Carbon monoxide induces hypothermia tolerance in Kupffer cells and attenuates liver ischemia/reperfusion injury in rats

Ligustrazine improves the compensative effect of Akt survival signaling to protect liver Kupffer cells in trauma-hemorrhagic shock rats

Trauma-hemorrhagic shock (THS) is a medical emergency that is encountered by physicians in the emergency department. Chuan Xiong is a traditional Chinese medicine and ligustrazine is a natural compound from it. Ligustrazine improves coronary blood flow and reduces cardiac ischemia in animals through Ca2+ and ATP-dependent vascular relaxation. It also decreases the platelets' bioactivity and reduces reactive oxygen species formation. We hypothesized that ligustrazine could protect liver by decreasing the inflammation response, protein production, and apoptosis in THS rats. Ligustrazine at doses of 100 and 1000 μg/mL was administrated in Kupffer cells isolated from THS rats. The protein expressions were detected via western blot. The THS showed increased inflammation response proteins, mitochondria-dependent apoptosis proteins, and had a compensation effect on the Akt pathway. After ligustrazine treatment, the hemorrhagic shock Kupffer cells decreased inflammatory response and mitochondria-dependent apoptosis and promoted a more compensative effect of the Akt pathway. It suggests ligustrazine reduces inflammation response and mitochondria-dependent apoptosis induced by THS in liver Kupffer cells and promotes more survival effects by elevating the Akt pathway. These findings demonstrate the beneficial effects of ligustrazine against THS-induced hepatic injury, and ligustrazine could be a potential medication to treat the liver injury caused by THS.

Deep-Depth Imaging of Hepatic Ischemia/Reperfusion Injury Using a Carbon Monoxide-Activated Upconversion Luminescence Nanosystem

Exploring a chemical imaging tool for visualizing the endogenous CO biosignaling molecule is of great importance in understanding the pathophysiological functions of CO in complex biological systems. Most of the existing CO fluorescent probes show excitation and emission in the region of ultraviolet and visible light, which are not suitable for application in in vivo deep-depth imaging of CO. Herein, a new near-infrared (NIR) to NIR upconversion luminescence (UCL) nanosystem for in vivo visualization of CO was developed, which possesses the merits of high selectivity and sensitivity, a deep tissue penetration depth, and a high signal-to-noise ratio. In this design, upon interaction with CO, the maxima absorption peak of the nanosystem showed a significant blue shift from 795 nm to 621 nm and triggered a remarkable turn-on NIR UCL signal due to the luminescence resonance energy transfer process. Leveraging this nanosystem, we achieved an NIR UCL visualization of the generation of CO biosignals caused by hypoxic, acute inflammation, or ischemic injury in living cells, zebrafish, and mice. Moreover, the protective effect of CO in zebrafish models of oxygen and glucose deprivation/reperfusion (OGD/R) and mice models of lipopolysaccharide-induced oxidative stress (LOS) and hepatic ischemia/reperfusion (HI/R) was also further verified. Therefore, this work discloses that the nanosystem not only serves as a promising nanoplatform to study biological signaling pathways of CO in pathophysiological events, but may also provide a powerful tool for HI/R injury diagnosis.

A Hemicyanine-Assembled Upconversion Nanosystem for NIR-Excited Visualization of Carbon Monoxide Bio-Signaling In Vivo

Carbon monoxide (CO) is considered as the second gasotransmitter involved in a series of physiological and pathological processes. Although a number of organic fluorescent probes have been developed for imaging CO, these probes display excitation within the ultraviolet or visible range, which restrict their applications in the complex biosystems. In the present work, a strategy is developed to construct an upconversion nanoparticles-based nanosystem for upconversion luminescent (UCL) sensing CO. This nanosystem exhibits a fast response to CO with high sensitivity and selectivity in aqueous solution by a near-infrared-excited ratiometric UCL detection method. Meanwhile, laser scanning upconversion luminescence microscope experiments demonstrate that this nanosystem can visualize the endogenous CO bio-signaling in living cells, deep tissues, zebrafish, and living mice by ratiometric UCL imaging. In particular, this nanosystem has been successfully employed in visualization of the endogenous CO bio-signaling through up-regulation of heme oxygenase-1 (HO-1) in the progression of hypoxia, acute inflammation, or ischemic injury. This work demonstrates that the outstanding performance of the nanosystem not only can provide an effective tool for further understanding the role of CO in the physiological and pathological environment, but also may have great potential ability for tracking the expression of HO-1 in living systems.

Aging deteriorated liver Ischemia and reperfusion injury by suppressing Tribble's proteins 1 mediated macrophage polarization

Aggravated liver injury has been reported in aged ischemia/reperfusion-stressed livers; however, the mechanism of aged macrophage inflammatory regulation is not well understood. Here, we found that the adaptor protein TRIB1 plays a critical role in the differentiation of macrophages and the inflammatory response in the liver after ischemia/reperfusion injury. In the present study, we determined that aging promoted macrophage-mediated liver injury and that inflammation was mainly responsible for lower M2 polarization in liver transplantation-exposed humans post I/R. Young and aged mice were subjected to hepatic I/R modeling and showed that aging aggravated liver injury and suppressed macrophage TRIB1 protein expression and anti-inflammatory function in I/R-stressed livers. Restoration of TRIB1 is mediated by lentiviral infection-induced macrophage anti-inflammatory M2 polarization and alleviated hepatic I/R injury. Moreover, TRIB1 overexpression in macrophages facilitates M2 polarization and anti-inflammation by activating MEK1-ERK1/2 signaling under IL-4 stimulation. Taken together, our results demonstrated that aging promoted hepatic I/R injury by suppressing TRIB1-mediated MEK1-induced macrophage M2 polarization and anti-inflammatory function.

Emerging role of carbon monoxide in intestinal transplantation

Intestinal transplantation has become an established therapeutic option that provides improved quality of life to patients with end-stage intestinal failure when total parenteral nutrition fails. Whereas this challenging life-saving intervention has shown exceptional growth over the past decade, illustrating the evolution of this complex and technical procedure from its preclinical origin in the mid-20th century to become a routine clinical practice today with several recent innovations, its success is hampered by multiple hurdles including technical challenges such as surgical manipulation during intestinal graft procurement, graft preservation and reperfusion damage, resulting in poor graft quality, graft rejection, post-operative infectious complications, and ultimately negatively impacting long-term recipient survival. Therefore, strategies to improve current intestinal transplantation protocol may have a significant impact on post-transplant outcomes. Carbon monoxide (CO), previously considered solely as a toxic gas, has recently been shown to be a physiological signaling molecule at low physiological concentrations with therapeutic potentials that could overcome some of the challenges in intestinal transplantation. This review discusses recent knowledge about CO in intestinal transplantation, the underlying molecular mechanisms of protection during intestinal graft procurement, preservation, transplantation and post-transplant periods. A section of the review also discusses clinical translation of CO and its challenges in the field of solid organ transplantation.

