Identification of 4-hydroxynonenal-modified retinal proteins induced by photooxidative stress prior to retinal degeneration.
4-Hydroxynonenal (4-HNE) is a reactive aldehyde species generated endogenously from the nonenzymatic oxidation of n-6 polyunsaturated fatty acids under physiological conditions. We have reported that intense white light exposure increases 4-HNE-protein modification in the retina prior to the onset of photoreceptor cell apoptosis. To understand the molecular mechanism(s) underlying the retinal degeneration induced by photooxidative stress, we identified 4-HNE-modified retinal proteins using a proteomic approach. Albino rats were exposed to 5 k lx white fluorescent light for 3 h and retinas were removed 24 h later and pooled. By Western dot blot analysis, the total intensity of 4-HNE-modified proteins was increased 1.5-fold following the exposure compared to dim light controls. In two independent sets of two-dimensional gel electrophoresis/Western blots followed by peptide mass fingerprinting (PMF), nine proteins including voltage-dependent anion channel, enolase 1alpha, aldolase C, crystallins alphaA and betaB3, heterogeneous nuclear ribonucleoprotein A2/B1, albumin, and glutamine synthetase were identified. We observed that 4-HNE modifications of retinal proteins are specific to a particular set of proteins rather than random events on abundant proteins. By immunohistochemistry, localization of 3 identified proteins overlapped with immunoreactivity of 4-HNE-modified proteins in light-exposed retinas. Intense light exposure increases 4-HNE-protein modifications on specific retinal proteins in several functional categories including energy metabolism, glycolysis, chaperone, phototransduction, and RNA processing. Together with previous reports that 4-HNE modification changes protein activities, these results suggest a close association of 4-HNE-protein modifications with the initiation of light-induced retinal degeneration.
Tanito
Masaki
M
Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA. tanito-oph@umin.ac.jp
Haniu
Hisao
H
Elliott
Michael H
MH
Singh
Anil K
AK
Matsumoto
Hiroyuki
H
Anderson
Robert E
RE
D000447:Aldehydes / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D015180:Electrophoresis, Gel, Two-Dimensional; D005136:Eye Proteins / Q000378:metabolism* / Q000528:radiation effects; D005260:Female; D008027:Light / Q000009:adverse effects; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D040901:Proteomics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000378:metabolism* / Q000528:radiation effects; D012162:Retinal Degeneration / Q000209:etiology / Q000378:metabolism*; D014018:Tissue Distribution
D000447:Aldehydes; D005136:Eye Proteins; C027576:4-hydroxy-2-nonenal