Dynamics of proteins: Light scattering study of dilute and dense colloidal suspensions of eye lens homogenates

We report a dynamic light scattering study on protein suspensions of bovine lens homogenates at conditions (pH and ionic strength) similar to the physiological ones. Light scattering data were collected at two temperatures, 20 oC and 37 oC, over a wide range of concentrations from the very dilute limit up to the dense regime approaching to the physiological lens concentration. A comparison with experimental data from intact bovine lenses was advanced revealing differences between dispersions and lenses at similar concentrations. In the dilute regime two scattering entities were detected and identified with the long-time, self-diffusion modes of alpha-crystallins and their aggregates, which naturally exist in lens nucleus. Self-diffusion coefficients are temperature insensitive, whereas the collective diffusion coefficient depends strongly on temperature revealing a reduction of the net repulsive interparticle forces with lowering temperature. While there are no rigorous theoretical approaches on particle diffusion properties for multi-component, non-ideal hard-sphere, polydispersed systems, as the suspensions studied here, a discussion of the volume fraction dependence of the long-time, self-diffusion coefficient in the context of existing theoretical approaches was undertaken. This study is purported to provide some insight into the complex light scattering pattern of intact lenses and the interactions between the constituent proteins that are responsible for lens transparency. This would lead to understand basic mechanisms of specific protein interactions that lead to lens opacification (cataract) under pathological conditions.Comment: To appear in J. Chem. Phy

Dynamic light scattering study on phase separation of a protein-water mixture: Application on cold cataract development in the ocular lens

We present a detailed dynamic light scattering study on the phase separation in the ocular lens emerging during cold cataract development. Cold cataract is a phase separation effect that proceeds via spinodal decomposition of the lens cytoplasm with cooling. Intensity auto-correlation functions of the lens protein content are analyzed with the aid of two methods providing information on the populations and dynamics of the scattering elements associated with cold cataract. It is found that the temperature dependence of many measurable parameters changes appreciably at the characteristic temperature ~16+1 oC which is associated with the onset of cold cataract. Extending the temperature range of this work to previously inaccessible regimes, i.e. well below the phase separation or coexistence curve at Tcc, we have been able to accurately determine the temperature dependence of the collective and self-diffusion coefficient of proteins near the spinodal. The analysis showed that the dynamics of proteins bears some resemblance to the dynamics of structural glasses where the apparent activation energy for particle diffusion increases below Tcc indicating a highly cooperative motion. Application of ideas developed for studying the critical dynamics of binary protein/solvent mixtures, as well as the use of a modified Arrhenius equation, enabled us to estimate the spinodal temperature Tsp of the lens nucleus. The applicability of dynamic light scattering as a non-invasive, early-diagnostic tool for ocular diseases is also demonstrated in the light of the findings of the present paper

Taxane induced cystoid macular edema: Case report and integrated pathogenic theory

Purpose: To report a case of a 73-year-old man who presented with decreased visual acuity due to bilateral macular edema after paclitaxel administration for prostate cancer. Methods: The ophthalmic evaluation consisted of medical and ocular history, Best Corrected Visual Acuity, slit-lamp biomicroscopy and Spectral-domain optical coherence tomography / Fluorescein Angiography. Results: Optical Coherence Tomography and Fluorescein Angiography revealed silent cystoid macular edema. After consulting with the oncologist, the cessation of paclitaxel therapy was decided. The patient presented a gradual but steady resumption of the retinal edema, with complete restoration of normal retinal morphology and function within two months. The pathogenesis of the silent Cystoid Macular Edema (CME) is still unclear. Based on our case and a critical review of the previous observations and published data, we propose that the underlying cause of Taxane induced CME is the functional failure of Aquaporin mediated water transport at the level of retinal Intermediate and Deep capillary plexuses, and at lesser extent at the level of the Retinal Pigment Epithelium. Conclusion: Taxane induced silent CME should be attributed to the action of Taxanes on the microtubule guided aquaporin vesicles transport to the cell membrane. In our case of Taxane induced silent CME, withdrawal of the taxane was enough for complete recovery, and no additional treatment was needed. © 2019 Bentham Science Publishers

Idiopathic retinal vasculitis, arteriolar macroaneurysms and neuroretinitis: Clinical course and treatment

