Hepatic reticuloendothelial system dysfunction after ischemia-reperfusion: role of P-selectin-mediated neutrophil accumulation

Rodent models of hepatic ischemia-reperfusion injury: time and percentage-related pathophysiological mechanisms

Ischemia and reperfusion (IR) injury remains one of the major problems in liver surgery and transplantation, which determines the viability of the hepatic tissue after resection and of the grafted organ. This review aims to elucidate the mechanisms involved in IR injury of the liver in rodent experimental studies and the preventative methods and pharmacologic agents that have been applied. Many time- and percentage-related liver IR injury rodent models have been used to examine the pathophysiological mechanisms and the parameters implicated with different morbidity, mortality, and pathology findings. The most preferred experimental rodent model of liver IR is the induction of 70% IR for 45 min, which is associated with almost 100% survival. In this model, plasma levels of several parameters such as alanine transaminase, aspartate aminotransferase, gamma-glutamyltransferase, endothelin-1, malonodialdehyde, tumor necrosis factor α, interleukin 1b, inducible nitric oxide synthase, and caspases are increased. The increase of caspases is associated with the initiation of hepatic cellular apoptosis. The main injuries observed 24 h after reperfusion are nuclear pyknosis, cytoplasmic hypereosinophilia, severe necrosis, and loss of intercellular borders. Both ischemic pre- and post-conditioning preventative methods and pharmacologic agents are successfully applied to alleviate the IR injuries. The selection of the time- and percentage-related liver IR injury rodent model and the potential preventative method should be related to the clinical question being answered.

Deficiency of interleukin-15 enhances susceptibility to acetaminophen-induced liver injury in mice

Hepatocytes have a direct necrotic role in acetaminophen (APAP)-induced liver injury (AILI), prolonged secondary inflammatory response through innate immune cells and cytokines also significantly contributes to APAP hepatotoxicity. Interleukin 15 (IL-15), a multifunction cytokine, regulates the adaptive immune system and influences development and function of innate immune cells. To better understand the role of IL-15 in liver injury, we treated wild-type (WT) and IL-15-knockout (Il15⁻/⁻) mice with a hepatotoxic dose of APAP to induce AILI and evaluated animal survival, liver damage, APAP metabolism in livers and the inflammatory response. Production of pro-inflammatory cytokines/chemokines was greater in Il15⁻/⁻ than WT mice. Subanalysis of hepatic infiltrated monocytes revealed greater neutrophil influx, along with greater hepatic induction of inducible nitric oxide synthase (iNOS), in Il15⁻/⁻ than WT mice. In addition, the level of hepatic hemeoxygenase 1 (HO-1) was partially suppressed in Il15⁻/⁻ mice, but not in WT mice. Interestingly, elimination of Kupffer cells and neutrophils did not alter the vulnerability to excess APAP in Il15⁻/⁻ mice. However, injection of galactosamine, a hepatic transcription inhibitor, significantly reduced the increased APAP sensitivity in Il15⁻/⁻ mice but had minor effect on WT mice. We demonstrated that deficiency of IL-15 increased mouse susceptibility to AILI. Moreover, Kupffer cell might affect APAP hepatotoxicity through IL-15.

Repercussões pulmonares após isquemia hepática parcial e reperfusão: modelo experimental

OBJETIVO: Descrever um modelo experimental de lesão de isquemia/reperfusão hepática com manifestações sistêmicas, representadas pelo envolvimento pulmonar, que possa ser utilizado por aqueles que pretendem compreender esse fenômeno. MÉTODOS: Ratos Wistar machos (200-250g) foram usados. Quatorze foram alocados em dois grupos, sendo G1 com oito submetidos somente à laparotomia e G2, seis à isquemia e reperfusão hepática. As funções hepática (aminotransferases séricas, respiração mitocondrial, histologia) e pulmonar (teste do azul de Evans) foram analisadas. RESULTADOS: houve diferença estatística significativa entre G1 e G2 ao se comparar valores de AST (24,3 ± 108 e 5406 ± 2263), ALT (88,5 ± 28,5 e 5169 ± 2690), razão de controle respiratório (3,41 ± 0,17 e 1,91 ± 0,55) e relação ADP/O (1,93 ± 0,03 e 1,45 ± 0,27), lesões histológicas (necrose, células inflamatórias, hemorragia, microesteatose) e teste do azul de Evans (194,31 ± 53 e 491,8 ± 141). CONCLUSÃO: O modelo mostrou-se útil para o estudo de lesão de isquemia/reperfusão hepática.

