Ischemic preconditioning impairs liver regeneration in extended reduced-size livers

Inhaled Argon Impedes Hepatic Regeneration after Ischemia/Reperfusion Injury in Rats

Organoprotective effects of noble gases are subject of current research. One important field of interest is the effect of noble gases on hepatic regenerative capacity. For the noble gas argon, promising studies demonstrated remarkable experimental effects in neuronal and renal cells. The aim of this study was to investigate the effects of argon on the regenerative capacity of the liver after ischemia/reperfusion injury (IRI). Male, Sprague-Dawley rats underwent hepatic IRI by clamping of the hepatic artery. Expression of hepatoproliferative genes (HGF, IL-1β, IL-6, TNF), cell cycle markers (BrdU, TUNEL, Ki-67), and liver enzymes (ALT, AST, Bilirubin, LDH) were assessed 3, 36, and 96 h after IRI. Expression of IL-1β and IL-6 was significantly higher after argon inhalation after 36 h (IL-1β 5.0 vs. 8.7 fold, p = 0.001; IL-6 9.6 vs. 19.1 fold, p = 0.05). Ki-67 was higher in the control group compared to the argon group after 36 h (214.0 vs. 38.7 positive cells/1000 hepatocytes, p = 0.045). Serum levels of AST and ALT did not differ significantly between groups. Our data indicate that argon inhalation has detrimental effects on liver regeneration after IRI as measured by elevated levels of the proinflammatory cytokines IL-1β and IL-6 after 36 h. In line with these results, Ki-67 is decreased in the argon group, indicating a negative effect on liver regeneration in argon inhalation.

Remote Ischemic Preconditioning in a Cirrhotic Patient Undergoing Major Hepatectomy

Remote ischemic preconditioning (RIPC) has been shown to reduce ischemic reperfusion injury for patients undergoing hepatectomy for colorectal liver metastasis. We present a case of a 69-year-old male who underwent right hepatectomy for a multifocal hepatocellular carcinoma of the right liver and concomitant liver cirrhosis (Child-Pugh stage A). We performed portal vein embolization prior to surgery and intraoperative RIPC of the iliac vessels. The postoperative course after major hepatectomy went uneventful.

Effect of Remote Ischemic Preconditioning in Patients Undergoing Hepatectomy With Portal Triad Clamping: A Randomized Controlled Trial

BACKGROUND

Remote ischemic preconditioning (RIPC) is reported to reduce liver injury in patients undergoing hepatectomy for colorectal liver metastasis, but its role is unclear in hepatocellular carcinoma patients with portal triad clamping during hepatectomy.

METHODS

In this prospective, randomized trial, 140 patients with hepatocellular carcinoma undergoing liver resection requiring portal triad clamping were randomized to a RIPC group or a control group. Patients in the RIPC group received RIPC (3 cycles of 5-minute ischemia and 5-minute reperfusion in right upper limb with cuff pressure at 30 kPa [225 mm Hg]) approximately 10 minutes after induction of anesthesia. In the control group, patients received sham RIPC (the cuff was not inflated). The primary outcome was the postoperative peak level of total bilirubin (TBIL) and was analyzed with the independent t test. Secondary outcomes were liver function test at postoperative days 1, 3, and 5; postoperative morbidity and mortality during the first month; and the length of postoperative hospital stay.

RESULTS

Data from 136 patients (69 in the RIPC group and 67 in the control group) were analyzed. The RIPC group had on average a 5.9 μmol lower peak level of TBIL than the control group; the mean difference is -5.9, and the 95% confidence interval (CI) reverses to -17.9 to 6.1. There were no significant differences between the 2 groups in liver function test at postoperative days 1, 3, and 5; postoperative morbidity and mortality during the first month; and the length of postoperative hospital stay.

CONCLUSIONS

We found no evidence that RIPC can reduce postoperative liver injury after hepatectomy.

The Impact of a Nitric Oxide Synthase Inhibitor (L-NAME) on Ischemia⁻Reperfusion Injury of Cholestatic Livers by Pringle Maneuver and Liver Resection after Bile Duct Ligation in Rats

The Pringle maneuver (PM) has been widely used to control blood loss during liver resection. However, hepatic inflow occlusion can also result in hepatic ischemia–reperfusion injury (IRI), especially in patients with a cholestatic, fibrotic, or cirrhotic liver. Here we investigate a nitric oxide synthase (NOS) inhibitor N-Nitroarginine methyl ester (L-NAME) on IRI after the PM and partial hepatectomy of cholestatic livers induced by bile duct ligation (BDL) in rats. Control group (non-BDL/no treatment), BDL + T group (BDL/L-NAME treatment) and BDL group (BDL/no treatment) were analyzed. Cholestasis was induced by BDL in the L-NAME and BDL group and a 50% partial hepatectomy with PM was performed. L-NAME was injected before PM in the BDL + T group. Hepatocellular damage, portal venous flow, microcirculation, endothelial lining, and eNOS, iNOS, interleukin (IL)-6, and transforming growth factor-β (TGF-β) were evaluated. Microcirculation of the liver in the BDL + T group tended to be higher. Liver damage and apoptotic index were significantly lower and Ki-67 labeling index was higher in the BDL + T group while iNOS and TGF-β expression was decreased. This was corroborated by a better preserved endothelial lining. L-NAME attenuated IRI following PM and improved proliferation/regeneration of cholestatic livers. These positive effects were considered as the result of improved hepatic microcirculation, prevention of iNOS formation, and TGF-β mRNA upregulation.

Remote ischaemic preconditioning in orthotopic liver transplantation (RIPCOLT trial): a pilot randomized controlled feasibility study

BACKGROUND

Ischaemia Reperfusion (IR) injury is a major cause of morbidity, mortality and graft loss following Orthotopic Liver Transplantation (OLT). Utilising marginal grafts, which are more susceptible to IR injury, makes this a key research goal. Remote Ischaemic Preconditioning (RIPC) has been shown to ameliorate hepatic IR injury in experimental models. Whether RIPC can reduce IR injury in human liver transplant recipients is unknown.

METHODS

Forty patients undergoing liver transplantation were randomized to RIPC or a sham. RIPC was induced through three 5 min cycles of alternate ischaemia and reperfusion of the left leg prior to surgery. Data on clinical outcomes was collected prospectively. Per-operative cytokine levels were measured.

RESULTS

Fourty five of 51 patients approached (88%) were willing to enroll in the study. Five patients were excluded and 40 randomized, of which 20 underwent RIPC which was successfully completed in all patients. There were no complications following RIPC. Median day 3 AST levels were slightly higher in the RIPC group (221 IU vs 149 IU, p = 1.00).

CONCLUSIONS

RIPC is acceptable and safe in liver transplant recipients. This study has not demonstrated evidence of a reduction in short-term measures of IR injury. Longer follow up will be required and consideration of an altered protocol.

Effect of Remote Ischaemic Preconditioning on Liver Injury in Patients Undergoing Major Hepatectomy for Colorectal Liver Metastasis: A Pilot Randomised Controlled Feasibility Trial

Background

Liver resection produces excellent long-term survival for patients with colorectal liver metastases but is associated with significant morbidity and mortality from ischaemia reperfusion injury (IRI). Remote ischaemic preconditioning (RIPC) can reduce the effect of IRI. This pilot randomised controlled trial evaluated RIPC in patients undergoing major hepatectomy at the Royal Free Hospital, London.

Methods

Sixteen patients were randomised to RIPC or sham control. RIPC was induced through three 10-min cycles of alternate ischaemia and reperfusion to the leg. At baseline and immediately post-resection, transaminases and indocyanine green (ICG) clearance were measured.

Findings

The RIPC group had lower ALT and AST levels immediately post-resection (ALT: 43% lower 497 ± 165 vs 889 ± 170 IU/L; p = 0.019 AST: 54% lower 408 ± 166 vs 836 ± 167 IU/L; p = 0.001) and at 24 h (ALT: 41% lower 412 ± 144 vs 698 ± 137 IU/L; p = 0.026 AST: 50% lower 316 ± 116 vs 668 ± 115 IU/L; p = 0.02). ICG clearance was reduced in controls versus RIPC immediately after resection (ICG-PDR: 11.1 ± 1.1 vs 16.5 ± 1.4%/min; p = 0.035).

Conclusions

This pilot study shows that RIPC has potential to reduce liver injury following hepatectomy justifying a prospective RCT powered to demonstrate clinical benefits.

