RESUMO
Heme oxygenase (HO) has antioxidant properties and is up-regulated by reactive oxygen species (ROS) in ultraviolet-B-irradiated soybean plants. This study shows that nitric oxide (NO) protects against oxidative damage and that nitric oxide synthase (NOS)-like activity is also required for HO-1 induction under UV-B radiation. Pre-treatments with sodium nitroprussiate (SNP), a NO-donor, prevented chlorophyll loss, H(2)O(2) and O(2)(*-) accumulation, and ion leakage in UV-B-treated plants. HO activity was significantly enhanced by NO and showed a positive correlation with HO-1 transcript levels. In fact, HO-1 mRNA levels were increased 2.1-fold in 0.8 mM SNP-treated plants, whereas subsequent UV-B irradiation augmented this expression up to 3.5-fold with respect to controls. This response was not observed using ferrocyanide, a SNP inactive analog, and was effectively blocked by 2-(4-carboxyphenil)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), a specific NO-scavenger. In addition, experiments carried out in the presence of N(G)-nitro-L-arginine methyl ester (L-NAME) or tungsten, well-known inhibitors of NOS and nitrate reductase, showed that NOS is the endogenous source of NO that mediates HO-1 expression. In summary, we found that NO is involved in the signaling pathway leading to HO-1 up-regulation under UV-B, and that a balance between NO and ROS is important to trigger the antioxidant response against oxidative stress.
Assuntos
Glycine max/metabolismo , Heme Oxigenase (Desciclizante)/metabolismo , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico/biossíntese , Raios Ultravioleta , Clorofila/análise , Clorofila/metabolismo , Clorofila/efeitos da radiação , Heme Oxigenase (Desciclizante)/efeitos da radiação , Peróxido de Hidrogênio/análise , NG-Nitroarginina Metil Éster/química , Óxido Nítrico Sintase/efeitos da radiação , Estresse Oxidativo/efeitos da radiação , Folhas de Planta/química , Espécies Reativas de Oxigênio/análise , Espécies Reativas de Oxigênio/metabolismo , Glycine max/genética , Glycine max/efeitos da radiação , Substâncias Reativas com Ácido Tiobarbitúrico/análiseRESUMO
In this study, we show that one single dose of gamma-irradiation at birth induces an inhibition of the cerebellar calcium dependent nitric oxide synthase (NOS) activity, probably correlated to the motor abnormalities and the disarrangement in the cerebellar cytoarchitecture observed in adult rats. This decrease in calcium dependent NOS activity could be associated with an increased protein kinase C (PKC) activity. PKC inhibition partially restores calcium dependent NOS activity, indicating that PKC activity could be negatively modulating the catalytic activity of calcium dependent NOS. These findings suggest that a decrease in nitric oxide (NO) production and the related increase in PKC activity could be intracellular events that participate in the onset of motor and cerebellar abnormalities induced by postnatal gamma-irradiation at early stages of life.
Assuntos
Cerebelo/enzimologia , Cerebelo/efeitos da radiação , Raios gama , Óxido Nítrico Sintase/efeitos da radiação , Proteína Quinase C/efeitos da radiação , Lesões Experimentais por Radiação/enzimologia , Análise de Variância , Animais , Animais Recém-Nascidos , Calbindinas , Cálcio/metabolismo , Cerebelo/patologia , Feminino , Marcha/efeitos da radiação , Masculino , Neurônios/enzimologia , Neurônios/patologia , Neurônios/efeitos da radiação , Ratos , Ratos Wistar , Proteína G de Ligação ao Cálcio S100/efeitos da radiação , Transdução de Sinais/efeitos da radiação , Fatores de TempoRESUMO
A characterization of nitric oxide synthase (NOS) in the golden hamster retina was performed. Enzymatic activity was partially Ca2+ and calmodulin-dependent, required NADPH, and was inhibited by L-arginine analogs. Retinal NOS activity was higher at midnight than at midday. When the hamster were placed under constant darkness for 24 or 48 h, and killed at equivalent time points, representing subjective day and subjective night respectively, the differences in NOS activity disappeared. One hour of darkness during the day increased, while the same period of light during the night decreased, retinal NOS activity. From these results, it might be presumed that hamster retinal NOS activity is regulated by the photic stimulus.