Evaluation of warm ischemia-reperfusion injury using heat shock protein in the rat liver

The Impact of Ischemia/Reperfusion Injury on Liver Allografts from Deceased after Cardiac Death versus Deceased after Brain Death Donors

BACKGROUND AND AIMS

The shortage of organs for transplantation has led to increased use of organs procured from donors after cardiac death (DCD). The effects of cardiac death on the liver remain poorly understood, however. Using livers obtained from DCD versus donors after brain death (DBD), we aimed to understand how ischemia/reperfusion (I/R) injury alters expression of pro-inflammatory markers ceramides and influences graft leukocyte infiltration.

METHODS

Hepatocyte inflammation, as assessed by ceramide expression, was evaluated in DCD (n = 13) and DBD (n = 10) livers. Allograft expression of inflammatory and cell death markers, and allograft leukocyte infiltration were evaluated from a contemporaneous independent cohort of DCD (n = 22) and DBD (n = 13) livers.

RESULTS

When examining the differences between transplant stages in each group, C18, C20, C24 ceramides showed significant difference in DBD (p<0.05) and C22 ceramide (p<0.05) were more pronounced for DCD. C18 ceramide is correlated to bilirubin, INR, and creatinine after transplant in DCD. Prior to transplantation, DCD livers have reduced leukocyte infiltration compared to DBD allografts. Following reperfusion, the neutrophil infiltration and platelet deposition was less prevalent in DCD grafts while cell death and recipients levels of serum aspartate aminotransferase (AST) of DCD allografts had significantly increased.

CONCLUSION

These data suggest that I/R injury generate necrosis in the absence of a strong inflammatory response in DCD livers with an appreciable effect on early graft function. The long-term consequences of increased inflammation in DBD and increased cell death in DCD allografts are unknown and warrant further investigation.

The effect of octreotide on hepatic ischemia-reperfusion injury in a rabbit model

BACKGROUND

Hepatic ischemic-reperfusion injury (HIRI) is a major cause of morbidity and mortality following liver surgery. Octreotide (Oct) has been reported to improve hepatocellular energy metabolism in a rat HIRI model. This study was designed to evaluate whether Oct could protect the liver of rabbits against ischemic-reperfusion (I/R) injury.

METHODS

Twenty-four adult New Zealand rabbits were randomly divided into a sham operated group (Control), an ischemia/reperfusion group (I/R), and an ischemia/reperfusion + Oct pretreatment group (I/R + Oct). The hemodynamic (mean arterial pressure [MAP] and heart rate [HR]) changes, liver enzymes (alanine aminotransferase [ALT], aspartate aminotransferase [AST], and lactate dehydrogenase [LDH]) release, inflammatory cytokines (tumor necrosis factor [TNF]α and interleukin [IL]-1β) levels, and endotoxin (ETX) levels were measured during I/R.

RESULTS

Compared with the Control group, the MAP decreased and HR increased in I/R and I/R + Oct groups at ischemia 15 minutes (P < .05) but were less in the I/R + Oct group relative to the I/R group (P < .05). ALT, AST, LDH, IL-1β, and ETX levels were increased in the I/R and I/R + Oct groups at ischemia 30 minutes (P < .05), however, the increase was lower in the I/R + Oct group relative to the I/R group (P < .05). Bcl-2 expression in the I/R + Oct group was higher compared with other groups (P < .05) and Bax expression in the I/R group was reduced compared with other groups (P < .05). Hepatocellular damage in the I/R + Oct group appeared to be less than in the I/R group by microscopy.

CONCLUSIONS

Oct pretreatment attenuated hemodynamic changes and decreased liver enzyme changes induced by HIRI in a rabbit model. The protection mechanisms of Oct may be related to reduced ETX levels, down-regulation of the inflammatory cytokines TNFα and IL-1β, and inhibition of hepatocellular apoptosis, as well as the modulation of the mitochondrion-mediated Bcl-2/Bax apoptosis pathway. Based on our study it appears that Oct may be useful in decreasing liver injury after liver surgery and/or transplantation and may serve as a promising agent against HIRI.

