Robert Rejdak

Vitamin deficiency and hyperhomocysteinemia in pseudoexfoliation glaucoma

Summary.Pseudoexfoliation syndrome (PEX) is a systemic disorder characterized by the deposition of an abnormal fibrillar material in ocular and various extraocular tissues. It represents the most common identifiable cause of glaucoma (PEX glaucoma = PEXG). Due to similar pathogenetic mechanisms, glaucoma has been called “ocular Alzheimer’s disease”. PEXG and Alzheimer’s disease share common associations such as the higher prevalence of hyperhomocysteinemia in both disorders.In order to investigate the cause of hyperhomocysteinemia in PEXG, we evaluated B-vitamin levels (folate, B12, B6) and their associations with homocysteine (Hcy) in plasma of 70 PEXG patients and 70 control subjects. Folate, vitamin B12 and B6 levels were significantly decreased and associated with elevated Hcy levels in PEXG. Low B-vitamin levels in PEX might also help explain, at least in part, the higher prevalence of B-vitamin deficiency in disorders associated with PEX such as Alzhemier’s disease.

Homocysteine in tear fluid of patients with pseudoexfoliation glaucoma.

PurposeTo evaluate homocysteine (Hcy) concentrations in tear fluid and plasma and their association with B-vitamin levels in patients with pseudoexfoliation glaucoma (PEXG). Patients and MethodsReflex tear and blood samples were obtained in 30 patients with PEXG and 30 controls. Hcy levels were determined by high-performance liquid chromatography. ResultsHcy was detected in all tear fluid samples of patients with PEXG and controls. Statistical analysis with t tests showed that patients with PEXG had significantly higher Hcy levels both in tear fluid (237±133 nmol/L vs. 128±54 nmol/L; P<0.001) and in plasma (14.51±4.43 μmol/L vs. 10.22±2.77 μmol/L; P<0.001) than control subjects. Hcy in tear fluid correlated significantly with Hcy in plasma (r=0.438, P=0.015) and with serum B12 levels (r=−0.424, P=0.019) in patients with PEXG, but not in controls. ConclusionsThe study suggests increased Hcy levels in tear fluid and plasma of patients with PEXG. Further investigations are needed to evaluate the possible clinical role of Hcy in ocular surface and systemic disorders associated with PEXG.

Proteomics of Vitreous Humor of Patients with Exudative Age-Related Macular Degeneration

Background There is absence of specific biomarkers and an incomplete understanding of the pathophysiology of exudative age-related macular degeneration (AMD). Methods and Findings Eighty-eight vitreous samples (73 from patients with treatment naïve AMD and 15 control samples from patients with idiopathic floaters) were analyzed with capillary electrophoresis coupled to mass spectrometry in this retrospective case series to define potential candidate protein markers of AMD. Nineteen proteins were found to be upregulated in vitreous of AMD patients. Most of the proteins were plasma derived and involved in biological (ion) transport, acute phase inflammatory reaction, and blood coagulation. A number of proteins have not been previously associated to AMD including alpha-1-antitrypsin, fibrinogen alpha chain and prostaglandin H2-D isomerase. Alpha-1-antitrypsin was validated in vitreous of an independent set of AMD patients using Western blot analysis. Further systems biology analysis of the data indicated that the observed proteomic changes may reflect upregulation of immune response and complement activity. Conclusions Proteome analysis of vitreous samples from patients with AMD, which underwent an intravitreal combination therapy including a core vitrectomy, steroids and bevacizumab, revealed apparent AMD-specific proteomic changes. The identified AMD-associated proteins provide some insight into the pathophysiological changes associated with AMD.

Pharmacodynamics of citicoline relevant to the treatment of glaucoma.

