Low-dose TNF-alpha protects against hepatic ischemia-reperfusion injury in mice: implications for preconditioning

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Dual Role of TNF and LTα in Carcinogenesis as Implicated by Studies in Mice

Tumor necrosis factor (TNF) and lymphotoxin alpha (LTα) are two related cytokines from the TNF superfamily, yet they mediate their functions in soluble and membrane-bound forms via overlapping, as well as distinct, molecular pathways. Their genes are encoded within the major histocompatibility complex class III cluster in close proximity to each other. TNF is involved in host defense, maintenance of lymphoid tissues, regulation of cell death and survival, and antiviral and antibacterial responses. LTα, known for some time as TNFβ, has pleiotropic functions including control of lymphoid tissue development and homeostasis cross talk between lymphocytes and their environment, as well as lymphoid tissue neogenesis with formation of lymphoid follicles outside the lymph nodes. Along with their homeostatic functions, deregulation of these two cytokines may be associated with initiation and progression of chronic inflammation, autoimmunity, and tumorigenesis. In this review, we summarize the current state of knowledge concerning TNF/LTα functions in tumor promotion and suppression, with the focus on the recently uncovered significance of host-microbiota interplay in cancer development that may explain some earlier controversial results.

Recent advances in the design of implantable insulin secreting heterocellular islet organoids

Islet transplantation has proved one of the most remarkable transmissions from an experimental curiosity into a routine clinical application for the treatment of type I diabetes (T1D). Current efforts for taking this technology one-step further are now focusing on overcoming islet donor shortage, engraftment, prolonged islet availability, post-transplant vascularization, and coming up with new strategies to eliminate lifelong immunosuppression. To this end, insulin secreting 3D cell clusters composed of different types of cells, also referred as heterocellular islet organoids, spheroids, or pseudoislets, have been engineered to overcome the challenges encountered by the current islet transplantation protocols. β-cells or native islets are accompanied by helper cells, also referred to as accessory cells, to generate a cell cluster that is not only able to accurately secrete insulin in response to glucose, but also superior in terms of other key features (e.g. maintaining a vasculature, longer durability in vivo and not necessitating immunosuppression after transplantation). Over the past decade, numerous 3D cell culture techniques have been integrated to create an engineered heterocellular islet organoid that addresses current obstacles. Here, we first discuss the different cell types used to prepare heterocellular organoids for islet transplantation and their contribution to the organoids design. We then introduce various cell culture techniques that are incorporated to prepare a fully functional and insulin secreting organoids with select features. Finally, we discuss the challenges and present a future outlook for improving clinical outcomes of islet transplantation.

Hepatogenic Potential and Liver Regeneration Effect of Human Liver-derived Mesenchymal-Like Stem Cells

Human liver-derived stem cells (hLD-SCs) have been proposed as a possible resource for stem cell therapy in patients with irreversible liver diseases. However, it is not known whether liver resident hLD-SCs can differentiate toward a hepatic fate better than mesenchymal stem cells (MSCs) obtained from other origins. In this study, we compared the differentiation ability and regeneration potency of hLD-SCs with those of human umbilical cord matrix-derived stem cells (hUC-MSCs) by inducing hepatic differentiation. Undifferentiated hLD-SCs expressed relatively high levels of endoderm-related markers (GATA4 and FOXA1). During directed hepatic differentiation supported by two small molecules (Fasudil and 5-azacytidine), hLD-SCs presented more advanced mitochondrial respiration compared to hUC-MSCs. Moreover, hLD-SCs featured higher numbers of hepatic progenitor cell markers on day 14 of differentiation (CPM and CD133) and matured into hepatocyte-like cells by day 7 through 21 with increased hepatocyte markers (ALB, HNF4A, and AFP). During in vivo cell transplantation, hLD-SCs migrated into the liver of ischemia-reperfusion injury-induced mice within 2 h and relieved liver injury. In the thioacetamide (TAA)-induced liver injury mouse model, transplanted hLD-SCs trafficked into the liver and spontaneously matured into hepatocyte-like cells within 14 days. These results collectively suggest that hLD-SCs hold greater hepatogenic potential, and hepatic differentiation-induced hLD-SCs may be a promising source of stem cells for liver regeneration.

Effect of Different Exercise Loads on Testicular Oxidative Stress and Reproductive Function in Obese Male Mice

This study is aimed at investigating the effect of different exercise loads on the reproductive function of obese male mice and the underlying mechanisms. Male mice with high-fat diet-induced obesity were divided into obesity control (OC), obesity moderate-load exercise (OME), and obesity high-load exercise (OHE) groups. The OME and OHE groups were subjected to swimming exercise 5 days per week over a duration of 8 weeks, with the exercise load progressively increased to 2 h per day in the OME group and 2 h twice per day in the OHE group. In the OC group mice without exercise regimen, we observed a decrease in mRNA expression of antioxidant enzymes, increase in free radical products, upregulation of mRNA and protein expression of nuclear factor-κB and proinflammatory cytokines, inhibition of mRNA and protein expression of testosterone synthases, decrease in the serum testosterone level and sperm quality, and increase in sperm apoptosis. Although both moderate-load exercise and high-load exercise reduced body fat, only moderate-load exercise effectively alleviated obesity-induced oxidative stress, downregulated the expression of nuclear factor-κB and proinflammatory cytokines, and reversed the decrease in mRNA and protein expression of testosterone synthases, serum testosterone level, and sperm quality. These changes were not observed in the OHE group mice. Obesity-induced testicular oxidative stress and inflammatory response decreased testosterone synthesis and sperm quality. Moderate-load exercise alleviated the negative effect of obesity on male reproductive function by decreasing testicular oxidative stress and inflammatory responses. Although high-load exercise effectively reduced body fat, its effects on alleviating oxidative stress and improving male reproductive function were limited.

Downregulation of DLGAP1-Antisense RNA 1 Alleviates Vascular Endothelial Cell Injury Via Activation of the Phosphoinositide 3-kinase/Akt Pathway Results from an Acute Limb Ischemia Rat Model

OBJECTIVE

This study aimed to investigate the effect of long non-coding RNA (lncRNA) DLGAP1 antisense RNA 1 (DLGAP1-AS1) on vascular endothelial cell (VEC) injury via the phosphoinositide 3-kinase (PI3K)/Akt pathway in rat models of acute lower limb ischaemia-reperfusion (I/R).

METHODS

Differentially expressed lncRNAs related to I/R were screened using the gene expression omnibus database. Acute lower limb I/R models were induced in male Wistar rats, in which the regulatory mechanisms of DLGAP1-AS1 silencing were analysed after the treatment of small interfering RNA (siRNA) against DLGAP1-AS1 or an inhibitor of the PI3K/Akt pathway. The relationship between DLGAP1-AS1 and the PI3K/Akt pathway was analysed. The levels of tumour necrosis factor (TNF)-α and vascular cell adhesion molecule-1 (VCAM-1), as well as malondialdehyde (MDA) concentration and creatine kinase (CK) activity, were measured. The number of circulating endothelial cells (CECs) and apoptosis of VECs were identified.

