Prevention of hepatic ischemia/reperfusion injury by prolonged delivery of nitric oxide to the circulating blood in mice. Transplantation. 2008;85:264-269. [PMID: 18212632 DOI: 10.1097/tp.0b013e31815e902b]

Hepatic ischemia reperfusion injury: effect of moderate intensity exercise and oxytocin compared to l-arginine in a rat model

Background

Hepatic ischemia reperfusion (IR) injury is considered as a main cause of liver damage and dysfunction. The l-arginine/nitric oxide pathway seems to be relevant during this process of IR. Although acute intense exercise challenges the liver with increased reactive oxygen species (ROS), regular training improves hepatic antioxidant status. Also, oxytocin (Oxy), besides its classical functions, it exhibits a potent antistress, anti-inflammatory, and antioxidant effects. This study was designed to evaluate the hepatic functional and structural changes induced by hepatic IR injury in rats and to probe the effect and potential mechanism of moderate intensity exercise training and/or Oxy, in comparison to a nitric oxide donor, l-arginine, against liver IR-induced damage.

Results

Compared to the sham-operated control group, the hepatic IR group displayed a significant increase in serum levels of ALT and AST, plasma levels of MDA and TNF-α, and significant decrease in plasma TAC and nitrite levels together with the worsening of liver histological picture. L-Arg, Oxy, moderate intensity exercise, and the combination of both Oxy and moderate intensity exercises ameliorated these deleterious effects that were evident by the significant decrease in serum levels of ALT and AST, significant elevation in TAC and nitrite, and significant decline in lipid peroxidation (MDA) and TNF-α, besides regression of histopathological score regarding hepatocyte necrosis, vacuolization, and nuclear pyknosis. Both the moderate intensity exercise-trained group and Oxy-treated group showed a significant decline in TNF-α and nitrite levels as compared to l-Arg-treated group. The Oxy-treated group showed statistical insignificant changes in serum levels of ALT, AST, and plasma levels of nitrite, MDA, TAC, and TNF-α as compared to moderate intensity exercise-trained group.

Conclusion

The combination of both moderate intensity exercise and Oxy displayed more pronounced hepatoprotection on comparison with l-Arg which could be attributed to their more prominent antioxidant and anti-inflammatory effects but not due to their NO-enhancing effect.

Inhaled nitric oxide and acute kidney injury risk: a meta-analysis of randomized controlled trials

Purpose

There are conflicting results as to the effect of inhaled nitric oxide (iNO) therapy on the risk of acute kidney injury (AKI). The aim of this study was to perform a meta-analysis to assess the updated data.

Methods

We systematically searched Web of Science, the Cochrane Library, Wanfang, and PubMed for relevant randomized control trials between database inception and 9/07/2020. Relative risks (RRs) with 95% confidence intervals (CIs) predicting the risk of AKI were extracted to obtain summary estimates using fixed-effects models. The Trim and Fill method was used to evaluate the sensitivity of the results and adjust for publication bias in meta-analysis.

Results

15 randomized controlled studies from 14 articles involving 1853 patients were included in the study. Analyzing the eligible studies we found: (1) iNO therapy significantly increased the risk of AKI in acute respiratory distress syndrome patients (RR 1.55, 95% CI 1.15–2.10, p = 0.004; I² for heterogeneity 0%; P_het = 0.649). (2) The use of iNO was associated with reduced AKI risk in patients undergoing cardiac surgery (RR 0.80, 95% CI 0.64–0.99, p = 0.037; I² for heterogeneity 0%; P_het = 0.528). (3) For organ transplantation recipients, there was no effect of iNO administration on the risk of AKI (RR 0.50, 95% CI 0.16–1.56, p = 0.233; I² for heterogeneity 0%; P_het = 0.842). The Trim and Fill analysis showed that the overall effect of this meta-analysis was stable.

Conclusions

The effect of iNO on AKI risk might be disease-specific. Future RCTs with larger patient populations should aim to validate our findings.