Pre-conditions for eliminating mitochondrial dysfunction and maintaining liver function after hepatic ischaemia reperfusion

The liver, the largest organ with multiple synthesis and secretion functions in mammals, consists of hepatocytes and Kupffer, stem, endothelial, stellate and other parenchymal cells. Because of early and extensive contact with the external environment, hepatic ischaemia reperfusion (IR) may result in mitochondrial dysfunction, autophagy and apoptosis of cells and tissues under various pathological conditions. Because the liver requires a high oxygen supply to maintain normal detoxification and synthesis functions, it is extremely susceptible to ischaemia and subsequent reperfusion with blood. Consequently, hepatic IR leads to acute or chronic liver failure and significantly increases the total rate of morbidity and mortality through multiple regulatory mechanisms. An increasing number of studies indicate that mitochondrial structure and function are impaired after hepatic IR, but that the health of liver tissues or liver grafts can be effectively rescued by attenuation of mitochondrial dysfunction. In this review, we mainly focus on the subsequent therapeutic interventions related to the conservation of mitochondrial function involved in mitigating hepatic IR injury and the potential mechanisms of protection. Because mitochondria are abundant in liver tissue, clarification of the regulatory mechanisms between mitochondrial dysfunction and hepatic IR should shed light on clinical therapies for alleviating hepatic IR‐induced injury.

Preconditioning methods in the management of hepatic ischemia reperfusion- induced injury: Update on molecular and future perspectives

Hepatic IR (ischemia reperfusion) injury is a commonly encountered obstacle in the post-operative management of hepatic surgery. Hepatic IR occurs during 'Pringle maneuver' for reduction of blood loss or during a brief period of cold storage followed by reperfusion of liver grafts. The stress induced during hepatic IR, triggers a spectrum of cellular responses leading to the varying degrees of hepatic complications which in turn affect the post operative care. Different preconditioning methods either activate or subdue different sets of molecular signals, resulting in varied levels of protection against hepatic IR injury. Yet, there is a serious lacuna in the knowledge regarding the choice of preconditioning methods and the resulting molecular changes in order to assess the efficiency and choice of these methods correctly. This review provides an update on the various preconditioning approaches such as surgical/ischemic, antioxidant, pharmaceutical and genetic preconditioning strategies published during last six years (2009-2015). Further, we discuss the attenuation or inhibition of specific inflammatory, apoptotic and necrotic markers in the various experimental models of liver IR subjected to different preconditioning strategies. While enlisting the controversies in the ischemic preconditioning strategy, we bring out the uncertainties in the existing molecular targets and their reliability in the attenuation of hepatic IR injury. Future research studies would include the novel preconditioning strategies employ i) the targeted gene silencing of key molecular targets inducing IR, ii) hyper expression of beneficial molecular signals against IR via gene transfer techniques. The above studies would see the combination of these latest techniques with the established preconditioning strategies for better post-operative hepatic management.

Hypothermia is better than ischemic preconditioning for preventing early hepatic ischemia/reperfusion in rats

BACKGROUND

Topical hypothermia (TH) and ischemic preconditioning (IPC) are used to decrease I/R injury. The efficacy of isolated or combined use of TH and IPC in the liver regarding inflammation and cytoprotection in early ischemia/reperfusion (I/R) injury needs to be evaluated.

MATERIAL AND METHODS

Wistar rats underwent 70% liver ischemia for 90 min followed by 120 min of reperfusion. Livers of animals allocated in the sham, normothermic ischemia (NI), IPC, TH, and TH+IPC groups were collected for molecular analyses by ELISA and Western blot, aiming to compare proinflammatory, anti-inflammatory, and antioxidant profiles.

RESULTS

Compared with NI, TH presented decreased tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-12 concentrations and increased IL-10 levels. TH animals displayed lower inducible nitric oxide synthase (iNOS) and higher endothelial nitric oxide synthase (eNOS) expressions. NAD(P)H-quinone oxidoreductase-1(NQO1) expression was also lower with TH. Isolated IPC and NI were similar regarding all these markers. TH+IPC was associated with decreased IL-12 concentration and reduced iNOS and NQO1 expressions, similarly to isolated TH. Expression of Kelch-like ECH-associated protein (Keap)-1 was increased and expression of nuclear and cytosolic nuclear erythroid 2-related factor 2 (Nrf2) was decreased with TH+IPC vs. NI.

CONCLUSION

TH was the most effective method of protection against early I/R injury. Isolated IPC entailed triggering of second-line antioxidant defense enzymes. Combined TH+IPC seemed to confer no additional advantage over isolated TH in relation to the inflammatory process, but had the advantage of completely avoid second-line antioxidant defense enzymes.

Serum levels of endothelin-1 after liver resection as an early predictor of postoperative liver failure. A prospective study

AIM

Besides the residual liver volume, damage of the microcirculation secondary to increased portal blood flow is a main determinant of postoperative liver failure (PLF). Endothelin-1 (ET-1), produced by sinusoidal endothelial cells, plays a key role in the regulation of hepatic microcirculation. The aim of this study was to determine whether ET-1 levels has any prognostic utility in predicting PLF.

METHODS

Patients undergoing liver resection for primary or secondary liver tumors at San Raffaele Hospital, Milan, were prospectively enrolled in the study. Serial postoperative serum ET-1 levels in patients undergoing liver resections were correlated with indices of inflammatory response, liver failure and death.

RESULTS

A total of 144 patients were included. ET-1 levels in patients who underwent major or extended liver resection were significantly higher than in patients who had a minor resection on postoperative day (POD) 1 (P = 0.003), POD 2 (P = 0.0001) and POD 5 (P = 0.0001). Eight patients developed PLF and ET-1 was significantly higher compared with patients without PLF on POD 2 (P = 0.002) and POD5 (P = 0.006). Serum ET-1 concentration on POD 2 was an independent predictor of PLF in multivariate analysis.

CONCLUSION

ET-1 is as an early index of PLF and provides a rationale for therapeutic manipulation, with many potential clinical implications to prevent PLF onset and reduce its severity.

Protocol for a prospective randomized controlled trial of recipient remote ischaemic preconditioning in orthotopic liver transplantation (RIPCOLT trial)

Abstract

Ischaemic reperfusion (IR) injury is a major cause of graft loss, morbidity and mortality following orthotopic liver transplantation (OLT). Demand for liver transplantation has resulted in increasing use of marginal grafts that are more prone to IR injury. Remote ischaemic preconditioning (RIPC) reduces IR injury in experimental models, but recipient RIPC has not been evaluated clinically.

Methods

A single-centre double-blind randomized controlled trial (RCT) is planned to test the hypothesis that recipient RIPC will reduce IR injury. RIPC will be performed following recipient anaesthetic induction but prior to skin incision. The protocol involves 3 cycles of 5 min of lower limb occlusion with a pneumatic tourniquet inflated to 200 mmHg alternating with 5 min of reperfusion. In the control group, the sham will involve the cuff being placed on the thigh but without being inflated.

The primary endpoint is ability to recruit patients to the trial and safety of RIPC. The key secondary endpoint is a reduction in serum aspartate transferase levels on the third post-operative day.

Discussion

RIPC is a promising strategy to reduce IR injury in liver transplant recipients as there is a clear experimental basis, and the intervention is both inexpensive and easy to perform. This is the first trial to investigate RIPC in liver transplant recipients.

Trial registration

Clinicaltrials.gov NCT00796588

Electronic supplementary material

The online version of this article (doi:10.1186/s13737-016-0033-4) contains supplementary material, which is available to authorized users.

Portal Hyperperfusion after Extended Hepatectomy Does Not Induce a Hepatic Arterial Buffer Response (HABR) but Impairs Mitochondrial Redox State and Hepatocellular Oxygenation

Background & Aims

Portal hyperperfusion after extended hepatectomy or small-for-size liver transplantation may induce organ dysfunction and failure. The underlying mechanisms, however, are still not completely understood. Herein, we analysed whether hepatectomy-associated portal hyperperfusion induces a hepatic arterial buffer response, i.e., an adaptive hepatic arterial constriction, which may cause hepatocellular hypoxia and organ dysfunction.

Methods

Sprague-Dawley rats underwent 30%, 70% and 90% hepatectomy. Baseline measurements before hepatectomy served as controls. Hepatic arterial and portal venous flows were analysed by ultrasonic flow measurement. Microvascular blood flow and mitochondrial redox state were determined by intravital fluorescence microscopy. Hepatic tissue pO2 was analysed by polarographic techniques. Hepatic function and integrity were studied by bromosulfophthalein bile excretion and liver histology.

Results

Portal blood flow was 2- to 4-fold increased after 70% and 90% hepatectomy. This, however, did not provoke a hepatic arterial buffer response. Nonetheless, portal hyperperfusion and constant hepatic arterial blood flow were associated with a reduced mitochondrial redox state and a decreased hepatic tissue pO2 after 70% and 90% hepatectomy. Microvascular blood flow increased significantly after hepatectomy and functional sinusoidal density was found only slightly reduced. Major hepatectomy further induced a 2- to 3-fold increase of bile flow. This was associated with a 2-fold increase of bromosulfophthalein excretion.

