Melatonin’s role in preventing toxin-related and sepsis-mediated hepatic damage: A review

Therapeutic benefit of melatonin in 5-fluorouracil-induced renal and hepatic injury

Nephrotoxicity and hepatotoxicity include increased oxidative stress and apoptosis; as a result, liver and kidney damage are related to its pathogenesis. These are significant side effects caused in cancer patients treated with 5-FU. In the research, 25 rats were divided into five groups, including control, 5-FU and 5-FU + 2.5, 5 and 10 mg/kg melatonin (MEL), and the protective impact of MEL against 5-FU-induced hepatorenal damage in rats was investigated. 5-FU caused significant harm, resulting in severe renal failure and histopathological changes. It also increased BUN, creatinine and hepatic function markers levels while decreasing superoxide dismutase and glutathione peroxidase activity. Additionally, 5-FU led to a notable increase in malondialdehyde content. However, MEL co-administration to rats reversed most biochemical and histologic effects. In the control and MEL + 5-FU groups, the values were comparable. The doses of MEL treatment had a significant positive impact on 5-FU-induced oxidative stress, apoptosis, lipid peroxidation and kidney damage. Our data concluded that MEL has an ameliorative effect on hepatorenal damage caused by 5-FU.

Melatonin-mediated actions and circadian functions that improve implantation, fetal health and pregnancy outcome

This review summarizes data related to the potential importance of the ubiquitously functioning antioxidant, melatonin, in resisting oxidative stress and protecting against common pathophysiological disorders that accompany implantation, gestation and fetal development. Melatonin from the maternal pineal gland, but also trophoblasts in the placenta, perhaps in the mitochondria, produce this molecule as a hedge against impairment of the uteroplacental unit. We also discuss the role of circadian disruption on reproductive disorders of pregnancy. The common disorders of pregnancy, i.e., stillborn fetus, recurrent fetal loss, preeclampsia, fetal growth retardation, premature delivery, and fetal teratology are all conditions in which elevated oxidative stress plays a role and experimental supplementation with melatonin has been shown to reduce the frequency or severity of these conditions. Moreover, circadian disruption often occurs during pregnancy and has a negative impact on fetal health; conversely, melatonin has circadian rhythm synchronizing actions to overcome the consequences of chronodisruption which often appear postnatally. In view of the extensive findings supporting the ability of melatonin, an endogenously-produced and non-toxic molecule, to protect against experimental placental, fetal, and maternal pathologies, it should be given serious consideration as a supplement to forestall the disorders of pregnancy. Until recently, the collective idea was that melatonin supplements should be avoided during pregnancy. The data summarized herein suggests otherwise. The current findings coupled with the evidence, published elsewhere, showing that melatonin is highly protective of the fertilized oocyte from oxidative damage argues in favor of its use for improving pregnancy outcome generally.

Melatonin: A potential adjuvant therapy for septic myopathy

Septic myopathy, also known as ICU acquired weakness (ICU-AW), is a characteristic clinical symptom of patients with sepsis, mainly manifested as skeletal muscle weakness and muscular atrophy, which affects the respiratory and motor systems of patients, reduces the quality of life, and even threatens the survival of patients. Melatonin is one of the hormones secreted by the pineal gland. Previous studies have found that melatonin has anti-inflammatory, free radical scavenging, antioxidant stress, autophagic lysosome regulation, mitochondrial protection, and other multiple biological functions and plays a protective role in sepsis-related multiple organ dysfunction. Given the results of previous studies, we believe that melatonin may play an excellent regulatory role in the repair and regeneration of skeletal muscle atrophy in septic myopathy. Melatonin, as an over-the-counter drug, has the potential to be an early, complementary treatment for clinical trials. Based on previous research results, this article aims to critically discuss and review the effects of melatonin on sepsis and skeletal muscle depletion.

Influence of constant lightning on liver health: an experimental study

Light pollution has become a serious problem in many urbanized areas of the world. The impact of prolonged exposure to light and consequent disruption of natural circadian rhythms has significant health implications. The current study was undertaken to evaluate the effect of prolonged exposure to light, simulating urban light pollution, on liver health. In order to evaluate the effect of prolonged exposure to light, we examined the morphofunctional state, immunohistochemical and micromorphometric parameters of rat liver in normal conditions and following prolonged lighting exposure. Our results show that nocturnal light disruption triggers a cell death in the liver within 3 weeks (necrosis and apoptosis of hepatocytes) and stimulates a change in normal cellular karyometric parameters. At the same time, intracellular regeneration takes place within the organ, which manifests through hepatocyte hypertrophy. Under the influence of constant illumination, the circadian rhythms (CRs) of the size of hepatocytes and their nuclei are restructured, and the rhythm of the nuclear-cytoplasmic ratio is destroyed. The destruction of the CR of expression of p53 and Ki-67 also occurs against the background of the rearrangement of the daily rhythmicity of Per2 and Bmal1. The revealed changes in the morphofunctional state of the liver under the influence of light pollution indicate that a violation of normal illumination regimes is a potent factor leading to significant structural changes in the liver.

