Interleukin-6 and STAT3 protect the liver from hepatic ischemia and reperfusion injury during ischemic preconditioning

Aloperine Attenuates Hepatic Ischemia/Reperfusion-Induced Liver Injury via STAT-3 Signaling in a Murine Model

Hepatic ischemia/reperfusion (I/R) damage is one of the most common side effects of liver surgery. This pathophysiological process may lead to excessive hepatic damage. Aloperine is an active ingredient isolated from Sophora alopecuroides Linn and has a variety of therapeutic effects, including organ protection. However, the hepatoprotective effect of aloperine against hepatic I/R damage has not yet been determined. C57BL/6 mice were allocated to the sham-operated (sham), hepatic ischemia/reperfusion (I/R), and aloperine groups. The mice were exposed to 30 min of hepatic hilum occlusion. Then a 3-h reperfusion was performed. Mice in the sham group underwent sham surgery. Hepatic injury was evaluated by plasma aspartate aminotransferase (AST) and transaminase alanine aminotransferase (ALT) levels, histological evaluation, cell apoptosis, the number of activated inflammatory cells, and the expression levels of inflammatory cytokines, including tumor necrosis factor-α and interleukin-6. The protein phosphorylation status of the reperfusion-associated survival pathways was evaluated. Mice with hepatic I/R injury presented increased plasma ALT and AST levels, increased hepatic apoptosis, abnormal histological structure, and elevated inflammatory responses. However, aloperine ameliorated hepatic I/R-induced injury. Moreover, aloperine enhanced the level of signal transducer and activator of transcription (STAT)-3 phosphorylation after I/R. Ag490, an agent that inhibits STAT-3 activity, abolished aloperine-induced STAT-3 phosphorylation and liver protection. Aloperine ameliorates hepatic I/R-induced liver injury via a STAT-3-mediated protective mechanism. Patients with hepatic I/R injury may benefit from aloperine treatment. SIGNIFICANCE STATEMENT: Hepatic I/R can cause excessive liver damage. This study revealed that aloperine, an active component isolated from Sophora alopecuroides Linn, ameliorates hepatic I/R injury and related liver damage in vivo. The underlying protective mechanism may involve the STAT-3 signaling pathway. These findings may lead to the development of a novel approach for treating hepatic I/R damage in clinical practice.

The Role of the JAK-STAT Signaling Pathway in the Protective Effects of Hepatic Ischemia Post-conditioning Against the Injury Induced by Ischemia/Reperfusion in the Rat Liver

Purpose

Hepatic ischemic post-conditioning (IPOC) is shown to protect the liver from injury induced by ischemia/reperfusion (IR). However, the mechanism underlying this protection has remained elusive. The present study aimed to investigate the role of the interleukin 6-Janus kinase-signal transducers and activators of transcription (IL-6-JAK-STAT) pathway in the protective effect of hepatic IPOC against the IR-induced injury in the liver.

Methods

Twenty-five rats were randomly divided into 5 groups of (1) sham-operated, (2) IR, (3) IR+hepatic IPOC, (4) IR+tofacitinib (TOFA), and (5) IR+TOFA+hepatic IPOC. The changes induced by IR and the effects of different treatments were assessed by enzyme release, histopathological observations, the serum level of IL-6, and the occurrence of apoptosis detected via the expression of the Bax/Bcl-2 ratio.

Results

The hepatic IPOC improved the liver injury induced by IR as shown by histological changes, reduction of IL-6 level, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) compared to the IR group (P<0.001, P<0.05, P<0.05, respectively). There was also downregulation of the Bax/Bcl2 ratio in the rats exposed to IR+hepatic IPOC compared with those in the IR group (P<0.05). However, TOFA, an inhibitor of JAK-STAT activity, inhibited the protective effect of hepatic IPOC.

Conclusion

It suggests that the protective effect of hepatic IPOC against IR-induced injury may be mediated by activating the IL-6-JAK-STAT pathway.

The research development of STAT3 in hepatic ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a common complication of surgery, which can cause rapid deterioration of the liver function, increase the risk of graft rejection, and seriously affect the prognosis of patients. The signal transducer and activator of transcription 3 (STAT3) protein has been implicated in pathogenesis of IRI. STAT3 influences the mitochondria through multiple pathways and is also involved in apoptosis and other forms of programmed cell death. STAT3 is associated with Janus kinase (JAK), phosphoinositide-3 kinase (PI3K), and heme oxygenase-1 (HO-1) in liver IRI. The STAT3 pathway plays a dual role in IRI as it can also regulate lipid metabolism which may have potential for treating IRI fatty liver. In this review, we summarize research on the function of STAT3 in liver IRI to provide references for its application in the clinic.

microRNA-9-5p protects liver sinusoidal endothelial cell against oxygen glucose deprivation/reperfusion injury

BACKGROUND

Maintenance of the function and survival of liver sinusoidal endothelial cells (LSECs) play a crucial role in hepatic ischemia/reperfusion (I/R) injury, a major cause of liver impairment during the surgical treatment. Emerging evidence indicates a critical role of microRNAs in I/R injury. This study aims to investigate whether miR-9-5p exerts a protective effect on LSECs.

METHODS

We transfected LSECs with miR-9-5p mimic or mimic NC. LSECs were treated with oxygen and glucose deprivation (OGD, 5% CO2, and 95% N2), followed by glucose-free Dulbecco's modified Eagle's medium (DMEM) medium for 6 h and high glucose (HG, 30 mmol/L glucose) DMEM medium for 12 h. The biological role of miR-9-5p in I/R-induced LSEC injury was determined.

RESULTS

In the in vitro model of OGD/HG injury in LSECs, the expression levels of miR-9-5p were significantly downregulated, and those of CXC chemokine receptor-4 (CXCR4) upregulated. LSEC I/R injury led to deteriorated cell death, enhanced oxidative stress, and excessive inflammatory response. Mechanistically, we showed that miR-9-5p overexpression significantly downregulated both mRNA and protein levels of CXCR4, followed by the rescue of LSECs, ameliorated inflammatory response, and deactivation of pro-apoptotic signaling pathways.

