Pharmacologic preconditioning effects: prostaglandin E1 induces heat-shock proteins immediately after ischemia/reperfusion of the mouse liver

A Simple and Easily Reproducible Model of Reversible Obstructive Jaundice in Rats

BACKGROUND/AIM

Cholangiocarcinoma and pancreatic carcinoma are major malignancies that cause obstructive jaundice (OJ). This study aimed to develop a simple and easily reproducible rat model of reversible OJ (ROJ).

MATERIALS AND METHODS

OJ was induced by clamping the common bile duct (CBD) using a U-shaped titanium hemoclip and its base was attached by ligation using 2-cm long 4-0 polypropylene suture. An anti-adhesive sheet was placed around the CBD. OJ was mitigated by pulling the suture to remove the clip under laparotomy 3 days later. Serum chemistry and liver histopathology were compared between the ROJ group and sham surgery (SH) groups.

RESULTS

Three days after inducing OJ, serum total bilirubin, aspartate aminotransferase, and alanine aminotransferase were remarkably elevated in the ROJ group and thereafter reduced significantly after mitigating OJ. Similar findings were confirmed by histopathology.

CONCLUSION

Our rat model of reversible OJ was considered simple and easily reproducible.

Prostaglandin E1 protects hepatocytes against endoplasmic reticulum stress-induced apoptosis via protein kinase A-dependent induction of glucose-regulated protein 78 expression

AIM

To investigate the protective effect of prostaglandin E1 (PGE1) against endoplasmic reticulum (ER) stress-induced hepatocyte apoptosis, and to explore its underlying mechanisms.

METHODS

Thapsigargin (TG) was used to induce ER stress in the human hepatic cell line L02 and hepatocarcinoma-derived cell line HepG2. To evaluate the effects of PGE1 on TG-induced apoptosis, PGE1 was used an hour prior to TG treatment. Activation of unfolded protein response signaling pathways were detected by western blotting and quantitative real-time RT-PCR. Apoptotic index and cell viability of L02 cells and HepG2 cells were determined with flow cytometry and MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay.

RESULTS

Pretreatment with 1 μmol/L PGE1 protected against TG-induced apoptosis in both L02 cells and HepG2 cells. PGE1 enhanced the TG-induced expression of C/EBP homologous protein (CHOP), glucose-regulated protein (GRP) 78 and spliced X box-binding protein 1 at 6 h. However, it attenuated their expressions after 24 h. PGE1 alone induced protein and mRNA expressions of GRP78; PGE1 also induced protein expression of DNA damage-inducible gene 34 and inhibited the expressions of phospho-PKR-like ER kinase, phospho-eukaryotic initiation factor 2α and CHOP. Treatment with protein kinase A (PKA)-inhibitor H89 or KT5720 blocked PGE1-induced up-regulation of GRP78. Further, the cytoprotective effect of PGE1 on hepatocytes was not observed after blockade of GRP78 expression by H89 or small interfering RNA specifically targeted against human GRP78.

CONCLUSION

Our study demonstrates that PGE1 protects against ER stress-induced hepatocyte apoptosis via PKA pathway-dependent induction of GRP78 expression.

Hepatocellular protein profiles after hepatic ischemia/reperfusion injury with or without octreotide preconditioning in a rabbit model

Hepatic ischemic/reperfusion injury (HIRI) is a major complication of liver resection and transplantation. Octreotide, a somatostatin analogue, has been used to treat hepatic fibrosis and portal hypertension; however, its function against HIRI remains unclear. To elucidate the effect of octreotide in HIRI, we investigated the hepatocellular protein profiles in response to octreotide preconditioning in a rabbit model by using proteomic analysis. Twenty-four rabbits were divided into 3 groups: the sham operative group (control), the ischemia/reperfusion group (IR), and the ischemia/reperfusion + octreotide group (IR+Oct). They were subjected to 30 minutes of normothermic ischemia followed by 120 minutes of reperfusion by using Pringle's maneuver method. Proteomic studies were then performed to compare the protein profiles of their left liver lobe. A total of 16 differential proteins were successfully identified. These findings suggest that octreotide might exert an effect against HIRI through up-regulating the expression of the anti-injury substances, such as heat-shock proteins 70 and 27 (confirmed by using Western blot analysis); significantly raising the phosphatidylethanolamine-binding protein that alleviates IR-related apoptosis; and down-regulating mitochondrial metabolic enzymes such as NADH2 dehydrogenase and triosephosphate isomerase.

