Cannabinol modulates neuroprotection and intraocular pressure: A potential multi-target therapeutic intervention for glaucoma

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease

“Objectives: Glaucoma is characterized by progressive damage of the retinal ganglion cells (RGCs), resulting in irreversible vision loss. Cannabinoids (CBs) ameliorate several factors that contribute to the progression of glaucoma, including increased intraocular pressure (IOP), degeneration of RGC and optical nerve (ON) damage. However, a direct correlation of specific CBs with the molecular events pertaining to glaucoma pathology is not well established. Therefore, this study aims to evaluate the role of cannabinol (CBN) on RGC protection, modulation of IOP, and its effects on the level of extracellular matrix (ECM) proteins using both in vitro and in vivo models of glaucoma.

Methods and results: When exposed to elevated hydrostatic pressure, CBN, in a dose-dependent manner, protected differentiated mouse 661W retinal ganglion precursor-like cells from pressure-induced toxicity. In human trabecular meshwork cells (hTM), CBN attenuated changes in the ECM proteins, including fibronectin and α-smooth muscle actin (α-SMA), as well as mitogen-activated protein kinases (phospho-ERK1/2) in the presence or absence of transforming growth factor-beta 2 (TGF-β2) induced stress. Ocular pharmacokinetic parameters were evaluated post-intravitreal (IVT) CBN delivery in vivo. Furthermore, we demonstrated that IVT-administered CBN improved pattern electroretinogram (pERG) amplitudes and reduced IOP in a rat episcleral vein laser photocoagulation model of glaucoma.

Conclusion: CBN promotes neuroprotection, abrogates changes in ECM protein, and normalizes the IOP levels in the eye. Therefore, our observations in the present study indicate a therapeutic potential for CBN in the treatment of glaucoma.”

“These results suggest CBN as a potential therapeutic intervention for patients with glaucoma.”

Neuroprotection of retinal ganglion cells in vivo using the activation of the endogenous cannabinoid signaling system in mammalian eyes

Neuronal Signaling

“Cannabinoid and glutamatergic signaling systems in the human retina coexist and greatly influence one another. Under glaucomatous conditions, excess levels of glutamate accrete in the retinal ganglion cell (RGC) layer. The present study tests the putative neuroprotective effect mediated by cannabinoids at the CB1 and CB2 receptors. In the first experiment, mice were given intravitreal injections of 160 nmol N-methyl-d-aspartic acid (NMDA) in one eye and saline in the paired eye. In the second experiment, both eyes were given NMDA, while one of the two was additionally given the cannabinoid agonist WIN 55,212-2. Ten days later, animals were perfused and the retinae were dissected as wholemounts and stained with Cresyl Violet. Quantitative analysis revealed that 70% of the neurons in the retinal ganglion cell (RGC) layer exposed to NMDA underwent cell death. The addition of the cannabinoid CB1/CB2 agonist doubled the number of neurons surviving the NMDA treatment. These data provide evidence that cannabinoids, either exogenous or endogenous, may be harnessed to provide protection from neurodegenerative diseases, including glaucoma, and from glutamate-induced, and potentially other forms of neurotoxicity, under chronic or acute conditions.”

“In summary, we have demonstrated that the cannabimimetic drug, the CB1 and CB2 receptor agonist WIN55,212-2, acts to protect RGCs from NMDA-induced excitotoxicity in an in vivo mouse model. This further indicates the potential for therapeutic applications of cannabinoids in neurodegenerative diseases, including glaucoma.”

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.”

The Endocannabinoid System: A Potential Target for the Treatment of Various Diseases

ijms-logo“The Endocannabinoid System (ECS) is primarily responsible for maintaining homeostasis, a balance in internal environment (temperature, mood, and immune system) and energy input and output in living, biological systems.

In addition to regulating physiological processes, the ECS directly influences anxiety, feeding behaviour/appetite, emotional behaviour, depression, nervous functions, neurogenesis, neuroprotection, reward, cognition, learning, memory, pain sensation, fertility, pregnancy, and pre-and post-natal development.

The ECS is also involved in several pathophysiological diseases such as cancer, cardiovascular diseases, and neurodegenerative diseases. In recent years, genetic and pharmacological manipulation of the ECS has gained significant interest in medicine, research, and drug discovery and development.

The distribution of the components of the ECS system throughout the body, and the physiological/pathophysiological role of the ECS-signalling pathways in many diseases, all offer promising opportunities for the development of novel cannabinergic, cannabimimetic, and cannabinoid-based therapeutic drugs that genetically or pharmacologically modulate the ECS via inhibition of metabolic pathways and/or agonism or antagonism of the receptors of the ECS. This modulation results in the differential expression/activity of the components of the ECS that may be beneficial in the treatment of a number of diseases.

This manuscript in-depth review will investigate the potential of the ECS in the treatment of various diseases, and to put forth the suggestion that many of these secondary metabolites of Cannabis sativa L. (hereafter referred to as “C. sativa L.” or “medical cannabis”), may also have potential as lead compounds in the development of cannabinoid-based pharmaceuticals for a variety of diseases.”

Cannabis sativa L. as a Natural Drug Meeting the Criteria of a Multitarget Approach to Treatment

ijms-logo“Cannabis sativa L. turned out to be a valuable source of chemical compounds of various structures, showing pharmacological activity. The most important groups of compounds include phytocannabinoids and terpenes.

The pharmacological activity of Cannabis (in epilepsy, sclerosis multiplex (SM), vomiting and nausea, pain, appetite loss, inflammatory bowel diseases (IBDs), Parkinson’s disease, Tourette’s syndrome, schizophrenia, glaucoma, and coronavirus disease 2019 (COVID-19)), which has been proven so far, results from the affinity of these compounds predominantly for the receptors of the endocannabinoid system (the cannabinoid receptor type 1 (CB1), type two (CB2), and the G protein-coupled receptor 55 (GPR55)) but, also, for peroxisome proliferator-activated receptor (PPAR), glycine receptors, serotonin receptors (5-HT), transient receptor potential channels (TRP), and GPR, opioid receptors.

