RESUMO
The aim of the present study was to analyse the morphology of white skeletal muscle in males and females from the GH-transgenic zebrafish (Danio rerio) lineage F0104, comparing the expression of genes related to the somatotrophic axis and myogenesis. Histological analysis demonstrated that transgenic fish presented enhanced muscle hypertrophy when compared to non-transgenic fish, with transgenic females being more hypertrophic than transgenic males. The expression of genes related to muscle growth revealed that transgenic hypertrophy is independent from local induction of insulin-like growth factor 1 gene (igf1). In addition, transgenic males exhibited significant induction of myogenin gene (myog) expression, indicating that myog may mediate hypertrophic growth in zebrafish males overexpressing GH. Induction of the α-actin gene (acta1) in males, independently from transgenesis, also was observed. There were no significant differences in total protein content from the muscle. Our results show that muscle hypertrophy is independent from muscle igf1, and is likely to be a direct effect of excess circulating GH and/or IGF1 in this transgenic zebrafish lineage.
Assuntos
Animais Geneticamente Modificados/genética , Hormônio do Crescimento/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Músculo Esquelético/patologia , Regulação para Cima , Peixe-Zebra/genética , Animais , Modelos Animais de Doenças , Feminino , Hormônio do Crescimento/genética , Humanos , Hipertrofia/genética , Hipertrofia/metabolismo , Fator de Crescimento Insulin-Like I/genética , Masculino , Desenvolvimento Muscular/genética , Músculo Esquelético/metabolismo , Fatores Sexuais , Peixe-Zebra/metabolismoRESUMO
The aim of this study was to evaluate the effects of growth hormone (GH) overexpression on the gene expression profile of multiple components of the antioxidant defense system (ADS) of different genotypes of a GH-transgenic zebrafish (Danio rerio) model. Several ADS-related genes were analyzed by semiquantitative reverse transcription-PCR in the liver of hemizygous (HE) and homozygous (HO) transgenic zebrafish. The results showed a significant reduction in the glutamate cysteine ligase catalytic subunit (GCLC) and the gene expression of two glutathione S-transferase (GST) isoforms and an increase in the glutathione reductase gene in the HO group compared to non-transgenic controls. The expression of the Cu, Zn-superoxide dismutase (SOD1) and catalase (CAT) genes was reduced in HO and HE groups, respectively. Among the ten genes analyzed, two were altered in HE transgenic zebrafish and five were altered in HO transgenic zebrafish. These findings indicate a genotype-dependent gene expression profile of the ADS-related genes in the liver of our GH-transgenic zebrafish model and are in agreement with the general effects of GH hypersecretion in the fish and mouse, which involves a reduction in the capability of the tissues to deal with oxidative stress situations. The GH-transgenic zebrafish model used here seems to be an interesting tool for analyzing the effect of different GH expression levels on physiological processes.
Assuntos
Animais Geneticamente Modificados/metabolismo , Antioxidantes/metabolismo , Perfilação da Expressão Gênica , Hormônio do Crescimento/genética , Fígado/enzimologia , Modelos Animais , Peixe-Zebra/metabolismo , Animais , Animais Geneticamente Modificados/genética , Regulação da Expressão Gênica , Genótipo , Glutamato-Cisteína Ligase/genética , Glutamato-Cisteína Ligase/metabolismo , Glutationa Transferase/genética , Glutationa Transferase/metabolismo , Hemizigoto , Homozigoto , Estresse Oxidativo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo , Peixe-Zebra/genéticaRESUMO
Polychaeta species like Laeonereis acuta (Nereididae) usually secrete great amounts of mucus that wrap the animal inside. Taking into account that fungi action in the sediment and UV radiation acting on dissolved organic matter in the water produces reactive oxygen species (ROS) like hydrogen peroxide (H(2)O(2)), it was considered that the mucus secretion could represent an antioxidant defense against environmental ROS. Antioxidant enzymes (catalase-CAT; superoxide dismutase-SOD; glutathione peroxidase-GPx and glutathione-S-transferase-GST) and total antioxidant capacity (TOSC) were determined in worms and mucus secretion. Higher (p<0.05) CAT, GPx and TOSC values were registered in mucus samples respect worms, SOD activity was similar (p>0.05) in both kind of samples, and absence of GST activity was observed in mucus samples, suggesting absence of catalyzed phase II reactions. In assays conducted with hepatoma cell lines exposed to H(2)O(2), it was verified that: (1) mucus co-exposure significantly (p<0.05) lowered DNA damage induced by H(2)O(2); (2) ROS production was significantly (p<0.05) reduced when cells were exposed simultaneously with mucus samples and H(2)O(2) respect H(2)O(2) alone. It can be concluded that the mucus production contributes substantially to the antioxidant defense system of the worm against environmental ROS through the interception or degradation of H(2)O(2), peroxyl and hydroxyl radicals.
