Proteomics Analysis of Molecular Risk Factors in the Ocular Hypertensive Human Retina.
OBJECTIVE
To better understand ocular hypertension-induced early molecular alterations that may determine the initiation of neurodegeneration in human glaucoma, this study analyzed retinal proteomic alterations in the ocular hypertensive human retina.


METHODS
Retina samples were obtained from six human donors with ocular hypertension (without glaucomatous injury) and six age- and sex-matched normotensive controls. Retinal proteins were analyzed by two-dimensional LC-MS/MS (liquid chromatography and linear ion trap mass spectrometry) using oxygen isotope labeling for relative quantification of protein expression. Proteomics data were validated by Western blot and immunohistochemical analyses of selected proteins.


RESULTS
Out of over 2000 retinal proteins quantified, hundreds exhibited over 2-fold increased or decreased expression in ocular hypertensive samples relative to normotensive controls. Bioinformatics linked the proteomics datasets to various pathways important for maintenance of cellular homeostasis in the ocular hypertensive retina. Upregulated proteins included various heat shock proteins, ubiquitin proteasome pathway components, antioxidants, and DNA repair enzymes, while many proteins involved in mitochondrial oxidative phosphorylation exhibited downregulation in the ocular hypertensive retina. Despite the altered protein expression reflecting intrinsic adaptive/protective responses against mitochondrial energy failure, oxidative stress, and unfolded proteins, no alterations suggestive of an ongoing cell death process or neuroinflammation were detectable.


CONCLUSIONS
This study provides information about ocular hypertension-related molecular risk factors for glaucoma development. Molecular alterations detected in the ocular hypertensive human retina as opposed to previously detected alterations in human donor retinas with clinically manifest glaucoma suggest that proteome alterations determine the individual threshold to tolerate the ocular hypertension-induced tissue stress or convert to glaucomatous neurodegeneration when intrinsic adaptive/protective responses are overwhelmed.
Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States.
Xiangjun
X
Yang
Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States.
Gözde
G
Hondur
Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky, United States.
Ming
M
Li
Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky, United States.
Jian
J
Cai
Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky, United States 3Robley Rex Veterans Administration Medical Center, Louisville, Kentucky, United States.
Jon B
JB
Klein
Department of Ophthalmology & Visual Sciences, University of Iowa Carver College of Medicine, Iowa City, Iowa, United States.
Markus H
MH
Kuehn
Department of Ophthalmology Columbia University College of Physicians and Surgeons, New York, New York, United States.
Gülgün
G
Tezel
D000369:Aged, 80 and over; D015153:Blotting, Western; D016022:Case-Control Studies; D002853:Chromatography, Liquid; D015180:Electrophoresis, Gel, Two-Dimensional; D005136:Eye Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007429:Intraocular Pressure; D008297:Male; D009798:Ocular Hypertension / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D040901:Proteomics / Q000379:methods; D012160:Retina / Q000378:metabolism*; D012307:Risk Factors; D053719:Tandem Mass Spectrometry
D005136:Eye Proteins