Comparison of the effect of adenoviral delivery of three superoxide dismutase genes against hepatic ischemia-reperfusion injury

SOD2 overexpression in bone marrow‑derived mesenchymal stem cells ameliorates hepatic ischemia/reperfusion injury

Hepatic ischemia/reperfusion injury (HIRI) is a complex pathophysiological process that may develop after liver transplantation and resection surgery, as well as in uncontrolled clinical conditions. Bone marrow‑derived mesenchymal stem cells (BM‑MSCs) are potential targets for liver diseases. Thus, the present study aimed to investigate the effects of superoxide dismutase 2 (SOD2) overexpression in BM‑MSCs on HIRI by constructing a HIRI rat model. The adenoviral vector containing SOD2 and the corresponding control vector were designed and constructed, and SOD2‑overexpressing BM‑MSCs were injected into the tail vein of the rats. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, as well as pathological changes and the remnant liver regeneration rate were determined. The activities of SOD and glutathione peroxidase (GSH‑Px), and malondialdehyde (MDA) content were measured. Reactive oxygen species (ROS) were determined with 2',7'‑-dichlorofluorescein diacetate and measured via fluorescence microscopy. Cell apoptosis was assessed using TUNEL staining. Moreover, the expression levels of Bax, Bcl‑2 and caspase‑3 were detected via western blotting. SOD2‑overexpressing BM‑MSCs significantly reduced the elevation of serum AST and ALT levels. Furthermore, SOD2‑overexpressing BM‑MSCs enhanced SOD and GSH‑Px activities, and suppressed the production of MDA and ROS. Histopathological findings revealed that SOD2‑overexpressing BM‑MSCs decreased the number of TUNEL‑positive cells in the liver. It was also found that SOD2‑overexpressing BM‑MSCs promoted Bcl‑2 expression, but inhibited Bax and caspase‑3 expression in HIRI. Collectively, these findings suggest that SOD2‑overexpressing BM‑MSCs may provide therapeutic support in HIRI by inhibiting oxidative stress and hepatocyte apoptosis.

SOD3 deficiency induces liver fibrosis by promoting hepatic stellate cell activation and epithelial-mesenchymal transition

Hepatic stellate cell (HSC) activation plays an important role in the pathogenesis of liver fibrosis, and epithelial-mesenchymal transition (EMT) is suggested to potentially promote HSC activation. Superoxide dismutase 3 (SOD3) is an extracellular antioxidant defense against oxidative damage. Here, we found downregulation of SOD3 in a mouse model of liver fibrosis induced by carbon tetrachloride (CCl4 ). SOD3 deficiency induced spontaneous liver injury and fibrosis with increased collagen deposition, and further aggravated CCl4 -induced liver injury in mice. Depletion of SOD3 enhanced HSC activation marked by increased α-smooth muscle actin and subsequent collagen synthesis primarily collagen type I in vivo, and promoted transforming growth factor-β1 (TGF-β1)-induced HSC activation in vitro. SOD3 deficiency accelerated EMT process in the liver and TGF-β1-induced EMT of AML12 hepatocytes, as evidenced by loss of E-cadherin and gain of N-cadherin and vimentin. Notably, SOD3 expression and its pro-fibrogenic effect were positively associated with sirtuin 1 (SIRT1) expression. SOD3 deficiency inhibited adenosine monophosphate-activated protein kinase (AMPK) signaling to downregulate SIRT1 expression and thus involving in liver fibrosis. Enforced expression of SIRT1 inhibited SOD3 deficiency-induced HSC activation and EMT, whereas depletion of SIRT1 counteracted the inhibitory effect of SOD3 in vitro. These findings demonstrate that SOD3 deficiency contributes to liver fibrogenesis by promoting HSC activation and EMT process, and suggest a possibility that SOD3 may function through modulating SIRT1 via the AMPK pathway in liver fibrosis.

Nanotheranostics for the Management of Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion injury (IRI), in which an insufficient oxygen supply followed by reperfusion leads to an inflammatory network and oxidative stress in disease tissue to cause cell death, always occurs after liver transplantations and sections. Although pharmacological treatments favorably prevent or protect the liver against experimental IRI, there have been few successes in clinical applications for patient benefits because of the incomprehension of complicated IRI-induced signaling events as well as short blood circulation time, poor solubility, and severe side reactions of most antioxidants and anti-inflammatory drugs. Nanomaterials can achieve targeted delivery and controllable release of contrast agents and therapeutic drugs in desired hepatic IRI regions for enhanced imaging sensitivity and improved therapeutic effects, emerging as novel alternative approaches for hepatic IRI diagnosis and therapy. In this review, the application of nanotechnology is summarized in the management of hepatic IRI, including nanomaterial-assisted hepatic IRI diagnosis, nanoparticulate systems-mediated remission of reactive oxygen species-induced tissue injury, and nanoparticle-based targeted drug delivery systems for the alleviation of IRI-related inflammation. The current challenges and future perspectives of these nanoenabled strategies for hepatic IRI treatment are also discussed.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Nanocarrier-mediated antioxidant delivery for liver diseases

Liver is the principal detoxifying organ and metabolizes various compounds that produce free radicals (FR) constantly. To maintain the oxidative/antioxidative balance in the liver, antioxidants would scavenge FR by preventing tissue damage through FR formation, scavenging, or by enhancing their decomposition. The disruption of this balance therefore leads to oxidative stress and in turn leads to the onset of various diseases. Supplying the liver with exogeneous antioxidants is an effective way to recreate the oxidative/antioxidative balance in the liver homeostasis. Nevertheless, due to the short half-life and instability of antioxidants in circulation, the methodology for delivering antioxidants to the liver needs to be improved. Nanocarrier mediated delivery of antioxidants proved to be an ingenious way to safely and efficiently deliver a high payload of antioxidants into the liver for circumventing liver diseases. The objective of this review is to provide an overview of the role of reactive oxygen species (oxidant) and ROS scavengers (antioxidant) in liver diseases. Subsequently, current nanocarrier mediated antioxidant delivery methods for liver diseases are discussed.

BacMam Delivery of a Protective Gene to Reduce Renal Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury remains the primary contributor to delayed graft function in kidney transplantation. The beneficial application of manganese superoxide dismutase (sod), delivered by a BacMam vector, against renal I/R injury has not been evaluated previously. Therefore, this study overexpressed sod-2 in proximal tubular epithelial (HK-2) cells and porcine kidney organs during simulated renal I/R injury. Incubation of HK-2 cells with antimycin A and 2-deoxyglucose resulted in a significant decrease in intracellular adenosine triphosphate (ATP) levels; following reperfusion, ATP levels significantly increased over time in cells overexpressing sod-2. In addition, lactate dehydrogenase (LDH) release declined over 72 h in BacMam-transduced injured cells. Ex vivo delivery of sod-2 significantly increased ATP levels in organs after 24 h of cold perfusion. In vitro and ex vivo results suggested that BacMam transduction successfully delivered sod-2, which reduced injury associated with I/R, by improving ATP cell content and decreasing LDH release with a subsequent increase in kidney tissue viability. These data provide further evidence for the potential application of BacMam as a gene delivery system for attenuating injury after cold preservation.

