Detection of retinal lipid hydroperoxides in experimental uveitis.
In our on-going studies of experimental uveitis, we previously obtained a preliminary indication of phagocyte-mediated retinal lipid peroxidation by measuring conjugated dienes (CD), thiobarbituric acid reactive substances (TBARS) and fluorescent chromolipids. Using gas chromatography/mass spectrometry (GC/MS), the current study detected hydroperoxide-derived 10-, 11-, 13-, 14-, and 17-hydroxydocosahexaenoic acid (HDHE) in retinal membranes. Docosahexaenoic acid (22:6) is the major polyunsaturated fatty acid (PUFA) in photoreceptor membranes. Hydroperoxides from other retinal PUFA were found also. Arachidonic acid (20:4) yielded 8-, 9-, 11-, 12-hydroxyeicosatetraenoic acid (HETE) as major products. Since 12-HETE could also arise from lipoxygenase catalyzed oxygenation of free 20:4, the source of 12-HETE could be both peroxidative and lipoxygenase pathways. Concomitantly, peroxidative loss of 22:6 and accumulation of 20:4 were also noted. At the peak of inflammation, loss of 22:6 was close to 50% of the original amount in the control retinas. In the same time period, 20:4 increased more than two-fold. The present data suggest that the oxygen radicals derived from phagocytes initiate the retinal lipid peroxidation, and the resultant formation of hydroperoxides, oxidative loss of 22:6 and accumulation of 20:4 appear to serve as amplification factors in subsequent biochemical events, such as chemotaxis of PMNs and activation of cyclooxygenase.
Wu
G S
GS
Doheny Eye Institute, Los Angeles, CA 90033.
Sevanian
A
A
Rao
N A
NA
D000818:Animals; D001327:Autoimmune Diseases / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000032:analysis / Q000096:biosynthesis; D005260:Female; D005609:Free Radicals; D015227:Lipid Peroxidation; D008054:Lipid Peroxides / Q000032:analysis* / Q000096:biosynthesis; D008563:Membrane Lipids / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D011917:Rats, Inbred Lew; D012160:Retina / Q000737:chemistry*; D014605:Uveitis / Q000378:metabolism*
D005231:Fatty Acids, Unsaturated; D005609:Free Radicals; D008054:Lipid Peroxides; D008563:Membrane Lipids