A preliminary study of the neuroprotective role of citicoline eye drops in glaucomatous optic neuropathy

Addressing neurodegeneration in glaucoma: Mechanisms, challenges, and treatments

Glaucoma is the leading cause of irreversible blindness globally. The disease causes vision loss due to neurodegeneration of the retinal ganglion cell (RGC) projection to the brain through the optic nerve. Glaucoma is associated with sensitivity to intraocular pressure (IOP). Thus, mainstay treatments seek to manage IOP, though many patients continue to lose vision. To address neurodegeneration directly, numerous preclinical studies seek to develop protective or reparative therapies that act independently of IOP. These include growth factors, compounds targeting metabolism, anti-inflammatory and antioxidant agents, and neuromodulators. Despite success in experimental models, many of these approaches fail to translate into clinical benefits. Several factors contribute to this challenge. Firstly, the anatomic structure of the optic nerve head differs between rodents, nonhuman primates, and humans. Additionally, animal models do not replicate the complex glaucoma pathophysiology in humans. Therefore, to enhance the success of translating these findings, we propose two approaches. First, thorough evaluation of experimental targets in multiple animal models, including nonhuman primates, should precede clinical trials. Second, we advocate for combination therapy, which involves using multiple agents simultaneously, especially in the early and potentially reversible stages of the disease. These strategies aim to increase the chances of successful neuroprotective treatment for glaucoma.

Efficacy of citicoline as a supplement in glaucoma patients: A systematic review

PURPOSE

Glaucoma is a leading cause of irreversible blindness worldwide. Retinal ganglion cells (RGC), the neurons that connect the eyes to the brain, specifically die in glaucoma, leading to blindness. Elevated intraocular pressure (IOP) is the only modifiable risk factor, however, many patients progress despite excellent IOP control. Thus, alternative treatment strategies to prevent glaucoma progression are an unmet need. Citicoline has demonstrated neuroprotective properties in central neurodegenerative diseases. However, conclusive evidence of the effect of citicoline on glaucoma progression is missing. This systematic review investigates first-time the therapeutic potential of citicoline in glaucoma patients.

METHODS

The present study was conducted according to the PRISMA 2020 statement. PubMed, Web of Science, Google Scholar, and Embase were accessed in July 2023 to identify all clinical studies investigating the efficacy of citicoline on IOP, the mean deviation of the 24-2 visual field testing (MD 24-2), retinal nerve fibre layer (RNFL), and the pattern electroretinogram (PERG) P50-N95 amplitude in glaucoma patients. The risk of bias was assessed using the Review Manager 5.3 software (The Nordic Cochrane Collaboration, Copenhagen) and the Risk of Bias in Non-randomised Studies of Interventions (ROBINS-I) tool.

RESULTS

Ten studies were eligible for this systematic review, including 424 patients. The mean length of the follow-up was 12.1 ± 11.6 months. The overall risk of bias was low to moderate. The mean age of the patients was 56.7 years. There were no significant differences in the IOP, MD 24-2, RNFL, or PERG P50-N95 amplitude between patients receiving citicoline and the control group. There was no improvement from baseline to the last follow-up in IOP, MD 24-2, RNFL, or PERG P50-N95 amplitude.

CONCLUSION

There is a lack of sufficient evidence to support that citicoline slows the progression of glaucoma.

Cholinergic modulation of sensory perception and plasticity

Sensory systems are highly plastic, but the mechanisms of sensory plasticity remain unclear. People with vision or hearing loss demonstrate significant neural network reorganization that promotes adaptive changes in other sensory modalities as well as in their ability to combine information across the different senses (i.e., multisensory integration. Furthermore, sensory network remodeling is necessary for sensory restoration after a period of sensory deprivation. Acetylcholine is a powerful regulator of sensory plasticity, and studies suggest that cholinergic medications may improve visual and auditory abilities by facilitating sensory network plasticity. There are currently no approved therapeutics for sensory loss that target neuroplasticity. This review explores the systems-level effects of cholinergic signaling on human visual and auditory perception, with a focus on functional performance, sensory disorders, and neural activity. Understanding the role of acetylcholine in sensory plasticity will be essential for developing targeted treatments for sensory restoration.

The Role of Citicoline and Coenzyme Q10 in Retinal Pathology

Ocular neurodegenerative diseases such as glaucoma, diabetic retinopathy, and age-related macular degeneration are common retinal diseases responsible for most of the blindness causes in the working-age and elderly populations in developed countries. Many of the current treatments used in these pathologies fail to stop or slow the progression of the disease. Therefore, other types of treatments with neuroprotective characteristics may be necessary to allow a more satisfactory management of the disease. Citicoline and coenzyme Q10 are molecules that have neuroprotective, antioxidant, and anti-inflammatory properties, and their use could have a beneficial effect in ocular neurodegenerative pathologies. This review provides a compilation, mainly from the last 10 years, of the main studies that have been published on the use of these drugs in these neurodegenerative diseases of the retina, analyzing the usefulness of these drugs in these pathologies.

Nanocarriers for the Delivery of Neuroprotective Agents in the Treatment of Ocular Neurodegenerative Diseases

Retinal neurodegeneration is considered an early event in the pathogenesis of several ocular diseases, such as diabetic retinopathy, age-related macular degeneration, and glaucoma. At present, there is no definitive treatment to prevent the progression or reversal of vision loss caused by photoreceptor degeneration and the death of retinal ganglion cells. Neuroprotective approaches are being developed to increase the life expectancy of neurons by maintaining their shape/function and thus prevent the loss of vision and blindness. A successful neuroprotective approach could prolong patients' vision functioning and quality of life. Conventional pharmaceutical technologies have been investigated for delivering ocular medications; however, the distinctive structural characteristics of the eye and the physiological ocular barriers restrict the efficient delivery of drugs. Recent developments in bio-adhesive in situ gelling systems and nanotechnology-based targeted/sustained drug delivery systems are receiving a lot of attention. This review summarizes the putative mechanism, pharmacokinetics, and mode of administration of neuroprotective drugs used to treat ocular disorders. Additionally, this review focuses on cutting-edge nanocarriers that demonstrated promising results in treating ocular neurodegenerative diseases.