Melatonin Attenuates Sepsis-Induced Acute Lung Injury Through Improvement of Epithelial Sodium Channel-Mediated Alveolar Fluid Clearance Via Activation of SIRT1/SGK1/Nedd4-2 Signaling Pathway

Acute lung injury is characterized by alveolar vascular barrier injury, and protein-rich pulmonary oedema. Alveolar fluid clearance is closely related to the prognosis of patients with acute lung injury. Melatonin has been shown to have a protective effect on multiple organ injury induced by sepsis. In this study we investigated the effect of melatonin on alveolar fluid clearance (AFC) and explored its potential mechanisms in sepsis-induced acute lung injury. The cecal ligation and puncture was adopted to establish mouse sepsis model. Morphological changes of lung tissues with the hematoxylin staining were observed. AFC and lung wet/dry weight ratio were measured to assess pulmonary edema. Inflammatory mediators in bronchoalveolar lavage fluid were analyzed via enzyme-linked immunosorbent assay. NAD+/NADH and SIRT1 activity were measured by colorimetric assay kit. The protein expressions of epithelial sodium channel (ENaC), silent information regulator1 (SIRT1), SGK1 and Nedd4-2 were immunoblotted by western blot in vivo and in vitro. The distribution of α-ENaC and SIRT1 was detected by immunofluorescence. We found that melatonin attenuated sepsis induced lung injury, improved survival rate, enhanced alveolar fluid clearance, improved SIRT1 activity, increased protein expressions of SIRT1 and ENaC, and activated SGK1/Nedd4-2 pathway. Furthermore, SIRT1 inhibitor EX527 counteracted the effects of melatonin on alveolar fluid clearance and ENaC. These results revealed that melatonin enhanced ENaC-mediated AFC via the SIRT1/SGK1/Nedd4-2 signaling pathway. Our study demonstrated that melatonin might provide a novel therapeutic strategy for sepsis-induced acute lung injury.

T-2 toxin in the diet suppresses growth and induces immunotoxicity in juvenile Chinese mitten crab (Eriocheir sinensis)

The T-2 toxin is a trichothecene mycotoxin and is highly toxic to aquatic animals, but little is known on its toxic effect in crustaceans. In the present study, the crab juveniles were fed with diets containing four levels of T-2 toxin: 0 (control), 0.6 (T1), 2.5 (T2) and 5.0 (T3) mg/kg diet for 56 days to evaluate its impact on the juvenile of Chinese mitten crab (Eriocheir sinensis). The crabs fed the T-2 toxin diets had significantly lower weight gain and specific growth rate than those fed the control diet. Moreover, crab survival in T3 group was obviously lower than that in the control. Oxidative stress occurred in all the treatment groups as indicated by higher activities of total superoxide dismutase, glutathione peroxidase, and total antioxidant capacity than those in the control. The total hemocyte count, respiratory burst, phenoloxidase in the hemolymph, and phenoloxidase, acid phosphatase and alkaline phosphatase in the hepatopancreas of crabs fed T-2 toxin were significantly lower than those in the control. The transcriptional expressions of lipopolysaccharide-induced TNF-alpha factor, relish, and the apoptosis genes in the hepatopancreas were induced by dietary T-2 toxin. The genes related to detoxication including cytochrome P450 gene superfamily and glutathione S transferase were induced in low concentration, then decreased in high concentration. Dietary T-2 toxin damaged the hepatopancreas structure, especially as seen in the detached basal membrane of hepatopancreatic tubules. This study indicates that dietary T-2 toxin can reduce growth performance, deteriorate health status and cause hepatopancreas dysfunction in crabs.

Possible application of melatonin treatment in human diseases of the biliary tract

Melatonin was discovered in 1958 by Aaron Lerner. Its name comes from the ability of melatonin to change the shape of amphibian melanophores from stellate to roundish. Starting from the 1980s, the role of melatonin in the regulation of mammalian circadian and seasonal clocks has been elucidated. Presently, several other effects have been identified in different organs. For example, the beneficial effects of melatonin in models of liver damage have been described. This review gives first a general background on experimental and clinical data on the use of melatonin in liver damage. The second part of the review focuses on the findings related to the role of melatonin in biliary functions, suggesting a possible use of melatonin therapy in human diseases of the biliary tree.

