Heat shock preconditioning ameliorates liver injury following normothermic ischemia-reperfusion in steatotic rat livers

Nanoparticle-Based Interventions for Liver Transplantation

Liver transplantation is the only treatment for hepatic insufficiency as a result of acute and chronic liver injuries/pathologies that fail to recover. Unfortunately, there remains an enormous and growing gap between organ supply and demand. Although recipients on the liver transplantation waitlist have significantly higher mortality, livers are often not allocated because they are (i) classified as extended criteria or marginal livers and (ii) subjected to longer cold preservation time (>6 h) with a direct correlation of poor outcomes with longer cold ischemia. Downregulating the recipient's innate immune response to successfully tolerate a graft having longer cold ischemia times or ischemia-reperfusion injury through induction of immune tolerance in the graft and the host would significantly improve organ utilization and post-transplant outcomes. Broadly, technologies proposed for development aim to extend the life of the transplanted liver through post-transplant or recipient conditioning. In this review, we focus on the potential benefits of nanotechnology to provide unique pre-transplant grafting and recipient conditioning of extended criteria donor livers using immune tolerance induction and hyperthermic pre-conditioning.

What is the role of heat shock protein in abdominal organ transplantation?

Ischemia-reperfusion injury is a pathophysiological event occuring after abdominal organ transplantation, and has a significant influence on prognosis and survival of the graft. It is involved in delaying the primary function or non-functioning of the graft. The objective of this study was to provide information on heat shock protein mechanisms in ischemia-reperfusion injuries in abdominal organ transplantations, and to indicate the possible factors involved that may influence the graft outcome. Several classes of heat shock proteins are part of the ischemia and reperfusion process, both as inflammatory agonists and in protecting the process. Studies involving heat shock proteins enhance knowledge on ischemia-reperfusion injury mitigation processes and the mechanisms involved in the survival of abdominal grafts, and open space to support therapeutic future clinical studies, minimizing ischemia and reperfusion injuries in abdominal organ transplantations. Expression of heat shock proteins is associated with inflammatory manifestations and ischemia-reperfusion injuries in abdominal organ transplantations and may influence graft outcomes.

Activation of heat shock response improves biomarkers of NAFLD in patients with metabolic diseases

Nonalcoholic fatty liver disease (NAFLD) is often accompanied by metabolic disorders such as metabolic syndrome and type 2 diabetes (T2DM). Heat shock response (HSR) is one of the most important homeostatic abilities but is deteriorated by chronic metabolic insults. Heat shock (HS) with an appropriate mild electrical stimulation (MES) activates HSR and improves metabolic abnormalities including insulin resistance, hyperglycemia and inflammation in metabolic disorders. To analyze the effects of HS + MES treatment on NAFLD biomarkers, three cohorts including healthy men (two times/week, n = 10), patients with metabolic syndrome (four times/week, n = 40), and patients with T2DM (n = 100; four times/week (n = 40) and two, four, seven times/week (n = 20 each)) treated with HS + MES were retrospectively analyzed. The healthy subjects showed no significant alterations in NAFLD biomarkers after the treatment. In patients with metabolic syndrome, many of the NAFLD steatosis markers, including fatty liver index, NAFLD-liver fat score, liver/spleen ratio and hepatic steatosis index and NAFLD fibrosis marker, aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio, were improved upon the treatment. In patients with T2DM, all investigated NAFLD steatosis markers were improved and NAFLD fibrosis markers such as the AST/ALT ratio, fibrosis-4 index and NAFLD-fibrosis score were improved upon the treatment. Thus, HS + MES, a physical intervention, may become a novel treatment strategy for NAFLD as well as metabolic disorders.

Ischemia–reperfusion injury in patients with fatty liver and the clinical impact of steatotic liver on hepatic surgery

Hepatic steatosis is one of the most common hepatic disorders in developed countries. The epidemic of obesity in developed countries has increased with its attendant complications, including metabolic syndrome and non-alcoholic fatty liver disease. Steatotic livers are particularly vulnerable to ischemia/reperfusion injury, resulting in an increased risk of postoperative morbidity and mortality after liver surgery, including liver transplantation. There is growing understanding of the molecular and cellular mechanisms and therapeutic approaches for treating ischemia/reperfusion injury in patients with steatotic livers. This review discusses the mechanisms underlying the susceptibility of steatotic livers to ischemia/reperfusion injuries, such as mitochondrial dysfunction and signal transduction alterations, and summarizes the clinical impact of steatotic livers in the setting of hepatic resection and liver transplantation. This review also describes potential therapeutic approaches, such as ischemic and pharmacological preconditioning, to prevent ischemia/reperfusion injury in patients with steatotic livers. Other approaches, including machine perfusion, are also under clinical investigation; however, many pharmacological approaches developed through basic research are not yet suitable for clinical application.

Induction of heat-shock protein 70 expression by geranylgeranylacetone shows cytoprotective effects in cardiomyocytes of mice under humid heat stress

Background

Increasing evidence has revealed that humid heat stress (HHS) causes considerable damage to human health. The cardiovascular system has been suggested to be the primary target of heat stress, which results in serious cardiovascular diseases. However, there is still a lack of effective approaches for the prevention and treatment of cardiovascular diseases induced by HHS.

Objective

Heat-shock proteins (Hsps), especially Hsp70, are reported to provide effective cytoprotection under various stress stimuli. In the present study, we evaluated the cytoprotective effect of geranylgeranylacetone (GGA), which was previously been reported to induce Hsp70 expression in cardiomyocytes under HHS.

Methods and Principal Findings

Using a mouse model of HHS, we showed that the pretreatment of GGA enhanced Hsp70 expression under HHS, as examined by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. We then examined the effect of GGA pretreatment on the cardiomyocyte apoptosis induced by HHS using terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) staining, and found that GGA pretreatment inhibited mitochondria-mediated apoptosis. GGA pretreatment could reverse the effect of HHS on cell apoptosis by increasing expression of Bcl-2, decreasing cytochrome c in cytosol, and increasing cytochrome c in mitochondria. However, GGA pretreatment had no effect on the oxidative stress induced by HHS as determined by levels of superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH).

Conclusion

We have demonstrated that GGA pretreatment suppressed HHS-induced apoptosis of cardiomyocytes through the induction of Hsp70 overexpression.

The impact of hepatic steatosis on hepatic ischemia-reperfusion injury in experimental studies: a systematic review

Background. The impact of hepatic steatosis on outcome following hepatic ischemia-reperfusion injury (IRI) remains controversial with conflicting clinical results. A number of experimental studies have been published examining the relationship between hepatic steatosis and IRI. This systematic review evaluates these experimental studies. Methods. An electronic search of the Medline and Embase databases (January 1946 to June 2012) was performed to identify studies that reported relevant outcomes in animal models of hepatic steatosis subjected to IRI. Results. A total of 1314 articles were identified, of which 33 met the predefined criteria and were included in the study. There was large variation in the type of animal model, duration, and type of IRI and reporting of histological findings. Increased macrovesicular steatosis (>30%) was associated with increased histological damage, liver function derangement, and reduced survival. Increased duration of warm or cold ischemia had a negative impact on all outcomes measured. Microvesicular steatosis did not influence outcome. Conclusions. Findings from this systemic review support the hypothesis that livers with >30% macrovesicular steatosis are less tolerant of IRI. Clinically, it is likely that these findings are applicable to patients undergoing hepatic resection, but further studies are required to confirm these data.

New routes to therapy for spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy's disease, is a genetically inherited neuromuscular disorder characterized by loss of lower motor neurons in the brainstem and spinal cord and skeletal muscle fasciculation, weakness, and atrophy. SBMA is caused by expansion of a polyglutamine (polyQ) tract in the gene coding for the androgen receptor (AR). PolyQ expansions cause at least eight other neurological disorders, which are collectively known as polyQ diseases. SBMA is unique in the family of polyQ diseases in that the disease manifests fully in male individuals only. The sex specificity of SBMA is the result of the interaction between mutant AR and its natural ligand, testosterone. Here, we will discuss emerging therapeutic perspectives for SBMA in light of recent findings regarding disease pathogenesis.

