AMPK involvement in endoplasmic reticulum stress and autophagy modulation after fatty liver graft preservation: a role for melatonin and trimetazidine cocktail

Gene microarray analysis of expression profiles in liver ischemia and reperfusion

Liver ischemia and reperfusion (I/R) injury is of primary concern in cases of liver disease worldwide and is associated with hemorrhagic shock, resection and transplantation. Numerous studies have previously been conducted to investigate the underlying mechanisms of liver I/R injury, however these have not yet been fully elucidated. To determine the difference between ischemia and reperfusion in signaling pathways and the relative pathological mechanisms, the present study downloaded microarray data GSE10657 from the Gene Expression Omnibus database. A total of two data groups from 1-year-old mice were selected for further analysis: i) A total of 90 min ischemia; ii) 90 min ischemia followed by 1 h of reperfusion, n=3 for each group. The Limma package was first used to identify the differentially expressed genes (DEGs). DEGs were subsequently uploaded to the Database for Annotation Visualization and Integrated Discovery online tool for Functional enrichment analysis. A protein-protein interaction (PPI) network was then constructed via STRING version 10.0 and analyzed using Cytoscape software. A total of 114 DEGs were identified, including 21 down and 93 upregulated genes. These DEGs were primarily enriched in malaria and influenza A, in addition to the tumor necrosis factor and mitogen activated protein kinase signaling pathways. Hub genes identified in the PPI network were C-X-C motif chemokine ligand (CXCL) 1, C-C motif chemokine ligand (CCL) 2, interleukin 6, Jun proto-oncogene, activator protein (AP)-1 transcription factor subunit, FOS proto-oncogene, AP-1 transcription factor subunit and dual specificity phosphatase 1. CXCL1 and CCL2 may exhibit important roles in liver I/R injury, with involvement in the immune and inflammatory responses and the chemokine-mediated signaling pathway, particularly at the reperfusion stage. However, further experiments to elucidate the specific roles of these mediators are required in the future.

Relevance of proteolysis and proteasome activation in fatty liver graft preservation: An Institut Georges Lopez-1 vs University of Wisconsin appraisal

AIM

To compare liver proteolysis and proteasome activation in steatotic liver grafts conserved in University of Wisconsin (UW) and Institut Georges Lopez-1 (IGL-1) solutions.

METHODS

Fatty liver grafts from male obese Zücker rats were conserved in UW and IGL-1 solutions for 24 h at 4 °Cand subjected to “ex vivo” normo-thermic perfusion (2 h; 37 °C). Liver proteolysis in tissue specimens and perfusate was measured by reverse-phase high performance liquid chromatography. Total free amino acid release was correlated with the activation of the ubiquitin proteasome system (UPS: measured as chymotryptic-like activity and 20S and 19S proteasome), the prevention of liver injury (transaminases), mitochondrial injury (confocal microscopy) and inflammation markers (TNF 1 alpha, high mobility group box-1 (HGMB-1) and PPAR gamma), and liver apoptosis (TUNEL assay, cytochrome c and caspase 3).

RESULTS

Profiles of free AA (alanine, proline, leucine, isoleucine, methionine, lysine, ornithine, and threonine, among others) were similar for tissue and reperfusion effluent. In all cases, the IGL-1 solution showed a significantly higher prevention of proteolysis than UW (P < 0.05) after cold ischemia reperfusion. Livers conserved in IGL-1 presented more effective prevention of ATP-breakdown and more inhibition of UPS activity (measured as chymotryptic-like activity). In addition, the prevention of liver proteolysis and UPS activation correlated with the prevention of liver injury (AST/ALT) and mitochondrial damage (revealed by confocal microscopy findings) as well as with the prevention of inflammatory markers (TNF1alpha and HMGB) after reperfusion. In addition, the liver grafts preserved in IGL-1 showed a significant decrease in liver apoptosis, as shown by TUNEL assay and the reduction of cytochrome c, caspase 3 and P62 levels.

CONCLUSION

Our comparison of these two preservation solutions suggests that IGL-1 helps to prevent ATP breakdown more effectively than UW and subsequently achieves a higher UPS inhibition and reduced liver proteolysis.

Melatonin alleviates lipopolysaccharide-compromised integrity of blood-brain barrier through activating AMP-activated protein kinase in old mice

Blood–brain barrier (BBB) dysfunction is considered to be an early event in the pathogenesis of a variety of neurological diseases in old patients, and this could occur in old people even when facing common stress. However, the mechanism remains to be defined. In this study, we tested the hypothesis that decreased melatonin levels may account for the BBB disruption in old mice challenged with lipopolysaccharide (LPS), which mimicked the common stress of sepsis. Mice (24–28 months of age) received melatonin (10 mg kg⁻¹ day⁻¹, intraperitoneally, i.p.) or saline for one week before exposing to LPS (1 mg kg⁻¹, i.p.). Evan's blue dye (EB) and immunoglobulin G (IgG) leakage were used to assess BBB permeability. Immunostaining and Western blot were used to detect protein expression and distribution. Our results showed that LPS significantly increased BBB permeability in old mice accompanied by the degradation of tight junction proteins occludin and claudin‐5, suppressed AMP‐activated protein kinase (AMPK) activation, and elevated gp91^phox protein expression. Interestingly, administration of melatonin for one week significantly decreased LPS‐induced BBB disruption, AMPK suppression, and gp91^phox upregualtion. Moreover, activation of AMPK with metformin significantly inhibited LPS‐induced gp91^phox upregualtion in endothelial cells. Taken together, our findings demonstrate that melatonin alleviates LPS‐induced BBB disruption through activating AMPK and inhibiting gp91^phox upregulation in old mice.

