Protective Effect of Glutathione Against Liver Warm Ischemia-Reperfusion Injury in Rats is Associated with Regulation of P-Selectin and Neutrophil Infiltration

Neutrophils: a cornerstone of liver ischemia and reperfusion injury

Ischemia-reperfusion injury (IRI) is the main cause of morbidity and mortality due to graft rejection after liver transplantation. During IRI, an intense inflammatory process occurs in the liver. This hepatic inflammation is initiated by the ischemic period but occurs mainly during the reperfusion phase, and is characterized by a large neutrophil recruitment to the liver. Production of cytokines, chemokines, and danger signals results in activation of resident hepatocytes, leukocytes, and Kupffer cells. The role of neutrophils as the main amplifiers of liver injury in IRI has been recognized in many publications. Several studies have shown that elimination of excessive neutrophils or inhibition of their function leads to reduction of liver injury and inflammation. However, the mechanisms involved in neutrophil recruitment during liver IRI are not well known. In addition, the molecules necessary for this type of migration are poorly defined, as the liver presents an atypical sinusoidal vasculature in which the classical leukocyte migration paradigm only partially applies. This review summarizes recent advances in neutrophil-mediated liver damage, and its application to liver IRI. Basic mechanisms of activation of neutrophils and their unique mechanisms of recruitment into the liver vasculature are discussed. In particular, the role of danger signals, adhesion molecules, chemokines, glycosaminoglycans (GAGs), and metalloproteinases is explored. The precise definition of the molecular events that govern the recruitment of neutrophils and their movement into inflamed tissue may offer new therapeutic alternatives for hepatic injury by IRI and other inflammatory diseases of the liver.

Effects of Glutathione on Mechanical Allodynia and Central Sensitization in Chronic Postischemic Pain Rats

Background

The chronic postischemia pain (CPIP) model is an animal model using ischemia/reperfusion injury that mimics the symptoms of complex regional pain syndrome type I. Glutathione (GSH) prevents ischemia/reperfusion injury by scavenging free radicals. We conducted this study to investigate the protective effect of GSH in CPIP rats via changes of mechanical allodynia and phospholyration of the N-methyl-D-aspartate receptor subunit GluN1.

Methods

We divided 45 rats into 5 groups: sham, CPIP, CPIP + GSH 100 mg/kg, CPIP + GSH 200 mg/kg, and CPIP + GSH 500 mg/kg. Rats in the sham and CPIP groups received normal saline and rats in the other groups received GSH at the designated doses thirty minutes prior to reperfusion. Withdrawal thresholds were evaluated before sugery as well as 1, 3, and 7 days after surgery. pGluN1 level in the spinal cord was also measured.

Results

GSH treated rats show a significant increase in the withdrawal thresholds of both hind paws as compared with the CPIP group dose-dependently. The expression of pGluN1 in the GSH treated rats significantly decreased as compared to the CPIP group (all P < 0.05).

Conclusion

These findings suggest that GSH inhibited the development of mechanical allodynia and central sensitization in CPIP rats.

Platelet aggregation but not activation and degranulation during the acute post-ischemic reperfusion phase in livers with no underlying disease

BACKGROUND

Platelets and P-selectin (CD62P) play an unequivocal role in the pathology of hepatic ischemia/reperfusion (I/R) injury. Inhibition or knock-out of P-selectin or immunodepletion of platelets results in amelioration of post-ischemic inflammation, reduced hepatocellular damage, and improved survival. However, P-selectin expression on platelets and endothelial cells, which concurs with platelet activation, has never been clearly demonstrated in I/R-subjected livers.

AIMS

To determine whether platelets become activated and degranulate in the acute phase of liver I/R and whether the platelets interact with neutrophils.

METHODS

Hepatic I/R was induced in male C57BL/6J mice (N = 12) using 37.5-min ischemia time. Platelets, endothelial cells, and neutrophils were fluorescently labeled by systemic administration of non-blocking antibodies. Cell kinetics were monitored by intravital spinning disk confocal microscopy during 90 min of reperfusion. Image analysis and quantification was performed with dedicated software.

RESULTS

Platelets adhered to sinusoids more extensively in post-ischemic livers compared to livers not subjected to I/R and formed aggregates, which occurred directly after ischemia. Platelets and endothelial cells did not express P-selectin in post-ischemic livers. There was no interaction between platelets and neutrophils.

CONCLUSIONS

Platelets aggregate but do not become activated and do not degranulate in post-ischemic livers. There is no platelet-neutrophil interplay during the early reperfusion phase in a moderate model of hepatic I/R injury. The mechanisms underlying the biological effects of platelets and P-selectin in this setting warrant further investigation.

RELEVANCE FOR PATIENTS

I/R in surgical liver patients may compromise outcome due to post-ischemic oxidative stress and sterile inflammation. Both processes are mediated in part by platelets. Understanding platelet function during I/R is key to developing effective interventions for I/R injury and improving clinical outcomes.

TNF-α suppression by glutathione preconditioning attenuates hepatic ischemia reperfusion injury in young and aged rats

BACKGROUND AND AIM

Hepatic ischemia reperfusion (I/R) stimulates Kupffer cells and initiates injury through tumor necrosis factor-α (TNF-α) upregulation. Aim of this study was to compare the variable effects of reduced glutathione (GSH) pre-treatment on I/R liver injury in young and aged rats.