HSF1 is essential for the resistance of zebrafish eye and brain tissues to hypoxia/reperfusion injury

Ischemia and subsequent reperfusion (IR) produces injury to brain, eye and other tissues, contributing to the progression of important clinical pathologies. The response of cells to IR involves activation of several signaling pathways including those activating hypoxia and heat shock responsive transcription factors. However, specific roles of these responses in limiting cell damage and preventing cell death after IR have not been fully elucidated. Here, we have examined the role of heat shock factor 1 (HSF1) in the response of zebrafish embryos to hypoxia and subsequent return to normoxic conditions (HR) as a model for IR. Heat shock preconditioning elevated heat shock protein expression and protected zebrafish embryo eye and brain tissues against HR-induced apoptosis. These effects were inhibited by translational suppression of HSF1 expression. Reduced expression of HSF1 also increased cell death in brain and eye tissues of embryos subjected to hypoxia and reperfusion without prior heat shock. Surprisingly, reduced expression of HSF1 had only a modest effect on hypoxia-induced expression of Hsp70 and no effect on hypoxia-induced expression of Hsp27. These results establish the zebrafish embryo as a model for the study of ischemic injury in the brain and eye and reveal a critical role for HSF1 in the response of these tissues to HR. Our results also uncouple the role of HSF1 expression from that of Hsp27, a well characterized heat shock protein considered essential for cell survival after hypoxia. Alternative roles for HSF1 are considered.

Modified mild heat shock modality attenuates hepatic ischemia/reperfusion injury

BACKGROUND

Hepatic ischemia/reperfusion (I/R) injury is a pathologic process caused by hepatic surgery and transplantation, and still remains a severe clinical problem. It was shown that preconditioning by hyperthermia might protect tissues against I/R injury. But hyperthermia could be laborious and time-consuming. Alternatively, the application of mild electrical stimulation (MES) has been reported to have positive effects in clinical settings on several medical ailments. Thus, we modified the preconditioning approach by combining short-term mild heat shock (HS) and MES, and evaluated the effect of HS+MES pretreatment on hepatic injury induced by I/R.

MATERIALS AND METHODS

C57BL/6J mice were sham treated or treated three times with HS (42 degrees C) and/or MES (12V) for 20min, carried out every other d within 1 wk. After the last treatment, mice were subjected to hepatic ischemia for 30 or 60min and reperfusion for 6h. Liver injury was assessed by evaluating the levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The expressions of pro-inflammatory cytokines and heat shock protein (Hsp) 72 in liver tissues were also assessed by real-time PCR and Western blotting analyses, respectively.

RESULTS

HS+MES pretreatment suppressed the hepatic I/R-induced release of serum AST and ALT and the mRNA levels of some pro-inflammatory cytokines. In addition, HS+MES up-regulated the expression of Hsp72 in mice liver.

CONCLUSIONS

HS+MES preconditioning ameliorated hepatic I/R injury possibly through Hsp72 induction, and suppressed pro-inflammatory cytokine expression in mice liver.

Current studies on therapeutic approaches for ischemia/reperfusion injury in steatotic livers

Steatotic livers are particularly vulnerable to ischemia/reperfusion (I/R) injury, resulting in poor outcomes following liver surgery and transplantation. Therapeutic approaches for I/R injury in steatotic livers are currently under intensive investigation. This review summarizes and discusses the approaches developed during the last few years to prevent hepatic I/R injury in steatotic livers. Among the proposed approaches, ischemic preconditioning and intermittent clamping are the two most promising approaches that have been applied in some clinical centers for liver surgery and transplantation, but most of others have not reached clinical application yet.

Ischemic preconditioning in solid organ transplantation: from experimental to clinics

This study reviews the current understanding of ischemic preconditioning (IP) in experimental and clinical setting, and the mechanisms that mediate the complex processes involved as a tool to protect against ischemia and reperfusion (I/R) injury, but is not intended as a complete literature review of preconditioning. IP has been mainly elucidated in cardiac ischemia. Recent reports confirm the efficacy of pre- and postconditioning in cardiac surgery and percutaneous coronary interventions in humans. IP utilizes endogenous as well as distant mechanisms in skeletal muscle, liver, lung, kidney, intestine and brain in animal models to convey varying degrees of protection from I/R injury. Specifically, preconditioned tissues exhibit altered energy metabolism, better electrolyte homeostasis and genetic reorganization, as well as less oxygen-free radicals and activated neutrophils release, reduced apoptosis and better microcirculatory perfusion. To date, there are few human studies, but recent trials suggest that human liver, lung and skeletal muscle acquire protection after IP. Present data address the potential therapeutic application of IP in the prevention of I/R damage specially aimed at clinical transplantation. IP is ubiquitous but more research is required to fully translate these findings to the clinical arena.

Effects of Huoxue Huayu injection I pretreatment and ischemic preconditioning on liver ischemia and reperfusion injury in rats

AIM: To investigate the effects of Huoxue Huayu injection I (HHI-I) pretreatment and ischemic preconditioning (IP) on hepatic ischemia and reperfusion (I/R) injury in rats and compare their efficacity.

METHODS: Eighty healthy adult male Sprague-Dawley rats were randomly and averagely divided into 4 groups: sham operation (SO) group, I/R group, ischemia preconditioning (IP) group, and HHI-I pretreatment group. After partial hepatic I/R model was made, the rats of each group were sacrificed to determine serum alanine aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), tissue malondialdehyde (MDA) and superoxide dismutase (SOD) level 1、3、6、24 h after reperfusion, respectively. Tissue tumor necrosis factor alpha (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) mRNA levels were determined by reverse transcription-polymerase chain reaction after 1 h of reperfusion. Liver histology was observed after 3 h of reperfusion.

RESULTS: The activities of ALT, AST, LDH, the level of MDA, and the expression of TNF-α, ICAM-1 mRNA in I/R, IP, and HHI-I group were significantly higher than those in SO group, but they were markedly lower in IP and HHI-I group than those in I/R group. The activities of ALT, AST, LDH in HHI-I group were significantly lower than those in IP group (ALT: 2378.8 ± 303.4 nkat/L vs 2840.6 ± 248.4 nkat/L; AST: 2887.2 ± 270.1 nkat/L vs 4567.6 ± 275.1 nkat/L; LDH: 10550.4 ± 710.1 nkat/L vs 12164.1 ± 735.1 nkat/L; all P < 0.05). As compared with that in the IP group, the level of MDA in HHI-I group was decreased at the 3^rd and 6^th hour (17.35 ± 1.39 nmol/g vs 21.66 ± 1.84 nmol/g, P < 0.05), and the mRNA expression of TNF-α and ICAM-1 were decreased (TNF-α: 0.54 ± 0.06 vs 0.78 ± 0.08; ICAM-1: 0.43 ± 0.03 vs 0.69 ± 0.11, both P < 0.01). The level of SOD in I/R, IP and HHI-I group was markedly lower than that in SO group (P < 0.05), but it was significantly higher in IP and HHI-I group than that in I/R group (P < 0.05). The SOD level in the animals received HHI-I was significantly increased in comparison with that in IP group (136.00 ± 12.50 nmol/g vs 124.70 ± 9.32 nmol/g, P < 0.05). Microscopy showed that liver injury in the HHI-I-treated animals and IP-treated animals were attenuated as compared with that in I/R group.

CONCLUSION: HHI-I and IP pretreatment can alleviate I/R-induced liver injury, and the former is superior to the latter. The protective mechanism of HHI-I may be associated with the improvement of liver microcirculation, elimination of tissue anoxia, transcription inhibition of cytokine and cell adhesion molecule such as TNF-α and ICAM-1, and decrease of neutrophil infiltration.

El preacondicionamiento isquémico del hígado: de las bases moleculares a la aplicación clínica

Ischemia-reperfusion injury is produced when an organ is deprived of blood flow (ischemia), which is then restored (reperfusion). In certain circumstances, this injury leads to irreversible organ damage. Several therapeutic strategies have been used to reduce the severity of this injury. One of these strategies is the application of brief and repetitive episodes of ischemia-reperfusion before prolonged ischemia-reperfusion (ischemic preconditioning). In the present article we review the molecular mechanisms through which ischemic preconditioning confers protection against ischemia-reperfusion injury. The application of ischemic preconditioning during liver surgery is discussed, both in normothermic situations such as liver resection and in situations of low temperature such as liver transplantation.

