Protective effect of liver ischemic preconditioning on liver and lung injury induced by hepatic ischemia-reperfusion in the rat

This study evaluates whether preconditioning could modulate the injurious effects of tumor necrosis factor (TNF) on liver and lung following hepatic ischemia-reperfusion (I/R) by inhibiting hepatic postischemic TNF release. The inhibition of hepatic TNF release from Kupffer cells with gadolinium chloride (GdCl(3)) previous to ischemia maintained TNF at control levels, attenuating the increases in transaminases, vascular permeability, and edema associated with hepatic I/R injury. TNF addition reverted this beneficial effect, indicating the implication of the TNF released mainly from Kupffer cells in hepatic I/R injury. Preconditioning prevented hepatic TNF increases, thus attenuating the liver injury, while TNF addition abolished the benefits of preconditioning. Inhibition of nitric oxide (NO) synthesis abolished the effect of preconditioning, whereas GdCl(3) addition avoided the injurious effect of NO inhibition. In addition, NO administration before I/R offered similar results to those found in preconditioning, while TNF addition abolished the benefits of NO. Thus, the effect of preconditioning on TNF release after hepatic I/R is mediated by NO. Inhibition of hepatic TNF release from Kupffer cells with GdCl(3) prevented both the increase in plasma TNF and the injurious effect in lung seen after hepatic I/R, and these effects were reverted with TNF addition. Preconditioning resulting in reduced hepatic TNF levels prevented the systemic TNF release, thus reducing the lung damage following hepatic I/R. However, TNF addition abolished the protective effect of preconditioning on lung injury. These findings indicate that preconditioning attenuates hepatic postischemic TNF release from Kupffer cells, thus probably reducing the liver and lung injury following hepatic I/R, and that this effect of preconditioning is mediated by NO.     

Preconditioning protects against systemic disorders associated with hepatic ischemia-reperfusion through blockade of tumor necrosis factor-induced P-selectin up-regulation in the rat

Previous studies indicate that ischemic preconditioning protects against lung injury resulting from hepatic ischemia-reperfusion (I/R) through inhibition of tumor necrosis factor (TNF) release from Kupffer cells. The present study investigated whether this effect is limited to the lung or is a generalized systemic response and explores the molecular mechanisms involved. Hepatic I/R led to an increase in neutrophil accumulation in liver, lung, and splanchnic organs. Although preconditioning did not modify neutrophil infiltration in liver during reperfusion, it conferred protection against hepatic injury associated with I/R. In remote organs, preconditioning abrogated the increase in P-selectin up-regulation, preventing neutrophil infiltration and thus reducing the oxidative stress and microvascular disorders following hepatic I/R in these organs. Administration of Abs against P-selectin or TNF previous to ischemia had the same effects as preconditioning. The effects of preconditioning on the blockade of P-selectin up-regulation probably results from inhibition of systemic TNF release from Kupffer cells. Supplementation of TNF abolished the benefits of preconditioning, whereas the injurious effects of TNF were prevented by previous blockade of P-selectin. The results of the present study suggest that ischemic preconditioning protects the liver against I/R injury by a mechanism independent of adhesion molecule expression and neutrophil accumulation. In remote organs, however, hepatic preconditioning prevents inflammatory damage by reducing the systemic TNF release from the liver and thus preventing P-selectin up-regulation.     

Protective effects of HGF-MSP chimer (metron factor-1) on liver ischemia-reperfusion injury in rat model

OBJECTIVE: It has been reported that metron factor-1 (MF-1), an engineered chimerical factor containing selected functional domains of hepatocyte growth factor and macrophage-stimulating protein (HGF–MSP), could prevent apoptosis and have an anti-inflammatory effect. In this study, we investigate the protective effect of MF-1 on liver ischemia-reperfusion (I/R) injury. METHODS: Overall 30 Sprague Dawley rats were randomly divided into three groups: the I/R model group (n = 12), the MF-1 treatment group (n = 12), and the sham-operated group (n = 6). Liver I/R injury was induced by clamping the blood supply to the left and median lobes of liver by an atraumatic clamp for 90 min, then removing the clamp and allowing reperfusion. Blood samples were obtained on days 1, 2, 3 and 7 to assess liver biochemistry and the histology of liver tissue. Levels of malondialdehyde (MDA), superoxide dismutase (SOD), nitric oxide (NO), endothelial nitric oxide synthase and inducible nitric oxide synthase were measured. In addition, the anti-oxidative effect of MF-1 on hepatocytes was assessed in vitro. RESULTS: MF-1 treatment improved the rat survival rate significantly (P < 0.05). Liver biochemistry and histological changes were significantly ameliorated. MDA increased and SOD and NO decreased in the liver tissue. In vitro, MF-1 protected the human hepatic cell line HL-7702 from damage of oxidative stress. CONCLUSION: MF-1 could protect the liver from I/R injury, which might involve the reduction of oxygen free radicals and the increase of NO synthesis in an injured liver.     