Co-administration of prostaglandin E1 with somatostatin attenuates acute liver damage after massive hepatectomy in rats via inhibition of inflammatory responses, apoptosis and endoplasmic reticulum stress

Acute liver damage is considered to be the major cause of mortality after massive hepatectomy. Prostaglandin E1 (PGE1) and somatostatin (SST) have been shown to protect against hepatic injury of rats after partial hepatectomy. However, the precise mechanisms remain largely unknown. In this study, we examined the effects of PGE1, SST and the combination of these two drugs on acute liver damage of rats after 90% hepatectomy. We found that animal survival was improved when pretreated with PGE1 and SST. Portal venous pressure (PVP), serum alanine aminotransferase (ALT) and aspartate aminotransaminase (AST), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were all reduced after administration of PGE1 and SST. In addition, apoptosis was inhibited via upregulation of Bcl-2 and downregulation of Bax and caspase-3 in drug treatment groups. Furthermore, pretreatment with PGE1 and SST alleviated endoplasmic reticulum (ER) stress by induction of heat shock protein 70 (HSP70) and glucose-regulated protein 78 (GRP78), but suppression of transcription factor C/EBP homologous protein (CHOP). Our data suggest that administration of PGE1 and SST, particularly in combination, may prevent acute liver damage of rats after massive hepatectomy by inhibiting inflammatory responses, apoptosis and ER stress.

Ischemic preconditioning-like effect of polyunsaturated fatty acid-rich diet on hepatic ischemia/reperfusion injury

AIM

The aim of this study was to investigate a possible preconditioning effect of oral diet enriched with polyunsaturated fatty acids (PUFAs) on liver ischemia/reperfusion (I/R) injuries.

METHODS

Wistar male rats were fed a standard diet or polyunsaturated fatty acid-rich diet (PRD) enriched with (GII) or without (GIII) ω-3 PUFA. Rats were submitted to partial liver ischemia during 1 h and evaluated in pre- and post-I/R conditions. In pre-I/R condition, livers were collected for determination of fatty acid composition, liver mitochondrial function, malondialdehyde (MDA) content, and histological analysis. Four hours after liver reperfusion serum activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), serum levels of tumor necrosis factor-alpha, interleukin-6, interleukin-10, and prostaglandin-E2, liver mitochondrial function, MDA content, and histology were evaluated.

RESULTS

In the pre-I/R condition, GII and GIII groups had an increase on PUFA content and exhibited slight increased macrosteatosis and microsteatosis in the liver. After 4 h of reperfusion, PRD-fed rats showed a marked decrease on steatosis, diminished necrosis, an increase in MDA formation, and mitochondrial uncoupling. We also observed a marked decrease in plasma levels of cytokines and ALT and AST activities in post-I/R condition in PRD groups.

CONCLUSION

In this experimental model in the rat, PRD has a preconditioning effect protecting the liver from I/R injury and should be object of future clinical studies.

Ischemia/reperfusion injury in liver resection: a review of preconditioning methods

Ischemic preconditioning is one of the therapeutic interventions aiming at preventing ischemia/reperfusion-related injury. Numerous experimental studies and a few clinical series have shown that during liver resections, ischemic preconditioning is a promising strategy for optimizing the postoperative outcome. Moreover, various types of pharmacological intervention as well as different types of preconditioning, such as remote preconditioning, the use of heat shock, and hyperbaric oxygen, have been developed to attenuate the functional impairment accompanying ischemia/reperfusion injury. This review summarizes the various forms of preconditioning, thus suggesting that close cooperation between surgeons and anesthesiologists paves the way to apply novel strategies to improve the outcome of liver resection.

Combined prostaglandin E1 and lithium exert potent neuroprotection in a rat model of cerebral ischemia

AIM

To examine the effects of a mixed formulation composed of prostaglandin E1 and lithium (PGE1+Li mixture) on brain damage after cerebral ischemia. The effects of the mixture on protein expression of heat shock proteins (HSPs), p53, and Bcl-2 were also determined.

METHODS

Brain ischemia was induced with a permanent middle cerebral artery occlusion (pMCAO) in rats. Rats were treated with a single intravenous administration of PGE1, lithium or a PGE1+Li mixture immediately after the ischemic insult. The infarct volume and motor behavior deficits were analyzed 24 h after the ischemic insult. The protein levels of HSP70, glucose-regulated protein 78 (GRP78), HSP60, Bcl-2, and p53 in the striatum of the ipsilateral hemisphere were examined using immunoblotting.