Citicoline: pharmacological and clinical review, 2022 update

This review is based on the previous one published in 2016 (Secades JJ. Citicoline: pharmacological and clinical review, 2016 update. Rev Neurol 2016; 63 (Supl 3): S1-S73), incorporating 176 new references, having all the information available in the same document to facilitate the access to the information in one document. This review is focused on the main indications of the drug, as acute stroke and its sequelae, including the cognitive impairment, and traumatic brain injury and its sequelae. There are retrieved the most important experimental and clinical data in both indications.

Neuroprotection in Glaucoma: Basic Aspects and Clinical Relevance

Glaucoma is a neurodegenerative disease that affects primarily the retinal ganglion cells (RGCs). Increased intraocular pressure (IOP) is one of the major risk factors for glaucoma. The mainstay of current glaucoma therapy is limited to lowering IOP; however, controlling IOP in certain patients can be futile in slowing disease progression. The understanding of potential biomolecular processes that occur in glaucomatous degeneration allows for the development of glaucoma treatments that modulate the death of RGCs. Neuroprotection is the modification of RGCs and the microenvironment of neurons to promote neuron survival and function. Numerous studies have revealed effective neuroprotection modalities in animal models of glaucoma; nevertheless, clinical translation remains a major challenge. In this review, we select the most clinically relevant treatment strategies, summarize preclinical and clinical data as well as recent therapeutic advances in IOP-independent neuroprotection research, and discuss the feasibility and hurdles of each therapeutic approach based on possible pathogenic mechanisms. We also summarize the potential therapeutic mechanisms of various agents in neuroprotection related to glutamate excitotoxicity.

Citicoline Eye Drops Protect Trabecular Meshwork Cells from Oxidative Stress Injury in a 3D In Vitro Glaucoma Model

Intraocular pressure (IOP) is considered an important modifiable risk factor for glaucoma, which is known as the second leading cause of blindness worldwide. However, lowering the IOP is not always sufficient to preserve vision due to other non-IOP-dependent mechanisms being involved. To improve outcomes, adjunctive therapies with IOP-independent targets are required. To date, no studies have shown the effect of citicoline on the trabecular meshwork (TM), even though it is known to possess neuroprotective/enhancement properties and multifactorial mechanisms of action. Given that reactive oxygen species seem to be involved in glaucomatous cascade, in this present study, an advanced millifluidic in vitro model was used to evaluate if citicoline could exert a valid TM protection against oxidative stress. To this end, the cellular behavior, in terms of viability, apoptosis, mitochondrial state, senescence and pro-inflammatory cytokines, on 3D human TM cells, treated either with H₂O₂ alone or cotreated with citicoline, was analyzed. Our preliminary in vitro results suggest a counteracting effect of citicoline eye drops against oxidative stress on TM cells, though further studies are necessary to explore citicoline’s potential as a TM-target therapy.

Citicoline and Vitamin B12 Eye Drops in Type 1 Diabetes: Results of a 36-Month Pilot Study Evaluating Macular Electrophysiological Changes

Introduction

Our aim was to evaluate the effects of 36 months of treatment with citicoline and vitamin B₁₂ eye drops on macular function in patients with type 1 diabetes (DM1) with mild signs of non-proliferative diabetic retinopathy (NPDR).

Methods

A prospective, randomized, interventional, monocentric, double-masked study was conducted. Twenty patients with DM1 were enrolled and randomly divided into two groups: the DC group (10 patients; mean age ± standard deviation 46.86 ± 8.78 years) in which one eye of each patient was treated with citicoline and vitamin B₁₂ eye drops (OMK2^®, Omikron Italia srl, Italy, one drop thrice daily) for a period of 36 months; the DP group (10 patients; mean age ± standard deviation 47.89 ± 7.74 years) in which one eye of each patient was treated with placebo (eye drops containing hypromellose 0.3%, one drop thrice daily) for a period of 36 months. A total of 18 eyes (10 from the DP and 8 from the DC group, respectively) completed the study. In both groups, multifocal electroretinogram (mfERG) recordings were assessed at baseline and after 36 months. In mfERG analysis, the N1–P1 response amplitude density (RAD) evaluated in the 0–2.5° (ring 1), in the 2.5–5° (ring 2), in the 5–10° (ring 3), and in the 0–10° (ring 1 + ring 2 + ring 3) were considered.

Results

With respect to baseline, after 36 months of follow-up, the mfERG RADs recorded in R1, R2, R3, and R1 + R2 + R3 were significantly increased (i.e., R1 + R2 + R3 RAD from 21.552 ± 2.522 nV/degree² at baseline to 26.912 ± 2.850 nV/degree² at 36 months) in DC eyes, whereas in DP eyes they were significantly reduced (i.e., R1 + R2 + R3 RAD from 21.033 ± 3.574 nV/degree² at baseline to 16.151 ± 3.571 nV/degree² at 36 months).

Conclusions

This study indicates that patients with NPDR treated with citicoline and vitamin B₁₂ eye drops for a 36-month period achieved an improvement of the macular bioelectrical responses detectable by mfERG recordings. By contrast, during the same period of follow-up, patients with NPDR treated with placebo showed a worsening of the macular function.

Protective effects of citicoline-containing eye drops against UVB-Induced corneal oxidative damage in a rat model

It has been reported that citicoline increases antioxidant activity in some tissues. However, the effect of citicoline on corneal wound-healing has not yet been demonstrated. The aim was to investigate the protective effects of citicoline on ultraviolet B (UVB) radiation-induced corneal oxidative damage in a rat model. Four groups (eight animals each) were investigated: controls; UVB only; UVB/citicoline; and citicoline only. Corneal oxidative damage was induced by exposure to UVB radiation at 560 μW/cm² for five days in the UVB-exposed groups and 1% citicoline eye drops were applied (3xday) for eight days in the two citicoline groups. Corneal surface damage was evaluated by opacity and fluorescein staining. Corneal injury was assessed biochemically by measuring the concentrations of glutathione (GSH) and malondialdehyde (MDA) and the activity of corneal superoxide dismutase (SOD) and catalase. Matrix metalloproteinase (MMP) -2 and -9 and caspase-3 were evaluated by immunofluorescent staining and microscopic examination and by Western blot analysis. Corneal gene expression analysis was performed for vascular endothelial growth factor (VEGF), interleukin-1 beta (IL-1β) and transforming growth factor-beta (TGF-β). UVB radiation caused significant epithelial damage and evident opacity in the cornea, together with a local decrease in SOD, catalase and GSH activity. Corneal MDA concentrations increased with UVB exposure. The UVB/Citicoline group had significantly less corneal damage, greater SOD, catalase and GSH activity, and decreased MDA concentrations compared to the UVB only group (p < 0.05). Expression of TGF-β, IL-1β and VEGF was significantly lower in the citicoline/UVB group compared to the UVB group (p < 0.05). Interestingly, TGF-β expression was lower in the citicoline only group compared with controls. Immunfluorescent staining and Western blot analysis showed increased MMP-2, -9 and caspase-3 in the UVB only group compared with the UVB/citicoline group. It was shown that citicoline treatment may be effective in suppressing oxidative stress and controlling inflammation in UVB corneal injury.

