Improvement of hepatic microhemodynamics by N-acetylcysteine after warm ischemia

Non-invasive diagnosis and treatment strategies for traumatic brain injury: an update

PURPOSE OF REVIEW

Traumatic Brain Injury (TBI) remains the leading cause of morbidity and mortality in U.S. Since the last decade, there have been several advances in the understanding and management of TBI that have shown the potential to improve outcomes. The aim of this review is to provide a useful overview of these potential diagnostic and treatment strategies that have yet to be proven, along with an assessment of their impact on outcomes after a TBI.

RECENT FINDINGS

Recent technical advances in the management of a TBI are grounded in a better understanding of the pathophysiology of primary and secondary insult to the brain after a TBI. Hence, clinical trials on humans should proceed in order to evaluate their efficacy and safety.

SUMMARY

Mortality associated with TBI remains high. Nonetheless, new diagnostic and therapeutic techniques have the potential to enhance early detection and prevention of secondary brain insult.

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.

N-acetylcysteine administration does not improve patient outcome after liver resection

BACKGROUND

Post-operative hepatic dysfunction is a major cause of concern when undertaking a liver resection. The generation of reactive oxygen species (ROS) as a result of hepatic ischaemia/reperfusion (I/R) injury can result in hepatocellular injury. Experimental evidence suggests that N-acetylcysteine may ameliorate ROS-mediated liver injury.

METHODS

A cohort of 44 patients who had undergone a liver resection and receiving peri-operative N-acetylcysteine (NAC) were compared with a further cohort of 44 patients who did not. Liver function tests were compared on post-operative days 1, 3 and 5. Peri-operative outcome data were retrieved from a prospectively maintained database within our unit.

RESULTS

Administration of NAC was associated with a prolonged prothrombin time on the third post-operative day (18.4 versus 16.4 s; P = 0.002). The incidence of grades B and C liver failure was lower in the NAC group although this difference did not reach statistical significance (6.9% versus 14%; P = 0.287). The overall complication rate was similar between groups (32% versus 25%; P = ns). There were two peri-operative deaths in the NAC group and one in the control group (P = NS).

CONCLUSION

In spite of promising experimental evidence, this study was not able to demonstrate any advantage in the routine administration of peri-operative NAC in patients undergoing a liver resection.

N-acetyl cysteine improves glycogenesis after segmental liver ischemia and reperfusion injury in pigs

OBJECTIVE

N-acetylcysteine (NAC) is an antioxidative molecule known to protect liver tissue from oxygen radical species generated during ischemia and reperfusion (IR). Nutritional and toxicology studies have shown that NAC also improves glucose metabolism and glycogen stores. We hypothesized that NAC improves glycogenesis and that impaired glycogenesis is a key element in IR injury.

MATERIAL AND METHODS

In an experimental model, 80 min of segmental liver ischemia was induced in 16 pigs and the reperfusion was followed for 360 min. Eight animals received NAC 150 mg/kg as a bolus injection followed by an infusion of NAC 50 mg/kg/h intravenously.

RESULTS

AST and leukocyte density were lower in the NAC-treated animals, unrelated to the glutathione levels or apoptosis. Glycogen stores returned to a higher degree in the NAC-treated animals and microdialysis revealed lower levels of lactate during the reperfusion phase. Nitrite/Nitrate levels in the NAC group were lower in both serum and microdialysates, indicating that NAC scavenges radical nitrosative species.

CONCLUSIONS

NAC treatment improves glycogenesis after liver IR injury and reduces the level of intraparenchymal lactate during reperfusion, possibly due to the scavenging of radical nitrosative species.

Decreased apoptosis in fatty livers submitted to subnormothermic machine-perfusion respect to cold storage

Machine perfusion at subnormothermic temperature (20°C), MP20, was developed by Vairetti et al. and showed to afford a better preservation of fatty livers respect to traditional cold storage (CS) in terms of enzyme release into the perfusate and bile, glycogen stores, energy charge and oxidative stress. Here we investigated whether it also caused decreased cell death by apoptosis. Fatty and lean Zucker rats were submitted to MP20 or CS for 6 h and reperfused normothermically for 2 h. Apoptotic cells were revealed by immunohistochemistry of activated caspase-3 and M30 (new epitope on CK18 degraded by caspase-3) and by the TUNEL assay. Portal pressure was also determined. A statistically significant reduction of hepatocyte apoptosis, but especially of sinusoidal cells was determined for fatty livers submitted to MP20 respect to CS. Portal pressure was significantly lower after MP20 respect to CS. The reduction of sinusoidal cell death by apoptosis without need for anti-apoptotic therapies appears particularly positive since apoptotic sinusoidal cells hinder microcirculation in the sinusoids and are thrombogenic. These results further confirm the potential of MP20 for preserving fatty livers that would be otherwise discarded as grafts, and thus for increasing the donor pool for liver transplantation.