CONCLUSIONS

miR-9-5p promotes LSEC survival and inhibits apoptosis and inflammatory response in LSECs following OGD/HG injury via downregulation of CXCR4.

Can Prohibitin 1 be a Safeguard against liver disease?

Prohibitin (PHB) 1 is involved in multiple regulatory pathways in liver disease to protect hepatocytes, and its function is associated with subcellular localization. PHB1 located in the nucleus, cytoplasm and the mitochondrial inner membrane has anti-oxidative stress and anti-inflammatory effects in hepatitis and cirrhosis, which can protect liver cells from damage caused by inflammatory factors and reactive oxygen species (ROS) stimulation. The low expression of PHB1 located in the nucleus of liver cancer cells inhibits the proliferation and metastasis of liver cancer; thus, PHB1 exhibits the function of a tumor suppressor gene. Understanding the mechanisms of PHB1 in liver diseases may be useful for further research on the disease and may provide new ideas for the development of targeted therapeutic drugs in the future. Therefore, this review puts forward an overview of the role of PHB1 and its protective mechanism in liver diseases.

Supplementation of Moringa oleifera leaf powder orally improved productive performance by enhancing the intestinal health in rabbits under chronic heat stress

Heat stress jeopardizes animal's growth and health mainly through induction of oxidative stress and inflammation. The current study investigated the effects of Moringa oleifera leaf powder (MOLP) supplementation on productive performance and intestinal health of rabbits under chronic heat stress (HS). Young New Zealand White rabbits (male) at the age of 32 weeks (n = 21, mean body weight of 3318 ± 171 g) for four weeks' period were reared on commercial pelleted diet and divided into three groups: control (CON, 25 °C), HS (35 ± 1 °C) and HS (35 ± 1 °C) with MOLP (HSM) supplemented orally (200 mg/kg body weight). The results demonstrated that rabbits in the HSM group had reduced rectal temperature, respiration rate and improved FCR due to improved daily gain and better crude fiber (NDF) digestibility (P < 0.05) compared with HS group. MOLP improved intestinal integrity and function as indicated by lower serum diamine oxidase level and increased jejunal weight, length, villus height and ratio of villus height to crypt depth than heat-stressed rabbits. MOLP reversed the increased levels of serum cortisol, metabolic indicators i.e. glucose, insulin, and reduced concentrations of serum triiodothyronine. MOLP supplementation also significantly down-regulated the mRNA expression of tumor necrosis factor alpha (α), heat shock protein A2, glutathione peroxidase-1, interleukin (IL)-1α and increased the expression of IL-6. In conclusion, MOLP supplementation could enhance intestinal health along with production and metabolic indicators by alleviating the oxidative stress and inflammatory response in small intestine of hyper-thermic rabbits.

Characteristics of Changes in Inflammatory Cytokines as a Function of Hepatic Ischemia-Reperfusion Injury Stage in Mice

Liver ischemia-reperfusion injury (IRI) can severely compromise the prognosis of patients receiving liver surgery. While inflammation contributes to the damage resulting from IRI, only a limited number of inflammation biomarkers have been identified as being associated with the different stages of hepatic IRI. As an approach to identify some of these inflammatory cytokines and the molecular mechanisms involved within different stages of hepatic IRI, we used an advanced antibody array assay to detect multiple proteins. With this technology, we observed specific differences in the content of inflammatory cytokines between ischemic and sham controls, as well as a function of the different reperfusion stages in a hepatic IRI mouse model. For example, while liver tissue content of IL-12p40/p70 was significantly increased in the ischemic stage, it was significantly decreased in the reperfusion stage as compared with that of the sham group. For other inflammatory cytokines, no changes were obtained between the ischemic and reperfusion stages with levels of IL-17, Eotaxin-2, Eotaxin, and sTNF RII all being consistently increased, while those of TIMP-1, TIMP-2, BLC, and MCSF consistently decreased as compared with that of the sham group at all reperfusion stages examined. Results from protein function annotation Gene Ontology and the KEGG pathway revealed that inflammatory cytokines are enriched in a network associated with activation of inflammatory response signaling pathways such as TLR, TNF, and IL-17 when comparing responses of the IR versus sham groups. The identification of cytokines along with their roles at specific stages of IRI may reveal important new biological markers for the diagnosis and prognosis of hepatic IRI.

Pretreatment With Diazoxide Attenuates Spinal Cord Ischemia-Reperfusion Injury Through Signaling Transducer and Activator of Transcription 3 Pathway

BACKGROUND

Delayed paraplegia remains a feared complication of thoracoabdominal aortic intervention. Pharmacologic preconditioning with diazoxide (DZ), an adenosine 5'-triphosphate-sensitive potassium channel opener, results in neuroprotection against ischemic insult. However, the effects of DZ in spinal cord ischemia-reperfusion injury have not been fully elucidated. We hypothesized that DZ attenuates spinal cord ischemia-reperfusion injury through the signaling transducer and activator of transcription (STAT) 3 pathway.

METHODS

Adult male C57/BL6 mice received DZ (20 mg/kg) by oral gavage. Spinal cords were harvested at 0, 12, 24, 36, 48, and 60 hours after administration of DZ. The expression of phosphorylated STAT3 was assessed by Western blot analysis. Five groups were studied: DZ (DZ pretreatment, n = 8), ischemic control (phosphate-buffered saline pretreatment, n = 11), DZ + STAT3 inhibitor LY5 (DZ pretreatment + LY5, n = 8), LY5 (phosphate-buffered saline pretreatment + LY5, n = 8), and sham (without cross-clamping, n = 5). Spinal cord ischemia was induced by 4 minutes of thoracic aortic cross-clamp. Functional scoring (Basso Mouse Score) was done at 12-hour intervals until 48 hours, and spinal cords were harvested for the evaluation of B-cell lymphoma 2 expression and histologic changes.