Citicoline Modulates Glaucomatous Neurodegeneration Through Intraocular Pressure-Independent Control

Glaucoma is a neurodegenerative disease that causes progressive, irreversible vision loss. Currently, intraocular pressure (IOP) is the only modifiable risk factor for glaucoma. However, glaucomatous degeneration may continue despite adequate IOP control. Therefore, there exists a need for treatment that protects the visual system, independent of IOP. This study sought, first, to longitudinally examine the neurobehavioral effects of different magnitudes and durations of IOP elevation using multi-parametric magnetic resonance imaging (MRI), optokinetics and histology; and, second, to evaluate the effects of oral citicoline treatment as a neurotherapeutic in experimental glaucoma. Eighty-two adult Long Evans rats were divided into six groups: acute (mild or severe) IOP elevation, chronic (citicoline-treated or untreated) IOP elevation, and sham (acute or chronic) controls. We found that increasing magnitudes and durations of IOP elevation differentially altered structural and functional brain connectivity and visuomotor behavior, as indicated by decreases in fractional anisotropy in diffusion tensor MRI, magnetization transfer ratios in magnetization transfer MRI, T1-weighted MRI enhancement of anterograde manganese transport, resting-state functional connectivity, visual acuity, and neurofilament and myelin staining along the visual pathway. Furthermore, 3 weeks of oral citicoline treatment in the setting of chronic IOP elevation significantly reduced visual brain integrity loss and visual acuity decline without altering IOP. Such effects sustained after treatment was discontinued for another 3 weeks. These results not only illuminate the close interplay between eye, brain, and behavior in glaucomatous neurodegeneration, but also support a role for citicoline in protecting neural tissues and visual function in glaucoma beyond IOP control.

Citicoline in Ophthalmological Neurodegenerative Disease: A Comprehensive Review

Cytidine 5'-diphosphocholine has been widely studied in systemic neurodegenerative diseases, like Alzheimer's disease, Parkinson's disease, and brain ischemia. The rationale for the use of citicoline in ophthalmological neurodegenerative diseases, including glaucoma, anterior ischemic optic neuropathy, and diabetic retinopathy, is founded on its multifactorial mechanism of action and the involvement in several metabolic pathways, including phospholipid homeostasis, mitochondrial dynamics, as well as cholinergic and dopaminergic transmission, all being involved in the complexity of the visual transmission. This narrative review is aimed at reporting both pre-clinical data regarding the involvement of citicoline in such metabolic pathways (including new insights about its role in the intracellular proteostasis through an interaction with the proteasome) and its effects on clinical psychophysical, electrophysiological, and morphological outcomes following its use in ophthalmological neurodegenerative diseases (including the results of the most recent prospective randomized clinical trials).

[The role of citicoline in glaucoma]

Hintergrund

In den letzten Jahren wurde in vielen experimentellen und klinischen Studien gezeigt, dass bei der Glaukomerkrankung die neuronale Degeneration nicht nur auf der Höhe von Netzhaut und Sehnerv, sondern im Verlauf der gesamten Sehbahn und des Gehirns erfolgt.

Fragestellung

Dargestellt werden die neuroprotektive Wirkung und ihre Mechanismen von Citicolin bei der Glaukomerkrankung.

Material und Methode

Vor dem Hintergrund der Neuroanatomie, des Neuroimaging und der Pathogenese der Glaukomerkrankung wird die Relevanz erläutert. Die Daten der experimentellen und klinischen Studien werden dargelegt und ein Fazit für die klinische Anwendung gezogen.

Ergebnisse

Citicolin wirkt neuroprotektiv über glaukomrelevante Mechanismen. Die neuroprotektive Wirkung von Citicolin bei Offenwinkelglaukomen ist funktionell und morphologisch nachweisbar. Sie ist unabhängig vom Glaukomschaden und Augeninnendruck und tritt i. d. R. erst nach einem Jahr auf. Die Effekte von oralem Citicolin treten bei einer Tagesdosis von 500–1000 mg auf. Die Einnahme von Citicolin kann dauerhaft oder in Zyklen erfolgen. In den Studien traten bei der Einnahme von Citicolin keine Nebenwirkungen auf. Citicolin kann kognitive Leistungen und somit Therapieadhärenz sowie die Lebensqualität bei Glaukompatienten verbessern

Schlussfolgerung

Diese relativ alte nootrope Substanz, welche jetzt als Nahrungsergänzungsmittel vertrieben wird, scheint eine wertvolle Ergänzung zur konventionellen Therapie der Glaukomerkrankung und eine rationale Option zur Neuroprotektion und Prophylaxe zu sein.

Can Treatment With Citicoline Eyedrops Reduce Progression in Glaucoma? The Results of a Randomized Placebo-controlled Clinical Trial

Precis:

Citicoline eyedrops in patients with progressing glaucoma.

Purpose:

This study aimed to test whether the additional therapy with citicoline eyedrops to intraocular pressure (IOP)-lowering treatment could slow glaucoma progression in patients with worsening of damage and IOP 18 mm Hg or less.

Design:

This was a randomized, double-masked, placebo-controlled, multicenter 3-year study.

Outcomes:

The outcomes studied were difference in the visual field (mean deviation, MD, of 24-2; MD of 10-2) rates of progression and difference in retinal nerve fiber layer (RNFL) thickness change between the 2 study groups at 3 years.

