JNK mediates hepatic ischemia reperfusion injury

Inhibition of cysteine-serine-rich nuclear protein 1 ameliorates ischemia-reperfusion injury during liver transplantation in an MAPK-dependent manner

Hepatic ischemia-reperfusion injury (HIRI) is a critical pathophysiological process during liver transplantation (LT). Multiple genes and signal pathways are dysregulated during HIRI. This study aims to identify genes as potential therapeutic targets for ameliorating HIRI. Datasets containing samples from the human donor liver (GSE151648) and mouse HIRI model (GSE117066) were analyzed to determine differentially expressed genes (DEGs). The selected DEGs were confirmed by real-time PCR and western blot in the hepatocyte hypoxia-reoxygenation (HR) model, mouse HIRI model, and human liver samples after transplantation. Genetic inhibition was used to further clarify the underlying mechanism of the gene in vitro and in vivo. Among the DEGs, CSRNP1 was significantly upregulated (|log FC|= 2.08, P < 0.001), and was positively correlated with the MAPK signal pathway (R = 0.67, P < 0.001). CSRNP1 inhibition by siRNA significantly suppressed apoptosis in the AML-12 cell line after HR (mean Annexin+ ratio = 60.62% vs 42.47%, P = 0.0019), but the protective effect was eliminated with an additional MAPK activator. Knocking down CSRNP1 gene expression by intravenous injection of AAV-shRNA markedly reduced liver injury in mouse HIRI model (ALT: AAV-NC vs AAV-shCsrnp1 = 26,673.5 ± 2761.2 vs 3839.7 ± 1432.8, P < 0.001; AST: AAV-NC vs AAV-shCsrnp1 = 8640.5 ± 1450.3 vs 1786.8 ± 518.3, P < 0.001). Liver-targeted delivery of siRNA by nanoparticles effectively inhibited intra-hepatic genetic expression of Csrnp1 and alleviated IRI by reducing tissue inflammation and hepatocyte apoptosis. Furthermore, CSRNP1 inhibition was associated with reduced activation of the MAPK pathway both in vitro and in vivo. In conclusion, our results demonstrated that CSRNP1 could be a potential therapeutic target to ameliorate HIRI in an MAPK-dependent manner.

Inter-patient heterogeneity in the hepatic ischemia-reperfusion injury transcriptome: Implications for research and diagnostics

Cellular responses induced by surgical procedure or ischemia-reperfusion injury (IRI) may severely alter transcriptome profiles and complicate molecular diagnostics. To investigate this effect, we characterized such pre-analytical effects in 143 non-malignant liver samples obtained from 30 patients at different time points of ischemia during surgery from two individual cohorts treated either with the Pringle manoeuvre or total vascular exclusion. Transcriptomics profiles were analyzed by Affymetrix microarrays and expression of selected mRNAs was validated by RT-PCR. We found 179 mutually deregulated genes which point to elevated cytokine signaling with NFκB as a dominant pathway in ischemia responses. In contrast to ischemia, reperfusion induced pro-apoptotic and pro-inflammatory cascades involving TNF, NFκB and MAPK pathways. FOS and JUN were down-regulated in steatosis compared to their up-regulation in normal livers. Surprisingly, molecular signatures of underlying primary and secondary cancers were present in non-tumor tissue. The reported inter-patient variability might reflect differences in individual stress responses and impact of underlying disease conditions. Furthermore, we provide a set of 230 pre-analytically highly robust genes identified from histologically normal livers (<2% covariation across both cohorts) that might serve as reference genes and could be particularly suited for future diagnostic applications.

The protective effects of phosphoserine aminotransferase 1 (PSAT1) against hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion (I/R) injury is a severe clinical syndrome, causing a profound medical and socioeconomic burden worldwide. This study aimed to explore underlying biomarkers and treatment targets in the progression of hepatic I/R injury. We screened gene expression profiles of the hepatic I/R injury from the Gene Expression Omnibus (GEO) database, downloaded expression profiles data (GSE117066). Differentially expressed genes (DEGs) were identified through cluster of the PPI network, and enrichment pathways were conducted based on gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) database. The bioinformatics analysis was used to identify biomarkers that alleviate hepatic I/R injury. Finally, the effects of hub gene were investigated by in vitro and in vivo experiments. A total of 162 DEGs (76 up-regulated and 86 down-regulated genes) were extracted between sham and I/R, and 248 DEGs (118 up-regulated and 130 down-regulated genes) were extracted between I/R and ischemic postconditioning (IPO). The cluster of the PPI network and maximal clique centrality (MCC) method of the common DEGs were performed to identify the phosphoserine aminotransferase 1 (PSAT1) as the potential gene for hepatic I/R injury. Then, the H-E, TUNEL and PCNA staining were indicated that the hepatic injury score was highest in I/R 6 h. The expression level of apoptosis-related proteins was consistent with the pathological results. Both gain- and loss-of-function assays demonstrated that hepatic I/R injury was alleviated by PSAT1. PSAT1 may play crucial roles in hepatic I/R injury and thus serves as a hub biomarker for hepatic I/R injury prognosis and individual-based treatment.

Defective efferocytosis by aged macrophages promotes STING signaling mediated inflammatory liver injury

Aged livers have shown aggravated liver ischemia and reperfusion (IR) injury. Timely efferocytosis of apoptotic cells is a key mechanism for avoiding excessive inflammation and tissue injury. Here, we investigated the alteration of efferocytosis by aged macrophages and its role in regulating macrophage STING (stimulator of interferon genes) signaling and liver IR injury. Aged and young mice were subjected to liver partial IR model. Liver injury and inflammation were measured. Efferocytosis by aged macrophages and the underlying regulatory mechanism were analyzed as well. Aged macrophages exhibited impaired efferocytosis with decreased MerTK (c-mer proto-oncogene tyrosine kinase) activation, which was reversed by treatment of the MerTK CRISPR activation plasmid. Increased MerTK cleavage by ADAM17 (a disintegrin and metalloproteinase 17) due to enhanced ROS (reactive oxygen species) levels contributed to defective efferocytosis by aged macrophages. MerTK activation by suppressing ADAM17 or ROS improved aged macrophage efferocytosis, leading to reduced inflammatory liver injury. Moreover, increased apoptotic hepatocytes, DNA accumulation, and macrophage STING activation were observed in aged ischemic livers. Improvement in efferocytosis by aged macrophages via MerTK activation suppressed STING activation and inflammatory liver injury. Our study demonstrates that aging suppresses MerTK- mediated macrophage efferocytosis to promote macrophage STING activation and inflammatory liver IR injury, suggesting a new mechanism and potential therapy to promote inflammation resolution and efferocytosis in aged livers.

Exploration of Optimal pH in Hypothermic Machine Perfusion for Rat Liver Grafts Retrieved after Circulatory Death

Ex vivo hypothermic machine perfusion (HMP) is a strategy for controlling ischemia-reperfusion injury in donation after circulatory death (DCD) liver transplantation. The pH of blood increases with a decrease in temperature and water dissociation, leading to a decrease in [H⁺]. This study aimed to verify the optimal pH of HMP for DCD livers. Rat livers were retrieved 30 min post-cardiac arrest and subjected to 3-h cold storage (CS) in UW solution (CS group) or HMP with UW-gluconate solution (machine perfusion [MP] group) of pH 7.4 (original), 7.6, 7.8, and 8.0 (MP-pH 7.6, 7.8, 8.0 groups, respectively) at 7-10 °C. The livers were subjected to normothermic perfusion to simulate reperfusion after HMP. All HMP groups showed greater graft protection compared to the CS group due to the lower levels of liver enzymes in the former. The MP-pH 7.8 group showed significant protection, evidenced by bile production, diminished tissue injury, and reduced flavin mononucleotide leakage, and further analysis by scanning electron microscopy revealed a well-preserved structure of the mitochondrial cristae. Therefore, the optimum pH of 7.8 enhanced the protective effect of HMP by preserving the structure and function of the mitochondria, leading to reduced reperfusion injury in the DCD liver.

Autophagy in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is a major complication of liver resection or liver transplantation that can seriously affect patient's prognosis. There is currently no definitive and effective treatment strategy for HIRI. Autophagy is an intracellular self-digestion pathway initiated to remove damaged organelles and proteins, which maintains cell survival, differentiation, and homeostasis. Recent studies have shown that autophagy is involved in the regulation of HIRI. Numerous drugs and treatments can change the outcome of HIRI by controlling the pathways of autophagy. This review mainly discusses the occurrence and development of autophagy, the selection of experimental models for HIRI, and the specific regulatory pathways of autophagy in HIRI. Autophagy has considerable potential in the treatment of HIRI.