Effects of propofol and etomidate on hydrogen peroxide-induced oxidative damage in hepatocyte

BACKGROUND

The present investigation was undertaken to evaluate the protective effect of propofol and etomidate against hydrogen peroxide (H2O2) induced oxidative damage in human hepatic SNU761 cells by measuring lactate dehydrogenase (LDH).

METHODS

The cell line of human hepatocellular carcinoma was grown for 24 hours in dissociated cell culture. They were divided into eight groups: negative control (NC) group with no drug administration, positive control (PC) group with H2O2 250 micrometer and other groups pretreated with propofol (P; 1, 10, 50 micrometer) or etomidate (ET; 1, 10, 50 micrometer) followed H2O2 administration. After 7 hours, cell death was assessed by morphology under the light microscope and quantified by measuring the LDH in the culture media.

RESULTS

In the light microscopic findings, the intact cells were increased in all three propofol groups compared to group PC. H2O2-induced LDH production was also significantly suppressed in all three propofol groups compared to group PC (P < 0.001). There were no significant differences in the microscopic findings and LDH production between the etomidate groups and group PC.

CONCLUSIONS

These results suggest that the propofol has protective effect on the hepatocyte against H2O2-induced oxidative stress.

Activated protein C prevents hepatic ischaemia-reperfusion injury in rats

BACKGROUND

Hepatic ischaemia-reperfusion injury (IRI) is a serious complication of liver surgery, especially extended hepatectomy and liver transplantation. Activated protein C (APC), a potent anticoagulant serine protease, has been shown to have cell-protective properties by virtue of its anti-inflammatory and anti-apoptotic activities.

METHODS

The present study was designed to examine the cytoprotective effects of APC in a 60-min warm-IRI rat model.

RESULTS

Following a single intravenous injection of APC before reperfusion, APC exerted cytoprotective effects 4 h after reperfusion, as evidenced by: (i) decreased levels of transaminase and improved histological findings of IRI, (ii) reduced infiltration and activation of neutrophils, macrophages and T cells, (iii) reduced expression of tumour necrosis factor-alpha, (iv) reduced expression of P-selectin and intracellular adhesion molecule-1, (v) inhibited coagulation and attenuated sinusoidal endothelial cell injury, (vi) improved hepatic microcirculation and (vii) decreased transferase-mediated dUTP nick end-labelling-positive cells. These effects of APC were observed 4 h but not 24 h after reperfusion. However, multiple injections of APC after reperfusion significantly decreased the levels of transaminase and the activity of myeloperoxidase, and improved histological findings of IRI 24 h after reperfusion.

CONCLUSION

These results suggest that APC is a promising therapeutic option for hepatic warm-IRI; however, multiple injections of APC are necessary to maintain its cell-protective action over the long term.

Acute kidney injury leads to inflammation and functional changes in the brain

Although neurologic sequelae of acute kidney injury (AKI) are well described, the pathogenesis of acute uremic encephalopathy is poorly understood. This study examined the short-term effect of ischemic AKI on inflammatory and functional changes of the brain in mice by inducing bilateral renal ischemia for 60 min and studying the brains 24 h later. Compared with sham mice, mice with AKI had increased neuronal pyknosis and microgliosis in the brain. AKI also led to increased levels of the proinflammatory chemokines keratinocyte-derived chemoattractant and G-CSF in the cerebral cortex and hippocampus and increased expression of glial fibrillary acidic protein in astrocytes in the cortex and corpus callosum. In addition, extravasation of Evans blue dye into the brain suggested that the blood-brain barrier was disrupted in mice with AKI. Because liver failure also leads to encephalopathy, ischemic liver injury was induced in mice with normal renal function; neuronal pyknosis and glial fibrillary acidic protein expression were not increased, suggesting differential effects on the brain depending on the organ injured. For evaluation of the effects of AKI on brain function, locomotor activity was studied using an open field test. Mice subjected to renal ischemia or bilateral nephrectomy had moderate to severe declines in locomotor activity compared with sham-operated mice. These data demonstrate that severe ischemic AKI induces inflammation and functional changes in the brain. Targeting these pathways could reduce morbidity and mortality in critically ill patients with severe AKI.