Methods:

Patients with mild to moderate open-angle glaucoma (OAG) showing damage progression of at least −0.5 dB/y in the 2 years before enrollment despite IOP ≤18 mm Hg were randomized to receive citicoline eyedrops or placebo 3 times daily for 3 years. Patients were followed every 3 months and underwent a visual field examination with 24-2 and 10-2 strategies and RNFL assessment. Analysis of variance and linear models were used to test the differences between groups.

Results:

Eighty patients were randomized in the trial. The mean 3-year rates of progression were −1.03 (2.14) dB in the citicoline group and −1.92 (2.23) dB in the placebo group (P=0.07) for 24-2 MD and −0.41 (3.45) dB in the citicoline group and −2.22 (3.63) dB in the placebo group (P=0.02) for 10-2 MD. On average, patients receiving citicoline eyedrops lost 1.86 μm of RNFL in 3 years, versus 2.99 μm in the placebo group (P=0.02).

Conclusions:

Additional treatment with citicoline eyedrops to IOP-lowering treatment might reduce disease progression in patients with progressing glaucoma despite IOP ≤18 mm Hg.

Neuroprotective Effect of Citicoline Eye Drops on Corneal Sensitivity After LASIK

PURPOSE

To evaluate the accelerator role of a topically administered neuroprotective eye drop (citicoline) on the recovery of corneal sensitivity after laser in situ keratomileusis (LASIK).

METHODS

In this prospective, controlled study, 78 eyes of 78 patients (mean age: 26.8 ± 7.6 years) were enrolled in the study group and their eyes were treated with topical citicoline three times a day for 1 month postoperatively. Seventy-eight eyes of 78 patients (mean age: 26.1 ± 7.4 years) were randomly selected as the control group and their eyes were treated with lubricant hyaluronic acid (0.15%) eye drops three times a day for 1 month. Corneal sensitivity was assessed in both groups using a Cochet-Bonnet esthesiometer at baseline and 1, 2, 3, 4, 6, 8, and 12 weeks after the LASIK procedure.

RESULTS

Corneal sensitivity at 1, 2, 3, 4, and 6 weeks after LASIK was significantly better in the citicoline group than the control group (P < .05 for all). Differences between the groups at 8 and 12 weeks after LASIK were not significant (P > .05).

CONCLUSIONS

Topically administered citicoline eye drops had beneficial effects in the early recovery of corneal sensitivity during the first 6 weeks after LASIK, suggesting that citicoline may play a significant role in accelerating corneal reinnervation. [J Refract Surg. 2019;35(12):764-770.].

Effect of neuroprotective citicoline eye drops on macular microcirculation

BACKGROUND AND OBJECTIVE

To use optical coherence tomography (OCTA) examination of the retinal microvascular structures to evaluate the effect of neuroprotective eye drops (citicoline, OMK1^®) administered for laser in situ keratomileusis (LASIK) surgery.

PATIENTS AND METHODS

This prospective study included 45 patients treated with citicoline after LASIK and 48 patients not treated with citicoline after LASIK as a control group. In both groups, the foveal avascular zone (FAZ), retinal superficial vascular density (SVD), and deep vascular density (DVD) in the foveal and parafoveal areas were measured preoperatively and at 1 and 3 months postoperatively using OCTA.

RESULTS

No significant difference was detected between the groups in terms of preoperative SVD or DVD in the foveal and parafoveal zones and all quadrants (superior, inferior, temporal, and nasal) (P > 0.05). Similarly, no significant difference was detected between the citicoline group and control group in terms of SVD or DVD in the foveal and parafoveal zones at 1 and 3 months after LASIK (P > 0.05).

CONCLUSIONS

Despite their neuroprotective effect, topical citicoline drops had no significant effect on the superficial and deep microvascular structures of the retina or choriocapillaris.

Cytidine 5'-Diphosphocholine (Citicoline): Evidence for a Neuroprotective Role in Glaucoma

Glaucoma, a heterogeneous set of progressively degenerative optic neuropathies characterized by a loss of retinal ganglion cells (RGCs) and typical visual field deficits that can progress to blindness, is a neurodegenerative disease involving both ocular and visual brain structures. Although elevated intraocular pressure (IOP) remains the most important modifiable risk factor of primary open-angle glaucoma (POAG) and is the main therapeutic target in treating glaucoma, other factors that influence the disease course are involved and reaching the optimal IOP target does not stop the progression of glaucoma, as the visual field continues to narrow. In addition to a managed IOP, neuroprotection may be beneficial by slowing the progression of glaucoma and improving the visual defects. Citicoline (cytidine 5'-diphosphocholine) is a naturally occurring endogenous compound that has been investigated as a novel therapeutic agent for the management of glaucoma. Citicoline has demonstrated activity in a range of central neurodegenerative diseases, and experimental evidence suggests a it performs a neuromodulator and neuroprotective role on neuronal cells, including RGCs, associated with improvement in visual function, extension of the visual field and central benefits for the patient. This review aims to critically summarize the current evidence for the neuroprotective properties of citicoline in glaucoma.

Assessing the Performance of Daily Intake of a Homotaurine, Carnosine, Forskolin, Vitamin B2, Vitamin B6, and Magnesium Based Food Supplement for the Maintenance of Visual Function in Patients with Primary Open Angle Glaucoma

Background

Glaucoma is a multifactorial optic neuropathy, which causes a continuous loss of retinal ganglion cells. Given the neurodegenerative nature of glaucoma, the necessity for neuroprotective intervention still arises, to be added alongside hypotonic therapy.

Objective

The objective of this study was to assess the effect of daily intake of a homotaurine, carnosine, forskolin, vitamins B1, B2, and B6, folic acid, and magnesium based supplement (GANGLIOLIFE®) on the progression rates of the visual field in patients with progressive POAG despite good tonometric compensation and to assess the most suitable dosage.

Methods

This is a monocentric nonrandomized experimental clinical study. Patients with mean deviation (MD) ranging from -2 dB to -15 dB with MD progression ≥1 dB in the previous year and IOP values of ≤18 mm Hg were included. All the patients underwent supplement therapy for a period of 6 months. For the first 2 months, they took 2 tablets a day, and for the following 4 months, 1 tablet a day. The patients were assessed before the start of treatment, time 0 (T ₀), after 2 months (T ₁), and after 6 months (T ₂) of therapy. At each check-up, patients were given a full eye test including perimetry, RNFL, and GCC using FD-OCT, PERG, contrast sensitivity, and QoL evaluation using the Glaucoma Symptom Scale questionnaire and National Eye Institute Visual Function Questionnaire 25.