Experimental and clinical evidence for modification of hepatic ischaemia-reperfusion injury by N-acetylcysteine during major liver surgery

BACKGROUND

Hepatic ischaemia-reperfusion (I/R) injury occurs in both liver resectional surgery and in transplantation. The biochemistry of I/R injury involves short-lived oxygen free radicals. N-acetylcysteine (NAC) is a thiol-containing synthetic compound used in the treatment of acetaminophen toxicity. The present study is a detailed overview of the experimental and clinical evidence for the use of NAC as a pharmaco-protection agent in patients undergoing major liver surgery or transplantation.

METHODS

A computerized search of the Medline, Embase and SCI databases for the period from 1st January 1988 to 31st December 2008 produced 40 reports. For clinical studies, the quality of reports was assessed according to the criteria reported by the Cochrane communication review group.

RESULTS

Nineteen studies evaluated NAC in experimental liver I/R injury. NAC was administered before induction of ischaemia in 13. The most widely used concentration was 150 mg/kg by intravenous bolus. Fifteen studies report an improvement in outcome, predominantly a reduction in transaminase. Seven studies used an isolated perfused liver model with all showing improvement (predominantly an improvement in bile production after N-acetylcysteine). Two out of four transplantation models showed an improvement in hepatic function. Clinical studies in transplantation show a modest improvement in transaminase levels with no beneficial effect on either patient or graft survival.

CONCLUSION

N-acetylcysteine, given before induction of a liver I/R injury in an experimental model can ameliorate liver injury. Clinical outcome data are limited and there is currently little evidence to justify use either in liver transplantation or in liver resectional surgery.

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

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

Effects of N-acetylcysteine on regeneration following partial hepatectomy in rats with nonalcoholic fatty liver disease

PURPOSE

To investigate the effect of N-acetylcysteine on regeneration following partial hepatectomy in rats with nonalcoholic fatty liver disease (NAFLD).

METHODS

N-Acetylcysteine was given to seven rats with NAFLD (group 1); physiological saline was given to seven rats with NAFLD (group 2); and physiological saline was given to seven rats with a normal liver (group 3). We performed two-thirds hepatectomy in all rats and removed the remnant liver tissue 48 h later to measure the mitotic index (MI), proliferating cell nuclear antigen, glutathione (GSH), and malondialdehyde (MDA) levels.

RESULTS

Mitotic index values were significantly higher in group 1 than in groups 2 and 3, and higher in group 3 than in group 2. Proliferating cell nuclear antigen values were significantly higher in group 1 than in group 2, but no significant difference was found in comparison with group 3. Glutathione values in group 1 were significantly higher than in group 2 and MDA values in group 1 were lower than in group 2. There was no significant difference between groups 1 and 3 in GSH and MDA values, in both the two-thirds hepatectomy and 48-h tissues.

CONCLUSIONS

N-Acetylcysteine enhanced regeneration after partial hepatectomy in rats with NAFLD. We believe that it exerted this effect through its influence on oxidative stress.

Ginkgo Biloba Extract EGb 761 Alleviates Hepatic Fibrosis and Sinusoidal Microcirculation Disturbance in Patients with Chronic Hepatitis B

Background

Few clinical data are available regarding the effect of Ginkgo biloba extract (EGb 761) on liver microcirculation and fibrosis. This randomized, controlled trial is to investigate the effect of Ginko biloba extract EGb 761 on liver fibrosis and hepatic microcirculation in patients with chronic hepatitis B.

Methods

Sixty-four patients with chronic hepatitis B were randomized for intention-to-treat. Thirty-two patients were assigned to treated group receiving EGb 761 plus polyunsaturated phosphatidylcholine (Essentiale), 32 patients received Essentiale as controls. Blood samples were taken for measurement of transforming growth factor beta-1 (TGF-β1), platelet activate factor (PAF), endothelin 1 (ET-1). Twenty-six patients in treated group and 21 patients in control group underwent liver biopsies for histology before and after treatment. Ultrastructural study for sinusoidal microcirculation before and after treatment was carried out on 10 randomly selected patients in each group.