Ischemia-Reperfusion Injury is More Severe in Older Versus Young Rat Livers

BACKGROUND

Hepatic warm ischemia during surgery remains a significant problem, particularly in organs with possible baseline dysfunction. The objective of this study was to investigate whether age influences the degree of warm ischemia-reperfusion injury in rat livers.

MATERIALS AND METHODS

The left and median lobes of young (3 months) and adult (9 months) male rats were exposed to 75 min of ischemia followed by reperfusion. Each age group was divided into two sub-groups. One sub-group was observed for 8 h, whereas the other was allowed to survive. Animals in the 8-h groups (young and adult) were sacrificed, and blood and tissue were taken to determine liver enzymes, neutrophil accumulation, and blood metabolic profiles and to examine the histology.

RESULTS

Hepatocellular injury was significantly greater in adult rats after 8 h of reperfusion, as determined by hepatic enzyme levels and histology. Liver enzyme levels were massively elevated in adult rats and were significantly higher compared with those of young rats. The degree of necrosis and neutrophil accumulation was significantly higher in adult rats. After 8 h of reperfusion, the metabolic profiling of the blood revealed elevated levels of creatine, creatinine, allantoin, and amino acids (tyrosine, methionine) in the adult rats. At 24 h of reperfusion, all adult rats died, in contrast to young rats, which all survived.

CONCLUSIONS

Aging in rats is associated with greater hepatocellular injury and poor survival rate after 75 min of warm hepatic ischemia.

Spatiotemporal expression of heme oxygenase-1 detected by in vivo bioluminescence after hepatic ischemia in HO-1/Luc mice

Upregulation of heme oxygenase-1 (HO-1) has been proposed as a critical mechanism protecting against cellular stress during liver transplantation, providing a potential target for new therapeutic interventions. We investigated the feasibility of in vivo bioluminescence imaging (BLI) to noninvasively quantify the spatiotemporal expression of HO-1 after warm hepatic ischemia in living animals. Luciferase activity was measured by BLI as an index of HO-1 transcription in transgenic reporter mice (Ho1-luc) at standardized time points after 60 minutes of warm hepatic ischemia. HO-1 mRNA levels were measured in postischemic livers of mice sacrificed at the same time points in separate experiments. Bioluminescent signals from postischemic liver lobes were first detected at 3 hours after reperfusion. Peak levels were reached at 9 hours, after which bioluminescent activity declined and returned to baseline values at 48 hours after reperfusion. Upregulation of HO-1 as detected by in vivo BLI was preceded by increased HO-1 mRNA expression and confirmed by enhanced immunohistochemical staining of hepatocytes. In conclusion, this study shows that in vivo BLI allows a sensitive assessment of HO-1 expression after hepatic ischemia in living animals. The capability of whole-body temporal imaging of HO-1 expression provides a valuable tool in the development of novel strategies to modulate HO-1 expression in liver transplantation.

Warm ischemia-induced alterations in oxidative and inflammatory proteins in hepatic Kupffer cells in rats

The aim of the study was to investigate the impact of ischemia/reperfusion injury on the proteome of Kupffer cells. Lean Zucker rats (n = 6 each group) were randomized to 75 min of warm ischemia or sham operation. After reperfusion for 8 h, Kupffer cells were isolated by enzymatic perfusion and density gradient centrifugation. Proteins were tryptically digested into peptides and differentially labeled with iTRAQ (isobaric tags for relative and absolute quantitation) reagent. After fractionation by cation exchange chromatography, peptides were identified by mass spectrometry (ESI-LC-MS/MS). Spectra were interrogated against the Swiss-Prot database and quantified using ProteinProspector. The results for heat shock protein 70 and myeloperoxidase were validated by ELISA. Quantitative information for more than 1559 proteins was obtained. In the ischemia group proteins involved in inflammation were significantly up-regulated. The ratio for calgranulin B in the ischemia/sham group was 1.81 +/- 0.97 (p < 0.0001), for complement C3 the ratio was 1.81 +/- 0.49 (p < 0.0001), and for myeloperoxidase the ratio was 1.30 +/- 0.32. Myeloperoxidase was only recently documented in Kupffer cells. The antioxidative proteins Cu,Zn-superoxide dismutase (1.34 +/- 0.19; p < 0.001) and catalase (1.23 +/- 0.43; p < 0.001) were also elevated. In conclusion, ischemia/reperfusion injury induces alterations in the Kupffer cell proteome. Isotope ratio mass spectrometry is a powerful tool to investigate these reactions. The ability to simultaneously monitor several pathways involved in reperfusion stress may result in important mechanistic insight and possibly new treatment options.