RESULTS

The expression of phosphorylated STAT3 was significantly upregulated 36 hours after the administration of DZ. The motor function in the DZ group was significantly preserved compared with all other groups. The expression of B-cell lymphoma 2 in the DZ group was significantly higher than in the ischemic control, DZ + LY5, and LY5 groups 48 hours after reperfusion.

CONCLUSIONS

DZ preserves motor function in spinal cord ischemia-reperfusion injury by the STAT3 pathway. DZ may be beneficial clinically for use in spinal protection in aortic intervention.

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.

Unique cytokine and chemokine responses to exertional heat stroke in mice

In heat stroke, cytokines are believed to play important roles in multiorgan dysfunction and recovery of damaged tissue. The time course of the cytokine response is well defined in passive heat stroke (PHS), but little is known about exertional heat stroke (EHS). In this study we used a recently developed mouse EHS model to measure the responses of circulating cytokines/chemokines and cytokine gene expression in muscle. A very rapid increase in circulating IL-6 was observed at maximum core temperature (T_c,max) that peaked at 0.5 h of recovery and disappeared by 3 h. IL-10 was not elevated at any time. This contrasts with PHS where both IL-6 and IL-10 peak at 3 h of recovery. Keratinocyte chemoattractant (KC), granulocyte-colony-stimulating factor (G-CSF), macrophage inflammatory protein (MIP)-2, MIP-1β, and monocyte chemoattractive factor-1 also demonstrated near peak responses at 0.5 h. Only G-CSF and KC remained elevated at 3 h. Muscle mRNA for innate immune cytokines (IL-6, IL-10, IL-1β, but not TNF-α) were greatly increased in diaphragm and soleus compared with similar measurements in PHS. We hypothesized that these altered cytokine responses in EHS may be due to a lower T_c,max achieved in EHS or a lower overall heat load. However, when these variables were controlled for, they could not account for the differences between EHS and PHS. We conclude that moderate exercise, superimposed on heat exposure, alters the pattern of circulating cytokine and chemokine production and muscle cytokine expression in EHS. This response may comprise an endocrine reflex to exercise in heat that initiates survival pathways and early onset tissue repair mechanisms.

NEW & NOTEWORTHY

Immune modulators called cytokines are released following extreme hyperthermia leading to heat stroke. It is not known whether exercise in hyperthermia, leading to EHS, influences this response. Using a mouse model of EHS, we discovered a rapid accumulation of interleukin-6 and other cytokines involved in immune cell trafficking. This response may comprise a protective mechanism for early induction of cell survival and tissue repair pathways needed for recovery from thermal injury.

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.

Hepatic Oncostatin M Receptor β Regulates Obesity-Induced Steatosis and Insulin Resistance

The liver is an essential insulin-responsive organ that is critical for maintaining glucose homeostasis and lipid metabolism. Oncostatin M receptor β chain (OSMRβ) is implicated in adipose tissue- and immune cell-mediated metabolic regulation. However, the role of hepatocyte-derived OSMRβ in metabolic disorders remains unclear. Here, we report on the central role of OSMRβ in the protection against obesity and deregulation of glucose and lipids. We observed significantly varied expression levels of OSMRβ in hepatic tissues in both human samples and mouse models of nonalcoholic fatty liver disease. Mice lacking either whole-body or hepatic OSMRβ displayed exacerbated diet-induced insulin resistance, hepatic steatosis, and inflammation, both in diet-induced and genetically (ob/ob) obese mice. These adverse effects were markedly attenuated by hepatocyte-specific overexpression of OSMRβ. Mechanistically, we showed that OSMRβ phosphorylates and activates the Janus kinase 2 (JAK2)/STAT3 signaling pathway in the liver. More importantly, the liver-restricted overexpression of STAT3 rescued glucose tolerance and ameliorated hepatic steatosis and inflammation in OSMRβ knockout mice, whereas OSMRβ overexpression failed to protect against hepatic steatosis, insulin resistance, and hepatic inflammation in STAT3-deficient mice. Thus, activation of STAT3 is both sufficient and required to produce OSMRβ-mediated beneficial effects. In conclusion, hepatic OSMRβ expression alleviates obesity-induced hepatic insulin resistance and steatosis through the activation of JAK2/STAT3 signaling cascades.

Ischemic preconditioning and remote ischemic preconditioning provide combined protective effect against ischemia/reperfusion injury

AIMS

Our objective was to compare the protective efficacy of ischemic preconditioning (IPC) and remote ischemic preconditioning (RIPC) against liver ischemia/reperfusion injury (IRI) and to evaluate their combined protective effect in mouse liver transplantation (MLT).

MATERIALS AND METHODS

Mice were randomly allocated to sham, IPC, RIPC, or IPC+RIPC groups. The animals were sacrificed at 2h, 24h, and 3 days after reperfusion. Blood samples were collected to evaluate alanine aminotransferase, TNF-α, and innate immune response. Liver tissue samples were obtained for histological evaluation, terminal deoxynucleotidyltransferased UTP nick end labeling, malondialdehyde (MDA) assay.

KEY FINDINGS

Mice given preconditioning measures had significantly lower increase in transaminase, TNF-α expression, MDA formation, liver injury scores, and apoptosis index at 2h, 24h and 3 days after liver transplantation. The percentages of CD11b(+), CD11b(+)CD16/32(+) and CD11b(+) CD16/32(high) in white blood cells at 3 days after MLT were significantly lower than in the sham group. The results of factorial analysis demonstrated no synergistic effect for IPC and RIPC, except for MDA formation 2h after reperfusion (p=0.038).