The Protective Role of the Heme Catabolic Pathway in Hepatic Disorders

Significance: As the central metabolic organ, the liver is exposed to a variety of potentially cytotoxic, proinflammatory, profibrotic, and carcinogenic stimuli. To protect the organism from these deleterious effects, the liver has evolved a number of defense systems, which include antioxidant substrates and enzymes, anti-inflammatory tools, enzymatic biotransformation systems, and metabolic pathways. Recent Advances: One of the pivotal systems that evolved during phylogenesis was the heme catabolic pathway. Comprising the important enzymes heme oxygenase and biliverdin reductase, this complex pathway has a number of key functions including enzymatic activities, but also cell signaling, and DNA transcription. It further generates two important bile pigments, biliverdin and bilirubin, as well as the gaseous molecule carbon monoxide. These heme degradation products have potent antioxidant, immunosuppressive, and cytoprotective effects. Recent data suggest that the pathway participates in the regulation of metabolic and hormonal processes implicated in the pathogenesis of hepatic and other diseases. Critical Issues: This review discusses the impact of the heme catabolic pathway on major liver diseases, with particular focus on the involvement of cellular targeting and signaling in the pathogenesis of these conditions. Future Directions: To utilize the biological consequences of the heme catabolic pathway, several unique therapeutic strategies have been developed. Research indicates that pharmaceutical, nutraceutical, and lifestyle modifications positively affect the pathway, delivering potentially long-term clinical benefits. However, further well-designed studies are needed to confirm the clinical benefits of these approaches. Antioxid. Redox Signal. 35, 734-752.

Carbon monoxide as an emerging pharmacological tool to improve lung and liver transplantation protocols

Carbon monoxide (CO) has long been considered purely as a toxic gas. It binds to hemoglobin at high concentrations and displaces oxygen from its binding site, resulting in carboxyhemoglobin formation, which reduces oxygen-carrying capacity of blood and culminates in tissue hypoxia and its associated complications. Recently, however, CO is quickly moving past its historic notorious tag as a poisonous gas to a physiological signaling molecule with therapeutic potentials in several clinical situations including transplant-induced injury. This review discusses current knowledge of CO gas and CO-releasing molecules (CO-RMs) in preclinical models of lung and liver transplantation, and underlying molecular mechanisms of cyto- and organ protection during organ procurement, preservation, implantation and post-transplant periods. In addition, a discussion of the future of CO in clinical organ transplantation is provided.

Hypertonic saline solution decreases oxidative stress in liver hypothermic ischemia

BACKGROUND

Liver ischemia reperfusion injury is still an unsolved problem in liver surgery and transplantation. In this setting, hypothermia is the gold standard method for liver preservation for transplantation. Hypertonic saline solution reduces inflammatory response with better hemodynamic recovery in several situations involving ischemia reperfusion injury. Here, we investigated the effect of hypertonic saline solution in hypothermic liver submitted to ischemia reperfusion injury.

METHODS

Fifty male rats were divided into 5 groups: SHAM, WI (animals submitted to 40 minutes of partial warm liver ischemia and reperfusion), HI (animals submitted to 40 minutes hypothermic ischemia), HSPI (animals submitted to hypothermic ischemia and treated with 7.5% hypertonic saline solution preischemia), and HSPR (animals submitted to hypothermic ischemia and treated with hypertonic saline solution previously to liver reperfusion). Four hours after reperfusion, the animals were euthanized to collect liver and blood samples.

RESULTS

Aspartate aminotransferase and alanine aminotransferase, histologic score, and hepatocellular necrosis were significantly decreased in animals submitted to hypothermia compared with the warm ischemia group. Malondialdehyde was significantly decreased in hypothermic groups with a further decrease when hypertonic saline solution was administrated preischemia. Hypothermic groups also showed decreased interleukin-6, interleukin-10, and tumor necrosis factor-α concentrations and better recovery of bicarbonate, base excess, lactate, and glucose blood concentrations. Moreover, hypertonic saline solution preischemia was more effective at controlling serum potassium concentrations.

CONCLUSION

Hypertonic saline solution before hypothermic hepatic ischemia decreases hepatocellular oxidative stress, cytokine concentrations, and promotes better recovery of acid-base disorders secondary to liver ischemia reperfusion.

Effect of Hepatic Macrophage Polarization and Apoptosis on Liver Ischemia and Reperfusion Injury During Liver Transplantation

Ischemia-reperfusion (I/R) injury is injury caused by a limited blood supply and subsequent blood supply recovery during liver transplantation. Serious ischemia-reperfusion injury is the main cause of transplant failure. Hepatic I/R is characterized by tissue hypoxia due to a limited blood supply and reperfusion inducing oxidative stress and an immune response. Studies have confirmed that Kupffer cells (KCs), resident macrophages in the liver, play a key role in aseptic inflammation induced by I/R. In liver macrophage polarization, M1 macrophages activated by interferon-γ (IFN-γ) and lipopolysaccharide (LPS) exert a pro-inflammatory effect and release a variety of inflammatory cytokines. M2 macrophages activated by IL-4 have an anti-inflammatory response. M1-type KCs are the dominant players in I/R as they secrete various pro-inflammatory cytokines that exacerbate the injury and recruit other types of immune cells via the circulation. In contrast, M2-type KCs can ameliorate I/R through unregulated anti-inflammatory factors. A new notion has been proposed that KC apoptosis may influence I/R in yet another manner as well. Management of KCs is expected to help improve I/R. This review summarizes the effects of hepatic macrophage polarization and apoptosis on liver I/R.

The Protective Effects of Carbon Monoxide Against Hepatic Warm Ischemia-Reperfusion Injury in MHC-Inbred Miniature Swine

BACKGROUND

The development of treatment strategies to protect against ischemia-reperfusion injury (IRI) to livers is important not only for liver surgeries but also in regard to increasing the utilization of livers from marginal donors. In this study, we examined whether inhalational carbon monoxide (CO) therapy reduced IRI after a 45-min (min) warm ischemia (WI) in a miniature swine model.

MATERIALS AND METHODS

Six CLAWN miniature swine underwent a 45-min hepatic WI induced by clamping the portal vein and proper hepatic artery. Three animals were subjected to control conditions while the remaining three were treated with CO inhalation for a total of 345-min, including 120-min after reperfusion to maintain a concentration of CO-Hb under 15% (CO-treated group). IRI of the livers was evaluated by liver function tests, serum pro-inflammatory cytokines, and liver biopsies.

RESULTS

All controls had statistically significant increased levels of liver enzymes compared to the CO-treated group (p < 0.05). In controls, liver biopsies at 2 h after reperfusion showed marked histological changes including diffuse hemorrhage, congestion, necrosis, vacuolization, and neutrophil infiltration with apoptosis. In contrast, the CO-treated group showed less obvious or only minimal histological changes. Furthermore, increases in high-mobility group box 1, TNF-α, and IL-6 in sera that were induced by IRI in controls were markedly inhibited by the CO treatment.

CONCLUSION

We demonstrated that low-dose CO inhalation reduces hepatic warm IRI, potentially through downregulation of pro-inflammatory mediators and activation of anti-apoptotic pathways. To our knowledge, this is the first report demonstrating CO inhalation attenuated hepatic IRI following WI in a large animal model.

