Melatonin treatment protects liver of Zucker rats after ischemia/reperfusion by diminishing oxidative stress and apoptosis

Melatonin attenuates liver ischemia-reperfusion injury via inhibiting the PGAM5-mPTP pathway

Phosphoglycerate mutase/protein phosphatase (PGAM5)-mediated cell death plays an important role in multiple liver diseases. However, few studies have confirmed the regulatory mechanism of melatonin acting on PGAM5-mediated cell death in the context of liver ischemia-reperfusion (I/R) injury. The liver I/R injury model and cell hypoxia-reoxygenation model were established after melatonin pretreatment. Liver injury, cell activity, cell apoptosis, oxidative stress index, and PGAM5 protein expression were detected. To investigate the role of PGAM5 in melatonin-mediated liver protection during I/R injury, PGAM5 silencing, and overexpression were performed before melatonin pretreatment. Our results indicated that PGAM5 was significantly elevated by I/R injury, and predominantly localized in the necrosis area. However, treatment with melatonin blocked PGAM5 activation and conferred a survival advantage of hepatocytes in liver I/R injury, similar to the results achieved by silencing PGAM5. In terms of mechanism, we illustrated that activated PGAM5 promoted mitochondrial permeability transition pore (mPTP) opening, and administration of melatonin inhibited mPTP opening and interrupted hepatocytes death via blocking PGAM5. Our data indicated that the PGAM5-mPTP axis is responsible for I/R-induced liver injury. In contrast, melatonin supplementation blocked the PGAM5-mPTP axis and thus decreased cell death, providing a protective advantage to hepatocytes in I/R. These results established a new paradigm in melatonin-mediated hepatocyte protection under the burden of I/R attack.

Cellular and molecular mechanisms of hepatic ischemia-reperfusion injury: The role of oxidative stress and therapeutic approaches

Ischemia-reperfusion (IR) or reoxygenation injury is the paradoxical exacerbation of cellular impairment following restoration of blood flow after a period of ischemia during surgical procedures or other conditions. Acute interruption of blood supply to the liver and subsequent reperfusion can result in hepatocyte injury, apoptosis, and necrosis. Since the liver requires a continuous supply of oxygen for many biochemical reactions, any obstruction of blood flow can rapidly lead to hepatic hypoxia, which could quickly progress to absolute anoxia. Reoxygenation results in the increased generation of reactive oxygen species and oxidative stress, which lead to the enhanced production of proinflammatory cytokines, chemokines, and other signaling molecules. Consequent acute inflammatory cascades lead to significant impairment of hepatocytes and nonparenchymal cells. Furthermore, the expression of several vascular growth factors results in the heterogeneous closure of numerous hepatic sinusoids, which leads to reduced oxygen supply in certain areas of the liver even after reperfusion. Therefore, it is vital to identify appropriate therapeutic modalities to mitigate hepatic IR injury and subsequent tissue damage. This review covers all the major aspects of cellular and molecular mechanisms underlying the pathogenesis of hepatic ischemia-reperfusion injury, with special emphasis on oxidative stress, associated inflammation and complications, and prospective therapeutic approaches.

Melatonin Preserves Fluidity in Cell and Mitochondrial Membranes against Hepatic Ischemia-Reperfusion

We evaluated the in vivo effects of melatonin treatment on oxidative damage in the liver in an experimental model of ischemia-reperfusion. A total of 37 male Sprague-Dawley rats were randomly divided into four groups: control, ischemia, ischemia + reperfusion, and ischemia + reperfusion + melatonin. Hepatic ischemia was maintained for 20 min, and the clamp was removed to initiate vascular reperfusion for 30 min. Melatonin (50 mg/kg body weight) was intraperitoneally administered. Fluidity was measured by polarization changes in 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene-p-toluene sulfonate). After 20 min of ischemia, no significant changes were observed in cell and mitochondrial membrane fluidity levels, lipid peroxidation, and protein carbonylation. However, after 30 min of reperfusion, membrane fluidity decreased compared to controls. Increases in lipid and protein oxidation were also seen in hepatic homogenates of animals exposed to reperfusion. Melatonin injected 30 min before ischemia and reperfusion fully prevented membrane rigidity and both lipid and protein oxidation. Livers from ischemia-reperfusion showed histopathological alterations and positive labeling with antibodies to oxidized lipids and proteins. Melatonin reduced the severity of these morphological changes and protected against in vivo ischemia-reperfusion-induced toxicity in the liver. Therefore, melatonin might be a candidate for co-treatment for patients with hepatic vascular occlusion followed by reperfusion.

Ameliorative effects of glycine on cobalt chloride-induced hepato-renal toxicity in rats

BACKGROUND

The important roles of liver and kidney in the elimination of injurious chemicals make them highly susceptible to the noxious activities of various toxicants including cobalt chloride (CoCl₂ ). This study was designed to investigate the role of glycine in the mitigation of hepato-renal toxicities associated with CoCl₂ exposure.

METHODS

Forty-two (42) male rats were grouped as Control; (CoCl₂ ; 300 ppm); CoCl₂  + Glycine (50 mg/kg); CoCl₂  + Glycine (100 mg/kg); Glycine (50 mg/kg); and Glycine (100 mg/kg). The markers of hepatic and renal damage, oxidative stress, the antioxidant defense system, histopathology, and immunohistochemical localization of neutrophil gelatinase associated lipocalin (NGAL) and renal podocin were evaluated.

RESULTS

Glycine significantly reduced the markers of oxidative stress (malondialdehyde content and H₂ O₂ generation), liver function tests (ALT, AST, and ALP), markers of renal function (creatinine and BUN), and decreased the expression of neutrophil gelatinase-associated lipocalin (NGAL) and podocin compared with rats exposed to CoCl₂ toxicity without glycine treatment. Histopathology lesions including patchy tubular epithelial necrosis, tubular epithelial degeneration and periglomerular inflammation in renal tissues, and severe portal hepatocellular necrosis, inflammation, and duct hyperplasia were observed in hepatic tissues of rats exposed to CoCl₂ toxicity, but were mild to absent in glycine-treated rats.

CONCLUSION

The results of this study clearly demonstrate protective effects of glycine against CoCl₂ -induced tissue injuries and derangement of physiological activities of the hepatic and renal systems in rats. The protective effects are mediated via augmentation of total antioxidant capacity and upregulation of NGAL and podocin expression.

Effects of iNOS in Hepatic Warm Ischaemia and Reperfusion Models in Mice and Rats: A Systematic Review and Meta-Analysis

Warm ischaemia is usually induced by the Pringle manoeuver (PM) during hepatectomy. Currently, there is no widely accepted standard protocol to minimise ischaemia-related injury, so reducing ischaemia-reperfusion damage is an active area of research. This systematic review and meta-analysis focused on inducible nitric oxide synthase (iNOS) as an early inflammatory response to hepatic ischaemia reperfusion injury (HIRI) in mouse- and rat-liver models. A systematic search of studies was performed within three databases. Studies meeting the inclusion criteria were subjected to qualitative and quantitative synthesis of results. We performed a meta-analysis of studies grouped by different HIRI models and ischaemia times. Additionally, we investigated a possible correlation of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) regulation with iNOS expression. Of 124 included studies, 49 were eligible for the meta-analysis, revealing that iNOS was upregulated in almost all HIRIs. We were able to show an increase of iNOS regardless of ischemia or reperfusion time. Additionally, we found no direct associations of eNOS or NO with iNOS. A sex gap of primarily male experimental animals used was observed, leading to a higher risk of outcomes not being translatable to humans of all sexes.