SIGNIFICANCE

Based on the synergistic and addictive effect on liver IRI induced by MLT between IPC and RIPC, the study suggested ways in which combined preconditionings could be elicited in patients undergoing planned procedures complicated by IRI to support better outcomes.

Effect of remote ischemic preconditioning in the expression of IL-6 and IL-10 in a rat model of liver ischemia-reperfusion injury

PURPOSE

To study the effect of remote ischemic preconditioning (RIPC) in ischemia-reperfusion (I/R) liver injury and in the expression of IL-6 and IL-10 in a rat model.

METHODS

Thirty-six male rats were divided in three groups: Sham; I/R injury, a 45 minutes lobar liver ischemia and reperfusion; and RIPC, six cycles of four minutes of ischemia and four minutes of reperfusion on the right hindlimb followed by a 45 minutes lobar liver ischemia and reperfusion. Tissue and blood samples were collected after 1h and 3h of reperfusion for histopathological study, plasma cytokines and alanine aminotransferase (ALT) measurement.

RESULTS

The histopathological study demonstrated a significant reduction in liver necrosis in the RIPC group (p<0,001). The ALT levels were also significant lower in the RIPC group (p<0.01). The cytokines assessment showed that IL-6 levels were increased in the RIPC group after 1h of reperfusion, in comparison to the I/R group (p<0.05). Interleukin-10 levels in RIPC groups did not differ significantly from I/R group.

CONCLUSIONS

Remote ischemic preconditioning is effective in decreasing liver necrosis in a rat model of ischemia-reperfusion. The IL-6 expression is up-regulated and peaked at 60 min of reperfusion. There was no difference in IL-10 expression between the groups.

Protection of intestinal injury during heat stroke in mice by interleukin-6 pretreatment

KEY POINTS

Heat stroke afflicts thousands of humans each year, worldwide. The immune system responds to hyperthermia exposure resulting in heat stroke by producing an array of immunological proteins, such as interleukin-6 (IL-6). However, the physiological functions of IL-6 and other cytokines in hyperthermia are poorly understood. We hypothesized that IL-6 plays a protective role in conditions of heat stroke. To test this, we gave small IL-6 supplements to mice prior to exposing them to hot environments sufficient to induce conditions of heat stroke. Pretreatment with IL-6 resulted in improved ability to withstand heat exposure in anaesthetized mice, it protected the intestine from injury, reducing the permeability of the intestinal barrier, and it attenuated the release of other cytokines involved in inflammation. The results support the hypothesis that IL-6 is a 'physiological stress hormone' that plays an important role in survival during acute life-threatening conditions such as heat stroke.

ABSTRACT

The role of interleukin-6 (IL-6) in hyperthermia and heat stroke is poorly understood. Plasma IL-6 is elevated following hyperthermia in animals and humans, and IL-6 knockout mice are more intolerant of severe hyperthermia. We evaluated the effect of IL-6 supplementation on organ injury following severe hyperthermia exposure in anaesthetized mice. Two hours prior to hyperthermia, mice were treated with 0.6 μg intraperitoneal IL-6, or identical volumes of saline in controls. Mice were anaesthetized, gavaged with FITC-dextran for measures of gastrointestinal permeability, and exposed to incremental (0.5°C every 30 min) increases in temperature. Heating stopped when maximum core temperature (Tc) of 42.4°C was attained (Tc,max). The mice recovered at room temperature (≈22°C) for 30 or 120 min, at which time plasma and tissues were collected. IL-6-treated mice, on average, required ≈25 min longer to attain Tc,max . Injury and swelling of the villi in the duodenum was present in untreated mice after 30 min of recovery. These changes were blocked by IL-6 treatment. IL-6 also reduced gastrointestinal permeability, assayed by the accumulation of FITC-dextran in plasma. Plasma cytokines were also attenuated in IL-6-treated animals, including significant reductions in TNFα, MCP-1 (CXCL2), RANTES (CCL5) and KC (CCL5). The results demonstrate that IL-6 has a protective influence on the pattern of physiological responses to severe hyperthermia, suggesting that early endogenous expression of IL-6 may provide a protection from the development of organ damage and inflammation.

Prohibitin 1 modulates mitochondrial function of Stat3

Mitochondrial dysfunction in intestinal epithelial cells (IEC) is thought to precede the onset of inflammatory bowel diseases (IBD). Expression of Prohibitin 1 (PHB), a mitochondrial protein required for optimal electron transport chain (ETC) activity, is decreased in mucosal biopsies during active and inactive IBD. In addition to its activities as a transcription factor, Signal Transducer and Activator of Transcription 3 (Stat3) resides in the mitochondria of cells where phosphorylation at S727 is required for optimal ETC activity and protects against stress-induced mitochondrial dysfunction. Here, we show that PHB overexpression protects against mitochondrial stress and apoptosis of cultured IECs induced by TNFα, which is a pro-inflammatory cytokine involved in IBD pathogenesis. Expression of pS727-Stat3 dominant negative eliminates protection by PHB against TNFα-induced mitochondrial stress and apoptosis. PHB interacts with pS727-Stat3 in the mitochondria of cultured IECs and in colonic epithelium from wild-type mice. Our data suggest a protective role of PHB that is dependent on pS727-Stat3 to prevent mitochondrial dysfunction in IECs. Reduced levels of PHB during IBD may be an underlying factor promoting mitochondrial dysfunction of the intestinal epithelium.

Different roles of hepatic hypothermic ischemia and ischemic preconditioning in chemically induced hepatocarcinogenesis in rats

BACKGROUND

Hepatic ischemia-reperfusion (IR) injury, an unfavorable complication of hepatectomy, could be prevented by hypothermic ischemia and ischemic preconditioning (IPC). However, the effects of these two approaches on hepatocarcinogenesis have not been examined. The aim of the study was to investigate roles of hypothermic ischemia and IPC in a chemically induced rat liver tumor model.