Carbon Monoxide Being Hydrogen Sulfide and Nitric Oxide Molecular Sibling, as Endogenous and Exogenous Modulator of Oxidative Stress and Antioxidative Mechanisms in the Digestive System

Oxidative stress reflects an imbalance between oxidants and antioxidants in favor of the oxidants capable of evoking tissue damage. Like hydrogen sulfide (H₂S) and nitric oxide (NO), carbon monoxide (CO) is an endogenous gaseous mediator recently implicated in the physiology of the gastrointestinal (GI) tract. CO is produced in mammalian tissues as a byproduct of heme degradation catalyzed by the heme oxygenase (HO) enzymes. Among the three enzymatic isoforms, heme oxygenase-1 (HO-1) is induced under conditions of oxidative stress or tissue injury and plays a beneficial role in the mechanism of protection against inflammation, ischemia/reperfusion (I/R), and many other injuries. According to recently published data, increased endogenous CO production by inducible HO-1, its delivery by novel pharmacological CO-releasing agents, or even the direct inhalation of CO has been considered a promising alternative in future experimental and clinical therapies against various GI disorders. However, the exact mechanisms underlying behind these CO-mediated beneficial actions are not fully explained and experimental as well as clinical studies on the mechanism of CO-induced protection are awaited. For instance, in a variety of experimental models related to gastric mucosal damage, HO-1/CO pathway and CO-releasing agents seem to prevent gastric damage mainly by reduction of lipid peroxidation and/or increased level of enzymatic antioxidants, such as superoxide dismutase (SOD) or glutathione peroxidase (GPx). Many studies have also revealed that HO-1/CO can serve as a potential defensive pathway against oxidative stress observed in the liver and pancreas. Moreover, increased CO levels after treatment with CO donors have been reported to protect the gut against formation of acute GI lesions mainly by the regulation of reactive oxygen species (ROS) production and the antioxidative activity. In this review, we focused on the role of H₂S and NO molecular sibling, CO/HO pathway, and therapeutic potential of CO-releasing pharmacological tools in the regulation of oxidative stress-induced damage within the GI tract with a special emphasis on the esophagus, stomach, and intestines and also two solid and important metabolic abdominal organs, the liver and pancreas.

Therapeutics administered during ex vivo liver machine perfusion: An overview

Although the use of extended criteria donors has increased the pool of available livers for transplant, it has also introduced the need to develop improved methods of protection against ischemia-reperfusion injury (IRI), as these "marginal" organs are particularly vulnerable to IRI during the process of procurement, preservation, surgery, and post-transplantation. In this review, we explore the current basic science research investigating therapeutics administered during ex vivo liver machine perfusion aimed at mitigating the effects of IRI in the liver transplantation process. These various categories of therapeutics are utilized during the perfusion process and include invoking the RNA interference pathway, utilizing defatting cocktails, and administering classes of agents such as vasodilators, anti-inflammatory drugs, human liver stem cell-derived extracellular vesicles, and δ-opioid agonists in order to reduce the damage of IRI. Ex vivo machine perfusion is an attractive alternative to static cold storage due to its ability to continuously perfuse the organ, effectively deliver substrates and oxygen required for cellular metabolism, therapeutically administer pharmacological or cytoprotective agents, and continuously monitor organ viability during perfusion. The use of administered therapeutics during machine liver perfusion has demonstrated promising results in basic science studies. While novel therapeutic approaches to combat IRI are being developed through basic science research, their use in clinical medicine and treatment in patients for liver transplantation has yet to be explored.

Protective role of heme oxygenase-1 in fatty liver ischemia-reperfusion injury

Ischemia-reperfusion (IR) injury is a kind of injury resulting from the restoration of the blood supply after blood vessel closure during liver transplantation and is the main cause of graft failure. The pathophysiological mechanisms of hepatic IR include a variety of oxidative stress responses. Hepatic IR is characterized by ischemia and hypoxia inducing oxidative stress, immune response and apoptosis. Fat-denatured livers are also used as donors due to the lack of liver donors. Fatty liver is less tolerant to IR than normal liver. Heme oxygenase (HO) is an enzyme that breaks down hemoglobin to bilirubin, ferrous iron and carbon monoxide (CO). Inducible HO subtype HO-1 is an important protective molecule in mammalian cells used to improve acute and chronic liver injury owing to its characteristic anti-inflammatory and anti-apoptotic qualities. HO-1 degrades heme, and its reaction product CO has been shown to reduce hepatic IR injury and increase the survival rate of grafts. As an induced form of HO, HO-1 also exerts a protective effect against liver IR injury and may be useful as a new strategy of ameliorating this kind of damage. This review summarizes the protective effects of HO-1 in liver IR injury, especially in fatty liver.

Hypothermia does not influence liver damage and function in a porcine polytrauma model

BACKGROUND

Previous studies revealed evidence that induced hypothermia attenuates ischemic organ injuries after severe trauma. In the present study, the effect of hypothermia on liver damage was investigated in a porcine long term model of multi-system injury, consisting of blunt chest trauma, penetrating abdominal trauma, musculoskeletal injury, and hemorrhagic shockMETHODS: In 30 pigs, a standardized polytrauma including blunt chest trauma, penetrating abdominal trauma, musculoskeletal injury, and hemorrhagic shock of 45% of total blood volume was induced. Following trauma, hypothermia of 33∘C was induced for 12 h and intensive care treatment was evaluated for 48 h. As outcome parameters, we assessed liver function and serum transaminase levels as well as a histopathological analysis of tissue samples. A further 10 animals served as controls.

RESULTS

Serum transaminase levels were increased at the end of the observation period following hypothermia without reaching statistical significance compared to normothermic groups. Liver function was preserved (p⩽ 0.05) after the rewarming period in hypothermic animals but showed no difference at the end of the observation period. In H&E staining, cell death was slightly increased hypothermic animals and caspase-3 staining displayed tendency towards more apoptosis in hypothermic group as well.

CONCLUSIONS

Induction of hypothermia could not significantly improve hepatic damage during the first 48 h following major trauma. Further studies focusing on multi-organ failure including a longer observation period are required to illuminate the impact of hypothermia on hepatic function in multiple trauma patients.

Activation of PPARγ by Curcumin protects mice from ischemia/reperfusion injury induced by orthotopic liver transplantation via modulating polarization of Kupffer cells

Curcumin shows protective effects on various diseases due to its anti-inflammatory and anti-oxidative functions; however, its effect on organ transplantation has not been fully elucidated. To understand its role in liver ischemia/reperfusion (I/R) injury, we studied its impact on orthotopic liver transplantation (OLT) and Kupffer cells (KCs) polarization and its underlying mechanisms. We first investigated the reactive oxygen species (ROS) accumulation and cytokines profile of KCs, intracellular ROS and the mRNA level of pro-inflammatory cytokines were downregulated while the mRNA level of anti-inflammatory cytokine was upregulated by the pretreatment of Curcumin; Then the liver injury was detected by histopathological examination and liver function. Pretreatment with Curcumin significantly alleviated liver injury while improving liver function and overall post-transplantation survival compared with the control groups. The Western blotting showed that Curcumin inhibited the function of KCs via down-regulating the nuclear factor κb (NF-κb) signaling pathway by activating peroxisome proliferator-activated receptor γ (PPARγ) and flow cytometry revealed that Curcumin suppressed pro-inflammatory phenotype (M1) of KCs while promoting its anti-inflammatory phenotype (M2) polarization. These results showed that Curcumin may exert positive effects on I/R injury after OLT through activating PPARγ by inhibiting the activation of NF-κb pathway and remodeling the polarization of KCs. This may reveal a potential therapy for I/R injury after liver transplantation.