Glycocalyx Preservation and NO Production in Fatty Livers-The Protective Role of High Molecular Polyethylene Glycol in Cold Ischemia Injury

Improving the protection of marginal liver grafts during static cold storage is a major hurdle to increase the donor pool of organs. The endothelium glycocalyx quality of preservation influences future inflammatory and oxidative responses. One cellular pathway responsible for the formation of nitric oxide by endothelial cells is dependent on the stimulation of proteoglycans present in the glycocalyx. We investigated the impact of the glycocalyx preservation in static cold storage of fatty liver preserved in different preservation solutions on the endothelium-mediated production of NO. Zucker fatty rat livers were preserved 24 h in static cold storage in either Institut Georges Lopez-1 (IGL-1) (n = 10), IGL-0 (i.e., without PEG35) (n = 5) or Histidine-Tryptophan-Ketoglutarate (HTK) (n = 10) preservation solutions before being processed for analysis. For Sham group (n = 5), the fatty livers were immediately analyzed after procurement. The level of transaminases and nitrites/nitrates were measured in the washing perfusate. Glycocalyx proteins expressions, Syndecan-1, glypican-1 and heparan sulfate (HS), were determined in the tissue (ELISA). Steatotic livers preserved 24 h in IGL-1 preservation solution have a significant lower level of transaminases (aspartate aminotransferase (AST), alanine aminotransferase (ALT)) and less histological damages than steatotic livers preserved 24 h with HTK (p = 0.0152). The syndecan-1 is significantly better preserved in IGL-1 group compared to HTK (p < 0.0001) and we observed the same tendency compared to IGL-0. No significant differences were observed with glypican-1. HS expression in HTK group was significantly higher compared to the three other groups. HS level in IGL-1 was even lower than IGL-0 (p = 0.0005) which was similar to Sham group. The better protection of the glycocalyx proteins in IGL-1 group was correlated with a higher production of NO than HTK (p = 0.0055) or IGL-0 (p = 0.0433). IGL-1 protective mechanisms through the formation of NO could be due to its better protective effects on the glycocalyx during SCS compared to other preservation solutions. This beneficial effect could involve the preservation state of syndecan-1 and the internalization of HS.

Emerging graft protective strategies in clinical liver transplantation

There have been remarkable efforts to characterize the key responsible pathophysiologic mechanisms, as well as to ameliorate the organ preservation and ischemia reperfusion injury with the ultimate goal of expanding the donor pool and further improvement of the outcomes of liver transplantation. Attempts to translate the experimental results from bench to bedside have yielded no valid protective concepts in the field of clinical liver transplantation yet. Nonetheless, there has been a considerable amount of ongoing clinical research to develop clinically relevant graft protective strategies. Areas covered: This review focuses on the most recent evidence based findings and ongoing clinical trials that might lead to emerging graft protective strategies in the field of clinical liver transplantation. New evidence-based findings in the donor preconditioning, organ preservation, and perioperative pharmacologic graft protection strategies in the recipient are reviewed. Expert commentary: Few strategies have been shown to exert some graft protective effects against ischemia reperfusion injury in recent clinical trials in liver transplantation. Among others, 'dynamic graft preservation' techniques have been emerging as more promising graft optimization strategies.

Role of nitric oxide in liver transplantation: Should it be routinely used?

Ischemia-reperfusion injury (IRI) continues to be a major contributor to graft dysfunction, thus supporting the need for therapeutic strategies focused on minimizing organ damage especially with growing numbers of extended criteria grafts being utilized which are more vulnerable to cold and warm ischemia. Nitric oxide (NO·) is highly reactive gaseous molecule found in air and regarded as a pollutant. Not surprising, it is extremely bioactive, and has been demonstrated to play major roles in vascular homeostasis, neurotransmission, and host defense inflammatory reactions. Under conditions of ischemia, NO· has consistently been demonstrated to enhance microcirculatory vasorelaxation and mitigate pro-inflammatory responses, making it an excellent strategy for patients undergoing organ transplantation. Clinical studies designed to test this hypothesis have yielded very promising results that includes reduced hepatocellular injury and enhanced graft recovery without any identifiable complications. By what means NO· facilitates extra-pulmonary actions is up for debate and speculation. The general premise is that they are NO· containing intermediates in the circulation, that ultimately mediate either direct or indirect effects. A plethora of data exists explaining how NO·-containing intermediate molecules form in the plasma as S-nitrosothiols (e.g., S-nitrosoalbumin), whereas other compelling data suggest nitrite to be a protective mediator. In this article, we discuss the use of inhaled NO· as a way to protect the donor liver graft against IRI in patients undergoing liver transplantation.