Reactive Oxygen Species Induce Fatty Liver and Ischemia-Reperfusion Injury by Promoting Inflammation and Cell Death

Liver transplantation is the ultimate method for treating end-stage liver disease. With the increasing prevalence of obesity, the number of patients with non-alcoholic fatty liver, a common cause of chronic liver disease, is on the rise and may become the main cause of liver transplantation in the future. With the increasing gap between the number of donor livers and patients waiting for liver transplantation and the increasing prevalence of non-alcoholic fatty liver, the proportion of steatosis livers among non-standard donor organs is also increasing. Ischemia-reperfusion injury has historically been the focus of attention in the liver transplantation process, and severe ischemia-reperfusion injury leads to adverse outcomes of liver transplantation. Studies have shown that the production of reactive oxygen species and subsequent oxidative stress play a key role in the pathogenesis of hepatic ischemia and reperfusion injury and non-alcoholic fatty liver. Furthermore, the sensitivity of fatty liver transplantation to ischemia-reperfusion injury has been suggested to be related to the production of reactive oxygen species (ROS) and oxidative stress. In ischemia-reperfusion injury, Kupffer cell and macrophage activation along with mitochondrial damage and the xanthine/xanthine oxidase system promote marked reactive oxygen species production and the inflammatory response and apoptosis, resulting in liver tissue injury. The increased levels of ROS and lipid peroxidation products, vicious circle of ROS and oxidative stress along with mitochondrial dysfunction promoted the progress of non-alcoholic fatty liver. In contrast to the non-fatty liver, a non-alcoholic fatty liver produces more reactive oxygen species and suffers more serious oxidative stress when subjected to ischemia-reperfusion injury. We herein review the effects of reactive oxygen species on ischemia-reperfusion injury and non-alcoholic fatty liver injury as well as highlight several treatment approaches.

Novel Targets and Therapeutic Strategies to Protect Against Hepatic Ischemia Reperfusion Injury

Hepatic ischemia reperfusion injury (IRI), a fascinating topic that has drawn a lot of interest in the last few years, is a major complication caused by a variety of clinical situations, such as liver transplantation, severe trauma, vascular surgery, and hemorrhagic shock. The IRI process involves a series of complex events, including mitochondrial deenergization, metabolic acidosis, adenosine-5'-triphosphate depletion, Kupffer cell activation, calcium overload, oxidative stress, and the upregulation of pro-inflammatory cytokine signal transduction. A number of protective strategies have been reported to ameliorate IRI, including pharmacological therapy, ischemic pre-conditioning, ischemic post-conditioning, and machine reperfusion. However, most of these strategies are only at the stage of animal model research at present, and the potential mechanisms and exact therapeutic targets have yet to be clarified. IRI remains a main cause of postoperative liver dysfunction, often leading to postoperative morbidity or even mortality. Very recently, it was reported that the activation of peroxisome proliferator-activated receptor γ (PPARγ), a member of a superfamily of nuclear transcription factors activated by agonists, can attenuate IRI in the liver, and FAM3A has been confirmed to mediate the protective effect of PPARγ in hepatic IRI. In addition, non-coding RNAs, like LncRNAs and miRNAs, have also been reported to play a pivotal role in the liver IRI process. In this review, we presented an overview of the latest advances of treatment strategies and proposed potential mechanisms behind liver IRI. We also highlighted the role of several important molecules (PPARγ, FAM3A, and non-coding RNAs) in protecting against hepatic IRI. Only after achieving a comprehensive understanding of potential mechanisms and targets behind IRI can we effectively ameliorate IRI in the liver and achieve better therapeutic effects.

Melatonin as a powerful antioxidant

Melatonin is a hormone that has many body functions and, for several decades, its antioxidant potential has been increasingly talked about. There is a relationship between failure in melatonin production in the pineal gland, an insufficient supply of this hormone to the body, and the occurrence of free radical etiology diseases such as neurodegenerative diseases, cardiovascular diseases, diabetes, cancer and others. Despite the development of molecular biology, numerous in vitro and in vivo studies, the exact mechanism of melatonin antioxidant activity is still unknown. Nowadays, the use of melatonin supplementation is more and more common, not only to prevent insomnia, but also to slow down the aging process and provide protection against diseases. The aim of this study is to get acquainted with current reports on melatonin, antioxidative mechanisms and their importance in diseases of free radical etiology.

SS-31 Protects Liver from Ischemia-Reperfusion Injury via Modulating Macrophage Polarization

Ischemia-reperfusion injury (IRI) is a common complication in liver surgeries. It is a focus to discover effective treatments to reduce ischemia-reperfusion injury. Previous studies show that oxidative stress and inflammation response contribute to the liver damage during IRI. SS-31 is an innovated mitochondrial-targeted antioxidant peptide shown to scavenge reactive oxygen species and decrease oxidative stress, but the protective effects of SS-31 against hepatic IRI are not well understood. The aim of our study is to investigate whether SS-31 could protect the liver from damages induced by IRI and understand the protective mechanism. The results showed that SS-31 treatment can significantly attenuate liver injury during IRI, proved by HE staining, serum ALT/AST, and TUNEL staining which can assess the degree of liver damage. Meanwhile, we find that oxidative stress and inflammation were significantly suppressed after SS-31 administration. Furthermore, the mechanism revealed that SS-31 can directly decrease ROS production and regulate STAT1/STAT3 signaling in macrophages, thus inhibiting macrophage M1 polarization. The proinflammation cytokines are then significantly reduced, which suppress inflammation response in the liver. Taken together, our study discovered that SS-31 can regulate macrophage polarization through ROS scavenging and STAT1/STAT3 signaling to ameliorate liver injury; the protective effects against hepatic IRI suggest that SS-31 may be an appropriate treatment for liver IRI in the clinic.

Alcohol and melatonin

Investigation of the pathogenesis of alcoholism in humans using different methodological approaches has facilitated detection of important biological factors of consequent metabolic diseases, endocrine disorders, and other medical conditions, such as alcoholic cardiomyopathy, alcoholic hypertension, heart and vascular lesions, alcoholic liver disease, alcoholic pancreatitis, etc. Alcohol abuse leads to damage to the nervous system, which can result in neurological and mental disorders, including alcoholic polyneuropathy, psychosis, and alcohol dementia. The complexity and versatility of the harmful effects of regular alcohol consumption on the human body can be considered in the perspective of a chronobiological approach, because alcohol is chronotoxic to biological processes. As a rhythm regulator, melatonin exerts a wide range of different effects: circadian rhythm regulation, thermoregulation, sleep induction, antioxidant, immunomodulatory, and anti-stress ones. This review presents from a chronobiological perspective the impact of melatonin on alcohol intoxication in terms of mental disorders, sleep and inflammation, hepatic injury, and mitochondrial function. It discusses the main clinical effects of melatonin on alcohol injury and the main targets as a therapy for alcohol disorders. Chronobiological effects of ethanol are related to melatonin suppression that has been associated with, among others, cancer risk. Exogenous melatonin seems to be a promising hepato- and immune-protector due to its antioxidant and anti-inflammatory properties, which in combination with other medicines makes it useful to prevent alcoholic organ damage. The reason for the scientific interest in melatonin as a treatment for alcoholism is obvious; the number of cases of this pathology that gives rise to metabolic syndrome, and its subsequent transformation into steatohepatitis, liver fibrosis, and cirrhosis, is increasing worldwide. Melatonin not only exerts antioxidant effects but it exerts various other effects contributing to the management of liver conditions. This review discusses the interaction between normal and pathological processes caused by alcohol consumption and the relationship between alcohol and melatonin in these conditions.