The effects of antibiotics and melatonin on hepato-intestinal inflammation and gut microbial dysbiosis induced by a short-term high-fat diet consumption in rats

High-fat diet (HFD) consumption leads to metabolic disorders, gastrointestinal dysfunction and intestinal dysbiosis. Antibiotics also disrupt the composition of intestinal microbiota. The aim of the present study was to investigate the impact of a short-term feeding with HFD on oxidative status, enteric microbiota, intestinal motility and the effects of antibiotics and/or melatonin treatments on diet-induced hepato-intestinal dysfunction and inflammation. Male Sprague-Dawley rats were pair-fed with either standard chow or HFD (45 % fat) and were given tap water or melatonin (4 mg/kg per d) or melatonin plus antibiotics (ABX; neomycin, ampicillin, metronidazole; each 1 g/l) in drinking water for 2 weeks. On the 14th day, colonic motility was measured and the next day intestinal transit was assessed using charcoal propagation. Trunk blood, liver and intestine samples were removed for biochemical and histopathological evaluations, and faeces were collected for microbiota analysis. A 2-week HFD feeding increased blood glucose level and perirenal fat weight, induced low-level hepatic and intestinal inflammation, delayed intestinal transit, led to deterioration of epithelial tight junctions and overgrowth of colonic bacteria. Melatonin intake in HFD-fed rats reduced ileal inflammation, colonic motility and perirenal fat accumulation. ABX abolished increases in fat accumulation and blood glucose, reduced ileal oxidative damage, suppressed HFD-induced overgrowth in colonic bacteria, and reversed HFD-induced delay in intestinal transit; however, hepatic neutrophil accumulation, hepatic injury and dysfunction were further enhanced. In conclusion, the results demonstrate that even a short-term HFD ingestion results in hepato-intestinal inflammatory state and alterations in bacterial populations, which may be worsened with antibiotic intake, but alleviated by melatonin.

Melatonin improves the structure and function of autografted mice ovaries through reducing inflammation: A stereological and biochemical analysis

Melatonin has anti-oxidant, anti-inflammatory and anti-apoptotic properties. We aimed to investigate the effect of melatonin on the structure and function of mice ovaries following autograft transplantation. NMRI mice were divided into: control, autografted + saline, autografted + melatonin (20 mg/kg/day i.p. injection for 1 day before until 7 days after transplantation). 28 days post transplantation, ovary compartments were studied stereologically. Follicle apoptosis and the level of progesterone and estradiol were also measured. The inflammation, serum MDA concentration and total antioxidant capacity were also assessed on day 7 post transplantation. The total volume of the ovary, cortex and medulla (P < 0.05) and the number of different types of follicles (P < 0.001), the concentration of IL-10, progesterone and estradiol (P < 0.001) and TAC (P < 0.01) significantly decreased in the autografted + saline group compared to the control. The levels of IL-6 (P < 0.01), TNF-α, MDA and the apoptotic rate (P < 0.001) increased significantly in the autografted + saline group compared to the control, while the total volume of the ovary, cortex and medulla (P < 0.05) and the number of different types of follicles (P < 0.001), the concentration of IL-10, progesterone and estradiol (P < 0.001) and TAC (P < 0.01) significantly increased in the autografted + melatonin group compared to the autografted + saline group. The levels of IL-6 (P < 0.01), TNF-α, MDA and the apoptotic rate (P < 0.001) decreased significantly in the autografted + melatonine group compared to the autografted + saline group. In the autografted + melatonin group, the localization of CD31-positive cells in the theca layer was similar to the control group. Melatonin can improve the structure and function of the grafted ovary.

Melatonin alleviates β-zearalenol and HT-2 toxin-induced apoptosis and oxidative stress in bovine ovarian granulosa cells

β-zearalenol (β-zol) and HT-2 are mycotoxins which cause apoptosis and oxidative stress in mammalian reproductive cells. Melatonin is an endogenous antioxidant involved in apoptosis and oxidative stress-related activities. This study investigated the effects of β-zol and HT-2 on bovine ovarian granulosa cells (BGCs), and how melatonin may counteract these effects. β-zol and HT-2 inhibited cell proliferation in a dose-dependent manner, and induced apoptosis of BGCs. They also yielded upregulation of the apoptosis-related genes Bax/Bcl-2 and Caspase3 and phosphorylation of p38MAPK. Increases in intracellular ROS were observed along with higher levels of mRNA anti-oxidation markers SOD1, SOD2, and CAT. SOD1, SOD2, malonaldehyde (MDA), and glutathione peroxidase (GSH-px) activities increased, as did the levels of SOD1 and SOD2 proteins. All of these effects were reduced or entirely attenuated in BGCs pre-treated with melatonin. Our results demonstrate that melatonin has protective effects against mycotoxin-induced apoptosis and oxidative stress in BGCs.