Overexpression of HSF2 binding protein suppresses endoplasmic reticulum stress via regulating subcellular localization of CDC73 in hepatocytes

BACKGROUND

Endoplasmic reticulum (ER) stress plays an important role in the occurrence and development of various liver diseases. However, there are no effective prevention and treatment strategies. We aimed to determine the role of heat shock factor 2 binding protein (HSF2BP) in ER stress.

METHODS

HSF2BP expression in mice and cultured hepatocytes was measured during ER stress induced by tunicamycin, and its importance in ER stress was evaluated in hepatocyte-specific HSF2BP transgenic (TG) and knockout (KO) mice. The effects and mechanisms of HSF2BP on ER stress were further probed in hepatic ischemia-reperfusion (I/R) injury.

RESULTS

HSF2BP expression was significantly upregulated during tunicamycin-induced ER stress in mice and cultured hepatocytes. Liver injury and ER stress were reduced in HSF2BP overexpressing mice after treating with tunicamycin, but were aggravated in HSF2BP knockout mice compared to the controls. In hepatic I/R injury, HSF2BP expression was significantly upregulated, and HSF2BP overexpressing mice had reduced liver injury and inflammation. These improvements were associated with ER stress inhibition. However, these results were reversed in hepatocyte-specific HSF2BP knockout mice. HSF2BP overexpression increased cytoplasmic CDC73 levels and inhibited the JNK signaling pathway. CDC73 knockdown using siRNA eliminated the protection exerted by HSF2BP overexpression in hypoxia/reoxygenation (H/R)-induced ER stress in hepatocytes.

CONCLUSION

HSF2BP is a previously uncharacterized regulatory factor in ER stress-likely acts by regulating CDC73 subcellular localization. The feasibility of HSF2BP-targeted treatment in ER stress-related liver disease deserves future research.

MAPK Signaling Pathways in Hepatic Ischemia/Reperfusion Injury

The mitogen-activated protein kinase signaling pathway can be activated by a variety of growth factors, cytokines, and hormones, and mediates numerous intracellular signals related to cellular activities, including cell proliferation, motility, and differentiation. It has been widely studied in the occurrence and development of inflammation and tumor. Hepatic ischemia-reperfusion injury (HIRI) is a common pathophysiological phenomenon that occurs in surgical procedures such as lobectomy and liver transplantation, which is characterized by severe inflammatory reaction after ischemia and reperfusion. In this review, we mainly discuss the role of p38, ERK1/2, JNK in MAPK family and TAK1 and ASK1 in MAPKKK family in HIRI, and try to find an effective treatment for HIRI.

Luteolin Pretreatment Attenuates Hepatic Ischemia-Reperfusion Injury in Mice by Inhibiting Inflammation, Autophagy, and Apoptosis via the ERK/PPARα Pathway

Hepatic ischemia-reperfusion (IR) injury is a clinically significant process that frequently occurs in liver transplantation, partial hepatectomy, and hemorrhagic shock. The aim of this study was to explore the effectiveness of luteolin in hepatic IR injury and the underlying mechanism. BALB/c mice were randomly divided into six groups, including normal controls (NC), luteolin (50 mg/kg), sham procedure, IR+25 mg/kg luteolin, and IR+50 mg/kg luteolin group. Serum and tissue samples were collected at 6 and 24 h after reperfusion to assay liver enzymes, inflammatory factors, expression of proteins associated with apoptosis and autophagy, and factors associated with the extracellular signal-regulated kinase/peroxisome proliferator-activated receptor alpha (ERK/PPARα) pathway. Luteolin preconditioning decreased hepatocyte injury caused by ischemia-reperfusion, downregulated inflammatory factors, and inhibited apoptosis and autophagy. Luteolin also inhibited ERK phosphorylation and activated PPARα.

Reactive Oxygen Species Induce Fatty Liver and Ischemia-Reperfusion Injury by Promoting Inflammation and Cell Death

Liver transplantation is the ultimate method for treating end-stage liver disease. With the increasing prevalence of obesity, the number of patients with non-alcoholic fatty liver, a common cause of chronic liver disease, is on the rise and may become the main cause of liver transplantation in the future. With the increasing gap between the number of donor livers and patients waiting for liver transplantation and the increasing prevalence of non-alcoholic fatty liver, the proportion of steatosis livers among non-standard donor organs is also increasing. Ischemia-reperfusion injury has historically been the focus of attention in the liver transplantation process, and severe ischemia-reperfusion injury leads to adverse outcomes of liver transplantation. Studies have shown that the production of reactive oxygen species and subsequent oxidative stress play a key role in the pathogenesis of hepatic ischemia and reperfusion injury and non-alcoholic fatty liver. Furthermore, the sensitivity of fatty liver transplantation to ischemia-reperfusion injury has been suggested to be related to the production of reactive oxygen species (ROS) and oxidative stress. In ischemia-reperfusion injury, Kupffer cell and macrophage activation along with mitochondrial damage and the xanthine/xanthine oxidase system promote marked reactive oxygen species production and the inflammatory response and apoptosis, resulting in liver tissue injury. The increased levels of ROS and lipid peroxidation products, vicious circle of ROS and oxidative stress along with mitochondrial dysfunction promoted the progress of non-alcoholic fatty liver. In contrast to the non-fatty liver, a non-alcoholic fatty liver produces more reactive oxygen species and suffers more serious oxidative stress when subjected to ischemia-reperfusion injury. We herein review the effects of reactive oxygen species on ischemia-reperfusion injury and non-alcoholic fatty liver injury as well as highlight several treatment approaches.

c-Jun N-terminal kinase (JNK) signaling contributes to cystic burden in polycystic kidney disease

Polycystic kidney disease is an inherited degenerative disease in which the uriniferous tubules are replaced by expanding fluid-filled cysts that ultimately destroy organ function. Autosomal dominant polycystic kidney disease (ADPKD) is the most common form, afflicting approximately 1 in 1,000 people. It primarily is caused by mutations in the transmembrane proteins polycystin-1 (Pkd1) and polycystin-2 (Pkd2). The most proximal effects of Pkd mutations leading to cyst formation are not known, but pro-proliferative signaling must be involved for the tubule epithelial cells to increase in number over time. The c-Jun N-terminal kinase (JNK) pathway promotes proliferation and is activated in acute and chronic kidney diseases. Using a mouse model of cystic kidney disease caused by Pkd2 loss, we observe JNK activation in cystic kidneys and observe increased nuclear phospho c-Jun in cystic epithelium. Genetic removal of Jnk1 and Jnk2 suppresses the nuclear accumulation of phospho c-Jun, reduces proliferation and reduces the severity of cystic disease. While Jnk1 and Jnk2 are thought to have largely overlapping functions, we find that Jnk1 loss is nearly as effective as the double loss of Jnk1 and Jnk2. Jnk pathway inhibitors are in development for neurodegeneration, cancer, and fibrotic diseases. Our work suggests that the JNK pathway should be explored as a therapeutic target for ADPKD.

Autosomal dominant polycystic kidney disease is a leading cause of end stage renal disease requiring dialysis or kidney transplant. During disease development, the cells lining the kidney tubules proliferate. This proliferation transforms normally small diameter tubules into fluid-filled cysts that enlarge with time, eventually destroying all kidney function. Despite decades of research, polycystic kidney disease remains incurable. Furthermore, the precise signaling events involved in cyst initiation and growth remain unclear. The c-Jun N-terminal kinase (JNK), is a major pathway regulating cellular proliferation and differentiation but its importance to polycystic kidney disease was not known. We show that JNK activity is elevated in cystic kidneys and that reducing JNK activity decreases cyst growth pointing to JNK inhibition as a therapeutic strategy for treating polycystic kidney disease.

Synergistic effect of the TLR5 agonist CBLB502 and its downstream effector IL-22 against liver injury

The toll-like receptor 5 (TLR5) agonist, CBLB502/Entolimod, is a peptide derived from bacterial flagellin and has been shown to protect against radiation-induced tissue damage in animal models. Here we investigated the protective mechanism of CBLB502 in the liver using models of ischemia-reperfusion injury and concanavalin A (ConA) induced immuno-hepatitis. We report that pretreatment of mice with CBLB502 provoked a concomitant activation of NF-κB and STAT3 signaling in the liver and reduced hepatic damage in both models. To understand the underlying mechanism, we screened for cytokines in the serum of CBLB502 treated animals and detected high levels of IL-22. There was no transcriptional upregulation of IL-22 in the liver, rather it was found in extrahepatic tissues, mainly the colon, mesenteric lymph nodes (MLN), and spleen. RNA-seq analysis on isolated hepatocytes demonstrated that the concomitant activation of NF-κB signaling by CBLB502 and STAT3 signaling by IL-22 produced a synergistic cytoprotective transcriptional signature. In IL-22 knockout mice, the loss of IL-22 resulted in a decrease of hepatic STAT3 activation, a reduction in the cytoprotective signature, and a loss of hepatoprotection following ischemia-reperfusion-induced liver injury. Taken together, these findings suggest that CBLB502 protects the liver by increasing hepatocyte resistance to acute liver injury through the cooperation of TLR5-NF-κB and IL-22-STAT3 signaling pathways.