Development of PEGylated Cysteine-Modified Lysine Dendrimers with Multiple Reduced Thiols To Prevent Hepatic Ischemia/Reperfusion Injury

To inhibit hepatic ischemia/reperfusion injury, we developed polyethylene glycol (PEG) conjugated (PEGylated) cysteine-modified lysine dendrimers with multiple reduced thiols, which function as scavengers of reactive oxygen species (ROS). Second, third, and fourth generation (K2, K3, and K4) highly branched amino acid spherical lysine dendrimers were synthesized, and cysteine (C) was conjugated to the outer layer of these lysine dendrimers to obtain K2C, K3C, and K4C dendrimers. Subsequently, PEG was reacted with the C residues of the dendrimers to obtain PEGylated dendrimers with multiple reduced thiols (K2C-PEG, K3C-PEG, and K4C-PEG). Radiolabeled K4C-PEG ((111)In-K4C-PEG) exhibited prolonged retention in the plasma, whereas (111)In-K2C-PEG and (111)In-K3C-PEG rapidly disappeared from the plasma. K4C-PEG significantly prevented the elevation of plasma alanine aminotransferase (ALT) activity, an index of hepatocyte injury, in a mouse model of hepatic ischemia/reperfusion injury. In contrast, K2C-PEG, K3C-PEG, l-cysteine, and glutathione, the latter two of which are classical reduced thiols, hardly affected the plasma ALT activity. These findings indicate that K4C-PEG with prolonged circulation time is a promising compound to inhibit hepatic ischemia/reperfusion injury.

Protection of rat liver against hepatic ischemia-reperfusion injury by a novel selenocysteine-containing 7-mer peptide

Hepatic ischemia-reperfusion (I-R) injury causes acute organ damage or dysfunction, and remains a problem for liver transplantation. In the I-R phase, the generation of reactive oxygen species aggravates the injury. In the current study, a novel selenocysteine-containing 7‑mer peptide (H-Arg-Sec-Gly-Arg-Asn-Ala-Gln-OH) was constructed to imitate the active site of an antioxidant enzyme, glutathione peroxidase (GPX). The 7‑mer peptide which has a lower molecular weight, and improved water‑solubility, higher stability and improved cell membrane permeability compared with other GPX mimics. Its GPX activity reached 13 U/µmol, which was 13 times that of ebselen (a representative GPX mimic). The effect of this GPX mimic on I‑R injury of the liver was assessed in rats. The 7‑mer peptide significantly inhibited the increase in serum hepatic amino‑transferases, tissue malondialdehyde, nitric oxide contents, myeloperoxidase activity and decrease of GPX activity compared with I‑R tissue. Following treatment with the 7‑mer peptide, the expression of B‑cell CLL/lymphoma‑2 (Bcl‑2) was significantly upregulated at the mRNA and protein level compared with the I‑R group, as determined by reverse transcription‑polymerase chain reaction and immunohistochemistry, respectively. By contrast, Bcl‑2 associated X protein (Bax) was downregulated by the 7‑mer peptide compared the I‑R group. Histological and ultrastructural changes of the rat liver tissue were also compared among the experimental groups. The results of the current study suggest that the 7‑mer peptide protected the liver against hepatic I‑R injury via suppression of oxygen‑derived free radicals and regulation of Bcl‑2 and Bax expression, which are involved in the apoptosis of liver cells. The findings of the present study will further the investigation of the 7-mer peptide as an effective therapeutic agent in hepatic I-R injury.

