Apoptotic cell death in the response of D-galactosamine-sensitized mice to lipopolysaccharide as an experimental endotoxic shock model

Olprinone, a Selective Phosphodiesterase III Inhibitor, Has Protective Effects in a Septic Rat Model after Partial Hepatectomy and Primary Rat Hepatocyte

Olprinone (OLP) is a selective inhibitor of phosphodiesterase III and is used clinically in patients with heart failure and those undergoing cardiac surgery; however, little is known about the effects of OLP on hepatoprotection. The purpose of this study aimed to determine whether OLP has protective effects in in vivo and in vitro rat models of endotoxin-induced liver injury after hepatectomy and to clarify the mechanisms of action of OLP. In the in vivo model, rats underwent 70% partial hepatectomy and lipopolysaccharide treatment (PH/LPS). OLP administration increased survival by 85.7% and decreased tumor necrosis factor-α, C-X-C motif chemokine ligand 1, and inducible nitric oxide synthase (iNOS) mRNA expression in the livers of rats treated with PH/LPS. OLP also suppressed nuclear translocation and/or DNA binding ability of nuclear factor kappa B (NF-κB). Pathological liver damage induced by PH/LPS was alleviated and neutrophil infiltration was reduced by OLP. Primary cultured rat hepatocytes treated with the pro-inflammatory cytokine interleukin-1β (IL-1β) were used as a model of in vitro liver injury. Co-treatment with OLP inhibited dose-dependently IL-1β-stimulated iNOS induction and NF-κB activation. Our results demonstrate that OLP may partially inhibit the induction of several inflammatory mediators through the suppression of NF-κB and thus prevent liver injury induced by endotoxin after liver resection.

Establishment of acute liver failure model in Tibetan miniature pig and verified by dual plasma molecular adsorption system

BACKGROUND

Acute liver failure (ALF) is a severe liver disease with high morbidity and mortality rates. Animal models are important for research on ALF. This study aimed to establish a reproducible, Tibetan miniature pig model of D-galactosamine-induced ALF and verify it using a dual plasma molecular adsorption system (DPMAS).

METHODS

Tibet miniature pigs were randomly divided into four groups (A, B, C, D) after catheterization. D-galactosamine (D-gal) at 0.45, 0.40, 0.35, and 0.35 g/kg body weight, respectively, was injected through the catheter. Group D was treated with DPMAS 48 h after D-gal administration. Vital signs and blood index values were recorded every 12 h after D-gal administration. H&E, TUNEL, Ki67, and Masson staining tests were performed.

RESULTS

After D-gal administration, Tibetan miniature pigs developed different degrees of debilitation, loss of appetite, and jaundice. Survival times of groups A, B, C, and D were 39.7 ± 5.9, 53.0 ± 12.5,61.3 ± 8.1, and 61 ± 7 h, respectively. Blood levels of ALT, AST, TBIL, ammonia, PT, and inflammation factors significantly increased compared with baseline levels in the different groups (Ps < 0.05). Pathological results revealed a clear liver cell necrosis positive correlation with D-gal dose. However, DPMAS did not increase the survival time in ALF, ammonia, or liver cell necrosis.

CONCLUSION

We successfully established a reproducible Tibetan miniature pig model of d-galactosamine-induced ALF, and we believe that a dosage of 0.35 g/kg is optimal.

Deficiency of Ninjurin1 attenuates LPS/D-galactosamine-induced acute liver failure by reducing TNF-α-induced apoptosis in hepatocytes