METHODS

Twenty-four Sprague-Dawley rats were treated with diethylnitrosamine and phenobarbital to induce hepatocellular carcinoma. Rats underwent hepatic ischemic injury, hypothermic ischemia, and IPC. Twenty-eight-wk-old rats were sacrificed to evaluate the morbidity and growth of liver tumor. Cytokines were measured at the protein and messenger RNA level.

RESULTS

IR injury significantly promoted liver tumor development. Intriguingly, hypothermic ischemia, but not IPC, delayed liver carcinogenesis, although both of them suppressed the hepatic IR injury. IPC-treated rats showed elevated interleukin (IL)-6 concentration in the serum and messenger RNA expression in liver. In addition, higher levels of IL-6 activated signal transducer and activator of transcription 3 in the liver of IPC-treated rats. The hepatic expression of target genes of signal transducer and activator of transcription 3 signaling, cyclin D1, c-myc, c-fos, and c-jun, all of which might participate in tumor progression, increased in IPC group, compared with that of IR group.

CONCLUSIONS

These data indicated hypothermic ischemia could ameliorate both IR injury and liver tumor development. However, IPC, another effective method to prevent hepatic IR injury, might exacerbate liver tumor growth. The elevated level of IL-6 was one of the reasons for the different effects of hypothermic ischemia and IPC on hepatocarcinogenesis in rats.

Endogenous signal transducer and activator of transcription 3 is required for the protection of hepatocytes against warm ischemia/reperfusion injury

Warm ischemia/reperfusion (I/R) is a common clinical problem during liver transplantation and liver resection. Warm ischemia also occurs during trauma and shock. However, there is still no safe and promising strategy for protecting the liver from I/R injury. Signal transducer and activator of transcription 3 (STAT3) is a major immediate response molecule for protecting cell survival. In this study, we first confirmed that a pharmacological STAT3 inhibitor, (E)-2-cyano-3-(3,4-dihydrophenyl)-N-(phenylmethyl)-2-propenamide (AG490), significantly reduced the survival of HepG2 cells, regardless of the serum condition. Furthermore, we created hepatocyte-specific STAT3-deficient mice with the cyclization recombination-locus of X-over P1 (Cre-LoxP) system to study the mechanisms of STAT3 in liver I/R injury. We found that the alanine aminotransferase level was significantly higher in hepatocyte-specific STAT3-deficient mice versus wild-type (WT) mice in a 70% liver I/R injury model. A histopathological examination showed that hepatocyte-specific STAT3-deficient mice suffered more severe damage than WT mice despite similar numbers of polymorphonuclear neutrophils in the 2 groups. These results indicate that endogenous STAT3 signaling in hepatocytes is required for protection of the liver in vitro and in vivo against warm I/R injury. In conclusion, endogenous STAT3 plays an important role in protecting the liver against I/R injury, and STAT3-targeting therapy could be a therapeutic approach to combating liver I/R injury.

Leptin attenuates ischemia-reperfusion injury in the rat liver

Leptin is an adipocytokine that reduces ischemic damage in several organs including brain and heart. STAT3 activation is a key step for the attainment of leptin effects in various tissues. We evaluated the possible effect of leptin on liver viability and STAT3 activation, in a rat model of ischemia-reperfusion injury. Rat livers, flushed and stored with Belzer solution (4° C for 24 h), were warmly reperfused (3.5 ml/min/g liver for 1 h at 37° C with O(2) ) with Krebs-Ringer bicarbonate. Treatment group underwent an identical protocol with the adjunct of Leptin (10 ng/ml). Liver effluent was harvested to assess LDH and AST output. Liver tissue was used for pSTAT3 expression (western blot and immunostaining), optical microscopy, TUNEL, and Cell Death Detection assays. The pSTAT3 expression was enhanced by administration of leptin. In parallel, LDH and AST output were reduced (P = 0.04 and P = 0.02 for LDH and AST, respectively). Optical microscopy, TUNEL, and Cell Death Detection assay results demonstrated increased viability in livers treated with leptin in comparison with others (Optical microscopy P = 0.02; TUNEL P = 0.01; Cell death Detection assay P = 0.003). In conclusion, cold storage and reperfusion with leptin reduce liver ischemia-reperfusion injury. This effect is associated with an increased expression of pSTAT-3.

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.

Ischaemic Preconditioning and Intermittent Clamping Does not Influence Mediators of Liver Regeneration in a Human Liver Sinusoidal Endothelial Cell Model of Ischaemia-Reperfusion Injury

BACKGROUND

The role of surgical technique on liver regeneration following surgery remains inconclusive. The aim of the study was to assess the effect of ischaemic preconditioning (IPC) and intermittent clamping (IC) on mediators of regeneration produced by human liver sinusoidal endothelial cells (SECs), using an in vitro hypoxia-reoxygenation model to mimic ischaemia-reperfusion injury (IRI).

METHODS

Following extraction from samples obtained from liver resection (n = 5), confluent culture flasks of SECs were subjected to IRI (1 hour hypoxia + 1 hour reoxygenation), IPC prior to IRI (10 minutes hypoxia + 10 minutes reoxygenation + 1 hour hypoxia + 1 hour reoxygenation), IC (15 minutes hypoxia + 5 minutes reoxygenation x 3 + 1 hour reoxygenation) and compared to controls. The production of various mediators was determined over 48 hours.

RESULTS

Interleukin (IL)-6, IL-8, granulocyte-colony stimulating factor (G-CSF) and hepatocyte growth factor (HGF) were produced by SECs. Both IPC and IC did not significantly influence the profile of IL-6, IL-8, G-CSF and HGF by SECs compared to IRI over the study period.

CONCLUSION

IPC and IC did not influence the production of pro-regenerative mediators in a SECs model of IRI. The role of surgical technique on liver regeneration remains to be determined.