Effect of ischemic preconditioning on P-selectin expression in hepatocytes of rats with cirrhotic ischemia-reperfusion injury

AIM: To investigate the effects and mechanisms of ischemic preconditioning (IPC) on the ischemia/reperfusion (I/R) injury of liver cirrhosis in rats and the effect of IPC on P-selectin expression in hepatocytes.METHODS: Forty male SD rats with liver cirrhosis were randomly divided into sham operation group (SO group),ischemia/reperfusion group (I/R group), ischemic preconditioning group (IPC group), L-Arginine preconditioning group (APC group), L-NAME preconditioning group (NPC group), eight rats in each group. Hepatocellular viability was assessed by hepatic adenine nucleotide level and energy charge (EC) determined by HPLC, ALT, AST and LDH in serum measured by auto- biochemical analyzer and bile output.The expression of P-selectin in the liver tissue was analyzed by immunohistochemical technique. Leukocyte count in ischemic hepatic lobe was calculated.RESULTS: At 120 min after reperfusion, the level of ATP and EC in IPC and APC groups was higher than that in I/R group significantly. The increases in AST, ALT and LDH were prevented in IPC and APC groups. The livers produced more bile in IPC group than in I/R group during 120 min after reperfusion (0.101±0.027 versus 0.066±0.027 ml/g liver,P=0.002). There was a significant difference between APC and I/R groups, (P=0.001). The leukocyte count in liver tissues significantly increased in I/R group as compared with SO group (P＜0.05). The increase in the leukocyte count was prevented in IPC group. Administration of L-arginine resulted in the same effects as in IPC group. However,inhibition of NO synthesis (NPC group) held back the beneficial effects of preconditioning. Significant promotion of P-selectin expression in hepatocytes in the I/R group was observed compared with the SO group (P＜0.01). IPC or L-arginine attenuated P-selectin expression remarkably (P＜0.01). However, inhibition of NO synthesis enhanced Pselectin expression (P＜0.01). The degree of P-selectin expression was positively correlated with the leukocyte counts infiltrating in liver (r=0.602, P=0.000).CONCLUSION: IPC can attenuate the damage induced by I/R in cirrhotic liver and increase the ischemic tolerance of the rats with liver cirrhosis. IPC can abolish I/R induced leukocyte adhesion and infiltration by preventing postischemic P-selectin expression in the rats with liver cirrhosis via a NO-initiated pathway.     

Adenosine monophosphate-activated protein kinase mediates the protective effects of ischemic preconditioning on hepatic ischemia-reperfusion injury in the rat.

Hepatic ischemia-reperfusion (I/R) injury associated with liver transplantation and hepatic resections are an unresolved problem in the clinical practice. Preconditioning is known to preserve energy metabolism in liver during sustained ischemia, but the molecular mechanisms underlying this effect are still unclear. Different metabolic signals, including adenosine monophosphate (AMP) and nitric oxide (NO), have been implicated in preconditioning. AMP-activated protein kinase (AMPK) protects cells by acting as a low-fuel warning system, becoming switched on by adenosine triphosphate (ATP) depletion. NO synthesis is induced by AMPK in the heart during ischemia. The aim of this study was to investigate: 1) whether preconditioning induces AMPK activation; and 2) if AMPK activation leads to ATP preservation and reduced lactate accumulation during prolonged ischemia and its relationship with NO. Preconditioning activated AMPK and concomitantly reduced ATP degradation, lactate accumulation, and hepatic injury. The administration of an AMPK activator, AICAR, before ischemia simulated the benefits of preconditioning on energy metabolism and hepatic injury. The inhibition of AMPK abolished the protective effects of preconditioning. The effect of AMPK on energy metabolism was independent of NO because the inhibition of NO synthesis in the preconditioned group and the administration of the NO donor before ischemia, or to the preconditioned group with previous inhibition of AMPK, had no effect on energy metabolism. Both preconditioning and AICAR pretreatment, through AMPK activation, may be useful surgical and pharmacologic strategies aimed at reducing hepatic I/R injury.     