The Relationship Between Daytime Salivary Melatonin and Gastrointestinal Symptoms in Young Adults Seeking Psychiatric Care

OBJECTIVE

The pathophysiology of irritable bowel syndrome (IBS) is not completely understood, although we do know that patients with IBS have a high prevalence of psychiatric comorbidity (mainly depression and anxiety disorders). Melatonin, produced in the gastrointestinal tract, influences gut motility. Psychiatric conditions are associated with circadian disturbances in peripheral melatonin levels. This study aimed to investigate associations between daytime salivary melatonin and gastrointestinal symptoms in young adult psychiatric patients.

METHODS

Ninety-six patients (86% women), aged 18-25 years (M (SD) = 21 (2)), seeking psychiatric care with primarily anxiety disorders, affective disorders, or both were included in the study. Total scores from the Gastrointestinal Symptoms Rating Scale - IBS were compared with salivary melatonin measured at three time points (30 minutes after waking up, at 11:00 hours and 30 minutes after lunch) during the waking hours of 1 day.

RESULTS

After adjustment for potential confounders, melatonin levels in saliva 30 minutes after lunch remained significantly correlated to the total Gastrointestinal Symptoms Rating Scale - IBS score after correction for multiple testing (B = 0.016, SE = 0.006, p = .015, q = 0.045). In a post hoc analysis, symptoms of gastrointestinal pain and bloating contributed most to this association.

CONCLUSIONS

In young adult psychiatric patients, salivary melatonin levels after lunch are associated with gastrointestinal symptoms, which is consistent with the proposed effect of elevated levels of gastrointestinal melatonin on gut motility. This result suggests a link between IBS symptoms and regulation of melatonin in patients with psychiatric disorders.

PBDE-47 and PBDE mixture (DE-71) toxicities and liver transcriptomic changes at PND 22 after in utero/postnatal exposure in the rat

Pentabromodiphenyl ethers (PBDE) are found in human tissue, in household dust, and in the environment, and a particular concern is the potential for the induction of cancer pathways from these fat-soluble persistent organic pollutants. Only one PBDE cancer study has been conducted and that was for a PBDE mixture (DE-71). Because it is not feasible to test all PBDE congeners in the environment for cancer potential, it is important to develop a set of biological endpoints that can be used in short-term toxicity studies to predict disease outcome after long-term exposures. In this study, PBDE-47 was selected as the test PBDE congener to evaluate and compare toxicity to that of the carcinogenic PBDE mixture. The toxicities of PBDE-47 and the PBDE mixture were evaluated at PND 22 in Wistar Han rat (Crl: WI (Han)) pups after in utero/postnatal exposure (0, 0.1, 15, or 50 mg/kg; dams, GD6-21; pups, PND 12-PND 21; oral gavage daily dosing). By PND 22, PBDE-47 caused centrilobular hypertrophy and fatty change in liver, and reduced serum thyroxin (T4) levels; similar effects were also observed after PBDE mixture exposure. Transcriptomic changes in the liver included induction of cytochrome p450 transcripts and up-regulation of Nrf2 antioxidant pathway transcripts and ABC membrane transport transcripts. Decreases in other transport transcripts (ABCG5 & 8) provided a plausible mechanism for lipid accumulation, characterized by a treatment-related liver fatty change after PBDE-47 and PBDE mixture exposure. The benchmark dose calculation based on liver transcriptomic data was generally lower for PBDE-47 than for the PBDE mixture. The up-regulation of the Nrf2 antioxidant pathway and changes in metabolic transcripts after PBDE-47 and PBDE mixture exposure suggest that PBDE-47, like the PBDE mixture (NTP 2016, TR 589), could be a liver toxin/carcinogen after long-term exposure.

Mitochondria: Central Organelles for Melatonin's Antioxidant and Anti-Aging Actions

Melatonin, along with its metabolites, have long been known to significantly reduce the oxidative stress burden of aging cells or cells exposed to toxins. Oxidative damage is a result of free radicals produced in cells, especially in mitochondria. When measured, melatonin, a potent antioxidant, was found to be in higher concentrations in mitochondria than in other organelles or subcellular locations. Recent evidence indicates that mitochondrial membranes possess transporters that aid in the rapid uptake of melatonin by these organelles against a gradient. Moreover, we predicted several years ago that, because of their origin from melatonin-producing bacteria, mitochondria likely also synthesize melatonin. Data accumulated within the last year supports this prediction. A high content of melatonin in mitochondria would be fortuitous, since these organelles produce an abundance of free radicals. Thus, melatonin is optimally positioned to scavenge the radicals and reduce the degree of oxidative damage. In light of the "free radical theory of aging", including all of its iterations, high melatonin levels in mitochondria would be expected to protect against age-related organismal decline. Also, there are many age-associated diseases that have, as a contributing factor, free radical damage. These multiple diseases may likely be deferred in their onset or progression if mitochondrial levels of melatonin can be maintained into advanced age.