JNK signaling pathway in metabolic disorders: An emerging therapeutic target

Metabolic Syndrome is a multifactorial disease associated with increased risk of cardiovascular disorders, type 2 diabetes mellitus, fatty liver disease, etc. Various stress stimuli such as reactive oxygen species, endoplasmic reticulum stress, mitochondrial dysfunction, increased cytokines, or free fatty acids are known to aggravate progressive development of hyperglycemia and hyperlipidemia. Although the exact mechanism contributing to altered metabolism is unclear. Evidence suggests stress kinase role to be a crucial one in metabolic syndrome. Stress kinase, c-jun N-terminal kinase activation (JNK) is involved in various metabolic manifestations including obesity, insulin resistance, fatty liver disease as well as cardiometabolic disorders. It emerged as a foremost mediator in regulating metabolism in the liver, skeletal muscle, adipose tissue as well as pancreatic β cells. It has three isoforms each having a unique and tissue-specific role in altered metabolism. Current findings based on genetic manipulation or chemical inhibition studies identified JNK isoforms to play a central role in the regulation of whole-body metabolism, suggesting it to be a novel therapeutic target. Hence, it is imperative to elucidate its role in metabolic syndrome onset and progression. The purpose of this review is to elucidate in vitro and in vivo implications of JNK signaling along with the therapeutic strategy to inhibit specific isoform. Since metabolic syndrome is an array of diseases and complex pathway, carefully examining each tissue will be important for specific treatment strategies.

Melatonin and its protective role in attenuating warm or cold hepatic ischaemia/reperfusion injury

Although the liver is the only organ with regenerative capacity, various injury factors induce irreversible liver dysfunction and end‐stage liver disease. Liver resection and liver transplantation (LT) are effective treatments for individuals with liver failure, liver cirrhosis and liver cancers. The remnant or transplanted liver tissues will undergo hepatic ischaemia/reperfusion (IR), which leads to oxidative stress, inflammation, immune injury and liver damage. Moreover, systemic ischaemia induced by trauma, stroke, myocardial ischaemia, haemorrhagic shock and other injury factors also induces liver ischaemia/reperfusion injury (IRI) in individuals. Hepatic IRI can be divided into warm IRI, which is induced by liver surgery and systemic ischaemia, and cold IRI, which is induced by LT. Multiple studies have shown that melatonin (MT) acts as an endogenous free radical scavenger with antioxidant capacity and is also able to attenuate hepatic IRI via its anti‐inflammatory and antiapoptotic capacities. In this review, we discuss the potential mechanisms and current strategies of MT administration in liver surgery for protecting against warm or cold hepatic IRI. We highlight strategies to improve the efficacy and safety of MT for attenuating hepatic IRI in different conditions. After the potential mechanisms underlying the interactions between MT and other important cellular processes during hepatic IR are clarified, more opportunities will be available to use MT to treat liver diseases in the future.

Effects of SP600125 and hypothermic machine perfusion on livers donated after cardiac death in a pig allograft transplantation model

BACKGROUND

Hypothermic machine perfusion (HMP) improves the quality of donor livers for transplantation, both in animal models and in clinical practice. Treatment with SP600125, an inhibitor of c-Jun N-terminal kinase (JNK), can suppress the JNK signaling pathway to alleviate donor liver ischemia-reperfusion injury (IRI). We performed the present study with the objective of exploring the protective effects exerted by a combination of HMP and SP600125 on liver xenograft viability for donation after cardiac death (DCD) in a porcine model.

METHODS

54 adult BAMA mini-pigs were randomly assigned to 5 groups, including sham, cold storage for 4 h (CS 4 h), CS 4 h + SP600125, CS 2 h + HMP 2 h, and CS 2 h + HMP 2 h + SP600125 groups. Donor livers in the CS 4 h and CS 4 h + SP600125 groups were conventionally cold preserved for 4 h, whereas donor livers in the CS 2 h + HMP 2 h and CS 2 h + HMP 2 h + SP600125 groups were cold preserved for 2 h and then treated with HMP for 2 h. The preservation and perfusion solutions contained SP600125 (20 µM). Follow-up was conducted for 5 days after liver transplantation to compare the surgical outcomes by means of serological examination, pathological results, and survival rate.

RESULTS

The most satisfactory outcome after liver transplantation was observed in the CS 2 h + HMP 2 h + SP600125 group, which presented with minimal damage of donor livers during 5 days' follow-up. Additionally, serological examination, pathological results, and survival rate concurred in showing better results in the CS 2 h + HMP 2 h ± SP600125 group than in the CS 4 h ± SP600125 group.

CONCLUSION

HMP in combination with SP600125 has hepatoprotective properties and improves the quality and viability of porcine livers collected after DCD, thus improving prognosis after liver transplantation.

The protective effects of fibroblast growth factor 10 against hepatic ischemia-reperfusion injury in mice

Hepatic ischemia-reperfusion injury (IRI) is a major complication of liver surgery and transplantation. IRI leads to hepatic parenchymal cell death, resulting in liver failure, and lacks effective therapeutic approaches. Fibroblast growth factor 10 (FGF10) is a paracrine factor which is well-characterized with respect to its pro-proliferative effects during embryonic liver development and liver regeneration, but its role in hepatic IRI remains unknown. In this study, we investigated the role of FGF10 in liver IRI and identified signaling pathways regulated by FGF10. In a mouse model of warm liver IRI, FGF10 was highly expressed during the reperfusion phase. In vitro experiments demonstrated that FGF10 was primarily secreted by hepatic stellate cells and acted on hepatocytes. The role of FGF10 in liver IRI was further examined using adeno-associated virus-mediated gene silencing and overexpression. Overexpression of FGF10 alleviated liver dysfunction, reduced necrosis and inflammation, and protected hepatocytes from apoptosis in the early acute injury phase of IRI. Furthermore, in the late phase of IRI, FGF10 overexpression also promoted hepatocyte proliferation. Meanwhile, gene silencing of FGF10 had the opposite effect. Further studies revealed that overexpression of FGF10 activated nuclear factor-erythroid 2-related factor 2 (NRF2) and decreased oxidative stress, mainly through activation of the phosphatidylinositol-3-kinase/AKT pathway, and the protective effects of FGF10 overexpression were largely abrogated in NRF2 knockout mice. These results demonstrate the protective effects of FGF10 in liver IRI, and reveal the important role of NRF2 in FGF10-mediated hepatic protection during IRI.

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FGF10 is markedly upregulated in the early phase of liver IRI.

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FGF10 overexpression exerts great potential in ameliorating hepatic IRI.

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FGF10 knockdown significantly aggravates hepatic IRI.

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FGF10 overexpression activates PI3K/AKT-NRF2 signaling and thus ameliorates hepatic IRI.

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NRF2 knockout abrogates the protective effects of FGF10 overexpression during liver IRI.

JNK inhibition alleviates oxidative DNA damage, germ cell apoptosis, and mitochondrial dysfunction in testicular ischemia reperfusion injury

The aim of this study is to determine whether the c-Jun N-terminal kinase (JNK) signaling is a regulator of oxidative DNA damage, germ cell apoptosis (GCA), and mitochondrial dysfunction during testicular ischemia reperfusion injury (tIRI) using the JNK inhibitor SP600125. Male Sprague Dawley rats (n = 36) were equally divided into three groups: sham, tIRI only, and tIRI + SP600125 (15 mg/kg). Testicular ischemia was induced for 1 h followed by 4 h of reperfusion prior to animal sacrifice. Spermatogenesis was evaluated by light microscopy, while expression of oxidative stress and GCA-related mRNAs and proteins were evaluated by real-time polymerase chain reaction and colorimetric assays, respectively. Expressions of JNK, p53, and survivin were detected by immunofluorescence (IF) staining. Indicators of mitochondrial dysfunction were examined by western blot analysis and colorimetric assay. In comparison to sham, the tIRI testes showed a significant increase in lipid and protein oxidation products. Oxidative DNA damage was reflected by a significant increase in the number of DNA strand breaks, increased concentration of 8-OHdG, and elevated poly (ADP-ribose) polymerase activity. Spermatogenic damage was associated with the activation of caspase 3 and elevated Bax to Bcl2 ratio. This was also accompanied by a significantly heightened IF expression of the phosphorylated forms of JNK and p53 paralled with the suppression of survivin. Mitochondrial dysfunction was reflected by NAD+ depletion, overexpression of uncoupling protein 2, and increased level of cytochrome c. Such tIRI-induced modulations were all attenuated by SP600125 treatment prior to reperfusion. In conclusion, JNK signaling regulates oxidative DNA damage, GCA, and mitochondrial dysfunction through activation of p53 and suppression of survivin during tIRI.