Melatonin modulates copper-induced anxiety-like, depression-like and memory impairments by acting on hippocampal oxidative stress in rat

Copper (Cu) is a heavy metal with the ability to induce, at high levels, neurobehavioral alterations, and oxidative stress (OS). On the other hand, melatonin (Mel) is a neurohormone that protects neurons from OS and has a modulatory effect on several behavioral processes. The present experiment was aimed to examine the effect of Mel treatment on Cu-induced anxiety-like, depression-like behaviors, memory impairment, and OS in hippocampus. Herein, adult Wistar rats of both genders received daily Mel (4 mg/kg) thirty minutes before CuCl₂ (1 mg/kg), by intraperitoneal injections for 8 weeks. After the administration period, all rats were submitted to the behavioral tests. Thereafter, OS parameters and histology of the hippocampus were evaluated. The results demonstrate that Mel treatment attenuated Cu-induced anxiety-like and depression-like behaviors, and it improved memory deficits Cu-treated rats. Furthermore, Mel attenuated Cu-provoked OS by reducing lipid peroxidation (LPO) and nitric oxide (NO) levels and enhancing superoxide dismutase (SOD) and catalase (CAT) activities in the hippocampus. The histopathological analysis also supported these results. In conclusion, these findings show that Mel treatment exerted neuroprotective effects against Cu-induced neurobehavioral changes which may be related to reduction of hippocampal OS. Besides, the effects of Cu and Mel were gender dependent, being more marked in females compared to male rats.

Use of natural anti-oxidants in experimental animal models of hepatic ischemia-reperfusion injury

Background

Ischemia-reperfusion injury (IRI) remains a clinical challenge in liver surgery, trauma and transplantation, contributing to morbidity and mortality worldwide. Thus, its impact, not only on the liver itself but also on remote tissues, has been studied during the last years. Different natural anti-oxidant substances have been researched in animal models, implementing different times of ischemia, aiming to test new therapeutic interventions.

Objective

A literature review has been conducted with two goals: (1) to identify different natural anti-oxidants studied in experimental models; and (2) to summarize the various times of ischemia employed.

Methods

Scientific papers published in PubMed for the period 2000–2020 were searched and reviewed.

Results

More than 30 natural anti-oxidants have been tested. The time of ischemia ranged from 15 to 90 min with 60 min used most frequently, followed by 45 min. No studies were found with time exceeding 90 min.

Conclusions

A significant number of research has been conducted on the use and protective effect of natural anti-oxidants in experimental animal models. Based on the published papers, 45–60 min seems to be the optimal duration of ischemia.

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Liver IRI is a multifactorial and complex process, involving many mechanisms, cells and mediators. Even though, most of these mechanisms have not been completely understood, several substances have been tested in experimental models in order to determine their protective or destructive role.

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Antioxidant therapy is a promising therapeutic pathway that can ameliorate the impact of liver ischemia-reperfusion injury.

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Non-pharmaceutical, natural extracts are increasingly gaining their place into the therapeutic options of physicians, in an attempt to avoid various adverse effects that the chemical drugs can cause.

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New unexplored research areas may include different strains of rats, more studies in larger mammals of comparable anatomy to humans, experiments on different liver diseases, publishing negative results regarding toxic doses of natural antioxidants, and testing different ischemia times.

Inhibitory effect of melatonin on hypoxia-induced vasculogenic mimicry via suppressing epithelial-mesenchymal transition (EMT) in breast cancer stem cells

Vasculogenic mimicry (VM) play an important role in breast cancer metastasis and anti- angiogenic drugs resistance. Hypoxia, the epithelial-mesenchymal transition (EMT), and cancer stem cells (CSCs) are known as essential factors for VM formation. Also, melatonin is an amino acid-derived hormone with many anti-tumor effects. Despite the antitumor effects of melatonin, its effect on VM formation in breast cancer has not been considered yet, so we investigated the effect of melatonin on VM formation through EMT process under hypoxia conditions in breast CSCs. The CSCs percentage and VM formation were determined in MCF-7 and MDA-MB-231, respectively. Also, analysis of HIF-1α expression under hypoxia in MDA-MB-231 and MCF-7 cell lines was performed using Western blot. The effect of melatonin on the VM formation, invasion, and migration was also investigated. Moreover, the effect of melatonin on the expression EMT markers was evaluated. CD44⁺ CD24^-phenotype as CSCs marker in MDA-MB-231 cell line, was 80.8%, while it was 11.1% in MCF-7 cell line. HIF-1α expression was up-regulated in the VM-positive breast cancer cell line MDA-MB-231, and consequently, affected the expression of the EMT markers E-cadherin, vimentin, snail, and MMP9. Melatonin had significant effect on EMT and formations of VM in breast CSCs. Melatonin could prevent the formation of VM by affecting the important molecules involved in the formation of VM structures and the EMT. Moreover, our data clearly showed that, melatonin represents molecule with significant anti-cancer activities that may potentially optimize the management of breast cancer through the overcoming drug resistance in anti-angiogenic drugs.

Use of Steatotic Grafts in Liver Transplantation: Current Status

In the field of liver transplantation, the demand for adequate allografts greatly exceeds the supply. Therefore, expanding the donor pool to match the growing demand is mandatory. The present review summarizes current knowledge of the pathophysiology of ischemia/reperfusion injury in steatotic grafts, together with recent pharmacological approaches aimed at maximizing the utilization of these livers for transplantation. We also describe the preclinical models currently available to understand the molecular mechanisms controlling graft viability in this specific type of donor, critically discussing the heterogeneity in animal models, surgical methodology, and therapeutic interventions. This lack of common approaches and interventions makes it difficult to establish the pathways involved and the relevance of isolated discoveries, as well as their transferability to clinical practice. Finally, we discuss how new therapeutic strategies developed from experimental studies are promising but that further studies are warranted to translate them to the bedside.

Low Serum Melatonin Levels Prior to Liver Transplantation in Patients with Hepatocellular Carcinoma are Associated with Lower Survival after Liver Transplantation

Melatonin administration has been associated with different benefits in animals and patients suffering from liver diseases. However, there is no published data about circulating melatonin levels in patients with hepatocellular carcinoma (HCC) who underwent liver transplantation (LT). Thus, the objective of this observational and retrospective study was to determine whether patients with HCC with lower serum melatonin levels prior to LT have a higher risk of one-year mortality after LT. We measured serum levels of melatonin, malondialdehyde (to assess lipid peroxidation), and total antioxidant capacity (to assess antioxidant state) before LT. One-year surviving LT patients (n = 129) showed higher serum levels of melatonin (p = 0.001) and total antioxidant capacity (p = 0.001) and lower serum levels of malondialheyde (p = 0.01) than non-surviving LT patients (n = 16). Logistic regression analysis showed that high serum melatonin levels prior to LT were associated with lower one-year LT mortality (odds ratio = 0.525; 95% confidence interval (CI) = 0.331–0.834; p = 0.006). We found an association between serum levels of melatonin with serum levels of malondialheyde (rho = −0.22; p = 0.01) and total antioxidant capacity (rho = 0.21; p = 0.01). Thus, the novel findings of our study were the association between high serum melatonin levels prior to LT and survival at first year after LT and the association between serum levels of melatonin with malondialheyde and total antioxidant capacity.

Hepatic ischemia-reperfusion injury in liver transplant setting: mechanisms and protective strategies

Hepatic ischemia-reperfusion injury is a major cause of liver transplant failure, and is of increasing significance due to increased use of expanded criteria livers for transplantation. This review summarizes the mechanisms and protective strategies for hepatic ischemia-reperfusion injury in the context of liver transplantation. Pharmacological therapies, the use of pre-and post-conditioning and machine perfusion are discussed as protective strategies. The use of machine perfusion offers significant potential in the reconditioning of liver grafts and the prevention of hepatic ischemia-reperfusion injury, and is an exciting and active area of research, which needs more study clinically.