Results

In the treated group, after EGb 761 treatment, there was a significant reduction of blood TGF- β1, PAF and ET-1 (p<0.05), whereas this was not observed in the controls. After treatment in both groups, there were significant decrease of ALT, TBil and PT (p<0.05), and significant increase of ALB (p<0.05). Hepatic inflammation and fibrosis significantly alleviated in the treated group, but not in the controls. After EGb 761 treatment, electron microscopy showed red blood cell aggregates and microthrombosis disappeared or decreased in sinusoids; collagen deposits in sinusoidal lumen and Disse space reduced; sinusoidal capillarization alleviated.

Conclusions

EGb 761 can improve sinusoidal microcirculation, alleviate inflammation and inhibit fibrosis through multiple mechanisms, it is effective in the treatment of chronic liver diseases.

Protective effects of N-acetylcysteine and Ginkgo biloba extract on ischaemia-reperfusion-induced hepatic DNA damage in rats

Hepatic ischaemia-reperfusion injury is a serious problem that occurs during various surgical operations such as liver transplantation, surgical revascularization, and partial organ resection. Different pharmacological agents have been used for the protection of organ function and for extending the tolerable ischaemic interval after the ischaemic insult. We aimed to determine the presence of 8-hydroxydeoxyguanosine (8-OHdG) in the DNA from liver undergoing ischaemia-reperfusion, and also to evaluate the protective effects of N-acetylcysteine (NAC) and EGb761 (Ginkgo biloba extract) against hepatic oxidative DNA damage. A total of 40 rats were divided into four groups of 10 animals each (sham-operation group, control group, NAC group, and EGb761 group). Oxidative damage to DNA was evaluated by measuring the increase in 8-OHdG formation in liver tissue and also the effects of NAC and EGb761 pretreatment. Hepatic ischaemia for 90 min followed by reperfusion caused a marked increase in tissue levels of 8-OHdG, thiobarbituric acid-reactive substance, serum ALT, AST and LDH activities compared to sham-operated group. Pretreatment with both NAC and EGb761 clearly diminished 8-OHdG formation and lipid peroxidation. These findings suggest that antioxidant molecules such as NAC and EGb761 may be useful in preventing postischaemic reperfusion injury in hepatic tissue.

Effects of N-acetylcysteine administration in hepatic microcirculation of rats with biliary cirrhosis

BACKGROUND/AIMS

Increased intrahepatic resistance (IHR) in cirrhosis is due to fibrosis and hepatic endothelial dysfunction (HED). Besides producing fibrosis, increased reactive oxygen species (ROS) promotes ROS-related nitration of anti-oxidative enzymes in cirrhotic livers. Tyrosine nitration (nitrotyrosilation)-related inactivation of anti-oxidative enzymes is increased in cirrhotic livers. This study investigates effects of N-acetylcysteine (NAC) administrations in bile-duct-ligation (BDL) rats.

METHODS

This study measured portal venous pressure (PVP), IHR, hepatic endothelial function, hepatic levels of anti-oxidants and oxidants, type III procollagen (PIIIP), proteins expression of thromboxane synthase (TXS), nitrotyrosine, manganese superoxide dismutase (MnSOD), and hepatic NOx and thromboxane A(2) (TXA(2)) production in perfusates.

RESULTS

The improvement of HED was associated with decreased PVP and IHR, hepatic protein and mRNA levels of PIIIP, protein expression of TXS and nitrotyrosine, oxidants and production of TXA(2) in NAC-treated BDL rat livers. Conversely, hepatic NOx production, anti-oxidants, and protein expression of MnSOD were increased in NAC-treated BDL rat livers.

CONCLUSIONS

In NAC-treated cirrhotic rats, the decrease in IHR was mainly caused by its anti-oxidative effect-related prevention of hepatic fibrogenesis associated with the decrease of oxidants-related nitrotyrosilation and improvement of HED.

N-Acetylcysteine Use in Ischemic Hepatitis

We describe a case of antidepressant-induced ischemic hepatitis that responded to intravenous administration of N-acetylcysteine. Cytoprotection in the setting of ischemic hepatitis may be a therapeutic effect of N-acetylcysteine.