RESULTS

Microarray based analysis indicated that DLGAP1-AS1 was highly expressed in I/R, which was further confirmed by detection of expression in rat models of acute lower limb I/R. Notably, the treatment of siRNA against DLGAP1-AS1 led to the activation of the PI3K/Akt pathway. In response to siRNA against DLGAP1-AS1, the levels of TNF-α and VCAM-1 were decreased, and MDA concentration and CK activity was downregulated. Reduced CEC numbers and suppressed VEC apoptosis were also observed.

CONCLUSION

DLGAP1-AS1 silencing could further suppress the oxidative stress, exert an anti-apoptosis effect, and reduce inflammatory reaction, whereby VEC injury is alleviated by activation of the PI3K/Akt pathway in rats with acute lower limb I/R.

Mitogen Activated Protein Kinases in Steatotic and Non-Steatotic Livers Submitted to Ischemia-Reperfusion

We analyzed the participation of mitogen-activated protein kinases (MAPKs), namely p38, JNK and ERK 1/2 in steatotic and non-steatotic livers undergoing ischemia-reperfusion (I-R), an unresolved problem in clinical practice. Hepatic steatosis is a major risk factor in liver surgery because these types of liver tolerate poorly to I-R injury. Also, a further increase in the prevalence of steatosis in liver surgery is to be expected. The possible therapies based on MAPK regulation aimed at reducing hepatic I-R injury will be discussed. Moreover, we reviewed the relevance of MAPK in ischemic preconditioning (PC) and evaluated whether MAPK regulators could mimic its benefits. Clinical studies indicated that this surgical strategy could be appropriate for liver surgery in both steatotic and non-steatotic livers undergoing I-R. The data presented herein suggest that further investigations are required to elucidate more extensively the mechanisms by which these kinases work in hepatic I-R. Also, further researchers based in the development of drugs that regulate MAPKs selectively are required before such approaches can be translated into clinical liver surgery.

Deletion of tumour necrosis factor α receptor 1 elicits an increased TH17 immune response in the chronically inflamed liver

Tumour necrosis factor α receptor 1 (TNFR1) activation is known to induce cell death, inflammation, and fibrosis but also hepatocyte survival and regeneration. The multidrug resistance protein 2 knockout (Mdr2-/) mice are a model for chronic hepatitis and inflammation-associated hepatocellular carcinoma (HCC) development. This study analysed how the absence of TNFR1 mediated signalling shapes cytokine and chemokine production, immune cell recruitment and ultimately influences liver injury and fibrotic tissue remodelling in the Mdr2-/- mouse model. We show that Tnfr1-/-/Mdr2-/- mice displayed increased plasma levels of ALT, ALP, and bilirubin as well as a significantly higher collagen content, and markers of fibrosis than Mdr2-/- mice. The expression profile of inflammatory cytokines (Il1b, Il23, Tgfb1, Il17a), chemokines (Ccl2, Cxcl1, Cx3cl1) and chemokine receptors (Ccr6, Cxcr6, Cx3cr1) in livers of Tnfr1-/-/Mdr2-/- mice indicated TH17 cell infiltration. Flow cytometric analysis confirmed that the aggravated tissue injury in Tnfr1-/-/Mdr2-/- mice strongly correlated with increased hepatic recruitment of TH17 cells and enhanced IL-17 production in the injured liver. Moreover, we observed increased hepatic activation of RIPK3 in Tnfr1-/-/Mdr2-/- mice, which was not related to necroptotic cell death. Rather, frequencies of infiltrating CX3CR1+ monocytes increased over time in livers of Tnfr1-/-/Mdr2-/- mice, which expressed significantly higher levels of Ripk3 than those of Mdr2-/- mice. Overall, we conclude that the absence of TNFR1-mediated signalling did not improve the pathological phenotype of Mdr2-/- mice. It instead caused enhanced infiltration of TH17 cells and CX3CR1+ monocytes into the injured tissue, which was accompanied by increased RIPK3 activation and IL-17 production.

Coculture With Ischemia/Reperfusion-Preconditioned Hepatocytes Improves Islet Function and Survival

In clinical islet transplantation, hepatic ischemia and insufficient neovascularization of transplanted islets are barriers to islet survival and function. However, hepatocytes have a potency to protect themselves against ischemia. We hypothesized that ischemia/reperfusion preconditioning (IRP) of hepatocytes might beneficially affect islet cells in a coculture system. Primary islets were cocultured with primary hepatocytes, and hepatocyte IRP was conducted by subjecting cells to hypoxic conditions for single 15-minute/30-minute hypoxia, or 2 tandem 15-minute/30-minute hypoxic treatments (hypoxic-normoxic-hypoxic). We show that gene expression levels of insulin-like growth factor 1 (IGF-1), hepatocyte growth factor (HGF), transforming growth factor-α (TGF-α), and TGF-β1 in hepatocytes were increased by IRP. IRP hepatocytes secreted hepatocyte growth factor and insulin-like growth factor-1. Coculture of islets with IRP hepatocytes enhanced islet insulin secretion in glucose challenge test and expression of the survival-related gene Bcl-2 and the regenerating gene-1α (Reg-1α). Islets cocultured with the 30-minute double-IRP hepatocytes displayed significantly higher viability in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and terminal deoxynucleotidyl transferase dUTP nick end labeling stain compared with that of islets subjected to 30 minutes of hypoxia. These results suggest that islet coculture with IRP hepatocytes can improve islet survival and insulin secretion.

Intermittent Ischemic Preconditioning Protects Against Hepatic Ischemia-Reperfusion Injury and Extensive Hepatectomy in Steatotic Rat Liver

BACKGROUND

Hepatic steatosis causes severe liver damage and has deleterious effects when associated with ischemia-reperfusion mechanisms. Ischemic preconditioning (IPC) protects lean liver against prolonged ischemia by improving micro-circulation and reducing lipid peroxidation. We investigated the effect of intermittent IPC on liver ischemia-reperfusion injury (IRI) and extensive hepatectomy in severe hepatic steatosis.

METHODS

Severe hepatic steatosis was performed by 12-14 weeks of choline-free diet in 108 Wistar rats. We induced 30-minute ischemia-reperfusion manipulations and extensive hepatectomy with or without prior IPC in steatotic livers and after 6 and 24 hours of reperfusion blood transaminases, and IL6, TNFα, NO and Lactate in blood and liver tissue were measured.