Background: The purpose of the study is to describe the clinical course and treatment of idiopathic retinitis, vasculitis, aneurysms and neuroretinitis. The study utilized non-randomized, retrospective and interventional case series. The eight eyes of six patients were analysed. Testing included wide fluorescein angiography, indocyanine green angiography and systemic evaluation. Treatment involved observation, panretinal laser photocoagulation (PRP) for peripheral retinal ischemia, grid laser for macular oedema and focal laser on the macroaneurysms. The main outcome measures were initial visual acuity (VA), initial stage at diagnosis, clinical course, surgical intervention, final VA, final stage and complications of disease. Results: Five out of eight eyes with retinal ischemia in more than two quadrants that were treated with PRP and grid laser for macular oedema maintained excellent VA and demonstrated no progression of retinal ischemia during follow-up. The two eyes which exhibited retinal ischemia in less than two quadrants and macular oedema were treated with grid laser and focal laser on the macroaneurysms, but did not undergo PRP. VA improved by two lines of the Snellen chart, and there was no progression of retinal ischemia during the 3 and 4 years of follow-up. One eye with neither retinal ischemia nor macular oedema was not treated, and the clinical picture remained stable during the follow-up. Conclusion: Early PRP may be considered in the presence of angiographic evidence of peripheral retinal nonperfusion. However, treatment could be withheld until the patient develops retinal ischemia in more than two quadrants. © 2013 Rouvas et al

UVB-mediated down-regulation of proteasome in cultured human primary pterygium fibroblasts

Background: Pterygium is a condition characterized by epithelial overgrowth of the cornea, inflammatory cell infiltration and an abnormal extracellular matrix accumulation. Chronic UV exposure is considered as a pathogenic factor of this disease. Proteasome is an intracellular multi-subunit protease complex that degrades intracellular proteins. Among proteasome subunits the β5 (PSMB5), bearing chymotrypsin-like activity. It is considered as the main proteasome subunit and its expression is mediated by Nrf2-ARE pathway in many cell types. This study investigates the expression of PSMB5 in pterygium and the effect of UVB irradiation on its expression and activity in pterygium fibroblasts. Methods: Normal conjunctival and pterygium specimens were obtained from the bulbar conjunctiva of patients undergoing cataract surgery and from patients with pterygium undergoing surgical removal of primary tissue, respectively. Fibroblasts were isolated upon treatment of specimens with clostridium collagenase. The expression of PSMB5 and Nrf2 in tissues and cells was ascertained by RT-PCR analysis and western blotting. Cell survival was measured by the MTT method and the proteasome chymotrypsin-like activity was determined by fluorometry. Results: RT-PCR analysis showed that the expression of PSMB5 was significantly lower in pterygium than in normal conjunctiva. The expression of PSMB5 was mediated by the Nrf2/ARE pathway as indicated by using the Nrf2 activator Oltipraz. The expression of PSMB5 and Nrf2 by pterygium fibroblasts was suppressed in a dose dependent manner following UVB radiation of 0-50 mJ/cm2 doses. The expression of PSMB5, but not of Nrf2, remained at almost the control levels, when UVB exposure was performed after pre-incubation of cells with the src kinases inhibitor PP2. UVB irradiation had very low deleterious effect on fibroblasts survival, while it did not affect the proteasome chymotrypsin-like activity. Conclusion: In pterygium fibroblasts, UVB exposure leads to down-regulation of Nrf2/ARE-mediated PSMB5 gene expression, in which src kinases may be implicated. This effect may be partially responsible for the lower expression of PSMB5 detected in pterygium as compared to normal conjunctiva. © 2018 The Author(s)

Efficacy of Topical Ofloxacin 0.3 % Administration on Conjunctival Bacterial Flora in Diabetic Patients Undergoing Intravitreal Injections

Purpose: This prospective, randomized case series study aims to evaluate the efficacy of ofloxacin 0.3% eye drops in eradication of conjunctival bacterial flora in diabetic patients undergoing intravitreal injections (IVI). Methods: Ninety-two diabetic patients (92 eyes) scheduled to undergo intravitreal injection of ranibizumab due to diabetic macular edema were enrolled in the study. Patients were randomly assigned to three different groups. Group 1 (n=32) received ofloxacin eye drops the day before before IVI (four times); patients in Group 2 (n=29) were administered ofloxacin one hour before IVI (every 15 minutes), while Group 3 (n=31) comprised patients that received combined administration of ofloxacin both one day and one hour before IVI (eight doses). Samples were collected from the injection site before and after antibiotic administration. Culture results from BACTEC broth and positive cultures in blood agar and Sabouraud’s dextrose agar plates were measured. Results: In Group 1, BACTEC broth positive cultures decreased from 84.4% at baseline to 50% after ofloxacin administration (p=0.007), and blood agar positive cultures reduced from 65.63% to 34.38% (p=0.02). In Group 2, positive cultures significantly decreased in BACTEC broth (from 79.3% at baseline to 48.28%; p=0.027) and in blood agar (from 68.97% to 37.13%; p=0.034). In Group 3, positive cultures decreased from 77.42% at baseline to 32.26% (p=0.0008) and from 58.06% at baseline to 22.58% (p=0.009) in BACTEC broth and blood agar, respectively. No microorganisms were isolated from Sabouraud’s dextrose agar plates. Conclusions: The combined one day/one hour (eight doses) ofloxacin administration in diabetic patients is extremely effective in reducing conjunctival bacterial flora. The application of topical ofloxacin for one day or one hour before IVI is also significantly effective. © 2017 Taylor & Francis

