cytochrome-c-t and Uveitis

Uveitis refers to a group of ocular inflammatory diseases that can lead to blindness. For years, researchers have been trying to decipher the underlying mechanisms and develop therapeutic strategies using the model of experimental autoimmune uveitis (EAU). Recently, αA-crystallin has been found to be upregulated in EAU and can even ameliorate its severity through different mechanisms, suggesting its use as a potent therapeutic factor against uveitis. Here we review the protective role of αA-crystallin and discuss its functional mechanisms in EAU.

Topics: alpha-Crystallin A Chain; Animals; Autoimmune Diseases; Cytochromes c; Cytokines; Disease Models, Animal; Gene Expression Regulation; Humans; Mitochondria; Oxidative Stress; Photoreceptor Cells; Retina; T-Lymphocyte Subsets; Toll-Like Receptors; Uveitis

During the early phase of experimental autoimmune uveitis (EAU), before macrophages infiltrate the retina and uvea, photoreceptor mitochondrial oxidative stress, nitration of photoreceptor mitochondrial proteins, and release of cytochrome c have been observed. However, no apoptosis has been detected during this phase. In this study, alphaA-crystallin upregulation in the retina and its antiapoptotic protective role were evaluated in early EAU.. Gene microarrays were first used to identify upregulated genes in retinas with early EAU. Among highly upregulated crystallins, alphaA was confirmed by real-time polymerase chain reaction and Western blot, and the site of upregulation was localized by immunohistochemistry. The association of alphaA-crystallin to nitrated cytochrome c and interaction with a procaspase-3 subunit was assayed. Photoreceptor apoptosis in alphaA knockout mice was compared with that in wild-type animals with EAU, by using the terminal transferase dUTP nick-end labeling assay and polymerase chain reaction.. In early EAU, alphaA-crystallin was increased 33-fold, and the site of increase was localized to the photoreceptor inner segments. This crystallin suppressed apoptosis by associating with the nitrated cytochrome c and p24. The association with nitrated cytochrome c, in particular, appeared to be restricted to nitrated cytochrome c, and thus, no association of non-nitrated cytochrome c was detected. The knockout mice showed signs of EAU development early and showed apoptosis in the retina; no such changes were seen in the wild-type control animals.. alphaA-Crystallin is highly upregulated in the retina during early EAU. This upregulation is localized primarily in the photoreceptor inner segments, the site of mitochondrial oxidative stress. Further, in early EAU, the photoreceptors preferentially use alphaA-crystallin to suppress mitochondrial oxidative stress-mediated apoptosis.

Topics: alpha-Crystallin A Chain; Animals; Apoptosis; Autoimmune Diseases; Blotting, Western; Caspase 3; Cytochromes c; Disease Models, Animal; Fluorescent Antibody Technique, Indirect; Gene Expression Regulation; Heat-Shock Proteins; In Situ Nick-End Labeling; Mice; Mice, Knockout; Oligonucleotide Array Sequence Analysis; Oxidative Stress; Photoreceptor Cells, Vertebrate; Retina; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Up-Regulation; Uveitis

In experimental autoimmune uveitis (EAU), phagocytes are thought to be the primary cells in the initiation and maintenance of pathologic tissue damage through the release of cytotoxic agents. Recently, the presence of nitric oxide synthase has been shown in mammalian mitochondria. In this study, the effect of mitochondrial peroxynitrite on the modification of cellular proteins was evaluated in the early phase of uveitis, before the infiltration of leukocytes.. Tyrosine nitration in proteins was detected by UV/Vis (visible) absorption and Western blot analysis. The identity of the nitrated protein was obtained by liquid chromatography-tandem mass spectrometry. The release of cytochrome c was assessed in whole retinal extract and in isolated mitochondria. The protein nitration in the inflamed retina was also localized by immunohistochemistry.. Before the leukocyte infiltration in the early phase of EAU, the mitochondria-originated peroxynitrite initiated the inflammatory insult by specifically nitrating three mitochondrial proteins. In vitro nitration of the control retina by peroxynitrite donor resulted in nonspecific nitration of all major retinal proteins. After nitration, cytochrome c was displaced from its original binding site in the respiratory chain. Further, the nitration appeared to commence in the early phase of inflammation, on postimmunization day 5, long before the peak of inflammation on day 14. Immunohistochemically, tyrosine-nitrated proteins were localized exclusively in the photoreceptor inner segments, which are known to be densely populated with mitochondria.. These data indicate that mitochondrial proteins are the prime targets of inactivation by the mitochondrial peroxynitrite and that photoreceptor mitochondria initiate the subsequent irreversible retinal damage in experimental uveitis.

Topics: Amino Acid Sequence; Animals; Autoimmune Diseases; Blotting, Western; Cytochromes c; Disease Models, Animal; Immunoenzyme Techniques; Mass Spectrometry; Mitochondrial Proteins; Molecular Chaperones; Molecular Sequence Data; Nitrosation; Peroxynitrous Acid; Phosphoglycerate Mutase; Photoreceptor Cells, Vertebrate; Rats; Rats, Inbred Lew; Retina; Spectrophotometry, Ultraviolet; Tyrosine; Uveitis