Conclusions

Portal hyperperfusion after extended hepatectomy does not induce a hepatic arterial buffer response but reduces mitochondrial redox state and hepatocellular oxygenation. This is not due to a deterioration of microvascular perfusion, but rather due to a relative hypermetabolism of the remnant liver after major resection.

Gut-liver axis improves with meloxicam treatment after cirrhotic liver resection

AIM: To investigate the effect of meloxicam on the gut-liver axis after cirrhotic liver resection.

METHODS: Forty-four male Wistar rats were assigned to three groups: (1) control group (CG); (2) bile duct ligation with meloxicam treatment (BDL + M); and (3) bile duct ligation without meloxicam treatment (BDL). Secondary biliary liver cirrhosis was induced via ligature of the bile duct in the BDL + M and BDL groups. After 2 wk, the animals underwent a 50% hepatectomy. In the BDL + M group 15 min prior to the hepatectomy, one single dose of meloxicam was administered. Parameters measured included: microcirculation of the liver and small bowel; portal venous flow (PVF); gastrointestinal (GI) transit; alanine aminotransferase (ALT); malondialdehyde; interleukin 6 (IL-6), transforming growth factor beta 1 (TGF-β1) and hypoxia-inducible factor 1 alpha (HIF-1α) levels; mRNA expression of cyclooxigenase-2 (COX-2), IL-6 and TGF-β1; liver and small bowel histology; immunohistochemical evaluation of hepatocyte and enterocyte proliferation with Ki-67 and COX-2 liver expression.

RESULTS: Proliferative activity of hepatocytes after liver resection, liver flow and PVF were significantly higher in CG vs BDL + M and CG vs BDL group (P < 0.05), whereas one single dose of meloxicam ameliorated liver flow and proliferative activity of hepatocytes in BDL + M vs BDL group. COX-2 liver expression at 24 h observation time (OT), IL-6 concentration and mRNA IL-6 expression in the liver especially at 3 h OT, were significantly higher in BDL group when compared with the BDL + M and CG groups (P < 0.01, P < 0.001, P < 0.01, respectively). Liver and small bowel histology, according to a semi quantitative scoring system, showed better integrity in BDL + M and CG as compared to BDL group. ALT release and HIF-1α levels at 1 h OT were significantly higher in BDL + M compared to CG and BDL group (P < 0.001 and P < 0.01, respectively). Moreover, ALT release levels at 3 and 24 h OT were significantly higher in BDL group compared to CG, P < 0.01. GI transit, enterocyte proliferative activity and number of goblet cells were in favor of meloxicam treatment vs BDL group (P < 0.05, P < 0.001, P < 0.01, respectively). Additionally, villus length were higher in BDL + M as compared to BDL group.

CONCLUSION: One single dose of meloxicam administered after cirrhotic liver resection was able to cause better function and integrity of the remaining liver and small bowel.

Ischemic preconditioning provides no additive clinical value in liver resection of cirrhotic and non-cirrhotic patients under portal triad clamping: a prospective randomized controlled trial

BACKGROUND AND OBJECTIVE

The clinical value of ischemic preconditioning (IP) on patients undergoing hepatectomy under portal triad clamping (PTC) is uncertain, especially for patients with liver cirrhosis. Hence, we conducted a prospective randomized controlled trial to test whether IP could protect liver against ischemic reperfusion (IR) injury after hepatectomy under PTC.

METHOD

One hundred patients, including 67 with cirrhosis, undergoing hepatectomy with PTC were randomly divided into IP and control groups. Liver function tests at postoperative days 1, 3, and 7 as well as postoperative morbidity, mortality, and duration of hospitalization were compared between the two groups.

RESULTS

The general clinical characteristics between both groups were comparable. The duration of the operation, the amount of intraoperative blood loss, and the need and amount of perioperative blood transfusion were similar in both groups. The postoperative levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, and albumin were not statistically different between the two groups. In addition, the morbidity and mortality rates and the duration of hospitalization were similar in both groups.

CONCLUSIONS

IP did not improve liver tolerance to IR injury after hepatectomy under PTC. Therefore, the clinical use of IP cannot be recommended as a standard procedure before PTC.

Effect of olprinone on liver microstructure in rat partial liver transplantation

BACKGROUND

Donor safety is a major concern in living-donor liver transplantation. However, partial grafts do not meet the functional demands of recipients and lead to small-for-size syndrome (SFSS). In a previous study, we showed that olprinone (OLP), a selective phosphodiesterase ІІІ inhibitor, up-regulates endothelial nitric oxide synthase level in the liver and attenuates shear stress, sinusoidal endothelial cell injury, and hepatocyte apoptosis after excessive liver resection in a rat model. We aimed to examine whether OLP treatment has beneficial effects on SFSS in a rat model of partial liver transplantation (PLT).

METHODS

We performed experiments in a rat model of 30% PLT. In the OLP group, we inserted an osmotic pump with OLP into the peritoneal cavity 48 h before liver graft sampling. Recipient rats were not treated with OLP. We examined the liver microstructure by electron microscopy and biochemical examination, and determined the 7-d survival of recipients.

RESULTS

In the OLP group 1 h after PLT, the sinusoidal endothelial cells of the liver were well preserved and we observed few vacuolar structures in hepatocytes. The total serum bilirubin level 1 wk after PLT tended to be lower in the OLP group than in the controls, and the liver microstructures were also well preserved in the OLP group. The probability of survival in the OLP group (100%; 14 of 14 rats) was significantly higher than that in the control group (75%; 15 of 20 rats).

CONCLUSIONS

Olprinone treatment was demonstrated to have therapeutic potential to overcome SFSS.

Ischemic preconditioning enhances hepatocyte proliferation in the early phase after ischemia under hemi-hepatectomy in rats

BACKGROUND

Ischemia/reperfusion (I/R) injury is an important barrier to liver surgery and transplantation because it impairs remnant liver/reduced-size-graft regeneration. Ischemic preconditioning (IPC), as an effective measure to overcome I/R injury, has been shown to enhance the regenerative capacity of hepatocytes. However, investigations have always focused on regeneration in the late phase after reperfusion. This study aimed to investigate whether IPC enhances hepatocyte proliferation in the early phase after reperfusion and possible underlying mechanisms.

METHODS

A total of 90 rats were divided into three groups: hemi-hepatectomy alone (PHx group), 60 minutes of ischemia plus hemi-hepatectomy (I/R group), and a cycle of 10 minutes of alternating I/R prior to 60 minutes of ischemia plus hemi-hepatectomy (IPC group). Each group was divided into five subgroups sacrificed after 0.5, 2, 6, 12 or 24 hours (n=6/subgroup). Subsequently, serum concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) were measured; caspase-3 and proliferating cell nuclear antigen (PCNA) proteins were also determined by Western blotting. Furthermore, PCNA was detected by immunohistochemistry to identify the expression site.

RESULTS

Serum ALT and AST levels after 2-24 hours of reperfusion in the PHx and IPC groups were remarkably decreased compared to the I/R group, and the serum TNF-alpha was relatively lower. A significant increase of serum IL-6 levels was found in the PHx and IPC groups compared with the I/R group at each time point. Furthermore, PCNA expression was remarkably increased in the IPC group after 6-12 hours of reperfusion, and in the earlier 0.5 and 6 hours time points after reperfusion have shown the massive PCNA-positive hepatocytes. At the same time, the expression of liver p-JNK was higher in the IPC group in the early phase after reperfusion than that of the I/R group and its expression was consistent with the PCNA.

CONCLUSION

IPC can initiate hepatocyte proliferation in the early phase after ischemia under hemi-hepatectomy, and may be associated with p-JNK expression and triggered by TNF-alpha/IL-6 signals.

The effect of warm liver ischaemia & reperfusion injury on circulating plasma lipid levels & lipolytic enzyme activity in rat & the impact of ischaemic preconditioning

BACKGROUND & OBJECTIVES

Ischaemia/reperfusion (I/R) associated with major liver surgery compromises liver function. Ischaemic preconditioning (IPC) may be effective in minimizing hepatic I/R injury. This study aimed to investigate the impact of liver ischaemic manipulations on lipid metabolism in rat during the process of liver recovery after liver surgery.

METHODS

Sixty three male Wistar rats were assigned to three groups: the sham group, the I/R group which underwent warm ischaemia and reperfusion (I/R), and the IPC group. The animals were subdivided in 3 groups [1 st , 3 rd and 7 th postoperative day (PO)]. Hepatic lipase (HL) and total lipase (TL) activity and the levels of aspartate and alanine transaminases (AST, ALT), triglycerides, HDL and cholesterol were measured in plasma.