Heat shock preconditioning inhibits CD4+ T lymphocyte activation in transplanted fatty rat livers

Heat shock preconditioning (HPc) of fatty donor livers significantly increases recipient survival in rats. We investigated to what extent the blockade of Kupffer cells by gadolinium chloride (GdCl3) can mimic the effect of HPc and the involvement of liver CD4+ T lymphocytes in HPc. Fatty liver was experimentally induced in Lewis rats by a choline- and methionine-deficient diet. Fatty liver donors were pretreated with HPc (42.5 degrees C for 10 min), the Kupffer cell inhibitor GdCl3, or placebo (sham group). Donors were then harvested, stored in University of Wisconsin preservation solution for 12 h at 4 degrees C, and transplanted into normal syngeneic rats. Hepatic injury (alanine aminotransferase) and serum cytokines (interleukin-12p70, tumor necrosis factor-alpha, and interleukin-10) of recipients increased at 3 h, then decreased, and increased again at 24 h after transplantation. HPc treatment diminished both the early and later phases of this biphasic response and improved recipient survival. GdCl3 reduced these cytokines in the early but not the later phase and did not reduce neutrophil accumulation or improve the recipient survival. HPc, but not GdCl3 treatment, also reduced the number of liver CD4+ T lymphocytes and their interferon-gamma production. We conclude that HPc, but not GdCl3 treatment, prevents biphasic liver injury and the activation of liver CD4+ T lymphocytes in transplanted fatty donor livers.

Heat shock proteins and mitogen-activated protein kinases in steatotic livers undergoing ischemia-reperfusion: some answers

Ischemic preconditioning protects steatotic livers against ischemia-reperfusion (I/R) injury, but just how this is achieved is poorly understood. Here, I/R or preconditioning plus I/R was induced in steatotic and nonsteatotic livers followed by investigating the effect of pharmacological treatments that modulate heat shock proteins (HSPs) and mitogen-activated protein kinases (MAPKs). MAPKs, HSPs, protein kinase C, and transaminase levels were measured after reperfusion. We report that preconditioning increased HSP72 and heme-oxygenase-1 (HO-1) at 6 and 24 hours of reperfusion, respectively. Unlike nonsteatotic livers, steatotic livers benefited from HSP72 activators (geranylgeranylacetone) throughout reperfusion. This protection seemed attributable to HO-1 induction. In steatotic livers, preconditioning and geranylgeranylacetone treatment (which are responsible for HO-1 induction) increased protein kinase C activity. HO-1 activators (cobalt(III) protoporphyrin IX) protected both liver types. Preconditioning reduced p38 MAPK and c-Jun N-terminal kinase (JNK), resulting in HSP72 induction though HO-1 remained unmodified. Like HSP72, both p38 and JNK appeared not to be crucial in preconditioning, and inhibitors of p38 (SB203580) and JNK (SP600125) were less effective against hepatic injury than HO-1 activators. These results provide new data regarding the mechanisms of preconditioning and may pave the way to the development of new pharmacological strategies in liver surgery.

Oral administration of geranylgeranylacetone plus local somatothermal stimulation: A simple, effective, safe and operable preconditioning combination for conferring tolerance against ischemia-reperfusion injury in rat livers

AIM: To explore a simple, effective, safe and operable pretreatment for conferring tolerance against ischemia-reperfusion (I-R) injury in rat livers.

METHODS: Forty-five rats were divided into five groups (each group n = 9). Group C: control group; group G: geranylgeranylacetone (GGA) was administered without heat stress; group S: local heat stress alone; group WG: GGA plus whole-body heat stress; group SG: GGA administration plus local heat stress. After completion of the I-R procedure, the ischemic-reperfused liver lobes in five groups were resected and tested for heat shock protein (HSP70) by RT-PCR, Western blotting analysis and immunohistochemical staining. The blood samples were collected for ALT and AST measurement at the end of occlusion of blood supply, 30 min after reperfusion, 24, 48, 72 h after surgery from the inferior vena cava. Survival was monitored for 1 wk.

RESULTS: The production of HSP70 after I-R injury increased, the liver enzyme levels after reperfusion decreased rapidly, and the survival rates increased in groups C-SG.

CONCLUSION: The combination of GGA plus local somatothermal stimulation is a simple, effective, safe and operable pretreatment to induce HSP70 in patients with liver tumor and cirrhosis before hepatectomy and in donors before harvesting graft for liver transplantation.

FK506 Donor Pretreatment Improves Intestinal Graft Microcirculation and Morphology by Concurrent Inhibition of Early NF-κB Activation and Augmented HSP72 Synthesis

FK506 protects against ischemia-reperfusion injury but the mechanisms remain unclear. We investigated the impact of donor pretreatment using FK506 on graft microcirculation and morphology after intestinal transplantation. FK506 was given intravenously to SD rats (0.3 mg/kg) 6 hours before graft harvesting while controls received saline (n = 7/group). Grafts were stored for 3 hours in saline, then transplanted. Preservation induced similar lesions in both groups, but pretreated grafts showed better morphology than controls at 20 minutes after reperfusion. Six hours post-reperfusion, preconditioned grafts revealed near-normal morphology, whereas controls showed short villi, denuded areas, and intense inflammation. Pretreated grafts displayed a lower apoptotic rate and reduced caspase-3 activity. Hsp72 expression was enhanced in preconditioned grafts at harvesting, after preservation, and 20 minutes post-reperfusion compared to controls. Control grafts showed intranuclear p65 (activation of NFkappaB) at 20 minutes post-reperfusion; whereas pretreated grafts displayed no intranuclear p65. However, at 6 hours, comparable intranuclear p65 levels were found in both groups. ICAM-1 was low in both groups after preservation and early post-reperfusion, but greatly increased in controls at 6 hours post-reperfusion. In contrast, pretreated grafts continued to lack ICAM-1. Microvascular perfusion was comparable at 20 minutes. Six hours later, pretreated grafts had 30% increased perfusion, while in controls it was slightly decreased. FK506 alleviated reperfusion injury by blocking NF-kappaB activation and ICAM-1 transcription, thus decreasing endothelial activation and improving the microcirculation. It also induces Hsp72, therefore inhibiting apoptosis and accelerating morphologic restoration.

Preconditioning: evolution of basic mechanisms to potential therapeutic strategies

Preconditioning describes the phenomenon by which a traumatic or stressful stimulus confers protection against subsequent injury. Originally recognized in dog heart subjected to ischemic challenges, preconditioning has been demonstrated in multiple species, can be induced by various stimuli, and is applicable in different organ systems. Tremendous progress has been made elucidating the signal transduction cascade of preconditioning. Preconditioning represents a potent tissue-protective condition, and mechanistic understanding may allow safe clinical application. This review recalls the history of preconditioning and how it relates to the history of the investigation of endogenous adaptation; summarizes the current mechanistic understanding of acute preconditioning; outlines the signal transduction cascade leading to the development of delayed preconditioning; discusses preconditioning in noncardiac tissue; and explores the potential of using preconditioning clinically.

Induction of a 72-kDa heat shock protein and protection against lipopolysaccharide-induced liver injury in cirrhotic rats

BACKGROUND AND AIM

A 70-kDa heat shock protein (stress-inducible HSP70, HSP72) has been reported to be a cytoprotectant in a variety of organs. It has been reported that HSP72 protected non-cirrhotic rats against endotoxemia. However, its cytoprotective effect against endotoxemia in cirrhotic rats has not yet been studied. In this study, we investigated the cytoprotective effect of HSP72 on lipopolysaccharide (LPS)-induced liver injury in carbon tetrachloride (CCl(4))-induced cirrhotic rats.

METHODS

Liver cirrhosis was produced by an 8-week intraperitoneal injection of CCl(4) in male Sprague-Dawley rats. Expression of HSP72 was investigated using western blot analysis. Cirrhotic rats were given an intraperitoneal injection of LPS (10 mg/kg) with or without hyperthermia (42.5 degrees C, 15 min) preconditioning. Liver injury was assessed biochemically (aspartate transaminase, alanine transaminase, bilirubin, lactate dehydrogenase, creatinine) and histologically. The plasma tumor necrosis factor (TNF)-alpha level was determined.