In vitro characterization of leukocyte mimetic for targeting therapeutics to the endothelium using two receptors

Selectins (E- and P-selectin) and other endothelial expressed leukocyte adhesion molecules (ELAMs) are potential targets for site-specific delivery of therapeutics to the vascular endothelium due to their specific and highly regulated expression in vascular disease. It was recently shown that degradable microspheres coated with antibodies against E-selectin or other ELAMs can target inflammation in vivo. However, targeting ELAMs alone cannot differentiate between normal and diseased state, as a basal level of these LAMs are expressed on endothelium in healthy tissues. Furthermore, leukocytes usually employ two separate adhesion molecules in parallel to home to diseased tissues, and we recently quantified the advantages of a two-receptor display for the targeting of leukocyte mimetics (Eniola AO, Willcox PJ, Hammer DA. Interplay between rolling and firm adhesion elucidated with a cell-free system engineered with two distinct receptor-ligand pairs. Biophys J 2003;85:2720-31). Here, we describe a leukocyte mimetic for targeting therapeutics to the vasculature in inflammatory diseases via two receptors, selectin and intercellular cell adhesion molecule-1 (ICAM-1), where biodegradable, polymer microspheres were co-functionalized with the selectin ligand, sialyl Lewis(X) (sLe(X)), and an antibody against ICAM-1, anti-ICAM-1 (aICAM-1). These two-receptor targeted particles, at given ratios of sLe(X)/aICAM-1, firmly adhere to substrate surface in flow only when both targeting ligands can interact with their respective receptors, mimicking the multi-step in vivo leukocyte adhesion in inflammation. Thus, we have faithfully recreated the specificity and extent of leukocyte adhesion in a platform that can allow for local delivery of therapeutics.

Gender differences in hepatic ischemic reperfusion injury in rats are associated with endothelial cell nitric oxide synthase-derived nitric oxide

AIM: This study was designed to examine the hypothesis that gender differences in I/R injury are associated with endothelial cell nitric oxide synthase (eNOS)-derived nitric oxide (NO).

METHODS: Wistar rats were randomized into seven experimental groups (12 animals per group). Except for the sham operated groups, all rats were subjected to total liver ischemia for 40 min followed by reperfusion. All experimental groups received different treatments 45 min before the laparotomy. For each group, half of the animals (six) were used to investigate the survival; blood samples and liver tissues were obtained in the remaining six animals after 3 h of reperfusion to assess serum NO, alanine aminotransferase (ALT) and TNF-α levels, liver tissue malondialdehyde (MDA) content, and severity of hepatic I/R injury.

RESULTS: Basal serum NO levels in female sham operated (FS) group were nearly 1.5-fold of male sham operated (MS) group (66.7±11.0 μmol/L vs 45.3±10.1 μmol/L, P<0.01). Although serum NO levels decreased significantly after hepatic I/R (P<0.01, vs sham operated groups), they were still significantly higher in female rat (F) group than in male rat (M) group (47.8±8.6 μmol/L vs 23.8±4.7 μmol/L, P<0.01). Serum ALT and TNF-α levels, and liver tissue MDA content were significantly lower in F group than in M group (370.5±46.4 U/L, 0.99±0.11 μg/L and 0.57±0.10 μmol/g vs 668.7±78.7 U/L, 1.71±0.18 μg/L and 0.86±0.11 μmol/g, respectively, P<0.01). I/R induced significant injury to the liver both in M and F groups (P<0.01 vs sham operated groups). But the degree of hepatocyte injury was significantly milder in F group than in M group (P<0.05 and P<0.01). The median survival time was six days in F group and one day in M group. The overall survival rate was significantly higher in F group than in M group (P<0.05). When compared with male rats pretreated with saline (M group), pretreatment of male rats with 17-β-estradiol (E₂) (M+E₂ group) significantly increased serum NO levels and significantly decreased serum ALT and TNF-α levels, and liver tissue MDA content after I/R (P<0.01). The degree of hepatocyte injury was significantly decreased and the overall survival rate was significantly improved in M+E₂ group than in M group (P<0.01 and P<0.05). The NOS inhibitor N^w-nitro-L-arginine methyl ester (L-NAME) treatment could completely abolish the protective effects of estrogen in both male and female rats.