The multiple protective roles and molecular mechanisms of melatonin and its precursor N-acetylserotonin in targeting brain injury and liver damage and in maintaining bone health

Melatonin is a neurohormone associated with sleep and wakefulness and is mainly produced by the pineal gland. Numerous physiological functions of melatonin have been demonstrated including anti-inflammation, suppressing neoplastic growth, circadian and endocrine rhythm regulation, and its potent antioxidant activity as well as its role in regeneration of various tissues including the nervous system, liver, bone, kidney, bladder, skin, and muscle, among others. In this review, we summarize the recent advances related to the multiple protective roles of melatonin receptor agonists, melatonin and N-acetylserotonin (NAS), in brain injury, liver damage, and bone health. Brain injury, including traumatic brain injury, ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, and newborn perinatal hypoxia-ischemia encephalopathy, is a major cause of mortality and disability. Liver disease causes serious public health problems and various factors including alcohol, chemical pollutants, and drugs induce hepatic damage. Osteoporosis is the most common bone disease in humans. Due in part to an aging population, both the cost of care of fracture patients and the annual fracture rate have increased steadily. Despite the discrepancy in the pathophysiological processes of these disorders, time frames and severity, they may share several common molecular mechanisms. Oxidative stress is considered to be a critical factor in these pathogeneses. We update the current state of knowledge related to the molecular processes, mainly including anti-oxidative stress, anti-apoptosis, autophagy dysfunction, and anti-inflammation as well as other properties of melatonin and NAS. Particularly, the abilities of melatonin and NAS to directly scavenge oxygen-centered radicals and toxic reactive oxygen species, and indirectly act through antioxidant enzymes are disscussed. In this review, we summarize the similarities and differences in the protection provided by melatonin and/or NAS in brain, liver and bone damage. We analyze the involvement of melatonin receptor 1A (MT1), melatonin receptor 1B (MT2), and melatonin receptor 1C (MT3) in the protection of melatonin and/or NAS. Additionally, we evaluate their potential clinical applications. The multiple mechanisms of action and multiple organ-targeted properties of melatonin and NAS may contribute to development of promising therapies for clinical trials.

Impact of Melatonin in Solid Organ Transplantation-Is It Time for Clinical Trials? A Comprehensive Review

Solid organ transplantation is the "gold standard" for patients with end-stage organ disease. However, the supply of donor organs is critical, with an increased organ shortage over the last few years resulting in a significant mortality of patients on waiting lists. New strategies to overcome the shortage of organs are urgently needed. Some experimental studies focus on melatonin to improve the donor pool and to protect the graft; however, current research has not reached the clinical level. Therefore, this review provides a comprehensive overview of the data available, indicating that clinical evaluation is warranted.

TXNIP knockdown alleviates hepatocyte ischemia reperfusion injury through preventing p38/JNK pathway activation

Hepatic ischemia and reperfusion (I/R) injury is a major cause of liver damage during liver transplantation, resection surgery, shock, and trauma. It has been reported that TXNIP expression was upregulated in a rat model of hepatic I/R injury. However, the role of TXNIP in the hepatic I/R injury is little known. In our study, we investigated the biological role of TXNIP and its potential molecular mechanism in the human hepatic cell line (HL7702 cells). Using oxygen-glucose deprivation and reoxygenation (OGD/R) to create a cell model of hepatic I/R injury, we found that the mRNA and protein expression levels of TXNIP were upregulated in HL7702 cells exposed to OGD/R. TXNIP overexpression remarkably promoted OGD/R-induced cell apoptosis and lactate dehydrogenase (LDH) release, both of which were significantly decreased by TXNIP knockdown. The production of malondialdehyde (MDA) was also increased by TXNIP overexpression, but was reduced by TXNIP knockdown. Moreover, TXNIP overexpression significantly upregulated the phosphorylation of p38 and JNK, which was remarkably inhibited by TXNIP knockdown. Additionally, p38-specific inhibitor SB203580 abrogated the effect of TXNIP overexpression on OGD/R-induced cell injury. Taken together, these results indicated that TXNIP knockdown alleviated hepatocyte I/R injury through preventing p38/JNK pathway activation. Thus, TXNIP might offer a novel potential therapeutic target for the treatment of hepatic I/R injury.

Melatonin and its metabolites vs oxidative stress: From individual actions to collective protection

Oxidative stress (OS) represents a threat to the chemical integrity of biomolecules including lipids, proteins, and DNA. The associated molecular damage frequently results in serious health issues, which justifies our concern about this phenomenon. In addition to enzymatic defense mechanisms, there are compounds (usually referred to as antioxidants) that offer chemical protection against oxidative events. Among them, melatonin and its metabolites constitute a particularly efficient chemical family. They offer protection against OS as individual chemical entities through a wide variety of mechanisms including electron transfer, hydrogen transfer, radical adduct formation, and metal chelation, and by repairing biological targets. In fact, many of them including melatonin can be classified as multipurpose antioxidants. However, what seems to be unique to the melatonin's family is their collective effects. Because the members of this family are metabolically related, most of them are expected to be present in living organisms wherever melatonin is produced. Therefore, the protection exerted by melatonin against OS may be viewed as a result of the combined antioxidant effects of the parent molecule and its metabolites. Melatonin's family is rather exceptional in this regard, offering versatile and collective antioxidant protection against OS. It certainly seems that melatonin is one of the best nature's defenses against oxidative damage.

The influence of ageing on the extrapineal melatonin synthetic pathway

Ageing affects various physiological and metabolic processes in a body and a progressive accumulation of oxidative damage stands out as often used explanation. One of the most powerful scavenger of reactive oxygen species (ROS) in all organs is melatonin. A majority of melatonin supplied to the body via blood originates from the pineal gland. However, we have been interested in a locally produced melatonin. We have used 2.5- and 36-months-old Wistar rats. Tissues were collected and gene expression of AA-NAT and ASMT, the two key enzymes in a synthesis of melatonin, was determined in brain, liver, kidney, heart, skin, and intestine. Since melatonin can influence antioxidant enzymes, the activity of superoxide dismutase (SOD) and catalase (CAT), and the level of GSH were measured in liver. In addition, Copper (Cu), Zinc (Zn), and Manganese (Mn) were also determined in liver since these microelements might affect the activity of antioxidant enzymes. The expression of AA-NAT and ASMT was increased in liver and skin of old animals. A positive correlation in AA-NAT and ASMT expression was observed in liver, intestine and kidney. Moreover, the activity of CAT enzyme in liver was increased while SOD activity was decreased. SOD and CAT were probably affected by the observed decreased amount of Cu, Zn, and Mn in liver of old animals. In our model, extrapineal melatonin pathway in ageing consisted of complex interplay of locally produced melatonin, activities of SOD and CAT, and adequate presence of Cu, Zn and Mn microelements in order to defend organs against oxidative damage.

Melatonin protects against diabetic cardiomyopathy through Mst1/Sirt3 signaling

This study investigated the effects of melatonin on diabetic cardiomyopathy (DCM) and determined the underlying mechanisms. Echocardiography indicated that melatonin notably mitigated the adverse left ventricle remodeling and alleviated cardiac dysfunction in DCM. The mechanisms were attributed to increased autophagy, reduced apoptosis, and alleviated mitochondrial dysfunction. Furthermore, melatonin inhibited Mst1 phosphorylation and promoted Sirt3 expression in DCM. These results indicated that melatonin may exert its effects through Mst1/Sirt3 signaling. To verify this hypothesis, a DCM model using Mst1 transgenic (Mst1 Tg) and Mst1 knockout (Mst1^-/- ) mice was constructed. As expected, melatonin increased autophagy, reduced apoptosis and improved mitochondrial biogenesis in Mst1 Tg mice subjected to DCM injury, while it had no effects on Mst1^-/- mice. In addition, cultured neonatal mouse cardiomyocytes were subjected to simulated diabetes to probe the mechanisms involved. Melatonin administration promoted autophagic flux as demonstrated by elevated LC3-II and lowered p62 expression in the presence of bafilomycin A1. The results suggest that melatonin alleviates cardiac remodeling and dysfunction in DCM by upregulating autophagy, limiting apoptosis, and modulating mitochondrial integrity and biogenesis. The mechanisms are associated with Mst1/Sirt3 signaling.

Treatment with dimethyl fumarate ameliorates liver ischemia/reperfusion injury

AIM

To investigate the hypothesis that treatment with dimethyl fumarate (DMF) may ameliorate liver ischemia/reperfusion injury (I/RI).