METHODS

Wistar male rats were sorted into young (groups I-III) and aged (groups IV-VI). All groups except sham (groups I and IV) were subjected to 90-min ischemia and 2-h reperfusion. The treatment groups received 200 mg/kg bwt (groups III and VI) of GSH, 30 min prior to I/R. Variable effects of GSH were studied by transaminase activities, thiobarbituric acid-reactive substances (TBARS), GSH level, GSH/oxidized GSH (GSSG) ratio, TNF-α level, apoptotic markers and confirmed by histopathological observations.

RESULTS

Our findings revealed that I/R inflicted more liver damage in aged rats than young rats. The GSH treatment prior to surgery significantly lowered the serum transaminase activities, hepatic TBARS level and effectively restored the GSH/GSSG ratio in both young and aged rats more remarkably in the mitochondria. Western analysis depicted that the GSH treatment effectively suppressed TNF-α expression and apoptotic markers in both young and aged rats. These findings were further confirmed by terminal deoxynucleotide transferase dUTP nick end labeling assay and histopathological observations of liver sections of young and aged rats.

CONCLUSION

Restoration of GSH/GSSG ratio through GSH pre-conditioning inhibits TNF-α and apoptosis in hepatic I/R injury. Hence, GSH pre-conditioning may be utilized in both young and aged individuals during liver transplantation/surgery for better post-operative outcomes.

Glutathione homeostasis and functions: potential targets for medical interventions

Glutathione (GSH) is a tripeptide, which has many biological roles including protection against reactive oxygen and nitrogen species. The primary goal of this paper is to characterize the principal mechanisms of the protective role of GSH against reactive species and electrophiles. The ancillary goals are to provide up-to-date knowledge of GSH biosynthesis, hydrolysis, and utilization; intracellular compartmentalization and interorgan transfer; elimination of endogenously produced toxicants; involvement in metal homeostasis; glutathione-related enzymes and their regulation; glutathionylation of sulfhydryls. Individual sections are devoted to the relationships between GSH homeostasis and pathologies as well as to developed research tools and pharmacological approaches to manipulating GSH levels. Special attention is paid to compounds mainly of a natural origin (phytochemicals) which affect GSH-related processes. The paper provides starting points for development of novel tools and provides a hypothesis for investigation of the physiology and biochemistry of glutathione with a focus on human and animal health.

Preconditioning with L-alanyl-glutamine reduces hepatic ischemia-reperfusion injury in rats

PURPOSE: To evaluate the effects of pre-conditioning with L-alanyl- glutamine (L-Ala-Gln) in rats subjected to total hepatic ischemia. METHODS: Thirty Wistar rats, average weight 300g, were randomly assigned to 3 groups (n=10): G-1 - Saline, G-2- L-Ala-Gln, G-3-control (Sham). G-1 and G-3 groups were treated with saline 2.0 ml or L-Ala-Gln (0.75mg/Kg) intraperitoneally (ip) respectively, 2 hours before laparotomy. Anesthetized rats were subjected to laparotomy and total hepatic ischemia (30 minutes) induced by by clamping of portal triad. Control group underwent peritoneal puncture, two hours before the sham operation (laparotomy only). At the end of ischemia (G1 and G2), the liver was reperfused for 60 minutes. Following reperfusion blood samples were collected for evaluation of alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels. Liver (medium lobe) was removed for immunohistochemistry study with antibody for Caspase-3. RESULTS: It was found a significant decrease (p<0.05) of ALT levels (270.6 +40.8 vs 83.3 +5.5 - p <0.05), LDH (2079.0 +262.4 vs. 206.6 +16.2 - p <0.05) and Caspase-3 expression (6.72 +1.35 vs. 2.19 +1.14, p <0.05) in rats subjected to I / R, comparing the group treated with L-Ala -Gln with G-2. Also, the ALT level was significantly lower (P<0.05) in G-1 and G-2 groups than in G-3 (control group). CONCLUSION: L-Ala-Gln preconditioning in rats submitted to hepatic I/R significantly reduces ALT, LDH and Caspase-3 expression, suggesting hepatic protection.

Protective effect of reduced glutathione on the liver injury induced by acute omethoate poisoning

Omethoate is an organophosphate insecticide with high toxicity. The aim of this study was to investigate the protective effect of exogenous reduced glutathione (GSH) on omethoate-induced liver injury. Sprague-Dawley rats were randomly divided into three groups: control, OM (omethoate poisoning), and OM+GSH (omethoate poisoning treated with GSH). The activities of acetylcholinesterase (AChE), aspartate aminotransferase (AST), alanine aminotransferase (ALT) in plasma, free organophosphate (FOP) in the liver were determined, and the histopathological changes in the liver were observed. Furthermore, TNF-α and NO in liver homogenate were assayed. The results showed that AChE activity was significantly inhibited by omethoate, but was not altered by GSH treatment. GSH was able to prevent hepatocellular edema and fatty degeneration, decrease liver FOP, attenuate the increased AST and ALT activity, and decline the increase of TNF-α and NO induced by omethoate. These results indicate GSH can attenuate liver injury, and suggest that GSH may be administered to protect the organ from injury in patients with acute organophosphate poisoning.