RESULTS

Steatotic rats subjected to hepatic ischemia-reperfusion alone after extensive hepatectomy, showed severe liver damage with significantly increased values of AST, ALT, TNFα and Lactate and significantly reduced IL6 and NO, while no one rat survived for more than 29 hours. On the contrary, steatotic rats subjected to intermittent IPC, 24 hours before ischemia-reperfusion, presented increased 30-day survival (67%), lower values of AST, ALT, TNFα and Lactate, and increased IL6 and NO levels. Simple and intermittent IPC manipulations, 1 hour before the IRI and extended hepatectomy, did not prolong survival more than 57 and 98 hours, respectively. Simple IPC, 24 hours before IRI and extended hepatectomy had the lowest possible survival (16.7%).

CONCLUSIONS

Hepatic steatosis and IRI after major liver surgery largely affect morbidity and mortality. Intermittent IPC, 24 hours before IRI and extensive hepatectomy, presents higher 30-day survival and improved liver function parameters.

Moderate (2%, v/v) Ethanol Feeding Alters Hepatic Wound Healing after Acute Carbon Tetrachloride Exposure in Mice

Wound healing consists of three overlapping phases: inflammation, proliferation, and matrix synthesis and remodeling. Prolonged alcohol abuse can cause liver fibrosis due to deregulated matrix remodeling. Previous studies demonstrated that moderate ethanol feeding enhances liver fibrogenic markers and frank fibrosis independent of differences in CCl₄-induced liver injury. Our objective was to determine whether or not other phases of the hepatic wound healing response were affected by moderate ethanol after CCl₄ exposure. Mice were fed moderate ethanol (2% v/v) for two days and then were exposed to CCl₄ and euthanized 24–96 h later. Liver injury was not different between pair- and ethanol-fed mice; however, removal of necrotic tissue was delayed after CCl₄-induced liver injury in ethanol-fed mice. Inflammation, measured by TNFα mRNA and protein and hepatic Ly6c transcript accumulation, was reduced and associated with enhanced hepatocyte apoptosis after ethanol feeding. Hepatocytes entered the cell cycle equivalently in pair- and ethanol-fed mice after CCl₄ exposure, but hepatocyte proliferation was prolonged in livers from ethanol-fed mice. CCl₄-induced hepatic stellate cell activation was increased and matrix remodeling was prolonged in ethanol-fed mice compared to controls. Taken together, moderate ethanol affected each phase of the wound healing response to CCl₄. These data highlight previously unknown effects of moderate ethanol exposure on hepatic wound healing after acute hepatotoxicant exposure.

Paeoniflorin attenuates hepatic ischemia/reperfusion injury via anti-oxidative, anti-inflammatory and anti-apoptotic pathways

During liver surgery, hepatic blood flow needs to be blocked in order to reduce bleeding, which inevitably results in hepatic ischemia/reperfusion injury (HI/R). Paeoniflorin (PF) is the main active ingredient of the traditional Chinese herbal medicine peony, which has been shown to exert anti-oxidative and anti-apoptotic properties. In the present study, a mouse model of HI/R was generated by clamping the hepatoportal vein, hepatic artery, and hepatic duct of BALB/c mice with a vascular clamp for 30 min, followed by reperfusion for 6 h under anesthesia. Six mice in the three PF treatment groups (5, 10 and 20 mg/kg) were then injected with PF, via the tail vein. A sham group, consisting of six mice that did not undergo the procedure, and a vehicle group, consisting of 6 mice that underwent the procedure but subsequently received injections of physiological saline only, were used as controls. Liver injury was indicated by serum levels of the enzymes alanine transaminase (ALT) and aspartate transaminase (AST). The activities of oxidative stress biomarkers, including superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GSH-PX) and malondialdehyde (MDA), were also measured. Furthermore, the activity of caspase-3 was analyzed in hepatic tissue using a commercial kit. Treatment with PF significantly attenuated HI/R injury histologically, as compared with the vehicle group. In addition, significant reductions in the serum levels of ALT and AST were observed in the PF-treated ischemic mice. Furthermore, treatment with PF enhanced the activities of hepatic tissue SOD, GSH and GSH-PX, but decreased the MDA content. Treatment of ischemic mice with PF markedly reduced the expression levels of inflammatory mediators, including nuclear factor-κB, tumor necrosis factor-α, interleukin (IL)-6, and IL-1β, and decreased the HI/R injury-induced expression of caspase-3. The results of the present study suggest that PF attenuates the HI/R injury of mice via anti-oxidative, anti-inflammatory and anti-apoptotic activities.

Isolation and Expansion of Hepatic Stem-like Cells from a Healthy Rat Liver and their Efficient Hepatic Differentiation of under Well-defined Vivo Hepatic like Microenvironment in a Multiwell Bioreactor

BACKGROUND

Currently, undifferentiated cells are found in all tissue and term as local stem cells which are quiescent in nature and less in number under normal healthy conditions but activate upon injury and repair the tissue or organs via automated activating mechanism. Due to very scanty presence of local resident somatic local stem cells in healthy organs, isolation and expansion of these adult stems is an immense challenge for medical research and cell based therapy. Particularly organ like liver, there is an ongoing controversy about existence of liver stem cells.

METHODS

Herein, Hepatic stem cells population was identified during culture of primary hepatocyte cells upon immediate isolation of primary hepatocyte cells. These liver stem cells has been expanded extensively and differentiated into primary hepatocytes under defined culture conditions in a nanostructured self assembling peptides modular bioreactor that mimic the state of art of liver microenvironment and compared with Matrigel as a positive control. Nanostructured self assembling peptides were used a defined extracellular matrix and Matrigel was used for undefined extracellular matrix. Proliferation of hepatic stem cells was investigated by two strategies. First strategy is to provide high concentration of hepatocyte growth factor (HGF) and second strategy is to evaluate the role of recombinant human erythropoietin (rHuEPO) in presence of trauma/ischemia cytokines (IL-6, TNF-α). Expansion to hepatic differentiation is observed by morphological analysis and was evaluated for the expression of hepatocyte-specific genes using RT-PCR and biochemical methods.

RESULTS

Hepatocyte-specific genes are well expressed at final stage (day 21) of differentiation period. The differentiated hepatocytes exhibited functional hepatic characteristics such as albumin secretion, urea secretion and cytochrome P450 expression. Additionally, immunofluorescence analysis revealed that hepatic stem cells derived hepatocytes exhibited mature hepatocyte markers (albumin, CK-19, CPY3A1, alpha 1-antitrypsin). Expansion and hepatic differentiation was efficiently in nanostructured self assembling peptides without such batch to batch variation while there was much variation in Matrigel coated bioreactor. In conclusion, the results of the study suggest that the nanostructured self assembling peptides coated bioreactor supports expansion as well as hepatic differentiation of liver stem cells which is superior than Matrigel.

CONCLUSION

This defined microenvironment conditions in bioreactor module can be useful for research involving bioartificial liver system, stem cell research and engineered liver tissue which could contribute to regenerative cell therapies or drug discovery and development.