Results

31 patients with a mean age of 70.80 ± 8.77 were included. At T ₁ and T ₂, the mean values of MD were lessened (MD = -5.37 ± -2.91, P < 0.01, and MD = -5.48 ± 3.15, P < 0.05, respectively) compared to T ₀ (MD = -5.98 ± 2.83). Patients also demonstrated a significant reduction in IOP (P < 0.01), improved light sensitivity (P < 0.01) and contrast sensitivity (P < 0.05), and a better quality of life (P < 0.05).

Conclusions

Treatment with a supplement which includes homotaurine, carnosine, forskolin, vitamins B1, B2, and B6, folic acid, and magnesium has been shown to be able to slow down the rate of progression of functional damage and improve visual function after 2 and 6 months of daily intake. Quality of life showed significant improvement.

Human vitreous concentrations of citicoline following topical application of citicoline 2% ophthalmic solution

PURPOSE

To evaluate the presence and concentration of citicoline and its metabolites (choline, cytidine and uridine) in the vitreous body in human eyes after topical application of an ophthalmic solution of citicoline 2%, in vivo.

METHODS

Twenty-one subjects affected by epiretinal membrane with surgical indication for pars-plana vitrectomy underwent treatment with 1 drop 3 times/day of a solution of citicoline 2%, 0.2% high molecular weight hyaluronic acid and 0.01% benzalkonium chloride (OMK1, Omikron Italia s.r.l., Rome, Italy) 14 days before surgery and 2 hours prior to surgery. Five additional patients served as controls and received an OMK1 vehicle solution without citicoline. The vitreous samples were taken at the beginning of the pars-plana vitrectomy and analyzed for qualitative/quantitative determination of vitreous concentration of citicoline and its metabolites by means of high performance liquid chromatography.

RESULTS

The overall mean concentration of citicoline in patients treated with citicoline 2% solution was 406.72 ± 52.99 μg/mL, while the mean concentration of choline, cytidine and uridine was 180.88 ± 41.49 μg/mL, 44.45 ± 10.19 μg/mL and 330.41 ± 75.8 μg/mL, respectively. The concentration of citicoline in phakic eyes (n = 13, 366.61 ± 129.61 μg/mL) was lower compared to that found in pseudophakic eyes (n = 8, 435.89 ± 131.42 μg/mL) and the difference was not statistically significant. The concentration of citicoline in the control eyes was 45.66 ± 26.36 μg/mL, while the concentration of choline, cytidine and uridine were 17.21 ± 9.93 μg/mL, 6.24 ± 3.6 μg/mL and 172.80 ± 99.76 μg/mL, respectively.

CONCLUSION

Citicoline can reach the human vitreous in high concentration when administered in ophthalmic solution. This evidence contributes to the build-up of the pyramid of the evidences required for determining the role of citicoline administered in ophthalmic formulation in retinal and optic nerve neurodegenerative diseases.

Cholinergic nervous system and glaucoma: From basic science to clinical applications

The cholinergic system has a crucial role to play in visual function. Although cholinergic drugs have been a focus of attention as glaucoma medications for reducing eye pressure, little is known about the potential modality for neuronal survival and/or enhancement in visual impairments. Citicoline, a naturally occurring compound and FDA approved dietary supplement, is a nootropic agent that is recently demonstrated to be effective in ameliorating ischemic stroke, traumatic brain injury, Parkinson's disease, Alzheimer's disease, cerebrovascular diseases, memory disorders and attention-deficit/hyperactivity disorder in both humans and animal models. The mechanisms of its action appear to be multifarious including (i) preservation of cardiolipin, sphingomyelin, and arachidonic acid contents of phosphatidylcholine and phosphatidylethanolamine, (ii) restoration of phosphatidylcholine, (iii) stimulation of glutathione synthesis, (iv) lowering glutamate concentrations and preventing glutamate excitotoxicity, (v) rescuing mitochondrial function thereby preventing oxidative damage and onset of neuronal apoptosis, (vi) synthesis of myelin leading to improvement in neuronal membrane integrity, (vii) improving acetylcholine synthesis and thereby reducing the effects of mental stress and (viii) preventing endothelial dysfunction. Such effects have vouched for citicoline as a neuroprotective, neurorestorative and neuroregenerative agent. Retinal ganglion cells are neurons with long myelinated axons which provide a strong rationale for citicoline use in visual pathway disorders. Since glaucoma is a form of neurodegeneration involving retinal ganglion cells, citicoline may help ameliorate glaucomatous damages in multiple facets. Additionally, trans-synaptic degeneration has been identified in humans and experimental models of glaucoma suggesting the cholinergic system as a new brain target for glaucoma management and therapy.

Neuroenhancement and neuroprotection by oral solution citicoline in non-arteritic ischemic optic neuropathy as a model of neurodegeneration: A randomized pilot study

Purpose

To evaluate whether treatment with Citicoline in oral solution (OS-Citicoline) would increase visual function, retinal ganglion cells (RGCs) function, and neural conduction along visual pathways (neuroenhancement), and/or induce preservation of RGCs fibers’ loss (neuroprotection) in non-arteritic ischemic optic neuropathy (NAION), a human model of neurodegeneration.

Methods

Thirty-six patients with NAION and 20 age-matched controls were enrolled. Nineteen NAION patients received 500 mg/day of OS-Citicoline for a 6-month period followed by 3-month of wash-out (NC Group); 17 NAION patients were not treated (NN Group) from baseline to 9 months. In all subjects at baseline, and in NC and NN eyes at 6 and 9 months of follow-up, we assessed Visual Acuity (VA), Pattern Electroretinogram (PERG), Visual Evoked Potentials (VEP), retinal nerve fiber layer thickness (RNFL-T), and Humphrey 24–2 visual field mean deviation (HFA MD). Mean differences were statistically evaluated with ANOVA between Groups, and linear correlations were analysed with Pearson’s test.

Results

At 6 months, significant differences between groups for all parameters were observed (ANOVA, p<0.01). In NC eyes, VA increased, PERG responses increased, VEP recordings improved and were significantly correlated with increases in HFA MD (p<0.01), and RNFL-T was unmodified or improved. In contrast, in NN eyes, VA, PERG, VEP responses, RNFL-T, and HFA MD were further worsened. Significant differences were still present at 9-month follow-up in the NN Group and after 3 months of OS-Citicoline wash-out in NC eyes.