Nerve injury‐induced protein 1 (Ninjurin1, Ninj1) is a membrane protein that mediates cell adhesion. The role of Ninj1 during inflammatory response has been widely investigated in macrophages and endothelial cells. Ninj1 is expressed in various tissues, and the liver also expresses high levels of Ninj1. Although the hepatic upregulation of Ninj1 has been reported in human hepatocellular carcinoma and septic mice, little is known of its function during the pathogenesis of liver diseases. In the present study, the role of Ninj1 in liver inflammation was explored using lipopolysaccharide (LPS)/D‐galactosamine (D‐gal)‐induced acute liver failure (ALF) model. When treated with LPS/D‐gal, conventional Ninj1 knock‐out (KO) mice exhibited a mild inflammatory phenotype as compared with wild‐type (WT) mice. Unexpectedly, myeloid‐specific Ninj1 KO mice showed no attenuation of LPS/D‐gal‐induced liver injury. Whereas, Ninj1 KO primary hepatocytes were relatively insensitive to TNF‐α‐induced caspase activation as compared with WT primary hepatocytes. Also, Ninj1 knock‐down in L929 and AML12 cells and Ninj1 KO in HepG2 cells ameliorated TNF‐α‐mediated apoptosis. Consistent with in vitro results, hepatocyte‐specific ablation of Ninj1 in mice alleviated LPS/D‐gal‐induced ALF. Summarizing, our in vivo and in vitro studies show that lack of Ninj1 in hepatocytes diminishes LPS/D‐gal‐induced ALF by alleviating TNF‐α/TNFR1‐induced cell death.

Investigation of Metabolome Underlying the Biological Mechanisms of Acute Heat Stressed Granulosa Cells

Heat stress affects granulosa cells and the ovarian follicular microenvironment, ultimately resulting in poor oocyte developmental competence. This study aims to investigate the metabo-lomics response of bovine granulosa cells (bGCs) to in vitro acute heat stress of 43 °C. Heat stress triggers oxidative stress-mediated apoptosis in cultured bGCs. Heat-stressed bGCs exhibited a time-dependent recovery of proliferation potential by 48 h. A total of 119 metabolites were identified through LC-MS/MS-based metabolomics of the spent culture media, out of which, 37 metabolites were determined as differentially involved in metabolic pathways related to bioenergetics support mechanisms and the physical adaptations of bGCs. Multiple analyses of metabolome data identified choline, citric acid, 3-hydroxy-3-methylglutaric acid, glutamine, and glycocyamine as being upregulated, while galactosamine, AICAR, ciliatine, 16-hydroxyhexadecanoic acid, lysine, succinic acid, uridine, xanthine, and uraconic acid were the important downregulated metabolites in acute heat stress. These differential metabolites were implicated in various important metabolic pathways directed towards bioenergetics support mechanisms including glycerophospholipid metabolism, the citrate cycle (TCA cycle), glyoxylate and dicarboxylate metabolism, and serine, threonine, and tyrosine metabolism. Our study presents important metabolites and metabolic pathways involved in the adaptation of bGCs to acute heat stress in vitro.

OTUB1 prevents lethal hepatocyte necroptosis through stabilization of c-IAP1 during murine liver inflammation

In bacterial and sterile inflammation of the liver, hepatocyte apoptosis is, in contrast to necroptosis, a common feature. The molecular mechanisms preventing hepatocyte necroptosis and the potential consequences of hepatocyte necroptosis are largely unknown. Apoptosis and necroptosis are critically regulated by the ubiquitination of signaling molecules but especially the regulatory function of deubiquitinating enzymes (DUBs) is imperfectly defined. Here, we addressed the role of the DUB OTU domain aldehyde binding-1 (OTUB1) in hepatocyte cell death upon both infection with the hepatocyte-infecting bacterium Listeria monocytogenes (Lm) and D-Galactosamine (DGal)/Tumor necrosis factor (TNF)-induced sterile inflammation. Combined in vivo and in vitro experiments comprising mice lacking OTUB1 specifically in liver parenchymal cells (OTUB1LPC-KO) and human OTUB1-deficient HepG2 cells revealed that OTUB1 prevented hepatocyte necroptosis but not apoptosis upon infection with Lm and DGal/TNF challenge. Lm-induced necroptosis in OTUB1LPC-KO mice resulted in increased alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) release and rapid lethality. Treatment with the receptor-interacting serine/threonine-protein kinase (RIPK) 1 inhibitor necrostatin-1s and deletion of the pseudokinase mixed lineage kinase domain-like protein (MLKL) prevented liver damage and death of infected OTUB1LPC-KO mice. Mechanistically, OTUB1 reduced K48-linked polyubiquitination of the cellular inhibitor of apoptosis 1 (c-IAP1), thereby diminishing its degradation. In the absence of OTUB1, c-IAP1 degradation resulted in reduced K63-linked polyubiquitination and increased phosphorylation of RIPK1, RIPK1/RIPK3 necrosome formation, MLKL-phosphorylation and hepatocyte death. Additionally, OTUB1-deficiency induced RIPK1-dependent extracellular-signal-regulated kinase (ERK) activation and TNF production in Lm-infected hepatocytes. Collectively, these findings identify OTUB1 as a novel regulator of hepatocyte-intrinsic necroptosis and a critical factor for survival of bacterial hepatitis and TNF challenge.