RESULTS

Hyperthermia preconditioning induced a 4-fold increase in HSP72 in the cirrhotic rat liver. Pre-induction of HSP72 prevented LPS-induced liver injury, as evaluated using serum biochemical parameters and histology with reduced TNF-alpha response.

CONCLUSION

These findings suggest that pre-induction of HSP72 may provide therapeutic strategies for Gram-negative sepsis-induced liver injury in liver cirrhosis.

Protein kinase C-dependent activation of P44/42 mitogen-activated protein kinase and heat shock protein 70 in signal transduction during hepatocyte ischemic preconditioning

AIM: To investigate the significance of protein kinase C (PKC), P44/42 mitogen-activated protein kinase (MAPKs) and heat shock protein (HSP)70 signal transduction during hepatocyte ischemic preconditioning.

METHODS: In this study we used an in vitro ischemic preconditioning (IP) model for hepatocytes and an in vivo model for rat liver to investigate the significance of protein kinase C (PKC), P44/42 mitogen-activated protein kinase (P44/42 MAPKs) and heat shock protein 70 (HSP70) signal transduction in IP. Through a normal liver cell hypoxic preconditioning (HP) model in which cultured normal liver cells were subjected to 3 cycles of 5 min of incubation under hypoxic conditions followed by 5 min of reoxygenation and subsequently exposed to hypoxia and reoxygenation for 6 h and 9 h respectively. PKC inhibitor, activator and MEK inhibitor were utilized to analyze the phosphorylation of PKC, the expression of P44/42 MAPKs and HSP70. Viability and cellular ultrastructure were also observed. By using rat liver as an in vivo model of liver preconditioning (3 cycles of 10-min occlusion and 10-min reperfusion), in vivo phosphorylation of PKC and P44/42MAPKs, HSP70 expression were further analyzed. AST/ALT concentration, cellular structure and ultrastruture were also observed. All the data were statistically analyzed.

RESULTS: Similar results were obtained in both in vivo and in vitro IP models. Compared with the control without IP (or HP), the phosphorylation of PKC and P44/42 MAPKs and the expression of HSP70 were obviously increased in IP (or HP) treated model in which cytoprotection could be found. The effects of preconditioning were mimicked by stimulating PKC with 4β phorobol-12-myristate13-acetate (PMA). Conversely, inhibiting PKC with chelerythrine abolished the protection given by preconditioning. PD98059, inhibitor of MEK (the upstream kinase of P44/42MAPKs), also reverted the cytoprotection exerted by preconditioning.

CONCLUSION: The results demonstrate that preconditioning induces a rapid activation of P44/42MAPKs and PKC activation plays a pivotal role in the activation of P44/42 MAPKs pathway that participates in the preservation of liver cells. HSP expression is regulated by signals in PKC dependent P44/ 42 MAPKs pathway.

Preconditioning-induced cytoprotection in hepatocytes requires Ca(2+)-dependent exocytosis of lysosomes

A short period of hypoxia reduces the cytotoxicity produced by a subsequent prolonged hypoxia in isolated hepatocytes. This phenomenon, termed hypoxic preconditioning, is mediated by the activation of adenosine A2A-receptor and is associated with the attenuation of cellular acidosis and Na+ overload normally occurring during hypoxia. Bafilomycin, an inhibitor of the vacuolar H+/ATPase, reverts the latter effects and abrogates the preconditioning-induced cytoprotection. Here we provide evidence that the acquisition of preconditioning-induced cytoprotection requires the fusion with plasma membrane and exocytosis of endosomal-lysosomal organelles. Poisons of the vesicular traffic, such as wortmannin and 3-methyladenine, which inhibit phosphatydilinositol 3-kinase, or cytochalasin D, which disassembles the actin cytoskeleton, prevented lysosome exocytosis and also abolished the preconditioning-associated protection from acidosis and necrosis provoked by hypoxia. Preconditioning was associated with the phosphatydilinositol 3-kinase-dependent increase of cytosolic [Ca2+]. Chelation of free cytosolic Ca2+ in preconditioned cells prevented lysosome exocytosis and the acquisition of cytoprotection. We conclude that lysosome-plasma membrane fusion is the mechanism through which hypoxic preconditioning allows hepatocytes to preserve the intracellular pH and survive hypoxic stress. This process is under the control of phosphatydilinositol 3-kinase and requires the integrity of the cytoskeleton and the rise of intracellular free calcium ions.

Technique for expanding the donor liver pool: heat shock preconditioning in a rat fatty liver model

Fatty liver is a common predisposing risk factor for postoperative liver failure and accounts for most discarded livers during triage of donors. We investigated the effect of heat shock preconditioning (HPc) on recipient survival in a rat fatty liver transplantation model. Fatty liver donor rats were exposed to brief whole-body hyperthermia (10 minutes at 42.5 degrees C) and allowed to recover. HPc induced heat shock proteins (HSPs) (HSP72, HSP90, and heme oxygenase [HO]-1) in donor livers, with levels peaking 12 to 48 hours after HPc. Subsequently, donor livers were harvested 24 hours after HPc, placed in cold storage for 10 hours, and transplanted into normal rats. At 3 hours posttransplantation, HPc reduced serum liver enzymes in the recipients and almost completely suppressed the release of tumor necrosis factor (TNF)-alpha and interleukin (IL)-10. Histologic evaluation 3 and 24 hours after transplantation showed that HPc significantly reduced hepatic inflammation and hepatocellular necrosis without affecting the steatotic appearance of hepatocytes. One week after transplantation, control non-heat-shocked and heat-shocked fatty liver recipients exhibited survival rates of less than 10% and more than 80%, respectively. The evaluation of the survival of recipients receiving fatty livers at different times after HPc showed that the protective effect of HPc was significant when donor livers were transplanted 3 to 48 hours after HPc, with the maximum effect seen 6 to 48 hours after HPc. In conclusion, HPc is a promising avenue to salvage rejected donor fatty livers and enhance the survival rate of fatty liver recipients. We estimate that this technique could increase the annual donor pool by 600 livers.

Recent insights on the mechanisms of liver preconditioning

Ischemia/reperfusion is the main cause of hepatic damage consequent to temporary clamping of the hepatoduodenal ligament during liver surgery as well as graft failure after liver transplantation. In recent years, a number of animal studies have shown that pre-exposure of the liver to transient ischemia, hyperthermia, or mild oxidative stress increases the tolerance to reperfusion injury, a phenomenon known as hepatic preconditioning. The development of hepatic preconditioning can be differentiated into 2 phases. An immediate phase (early preconditioning) occurs within minutes and involves the direct modulation of energy supplies, pH regulation, Na(+) and Ca(2+) homeostasis, and caspase activation. The subsequent phase (late preconditioning) begins 12-24 hours after the stimulus and requires the synthesis of multiple stress-response proteins, including heat shock proteins HSP70, HSP27, and HSP32/heme oxygenase 1. Hepatic preconditioning is not limited to parenchymal cells but ameliorates sinusoidal perfusion, prevents postischemic neutrophil infiltration, and decreases the production of proinflammatory cytokines by Kupffer cells. This latter effect is important in improving systemic disorders associated with hepatic ischemia/reperfusion. The signals triggering hepatic preconditioning have been partially characterized, showing that adenosine, nitric oxide, and reactive oxygen species can activate multiple protein kinase cascades involving, among others, protein kinase C and p38 mitogen-activated protein kinase. These observations, along with preliminary studies in humans, give a rationale to perform clinical trials aimed at verifying the possible application of hepatic preconditioning in preventing ischemia/reperfusion injury during liver surgery.