Preserving hepatic artery flow during portal triad blood inflow occlusion improves remnant liver regeneration in rats after partial hepatectomy

BACKGROUND

In the present study, we compared preservation of the hepatic artery flow during liver blood inflow occlusion with total portal triad blood flow clamping (the Pringle maneuver) to examine their effects on liver regeneration in rats after partial hepatectomy.

MATERIALS AND METHODS

Male Wistar rats were randomized to a control group (without hepatic inflow occlusion), an occlusion of the portal triad (OPT) group (OPT for 30 min under portal blood bypass), and an occlusion of the portal vein (OPV) group (OPV only for 30 min under portal blood bypass). All the rats underwent partial hepatectomy at the end of hepatic blood control. Liver regeneration was assessed on days 3 and 7 after hepatectomy. Liver damage, extracellular signal-regulated kinase-1/2 activation, and cytokine expression of the remnant liver in the first 24 h after hepatectomy were also assessed.

RESULTS

Significantly greater liver regeneration, at a level similar to that of the control group, as indicated by the percentage of the initial liver weight, proliferating cell nuclear antigen and Ki-67 labeling indexes, and technetium-99m galactosyl human serum albumin liver uptake, was observed in the OPV group on day 3 after hepatectomy (P < 0.05 versus the OPT group). Liver damage, as represented by alanine aminotransferase and aspartate aminotransferase measurement and histopathologic examination, was substantially alleviated in the OPV group compared with the OPT group. In contrast to the control and OPV groups, the OPT group had markedly increased extracellular signal-regulated kinase-1/2 activation, heat shock protein 70, and interleukin-6 expression in response to ischemia and partial hepatectomy.

CONCLUSIONS

Our results have indicated that compared with the Pringle maneuver, clamping the portal vein while preserving the hepatic artery flow during partial hepatectomy is better for remnant liver regeneration at an early posthepatectomy stage.

HSP70 immune reactivity and TUNEL positivity in the liver of toluene-inhaled and melatonin-treated rats

Toluene is a clear, colorless and volatile hydrocarbon that is metabolized in liver, produced free oxygen radicals and can mediate cellular damage. Melatonin which is a pineal gland hormone is a very potent antioxidant. It can make the cellular membrane more durable against oxidative attacks and protect nuclear DNA from oxidative damage. This study aimed to investigate heat shock protein (HSP)70 immune reactivity and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positivity (apoptotic activity) in the liver of toluene-inhaled and melatonin-treated rats. A total of 21 adult male Wistar albino rats were divided at random into 3 equal groups. Animals in group I were designated as control. The rats in group II were exposed to toluene (3000 ppm/1 h/day) for 30 days, while the rats in group III were treated with melatonin (10 mg/kg/day, intraperitoneally) plus toluene inhalation. At the end of the 30-day experimental period, all rats were killed by decapitation. Then the liver tissues of rats were removed and tissue specimens were embedded in paraffin blocks. The specimens were stained with periodic acid-schiff (PAS) following routine histological procedures. Sections obtained from paraffin blocks were used for immune detection of TUNEL and HSP70. In light microscopic observations of tissues from toluene-inhaled rats, massive hepatocyte degeneration, ballooning degeneration and decreased PAS positivity were observed. Increased TUNEL positivity and HSP70 immune reactivity were determined in toluene-inhaled group and melatonin treatment decreased all these adverse effects.

Heat preconditioning ameliorates hepatocyte viability after cold preservation and rewarming, and modulates its immunoactivity

BACKGROUND

Heat preconditioning significantly preserved liver graft function after cold preservation in animal experimental model. The elevation of heat shock protein 70 (HSP70) was claimed to play a critical role in protecting grafts against cold preservation-induced hepatocyte apoptosis. However, little is known about whether HSP70 also plays an immunomodulatory role in cold preserved cells. This study aimed at investigating the relationship between HSP70 protein and the immunoactivity in response to lipopolysaccharide (LPS) stimulation.