The protection mechanism of proline from D-galactosamine hepatitis involves the early activation of ROS-eliminating pathway in the liver

The oral pre-administration of proline, one on the non-essential amino acids, has been shown to effectively protect the liver from D-galactosamine (GalN)-induced liver injury and dramatically improve the survival rate. In the previous study, we reported that protective effect of proline involves the early activation of IL-6/STAT-3 pathway, an anti-inflammatory and regenerative signaling in the liver. Reactive oxygen species (ROS) are mediator of cellular injury and play an important role in hepatic damage during GalN-induced hepatitis. The aim of this study is to investigate the effect of proline on ROS-eliminating system. The activities of major ROS-detoxifying enzymes, i.e., glutathione peroxidase (GP), glutathione reductase (GR), catalase, and the level of glutathione in the liver were determined. Catalase activity was significantly upregulated in proline group from 0 to 3 h after GalN-injection, although GP and GR were downregulated during this period, compared with control group. From 6 to 12 h, the level of reduced glutathione (GSH) was significantly higher and the ratio of GSH/oxidized glutathione (GSSG) tended to be higher in proline group. Consistently with this, at 6 h, the GR activity in the proline group was significantly higher, followed with the higher tendency of GP activity at 12 h. Catalase activity was also significantly higher at 12 h. Taken together, catalase was activated at the beginning, followed with the significant activation of glutathione redox system around 6 to 12 h in proline group. These results suggest that the elimination of ROS in the liver was accelerated in proline group compared with control group at the very early stage of GalN-induced hepatitis.

Etanercept blocks inflammatory responses orchestrated by TNF-α to promote transplanted cell engraftment and proliferation in rat liver

Engraftment of transplanted cells is critical for liver-directed cell therapy, but most transplanted cells are rapidly cleared from liver sinusoids by proinflammatory cytokines/chemokines/receptors after activation of neutrophils or Kupffer cells (KCs). To define whether tumor necrosis factor alpha (TNF-α) served roles in cell-transplantation-induced hepatic inflammation, we used the TNF-α antagonist, etanercept (ETN), for studies in syngeneic rat hepatocyte transplantation systems. After cell transplantation, multiple cytokines/chemokines/receptors were overexpressed, whereas ETN before cell transplantation essentially normalized these responses. Moreover, ETN down-regulated cell-transplantation-induced intrahepatic release of secretory cytokines, such as high-mobility group box 1. These effects of ETN decreased cell-transplantation-induced activation of neutrophils, but not of KCs. Transplanted cell engraftment improved by several-fold in ETN-treated animals. These gains in cell engraftment were repeatedly realized after pretreatment of animals with ETN before multiple cell transplantation sessions. Transplanted cell numbers did not change over time, indicating absence of cell proliferation after ETN alone. By contrast, in animals preconditioned with retrorsine and partial hepatectomy, cell transplantation after ETN pretreatment significantly accelerated liver repopulation, compared to control rats.

CONCLUSION

TNF-α plays a major role in orchestrating cell-transplantation-induced inflammation through regulation of multiple cytokines/chemokines/receptor expression. Because TNF-α antagonism by ETN decreased transplanted cell clearance, improved cell engraftment, and accelerated liver repopulation, this pharmacological approach to control hepatic inflammation will help optimize clinical strategies for liver cell therapy.

Iron-induced oxidative rat liver injury after non-heart-beating warm ischemia is mediated by tumor necrosis factor α and prevented by deferoxamine

This study investigated iron-induced injury after warm ischemia in a non-heart-beating (NHB) rat liver model and the effects of deferoxamine (DFO). Livers from heart-beating (HB) rats or rats that were NHB for 60 minutes were stored in University of Wisconsin solution for 5 hours at 4°C [cold storage (CS)] and then were subjected to 2 hours of machine reperfusion (MRP) at 37°C. Three NHB groups were compared: (1) no DFO, (2) DFO 30 minutes before cardiac arrest and during CS and MRP, and (3) DFO during CS and MRP. Aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) levels in the NHB perfusate were significantly elevated (P < 0.01) in comparison with levels in HB controls after CS and MRP. After CS, the levels of iron and tumor necrosis factor α (TNF-α) were 0.077 ± 0.007 μmol/g and 151 ± 26 pg/g, respectively, in the NHB group and 0.022 ± 0.004 μmol/g and 17 ± 7 pg/g, respectively, in the HB group (P < 0.01). After MRP, LDH significantly correlated with iron (R(2)  = 0.81, P < 0.01). The DFO pretreatment of NHB donors decreased AST (7.3 ± 0.8 versus 4.0 ± 0.5 U/g of liver, P < 0.05) and LDH (42.5 ± 4.1 versus 20.4 ± 2.5 U/g of liver, P < 0.05) with 2 hours of MRP and increased bile flow during MRP (142 ± 34 versus 240 ± 18 μL/g, P < 0.05). It also reduced the levels of iron (0.077 ± 0.007 versus 0.050 ± 0.008 μmol/g, P < 0.05) and TNF-α (151 ± 26 versus 51 ± 13 pg/g, P < 0.05) after CS and the levels of lipid peroxidation products F2-isoprostane (149 ± 11 versus 99 ± 10 ng/g, P < 0.05) and malondialdehyde (1.58 ± 0.1 versus 1.14 ± 0.08 μmol/g, P < 0.05) after MRP. In conclusion, iron-initiated oxidative stress is likely involved in NHB donor liver injury, and importantly, DFO pretreatment reduces liver damage.

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.

Study of hepatocellular function in the murine model following hepatic artery selective clamping

PURPOSE

To investigate the impact of selective hepatic artery clamping (SHAC) in hepatocellular function.

METHODS

Three groups of Wistar male rats were subjected to SHAC ischemia period of 60min: Group A continuous SHAC were subjected to SHAC ischemia period of 60min, Group B intermittent SHAC of 30min with 5min of reperfusion and Group C intermittent SHAC of 15min with 5min of reperfusion. Animals without SHAC were included-Group D. To evaluate hepatocellular function blood markers and hepatic extraction function (HEF) using 99mTc-mebrofenin were performed before and after surgery. Flow cytometry was used to analyze oxidative stress and cell viability.

RESULTS

A mortality rate of 7.6% in Group A was observed. HEF maintained normal values between the groups. Flow cytometry demonstrated no significant differences between the groups in viability, type of cell death as well as in the production of reactive oxygen species.

CONCLUSIONS

The selective hepatic artery clamping compared to other clamping techniques results on increased cell viability and decreased hepatocyte death. The SHAC is a potential alternative to decrease per-operative bleeding while maintaining hepatocellular function.