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.

Use of RNA interference to minimize ischemia reperfusion injury

RNA interference (RNAi) is an endogenous mechanism of cellular RNA control through degradation of specific messenger RNA sequences. This process of gene silencing may be exploited by the use of small interfering RNA (siRNA) to mediate precise control of targeted cellular functions. The nature of transplantation leads invariably to tissue injury, as organs are damaged by the loss of blood supply and resultant ischemia associated with the procurement procedure. Upon reperfusion, an inflammatory program is activated, and subsequent injury results in delayed graft function and, potentially, organ failure. Many of the molecular components in ischemia-reperfusion injury (IRI) have been identified, but effective therapeutics are not currently available. Accumulating evidence supports a role for siRNA in controlling IRI, as siRNA is specific, relatively low in toxicity, and limited in duration of effect. The capacity of siRNA to control IRI-related transcription factors, cell death and apoptosis, complement factors, and oxidative stress molecules supports the concept that RNAi-based therapeutics represent a novel and promising strategy for the control of IRI. However, there are issues of RNAi strategies, including siRNA design, "off-target" effects, and delivery that merit consideration in approaching IRI with gene silencing. This review will provide an overview of current concepts in RNAi and the potential application to IRI in solid organ transplantation.

Interleukin 6 protects H(2)O(2)-induced cardiomyocytes injury through upregulation of prohibitin via STAT3 phosphorylation

OBJECTIVE

Hydrogen peroxide (H(2)O(2)) is a potent reactive oxygen species that causes cardiomyocytes injury. As an important cytokine, interleukin 6 (IL-6) has cardioprotective effects as it plays an essential role in the late phase of preconditioning. Our work is to investigate if IL-6 preconditioning has protective effects on neonatal rat ventricular cardiomyocytes in response to H(2)O(2) and its underlying mechanism.

METHODS

Gel-based comparative proteomic approach along with small interfering RNA (siRNA) and Western blot analysis was used to analyse mechanisms of IL-6 preconditioning on H(2)O(2)-induced neonatal rat ventricular cardiomyocytes injury.

RESULTS

IL-6 preconditioning protected cardiomyocytes against H(2)O(2)-induced cell death. Proteomic analysis showed that IL-6 pretreatment further increased the expression of prohibitin and improved the viability of cardiomyocytes exposed to H(2)O(2). Knocking down of prohibitin with siRNA abrogated this protection by increasing apoptosis rate. Tyrosine kinase inhibitor AG490 decreased signal transducers and activators of transcription 3 (STAT3) phosphorylation and down-regulated prohibitin expression in cardiomyocytes pretreated with IL-6 and exposed to H(2)O(2), which further dampened the protective effects of IL-6 preconditioning.

CONCLUSION

Our results provide direct evidence that prohibitin is a protective factor of IL-6 preconditioning in H(2)O(2)-induced neonatal rat ventricular cardiomyocytes death. The upregulation of prohibitin by IL-6 is, at least, partially regulated through STAT3 phosphorylation.

STAT3 does not regulate acute liver injury after ischemia/reperfusion

BACKGROUND

Hepatic ischemia/reperfusion (I/R) injury is a serious complication of liver surgery and transplantation. Regulation of this injury response occurs at the cellular and molecular levels. Previous studies have shown that interleukin-6 (IL-6) is a negative regulator of the acute inflammatory injury occurring as a result of hepatic I/R. The signal transducer and activator of transcription-3 (STAT3) is a key target of receptor signaling for IL-6. Both IL-6 and STAT3 have been implicated in the protective effects of ischemic preconditioning of the liver. However, there have been no studies that have directly addressed the potential role of STAT3 in regulating acute inflammatory liver injury induced by I/R. In the current study, we investigated whether blockade of STAT3 phosphorylation altered the injury response to hepatic I/R injury.

METHODS

Male Balb/c mice were subjected to 90 min of partial hepatic ischemia followed by reperfusion with or without treatment with specific inhibitors of STAT3 activation, AG490 (selective JAK2 inhibitor), or STATTIC (direct inhibitor of STAT3 phosphorylation). Mice were sacrificed at 8 and 24 h after reperfusion.

RESULTS

STAT3 activation was induced by I/R. This activation was partially inhibited by administration of AG490 and almost completely abrogated by treatment with STATTIC. Despite the blockade of STAT3, neither AG490 nor STATTIC had any effect on acute liver injury induced by I/R. Treatment with STATTIC did reduce hepatic neutrophil accumulation.

CONCLUSION

The data suggest that STAT3 is not a central regulator of acute liver injury induced by I/R.

Molecular mechanisms of liver preconditioning

Ischemia/reperfusion (I/R) injury still represents an important cause of morbidity following hepatic surgery and limits the use of marginal livers in hepatic transplantation. Transient blood flow interruption followed by reperfusion protects tissues against damage induced by subsequent I/R. This process known as ischemic preconditioning (IP) depends upon intrinsic cytoprotective systems whose activation can inhibit the progression of irreversible tissue damage. Compared to other organs, liver IP has additional features as it reduces inflammation and promotes hepatic regeneration. Our present understanding of the molecular mechanisms involved in liver IP is still largely incomplete. Experimental studies have shown that the protective effects of liver IP are triggered by the release of adenosine and nitric oxide and the subsequent activation of signal networks involving protein kinases such as phosphatidylinositol 3-kinase, protein kinase C δ/ε and p38 MAP kinase, and transcription factors such as signal transducer and activator of transcription 3, nuclear factor-κB and hypoxia-inducible factor 1. This article offers an overview of the molecular events underlying the preconditioning effects in the liver and points to the possibility of developing pharmacological approaches aimed at activating the intrinsic protective systems in patients undergoing liver surgery.

