Melatonin is able to prevent the liver of old castrated female rats from oxidative and pro-inflammatory damage

Effects of diphenyl diselenide on lipid profile and hepatic oxidative stress parameters in ovariectomized female rats

Objectives

Ovarian hormone decline after menopause is linked to many pathophysiological reactions. Female rats submitted to ovariectomy are employed as a model of post-menopausal condition. This study investigated the effects of diphenyl diselenide (PhSe)2 on body weight gain, intra-abdominal fat deposition, plasma lipid profile and hepatic oxidative stress in ovariectomized rats.

Methods

Female adult Wistar rats were ovariectomized (OVX rats) or sham-operated and divided into four groups: (i) sham-operated, (ii) (PhSe)2, (iii) OVX and (iv) OVX + (PhSe)2. (PhSe)2 (5 mg/kg; 5 ml/kg, p.o.) was administered once a day for 30 days to groups (ii) and (iv). After that, rats were anaesthetized for blood sample gathering and submitted to euthanasia.

Key findings

(PhSe)2 (5 mg/kg) was effective in preventing the rise in body weight gain and intra-abdominal fat deposition induced in OVX rats. Although (PhSe)2 was not effective in avoiding the increase in plasma total cholesterol and non-HDL levels induced in OVX rats, (PhSe)2 reduced plasma triglycerides and augmented HDL levels in OVX rats. (PhSe)2 also increased hepatic ascorbic acid levels, reduced glutathione content, glutathione S-transferase activity and restored catalase activity in liver of OVX rats.

Conclusions

These findings suggest that (PhSe)2 could be a promising alternative to minimize menopause related symptoms.

Beneficial effects of melatonin on cardiological alterations in a murine model of accelerated aging

This study investigated the effect of aging-related parameters such as inflammation, oxidative stress and cell death in the heart in an animal model of accelerated senescence and analyzed the effects of chronic administration of melatonin on these markers. Thirty male mice of senescence-accelerated prone (SAMP8) and 30 senescence-accelerated-resistant mice (SAMR1) at 2 and 10 months of age were used. Animals were divided into eight experimental groups, four from each strain: two young control groups, two old untreated control groups, and four melatonin-treated groups. Melatonin was provided at two different dosages (1 and 10 mg/kg/day) in the drinking water. After 30 days of treatment, the expression of inflammatory mediators (tumor necrosis factor-alpha, interleukin 1 and 10, NFkBp50 and NFkBp52), apoptosis markers (BAD, BAX and Bcl2) and parameters related to oxidative stress (heme oxygenases 1 and 2, endothelial and inducible nitric oxide synthases) were determined in the heart by real-time reverse transcription polymerase chain reaction (RT-PCR). Inflammation, as well as, oxidative stress and apoptosis markers was increased in old SAMP8 males, when compared to its young controls. SAMR1 mice showed significantly lower basal levels of the measured parameters and smaller increases with age or no increases at all. After treatment with melatonin, these age-altered parameters were partially reversed, especially in SAMP8 mice. The results suggest that oxidative stress and inflammation increase with aging and that chronic treatment with melatonin, a potent antioxidant, reduces these parameters. The effects were more marked in the SAMP8 animals.

Protective effect of melatonin against Opisthorchis viverrini-induced oxidative and nitrosative DNA damage and liver injury in hamsters

The liver fluke, Opisthorchis viverrini, is the risk factor of cholangiocarcinoma, which is a major health problem in northeastern Thailand. Production of reactive oxygen and nitrogen species during the host's response leads to oxidative and nitrosative stress contributing to carcinogenesis. We investigated the protective effect of melatonin against O. viverrini-induced oxidative and nitrosative stress and liver injury. Hamsters were infected with O. viverrini followed by oral administration of various doses of melatonin (5, 10, and 20 mg/kg body weight) for 30 days. Uninfected hamsters served as controls. Compared to the levels in O. viverrini-infected hamsters without melatonin treatment, the indoleamine decreased the formation of oxidative and nitrosative DNA lesions, 8-oxo-7,8-dihydro-2'-deoxyguanosine and 8-nitroguanine, in the nucleus of bile duct epithelium and inflammatory cells, in parallel with a reduction in 3-nitrotyrosine. Melatonin also reduced the expression of heme oxygenase-1 and cytokeratin 19, nitrate/nitrite levels, and bile duct proliferation in the liver. Alanine transaminase activity and the levels of 8-isoprostane and vitamin E were also dose dependently decreased in the plasma of melatonin-treated hamsters. Melatonin reduced the mRNA expression of oxidant-generating genes [inducible nitric oxide synthase, nuclear factor-kappa B (NF-κB), and cyclooxygenase-2] and proinflammatory cytokines (TNF-α and IL-1β), accompanied by an increase in the expression of antioxidant genes [nuclear erythroid 2-related factor 2 (Nrf2) and manganese superoxide dismutase]. Thus, melatonin may be an effective chemopreventive agent against O. viverrini-induced cholangiocarcinoma by reducing oxidative and nitrosative DNA damage via induction of Nrf2 and inhibition of NF-κB-mediated pathways.