Interleukin-6 and C-reactive protein are overexpressed in the liver of perinatal deaths diagnosed with fetal inflammatory response syndrome

Anatomopathologic studies have failed to define the fetal inflammatory response syndrome (FIRS) as a cause of fetal death. Here, liver fragments of perinatal autopsies were collected at a university hospital from 1990 to 2009 and classified according to the cause of death, perinatal stress, and gestational age (GA) of the fetus. IL-6, TNF-α, and C-reactive protein (CRP) expression were immunostained, respectively, with primary antibody. Cases with congenital malformation, ascending infection, and perinatal anoxia showed increased IL-6, CRP, and TNF-α, respectively. Prematures presented higher expression of IL-6 whereas term births showed higher expression of CRP. Cases classified as acute stress presented higher expression of IL-6 and TNF-α and cases with chronic stress presented higher expression of CRP. GA correlated negatively with IL-6 and positively with CRP and TNF-α. Body weight correlated negatively with IL-6 and positively with CRP and TNF-α. Despite the diagnosis of FIRS being clinical and based on serum parameters, the findings in the current study allow the inference of FIRS diagnosis in the autopsied infants, based on an in situ liver analysis of these markers.

Ischemic preconditioning improves liver tolerance to congestion-reperfusion injury in mice

BACKGROUND

Congestion-reperfusion injury (CRI) is a common complication after living donor liver transplantation, which has not been fully understood. It causes more severe inflammatory response as compared with ischemia-reperfusion injury (IRI). Ischemic preconditioning (IPC) has been endowed with powerful protective properties toward IRI. This study aimed to investigate whether IPC also has a protective effect against CRI and potential underlying mechanisms.

MATERIALS AND METHODS

Mice were randomly divided into sham operation, CRI, IPC-CRI, and congestion precondition (CPC-CRI) group. The hepatic vein of the left anterior hepatic lobe was occluded for 75 min followed by reperfusion in the CRI group. The blood inflow was previously clamped for 10 min followed by 10 min of reperfusion just before occluding the hepatic vein in the IPC-CRI group. To imitating IPC in the CPC-CRI group, 10 min of congestion followed by 10 min of reperfusion just before CRI was performed. The animals were sacrificed at 2, 6, 24, 48 h, and 7 d after reperfusion. The blood and liver samples were collected for hepatic function assay, histology, terminal deoxynucleotidyl transferase dUTP nick end labeling, myeloperoxidase, and real-time polymerase chain reaction analysis.

RESULTS

Mice in the CRI, IPC-CRI, and CPC-CRI group demonstrated elevated liver enzymes, histologic damage, cellular apoptosis, and inflammatory response compared with those in the sham operation group. Compared with the CRI group, mice in the IPC-CRI group expressed lower alanine transaminase activities (2 h: 839.2 ± 132.5 versus 384.2 ± 94.8, P < 0.01; and 6 h: 680 ± 142.4 versus 342.3 ± 99.7, P < 0.01) and lower myeloperoxidase levels (2 h: 7.1 ± 4.0 U/g versus 3.8 ± 1.6 U/g, P < 0.05; and 6 h: 8.1 ± 1.3 U/g versus 5.2 ± 3.0 U/g, P < 0.05). However, the alanine transaminase level in the CPC-CRI group was notably higher at 2 h (839.2 ± 132.5 versus 1087.5 ± 192.5, P < 0.05). Livers from mice in the IPC-CRI group showed better tissue integrity, diminished hepatocellular injury, and apoptosis at 2 and 6 h. The messenger RNA transcriptions of interleukin 1 and interleukin 6 were significantly lower after 2-24 h of reperfusion, whereas tumor necrosis factor α and monocyte chemoattractant protein 1 were significantly lower after 24 h of reperfusion in the IPC-CRI group.

CONCLUSIONS

IPC can significantly improve liver tolerance to CRI by attenuating neutrophil infiltration, proinflammatory cytokine formation, and hepatocytes apoptosis. This pretreatment strategy holds greater prospect of being translated into clinical use in living donor liver transplantation.

Inhibition of tumor necrosis factor alpha reduces the outgrowth of hepatic micrometastasis of colorectal tumors in a mouse model of liver ischemia-reperfusion injury

Background

Patients with colorectal cancer (CRC) often develop liver metastases, in which case surgery is considered the only potentially curative treatment option. However, liver surgery is associated with a risk of ischemia-reperfusion (IR) injury, which is thought to promote the growth of colorectal liver metastases. The influence of IR-induced tumor necrosis factor alpha (TNF-α) elevation in the process still is unknown. To investigate the role of TNF-α in the growth of pre-existing micrometastases in the liver following IR, we used a mouse model of colorectal liver metastases. In this model, mice received IR treatment seven days after intrasplenic injections of colorectal CT26 cells. Prior to IR treatment, either TNF-α blocker Enbrel or low-dose TNF-α, which could inhibit IR-induced TNF-α elevation, was administered by intraperitoneal injection.

Results

Hepatic IR treatment significantly promoted CT26 tumor growth in the liver, but either Enbrel or low-dose TNF-α pretreatment reversed this trend. Further studies showed that the CT26 + IR group prominently increased the levels of ALT and AST, liver necrosis, inflammatory infiltration and the expressions of hepatic IL-6, MMP9 and E-selectin compared to those of CT26 group. Inhibition of TNF-α elevation remarkably attenuated the increases of these liver inflammatory damage indicators and tumor-promoting factors.

Conclusion

These findings suggested that inhibition of TNF-α elevation delayed the IR-enhanced outgrowth of colorectal liver metastases by reducing IR-induced inflammatory damage and the formation of tumor-promoting microenvironments. Both Enbrel and low-dose TNF-α represented the potential therapeutic approaches for the protection of colorectal liver metastatic patients against IR injury-induced growth of liver micrometastases foci.

Tumor necrosis factor-α mediates JNK activation response to intestinal ischemia-reperfusion injury

AIM: To investigate whether tumor necrosis factor-α (TNF-α) mediates ischemia-reperfusion (I/R)-induced intestinal mucosal injury through c-Jun N-terminal kinase (JNK) activation.

METHODS: In this study, intestinal I/R was induced by 60-min occlusion of the superior mesenteric artery in rats followed by 60-min reperfusion, and the rats were pretreated with a TNF-α inhibitor, pentoxifylline, or the TNF-α antibody infliximab. After surgery, part of the intestine was collected for histological analysis. The mucosal layer was harvested for RNA and protein extraction, which were used for further real-time polymerase chain reaction, enzyme-linked immunosorbent assay and Western blotting analyses. The TNF-α expression, intestinal mucosal injury, cell apoptosis, activation of apoptotic protein and JNK signaling pathway were analyzed.