Dihydrolipoyl histidinate zinc complex, a new antioxidant, attenuates hepatic ischemia-reperfusion injury in rats

Background and Aims: Ischemia/reperfusion (I/R) injury is characterized by significant oxidative stress, which induces characteristic changes in the antioxidant system and organ injury leading to significant morbidity and mortality. The aim of this study was to evaluate the protective effect of dihydrolipoyl histidinate zinc complex (DHLHZn) on oxidative damage after severe hepatic I/R injury. Methods: Thirty male Wistar rats were subjected to 45 min of hepatic ischemia by clamping of the hepatic artery and portal vein, followed by a 6‐h reperfusion period. DHLHZn (10 mg/kg) (I/R + DHLHZn group) or saline (I/R group) was administered intraperitoneally twice, 30 min before ischemia and at the beginning of the reperfusion. Sham‐operated animals (sham group) received equal amounts of saline. The rats were killed at the end of the reperfusion period. Serum levels of aspartate aminotransferase and alanine aminotransferase were determined, and histological examination and oxidative stress were evaluated in liver tissues. In addition, antimycin A‐stimulated RAW264.7 cells (murine macrophage‐like cells) were treated with DHLHZn to estimate its antioxidant effect. Results: Serum aspartate aminotransferase and alanine aminotransferase levels were increased in the I/R group, but these increases were significantly inhibited in the I/R + DHLHZn group. Similarly, liver tissue damage observed in the I/R group was attenuated in the I/R + DHLHZn group. Cells treated in vitro with both DHLHZn and antimycin A showed reduced reactive oxygen species activity compared to cells treated with antimycin A alone. Conclusion: The new antioxidant DHLHZn may have potential for therapeutic application in liver I/R injury, although this is a limited animal study.     

Remote ischemic preconditioning protects liver ischemia-reperfusion injury by regulating eNOS-NO pathway and liver microRNA expres-sions in fatty liver rats

BACKGROUND: Ischemic preconditioning (IPC) is a strategy to reduce ischemia-reperfusion (I/R) injury. The protective effect of remote ischemic preconditioning (RIPC) on liver I/R injury is not clear. This study aimed to investigate the roles of RIPC in liver I/R in fatty liver rats and the involvement of en-dothelial nitric oxide synthase-nitric oxide (eNOS-NO) path-way and microRNA expressions in this process. METHODS: A total of 32 fatty rats were randomly divided into the sham group, I/R group, RIPC group and RIPC+I/R group. Serum alanine aminotransferase (ALT), aspartate ami-notransferase (AST) and nitric oxide (NO) were measured. Hematoxylin-eosin staining was used to observe histological changes of liver tissues, TUNEL to detect hepatocyte apoptosis, and immunohistochemistry assay to detect heat shock protein 70 (HSP70) expression. Western blotting was used to detect liver inducible NOS (iNOS) and eNOS protein levels and real-time quantitative polymerase chain reaction to detect miR-34a, miR-122 and miR-27b expressions. RESULTS: Compared with the sham and RIPC groups, serum ALT, AST and iNOS in liver tissue were significantly higher in other two groups,while serum NO and eNOS in liver tissue were lower, and varying degrees of edema, degeneration and in-flammatory cell infiltration were found. Cell apoptosis num-ber was slightly lower in the RIPC+I/R group than that in I/R group. Compared with the sham group, HSP70 expressions were significantly increased in other three groups (all P<0.05). Compared with the sham and RIPC groups, elevated miR-34a expressions were found in I/R and RIPC+I/R groups (P<0.05). MiR-122 and miR-27b were found significantly decreased in I/R and RIPC+I/R groups compared with the sham and RIPC groups (all P<0.05). CONCLUSION: RIPC can reduce fatty liver I/R injury by affect-ing the eNOS-NO pathway and liver microRNA expressions.     