Melatonin ameliorates cerulein-induced pancreatitis by the modulation of nuclear erythroid 2-related factor 2 and nuclear factor-kappaB in rats

Melatonin exhibits a wide variety of biological effects, including antioxidant and anti-inflammatory functions. Its antioxidant role impedes the etiopathogenesis of pancreatitis, but little is known about the signaling pathway of melatonin in the induction of antioxidant enzymes in acute pancreatitis (AP). The aim of this study was to determine whether melatonin could prevent cerulein-induced AP through nuclear factor erythroid 2-related factor 2 (Nrf2) and curtail inflammation by inhibition of NF-kappaB. AP was induced by two intraperitoneal (i.p.) injections of cerulein at 2 h intervals (50 microg/kg) in Sprague-Dawley rats. Melatonin (10 or 50 mg/kg/daily, i.p.) was administered 24 h before each injection of cerulein. The rats were killed 12 h after the last injection. Acinar cell degeneration, pancreatic edema, and inflammatory infiltration were significantly different in cerulein- and melatonin-treated rats. Melatonin significantly reduced amylase, lipase, MPO, and MDA levels, and increased antioxidant enzyme activities including SOD and GPx, which were decreased in AP (P < 0.05). Melatonin increased the expression of NQO1, HO-1, and SOD2 when compared with the cerulein-induced AP group (P < 0.05). In addition, melatonin increased Nrf2 expression, and reduced expressions of tumor necrosis factor-alpha, IL-1beta, IL-6, IL-8, and iNOS. The elevated nuclear binding of NF-kappaB in the cerulein-induced pancreatitis group was inhibited by melatonin. These results show that melatonin increases antioxidant enzymes and Nrf2 expression, and limits inflammatory mediators in cerulein-induced AP. It is proposed that melatonin may play an important role in oxidative stress via the Nrf2 pathway in parallel with reduction of inflammation by NF-kappaB inhibition.

Role of melatonin in metabolic regulation

Although the human genome has remained unchanged over the last 10,000 years, our lifestyle has become progressively more divergent from those of our ancient ancestors. This maladaptive change became apparent with the Industrial Revolution and has been accelerating in recent decades. Socially, we are people of the 21st century, but genetically we remain similar to our early ancestors. In conjunction with this discordance between our ancient, genetically-determined biology and the nutritional, cultural and activity patterns in contemporary Western populations, many diseases have emerged. Only a century ago infectious disease was a major cause of mortality, whereas today non-infectious chronic diseases are the greatest cause of death in the world. Epidemics of metabolic diseases (e.g., cardiovascular diseases, type 2 diabetes, obesity, metabolic syndrome and certain cancers) have become major contributors to the burden of poor health and they are presently emerging or accelerating, in most developing countries. One major lifestyle consequence is light at night and subsequent disrupted circadian rhythms commonly referred to as circadian disruption or chronodisruption. Mounting evidence reveals that particularly melatonin rhythmicity has crucial roles in a variety of metabolic functions as an anti-oxidant, anti-inflammatory chronobiotic and possibly as an epigenetic regulator. This paper provides a brief outline about metabolic dysregulation in conjunction with a disrupted melatonin rhythm.

Melatonin reduces cardiac inflammatory injury induced by acute exercise

Cardiac muscle tissue, when stimulated by acute exercise, presents increased signs of cell damage. This study was designed to investigate whether overexpression of inflammatory mediators induced in the heart by acute exercise could be prevented by melatonin and whether the protective effect of melatonin was related with inhibition of nuclear factor kappa B (NF-kappaB) activation. Male Wistar rats received melatonin i.p. at a dose of 1.0 mg/kg body weight 3 min before being exercised for 60 min on a treadmill at a speed of 25 m/min and a 10% slope. Exercise was associated with a significant increase in myeloperoxidase activity and in TNF-alpha, IL-1 and IL-6 mRNA levels. Both mRNA level and protein concentrations of intercellular adhesion molecule-1, inducible nitric oxide synthase, and cyclooxygenase-2 were also significantly elevated. A significant activation of nuclear factor kappa B (NF-kappaB) was observed in exercised rats. These effects were totally or partially prevented by melatonin administration. Data obtained indicate that melatonin protects against heart damage caused by acute exercise. Impaired production of noxious mediators involved in the inflammatory process and down-regulation of the NF-kappaB signal transduction pathway appear to contribute to the beneficial effects of melatonin.