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.

Acute effects of N-acetylcysteine on skeletal muscle microcirculation following closed soft tissue trauma in rats

Trauma-induced microcirculatory dysfunction, formation of free radicals and decreased endothelial release of nitric oxide (NO) contribute to evolving tissue damage following skeletal muscle injury. Administration of N-acetylcysteine (NAC) known to scavenge free radicals and generate NO is considered a valuable therapeutic approach. Thus, the objective of this study was to quantitatively analyze the acute effects of NAC on skeletal muscle microcirculation and leukocyte-endothelial cell interaction following severe standardized closed soft tissue injury (CSTI). Severe CSTI was induced in the hindlimbs of 14 male anesthetized Sprague-Dawley rats using the controlled impact injury technique. Rats were randomly assigned (n = 7) to high-dose intravenous infusion of NAC (400 mg/kg body weight) or isovolemic normal saline (NS). Non-injured, sham-operated animals (n = 7) were subjected to the same surgical procedures but did not receive any additional fluid. Creatin kinase (CK) activity was assessed at baseline, 1 h before and 2 h following posttraumatic NAC or NS infusion. Microcirculation of the extensor digitorum longus (EDL) muscle was analyzed using intravital microscopy and Laser-Doppler flowmetry (LDF). Edema index (EI) was calculated by measuring the EDL wet-to-dry weight ratio (EI=injured/contralateral limb). EDL-muscles were analyzed for desmin immunoreactivity and granulocyte infiltration. Microvascular deteriorations observed following NS-infusion were effectively reversed by NAC: Functional capillary density was restored to levels found in sham-operated animals and leukocyte adherence was significantly (p < 0.05) reduced compared to the NS group. NAC significantly (p < 0.05) increased erythrocyte flux determined by Laser-Doppler flowmetry. Posttraumatic serum CK levels and EI were significantly (p < 0.05) decreased by NAC. During the posttraumatic acute phase, single infusion of NAC markedly reduced posttraumatic microvascular dysfunction, attenuated both leukocyte adherence and tissue infiltration. NAC also decreased CSTI-induced edema formation and myonecrosis as reflected by attenuated serum CK levels and attenuated loss of desmin immunoreactivity. NAC may serve as an effective therapeutic strategy by supporting microvascular blood supply and tissue viability in the early posttraumatic period. Additional studies aimed at long-term analysis and investigation of injury severity--or dosage dependency are needed.

Continuous infusion of N-acetylcysteine reduces liver warm ischaemia–reperfusion injury

Background

N-acetylcysteine (NAC) may modulate the initial phase (less than 2 h) of liver warm ischaemia–reperfusion (IR) injury but its effect on the late phase remains unclear. The present study investigated the role of NAC during the early and late phases in a rabbit lobar IR model.

Methods

Liver ischaemia was induced by inflow occlusion to the median and left liver lobes for 60 min, followed by 7 h of reperfusion. In the NAC group (n = 6), NAC was administered intravenously at 150 mg per kg over the 15 min before reperfusion and maintained at 10 mg per kg per h during reperfusion. In the IR group (n = 6), 20 ml 5 per cent dextrose was infused over the 15 min before reperfusion and continued at a rate of 10 ml/h. Animals in a sham operation group (n = 6) underwent laparotomy but no liver ischaemia. All animals were killed at the end of the experiment.

Results

Intracellular tissue oxygenation was improved after the second hour of reperfusion in animals treated with NAC compared with that in the IR group (P = 0·023). Hepatic microcirculation improved after 5 h of reperfusion (P = 0·036) and liver injury was reduced after 5 h, as indicated by alanine aminotransferase activity (P = 0·007) and indocyanine green clearance (uptake, P = 0·001; excretion, P = 0·032).

Conclusion

The main protective effect of NAC becomes apparent 5 h after hepatic ischaemic injury.

N-acetylcysteine decreases lactate signal intensities in liver tissue and improves liver function in septic shock patients, as shown by magnetic resonance spectroscopy: extended case report

Background

N-acetylcysteine (NAC) has been shown to improve splanchnic blood flow in experimental studies. This report evaluates the effects of NAC on liver perfusion and lactate signal intensities in the liver tissue of septic shock patients using proton magnetic resonance imaging and spectroscopy. Furthermore, the monoethylglycinexylidide (MEGX) test was used to investigate hepatic function.