P38-β/SAPK-inhibiting and apoptosis-inducing activities of (E)-4-chloro-2-((3-ethoxy-2-hydroxybenzylidene) amino)phenol

The present study has three purposes; first evaluating cytotoxicity of (E)-4-chloro-2-((3-ethoxy-2-hydroxybenzylidene)amino)phenol (ACES), second deciphering ACES-mediated cellular death mechanism, and third estimating ACES-mediated alterations in the expressions of mitogen-activated protein kinase (MAPK) pathway-related genes. Neutral red uptake assay, cell cycle analysis, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) measurements, caspase 3/7 and 9 activations, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were implemented. IC₅₀ values of ACES-treated five cells were around 4-6 µg/mL. However, Caco-2 and Huh-7 cells were found to be twofold resistant and fivefold sensitive with IC₅₀ values of 11 µg/mL and 0.93 µg/mL, respectively. In this study, it was initially reported that ACES exhibits selective cytotoxicity to Huh-7 cells. In addition, ACES induced apoptosis by nuclear fragmentation, MMP disruption, and intracellular ROS elevation in MCF-7 cells. qRT-PCR experiment indicated the expressions of 30 genes including ATF2, CREB1, MYC, NFATC4 (NFAT3), CCNA1, CCNB1, CCND2, CDK2, CDKN1A (p21CIP1), CDKN1C (p57KIP2), CDKN2A (p16INK4a), CDKN2B (p15INK4b), DLK1, NRAS, CDC42, PAK1, MAP4K1 (HPK1), MAP3K3 (MEKK3), MAP2K3 (MEK3), MAP2K6 (MEK6), MOS, MAPK1 (ERK2), MAPK8 (JNK1), MAPK10 (JNK3), MAPK11 (p38-β), LAMTOR3 (MP1), MAPK8IP2 (JIP-1), PRDX6 (AOP2), COL1A1, and HSPA5 (Grp78) were downregulated at least 1.5-fold. Moreover, ACES effectively inhibited expressions of genes that code for elements of p38-β/stress-activated protein kinase (SAPK) pathway. ACES has the potential to be used for the reversal of trastuzumab resistance in breast cancer patients by inhibiting p38/SAPK pathway in MCF-7 cells. Therefore, with the selective cytotoxic, apoptosis-inducing, and p38-β/SAPK-inhibiting activities, ACES can be utilized for developing a novel anticancer drug.

Six-Transmembrane Epithelial Antigen of the Prostate 3 Deficiency in Hepatocytes Protects the Liver Against Ischemia-Reperfusion Injury by Suppressing Transforming Growth Factor-β-Activated Kinase 1

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion (I/R) injury remains a major challenge affecting the morbidity and mortality of liver transplantation. Effective strategies to improve liver function after hepatic I/R injury are limited. Six-transmembrane epithelial antigen of the prostate 3 (Steap3), a key regulator of iron uptake, was reported to be involved in immunity and apoptotic processes in various cell types. However, the role of Steap3 in hepatic I/R-induced liver damage remains largely unclear.

APPROACH AND RESULTS

In the present study, we found that Steap3 expression was significantly up-regulated in liver tissue from mice subjected to hepatic I/R surgery and primary hepatocytes challenged with hypoxia/reoxygenation insult. Subsequently, global Steap3 knockout (Steap3-KO) mice, hepatocyte-specific Steap3 transgenic (Steap3-HTG) mice, and their corresponding controls were subjected to partial hepatic warm I/R injury. Hepatic histology, the inflammatory response, and apoptosis were monitored to assess liver damage. The molecular mechanisms of Steap3 function were explored in vivo and in vitro. The results demonstrated that, compared with control mice, Steap3-KO mice exhibited alleviated liver damage after hepatic I/R injury, as shown by smaller necrotic areas, lower serum transaminase levels, decreased apoptosis rates, and reduced inflammatory cell infiltration, whereas Steap3-HTG mice had the opposite phenotype. Further molecular experiments showed that Steap3 deficiency could inhibit transforming growth factor-β-activated kinase 1 (TAK1) activation and downstream c-Jun N-terminal kinase (JNK) and p38 signaling during hepatic I/R injury.

CONCLUSIONS

Steap3 is a mediator of hepatic I/R injury that functions by regulating inflammatory responses as well as apoptosis through TAK1-dependent activation of the JNK/p38 pathways. Targeting hepatocytes, Steap3 may be a promising approach to protect the liver against I/R injury.

Tle1 attenuates hepatic ischemia/reperfusion injury by suppressing NOD2/NF-κB signaling

Liver damage induced by ischemia/reperfusion (I/R) remains a primary issue in multiple hepatic surgeries. Innate immune-mediated inflammatory responses during the reperfusion stage aggravate the injury. Nevertheless, the detailed mechanism of hepatic I/R has not been fully clarified yet. Our research focuses on the role of Transducin-like enhancer of split-1 (Tle1) in the liver I/R injury and the relation between Tle1 and Nucleotide-binding oligomerization domain 2 (NOD2). To answer these questions, we constructed mouse models of I/R and cell models of hypoxia/reoxygenation (H/R). We found decreased Tle1 accompanied by increased NOD2 during reperfusion. Mice pro-injected with Tle1-siRNA emerged aggravated liver dysfunction. Repression of Tle1 had a significant impact on NOD2 and downstream NF-κB signaling in vitro. However, alteration of NOD2 failed to affect the expression of Tle1. To conclude, our study demonstrates that Tle1 shelters the liver from I/R injury through suppression of NOD2-dependent NF-κB activation and subsequent inflammatory responses.

Inhibition of Frizzled-2 by small interfering RNA protects rat hepatic BRL-3A cells against cytotoxicity and apoptosis induced by Hypoxia/Reoxygenation

Frizzled-2 plays an important role in maintaining normal hepatic cell functionality. This study aimed to investigate the role of inhibition of Frizzled-2 in protecting rat liver BRL-3A cells from Hypoxia/Reoxygenation (H/R). In vitro H/R hepatic cell model was established by culturing BRL-3A cells under H/R condition. Frizzled-2 siRNA was transfected into BRL-3A cells to inhibit Frizzled-2 signaling. Wnt5a and Frizzled-2 were significantly increased in BRL-3A cells upon H/R treatment. H/R treatment induced cell cytotoxicity, the early apoptosis rate and the intracellular Ca²⁺ level in BRL-3A cells while silencing frizzled-2 gene decreased the H/R induced cell cytotoxicity, apoptosis and intracellular Ca²⁺ level. In vivo mice study further showed the up-regulation of Frizzled-2/Wnt 5 pathway and cleaved Caspase-3 expression in liver tissues under ischemia and reperfusion injury (IRI). In summary, inhibition of Frizzled-2 by its siRNA may protects BRL-3A cells by attenuating the H/R induced cell cytotoxicity and apoptosis.

Identification of Key Transcription Factors AP-1 and AP-1-Dependent miRNAs Forming a Co-Regulatory Network Controlling PTEN in Liver Ischemia/Reperfusion Injury

Liver ischemia/reperfusion (I/R) injury is a complex and common clinical disease with limited therapeutic options. The aim of our study was to discover the candidate target genes in liver I/R injury and to further elucidate the potential regulatory mechanisms, especially the ones involving transcription factors and miRNAs. The analysis of mouse data set GSE10657 from Gene Expression Omnibus database (GEO) revealed 203 differentially expressed genes (DEGs) including 19 transcription factors (TFs). Functional and pathway enrichment analyses were conducted to explore their biological functions. We further obtained the targets of TFs and miRNAs, to form our TF-mRNA/TF-miRNA-mRNA co-regulatory network. In our network, we found that the important subunits of activator protein 1 (AP-1) including JUN, FOS and ATF3, were hub genes in liver I/R injury. AP-1 target genes were activated in our mouse models. AP-1 could transcriptionally activate phosphatase and tensin homolog (PTEN) while AP-1-dependent miRNAs countered this effect. In conclusion, this study suggested that AP-1, together with AP-1-dependent miRNAs formed a co-regulatory network enabling AP-1 target genes to be tightly controlled, which will complete the mechanism of liver ischemia/reperfusion injury and provide direction for finding potential therapeutic targets.