Melatonin and tryptophan counteract lipid peroxidation and modulate superoxide dismutase activity in ringdove heterophils in vivo. Effect of antigen-induced activation and age

Aging is associated with an increased production of free radicals and alterations in the mechanisms of adaptation to stress. A number of studies have shown a causal connection between age-related oxidant/antioxidant imbalance and the diminution of an organism's melatonin levels in old age. Restoration of this rhythm may contribute to the re-stabilization of cellular homeostasis. The present work was aimed at examining the effect of the administration of melatonin or its precursor, the amino acid tryptophan, on heterophil lipid peroxidation (LPO) levels and superoxide dismutase (SOD) activity in heterophils from young (4-5 year) and old (12-14 year) ringdoves (Streptopelia risoria) under both basal and antigen-induced (stressful) conditions. Young animals were treated for 3 consecutive days with a single daily oral dose (0.25 mg) of melatonin at 1900 hours while old animals were treated for 3 consecutive days with either an oral dose (2.5 mg) of melatonin at 1900 hours or an oral capsule of 300 mg/kg body weight of L-tryptophan at 0900 hours. Non-treated old animals presented lower circulating levels of melatonin at night and higher levels of malonaldehyde (MDA) both day and night when compared to young birds. In both age groups, LPO levels were lower at night than during the day. Melatonin or tryptophan treatments significantly increased serum melatonin levels, reinforced SOD activity, and reduced MDA levels induced by the antigen. Melatonin and tryptophan may be useful agents for the treatment of disease states and processes in which an excessive production of oxidative damage occurs.

Melatonin downregulates nuclear erythroid 2-related factor 2 and nuclear factor-kappaB during prevention of oxidative liver injury in a dimethylnitrosamine model

Melatonin has potent hepatoprotective effects as an antioxidant. However, the signaling pathway of melatonin in the induction of antioxidant enzymes against acute liver injury is not fully understood. The study aimed to determine whether melatonin could prevent dimethylnitrosamine (DMN)-induced liver injury through nuclear erythroid 2-related factor 2 (Nrf2) and inflammation. Liver injury was induced in rats by a single injection of DMN (30 mg/kg, i.p.). Melatonin treatment (50 mg/kg/daily, i.p.) was initiated 24 hr after DMN injection for 14 days, after which the rats were killed and samples were collected. Serum and antioxidant enzyme activities improved in melatonin-treated rats, compared with DMN-induced liver injury group (P < 0.01). Melatonin reduced the infiltration of inflammatory cells and necrosis in the liver, and increased the expression of NADPH: quinone oxidoreductase-1, heme oxygenase-1, and superoxide dismutase-2, which were decreased by DMN. Melatonin increased expression of novel transcription factor, Nrf2, and decreased expression of inflammatory mediators including tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, and inducible nitric oxide synthase. The increased nuclear binding of nuclear factor-kappa B (NF-kappaB) in the DMN-induced liver injury group was inhibited by melatonin. Our results show that melatonin increases antioxidant enzymes and Nrf2 expression in parallel with the decrease of inflammatory mediators in DMN-induced liver injury, suggesting that melatonin may play a role of antioxidant defense via the Nrf2 pathway, by reducing inflammation by NF-kappaB inhibition.

Melatonin ameliorates methionine- and choline-deficient diet-induced nonalcoholic steatohepatitis in rats

Nonalcoholic steatohepatitis (NASH) may progress to advanced fibrosis and cirrhosis. Mainly, oxidative stress and excessive hepatocyte apoptosis are implicated in the pathogenesis of progressive NASH. Melatonin is not only a powerful antioxidant but also an anti-inflammatory and anti-apoptotic agent. We aimed to evaluate the effects of melatonin on methionine- and choline-deficient diet (MCDD)-induced NASH in rats. Thirty-two male Wistar rats were divided into four groups. Two groups were fed with MCDD while the other two groups were fed a control diet, pair-fed. One of the MCDD groups and one of the control diet groups were administered melatonin 50 mg/kg/day intraperitoneally, and the controls were given a vehicle. After 1 month the liver tissue oxidative stress markers, proinflammatory cytokines and hepatocyte apoptosis were studied by commercially available kits. For grading and staging histological lesions, Brunt et al.'s system was used. Melatonin decreased oxidative stress, proinflammatory cytokines and hepatocyte apoptosis. The drug ameliorated the grade of NASH. The present study suggests that melatonin functions as a potent antioxidant, anti-inflammatory and antiapoptotic agent in NASH and may be a therapeutic option.