GSK3β and VDAC Involvement in ER Stress and Apoptosis Modulation during Orthotopic Liver Transplantation

We investigated the involvement of glycogen synthase kinase-3β (GSK3β) and the voltage-dependent anion channel (VDAC) in livers subjected to cold ischemia-reperfusion injury (I/R) associated with orthotopic liver transplantation (OLT). Rat livers were preserved in University of Wisconsin (UW) and Institute Georges Lopez (IGL-1) solution, the latter enriched or not with trimetazidine, and then subjected to OLT. Transaminase (ALT) and HMGB1 protein levels, glutamate dehydrogenase (GLDH), and oxidative stress (MDA) were measured. The AKT protein kinase and its direct substrates, GSK3β and VDAC, as well as caspases 3, 9, and cytochrome C and reticulum endoplasmic stress-related proteins (GRP78, pPERK, ATF4, and CHOP), were determined by Western blot. IGL-1+TMZ significantly reduced liver injury. We also observed a significant phosphorylation of AKT, which in turn induced the phosphorylation and inhibition of GSK3β. In addition, TMZ protected the mitochondria since, in comparison with IGL-1 alone, we found reductions in VDAC phosphorylation, apoptosis, and GLDH release. All these results were correlated with decreased ER stress. Addition of TMZ to IGL-1 solution increased the tolerance of the liver graft to I/R injury through inhibition of GSK3β and VDAC, contributing to ER stress reduction and cell death prevention.

Snapshot: implications for melatonin in endoplasmic reticulum homeostasis

The endoplasmic reticulum (ER) is an important intracellular membranous organelle. Previous studies have demonstrated that the ER is responsible for protein folding and trafficking, lipid synthesis and the maintenance of calcium homeostasis. Interestingly, the morphology and structure of the ER were recently found to be important. Melatonin is a hormone that anticipates the daily onset of darkness in mammals, and it is well known that melatonin acts as an antioxidant by scavenging free radicals and increasing the activity of antioxidant enzymes in the body. Notably, the existing evidence demonstrates that melatonin is involved in ER homeostasis, particularly in the morphology of the ER, indicating a potential protective role of melatonin. This review discusses the existing knowledge regarding the implications for the involvement of melatonin in ER homeostasis.

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.

Relevance of Endoplasmic Reticulum Stress Cell Signaling in Liver Cold Ischemia Reperfusion Injury

The endoplasmic reticulum (ER) is involved in calcium homeostasis, protein folding and lipid biosynthesis. Perturbations in its normal functions lead to a condition called endoplasmic reticulum stress (ERS). This can be triggered by many physiopathological conditions such as alcoholic steatohepatitis, insulin resistance or ischemia-reperfusion injury. The cell reacts to ERS by initiating a defensive process known as the unfolded protein response (UPR), which comprises cellular mechanisms for adaptation and the safeguarding of cell survival or, in cases of excessively severe stress, for the initiation of the cell death program. Recent experimental data suggest the involvement of ERS in ischemia/reperfusion injury (IRI) of the liver graft, which has been considered as one of major problems influencing outcome after liver transplantation. The purpose of this review is to summarize updated data on the molecular mechanisms of ERS/UPR and the consequences of this pathology, focusing specifically on solid organ preservation and liver transplantation models. We will also discuss the potential role of ERS, beyond the simple adaptive response and the regulation of cell death, in the modification of cell functional properties and phenotypic changes.

Melatonin enhances mitophagy and mitochondrial biogenesis in rats with carbon tetrachloride-induced liver fibrosis

Liver fibrosis leads to liver cirrhosis and failure, and no effective treatment is currently available. Growing evidence supports a link between mitochondrial dysfunction and liver fibrogenesis and mitochondrial quality control-based therapy has emerged as a new therapeutic target. We investigated the protective mechanisms of melatonin against mitochondrial dysfunction-involved liver fibrosis, focusing on mitophagy and mitochondrial biogenesis. Rats were treated with carbon tetrachloride (CCl4) dissolved in olive oil (0.5 mL/kg, twice a week, i.p.) for 8 wk. Melatonin was administered orally at 2.5, 5, and 10 mg/kg once a day. Chronic CCl4 exposure induced collagen deposition, hepatocellular damage, and oxidative stress, and melatonin attenuated these increases. Increases in mRNA and protein expression levels of transforming growth factor β1 and α-smooth muscle actin in response to CCl4 were attenuated by melatonin. Melatonin attenuated hallmarks of mitochondrial dysfunction, such as mitochondrial swelling and glutamate dehydrogenase release. Chronic CCl4 exposure impaired mitophagy and mitochondrial biogenesis, and melatonin attenuated this impairment, as indicated by increases in mitochondrial DNA and in protein levels of PTEN-induced putative kinase 1 (PINK1); Parkin; peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α); nuclear respiratory factor 1 (NRF1); and transcription factor A, mitochondrial (TFAM). CCl4-mediated decreases in mitochondrial fission- and fusion-related proteins, such as dynamin-related protein 1 (DRP1) and mitofusin 2, were also attenuated by melatonin. Moreover, melatonin induced AMP-activated protein kinase (AMPK) phosphorylation. These results suggest that melatonin protects against liver fibrosis via upregulation of mitophagy and mitochondrial biogenesis, and may be useful as an anti-fibrotic treatment.