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

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

A Central Role for JNK/AP-1 Pathway in the Pro-Oxidant Effect of Pyrrolidine Dithiocarbamate through Superoxide Dismutase 1 Gene Repression and Reactive Oxygen Species Generation in Hematopoietic Human Cancer Cell Line U937

Pyrrolidine dithiocarbamate (PDTC) known as antioxidant and specific inhibitor of NF-κB was also described as pro-oxidant by inducing cell death and reactive oxygen species (ROS) accumulation in cancer. However, the mechanism by which PDTC indices its pro-oxidant effect is unknown. Therefore, we aimed to evaluate the effect of PDTC on the human Cu/Zn superoxide dismutase 1 (SOD1) gene transcription in hematopoietic human cancer cell line U937. We herein show for the first time that PDTC decreases SOD1 transcripts, protein and promoter activity. Furthermore, SOD1 repression by PDTC was associated with an increase in oxidative stress as evidenced by ROS production. Electrophoretic mobility-shift assays (EMSA) show that PDTC increased binding of activating protein-1 (AP-1) in dose dependent-manner suggesting that the MAPkinase up-stream of AP-1 is involved. Ectopic NF-κB p65 subunit overexpression had no effect on SOD1 transcription. In contrast, in the presence of JNK inhibitor (SP600125), p65 induced a marked increase of SOD1 promoter, suggesting that JNK pathway is up-stream of NF-κB signaling and controls negatively its activity. Indeed, using JNK deficient cells, PDTC effect was not observed nether on SOD1 transcription or enzymatic activity, nor on ROS production. Finally, PDTC represses SOD1 in U937 cells through JNK/c-Jun phosphorylation. Taken together, these results suggest that PDTC acts as pro-oxidant compound in JNK/AP-1 dependent-manner by repressing the superoxide dismutase 1 gene leading to intracellular ROS accumulation.

Overexpression of superoxide dismutase 3 gene blocks high-fat diet-induced obesity, fatty liver and insulin resistance

Oxidative stress plays an important role in the development of obesity and obesity-associated metabolic disorders. As an endogenous antioxidant enzyme, superoxide dismutase 3 (SOD3) has the potential to affect diet-induced obesity and obesity associated complications. In the current work, we overexpressed SOD3 in C57BL/6 mice fed a high fat diet to study its effect on high fat diet-induced obesity, fatty liver and insulin resistance. We demonstrated that the Sod3 gene transfer blocked high fat diet induced obesity, fatty liver and insulin resistance. Real Time PCR analysis of adipose and liver tissues revealed that overexpression of the Sod3 gene suppressed expression of pro-inflammatory genes in adipose tissue including F4/80, Tnfα, Cd11c, Mcp1 and Il6, and increased expression of anti-inflammatory genes such as adiponectin. In the liver, high levels of SOD3 activity in animals enhanced expression of the genes responsible for energy expenditure including Cpt1α, Cpt1β, Pgc1α, Pgc1β and Ucp2. These results suggest that overexpression of the Sod3 gene through gene transfer is an effective approach in preventing diet induced obesity and obesity-associated complications.

Redox therapeutics in hepatic ischemia reperfusion injury

Ischemia-reperfusion plays a major role in the injury experienced by the liver during transplantation. Much work has been done recently investigating the role of redox species in hepatic ischemia-reperfusion. As animal models are better characterized and developed, and more insights are gained into the pathophysiology of hepatic ischemia reperfusion injury in humans the questions into exactly how oxidants participate in this injury are becoming more refined. These questions include effects of cellular location, timing of injury, and ability of therapeutics to access this site are increasing our appreciation of the complexity of ischemia reperfusion and improving attempts to ameliorate its effects. In this review, we aim to discuss the various methods to alter redox chemistry during ischemia reperfusion injury and future prospects for preventing organ injury during hepatic ischemia reperfusion.

Current knowledge on oxidative stress in hepatic ischemia/reperfusion

Ischemia/reperfusion (I/R) injury associated with hepatic resections and liver transplantation remains a serious complication in clinical practice, despite several attempts to solve the problem. The redox balance, which is pivotal for normal function and integrity of tissues, is dysregulated during I/R, leading to an accumulation of reactive oxygen species (ROS). Formation of ROS and oxidant stress are the disease mechanisms most commonly invoked in hepatic I/R injury. The present review examines published results regarding possible sources of ROS and their effects in the context of I/R injury. We also review the effect of oxidative stress on marginal livers, which are more vulnerable to I/R-induced oxidative stress. Strategies to improve the viability of marginal livers could reduce the risk of dysfunction after surgery and increase the number of organs suitable for transplantation. The review also considers the therapeutic strategies developed in recent years to reduce the oxidative stress induced by hepatic I/R, and we seek to explain why some of them have not been applied clinically. New antioxidant strategies that have yielded promising results for hepatic I/R injury are discussed.

Antioxidant Stress and Anti-Inflammation of PPARα on Warm Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion (IR) injury is a serious clinical problem. Minimizing the adverse effect of ischemia-reperfusion injury after liver surgery or trauma is an urgent need. It has been proved that besides the effect of regulating the lipid and lipoprotein metabolism, PPARα also undertakes the task of organ protection. In this paper, related literature has been summarized and we come to the conclusion that administration of PPARα agonists can strengthen the antioxidant and anti-inflammation defense system by the upregulation of the expression of antioxidant enzymes and inhibition of NF-κB activity. This may provide a potential clinical treatment for hepatic ischemia-reperfusion injury.

Current strategies to minimize hepatic ischemia-reperfusion injury by targeting reactive oxygen species

Ischemia-reperfusion is a major component of injury in vascular occlusion both during liver surgery and during liver transplantation. The pathophysiology of hepatic ischemia-reperfusion includes a number of mechanisms including oxidant stress that contribute to various degrees to the overall organ damage. A large volume of recent research has focused on the use of antioxidants to ameliorate this injury, although results in experimental models have not translated well to the clinic. This review focuses on critical sources and mediators of oxidative stress during hepatic ischemia-reperfusion, the status of current antioxidant interventions, and emerging mechanisms of protection by preconditioning. While recent advances in regulation of antioxidant systems by Nrf2 provide interesting new potential therapeutic targets, an increased focus must be placed on more in-depth mechanistic investigations in hepatic ischemia-reperfusion injury and translational research in order to refine current strategies in disease management.