RESULTS

There was no significant difference in the activity of HL and TL between the groups. Significant higher levels of HDL (P<0.0001) were observed in the IPC group when compared to the other groups on the 3 rd PO day. Triglycerides (P<0.0001) and HDL (P=0.003) in the IPC group were higher than the sham group on the 7 th PO day while HDL was also higher in the I/R group. Significantly higher cholesterol levels were found in the I/R and IPC groups on the 7 th PO day, which were not observed in the sham group. There was a similar curve for triglycerides in the sham and IPC groups while there were significantly higher levels of triglycerides on day 7 for the I/R group. The levels of HDL in the IPC group were higher on the 3 rd and 7 th PO day, compared to day 1.

INTERPRETATION & CONCLUSION

Warm ischaemia and I/R injury do not seem to affect lipolytic enzyme activity after the 1 st PO day despite the effects on plasma lipids. IPC seems to prevent accumulation of triglycerides and cholesterol in plasma.

Hepatic arterial infusion with tumor necrosis factor-α induces early hepatic hyperperfusion

BACKGROUND

Hepatic arterial infusion (HAI) has been developed for high-dose regional chemotherapy of unresectable liver metastases or primary liver malignancies. While it is well known that high concentrations of tumor necrosis factor (TNF)-α damage tumor blood perfusion, there is no information on whether autochthonous liver perfusion is affected by HAI with TNF-α. Therefore, we investigated the effects of HAI with TNF-α on hepatic macro- and microvascular perfusion.

METHODS

Swabian Hall pigs were randomized into three groups. HAI was performed with either 20 or 40 µg/kg body weight TNF-α (n = 6 each group). Saline-treated animals served as controls (n = 6). Analyses during a 2-hour post-HAI observation period included systemic hemodynamics, portal venous and hepatic arterial blood flow, portal venous pressure, and the blood flow in the hepatic microcirculation.

RESULTS

HAI with TNF-α caused a slight decrease of mean arterial blood pressure (p < 0.001), which was compensated by a moderate increase of heart rate (p < 0.001). No further systemic side effects of TNF-α were observed. HAI with TNF-α further caused a slight but not significant decrease of portal venous blood flow (p = 0.737) in both experimental groups, paralleled by an increase of hepatic arterial blood flow (p = 0.023, 20 µg/kg; p = 0.034, 40 µg/kg) resulting in an overall hepatic hyperperfusion. The hepatic hyperperfusion after HAI with 20 µg/kg TNF-α was more pronounced and associated with a 40% decrease of the blood flow in the hepatic microcirculation (p = 0.009). HAI with 40 µg/kg TNF-α was only associated with a temporary and moderate total hepatic hyperperfusion and did not affect the blood flow in the hepatic microcirculation.

CONCLUSION

HAI with TNF-α causes a decrease of portal venous flow; however, this is overcompensated by an increased hepatic arterial blood flow, resulting in a total hepatic hyperperfusion. Moderate total hepatic hyperperfusion does not affect the blood flow in the hepatic microcirculation, while a persistent and more pronounced hyperperfusion may cause hepatic microcirculatory disturbances.

Anesthetic Considerations in Hepatectomies under Hepatic Vascular Control

Background. Hazards of liver surgery have been attenuated by the evolution in methods of hepatic vascular control and the anesthetic management. In this paper, the anesthetic considerations during hepatic vascular occlusion techniques were reviewed. Methods. A Medline literature search using the terms "anesthetic," "anesthesia," "liver," "hepatectomy," "inflow," "outflow occlusion," "Pringle," "hemodynamic," "air embolism," "blood loss," "transfusion," "ischemia-reperfusion," "preconditioning," was performed. Results. Task-orientated anesthetic management, according to the performed method of hepatic vascular occlusion, ameliorates the surgical outcome and improves the morbidity and mortality rates, following liver surgery. Conclusions. Hepatic vascular occlusion techniques share common anesthetic considerations in terms of preoperative assessment, monitoring, induction, and maintenance of anesthesia. On the other hand, the hemodynamic management, the prevention of vascular air embolism, blood transfusion, and liver injury are plausible when the anesthetic plan is scheduled according to the method of hepatic vascular occlusion performed.

Splenectomy affects the balance between hepatic growth factor and transforming growth factor-β and its effect on liver regeneration is dependent on the amount of liver resection in rats

Purpose

Small-for-size syndrome (SFSS) is a major problem in liver surgery, and splenectomy has been used to prevent SFSS. However, it is unknown whether splenectomy has the same effect on liver regeneration in both standard and marginal hepatectomy. The aim of this study is to see a difference in effect of splenectomy on liver regeneration according to the amount of liver resection.

Methods

Thirty male Sprague-Dawley rats (220 to 260 g) were divided into the following five groups: control (n = 6), 70% hepatectomy (n = 6), 70% hepatectomy with splenectomy (n = 6), 90% hepatectomy (n = 6), and 90% hepatectomy with splenectomy (n = 6). The animals were euthanized 24 hours after surgery and liver specimens were obtained. To assess liver regeneration, we performed immunohistochemistry of liver tissue using 5-bromo-2-deoxyuridine (BrdU) labeling and Western blot analysis of hepatic growth factor (HGF) and transforming growth factor-β (TGF-β) in the liver tissue.

Results

The splenectomized subgroup had a higher BrdU-positive cell count in the 90% hepatectomy group, but not in the 70% hepatectomy group (P < 0.001). Splenectomy significantly decreased TGF-β expression (P = 0.005) and increased the HGF to TGF-β ratio (P = 0.002) in the 90% hepatectomy group, but not in the 70% hepatectomy group.

Conclusion

The positive effect of splenectomy on liver regeneration was greater in the group with the larger liver resection. This phenomenon may be related to the relative balance between HGF and TGF-β in the liver.

Impact of portal branch ligation on tissue regeneration, microcirculatory response and microarchitecture in portal blood-deprived and undeprived liver tissue

Partial ligation of portal branches leads to atrophy of the deprived lobes and hypertrophy of the intact lobes. In this study we investigated the microcirculatory response and their consequences on tissue regeneration after left-sided portal branch ligation (PBL) in Sprague-Dawley rats. At day 1 and 3 after PBL the hepatic microcirculation was assessed by intravital microscopy (IVM). In addition histological, immunohistochemical and biochemical techniques were used to determine alterations of hepatic microarchitecture. IVM analysis of the microcirculation of the ligated hepatic lobes revealed significant alterations with a reduction in sinusoidal perfusion rate, a decrease of red blood cell velocity, an increase of sinusoidal diameter and a marked reduction in shear stress at days 1 and 3 after PBL. On the contrary, the non-ligated lobes presented with higher blood flow velocities, marked sinusoidal vasoconstriction and thus, shear stress elevation. In consequence, ligated liver lobes exhibited marked cell apoptosis and necrosis, being accompanied by massive intrahepatic leukocyte accumulation and a ~30% weight loss. The non-ligated liver tissue showed marked PCNA expression and thereby completely compensated weight loss. Beside full restoration of liver mass, sinusoidal blood flow was comparable in ligated and non-ligated lobes as well as in sham-treated controls. This study shows that the liver aims at constant tissue mass and blood flow, most probably for maintenance of adequate clearance function. In addition, it supports the hypothesis that shear stress plays a pivotal role in triggering liver hypertrophy in the non-ligated lobes.

Splenectomy improves survival by increasing arterial blood supply in a rat model of reduced-size liver

Prevention of acute portal hyperperfusion in small-for-size livers by inflow modulation results in beneficial postoperative outcome. The objective of this study was to unravel the underlying mechanism, emphasizing the intimate relationship between portal venous (PV) and hepatic arterial (HA) blood flow (BF). Rats underwent partial hepatectomy (pHx), splenectomy before pHx or splenectomy and ligation of the A. hepatica before pHx. Portal venous blood flow (PVBF), hepatic arterial blood flow (HABF), and tissue pO₂ were assessed during stepwise resection from 30% to 90%. Hepatic regeneration and hypoxia-responsive gene expression were analyzed in each group after nonlethal 85% pHx. 90% pHx caused a fourfold rise in PVBF, a slight decrease in HABF with a 50% reduction in pO₂, and high mortality. Splenectomy before pHx reduced the PVBF and caused a rise in HABF with doubling in tissue pO₂. An attenuation of hypoxia-responsive gene expression turned into enhanced hepatocellular regeneration and improved survival. A. hepatica ligation abolished the beneficial effect of splenectomy on tissue oxygenation, proliferation, and outcome. In conclusion, the beneficial effect of splenectomy in small-for-size livers can be attributed to a rise in HABF with sufficient oxygen supply rather than to a reduced portal venous hyperperfusion to the remnant liver.

