Melatonin receptor agonist ramelteon activates the extracellular signal-regulated kinase 1/2 in mouse cerebellar granule cells

Ramelteon ameliorated 1-methyl-4-phenylpyridinium (MPP+)-induced neurotoxicity in neuronal cells in a mitochondrial-dependent pathway

Parkinson's disease (PD) is a common neurodegenerative disease with global health and economic impact. 1-methyl-4-phenylpyridinium (MPP+)-induced mitochondrial dysfunction and oxidative stress are reported to participate in the pathological mechanism of PD. Ramelteon is a novel oral hypnotic agent that has recently been reported to display neuronal protective effects. However, it is unknown whether Ramelteon possesses a beneficial effect in PD. In this study, we aimed to examine the potential function of Ramelteon in MPP+-challenged neurons. We found that Ramelteon rescued the cell viability reduced by MPP+-stimulation. Further, oxidative stress in MPP+-challenged SH-SY5Y cells was mitigated by Ramelteon as verified by the upregulated levels of mitochondrial reactive oxygen species (ROS) and protein carboxyl, and the upregulation of NADPH oxidase 4 (NOX-4). Furthermore, the declined mitochondrial membrane potential (ΔΨm) caused by MPP+ was reversed by Ramelteon. Importantly, Ramelteon attenuated MPP+-induced apoptosis, accompanied by a decreased ratio of Bax/Bcl-2, inhibition of cytochrome C release, and downregulation of cleaved caspase-3. For the first time, we conclude that Ramelteon might ameliorate MPP+-induced neurotoxicity in neuronal cells in a mitochondrial-dependent pathway.

Melatonin or ramelteon therapy differentially affects hepatic gene expression profiles after haemorrhagic shock in rat--A microarray analysis

BACKGROUND & AIMS

Melatonin has been demonstrated to reduce liver damage in different models of stress. However, there is only limited information on the impact of this hormone on hepatic gene expression. The aim of this study was, to investigate the influence of melatonin or the melatonergic agonist ramelteon on hepatic gene expression profiles after haemorrhagic shock using a whole genome microarray analysis.

METHODS

Male Sprague-Dawley rats (200-300 g, n=4/group) underwent haemorrhagic shock (mean arterial pressure 35±5 mmHg). After 90 min of shock, animals were resuscitated with shed blood and Ringer's and treated with vehicle (5% dimethyl sulfoxide), melatonin or ramelteon (each 1.0 mg/kg intravenously). Sham-operated animals were treated likewise but did not undergo haemorrhage. After 2 h of reperfusion, the liver was harvested, and a whole genome microarray analysis was performed. Functional gene expression profiles were determined using the Panther® classification system; promising candidate genes were evaluated by quantitative polymerase chain reaction (PCR).

RESULTS

Microarray and PCR data showed a good correlation (r(2)=0.84). A strong influence of melatonin on receptor mediated signal transduction was revealed using the functional gene expression profile analysis, whereas ramelteon mainly influenced transcription factors. Shock-induced upregulation of three candidate genes with relevant functions for hepatocytes (ppp1r15a, dusp5, rhoB) was significantly reduced by melatonin (p<0.05 vs. shock/vehicle), but not by ramelteon. Two genes previously known as haemorrhage-induced (il1b, s100a8) were transcriptionally repressed by both drugs.

CONCLUSIONS

Melatonin and ramelteon appear to induce specific hepatic gene expression profiles after haemorrhagic shock in rats. The observed differences between both substances are likely to be attributable to a distinct mechanism of action in these agents.

Does melatonin ameliorate neurological changes associated with Alzheimer's disease in ovariectomized rat model?

This study aimed to elucidate the mechanisms of melatonin to manage neurological damage in Alzheimer's disease (AD) induced in ovariectomized rats. Forty adult female rats were enrolled in our study and were classified as; gonad intact control, ovariectomized control group, ovariectomized rats received melatonin, ovariectomized rats injected with AlCl3 to induce AD and AD-induced rats treated with melatonin. Hydrogen peroxide (H2O2), malondialdehyde (MDA), total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase (CAT), B cell lymphoma 2 (Bcl-2), brain derived neurotrophic factor (BDNF), acetylcholinesterase (AchE) and acetylcholine (Ach) were estimated in the brain tissues of the different groups. Treatment of AD-induced rats with melatonin produced marked improvement in the most studied biomarkers which was confirmed by histological investigation of the brain. In Conclusion, melatonin significantly ameliorates the neurodegeneration characteristic of AD in experimental animal model due to its antioxidant, antiapoptotic, neurotrophic and anti-amyloidogenic activities.