Activation of PPAR-alpha in streptozotocin-induced diabetes is essential for resistance against acetaminophen toxicity

Diabetic (DB) mice exhibit significant resistance to hepatotoxicants. The role of peroxisome proliferator receptor (PPAR)-alpha activation in diabetes, in protection against lethal acetaminophen (APAP) challenge, was investigated. Upon treatment with APAP (600 mg/kg, i.p., a LD100 dose in wild-type [WT] non-DB mice), WT-DB mice showed only 30% mortality and 40% less liver injury as measured by alanine aminotransferase and histopathology. In contrast, diabetes in PPAR knockout (PPAR-alpha-/-) mice failed to protect against APAP toxicity, suggesting the importance of PPAR-alpha in diabetes-induced protection. S-phase DNA synthesis and PCNA immunohistochemical staining after injury showed early and robust tissue repair in WT-DB mice, but not in the PPAR-alpha-/--DB mice. Microarray analyses were performed on livers from non-DB and DB (WT and PPAR-alpha-/-) mice at 0 and 12 h after APAP. Microarray data were confirmed via real-time polymerase chain reaction analysis of several genes, including stress response, immediate early genes, DNA damage, heat shock proteins, and cell cycle regulators, followed by Western analyses of selected proteins. Gel shift assays revealed higher activation of nuclear factor-kappaB in WT-DB mice after APAP treatment. These findings suggest PPAR-alpha activation as a hepatoprotective adaptive response mediating protection against APAP in diabetes.

Ischemic preconditioning protects the steatotic mouse liver against reperfusion injury: an ATP dependent mechanism

BACKGROUND/AIMS

Hepatic steatosis is a major risk factor for liver surgery and transplantation. The increased susceptibility of fatty livers to ischemic injury is associated with a necrotic form of cell death as opposed to apoptosis in lean animals, and is possibly related to low contents of ATP. Ischemic preconditioning, a brief period of ischemia prior to a prolonged period, protects the lean liver against ischemia through anti-apoptotic properties. We evaluated whether ischemic preconditioning also confers protection in the fatty liver and whether it protects against the ATP loss.

METHODS

The effect of ischemic preconditioning was tested in steatotic and lean livers subjected to 75 min of ischemia and 4 or 24 h of reperfusion. Tissue ATP contents were assessed at various times, and a model of low hepatic ATP contents (starvation) was studied to assess the type of injury following ischemia and the effects of preconditioning.

RESULTS

Ischemic preconditioning protected steatotic livers against massive necrosis. ATP levels were significantly higher before and after reperfusion in liver subjected to preconditioning when compared to controls. Liver with low baseline ATP levels (starvation) were also associated with necrosis, and were protected by ischemic preconditioning.

CONCLUSIONS

Ischemic preconditioning mainly protects the fatty liver against necrosis possibly through preservation and restoration of tissue ATP contents.

Hypothermic preservation of hepatocytes

This paper presents a review of recent research on the hypothermic storage of hepatocytes. The first focus is on the diversity of methodologies currently employed in this area. The cell damage caused by hypothermic preservation and its possible mechanism are then investigated on both morphological and molecular biology. Later, the gene expressions on a mRNA level or enzyme level after hypothermic preservation are further discussed. Finally, the improvement of hypothermic storage by preconditioning, such as by increasing temperature, is explored.

Pharmacological preconditioning protects lung injury induced by intestinal ischemia/reperfusion in rat

Intestinal ischemia/reperfusion (IIR) is a critical and triggering event in the development of distal organ dysfunction, frequently involving the lungs. Respiratory failure is a common cause of death and complications after intestinal I/R. Stress protein heme oxygenase-1 (HO-1) confers the protection against a variety of oxidant-induced cell and tissue injuries. The aim of this study was to investigate the hypothesis that the induced HO-1 expression by pharmacological preconditioning with anticancer drug doxorubicin (Dox) could protect the lung injury induced by intestinal I/R. Intravenous administration of Dox induced HO-1 expression in the lungs and high levels of the expression were sustained at least to 48 h after the injection. Therefore, as pharmacological preconditioning, a low dose of Dox was injected intravenously into rats at 48 h before the start of intestinal ischemia. Rats underwent intestinal I/R by superior mesenteric artery occlusion for 120 min followed by 120 min of reperfusion. Preconditioning with Dox significantly ameliorated the lung injury induced by the intestinal I/R. Administration of a specific inhibitor of HO activity reduced the efficacy of the preconditioning. Our results suggest that this improvement may be mediated at least in part by the HO-1 induction. These findings may offer interesting perspectives for patient management In Intestinal surgical operation and intestine transplantation.

Heat-shock preconditioning protects fatty livers in genetically obese Zucker rats from microvascular perfusion failure after ischemia reperfusion

Reduced tolerance of steatotic livers to ischemic injury is considered to correlate with impaired microcirculation. The aim of this study was to investigate the impact of heat-shock preconditioning (HSPC) on microcirculatory failure after ischemia/reperfusion (I/R) in steatotic livers by means of intra-vital fluorescence microscopy. Obese Zucker rats were used. In the HS group, rats underwent whole-body hyperthermia followed by 60-min partial liver ischemia. In group IR, rats were exposed only to ischemia. Microcirculation parameters (sinusoidal perfusion rate, sinusoidal diameter, leukocyte-endothelial interaction) were significantly better preserved in the HS group than in the IR group. Liver enzymes, oxygenated glutathione/reduced glutathione (GSSG/GSH) ratio, and electron microscopy showed less damage in the HS group. A marked expression of heat shock protein 72 (HSP72) and heme oxygenase (HO-1) was found only in the livers of group HS. HSPC mitigated the I/R injury of steatotic livers by preventing post-ischemic failure of microcirculation. This beneficial effect was found to be associated with the induction of HSP72 and HO-1.

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

We focused on heat shock protein 70 (HSP70) as a marker of viability in hepatic warm ischemia-reperfusion. Segmental hepatic warm ischemia was produced in rats for 15, 30, 60, 90, 120, or 180 min. Liver sections were evaluated at 30, 60, and 120 min of reperfusion. Expression of HSP70 and messenger RNA (mRNA), apoptosis, and apoptosis-associated genes such as Bcl-2 and Bax were studied. Expression of HSP70 and mRNA was augmented as warm ischemia was prolonged, but was markedly suppressed in livers with more than 120 min of ischemia. The highest accumulation of HSP70 was observed in the nucleus. In livers subjected to longer duration of warm ischemia, necrosis and apoptosis were evident and Bcl-2 mRNA expression and Bcl-2/Bax protein ratio were markedly diminished. Apoptosis may be related to the process of cellular injury induced by warm ischemia-reperfusion. Expression of HSP70 and the Bcl-2 family can be effective markers of viability in hepatic warm ischemia-reperfusion.

Ischemic preconditioning attenuates the oxidant-dependent mechanisms of reperfusion cell damage and death in rat liver

In an in vivo rat model of liver ischemia followed by reperfusion a consistent appearance of necrosis and activation of biochemical pathways of apoptosis was reproduced and monitored after 30 minutes reperfusion. Preconditioning by application of a short cycle of ischemia-reperfusion (10 minutes + 10 minutes) positively conditioned recovery of the organ at reperfusion, attenuating both necrotic and apoptotic events. Preconditioning at least halved cell oxidative damage occurring early at reperfusion, and as a major consequence, the increase of cytolysis and apoptosis occurring at reperfusion was about 50% less. The attenuation of both pathways of cell death by preconditioning appeared at least partly related to its modulate action on H(2)O(2) and 4-hydroxy-2,3-trans-nonenal production. The overall data point to a marked diminished oxidant generation and oxidative reactions as one major possible mechanism through which ischemic preconditioning exerts protection against necrotic and apoptotic insult to the postischemic liver.

Geranylgeranylacetone suppresses inflammatory responses and improves survival after massive hepatectomy in rats

Overproduction of heat shock protein 70 (HSP70) in the liver protects hepatocytes under various pathologic conditions. In this study we examined the effects of a nontoxic HSP70 inducer, geranylgeranylacetone (GGA), on acute hepatic failure after 95% hepatectomy in rats. When GGA (100 mg/kg) or vehicle was intragastrically administered to rats 4 hours before 95% hepatectomy, all 25 rats pretreated with vehicle died within 60 hours after the operation, whereas 10 of 25 rats pretreated with GGA survived. During the 24-hour postoperative period, GGA significantly suppressed the release of aspartate or alanine aminotransferase and elevation of the serum interleukin-6 level, and completely inhibited an increase in the serum level of tumor necrosis factor-alpha. Histologic examinations showed that GGA prevented hemorrhagic necrosis, which was observed in vehicle-treated livers more than 12 hours after the operation. During the 24-hour postoperative period, HSP70 induction was absent in remnant livers of vehicle-treated rats. In contrast, GGA stimulated the HSP70 mRNA expression and HSP70 accumulation within 4 hours, and viable hepatocytes contained abundant HSP70 in their nuclei. Our results suggest that GGA may prevent acute liver failure after massive hepatectomy, at least in part, by enhancing HSP70 induction in the remnant liver.