In vivo pharmacological activity and biodistribution of S-nitrosophytochelatins after intravenous and intranasal administration in mice

S-nitrosophytochelatins (SNOPCs) are novel analogues of S-nitrosoglutathione (GSNO) with the advantage of carrying varying ratios of S-nitrosothiol (SNO) moieties per molecule. Our aim was to investigate the in vivo pharmacological potency and biodistribution of these new GSNO analogues after intravenous (i.v.) and intranasal (i.n.) administration in mice. SNOPCs with either two or six SNO groups and GSNO were synthesized and characterized for purity. Compounds were administered i.v. or i.n. at 1 μmol NO/kg body weight to CD-1 mice. Blood pressure was measured and biodistribution studies of total nitrate and nitrite species (NOx) and phytochelatins were performed after i.v. administration. At equivalent doses of NO, it was observed that SNOPC-6 generated a rapid and significantly greater reduction in blood pressure (∼60% reduction compared to saline) whereas GSNO and SNOPC-2 only achieved a 30-35% decrease. The reduction in blood pressure was transient and recovered to baseline levels within ∼2 min for all compounds. NOx species were transiently elevated (over 5 min) in the plasma, lung, heart and liver. Interestingly, a size-dependent phytochelatin accumulation was observed in several tissues including the heart, lungs, kidney, brain and liver. Biodistribution profiles of NOx were also obtained after i.n. administration, showing significant lung retention of NOx over 15 min with minor systemic increases observed from 5 to 15 min. In summary, this study has revealed interesting in vivo pharmacological properties of SNOPCs, with regard to their dramatic hypotensive effects and differing biodistribution patterns following two different routes of administration.

Potential Use of Biological Proteins for Liver Failure Therapy

Biological proteins have unlimited potential for use as pharmaceutical products due to their various biological activities, which include non-toxicity, biocompatibility, and biodegradability. Recent scientific advances allow for the development of novel innovative protein-based products that draw on the quality of their innate biological activities. Some of them hold promising potential for novel therapeutic agents/devices for addressing hepatic diseases such as hepatitis, fibrosis, and hepatocarcinomas. This review attempts to provide an overview of the development of protein-based products that take advantage of their biological activity for medication, and discusses possibilities for the therapeutic potential of protein-based products produced through different approaches to specifically target the liver (or hepatic cells: hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells, and Kupffer cells) in the treatment of hepatic diseases.

Pharmacokinetics and preventive effects of platinum nanoparticles as reactive oxygen species scavengers on hepatic ischemia/reperfusion injury in mice

Reactive oxygen species (ROS) are involved in the pathophysiology of ischemia/reperfusion injury. To protect mouse hepatocytes from ischemia/reperfusion injury, we prepared two different sizes of citric acid-protected platinum nanoparticles (Pt-NPs), which exhibited ROS-scavenging activities and selective delivery to a specific type of liver cell. Small Pt-NPs (30 nm) reduced the superoxide anion, hydrogen peroxide, and hydroxyl radical levels in solution to a greater extent than did large Pt-NPs (106 nm). Large and small Pt-NPs predominantly accumulated in hepatic nonparenchymal cells after intravenous injection into mice. In a mouse model of ischemia/reperfusion injury, in which hepatic injury was induced by occluding the portal vein for 15 min followed by 6 h reperfusion, the increase in plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities was inhibited by a bolus intravenous injection of either large or small Pt-NPs. However, small Pt-NPs inhibited the increase in these markers of hepatic injury to a greater extent than did large Pt-NPs. These results indicate that Pt-NPs can be used to prevent hepatic ischemia/reperfusion injury. To our knowledge, this is the first report demonstrating the pharmacokinetics and efficacy of Pt-NPs to prevent hepatic ischemia/reperfusion injury.