An insight into the protection of rat liver against ischemia/reperfusion injury by 2-selenium-bridged β-cyclodextrin

Aim:  The reperfusion following liver ischemia results in the damage and apoptosis of hepatocytes. The aim of this study was to investigate the possible effects and mechanism of a new synthesized glutathione peroxidase (GPX) mimic, 2-selenium-bridged β-cyclodextrin (2-SeCD), on rat liver ischemia-reperfusion (I/R) injury.
Methods:  Male Wistar rats ( n  = 32) were randomly divided into four groups: I. sham-operated group, II. I/R group, III. I/R +2-SeCD group, IV. I/R + Ebselen group. Hepatic I/R was administered by 90 min of ischemia and 12 h of reperfusion. Liver tissues were collected at the end of reperfusion period for measurement of various biochemical parameters.
Results:  The serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) activity and tissue malondialdehyde, myeloperoxidase levels were increased in I/R group, while the increase was significantly reduced by 2-SeCD treatment. The glutathione level, depressed by I/R, was elevated back to normal levels by treatment with 2-SeCD. Severe hepatic damage were observed by light and transmission electron microscopy whilst pretreatment with 2-SeCD resulted in tissue and cellular preservation. Furthermore, 2-SeCD reduced cytochrome c release from mitochondria and subsequent DNA fragmentation by regulating Bcl-2/Bax expression ratio. Results suggested that 2-SeCD was more effective than ebselen in the reversal of the alteration in tissue structural and biochemical parameters caused by I/R injury.
Conclusion:  2-selenium-bridged β-cyclodextrin playes an important role in the protection of liver against I/R injury and this treatment may be a novel pharmacological agent for liver surgery.     

Protective effect of curcumin against liver warm ischemia/reperfusion injury in rat model is associated with regulation of heat shock protein and antioxidant enzymes

AIM： To investigate the hypothesis that the protective effects of curcumin in hepatic warm ischemia/reperfusion （I/R） injury are associated with increasing heat shock protein 70 （Hsp70） expression and antioxidant enzyme activity. METHODS： Sixty Sprague-Dawley male rats were randomly divided into sham, I/R, C ＋ I/R groups. The model of reduced-size liver warm ischemia and reperfusion was used. Curcumin （50 mg/kg） was administered by injection through a branch of superior mesenteric vein at 30 min before ischemia in C ＋ I/R group. Five rats were used to investigate the survival during 1 wk after operation in each group. Blood samples and liver tissues were obtained in the remaining animals after 3, 12, and 24 h of reperfusion to assess serum alanine aminotransferase （ALT）, aspartate aminotransferase （AST）, liver tissue NO2- ＋ NO3-, malondialdehyde （MDA） content, superoxide dismutase （SOD）, catalase （CAT）, nitricoxide synthase （NOS） and myeloperoxidase （MPO） activity, HspT0 expression and apoptosis ratio. RESULTS： Compared with I/R group, curcumin pretreatment group showed less ischemia/reperfusioninduced injury. CAT and SOD activity and Hsp70 expression increased significantly. A higher rate of apoptosis was observed in I/R group than in C ＋ I/R group, and a significant increase of MDA, NO2^- ＋ NO3^- and MPO level in liver tissues and serum transaminase concentration was also observed in I/R group compared to C ＋ I/R group. Curcumin also decreased the activity of inducible NO synthase （iNOS） in liver after reperfusion,but had no effect on the level of endothelial NO synthase （eNOS） after reperfusion in liver. The 7 d survival rate was significantly higher in C ＋ I/R group than in I/R group. CONCLUSION： Curcumin has protective effects against hepatic I/R injury. Its mechanism might be related to the overexpression of Hsp70 and antioxidant enzymes.     

Liver-lung interactions following Escherichia coli bacteremic sepsis and secondary hepatic ischemia/reperfusion injury

We hypothesized that ischemia/reperfusion (I/R) injury of the liver during normotensive gram-negative bacteremic sepsis alters the kinetics of circulating endotoxin, tumor necrosis factor-alpha (TNF-alpha), and coinduced mediators, thereby exacerbating sepsis-induced lung inflammation. Liver and lung dysfunction were studied after hematogenous infection of Sprague-Dawley rats with 10(9) Escherichia coli serotype O55:B5 (EC) and 90 min of secondary hepatic ischemia in EC + I/R and saline-infused (normal saline NS) x I/R rats, followed by brief (1 h) or longer reperfusion (24 h). TNF- alpha:leukotriene interactions in this model were examined using the 5-lipoxygenase-activating protein inhibitor MK-886. Compared with sham-operated EC + Sham animals, peak serum endotoxin, TNF-alpha, alanine aminotransferase, interleukin-6 (IL-6), and hepatic neutrophil (PMN) influx were higher in EC + I/R rats through 24 h (p < 0.05) despite comparable arterial pressure. Lung PMN influx and wet/dry weight ratios were likewise enhanced in EC + I/R versus EC + Sham or NS + I/R rats. MK-886 attenuated TNF-alpha concentrations and ischemic liver injury but not mortality. Thus, focal hepatic I/R augments circulating endotoxin, TNF-alpha, and postbacteremic lung inflammation early after normotensive E. coli bacteremic sepsis.     

