The Effect of Molecular Weight on Passage of Proteins Through the Blood-Aqueous Barrier

Purpose: To determine the effect of molecular weight (MW) on the concentration of plasma-derived proteins in aqueous humor and to estimate the plasma-derived and eye-derived fractions for each protein. Methods: Aqueous humor and plasma samples were obtained during cataract surgery on an institutional review board–approved protocol. Protein concentrations were determined by ELISA and quantitative antibody microarrays. A total of 93 proteins were studied, with most proteins analyzed using 27 to 116 aqueous and 6 to 30 plasma samples. Results: Plasma proteins without evidence of intraocular expression by sequence tags were used to fit a logarithmic model relating aqueous-plasma ratio (AH:PL) to MW. The log(AH:PL) appears to be well predicted by the log(MW) (P 80), and 17 proteins had contribution from both plasma and eye tissue (IOF 20–80). Conclusions: Protein concentration of plasma-derived proteins in aqueous is nonlinearly dependent on MW in favor of smaller proteins. Our study demonstrates that for proper interpretation of results, proteomic studies evaluating changes in aqueous humor protein levels should take into account the plasma and eye-derived fractions

Dysfunctional regulation of ocular blood flow: A risk factor for glaucoma?

Primary open angle glaucoma (OAG) is a multifactorial optic neuropathy characterized by progressive retinal ganglion cell death and associated visual field loss. OAG is an emerging disease with increasing costs and negative outcomes, yet its fundamental pathophysiology remains largely undetermined. A major treatable risk factor for glaucoma is elevated intraocular pressure (IOP). Despite the medical lowering of IOP, however, some glaucoma patients continue to experience disease progression and subsequent irreversible vision loss. The scientific community continues to accrue evidence suggesting that alterations in ocular blood flow play a prominent role in OAG disease processes. This article develops the thesis that dysfunctional regulation of ocular blood flow may contribute to glaucomatous optic neuropathy. Evidence suggests that impaired vascular autoregulation renders the optic nerve head susceptible to decreases in ocular perfusion pressure, increases in IOP, and/or increased local metabolic demands. Ischemic damage, which likely contributes to further impairment in autoregulation, results in changes to the optic nerve head consistent with glaucoma. Included in this review are discussions of conditions thought to contribute to vascular regulatory dysfunction in OAG, including atherosclerosis, vasospasm, and endothelial dysfunction

The acute and chronic effects of intravitreal anti-vascular endothelial growth factor injections on intraocular pressure: A review

The acute and chronic effects of repeated intravitreal antivascular endothelial growth factor (VEGF) injections on intraocular pressure have not been fully characterized, and the development of sustained ocular hypertension could adversely affect patients who are at risk of glaucomatous optic neuropathy. As expected, volume-driven, acute ocular hypertension immediately follows intravitreal injection, but this pressure elevation is generally transient and well tolerated. Several medications have been investigated to limit acute ocular hypertension following anti-VEGF therapy, but the benefits of pretreatment are not conclusive. Chronic, sustained ocular hypertension, distinct from the short-term acute ocular hypertension after each injection, has also been associated with repeated intravitreal anti-VEGF injections. Risk factors for chronic ocular hypertension include the total number of injections, a greater frequency of injection, and preexisting glaucoma. Proposed mechanisms for chronic ocular hypertension include microparticle obstruction, toxic or inflammatory effects on trabecular meshwork, as well as alterations in outflow facility by anti-VEGF agents. Although limiting anti-VEGF therapy could minimize the risk of both acute and chronic ocular hypertension, foregoing anti-VEGF therapy risks progression of various macular diseases with resulting permanent central vision loss. While definitive evidence of damage to the retinal nerve fiber layer is lacking, patients receiving repeated injections should be monitored for ocular hypertension and patients in whom sustained ocular hypertension subsequently developed should be periodically monitored for glaucomatous changes with optic nerve optical coherence tomography and static visual fields

Differences in Ocular Blood Flow Between People of African and European Descent With Healthy Eyes

Purpose: To investigate differences in ocular blood flow between people of African descent (AD) and European descent (ED) with healthy eyes. Materials and Methods: Retrobulbar and retinal capillary blood flow was assessed in 1 eye of 58 participants (24 AD, 34 ED) with healthy eyes with systemic blood pressure lower than 140/90. Retrobulbar blood flow was measured in the ophthalmic artery (OA), central retinal artery (CRA), nasal posterior ciliary artery (NPCA) and temporal posterior ciliary artery (TPCA). Peak systolic velocity (PSV), end diastolic velocity (EDV), and resistive index (RI) were assessed. Retinal capillary blood flow was assessed using mean retinal flow and avascular space defined as the percent of area measured with no blood flow. Groups were compared using t tests and Pearson correlations were compared using Fisher r-to-z transformation. Results: Compared with people of ED, people of AD had significantly lower EDV in the NPCA (P=0.01), and higher RI in the CRA (P=0.04) and TPCA (P=0.01). No significant differences were observed in mean retinal capillary flow or avascular area. In the CRA, a significant negative correlation was observed between pattern standard deviation and peak systolic velocity (P=0.02) in the AD group and this correlation was significantly different from that observed in the ED group (P=0.01). A significant correlation was also observed between pattern standard deviation and EDV (0.04) in the AD group. Conclusions: This study suggests that retrobulbar blood flow is lower in healthy eyes in persons of AD compared with ED. This may provide a mechanism through which people of AD are at increased risk for ophthalmic diseases such as glaucoma