A randomized clinical trial testing the anti-inflammatory effects of preemptive inhaled nitric oxide in human liver transplantation

Decreases in endothelial nitric oxide synthase derived nitric oxide (NO) production during liver transplantation promotes injury. We hypothesized that preemptive inhaled NO (iNO) would improve allograft function (primary) and reduce complications post-transplantation (secondary). Patients at two university centers (Center A and B) were randomized to receive placebo (n = 20/center) or iNO (80 ppm, n = 20/center) during the operative phase of liver transplantation. Data were analyzed at set intervals for up to 9-months post-transplantation and compared between groups. Patient characteristics and outcomes were examined with the Mann-Whitney U test, Student t-test, logistic regression, repeated measures ANOVA, and Cox proportional hazards models. Combined and site stratified analyses were performed. MELD scores were significantly higher at Center B (22.5 vs. 19.5, p<0.0001), surgical times were greater at Center B (7.7 vs. 4.5 hrs, p<0.001) and warm ischemia times were greater at Center B (95.4 vs. 69.7 min, p<0.0001). No adverse metabolic or hematologic effects from iNO occurred. iNO enhanced allograft function indexed by liver function tests (Center B, p<0.05; and p<0.03 for ALT with center data combined) and reduced complications at 9-months (Center A and B, p = 0.0062, OR = 0.15, 95% CI (0.04, 0.59)). ICU (p = 0.47) and hospital length of stay (p = 0.49) were not decreased. iNO increased concentrations of nitrate (p<0.001), nitrite (p<0.001) and nitrosylhemoglobin (p<0.001), with nitrite being postulated as a protective mechanism. Mean costs of iNO were $1,020 per transplant. iNO was safe and improved allograft function at one center and trended toward improving allograft function at the other. ClinicalTrials.gov with registry number 00582010 and the following URL:http://clinicaltrials.gov/show/NCT00582010.

Protective effect of lisinopril on hepatic ischemia/reperfusion injury in rats

Objective:

Ischemia/reperfusion (I/R) injury plays a key role in the pathogenesis of hepatic failure in several clinical settings such as liver resection or transplantation. Lisinopril, a widely prescribed drug for various cardiovascular conditions, has been reported to have diverse pharmacological properties. The aim of this study, therefore, was to evaluate a potential protective effect of lisinopril on hepatic I/R injury in rats.

Materials and Methods:

In anesthetized rats, partial hepatic ischemia was applied for one hour followed by two hours reperfusion. Biochemical analysis of serum and hepatic tissue was done. Hepatic tissue was also subjected to electron microscopy.

Results:

Pre-ischemic treatment with lisinopril (10 mg/kg) exerted protection against I/R-induced hepatocellular injury as evident by significant decrease in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin levels, along with hepatic lipid peroxidation, expressed as malondialdehyde content, with a concurrent increase in hepatic nitric oxide content as compared to I/R group. The electron microscopic examination indicated that lisinopril can effectively protect against hepatic I/R injury.

Conclusion:

Lisinopril provides a protection against hepatic I/R injury in rats. The protective effect is associated with reduction of oxidative stress-induced lipid peroxidation level and enhancement of nitric oxide availability.

The nitric oxide pathway--evidence and mechanisms for protection against liver ischaemia reperfusion injury

Ischaemia reperfusion (IR) injury is a clinical entity with a major contribution to the morbidity and mortality of liver surgery and transplantation. A central pathway of protection against IR injury utilizes nitric oxide (NO). Nitric oxide synthase (NOS) enzymes manufacture NO from L-arginine. NO generated by the endothelial NOS (eNOS) isoform protects against liver IR injury, whereas inducible NOS (iNOS)-derived NO may have either a protective or a deleterious effect during the early phase of IR injury, depending on the length of ischaemia, length of reperfusion and experimental model. In late phase hepatic IR injury, iNOS-derived NO plays a protective role. In addition to NOS consumption of L-arginine during NO synthesis, this amino acid may also be metabolized by arginase, an enzyme whose release is increased during prolonged ischaemia, and therefore diverts L-arginine away from NOS metabolism leading to a drop in the rate of NO synthesis. NO most commonly acts through the soluble guanylyl cyclase-cyclic GMP- protein kinase G pathway to ameliorate hepatic IR injury. Both endogenously generated and exogenously administered NO donors protect against liver IR injury. The beneficial effects of NO on liver IR are not, however, universal, and certain conditions, such as steatosis, may influence the protective effects of NO. In this review, the evidence for, and mechanisms of these protective actions of NO are discussed, and areas in need of further research are highlighted.