Calpain 2-mediated autophagy defect increases susceptibility of fatty livers to ischemia-reperfusion injury

Hepatic steatosis is associated with significant morbidity and mortality after liver resection and transplantation. This study focuses on the role of autophagy in regulating sensitivity of fatty livers to ischemia and reperfusion (I/R) injury. Quantitative immunohistochemistry conducted on human liver allograft biopsies showed that, the reduction of autophagy markers LC3 and Beclin-1 at 1 h after reperfusion, was correlated with hepatic steatosis and poor survival of liver transplant recipients. In animal studies, western blotting and confocal imaging analysis associated the increase in sensitivity to I/R injury with low autophagy activity in fatty livers. Screening of autophagy-related proteins showed that Atg3 and Atg7 expression levels were marked decreased, whereas calpain 2 expression was upregulated during I/R in fatty livers. Calpain 2 inhibition or knockdown enhanced autophagy and suppressed cell death. Further point mutation experiments revealed that calpain 2 cleaved Atg3 and Atg7 at Atg3Δ92-97 and Atg7Δ344-349, respectively. In vivo and in vitro overexpression of Atg3 or Atg7 enhanced autophagy and suppressed cell death after I/R in fatty livers. Collectively, calpain 2-mediated degradation of Atg3 and Atg7 in fatty livers increases their sensitivity to I/R injury. Increasing autophagy may ameliorate fatty liver damage and represent a valuable method to expand the liver donor pool.

Melatonin facilitates adipose-derived mesenchymal stem cells to repair the murine infarcted heart via the SIRT1 signaling pathway

Mesenchymal stem cells (MSCs)-based therapy provides a promising therapy for the ischemic heart disease (IHD). However, engrafted MSCs are subjected to acute cell death in the ischemic microenvironment, characterized by excessive inflammation and oxidative stress in the host's infarcted myocardium. Melatonin, an indole, which is produced by many organs including pineal gland, has been shown to protect bone marrow MSCs against apoptosis although the mechanism of action remains elusive. Using a murine model of myocardial infarction (MI), this study was designed to evaluate the impact of melatonin on adipose-derived mesenchymal stem cells (AD-MSCs)-based therapy for MI and the underlying mechanism involved with a focus on silent information regulator 1(SIRT1) signaling. Our results demonstrated that melatonin promoted functional survival of AD-MSCs in infarcted heart and provoked a synergetic effect with AD-MSCs to restore heart function. This in vivo effect of melatonin was associated with alleviated inflammation, apoptosis, and oxidative stress in infarcted heart. In vitro studies revealed that melatonin exert cytoprotective effects on AD-MSCs against hypoxia/serum deprivation (H/SD) injury via attenuating inflammation, apoptosis, and oxidative stress. Mechanistically, melatonin enhanced SIRT1 signaling, which was accompanied with the increased expression of anti-apoptotic protein Bcl2, and decreased the expression of Ac-FoxO1, Ac-p53, Ac-NF-ΚB, and Bax. Taken together, our findings indicated that melatonin facilitated AD-MSCs-based therapy in MI, possibly through promoting survival of AD-MSCs via SIRT1 signaling. Our data support the promise of melatonin as a novel strategy to improve MSC-based therapy for IHD, possibly through SIRT1 signaling evocation.

Melatonin reverses flow shear stress-induced injury in bone marrow mesenchymal stem cells via activation of AMP-activated protein kinase signaling

Tissue-engineered heart valves (TEHVs) are a promising treatment for valvular heart disease, although their application is limited by high flow shear stress (FSS). Melatonin has a wide range of physiological functions and is currently under clinical investigation for expanded applications; moreover, extensive protective effects on the cardiovascular system have been reported. In this study, we investigated the protection conferred by melatonin supplementation against FSS-induced injury in bone marrow mesenchymal stem cells (BMSCs) and elucidated the potential mechanism in this process. Melatonin markedly reduced BMSC apoptotic death in a concentration-dependent manner while increasing the levels of transforming growth factor β (TGF-β), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF) and B-cell lymphoma 2 (Bcl2), and decreasing those of Bcl-2-associated X protein (Bax), p53 upregulated modulator of apoptosis (PUMA), and caspase 3. Notably, melatonin exerted its protective effects by upregulating the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK), which promotes acetyl-CoA carboxylase (ACC) phosphorylation. Further molecular experiments revealed that luzindole, a nonselective antagonist of melatonin receptors, blocked the anti-FSS injury (anti-FSSI) effects of melatonin. Inhibition of AMPK by Compound C also counteracted the protective effects of melatonin, suggesting that melatonin reverses FSSI in BMSCs through the AMPK-dependent pathway. Overall, our findings indicate that melatonin contributes to the amelioration of FSS-induced BMSC injury by activating melatonin receptors and AMPK/ACC signaling. Our findings may provide a basis for the design of more effective strategies that promote the use of TEHCs in patients.

