Mitochondrial Oxidative DNA Damage In Experimental Autoimmune Uveitis
Rahul N Khurana 1,
Jignesh G Parikh 1,
Sindhu Saraswathy 1,
Guey Shuang Wu 1,
and
Narsing A. Rao 2*
1 Ophthalmology, Doheny Eye Institute, Los Angeles, California, United States
2 Ophthalmology, Doheny Eye Insitute, 1450 San Pablo Street, DVRC211, Los Angeles, California, 90025, United States
* To whom correspondence should be addressed. E-mail: nrao{at}usc.edu.
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Abstract |
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Abstract
Purpose: In experimental autoimmune uveitis (EAU), recent work has demonstrated that retinal damage involves oxidative stress early in the uveitis before macrophage cellular infiltration. The purpose of this study is to determine whether oxidative mitochondrial DNA damage occurs early in EAU before the leukocyte infiltration.
Methods: Lewis rats were immunized with S-antigen mixed with complete Freund’s adjuvant (CFA) to induce EAU. Nonimmunized animals and animals injected with CFA served as controls. Animals were killed on days 3, 4, 7, and 12 after immunization. Damage to mitochondrial DNA and nuclear DNA was assessed using a novel long quantitative polymerase chain reaction (PCR) technique. TUNEL staining to detect apoptosis and immunohistochemical detection of leukocyte infiltration in EAU retinas were also performed at the above time points.
Results: Mitochondrial DNA damage occurred early in EAU beginning at day 4 and continued throughout until Day 12. At early phase of EAU, (day 4 through Day 7), there was no inflammatory cell infiltration. On day 12 there was infiltration of inflammatory cells in the retina and uvea. Nuclear DNA damage occurred later in EAU at day 12. There was neither mitochondrial nor nuclear DNA damage in the controls. TUNEL positive staining for apoptosis was only detected at day 12 in EAU retina.
Conclusions: Oxidative mitochondrial DNA damage begins at day 4 in EAU. This further supports that oxidative stress selectively occurs in the mitochondria in the early phase of EAU before leukocyte infiltration. Such oxidative damage in the mitochondria may be the initial event leading to retinal degeneration in EAU.
Key Words:
mitochondria, oxidative damage, uveoretinitis, autoimmune response/disease