RESULTS

The mixture (PGE1 22.6 nmol/kg+Li 0.5 mmol/kg) reduced infarct volume and neurological deficits induced by focal cerebral ischemia. Moreover, the mixture had a greater neuroprotective effect against cerebral ischemia compared with PGE1 or lithium alone. The mixture was effective even if it was administered 3 h after ischemia. PGE1+Li also significantly upregulated cytoprotective HSP70, GRP78, HSP60, and Bcl-2 protein levels, while decreasing p53 expression.

CONCLUSION

These results demonstrated a PGE1+Li mixture with a therapeutic window of up to 3 h for clinical treatment of cerebral ischemia. The PGE1+Li mixture potentially exerts a protective effect after stroke through the induction of HSPs and Bcl-2 proteins.

Hepatic ischemia-reperfusion injury and therapeutic strategies to alleviate cellular damage

Warm hepatic ischemia-reperfusion injury is a significant medical problem in many clinical conditions such as liver transplantation, hepatic surgery for tumor excision, trauma and hepatic failure after hemorrhagic shock. Partial or, mostly, total interruption of hepatic blood flow is often necessary when liver surgery is performed. This interruption of blood flow is termed "warm ischemia" and upon revascularization, when molecular oxygen is reintroduced, the organ undergoes a process called "reperfusion injury" that causes deterioration of organ function. Ischemia reperfusion results in cellular damage and tissue injury associated with a complex series of events. Pathophysiological mechanisms leading to tissue injury following ischemia-reperfusion will be discussed and therapies targeted to reduce liver damage will be summarized within this review.

Prostaglandin E2 potentiates heat shock-induced heat shock protein 72 expression in A549 cells

The heat shock (HS) response is an important cytoprotective response comprising the expression of heat shock proteins (HSPs) and orchestrated by the heat/stress-induced transcription factor, heat shock factor-1 (HSF-1). Previous studies suggest that the activation threshold and magnitude of the HS response may be modified by treatment with arachidonic acid (AA). We analyzed the effect of exogenous AA and its metabolites, PGE(2), LTD(4), and 15-HETE on HSF-1-dependent gene expression in A549 human respiratory epithelial-like cells. When added at 1microM, PGE(2) much more than LTD(4), but not 15-HETE increased activity of a synthetic HSF-1-dependent reporter after HS exposure (42 degrees C for 2h), but had no effect in the absence of HS. Exposing A549 cells to HS stimulated the release of PGE(2) and treatment with the cyclooxygenase inhibitor, ibuprofen, reduced HS-induced HSF-1-dependent transcription. PGE(2) increased HS-induced HSP72 mRNA and protein expression but EMSA and Western blot analysis failed to show an effect on HSF-1 DNA binding activity or post-translational modification. In summary, we showed that HS stimulates the generation of PGE(2), which augments the generation of HSPs. The clinical consequences of this pathway have yet to be determined.

Synergistic effects of prostaglandin E1 and lithium in a rat model of cerebral ischemia

AIM

Heat shock proteins (HSPs) are important regulators of cellular survival and exert neuroprotective effects against cerebral ischemia. Both prostaglandin E1 (PGE1) and lithium have been reported to protect neurons against ischemic injury. The present study was undertaken to examine if lithium could potentiate the neuroprotection of PGE1 against cerebral ischemia, and if the synergetic effects take place at the level of HSPs.

METHODS

Brain ischemia was induced by a permanent middle cerebral artery occlusion (pMCAO) in rats. Rats were pretreated with subcutaneous injection of lithium for 2 d and a single intravenous administration of PGE1 immediately after ischemic insult. Cerebrocortical blood flow of each group was closely monitored prior to onset of ischemia, 5 min, 15 min, 30 min and 60 min after surgical operation. Body temperature was measured before, 5 min, 2 h and 24 h after the onset of pMCAO. The infarct volume, brain edema and motor behavior deficits were analyzed 24 h after ischemic insult. Cytoprotective HSP70 and heme oxygenase-1 (HO-1) in the striatum of the ipsilateral hemisphere were detected by immunoblotting. Brain sections from the striatum of the ipsilateral hemisphere were double-labeled with the anti-HSP70 antibody and 4,6-diamidino-2-phenylindole (DAPI).