RESULTS: I/R significantly enhanced expression of mucosal TNF-α at both the mRNA and protein levels, induced severe mucosal injury and cell apoptosis, activated caspase-9/caspase-3, and activated the JNK signaling pathway. Pretreatment with pentoxifylline markedly downregulated TNF-α at both the mRNA and protein levels, whereas infliximab pretreatment did not affect the expression of TNF-α induced by I/R. However, pretreatment with pentoxifylline or infliximab dramatically suppressed I/R-induced mucosal injury and cell apoptosis and significantly inhibited the activation of caspase-9/3 and JNK signaling.

CONCLUSION: The results indicate there was a TNF-α-mediated JNK activation response to intestinal I/R injury.

Protective effect of sildenafil on liver injury induced by intestinal ischemia/reperfusion

BACKGROUND

This study evaluated the protective effect of sildenafil on liver injury induced by intestinal ischemia-reperfusion.

METHODS

Forty female Sprague Dawley rats were divided into 4 groups: sham-control (SC), ischemia (I), ischemia-reperfusion (IR), and ischemia-reperfusion+sildenafil (SIL; sildenafil gavaged at 50mg/kg before operating). A 2-h ischemia-reperfusion was performed by clamping the superior mesenteric artery. Liver function, plasma alanine (ALT) and aspartate (AST) aminotransferase, and intestinal and liver malondialdehyde (MDA) were measured at the end of the experiment. Intestinal and liver tissue damage was examined by histology. Liver samples were immunologically stained for endothelial nitric oxide synthase (eNOS) and proliferating cell nuclear antigen (PCNA).

RESULTS

The ALT and AST levels were highest in the IR group and were lower in the SIL group (p<0.05). Intestinal MDA levels were statistically higher in the IR group than in the SC, I and SIL groups. Liver MDA levels were significantly higher in the IR group than in the I and SC groups (p<0.05) and higher than in the SIL group (p>0.05). Intestinal damage based on Chiu scoring was more severe in the IR than in the SIL group (p<0.05). Sildenafil reduced damage and also increased eNOS and PCNA immunoreactivity in liver tissue.

CONCLUSIONS

Sildenafil shows a protective effect on intestinal ischemia-reperfusion-induced liver injury, possibly by decreasing vascular resistance through increased nitric oxide levels.

Hepatocytes produce TNF-α following hypoxia-reoxygenation and liver ischemia-reperfusion in a NADPH oxidase- and c-Src-dependent manner

Cell line studies have previously demonstrated that hypoxia-reoxygenation (H/R) leads to the production of NADPH oxidase 1 and 2 (NOX1 and NOX2)-dependent reactive oxygen species (ROS) required for the activation of c-Src and NF-κB. We now extend these studies into mouse models to evaluate the contribution of hepatocytes to the NOX- and c-Src-dependent TNF-α production that follows H/R in primary hepatocytes and liver ischemia-reperfusion (I/R). In vitro, c-Src-deficient primary hepatocytes produced less ROS and TNF-α following H/R compared with controls. In vivo, c-Src-KO mice also had impaired TNF-α and NF-κB responses following partial lobar liver I/R. Studies in NOX1 and p47phox knockout primary hepatocytes demonstrated that both NOX1 and p47phox are partially required for H/R-mediated TNF-α production. To further investigate the involvement of NADPH oxidases in the production of TNF-α following liver I/R, we performed additional in vivo experiments in knockout mice deficient for NOX1, NOX2, p47phox, Rac1, and/or Rac2. Cumulatively, these results demonstrate that NOX2 and its activator subunits (p47phox and Rac) control the secretion of TNF-α by the liver following I/R. Interestingly, in the absence of Kupffer cells and NOX2, NOX1 played a dominant role in TNF-α production following hepatic I/R. However, NOX1 deletion alone had little effect on I/R-induced TNF-α. Thus Kupffer cell-derived factors and NOX2 act to suppress hepatic NOX1-dependent TNF-α production. We conclude that c-Src and NADPH oxidase components are necessary for redox-mediated production of TNF-α following liver I/R and that hepatocytes play an important role in this process.

Typical cell signaling response to ionizing radiation: DNA damage and extranuclear damage

To treat many types of cancer, ionizing radiation (IR) is primarily used as external-beam radiotherapy, brachytherapy, and targeted radionuclide therapy. Exposure of tumor cells to IR can induce DNA damage as well as generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) which can cause non-DNA lesions or extracellular damage like lipid perioxidation. The initial radiation-induced cell responses to DNA damage and ROS like the proteolytic processing, as well as synthesis and releasing ligands (such as growth factors, cytokines, and hormone) can cause the delayed secondary responses in irradiated and unirradiated bystander cells through paracrine and autocrine pathways.

Rho-kinase-dependent pathway mediates the hepatoprotective effects of sorafenib against ischemia/reperfusion liver injury in rats with nonalcoholic steatohepatitis

During liver transplantation, nonalcoholic steatohepatitis (NASH) aggravates ischemia/reperfusion (IR) injury by activating various kinases and subsequently releasing cytokines and chemokines. Nonetheless, the effect of the multikinase inhibitor sorafenib on IR liver injury in rats with NASH has never been explored. Our study was designed to determine this effect and associated mechanisms in NASH rats. Sorafenib was acutely administered to NASH rats with IR liver injury that were or were not chronically pretreated with the Rho-kinase-specific inhibitor fasudil. Then, the following were evaluated: mean arterial pressure; hepatic blood flow and microcirculatory dysfunction; hepatic inflammation (serum alanine aminotransferase); necrosis; apoptosis; leukocyte infiltration; CD45 staining; caspase levels and DNA fragmentation; various serum and hepatic cytokines; and proteins and genes of the Raf/mitogen-activated protein-extracellular signal-regulated kinase kinase (MEK)/extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase, and apoptosis pathways. In NASH rats with IR liver injury, hepatic inflammation, necrosis, apoptosis, leukocyte infiltration, and microcirculatory dysfunction were significantly attenuated by the acute administration of sorafenib through the inhibition of the hepatic release of macrophage inflammatory protein 2, keratinocyte chemoattractant, granulocyte-monocyte colony-stimulating factor, and hepatic caspase-3 and caspase-9 as well as DNA fragmentation. Furthermore, there was decreased expression of p-Raf1 (where p indicates the phosphorylated form), p-MEK1/2, p-ERK1/2, p-Rho-kinase, B cell lymphoma 2-associated death promoter, and B cell lymphoma 2-associated X protein at the protein and messenger RNA levels. Notably, the aforementioned beneficial effects of sorafenib were significantly abolished by chronic pretreatment with the Rho-kinase-specific inhibitor fasudil. This study demonstrated that the multikinase inhibitor sorafenib protects NASH rats from IR injury by interfering with the inflammation, necrotic, and apoptotic responses causing leukocyte-dependent hepatic microcirculatory dysfunction. The hepatoprotective effects of sorafenib seem to work through the inhibition of the Rho-kinase-dependent Raf/MEK/ERK pathway, which is up-regulated during IR injury in the livers of NASH rats.

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.