Guanine nucleotide-binding protein G(i)α2 aggravates hepatic ischemia-reperfusion injury in mice by regulating MLK3 signaling

Hepatic ischemia-reperfusion (I/R) injury is a major challenge in liver resection and transplantation surgeries. Previous studies have revealed that guanine nucleotide-binding protein G(i)α2 (GNAI2) was involved in the progression of myocardial and cerebral I/R injury, but the role and function of GNAI2 in hepatic I/R have not been elucidated. The hepatocyte-specific GNAI2 knockout (GNAI2hep-/-) mice were generated and subjected to hepatic I/R injury. Primary hepatocytes isolated from GNAI2hep-/- and GNAI2flox/flox mice were cultured and challenged to hypoxia-reoxygenation insult. The specific function of GNAI2 in I/R-triggered hepatic injury and the underlying molecular mechanism were explored by various phenotypic analyses and molecular biology methods. In this study, we demonstrated that hepatic GNAI2 expression was significantly increased in liver transplantation patients and wild-type mice after hepatic I/R. Interestingly, hepatocyte-specific GNAI2 deficiency attenuated I/R-induced liver damage, inflammation cytokine expression, macrophage/neutrophil infiltration, and hepatocyte apoptosis in vivo and in vitro. Mechanistically, up-regulation of GNAI2 phosphorylates mixed-lineage protein kinase 3 (MLK3) through direct binding, which exacerbated hepatic I/R damage via MAPK and NF-κB pathway activation. Furthermore, blocking MLK3 signaling reversed GNAI2-mediated hepatic I/R injury. Our study firstly identifies GNAI2 as a promising target for prevention of hepatic I/R-induced injury and related liver diseases.-Sun, Q., He, Q., Xu, J., Liu, Q., Lu, Y., Zhang, Z., Xu, X., Sun, B. Guanine nucleotide-binding protein G(i)α2 aggravates hepatic ischemia-reperfusion injury in mice by regulating MLK3 signaling.

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.

Indispensable role of β-arrestin2 in the protection of remifentanil preconditioning against hepatic ischemic reperfusion injury

Our previous study demonstrated that remifentanil, an opioid agonist, conferred profound liver protection during hepatic ischemia reperfusion injury (HIRI), in which Toll-like receptors (TLRs) played a crucial role in mediating the inflammatory responses. β-arrestin2, a well-known mu opioid receptor desensitizer, is also a negatively regulator of Toll-like receptor 4 (TLR4)-mediated inflammatory reactions in a mitogen-activated protein kinase (MAPK)-dependent manner. Using the rodent models of hepatic ischemia reperfusion injury both in wild type and TLR4 knockout (TLR4 KO) mice, we found that remifentanil preconditioning could inhibit the expression of TLR4 and reduce the inflammatory response induced by HIRI in wild type but not in TLR4 KO mice. For the in-vitro study, LPS was used to treat RAW264.7 macrophage cells to mimic the inflammatory response induced by HIRI. Remifentanil increased β-arrestin2 expression both in vivo and in vitro, while after silencing β-arrestin2 RNA, the effect of remifentanil in reducing cell death and apoptosis, as well as decreasing phosphorylation of ERK and JNK were abolished in RAW264.7 cells. These data suggested that remifentanil could ameliorate mice HIRI through upregulating β-arrestin2 expression, which may function as a key molecule in bridging opioid receptor and TLR4 pathway.

Gene Expression Profiling in Ischemic Postconditioning to Alleviate Mouse Liver Ischemia/Reperfusion Injury

Ischemic postconditioning (IPO) attenuates hepatic ischemia/reperfusion (I/R) injury. However, little is known about the underlying biological pathophysiology, which could be, at least in part, informed by exploring the transcriptomic changes using next-generation RNA sequencing (RNA-Seq). In this study, 18 mice (C57BL/6) were involved and randomly assigned to three groups: normal (n=6), I/R (n=6, subjected to 70% hepatic I/R), and IR+IPO (n=6, applying IPO to mice with I/R injury). We randomly selected 3 mice per group and extracted their liver tissues for next-generation RNA-Seq. We performed a bioinformatics analysis for two comparisons: normal vs. I/R and I/R vs. IR+IPO. From the analysis, 2416 differentially expressed genes (DEGs) were identified (p < 0.05 and fold change ≥ 1.5). Gene ontology (GO) analysis revealed that these genes were mainly related to cellular metabolic processes, nucleic acids and protein binding processes. The enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for the DEGs were the mitogen-activated protein kinase (MAPK), IL-17 signalling pathway, regulating pluripotency of stem cells, and insulin resistance pathway. Validation of 12 selected DEGs by qRT-PCR showed that Cyr61, Atf3, Nr4a1, Gdf15, Osgin1, Egr1, Epha2, Dusp1, Dusp6, Gadd45a and Gadd45b were significantly amplified. Finally, a protein-protein interaction (PPI) network constructed to determine interactions of these 11 DEGs. In summary, by exploring gene expression profiling in regard to hepatic I/R and IPO using next-generation RNA-Seq, we suggested a few progression-related genes and pathways, providing some clues for future experimental research.

Beraprost sodium preconditioning prevents inflammation, apoptosis, and autophagy during hepatic ischemia-reperfusion injury in mice via the P38 and JNK pathways

OBJECTIVE

The goal of this study was to determine the effects of beraprost sodium (BPS) preconditioning on hepatic ischemia-reperfusion (IR) injury and its underlying mechanisms of action.

MATERIALS AND METHODS

Mice were randomly divided into sham, IR, IR+BPS (50 µg/kg), and IR+BPS (100 µg/kg) groups. Saline or BPS was given to the mice by daily gavage for 1 week before the hepatic IR model was established. Liver tissues and orbital blood were collected at 2, 8, and 24 hours after reperfusion for the determination of liver enzymes, inflammatory mediators, apoptosis- and autophagy-related proteins, key proteins in P38 and c-Jun N-terminal kinase (JNK) cascades, and evaluation of liver histopathology.

RESULTS

BPS preconditioning effectively reduced serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, improved pathological damage, ameliorated production of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), and affected expressions of Bax, Bcl-2, Caspase-3, Caspase-8, and Caspase-9, microtubule-associated protein 1 light chain 3 (LC3), Beclin-1, and P62. The protective effects of BPS preconditioning were associated with reduced P38 and JNK phosphorylation.

CONCLUSION

BPS preconditioning ameliorated hepatic IR injury by suppressing inflammation, apoptosis, and autophagy, partially via inhibiting activation of the P38 and JNK cascades.

Role of JNK signalling pathway and platelet‑lymphocyte aggregates in myocardial ischemia‑reperfusion injury and the cardioprotective effect of ischemic postconditioning in rats

In myocardial ischemia‑reperfusion injury (MIRI), increased activity of the c‑Jun N‑terminal kinase (JNK) pathway and the activation of platelets that leads to the formation of platelet‑leukocyte aggregates (PLAs) have been observed. It was hypothesized that ischemic postconditioning in MIRI exerts cardioprotective effects by altering JNK activity, which in turn leads to reduced PLA levels. A total of 60 rats were randomly divided into 6 groups (n=10 for each group): i) Control; ii) ischemia‑reperfusion injury alone; iii) ischemia‑reperfusion with postconditioning (PostC group), iv) treatment with the JNK inhibitor‑SP600125; v) postC and treatment with anisomycin; and vi) treatment with the JNK activator‑anisomycin. Subsequently, the levels of PLA, infarct size, myocardial injury markers (creatinine kinase‑muscle/brain and troponin I) and were measured. Western blotting was used to determine the protein expression of phosphorylated‑JNK. MIRI led to increased myocardial infarct size that was associated with raised troponin I and creatine kinase‑muscle/brain. At different time points of MIRI, the level of PLA gradually increased. Compared with the injury‑reperfusion group, the level of PLA in the PostC and Inhibitor‑JNK groups was significantly reduced at 60 min and 3 h following reperfusion. MIRI was able to increase the expression of phosphorylated JNK. These effects were significantly reduced by ischemic postC or by treatment with SP600125. By contrast, the addition of anisomycin attenuated these protective effects. JNK is a critical mediator of MIRI. Ischemic postC can reduce the level of PLA during reperfusion by inhibiting the phosphorylation of JNK MAPK, thereby reducing MIRI. Pharmacological inhibition and activation of JNK can improve and reduce cardioprotective effects, respectively. These results explained the mechanism of the cardioprotection of postC and provided novel insight and target for the therapeutic strategy of MIRI.

Preoperative erythropoietin treatment improves survival following major hepatic resection in a cirrhotic rat model

AIM

Major hepatic resection of a cirrhotic liver may result in a fatal clinical course. Preoperative erythropoietin (EPO) treatment has been shown to have protective properties and to stimulate liver regeneration. This study aims to investigate the effect of preoperative EPO on survival following major hepatic resection in a cirrhotic rat model.