Methods

Five septic shock patients received 150 mg/kg body weight NAC as an intravenous bolus injection over 15 min. Lidocaine was injected both prior to and following NAC administration in order to determine MEGX formation. Measurements (hemodynamics, oxygen transport-related variables, blood samples for lactate, liver-related markers) were performed 1 hour before and 1 hour after NAC injection. In addition to the proton magnetic resonance imaging patients received two proton magnetic resonance spectra, one prior to and one 30 min subsequent to the onset of the NAC infusion at a 1.5 Tesla clinical scanner, for measurement of liver perfusion and liver lactate signal intensity.

Main findings

Following NAC infusion, the lactate signal intensity in the liver tissue showed a median decrease of 89% (11–99%), there was a median increase in liver perfusion of 41% (-14 to 559%), and the MEGX serum concentration increased three times (1.52–5.91).

Conclusions

A decrease in the lactate signal intensity in the liver tissue and an increase in the MEGX serum concentration and in liver perfusion might indicate improved liver function as a result of NAC administration. Patients with compromised hepatosplanchnic function, such as patients with septic shock due to peritonitis, may therefore benefit from NAC therapy.

Administration of N-acetylcysteine after focal cerebral ischemia protects brain and reduces inflammation in a rat model of experimental stroke

Free radicals and inflammatory mediators are involved in transient focal cerebral ischemia (FCI). Preadministration of N-acetylcysteine (NAC) has been found to attenuate the cerebral ischemia-reperfusion injury in a rat model of experimental stroke. This study was undertaken to investigate the neuroprotective potential of NAC administered after ischemic events in experimental stroke. FCI was induced for 30 min by occluding the middle cerebral artery (MCA). NAC (150 mg/kg) was administered intraperitoneally at the time of reperfusion followed by another dose 6 hr later. Animals were sacrificed after 24 hr of reperfusion. The cerebral infarct consistently involved the cortex and striatum. Infarction was assessed by staining the brain sections with 2,3,5-triphenyltetrazolium chloride. Animals treated with NAC showed a significant reduction in infarct area and infarct volume and an improvement in neurologic scores and glutathione level. Reduction in infarction was significant even when a single dose of NAC was administered at 6 hr of reperfusion. Immunohistochemical and quantitative real-time PCR studies demonstrated a reduction in the expression of proinflammatory cytokines such as tumor necrosis factor alpha (TNFalpha) and interleukin 1beta (IL-1beta) and inducible nitric oxide synthase (iNOS) in NAC compared to that in vehicle-treated animals. The expression of activated macrophage/microglia (ED1) and apoptotic cell death in ischemic brain was also reduced by NAC treatment. These results indicate that in a rat model of experimental stroke, administration of NAC even after ischemia onset protected the brain from free radical injury, apoptosis, and inflammation, with a wide treatment window.

N-Acetyl cysteine protects against injury in a rat model of focal cerebral ischemia

Ischemic cerebrovascular disease (stroke) is one of the leading causes of death and long-time disability. Ischemia/reperfusion to any organ triggers a complex series of biochemical events, which affect the structure and function of every organelle and subcellular system of the affected cells. The purpose of this study was to investigate the therapeutic efficacy of N-acetyl cysteine (NAC), a precursor of glutathione and a potent antioxidant, to attenuate ischemia/reperfusion injury to brain tissue caused by a focal cerebral ischemia model in rats. A total of 27 male Sprague-Dawley rats weighing 250-300 g were used in this study. Focal cerebral ischemia (45 min) was induced in anesthetized rats by occluding the middle cerebral artery (MCA) with an intra-luminal suture through the internal carotid artery. The rats were scored post-reperfusion for neurological deficits. They were then sacrificed after 24 h of reperfusion and infarct volume in the brain was assessed by 2,3,5-triphenyl tetrazolium chloride (TTC). Brain sections were immunostained for tumor necrosis factor (TNF-alpha) and inducible nitric oxide synthase (iNOS). Animals treated with NAC showed a 49.7% (S.E.M.=1.25) reduction in brain infarct volume and 50% (S.E.M.=0.48) reduction in the neurological evaluation score as compared to the untreated animals. NAC treatment also blocked the ischemia/reperfusion-induced expression of tumor necrosis factor and inducible nitric oxide synthase. The data suggest that pre-administration of NAC attenuates cerebral ischemia and reperfusion injury in this brain ischemia model. This protective effect may be as a result of suppression of TNF-alpha and iNOS.