Assuntos
Antioxidantes/metabolismo , Muco/metabolismo , Poliquetos/metabolismo , Animais , Catalase/metabolismo , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Contagem de Colônia Microbiana , Dano ao DNA , Poluentes Ambientais/toxicidade , Glutationa Peroxidase/metabolismo , Glutationa Transferase/metabolismo , Peróxido de Hidrogênio/toxicidade , Radical Hidroxila/metabolismo , Muco/enzimologia , Muco/microbiologia , Peróxidos/metabolismo , Poliquetos/enzimologia , Ratos , Espécies Reativas de Oxigênio/toxicidade , Superóxido Dismutase/metabolismoRESUMO
Hydrogen peroxide (H(2)O(2)) is a naturally occurring prooxidant molecule, and its effects in the macroinvertebrate infauna were previously observed. The existence of a gradient of antioxidant enzymes activity (catalase [CAT], glutathione peroxidase [GPx], superoxide dismutase [SOD], and glutathione-S-transferase [GST]) and/or oxidative damage along the body of the estuarine polychaeta Laeonereis acuta (Polychaeta, Nereididae) was analyzed after exposure to H(2)O(2). Because this species secretes conspicuous amounts of mucus, its capability in degrading H(2)O(2) was studied. The results suggest that L. acuta deal with the generation of oxidative stress with different strategies along the body. In the posterior region, higher CAT and SOD activities ensure the degradation of inductors of lipid peroxidation such as H(2)O(2) and superoxide anion (O(2)(.-)). The higher GST activity in anterior region aids to conjugate lipid peroxides products. In the middle region, the lack of high CAT, SOD, or GST activities correlates with the higher lipid hydroperoxide levels found after H(2)O(2) exposure. Ten days of exposure to H(2)O(2) also induced oxidative stress (lipid peroxidation and DNA damage) in the whole animal paralleled by a lack of CAT induction. The mucus production contributes substantially to H(2)O(2) degradation, suggesting that bacteria that grow in this secretion provide this capability.
Assuntos
Adaptação Fisiológica/fisiologia , Peróxido de Hidrogênio/metabolismo , Estresse Oxidativo/fisiologia , Poliquetos/enzimologia , Análise de Variância , Animais , Catalase/metabolismo , Ensaio Cometa , Dano ao DNA/fisiologia , Glutationa Peroxidase/metabolismo , Glutationa Transferase/metabolismo , Muco/metabolismo , Poliquetos/fisiologia , Superóxido Dismutase/metabolismo , Fatores de TempoRESUMO
In January of 2003, a cyanobacterial bloom in the Patos' Lagoon (Southern Brazil) (32 degrees 05'S-52 degrees 12'W) was observed. Water samples were taken to identify the composition and abundance of the bloom, as well as the occurrence of toxins. The effects of this occurrence on the estuarine worm Laeonereis acuta (Polychaeta, Nereididae) was also evaluated. Predominance of cyanobacteria, particularly Anabaena trichomes ( approximately 2.5.10(6) individuals per liter) was observed, and low concentrations of microcystins and anticholinesterasic toxins were detected. Augmented levels of lipid hydroperoxides (LPO) and glutathione-S-transferase activity, and lowering of total protein content were also observed in organisms collected during the bloom event. Although non-toxic, the cyanobacterial bloom could augment the cycle of hyper-oxygenation and hypoxia in the water. During hyperoxia, L. acuta, an oxyconformer, should consume more oxygen, thus augmenting the rate of reactive oxygen species generation. A repeated cycle of hyper-oxygenation and hypoxia would finally induce oxidative stress, as evidenced by the high levels of LPO and glutathione-S-transferase activity.