METHODS

Cirrhotic liver was induced by intraperitoneal injection of thioacetamide (200mg/kg/mL) in 72 Lewis rats. Each 36 rats received EPO (1IU/g, every second day, 5 times preoperatively) or saline (control) and major hepatectomy (removal of the left and half of the median lobe) was performed. Biochemical and immunohistochemical parameters, cytokines and overall survival were compared following surgery.

RESULTS

Rats that received preoperative EPO had decreased hepatic aspartate aminotransferase, alanine aminotransferase and interleukin (IL)-1β expression, 48hours following surgery. They had increased hepatocyte growth factor and vascular endothelial growth factor expression at 1hour, increased IL-6 expression at 24, 48 and 120hours and increased Ki-67, 120hours following surgery. Overall, survival was significantly improved among EPO-treated rats (P=0.034).

CONCLUSION

Preoperative EPO treatment has a protective effect and stimulates liver regeneration, leading to improved overall survival following major hepatectomy in a cirrhotic rat model.

Saponins isolated from Schizocapsa plantaginea inhibit human hepatocellular carcinoma cell growth in vivo and in vitro via mitogen-activated protein kinase signaling

The underground cane of Schizocapsa plantaginea (Hance) has long been used by Chinese ethnic minority as a constituent of anti-cancer formulae. Saponins are abundant secondary metabolic products located in the underground cane of this plant. The potential therapeutic effects of total saponins isolated from Schizocapsa plantaginea (Hance) (SSPH) on human hepatocellular carcinoma (HCC) were tested in vitro in human liver cancer cell lines, SMMC-7721 and Bel-7404. Apoptosis and cell cycle arrest were determined using flow cytometry, caspase activation was determined by ELISA, and PARP, cleaved PARP, mitogen-activated protein kinase (MAPK) expression and phosphorylation were measured using Western blotting analysis. In vivo anti-HCC effects of SSPH were verified in nude mouse xenograft model. SSPH exerted markedly inhibitory effect on HCC cell proliferation in time- and concentration-dependent manner. Moreover, SSPH significantly induced apoptosis through caspase-dependent signaling and arrested cell cycle at G₂/M phase. These anti-proliferation effects of SSPH were associated with up-regulated phosphorylation of extracellular signal-regulated kinase-1/2 (Erk1/2) and c-jun-NH2-kinase-1/2 (JNK1/2) and reduced phosphorylation of p38MAPK. Furthermore, inhibitors of ERK, UO126, and JNK, SP600125 inhibited the anti-proliferation effects by SSPH, suggesting that Erk and JNK were the effector molecules in SSPH induced anti-proliferative action. During in vivo experiments, SSPH was found to inhibit xenograft tumor growth in nude mice, with a similar mechanism in vitro. Our study confirmed that SSPH exerted antagonistic effects on human liver cancer cells both in vitro and in vivo. Molecular mechanisms underlying SSPH action might be closely associated with MAPK signaling pathways. These results indicated that SSPH has potential therapeutic effects on HCC.

Mild Hypothermia Pretreatment Attenuates Liver Ischemia Reperfusion Injury Through Inhibiting c-Jun NH2-terminal Kinase Phosphorylation in Rats

BACKGROUND

Mild hypothermia is known to be protected against ischemia reperfusion (IR) injury. But the exact mechanisms of protection have not yet been fully understood and its usage has been limited. Mild hypothermia pretreatment (MHP) is used to investigate the mechanisms of the protective effects against liver IR injury.

METHODS

Anesthetized male Sprague-Dawley rats were randomly divided into five groups including the normal group (N), sham group (S), MHP group, normothermia pretreatment (NP) + IR group, and the MHP + IR group. In the pretreatment groups, mild hypothermia (32.2 ± 0.3°C) and normothermia (37 ± 0.5°C) pretreatment were applied for 2 hours, respectively. Then the IR groups suffered partial (70%) hepatic ischemia for 1 hour and reperfusion for 6 hours. At last, hepatic injury, apoptosis, and protein expression were assessed.

RESULTS

Levels of serum alanine transaminase, hepatic injury, hepatocyte apoptosis, and c-Jun N-terminal kinase (JNK) phosphorylation were significantly higher in the IR groups. But when compared to NP, all these changes induced by IR were markedly attenuated by MHP. Serum alanine transaminase levels were 383.4 ± 13.1U/L in the MHP + IR group and 951.3 ± 39.4 U/L in the NP + IR group. The histologic score of liver injury in the MHP + IR group was 4.83 ± 1.17, whereas in the NP + IR group it was 10.5 ± 1.05. The proportion of apoptotic cells in the MHP + IR group was 11.58 ± 0.60, but in the NP + IR group, it was 44.95 ± 1.61. The phosphorylation of JNK was also significantly reduced in the MHP + IR group. All these differences are statistically significant (P < .05).

CONCLUSIONS

MHP could markedly reduce liver IR injury, and these protective effects may be mainly exerted via inhibition of JNK phosphorylation.

Post-reperfusion hydrogen gas treatment ameliorates ischemia reperfusion injury in rat livers from donors after cardiac death: a preliminary study

BACKGROUND AND PURPOSE

We reported previously that hydrogen gas (H₂) reduced hepatic ischemia and reperfusion injury (IRI) after prolonged cold storage (CS) of livers retrieved from heart-beating donors. The present study was designed to assess whether H₂ reduced hepatic IRI during donation of a cardiac death (DCD) graft with subsequent CS.

METHODS

Rat livers were harvested after 30-min cardiac arrest and stored for 4 h in University of Wisconsin solution. The graft was reperfused with oxygenated buffer, with or without H₂ (H₂ or NT groups, respectively), at 37° for 90 min on isolated perfused rat liver apparatus.

RESULTS

In the NT group, liver enzyme leakage, apoptosis, necrosis, energy depletion, redox status, impaired microcirculation, and bile production were indicative of severe IRI, whereas in the H₂ group these impairments were significantly suppressed. The phosphorylation of cytoplasmic MKK4 and JNK were enhanced in the NT group and suppressed in the H₂ group. NFkB-p65 and c-Fos in the nucleus were unexpectedly unchanged by IRI regardless of H₂ treatment, indicating the absence of inflammation in this model.

CONCLUSION

H₂ was observed to ameliorate IRI in the DCD liver by maintaining microcirculation, mitochondrial functions, and redox status, as well as suppressing the cytoplasmic MKK4-JNK-mediated cellular death pathway.

Editor's Highlight: Farnesoid X Receptor Protects Against Low-Dose Carbon Tetrachloride-Induced Liver Injury Through the Taurocholate-JNK Pathway

Hepatotoxicity is of major concern for humans exposed to industrial chemicals and drugs. Disruption of farnesoid X receptor (FXR), a master regulator of bile acid (BA) metabolism, enhanced the sensitivity to liver injury in mice after toxicant exposure, but the precise mechanism remains unclear. In this study, the interconnection between BA metabolism, FXR, and chemically induced hepatotoxicity was investigated using metabolomics, Fxr-null mice (Fxr-/-) and hepatocytes, and recombinant adenoviruses. A single low-dose intraperitoneal injection of carbon tetrachloride (CCl4), an inducer of acute hepatitis in mice, resulted in more severe hepatocyte damage and higher induction of pro-inflammatory mediators, such as chemokine (C-C motif) ligand 2 (Ccl2), in Fxr-/-. Serum metabolomics analysis revealed marked increases in circulating taurocholate (TCA) and tauro-β-muricholate (T-β-MCA) in these mice, and forced expression of bile salt export protein (BSEP) by recombinant adenovirus in Fxr-/- ameliorated CCl4-induced liver damage. Treatment of Fxr-null hepatocytes with TCA, but not T-β-MCA, significantly increased c-Jun-N-terminal kinase (JNK) activation and Ccl2 mRNA levels, and up-regulation of Ccl2 mRNA was attenuated by co-treatment with a JNK inhibitor SP600125, indicating that TCA directly amplifies hepatocyte inflammatory signaling mainly mediated by JNK under FXR-deficiency. Additionally, pretreatment with SP600125 or restoration of FXR expression in liver by use of recombinant adenovirus, attenuated CCl4-induced liver injury. Collectively, these results suggest that the TCA-JNK axis is likely associated with increased susceptibility to CCl4-induced acute liver injury in Fxr-/-, and provide clues to the mechanism by which FXR and its downstream gene targets, such as BSEP, protects against chemically induced hepatotoxicity.