Racial differences in correlations between optic nerve head morphology and ocular blood flow in healthy eyes

poster abstractPurpose: To assess differences in the relationship between optic nerve head (ONH) morphology and ocular blood flow between persons of African descent (AD) and European descent (ED) with healthy eyes. Methods: 46 participants (20 AD, 26 ED) with normal fundoscopic exam and intraocular pressure were included. Each participant was assessed for disc area (DA), rim area (RA), linear cup to disc ratio (CDR), mean retinal nerve fiber layer (RNFL) thickness by Heidelberg retina tomograph. Retrobulbar blood flow was assessed by color Doppler imaging in the ophthalmic (OA), central retinal (CRA), nasal short posterior ciliary (NPCA) and temporal short posterior ciliary (TPCA) arteries. Peak systolic velocity (PSV), end diastolic velocity (EDV) and the resistive index (RI) were assessed in each artery. Mean retinal capillary blood flow and % of the area with no blood flow in both hemifields were measured with Heidelberg retinal flowmeter. Correlations between ONH morphology and ocular blood flow were derived using Pearson correlations. Differences between the correlations in the AD and ED groups were assessed using the Fisher r-to-z transformation method. Results: Age, gender, IOP and blood pressure were not significantly different between groups. Significant differences in correlations were observed between groups in the CRA. In this artery, PSV and DA were positively correlated in AD (r=0.43) and negatively correlated in ED (r=-0.35) (Δr=0.78; p=0.01). A similar finding was observed for PSV and RA (AD: r=0.39; ED: r=-0.22; Δr=0.61; p=0.04). Significant negative correlations between RI and CDR were observed in all arteries in the ED group (r coefficients range=-0.48 to -0.39), but not in the AD group (r coefficients range=-0.14 to 0.17). No significant differences were observed in the correlations of ONH morphology and capillary blood flow. Conclusion: ONH morphology and ocular blood flow relationship was significantly different in the healthy eyes of AD compared to ED

Visual contrast sensitivity is associated with the presence of cerebral amyloid and tau deposition

Visual deficits are common in neurodegenerative diseases including Alzheimer’s disease. We sought to determine the association between visual contrast sensitivity and neuroimaging measures of Alzheimer’s disease-related pathophysiology, including cerebral amyloid and tau deposition and neurodegeneration. A total of 74 participants (7 Alzheimer’s disease, 16 mild cognitive impairment, 20 subjective cognitive decline, 31 cognitively normal older adults) underwent the frequency doubling technology 24-2 examination, a structural MRI scan and amyloid PET imaging for the assessment of visual contrast sensitivity. Of these participants, 46 participants (2 Alzheimer’s disease, 9 mild cognitive impairment, 12 subjective cognitive decline, 23 cognitively normal older adults) also underwent tau PET imaging with [18F]flortaucipir. The relationships between visual contrast sensitivity and cerebral amyloid and tau, as well as neurodegeneration, were assessed using partial Pearson correlations, covaried for age, sex and race and ethnicity. Voxel-wise associations were also evaluated for amyloid and tau. The ability of visual contrast sensitivity to predict amyloid and tau positivity were assessed using forward conditional logistic regression and receiver operating curve analysis. All analyses first were done in the full sample and then in the non-demented at-risk individuals (subjective cognitive decline and mild cognitive impairment) only. Significant associations between visual contrast sensitivity and regional amyloid and tau deposition were observed across the full sample and within subjective cognitive decline and mild cognitive impairment only. Voxel-wise analysis demonstrated strong associations of visual contrast sensitivity with amyloid and tau, primarily in temporal, parietal and occipital brain regions. Finally, visual contrast sensitivity accurately predicted amyloid and tau positivity. Alterations in visual contrast sensitivity were related to cerebral deposition of amyloid and tau, suggesting that this measure may be a good biomarker for detecting Alzheimer’s disease-related pathophysiology. Future studies in larger patient samples are needed, but these findings support the power of these measures of visual contrast sensitivity as a potential novel, inexpensive and easy-to-administer biomarker for Alzheimer’s disease-related pathology in older adults at risk for cognitive decline

A polymorphism at codon 31 of gene p21 is not associated with primary open angle glaucoma in Caucasians