The atrial natriuretic peptide and cGMP: novel activators of the heat shock response in rat livers

Preischemic treatment with atrial natriuretic peptide (ANP) attenuates ischemia-reperfusion injury of the rat liver via cyclic guanosine monophosphate (cGMP). The attenuated activation of nuclear factor kappaB (NF-kappaB) seems to contribute to this effect. The aim of this study was to determine whether heat shock proteins are involved in these molecular pathways. Livers of male Sprague-Dawley rats were continuously perfused with Krebs-Henseleit (KH) buffer with or without ANP or 8-Br-cGMP. In different experiments livers were perfused with or without ANP for 20 minutes, kept in cold storage solution for 24 hours, and reperfused. Activation of heat shock transcription factor (HSF) (by electrophoretic mobility shift assay), heat shock protein 70 (HSP70), and glyceraldehyde phosphate dehydrogenase (GAPDH) mRNA (by reverse transcription polymerase chain reaction [RT-PCR]), as well as HSP70 (by Western blot) were investigated in freeze-clamped liver samples. During continuous perfusion ANP as well as 8-Br-cGMP activated HSF, HSP70 protein concentrations paralleled HSF-activation. ANP pretreated livers exhibited elevated HSF after 24 hours of ischemia and elevated HSP70 mRNA levels during reperfusion. ANP prevented the marked decrease of HSP70 protein during reperfusion. Coimmunoprecipitation studies showed increased binding of HSP70 to inhibitory factor kappaB (IkappaB) in ANP-treated livers. In conclusion, we showed the cGMP-mediated activation of HSF by ANP, which resulted in elevated HSP70 mRNA and protein concentrations and correlated with enhanced binding of HSP70 to IkappaB. This could be an important mechanism of ANP-mediated prevention of hepatic preservation damage.

Pharmacological preconditioning with doxorubicin. Implications of heme oxygenase-1 induction in doxorubicin-induced hepatic injury in rats

Heme oxygenase (HO) is the rate-limiting enzyme in the degradation of heme into biliverdin, carbon monoxide, and iron. HO-1, an inducible form, is thought to contribute to resistance to various types of oxidative stress. Doxorubicin (DOX) produces clinically useful responses in a variety of human cancers. We reported previously that prior administration of DOX ameliorated subsequent hepatic ischemia and reperfusion injury. The aim of this study was to examine whether this pharmacological preconditioning was useful for another type of hepatic injury induced by a non-surgical method. When a high dose of DOX (10 mg/kg body weight) was administered directly to rat liver via the portal vein, serum aspartate transaminase (AST) and alanine transaminase (ALT) levels increased markedly 24 hr after the injection. Under this condition, zinc-protoporphyrin IX, a specific inhibitor of HO-1, caused both serum AST and ALT levels to be elevated further. When a low dose of DOX (5 mg/kg body weight) was administered to rats via the tail vein as pharmacological preconditioning 3 days before the injection of a high dose of DOX via the portal vein, the levels of serum AST and ALT in rats clearly were improved as compared with rats without the preconditioning. Expression of HO-1 in the liver was confirmed 3 days after the administration of a low dose of DOX. In addition, prior administration of zinc-protoporphyrin IX abolished the effect of DOX preconditioning. Immunohistochemical analysis showed that the positive staining of HO-1 protein induced by a low dose of DOX was localized to histiocytes infiltrating periportal areas. These results strongly suggest that pharmacological preconditioning with DOX may generally help to attenuate subsequent oxidant-induced hepatic injury.

Suppression of tumor necrosis factor-alpha production and neutrophil infiltration during ischemia-reperfusion injury of the liver after heat shock preconditioning

BACKGROUND/AIMS

Heat shock preconditioning provides the liver with ischemic tolerance. In this study we examined the effects of heat shock preconditioning on hepatic nonparenchymal cells in light of tumor necrosis factor-alpha (TNF-alpha) production and neutrophil infiltration.

METHODS

Rats were exposed to heat shock pretreatment at 42 degrees C in the heat shock group (group HS) and at 37 degrees C in the control group (group C). After a 48-h recovery, the left hepatic lobes were given a 90-min ischemia and reperfused. Plasma concentrations of TNF-alpha, cytokine-induced neutrophil chemoattractant (CINC) and alanine aminotransferase (ALT) were measured. Liver tissues were checked for the presence of TNF-alpha mRNA. Histological staining for CINC and polymorphonuclear leukocyte (PMN) was also evaluated.

RESULTS

In group HS, plasma TNF-alpha levels were significantly more suppressed than in group C (P<0.0001). Expressions of TNF-alpha mRNA in the liver was suppressed in group HS. Production of CINC 2 h after reperfusion was reduced in group HS (P<0.05). PMN infiltration was significantly reduced in group HS (P<0.01). In group HS, liver histology revealed less cellular damage and the plasma level of ALT was significantly reduced (P<0.0001).

CONCLUSIONS

Heat shock preconditioning suppressed the production of TNF-alpha and CINC in the liver during reperfusion and consequently reduced neutrophil infiltration.

Preconditioning somatothermal stimulation on right seventh intercostal nerve territory increases hepatic heat shock protein 70 and protects the liver from ischemia-reperfusion injury in rats

Hyperthermic preconditioning attenuates the heat-induced cellular response to a subsequent severe heat challenge. However, it is impractical to perform whole-body hyperthermia in humans. This study was designed to test the hypotheses that hepatic heat shock protein 70 (Hsp70) could be induced by local somatothermal stimulation (LSTS) on right seventh intercostal nerve territory and that preconditioning the rats with LSTS protects the liver from subsequent ischemia-reperfusion injury. LSTS was brought about by application of a heating rod above right seventh intercostal nerve territory in male Sprague-Dawley rats. Hepatic gene expression of Hsp70 was assessed by Western blot and reverse transcription polymerase chain reaction (RT-PCR). Finally, serum ALT and AST and the lipid peroxidation product malondialdehyde (MDA) were evaluated in ischemic-reperfused rats preconditioned by application of LSTS on right seventh intercostal nerve territory. The results showed that hepatic gene expression of Hsp70 was upregulated in rats treated with LSTS. When animals were preconditioned with LSTS, followed by subsequent ischemia-reperfusion injury of the liver, there were significant decreases in liver enzymes (ALT/AST) and MDA formation in rats pretreated with one dose of LSTS (LSTS-1 group) as compared with those not treated with LSTS (control group) or treated with three doses of LSTS (LSTS-3 group). We conclude that mild local heat stress (one dose) on right seventh intercostal nerve territory upregulates hepatic gene expression of Hsp70 and protects the liver from subsequent ischemia-reperfusion injury. This might provide an easily applicable method for those patients facing ischemia-reperfusion challenge of the liver, as in liver resection and liver transplantation.

Geranylgeranylacetone, a heat shock protein inducer, prevents primary graft nonfunction in rat liver transplantation

BACKGROUND

Heat shock proteins (HSPs) are well known as cytoprotective proteins. Geranylgeranylacetone (GGA), a nontoxic anti-ulcer drug, was recently shown to have HSP-inducing capacity. In the present study, the activity of GGA was tested in a rat orthotopic liver transplantation (OLT) model to determine whether the compound has beneficial effects in warm ischemia-reperfusion injury.

METHODS

Either GGA or a control vehicle was orally administered to donor rats before graft harvest. Harvested livers were subjected to 45-min warm ischemia (37 degrees C) followed by OLT. HSP mRNA expressions and HSP syntheses in the graft livers were evaluated by reverse transcriptase polymerase chain reaction and Western blot analysis, respectively.