How to protect liver graft with nitric oxide

Organ preservation and ischemia reperfusion injury associated with liver transplantation play an important role in the induction of graft injury. One of the earliest events associated with the reperfusion injury is endothelial cell dysfunction. It is generally accepted that endothelial nitric oxide synthase (e-NOS) is cell-protective by mediating vasodilatation, whereas inducible nitric oxide synthase mediates liver graft injury after transplantation. We conducted a critical review of the literature evaluating the potential applications of regulating and promoting e-NOS activity in liver preservation and transplantation, showing the most current evidence to support the concept that enhanced bioavailability of NO derived from e-NOS is detrimental to ameliorate graft liver preservation, as well as preventing subsequent graft reperfusion injury. This review deals mainly with the beneficial effects of promoting “endogenous” pathways for NO generation, via e-NOS inducer drugs in cold preservation solution, surgical strategies such as ischemic preconditioning, and alternative “exogenous” pathways that focus on the enrichment of cold storage liquid with NO donors. Finally, we also provide a basic bench-to-bed side summary of the liver physiology and cell signalling mechanisms that account for explaining the e-NOS protective effects in liver preservation and transplantation.

Divergent roles of superoxide and nitric oxide in liver ischemia and reperfusion injury

Liver ischemia and reperfusion-induced injury is a major clinical complication associated with hemorrhagic or endotoxin shock and thermal injury as well as liver transplantation and resectional surgery. Data obtained from several different studies suggest that an important initiating event in the pathophysiology of ischemia and reperfusion-induced tissue injury is enhanced production of superoxide concomitant with a decrease in the bioavailability of endothelial cell-derived nitric oxide. This review will summarize the evidence supporting the hypothesis that the redox imbalance induced by alterations in superoxide and nitric oxide generation creates a more oxidative environment within the different cells of the liver that enhances the nuclear transcription factor-κB-dependent expression of a variety of different cytokines and mediators that may promote as well as limit ischemia and reperfusion-induced hepatocellular injury. In addition, the evidence implicating endothelial cell nitric oxide synthase-dependent and -independent generation of nitric oxide as important regulatory pathways that act to limit ischemia and reperfusion-induced liver injury and inflammation is also presented.

Role of nitric oxide in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) occurs upon restoration of hepatic blood flow after a period of ischemia. Decreased endogenous nitric oxide (NO) production resulting in capillary luminal narrowing is central in the pathogenesis of IRI. Exogenous NO has emerged as a potential therapy for IRI based on its role in decreasing oxidative stress, cytokine release, leukocyte endothelial-adhesion and hepatic apoptosis. This review will highlight the influence of endogenous NO on hepatic IRI, role of inhaled NO in ameliorating IRI, modes of delivery, donor drugs and potential side effects of exogenous NO.

Effects of a calcium-channel blocker (CV159) on hepatic ischemia/reperfusion injury in rats: evaluation with selective NO/pO2 electrodes and an electron paramagnetic resonance spin-trapping method

Nitric oxide (NO) and the partial pressure of oxygen (pO(2)) in the liver were simultaneously quantified in rats with partial hepatic ischemia/reperfusion injury (PHIRI). Real-time NO/pO(2) monitoring and immunohistochemical analysis for superoxide dismutase and inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) were performed to evaluate the protective effects of a dihydropyridine-type calcium-channel blocker--CV159--on PHIRI. Serum high-mobility-group box-1 (HMGB-1) was measured to assess cellular necrosis. Moreover, we used in vitro/ex vivo electron paramagnetic resonance spin trapping to assess the hydroxyl radical (*OH)-scavenging activity (OHSA) of CV159 and the liver tissue. The NO levels were significantly higher in CV159-treated rats than in control rats throughout the ischemic phase. Immediately after reperfusion, the levels temporarily increased in waves and then gradually decreased in the treated rats but remained constant in the control rats. pO(2) was continually higher in the treated rats. In these rats, hepatic eNOS expression increased, whereas iNOS expression decreased. The treated rats exhibited significantly higher cytosolic and mitochondrial concentrations NOx (NO(2)+NO(3)). The serum HMGB-1 levels significantly decreased in the treated rats. Moreover, CV159 directly scavenged *OH and both mitochondrial and cytosolic OHSA were preserved in the treated rats. Thus, CV159-mediated inhibition of intracellular Ca(2+) overloading may effectively minimize organ damage and also have *OH-scavenging activity and the cytoprotective effects of eNOS-derived NO.