METHODS AND RESULTS

A normal rat hepatocyte cell line was preserved with University of Wisconsin (UW) solution, Ringer's lactate solution (RL), and phosphate-buffered saline (PBS) at 4 degrees C. No significant morphological alteration was noted in UW-preserved cells after 24 h through phase-contrast microscopic observation and fluorescent viability stain. Western blotting showed a two-fold increase in the ratio of HSP70/Bax proteins in cells after 24 h of UW preservation. Heat preconditioning significantly enhanced the recovery of lactate dehydrogenase (LDH) activity in both RL- and UW-preserved cells that were stored for a period of 12 h or less. Moreover, heat preconditioning promoted HSP70 and NF-kappaB p50 nuclear translocation and suppressed the LPS-induced nuclear p50 accumulation in cells before UW preservation. Immunofluorescent stain revealed that the LPS-induced p50 protein redistribution to nuclear membrane might contribute to NF-kappaB activation, while heat preconditioning and UW cold preservation completely abrogated the p50 intranuclear redistribution. Thus NF-kappaB p50 might be responsible for the endotoxin tolerance induction.

CONCLUSIONS

These findings strongly suggest that heat preconditioning not only preserves hepatocyte viability after cold preservation and rewarming, but also ameliorates its immunoactivity.

Timing of ischaemia/reperfusion before hepatectomy without inflow occlusion determines liver damage in rats: role of heat shock protein 70

BACKGROUND

Living donor hepatectomies in liver transplantation are usually performed without inflow occlusion. We hypothesized that selective ischaemia/reperfusion (SIR) before partial hepatectomy (PH) without inflow occlusion might exert a hepatoprotective effect.

METHODS

In the SIR groups, rats were subjected to a selective 30-min ischaemia to the liver that remained after PH, followed by various durations of reperfusion before 70% PH without inflow occlusion. The control group underwent 70% PH alone.

RESULTS

As assessed by serum aspartate and alanine aminotransferase levels, 30-min reperfusion was highly protective against liver injury compared with 10-min reperfusion, showing the same levels as that of the control group. After PH in the 10-min reperfusion group, apoptotic cells were significantly higher and the 7-day survival rate was significantly lower than that of the 30-min reperfusion group and the control group. In the 30-min reperfusion group, the expression of heat shock protein 70 (HSP70) was significantly higher than that in the 10-min reperfusion group, while apoptosis was improved to the levels of the control group. In the SIR groups, liver regeneration was significantly enhanced, with markedly increased levels of interleukin 6 (IL-6) compared with the control group.

CONCLUSIONS

The timing of SIR before PH without inflow occlusion seemed to be the most important factor for determining liver damage and survival in the context of HSP70 production, while high levels of IL-6 appear to be associated with liver regeneration after PH. The procedure of SIR before PH is not recommended because the SIR groups did not overcome the control group.

2-APB protects against liver ischemia-reperfusion injury by reducing cellular and mitochondrial calcium uptake

Ischemia-reperfusion (I/R) injury is a commonly encountered clinical problem in liver surgery and transplantation. The pathogenesis of I/R injury is multifactorial, but mitochondrial Ca(2+) overload plays a central role. We have previously defined a novel pathway for mitochondrial Ca(2+) handling and now further characterize this pathway and investigate a novel Ca(2+)-channel inhibitor, 2-aminoethoxydiphenyl borate (2-APB), for preventing hepatic I/R injury. The effect of 2-APB on cellular and mitochondrial Ca(2+) uptake was evaluated in vitro by using (45)Ca(2+). Subsequently, 2-APB (2 mg/kg) or vehicle was injected into the portal vein of anesthetized rats either before or following 1 h of inflow occlusion to 70% of the liver. After 3 h of reperfusion, liver injury was assessed enzymatically and histologically. Hep G2 cells transfected with green fluorescent protein-tagged cytochrome c were used to evaluate mitochondrial permeability. 2-APB dose-dependently blocked Ca(2+) uptake in isolated liver mitochondria and reduced cellular Ca(2+) accumulation in Hep G2 cells. In vivo I/R increased liver enzymes 10-fold, and 2-APB prevented this when administered pre- or postischemia. 2-APB significantly reduced cellular damage determined by hematoxylin and eosin and terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining of liver tissue. In vitro I/R caused a dissociation between cytochrome c and mitochondria in Hep G2 cells that was prevented by administration of 2-APB. These data further establish the role of cellular Ca(2+) uptake and subsequent mitochondrial Ca(2+) overload in I/R injury and identify 2-APB as a novel pharmacological inhibitor of liver I/R injury even when administered following a prolonged ischemic insult.