ER stress: Autophagy induction, inhibition and selection

An accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER) leads to stress conditions. To mitigate such circumstances, stressed cells activate a homeostatic intracellular signaling network cumulatively called the unfolded protein response (UPR), which orchestrates the recuperation of ER function. Macroautophagy (hereafter autophagy), an intracellular lysosome-mediated bulk degradation pathway for recycling and eliminating wornout proteins, protein aggregates, and damaged organelles, has also emerged as an essential protective mechanism during ER stress. These 2 systems are dynamically interconnected, and recent investigations have revealed that ER stress can either stimulate or inhibit autophagy. However, the stress-associated molecular cues that control the changeover switch between induction and inhibition of autophagy are largely obscure. This review summarizes the crosstalk between ER stress and autophagy and their signaling networks mainly in mammalian-based systems. Additionally, we highlight current knowledge on selective autophagy and its connection to ER stress.

β-Guanidinopropionic acid extends the lifespan of Drosophila melanogaster via an AMP-activated protein kinase-dependent increase in autophagy

Previous studies have demonstrated that AMP‐activated protein kinase (AMPK) controls autophagy through the mammalian target of rapamycin (mTOR) and Unc‐51 like kinase 1 (ULK1/Atg1) signaling, which augments the quality of cellular housekeeping, and that β‐guanidinopropionic acid (β‐GPA), a creatine analog, leads to a chronic activation of AMPK. However, the relationship between β‐GPA and aging remains elusive. In this study, we hypothesized that feeding β‐GPA to adult Drosophila produces the lifespan extension via activation of AMPK‐dependent autophagy. It was found that dietary administration of β‐GPA at a concentration higher than 900 mm induced a significant extension of the lifespan of Drosophila melanogaster in repeated experiments. Furthermore, we found that Atg8 protein, the homolog of microtubule‐associated protein 1A/1B‐light chain 3 (LC3) and a biomarker of autophagy in Drosophila, was significantly upregulated by β‐GPA treatment, indicating that autophagic activity plays a role in the effect of β‐GPA. On the other hand, when the expression of Atg5 protein, an essential protein for autophagy, was reduced by RNA interference (RNAi), the effect of β‐GPA on lifespan extension was abolished. Moreover, we found that AMPK was also involved in this process. β‐GPA treatment significantly elevated the expression of phospho‐T172‐AMPK levels, while inhibition of AMPK by either AMPK‐RNAi or compound C significantly attenuated the expression of autophagy‐related proteins and lifespan extension in Drosophila. Taken together, our results suggest that β‐GPA can induce an extension of the lifespan of Drosophila via AMPK‐Atg1‐autophagy signaling pathway.

Melatonin and endoplasmic reticulum stress: relation to autophagy and apoptosis

Endoplasmic reticulum (ER) is a dynamic organelle that participates in a number of cellular functions by controlling lipid metabolism, calcium stores, and proteostasis. Under stressful situations, the ER environment is compromised, and protein maturation is impaired; this causes misfolded proteins to accumulate and a characteristic stress response named unfolded protein response (UPR). UPR protects cells from stress and contributes to cellular homeostasis re-establishment; however, during prolonged ER stress, UPR activation promotes cell death. ER stressors can modulate autophagy which in turn, depending of the situation, induces cell survival or death. Interactions of different autophagy- and apoptosis-related proteins and also common signaling pathways have been found, suggesting an interplay between these cellular processes, although their dynamic features are still unknown. A number of pathologies including metabolic, neurodegenerative and cardiovascular diseases, cancer, inflammation, and viral infections are associated with ER stress, leading to a growing interest in targeting components of the UPR as a therapeutic strategy. Melatonin has a variety of antioxidant, anti-inflammatory, and antitumor effects. As such, it modulates apoptosis and autophagy in cancer cells, neurodegeneration and the development of liver diseases as well as other pathologies. Here, we review the effects of melatonin on the main ER stress mechanisms, focusing on its ability to regulate the autophagic and apoptotic processes. As the number of studies that have analyzed ER stress modulation by this indole remains limited, further research is necessary for a better understanding of the crosstalk between ER stress, autophagy, and apoptosis and to clearly delineate the mechanisms by which melatonin modulates these responses.

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.