The Current Knowledge of the Role of PPAR in Hepatic Ischemia-Reperfusion Injury

Strategies to improve the viability of steatotic livers could reduce the risk of dysfunction after surgery and increase the number of organs suitable for transplantation. Peroxisome proliferator-activated receptors (PPARs) are major regulators of lipid metabolism and inflammation. In this paper, we review the PPAR signaling pathways and present some of their lesser-known functions in liver regeneration. Potential therapies based on PPAR regulation will be discussed. The data suggest that further investigations are required to elucidate whether PPAR could be a potential therapeutic target in liver surgery and to determine the most effective therapies that selectively regulate PPAR with minor side effects.

Mechanistic overview of reactive species-induced degradation of the endothelial glycocalyx during hepatic ischemia/reperfusion injury

Endothelial cells are covered by a delicate meshwork of glycoproteins known as the glycocalyx. Under normophysiological conditions the glycocalyx plays an active role in maintaining vascular homeostasis by deterring primary and secondary hemostasis and leukocyte adhesion and by regulating vascular permeability and tone. During (micro)vascular oxidative and nitrosative stress, which prevails in numerous metabolic (diabetes), vascular (atherosclerosis, hypertension), and surgical (ischemia/reperfusion injury, trauma) disease states, the glycocalyx is oxidatively and nitrosatively modified and degraded, which culminates in an exacerbation of the underlying pathology. Consequently, glycocalyx degradation due to oxidative/nitrosative stress has far-reaching clinical implications. In this review the molecular mechanisms of reactive oxygen and nitrogen species-induced destruction of the endothelial glycocalyx are addressed in the context of hepatic ischemia/reperfusion injury as a model disease state. Specifically, the review focuses on (i) the mechanisms of glycocalyx degradation during hepatic ischemia/reperfusion, (ii) the molecular and cellular players involved in the degradation process, and (iii) its implications for hepatic pathophysiology. These topics are projected against a background of liver anatomy, glycocalyx function and structure, and the biology/biochemistry and the sources/targets of reactive oxygen and nitrogen species. The majority of the glycocalyx-related mechanisms elucidated for hepatic ischemia/reperfusion are extrapolatable to the other aforementioned disease states.

Hepatic ischemia-reperfusion injury and therapeutic strategies to alleviate cellular damage

Warm hepatic ischemia-reperfusion injury is a significant medical problem in many clinical conditions such as liver transplantation, hepatic surgery for tumor excision, trauma and hepatic failure after hemorrhagic shock. Partial or, mostly, total interruption of hepatic blood flow is often necessary when liver surgery is performed. This interruption of blood flow is termed "warm ischemia" and upon revascularization, when molecular oxygen is reintroduced, the organ undergoes a process called "reperfusion injury" that causes deterioration of organ function. Ischemia reperfusion results in cellular damage and tissue injury associated with a complex series of events. Pathophysiological mechanisms leading to tissue injury following ischemia-reperfusion will be discussed and therapies targeted to reduce liver damage will be summarized within this review.

Hepatic ischaemia-reperfusion injury from bench to bedside

BACKGROUND

Vascular occlusion to prevent haemorrhage during liver resection causes ischaemia-reperfusion (IR) injury. Insights into the mechanisms of IR injury gathered from experimental models have contributed to the development of therapeutic approaches, some of which have already been tested in randomized clinical trials.

METHODS

The review was based on a PubMed search using the terms 'ischemia AND hepatectomy', 'ischemia AND liver', 'hepatectomy AND drug treatment', 'liver AND intermittent clamping' and 'liver AND ischemic preconditioning'; only randomized controlled trials (RCTs) were included.

RESULTS

Twelve RCTs reported on ischaemic preconditioning and intermittent clamping. Both strategies seem to confer protection and allow extension of ischaemia time. Fourteen RCTs evaluating pharmacological interventions, including antioxidants, anti-inflammatory drugs, vasodilators, pharmacological preconditioning and glucose infusion, were identified.

CONCLUSION

Several strategies to prevent hepatic IR have been developed, but few have been incorporated into clinical practice. Although some pharmacological strategies showed promising results with improved clinical outcome there is not sufficient evidence to recommend them.

Bench-to-bedside review: Targeting antioxidants to mitochondria in sepsis

Development of organ dysfunction associated with sepsis is now accepted to be due at least in part to oxidative damage to mitochondria. Under normal circumstances, complex interacting antioxidant defense systems control oxidative stress within mitochondria. However, no studies have yet provided conclusive evidence of the beneficial effect of antioxidant supplementation in patients with sepsis. This may be because the antioxidants are not accumulating in the mitochondria, where they are most needed. Antioxidants can be targeted selectively to mitochondria by several means. This review describes the in vitro studies and animal models of several diseases involving oxidative stress, including sepsis, in which antioxidants targeted at mitochondria have shown promise, and the future implications for such approaches in patients.

Prevention of hepatic ischemia-reperfusion injury by pre-administration of catalase-expressing adenovirus vectors

Liver ischemia/reperfusion (I/R) injury, which is mainly caused by the generation of reactive oxygen species (ROS) during the reperfusion, remains an important clinical problem associated with liver transplantation and major liver surgery. Therefore, ROS should be detoxified to prevent hepatic I/R-induced injury. Delivery of antioxidant genes into liver is considered to be promising for prevention of hepatic I/R injury; however, therapeutic effects of antioxidant gene transfer to the liver have not been fully examined. The aim of this study was to examine whether adenovirus (Ad) vector-mediated catalase gene transfer in the liver is an effective approach for scavenging ROS and preventing hepatic I/R injury. Intravenous administration of Ad vectors expressing catalase, which is an antioxidant enzyme scavenging H(2)O(2), resulted in a significant increase in catalase activity in the liver. Pre-injection of catalase-expressing Ad vectors dramatically prevented I/R-induced elevation in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, and hepatic necrosis. The livers were also protected in another liver injury model, CCl(4)-induced liver injury, by catalase-expressing Ad vectors. Furthermore, the survival rates of mice subjected to both partial hepatectomy and I/R treatment were improved by pre-injection of catalase-expressing Ad vectors. On the other hand, control Ad vectors expressing beta-galactosidase did not show any significant preventive effects in the liver on the models of I/R-induced or CCl(4)-induced hepatic injury described above. These results indicate that hepatic delivery of the catalase gene by Ad vectors is a promising approach for the prevention of oxidative stress-induced liver injury.