Angiotensin IV improves subnormothermic machine perfusion preservation of rat liver graft

This study aims to determine whether Angiotensin IV (Ang IV) addition to Celsior preservation solution could improve hepatic endothelium function and provide better liver protection during subnormothermic machine preservation (SMP). Two experimental models were used: In the first part of the study, rings isolated from rat hepatic artery were preserved in Celsior solution (6 h, 20 °C) with and without Ang IV (10^-9 M), then, endothelium-dependent relaxation (EDR) and the concentration of acetylcholine inducing half-maximal relaxation of pre-contracted rings (EC50) were measured. Also, in order to investigate the implication of nitric oxide (NO) on EDR, the rings of hepatic artery were incubated with L-NG-nitroarginine metyl ester (L-NAME). In the second part of the study, rat livers were subjected to SMP with oxygenated Celsior solution (6 h, 20 °C), supplemented or not with Ang IV (10^-9 M) and then perfused (2 h, 37 °C) with Krebs Henseleit solution. We found that Ang IV supplementation to Celsior solution decreased EC50 value and improved EDR of hepatic artery rings, 6h after sub-normothermic preservation. Interestingly, Ang IV amplified the vessel relaxation in a NO-dependent manner. Moreover, liver SMP with Ang IV reduced oxidative stress and cell injury and improved organ function. Ang IV activated pAkt, increased eNOS protein level and decreased apoptosis in the preserved liver grafts. In conclusion, we showed that the use of Ang IV in Celsior solution for sub-normothermic graft preservation insured a better NO-dependent relaxation and improved liver functional recovery.

Molecular hydrogen upregulates heat shock response and collagen biosynthesis, and downregulates cell cycles: meta-analyses of gene expression profiles

Molecular hydrogen exerts its effect on multiple pathologies, including oxidative stress, inflammation, and apoptosis. However, its molecular mechanisms have not been fully elucidated. In order to explore the effects of molecular hydrogen, we meta-analysed gene expression profiles modulated by molecular hydrogen. We performed microarray analysis of the mouse liver with or without drinking hydrogen water. We also integrated two previously reported microarray datasets of the rat liver into meta-analyses. We used two categories of meta-analysis methods: the cross-platform method and the conventional meta-analysis method (Fisher's method). For each method, hydrogen-modulated pathways were analysed by (i) the hypergeometric test (HGT) in the class of over-representation analysis (ORA), (ii) the gene set enrichment analysis (GSEA) in the class of functional class scoring (FCS), and (iii) the signalling pathway impact analysis (SPIA), pathway regulation score (PRS), and others in the class of pathway topology-based approach (PTA). Pathways in the collagen biosynthesis and the heat-shock response were up-regulated according to (a) HGT with the cross-platform method, (b) GSEA with the cross-platform method, and (c) PRS with the cross-platform method. Pathways in cell cycles were down-regulated according to (a) HGT with the cross-platform method, (b) GSEA with the cross-platform method, and (d) GSEA with the conventional meta-analysis method. Because the heat-shock response leads to up-regulation of collagen biosynthesis and a transient arrest of cell cycles, induction of the heat-shock response is likely to be a primary event induced by molecular hydrogen in the liver of wild-type rodents.

Novel Insights on Notch signaling pathways in liver fibrosis

Liver fibrosis is characterized by an increased and altered deposition of extracellular matrix (ECM) proteins that make up excessive tissue scarring and promote chronic liver injury. Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in the progression of liver fibrosis. However, the mechanisms involved in the development of liver fibrosis are only now beginning to be unveiled. The Notch pathway is a fundamental and highly conserved pathway able to control cell-fate, including cell proliferation, differentiation, apoptosis, regeneration and other cellular activities. Recently, the deregulation of Notch cascade has been found involved in many pathological processes, including liver fibrosis. These data give evidence for a role for Notch signaling in liver fibrosis. In addition，more and more date are available on the role of Notch pathways in the process. Therefore, this review focuses on the current knowledge about the Notch signaling pathway, which dramatically takes part in HSC activation and liver fibrosis, and look ahead on new perspectives of Notch signaling pathway research. Furthermore, we will summarize this new evidence on the different interactions in Notch signaling pathway-regulated liver fibrosis, and support the potentiality of putative biomarkers and unique therapeutic targets.

Vagus Nerve Attenuates Hepatocyte Apoptosis upon Ischemia-Reperfusion via α7 Nicotinic Acetylcholine Receptor on Kupffer Cells in Mice

BACKGROUND

Hepatic ischemia-reperfusion (HIR) injury is a complication of liver surgery. As much as 50% of hepatocytes undergo apoptosis within the first 24 h of reperfusion. The neurotransmitters of the vagus nerve can activate α7 nicotinic acetylcholine receptor (α7nAChR) on macrophages. The function of Kupffer cells (KCs) determines HIR injury. We hypothesize that the vagus nerve could attenuate HIR-induced hepatocyte apoptosis by activating α7nAChR on KCs.

METHODS

Hepatic vagotomized C57BL/6J mice, KC-eliminated C57BL/6J mice, and α7nAChR mice were used for HIR. Primary KCs and hepatocytes were subjected to hypoxia/reoxygenation (HR). Liver injury, hepatocyte apoptosis, reactive oxygen species (ROS) production, and soluble CD163 were measured.

RESULTS

Hepatic vagotomy and α7nAChR caused higher levels of alanine transaminase and liver caspase-3 and -8 activity by HIR. Activating α7nAChR attenuated these changes in wild-type but not in the α7nAChR mice. Furthermore, activating α7nAChR diminished hepatic injury and reduced liver apoptosis by HIR in vagotomized mice. In vitro, activating α7nAChR reduced apoptosis of hepatocytes cocultured with KCs that suffered HR. Similar to the effects by catalase, activating α7nAChR on KCs reduced ROS and H2O2 by HR. The supernatant from KCs, with α7nAChR activated or catalase treated, prevented hepatocyte apoptosis by HR. Finally, KC elimination reduced HIR-induced H2O2 production in mice. Activating α7nAChR significantly attenuated soluble CD163 both in mice by HIR (serum: 240 ± 34 vs. 446 ± 72; mean ± SD; n = 8; P < 0.01) and in KCs by HR (supernatant: 4.23 ± 0.06 vs. 5.60 ± 0.18; n = 3; P < 0.01).

CONCLUSIONS

The vagus nerve could minimize HIR-induced liver apoptosis through activating α7nAChR on KCs possibly by preventing their excessive ROS production.

Carbon monoxide as a promising molecule to promote nerve regeneration after traumatic brain injury

Carbon monoxide (CO) is known as a toxic gas. Although there have been many studies on both toxic and protective effects of CO, most of these studies lack novelty, except for Eng H Lo team's study on the therapeutic effect of CO on brain injuries. In this commentary, we summarize the potential application value of CO in the treatment of some clinical diseases, especially its protective effect and nerve regeneration in brain injuries, hoping that our interest in CO could promote related clinical application studies.

Carbon monoxide ameliorates hepatic ischemia/reperfusion injury via sirtuin 1-mediated deacetylation of high-mobility group box 1 in rats

Carbon monoxide (CO) exerts protective effects on hepatic ischemia/reperfusion injury (IRI), but the underlying molecular mechanisms are not fully understood. High-mobility group box 1 (HMGB1) is an important mediator of injury and inflammation in hepatic IRI. Here, we investigated whether CO could attenuate hepatic IRI via inhibition of HMGB1 release, particularly through sirtuin 1 (SIRT1). CO was released by treatment with carbon monoxide-releasing molecule (CORM)-2. CORM-2-delivered CO ameliorated hepatic IRI, as indicated by lower serum aminotransferase levels, lower hepatic inflammatory responses, and less severe ischemia/reperfusion-associated histopathologic changes. Treatment with CORM-2 significantly inhibited IRI-induced HMGB1 translocation and release. SIRT1 expression was increased by CORM-2 pretreatment. When CORM-2-induced SIRT1 expression was inhibited using EX527, HMGB1 translocation and release were increased and hepatic IRI was worsened, whereas SIRT1 activation by resveratrol reversed this trend. In vitro, CORM-2 reduced hypoxia/reoxygenation-induced HMGB1 translocation and release, these inhibitions were blocked by SIRT1 inhibition using EX527 or SIRT1 small interfering RNA both in alpha mouse liver 12 cells and RAW264.7 macrophages. Moreover, SIRT1 directly interacted with and deacetylated HMGB1. IRI increased HMGB1 acetylation, which was abolished by CORM-2 treatment via SIRT1. In conclusion, these results suggest that CO may increase SIRT1 expression, which may decrease HMGB1 acetylation and subsequently reduce its translocation and release, thereby protecting against hepatic IRI. Liver Transplantation 23 510-526 2017 AASLD.