Pre-treatment with melatonin decreases abamectin induced toxicity in a nocturnal insect Spodoptera litura (Lepidoptera: Noctuidae)

AIM

Oxidative stress is an important component of the mechanism of pesticide toxicity. The aim of the present study was to investigate the time-dependent melatonin effects against abamectin-induced oxidative stress in a S.litura model. Larvae were divided into 5 different groups; (1) control group,(2) Melatonin group (4.3×10^-5M/100ml diet), (3) Abamectin group 1.5ml/L, (4) Pre-melatonin treated group (PM) (4.3×10^-5M/100ml diet) before abamectin exposure 1.5ml/L, (5) Post-melatonin treated group (TM) after abamectin exposure. Melatonin was supplemented via artificial diet in PM and TM animals during 24h.

MAIN METHODS

Midgut, fatbody, and hemolymph, were collected for the analysis of oxidative stress markers (Total ROS, GSH, nitrite, TBARS, LPO), antioxidant enzyme levels (SOD, GST, CAT, POX, APOX) in fifth instar larvae. Midgut damage was examined by using morphological analysis.

KEY FINDINGS

Our results observed that ABA group showed significant changes (p<0.001) in the ROS and carbonyl content in midgut. The increase of antioxidant enzyme levels (SOD, CAT, POX, and APOX) in midgut was led by the continuous free radical scavenger cascade of melatonin. Significant (p<0.01) increases in CAT and APOX levels were seen in the fatbody of PM and TM treated insects.

SIGNIFICANCE

In conclusion, the results of the study revealed that abamectin toxicity generates oxidative stress in the insect, while pre-melatonin treatment reduces this damage due to its antioxidant properties, especially POX levels in midgut, fatbody, and hemolymph. Therefore, indoleamine can play a vital role curtailing the abamectin toxicity in time dependent manner in S.litura.

Melatonin, clock genes and mitochondria in sepsis

After the characterization of the central pacemaker in the suprachiasmatic nucleus, the expression of clock genes was identified in several peripheral tissues including the immune system. The hierarchical control from the central clock to peripheral clocks extends to other functions including endocrine, metabolic, immune, and mitochondrial responses. Increasing evidence links the disruption of the clock genes expression with multiple diseases and aging. Chronodisruption is associated with alterations of the immune system, immunosenescence, impairment of energy metabolism, and reduction of pineal and extrapineal melatonin production. Regarding sepsis, a condition coursing with an exaggerated response of innate immunity, experimental and clinical data showed an alteration of circadian rhythms that reflects the loss of the normal oscillation of the clock. Moreover, recent data point to that some mediators of the immune system affects the normal function of the clock. Under specific conditions, this control disappears reactivating the immune response. So, it seems that clock gene disruption favors the innate immune response, which in turn induces the expression of proinflammatory mediators, causing a further alteration of the clock. Here, the clock control of the mitochondrial function turns off, leading to a bioenergetic decay and formation of reactive oxygen species that, in turn, activate the inflammasome. This arm of the innate immunity is responsible for the huge increase of interleukin-1β and entrance into a vicious cycle that could lead to the death of the patient. The broken clock is recovered by melatonin administration, that is accompanied by the normalization of the innate immunity and mitochondrial homeostasis. Thus, this review emphasizes the connection between clock genes, innate immunity and mitochondria in health and sepsis, and the role of melatonin to maintain clock homeostasis.

Melatonin as an Anti-Inflammatory Agent Modulating Inflammasome Activation

Inflammation may be defined as the innate response to harmful stimuli such as pathogens, injury, and metabolic stress; its ultimate function is to restore the physiological homeostatic state. The exact aetiology leading to the development of inflammation is not known, but a combination of genetic, epigenetic, and environmental factors seems to play an important role in the pathogenesis of many inflammation-related clinical conditions. Recent studies suggest that the pathogenesis of different inflammatory diseases also involves the inflammasomes, intracellular multiprotein complexes that mediate activation of inflammatory caspases thereby inducing the secretion of proinflammatory cytokines. Melatonin, an endogenous indoleamine, is considered an important multitasking molecule with fundamental clinical applications. It is involved in mood modulation, sexual behavior, vasomotor control, and immunomodulation and influences energy metabolism; moreover, it acts as an oncostatic and antiaging molecule. Melatonin is an important antioxidant and also a widespread anti-inflammatory molecule, modulating both pro- and anti-inflammatory cytokines in different pathophysiological conditions. This review, first, gives an overview concerning the growing importance of melatonin in the inflammatory-mediated pathological conditions and, then, focuses on its roles and its protective effects against the activation of the inflammasomes and, in particular, of the NLRP3 inflammasome.