Nitric oxide and redox regulation in the liver: part II. Redox biology in pathologic hepatocytes and implications for intervention

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are created in normal hepatocytes and are critical for normal physiologic processes, including oxidative respiration, growth, regeneration, apoptosis, and microsomal defense. When the levels of oxidation products exceed the capacity of normal antioxidant systems, oxidative stress occurs. This type of stress, in the form of ROS and RNS, can be damaging to all liver cells, including hepatocytes, Kupffer cells, stellate cells, and endothelial cells, through induction of inflammation, ischemia, fibrosis, necrosis, apoptosis, or through malignant transformation by damaging lipids, proteins, and/or DNA. In Part I of this review, we will discuss basic redox biology in the liver, including a review of ROS, RNS, and antioxidants, with a focus on nitric oxide as a common source of RNS. We will then review the evidence for oxidative stress as a mechanism of liver injury in hepatitis (alcoholic, viral, nonalcoholic). In Part II of this review, we will review oxidative stress in common pathophysiologic conditions, including ischemia/reperfusion injury, fibrosis, hepatocellular carcinoma, iron overload, Wilson's disease, sepsis, and acetaminophen overdose. Finally, biomarkers, proteomic, and antioxidant therapies will be discussed as areas for future therapeutic interventions.

Prevention of ischemia/reperfusion injury by hepatic targeting of nitric oxide in mice

Macromolecular nitric oxide (NO) donors possessing the ability to target a specific type of liver cells were developed for delivering NO to the liver. Six NO molecules were covalently bound to mannosylated (Man) or galactosylated (Gal) bovine serum albumin (BSA) through an S-nitrosothiol linkage to obtain Man-poly SNO-BSA and Gal-poly SNO-BSA, respectively. The carrier parts of Man-poly SNO-BSA and Gal-poly SNO-BSA predominantly accumulated in the liver after intravenous injection in mice. In an ischemia/reperfusion injury mouse model, in which hepatic injury was induced by occluding the portal vein for 15 min followed by a 6 h reperfusion, the elevation of plasma alanine aminotransferase and aspartate aminotransferase levels was significantly inhibited by a bolus intravenous injection of Man-poly SNO-BSA or Gal-poly SNO-BSA, just before the start of reperfusion. In marked contrast, S-nitroso-N-acetyl penicillamine and NO-conjugated BSA, two classical S-nitrosothiols, had no statistically significant effects on the serum levels of the markers. The released NO in mouse liver was detected by electron spin resonance spectrometry only in the liver of mice receiving Man-poly SNO-BSA or Gal-poly-SNO-BSA. These findings indicate that Man-poly SNO-BSA and Gal-poly SNO-BSA are promising compounds for preventing hepatic ischemia/reperfusion injury by delivering pharmacologically active NO to the liver.

Hepatocellular protection by nitric oxide or nitrite in ischemia and reperfusion injury

Ischemia and reperfusion (I/R)-induced liver injury occurs in several pathophysiological disorders including hemorrhagic shock and burn as well as resectional and transplantation surgery. One of the earliest events associated with reperfusion of ischemic liver is endothelial dysfunction characterized by the decreased production of endothelial cell-derived nitric oxide (NO). This rapid post-ischemic decrease in NO bioavailability appears to be due to decreased synthesis of NO, enhanced inactivation of NO by the overproduction of superoxide or both. This review presents the most current evidence supporting the concept that decreased bioavailability of NO concomitant with enhanced production of reactive oxygen species initiates hepatocellular injury and that endogenous NO or exogenous NO produced from nitrite play important roles in limiting post-ischemic tissue injury.

