title: Nitric oxide synthesis is increased in cybrid cells with m.3243A>G mutation.
abstract: Nitric oxide (NO) is a free radical and a signaling molecule in several pathways, produced by nitric oxide synthase (NOS) from the conversion of L-arginine to citrulline. Supplementation of L-arginine has been used to treat MELAS (mitochondrial encephalopathy with lactic acidosis and stroke like syndrome), a mitochondrial disease caused by the m.3243A>G mutation. Low levels of serum arginine and endothelium dysfunction have been reported in MELAS and this treatment may increase NO in endothelial cells and promote vasodilation, decreasing cerebral ischemia and strokes. Although clinical benefits have been reported, little is known about NO synthesis in MELAS. In this study we found that osteosarcoma derived cybrid cells with high levels of m.3243A>G had increased nitrite, an NO metabolite, and increased intracellular NO, demonstrated by an NO fluorescent probe (DAF-FM). Muscle vessels from patients with the same mutation had increased staining in NADPH diaphorase, suggestive of increased NOS. These results indicate increased production of NO in cells harboring the m.3243A>G, however no nitrated protein was detected by Western blotting. Further studies are necessary to clarify the exact mechanisms of L-arginine effect to determine the appropriate clinical use of this drug therapy.
authors.affiliation: Department of Neurology and Neurosurgery, Escola Paulista de Medicina,  Universidade Federal de São Paulo, R. Pedro de Toledo, 781, São Paulo 04039-032, Brazil. chtengan@unifesp.br.
authors.forename: Juliana
authors.initials: J
authors.lastname: Gamba
authors.forename: Luana T
authors.initials: LT
authors.lastname: Gamba
authors.forename: Gabriela S
authors.initials: GS
authors.lastname: Rodrigues
authors.forename: Beatriz H
authors.initials: BH
authors.lastname: Kiyomoto
authors.forename: Carlos T
authors.initials: CT
authors.lastname: Moraes
authors.forename: Celia H
authors.initials: CH
authors.lastname: Tengan
mesh_terms: D000328:Adult; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002675:Child, Preschool; D004272:DNA, Mitochondrial / Q000235:genetics*; D004579:Electron Transport; D005452:Fluoresceins / Q000378:metabolism; D005453:Fluorescence; D006801:Humans; D008875:Middle Aged; D009132:Muscles / Q000098:blood supply / Q000473:pathology; D009154:Mutation / Q000235:genetics*; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D009573:Nitrites / Q000378:metabolism; D015538:Nitrosation; D013053:Spectrophotometry; D055815:Young Adult
chemical_list: C503301:4-amino-5-methylamino-2',7'-difluorofluorescein diacetate; D004272:DNA, Mitochondrial; D005452:Fluoresceins; D009573:Nitrites; D009569:Nitric Oxide; D009252:NADPH Dehydrogenase