Remodeling adipose tissue through in silico modulation of fat storage for the prevention of type 2 diabetes

BACKGROUND

Type 2 diabetes is one of the leading non-infectious diseases worldwide and closely relates to excess adipose tissue accumulation as seen in obesity. Specifically, hypertrophic expansion of adipose tissues is related to increased cardiometabolic risk leading to type 2 diabetes. Studying mechanisms underlying adipocyte hypertrophy could lead to the identification of potential targets for the treatment of these conditions.

RESULTS

We present iTC1390adip, a highly curated metabolic network of the human adipocyte presenting various improvements over the previously published iAdipocytes1809. iTC1390adip contains 1390 genes, 4519 reactions and 3664 metabolites. We validated the network obtaining 92.6% accuracy by comparing experimental gene essentiality in various cell lines to our predictions of biomass production. Using flux balance analysis under various test conditions, we predict the effect of gene deletion on both lipid droplet and biomass production, resulting in the identification of 27 genes that could reduce adipocyte hypertrophy. We also used expression data from visceral and subcutaneous adipose tissues to compare the effect of single gene deletions between adipocytes from each compartment.

CONCLUSIONS

We generated a highly curated metabolic network of the human adipose tissue and used it to identify potential targets for adipose tissue metabolic dysfunction leading to the development of type 2 diabetes.

The Effects of Melatonin on Elevated Liver Enzymes during Statin Treatment

Taking statins can cause increase in the level of aspartate and alanine aminotransferase. The aim of this study was to assess the usefulness of melatonin in counteracting the adverse hepatic events from statins. Methods. The research program included 60 patients (aged 47–65 years, 41 women and 19 men) with hyperlipidemia taking atorvastatin or rosuvastatin at a dose of 20–40 mg daily. The patients were randomly allocated in two groups. Group I (n = 30) was recommended to take the same statin at a standardized daily dose of 20 mg together with melatonin at a dose of 2 × 5 mg. Group II (n = 30) patients took statin with placebo at the same dose and time of the day. Follow-up laboratory tests (AST, ALT, GGT, and ALP) were evaluated after 2, 4, and 6 months of treatment. Results. In Group I the levels of all enzymes decreased after 6 months, particularly AST, 97,2 ± 19,1 U/L versus 52,8 ± 12,3 U/L (p < 0,001); ALT, 87,4 ± 15,6 U/L versus 49,8 ± 14,5 U/L (p < 0,001); and GGT, 84,1 ± 14,8 U/L versus 59,6 U/L (p < 0,001). Conclusion. Melatonin exerts a hepatoprotective effect in patients taking statins.

Melatonin alleviates cadmium-induced liver injury by inhibiting the TXNIP-NLRP3 inflammasome

Cadmium (Cd) is a persistent environmental and occupational contaminant that accumulates in the liver and induces oxidative stress and inflammation. Melatonin possesses potent hepatoprotective properties against the development and progression of acute and chronic liver injury. Nevertheless, the molecular mechanism underlying the protective effects of melatonin against Cd-induced hepatotoxicity remains obscure. In this study, we aimed to investigate the effects of melatonin on Cd-induced liver inflammation and hepatocyte death. Male C57BL/6 mice were intraperitoneally injected with melatonin (10 mg/kg) once a day for 3 days before exposure to CdCl₂ (2.0 mg/kg). We found that Cd induced hepatocellular damage and inflammatory infiltration as well as increased serum ALT/AST enzymes. In addition, we showed that Cd triggered an inflammatory cell death, which is mediated by the NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome. Moreover, melatonin treatment significantly alleviated Cd-induced liver injury by decreasing serum ALT/AST levels, suppressing pro-inflammatory cytokine production, inhibiting NLRP3 inflammasome activation, ameliorating oxidative stress, and attenuating hepatocyte death. Most importantly, melatonin markedly abrogated Cd-induced TXNIP overexpression and decreased the interaction between TXNIP and NLRP3 in vivo and in vitro. However, treatment with siRNA targeting TXNIP blocked the protective effects of melatonin in Cd-treated primary hepatocytes. Collectively, our results suggest that melatonin confers protection against Cd-induced liver inflammation and hepatocyte death via inhibition of the TXNIP-NLRP3 inflammasome pathway.