Reduction of hepatic ischemia/reperfusion-induced injury by a specific ROCK/Rho kinase inhibitor Y-27632

BACKGROUND

The low-molecular-weight GTPase Rho is known to act as a molecular switch by activating several downstream effectors, one of which is Rho-associated coiled-coil forming protein kinase (ROCK). ROCK/Rho kinase mediates cytoskeleton-dependent cell functions, such as actomyosin-based smooth muscle contraction and integrin-mediated cell adhesion. A specific inhibitor of ROCK/Rho kinase, Y-27632, was recently developed. The present study examined whether Y-27632 could provide a beneficial effect on hepatic ischemia/reperfusion (I/R)-induced injury through the attenuation of microcirculatory disturbance.

MATERIALS AND METHODS

In male Sprague-Dawley rats, normothermic partial ischemia was induced by clamping the hepatic pedicle to the left and median lobes for 90 min, followed by 2 h of reperfusion. In the treatment group, Y-27632 was intravenously administered prior to ischemic insult. Hepatic microcirculation was investigated by using intravital fluorescence microscopy. Liver enzyme release and histological changes of the liver tissue were also evaluated.

RESULTS

Y-27632 significantly improved sinusoidal perfusion and reduced the number of leukocytes sticking in hepatic sinusoids and adhering in postsinusoidal venules. The postischemic narrowing of both sinusoids and postsinusoidal venules was also markedly suppressed. Consequently, liver enzyme release was reduced and postischemic histological damage was suppressed.

CONCLUSIONS

A specific ROCK/Rho kinase inhibitor, Y-27632, was useful to alleviate hepatic I/R-induced injury through ameliorating postischemic microcirculation. The administration of Y-27632 may be a novel strategy for conquering hepatic I/R-induced injury.

Combination therapy of N-acetylcysteine, sodium nitroprusside and phosphoramidon attenuates ischemia-reperfusion injury in rat kidney

Renal ischemia is of clinical interest because of its role in renal failure and also renal graft rejection. To evaluate the effect of the combination of N-acetylcysteine (NAC), a potent antioxidant, sodium nitroprusside (SNP), a nitric oxide donor, and phosphoramidon (P), an endothelin converting enzyme inhibitor, on tissue protection against ischemia-reperfusion injury, we studied the biochemical and morphological changes due to 90 min of renal ischemia-reperfusion in the rat model. Ninety min of ischemia caused very severe injury and the animals could not survive after 4 days without any treatment. Whereas, animals in the treated groups survived i.e. the NAC group (25%), NAC + SNP group (43%) and in the NAC + SNP + P group (100%), 2 weeks after 90 min of ischemia. A significant increase in the serum levels of creatinine and urea nitrogen was shown in the untreated group and to a much lesser extent in the treated group, especially in the NAC + SNP + P group. The protective effect was also supported by light microscopic studies on renal tissue sections. We also measured the activities of antioxidant enzymes in tissue homogenates. With the exception of Mn-superoxide dismutase, the activities of antioxidant enzymes (catalase, glutathione peroxidase, CuZn-superoxide dismutase) were decreased in the untreated kidney. The administration of NAC alone and NAC + SNP protected against the loss of activities. Treatment with a combination of NAC, SNP and P showed a synergistic effect as evidenced by the best protection. These results suggest that pre-administration of a combination of antioxidant (NAC) with endothelin derived vasodilators (sodium nitroprusside and Phosphoramidon) attenuates renal ischemia-reperfusion injury, e.g. in donor kidney for transplantation, by protecting cells against free radical damage.