Regulation of hepatic blood flow: The hepatic arterial buffer response revisited

The interest in the liver dates back to ancient times when it was considered to be the seat of life processes. The liver is indeed essential to life, not only due to its complex functions in biosynthesis, metabolism and clearance, but also its dramatic role as the blood volume reservoir. Among parenchymal organs, blood flow to the liver is unique due to the dual supply from the portal vein and the hepatic artery. Knowledge of the mutual communication of both the hepatic artery and the portal vein is essential to understand hepatic physiology and pathophysiology. To distinguish the individual importance of each of these inflows in normal and abnormal states is still a challenging task and the subject of ongoing research. A central mechanism that controls and allows constancy of hepatic blood flow is the hepatic arterial buffer response. The current paper reviews the relevance of this intimate hepatic blood flow regulatory system in health and disease. We exclusively focus on the endogenous interrelationship between the hepatic arterial and portal venous inflow circuits in liver resection and transplantation, as well as inflammatory and chronic liver diseases. We do not consider the hepatic microvascular anatomy, as this has been the subject of another recent review.

Platelet transfusion can be related to liver regeneration after living donor liver transplantation

BACKGROUND

Although liver regeneration is a fundamental aspect of living donor liver transplantation (LDLT), the factors that affect liver regeneration during the early post-transplantation period have not been thoroughly investigated. Recently it was suggested that platelets contribute to liver regeneration. The aim of the present study was to identify the major factors that affect liver graft regeneration during the early post-transplantation period.

MATERIALS AND METHODS

Eighty-seven right liver grafted, adult-to-adult LDLT patients were retrospectively analyzed. Liver regeneration was assessed by volumetry from computed tomographic (CT) scans obtained between the 9th and 11th postoperative days. The authors investigated relationships between clinical variables and liver graft regeneration rates, and they conducted multiple regression analysis on factors found to be significant by univariate analysis.

RESULTS

Mean graft weight at operation was 722.9 +/- 109.7 g, and mean graft volume assessed by follow-up CT was 1,042.2 +/- 155.6 ml, reflecting a mean liver graft regeneration of 45.9 +/- 22.3%. The graft regeneration was found to correlate inversely with graft-to-recipient weight ratio (GRWR, r = -0.406, p < 0.001) and directly with portal flow velocity (cm/s; r = 0.307; p = 0.004) and splenic index (cm(3); r = 0.282; p = 0.009). Moreover, the total amount (units) of platelets transfused was found to be significantly associated with graft regeneration (r = 0.293; p = -.006). Stepwise regression analysis showed that GRWR (beta = -33.124; p = 0.001), total amount of platelets transfused (beta = 0.771; p = 0.012), and splenic index (beta = -0.010; p = 0.049) were independently associated with graft regeneration.

CONCLUSIONS

The results of the present study suggest that platelets play a significant role in human liver regeneration after LDLT.

Uncoupling protein-2 deficient mice are not protected against warm ischemia/reperfusion injury of the liver

BACKGROUND

Uncoupling protein-2 (UCP2) might play an important role in mediating ischemia/reperfusion (I/R) injury due to its function in uncoupling of oxidative phosphorylation and in the proton leak-associated increase of reactive oxygen species (ROS) production. The aim of this study was to elucidate the role of UCP2 in hepatic I/R injury.

MATERIALS AND METHODS

UCP2 wild type and UCP2 deficient mice were subjected to I/R of the left liver lobe. Sham-operated animals without I/R served as controls. Intravital fluorescence microscopy was used for assessing postischemic microcirculatory dysfunction. Indicators of hepatic inflammatory response, oxidative stress, and bioenergetic status as well as histomorphology were investigated.

RESULTS

Under sham conditions UCP2-/-mice presented slightly but not significantly higher levels of hepatic ATP and energy charge than wild type mice. In addition, they exhibited higher systemic IL-6 levels and intrahepatic leukocyte adherence. After exposure to I/R, the extent of reperfusion injury did not differ between UCP2+/+ and UCP2-/-mice, as indicated by a comparable loss of sinusoidal perfusion, hepatic ATP, and energy charge levels, as well as rise of transaminases and disintegration of liver structures. Intrahepatic leukocyte adherence and plasma IL-6 levels of postischemic UCP2-/-mice still exceeded those of UCP2+/+mice.

CONCLUSIONS

UCP2 appears to be of minor relevance for the manifestation and extent of postischemic reperfusion injury in nondiseased livers with the increased ATP availability being counteracted by the higher pro-inflammatory IL-6 levels in UCP2 deficient mice.

Reperfusion stress induced during intermittent selective clamping accelerates rat liver regeneration through JNK pathway

BACKGROUND & AIMS

Liver resection includes temporal vascular inflow occlusion resulting in ischemia/reperfusion injury in the remnant liver. Here, we developed a rat model of selective lobe occlusion to isolate reperfusion stress from ischemia and to analyze its effect on liver regeneration.

METHODS

Left lateral and median lobes of liver were either mobilized or subjected twice for 10min to ischemia followed by 5min reperfusion prior to resection while the regenerative lobes were only subjected to reperfusion.

RESULTS

Although intermittent reperfusion stress induced higher levels of serum transaminases, analysis of cell cycle regulators revealed accelerated regenerative response compared to standard partial hepatectomy. The G0/G1 transition occurred before tissue resection, as evidenced by c-fos, junB, and IL-6 induction. Following hepatectomy, Cyclin D1 up-regulation, G1/S transition, and cell division occurred earlier than normal. Unexpectedly, liver mobilization, a component of the clamping procedure, also resulted in earlier G1/S transition. The shortened G1-phase was driven by the c-Jun N-terminal Kinase pathway and was associated with an oxidative stress response as evidenced by the expression of inducible nitric oxide synthase.

CONCLUSION

Intermittent selective clamping of lobes to be resected induced reperfusion stress on remnant liver that was beneficial for liver regeneration, suggesting this procedure could be applied in clinical practice.

Protective effect of reduced glutathione and venous systemic oxygen persufflation on rat steatotic graft following liver transplantation

BACKGROUND

The aim of this study is to explore the protective effect of high-dose reduced glutathione (GSH) preconditioning and venous systemic oxygen persufflation (VSOP) on rat steatotic liver grafts following transplantation.

METHODS

Steatotic liver model was established by feeding rats a high-fat, high-cholesterol diet, and infusing stomach with 50% alcohol (1 mL/100g body weight/d) for 6 wk. In the pretreated group, short-term and high-dose of GSH administration and VSOP were performed. In rat orthotopic liver transplantation model, the recipient survival, liver function, hepatic microcirculation blood flow, hepatic redox, hepatocytes apoptosis and necrosis, and hepatic ultrastructure alteration were observed.

RESULTS

In the pretreated rat steatotic grafts, hepatic GSH (from 29.43 +/- 4.83 to 41.56 +/- 8.51mg/mgprot), superoxide dismutase (SOD) (from 48.32 +/- 6.27 to 67.74 +/- 7.68 NU/mgprot), and adenosine triphosphate (ATP) (from 1.61 +/- 0.20 to 2.28 +/- 0.09 micromoles/g) were significantly increased (P < 0.05), whereas malondialdehyde (MDA) was significantly decreased (from 7.20 +/- 2.18 to 4.63 +/- 0.58 nmol/mgprot, P < 0.05). The hepatocyte necrosis of fatty liver graft was significantly reduced in the pretreated group when compared with non-treated fatty ones (37.71% +/- 9.69% versus 16.63% +/- 5.53%; t = 3.777, P = 0.014), and significantly improved liver function and hepatic ultrastructure were observed in the pretreated fatty liver group after operation. The animal survival after transplanted with fatty liver was significantly improved (chi(2) = 4.07, P = 0.0436).

CONCLUSION

A short course pretreatment with high-dose GSH and oxygen persufflation during cold preservation effectively protect steatotic liver grafts from ischemic damage and significantly improve early survival rate in a rat fatty liver transplantation model.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Predicting liver failure following major hepatectomy

Pre-operative determination of the risk of liver dysfunction has come under criticism with regards to its usefulness in clinical practice. Opinion is split between centres which use such tests uniformly on all patients and those where clinical judgment alone is used. Published data would not suggest any difference in mortality, morbidity or liver failure rates between these groups. This review outlines and presents the evidence for pre-operative quantification of functional liver remnant volume.

Influence of portosystemic shunt on liver regeneration after hepatic resection in pigs

Objective. The minimal amount of liver mass necessary for regeneration is still a matter of debate. The aim of the study was to analyze liver regeneration factors after extended resection with or without portosystemic shunt. Methods. An extended left hemihepatectomy was performed in 25 domestic pigs, in 15 cases after a portosystemic H-shunt. The expression of Ki-67, VEGF, TGF-α, FGF, and CK-7 was analyzed in paraffin-embedded tissue sections. Results. The volume of the remnant liver increased about 2.5-fold at the end of the first week after resection. With 19 cells/10 Glisson fields versus 4/10, Ki-67-expression was significantly higher in the H-shunt group. VEGF- and CK-7-expressions were significantly higher in the control group. No significant change was found in FGF-expression. The expression of TGF-α was higher, but not significantly, in the control group. Conclusions. The expression of Ki-67, and therefore hepatocyte regeneration, was increased in the shunt group. The expression of CK-7 on biliary epithelium and the expression of VEGF, however, were stronger in the control group.