Acute allograft rejection occurs independently of inducible heat shock protein-70

Dendritic cells (DCs) are key mediators of the innate response to transplantation. Yet, the substances that activate these cells during acute allograft rejection remain elusive. Previous work has suggested that heat shock protein (HSP)-70 is associated with acute allograft rejection. Hence, the goal of this study was to determine whether HSP-70 activates DCs and plays a critical role in acute allograft rejection in an experimental model that is dependent on innate MyD88 signaling. Our in vitro data indicate that HSP-70 does not activate DCs. In vivo transplant studies demonstrate that HSP-70 levels are not increased during acute allograft rejection and that an absence of the inducible form of HSP-70 neither delays acute allograft rejection, impairs DCs maturation, nor alters Th1 immune responses during acute allograft rejection. In conclusion, our results indicate that HSP-70 in our experimental models does not play an essential role in acute allograft rejection.

Wide gene expression profiling of ischemia-reperfusion injury in human liver transplantation

Ischemia-reperfusion injury (IRI) causes up to 10% of early liver failures in humans and can lead to a higher incidence of acute and chronic rejection. So far, very few studies have investigated wide gene expression profiles associated with the IRI process. The discovery of novel genes activated by IRI might lead to the identification of potential target genes for the prevention or treatment of the injury. In our study, we compared gene expression levels in reperfused livers (RL group) vs. the basal values before retrieval from the donor (basal liver [BL] group) using oligonucleotide array technology. We examined 10 biopsies from 5 livers, analyzing approximately 33,000 genes represented on the Affymetrix HG-U133APlus 2.0 oligonucleotide arrays (Affymetrix, Santa Clara, CA). About 13,000 individual genes were considered expressed in at least 1 condition. A total of 795 genes whose expression is significantly modified by ischemia-reperfusion in human liver transplantation were identified in this study. Some of them are likely to be completely activated by IRI, as they are not expressed in basal livers. The supervised gene expression analysis revealed that at least 12% of the genes involved in the apoptotic process, 12.5% of the genes involved in inflammatory processes, and 22.5% of the genes encoding for heat shock proteins are differentially expressed in RL samples vs. BL samples. Furthermore, IRI induces the upregulation of some genes' coding for adhesion molecules and integrins. In conclusion, we have identified a relevant amount of early genes regulated in the human liver after 7-9 hours of cold ischemia and 2 hours from reperfusion, many of them not having been described before in this process. Their analyses may help us to better understand the pathophysiology of IRI and to characterize potential target genes for the prevention or treatment of the liver injury in order to increase the number of patients that successfully undergo transplantation.

Effects of Ischemia-Reperfusion Injury on Apolipoprotein M Expression in the Liver

The present study investigated the expression pattern of apolipoprotein M (apoM) mRNA in a rat model of hepatic ischemia-reperfusion injury (IRI). Animals were ischemic for 1 hour followed by various reperfusion times. As expected, serum alanine aminotransferase levels were significantly increased under IRI, which indicated the severity of liver injury. Hepatic mRNA levels of HSP70, which is the most common characterized protein within the family of heat-shock proteins (HSP), were significantly increased after 0.5 to 3 hours of IRI. Plasma C-reactive protein, high-density lipoprotein-cholesterol, and lipoprotein (a) levels were significantly increased after 1-hour ischemia followed by 0.5 to 3 hours of reperfusion. Interestingly, similar to HSP70, apoM mRNA levels in the liver were gradually increased after 0.5 to 3 hours of IRI, whereas it returned to a lower level after 6 or 24 hours of IRI, which indicated that hepatic apoM expression was significantly influenced by the acute phase of IRI. However, plasma apoM levels were not increased in parallel, even slightly decreasing after 0.5 or 1 hour of IRI. We concluded that apoM mRNA expression pattern, like HSP70, in the liver showed rapid, significant changes during hepatic local IRI.

Effects of high peak airway pressure on the expression of heat shock protein 70 in rat lungs: a preliminary study

BACKGROUND

Heat shock protein 70 (HSP70) is induced by a wide variety of stresses in addition to hyperthermia. Recent studies have clarified that mechanical stretching and pressure overload can induce HSP70 in some tissues and cells. However, it remains unclear whether HSP70 is induced in stretch-subjected lungs, such as those under mechanical ventilation. This study was designed to investigate the effects of high peak airway pressure (PAP) ventilation on HSP70 expression in intact rat lungs.

