated and marketed in many mixed forms, and thus can cause unforeseen effects on susceptible individuals. This warrants Food and Drug Administration (FDA) regulation of such products and extensive research before considering them for therapeutic usage.

Cannabinoids in Glaucoma Patients: The Never-Ending Story

Glaucoma is one of the principal causes of irreversible blindness worldwide. Yet, intraocular pressure (IOP) is the main modifiable risk factor for disease progression. In the never-ending challenge to develop new and effective drugs, several molecules have been tested as anti-glaucoma agents thanks to their pressure-lowering capabilities. Among these molecules, the cannabinoids have been investigated as possible anti-glaucoma drugs since the early 1970s. Cannabinoids are a large class of chemical compounds that exploit their effects by interaction with cannabinoid receptors 1 and 2. These receptors are widely expressed in the human retina where they may influence important functions such as photo-transduction, amacrine cell network maintenance, and IOP regulation. Therefore, in past years several studies have been conducted in order to assess the IOP lowering effects of cannabinoids. PRISMA guidelines have been used to perform a literature search on Pubmed and Scopus aiming to investigate the mechanism of IOP lowering effects and the potential benefits of orally administered, inhaled, topical, and intravenous cannabinoids in the treatment of glaucoma patients.