CONCLUSION: The protective effects afforded to female rats subjected to hepatic I/R are associated with eNOS-derived NO.

In vivo suppressive effect of nuclear factor-κB inhibitor on neutrophilic inflammation of grafts after orthotopic liver transplantation in rats

AIM: To investigate the effect of pyrrolidine dithiocarbamate (PDTC), a novel nuclear factor-κB (NF-κB) inhibitor, on expression of multiple inflammatory mediators and neutrophilic inflammation of cold preserved grafts after rat liver transplantation and its significance.

METHODS: Orthotopic liver transplantation (OLT) was performed after 24 h of cold storage using University of Wisconsin solution with varied concentrations of PDTC. We determined the time course of NF-κB activation and expression of multiple inflammatory signals, such as tumor necrosis factor-α (TNF-α), cytokine-inducible neutrophil chemoattractant (CINC), and intercellular adhesion molecule-1 (ICAM-1) by ELISA methods. Serum alanine aminotransferase (ALT), intrahepatic myeloperoxidase (MPO)/WBC (a measure of neutrophil accumulation) and Mac-1 expression (a measure of circulating neutrophil activity) were also evaluated.

RESULTS: PDTC decreased NF-κB activation induced by prolonged cold preservation in a dose dependent manner (from 20 mmol/L to 60 mmol/L), diminished TNF-α, CINC, ICAM-1 proteins in the grafts, and reduced the expression of increases in plasma TNF-α levels induced by prolonged cold preservation. Neutrophilic inflammation of the graft was significantly suppressed after preservation with PDTC (P < 0.05). The total neutrophil accumulation in PDTC (40 mmol/L) group (7.04 ± 0.97) was markedly reduced compared to control group (14.07 ± 1.31) (P < 0.05). Mac-1 expression was significantly reduced in PDTC (40 mmol/L) group (181 ± 11.3%) compared with the control group (281 ± 13.2%) (P < 0.05) at 6 h after reperfusion. Furthermore, PDTC inhibited the increased serum ALT levels after liver transplantation.

CONCLUSION: PDTC can inhibit B NF-κB activation and expression of the inflammatory mediators, which are associated with improved graft viability via inhibiting intrahepatic neutrophilic inflammation. Our study suggests that a therapeutic strategy directed at inhibition of NF-κB activation in the transplanted liver might be effective in reducing intrahepatic neutrophilic inflammation, and would be beneficial to cold preserved grafts.

Mechanism of delayed resuscitation in promoting loss of intestinal mucous membrane barrier function after rats scalding

AIM: To investigate the effect of delayed resuscitation on intestinal mucous membrane barrier function and its relationship with neutrophil infiltration of local tissue after rats scalding.

METHODS: Rats with 40% full-thickness scald burn were randomly divided into two group: immediately resuscitation group (IR group) and delayed resuscitation group (DR group). The content of D-lactate, diamine oxidase (DAO) in plasma and myeloperoxidase (MPO), superoxide dismutase (SOD) and malondialdehyde (MDA) in intestinal mucous tissue were determined at different time points after burn. Apoptosis of mucous epithelial cells were identified by terminal deoxynucletidyl-transferase mediated dUTP-biotin nick end labeling (TUNEL) histochemical methods.

RESULTS: The contents of D-lactate in plasma in DR group were much higher than those of IR group (P < 0.01 or 0.05), MPO activity in intestinal mucous tissue of DR group were dramatically increased accompanying with decrease of SOD activity and increase of MDA contents. Herein, we found a close correlation between the contents of D-lactate and activity of MPO. Meanwhile, we also found an increase of the activity of DAO in plasma and number of TUNEL positive staining epithelial cells in DR group.

CONCLUSION: Delayed resuscitation promotes the loss of intestinal mucous membrane barrier function due to the increase of both cell necrosis and cell apoptosis, which may be related to increased neutrophil infiltration in local tissue.