Conclusions

OS-Citicoline treatment induced neuroenhancement (improvement in RGCs function and neural conduction along visual pathways related to improvement of visual field defects) and neuroprotection (unmodified or improved RNFL morphological condition) in a human model of NAION involving fast RGCs degeneration.

Trial registration

ClinicalTrials.gov NCT03758118.

Role of Pattern Electroretinogram in Ocular Hypertension and Early Glaucoma

PURPOSE

To test whether pattern electroretinogram (PERG) can early detect retinal ganglion cells dysfunction in ocular hypertension.

DESIGN

Cross-sectional observational study.

PARTICIPANTS

The study included 3 groups: control, primary open-angle glaucoma (POAG) and ocular hypertension (OHT) groups with 30 eyes in each group.

MATERIALS AND METHODS

Visual fields were examined using automated perimetry with central 24-2 program. Optical coherent tomography (OCT) was done to assess the neuroretinal rim area, vertical cup/disc ratio, and average superior and inferior retinal nerve fiber layer thickness. PERG was recorded using skin electrodes. Amplitude and latency of P50 and N95 were documented.

RESULTS

PERG data: the mean P50 and N95 latency were significantly higher in the POAG group and the OHT group compared with the control group (P<0.001, <0.001, respectively). Also, the mean P50 and N95 amplitude were significantly lower in the POAG group and the OHT group compared with the control group (P<0.001,<0.001, respectively). In the POAG group, there was a significant negative correlation between PSD on one hand and P50 amplitude (r=-0.620, P=0.001) and N95 amplitude (r=-0.61, P<0.001) on the other hand. Also, the mean deviation was positively correlated with P50 amplitude (r=0.51, P=0.007) and N95 amplitudes (r=0.50, P=0.002). However, there was no significant correlation between PERG parameters and OCT parameters. In the OHT group, PERG parameters did not correlate with visual field and OCT parameters.

CONCLUSIONS

PERG can detect the dysfunctional, but still live retinal ganglion cells earlier than OCT in OHT cases, allowing the early start of treatment that can restore the ganglion cell function before irreversible damage occurs.

Enhancement of Retinal Function and of Neural Conduction Along the Visual Pathway Induced by Treatment with Citicoline Eye Drops in Liposomal Formulation in Open Angle Glaucoma: A Pilot Electrofunctional Study

INTRODUCTION

To evaluate the retinal function and the relative neural conduction along the visual pathway after treatment with citicoline in liposomal formulation (CLF) eye drops in patients with open angle glaucoma (OAG).

METHODS

Twelve OAG patients (mean age ± standard deviation 52.58 ± 11.39 years, intraocular pressure < 18 mmHg under topical hypotensive treatment, Humphrey field analyzer mean deviation - 4.49 ± 2.46 dB) were enrolled. Only one eye of studied patients was treated with CLF eye drops (OMK1-LF^®, Omikron Italia, 3 drops/day) (CLF group, 12 eyes) over a period of 4 months. In CLF eyes, pattern electroretinogram (PERG), visual evoked potentials (VEP), and visual field test were assessed at baseline and at the end of treatment (month 4).

RESULTS

After treatment with CLF eye drops, a significant increase of PERG P50-N95 amplitude and a significant shortening of VEP P100 implicit time were found. In CLF eyes, the shortening of VEP P100 implicit time was significantly correlated with the increase of PERG P50-N95 amplitude.

CONCLUSION

Data from this pilot study suggest that treatment with CLF eye drops induces an enhancement of the retinal bioelectrical responses (increase of PERG amplitude) with a consequent improvement of the bioelectrical activity of the visual cortex (shortening of VEP implicit time).

FUNDING

Omikron Italia S.r.l. and Opko Health Europe.

In vivo effects of single or combined topical neuroprotective and regenerative agents on degeneration of retinal ganglion cells in rat optic nerve crush model

To determine the effectiveness of a single or a combination of topical neurotrophic factors (NFs) in protecting retinal ganglion cells (RGCs) in the rat optic nerve crush (ONC) model, the left ONC was performed to induce the death of the RGCs in adult Sprague-Dawley rats. The NFs studied were tauroursodeoxycholic acid (TUDCA), citicoline, neurotrophin-4 (NT-4), combined TUDCA/citicoline (Doublet-1), combined TUDCA/NT-4 (Doublet-2), combined TUDCA/citicoline/NT-4 (Triplet), and PBS. After 2 weeks, the number of RGCs was determined by Brn3a immunostaining. The optic nerves were immunostained for anti-Growth Associated Protein-43(GAP-43) and -200kD neurofilament heavy antibody to study optic nerve regeneration. Two weeks after the ONC, the densities of RGCs in all treated eyes were significantly higher than that of the PBS treated eyes. In the Triplet group, the number of RGC axons after ONC was significantly higher than that in all of the single treatment groups and the number of TUNEL positive cells was significantly reduced and the number of GAP-43 immunopositive axons was significantly greater than those in the PBS group. Neovascularization was observed only in the Doublet-1 group. We conclude that the combination of the three NFs was the most effective way to protect RGCs after the ONC.

Citicoline and Retinal Ganglion Cells: Effects on Morphology and Function

BACKGROUND

Retinal ganglion cells (RGCs) are the nervous retinal elements which connect the visual receptors to the brain forming the nervous visual system. Functional and/or morphological involvement of RGCs occurs in several ocular and neurological disorders and therefore these cells are targeted in neuroprotective strategies. Cytidine 5-diphosphocholine or Citicoline is an endogenous compound that acts in the biosynthesis of phospholipids of cell membranes and increases neurotransmitters' levels in the Central Nervous System. Experimental studies suggested the neuromodulator effect and the protective role of Citicoline on RGCs. This review aims to present evidence of the effects of Citicoline in experimental models of RGCs degeneration and in human neurodegenerative disorders involving RGCs.

METHODS

All published papers containing experimental or clinical studies about the effects of Citicoline on RGCs morphology and function were reviewed.