Citicoline (exogenous CDP‐choline) is a nontoxic and well‐tolerated drug used in pharmacotherapy of brain insufficiency and some other neurological disorders, such as stroke, brain trauma, and Parkinsons disease. A few reports indicate that citicoline treatment may also be beneficial in glaucoma. Currently glaucoma is considered a neurodegenerative disease in which retinal ganglion cells (RGC) slowly die, likely in the apoptotic mechanism. Endogenous CDP‐choline is a natural precursor of cellular synthesis of phospholipids, mainly phosphatydylcholine (PtdCho). Enhancement of PtdCho synthesis may counteract neuronal apoptosis and provide neuroprotection. Citicoline, when administered, undergoes a quick transformation to cytidine and choline, which are believed to enter brain cells separately and provide neuroprotection by enhancing PtdCho synthesis; similar effect may be expected to occur in glaucomatous RGC. Furthermore, citicoline stimulates some brain neurotransmitter systems, including the dopaminergic system, and dopamine is known as a major neurotransmitter in retina and postretinal visual pathways. In a double‐blind, placebo‐controlled study, treatment of glaucoma resulted in functional improvement in the visual system noted with electrophysiological methods. Development of citicoline as a treatment for glaucoma is indicated.

Early electroretinographic features of streptozotocin-induced diabetic retinopathy

Background:  This study set out to document the early electrophysiological and immunohistochemical changes that occur in the retina of experimentally induced diabetic rats.

Homocysteine levels in aqueous humor and plasma of patients with primary open-angle glaucoma

SummaryWe determined homocysteine (Hcy) levels in aqueous humor (AH) and plasma and their association with B-vitamin levels in patients with primary open-angle glaucoma (POAG) and controls. Both AH Hcy and plasma Hcy levels were significantly increased in POAG, and elevation of AH Hcy and plasma Hcy was a significant risk factor for POAG. In contrast to controls, neither plasma nor AH Hcy of POAG patients demonstrated a significant association with important non-genetic determinants of elevated Hcy such as low B-vitamin levels, increasing age and caffeine consumption. Considering that Hcy is a neurotoxin that induces apoptotic retinal ganglion cell death via stimulation of the N-methyl-D-asparate (NMDA) receptor, increased Hcy concentrations in AH and plasma might contribute to the optic nerve damage in POAG.

Citicoline Treatment Increases Retinal Dopamine Content in Rabbits

Citicoline (exogenous cytidine-5′-diphosphocholine) was reported to enhance dopaminergic neurotransmission in the brain. A few clinical studies showed beneficial effects of this drug on the function of the visual pathway in patients with glaucoma or amblyopia. The present study was aimed at determining whether citicoline could influence retinal catecholamine levels in adult male Albino rabbits. The animals received the drug (50 mg/kg i.p., twice daily) or vehicle for 7 days, and retinal catecholamine concentrations were determined by HPLC. Compared to vehicle-treated controls, citicoline-treated animals displayed a significantly higher retinal dopamine concentration and a tendency toward an increase in adrenaline concentration, while the noradrenaline concentration remained unchanged. It is, therefore, conceivable that citicoline reinforces dopaminergic transmission in the retina.

In vivo toxicity study of rhodamine 6G in the rat retina.

PURPOSE To investigate the intraocular effect of rhodamine 6G (R6G) on retinal structures and function in an in vivo rat model and to develop an in vivo method for accurate evaluation of new dyes for intraocular surgery. METHODS R6G in physiologic saline solution (PSS) was injected into the vitreous of adult Brown Norway rats at concentrations of 0.0002%, 0.002%, 0.02%, 0.2%, and 0.5%. Control animals received only PSS. Retinal toxicity was assessed by retinal ganglion cell (RGC) counts, light microscopy 7 days later, photopic electroretinography (ERG), and measurement of scotopic sensitivity and recovery of dark adaptation 48 hours and 7 days after intravitreous injection. RESULTS R6G at concentrations of 0.2% and 0.5% led to a dose-dependent loss of RGC. The most significant loss occurred at 0.5%. Lower concentrations (0.0002%, 0.002%, and 0.02%) produced no statistically significant retinal ganglion cell loss. Analysis of the eyes by light microscopy showed no structural changes in the central retina, although injections of 0.5% R6G were followed by impressive degenerative changes adjacent to the injection sites. ERGs showed no effects of the highest R6G concentration on rods, kinetics of rhodopsin recovery after bleaching, or cone-driven responses. CONCLUSIONS R6G can be safely injected in doses of up to 0.02% in rats, but has a toxic effect on retinal ganglion cells at higher concentrations. Accumulation of R6G may be a problem at higher concentrations, particularly at the injection site.