Ischemic preconditioning affects interleukin release in fatty livers of rats undergoing ischemia/reperfusion

The present study evaluates the effect of ischemic preconditioning on interleukin-1 (IL-1) and interleukin-10 (IL-10) generation following hepatic ischemia/reperfusion (I/R) in normal and steatotic livers as well as the role of nitric oxide (NO) in this process. Increased IL-1beta and IL-10 levels were observed in normal livers after I/R. Steatotic livers showed higher IL-1beta levels than normal livers, and IL-10 at control levels. The injurious role of IL-1beta and the benefits of IL-10 on hepatic I/R injury was shown with the use of IL-1 receptor antagonist (IL-1ra), anti-IL-10 polyclonal antibody against IL-10 (anti-IL-10) and exogenous IL-10. The effective dose of these treatments was different in both types of livers. Preconditioning prevented IL-1beta release and increased IL-10 generation after I/R in normal and steatotic livers. IL-1beta or anti-IL-10 pretreatments reversed the benefits of preconditioning. IL-1beta action inhibition in a preconditioned group that was pretreated with anti-IL-10 did not modify the benefits of preconditioning. In addition, anti-IL-10 pretreatment in the preconditioned group resulted in IL-1beta levels comparable to those observed after I/R. NO inhibition eliminated the benefits of preconditioning on IL-10 release, IL-1beta levels, and hepatic injury. In conclusion, preconditioning, through IL-10 overproduction, inhibits IL-1beta release and the ensuing hepatic I/R injury in normal and steatotic livers. IL-10 generation induced by preconditioning could be mediated by NO.     

Relationships between NOS2 and HO-1 in liver of rats with chronic bile duct ligation.

An increased expression and activity of the heme oxygenase-1 (HO-1) in the liver has been observed in models of hepatic damage. Nitric oxide (NO) seems to be involved in HO-1 regulation. The aim of this work is to assess HO-1 induction and heme oxygenase (HO) activity in rats with bile duct ligation (BDL). We have assessed the effect of chronic inhibition of the NO synthesis by N(G)-nitro-l-arginine methyl ester (l-NAME) on HO-1 induction and HO activity. In the BDL animals, compared with sham-operated ones, we found an increased plasma nitrite and bilirubin concentration, and a marked liver expression of inducible nitric oxide synthase and HO-1, assessed by both Western blot and immunohistochemistry. Chronic l-NAME treatment prevented plasma nitrite increase in animals subjected to BDL. BDL animals treated with l-NAME, compared with untreated BDL rats, showed an important decrease in HO-1 expression and in HO activity (assessed as a decreased plasma bilirubin and bilirubin excretion). In conclusion, our experiments show parallel changes in expression and activity of HO-1 and NOS2 activity in the BDL model of liver damage and suggest that increased NO production is involved in HO-1 overexpression.     

Mechanisms of the beneficial actions of ischemic preconditioning on subcellular remodeling in ischemic-reperfused heart

Cardiac function is compromised by oxidative stress which occurs upon exposing the heart to ischemia reperfusion (I/R) for a prolonged period. The reactive oxygen species (ROS) that are generated during I/R incur extensive damage to the myocardium and result in subcellular organelle remodeling. The cardiac nucleus, glycocalyx, myofilaments, sarcoplasmic reticulum, sarcolemma, and mitochondria are affected by ROS during I/R injury. On the other hand, brief periods of ischemia followed by reperfusion, or ischemic preconditioning (IPC), have been shown to be cardioprotective against oxidative stress by attenuating the cellular damage and alterations of subcellular organelles caused by subsequent I/R injury. Endogenous defense mechanisms, such as antioxidant enzymes and heat shock proteins, are activated by IPC and thus prevent damage caused by oxidative stress. Although these cardioprotective effects of IPC against I/R injury are considered to be a consequence of changes in the redox state of cardiomyocytes, IPC is considered to promote the production of NO which may protect subcellular organelles from the deleterious actions of oxidative stress. The article is intended to focus on the I/R-induced oxidative damage to subcellular organelles and to highlight the cardioprotective effects of IPC. In addition, the actions of various endogenous cardioprotective interventions are discussed to illustrate that changes in the redox state due to IPC are cardioprotective against I/R injury to the heart.     