METHODS

Rats were divided into 3 groups: sham, control (CTL), and DMF. DMF (25 mg/kg, twice/d) was orally administered for 2 d before the procedure. The CTL and DMF rats were subjected to ischemia for 1 h and reperfusion for 2 h. The serum alanine aminotransferase (ALT) and malondialdehyde (MDA) levels, adenosine triphosphate (ATP), NO × metabolites, anti-oxidant enzyme expression level, anti-inflammatory effect, and anti-apoptotic effect were determined.

RESULTS

Histological tissue damage was significantly reduced in the DMF group (Suzuki scores: sham: 0 ± 0; CTL: 9.3 ± 0.5; DMF: 2.5 ± 1.2; sham vs CTL, P < 0.0001; CTL vs DMF, P < 0.0001). This effect was associated with significantly lower serum ALT (DMF 5026 ± 2305 U/L vs CTL 10592 ± 1152 U/L, P = 0.04) and MDA (DMF 18.2 ± 1.4 μmol/L vs CTL 26.0 ± 1.0 μmol/L, P = 0.0009). DMF effectively improved the ATP content (DMF 20.3 ± 0.4 nmol/mg vs CTL 18.3 ± 0.6 nmol/mg, P = 0.02), myeloperoxidase activity (DMF 7.8 ± 0.4 mU/mL vs CTL 6.0 ± 0.5 mU/mL, P = 0.01) and level of endothelial nitric oxide synthase expression (DMF 0.38 ± 0.05-fold vs 0.17 ± 0.06-fold, P = 0.02). The higher expression levels of anti-oxidant enzymes (catalase and glutamate-cysteine ligase modifier subunit and lower levels of key inflammatory mediators (nuclear factor-kappa B and cyclooxygenase-2 were confirmed in the DMF group.

CONCLUSION

DMF improved the liver function and the anti-oxidant and inflammation status following I/RI. Treatment with DMF could be a promising strategy in patients with liver I/RI.

Preconditioning methods in the management of hepatic ischemia reperfusion- induced injury: Update on molecular and future perspectives

Hepatic IR (ischemia reperfusion) injury is a commonly encountered obstacle in the post-operative management of hepatic surgery. Hepatic IR occurs during 'Pringle maneuver' for reduction of blood loss or during a brief period of cold storage followed by reperfusion of liver grafts. The stress induced during hepatic IR, triggers a spectrum of cellular responses leading to the varying degrees of hepatic complications which in turn affect the post operative care. Different preconditioning methods either activate or subdue different sets of molecular signals, resulting in varied levels of protection against hepatic IR injury. Yet, there is a serious lacuna in the knowledge regarding the choice of preconditioning methods and the resulting molecular changes in order to assess the efficiency and choice of these methods correctly. This review provides an update on the various preconditioning approaches such as surgical/ischemic, antioxidant, pharmaceutical and genetic preconditioning strategies published during last six years (2009-2015). Further, we discuss the attenuation or inhibition of specific inflammatory, apoptotic and necrotic markers in the various experimental models of liver IR subjected to different preconditioning strategies. While enlisting the controversies in the ischemic preconditioning strategy, we bring out the uncertainties in the existing molecular targets and their reliability in the attenuation of hepatic IR injury. Future research studies would include the novel preconditioning strategies employ i) the targeted gene silencing of key molecular targets inducing IR, ii) hyper expression of beneficial molecular signals against IR via gene transfer techniques. The above studies would see the combination of these latest techniques with the established preconditioning strategies for better post-operative hepatic management.

The effect of commercial conjugated linoleic acid products on experimental periodontitis and diabetes mellitus in Wistar rats

OBJECTIVE

The aim of present study was to determine the effects of conjugated linoleic acid enriched milk on alveolar bone loss, hyperglycaemia, oxidative stress and apoptosis in ligature-induced periodontal disease in diabetic rat model.

METHODS

Wistar rats were divided into six experimental groups: 1; non-ligated (NL, n = 6) group, 2; ligature only (LO, n = 6) group, 3; streptozotocin only (STZ, n = 8) group, 4; STZ and ligature (STZ + L, n = 8) group, 5; ligature and conjugated linoleic acid (CLA) (L + CLA, n = 8) group, 6; STZ, ligature and CLA group (STZ + L + CLA, n = 8) group. Diabetes mellitus was induced by 60 mg/kg streptozotocin. Rats were fed with CLA enriched milk for four weeks. Silk ligatures were placed at the gingival margin of lower first molars of mandibular quadrant. The study duration was four weeks after diabetes induction and the animals were sacrificed at the end of this period. Changes in alveolar bone levels were clinically measured and tissues were histopathologically examined. Inducible nitric oxide synthase (iNOS) and Bax protein expressions, serum interleukin-1β (IL-1β), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglyceride levels and tartrate resistant acid phosphatase (TRAP)+ osteoclast numbers were also evaluated.

RESULTS

At the end of four weeks, alveolar bone loss was significantly higher in the STZ + LO group compared to the other groups (p < .05). CLA decreased alveolar bone loss in L + CLA and STZ + L + CLA groups. CLA significantly decreased TRAP + osteoclast numbers and increased osteoblastic activity compared to the STZ + L group (p < .05). Diabetes and CLA increased Bax protein levels (p < .05) however CLA had no effect on iNOS expression (p > .05).

CONCLUSION

Within the limits of this study, commercial CLA product administration in addition to diet significantly reduced alveolar bone loss, increased osteoblastic activity and decreased osteoclastic activity in the diabetic Wistar rats.

Melatonin alleviates postinfarction cardiac remodeling and dysfunction by inhibiting Mst1

Melatonin reportedly protects against several cardiovascular diseases including ischemia/reperfusion (I/R), atherosclerosis, and hypertension. The present study investigated the effects and mechanisms of melatonin on cardiomyocyte autophagy, apoptosis, and mitochondrial injury in the context of myocardial infarction (MI). We demonstrated that melatonin significantly alleviated cardiac dysfunction after MI. Four weeks after MI, echocardiography and Masson staining indicated that melatonin notably mitigated adverse left ventricle remodeling. The mechanism may be associated with increased autophagy, reduced apoptosis, and alleviated mitochondrial dysfunction. Furthermore, melatonin significantly inhibited Mst1 phosphorylation while promoting Sirt1 expression after MI, which indicates that Mst1/Sirt1 signaling may serve as the downstream target of melatonin. We thus constructed a MI model using Mst1 transgenic (Mst1 Tg) and Mst1 knockout (Mst1^-/- ) mice. The absence of Mst1 abolished the favorable effects of melatonin on cardiac injury after MI. Consistently, melatonin administration did not further increase autophagy, decrease apoptosis, or alleviate mitochondrial integrity and biogenesis in Mst1 knockout mice subjected to MI injury. These results suggest that melatonin alleviates postinfarction cardiac remodeling and dysfunction by upregulating autophagy, decreasing apoptosis, and modulating mitochondrial integrity and biogenesis. The attributed mechanism involved, at least in part, Mst1/Sirt1 signaling.

A review of the protective role of melatonin during phosphine-induced cardiotoxicity: focus on mitochondrial dysfunction, oxidative stress and apoptosis

OBJECTIVES

Acute poisoning with aluminium phosphide (AlP) is a major cause of mortality in developing countries. AlP mortality is due to cardiac dysfunction leading to cardiomyocyte death. The main mechanism is an inhibition of cytochrome c oxidase in the cardiomyocyte mitochondria, resulting in a decreased ATP production and oxidative stress. Unfortunately, the administration of exogenous drugs does not meet the desired requirements of an effective therapy. Melatonin is an amphiphilic molecule and can easily pass through all cellular compartments with the highest concentration recorded in mitochondria. It is known as a vigorous antioxidant, acting as a potent reactive oxygen species (ROS) scavenger. Our aim is to summarize the mechanisms by which melatonin may modulate the deteriorating effects of AlP poisoning on cardiac mitochondria.

