Methylene blue application as a therapeutic strategy to treat experimental ROP.

REY-FUNES, M.; FERNANDEZ, JC; CONTARTESE, DS.; ROLÓN, F.; PEÑA, E.; SAROTTO, A.; IBARRA, ME.; INSERRA, PF:; MARTÍNEZ-MURILLO, R.; MARTÍNEZ, A.; LOPEZ, JJ.; DORFMAN, VB.; LOIDL, CF.

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Congreso; Congreso de la Sociedad Española de Histología e Ingeniería Tisular (SEHIT); 2013

Sociedad Española de Histología e Ingeniería Tisular (SEHIT)

Perinatal asphyxia is able to induce retinal lesions, generating ischemic proliferative retinopathy (IPR) resulting, in severe cases, in blindness. Previously we have demonstrated in this model retinal neurodegeneration, gliosis, and neovascularization, which are compatible with retinopathy of prematurity (ROP). Furthermore we have identified the involvement of the nitrergic system in this physiopathology. We hypothesize the participation of nitric oxide (NO) through the neuronal isoform of the enzyme nitric oxide synthase (nNOS) as trigger of the previously observed structural and molecular alterations, and analyze the application of methylene blue (MB), a NOS inhibitor, as a therapeutic strategy. We used 30 days-old male Sprague-Dawley rats (n=5/group) obtained as follows: 1) PA were animals exposed to perinatal asphyxia (20 min., at 37ºC), 2) PA+MB were animals born from pregnant to term female rats treated with MB (2 mg/kg) 30 and 5 min before delivery and subjected to PA induction during 20 min. at 37ºC, 3) CTL were born to term animals. Constitutive NOS enzymatic activity, NADPH diaphorase histochemical method, immunohistochemistry and Western-blot assay for nNOS were used to evaluate retinas. A significant increase of nNOS activity was observed in retinas of 30 day-old animals subjected to PA compared to CTL (PA=10,8±0,4; CTL=9,1±0,3 pmol/min/mg protein, p<0,05), while PA+MB animals showed no significant differences with CTL. This was correlated with a 28% significant increment in nNOS expression in PA vs CTL with a significant 60% reduction in PA+MB vs CTL. Histochemical and immunohistochemical studies support these results, with nNOS localization in ganglionar and amacrine cells. Application of MB as a therapeutic strategy showed a strong effect inhibiting constitutive NOS activity and nNOS expression. This finding stimulates future studies aiming to use MB as a new treatment to avoid or decrease retinal damage in the context of ROP.