A20 protects mice from lethal liver ischemia/reperfusion injury by increasing peroxisome proliferator-activated receptor-alpha expression

The nuclear factor-kappaB inhibitory protein A20 demonstrates hepatoprotective abilities through combined antiapoptotic, anti-inflammatory, and pro-proliferative functions. Accordingly, overexpression of A20 in the liver protects mice from toxic hepatitis and lethal radical hepatectomy, whereas A20 knockout mice die prematurely from unfettered liver inflammation. The effect of A20 on oxidative liver damage, as seen in ischemia/reperfusion injury (IRI), is unknown. In this work, we evaluated the effects of A20 upon IRI using a mouse model of total hepatic ischemia. Hepatic overexpression of A20 was achieved by recombinant adenovirus (rAd.)-mediated gene transfer. Although only 10%-25% of control mice injected with saline or the control rAd.beta galactosidase survived IRI, the survival rate reached 67% in mice treated with rAd.A20. This significant survival advantage in rAd.A20-treated mice was associated with improved liver function, pathology, and repair potential. A20-treated mice had significantly lower bilirubin and aminotransferase levels, decreased hemorrhagic necrosis and steatosis, and increased hepatocyte proliferation. A20 protected against liver IRI by increasing hepatic expression of peroxisome proliferator-activated receptor alpha (PPARalpha), a regulator of lipid homeostasis and of oxidative damage. A20-mediated protection of hepatocytes from hypoxia/reoxygenation and H(2)O(2)-mediated necrosis was reverted by pretreatment with the PPARalpha inhibitor MK886. In conclusion, we demonstrate that PPARalpha is a novel target for A20 in hepatocytes, underscoring its novel protective effect against oxidative necrosis. By combining hepatocyte protection from necrosis and promotion of proliferation, A20-based therapies are well-poised to protect livers from IRI, especially in the context of small-for-size and steatotic liver grafts. Liver Transpl 15:1613-1621, 2009. (c) 2009 AASLD.

Antioxidant enzyme gene transfer for ischemic diseases

The balance of redox is pivotal for normal function and integrity of tissues. Ischemic insults occur as results of a variety of conditions, leading to an accumulation of reactive oxygen species (ROS) and an imbalanced redox status in the tissues. The oxidant stress may activate signaling mechanisms provoking more toxic events, and eventually cause tissue damage. Therefore, treatments with antioxidants, free radical scavengers and their mimetics, as well as gene transfer approaches to overexpress antioxidant genes represent potential therapeutic options to correct the redox imbalance. Among them, antioxidant gene transfer may enhance the production of antioxidant scavengers, and has been employed to experimentally prevent or treat ischemic injury in cardiovascular, pulmonary, hepatic, intestinal, central nervous or other systems in animal models. With improvements in vector systems and delivery approaches, innovative antioxidant gene therapy has conferred better outcomes for myocardial infarction, reduced restenosis after coronary angioplasty, improved the quality and function of liver grafts, as well as outcome of intestinal and cerebral ischemic attacks. However, it is crucial to be mindful that like other therapeutic armentarium, the efficacy of antioxidant gene transfer requires extensive preclinical investigation before it can be used in patients, and that it may have unanticipated short- or long-term adverse effects. Thus, it is critical to balance between the therapeutic benefits and potential risks, to develop disease-specific antioxidant gene transfer strategies, to deliver the therapy with an optimal time window and in a safe manner. This review attempts to provide the rationale, the most effective approaches and the potential hurdles of available antioxidant gene transfer approaches for ischemic injury in various organs, as well as the possible directions of future preclinical and clinical investigations of this highly promising therapeutic modality.

Lentivirus-mediated superoxide dismutase1 gene delivery protects against oxidative stress-induced liver injury in mice

BACKGROUND

The exposure of liver to hepatotoxins, and their subsequent metabolism, results in increased reactive oxygen species (ROS), one of the major culprits in causing both acute liver cell injury and chronic liver diseases. The aim of this present study is to investigate the protective effects of lentiviral vector-mediated copper-zinc superoxide dismutase (LV-SOD1) gene transfer against ROS-induced cytotoxicity in Hep G2 cells and liver injury in mice.

METHODS

In vitro SOD1 efficacy was tested against two ROS-generating systems: hypoxanthine/xanthine oxidase (HX/XO) and hydroxyethyl radicals (HER), whereas in vivo SOD1 efficacy was evaluated in carbon tetrachloride (CCl4)-induced liver injury in C57BL/6 mice.

RESULTS

LV-SOD1 transduction in Hep G2 cells resulted in a significant increase in SOD activity in cell lysates, and it significantly decreased the toxicity induced by HX/XO and HER. High SOD1 expression in the liver was achieved via portal vein injection of LV-SOD1 in mice and these high levels were observed for 30 days, the length of the experiment to date. SOD1 overexpression significantly decreased the toxicity and restored liver function in the CCl4-treated mice.

CONCLUSIONS

These findings demonstrate for the first time that LV transduction led to the long-term expression of fully functional transgene expression in both in vitro and in vivo systems.

Nitric oxide and peroxynitrite in health and disease

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

Delivery of antioxidative enzyme genes protects against ischemia/reperfusion-induced liver injury in mice

Hepatic ischemia/reperfusion (I/R) injury is characterized by the generation of reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide. The aim of this study is to investigate whether antioxidative gene delivery by our polylipid nanoparticles (PLNP) is an effective approach for prevention of the injury. Polyplexes of extracellular superoxide dismutase (EC-SOD) and/or catalase genes were injected via the portal vein 1 day prior to a warm I/R procedure in mice. The effects of the gene delivery were determined 6 hours after starting reperfusion. PLNP-mediated antioxidative gene delivery led to a marked increase in human EC-SOD and catalase gene expression in the liver. Liver superoxide dismutase (SOD) and catalase activity both increased approximately 10-fold. Increased liver superoxide anion levels caused by the I/R procedure were reduced to normal levels by EC-SOD gene delivery. The overexpression of these 2 antioxidative genes significantly suppressed the I/R-induced elevation of serum alanine aminotransferase (ALT) levels, decreased liver malondialdehyde content, restored glutathione reserve, and improved liver histology. In conclusion, EC-SOD or catalase gene delivery by PLNP resulted in high levels of the transgene activity in the liver, and markedly attenuated hepatic I/R injury. The protection is directly associated with elevated antioxidative enzyme activity as the result of the gene delivery. This novel approach may become a potential therapy to improve graft function and survival after liver transplantation.