KEY FINDINGS

Melatonin not only mitigates the inhibition of respiratory chain complexes, but also increases ATP generation. Moreover, it can directly inhibit the mitochondrial permeability transition pore (mPTP) opening, thus preventing apoptosis. In addition, melatonin inhibits the release of cytochrome c from mitochondria to hinder caspase activation leading to cell survival.

SUMMARY

Based on the promising effects of melatonin on mitochondria, melatonin may mitigate AlP-induced cardiotoxicity and might be potentially suggested as cardioprotective in AlP-intoxicated patients.

Phenolic Melatonin-Related Compounds: Their Role as Chemical Protectors against Oxidative Stress

There is currently no doubt about the serious threat that oxidative stress (OS) poses to human health. Therefore, a crucial strategy to maintain a good health status is to identify molecules capable of offering protection against OS through chemical routes. Based on the known efficiency of the phenolic and melatonin (MLT) families of compounds as antioxidants, it is logical to assume that phenolic MLT-related compounds should be (at least) equally efficient. Unfortunately, they have been less investigated than phenols, MLT and its non-phenolic metabolites in this context. The evidence reviewed here strongly suggests that MLT phenolic derivatives can act as both primary and secondary antioxidants, exerting their protection through diverse chemical routes. They all seem to be better free radical scavengers than MLT and Trolox, while some of them also surpass ascorbic acid and resveratrol. However, there are still many aspects that deserve further investigations for this kind of compounds.

Melatonin role preventing steatohepatitis and improving liver transplantation results

Liver steatosis is a prevalent process that is induced due to alcoholic or non-alcoholic intake. During the course of these diseases, the generation of reactive oxygen species, followed by molecular damage to lipids, protein and DMA occurs generating organ cell death. Transplantation is the last-resort treatment for the end stage of both acute and chronic hepatic diseases, but its success depends on ability to control ischemia-reperfusion injury, preservation fluids used, and graft quality. Melatonin is a powerful endogenous antioxidant produced by the pineal gland and a variety of other because of its efficacy in organs; melatonin has been investigated to improve the outcome of organ transplantation by reducing ischemia-reperfusion injury and due to its synergic effect with organ preservation fluids. Moreover, this indolamine also prevent liver steatosis. That is important because this disease may evolve leading to an organ transplantation. This review summarizes the observations related to melatonin beneficial actions in organ transplantation and ischemic-reperfusion models.

Potential benefits of melatonin in organ transplantation: a review

Organ transplantation is a useful therapeutic tool for patients with end-stage organ failure; however, graft rejection is a major obstacle in terms of a successful treatment. Rejection is usually a consequence of a complex immunological and nonimmunological antigen-independent cascade of events, including free radical-mediated ischemia-reperfusion injury (IRI). To reduce the frequency of this outcome, continuing improvements in the efficacy of antirejection drugs are a top priority to enhance the long-term survival of transplant recipients. Melatonin (N-acetyl-5-methoxytryptamine) is a powerful antioxidant and ant-inflammatory agent synthesized from the essential amino acid l-tryptophan; it is produced by the pineal gland as well as by many other organs including ovary, testes, bone marrow, gut, placenta, and liver. Melatonin has proven to be a potentially useful therapeutic tool in the reduction of graft rejection. Its benefits are based on its direct actions as a free radical scavenger as well as its indirect antioxidative actions in the stimulation of the cellular antioxidant defense system. Moreover, it has significant anti-inflammatory activity. Melatonin has been found to improve the beneficial effects of preservation fluids when they are enriched with the indoleamine. This article reviews the experimental evidence that melatonin is useful in reducing graft failure, especially in cardiac, bone, otolaryngology, ovarian, testicular, lung, pancreas, kidney, and liver transplantation.

Hepatic ischemia reperfusion injury: A systematic review of literature and the role of current drugs and biomarkers

Hepatic ischemia reperfusion injury (IRI) is not only a pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. Hepatic IRI can seriously impair liver function, even producing irreversible damage, which causes a cascade of multiple organ dysfunction. Many factors, including anaerobic metabolism, mitochondrial damage, oxidative stress and secretion of ROS, intracellular Ca(2+) overload, cytokines and chemokines produced by KCs and neutrophils, and NO, are involved in the regulation of hepatic IRI processes. Matrix Metalloproteinases (MMPs) can be an important mediator of early leukocyte recruitment and target in acute and chronic liver injury associated to ischemia. MMPs and neutrophil gelatinase-associated lipocalin (NGAL) could be used as markers of I-R injury severity stages. This review explores the relationship between factors and inflammatory pathways that characterize hepatic IRI, MMPs and current pharmacological approaches to this disease.

[Effect of melatonin on antioxidant enzyme activities in blood erythrocytes of rats during acute emotional stress]

The effect of the epiphyseal hormone melatonin on the activity of antioxidant enzymes, glutathione peroxidase (GPx), glutathione reductase (GR), and Cu/Zn-superoxide dismutase (Cu/Zn-SOD) was studied in peripheral blood erythrocytes of behaviorally passive and active Wistar rats. Acute emotional stress was modeled by immobilization of animals for1 h with simultaneous electrocutaneous stimulation. Basal activity of antioxidant glutathione enzymes in erythrocytes of behaviorally passive rats was higher than that in active animals. Administration of melatonin (2 mg/kg, intraperitoneally) was accompanied by a decrease in the activity of GPx and GR in erythrocytes from non-stressed passive animals. After experimental stress, passive rats demonstrated a significant increase in the activity of Cu/Zn-SOD and GPx in peripheral blood erythrocytes. The absence of stress-induced changes in functional activity of antioxidant defense enzymes in the blood of behaviorally active animals suggests a relatively constant oxidative status of tissues in these animals under stress conditions. Melatonin administration had little effect on stress-induced changes in functional activity of the erythrocyte antioxidant system in passive rats. Active specimens pretreated with melatonin before stress exposure were characterized by activation of study antioxidant enzymes. Quantitative parameters of the erythrocyte antioxidant defense enzymes did not differ in behaviorally active and passive rats subjected to experimental stress after melatonin injection. Thus, exogenous melatonin abolishes differences in the activity of study antioxidant enzymes in erythrocytes of animals with different behavioral parameters under basal conditions and after experimental stress. In passive rats melatonin mainly reduced the initial tension of oxidative processes. By contrast, administration of this hormone to active specimens is followed by an increase in functional activity of the antioxidant enzyme system under conditions of acute stress.

Effects of melatonin on liver function and lipid peroxidation in a rat model of hepatic ischemia/reperfusion injury

The present study aimed to investigate the effects of melatonin (MT) on liver function and lipid peroxidation following hepatic ischemia-reperfusion injury (IRI). A total of 66 male Sprague-Dawley rats were randomly assigned into three groups: Normal control (N) group, ischemia-reperfusion (IR) group and the MT-treated group. A hepatic IRI model was developed by blocking the first porta hepatis, and subsequently restoring hepatic blood inflow after 35 min. Following reperfusion, changes in the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione (GSH) were detected by a chemical method at various time points. In the MT group, the MDA levels were significantly reduced (P<0.05) at all time points, as compared with the IR group. Furthermore, SOD activity was significantly increased (P<0.05) in the MT group, as compared with the IR group at all time points; and the levels of GSH in the MT group were significantly higher (P<0.05) than those of the IR group at 2, 4, and 8 h post-reperfusion. The levels of ALT, AST and LDH were significantly reduced in the MT group at each time point, as compared with that of the IR group (P<0.05). In conclusion, MT exhibits potent antioxidant properties that may create favorable conditions for the recovery of liver function following IRI.

