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: 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: Dementias are progressive and neurodegenerative neuropsychiatry disorders, with a high worldwide prevalence. These disorders affect memory and behavior, causing impairment in the performance of daily activities and general disability in the elders. Cognitive impairment in these patients is related to anatomical and structural alterations at cellular and sub-cellular levels in the Central Nervous System. In particular, amyloid plaques and neurofibrillar tangles have been defined as histopathological hallmarks of Alzheimer's disease. Likewise, oxidative stress and neuroinflammation are implicated in the etiology and progression of the disease.Salud Mental 05/2013; 36(3):193. · 0.42 Impact Factor
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ABSTRACT: Rotenone, a pesticide, causes neurotoxicity via the mitochondrial complex-I inhibition. The present study was conducted to evaluate the role of endoplasmic reticulum (ER) stress in rotenone-induced neuronal death. Cell viability, cytotoxicity, reactive oxygen species (ROS) generation, nitrite level, mitochondrial membrane potential (MMP), and DNA damage were assessed in rotenone-treated neuro-2A cells. Protein levels of ER stress markers glucose regulated protein 78 (GRP78), growth arrest- and DNA damage-inducible gene 153 (GADD153), and phosphorylation of eukaryotic translation initiation factor 2 subunit α (eIF2-α) were estimated to assess the ER stress. To confirm the apoptotic death of neurons, mRNA levels of caspase-9, caspase-12 and caspase-3 were estimated. Further, to confirm the involvement of ER stress, neuro-2A cells were pretreated with ER stress inhibitor salubrinal. Co-treatment of antioxidant melatonin was also given to assess the role of oxidative stress in rotenone-induced apoptosis. Rotenone (0.1, 0.5, and 1 μM) treatment to neurons caused significantly decreased cell viability, increased cytotoxicity, increased ROS generation, increased expression of GRP78 and GADD, DNA damage and activation of caspase-12 and caspase-3 which were significantly attenuated by pretreatment of salubrinal (25 μM). Rotenone-induced dephosphorylation of eIF2α was also inhibited with salubrinal treatment. However, pretreatment of salubrinal did not affect the rotenone-induced increased nitrite levels, decreased MMP and caspase-9 activation. Co-treatment of antioxidant melatonin (1 mM) did not offer attenuation against rotenone-induced increased expression of caspase-9, caspase-12 and caspase-3. In conclusion, results indicated that ER stress plays a key role in rotenone-induced neuronal death, rather than oxidative stress.Molecular neurobiology. 11/2014;