Melatonin attenuates thiocyanate-induced vasoconstriction in aortic rings

Cigarette smoking not only has a carcinogenic effect but also leads to an increase in arterial blood pressure. Besides its main components, i.e. nicotine, tar, and carbon monoxide, cigarette smoke also contains thiocyanate. Thiocyanate anions (SCN^-) arise from the detoxification of hydrogen cyanide and its plasma concentrations were found to correlate significantly with cigarette consumption. There is also evidence that atherosclerotic disease progression is much more rapid when serum SCN^- levels are increased. Melatonin, a non-toxic indolamine with various physiologic functions, is believed to protect against inflammatory processes and oxidative stress. It has been demonstrated that melatonin serves as free radical scavenger and represents a potent antioxidant. Therefore, it is believed that melatonin with its atheroprotective effects may be useful either as a sole therapy or in conjunction with others. The aim of this study was to quantify the thiocyanate-induced vasomotor response in aortic tissue and further to examine the potential of melatonin in affecting the generated vasoreactivity. Aortic rings of adult male normotensive Wistar rats were cut into 4-mm rings. Following the administration of thiocyanate in various concentrations, vasomotor response of aortic vessel segments was measured. To assess the effect of melatonin on vasomotor activity, organ bath concentrations were modulated from 60 to 360 pM, which corresponds to physiologic plasma up to the levels of patients with regular oral intake of 3 mg of melatonin as a supplement. Thirty-six rat aortic rings were studied. When exposed to thiocyanate, vessel segments revealed vasoconstriction in a concentration-dependent manner. In rings which were preincubated with melatonin at a concentration of 360 pM, a 56.5% reduction of effect size could be achieved (4.09 ± 1.22 mN versus 9.41 ± 1.74 mN, P < 0.0001). Additionally, administration of 360 pM melatonin at a norepinephrine concentration of 80 mM resulted in a relaxation of 10.9 ± 2.2%. The vasodilatatory effect of melatonin was significantly reduced to 1.3 ± 0.5% when concentration of norepinephrine was doubled (P < 0.002). This study indicates that vessel segments that were exposed to thiocyanate responded with a dose-dependent vasoconstriction. The effect could be markedly attenuated in segments preincubated in melatonin.

Melatonin prevents deregulation of the sphingosine kinase/sphingosine 1-phosphate signaling pathway in a mouse model of diethylnitrosamine-induced hepatocellular carcinoma

The sphingosine kinase (SphK)/sphingosine 1-phosphate (S1P) pathway is involved in multiple biological processes, including carcinogenesis. Melatonin shows beneficial effects in cell and animal models of hepatocellular carcinoma, but it is unknown if they are associated with the modulation of the SphK/S1P system, along with different downstream signaling pathways modified in cancer. We investigated the effects of melatonin in mice which received diethylnitrosamine (DEN) (35 mg/kg body weight i.p) once a week for 8 weeks. Melatonin was given at 5 or 10 mg/kg/day i.p. beginning 4 weeks after the onset of DEN administration and ending at the sacrifice time (10, 20, 30, or 40 weeks). Melatonin alleviated the distortion of normal hepatic architecture, lowered the incidence of preneoplastic/neoplastic lesions, and inhibited the expression of proliferative/cell cycle regulatory proteins (Ki67, PCNA, cyclin D1, cyclin E, CDK4, and CDK6). S1P levels and expression of SphK1, SphK2, and S1P receptors (S1PR1/S1PR3) were significantly elevated in DEN-treated mice. However, there was a decreased expression of S1P lyase. These effects were significantly abrogated in a time- and dose-dependent manner by melatonin, which also increased S1PR2 expression. Following DEN treatment, mice exhibited increased phosphorylation of PI3K, AKT, mTOR, STAT3, ERK, and p38, and a higher expression of NF-κB p50 and p65 subunits. Melatonin administration significantly inhibited those changes. Data obtained suggest a contribution of the SphK/S1P system and related signaling pathways to the protective effects of melatonin in hepatocarcinogenesis.

WOMEN IN CANCER THEMATIC REVIEW: Circadian rhythmicity and the influence of 'clock' genes on prostate cancer

The androgen receptor (AR) plays a key role in the development and progression of prostate cancer (CaP). Since the mid-1990s, reports in the literature pointed out higher incidences of CaP in some select groups, such as airline pilots and night shift workers in comparison with those working regular hours. The common finding in these 'high-risk' groups was that they all experienced a deregulation of the body's internal circadian rhythm. Here, we discuss how the circadian rhythm affects androgen levels and modulates CaP development and progression. Circadian rhythmicity of androgen production is lost in CaP patients, with the clock genes Per1 and Per2 decreasing, and Bmal1 increasing, in these individuals. Periodic expression of the clock genes was restored upon administration of the neurohormone melatonin, thereby suppressing CaP progression. Activation of the melatonin receptors and the AR antagonized each other, and therefore the tumour-suppressive effects of melatonin and the clock genes were most clearly observed in the absence of androgens, that is, in conjunction with androgen deprivation therapy (ADT). In addition, a large-scale study found that high-dose radiation was more effective in CaP patients when it was delivered before 17:00 h, compared with those delivered after 17:00 h, suggesting that the therapy was more effective when delivered in synchrony with the patient's circadian clock. As CaP patients are shown to become easily resistant to new therapies, perhaps circadian delivery of these therapeutic agents or delivery in conjunction with melatonin and its novel analogs should be tested to see if they prevent this resistance.