RESULTS

In rodent retinal cultures and animal models, Citicoline induces antiapoptotic effects, increases the dopamine retinal level, and counteracts retinal nerve fibers layer thinning. Human studies in neurodegenerative visual pathologies such as glaucoma or non-arteritic ischemic neuropathy showed a reduction of the RGCs impairment after Citicoline administration. By reducing the RGCs' dysfunction, a better neural conduction along the post-retinal visual pathways with an improvement of the visual field defects was observed.

CONCLUSION

Citicoline, with a solid history of experimental and clinical studies, could be considered a very promising molecule for neuroprotective strategies in those pathologies (i.e. Glaucoma) in which morpho-functional changes of RGCc occurs.

Effects of Liposomal Formulation of Citicoline in Experimental Diabetes-Induced Retinal Neurodegeneration

Diabetic retinopathy (DR) has been classically considered a microcirculatory disease of the retina. However, there is growing evidence to suggest that retinal neurodegeneration is also an early event in the pathogenesis of DR. Citicoline has been successfully used as a neuroprotective agent in the treatment of glaucoma but their effects on DR remain to be elucidated. On this basis, the main aim of the present study was to evaluate the effect of topical administration of citicoline in liposomal formulation on retinal neurodegeneration in db/db mouse and to investigate the underlying mechanisms of action. The treatment (citicoline or vehicle) was topically administered twice daily for 15 days. Retinal analyses were performed in vivo by electroretinography and ex vivo by using Western blot and immunofluorescence measurements. We found that the liposomal formulation of citicoline prevented glial activation and neural apoptosis in the diabetic retina. The main mechanism implicated in these beneficial effects were the inhibition of the downregulation of synaptophysin and its anti-inflammatory properties by means of preventing the upregulation of NF-κB and TNF-α (Tumor Necrosis Factor α) induced by diabetes. Overall, these results suggest that topical administration of citicoline in liposomal formulation could be considered as a new strategy for treating the early stages of DR.

Citicoline - a neuroprotector with proven effects on glaucomatous disease

Citicoline is the generic name of cytidine-5’-diphosphocholine (CDP-choline), an endogenous compound that is able to increase the levels of neurotransmitters in the central nervous system by interacting with the synthesis of cellular membranes phospholipids, especially phosphatidylcholine. Exogenous Citicoline, administered by ingestion or injection, is hydrolyzed and dephosphorylated in order to form cytidine and choline, which resynthesize CDP-choline inside brain cells. It has proven neuroprotective effects in Alzheimer disease, stroke, and Parkinson’s disease, as well as in glaucoma and amblyopia. Citicoline acts as a neuroprotector for those patients with progressive glaucomatous disease in spite of well-controlled intraocular pressure. The purpose of this review was to outline the main features of Citicoline and the evidences of its effect in glaucoma.

Neuroprotective agents in the management of glaucoma

Glaucoma is an optic neuropathy, specifically a neurodegenerative disease characterized by loss of retinal ganglion cells (RGCs) and their axons. The pathogenesis of RGC loss in glaucoma remains incompletely understood and a broad range of possible mechanisms have been implicated. Clinical evidence indicates that lowering intraocular pressure (IOP) does not prevent progression in all patients; therefore, risk factors other than those related to IOP are involved in the disease. The need for alternative, non-IOP-lowering treatments focused at preventing progression, that is, neuroprotectants, has become of interest to both the patient and the physician. Experimental evidence accumulated during the past two decades lend a great deal of support to molecules endowed with neuroprotective features. However, translation to the clinic of the latter drugs results unsuccessful mostly because of the lack of reliable in vivo measure of retinal damage, thus hampering the good therapeutic potential of neuroprotective agents given alone or as adjuvant therapy to IOP-lowering agents. Further research effort is needed to better understand the mechanisms involved in glaucoma and the means to translate into clinic neuroprotective drugs.

Combination of Neuroprotective and Regenerative Agents for AGE-Induced Retinal Degeneration: In Vitro Study

To determine the most effective combination of neuroprotective and regenerative agents for cultured retinal neurons from advanced glycation end products- (AGEs-) induced degeneration, retinal explants of 7 adult Sprague-Dawley rats were three-dimensionally cultured in collagen gel and incubated in serum-free media and in 7 media; namely, AGEs, AGEs + 100 μM citicoline, AGEs + 10 ng/mL NT-4, AGEs + 100 μM TUDCA, AGEs + 100 μM citicoline + TUDCA (doublet), and AGEs + 100 μM citicoline + TUDCA + 10 ng/mL NT-4 (triplet) were examined. The number of regenerating neurites was counted after 7 days of culture, followed by performing TUNEL and DAPI staining. The ratio of TUNEL-positive cells to the number of DAPI-stained nuclei was calculated. Immunohistochemical examinations for the active form of caspase-9 and JNK were performed. All of the neuroprotectants increased the number of neurites and decreased the number of TUNEL-positive cells. However, the number of neurites was significantly higher, and the number of TUNEL-positive cells and caspase-9- and JNK-immunopositive cells was fewer in the retinas incubated with the combined three agents. Combination solutions containing citicoline, TUDCA, and NT-4 should be considered for neuroprotective and regenerative therapy for AGE-related retinal degeneration.

Neuroprotection for treatment of glaucoma in adults

BACKGROUND

Glaucoma is a heterogeneous group of conditions involving progressive damage to the optic nerve, deterioration of retinal ganglion cells, and ultimately visual field loss. It is a leading cause of blindness worldwide. Open angle glaucoma (OAG), the most common form of glaucoma, is a chronic condition that may or may not present with increased intraocular pressure (IOP). Neuroprotection for glaucoma refers to any intervention intended to prevent optic nerve damage or cell death.

OBJECTIVES

The objective of this review was to systematically examine the evidence regarding the effectiveness of neuroprotective agents for slowing the progression of OAG in adults compared with no neuroprotective agent, placebo, or other glaucoma treatment.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2016, Issue 7), Ovid MEDLINE, Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE Daily (January 1946 to August 2016), Embase (January 1980 to August 2016), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to August 2016), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 16 August 2016.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in which topical or oral treatments were used for neuroprotection in adults with OAG. Minimum follow-up time was four years.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed titles and abstracts from the literature searches. We obtained full-text copies of potentially relevant studies and re-evaluated for inclusion. Two review authors independently extracted data related to study characteristics, risk of bias, and outcomes. We identified one trial for this review, thus we performed no meta-analysis. Two studies comparing memantine to placebo are currently awaiting classification until study investigators provide additional study details. We documented reasons for excluding studies from the review.

