RESUMO
Light at Night (LAN) suppresses melatonin (MLT) production, and effects metabolism, hormone secretion, gene expression and enzyme activity. Changes in antioxidant enzymes glutathione peroxidase (GPx) and superoxide dismutase (SOD), can be used as an indication for oxidative stress level. We assayed activity and expression of these enzymes in the liver of Acomys russatus exposed to LAN and treated with MLT. Short day (SD)-acclimated A. russatus, was exposed to 30min of LAN for two, seven or 21 nights. MLT impact was assessed simultaneously with two and seven nights of LAN exposure. GPx and SOD activities were measured. Gpx1 expression was evaluated by RT-PCR. There was a significant increase in GPx activity following LAN exposure for all acclimation durations, GPx activity was elevated after two nights of LAN and MLT treatment, Gpx1 expression was elevated by MLT after seven nights of LAN. SOD activity increased after two nights of LAN in MLT-treated A. russatus, GPx activity increased with the duration of LAN acclimation, indicating changes in liver redox status. Our results suggest that LAN is a stressor that influences oxidative stress. As in the other studies, MLT increases antioxidant activities, presumably attenuating stress response, in order to restore homeostasis.
Assuntos
Fígado/enzimologia , Fígado/metabolismo , Murinae/metabolismo , Estresse Oxidativo/fisiologia , Animais , Antioxidantes/metabolismo , Biomarcadores/metabolismo , Escuridão , Glutationa Peroxidase/metabolismo , Luz , Masculino , Melatonina/metabolismo , Camundongos , Oxirredução , Superóxido Dismutase/metabolismo , Glutationa Peroxidase GPX1RESUMO
Light at night and light interference (LI) disrupt the natural light:dark cycle, causing alterations at physiological and molecular levels, partly by suppressing melatonin (MLT) secretion at night. Heat shock proteins (HSPs) can be activated in response to environmental changes. We assessed changes in gene expression and protein level of HSP70 in brain and hepatic tissues of golden spiny mice (Acomys russatus) acclimated to LI for two (SLI), seven (MLI) and 21 nights (LLI). The effect of MLT treatment on LI-mice was also assessed. HSP70 levels increased in brain and hepatic tissues after SLI, whereas after MLI and LLI, HSP70 decreased to control levels. Changes in HSP70 levels as a response to MLT occurred after SLI only in hepatic tissue. However, hsp70 expression following SLI increased in brain tissue, but not in hepatic tissue. MLT treatment and SLI caused a decrease in hsp70 levels in brain tissue and an increase in hsp70 in hepatic tissue. SLI acclimation elicited a stress response in A. russatus, as expressed by increased HSP70 levels and gene expression. Longer acclimation decreases protein and gene expression to their control levels. We conclude that for brain and hepatic tissues of A. russatus, LI is a short-term stressor. Our results also revealed that A. russatus can acclimate to LI, possibly because of its circadian system plasticity, which allows it to behave both as a nocturnal and as a diurnal rodent. To the best of our knowledge, this is the first study showing the effect of LI as a stressor at the cellular level, by activating HSP70.
Assuntos
Encéfalo/metabolismo , Regulação da Expressão Gênica/efeitos da radiação , Proteínas de Choque Térmico HSP70/genética , Luz , Fígado/metabolismo , Muridae/genética , Estresse Fisiológico/genética , Aclimatação/efeitos dos fármacos , Aclimatação/genética , Aclimatação/efeitos da radiação , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/efeitos da radiação , Ritmo Circadiano/efeitos dos fármacos , Ritmo Circadiano/genética , Ritmo Circadiano/efeitos da radiação , Regulação da Expressão Gênica/efeitos dos fármacos , Proteínas de Choque Térmico HSP70/metabolismo , Fígado/efeitos dos fármacos , Fígado/efeitos da radiação , Masculino , Melatonina/farmacologia , Camundongos , Fotoperíodo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/efeitos da radiaçãoRESUMO
Introduction: Melatonin is an antioxidant, a circadian pacemaker, and an immune system stimulator. Studies have demonstrated beneficial effects of melatonin on various conditions in neonates. Melatonin is secreted in breast milk in circadian rhythm, but its half-life and stability in this medium and in real-life conditions of freezing and defrosting is unknown. The objective of this feasibility study was to evaluate stability of melatonin in breast milk after freezing and defrosting. Methods and Results: Breast milk samples of nocturnal milk and daytime milk were collected from 13 healthy breastfeeding mothers and were immediately frozen. Samples were defrosted in room temperature and were sampled for melatonin immediately and every hour for 4 hours and at 24 hours after defrosting. Melatonin levels were measured with Melatonin direct Saliva ELISA kit (IBL International).There was no statistically significant difference between levels at the different time points (p = 0.696). Melatonin levels in daytime milk were significantly lower than night-time levels (p = 0.028). Conclusion: Melatonin is stable in human milk for at least 4 hours after defrosting and even up to 24 hours. Further research of the therapeutic potential of night breast milk high in melatonin is needed.