BACKGROUND: Primary open angle glaucoma (POAG) is considered to be a neurodegenerative optic neuropathy, in which cell death occurs by apoptosis. p21, is an important protective component of the apoptotic pathway, regulating cellular arrest in the presence of DNA damage. An unstable or altered p21 protein could modify the cellular response to genomic injury and abolish the effect of p21. A previous study on a Chinese cohort suggested that the p21 codon 31 polymorphism may alter the state of apoptosis in glaucomatous optic neuropathy, failing to protect the ganglion cells. The aim of this study was to test the hypothesis that a p21 codon 31 polymorphism is associated with POAG on a Caucasian cohort. METHODS: 140 POAG patients and a control group of 73 healthy individuals were included in the study. All the subjects were of Caucasian origin. Genomic DNA was amplified by polymerase chain reaction, followed by enzymatic restriction fragment length polymorphism technique (PCR-RFLP). Patients and controls were genotyped for a single nucleotide polymorphism (C/A transversion) in the third base of codon 31 of p21, which leads to a serine (Ser)/arginine (Arg) substitution. RESULTS: The distribution of the genotypes in the POAG patients showed 128 (91.4%) Ser homozygotes, 10 (7.1%) Ser/Arg heterozygotes and 2 (1.5%) Arg homozygotes. In the control cohort, there were 61 (83.6%) Ser homozygotes and 12 (16.4%) Ser/Arg heterozygotes. No Arg homozygotes were present amongst the control group. Both the allelic and genotypic frequencies of the Ser or Arg residues at codon 31 were not significantly different between POAG patients and controls (Fisher's exact test, P = 0.20 for alleles and P = 0.0561 for genotypes). CONCLUSION: This study suggests that the p21 codon 31 polymorphism does not contribute to the risk of POAG in the Caucasian population

Therapeutic Approaches Using Host Defence Peptides to Tackle Herpes Virus Infections

One of the most common viral infections in humans is caused by herpes simplex virus (HSV). It can easily be treated with nucleoside analogues (e.g., acyclovir), but resistant strains are on the rise. Naturally occurring antimicrobial peptides have been demonstrated to possess antiviral activity against HSV. New evidence has also indicated that these host defence peptides are able to selectively stimulate the innate immune system to fight of infections. This review will focus on the anti-HSV activity of such peptides (both natural and synthetic), describe their mode of action and their clinical potential

Herpes Virus Amplicon Vectors

Since its emergence onto the gene therapy scene nearly 25 years ago, the replication-defective Herpes Simplex Virus Type-1 (HSV-1) amplicon has gained significance as a versatile gene transfer platform due to its extensive transgene capacity, widespread cellular tropism, minimal immunogenicity, and its amenability to genetic manipulation. Herein, we detail the recent advances made with respect to the design of the HSV amplicon, its numerous in vitro and in vivo applications, and the current impediments this virus-based gene transfer platform faces as it navigates a challenging path towards future clinical testing

ISRCTN12125882 - Influence of topical anti-VEGF (Ranibizumab) on the outcome of filtration surgery for glaucoma - Study Protocol

<p>Abstract</p> <p>Background</p> <p>Excessive wound healing, with scarring of the episcleral tissue or encapsulation of the filtering bleb is the main reason for failure in trabeculectomy. Ranibizumab, an inhibitor of the Vascular Endothelial Growth Factor (VEGF), is seen as a promising candidate to prevent or treat extensive wound healing. We describe the design of a two phased study, i) assessing the local tolerability and safety of topical ranibizumab and ii) assessing the efficacy of topical ranibizumab against placebo in patients who underwent trabeculectomy with mitomycin C combined with phacoemulsification and intra ocular lens (IOL) implantation.</p> <p>Methods/Design</p> <p>In the first phase five patients that had trabeculectomy with mitomycin C combined with phacoemulsification and IOL implantation will be treated with topical ranibizumab (Lucentis^®) eye drops (2 mg/ml) four times daily for one month. The treatment will be started at the first postoperative day. Patients will be assessed for local and systemic side effects using a standardised schedule. In the second phase, after successful completion of phase 1, consenting eligible patients who underwent trabeculectomy with mitomycin C combined with phacoemulsification and IOL implantation will be randomised to either receive topical ranibizumab eye drops (2 mg/ml) four times daily for 1 month or placebo (BSS 4x/d for 1 month). Patients will be reviewed weekly for 4 weeks until conjunctival sutures are removed. Further follow up examinations are planned after 3 and six months. Assessment of differences in the intraocular eye pressure will be considered primary, and bleb appearance/vascularisation using a standardized photography and the Moorfields bleb grading system, postoperative intraocular pressure and conjunctival wound healing problems will be considered secondary outcome parameters.</p> <p>Discussion</p> <p>Anti-VEGF-antibodies might be more effective in preventing scaring and might have fewer toxic side effects than the currently used anti-metabolites and may replace them in the long term.</p> <p>Trial Registration</p> <p>ISRCTN: <a href="http://www.controlled-trials.com/ISRCTN12125882">ISRCTN12125882</a></p