Supuran C, Rosselló-Catafau J. Carbonic Anhydrase Protects Fatty Liver Grafts against Ischemic Reperfusion Damage

Carbonic anhydrases (CAs) are ubiquitous metalloenzymes that catalyze the reversible hydration of carbon dioxide to bicarbonate and a proton. CAs are involved in numerous physiological and pathological processes, including acid-base homeostasis, electrolyte balance, oxygen delivery to tissues and nitric oxide generation. Given that these processes are found to be dysregulated during ischemia reperfusion injury (IRI), and taking into account the high vulnerability of steatotic livers to preservation injury, we hypothesized a new role for CA as a pharmacological agent able to protect against ischemic damage. Two different aspects of the role of CA II in fatty liver grafts preservation were evaluated: 1) the effect of its addition to Institut Georges Lopez (IGL-1) storage solution after cold ischemia; 2) and after 24h of cold storage followed by two hours of normothermic ex-vivo perfusion. In all cases, liver injury, CA II protein concentration, CA II mRNA levels and CA II activity were determined. In case of the ex-vivo perfusion, we further assessed liver function (bile production, bromosulfophthalein clearance) and Western blot analysis of phosphorylated adenosine monophosphate activated protein kinase (AMPK), mitogen activated protein kinases family (MAPKs) and endoplasmic reticulum stress (ERS) parameters (GRP78, PERK, IRE, eIF2α and ATF6). We found that CA II was downregulated after cold ischemia. The addition of bovine CA II to IGL-1 preservation solution efficiently protected steatotic liver against cold IRI. In the case of reperfusion, CA II protection was associated with better function, AMPK activation and the prevention of ERS and MAPKs activation. Interestingly, CA II supplementation was not associated with enhanced CO₂ hydration. The results suggest that CA II modulation may be a promising target for fatty liver graft preservation.

Melatonin modulates endoplasmic reticulum stress and Akt/GSK3-beta signaling pathway in a rat model of renal warm ischemia reperfusion

Melatonin (Mel) is widely used to attenuate ischemia/reperfusion (I/R) injury in several organs. Nevertheless, the underlying mechanisms remain unclear. This study was conducted to explore the effect of Mel on endoplasmic reticulum (ER) stress, Akt and MAPK cascades after renal warm I/R. Eighteen Wistar rats were randomized into three groups: Sham, I/R, and Mel + I/R. The ischemia period was 60 min followed by 120 min of reperfusion. Mel (10 mg/kg) was administrated 30 min prior to ischemia. The creatinine clearance, MDA, LDH levels, and histopathological changes were evaluated. In addition, Western blot was performed to study ER stress and its downstream apoptosis as well as phosphorylation of Akt, GSK-3β, VDAC, ERK, and P38. Mel decreased cytolysis and lipid peroxidation and improved renal function and morphology compared to I/R group. Parallely, it significantly reduced the ER stress parameters including GRP 78, p-PERK, XBP 1, ATF 6, CHOP, and JNK. Simultaneously, p-Akt level was significantly enhanced and its target molecules GSK-3β and VDAC were inhibited. Furthermore, the ERK and P38 phosphorylation were evidently augmented after Mel administration in comparison to I/R group. In conclusion, Mel improves the recovery of renal function by decreasing ER stress and stimulating Akt pathway after renal I/R injury.

Ischemic conditioning-induced endogenous brain protection: Applications pre-, per- or post-stroke

In the area of brain injury and neurodegenerative diseases, a plethora of experimental and clinical evidence strongly indicates the promise of therapeutically exploiting the endogenous adaptive system at various levels like triggers, mediators and the end-effectors to stimulate and mobilize intrinsic protective capacities against brain injuries. It is believed that ischemic pre-conditioning and post-conditioning are actually the strongest known interventions to stimulate the innate neuroprotective mechanism to prevent or reverse neurodegenerative diseases including stroke and traumatic brain injury. Recently, studies showed the effectiveness of ischemic per-conditioning in some organs. Therefore the term ischemic conditioning, including all interventions applied pre-, per- and post-ischemia, which spans therapeutic windows in 3 time periods, has recently been broadly accepted by scientific communities. In addition, it is extensively acknowledged that ischemia-mediated protection not only affects the neurons but also all the components of the neurovascular network (consisting of neurons, glial cells, vascular endothelial cells, pericytes, smooth muscle cells, and venule/veins). The concept of cerebroprotection has been widely used in place of neuroprotection. Intensive studies on the cellular signaling pathways involved in ischemic conditioning have improved the mechanistic understanding of tolerance to cerebral ischemia. This has added impetus to exploration for potential pharmacologic mimetics, which could possibly induce and maximize inherent protective capacities. However, most of these studies were performed in rodents, and the efficacy of these mimetics remains to be evaluated in human patients. Several classical signaling pathways involving apoptosis, inflammation, or oxidation have been elaborated in the past decades. Newly characterized mechanisms are emerging with the advances in biotechnology and conceptual renewal. In this review we are going to focus on those recently reported methodological and mechanistic discoveries in the realm of ischemic conditioning. Due to the varied time differences of ischemic conditioning in different animal models and clinical trials, it is important to define optimal timing to achieve the best conditioning induced neuroprotection. This brings not only an opportunity in the treatment of stroke, but challenges as well, as data is just becoming available and the procedures are not yet optimized. The purpose of this review is to shed light on exploiting these ischemic conditioning modalities to protect the cerebrovascular system against diverse injuries and neurodegenerative disorders.