RESULTS

Treatment with PGE1 (8 and 16 microg/kg, iv) or lithium (0.5 mEq/kg, sc) alone reduced infarct volume, neurological deficits and brain edema induced by focal cerebral ischemia in rats. Moreover, a greater neuroprotection was observed when PGE1 and lithium were given together. Co-administration of PGE1 and lithium significantly upregulated cytoprotective HSP70 and HO-1 protein levels.

CONCLUSION

Lithium and PGE1 may exert synergistic effects in treatment of cerebral ischemia and thus may have potential clinical value for the treatment of stroke.

Bicyclol: a novel antihepatitis drug with hepatic heat shock protein 27/70-inducing activity and cytoprotective effects in mice

Heat shock proteins (HSPs) are the best-known endogenous factors that protect against cell injury under various pathological conditions and that can be induced by various physical, chemical, and biological stressors. New research seeks to discover a compound that is clinically safe and can induce the accumulation of HSPs in patients. This paper reports that the oral administration of three doses of bicyclol, a novel antihepatitis drug, induced hepatic HSP27 and HSP70 expression in a time- and dose-dependent manner, and that bicyclol treatment stimulated heat shock factor 1 (HSF1) activation in mice. The inducing effects of bicyclol on HSP27, HSP70 and HSF1 were all blocked by quercetin, an inhibitor of HSP biosynthesis. The cytoprotective effect of HSP27/70 induced by bicyclol against hepatotoxicity of acetaminophen (AP) was assessed in mice. The prior administration of bicyclol markedly suppressed AP-induced liver injury as indicated by the reduction in the elevation of serum alanine aminotransferase and aspartate aminotransferase, in liver necrosis, in the release of cytochrome c and apoptosis-inducing factor from mitochondria, as well as in hepatic deoxyribonucleic acid fragmentation in mice. However, all the above actions of bicyclol against AP-induced mouse liver injuries were significantly attenuated by quercetin. This is the first report to show that bicyclol induces hepatic HSP27/70 expression via activation of HSF1 and that the cytoprotective action of bicyclol against liver injury is mediated by its induction of HSP27/70. These results provide new evidence for elucidating the mechanism of the hepatoprotective action of bicyclol in animals and patients.

Beneficial effects of hyperbaric oxygen pretreatment on massive hepatectomy model in rats

BACKGROUND

The purpose of this study was to investigate the impact of hyperbaric oxygen (HBO) pretreatment in massive hepatectomy model, a surrogate model of small-for-size graft, using rats.

METHODS

(Experiment I) Rats were divided into the following four groups: HBO (-), HBO-1D (day), HBO-3D, and HBO-5D. Samples were taken after the completion of HBO pretreatment, and the following parameters were evaluated: reverse transcription polymerase chain reaction and immunohistochemical staining for HSP 70 and HO-1; biochemical parameters; and liver weight to body weight ratio (Lw/Bw ratio). (Experiment II) Rats were divided into four groups as follows; 70% hepatectomy (Hx), 70% Hx-HBO, 90% Hx, and 90% Hx-HBO group. Samples were taken 12, 24, 48, and 72 hr after hepatectomy and the following parameters were investigated: biochemical analysis; Lw/Bw ratio; PCNA labeling index; and survival.

RESULTS

(Experiment I) The expression of HSP70 mRNA was significantly increased in the HBO-3D group compared with the HBO (-) group (P<0.05). HSP70- and HO-1-positive hepatocytes were significantly increased in the HBO-3D group compared with the HBO (-) group (P<0.05). (Experiment II) Transaminases were significantly decreased in both 70% and 90% Hx-HBO groups compared with Hx alone group (P<0.05). The Lw/Bw ratio and PCNA labeling index of the 90% Hx-HBO group were significantly increased compared with the 90% Hx group, 24, 48 and 72 hr after hepatectomy (P<0.05). The survival rate in the 90% Hx-HBO group was significantly higher than that in the 90% Hx group (P=0.01).

CONCLUSIONS

HBO pretreatment had beneficial effects in a massive hepatectomy model in rats via the induction of HSP70 and HO-1.