Pre-conditioning with tanshinone IIA attenuates the ischemia/reperfusion injury caused by liver grafts via regulation of HMGB1 in rat Kupffer cells

OBJECTIVE

We have evaluated the protective mechanism of tanshinone IIA in ischemia/reperfusion injury (IRI) induced by liver grafts, revealing novel supplementary immunotherapy for liver transplantation.

METHODS

The tanshinone IIA preconditioning group (TP group) was pretreated with tanshinone IIA via intraperitoneal injection for 1 week before receiving orthotopic liver transplantation with hepatic arterial ischemia for 30min. The sham-operation group (SO group), control graft group (CG group) and IRI group were pretreated with an equivalent volume of normal saline. The IRI group and CG group received orthotopic liver transplantation with or without hepatic arterial ischemia. Rats were sacrificed at each time point, serum was collected for ELISA detection, and Kupffer cells (KCs) were isolated to extract total protein and RNA for western blotting and real-time PCR, respectively.

RESULTS

The levels of TNF-α and IL-4 in the TP group were significantly lower than those of in the IRI group; meanwhile the IL-10 and TGF-β levels were significantly higher than in the IRI group. The protein and mRNA expression levels of HMGB1 were significantly lower in TP group than in the IRI group at each time point. The TLR-4, Myd88, NLRP3 and p-NF-κb p65 expression levels in the TP groups were significantly lower than those in the IRI group, while the PTEN, PI3K and AKT phosphorylation levels in the TP groups were significantly higher than those in the IRI group.

CONCLUSIONS

Tanshinone IIA attenuates IRI caused by liver grafts via down-regulation of the HMGB1-TLR-4/NF-κb pathway in KCs and activation of PTEN/PI3K/AKT pathway, suggesting a potential role for prevention of liver cell IRI during liver transplantation.

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.

Anti-inflammatory signaling during ex vivo liver perfusion improves the preservation of pig liver grafts before transplantation

Normothermic ex vivo liver perfusion (NEVLP) improves graft preservation by avoiding cold ischemia injury. We investigated whether the protective effects of NEVLP can be further improved by applying strategies targeted on reducing the activation of proinflammatory cytokines during perfusion. Livers retrieved under heart-beating conditions were perfused for 4 hours. Following the preservation period, a pig liver transplantation was performed. In group 1 (n = 5), anti-inflammatory strategies (alprostadil, n-acetylcysteine, carbon monoxide, sevoflurane, and subnormothermic temperature [33°C]) were applied. This was compared with a perfused control group (group 2) where livers (n = 5) were perfused at 37°C without anti-inflammatory agents, similar to the setup used in current European clinical trials, and to a control group preserved with static cold storage (group 3). During 3-day follow-up, markers of reperfusion injury, bile duct injury, and liver function were examined. Aspartate aminotransferase (AST) levels during perfusion were significantly lower in the study versus control group at 1 hour (52 ± 6 versus 162 ± 86 U/L; P = 0.01), 2 hours (43 ± 5 versus 191 ± 111 U/L; P = 0.008), and 3 hours (24 ± 16 versus 218 ± 121 U/L; P = 0.009). During perfusion, group 1 versus group 2 had reduced interleukin (IL) 6, tumor necrosis factor α, and galactosidase levels and increased IL10 levels. After transplantation, group 1 had lower AST peak levels compared with group 2 and group 3 (1400 ± 653 versus 2097 ± 1071 versus 1747 ± 842 U/L; P = 0.47) without reaching significance. Bilirubin levels were significantly lower in group 1 versus group 2 at day 1 (3.6 ± 1.5 versus 6.60 ± 1.5 μmol/L; P = 0.02) and 3 (2 ± 1.1 versus 9.7 ± 7.6 μmol/L; P = 0.01). A trend toward decreased hyaluronic acid, as a marker of improved endothelial cell function, was observed at 1, 3, and 5 hours after reperfusion in group 1 versus group 2. Only 1 early death occurred in each group (80% survival). In conclusion, addition of anti-inflammatory strategies further improves warm perfused preservation. Liver Transplantation 22 1573-1583 2016 AASLD.

Subnormothermic ex vivo liver perfusion is a safe alternative to cold static storage for preserving standard criteria grafts

We developed a novel technique of subnormothermic ex vivo liver perfusion (SNEVLP) for the storage of liver grafts before transplantation. To test the safety of SNEVLP for the nonextended criteria grafts (standard grafts), we compared it to a control group with minimal cold static storage (CS) time. Heart-beating pig liver retrieval was performed. Grafts were either stored in cold unmodified University of Wisconsin solution (CS-1), in cold University of Wisconsin solution with ex vivo perfusion additives (CS-2), or preserved with a sequence of 3 hours CS and 3 hours SNEVLP (33°C), followed by orthotopic liver transplantation. Liver function tests and histology were investigated. Aspartate aminotransferase (AST) levels during SNEVLP remained stable (54.3 ± 12.6 U/L at 1 hour to 47.0 ± 31.9 U/L at 3 hours). Posttransplantation, SNEVLP versus CS-1 livers had decreased AST levels (peak at day 1, 1081.9 ± 788.5 versus 1546.7 ± 509.3 U/L; P = 0.14; at day 2, 316.7 ± 188.1 versus 948.2 ± 740.9 U/L; P = 0.04) and alkaline phosphatase levels (peak at day 1, 150.4 ± 19.3 versus 203.7 ± 33.6 U/L; P = 0.003). Bilirubin levels were constantly within the physiological range in the SNEVLP group, whereas the CS-1 group presented a large standard deviation, including pathologically increased values. Hyaluronic acid as a marker of endothelial cell (EC) function was markedly improved by SNEVLP during the early posttransplant phase (5 hours posttransplant, 1172.75 ± 598.5 versus 5540.5 ± 2755.4 ng/mL). Peak international normalized ratio was similar between SNEVLP and CS-1 groups after transplantation. Immunohistochemistry for cleaved caspase 3 demonstrated more apoptotic sinusoidal cells in the CS-1 group when compared to SNEVLP grafts 2 hours after reperfusion (19.4 ± 19.5 versus 133.2 ± 48.8 cells/high-power field; P = 0.002). Adding normothermic CS-2 had no impact on liver injury or function after transplantation when compared to CS-1. In conclusion, SNEVLP is safe to use for standard donor grafts and is associated with improved EC and bile duct injury even in grafts with minimal CS time.

Effects of sodium methyldithiocarbamate on selected parameters of innate immunity and clearance of bacteria in a mouse model of sepsis

AIMS

Sodium methyldithiocarbamate (SMD), the third most widely used conventional pesticide in the United States, has been reported to inhibit several parameters associated with inflammation and to decrease resistance to infection. In a previous study, survival time was markedly decreased when mice were treated orally with SMD shortly before challenge with a high dose of Escherichia coli (E. coli) that was lethal to most of the control mice. In the present study, we evaluated selected parameters of the innate immune system using a lower challenge dose of E. coli, to determine which (if any) of these parameters reflected continued changes through 24h.