Effects of Institut Georges Lopez-1 and Celsior preservation solutions on liver graft injury

AIM: To compare Institut Georges Lopez (IGL-1) and Celsior preservation solutions for hepatic endothelium relaxation and liver cold ischemia reperfusion injury (IRI).

METHODS: Two experimental models were used. In the first one, acetylcholine-induced endothelium-dependent relaxation (EDR) was measured in isolated ring preparations of rat hepatic arteries preserved or not in IGL-1 or Celsior solutions (24 h at 4 °C). To determine nitric oxide (NO) and cyclooxygenase EDR, hepatic arteries were incubated with L-NG-nitroarginine methyl ester (L-NAME), an inhibitor of endothelium nitric oxide synthase (eNOS), or with L-NAME plus indomethacin, an inhibitor of cyclooxygenase. In the second experiment, rat livers were cold-stored in IGL-1 or Celsior solutions for 24 h at 4 °C and then perfused “ex vivo” for 2 h at 37 °C. Liver injury was assessed by transaminase measurements, liver function by bile production and bromosulfophthalein clearance, oxidative stress by malondialdehyde levels and catalase activity and alterations in cell signaling pathways by pAkt, pAMPK, eNOS and MAPKs proteins level.

RESULTS: After cold storage for 24 h with either Celsior or IGL-1, EDR was only slightly altered. In freshly isolated arteries, EDR was exclusively mediated by NO. However, cold-stored arteries showed NO- and COX-dependent relaxation. The decrease in NO-dependent relaxation after cold storage was significantly more marked with Celsior. The second study indicated that IGL-1 solution obtained better liver preservation and protection against IRI than Celsior. Liver injury was reduced, function was improved and there was less oxidative stress. IGL-1 solution activated Akt and AMPK, which was concomitant with increased eNOS expression and nitrite/nitrate levels. Furthermore, MAPKs kinases were regulated in livers preserved with IGL-1 solution since reductions in p-p38, p-ERK and p-JNK protein levels were observed.

CONCLUSION: IGL-1 solution preserved NO-dependent relaxation better than Celsior storage solution and enhanced liver graft preservation.

Autophagy and liver ischemia-reperfusion injury

Liver ischemia-reperfusion (I-R) injury occurs during liver resection, liver transplantation, and hemorrhagic shock. The main mode of liver cell death after warm and/or cold liver I-R is necrosis, but other modes of cell death, as apoptosis and autophagy, are also involved. Autophagy is an intracellular self-digesting pathway responsible for removal of long-lived proteins, damaged organelles, and malformed proteins during biosynthesis by lysosomes. Autophagy is found in normal and diseased liver. Although depending on the type of ischemia, warm and/or cold, the dynamic process of liver I-R results mainly in adenosine triphosphate depletion and in production of reactive oxygen species (ROS), leads to both, a local ischemic insult and an acute inflammatory-mediated reperfusion injury, and results finally in cell death. This process can induce liver dysfunction and can increase patient morbidity and mortality after liver surgery and hemorrhagic shock. Whether autophagy protects from or promotes liver injury following warm and/or cold I-R remains to be elucidated. The present review aims to summarize the current knowledge in liver I-R injury focusing on both the beneficial and the detrimental effects of liver autophagy following warm and/or cold liver I-R.

Emerging concepts in liver graft preservation

The urgent need to expand the donor pool in order to attend to the growing demand for liver transplantation has obliged physicians to consider the use of suboptimal liver grafts and also to redefine the preservation strategies. This review examines the different methods of liver graft preservation, focusing on the latest advances in both static cold storage and machine perfusion (MP). The new strategies for static cold storage are mainly designed to increase the fatty liver graft preservation via the supplementation of commercial organ preservation solutions with additives. In this paper we stress the importance of carrying out effective graft washout after static cold preservation, and present a detailed discussion of the future perspectives for dynamic graft preservation using MP at different temperatures (hypothermia at 4 °C, normothermia at 37 °C and subnormothermia at 20 °C-25 °C). Finally, we highlight some emerging applications of regenerative medicine in liver graft preservation. In conclusion, this review discusses the "state of the art" and future perspectives in static and dynamic liver graft preservation in order to improve graft viability.

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.