Hypothermia is better than ischemic preconditioning for preventing early hepatic ischemia/reperfusion in rats

Background. Topical hypothermia (TH) and ischemic preconditioning (IPC) are used to decrease I/R injury. The efficacy of isolated or combined use of TH and IPC in the liver regarding inflammation and cytoprotection in early ischemia/reperfusion (I/R) injury needs to be evaluated.Material and methods. Wistar rats underwent 70% liver ischemia for 90 min followed by 120 min of reperfusion. Livers of animals allocated in the sham, normothermic ischemia (NI), IPC, TH, and TH+IPC groups were collected for molecular analyses by ELISA and Western blot, aiming to compare proinflammatory, anti-inflammatory, and antioxidant profiles.Results. Compared with NI, TH presented decreased tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-12 concentrations and increased IL-10 levels. TH animals displayed lower inducible nitric oxide synthase (iNOS) and higher endothelial nitric oxide synthase (eNOS) expressions. NAD(P)H-quinone oxidoreductase-1(NQO1) expression was also lower with TH. Isolated IPC and NI were similar regarding all these markers. TH+IPC was associated with decreased IL-12 concentration and reduced iNOS and NQO1 expressions, similarly to isolated TH. Expression of Kelch-like ECH-associated protein (Keap)-1 was increased and expression of nuclear and cytosolic nuclear erythroid 2-related factor 2 (Nrf2) was decreased with TH+IPC vs. NI.Conclusion. TH was the most effective method of protection against early I/R injury. Isolated IPC entailed triggering of second-line antioxidant defense enzymes. Combined TH+IPC seemed to confer no additional advantage over isolated TH in relation to the inflammatory process, but had the advantage of completely avoid second-line antioxidant defense enzymes.     

Sterile inflammation in hepatic ischemia/reperfusion injury: Present concepts and potential therapeutics

Ischemia and reperfusion (I/R) injury is an often unavoidable consequence of major liver surgery and is characterized by a sterile inflammatory response that jeopardizes the viability of the organ. The inflammatory response results from acute oxidative and nitrosative stress and consequent hepatocellular death during the early reperfusion phase, which causes the release of endogenous self‐antigens known as damage‐associated molecular patterns (DAMPs). DAMPs, in turn, are indirectly responsible for a second wave of reactive oxygen and nitrogen species (ROS and RNS) production by driving the chemoattraction of various leukocyte subsets that exacerbate oxidative liver damage during the later stages of reperfusion. In this review, the molecular mechanisms underlying hepatic I/R injury are outlined, with emphasis on the interplay between ROS/RNS, DAMPs, and the cell types that either produce ROS/RNS and DAMPs or respond to them. This theoretical background is subsequently used to explain why current interventions for hepatic I/R injury have not been very successful. Moreover, novel therapeutic modalities are addressed, including MitoSNO and nilotinib, and metalloporphyrins on the basis of the updated paradigm of hepatic I/R injury.     

Preconditioning protects liver and lung damage in rat liver transplantation: role of xanthine/xanthine oxidase

This study was designed to evaluate whether ischemic preconditioning could confer protection against liver and lung damage associated with liver transplantation. The effect of preconditioning on the xanthine/xanthine oxidase (XOD) system in liver grafts subjected to 8 and 16 hours of cold ischemia was also evaluated. Increased xanthine levels and marked conversion of xanthine dehydrogenase (XDH) to XOD were observed after hepatic cold ischemia. Xanthine/XOD could play a role in the liver and lung damage associated with liver transplantation. This assumption is based on the observation that inhibition of XOD reduced postischemic reactive oxygen species (ROS) generation and hepatic injury as well as ensuing lung inflammatory damage, including neutrophil accumulation, oxidative stress, and edema formation. Ischemic preconditioning reduced xanthine accumulation and conversion of XDH to XOD in liver grafts during cold ischemia. This could diminish liver and lung damage following liver transplantation. In the liver, preconditioning prevented postischemic ROS generation and hepatic injury as well as the injurious effects in the lung following liver transplantation. Administration of xanthine and XOD to preconditioned rats led to hepatic ROS and transaminase levels similar to those found after reperfusion and abolished the protective effect of preconditioning on the lung inflammatory damage. In conclusion, ischemic preconditioning reduces both liver and lung damage following liver transplantation. This endogenous protective mechanism is capable of blocking xanthine/XOD generation in liver grafts during cold ischemia.     