Oxidative stress in follicular fluid of young women with low response compared with fertile oocyte donors

The aim of this study was to determine the concentrations of oxidative stress markers, antioxidant enzymes and cytokines in the follicular fluid of young women with low response in ovarian stimulation cycles compared with high responders and fertile oocyte donors of the same age, to assess the impact of oxidative stress on ovarian reserve. The activity of follicular fluid antioxidant enzymes glutathione transferase, glutathione reductase and glutathione peroxidase was significantly lower in young women with reduced ovarian reserve compared with that in high responders and oocyte donors. Follicular fluid concentrations of oxidative stress marker malondialdehyde combined with 4-hydroxyalkenals and nitric oxide were higher in low responders than in high responders and oocyte donors. Significant differences between low responders and donors in concentrations of IL-2, IL-6, IL-8 and vascular endothelial growth factor were observed, with higher concentrations in low responders. However, IL-10 concentration was lower in low responders than in high responders and donors. No significant differences were found in follicular fluid concentrations of tumour necrosis factor alpha between the three groups. These results demonstrate that different concentrations of oxidative stress markers, oxidant enzymes and cytokines in low responders compared with high responders and oocyte donors may negatively impact ovarian response.

Oxidative Stress and Inflammation in Hepatic Diseases: Therapeutic Possibilities of N-Acetylcysteine

Liver disease is highly prevalent in the world. Oxidative stress (OS) and inflammation are the most important pathogenetic events in liver diseases, regardless the different etiology and natural course. N-acetyl-l-cysteine (the active form) (NAC) is being studied in diseases characterized by increased OS or decreased glutathione (GSH) level. NAC acts mainly on the supply of cysteine for GSH synthesis. The objective of this review is to examine experimental and clinical studies that evaluate the antioxidant and anti-inflammatory roles of NAC in attenuating markers of inflammation and OS in hepatic damage. The results related to the supplementation of NAC in any form of administration and type of study are satisfactory in 85.5% (n = 59) of the cases evaluated (n = 69, 100%). Within this percentage, the dosage of NAC utilized in studies in vivo varied from 0.204 up to 2 g/kg/day. A standard experimental design of protection and treatment as well as the choice of the route of administration, with a broader evaluation of OS and inflammation markers in the serum or other biological matrixes, in animal models, are necessary. Clinical studies are urgently required, to have a clear view, so that, the professionals can be sure about the effectiveness and safety of NAC prescription.

The Effect of Melatonin on Bone Loss, Diabetic Control, and Apoptosis in Rats With Diabetes With Ligature-Induced Periodontitis

BACKGROUND

The aim of this study examines the effect of systemic melatonin administration on proinflammatory cytokine levels, apoptosis, alveolar bone loss (ABL), lipid metabolism, and diabetic control in in rats with diabetes mellitus (DM) and ligature-induced periodontitis.

METHODS

Fifty-two male Wistar rats were used in this study. Study groups were as follows: 1) non-ligated control (NL, n = 6); 2) streptozotocin (STZ, n = 8); 3) STZ and melatonin (STZ+Mel, n = 8); 4) ligature (L, n = 6); 5) ligature and melatonin (L+Mel, n = 8); 6) STZ and ligature (STZ+L, n = 8); and 7) STZ, ligature, and melatonin (STZ+L+Mel, n = 8). DM was induced by intraperitoneal injection of a single dose of STZ (60 mg/kg). Melatonin was administered by intraperitoneal injection of a dose of 10 mg/kg/day for 4 weeks. Silk ligatures were placed subgingivally around the mandibular right first molars. The study period was 4 weeks, and animals were sacrificed at the end of 4 weeks. Morphometric analysis of bone loss was performed. Tissues were histopathologically examined. Inducible nitric oxide synthase (iNOS) and B-cell lymphoma-2-associated X (bax) protein expressions, serum interleukin (IL)-1β levels, and tartrate-resistant acid phosphatase-positive (TRAP+) osteoclast numbers were also evaluated.

RESULTS

After 4 weeks, the highest ABL was observed in the STZ+L group, and the difference was significant (P <0.05). Systemically administered melatonin significantly decreased ABL in the STZ+L+Mel group compared with that in the STZ+L group (P <0.05). TRAP+ osteoclast numbers were the highest in the STZ+L group, and melatonin significantly decreased osteoclast numbers (P <0.05) but had no effect on iNOS, IL-1β, or bax levels.

CONCLUSIONS

Within the limits of this study, it can be concluded that systemic melatonin treatment may decrease osteoclastic activity and reduce ABL in the model using rats with DM.

The Role of Oxidative Stress and Antioxidants in Liver Diseases

A complex antioxidant system has been developed in mammals to relieve oxidative stress. However, excessive reactive species derived from oxygen and nitrogen may still lead to oxidative damage to tissue and organs. Oxidative stress has been considered as a conjoint pathological mechanism, and it contributes to initiation and progression of liver injury. A lot of risk factors, including alcohol, drugs, environmental pollutants and irradiation, may induce oxidative stress in liver, which in turn results in severe liver diseases, such as alcoholic liver disease and non-alcoholic steatohepatitis. Application of antioxidants signifies a rational curative strategy to prevent and cure liver diseases involving oxidative stress. Although conclusions drawn from clinical studies remain uncertain, animal studies have revealed the promising in vivo therapeutic effect of antioxidants on liver diseases. Natural antioxidants contained in edible or medicinal plants often possess strong antioxidant and free radical scavenging abilities as well as anti-inflammatory action, which are also supposed to be the basis of other bioactivities and health benefits. In this review, PubMed was extensively searched for literature research. The keywords for searching oxidative stress were free radicals, reactive oxygen, nitrogen species, anti-oxidative therapy, Chinese medicines, natural products, antioxidants and liver diseases. The literature, including ours, with studies on oxidative stress and anti-oxidative therapy in liver diseases were the focus. Various factors that cause oxidative stress in liver and effects of antioxidants in the prevention and treatment of liver diseases were summarized, questioned, and discussed.

Reduced silent information regulator 1 signaling exacerbates myocardial ischemia-reperfusion injury in type 2 diabetic rats and the protective effect of melatonin

Diabetes mellitus (DM) increases myocardial oxidative stress and endoplasmic reticulum (ER) stress. Melatonin confers cardioprotective effect by suppressing oxidative damage. However, the effect and mechanism of melatonin on myocardial ischemia-reperfusion (MI/R) injury in type 2 diabetic state are still unknown. In this study, we developed high-fat diet-fed streptozotocin (HFD-STZ) rat, a well-known type 2 diabetic model, to evaluate the effect of melatonin on MI/R injury with a focus on silent information regulator 1 (SIRT1) signaling, oxidative stress, and PERK/eIF2α/ATF4-mediated ER stress. HFD-STZ treated rats were exposed to melatonin treatment in the presence or the absence of sirtinol (a SIRT1 inhibitor) and subjected to MI/R surgery. Compared with nondiabetic animals, type 2 diabetic rats exhibited significantly decreased myocardial SIRT1 signaling, increased apoptosis, enhanced oxidative stress, and ER stress. Additionally, further reduced SIRT1 signaling, aggravated oxidative damage, and ER stress were found in diabetic animals subjected to MI/R surgery. Melatonin markedly reduced MI/R injury by improving cardiac functional recovery and decreasing myocardial apoptosis in type 2 diabetic animals. Melatonin treatment up-regulated SIRT1 expression, reduced oxidative damage, and suppressed PERK/eIF2α/ATF4 signaling. However, these effects were all attenuated by SIRT1 inhibition. Melatonin also protected high glucose/high fat cultured H9C2 cardiomyocytes against simulated ischemia-reperfusion injury-induced ER stress by activating SIRT1 signaling while SIRT1 siRNA blunted this action. Taken together, our study demonstrates that reduced cardiac SIRT1 signaling in type 2 diabetic state aggravates MI/R injury. Melatonin ameliorates reperfusion-induced oxidative stress and ER stress via activation of SIRT1 signaling, thus reducing MI/R damage and improving cardiac function.