Alcoholic pancreatitis: mechanisms of viral infections as cofactors in the development of acute and chronic pancreatitis and fibrosis

Acute and chronic pancreatitis is associated with alcohol abuse, but symptomatic pancreatitis develops in only a small proportion of persons (10-20%) who abuse alcohol. This apparent paradox has led to the notion that additional cofactors are involved in the development of alcoholic pancreatitis. Potential cofactors, such as diet and smoking, have been suggested, but there are no compelling epidemiologic data to support this idea. A number of viruses and some bacteria have been shown to infect the pancreas and produce pancreatitis. One important mediator of pancreatitis in persons with a compromised immune system is a viral infection. The increased susceptibility of immunocompromised persons to viral pancreatitis led to the hypothesis, described in this paper, that the well-known immunosuppression associated with alcohol abuse would result in a more severe viral pancreatitis in mice, which are provided ethanol, than in control animals. To test this hypothesis, C57BL/6 mice were infected with a virulent strain of coxsackievirus B3, which preferentially induces pancreatitis, or with a strain that is naturally avirulent. The study findings presented in this paper show that ethanol consumption alone does not produce pancreas damage but results in a more severe and prolonged pancreatitis after infection with a virulent virus and interestingly, after infection with the avirulent strain of virus. This was associated with an increased number of viruses in the pancreas and spleen, which correlated with decreased humoral immune responses to the virus.

Tumor necrosis factor-alpha down-regulates human Cu/Zn superoxide dismutase 1 promoter via JNK/AP-1 signaling pathway

Overexpression of Cu/Zn superoxide dismutase 1 (SOD1) in monocytes blocks reactive oxygen species-induced inhibition of cell growth and apoptosis and renders cells resistant to the toxic effect of tumor necrosis factor (TNF)-alpha, suggesting that TNF-alpha represses the SOD1 gene in these cells. We herein show that TNF-alpha decreases SOD1 mRNA, protein, and promoter activity in U937 cells. Electrophoretic mobility-shift assays (EMSA) show that TNF-alpha decreased binding of three different complexes. Ectopic Sp1 overexpression markedly increased SOD1-basal promoter activity and partially antagonized the TNF-alpha inhibitory effect. In contrast, ectopic c-Jun overexpression mimics TNF-alpha inhibitory effects and antagonizes Sp1 stimulatory effects. In agreement with these findings, EMSA shows a TNF-alpha-induced increase in AP-1 and a decrease in Sp1 DNA binding. Disruption of the C/EBP site decreases, whereas mutation in the Sp1/Egr-1 site completely abolishes DNA-binding and promoter activity. A JNK inhibitor antagonized the negative effects of TNF-alpha on SOD1 promoter activity, suggesting that JNK signaling through c-Jun protein activation is critical for the TNF-alpha-dependent SOD1 repression. A greater understanding of the mechanisms of TNF-alpha-induced SOD1 repression could facilitate the design and development of novel therapeutic drugs for inflammatory conditions.

[Ischemia-reperfusion syndrome associated with liver transplantation: an update]

Ischemia-reperfusion (I/R) injury is the main cause of both initial graft dysfunction and primary failure in liver transplantation. The search for therapeutic strategies to prevent I/R injury has led to research into promising drugs, although most have not been used clinically. Gene therapy requires better transfection techniques, avoiding vector toxicity, and ethical debate before being used clinically. Ischemic preconditioning is the first therapeutic strategy used in clinical practice to reduce I/R injury in hepatectomies for tumors. Future research will provide data on the effectiveness of ischemic preconditioning in reducing I/R injury associated with liver transplantation, and in reducing the vulnerability of steatotic grafts to I/R syndrome so that they can be used in transplantation, thus relieving the organ shortage.

Past and future approaches to ischemia-reperfusion lesion associated with liver transplantation

Ischemia-reperfusion (I/R) injury associated with liver transplantation remains a serious complication in clinical practice, in spite of several attempts to solve the problem. The present review focuses on the complexity of I/R injury, summarizing conflicting results obtained from the literature about the mechanisms responsible for it. We also review the therapeutic strategies designed in past years to reduce I/R injury, attempting to explain why most of them have not been applied clinically. These strategies include improvements in pharmacological treatments, modifications of University of Wisconsin (UW) preservation solution based on a variety of additives, and gene therapy. Finally, we will consider new potential protective strategies using trimetazidine, 5-amino-4-imidazole carboxamide riboside (AICAR), melatonin, modulators of the renin-angiotensin system (RAS) and the phosphatidylinositol-3-OH kinase (PI3K)-Akt and the p42/p44 extracellular signal-regulated kinases (Erk 1/2) pathway. These strategies have shown promising results for I/R injury but have not been tested in experimental liver transplantation to date. Moreover, we will review ischemic preconditioning, taking into account the recent clinical studies that suggest that this surgical strategy could be appropriate for liver transplantation.

Molecular therapy for hepatic injury and fibrosis: Where are we?

Hepatic fibrosis is a wound healing response, involving pathways of inflammation and fibrogenesis. In response to various insults, such as alcohol, ischemia, viral agents, and medications or hepatotoxins, hepatocyte damage will cause the release of cytokines and other soluble factors by Kupffer cells and other cell types in the liver. These factors lead to activation of hepatic stellate cells, which synthesize large amounts of extracellular matrix components. With chronic injury and fibrosis, liver architecture and metabolism are disrupted, eventually manifesting as cirrhosis and its complications. In addition to eliminating etiology, such as antiviral therapy and pharmacological intervention, it is encouraging that novel strategies are being developed to directly address hepatic injury and fibrosis at the subcellular and molecular levels. With improvement in understanding these mechanisms and pathways, key steps in injury, signaling, activation, and gene expression are being targeted by molecular modalities and other molecular or gene therapy approaches. This article intends to provide an update in terms of the current status of molecular therapy for hepatic injury and fibrosis and how far we are from clinical utilization of these new therapeutic modalities.

The contemporary role of antioxidant therapy in attenuating liver ischemia-reperfusion injury: a review

Oxidative stress is an important factor in many pathological conditions such as inflammation, cancer, ageing and organ response to ischemia-reperfusion. Humans have developed a complex antioxidant system to eliminate or attenuate oxidative stress. Liver ischemia-reperfusion injury occurs in a number of clinical settings, including liver surgery, transplantation, and hemorrhagic shock with subsequent fluid resuscitation, leading to significant morbidity and mortality. It is characterized by significant oxidative stress but accompanied with depletion of endogenous antioxidants. This review has 2 aims: firstly, to highlight the clinical significance of liver ischemia-reperfusion injury, the underlying mechanisms and the main pathways by which the antioxidants function, and secondly, to describe the new developments that are ongoing in antioxidant therapy and to present the experimental and clinical evidence about the role of antioxidants in modulating hepatic ischemia-reperfusion injury.

