Timothy W. Olsen

Transformation of the proteasome with age-related macular degeneration

The proteasome mediates pathways associated with oxidative stress and inflammation, two pathogenic events correlated with age‐related macular degeneration (AMD). In human donor eyes corresponding to four stages of AMD, we found the proteasomal chymotrypsin‐like activity increased in neurosensory retina with disease progression. Increased activity correlated with a dramatic increase in the inducible subunits of the immunoproteasome, which was not due to an increase in CD45 positive immune cells in the retina. The novel observation of proteasome transformation may reflect retinal response to local inflammation or oxidative stress with AMD.

Human Retinal Pigment Epithelium Proteome Changes in Early Diabetes

Aims/hypothesisDiabetic retinopathy is the most common complication of diabetes and a leading cause of blindness among working-age adults. Anatomical and functional changes occur in the retina and retinal pigment epithelium (RPE) prior to clinical symptoms of the disease. However, the molecular mechanisms responsible for these early changes, particularly in the RPE, remain unclear. To begin defining the molecular changes associated with pre-retinopathic diabetes, we conducted a comparative proteomics study of human donor RPE.MethodsThe RPE was dissected from diabetic human donor eyes with no clinically apparent diabetic retinopathy (n = 6) and from eyes of age-matched control donors (n = 17). Soluble proteins were separated based upon their mass and charge using two-dimensional (2-D) gel electrophoresis. Protein spots were visualised with a fluorescent dye and spot densities were compared between diabetic and control gels. Proteins from spots with significant disease-related changes in density were identified using mass spectrometry.ResultsAnalysis of 325 spots on 2-D gels identified 31 spots that were either up- or downregulated relative to those from age-matched control donors. The protein identity of 18 spots was determined by mass spectrometry. A majority of altered proteins belonged to two major functional groups, metabolism and chaperones, while other affected categories included protein degradation, synthesis and transport, oxidoreductases, cytoskeletal structure and retinoid metabolism.Conclusions/interpretationChanges identified in the RPE proteome of pre-retinopathic diabetic donor eyes compared with age-matched controls suggest specific cellular alterations that may contribute to diabetic retinopathy. Defining the pre-retinopathic changes affecting the RPE could provide important insight into the molecular events that lead to this disease.

The HtrA1 Promoter Polymorphism, Smoking, and Age-related Macular Degeneration in Multiple Case-control Samples

OBJECTIVE To assess the association and combined effect on the risk of age-related macular degeneration (AMD) by the HtrA1 and complement factor H (CFH) polymorphisms, smoking, and serum cholesterol. DESIGN Clinic-based and population-based case control study. PARTICIPANTS A total of 805 AMD cases and 921 controls from The Eye Clinic of National Eye Institute, Age-Related Eye Diseases Study, Blue Mountain Eye Study Cohort, and Minnesota Lions Eye Bank. METHODS DNA samples were genotyped for polymorphisms of rs11200638 in HtrA1 promoter and rs380390 in CFH. HtrA1 protein in ocular tissue was measured. Interactions of the HtrA1 risk allele with the CFH risk variant, smoking status, and cholesterol were assessed. MAIN OUTCOME MEASURES AMD was evaluated by retinal specialists, and AMD subtypes (geographic atrophy and neovascularization) were determined. RESULTS Strong associations of the HtrA1 risk allele (A) with AMD were present in all sample sets. A similar magnitude of association was observed for central geographic atrophy and neovascular AMD. The combination of the HtrA1 and CFH risk alleles increased AMD susceptibility, as did the combination of the HtrA1 risk allele with smoking. No combined effect of HtrA1 risk allele and cholesterol level was found. Enhanced expression of HtrA1 protein was detected in retina with AMD. CONCLUSIONS Findings from multiple samples support an AMD genetic variant harbored within HtrA1. The risk of advanced AMD increased when the presence of risk alleles from HtrA1 was combined with either CFH risk alleles or history of smoking.

Predicting Visual Acuity in Children With Colobomas Involving the Optic Nerve

BACKGROUND This study evaluates the relationship to visual acuity of four ophthalmoscopic features of colobomas involving the optic nerve. The goal was to identify those features that could predict potential visual acuity of children with these colobomas. METHODS Fundus photographs of 23 eyes with colobomas involving the optic nerve met the entry criteria and were evaluated by two masked observers. The following features were evaluated: coloboma size, optic nerve color, foveal development, and subfoveal retinal pigment epithelial changes. Simple linear regression was used to identify the feature that most closely correlated with visual acuity. Refractive status was assessed by cycloplegic refraction. RESULTS The only component that correlated with the development of good visual acuity was the degree of foveal involvement by the optic nerve coloboma (P = .002, R = 0.8). Significant refractive error and anisometropia were common in patients with colobomas involving the optic nerve. CONCLUSION Central visual acuity in children born with colobomas involving the optic nerve correlates with the development of normal foveal anatomy, regardless of the size of the coloboma, the color of the optic nerve, or the presence of subfoveal pigmentary changes. Because refractive error is common, these children should receive an accurate refraction and amblyopia treatment.

IRIS stiffening following drug stimulation

Glaucoma is a general term for the deterioration of the optic nerve head usually associated with an increase of intraocular pressure (IOP). Certain types of glaucoma are associated directly with the displacement of the iris from its normal morphology [1]. For example, angle closure glaucoma and pigment dispersion syndrome involve abnormal anterior or posterior displacement of the iris, respectively [2]. In angle closure, the abnormal position of the peripheral iris blocks aqueous humor access to the outflow pathway (trabecular meshwork), increasing the IOP. Although there has been a considerable amount of ultrastructural characterization of the iris [3], to our knowledge, there as been little done on the mechanical characterization of the iris other than a previous study by Heys and Barocas on passive bovine irides [4]. To have a complete understanding of these it requires that we understand the mechanical properties of the iris in both its passive and stimulated states. Mechanical analysis of the iris requires the consideration of its two constituent muscles, the inner sphincter iridis and the outer dilator pupillae, see Fig. 1. The sphincter iridis is innervated parasympathetically whereas the dilator is innervated sympathetically.Copyright