Elevated albumin in retinas of monkeys with experimental glaucoma.
OBJECTIVE
To establish the identity of a prominent protein, approximately 70 kDa, that is markedly increased in the retina of monkeys with experimental glaucoma compared with the fellow control retina, the relationship to glaucoma severity, and its localization in the retina.


METHODS
Retinal extracts were subjected to 2-D gel electrophoresis to identify differentially expressed proteins. Purified peptides from the abundant 70 kDa protein were analyzed and identified by liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) separation, and collision-induced dissociation sequencing. Protein identity was performed on MASCOT (Matrix Science, Boston, MA) and confirmed by Western blot. The relationship between the increase in this protein and glaucoma severity was investigated by regression analyses. Protein localization in retina was evaluated by immunohistochemistry with confocal imaging.


RESULTS
The abundant protein was identified as Macaca mulatta serum albumin precursor (67 kDa) from eight non-overlapping proteolytic fragments, and the identity was confirmed by Western blot. The average increase in retinal albumin content was 2.3 fold (P = 0.015). In glaucoma eyes, albumin was localized to some neurons of the inner nuclear layer, in the inner plexiform layer, and along the vitreal surface, but it was only found in blood vessels in control retinas.


CONCLUSIONS
Albumin is the abundant protein found in the glaucomatous monkey retinas. The increased albumin is primarily localized to the inner retina where oxidative damage associated with experimental glaucoma is known to be prominent. Since albumin is a major antioxidant, the increase of albumin in the retinas of eyes with experimental glaucoma may serve to protect the retina against oxidative damage.
Richard S. Ruiz Department of Ophthalmology and Visual Science, University of Texas Medical School at Houston, Houston, Texas 77030, USA. louvenia.carter-dawson@uth.tmc.edu
Louvenia
L
Carter-Dawson
Yujin
Y
Zhang
Ronald S
RS
Harwerth
Ricky
R
Rojas
Pramod
P
Dash
Xinping C
XC
Zhao
Elizabeth
E
WoldeMussie
Guadalupe
G
Ruiz
Alice
A
Chuang
William P
WP
Dubinsky
John B
JB
Redell
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005901:Glaucoma / Q000378:metabolism* / Q000503:physiopathology; D007429:Intraocular Pressure; D008253:Macaca mulatta; D008297:Male; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism; D040901:Proteomics; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000378:metabolism*; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D014065:Tonometry, Ocular
D011498:Protein Precursors; D012709:Serum Albumin