Cellular liver regeneration after extended hepatic resection in pigs

BACKGROUND

The liver has an enormous capacity to regenerate itself. The aim of this study was to evaluate whether the regeneration is due to hypertrophy or hyperplasia of the remnant liver after extended resection and whether a portosystemic shunt is beneficial.

MATERIAL AND METHODS

An extended left hemihepatectomy was performed in 25 pigs, and in 14 after performing a portosystemic shunt. During follow up, liver regeneration was estimated by macroscopic markers such as liver volume and size of the portal fields [mm(2)] as well as the amount of hepatocytes per portal field and the amount of hepatocytes per mm(2).

RESULTS

Regardless of the operation procedure, the volume of the remnant liver increased about 2.5 fold at the end of the first week after resection. The size of the portal fields increased significantly as well as the number of hepatocytes in the portal fields. Interestingly, the number of hepatocytes per mm(2) remained the same.

CONCLUSION

After extended resection, liver regeneration was achieved by an extensive and significant hyperplasia of hepatocytes within the preexisting portal fields and not by de novo synthesis of new portal fields. However, there was no difference in liver regeneration regarding the operation procedure performed with or without portosystemic shunt.

Liver failure after major hepatic resection

INTRODUCTION

The consequence of excessive liver resection is the inexorable development of progressive liver failure characterised by the typical stigmata associated with this condition, including worsening coagulopathy, hyperbilirubinaemia and encephalopathy. The focus of this review will be to investigate factors contributing to hepatocyte loss and impaired regeneration.

METHODS

A literature search was undertaken of Pubmed and related search engines, examining for articles relating to hepatic failure following major hepatectomy.

RESULTS

In spite of improvements in adjuvant chemotherapy and increasing surgical confidence and expertise, the parameters determining how much liver can be resected have remained largely unchanged. A number of preoperative, intraoperative and post-operative factors all contribute to the likelihood of liver failure after surgery.

CONCLUSIONS

Given the magnitude of the surgery, mortality and morbidity rates are extremely good. Careful patient selection and preservation of an obligate volume of remnant liver is essential. Modifiable causes of hepatic failure include avoidance of sepsis, drainage of cholestasis with restoration of enteric bile salts and judicious use of portal triad inflow occlusion intra-operatively. Avoidance of post-operative sepsis is most likely to be achieved by patient selection, meticulous intra-operative technique and post-operative care. Modulation of portal vein pressures post-operatively may further help reduce the risk of liver failure.

Lack of protection of ischaemic preconditioning in the rat model of major hepatectomy with ischaemia reperfusion injury

OBJECTIVE

To investigate the effects of ischaemic preconditioning (IP) on residual liver regeneration after major hepatectomy without portal blood bypass in rats, and to verify whether it can protect the residual liver from ischaemia reperfusion (IR) injury.

METHODS

Ninety rats were randomized into three groups: Group PH, rats were subjected to 70% hepatectomy alone; Group IR, rats were subjected to 30 minutes of total hepatic ischaemia, and 70% hepatectomy was performed just before reperfusion; Group IP, rats were pretreated with IP (5/10 minutes). During the preoperative period and at 0.5, 6, 12, 24 and 48 hours after the operation, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were measured using an autoanalyser. Serum hyaluronic acid (HA) was measured by radioimmunoassay. Regenerated liver weight (RLW) of the rats was measured and the expressions of Ki-67 and cyclin D1 were determined by immunohistochemistry in remnant liver tissue.

RESULTS

There were no significant differences in serum AST and ALT levels in all the groups before the operation. After partial hepatectomy, AST and ALT levels increased rapidly. From 0.5 to 24 hours after operation, serum AST and ALT levels were significantly higher in IP group rats than in PH and IR rats (p < 0.05). There were no significant differences in serum HA levels in all the groups before the operation. After partial hepatectomy, HA levels increased rapidly, reaching peak values at 12 hours. In the early stage (during 12 hours) after the operation, HA level was significantly higher in IP rats than in PH and IR rats (p < 0.05). The RLW of the rats rapidly increased after partial hepatectomy, and significantly decreased in IP rats compared with PH and IR rats (p < 0.05). Cyclin D1 and Ki-67 expression in all groups before the operation were low and were not significantly different. After partial hepatectomy, they rapidly increased. The expression of Ki-67 and cyclin D1 reached a peak at 24 hours after the operation in PH rats, and they were significantly higher compared with IR and IP rats (p < 0.05). In groups IR and IP, the expression of cyclin D1 and Ki-67 reached peak values at 48 hours. A significant decrease (p < 0.05) was observed after 24 and 48 hours of reperfusion in group IP compared with groups PH and IR.

CONCLUSION

IP impairs residual liver regeneration after major hepatectomy without portal blood bypass in rats, and protection from IR injury disappears. IP-induced hyperperfusion may be the cause of reduced liver regeneration.

Ischemic preconditioning in hepatic ischemia and reperfusion

PURPOSE OF REVIEW

Ischemic preconditioning that consists of a short period of hepatic inflow occlusion followed by reperfusion has the potential to increase tolerance to a subsequent prolonged ischemic insult. This review outlines current insight into ischemic preconditioning for hepatic ischemia and reperfusion injury in experimental and clinical settings.

RECENT FINDINGS

Experimental evidence suggests that interleukin-6 signaling and increased phosphorylation of STAT3 (signal transducer and activator of transcription-3) are involved in the protective effects of ischemic preconditioning. The benefit of ischemic preconditioning is restricted, however, by old liver and prolonged ischemic time (>60 min). To overcome this, ascorbic acid or glucose administration combined with ischemic preconditioning potentially can maintain the integrity of hepatic mitochondrial function through signal transduction pathways. The influence of ischemic preconditioning on hepatic regeneration varies with partial hepatectomy or small-for-size liver graft models, and remains controversial. Clinically, ischemic preconditioning in deceased donors protects against ischemia and reperfusion injury, as demonstrated by lowered liver enzyme levels, reduced incidence of primary nonfunction, and increased hepatic hypoxia-induced factor-1alpha concentrations.

SUMMARY

Enhanced understanding of the mechanisms of organ tolerance induced by ischemic preconditioning would strengthen the significance of this potential therapeutic strategy in liver transplantation.

Effects of prophylactic splenic artery modulation on portal overperfusion and liver regeneration in small-for-size graft

BACKGROUND

The small-for-size (SFS) syndrome is caused by excessive portal inflow into a small-sized liver graft. Various approaches for portal decompression have been used, but details of their impact on liver regeneration in SFS graft remain unclear. We examined the effect of prophylactic splenic artery modulation (SAM).

METHODS

We conducted a retrospective cohort study. The study group was 39 consecutive adult-to-adult living liver transplantation recipients, with a graft-to-recipient body weight ratio of less than 0.8. Patients were assigned into the non-SAM group (n=18, without any portal inflow attenuation) or SAM group (n=21, preoperative embolization in 15 patients and intraoperative ligation in 6 patients). Hepatic hemodynamics, graft function, liver regeneration, and outcome were evaluated.

RESULTS

In the SAM group, the excessive portal flow was significantly reduced (P<0.01) and the effect of embolization on portal decompression was equivalent to that of ligation. In the acute postoperative phase, serum transaminases, interleukin-6, and tumor necrosis factor-alpha, were lower in the SAM group than in non-SAM group. In both groups, a negative correlation was observed between graft-to-recipient body weight ratio and liver regeneration rate at 2 weeks after living donor liver transplantation. Splenic artery modulation was advantageous for liver regeneration, and significantly improved clinical features, hyperbilirubinemia, and prolonged ascites. Small-for-size syndrome occurred in five patients of the non-SAM group, and only one of SAM group (P=0.038).

CONCLUSION

In SFS graft with severe portal hypertension, prophylactic splenic embolization/ligation seems to relieve portal overperfusion injury and contributes in improvement of posttransplantation prognosis through liver regeneration.

Nitric oxide reduces organ injury and enhances regeneration of reduced-size livers by increasing hepatic arterial flow

Background

Reduced-size livers suffer from portal hyperperfusion, diminished arterial blood flow and the risk of postoperative liver injury. The aim of this experimental study was to unravel the role of nitric oxide in this setting.

Methods

Rats underwent 85 per cent partial hepatectomy and either substitution of nitric oxide with molsidomine or inhibition of nitric oxide synthase (NOS) with NG-nitro-l-arginine methyl ester. Untreated hepatectomized animals served as controls and unresected animals as the sham group.