Attenuation of ischemia/reperfusion induced MAP kinases by N-acetyl cysteine, sodium nitroprusside and phosphoramidon

Ischemia followed by reperfusion has a number of clinically significant consequences. A number of pathophysiological processes appear to be involved in ischemia/reperfusion (I/R) injury. The mitogen activated protein kinases (MAPK) are integral components of the parallel MAP kinase cascades activated in response to a variety of cellular stress inducing ischemia/ATP depletion and inflammatory cytokines. Many studies suggest that members of the MAP kinase family in particular Jun N-terminal kinase (JNK) are activated in kidney following ischemia/reperfusion of this tissue. The present study underlines the therapeutic potential of the combination of N-acetyl cysteine (NAC), a potent antioxidant, sodium nitroprusside (SNP), a nitric oxide donor and phosphoramidon (P), an endothelin-1 converting enzyme inhibitor in ameliorating the MAPK induced damage during renal ischemia/reperfusion injury. Our previous results showed that 90 min of ischemia followed by reperfusion caused very severe injury and that the untreated animals had 100% mortality after the 3rd day whereas there was improved renal function and 100% survival of animals in the three drug combination treatment group. The present study, mainly on tissue sections, further supports the protection provided by the triple drug therapy. A higher degree of expression of all the three classes of MAPK, i.e. JNK, P38 MAP kinases and P-extracellular signal regulated kinases (ERKs) can be seen in kidneys subjected to ischemia/reperfusion insult. Pretreatment with a combination of N-acetyl cysteine, sodium nitroprusside, and phosphoramidon completely inhibits all three classes of MAPK and ameliorates AP-1 whereas individual or a combination of any two drugs is not as effective.

Bucillamine, a thiol antioxidant, prevents transplantation-associated reperfusion injury

Ischemia/reperfusion (I/R) injury is a serious potential threat to outcomes in organ transplantation and other clinical arenas in which there is temporary interruption of blood flow. I/R is a frequent cause of primary failure in organ transplantation. We hypothesized that the antioxidant bucillamine, a potent sulfhydryl donor, would protect against I/R injury in high-risk organ transplants. Because livers subjected to prolonged ischemia and very fatty livers are highly susceptible to severe I/R injury, we studied the effect of bucillamine in three animal models of liver transplantation: two ex vivo models of isolated perfused livers, either normal or fatty rat livers, and an in vivo model of syngenic orthotopic liver transplants in rats. In all models, livers were deprived of oxygen for 24 h before either ex vivo reperfusion or transplantation. In the ex vivo models, bucillamine treatment significantly improved portal vein blood flow and bile production, preserved normal liver architecture, and significantly reduced liver enzyme release and indices of oxidative stress. Moreover, bucillamine treatment significantly increased levels of reduced glutathione in the liver and lowered levels of oxidized glutathione in both liver and blood. In rats subjected to liver transplants, bucillamine significantly enhanced survival and protected against hepatic injury. Possible mechanisms of this protection include prevention of excessive accumulation of toxic oxygen species, interruption of redox signaling in hepatocytes, and inhibition of macrophage activation. This study demonstrates the potential utility of bucillamine or other cysteine-derived thiol donors for improving outcomes in organ transplantation and other clinical settings involving I/R injury.

N-acetylcysteine induces shedding of selectins from liver and intestine during orthotopic liver transplantation

In orthotopic liver transplantation (OLT), N-acetylcysteine (NAC) reduces ischaemia/reperfusion (I/R) injury, improves liver synthesis function and prevents primary nonfunction of the graft. To further elucidate the mechanisms of these beneficial effects of NAC, we investigated influence of high-dose NAC therapy on the pattern of adhesion molecule release from liver and intestine during OLT. Nine patients receiving allograft OLT were treated with 150 mg NAC/kg during the first hour after reperfusion; 10 patients received the carrier only. One hour after reperfusion, samples of arterial, portal venous and hepatic venous plasma were taken and blood flow in the hepatic artery and the portal vein was measured. Absolute concentrations of sICAM-1, sVCAM-1, sP-selectin and sE-selectin were not markedly different. However, balance calculations showed release of selectins from NAC-treated livers as opposed to net uptake in controls (P < or = 0.02 for sP-selectin). This shedding of selectins might be a contributing factor to the decrease in leucocyte adherence and improved haemodynamics found experimentally with NAC-treatment.

N-acetylcysteine increases liver blood flow and improves liver function in septic shock patients: results of a prospective, randomized, double-blind study

OBJECTIVE

In septic shock, decreased splanchnic blood flow is reported, despite adequate systemic hemodynamics. Aacetylcysteine (NAC) was found to increase hepatosplanchnic blood flow in experimental settings. In septic shock patients, NAC improved the clearance of indocyanine green and the relationship of systemic oxygen consumption to oxygen demand. We investigated the influence of NAC on liver blood flow, hepatosplanchnic oxygen transport-related variables, and liver function during early septic shock.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Septic shock patients admitted to an interdisciplinary surgical intensive care unit.