MAIN METHODS

Bacterial clearance from the peritoneal cavity, production of chemokines and cytokines, and body temperature were measured.

KEY FINDINGS

All these parameters were reduced by SMD up to 12h after bacterial challenge, but the concentration of the anti-inflammatory cytokine IL-10 was increased. Even so, mice in the control and SMD-treated groups cleared most bacteria by 24h. Other parameters (cytokine concentrations and body temperature) were also normal or near normal by 24h. The same dosage of SMD administered intranasally also did not significantly decrease survival. Hypothermia from 16 to 28 h correlated with lethal outcome, but SMD significantly increased hypothermia only at 2 and 4h after challenge.

SIGNIFICANCE

In spite of substantial early inhibition by SMD of parameters known to be important for resistance to infection, bacterial clearance and survival were not altered, suggesting immunological reserve and/or rapid recovery after transient effects of SMD.

Kupffer cell inactivation by carbon monoxide bound to red blood cells preserves hepatic cytochrome P450 via anti-oxidant and anti-inflammatory effects exerted through the HMGB1/TLR-4 pathway during resuscitation from hemorrhagic shock

Red blood cell (RBC) transfusions for controlling hemorrhaging induce systemic ischemia reperfusion, resulting in a decrease in hepatic cytochrome P450 (CYP) levels. Carbon monoxide (CO), when bound to red blood cells (CO-RBC) has the potential to protect the hepatic CYP protein to produce a resuscitative effect in a hemorrhagic shock rat model. The aim of this study was to investigate the mechanism by which CO-RBC resuscitation from a massive hemorrhage protects against a decrease in hepatic CYP. In the early phase (∼1h) after a hemorrhage and RBC resuscitation, hepatic CYP protein levels were significantly decreased with increasing hepatic free heme levels, but were maintained by a pre-treatment of gadolinium chloride (GdCl3), a Kupffer cell inhibitor, and Trolox, an anti-oxidant agent, as well as CO-RBC resuscitation. Under these conditions, the production of reactive oxygen species (ROS) derived from activated Kupffer cells was increased, but this increase was suppressed by CO-RBC resuscitation. At a late phase (6∼24h), CYP mRNA levels decreased after hemorrhage and RBC resuscitation, but not in the case of CO-RBC resuscitation. The increases in plasma IL-6 and TNF-α levels were decreased by CO-RBC resuscitation via the suppression of the toll-like receptor-4 (TLR-4) and the expression of the high mobility group box-1 (HMGB-1). Hepatic CYP protection after a hemorrhage and CO-RBC resuscitation can be attributed to the inactivation of Kupffer cells, resulting in the suppression of ROS production in the early phase and the suppression of inflammatory cytokine production via the TLR-4/HMGB-1signal pathway in the late phase.

Carbon monoxide protects against hepatic ischemia/reperfusion injury by modulating the miR-34a/SIRT1 pathway

Hepatic ischemia/reperfusion (I/R) injury can arise as a complication of liver surgery and transplantation. Sirtuin 1 (SIRT1), an NAD+-dependent deacetylase, modulates inflammation and apoptosis in response to oxidative stress. SIRT1, which is regulated by p53 and microRNA-34a (miR-34a), can modulate non-alcoholic fatty liver disease, fibrosis and cirrhosis. Since carbon monoxide (CO) inhalation can protect against hepatic I/R, we hypothesized that CO could ameliorate hepatic I/R injury by regulating the miR-34a/SIRT1 pathway. Livers from mice pretreated with CO, or PFT, a p53 inhibitor, displayed reduced production of pro-inflammatory mediators, including TNF-α, iNOS, interleukin (IL)-6, and IL-1β after hepatic I/R injury. SIRT1 expression was increased by CO or PFT in the liver after I/R, whereas acetylated p65, p53 levels, and miR-34a expression were decreased. CO increased SIRT1 expression by inhibiting miR-34a. Both CO and PFT diminished pro-inflammatory cytokines production in vitro. Knockdown of SIRT1 in LPS-stimulated macrophages increased NF-κB acetylation, and increased pro-inflammatory cytokines. CO treatment reduced miR-34a expression and increased SIRT1 expression in oxidant-challenged hepatocytes; and rescued SIRT1 expression in p53-expressing or miR-34a transfected cells. In response to CO, enhanced SIRT1 expression mediated by miR-34a inhibition protects against liver damage through p65/p53 deacetylation, which may mediate inflammatory responses and hepatocellular apoptosis. The miR-34a/SIRT1 pathway may represent a therapeutic target for hepatic injury.

Therapeutic roles of carbon monoxide in intestinal ischemia-reperfusion injury

Intestinal ischemia-reperfusion (I-R) injury is a complex, multifactorial, pathophysiological process with high morbidity and mortality, leading to serious difficulty in treatment. The mechanisms involved in the pathogenesis of intestinal I-R injury have been examined in detail and various therapeutic approaches for intestinal I-R injury have been developed; however, existing circumstances have not yet led to a dramatic change of treatment. Carbon monoxide (CO), one of the by-products of heme degradation by heme oxygenase (HO), is considered as a candidate for treatment of intestinal I-R injury and indeed HO-1-derived endogenous CO and exogenous CO play a pivotal role in protecting the gastrointestinal tract from intestinal I-R injury. Interestingly, anti-inflammatory effects of CO have been elucidated sufficiently in various cell types including endothelial cells, circulating leukocytes, macrophages, lymphocytes, epithelial cells, fibroblast, organ-specific cells, and immune-presenting cells. In this review, we herein focus on the therapeutic roles of CO in intestinal I-R injury and the cell-specific anti-inflammatory effects of CO, clearly demonstrating future therapeutic strategies of CO for treating intestine I-R injury.

Liver protection strategies in liver transplantation

BACKGROUND

Liver transplantation is the therapy of choice for patients with end-stage liver diseases. However, the gap between the low availability of organs and high demand is continuously increasing. Innovative strategies for organ protection are necessary to expand donor pool and to achieve better outcomes for liver transplantation. The present review analyzed and compared various strategies of liver protection.

DATA SOURCES

Databases such as PubMed, Embase and Ovid were searched for the literature related to donor liver protection strategies using following key words: "ischemia reperfusion injury", "graft preservation", "liver transplantation", "machine perfusion" and "conditioning". Of the 146 studies identified, only those with cutting edge strategies were analyzed.

RESULTS

A variety of therapeutic approaches were proposed to alleviate graft ischemia/reperfusion injury, which included static cold storage, machine perfusion (hypothermic, normothermic and subnormothermic), manual conditioning (pre, post and remote), and pharmacological conditioning. Evidences from animal experiments and clinical trials suggested that all these strategies could potentially protect liver graft; however, their clinical applications are limited partially due to their own disadvantages.

CONCLUSIONS

There are a plenty of methods suggested to decrease the degree of donor liver transplantation-related injury. However, none of these approaches is perfect in clinical practice. More translational researches (molecular and clinical studies) are needed to improve the techniques in liver graft protection.

