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Relevance of reactive oxygen and nitrogen species interaction in Leber’s hereditary optic neuropathy

Leber’s hereditary optic neuropathy (LHON) is a mitochondrial disorder caused by point mutations in complex I subunit genes and characterized by the preferential loss of retinal ganglion cells, leading to optic nerve degeneration [1, 2]. The mechanisms of LHON pathogenesis are still not well understood ; cell and animal models point to oxidative stress and impairment of redox homeostasis as important factors contributing to LHON pathophysiology. Long-term exposure to nitric oxide (NO) is known to impair mitochondrial proteins, leading to persistent inhibition of mitochondrial function and to cell death. We have collected evidence that allowed us to hypothesize that chronic changes in the NO homeostasis could contribute to cell dysfunction in LHON patients [3]. We found that peripheral blood mononuclear cells, derived from a female LHON patient with bilateral reduced vision and carrying the pathogenic mutation 11778/ND4, display increased cellular levels of reactive oxygen and nitrogen species, with accumulation of nitrite/nitrate and 3- nitrotyrosine. Moreover, we show that lymphoblasts from the same patient are more susceptible to prolonged NO exposure. These unprecedented observations suggest that oxidative and nitrosative stress can play a role in driving the pathology when excess NO is available.

Leber’s hereditary optic neuropathy ; nitric oxide

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