Molecular pathways in protecting the liver from ischaemia/reperfusion injury: a 2015 update

Ischaemia/reperfusion injury is an important cause of liver damage during surgical procedures such as hepatic resection and liver transplantation, and represents the main cause of graft dysfunction post-transplantation. Molecular processes occurring during hepatic ischaemia/reperfusion are diverse, and continuously include new and complex mechanisms. The present review aims to summarize the newest concepts and hypotheses regarding the pathophysiology of liver ischaemia/reperfusion, making clear distinction between situations of cold and warm ischaemia. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field are described.

Abroma augusta L. (Malvaceae) leaf extract attenuates diabetes induced nephropathy and cardiomyopathy via inhibition of oxidative stress and inflammatory response

BACKGROUND

Abroma augusta L. (Malvaceae) leaf is traditionally used to treat diabetes in India and Southern Asia. Therefore, current study was performed to evaluate the protective effect of defatted methanol extract of A. augusta leaves (AA) against type 2 diabetes mellitus (T2DM) and its associated nephropathy and cardiomyopathy in experimental rats.

METHODS

Antidiabetic activity of AA extracts (100 and 200 mg/kg, p.o.) was measured in streptozotocin-nicotinamide induced type 2 diabetic (T2D) rat. Fasting blood glucose level (at specific interval) and serum biochemical markers (after sacrifice) were measured. Redox status, transcription levels of signal proteins (NF-κB and PKCs), mitochondria dependent apoptotic pathway (Bad, Bcl-2, caspase cascade) and histological studies were performed in kidneys and hearts of controls and AA treated diabetic rats.

RESULTS

Phytochemical screening of extracts revealed the presence of taraxerol, flavonoids and phenolic compounds in the AA. T2D rats showed significantly (p < 0.01) elevated fasting blood glucose level. Alteration in serum lipid profile and release of membrane bound enzymes like lactate dehydrogenase and creatine kinase, which ensured the participation of hyperlipidemia and cell membrane disintegration in diabetic pathophysiology. T2DM caused alteration in the serum biochemical markers related to diabetic complications. T2DM altered the redox status, decreased the intracellular NAD and ATP concentrations in renal and myocardial tissues of experimental rats. Investigating the molecular mechanism, activation PKC isoforms was observed in the selected tissues. T2D rats also exhibited an up-regulation of NF-κB and increase in the concentrations of pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) in the renal and cardiac tissues. The activation of mitochondria dependent apoptotic pathway was observed in renal and myocardial tissues of the T2D rats. However, Oral administration of AA at the doses of 100 and 200 mg/kg body weight per day could reduce hyperglycemia, hyperlipidemia, membrane disintegration, oxidative stress, vascular inflammation and prevented the activation of oxidative stress induced signaling cascades leading to cell death. Histological studies also supported the protective characteristics of AA.

CONCLUSIONS

Results suggest that AA could offer prophylactic role against T2DM and its associated reno- and cardio- toxicity.

A review of melatonin in hepatic ischemia/reperfusion injury and clinical liver disease

Ischemia/reperfusion injury (IRI) can lead to cellular and, eventually, organ dysfunction, with the liver being one of the most frequently affected organs. Melatonin, a molecule that has notable antioxidant and anti-inflammatory properties, has been shown to protect against hepatic IRI. The purpose of this review is to summarize the protective effects of melatonin on hepatic IRI. The review initially summarizes the antioxidant properties of melatonin. We then discuss the protective effects of melatonin against endothelial and mitochondrial dysfunction. Thereafter, we introduce some information covering melatonin-related signaling pathways, including heme oxygenase-1 (HO-1), toll-like receptor (TLR), c-Jun N-terminal kinase (JNK), and so on. Furthermore, the clinical application of melatonin to hepatic diseases is considered. Finally, the safety of melatonin is evaluated. Taken together, the information compiled in this review will serve as a comprehensive reference regarding the pharmacological benefits of melatonin on hepatic IRI, aid in the design of future experimental research, and promote melatonin as a new therapeutic target.

Oxidative stress as a crucial factor in liver diseases

Redox state constitutes an important background of numerous liver disorders. The redox state participates in the course of inflammatory, metabolic and proliferative liver diseases. Reactive oxygen species (ROS) are primarily produced in the mitochondria and in the endoplasmic reticulum of hepatocytes via the cytochrome P450 enzymes. Under the proper conditions, cells are equipped with special molecular strategies that control the level of oxidative stress and maintain a balance between oxidant and antioxidant particles. Oxidative stress represents an imbalance between oxidant and antioxidant agents. Hepatocytic proteins, lipids and DNA are among the cellular structures that are primarily affected by ROS and reactive nitrogen species. The process results in structural and functional abnormalities in the liver. Thus, the phenomenon of oxidative stress should be investigated for several reasons. First, it may explain the pathogenesis of various liver disorders. Moreover, monitoring oxidative markers among hepatocytes offers the potential to diagnose the degree of liver damage and ultimately to observe the response to pharmacological therapies. The present report focuses on the role of oxidative stress in selected liver diseases.

Potential impact of silymarin in combination with chlorogenic acid and/or melatonin in combating cardiomyopathy induced by carbon tetrachloride

The aim of this study was to investigate the effective role of silymarin either alone or in combination with chlorogenic acid and/or melatonin against the toxic impact of carbon tetrachloride (CCl4) induced cardiac infarction. CCl4 (l.2 ml/kg body weight) was administered as a single dose intraperitoneally. The results revealed that the administration of silymarin alone or in combination with chlorogenic acid (CGA) and/or melatonin for 21 consecutive days, 24 h after CCl4 injection to rats, markedly ameliorated the increases in serum markers of cardiac infarction, including troponin T and creatine kinase-MB (CK-MB), as well as increases in the pro-inflammatory biomarkers, including interleukin-6 (IL-6), interferon-γ (IFN-γ) in serum and tumor necrosis factor-α (TNF-α) and C-reactive protein in cardiac tissue compared to CCl4 intoxicated rats. The used agents also successfully modulated the alteration in vascular endothelial growth factor (VEGF) in serum and the oxidative DNA damage and the increase in the apoptosis marker caspase 3 in cardiac tissue in response to CCl4 toxicity. The present biochemical results are supported by histo-pathological examination. The current results proved that treatment with silymarin in combination with CGA and melatonin was the most effective one in ameliorating the toxicity of CCl4 induced cardiac damage and this may support the use of this combination as an effective drug to treat cardiac damage induced by toxic agents.

Adalimumab ameliorates abdominal aorta cross clamping which induced liver injury in rats

The aim of this study was to investigate the possible protective effects of adalimumab (ADA) on cell damage in rat liver tissue during ischemia/reperfusion (I/R) injury of infrarenal abdominal aorta. Thirty male Wistar-albino rats were divided into three groups: control, I/R, and I/R+ADA, each group containing 10 animals. Laparotomy without I/R injury was performed in the control group animals. Laparotomy in the I/R group was followed by two hours of infrarenal abdominal aortic cross ligation and then two hours of reperfusion. ADA (50 mg/kg) was administered intraperitoneally as a single dose, to the I/R+ADA group, five days before I/R. The tumor necrosis factor-alpha (TNF-α) (pg/mg protein) and nitric oxide (NO) (µmol/g protein) levels in the I/R group (430.8 ± 70.1, 8.0 ± 1.1, resp.) were significantly higher than those in the I/R+ADA group (338.0 ± 71.6, P = 0.006; 6.3 ± 1.2, P = 0.008) and the control group (345.5 ± 53.3, P = 0.008; 6.5 ± 1.5, P = 0.010, resp.). I/R causes severe histopathological injury to the liver tissue, but ADA leads to much less histopathological changes. ADA treatment significantly decreased the severity of liver I/R injury. ADA pretreatment may have protective effects on experimental liver injury.