Reviews of Interleukin-37: Functions, Receptors, and Roles in Diseases

Interleukin-37 (IL-37) is an IL-1 family cytokine discovered in recent years and has 5 different isoforms. As an immunosuppressive factor, IL-37 can suppress excessive immune response. IL-37 plays a role in protecting the body against endotoxin shock, ischemia-reperfusion injury, autoimmune diseases, and cardiovascular diseases. In addition, IL-37 has a potential antitumor effect. IL-37 and its receptors may serve as novel targets for the study, diagnosis, and treatment of immune-related diseases and tumors.

SIRT6 protects against hepatic ischemia/reperfusion injury by inhibiting apoptosis and autophagy related cell death

Silent information regulator 6 (SIRT6), a class III histone deacetylase, has been revealed to participate in multiple metabolic processes in the liver, and it plays important roles in protecting against ischemia/reperfusion (I/R) injury in multiple organs. In this study, we explored whether SIRT6 is protective against hepatic I/R injury and elucidated the underlying mechanisms. The expression of SIRT6 was significantly decreased during reperfusion compared with the control group. SIRT6-LKO mice exhibited significantly aggravated oxidative stress, mitochondrial dysfunction, inflammatory responses, mitogen-activated protein kinase (MAPK) signaling activation, and apoptosis and autophagy related hepatocyte death compared with control mice. In vitro studies in SIRT6-KO hepatocytes exhibited similar results. In contrast, SIRT6 upregulation alleviated liver damage during hepatic I/R injury. Our study demonstrated for the first time that SIRT6 upregulation effectively protects against hepatic I/R injury. The underlying mechanisms involve the maintenance of oxidative homeostasis and mitochondrial function, which subsequently inhibit the inflammatory responses and MAPK signaling, and finally attenuate apoptosis and autophagy related hepatocyte death. These results suggest that the activation of SIRT6 exerts multifaceted protective effects during hepatic I/R injury, which can provide a novel therapeutic target for hepatic I/R injury.

JNK, p38, ERK, and SGK1 Inhibitors in Cancer

Mitogen-activated protein kinases (MAP kinases) are a family of kinases that regulates a range of biological processes implicated in the response to growth factors like latelet-derived growth factor (PDGF), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and stress, such as ultraviolet irradiation, heat shock, and osmotic shock. The MAP kinase family consists of four major subfamilies of related proteins (extracellular regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38, and extracellular regulated kinase 5 (ERK5)) and regulates numerous cellular activities, such as apoptosis, gene expression, mitosis, differentiation, and immune responses. The deregulation of these kinases is shown to be involved in human diseases, such as cancer, immune diseases, inflammation, and neurodegenerative disorders. The awareness of the therapeutic potential of the inhibition of MAP kinases led to a thorough search for small-molecule inhibitors. Here, we discuss some of the most well-known MAP kinase inhibitors and their use in cancer research.

Silencing of phospholipase C gamma 2 promotes proliferation of rat hepatocytes in vitro

The management of hepatic failure is undoubtedly difficult, and poor results have led to the search for novel therapeutic approaches. Nowadays, anti-apoptotic gene therapy is considered as an ideal approach. It has been proved that phospholipase Cγ2 (PLCγ2) is involved in the apoptosis of immune cells and tumor cells; however, whether this gene is related to hepatocyte death is still unclear. This study examined the role of PLCγ2 by inhibiting its expression in rat hepatocytes with siRNA. We also further analyzed the cellular mechanism by which the expression inhibition of PLCγ2 induces cell death. Silencing PLCγ2 gene by adenovirus vector expressing PLCγ2-targeted siRNA caused the great decline in the number of G1- and G2/M phase cells, the significant increase in the number of S phase cells, and the obvious reduction in apoptosis index. In addition, silencing PLCγ2 gene relieved the rat hepatocyte damage, such as the cell shrinkage and chromatin condensation, nuclear fragmentation. Further analysis of Ad-PLCγ2 siRNA-transfected hepatocytes demonstrated that suppression of PLCγ2 gene expression could cause the caspase dependent cell death by inhibiting the signal pathway MEKK1/MKK4/JNK1/2/c-Jun. In conclusion, these findings suggest that interference with PLCγ2 expression could relieve the inhibitory effect of PLCγ2 on hepaocyte apoptosis, thus, promote proliferation through inactivating PKCδ-mediated JNK1/2 signaling pathway.

The novel JNK inhibitor AS602801 inhibits cancer stem cells in vitro and in vivo

A phase 2 clinical trial investigating the efficacy and safety of AS602801, a newly developed JNK inhibitor, in the treatment of inflammatory endometriosis is complete. We are now examining whether AS602801 acts against human cancer cells in vitro and in vivo. In vitro, AS602801 exhibited cytotoxicity against both serum-cultured non-stem cancer cells and cancer stem cells derived from human pancreatic cancer, non-small cell lung cancer, ovarian cancer and glioblastoma at concentrations that did not decrease the viability of normal human fibroblasts. AS602801 also inhibited the self-renewal and tumor-initiating capacity of cancer stem cells surviving AS602801 treatment. Cancer stem cells in established xenograft tumors were reduced by systemic administration of AS602801 at a dose and schedule that did not adversely affect the health of the tumor-bearing mice. These findings suggest AS602801 is a promising anti-cancer stem cell agent, and further investigation of the utility of AS602801 in the treatment of cancer seems warranted.

Biochemical targets of drugs mitigating oxidative stress via redox-independent mechanisms

Acute or chronic oxidative stress plays an important role in many pathologies. Two opposite approaches are typically used to prevent the damage induced by reactive oxygen and nitrogen species (RONS), namely treatment either with antioxidants or with weak oxidants that up-regulate endogenous antioxidant mechanisms. This review discusses options for the third pharmacological approach, namely amelioration of oxidative stress by 'redox-inert' compounds, which do not inactivate RONS but either inhibit the basic mechanisms leading to their formation (i.e. inflammation) or help cells to cope with their toxic action. The present study describes biochemical targets of many drugs mitigating acute oxidative stress in animal models of ischemia-reperfusion injury or N-acetyl-p-aminophenol overdose. In addition to the pro-inflammatory molecules, the targets of mitigating drugs include protein kinases and transcription factors involved in regulation of energy metabolism and cell life/death balance, proteins regulating mitochondrial permeability transition, proteins involved in the endoplasmic reticulum stress and unfolded protein response, nuclear receptors such as peroxisome proliferator-activated receptors, and isoprenoid synthesis. The data may help in identification of oxidative stress mitigators that will be effective in human disease on top of the current standard of care.

Role of C-Jun N-terminal Kinase in Hepatocellular Carcinoma Development

Hepatocellular carcinoma (HCC) is among the most frequently occurring cancers and the leading causes of cancer mortality worldwide. Identification of the signaling pathways regulating liver carcinogenesis is critical for developing novel chemoprevention and targeted therapies. C-Jun N-terminal kinase (JNK) is a member of a larger group of serine/threonine (Ser/Thr) protein kinases known as the mitogen-activated protein kinase (MAPK) family. JNK is an important signaling component that converts external stimuli into a wide range of cellular responses, including cell proliferation, differentiation, survival, migration, invasion, and apoptosis, as well as the development of inflammation, fibrosis, cancer growth, and metabolic diseases. Because of the essential roles of JNK in these cellular functions, deregulated JNK is often found to contribute to the development of HCC. Recently, the functions and molecular mechanisms of JNK in HCC development have been addressed using mouse models and human HCC cell lines. Furthermore, recent studies demonstrate that the activation of JNK by oncogenes can promote the development of cancers by regulating the transforming growth factor (TGF)-β/Smad pathway, which makes the oncogenes/JNK/Smad signaling pathway an attractive target for cancer therapy. Additionally, JNK-targeted therapy has a broad potential for clinical applications. In summary, we are convinced that promising new avenues for the treatment of HCC by targeting JNK are on the horizon, which will undoubtedly lead to better, more effective, and faster therapies in the years to come.

Potential role of IL-37 in atherosclerosis

IL-37 is a member of the IL-1 family, but unlike most other members of this family of cytokines, it has wide-ranging anti-inflammatory properties. Initially shown to bind IL-18 binding protein and prevent IL-18-mediated inflammation, its known role has been expanded to include distinct pathways, both intracellular involving the transcription factor Smad3, and extracellular via binding to the orphan receptor IL-1R8. A number of recent publications investigating the role of IL-37 in atherosclerosis and ischemic heart disease have revealed promising therapeutic value of the cytokine. Although research concerning the role of IL-37 and its mechanism in atherosclerosis is relatively scant, there are a number of well-known atherosclerotic processes that this cytokine can mediate with the potential of modulating the disease progression itself. This review will probe in detail the effects of IL-37 on important pathological processes such as inflammation, dysregulated lipid metabolism, and apoptosis, by analyzing existing data as well as exploring the potential of this cytokine to influence these properties.