Activation level of JNK and Akt/ERK signaling pathways determinates extent of DNA damage in the liver of diabetic rats

AIMS

Diabetes-related oxidative stress conditions lead to progressive tissue damage and disfunctionality. Mechanisms underlying liver pathophysiology during diabetes are not fully understood. The aim of this study was to find relationship between diabetes-related DNA damage in the rat liver and activities of prosurvival signaling pathways.

METHODS

Effect of diabetes was analyzed two (development stage) and eight weeks (stable diabetes) after single intraperitoneal injection of streptozotocin. Extent of DNA damage, analysed by comet assay, was corelated with oxidative status (plasma level of ROS, liver antioxidant capacity) and activity/abundance of kinases (Akt, p38, ERK1, JNK, JAK) and transcription factors NF-κB p65 and STAT3.

RESULTS

Significant DNA damage in development stage is accompanied by elevated plasma levels of O(2)(-) and H(2)O(2), decreased activities of CAT, MnSOD, and GST in the liver and increased activation of proapoptotic JNK signal pathway. Lower DNA damage in stable diabetes, is accompanied by elevated plasma level of O(2)(-), restored antioxidative liver enzyme activity, decreased activation of JNK and increased activation of prosurvival Akt and ERK signal pathways.

CONCLUSION

These findings indicate that level of DNA damage in diabetic liver depends on the extent of oxidative stress, antioxidant activity and balance between JNK and Akt/ERK signal pathways activation .

Proline protects liver from D-galactosamine hepatitis by activating the IL-6/STAT3 survival signaling pathway

The oral administration of proline, one of the non-essential amino acids, has been shown to effectively protect the liver from D-galactosamine (GalN)-induced liver injury and to improve the survival rate. The aim of this study was to investigate the mechanism of this protective action of proline. We paid particular attention to the effect of proline on inflammatory activation, regenerative response, and the associated signal transduction in the liver. Male Fischer rats received intraperitoneal injections of GalN (1.4 g/kg) with or without the oral administration of proline (2 g/kg) 1 h before GalN treatment. Liver pathology, plasma indices of inflammation, and the level of proliferative marker in the liver were monitored. The hepatic activation of interleukin-6 (IL-6)/signal transducer and activator of transcription (STAT)-3 pathway, which is downstream of tumor necrosis factor (TNF)-α/nuclear factor-κB, was also studied. GalN induced massive inflammatory expansion in the liver, leading to a high death rate (60 %) more than 72 h after the treatment. Proline administration significantly suppressed inflammatory infiltration in the live after 48 h, which was accompanied by depletion of plasma TNF-α, glutamic oxaloacetic transaminase, and glutamic pyruvic transaminase. The mRNA expression of histone H3, a marker of proliferation, was significantly upregulated in the liver of proline-treated animals. Furthermore, IL-6/STAT-3 pathway, an anti-inflammatory and regenerative signaling pathway, was strongly activated prior to these observations, with the upregulated expression of downstream genes. These results suggest that the tissue-protective mechanism of proline involves the early activation of IL-6/STAT-3 pathway in the liver, with subsequent activation of the regenerative response and suppression of massive inflammatory activation.

Remote ischemic preconditioning promotes early liver cell proliferation in a rat model of small-for-size liver transplantation

BACKGROUND

The size of the liver donor graft is a major concern in living donor liver transplantation. Rapid regeneration is essential for the survival of these grafts. The purpose of this study was to investigate the effect of remote ischemic preconditioning (RIPC) on liver regeneration in a rat small-for-size liver transplantation model.

METHODS

We established rat models of small-for-size liver transplantation (30%) in the presence or absence (control) of remote ischemic preconditioning. We observed liver mass regeneration, serum alanine aminotransferase, hepatic pathologic alterations, flow cytometry, and Ki-67 antigen immunohistochemistry. In addition, using Western blotting and reverse-transcriptase-polymerase chain reaction, we assessed the activation of cell cycle progression as well as tumor necrosis factor-α and interleukin-6 expression.

RESULTS

Compared with the control group, serum alanine aminotransferase activity was significantly lower and histopathology changes were significantly attenuated in the RIPC group. Remote ischemic preconditioning induced a high level of interleukin-6 mRNA in small grafts, but suppressed the expression of tumor necrosis factor-α. The proliferation index, indicated by the S-phase and G2/M-phase ratio [(S+G2/M)/(G0/G1+S+G2/M)], was significantly increased in the RIPC group at 24 h (58.25% ± 0.506% versus 53.405% ± 1.25%; P = .007). Meanwhile, cell cycle progression and regeneration (Ki-67) were initiated early in liver grafts treated with RIPC.

CONCLUSIONS

These results suggest that RIPC can protect liver cells against ischemia reperfusion injury in the small grafts and enhance liver regeneration. Interleukin-6 may be a critical mediator in the stimulatory effect on liver cell regeneration, which may make RIPC valuable as a hepatoprotective modality.

Interaction of the nitric oxide signaling system with the sphingomyelin cycle and peroxidation on transmission of toxic signal of tumor necrosis factor-α in ischemia-reperfusion

This review discusses the functional role of nitric oxide in ischemia-reperfusion injury and mechanisms of signal transduction of apoptosis, which accompanies ischemic damage to organs and tissues. On induction of apoptosis an interaction is observed of the nitric oxide signaling system with the sphingomyelin cycle, which is a source of a proapoptotic agent ceramide. Evidence is presented of an interaction of the sphingomyelin cycle enzymes and ceramide with nitric oxide and enzymes synthesizing nitric oxide. The role of a proinflammatory cytokine TNF-α in apoptosis and ischemia-reperfusion and mechanisms of its cytotoxic action, which involve nitric oxide, the sphingomyelin cycle, and lipid peroxidation are discussed. A comprehensive study of these signaling systems provides insight into the molecular mechanism of apoptosis during ischemia and allows us to consider new approaches for treatment of diseases associated with the activation of apoptosis.

Inhibition of TNF-α protects against hepatic ischemia-reperfusion injury in rats via NF-κB dependent pathway

Hepatic ischemia-reperfusion injury (I/R) is a serious health problem associated with liver transplantation, resection surgery, and various types of shock especially hemorrhagic shock. In the present investigation, the effect of inhibition of tumor necrosis factor-alpha (TNF-α) using pentoxifylline or infliximab against hepatic I/R injury induced in rats by 45-min ischemia and 1-h reperfusion was studied. It was observed that both pentoxifylline and infliximab-treated groups showed a significantly lower extent and severity of liver injury. This is attributed to (1) a decrease in oxidative stress markers, (2) reduction of the expression of TNF-α, TNF-α type-1 receptors, and nuclear factor kappa B (NF-κB). Thus TNF-α inhibition may be one of the therapeutic interventions to overcome the deleterious effects of I/R on liver via reduction of oxidative stress and inhibition of inflammatory cascade.