Melatonin Reverses Fas, E2F-1 and Endoplasmic Reticulum Stress Mediated Apoptosis and Dysregulation of Autophagy Induced by the Herbicide Atrazine in Murine Splenocytes

Exposure to the herbicide Atrazine (ATR) can cause immunotoxicity, apart from other adverse consequences for animal and human health. We aimed at elucidating the apoptotic mechanisms involved in immunotoxicity of ATR and their attenuation by Melatonin (MEL). Young Swiss mice were divided into control, ATR and MEL+ATR groups based on daily (x14) intraperitoneal administration of the vehicle (normal saline), ATR (100 mg/kg body weight) and MEL (20 mg/kg body weight) with ATR. Isolated splenocytes were processed for detection of apoptosis by Annexin V-FITC and TUNEL assays, and endoplasmic reticulum (ER) stress by immunostaining. Key proteins involved in apoptosis, ER stress and autophagy were quantified by immunoblotting. ATR treatment resulted in Fas-mediated activation of caspases 8 and 3 and inactivation of PARP1 which were inhibited significantly by co-treatment with MEL. MEL also attenuated the ATR-induced, p53 independent mitochondrial apoptosis through upregulation of E2F-1 and PUMA and suppression of their downstream target Bax. An excessive ER stress triggered by ATR through overexpression of ATF-6α, spliced XBP-1, CREB-2 and GADD153 signals was reversed by MEL. MEL also reversed the ATR-induced impairment of autophagy which was indicated by a decline in BECN-1, along with significant enhancement in LC3B-II and p62 expressions. Induction of mitochondrial apoptosis, ER stress and autophagy dysregulation provide a new insight into the mechanism of ATR immunotoxicity. The cytoprotective role of MEL, on the other hand, was defined by attenuation of ER stress, Fas-mediated and p53 independent mitochondria-mediated apoptosis as well as autophagy signals.

Melatonin reduces endoplasmic reticulum stress and preserves sirtuin 1 expression in neuronal cells of newborn rats after hypoxia-ischemia

Conditions that interfere with the endoplasmic reticulum (ER) functions cause accumulation of unfolded proteins in the ER lumen, referred to as ER stress, and activate a homeostatic signaling network known as unfolded protein response (UPR). We have previously shown that in neonatal rats subjected to hypoxia-ischemia (HI), melatonin administration significantly reduces brain damage. This study assessed whether attenuation of ER stress is involved in the neuroprotective effect of melatonin after neonatal HI. We found that the UPR was strongly activated after HI. Melatonin significantly reduced the neuron splicing of XBP-1 mRNA, the increased phosphorylation of eIF2α, and elevated expression of chaperone proteins GRP78 and Hsp70 observed after HI in the brain. CHOP, which plays a convergent role in the UPR, was reduced as well. Melatonin also completely prevented the depletion of SIRT-1 induced by HI, and this effect was observed in the same neurons that over-express CHOP. These results demonstrate that melatonin reduces ER stress induced by neonatal HI and preserves SIRT-1 expression, suggesting that SIRT-1, due to its action in the modulation of a wide variety of signaling pathways involved in neuroprotection, may play a key role in the reduction of ER stress and neuroprotection observed after melatonin.

Ischemic preconditioning provides neuroprotection by induction of AMP-activated protein kinase-dependent autophagy in a rat model of ischemic stroke

Accumulating evidence suggests that ischemic preconditioning (IPC) increases cerebral tolerance to the subsequent ischemic exposure. However, the underlying mechanisms are still not fully understood. In the present study, we tested the hypothesis that AMP-activated protein kinase (AMPK)-dependent autophagy contributed to the neuroprotection of IPC in rats with permanent cerebral ischemia. Male Sprague-Dawley rats were pretreated with vehicle, compound C (an AMPK inhibitor), or 3-methyladenine (3-MA, an autophagy inhibitor) and then were subjected to IPC induced by a 10-min middle cerebral artery occlusion. Afterward, the brain AMPK activity and autophagy biomarkers were measured. At 24 h after IPC, permanent cerebral ischemia was induced in these rats, and infarct volume, neurological deficits as well as cell apoptosis were evaluated 24 h later. We demonstrated that IPC activated AMPK and induced autophagy in the brain, which was accompanied by a reduction of infract volume, neurological deficits, and cell apoptosis after cerebral ischemia. Meanwhile, the IPC-induced autophagy was inhibited by compound C while the neuroprotection of IPC was abolished by compound C or 3-MA. These findings suggest that AMPK-mediated autophagy contributes to the neuroprotection of IPC, highlighting AMPK as a therapeutic target for stroke prevention and treatment.

Liver autophagy: much more than just taking out the trash

Studies performed in the liver in the 1960s led to the identification of lysosomes and the discovery of autophagy, the process by which intracellular proteins and organelles are degraded in lysosomes. Early studies in hepatocytes also uncovered how nutritional status regulates autophagy and how various circulating hormones modulate the activity of this catabolic process in the liver. The intensive characterization of hepatic autophagy over the years has revealed that lysosome-mediated degradation is important not only for maintaining liver homeostasis in normal physiological conditions, but also for an adequate response of this organ to stressors such as proteotoxicity, metabolic dysregulation, infection and carcinogenesis. Autophagic malfunction has also been implicated in the pathogenesis of common liver diseases, suggesting that chemical manipulation of this process might hold potential therapeutic value. In this Review--intended as an introduction to the topic of hepatic autophagy for clinical scientists--we describe the different types of hepatic autophagy, their role in maintaining homeostasis in a healthy liver and the contribution of autophagic malfunction to liver disease.