RESULTS

When the donors were treated with a vehicle, all recipients died of primary nonfunction within 2 days after OLT. In contrast, when the donors were treated with GGA (200 mg/kg per day) for 4 weeks, the 7-day survival rate of recipients was dramatically improved (90%). By giving a high dose of GGA (600 mg/kg per day) for 1 week, a similar improvement in recipient survival was seen (83.3%). GGA administration accumulated mRNA for both HSP72 and HSP90 in the livers even before warm ischemia and facilitated the syntheses of HSP72 and HSP90 after warm ischemia. In addition, GGA pretreatment also significantly reduced the serum levels of tumor necrosis factor-alpha (TNF-alpha) after reperfusion.

CONCLUSIONS

These findings indicate that both the enhanced induction of HSPs and the suppression of a cytotoxic mediator (TNF-alpha) might be involved in the beneficial effects of GGA on ischemia-reperfusion injury. Thus, oral administration of GGA would be a useful tool for preventing primary nonfunction in liver transplantation.

A non-toxic heat shock protein 70 inducer, geranylgeranylacetone, suppresses apoptosis of cultured rat hepatocytes caused by hydrogen peroxide and ethanol

BACKGROUND/AIMS

A stress-inducible heat shock protein 70 (HSP70) is one of the best-known endogenous factors protecting cell injury under various pathological conditions. The aim of this study was to examine anti-apoptotic actions of a non-toxic HSP70 inducer, geranylgeranylacetone (GGA), on hepatocytes exposed to hydrogen peroxide (H2O2) or ethanol.

METHODS

Primary cultures of rat hepatocytes were treated with different concentrations of GGA and exposed to 0.5 mM H202 or 100 mM ethanol. The heat shock response was assessed by measuring the activation of heat shock factor 1 (HSF1), HSP70 mRNA expression, and accumulations of HSP70, HSP90, and HSP27. Apoptosis was evaluated by DNA fragmentation.

RESULTS

Pretreatment with 1 microM GGA for 2 h enhanced nuclear translocation and phosphorylation of HSF1, HSF1-DNA binding, HSP70 mRNA expression, and its accumulation, when the cells were exposed to H202 or ethanol. In association with this accelerated response, GGA suppressed the insult-induced activation of c-Jun N-terminal kinases, caspase 9, and caspase 3-like proteases, leading to significant inhibition of apoptosis.

CONCLUSIONS

GGA exerted anti-apoptotic actions, at least in part, by priming hepatocytes for enhanced HSP70 induction. Our results suggest that GGA may have a potential benefit for the treatment of alcoholic and ischemia-reperfusion liver injuries.

Metallothionein and heat shock protein expression during acute liver injury and regeneration in rats

Metallothioneins (MT) are cytosolic proteins rich in cysteine which play a physiological role in metal ion homeostasis. Heat shock proteins (HSPs) are expressed in various organs in response to different stress stimuli. The purpose of the present study was to examine the intrahepatic distribution of MT and HSP-27, -70 and -90 in two different experimental models of acute liver injury and regeneration, induced by either thioacetamide, or carbon tetrachloride administration in male Wistar rats. Toxicological endpoints and markers of hepatocellular regeneration were assessed at various time points following toxin administration. The enzymatic activities of aspartate and alanine aminotransferases in serum, and histological findings in the liver were used to estimate toxin-induced injury. Tritiated thymidine incorporation into hepatic DNA, liver thymidine kinase activity and hepatocyte mitotic index were used to estimate liver regeneration. MT and HSPs were detected immunohistochemically. At the time of maximum liver injury, moderate MT and intense HSPs expression was prominent in hepatocytes in the vicinity of necrotic areas. At the time of maximum hepatocellular proliferation, intense MT and HSP-90 staining was evident in all hepatocytes, while at the same time, mild HSP-27 and HSP-70 immunoreactivity was noted. Our findings indicate that the differential distribution of MT and HSPs in the liver after toxin-induced injury, in common with the observed pattern of staining, reflect liver proliferating capacity.

Pharmacological hepatic preconditioning: involvement of 70-kDa heat shock proteins (HSP72 and HSP73) in ischaemic tolerance after intravenous administration of doxorubicin

BACKGROUND

Pharmacological preconditioning may induce a stress response which protects liver against ischaemia-reperfusion injury (IRI). The aim of this study was to determine, in an animal model, whether intravenous administration of doxorubicin induces heat shock proteins (HSPs) in liver tissue and facilitates liver tolerance to subsequent warm IRI.

METHODS

Male Wistar rats were used. Production of HSPs was determined in liver tissue sequentially after the injection of doxorubicin 1 mg/kg body-weight. Acquisition of tolerance for 30 min warm ischaemia and reperfusion of the liver was determined in animals pretreated (48 h beforehand) with doxorubicin, and in controls. Biochemical liver function and liver adenine nucleotide concentration 40 min after reperfusion and survival rate at 7 days after the ischaemic insult were recorded.

RESULTS

Expression of HSP72 and HSP73 in the liver was confirmed 48 h after doxorubicin administration. Biochemical parameters and survival rates were significantly better in pretreated animals than in controls.

CONCLUSION

These results indicate that doxorubicin has the potential to provide the liver with tolerance against IRI. A simultaneous increase of both HSP72 and HSP73 in liver tissue may explain the acquisition of tolerance following the administration of doxorubicin.

Effects of geranyl-geranyl-acetone administration before heat shock preconditioning for conferring tolerance against ischemia-reperfusion injury in rat livers

The effect of geranyl-geranyl-acetone (GGA) administration before heat shock preconditioning on heat shock protein (HSP) 72 induction and on the acquisition of tolerance against ischemia-reperfusion Injury was studied in rat livers. Male Wistar rats were divided into four groups: a control group (group C); a GGA group (group G); a simple heat shock group (group VH); and a heat shock with GGA premedication group (group GH). Five-, 10-, and 15-minute periods of heat shock preconditioning at 42 degrees C were performed in groups VH and GH. Subgroups were determined according to the period of heat shock exposure. After a 48-hour recovery, rats in groups C, VH5, VH15, and GH5 received a 30-minute period of hepatic ischemia. Induction of HSP72, survival rates, and changes in biochemical and histologic parameters were compared among the groups. Five-minute heat shock preconditioning was not enough to Induce HSP72. However, livers in group GH5 expressed approximately the same amount of HSP72 as those in group VH15. The expression of HSP72 in group GH15 was stronger than that found in group VH15. The degree and location of HSP72 expression were not different between groups GH5 and VH15. Seven-day survival was significantly better in groups GH5 (16/16) and VH15 (15/16) than in group C (8/16) or VH5 (9/16). The recovery of adenosine triphosphate in liver tissue was faster, and the release of liver-related enzymes during reperfusion was lower in groups GH5 and VH15 than in group C or VH5. Administration of GGA before heat shock preconditioning augmented the induction of HSP72 by decreasing the threshold for triggering the stress response.

The augmentative effect of repeated heat shock preconditioning on the production of heat shock protein 72 and on ischemic tolerance in rat liver tissue

OBJECTIVE

Heat shock pretreatment induces heat shock protein (HSP)72 strongly in rat livers and provides the tolerance against subsequent ischemia-reperfusion injury. In this study, the effects of repeated heat shock pretreatment on the production of HSP72 in rat livers and on subsequent ischemic tolerance were investigated.

METHODS

Rats pretreated with repeated heat shock were compared with those that received a single heat shock pretreatment. The production of HSP72 was analysed using Western-blotting and densitometer. At 48 h after heat shock pretreatment, all rats were subjected to warm liver ischemia for 30 or 45 min and then reperfused. Survival rate of the animals and liver functions during reperfusion were analysed.

RESULTS

The production of HSP72 increased in the repeated heat shock group more than in the single heat shock group. Although there were no significant differences in animal survival or in liver functions after a 30-min ischemia between the single heat shock group and the repeated heat shock group, animal survival and liver functions after a 45-min ischemia were significantly better in the repeated heat shock group.