Composite ammonium glycyrrhizin has hepatoprotective effects in chicken hepatocytes with lipopolysaccharide/enrofloxacin-induced injury

Composite ammonium glycyrrhizin (CAG) has anti-inflammatory activity. Lipopolysaccharide (LPS) and enrofloxacin (ENR) induce liver damage; however, the mechanism underlying LPS/ENR-induced hepatic injury remains to be elucidated. In the present study, the mechanism of LPS/ENR-induced liver injury was investigated in vitro and the protective effects of CAG were also evaluated. Primary chicken hepatocytes were isolated and a model of LPS/ENR-induced hepatocyte injury was established. mRNA and protein expression levels were evaluated by reverse transcription-quantitative polymerase chain reaction and western blot, respectively. LPS/ENR exposure significantly increased supernatant aspartate aminotransferase (AST) and alanine aminotransferase (ALT). In the LPS/ENR-treated group, glutathione (GSH) and the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities were significantly increased. Flow cytometry results revealed that the apoptotic rate significantly increased in the LPS/ENR-treated group compared with the control, while treatment with CAG given 24 h prior to LPS/ENR caused a significant decrease in the apoptotic rate compared with the model group. Furthermore, CAG treatment reversed LPS/ENR-associated alterations in the mRNA and protein expression of Caspase-3, apoptosis regulator Bcl-2 (Bcl-2) and Bcl-2 associated X-protein. The mitochondrial membrane potential significantly decreased and the mitochondrial microstructure was notably altered following exposure to LPS/ENR compared with the control. In conclusion, these results suggested that LPS/ENR-treated hepatocytes were damaged via apoptotic signaling pathways and CAG prevented LPS/ENR-induced hepatocyte injury.

Compound ammonium glycyrrhizin protects hepatocytes from injury induced by lipopolysaccharide/florfenicol through oxidative stress and a MAPK pathway

Compound ammonium glycyrrhizin (CAG) protects hepatocytes from injury induced by lipopolysaccharide (LPS)/florfenicol (FFC) through a mitochondrial pathway. On this basis, the research was aimed to investigate whether CAG protects hepatocytes from injury induced by LPS/FFC through oxidative stress and the MAPK pathway. For liver injury induced by LPS/FFC, not only CAG can protect hepatocytes and prevent membrane permeability from being increased, but also the activities of ALT and AST were decreased significantly by CAG. Flow cytometry analysis indicated that the apoptosis rate (35.65 ± 2.48%) of LPS/FFC group was significantly higher than that of the control group (8.60 ± 0.32%). CAG (concentration of 0.01 μg/mL, 0.1 μg/mL, 1 μg/mL) significantly decreased the apoptosis rate (23.69 ± 0.54%, 14.92 ± 2.45% and 9.47 ± 1.28%) for the liver injury induced by LPS/FFC. The activities of SOD and GSH were increased with the increased concentration of CAG, and the activity of MDA was decreased with the increased concentration of CAG. All the mRNA and proteins expression levels were increased by LPS/FFC-induced liver injury which associated with the MAPK pathway, and those of the CAG group were decreased with the increased concentration of CAG. And the change of caspase-3 activity was consistent with that of proteins and mRNA. It is suggested that LPS/FFC can induce liver injury through apoptosis and the CAG can protect hepatocytes from injury through the MAPK pathway and oxidative stress.