MAIN RESULTS

We included one multicenter RCT of adults with low-pressure glaucoma (Low-pressure Glaucoma Treatment Study, LoGTS) conducted in the USA. The primary outcome was progression of visual field loss after four years of treatment with either brimonidine or timolol. Of the 190 adults enrolled in the study, the investigators excluded 12 (6.3%) after randomization; 77 participants (40.5%) did not complete four years of follow-up. The rate of attrition was unbalanced between groups with more participants dropping out of the brimonidine group (55%) than the timolol group (29%).Of those remaining in the study at four years, participants assigned to brimonidine showed less progression of visual field loss than participants assigned to timolol (risk ratio (RR) 0.35, 95% confidence interval (CI) 0.14 to 0.86; 101 participants). Because of high risk of attrition bias and potential selective outcome reporting, we graded the certainty of evidence for this outcome as very low. At the four-year follow-up, the mean IOP was similar in both groups among those for whom data were available (mean difference 0.20 mmHg, 95% CI -0.73 to 1.13; 91 participants; very low-certainty evidence). The study authors did not report analyzable data for visual acuity or any data related to vertical cup-disc ratio, quality of life, or economic outcomes. The most frequent adverse event was ocular allergy to the study drug, which affected more participants in the brimonidine group than the timolol group (RR 5.32, 95% CI 1.64 to 17.26; 178 participants; very low-certainty evidence).

AUTHORS' CONCLUSIONS

Although the only trial we included in this review found less visual field loss in the brimonidine-treated group, the evidence was of such low certainty that we can draw no conclusions from this finding. Further clinical research is needed to determine whether neuroprotective agents may be beneficial for individuals with OAG. Such research should focus on outcomes important to patients, such as preservation of vision, and how these outcomes relate to cell death and optic nerve damage. As OAG is a chronic, progressive disease with variability in symptoms, RCTs designed to measure the effectiveness of neuroprotective agents require a long-term follow-up of five years or longer to detect clinically meaningful effects.

Cytidine 5'-Diphosphocholine (Citicoline) in Glaucoma: Rationale of Its Use, Current Evidence and Future Perspectives

Cytidine 5'-diphosphocholine or citicoline is an endogenous compound that acts in the biosynthetic pathway of phospholipids of cell membranes, particularly phosphatidylcholine, and it is able to increase neurotrasmitters levels in the central nervous system. Citicoline has shown positive effects in Parkinson's disease and Alzheimer's disease, as well as in amblyopia. Glaucoma is a neurodegenerative disease currently considered a disease involving ocular and visual brain structures. Neuroprotection has been proposed as a valid therapeutic option for those patients progressing despite a well-controlled intraocular pressure, the main risk factor for the progression of the disease. The aim of this review is to critically summarize the current evidence about the effect of citicoline in glaucoma.

Retinal ganglion cell neuroprotection induced by activation of alpha7 nicotinic acetylcholine receptors

The α7nAChR agonist, PNU-282987, has previously been shown to have a neuroprotective effect against loss of retinal ganglion cells (RGCs) in an in vivo glaucoma model when the agent was injected into the vitreous chamber of adult Long Evans rat eyes. Here, we characterized the neuroprotective effect of PNU-282987 at the nerve fiber and retinal ganglion cell layer, determined that neuroprotection occurred when the agonist was applied as eye drops and verified detection of the agonist in the retina, using LC/MS/MS. To induce glaucoma-like conditions in adult Long Evans rats, hypertonic saline was injected into the episcleral veins to induce scar tissue and increase intraocular pressure. Within one month, this procedure produced significant loss of RGCs compared to untreated conditions. RGCs were quantified after immunostaining with an antibody against Thy 1.1 and imaged using a confocal microscope. In dose-response studies, concentrations of PNU-282987 were applied to the animal's right eye two times each day, while the left eye acted as an internal control. Eye drops of PNU-282987 resulted in neuroprotection against RGC loss in a dose-dependent manner using concentrations between 100 μM and 2 mM PNU-282987. LC/MS/MS results demonstrated that PNU-282987 was detected in the retina when applied as eye drops, relatively small amounts of PNU-282987 were measured in blood plasma and no PNU-282987 was detected in cardiac tissue. These results support the hypothesis that eye drop application of PNU-282987 can prevent loss of RGCs associated with glaucoma, which can lead to neuroprotective treatments for diseases that involve α7nAChRs.

Treatment with citicoline eye drops enhances retinal function and neural conduction along the visual pathways in open angle glaucoma

PURPOSE

To evaluate the retinal function and the neural conduction along the visual pathways after treatment with citicoline eye drops in patients with open angle glaucoma (OAG).

METHODS

Fifty-six OAG patients (mean age 52.4 ± 4.72 years, IOP <18 mmHg with beta-blocker monotherapy only) were enrolled. Of these, 47 eyes completed the study: 24 OAG eyes were treated with topical citicoline (OMK1®, Omikron Italia, 3 drops/day) (GC eyes) over a 4-month period (month 4) followed by a 2-month period of citicoline wash-out (month 6), and another 23 OAG eyes were only treated with beta-blocker monotherapy (GP eyes). In GC and GP eyes, pattern electroretinogram (PERG) and visual evoked potentials (VEP) were assessed at baseline and at months 4 and 6 in both groups.

RESULTS

At baseline, similar (ANOVA, p > 0.01) PERG and VEP values in GC and GP eyes were observed. After treatment with topical citicoline, a significant (p < 0.01) increase of PERG P50-N95 and VEP N75-P100 amplitudes, and a significant (p < 0.01) shortening of VEP P100 implicit times were found. In GC eyes, the shortening of VEP P100 implicit times was correlated significantly (p < 0.01) with the increase of PERG P50-N95 amplitudes. After a 2-month period of topical Citicoline wash-out, PERG and VEP values were similar (p > 0.01) to baseline ones. GP eyes showed not significant changes of PERG and VEP values during the entire follow-up.

CONCLUSIONS

Topical treatment with citicoline in OAG eyes induces an enhancement of the retinal bioelectrical responses (increase of PERG amplitude) with a consequent improvement of the bioelectrical activity of the visual cortex (shortening and increase of VEP implicit time and amplitude, respectively).