Melatonin as an antioxidant: under promises but over delivers

Melatonin is uncommonly effective in reducing oxidative stress under a remarkably large number of circumstances. It achieves this action via a variety of means: direct detoxification of reactive oxygen and reactive nitrogen species and indirectly by stimulating antioxidant enzymes while suppressing the activity of pro-oxidant enzymes. In addition to these well-described actions, melatonin also reportedly chelates transition metals, which are involved in the Fenton/Haber-Weiss reactions; in doing so, melatonin reduces the formation of the devastatingly toxic hydroxyl radical resulting in the reduction of oxidative stress. Melatonin's ubiquitous but unequal intracellular distribution, including its high concentrations in mitochondria, likely aid in its capacity to resist oxidative stress and cellular apoptosis. There is credible evidence to suggest that melatonin should be classified as a mitochondria-targeted antioxidant. Melatonin's capacity to prevent oxidative damage and the associated physiological debilitation is well documented in numerous experimental ischemia/reperfusion (hypoxia/reoxygenation) studies especially in the brain (stroke) and in the heart (heart attack). Melatonin, via its antiradical mechanisms, also reduces the toxicity of noxious prescription drugs and of methamphetamine, a drug of abuse. Experimental findings also indicate that melatonin renders treatment-resistant cancers sensitive to various therapeutic agents and may be useful, due to its multiple antioxidant actions, in especially delaying and perhaps treating a variety of age-related diseases and dehumanizing conditions. Melatonin has been effectively used to combat oxidative stress, inflammation and cellular apoptosis and to restore tissue function in a number of human trials; its efficacy supports its more extensive use in a wider variety of human studies. The uncommonly high-safety profile of melatonin also bolsters this conclusion. It is the current feeling of the authors that, in view of the widely diverse beneficial functions that have been reported for melatonin, these may be merely epiphenomena of the more fundamental, yet-to-be identified basic action(s) of this ancient molecule.

Melatonin Alleviates Liver Apoptosis in Bile Duct Ligation Young Rats

Bile duct ligation (BDL)-treated rats display cholestasis and liver damages. The potential protective activity of melatonin in young BDL rats in terms of apoptosis, mitochondrial function, and endoplasmic reticulum (ER) homeostasis has not yet been evaluated. Three groups of young male Sprague-Dawley rats were used: one group received laparotomy (Sham), a second group received BDL for two weeks (BDL), and a third group received BDL and intraperitoneal melatonin (100 mg/day) for two weeks (BDL + M). BDL group rats showed liver apoptosis, increased pro-inflamamtory mediators, caspases alterations, anti-apoptotic factors changes, and dysfunction of ER homeostasis. Melatonin effectively reversed apoptosis, mainly through intrinsic pathway and reversed ER stress. In addition, in vitro study showed melatonin exerted its effect mainly through the melatonin 2 receptor (MT2) in HepG2 cells. In conclusion, BDL in young rats caused liver apoptosis. Melatonin rescued the apoptotic changes via the intrinsic pathway, and possibly through the MT2 receptor. Melatonin also reversed ER stress induced by BDL.

Constitutive photomorphogenesis protein 1 (COP1) and COP9 signalosome, evolutionarily conserved photomorphogenic proteins as possible targets of melatonin

The ubiquitin proteasome system has been proposed as a possible mechanism involved in the multiple actions of melatonin. COP1 (constitutive photomorphogenesis protein 1), a RING finger-type ubiquitin E3 ligase formerly identified in Arabidopsis, is a central switch for the transition from plant growth underground in darkness (etiolation) to growth under light exposure (photomorphogenesis). In darkness, COP1 binds to photomorphogenic transcription factors driving its degradation via the 26S proteasome; blue light, detected by cryptochromes, and red and far-red light detected by phytochromes, negatively regulate COP1. Homologues of plant COP1 containing all the structural features present in Arabidopsis as well as E3 ubiquitin ligase activity have been identified in mice and humans. Substrates for mammalian (m) COP1 include p53, AP-1 and c-Jun, p27(Kip1) , ETV1, MVP, 14-3-3σ, C/EBPα, MTA1, PEA3, ACC, TORC2 and FOXO1. This mCOP1 target suggests functions related to tumorigenesis, gluconeogenesis, and lipid metabolism. The role of mCOP1 in tumorigenesis (either as a tumor promoter or tumor suppressor), as well as in glucose metabolism (inhibition of gluconeogenesis) and lipid metabolism (inhibition of fatty acid synthesis), has been previously demonstrated. COP1, along with numerous other ubiquitin ligases, is regulated by the COP9 signalosome; this protein complex is associated with the oxidative stress sensor Keap1 and the deubiquitinase USP15. The objective of this review was to provide new information on the possible role of COP1 and COP9 as melatonin targets. The hypothesis is based on common functional aspects of melatonin and COP1 and COP9, including their dependence on light, regulation of the metabolism, and their control of tumor growth.