Lentivirus-mediated expression of glutathione peroxidase: neuroprotection in murine models of Parkinson's disease

Reactive oxygen species are considered to contribute to the pathogenesis of Parkinson's disease (PD). In order to study viral vector-mediated overexpression of the antioxidant enzyme glutathione peroxidase (GPX) as a potential neuroprotective approach in both an in vitro and in vivo model of PD, we have developed a lentiviral vector carrying the human GPX1 gene. Neuroblastoma cells infected with this vector showed a 2-fold increase in GPX activity compared to cells infected with a control vector. In addition, overexpression of GPX protected 83.0 +/- 14.2% of these cells against 6-hydroxydopamine (6-OHDA)-induced toxicity, while only 22.9 +/- 4.6% of the cells infected with a control vector survived. Furthermore, lentivirus-mediated expression of GPX1 in nigral dopaminergic neurons in vivo prior to intrastriatal injection of 6-OHDA led to a small, but significant protection of these cells against drug-induced toxicity. These results indicate that antioxidative gene therapy strategies may be relevant for PD.

Role of protein synthesis in the protection conferred by ozone-oxidative-preconditioning in hepatic ischaemia/reperfusion

The liver is damaged by sustained ischaemia during liver transplantation, and the reperfusion after ischaemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischaemia/reperfusion (I/R) injury through different mechanisms. The aim of this study was to investigate the influence of the inhibition of protein synthesis on the protective actions conferred by OzoneOP in hepatic I/R. Rats were treated with cycloheximide (CHX) in order to promote protein synthesis inhibition after OzoneOP treatment. Plasma transaminases, malondialdehyde and 4-hydroxyalkenals and morphological characteristics were measured as an index of hepatocellular damage; Cu/Zn-superoxide dismutase (SOD), Mn-SOD, catalase, total hydroperoxides and glutathione levels as markers of endogenous antioxidant system. OzoneOP increased Mn-SOD isoform and ameliorated mitochondrial damage. CHX abrogated the protection conferred by OzonoOP and decreased Mn-SOD activity. Cellular redox balance disappeared when CHX was introduced. Protein synthesis is involved in the protective mechanisms mediated by OzoneOP. Ozone treatment preserved mitochondrial functions and cellular redox balance.

Hemagglutinating Virus of Japan–Artificial Viral Envelope Liposome-Mediated Cotransfer of bag-1 and bcl-2 Genes Protects Hepatic Cells Against Ischemic Injury Through BAG-1-Assisted Preferential Enhancement of Bcl-2 Protein Expression

Hepatic injury subsequent to ischemia-reperfusion (I/R) was demonstrated in our previous study to be prevented by hemagglutinating virus of Japan (HVJ)-artificial viral envelope (AVE) liposome-mediated gene transfer of the antiapoptotic gene, human bcl-2 (h-bcl-2). In the present study, we introduced simultaneously both mouse Bcl-2-associated athanogene 1 (m-bag-1) and the h-bcl-2 gene by the same HVJ-AVE liposome transfection method, and found that I/R-induced hepatic injuries such as release of hepatic marker enzymes into blood, cell morphological degeneration, and cellular DNA strand cleavage were suppressed more effectively than by transfection with either gene singly. In addition, the h-Bcl-2 expression level in the ischemic state, but not in the nonischemic state, was markedly higher in h-bcl-2/m-bag-1-cotransfected liver than in h-bcl-2-transfected liver. In contrast, the m-BAG-1 expression level in the ischemic state, but not in the nonischemic state, was only slightly higher in h-bcl-2/m-bag-1-cotransfected liver than in m-bag-1-transfected liver. Thus, with dual gene cotransfer, coexistent Bcl-2 protein exerts no activity to assist a marked enhancement of BAG-1 protein, whereas the function of overexpressed BAG-1 as a Bcl-2-binding protein may lead to the enhancement of efficient expression of h-Bcl-2 in I/R-treated liver as compared with nonischemic liver, which results in repression of diverse I/R-induced cell death symptoms, presumably through the formation of functional complexes of BAG-1 and Bcl-2.

Liposome-mediated extracellular superoxide dismutase gene delivery protects against acute liver injury in mice

Our previous study demonstrated that polycationic liposomes are highly stable in the bloodstream and represent an effective agent for liver gene delivery. We report here that liposome-mediated extracellular superoxide dismutase (EC-SOD) gene delivery successfully prevented acute liver injury in mice. The therapeutic efficacy of EC-SOD gene delivery by polycationic liposomes was determined against the toxicity of superoxide anions and hydroxyethyl radicals in HepG2 cells and in a mouse model of acute liver injury caused by D-galactosamine and lipopolysaccharide intoxication. Transfection of HepG2 cells with an EC-SOD plasmid led to a striking increase in superoxide dismutase activity in the medium. The transfected cells had much less cell death after reactive oxygen species exposure compared with untransfected or control plasmid-transfected cells. In a model of acute liver injury, serum alanine aminotransferase levels in mice receiving portal vein injections of EC-SOD lipoplexes were much lower than in those receiving normal saline, liposomes alone, or control lipoplexes. Liver histology confirmed that there was less cell death in the EC-SOD lipoplex-treated group. Quantitative reverse transcriptase polymerase chain reaction showed a 55-fold increase in human EC-SOD gene expression in the liver of mice injected with EC-SOD lipoplexes. Serum superoxide dismutase activity in EC-SOD lipoplex-treated mice was higher than in the control groups; this was associated with higher liver glutathione levels and reduced lipid peroxidation. In conclusion, polycationic liposome-mediated EC-SOD gene delivery protects against reactive oxygen species toxicity in vitro and against lipopolysaccharide-induced acute liver injury in D-galactosamine-sensitized mice.

Mitochondrial dysfunction in schizophrenia: evidence for compromised brain metabolism and oxidative stress

The etiology and pathophysiology of schizophrenia remain unknown. A parallel transcriptomics, proteomics and metabolomics approach was employed on human brain tissue to explore the molecular disease signatures. Almost half the altered proteins identified by proteomics were associated with mitochondrial function and oxidative stress responses. This was mirrored by transcriptional and metabolite perturbations. Cluster analysis of transcriptional alterations showed that genes related to energy metabolism and oxidative stress differentiated almost 90% of schizophrenia patients from controls, while confounding drug effects could be ruled out. We propose that oxidative stress and the ensuing cellular adaptations are linked to the schizophrenia disease process and hope that this new disease concept may advance the approach to treatment, diagnosis and disease prevention of schizophrenia and related syndromes.

The protective mechanism of Yisheng Injection against hepatic ischemia reperfusion injury in mice

AIM: Hepatic ischemia/reperfusion injury may cause acute inflammatory, significant organ damage or dysfunction, and remains an important problem for liver transplantation. Our previous in vivo and in vitro studies demonstrated that Yisheng injection (YS), a traditional Chinese medicine, had protective effect on ischemia/reperfusion injury. In this study, we examined whether YS had protective effect for hepatic ischemia/reperfusion injury and explored its protective mechanism.