Subnormothermic ex vivo liver perfusion reduces endothelial cell and bile duct injury after donation after cardiac death pig liver transplantation

An ischemic-type biliary stricture (ITBS) is a common feature after liver transplantation using donation after cardiac death (DCD) grafts. We compared sequential subnormothermic ex vivo liver perfusion (SNEVLP; 33°C) with cold storage (CS) for the prevention of ITBS in DCD liver grafts in pig liver transplantation (n = 5 for each group). Liver grafts were stored for 10 hours at 4°C (CS) or preserved with combined 7-hour CS and 3-hour SNEVLP. Parameters of hepatocyte [aspartate aminotransferase (AST), international normalized ratio (INR), factor V, and caspase 3 immunohistochemistry], endothelial cell (EC; CD31 immunohistochemistry and hyaluronic acid), and biliary injury and function [alkaline phosphatase (ALP), total bilirubin, and bile lactate dehydrogenase (LDH)] were determined. Long-term survival (7 days) after transplantation was similar between the SNEVLP and CS groups (60% versus 40%, P = 0.13). No difference was observed between SNEVLP- and CS-treated animals with respect to the peak of serum INR, factor V, or AST levels within 24 hours. CD31 staining 8 hours after transplantation demonstrated intact EC lining in SNEVLP-treated livers (7.3 × 10(-4) ± 2.6 × 10(-4) cells/μm(2)) but not in CS-treated livers (3.7 × 10(-4) ± 1.3 × 10(-4) cells/μm(2) , P = 0.03). Posttransplant SNEVLP animals had decreased serum ALP and serum bilirubin levels in comparison with CS animals. In addition, LDH in bile fluid was lower in SNEVLP pigs versus CS pigs (14 ± 10 versus 60 ± 18 μmol/L, P = 0.02). Bile duct histology revealed severe bile duct necrosis in 3 of 5 animals in the CS group but none in the SNEVLP group (P = 0.03). Sequential SNEVLP preservation of DCD grafts reduces bile duct and EC injury after liver transplantation.

Hedgehog signaling pathway as key player in liver fibrosis: new insights and perspectives

INTRODUCTION

Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in liver fibrosis. Therefore, improving our understanding of the molecular pathways that are involved in these processes is essential to generate new therapies for liver fibrosis. Greater knowledge of the role of the hedgehog signaling pathway in liver fibrosis could improve understanding of the liver fibrosis pathogenesis.

AREAS COVERED

The aim of this review is to describe the present knowledge about the hedgehog signaling pathway, which significantly participates in liver fibrosis and HSC activation, and look ahead on new perspectives of hedgehog signaling pathway research. Moreover, we will discuss the different interactions with hedgehog signaling pathway-regulated liver fibrosis.

EXPERT OPINION

The hedgehog pathway modulates several important aspects of function, including cell proliferation, activation and differentiation. Targeting the hedgehog pathway can be a promising direction in liver fibrosis treatment. We discuss new perspectives of hedgehog signaling pathway activation in liver fibrosis and HSC fate, including DNA methylation, methyl CpG binding protein 2, microRNA, irradiation and metabolism that influence hedgehog signaling pathway transduction. These findings identify the hedgehog pathway as a potentially important for biomarker development and therapeutic targets in liver fibrosis. Future studies are needed in order to find safer and more effective hedgehog-based drugs.

Protective effects elicited by levosimendan against liver ischemia/reperfusion injury in anesthetized rats

As in other organs, oxidative stress-induced injury and cell death may result from free oxygen radical-dependent mechanisms and alterations in signal transduction pathways leading to apoptosis. Among the new suggested therapies for injuries caused by oxidative stress, the use of levosimendan has been reported to be quite promising. In the present study, we aimed to examine the protective effects of levosimendan against liver oxidative stress in anesthetized rats and to analyze the involvement of mitochondrial adenosine triphosphate-dependent potassium (mitoK(ATP)) channels and nitric oxide (NO). In 50 anesthetized rats, liver ischemia/reperfusion (I/R) was performed via nontraumatic portal occlusion. In some animals, levosimendan was infused into the portal vein at the onset of reperfusion, whereas other rats received the vehicle only. Moreover, in some rats, levosimendan was given after the intraportal administration of L-Nω-nitro-arginine methyl ester (L-NAME) or 5-hydroxydecanoate (5HD). The portal vein blood flow was measured, and blood samples were taken for the determination of transaminases, thiobarbituric acid reactive substances (TBARS), and reduced glutathione (GSH); liver biopsy samples were used for B cell lymphoma 2-associated X protein, caspase-9, Akt, and endothelial nitric oxide synthase (eNOS) activation through western blotting. Also, caspase-3 activity was measured. In rats, I/R caused an increase in apoptotic markers, transaminases, and TBARS and a decrease in GSH and Akt activation. Levosimendan administration was able to counteract oxidative damage and apoptosis in a dose-dependent way and to increase GSH, Akt, and eNOS activation. All effects of levosimendan were abolished by pretreatment with L-NAME and 5HD. In conclusion, the results of the present study show that levosimendan can exert protection against ischemic liver damage through mechanisms related to NO production and mitoKATP channel function. These data provide interesting perspectives into the use of levosimendan in hepatic surgery and transplantation.

Carbon monoxide protects against hepatic ischemia/reperfusion injury via ROS-dependent Akt signaling and inhibition of glycogen synthase kinase 3β

Carbon monoxide (CO) may exert important roles in physiological and pathophysiological states through the regulation of cellular signaling pathways. CO can protect organ tissues from ischemia/reperfusion (I/R) injury by modulating intracellular redox status and by inhibiting inflammatory, apoptotic, and proliferative responses. However, the cellular mechanisms underlying the protective effects of CO in organ I/R injury remain incompletely understood. In this study, a murine model of hepatic warm I/R injury was employed to assess the role of glycogen synthase kinase-3 (GSK3) and phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathways in the protective effects of CO against inflammation and injury. Inhibition of GSK3 through the PI3K/Akt pathway played a crucial role in CO-mediated protection. CO treatment increased the phosphorylation of Akt and GSK3-beta (GSK3β) in the liver after I/R injury. Furthermore, administration of LY294002, an inhibitor of PI3K, compromised the protective effect of CO and decreased the level of phospho-GSK3β after I/R injury. These results suggest that CO protects against liver damage by maintaining GSK3β phosphorylation, which may be mediated by the PI3K/Akt signaling pathway. Our study provides additional support for the therapeutic potential of CO in organ injury and identifies GSK3β as a therapeutic target for CO in the amelioration of hepatic injury.

Oxidative stress and apoptosis in a pig model of brain death (BD) and living donation (LD)

Background

As organ shortage is increasing, the acceptance of marginal donors increases, which might result in poor organ function and patient survival. Mostly, organ damage is caused during brain death (BD), cold ischemic time (CIT) or after reperfusion due to oxidative stress or the induction of apoptosis. The aim of this study was to study a panel of genes involved in oxidative stress and apoptosis and compare these findings with immunohistochemistry from a BD and living donation (LD) pig model and after cold ischemia time (CIT).

Methods

BD was induced in pigs; after 12 h organ retrieval was performed; heart, liver and kidney tissue specimens were collected in the BD (n = 6) and in a LD model (n = 6). PCR analysis for NFKB1, GSS, SOD2, PPAR-alpha, OXSR1, BAX, BCL2L1, and HSP 70.2 was performed and immunohistochemistry used to show apoptosis and nitrosative stress induced cell damage.

Results

In heart tissue of BD BAX, BCL2L1 and HSP 70.2 increased significantly after CIT. Only SOD2 was over-expressed after CIT in BD liver tissue. In kidney tissue, BCL2L1, NFKB, OXSR1, SOD2 and HSP 70.2 expression was significantly elevated in LD. Immunohistochemistry showed a significant increase in activated Caspase 3 and nitrotyrosine positive cells after CIT in BD in liver and in kidney tissue but not in heart tissue.

