Signal transduction pathways involved in protective effects of melatonin in C6 glioma cells.
ABSTRACT Melatonin (N-acetyl-5-methoxytryptamine), an indole hormone, is the chief secretory product of the pineal gland and is an efficient free radical scavenger and antioxidant, both in vitro and in vivo. The role of melatonin as an immunomodulator is, in some cases, contradictory. Although melatonin is reported to influence a variety of inflammatory and immune responses, evidence supporting its effects on important glioma cells-derived mediators is incomplete. We studied, in rat glioma cell line (C6), the role of melatonin (100 microm-1 mm) in the regulation of the expression of nitric oxide synthase (NOS) caused by incubation with lipopolysaccharide (LPS)/interferon (IFN)-gamma (1 microg/mL and 100 U/mL, respectively) and defined the mode of melatonin's action. Treatment with LPS/IFN-gamma for 24 hr elicited the induction of inducible (iNOS) activity as determined by nitrite and nitrate (NO(x)) accumulation in the culture medium. Preincubation with melatonin abrogated the mixed cytokines-mediated induction of iNOS. The effect of melatonin was concentration-dependent. Moreover, Western blot analysis showed that melatonin inhibited LPS/IFN-gamma-induced expression of COX-2 protein, but not that of constitutive cyclooxygenase. Inhibition of iNOS and COX-2 expression was associated with inhibition of activation of the transcription factor nuclear factor kappa B (NF-kappaB). The ability of melatonin to inhibit NF-kappaB activation was further confirmed by studies on the degradation of the inhibitor of NF-kappaB, IkappaB-alpha. Increased production of lipid peroxidation products using thiobarbituric acid assay were found in cellular contents from activated cultures. Lipid peroxidation was decreased by melatonin treatment in a concentration-dependent manner. Moreover, several genes having roles in heat-shock response were downregulated in melatonin-treated cells, such as 70 proteins, reflecting the reduced oxidative stress in these cells. The mechanisms underlying in vitro the neuroprotective properties of melatonin involve modulation of transcription factors and consequent altered gene expression, resulting in downregulation of inflammation.
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ABSTRACT: Ischemia-reperfusion (I/R) injury induces the generation of reactive oxygen species (ROS) which affect many organs. This study was designed to investigate the roles of melatonin and 1,25-dihydroxyvitamin D(3) (VD3) on renal I/R injury. Thirty male Wistar albino rats were divided into five groups: group 1, control; group 2, right nephrectomy (RN) + I/R in the contralateral kidney; group 3, melatonin + RN + I/R; group 4, VD(3) + RN + I/R; and group 5, melatonin + VD(3) + RN + I/R. Melatonin (10 mg/kg), VD3 (0.5 μg/kg), and melatonin plus VD3 were injected intraperitoneally for 7 days before renal I/R. After 7 days, right nephrectomy was initially performed and left renal artery was clamped for 45 min. After 45-min reperfusion, the serum and kidney tissue samples were obtained for assays. Melatonin and VD3 had an ameliorative effect on biochemical parameters such as serum creatinine (SCr) and blood urea nitrogen (BUN). Renal tissue malondialdehyde (MDA), glutathione (GSH), nitric oxide (NO) levels, and superoxide dismutase (SOD) activity were determined. Renal I/R decreased the kidney tissue GSH levels and SOD activity and increased the NO levels as compared with control group. However, melatonin and VD3 and melatonin plus VD3 treatment significantly increased the tissue GSH levels and SOD activity and decreased the NO levels compared with those of I/R group. Meanwhile, MDA levels were not different between the control and I/R groups. But, MDA levels decreased in all treated groups compared to I/R and control groups. These data support that melatonin and VD3 have beneficial effects on renal injury.Renal Failure 01/2013; · 0.94 Impact Factor
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ABSTRACT: Neurodegenerative diseases are chronic and progressive disorders characterized by selective destruction of neurons in motor, sensory and cognitive systems. Despite their different origin, free radicals accumulation and consequent tissue damage are importantly concerned for the majority of them. In recent years, research on melatonin revealed a potent activity of this hormone against oxidative and nitrosative stress-induced damage within the nervous system. Indeed, melatonin turned out to be more effective than other naturally occurring antioxidants, suggesting its beneficial effects in a number of diseases where oxygen radical-mediated tissue damage is involved. With specific reference to the brain, the considerable amount of evidence accumulated from studies on various neurodegeneration models and recent clinical reports support the use of melatonin for the preventive treatment of major neurodegenerative disorders. This review summarizes the literature on the protective effects of melatonin on Alzheimer disease, Parkinson disease, Huntington's disease and Amyotrophic Lateral Sclerosis. Additional studies are required to test the clinical efficacy of melatonin supplementation in such disorders, and to identify the specific therapeutic concentrations needed.Frontiers in Bioscience 01/2014; 19:429-46. · 3.29 Impact Factor
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ABSTRACT: A number of studies have suggested that melatonin possesses anticancer properties. However, conflicting data exists with regard to the role of melatonin in the treatment of cancer. In the present study, the effects of melatonin on the transcriptional regulation of three genes associated with cell proliferation (Nestin, Bmi-1 and Sox2), and on C6 glioma cell survival and viability, were investigated in vitro to evaluate the use of melatonin in cancer therapy. Melatonin was shown to increase the mRNA levels of Nestin, Bmi-1 and Sox2 in a similar pattern, with the highest mRNA levels noted at a concentration of 3 mM. At higher concentrations of melatonin (5 mM), the mRNA levels of Nestin, Bmi-1 and Sox2 were reduced from their peak levels, and were correlated with changes observed in immunofluorescence morphology studies, cell viability and survival assays. Immunofluorescence studies of Nestin-stained cells demonstrated that treatment with a higher concentration of melatonin (3 and 5 mM) led to the Nestin filaments condensing and rearranging around the cell nuclei, and an alteration in the cell morphology. C6 cell viability was also significantly decreased at 3 mM melatonin, and cell death was observed at 5 and 10 mM melatonin. These results suggested that Nestin, Bmi-1 and Sox2 were strongly correlated with the survival of C6 cells following treatment with melatonin, and that high therapeutic concentrations of melatonin (>5 mM) were required to induce cell death. These findings suggested that the implementation of melatonin in the treatment of glioma and other types of cancer may be inhibited by conflicting cell growth signals in cells. Therefore, adjunct therapy is required to improve the efficacy of melatonin in the treatment of cancer.Oncology letters 08/2013; 6(2):347-352. · 0.24 Impact Factor