Toxicity Study of Erucylphosphocholine in a Rat Model

Purpose: To investigate the effect of intraocular erucylphosphocholine (ErPC) on the retina, the retinal pigment epithelium (RPE), and the choroid in an in vivo rat model. Methods: Adult male Brown Norway rats were injected intravitreally with ErPC dissolved in balanced salt solution (BSS) at a final concentration of 10 or 100 μ M with BSS serving as control. Adverse effects on the anterior and posterior segment were assessed by slit-lamp biomicroscopy and ophthalmoscopy. Retinal toxicity was assessed by electroretinography (ERG), retinal ganglion cell (RGC) quantification, and histology 7 days after intravitreal administration of ErPC. Results: There was neither a statistically significant difference in the clinical examination nor in the ERG waves of treated versus control rats 7 days after intravitreal administration of ErPC. Correspondingly, the number of RGC after BSS injection did not differ significantly from ErPC-injected animals. Histologic sections of the posterior segment of 10 and 100 μ M ErPC-injected rats did not show any signs of retinal toxicity. Electron microscopy did not display a difference between the 10 μM and the control group. Only the 100 μM-injected animals showed a discrete irregularity of the Müller cell and the retinal ganglion cell cytoplasm at the ultrastructural level. Conclusions: ErPC can safely be injected into the vitreous of adult rats at a concentration of 10 μM without any retinal toxicity. Even a 10-fold increase in ErPC concentration leads only to a discrete cytoplasmic irregularity of the innermost retinal layers.

Levels of Aqueous Humor Trace Elements in Patients with Non-Exsudative Age-related Macular Degeneration: A Case-control Study

Trace elements might play a role in the complex multifactorial pathogenesis of age-related macular degeneration (AMD). The aim of this study was to measure alterations of trace elements levels in aqueous humor of patients with non-exsudative (dry) AMD. For this pilot study, aqueous humor samples were collected from patients undergoing cataract surgery. 12 patients with dry AMD (age 77.9±6.62, female 8, male 4) and 11 patients without AMD (age 66.6±16.7, female 7, male 4) were included. Aqueous levels of cadmium, cobalt, copper, iron, manganese, selenium, and zinc were measured by use of Flow-Injection-Inductively-Coupled-Plasma-Mass-Spectrometry (FI-ICP-MS), quality controlled with certified standards. Patients with AMD had significantly higher aqueous humor levels of cadmium (median: 0.70 µmol/L, IQR: 0.40–0.84 vs. 0.06 µmol/L; IQR: 0.01–.018; p = 0.002), cobalt (median: 3.1 µmol/L, IQR: 2.62–3.15 vs. 1.17 µmol/L; IQR: 0.95–1.27; p<0.001), iron (median: 311 µmol/L, IQR: 289–329 vs. 129 µmol/L; IQR: 111–145; p<0.001) and zinc (median: 23.1 µmol/L, IQR: 12.9–32.6 vs. 5.1 µmol/L; IQR: 4.4–9.4; p = 0.020) when compared with patients without AMD. Copper levels were significantly reduced in patients with AMD (median: 16.2 µmol/L, IQR: 11.4–31.3 vs. 49.9 µmol/L; IQR: 32.0–.142.0; p = 0.022) when compared to those without. No significant differences were observed in aqueous humor levels of manganese and selenium between patients with and without AMD. After an adjustment for multiple testing, cadmium, cobalt, copper and iron remained a significant factor in GLM models (adjusted for age and gender of the patients) for AMD. Alterations of trace element levels support the hypothesis that cadmium, cobalt, iron, and copper are involved in the pathogenesis of AMD.