Improving outcome in patients undergoing liver surgery

Liver surgery is associated with many factors, which may affect outcome. Preoperative assessment of patient's general condition, resectability, and liver reserve are paramount for success. The Child-Pugh score and other scoring systems only partially enables to assess the risk associated with liver surgery. The presence of portal hypertension per se is a major risk factor for hepatectomy. Intraoperatively, any attempts should be made to minimize blood loss. Low central venous pressure and inflow occlusion best prevent bleeding. Ischemic preconditioning and intermittent clamping are routinely applied in many centers to protect against long periods of ischemia, although the mechanisms of protection remain unclear. In this review we describe recent advances in activated pathways associated with protection against ischemia. Postoperatively, the best factor impacting on outcome probably resides in experienced medical care particularly in the intensive care setting. Currently, no drug or gene therapy approaches has reached the clinic. The future relies on new insight into mechanisms of ischemia-reperfusion injury.

Mechanism of lung injury and protective effect of prostaglandin E1 in experimental acute pancreatitis

AIM: To explore the mechanism of lung injury in experimental acute pancreatitis (AP) and the protective effect of prostaglandin E₁ (PGE₁).

METHODS: Seventy-eight rats were averagely and randomly divided into sham operation, AP, and PGE₁ group. AP model was induced by creating a closed duod enal loop in rats. The rats in PGE₁ group were intravenously injected with PGE₁ (60 ng/kg). The histopathological changes of pancreatic and pulmonary tissues were examined by microscopy. The serum level of amylase, the activity of myeloperoxidase (MPO), the pulmonary level of lipid peroxidation (LPO), and lung capillary permeability (LCP) were measured. The expression of pulmonary intercellular adhesion molecule-1 (ICAM-1) was determined by immunohistochemical technique (ABC).

RESULTS: In AP group, the progressive pathological damages in the pancreas and lung tissues were clearly observed. The activity of pulmonary MPO (12 h: 5.65 ± 0.80 vs 1.22 ± 0.71 kat/g, P < 0.01; 24 h: 7.22 ± 1.05 vs 1.48 ± 0.57 kat/g, P < 0.01), the level of LPO (12 h: 1.44 ± 0.63 vs 0.38 ± 0.07 μmol/g, P < 0.01; 24 h: 3.64 ± 0.83 vs 0.44 ± 0.15 μmol/g, P < 0.01) and LCP (12 h: 145.4 ± 23.0 vs 47.3 ± 5.5 μg/g wet weight, P < 0.01), as well as pulmonary ICAM-1 expression were markedly increased as compared with those in sham operation group. In comparison with those in AP group, the activity of MPO (12 h: 2.96 ± 1.04 vs 5.65 ± 0.80 kat/g, P < 0.05; 24 h: 3.68 ± 1.15 vs 7.22 ± 1.05 kat/g, P < 0.05) and the level of LPO (12 h: 0.86 ± 0.34 vs 1.44 ± 0.63 μmol/g, P < 0.05; 24 h: 1.69 ± 0.45 vs 3.64 ± 0.83 μmol/g, P < 0.05) in the lung tissues were significantly decreased, and the level of LCP (12 h: 105.9 ± 23.9 vs 145.4 ± 23.0 μg/g wet weight, P < 0.05), as well as pulmonary ICAM-1 expression was down-regulated (12 h: P < 0.05; 24 h: P < 0.01) in PGE1 group. Pathological examination revealed that intra-alveolar hemorrhage, edema and polymorphonuclear leukocytes (PMN) infiltration in the lung tissues were attenuated after PGE₁ treatment, although pancreatic damages were not alleviated.

CONCLUSION: The over-expression of ICAM-1, PMN infiltration and the release of free oxygen radicals in lung tissues may be closely related to pancreatitis-associated lung injury. PGE₁ can ameliorate lung injury by reducing ICAM-1 expression and inhibiting PMN activation and the release of free oxygen radicals.

Proteomic analysis of liver tissues subjected to early ischemia/reperfusion injury during human orthotopic liver transplantation

Knowledge of early molecular events occurring upon ischemia/reperfusion (I/R) during liver transplantation (LT) is of great importance to improve the therapeutic intervention of surgical treatment. However, nowadays, few data are available on early protein targets of I/R injury. To identify these proteins, we used a differential proteomics approach in the characterization human liver biopsies during I/R upon LT. Analyses were performed on nine donor livers during LT. By using 2-DE and MALDI-TOF MS, we identified 36 proteins which resulted significantly altered upon I/R injury. The majority of these proteins are functionally involved in lipid and energy metabolism, in different metabolic pathways, in redox signalling and in oxidative-stress response. Our data represent the first global approach in the study of I/R injury in liver.