Guidelines for the Management of Wet Age-Related Macular Degeneration: Recommendations from a Panel of Greek Experts

Purpose: To propose guidelines for the management of patients with wet age-related macular degeneration (wAMD), taking into account the results of large multicenter studies and clinical experience of retina experts. Method: A team of retina experts developed a consensus paper after three consecutive meetings. The group was focused on guidelines to help clinical decision-making around the definition of successful treatment and the definition of non-response to therapy. Results: Parameters suggestive of a successful response to treatments included: any gain in best corrected visual acuity (BCVA) or vision loss that is less than 5–10 Early Treatment Diabetic Retinopathy Study (ETDRS) letters, reduction of central retinal thickness, partial or complete absorption of subretinal fluid (SRF), reduction of intraretinal fluid, reduction of pigment epithelial detachment or restoration of the anatomy of outer retinal layers. Non-response to current treatment was considered in the case of loss of BCVA greater than 10 ETDRS letters, increased retinal edema or increase of SRF as evidenced by optical coherence tomography or new bleeding in biomicroscopy. Conclusion: The introduction of anti-VEGF agents revolutionized the treatment of wAMD. Given the complexity of the disease, the emerging new agents and the difference of cases recruited in clinical trials compared to those appearing in every-day practice, it is essential to individualize treatment options taking into account the results of clinical trials. © 2016, The Author(s)

A Real-World, Multicenter, 6-Month Prospective Study in Greece of the Effectiveness and Safety of Ranibizumab in Patients with Age-Related Macular Degeneration Who Have Inadequately Responded to Aflibercept: The “ELEVATE” Study

Purpose: Real-world evidence on short-term outcomes of ranibizumab in wet age-related macular degeneration (wAMD) following inadequate response to aflibercept is scarce. This study aimed to evaluate the functional and anatomic effects of switching to ranibizumab in cases of wAMD previously treated with aflibercept with inadequate response. Patients and Methods: Prospective, observational study performed in eight ophthalmology hospital/private clinics in Greece, enrolling consented patients with active wAMD, ≥50 years-old, who had initiated ranibizumab ≥28 days and <2 months after their last aflibercept injection. Data were collected at enrollment, and at 1, 3 and 6 months post-treatment onset (post-baseline). Results: Between September-2015 and November-2017, 103 eligible patients (56.3% females; mean age: 74.8±8.6 years) were consecutively enrolled. The age at AMD diagnosis in the study eye was 71.3±8.8 years. Aflibercept (median of 5 injections received over 11.3 months) had been discontinued for anatomical (in 69.9%) and/or functional (38.8%) reasons. At baseline (median: 24.3 months after wAMD diagnosis), choroidal neovascularization was occult in 69.1% of evaluable study eyes; 60.2% of the study eyes had pigment epithelial detachment (PED); 42.7% cysts; 21.4% fibrosis; 66.0% subretinal, and 59.2% intraretinal fluid. At 6 months post-baseline: a median of 3 ranibizumab injections (range: 1–6) had been received; the best-corrected visual acuity (BCVA)≥0 letter gain rate was 81.8%; the BCVA ≥15 letter gain rate was 17.0%; BCVA gain was 3.2 letters [mean increase: 3.2±10.0 letters; median: 0.0; p = 0.002]; PED greatest basal diameter (GBD; median: 1470.5 μm) also decreased (median decrease: 114.0 μm; p = 0.019). Baseline central retinal thickness (CRT; median: 312.0 μm) remained unchanged. One patient permanently discontinued ranibizumab due to adverse event occurrence, assessed as not causally related to ranibizumab. There were no ranibizumab-related adverse reactions. Conclusion: Six-month treatment with ranibizumab in aflibercept inadequate responders led to visual acuity and PED GBD improvements, with no statistically significant CRT change. © 2022 Rouvas et al