Gender differences in hepatic ischemic reperfusion injury in rats are associated with endothelial cell nitric oxide synthase-derived nitric oxide

AIM: This study was designed to examine the hypothesis that gender differences in I/R injury are associated with endothelial cell nitric oxide synthase (eNOS)-derived nitric oxide (NO). METHODS: Wistar rats were randomized into seven experimental groups (12 animals per group). Except for the sham operated groups, all rats were subjected to total liver ischemia for 40 min followed by reperfusion. All experimental groups received different treatments 45 min before the laparotomy. For each group, half of the animals (six) were used to investigate the survival; blood samples and liver tissues were obtained in the remaining six animals after 3 h of reperfusion to assess serum NO, alanine aminotransferase (ALT) and TNF-α levels, liver tissue malondialdehyde (MDA) content, and severity of hepatic I/R injury. RESULTS: Basal serum NO levels in female sham operated (FS) group were nearly 1.5-fold of male sham operated (MS) group (66.7±11.0 μmol/L vs45.3μ10.1 μmol/L, P<0.01). Although serum NO levels decreased significantly after hepatic I/R (P<0.01, vs sham operated groups), they were still significantly higher in female rat (F) group than in male rat (M) group (47.8±8.6 μmol/L vs 23.8±4.7 μmol/L, P<0.01). Serum ALT and TNF-α levels, and liver tissue MDA content were significantly lower in F group than in M group (370.5±46.4 U/L, 0.99±0.11 μg/L and 0.57±0.10 μmol/g vs668.7±78.7 U/L, 1.71±0.18μg/L and 0.86±0.11 μmol/g, respectively, P<0.01). I/R induced significant injury to the liver both in M and F groups (P<0.01 vs sham operated groups). But the degree of hepatocyte injury was significantly milder in F group than in M group (P<0.05 and P<0.01). The median survival time was six days in F group and one day in M group. The overall survival rate was significantly higher in F group than in M group (P<0.05). When compared with male rats pretreated with saline (M group), pretreatment of male rats with 17-β-estradiol (E2) (M+E2 group) significantly increased serum NO levels and significantly decreased serum ALT and TNF-α levels, and liver tissue MDA content after I/R (P<0.01). The degree of hepatocyte injury was significantly decreased and the overall survival rate was significantly improved in M+E2 group than in M group (P<0.01 and P<0.05). The NOS inhibitor Nw-nitro-L-arginine methyl ester (L-NAME) treatment could completely abolish the protective effects of estrogen in both male and female rats. CONCLUSION: The protective effects afforded to female rats subjected to hepatic I/R are associated with eNOS-derived NO.     

Adenosine monophosphate-activated protein kinase and nitric oxide in rat steatotic liver transplantation

BACKGROUND/AIMS: Hepatic steatosis is a risk factor for transplantation. We examined the role of AMP-activated protein kinase (AMPK) and nitric oxide (NO) in the benefits of preconditioning in steatotic liver transplantation. METHODS: Steatotic liver transplantation with or without preconditioning was induced in Zucker rats. The activities of AMPK and NO synthase (NOS) were measured and altered pharmacologically. RESULTS: Preconditioning or AMPK activation with aminoimidazole-4-carboxamide ribonucleoside (AICAR) increased AMPK and constitutive NOS activities and protected against lipid peroxidation, nitrotyrosine formation and hepatic injury in both grafts. Inhibition of AMPK activity removed the benefits of preconditioning. NO synthesis inhibition abolished the benefits of preconditioning or AICAR. Therefore, preconditioning or AICAR, through AMPK activation, may induce NO synthesis, thus protecting against hepatic injury in both steatotic and non-steatotic liver transplantation. In non-steatotic grafts, NO donors simulated the benefits of preconditioning. However, in steatotic grafts, NO supplementation was ineffective. CONCLUSIONS: These results indicate (a) a potential relationship between AMPK and NO in the benefits of preconditioning in steatotic liver transplantation, (b) AICAR as a new phamacological strategy in steatotic liver transplantation and (c) a differential effect of NO supplementation in both grafts.