Induction of autophagy reduces ischemia/reperfusion injury in steatotic rat livers

BACKGROUND

Steatotic livers are particularly vulnerable to ischemia/reperfusion injury (IRI). One of the reasons is an underlying impairment of autophagy. Autophagy is regulated by glycogen synthase kinase 3b (GSK3b) and extracellular signal-regulated kinases (ERK1/2) pathways. Both of them are target proteins of a cell-protective drug, lithium chloride. Lithium chloride treatment reduces IRI in many organs including liver. Therefore, we aimed to investigate the effect of lithium chloride treatment on autophagy induction in steatotic rat livers. We also wanted to evaluate the related cell-protective effects on the enhanced hepatic IRI.

MATERIALS AND METHODS

After inducing hepatic steatosis, rats were injected with lithium chloride or normal saline for 3 d before being subjected to 70% selective warm ischemia for 60 min. After reperfusion, rats were observed for 30 min, 6, 24, and 48 h.

RESULTS

Lithium chloride appeared to protect hepatocytes from IRI via its ability to induce autophagy by modulation of both GSK3b and ERK1/2 pathways. Hepatic damage was significantly decreased in the treatment group as indicated by a reduced inflammatory response, less apoptosis, less necrosis, and lower liver enzyme levels.

CONCLUSIONS

Simultaneous modulation of GSK3b and ERK1/2 pathways might be an interesting strategy to reduce IRI in steatotic livers with an impairment of autophagy.

Sirtuin 2 aggravates postischemic liver injury by deacetylating mitogen-activated protein kinase phosphatase-1

Sirtuin 2 (Sirt2) is known to negatively regulate anoxia-reoxygenation injury in myoblasts. Because protein levels of Sirt2 are increased in ischemia-reperfusion (I/R)-injured liver tissues, we examined whether Sirt2 is protective or detrimental against hepatic I/R injury. We overexpressed Sirt2 in the liver of C57BL/6 mice using a Sirt2 adenovirus. Wild-type and Sirt2 knockout mice were subjected to a partial (70%) hepatic ischemia for 45 minutes, followed by various periods of reperfusion. In another set of experiments, wild-type mice were pretreated intraperitoneally with AGK2, a Sirt2 inhibitor. Isolated hepatocytes and Kupffer cells from wild-type and Sirt2 knockout mice were subjected to hypoxia-reoxygenation injury to determine the in vitro effects of Sirt2. Mice subjected to I/R injury showed typical patterns of hepatocellular damage. Prior injection with Sirt2 adenovirus aggravated liver injury, as demonstrated by increases in serum aminotransferases, prothrombin time, proinflammatory cytokines, hepatocellular necrosis and apoptosis, and neutrophil infiltration relative to control virus-injected mice. Pretreatment with AGK2 resulted in significant improvements in serum aminotransferase levels and histopathologic findings. Similarly, experiments with Sirt2 knockout mice also revealed reduced hepatocellular injury. The molecular mechanism of Sirt2's involvement in this aggravation of hepatic I/R injury includes the deacetylation and inhibition of mitogen-activated protein kinase phosphatase-1 and consequent activation of mitogen-activated protein kinases.

CONCLUSION

Sirt2 is an aggravating factor during hepatic I/R injury. (Hepatology 2017;65:225-236).

Thrombomodulin Attenuates Inflammatory Damage Due to Liver Ischemia and Reperfusion Injury in Mice in Toll-Like Receptor 4-Dependent Manner

Liver ischemia reperfusion injury (IRI) is an important problem in liver transplantation. Thrombomodulin (TM), an effective drug for disseminated intravascular coagulation, is also known to exhibit an anti-inflammatory effect through binding to the high-mobility group box 1 protein (HMGB-1) known as a proinflammatory mediator. We examined the effect of recombinant human TM (rTM) on a partial warm hepatic IRI model in wild-type (WT) and toll-like receptor 4 (TLR-4) KO mice focusing on the HMGB-1/TLR-4 axis. As in vitro experiments, peritoneal macrophages were stimulated with recombinant HMGB-1 protein. The rTM showed a protective effect on liver IRI. The rTM diminished the downstream signals of TLR-4 and also HMGB-1 expression in liver cells, as well as release of HMGB-1 from the liver. Interestingly, neither rTM treatment in vivo nor HMGB-1 treatment in vitro showed any effect on TLR-4 KO mice. Parallel in vitro studies have confirmed that rTM interfered with the interaction between HMGB-1 and TLR-4. Furthermore, the recombinant N-terminal lectin-like domain 1 (D1) subunit of TM (rTMD1) also ameliorated liver IRI to the same extent as whole rTM. Not only rTM but also rTMD1 might be a novel and useful medicine for liver transplantation. This is the first report clarifying that rTM ameliorates inflammation such as IRI in a TLR-4 pathway-dependent manner.

Neuroprotection of Cilostazol against ischemia/reperfusion-induced cognitive deficits through inhibiting JNK3/caspase-3 by enhancing Akt1

Cilostazol(CTL) is a phosphodiesterase inhibitor, which has been widely used as anti-platelet agent. It also has preventive effects on various central nervous system (CNS) diseases, including ischemic stroke, Parkinson's disease and Alzheimer disease. However, the molecular mechanism underlying the protective effects of CTL is still unclear, and whether CTL can prevent I/R induced cognitive deficit has not been reported. Transient global brain ischemia was induced by 4-vessel occlusion in adult male Sprague-Dawley rats. The open field tasks and Morris water maze were used to assess the effect of CTL on anxiety-like behavioral and cognitive impairment after I/R. Western blotting were performed to examine the expression of related proteins, and HE-staining was used to detect the percentage of neuronal death in the hippocampal CA1 region. Here we found that CTL significantly improved cognitive deficits and the behavior of rats in Morris water maze and open field tasks (P<0.05). HE staining results showed that CTL could significantly protect CA1 neurons against cerebral I/R (P<0.05). Additionally, Akt1 phosphorylation levels were evidently up-regulated (P<0.05), while the activation of JNK3, which is an important contributor to I/R-induced neuron apoptosis, was reduced by CTL after I/R (P<0.05), and caspase-3 levels were also decreased by CTL treatment. Furthermore, all of CTL's protective effects were reversed by LY294002, which is a PI3K/Akt1 inhibitor. Taken together, our results suggest that CTL could protect hippocampal neurons and ameliorate the impairment of learning/memory abilities and locomotor/ exploratory activities in ischemic stroke via a PI3K-Akt1/JNK3/caspase-3 dependent mechanism.

HDACi Valproic Acid (VPA) and Suberoylanilide Hydroxamic Acid (SAHA) Delay but Fail to Protect against Warm Hepatic Ischemia-Reperfusion Injury

BACKGROUND

Histone deacetylases (HDAC) catalyze N-terminal deacetylation of lysine-residues on histones and multiple nuclear and cytoplasmic proteins. In various animal models, such as trauma/hemorrhagic shock, ischemic stroke or myocardial infarction, HDAC inhibitor (HDACi) application is cyto- and organoprotective and promotes survival. HDACi reduce stress signaling, cell death and inflammation. Hepatic ischemia-reperfusion (I/R) injury during major liver resection or transplantation increases morbidity and mortality. Assuming protective properties, the aim of this study was to investigate the effect of the HDACi VPA and SAHA on warm hepatic I/R.

MATERIAL AND METHODS

Male Wistar-Kyoto rats (age: 6-8 weeks) were randomized to VPA, SAHA, vehicle control (pre-) treatment or sham-groups and underwent partial no-flow liver ischemia for 90 minutes with subsequent reperfusion for 6, 12, 24 and 60 hours. Injury and regeneration was quantified by serum AST and ALT levels, by macroscopic aspect and (immuno-) histology. HDACi treatment efficiency, impact on MAPK/SAPK-activation and Hippo-YAP signaling was determined by Western blot.

RESULTS

Treatment with HDACi significantly enhanced hyperacetylation of Histone H3-K9 during I/R, indicative of adequate treatment efficiency. Liver injury, as measured by macroscopic aspect, serum transaminases and histology, was delayed, but not alleviated in VPA and SAHA treated animals. Importantly, tissue destruction was significantly more pronounced with VPA. SAPK-activation (p38 and JNK) was reduced by VPA and SAHA in the early (6h) reperfusion phase, but augmented later on (JNK, 24h). Regeneration appeared enhanced in SAHA and VPA treated animals and was dependent on Hippo-YAP signaling.

CONCLUSIONS

VPA and SAHA delay warm hepatic I/R injury at least in part through modulation of SAPK-activation. However, these HDACi fail to exert organoprotective effects, in this setting. For VPA, belated damage is even aggravated.