Impact of cell cycle disruption on impaired hepatic regeneration in aged livers with ischemic insult

BACKGROUND

The number of elderly patients with hepatobiliary malignancies has increased with the steady growth of elderly population. However, the safety of major hepatectomy for elderly patients remains controversial. This study investigated the effect of aging on the hepatic regenerative response after partial resection of livers subjected to ischemic insult.

METHODS

Two-thirds hepatectomy following 1-h hepatic ischemia was performed in young (12-wk-old) and old (18-mo-old) rats under portosystemic shunt establishment by subcutaneous transposition of the spleen.

RESULTS

The survival rate 48 h after hepatectomy of the old rats was significantly lower (20%) than that of the young rats (53%), whereas all animals without hepatic ischemia were alive at 48 h. Hepatic necrosis and hepatocyte apoptosis during the early post-hepatectomy phase were more severe in the aged livers, which also showed delayed Akt activation. Liver mass restoration was significantly retarded in the old rats, despite higher plasma IL-6 levels, rapid and prolonged activation of hepatic STAT3, and increased hepatocyte nuclear cyclin D1 levels. In the young livers, cyclin E, which is essential for G1/S transition, and cyclin A, a marker of S phase, were observed in the nucleus from 24 h, reaching peaks 48 h after hepatectomy. In contrast, the old livers showed greatly delayed and decreased nuclear cyclin E and cyclin A levels.

CONCLUSION

Age-related reductions in the regenerative ability of ischemically damaged livers may be caused by cell cycle disruption at either the late G1 phase or the G1/S transition, despite increased cyclin D1 levels and compensatory IL-6/STAT3 activation.

Liver ischemia/reperfusion injury: processes in inflammatory networks--a review

Liver ischemia/reperfusion (IR) injury is typified by an inflammatory response. Understanding the cellular and molecular events underpinning this inflammation is fundamental to developing therapeutic strategies. Great strides have been made in this respect recently. Liver IR involves a complex web of interactions between the various cellular and humoral contributors to the inflammatory response. Kupffer cells, CD4+ lymphocytes, neutrophils, and hepatocytes are central cellular players. Various cytokines, chemokines, and complement proteins form the communication system between the cellular components. The contribution of the danger-associated molecular patterns and pattern recognition receptors to the pathophysiology of liver IR injury are slowly being elucidated. Our knowledge on the role of mitochondria in generating reactive oxygen and nitrogen species, in contributing to ionic disturbances, and in initiating the mitochondrial permeability transition with subsequent cellular death in liver IR injury is continuously being expanded. Here, we discuss recent findings pertaining to the aforementioned factors of liver IR, and we highlight areas with gaps in our knowledge, necessitating further research.

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.

CXC chemokines play a critical role in liver injury, recovery, and regeneration

BACKGROUND

Hepatic ischemia/reperfusion (I/R) injury is a principal consideration of trauma, resectional liver surgery, and transplantation. Despite improvements in supportive care, hepatic I/R injury continues to negatively impact patient outcomes because of significant tissue damage and organ dysfunction. CXC chemokines have been implicated as key mediators in the deleterious inflammatory cascade after hepatic I/R and also as important, beneficial regulators of liver recovery and regeneration. As such, their potential to mediate both beneficial and detrimental effects on hepatocytes makes them a key target for therapy. Herein, we provide a review of the inflammatory mechanisms of hepatic I/R injury, with a focus on the divergent functions of CXC chemokines in this response compared with other liver insults, and offer an explanation of this apparent paradox.

DATA SOURCES

MEDLINE and PubMed.

CONCLUSIONS

CXC chemokines are key mediators of both the inflammatory response to hepatic I/R as well as the recovery from this injury. Their contrasting functions in the regeneration of liver mass after an ischemic insult indicates that therapeutic manipulation of these mediator pathways should differ depending on the surgical milieu.

Impaired liver regeneration with humoral and genetic disturbances in urinary trypsin inhibitor-deficient mice

BACKGROUND/AIMS

Urinary trypsin inhibitor (UTI) is an innate anti-inflammatory regulator. It can block the release of inflammatory factors, prevent the cascade reaction of cytokines and inhibit excessive activation of leukocytes. Liver regeneration (LR) is a dynamic molecular phenomenon without inflammation. Many cytokines, including tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), have been implicated in regulating LR. However, the role of UTI in LR is totally unknown. The aim of this study was to elucidate the role of UTI in LR using genetically UTI-deficient mice.

METHODS

We performed 68% hepatectomy, comparing UTI (-/-) and UTI (+/+) mice. Recovery of liver weight was recorded and we calculated labelling indices after 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry. A DNA microarray was used to examine gene expression followed by real-time polymerase chain reaction. Serum IL-6, IL-10, monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1beta (MIP-1beta) were measured.

RESULTS

LR in UTI (-/-) mice was delayed at 36 h after hepatectomy, at which time the DNA profile was different. One hundred and fourteen genes were upregulated and 100 genes were downregulated in UTI (-/-) mice at 36 h after hepatectomy among the 21, 977 mRNAs examined. Furthermore, serum IL-6, IL-10, MCP-1 and MIP-1beta levels at 36 h after hepatectomy in the UTI (-/-) mice were significantly higher than in the UTI (+/+) mice.

CONCLUSION

UTI appears to important cytokine and chemokine regulation in normal liver regeneration.