PATIENTS

We examined 60 septic shock patients within 24 hrs after onset of sepsis. They were conventionally resuscitated with volume and inotropes and were in stable condition. A gastric tonometer was inserted into the stomach and a catheter into the hepatic vein. Microsomal liver function was assessed by using the plasma appearance of monoethylglycinexylidide (MEGX).

INTERVENTIONS

Subjects randomly received either a bolus of 150 mg/kg iv NAC over 15 mins and a subsequent continuous infusion of 12.5 mg/kg/hr NAC over 90 mins (n = 30) or placebo (n = 30).

MEASUREMENTS AND MAIN RESULTS

Measurements were performed before (baseline) and 60 mins after beginning the infusion (infusion). After NAC, a significant increase in absolute liver blood flow index (2.7 vs. 3.3 L/min/m2; p = .01) and cardiac index (5.0 vs. 5.7 L/min/m2; p = .02) was observed. Fractional liver blood flow index (cardiac index-related liver blood flow index) did not change. The difference between arterial and gastric mucosal carbon dioxide tension decreased (p = .05) and MEGX increased (p = .04). Liver blood flow index and MEGX correlated significantly (r(s) = .57; p < or = .01).

CONCLUSIONS

After NAC treatment, hepatosplanchnic flow and function improved and may, therefore, suggest enhanced nutritive blood flow. The increase of liver blood flow index was not caused by redistribution to the hepatosplanchnic area, but by an increase of cardiac index. Because of its correlation with liver blood flow index, MEGX may be helpful in identifying patients who benefit from NAC treatment in early septic shock.

Free radical scavengers to prevent reperfusion injury following experimental warm liver ischaemia. Is there a real physiological benefit?

Free radical scavengers have been utilized to prevent the consequences of ischemia, however, results do not seem conclusive. In our study we analyzed the blood flow, function, and histology of rat liver tissue after warm liver ischemia, in order to assess the effect of free radicals in liver reperfusion injury. N-acetyl cysteine (NAC), tocopherol, allopurinol, and superoxide dismutase (SOD), pharmacological agents expected to protect from injury mediated by free radicals, were investigated. Laser Doppler flowmetry and photometry were utilized to measure post-ischemic microcirculatory changes as an expression of ischemia-reperfusion injury in a model of segmental liver ischemia in the rat, with an ischemic time of 45 min. Galactose elimination capacity, ALT and histology were used to assess the functional and morphological consequences of ischemia after 24 h of reperfusion. The overall mean blood flow over 1 hour after reperfusion was of 33.9% (SD 11.2) of the normal, non-ischemic control. NAC (31.2% SD 10.9) did not show any protective effect and in some cases the effect seemed to be negative. Tocopherol (41.7% SD 5.1) marginally improved post ischemic liver tissue blood flow. Treatment with allopurinol did not show any beneficial effects (37.5% SD 14.2). Only animals treated with SOD showed an improvement of the post ischemic liver microcirculation (57.9% SD 14.4)(P < 0.001) and function. Only SOD produced statistically significant differences in galactose elimination capacity, compared with those of the ischemic control group. This moderately protective effect of SOD is encouraging, however, the relevance of all these compounds in a broader pathophysiological setting remains unproven.

Evaluation of hepatic microcirculation by in vivo microscopy

In vivo microscopy is an excellent technique for investigating the microcirculation and until recently the only one that allowed direct visualization. Rat liver has been widely studied, because microcirculatory disorders play a pivotal role in the pathogenesis of organ failure during hepatic ischemia, transplantation, hemorrhagic shock, endotoxemia, and sepsis. The state of the microcirculation is an important prognostic factor for the reestablishment of organ function after these injuries. This article introduces the most common procedures for in vivo microscopy of the rat liver, summarizes the available fluorescent dyes, and gives an overview of criteria for the expression and evaluation of microscopic findings. Particular emphasis is given to a description of the different parameters assessed by direct observation of hepatic microcirculation, such as perfusion rate, leukocyte-endothelium interactions, leukocyte velocities, and phagocytic activity. Examples of normal range values are given. This overview is intended to help those wanting to introduce this method into their research and who are embarking on intravital microscopy for the first time, and to enable them to decide which techniques are appropriate for answering special questions.