METHODS: Hepatic warm ischemia/reperfusion was induced in mice. YS at different doses (5, 10, 20 mg/kg) was injected intraperitoneally 24 h and 1 h before ischemia and a third dose was injected intravenously just before reperfusion. The hepatocellular injury, oxidative stress, neutrophil recruitment, proinflammatory mediators and adhesion molecules associated with hepatic ischemia/ reperfusion injury were assayed by enzyme-linked immunosorbent assay (ELISA), immunohistochemical assay and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: Undergoing 90 min of ischemia and 6 h of reperfusion caused dramatical injuries in mouse livers. Administration of YS at doses of 5, 10 and 20 mg/kg effectively reduced serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH), from 3 670 ± 463 U/L, 2 362 ± 323 U/L and 12 752 ± 1 455 U/L in I/R group to 1 172 ± 257 U/L, 845 ± 193 U/L and 2 866 ± 427 U/L in YS (20 mg/kg) treated group, respectively (P < 0.01). The liver myeloperoxidase (MPO) and malondialdehyde (MDA) contents were decreased from 1.1 ± 0.2 (U/mg protein) and 9.1 ± 0.7 (nmol/mg protein) in I/R group to 0.4 ± 0.1 (U/mg protein) and 5.5 ± 0.9 (nmol/mg protein) in YS (20 mg/kg) treated group, respectively (P < 0.01). Moreover, the serum levels of tumor necrosis factor-alpha (TNF-α) were reduced from 55 ± 9.9 (pg/mL) in I/R group to 16 ± 4.2 (pg/mL) (P < 0.01). Furthermore, the over-expressions of TNF-α and intercellular adhesion molecule-1 (ICAM-1) were suppressed by YS treatment in a dose-dependent manner.

CONCLUSION: YS attenuates hepatic warm ischemia/reperfusion injury by reducing oxidative stress and suppressing the over-expression of proinflammatory mediators and adhesion molecules.

Protective effect of melatonin on liver ischemia reperfusion injury in rats

AIM: To investigate the effect of melatonin (Mel) on liver ischemia reperfusion (I/R) injury in rats.

METHODS: 150 male Wistar rats (190-210 g, 6-7weeks age) were divided into three groups at random: Mel exposure group, alcohol solvent control group and saline control group. The left branches of portal vein, hepatic artery, hepatic duct were blocked up for 60 min and then opened to establish liver I/R I models in rats. In each group, samples were collected in 0.5, 1, 6, 12, and 24 h after reperfusion respectively. 20 mg/kg of Mel was injected peritoneally in rats 30 min before experimentation in Mel exposure group. The duplicate concentration of alcohol and the same volume of saline were injected in control group as a substitution. Serum alanine aminotransferase (ALT) by auto biochemical analyzer, and superoxide dismutase (SOD) and terminal productions of lipid peroxidationin (MDA) in liver tissue were measured. Pathological changes in liver and immunohistochemical straining of ICAM-1 were determined with optical microscope.

RESULTS: The level of ALT measured in various time after reperfusion in Mel group was totally significantly lower than that in alcohol and saline control groups (P < 0.05). The level of MDA measured in 6 h, 12 h, and 24 h after reperfusion in Mel group was significantly lower than that in alcohol and saline control groups (P < 0.05). The level of SOD measured in 12, 24 h after reperfusion in Mel group was significantly higher than that in alcohol and saline control groups (P < 0.05). The expression level of ICAM-1 (%) measured in various time after reperfusion in Mel group was significantly lower than that in alcohol and saline control groups (P < 0.05).

CONCLUSION: Exotic Mel inhibits the activities of ALT, increases activities of superoxide dismutase (SOD), and decreases the cumulation of MDA in liver reperfusion tissue and expression of ICAM-1 in liver reperfusion tissue. Therefore, it can improve the hepatic function after reperfusion and plays a definitely protective role in liver I/R.

Effects of different operations on cirrhotic portal hypertensive liver in rats

AIM: To evaluate respectively the effects of portaazygous disconnection (PAD), mesocaval shunt (MCS) and distal splenocaval shunt (DSCS) on the portasytemic shunting (PSS), hepatic function (HF), hepatic mitochondrial respiratory function (HMRF) and its ultrastructure, anti-oxidation ability (HAOA) and lipoperoxide (LPO), so as to provide theoretical basis to select a suitable operation.

METHODS: Using the cirrhotic portal hypertensive model induced by CCl₄/ethanol in Wristar rats, we investigated PSS, HF, HMRF and its HAOA and LPO during three wks after MCS, DSCS and PAD.

RESULTS: After MCS, the PSS were further increased, HF, HMRF and HAOA were significantly decreased, and LPO increased. Hepatic mitochondrial ultrastructure showed severely damaged. Only a little improvement was found on the third wk. After DSCS and PAD, above mentioned indexes were less influenced, and they were restored a little more quickly in DSCS groups than that in PAD groups. During the first postoperative wk, the PAD group showed the highest mortality.

CONCLUSION: DSCS may be a desirable operation among the three kinds of operation.

Antioxidant Gene Therapy Can Protect Hearing and Hair Cells from Ototoxicity

Aminoglycosides are commonly used antibiotics that often induce ototoxicity leading to permanent hair cell loss and hearing impairment. The ototoxic effects of aminoglycosides have been linked to oxidative stress. To determine the feasibility of antioxidant gene therapy for protecting the inner ear against aminoglycoside-induced oxidative stress, we used adenoviral vectors for overexpression of catalase, Cu/Zn superoxide dismutase (SOD1), and Mn superoxide dismutase (SOD2). We inoculated adenoviruses designated Ad.cat, Ad.SOD1, and Ad.SOD2 into the left guinea pig cochlea. Five days later, an ototoxic combination of kanamycin and ethacrynic acid was systemically administered. Artificial perilymph and adenovirus without a gene cassette (Ad.null) were used as controls. Biochemical analysis showed significant increase in catalase and a moderate elevation in SOD2 levels in tissues of the cochlea inoculated with the respective vectors. Auditory brain-stem responses were measured to monitor hearing thresholds. Animals were sacrificed 7 days after the ototoxic insult and their hair cells counted. Hair cells and hearing thresholds were significantly protected by Ad.cat and Ad.SOD2, while results with Ad.SOD1 were inconsistent. Control ears showed no significant protective effects. The results demonstrate that the expression of functional enzymes in the inner ear is feasible using adenoviral-mediated gene delivery. Furthermore, they confirm that reactive oxygen species contribute to aminoglycoside ototoxicity and suggest antioxidant gene therapy as a potential therapeutic strategy to reduce inner ear oxidative stress.