Early renal ischemia-reperfusion injury in humans is dominated by IL-6 release from the allograft

The pathophysiology of ischemia/reperfusion (I/R) injury is complex, and current knowledge of I/R injury in humans is incomplete. In the present study, human living-donor kidney transplantation was used as a highly reproducible model to systematically study various processes potentially involved in early I/R injury. Unique, direct measurements of arteriovenous concentration differences over the kidney revealed massive release of interleukin (IL)-6 in the first 30 minutes of graft reperfusion and a modest release of IL-8. Among the assessed markers of oxidative and nitrosative stress, only 15(S)-8-iso-PGF(2alpha) was released. When assessing cell activation, release of prothrombin factor 1 + 2 indicated thrombocyte activation, whereas there was no release of markers for endothelial activation or neutrophil activation. Common complement activation complex sC5b-9 was not released into the bloodstream, but was released into urine rapidly after reperfusion. To investigate whether IL-6 plays a modulating role in I/R injury, a mouse experiment of renal I/R injury was performed. Neutralizing anti-IL-6 antibody treatment considerably worsened kidney function. In conclusion, this study shows that renal I/R in humans is dominated by local IL-6 release. Neutralization of IL-6 in mice resulted in a significant aggravation of renal I/R injury.

Inhibition of Kupffer cell-mediated early proinflammatory response with carbon monoxide in transplant-induced hepatic ischemia/reperfusion injury in rats

Proinflammatory responses play critical roles in hepatic ischemia/reperfusion (I/R) injury associating with liver transplantation (LTx), and carbon monoxide (CO) can effectively down-regulate them. Using wild-type (WT) to enhanced green fluorescent protein (EGFP)-transgenic rat LTx with 18-hour cold preservation in University of Wisconsin solution, this study analyzed the relative contribution of donor and host cells during early posttransplantation period and elucidated the mechanism of hepatic protection by CO. CO inhibited hepatic I/R injury and reduced peak alanine aminotransferase levels at 24 hours and hepatic necrosis at 48 hours. Abundant EGFP(+) host cells were found in untreated WT liver grafts at 1 hour and included nucleated CD45(+) leukocytes (myeloid, T, B, and natural killer cells) and EGFP(+) platelet-like depositions in the sinusoids. However, reverse transcription polymerase chain reaction (RT-PCR) analysis of isolated graft nonparenchymal cells (NPCs) revealed that I/R injury-induced proinflammatory mediators [for example, tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS)] were not up-regulated in purified CD45(+) cells of donor or host origin. Instead, TNF-alpha and IL-6 messenger RNA (mRNA) elevation was exclusively seen in isolated CD68(+) cells, whereas iNOS mRNA up-regulation was seen in hepatocytes. Nearly all CD68(+) cells at 1 hour after LTx were EGFP(-) donor Kupffer cells, and CO efficiently inhibited TNF-alpha and IL-6 up-regulation in the CD68(+) Kupffer cell fraction. When graft Kupffer cells were inactivated with gadolinium chloride, activation of inflammatory mediators in liver grafts was significantly inhibited. Furthermore, in vitro rat primary Kupffer cell culture also showed significant down-regulation of lipopolysaccharide (LPS)-induced inflammatory responses by CO.

CONCLUSION

These results indicate that CO ameliorates hepatic I/R injury by down-regulating graft Kupffer cells in early postreperfusion period. The study also suggests that different cell populations play diverse roles by up-regulating distinctive sets of mediators in the acute phase of hepatic I/R injury.

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.

Suppressor of cytokine signaling expression with increasing severity of murine hepatic ischemia-reperfusion injury

BACKGROUND/AIMS

Preservation of function requires tight regulation of the cellular events initiated when hepatic ischemia is followed by reperfusion (IR). One important mechanism modulating the cytokine-directed response to injury is Suppressors of Cytokine Signaling. SOCS1 and SOCS3 ensure appropriate intensity and duration of cytokine signaling through negative feedback on JAK-STAT signaling. The contribution of SOCS1 and SOCS3-mediated regulation to the evolution of hepatic IR injury is unknown.

METHODS

C57Blk6 mice were subjected to mild (20 min) or severe (90 min) hepatic ischemia. Liver was analyzed for cytokine and SOCS1/3 induction as well as JAK-STAT activation at intervals after reperfusion.

RESULTS

Tnf, Il-1beta, and Il-6 expression paralleled increasing injury severity. Despite early phosphorylation of both STAT1 and STAT3 after severe injury, only nuclear translocation of activated STAT3, suggesting that the induction of target genes through JAK-STAT after IR is predominantly via STAT3. Socs3 was expressed across the injury spectrum while Socs1 was induced only in the face of severe IR injury. Severe IR in Il-6 deficient mice confirmed that Il-6, acting via STAT3, serves as a primary inducer of both regulatory mechanisms.

CONCLUSIONS

Under the influence of IL-6-mediated STAT3 signaling, Socs1 serves as a complimentary regulatory mechanism when Socs3 is insufficient to limit cytokine-mediated inflammation after hepatic IR.

The ischemic preconditioning paradox in deceased donor liver transplantation-evidence from a prospective randomized single blind clinical trial

While animal studies show that ischemic preconditioning (IPC) is beneficial in liver transplantation (LT), evidence from few smaller clinical trials is conflicting. From October 2003 to July 2006, 101 deceased donors (DD) were randomized to 10 min IPC (n = 50) or No IPC (n = 51). Primary objective was efficacy of IPC to decrease reperfusion (RP) injury. Both groups had similar donor risk index (DRI) (1.54 vs. 1.57). Aminotransferases on days 1 and 2 were significantly greater (p < 0.05) in IPC recipients. In multivariate analyses, IPC had an independent effect only on day 2 aspartate transferase. Prothrombin time, bilirubin and histological injury were similar in both groups. IPC had no significant effect on plasma TNF-alpha, IL-6 and IL-10 in the donor and TNF-alpha and IL-6 in the recipient. In contrast, IPC recipients had a significant rise in systemic IL-10 levels after RP (p < 0.05) and had fewer moderate/severe rejections within 30 days (p = 0.09). Hospital stay was similar in both groups. One-year patient and graft survival in IPC versus No IPC were 88% versus 78% (p = 0.1) and 86 versus 76% (p = 0.25), respectively. IPC increases RP injury after DDLT, an 'IPC paradox'. Other potential benefits of IPC are limited. IPC may be more effective in combination with other preconditioning regimens.