CONCLUSION

In rats, repetition of heat shock pretreatment augmented the production of HSP72 in liver tissue and protected the liver from ischemia-reperfusion injury.

Doxorubicin preconditioning: a protection against rat hepatic ischemia-reperfusion injury

Doxorubicin produces clinically useful responses in a variety of human cancers. However, the toxicity of doxorubicin has limited its usefulness. This side effect is mainly due to the doxorubicin-mediated free radical formation. Administration of doxorubicin (10 mg/kg body weight) to rats intravenously induces heme oxygenase-1 (HO-1) in the liver. The levels of HO-1 protein were first detected at 6 hours and peaked at about 18 to 24 hours after the injection. It is known that HO-1 plays a protective role against the oxidative injury. Therefore, we have examined the protective effect of doxorubicin preconditioning against the hepatic ischemia-reperfusion injury. Partial hepatic ischemia was produced in the left and medium lobes for 45 minutes followed by 120 minutes reperfusion. When low doses of doxorubicin (1 mg/kg body weight) was intravenously administered to rats 2 days before the ischemia, the serum alanine transaminase (ALT) levels in the preconditioning rat were clearly improved compared with those in the rat without preconditioning. Under this situation, zinc-protoporphyrin IX, a specific inhibitor of HO-1, was injected subcutaneously to rats at 3 and 16 hours before the ischemia, the ALT levels were not improved by doxorubicin preconditioning. Histopathologic examination also supported these results. Although the HO-1 protein level was fairly low 2 days after the doxorubicin administration, significant amounts of HO-1 protein were detected. Our results indicated that the induction of HO-1 played a protective role against hepatic ischemia-reperfusion injury and that doxorubicin preconditioning is more clinically useful than other preconditioning methods.

Ischemic preconditioning reduces Na(+) accumulation and cell killing in isolated rat hepatocytes exposed to hypoxia

Short periods of ischemia followed up by reperfusion are known to protect the heart against injury caused by a subsequent sustained ischemia. This phenomenon, known as ischemic preconditioning, has also been recently shown to reduce ischemic liver damage, but the mechanisms involved are still unknown. By using isolated hepatocytes as an in vitro model of liver preconditioning, we have investigated the possible effect of preconditioning on intracellular pH and Na(+) homeostasis. Freshly isolated rat hepatocytes were preconditioned by 10 minutes of incubation under hypoxic conditions followed up by 10 minutes of reoxygenation and subsequently exposed to 90 minutes of hypoxia. Although preconditioning did not ameliorate adenosine triphosphate (ATP) depletion, preconditioned hepatocytes exhibited an increased resistance to cell killing during hypoxic incubation. Intracellular acidosis and Na(+) accumulation developing during hypoxia were appreciably reduced in preconditioned cells. The effects of preconditioning on intracellular pH, Na(+) homeostasis, and cytotoxicity were mimicked by stimulating protein kinase C (PKC) with 4beta-phorbol-12-myristate-13-acetate (PMA) or 1,2 dioctanoyl-glycerol (1,2 DOG). Conversely, inhibiting PKC with chelerythrine or blocking vacuolar proton ATPase (V-ATPase) with bafilomycin A(1) abolished the protection given by preconditioning or by PMA treatment on hypoxic acidosis, Na(+) overload, and hepatocyte killing. Similarly, the addition of Na(+) ionophore monensin also reverted the cytoprotection exerted by preconditioning. This indicated that ischemic preconditioning of isolated hepatocytes decreased cell killing during hypoxia by preventing intracellular Na(+) accumulation. We propose that, after preconditioning, the stimulation of PKC might activate proton extrusion through V-ATPase, thus, limiting intracellular acidosis and Na(+) overload promoted by Na(+)-dependent acid buffering systems.

Formation of 8-hydroxy-2'-deoxyguanosine and 4-hydroxy-2-nonenal-modified proteins in rat liver after ischemia-reperfusion: distinct localization of the two oxidatively modified products

Ischemia-reperfusion (IR) injury is an intractable process associated not only with therapeutic recanalization of vessels, but also with partial resection or transplantation of solid organs including liver. To develop methods for predicting the degree of hepatic IR injury and further to identify injured cells, we studied the formation of 8-hydroxy-2'-deoxy-guanosine (8-OHdG) and 4-hydroxy-2-nonenal (HNE)-modified proteins in the normothermic hepatic IR model of rats using immunohistochemistry, high-performance liquid chromatography (HPLC) determination and Western blot. The Pringle maneuver for either 15 or 30 min duration produced reversible or lethal damage, respectively. The levels of both products were significantly increased in proportion to ischemia duration 40 min after reperfusion, suggesting the involvement of hydroxyl radicals. Increased immunoreactivity of 8-OHdG was observed not only in the nuclei of hepatocytes but also in those of bile canalicular and endothelial cells. However, immunoreactivity of HNE-modified proteins was detected in the cytoplasm of hepatocytes, which was confirmed by Western blot, and in addition, in the nuclei of hepatocytes after severe injury. Thus, localization of the two oxidatively modified products was not identical. Our data suggest that these two products could be used for the assessment of hepatic IR injury in tissue, but that the biological significance of the two products might be different.

Heat shock preconditioning on mitochondria during warm ischemia in rat livers

BACKGROUND

The aim of this study was to investigate the effects of stress tolerance from heat shock preconditioning on changes in mitochondrial functions during ischemia-reperfusion injury of the liver.

MATERIALS AND METHODS

Rats were divided into a heat shock group (group HS) and a control group (group C). In group HS, rats received heat shock pretreatment 48 h prior to ischemia-reperfusion. Heat shock pretreatment was performed in a water bath at 42 degrees C for 15 min under general anesthesia. In group C, the same treatment was done with the water bath at 37 degrees C instead of at 42 degrees C. A 30-min warm ischemia by cramping the hepatoduodinal ligament (Pringle's maneuver) followed by a 60-min reperfusion was administered to all rats. Changes in membrane potential of hepatic mitochondria (MPM); mitochondrial respiratory function before ischemia (n = 5), after ischemia (n = 10), and after reperfusion (n = 10); and ATP recovery after reperfusion were compared between the groups.

RESULTS

After a 30-min ischemia, MPM in group C decreased significantly and did not recover even after reperfusion. On the other hand, MPM in group HS was maintained even after a 30-min ischemia and 60 min into reperfusion as well. The respiratory control ratio (RCR) of the mitochondria in group C decreased to as low as 5.06 +/- 0.72 after a 30-min ischemia, but in group HS, RCR was maintained near a normal level. The ATP level recovered significantly earlier in group HS than in group C after reperfusion.

CONCLUSIONS

Heat shock preconditioning of the liver protected mitochondria from loss of membrane integrity during ischemia and contributed to their ability to produce energy-rich phosphates during reperfusion.

Pharmacologic stimulation of adenosine A2 receptor supplants ischemic preconditioning in providing ischemic tolerance in rat livers

BACKGROUND

Ischemic preconditioning (IPC) is a promising strategy for conferring ischemic tolerance. We confirmed the acquisition of ischemic tolerance in the liver immediately after IPC and the role of adenosine kinetics in this process.

METHODS

Male Lewis rats were used. IPC was administered with a 10-minute ischemia followed by a 10-minute reperfusion. Ischemic tolerance was tested with a 45-minute ischemia. Changes in the adenosine concentrations in liver tissue were evaluated, and the effects of adenosine A1 or A2 receptor agonists or antagonists were examined either in place of or against IPC.

RESULTS

The 7-day animal survival was significantly better in the IPC group than in the control group (87% vs 53%; n = 15, P < .05). The release of liver-related enzymes during reperfusion was suppressed better in the IPC group (P < .01). Recovery of adenosine triphosphate levels was faster in the IPC group (P < .01). After IPC, adenosine concentrations in liver tissue immediately increased to 1555 +/- 299 pmol/g wet tissue and were maintained at that level during a subsequent 45-minute ischemia. The ischemic tolerance generated by IPC was mimicked by the administration of adenosine A2 receptor agonist and opposed by adenosine A2 receptor antagonist.

CONCLUSIONS

The ischemic tolerance of the liver immediately after IPC can be supplanted by selective pharmacologic stimulation of adenosine A2 receptors.