Sub-lethal oxidative stress triggers the protective effects of ischemic preconditioning in the mouse liver

BACKGROUND/AIMS

While ischemic preconditioning confers significant protection against subsequent prolonged periods of ischemia, the mechanisms triggering protection remain speculative. We hypothesize that a sub-lethal oxidative stress during ischemic preconditioning induces defense mechanisms preventing subsequent lethal injury.

METHODS

We used mouse models of partial and total hepatic ischemia for 75 min. Ischemic preconditioning consisted of 10-min ischemia and 15-min reperfusion prior to the prolonged ischemic insult.

RESULTS

Tissue levels of peroxides increased about three times after 10 min of ischemia and normalized within 15 min of reperfusion. This limited oxidative stress during ischemic preconditioning prevented the negative effects of subsequent prolonged ischemia as assessed by AST-levels, TUNEL-staining of hepatocytes and animal survival. N-Acetylcysteine inhibited the mild oxidative burst of ischemic preconditioning, and fully reversed the protective effects of preconditioning. The protective role of a sub-lethal oxidative stress was supported by the benefit of delivery of an H2O2-analog through the portal vein prior to a long ischemic insult. This challenge conferred similar protection as ischemic preconditioning.

CONCLUSIONS

We conclude that the mild burst of oxidative stress generated during ischemic preconditioning triggers protective mechanisms against subsequent, otherwise lethal, ischemic injury. The pathway possibly includes enhancement of natural anti-oxidative stress mechanisms.

Effects of three superoxide dismutase genes delivered with an adenovirus on graft function after transplantation of fatty livers in the rat

BACKGROUND

Oxygen-derived free radicals play a central role in ischemia/reperfusion injury after organ transplantation and are degraded by endogenous radical scavengers such as superoxide dismutase (SOD). Overexpression of SOD by delivery of the cytosolic SOD gene with an adenovirus (Ad.SOD1) decreases organ injury and increases survival in a rat model of liver transplantation. However, it is unclear which of the three isoforms of SOD provides the most protective effect. The purpose of this study was to identify the isoform with the highest effectiveness against ischemia/reperfusion injury after transplantation of fatty livers, which are particularly susceptible.

METHODS

Donor rats were given ethanol by gavage before harvest to induce steatotic livers. Some of the donors were infected with adenoviruses expressing either the gene lacZ encoding bacterial beta-galactosidase (Ad.lacZ), Ad.SOD1, Ad.SOD2 (mitochondrial isoform), or Ad.SOD3 (extracellular isoform). After transplantation, SOD activity in liver, survival, histopathology, transaminases, and activation of nuclear factor (NF)-kappaB, IkappaB kinase, Jun-N-terminal kinase (JNK), and tumor necrosis factor (TNF)-alpha were evaluated.

RESULTS

Ad.SOD1 treatment increased survival, blunted transaminase release, and reduced necrosis, whereas Ad.SOD3 had no protective effect. Ad.SOD2 was not as protective as Ad.SOD1. Ad.SOD1 reduced the activation of NF-kappaB, blunted JNK activity, and reduced TNF-alpha activity. Ad.SOD2 treatment resulted in lower kinase, TNF-alpha, and NF-kappaB activities but was not as effective as Ad.SOD1. IkappaB kinase activity was not affected.

CONCLUSION

This study demonstrates that cytosolic SOD represents the most effective isoform of SOD to protect transplanted livers from failure; this may be related to lowered NF-kappaB and JNK activities because of reduced oxygen-derived radical production.

Gene Therapy for Cardiovascular Disease

The last decade has seen substantial advances in the development of gene therapy strategies and vector technology for the treatment of a diverse number of diseases, with a view to translating the successes observed in animal models into the clinic. Perhaps the overwhelming drive for the increase in vascular gene transfer studies is the current lack of successful long-term pharmacological treatments for complex cardiovascular diseases. The increase in cardiovascular disease to epidemic proportions has also led many to conclude that drug therapy may have reached a plateau in its efficacy and that gene therapy may represent a realistic solution to a long-term problem. Here, we discuss gene delivery approaches and target diseases.

Molecular mechanisms of hepatic ischemia-reperfusion injury and preconditioning

Ischemia-reperfusion injury is, at least in part, responsible for the morbidity associated with liver surgery under total vascular exclusion or after liver transplantation. The pathophysiology of hepatic ischemia-reperfusion includes a number of mechanisms that contribute to various degrees in the overall injury. Some of the topics discussed in this review include cellular mechanisms of injury, formation of pro- and anti-inflammatory mediators, expression of adhesion molecules, and the role of oxidant stress during the inflammatory response. Furthermore, the roles of nitric oxide in preventing microcirculatory disturbances and as a substrate for peroxynitrite formation are reviewed. In addition, emerging mechanisms of protection by ischemic preconditioning are discussed. On the basis of current knowledge, preconditioning or pharmacological interventions that mimic these effects have the greatest potential to improve clinical outcome in liver surgery involving ischemic stress and reperfusion.

New method of delivering gene-altered Kupffer cells to rat liver: studies in an ischemia-reperfusion model

BACKGROUND & AIMS

Kupffer cells play a major role in the pathogenesis of several diseases. They release physiologically active substances that often lead to localized tissue injury. Therefore, the aim of this study was to establish a model to protect the liver through supplementation of Kupffer cells that have been transduced by recombinant adenovirus.

METHODS

Optimal conditions for intravenous injection in rats were established using carbon-labeled Kupffer cells. Adenoviral-transduced Kupffer cells encoding the Cu/Zn-SOD gene (Ad.SOD1) or beta-galactosidase reporter gene (Ad.LacZ) were transplanted into recipient rats. Twenty-four hours after transplantation, 70% hepatic ischemia-reperfusion was used to induce hepatic oxidative stress, and liver injury was determined 8 or 24 hours later.

RESULTS

In initial experiments, 10%-20% of the injected carbon-labeled cells were localized in the host liver after 24 hours, representing approximately 1% of the total population of Kupffer cells. Pretreatment of the recipient with a single dose of cyclosporin A maximized Kupffer cell reseeding up to 4%-10% of the total Kupffer cell population, suggesting that efficiency is limited by host immune response. Moreover, reseeded Kupffer cells were retained in host livers for up to 14 days after transplant. In livers of animals injected with Kupffer cells transduced with Ad.LacZ, transgene expression was observed, indicating Kupffer cell functional integrity. Injection of Kupffer cells transduced with Ad.SOD1 significantly blunted the increase in serum transaminases and liver injury because of ischemia-reperfusion compared with controls.

CONCLUSIONS

This novel approach allows delivery of transduced Kupffer cells in rats, which can be used as an investigative tool as well as a therapeutic strategy against inflammatory liver diseases.