Technical feasibility of liver transplantation without cold storage

PURPOSE

The success of liver transplantation (LT) is accompanied by an increased need for organs. The wider use of older donors and marginal organs with risk factors such as steatosis has lead to a new interest to improve the outcome with marginal organs. We herewith report a novel technique for LT with in situ preparation and immediate warm-ischemia liver transplantation (WI-LT). The aim of our study was to demonstrate the technical feasibility and report the transplant course.

METHODS

Six patients underwent WI-LT at our institution. Hepatectomies during procurement and LT were both performed in parallel by different surgical teams. Technical factors and postoperative allograft function were analyzed.

RESULTS

All six WI-LTs were performed without intraoperative complications with a mean warm-ischemia time (WIT) of 29.0 min. No patient developed primary non-function or required retransplantation. Mean alanine aminotransferase (194.0 ± 170.4 U/l) and aspartate aminotransferase (316.3 ± 222.1 U/l) values on the first postoperative day were low, indicating a low ischemia/reperfusion injury and an excellent liver function.

CONCLUSIONS

These results demonstrate that WI-LT is a safe and technically feasible approach for LT with possibly reduced IRI and an excellent postoperative allograft quality. WI-LT may therefore be considered in individual patients especially with extended criteria donors to eventually improve postoperative allograft quality.

Melatonin and the theories of aging: a critical appraisal of melatonin's role in antiaging mechanisms

The classic theories of aging such as the free radical theory, including its mitochondria-related versions, have largely focused on a few specific processes of senescence. Meanwhile, numerous interconnections have become apparent between age-dependent changes previously thought to proceed more or less independently. Increased damage by free radicals is not only linked to impairments of mitochondrial function, but also to inflammaging as it occurs during immune remodeling and by release of proinflammatory cytokines from mitotically arrested, DNA-damaged cells that exhibit the senescence-associated secretory phenotype (SASP). Among other effects, SASP can cause mutations in stem cells that reduce the capacity for tissue regeneration or, in worst case, lead to cancer stem cells. Oxidative stress has also been shown to promote telomere attrition. Moreover, damage by free radicals is connected to impaired circadian rhythmicity. Another nexus exists between cellular oscillators and metabolic sensing, in particular to the aging-suppressor SIRT1, which acts as an accessory clock protein. Melatonin, being a highly pleiotropic regulator molecule, interacts directly or indirectly with all the processes mentioned. These influences are critically reviewed, with emphasis on data from aged organisms and senescence-accelerated animals. The sometimes-controversial findings obtained either in a nongerontological context or in comparisons of tumor with nontumor cells are discussed in light of evidence obtained in senescent organisms. Although, in mammals, lifetime extension by melatonin has been rarely documented in a fully conclusive way, a support of healthy aging has been observed in rodents and is highly likely in humans.

Fish-oil emulsion (omega-3 polyunsaturated fatty acids) attenuates acute lung injury induced by intestinal ischemia-reperfusion through Adenosine 5'-monophosphate-activated protein kinase-sirtuin1 pathway

BACKGROUND

Activated macrophage infiltration into the lungs is paramount in the pathogenesis of acute lung injury (ALI) induced by intestinal ischemia-reperfusion (I/R). Omega-3 polyunsaturated fatty acid (ω-3 PUFA) is a potent activator of the Adenosine 5'-monophosphate-activated protein kinase-sirtuin1 (AMPK/SIRT1) pathway against macrophage inflammation. We aimed to evaluate whether ω-3 PUFAs may protect against ALI induced by intestinal I/R via the AMPK/SIRT1 pathway.

METHODS

Ischemia in male Wistar rats was induced by superior mesenteric artery occlusion for 60 min and reperfusion for 240 min. One milliliter per day of fish-oil emulsion (FO emulsion, containing major ingredients as ω-3 PUFAs) or normal saline (control) was administered by intraperitoneal injection for three consecutive days to each animal. All animals were sacrificed at the end of reperfusion. Blood and tissue samples were collected for analysis.

RESULTS

Intestinal I/R caused intestinal and lung injury, evidenced by severe lung tissue edema and macrophage infiltration. Pretreatment with FO emulsion improved the integrity of microscopic structures in the intestine and lungs. Intestinal I/R induced the expression of macrophage-derived mediators (macrophage migration inhibitory factor and macrophage chemoattractant protein-1), inflammatory factors (nuclear factor κB, tumor necrosis factor α, interleukin 6, and interleukin 1β), and proapoptosis factor p66shc. There was a decrease in the expression of AMPK, SIRT1, and claudin 5. FO emulsion significantly inhibited macrophage infiltration into the lungs, inflammatory factor expression, and p66shc phosphorylation. Importantly, FO emulsion restored AMPK, SIRT1, and claudin 5 in the lungs.

CONCLUSIONS

Pretreatment with ω-3 PUFAs effectively protects intestinal and lung injury induced by intestinal I/R, reduces macrophage infiltration, suppresses inflammation, inhibits lung apoptosis, and improves the lung endothelial barrier after intestinal I/R in a manner dependent on AMPK/SIRT1. Thus, there is a potential for developing AMPK/SIRT1 as a novel target for patients with intestinal I/R-induced ALI.