Results

Ultrasonic flowmetry following partial hepatectomy revealed a marked increase in portal venous inflow with a concomitant decrease in hepatic arterial inflow. Nitric oxide substitution counteracted the decline in hepatic arterial inflow and caused a significantly greater increase in cell proliferation after partial hepatectomy compared with control or NOS-inhibited animals. Hepatectomized animals further profited from nitric oxide substitution, as indicated by reduced aminotransferase release and improved liver function.

Conclusion

Nitric oxide improves the postoperative course of rats with reduced-size livers by modulating hepatic macrohaemodynamics and mediating regeneration and cytoprotection, but not by reducing hepatic hyperperfusion and the accompanying sinusoidal shear stress.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Local interaction of apoptotic hepatocytes and Kupffer cells in a rat model of systemic endotoxemia

AIM

There is strong evidence that hepatocellular apoptosis is not only initiated by circulating blood cells which become adherent within the endotoxemic liver, but also contributes to further sustain the inflammatory cell-cell response.

METHODS

Because previous studies assumed the importance of the role of cellular cross-talk in mediating inflammatory liver injury, we herein examined the activation of Kupffer cells (KCs) and their spatial coincidence with intrahepatic leukocyte adherence and hepatocellular apoptosis at 6 h after intraperitoneal exposure of rats with lipopolysaccharide (10 mg/kg).

RESULTS

In vivo multifluorescence microscopy revealed liver injury including nutritive perfusion failure, tissue hypoxia, leukocyte accumulation, as well as KC activation and parenchymal apoptotic cell death. Detailed spatial analysis revealed frequent colocalization of activated KCs with apoptotic hepatocytes. Colocalization was absent in saline-treated controls.Colocalization was confirmed by histochemistry, which showed ED1-positive KCs neighboring and engulfing TUNEL-positive hepatocytes. Colocalization of KCs with leukocytes ranged between 4% and 5% and did not increase in endotoxemic animals. Taken together, the present results indicate that apoptotic cell death of hepatocytes may stimulate phagocytosis by neighboring KCs. Direct KC-leukocyte contact seems not to be mandatory for cellular communication in the process of hepatocellular apoptosis.

CONCLUSION

With respect to the fundamental importance of cell apoptosis, improved knowledge of these cell-cell interactions might allow the development of new therapeutic strategies through the regulation of apoptotic cell death.

Interleukin-6 inhibits oxidative injury and necrosis after extreme liver resection

Extreme hepatectomy or resection of more than 80% of liver mass often leads to liver failure and death and is a major limitation to therapeutic liver resection for patients with liver tumors. We sought to define the mechanisms leading to liver failure and to determine the utility of interleukin-6 (IL-6) administration to improve outcomes. Mice were injected with Chinese hamster ovary cells expressing human IL-6 or no recombinant protein, or were administered recombinant IL-6 or carrier by osmotic mini-pump. Mice were then subjected to 70% or 87% hepatectomy. Light and electron microscopy of liver sections after 87% hepatectomy showed ballooning hepatocytes, vacuolar changes, and mitochondrial abruption, with absence of anoikic nuclei. No significant activation of executor caspases or DNA laddering was observed, although a dramatic decrease in cellular adenosine triphosphate (ATP) stores was measured, suggesting cell death was by a necrotic pathway involving mitochondrial dysfunction. A large increase in protein oxidation was observed, indicative of significant oxidative stress. IL-6 treatment before 87% hepatectomy resulted in less biochemical and histological evidence of liver injury as well as earlier proliferating chain nuclear antigen (PCNA) expression and accelerated recovery of liver mass. IL-6 pretreatment induced the antioxidative injury proteins, ref-1 and GPX1, decreased protein oxidation, vacuolar changes and leakage of mitochondrial products, improved ATP stores, and maintained cellular ultrastructure after 87% hepatectomy.

CONCLUSION

Massive oxidative injury and mitochondrial dysfunction occurs in the liver after extreme hepatectomy. IL-6 improves recovery and survival from extreme liver resection by enhancing pro-growth pathways, reducing oxidative stress, and maintaining mitochondrial function.

Protection from hepatic ischemia/reperfusion injury and improvement of liver regeneration by alpha-lipoic acid

The aim of this study was to characterize the in vivo action of lipoic acid (LA) in hepatic ischemia/reperfusion injury (IRI) and its effects on liver regeneration involving the investigation of mechanisms of action and effects on animal survival. Two groups of rats were compared: one group received 500 micromol alpha-LA injected via the inferior vena cava 15 min before the induction of 90 min of selective ischemia. The untreated group received vehicle. Influence of LA on IRI of the liver was determined in short- and long-term experiments. Cellular damage was decreased under preconditioning conditions with LA. Caspase 3, 8, and 9 activities were significantly lower in the LA group accompanied by a decrease in terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive hepatocytes. Electron micrographs in the untreated group showed massive mitochondrial damage. The survival rate as end point of liver function was markedly increased after pretreatment with LA. Increased levels of tumor necrosis factor alpha was shown by enzyme-linked immunosorbent assay as well as real-time reverse transcription-polymerase chain reaction in the LA group accompanied by increased mitotic index and Ki-67 staining in liver tissue. Attenuation of IRI of the rat liver in vivo by LA is accompanied by reduction of necrosis and apoptosis-related cell death, whereas liver regeneration is increased.

Attenuation of inflammation and apoptosis by pre- and posttreatment of darbepoetin-alpha in acute liver failure of mice

In many liver disorders inflammation and apoptosis are important pathogenic components, finally leading to acute liver failure. Erythropoietin and its analogues are known to affect the interaction between apoptosis and inflammation in brain, kidney, and myocardium. The present study aimed to determine whether these pleiotropic actions also exert hepatoprotection in a model of acute liver injury. C57BL/6J mice were challenged with d-galactosamine (Gal) and Escherichia coli lipopolysaccharide (LPS) and studied 6 hours thereafter. Animals were either pretreated (24 hours before Gal-LPS exposure) or posttreated (30 minutes after Gal-LPS exposure) with darbepoetin-alpha (DPO, 10 mug/kg i.v.). Control mice received physiological saline. Administration of Gal-LPS caused systemic cytokine release and provoked marked hepatic damage, characterized by leukocyte recruitment and microvascular perfusion failure, caspase-3 activation, and hepatocellular apoptosis as well as enzyme release and necrotic cell death. DPO-pretreated and -posttreated mice showed diminished systemic cytokine concentrations, intrahepatic leukocyte accumulation, and hepatic perfusion failure. Hepatocellular apoptosis was significantly reduced by 50 to 75% after DPO pretreatment as well as posttreatment. In addition, treatment with DPO also significantly abrogated necrotic cell death and liver enzyme release. In conclusion, these observations may stimulate the evaluation of DPO as hepatoprotective therapy in patients with acute liver injury.

IL-10 attenuates hepatic I/R injury and promotes hepatocyte proliferation

BACKGROUND

One of the most important determinants of the outcome of hepatic ischemia and reperfusion (I/R) injury is the onset of the inflammatory response. Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine. It inhibits the production of interleukin-6 (IL-6), which however, also is involved in priming hepatocyte proliferation. The aim of this study was to examine the protective effects and the influence on the regenerative response of exogenous as well as endogenous IL-10 in a rat model of hepatic I/R injury.

MATERIALS AND METHODS

Seventy percent Liver I/R was induced in male Wistar rats for 60 min followed by 24 h reperfusion. One group underwent a midline laparotomy with recombinant rat (rr)IL-10 administration (SHAM + IL-10). The other groups underwent 60 min ischemia with administration of saline (I/R + saline), rrIL-10 [at two different time-points, i.e., I/R + IL-10pre(ischemia) and I/R + IL-10end(ischemia)] or anti-rat IL-10 antibody (I/R + antiIL-10).

RESULTS

Parenchymal damage, as assessed by plasma alanine aminotransferase and aspartate aminotransferase, was significantly reduced by rrIL-10 and by endogenous IL-10 (P < 0.05). Also, rrIL-10 significantly reduced IL-6 production and the accumulation of neutrophils in liver and lung tissue, as measured by myeloperoxidase activity. Necrosis and apoptosis were significantly reduced and hepatocyte proliferation was stimulated by rrIL-10.

CONCLUSIONS

RrIL-10 and, to a lesser extent, endogenous IL-10, attenuate damage and inflammation, while rrIL-10 also promotes proliferation after hepatic I/R injury in rats. Therefore, rrIL-10 has potential use to prevent I/R injury and to promote liver regeneration after partial liver resection with temporary inflow occlusion.