The synergism of action of phytochemicals present in Cannabis sp. raw material is also expressed in their increased bioavailability and penetration through the blood-brain barrier. This review provides an overview of phytochemistry and pharmacology of compounds present in Cannabis extracts in the context of the current knowledge about their synergistic actions and the implications of clinical use in the treatment of selected diseases.”

Flavonoid and cannabinoid impact on the ocular surface

 Media Kit - Current Opinion in Allergy and Clinical Immunology | Lippincott  Audience Solutions | Wolters Kluwer“Purpose of review: To evaluate the impact of flavonoids and cannabinoids as anti-inflammatory and antiallergic treatments on the anterior surface of the eye.

Recent findings: Allergic conjunctivitis and dry eye syndrome are common ocular surface diseases that have been treated with traditional pharmacological measures, e.g. corticosteroids, antihistamines. Given the side-effect profiles of these medications and the growing interest in complementary treatment modalities as part of integrative medical interventions, well known flavonoids, such as quercetin and catechin, are under investigation for topical and systemic application methods for relief. As flavonoid derivatives, pycnogenol and epigallocatechin gallate have alleviated dry eye symptoms, including lacrimal gland inflammation, tear secretion, and the stability of the tear film. Research on ocular cannabinoid receptors and response to synthetic cannabinoids are also being considered for therapy of anterior ocular disorders. The expansion of herbal formulations provides a framework for future treatment regimens for ocular surface disorders.

Summary: Flavonoids and cannabinoids show promise as potential complementary treatment for allergic diseases because of their anti-inflammatory and antiallergic properties. Several studies implementing ocular and systemic application of these compounds show potential in becoming adjuvant treatment strategies for improving quality of life while also managing ocular surface disease processes.”

Cannabis and the Cornea.

Publication Cover

“While cannabis has the potential to reduce corneal pain, cannabinoids might induce side effects. This review article examines the effects of cannabinoids on the cornea. As more states and countries consider the legalization of adult cannabis use, health-care providers will need to identify ocular effects of cannabis consumption.

Methods: Studies included in this review examined the connection between cannabis and the cornea, more specifically anti-nociceptive and anti-inflammatory actions of cannabinoids. NCBI Databases from 1781 up to December 2019 were consulted.

Conclusion: More than half of the studies examined the therapeutic effects of cannabinoids on the cornea. As the field is still young, more studies should be conducted to develop safe cannabinoid treatments for corneal diseases.

Allosteric Cannabinoid Receptor 1 (CB1) Ligands Reduce Ocular Pain and Inflammation.

molecules-logo“Cannabinoid receptor 1 (CB1) activation has been reported to reduce transient receptor potential cation channel subfamily V member 1 (TRPV1)-induced inflammatory responses and is anti-nociceptive and anti-inflammatory in corneal injury.

We examined whether allosteric ligands, can modulate CB1 signaling to reduce pain and inflammation in corneal hyperalgesia.

Corneal hyperalgesia was generated by chemical cauterization of cornea in wildtype and CB2 knockout (CB2-/-) mice. The novel racemic CB1 allosteric ligand GAT211 and its enantiomers GAT228 and GAT229 were examined alone or in combination with the orthosteric CB1 agonist Δ8-tetrahydrocannabinol (Δ8-THC). Pain responses were assessed following capsaicin (1 µM) stimulation of injured corneas at 6 h post-cauterization. Corneal neutrophil infiltration was also analyzed. GAT228, but not GAT229 or GAT211, reduced pain scores in response to capsaicin stimulation.

Combination treatments of 0.5% GAT229 or 1% GAT211 with subthreshold Δ8-THC (0.4%) significantly reduced pain scores following capsaicin stimulation. The anti-nociceptive effects of both GAT229 and GAT228 were blocked with CB1 antagonist AM251, but remained unaffected in CB2-/- mice. Two percent GAT228, or the combination of 0.2% Δ8-THC with 0.5% GAT229 also significantly reduced corneal inflammation.

CB1 allosteric ligands could offer a novel approach for treating corneal pain and inflammation.”

The effect of orally administered dronabinol on optic nerve head blood flow in healthy subjects- a randomized clinical trial.

Publication cover image“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 twenty-four healthy subjects. For each study participant, two study days were scheduled, on which they either received capsules containing 5mg dronabinol or placebo. ONHBF was measured with laser Doppler flowmetry at rest and while the study participants performed isometric exercise for six minutes to increase mean arterial blood pressure (MAP). This was repeated one 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 glaucoma patients.”

Effects of Cannabis and Its Components on the Retina: A Systematic Review.

 Publication Cover“Cannabis is the most prevalent drug in the world and its consumption is growing. Cannabinoid receptors are present in the human central nervous system. Recent studies show evidence of the effects of cannabinoids on the retina, and synthesizing the results of these studies may be relevant for ophthalmologists. Thus, this review adopts standardized, systematic review methodology to investigate the effects of exposure to cannabis and components on the retina.


We retrieved 495 studies, screened 229 studies, assessed 52 studies for eligibility, and included 16 studies for qualitative analysis. The cannabinoids most frequently investigated were delta-9-tetrahydrocannabinol (THC), abnormal cannabidiol, synthetic cannabinoid, and cannabidiol (CDB). The outcomes most studied were neuroretinal dysfunction, followed by vascular effects. The studies also included investigation of neuroprotective and anti-inflammatory effects and teratogenic effects.


This review suggests that cannabinoids may have an important role in retinal processing and function.”