Melatonin and oestrogen treatments were able to improve neuroinflammation and apoptotic processes in dentate gyrus of old ovariectomized female rats.

The aim of this study was to determine the outcomes of oestrogen and melatonin treatments following long-term ovarian hormone depletion on neuroinflammation and apoptotic processes in dentate gyrus of hippocampi. Forty-six female Wistar rats of 22 months of age were used. Twelve of them remained intact, and the other 34 were ovariectomized at 12 months of age. Ovariectomized animals were divided into three groups and treated for 10 weeks with oestrogens, melatonin or saline. All rats were killed by decapitation at 24 months of age, and dentate gyri were collected. A group of 2 month-old intact female rats was used as young control. The levels of pro-inflammatory cytokines and heat shock protein 70 (HSP 70) were analysed by ELISA. The expressions of TNFα, IL1ß, GFAP, nNOS, iNOS, HO-1, NFκB, Bax, Bad, AIF, Bcl2 and SIRT1 genes were detected by real-time (RT)-PCR. Western blots were used to measure the protein expression of NFκB p65, NFκB p50/105, IκBα, IκBß, p38 MAPK, MAP-2 and synapsin I. We have assessed the ability of 17ß-oestradiol and melatonin administration to downregulate markers of neuroinflammation in the dentate gyrus of ovariectomized female rats. Results indicated that 17ß-oestradiol and melatonin treatments were able to significantly decrease expression of pro-inflammatory cytokines, iNOS and HO-1 in the hippocampus when compared to non-treated animals. A similar age- and long-term ovarian hormone depletion- related increase in GFAP was also attenuated after both melatonin and oestradiol treatments. In a similar way to oestradiol, melatonin decreased the activation of p38 MAPK and NFκB pathways. The treatments enhanced the levels of synaptic molecules synapsin I and MAP-2 and have been shown to modulate the pro-antiapoptotic ratio favouring the second and to increase SIRT1 expression. These findings support the potential therapeutic role of melatonin and oestradiol as protective anti-inflammatory agents for the central nervous system during menopause.

Beneficial effect of melatonin treatment on age-related insulin resistance and on the development of type 2 diabetes.

Abstract This paper will review the effect of aging on glucose metabolism and insulin resistance in pancreas and in peripheral tissues and how melatonin administration could affect these parameters. In SAMP8 mice insulin levels in plasma were found to be increased together with enhanced HOMA-IR values, whereas insulin content in pancreas showed a decrease with aging. Aging in SAMP8 mice was also associated with a significant increase in the relative expression of both protein and mRNA of different pro-inflammatory mediators. Furthermore, aging was associated with a decrease in the expression of Pdx-1, FoxO 1 and FoxO 3A and Sirt 1 in pancreas SAMP8 samples. Melatonin administration was able to reduce these age-related alterations, decreasing plasma insulin levels and increasing its pancreatic content in SAMP8 mice. HOMA-IR was decreased with melatonin treatment in all animals. Conversely, in SAMP8 mice, melatonin treatment decreased the expression of glucagon, GLUT2, somatostatin and insulin. Furthermore it was also able to increase the expression of Sirt 1, Pdx-1 and FoxO 3A. The present study has shown that aging is associated with significant alterations in the relative expression of pancreatic genes involved in both insulin secretion and glucose metabolism and that these are associated with an increase in inflammation and oxidative stress. Melatonin administration was able to reduce oxidative stress and inflammation and thus to improve pancreatic function in old mice. By doing so, insulin resistance is diminished and plasma insulin is reduced, enhancing insulin pancreatic content and reducing plasma glucose levels and HOMA index.

Age-related differences in hepatic ischemia/reperfusion: gene activation, liver injury, and protective effect of melatonin.

BACKGROUND: Ischemia/reperfusion (I/R) causes functional and structural damage to liver cells, this being more pronounced with increasing age of the tissue. Melatonin is a pineal indole that has been shown to play an important role as a free radical scavenger and anti-inflammatory molecule. MATERIAL AND METHODS: The age-dependent responses to I/R were compared in 2-mo-old and 14-mo-old male Wistar rats. After 35 min of hepatic ischemia followed by 36 h of reperfusion, rats were sacrificed. Sham-operated control rats underwent the same protocol without real vascular occlusion. Animals were intraperitoneally injected with 10 mg/kg melatonin 24 h before the operation, at the time of surgery, and 12 and 24 h after it. The tissues were submitted to histopathologic evaluation. The levels of ALT and AST were analyzed in plasma. The expression of TNF-α, IL-1ß, IL-10, MCP-1, IFN-γ, iNOS, eNOS, Bad, Bax, Bcl2, AIF, PCNA, and NFKB1 genes were detected by RT-PCR in hepatic tissue. RESULTS: I/R was associated with significant increases in the expression of pro-inflammatory and pro-apoptotic genes in liver. Older rats submitted to I/R were found to respond with increased liver damage as compared with young rats, with serum ALT and AST levels significantly higher than in young animals. Mature rats also showed more evident increases in expression of pro-inflammatory cytokines (IL-1ß, MCP-1, and IFN-γ) as well as a decrease in the mRNA expression of IL-10 as compared with young animals. Pro-apoptotic genes (Bax, Bad, and AIF) were significantly enhanced in liver after I/R, without differences between young and mature animals. However, the expression of Bcl2 gene did not show any change. Melatonin treatment was able to lower the expression of pro-inflammatory cytokines and pro-apoptotic genes and to improve liver function, as indicated by normalization of plasma AST and ALT levels and by reduction of necrosis and microsteatosis areas. CONCLUSIONS: Melatonin treatment was able to reduce the I/R-stimulated pro-inflammatory and pro-apoptotic genes in the rat liver. Since older animals showed a more marked increase in inflammation and in liver injury, the treatment was more effective in those subjects.

Effect of growth hormone and melatonin on the brain: from molecular mechanisms to structural changes.

Aging of the brain causes important reductions in quality of life and has wide socio-economic consequences. An increase in oxidative stress, and the associated inflammation and apoptosis, could be responsible for the pathogenesis of aging associated brain lesions. Melatonin has neuroprotective effects, by limiting the negative effects of oxygen and nitrogen free radicals. Growth hormone (GH) might exert additional neuro-protective and or neurogenic effects on the brain. The molecular mechanisms of the protective effects of GH and melatonin on the aging brain have been investigated in young and old Wistar rats. A reduction in the total number of neurons in the hilus of the dentate gyrus was evident at 24 months of age and was associated with a significant increase in inflammation markers as well as in pro-apoptotic parameters, confirming the role of apoptosis in its reduction. Melatonin treatment was able to enhance neurogenesis in old rats without modification of the total number of neurons, whereas GH treatment increased the total number of neurons without enhancing neurogenesis. Both GH and melatonin were able to reduce inflammation and apoptosis in the hippocampus. In conclusion, neuroprotective effects demonstrated by GH and melatonin in the hippocampus were exerted by decreasing inflammation and apoptosis.