Aggravation of post-ischemic liver injury by overexpression of A20, an NF-κB suppressor

BACKGROUND & AIMS

A20 is an intracellular ubiquitin-editing enzyme that plays an important role in the negative feedback regulation of NF-κB activation in response to a diverse range of stimuli. Liver ischemia/reperfusion injury is associated with rapid activation of NF-κB signaling, but the role of NF-κB in hepatic ischemia/reperfusion injury remains controversial. The NF-κB signaling pathway mediates both protective and deleterious effects in the liver. Here, we examined whether A20 inhibited or aggravated hepatic ischemia/reperfusion injury.

METHODS

We used IκBα super-repressor as a positive control and overexpressed A20 and IκBα super-repressor in the liver of C57BL/6 mice. Mice underwent 45min of partial hepatic ischemia and were then reperfused.

RESULTS

Protein level of A20 was increased after reperfusion. Mice subjected to ischemia/reperfusion injury showed increased NF-κB activation, as evidenced by phosphorylation of IκBα and nuclear translocation of NF-κB. Prior transfection with Ad-A20 or Ad-IκBα super-repressor attenuated NF-κB activation and aggravated liver injury. Serum aminotransferases and proinflammatory cytokines, hepatocellular necrosis, and hepatic neutrophil infiltration were markedly increased compared to those of uninfected or control virus infected mice. In addition, A20 abolished the beneficial effect of ischemic preconditioning.

CONCLUSIONS

Our results suggest that inhibition of NF-κB activation by A20 aggravated partial hepatic ischemia/reperfusion injury. Understanding how the NF-κB pathway plays a role in directing a clinical outcome may lead to better prospects of more rational approaches to reduce post-ischemic liver injury.

Advances in the regulation of liver regeneration

Liver regeneration is known to be a process involving highly organized and ordered tissue growth triggered by the loss of liver tissue, and remains a fascinating topic. A large number of genes are involved in this process, and there exists a sequence of stages that results in liver regeneration, while at the same time inhibitors control the size of the regenerated liver. The initiation step is characterized by priming of quiescent hepatocytes by factors such as TNF-α, IL-6 and nitric oxide. The proliferation step is the step during which hepatocytes enter into the cell cycle's G1 phase and are stimulated by complete mitogens including HGF, TGF-α and EGF. Hepatic stimulator substance, glucagon, insulin, TNF-α, IL-1 and IL-6 have also been implicated in regulating the regeneration process. Inhibitors and stop signals of hepatic regeneration are not well known and only limited information is available. Furthermore, the effects of other factors such as VEGF, PDGF, hypothyroidism, proliferating cell nuclear antigen, heat shock proteins, ischemic-reperfusion injury, steatosis and granulocyte colony-stimulating factor on liver regeneration are also systematically reviewed in this article. A tissue engineering approach using isolated hepatocytes for in vitro tissue generation and heterotopic transplantation of liver cells has been established. The use of stem cells might also be very attractive to overcome the limitation of donor liver tissue. Liver-specific differentiation of embryonic, fetal or adult stem cells is currently under investigation.

Hepatic ischaemia-reperfusion injury from bench to bedside

BACKGROUND

Vascular occlusion to prevent haemorrhage during liver resection causes ischaemia-reperfusion (IR) injury. Insights into the mechanisms of IR injury gathered from experimental models have contributed to the development of therapeutic approaches, some of which have already been tested in randomized clinical trials.

METHODS

The review was based on a PubMed search using the terms 'ischemia AND hepatectomy', 'ischemia AND liver', 'hepatectomy AND drug treatment', 'liver AND intermittent clamping' and 'liver AND ischemic preconditioning'; only randomized controlled trials (RCTs) were included.

RESULTS

Twelve RCTs reported on ischaemic preconditioning and intermittent clamping. Both strategies seem to confer protection and allow extension of ischaemia time. Fourteen RCTs evaluating pharmacological interventions, including antioxidants, anti-inflammatory drugs, vasodilators, pharmacological preconditioning and glucose infusion, were identified.

CONCLUSION

Several strategies to prevent hepatic IR have been developed, but few have been incorporated into clinical practice. Although some pharmacological strategies showed promising results with improved clinical outcome there is not sufficient evidence to recommend them.

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.

Role of ischemic preconditioning in liver surgery and hepatic transplantation

INTRODUCTION

The purpose of this review is to summarize intraoperative surgical strategies available to decrease ischemia-reperfusion injury associated with liver resection and liver transplantation.

MATERIAL AND METHOD

We conducted a critical review of the literature evaluating the potential applications of hepatic ischemic preconditioning (IPC) for hepatic resection surgery and liver transplantation. In addition, we provide a basic bench-to-bedside summary of the liver physiology and cell signaling mechanisms that account for the protective effects seen with hepatic IPC.

Rosiglitazone-enriched diet did not protect liver ischemia-reperfusion injury in a rat model

PURPOSE

To determine whether rosiglitazone-enriched diet offer protection in a classical model of liver ischemia-reperfusion injury in rats.

METHODS

Two days before the experiment, rats were divided into 2 groups: Control Group (n=13) rats fed with standard diet; Rosi Group (n=13): rats fed with a powdered standard diet supplemented with rosiglitazone. The animals were submitted to liver ischemia-reperfusion by clamping the pedicle of median and left anterolateral lobes. After 1 hour of partial hepatic ischemia, the clamp was removed for reperfusion. After 2 or 24 hours (Control and Rosi Groups), blood was collected for enzymes and cytokines analysis. Ischemic and non-ischemic liver were collected for malondialdehyde analysis and histological assessment. Lungs were removed for tissue myeloperoxidase quantification.

RESULTS

There were no statistical differences between groups for all analysed parameters.

CONCLUSION

In this model, rosiglitazone-enriched diet did not protect liver against ischemia-reperfusion injury.

Role of p38 and JNK in liver ischemia and reperfusion

BACKGROUND/PURPOSE

The signal transduction of mitogen-activated protein kinases (MAPKs) has appeared to be an important mediator of ischemic-related events. Because of this, we analyzed the participation of p38 and JNK in liver ischemia and reperfusion, as two individual members of the MAPK family of proteins.

METHODS

All papers referred to in PubMed for the past 15 years were analyzed to determine how and when these MAPKs were considered to be an intricate part of the ischemic event. References were cross-studied to ascertain whether other papers could be found in the literature.

RESULTS

The role of p38 and JNK in liver ischemia was confirmed in the literature. The activation of these mediators was associated with the induction of apoptosis and necrosis. Inhibitors of p38 and JNK reduced the liver ischemia and reperfusion damage, probably through the mechanisms mentioned before.

CONCLUSIONS

The development of effective inhibitors of p38 and JNK protein mediators is important for minimizing the harmful effects associated with liver ischemia and reperfusion.