Portal branch ligation induces a hepatic arterial buffer response, microvascular remodeling, normoxygenation, and cell proliferation in portal blood-deprived liver tissue

Portal branch ligation (PBL) may prevent liver failure after extended hepatic resection. However, clinical studies indicate that tumors within the ligated lobe develop accelerated growth. Although it is well known that tumor growth depends on the host's microvascularization, there is no information about how PBL affects the hepatic microcirculation. Our aims were to determine hepatic artery response, liver microcirculation, tissue oxygenation, and cell proliferation after PBL. Therefore, we used intravital multifluorescence microscopy, laser-Doppler flowmetry, immunohistochemistry, and biochemical techniques to examine microcirculatory responses, microvascular remodeling, and cellular consequences after left lateral PBL in BALB/c mice. During the first 7 days, PBL induced a reduction of left hilar blood flow by approximately 50%. This resulted in 80% sinusoidal perfusion failure, significant parenchymal hypoxia, and liver atrophy. After 14 days, however, left hilar blood flow was found to be restored. However, remodeling of the microvasculature included a rarefaction of the sinusoidal network, however, without substantial perfusion failure, compensated by a hepatic arterial buffer response and significant sinusoidal dilatation. This resulted in normalization of tissue oxygenation, indicating arterialization of the ligated lobe. Interestingly, late microvascular remodeling was associated with increased endothelial nitric oxide synthase expression, significant hepatocellular proliferation, and weight gain of the ligated lobe. Thus PBL induces only an initial microcirculatory failure with liver atrophy, followed by a hepatic arterial buffer response, microvascular remodeling, normoxygenation, and hepatocellular proliferation. This may explain the accelerated tumor progression occasionally observed in patients after PBL.

Antileukoproteinase protects against hepatic inflammation, but not apoptosis in the response of D-galactosamine-sensitized mice to lipopolysaccharide

BACKGROUND AND PURPOSE

There is major evidence for the strong bi-directional interrelation of parenchymal cell apoptosis and leukocyte accumulation and inflammation in acute liver injury. Therefore, the aim of this in vivo study was to investigate the anti-apoptotic and anti-inflammatory potential of antileukoproteinase (ALP) in a murine model of acute liver failure.

EXPERIMENTAL APPROACH

C57BL/6J mice were given galactosamine (D-GalN) and E. coli lipopolysaccharide (LPS) followed by administration of saline or ALP. Besides survival rate, hepatic tissue damage and inflammatory response were analyzed by intravital fluorescence microscopy 6 hours after treatment. In addition, immunohistochemical analysis of NFkappaB-p65 and hepatocellular apoptosis, plasma levels of AST/ALT, TNF-alpha and IL-10 were determined.

KEY RESULTS

Administration of D-GalN/LPS provoked hepatic damage, including marked leukocyte recruitment and microvascular perfusion failure, as well as hepatocellular apoptosis and enzyme release. NFkappaB-p65 became increasingly detectable in hepatocellular nuclei, accompanied by a rise of TNF-alpha and IL-10 plasma levels. ALP markedly reduced intrahepatic leukocyte accumulation, nuclear translocation of NFkappaB and plasma levels of TNF-alpha and IL-10. Moreover, liver enzyme levels indicated the absence of necrotic parenchymal cell death. In contrast, ALP failed to block both apoptosis and caspase-3 levels and the mortality rate of ALP-treated animals was comparable to that of saline-treated mice.

CONCLUSIONS AND IMPLICATIONS

ALP could effectively prevent D-GalN/LPS-associated intrahepatic inflammatory responses by inhibition of NFkappaB activity, but not apoptosis-driven mortality. Thus, a protease-inactivating approach such as application of ALP seems to be inadequate in damaged liver where apoptosis represents the predominant mode of cell death.

Protective Effect of Ischemic Preconditioning against Liver Injury after Major Hepatectomy Using the Intermittent Pringle Maneuver in Swine

OBJECTIVE

To investigate whether ischemic preconditioning (IP) protects the liver against ischemia-reperfusion injury (I/R-I) after major hepatectomy through intermittent hepatic pedicle clamping (IC) in a swine liver resection model.

BACKGROUND

Although many studies have reported a protective effect of IP against continuous hepatic ischemia, it has not been elucidated whether IP protects the liver against I/R-I after hepatectomy using IC. This is the first study to evaluate the effect of IP in a swine major hepatectomy model using IC.

METHODS

Pigs (n = 12) were divided into 2 groups (IP or non-IP). In the IP group, livers were subjected to IP (10 min ischemia and 10 min reperfusion) before liver resection using IC (15 min ischemia and 5 min reperfusion). A left hemihepatectomy was then performed using IC in both groups. Hemodynamic changes and plasma concentrations of aspartate aminotransferase, lactate dehydrogenase, lactic acid and hyaluronic acid were measured at 60, 120 and 180 min after hepatectomy. Apoptosis (TUNEL staining and electron microscopy), plasma tumor necrosis factor-alpha (TNF-alpha) and NO(2)(-)/NO(3)(-) were evaluated for 180 min after hepatectomy.

RESULTS

There were no significant differences in body weight, blood loss, resected liver weight, Pringle time or hemodynamic changes between the 2 groups. IP significantly reduced plasma aspartate aminotransferase levels for 180 min after hepatectomy (IP: 135.8 +/- 13.5 vs. non-IP: 199 +/- 16.8 IU/l; p = 0.018). In the non-IP group, apoptotic changes in sinusoidal endothelial cells were observed with increased plasma TNF-alpha levels. IP protected liver injury from increase in plasma TNF-alpha (p = 0.042). Significantly fewer apoptotic cells were seen in the IP than in the non-IP group (p = 0.002). Plasma levels of lactate dehydrogenase, lactic acid and NO(2)(-)/NO(3)(-) in the IP group tended to be lower than those in the non-IP group.

CONCLUSIONS

IP prior to hepatectomy with IC resulted in less hepatic injury and apoptotic cell death than in livers not subjected to IP. IP with IC has the potential to improve the clinical postoperative course of patients undergoing hepatectomy.

Vascular endothelial growth factor does not improve liver regeneration and survival after 90% subtotal liver resection

AIM

Vascular endothelial growth factor (VEGF) has been shown to stimulate liver regeneration after 70% partial hepatectomy (PH). It is unclear, however, whether exogenous administration of VEGF can also be used to improve liver regeneration and survival after 90% subtotal liver resection. The aim of this study was to determine the effect of exogenous and endogenous VEGF after 90% subtotal hepatectomy (SH).

METHODS

Rats were subjected to 90% SH and treated with VEGF, anti-VEGF or NaCl. Postoperatively (3 h - 5 days) liver body weight ratio (LBR), hepatocyte proliferation and biochemical markers were assessed. ELISA was performed to measure protein levels for VEGF. Gene expression was determined by customized cDNA arrays and quantitative RT-PCR.

RESULTS

Administration of VEGF did not enhance LBR or hepatic proliferation, or reduce the serum parameters. VEGF levels were the highest in VEGF-treated animals. The overall survival after 90% SH reached 78% in VEGF-treated animals, but did not differ significantly from that of anti-VEGF or NaCl-treated animals (74% and 75%, respectively). Gene expression analysis showed a modulation of anti-apoptotic and cell cycle control genes that was independent of VEGF.

CONCLUSIONS

In contrast to PH, liver regeneration and survival after SH cannot be modulated by VEGF. This indicates that the relevant mechanisms that stimulate liver regeneration after hepatectomy at least partially depend upon the extent of liver resection.

Impaired hepatic regeneration by ischemic preconditioning in a rat model of small-for-size liver transplantation

OBJECTIVE

Graft size is one of the major risk factors in adult-to-adult living donor liver transplantation and rapid regeneration is an essential post-operative requirement. Ischemic preconditioning (IPC) has been shown to be an effective strategy in the reduction of hepatic ischemia-reperfusion injury and stimulation of liver regeneration. This study was designed to evaluate the effects of IPC on liver regeneration in small-for-size liver grafts.

METHODS

We employed a rat orthotopic liver transplantation model using small-for-size (30%) grafts, in the presence or absence (control) of IPC (10 min of ischemia followed by 15 min of reperfusion). Survival rate, graft injury, hepatocellular proliferation, cell cycle progression, Stat3 activation, as well as TNF-alpha and IL-6 expression were assessed.

RESULTS

IPC significantly enhanced the extent of graft injury and hindered hepatic regeneration in small-for-size liver grafts. The 7-day survival rate was also reduced by IPC, but failed to reach statistical significance. IPC did not affect TNF-alpha levels, but significantly decreased the elevation of IL-6 after reperfusion. These findings were correlated with down-regulation of cyclin E and cyclin D1, and decreased numbers of PCNA-positive nuclei in IPC grafts. These results were inconsistent with Stat3 activation, as P-Stat3 exhibited a stronger and prolonged pattern of expression in the IPC group, compared to controls.

CONCLUSIONS

Ischemic preconditioning may impair liver regeneration in small-for-size liver grafts by decreasing IL-6 and blunting cell cycle progression, through a mechanism at least partially independent of Stat3.