METHODS

Male Sprague-Dawley rats were randomly allocated to one of three groups: non-ventilated (anesthesia alone) control group; PAP 15 cm H(2)O group (P15); and PAP 30 cm H(2)O group (P30). The rats in the PAP groups were subjected to pressure-controlled assisted ventilation at the appropriate PAP for 30 min. Rats were killed at 12, 24 and 48 h after ventilation or anesthesia alone, and the lungs were removed. The lung tissues were processed for immunohistochemical and Western blotting analyses of HSP70.

RESULTS

Following 30 min of pressure-controlled assisted ventilation, HSP70 expression in the P30 group was significantly up-regulated in bronchiolar cells and subepithelial tissues at 12 h, and this up-regulation continued throughout the observation period. In contrast, there were no significant differences between the control and P15 groups, although the expression of HSP70 was higher in the P15 group than in the control group at all time points.

CONCLUSIONS

HSP70 was induced by high PAP ventilation, but its specific role and induction mechanism remain unclear. Therefore, further investigations should be encouraged.

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.

Identification of differentially expressed genes after partial rat liver ischemia/reperfusion by suppression subtractive hybridization

AIM: To identify potential diagnostic target genes in early reperfusion periods following warm liver ischemia before irreversible liver damage occurs.

METHODS: We used two strategies (SSH suppression subtractive hybridization and hybridization of cDNA arrays) to determine early changes in gene expression profiles in a rat model of partial WI/R, comparing postischemic and adjacent nonischemic liver lobes. Differential gene expression was verified (WI/R; 1 h/2 h) and analyzed in more detail after warm ischemia (1 h) in a reperfusion time kinetics (0, 1, 2 and 6 h) and compared to untreated livers by Northern blot hybridizations. Protein expression was examined on Western blots and by immunohistochemistry for four differentially expressed target genes (Hsp70, Hsp27, Gadd45a and IL-1rI).

RESULTS: Thirty-two individual WI/R target genes showing altered RNA levels after confirmation by Northern blot analyzes were identified. Among them, six functionally uncharacteristic expressed sequences and 26 known genes (12 induced in postischemic liver lobes, 14 with higher transcriptional expression in adjacent nonischemic liver lobes). Functional categories of the verified marker genes indicate on the one hand cellular stress and tissue damage but otherwise activation of protective cellular reactions (AP-1 transcription factors, apoptosis related genes, heat shock genes). In order to assign the transcriptional status to the biological relevant protein level we demonstrated that Hsp70, Hsp27, Gadd45a and IL-1rI were clearly up-regulated comparing postischemic and untreated rat livers, suggesting their involvement in the WI/R context.

CONCLUSION: This study unveils a WI/R response gene set that will help to explore molecular pathways involved in the tissue damage after WI/R. In addition, these genes especially Hsp70 and Gadd45a might represent promising new candidates indicating WI/R liver damage.

Differential modulation of gene expression among rat tissues with warm ischemia

The aim of this study is to determine if warm ischemia after surgical extirpation impacts gene expression in tissue samples which will be used for cDNA array analysis. We investigated effects of warm ischemia on gene expression in lung, liver, kidney, and spleen of rats, chronologically, using an original cDNA array, real-time quantitative RT-PCR and immunohistochemistry. Although no visible alteration was found in RNA quality, cDNA array showed that expression of many genes was modulated by warm ischemia within 60 min in these tissues, 19.1% of the tested genes in lung, 11.0% in liver, 5.1% in kidney, and 16.2% in spleen. Quantitative RT-PCR revealed that warm ischemia significantly induced up-regulation of immediate early genes, c-fos, Egr-1, and c-jun, in lung, but not in liver. These findings suggest that genes may show tissue-dependent differential transcriptional response against warm ischemia. Tissue samples obtained from patients during surgery cannot completely escape effects of ischemia. In case of examination by cDNA array analysis, biologists should keep in mind that tissue samples come equipped with particular footprints.

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