Treatment of liver ischemia-reperfusion injury by limiting thrombospondin-1/CD47 signaling

BACKGROUND

Ischemia-reperfusion (I/R) injury remains a primary complication of transplant surgery, accounting for about 80% of liver transplant failures, and is a major source of morbidity in other pathologic conditions. Activation of endothelium and inflammatory cell recruitment are central to the initiation and promulgation of I/R injury, which can be limited by the bioactive gas nitric oxide (NO). The discovery that thrombsospondin-1 (TSP1), via CD47, limits NO signaling in vascular cells and ischemic injuries in vivo suggested that I/R injury could be another important target of this signaling pathway.

METHODS

Wild-type, TSP1-null, and CD47-null mice underwent liver I/R injury. Wild-type animals were pretreated with CD47 or control antibodies before liver I/R injury. Tissue perfusion via laser Doppler imaging, serum enzymes, histology, and immunohistology were assessed.

RESULTS

TSP1-null and CD47-null mice subjected to subtotal liver I/R injury showed improved perfusion relative to wild-type mice. Null mice subjected to liver I/R had decreased liver enzyme release and less histologic evidence of injury. Elevated TSP1 expression in liver tissue after I/R injury suggested that preventing its interaction with CD47 could be protective. Thus, pretreatment of wild-type mice using a blocking CD47 antibody improved recovery of tissue perfusion and preserved liver integrity after I/R injury.

CONCLUSIONS

Tissue survival and perfusion after liver I/R injury are limited by TSP1 and CD47. Targeting CD47 before I/R injury enhances tissue survival and perfusion in a model of liver I/R injury and suggests therapeutics for enhancing organ survival in transplantation surgery.

Ischemia of the lung causes extensive long-term pulmonary injury: an experimental study

Background

Lung ischemia-reperfusion injury (LIRI) is suggested to be a major risk factor for development of primary acute graft failure (PAGF) following lung transplantation, although other factors have been found to interplay with LIRI. The question whether LIRI exclusively results in PAGF seems difficult to answer, which is partly due to the lack of a long-term experimental LIRI model, in which PAGF changes can be studied. In addition, the long-term effects of LIRI are unclear and a detailed description of the immunological changes over time after LIRI is missing. Therefore our purpose was to establish a long-term experimental model of LIRI, and to study the impact of LIRI on the development of PAGF, using a broad spectrum of LIRI parameters including leukocyte kinetics.

Methods

Male Sprague-Dawley rats (n = 135) were subjected to 120 minutes of left lung warm ischemia or were sham-operated. A third group served as healthy controls. Animals were sacrificed 1, 3, 7, 30 or 90 days after surgery. Blood gas values, lung compliance, surfactant conversion, capillary permeability, and the presence of MMP-2 and MMP-9 in broncho-alveolar-lavage fluid (BALf) were determined. Infiltration of granulocytes, macrophages and lymphocyte subsets (CD45RA⁺, CD5⁺CD4⁺, CD5⁺CD8⁺) was measured by flowcytometry in BALf, lung parenchyma, thoracic lymph nodes and spleen. Histological analysis was performed on HE sections.

Results

LIRI resulted in hypoxemia, impaired left lung compliance, increased capillary permeability, surfactant conversion, and an increase in MMP-2 and MMP-9. In the BALf, most granulocytes were found on day 1 and CD5⁺CD4⁺ and CD5⁺CD8⁺-cells were elevated on day 3. Increased numbers of macrophages were found on days 1, 3, 7 and 90. Histology on day 1 showed diffuse alveolar damage, resulting in fibroproliferative changes up to 90 days after LIRI.

Conclusion

The short-, and long-term changes after LIRI in this model are similar to the changes found in both PAGF and ARDS after clinical lung transplantation. LIRI seems an independent risk factor for the development of PAGF and resulted in progressive deterioration of lung function and architecture, leading to extensive immunopathological and functional abnormalities up to 3 months after reperfusion.