Conclusion

The up-regulation of protective and apoptotic genes seems to be divergent in the different organs in the BD and LD setting; however, immunohistochemistry revealed more apoptotic and nitrotyrosine positive cells in the BD setting in liver and kidney tissue whereas in heart tissue both BD and LD showed an increase.

Heme oxygenase-1 and gut ischemia/reperfusion injury: A short review

Ischemia/reperfusion (I/R) injury of the gut is a significant problem in a variety of clinical settings and is associated with a high morbidity and mortality. Although the mechanisms involved in the pathogenesis of gut I/R injury have not been fully elucidated, it is generally believed that oxidative stress with subsequent inflammatory injury plays an important role. Heme oxygenase (HO) is the rate-limiting enzyme in the catabolism of heme, followed by production of CO, biliverdin, and free iron. The HO system is believed to confer cytoprotection by inhibiting inflammation, oxidation, and apoptosis, and maintaining microcirculation. HO-1, an inducible form of HO, serves a vital metabolic function as the rate-limiting step in the heme degradation pathway, and affords protection in models of intestinal I/R injury. HO-1 system is an important player in intestinal I/R injury condition, and may offer new targets for the management of this condition.

Protective effect of heme oxygenase-1 on hepatic ischemia-reperfusion injury through inhibition of platelet adhesion to the sinusoids

BACKGROUND AND AIM

Heme oxygenase-1 (HO-1) acts as a protector against hepatic inflammatory injury. HO-1 catalyzes the conversion of heme protein to biliverdin, free iron, and carbon monoxide. Pro-inflammatory responses play critical roles in hepatic ischemia-reperfusion (I/R) injury, and carbon monoxide effectively downregulates I/R injury. The aim of this study was to evaluate the mechanism by which HO-1 reduces warm I/R injury.

METHODS

Sprague-Dawley rats were divided into two groups: the 20-min ischemia group (control group; n = 6) and the 20-min ischemia with cobalt protoporphyrin (CoPP group; n = 6). CoPP is an inducer of HO-1 in the sinusoids. Kupffer cells were labeled using the liposome entrapment method, and platelets were labeled with rhodamine-6G. The adherent platelets were observed for up to 120 min after reperfusion by intravital microscopy.

RESULTS

In the control group, the number of adherent platelets significantly increased than in the CoPP group. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were observed after 120 min of reperfusion in the control group. They were not observed in the CoPP group. In the CoPP group, serum alanine transaminase and interleukin-6 levels reduced after reperfusion. Moreover, the flow velocity of platelets in the hepatic sinusoid markedly increased.

CONCLUSIONS

This study suggests that HO-1 inhibits platelet adhesion to sinusoids. Such inhibition leads to the prevention of hepatic I/R injury.

The immunomodulatory role of carbon monoxide during transplantation

The number of organ and tissue transplants has increased worldwide in recent decades. However, graft rejection, infections due to the use of immunosuppressive drugs and a shortage of graft donors remain major concerns. Carbon monoxide (CO) had long been regarded solely as a poisonous gas. Ultimately, physiological studies unveiled the endogenous production of CO, particularly by the heme oxygenase (HO)-1 enzyme, recognizing CO as a beneficial gas when used at therapeutic doses. The protective properties of CO led researchers to develop uses for it, resulting in devices and molecules that can deliver CO in vitro and in vivo. The resulting interest in clinical investigations was immediate. Studies regarding the CO/HO-1 modulation of immune responses and their effects on various immune disorders gave rise to transplantation research, where CO was shown to be essential in the protection against organ rejection in animal models. This review provides a perspective of how CO modulates the immune system to improve transplantation and suggests its use as a therapy in the field.

Emulsified isoflurane preconditioning protects isolated rat Kupffer cells against hypoxia/reoxygenation-induced injury

OBJECTIVE

To investigate the protective effect of emulsified isoflurane (EI) preconditioning on isolated rat Kupffer cells (KCs) subjected to hypoxia/reoxygenation (H/R)-induced injury.

MATERIALS AND METHODS

KCs were isolated by collagenase digestion and purified by Percoll density gradient centrifugation. Primary cultured KCs were divided into five groups: control, H/R plus 0.1% lipid preconditioning, and H/R plus 0.05%, 0.1% or 0.2% emulsified isoflurane preconditioning groups. H/R was induced by 4 h of hypoxia followed by 6 h of reoxygenation. Reactive oxygen species (ROS) production in the KCs and the concentration of tumor necrosis factor-α (TNF-α) in the KC culture media were measured, and the apoptosis of KCs was assayed concomitantly.

RESULTS

ROS and TNF-α production were markedly induced in the H/R + lipid group, and lower in the 0.2% and 0.1% EI groups (P<0.05). The apoptotic rate in the H/R + lipid group was significantly higher than that in the 0.2% and 0.1% EI groups (P<0.05).

CONCLUSIONS

Emulsified isoflurane protects isolated rat KCs against H/R induced injury by decreasing the production of ROS and TNF-α and attenuating apoptosis in KCs.

Liver-protecting effects of omega-3 fish oil lipid emulsion in liver transplantation

AIM

To investigate the liver-protecting effect of parenteral nutrition (PN) support with omega-3 fatty acids in a randomized controlled clinical trial.

METHODS

Sixty-six patients with the diagnosis of end-stage liver disease or hepatic cellular carcinoma were admitted to the Affiliated Drum Tower Hospital, Nanjing University, China for orthotopic liver transplantation. The patients were randomly divided into two groups: PN group (n = 33) and polyunsaturated fatty acid (PUFA) group (n = 33). All patients received isocaloric and isonitrogenous PN for seven days after surgery, and in PUFA group omega-3 fish oil lipid emulsion replaced part of the standard lipid emulsion. Liver function was tested on days 2 and 9 after surgery. Pathological examination was performed after reperfusion of the donor liver and on day 9. Clinical outcome was assessed based on the post-transplant investigations, including: (1) post-transplant mechanical ventilation; (2) total hospital stay; (3) infectious morbidities; (4) acute and chronic rejection; and (5) mortality (intensive care unit mortality, hospital mortality, 28-d mortality, and survival at a one-year post-transplant surveillance period).

RESULTS

On days 2 and 9 after operation, a significant decrease of alanine aminotransferase (299.16 U/L ± 189.17 U/L vs 246.16 U/L ± 175.21 U/L, P = 0.024) and prothrombin time (5.64 s ± 2.06 s vs 2.54 s ± 1.15 s, P = 0.035) was seen in PUFA group compared with PN group. The pathological results showed that omega-3 fatty acid supplement improved the injury of hepatic cells. Compared with PN group, there was a significant decrease of post-transplant hospital stay in PUFA group (18.7 d ± 4.0 d vs 20.6 d ± 4.6 d, P = 0.041). Complications of infection occurred in 6 cases of PN group (2 cases of pneumonia, 3 cases of intra-abdominal abscess and 1 case of urinary tract infection), and in 3 cases of PUFA group (2 cases of pneumonia and 1 case of intra-abdominal abscess). No acute or chronic rejection and hospital mortality were found in both groups. The one-year mortality in PN group was 9.1% (3/33), one died of pulmonary infection, one died of severe intra-hepatic cholangitis and hepatic dysfunction and the other died of hepatic cell carcinoma recurrence. Only one patient in PUFA group (1/33, 3.1%) died of biliary complication and hepatic dysfunction during follow-up.

CONCLUSION

Post-transplant parenteral nutritional support combined with omega-3 fatty acids can significantly improve the liver injury, reduce the infectious morbidities, and shorten the post-transplant hospital stay.