The Proton Pump Inhibitor Lansoprazole Has Hepatoprotective Effects in In Vitro and In Vivo Rat Models of Acute Liver Injury

BACKGROUND/AIMS

The proton pump inhibitor lansoprazole (LPZ) is clinically used to reduce gastric acid secretion, but little is known about its possible hepatoprotective effects. This study aimed to investigate the hepatoprotective effects of LPZ and its potential mechanisms using in vitro and in vivo rat models of liver injury.

METHODS

For the in vitro model of liver injury, primary cultured rat hepatocytes were treated with interleukin-1β in the presence or absence of LPZ. The influence of LPZ on inducible nitric oxide synthase (iNOS) induction and nitric oxide (NO) production and on the associated signaling pathways was analyzed. For the in vivo model, rats were treated with D-galactosamine (GalN) and lipopolysaccharide (LPS). The effects of LPZ on survival and proinflammatory mediator expression (including iNOS and tumor necrosis factor-α) in these rats were examined.

RESULTS

LPZ inhibited iNOS induction partially through suppression of the nuclear factor-kappa B signaling pathway in hepatocytes, thereby reducing potential liver injury from excessive NO levels. Additionally, LPZ increased survival by 50% and decreased iNOS, tumor necrosis factor-α, and cytokine-induced neutrophil chemoattractant-1 mRNA expression in the livers of GalN/LPS-treated rats. LPZ also inhibited nuclear factor-kappa B activation by GalN/LPS.

CONCLUSIONS

LPZ inhibits the induction of several inflammatory mediators (including cytokines, chemokines, and NO) partially through suppression of nuclear factor-kappa B, resulting in the prevention of fulminant liver failure. The therapeutic potential of LPZ for liver injuries warrants further investigation.

Methyl 3,4-dihydroxybenzoate protects against d-galN/LPS-induced acute liver injury by inhibiting inflammation and apoptosis in mice

Objectives

Aimed to investigate the effect and mechanism of methyl 3,4-dihydroxybenzoate (MDHB) on d-galactosamine/lipopolysaccharide (d-galN/LPS)-induced acute liver failure (ALF).

Methods

Confirmed the hepatoprotective effect and hepatotoxicity of MDHB by histopathological examination (HE) and examination of alanine aminotransferase (ALT) and aspartate aminotransferase (AST); the expression of serum tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) was detected by ELISA; transcription levels of TNF-α, IL-1β, IL-6 and Toll-like receptor 4 (TLR4) were detected by qRT-PCR; and phosphorylation levels of p38 and p65 were analysed by Western blot.

Results

Histopathological examination and examination of ALT and AST confirmed that MDHB is a low toxicity drug that can resist d-galN/LPS-induced ALF; MDHB can effectively reduce high transcription and expression of TNF-α, IL-1β, IL-6 and TLR4 in d-galN/LPS-induced ALF; and Western blot showed that MDHB could down-regulate the expression of bax, up-regulate the expression of bcl-xl and bcl-2, and inhibit the phosphorylation of p38 and p65.

Conclusions

Methyl 3,4-dihydroxybenzoate can effectively resist d-galN/LPS-induced acute liver failure, which is related to the inhibition of inflammation and apoptosis.

Dimethylglycine sodium salt protects against oxidative damage and mitochondrial dysfunction in the small intestines of mice

Few studies have investigated the use of dimethylglycine sodium salt (DMG‑Na) to protect against small intestinal damage, despite its prevalence in the treatment of human diseases. The present study aimed to evaluate the protective effects of DMG‑Na against oxidative damage and mitochondrial dysfunction in the small intestines of mice. A total of 100 male Kunming mice were randomly assigned to five groups (n=20 per group): i) Mice gastric intubation with 0.3 ml sterile saline solution (once), then subcutaneously injected with sterile saline solution (0.5 ml) after 1 h (CON); ii) mice gastric intubation with 12 mg DMG‑Na/0.3 ml of sterile saline solution once, then subcutaneously injected with sterile saline solution (0.5 ml) 1 h later (D); iii) mice gastric intubation with 0.3 ml sterile saline solution once, then subcutaneously injected with indomethacin (10 mg/kg BW) 1 h later (IN); iv) mice gastric intubation with 12 mg DMG‑Na/0.3 ml sterile saline solution once, then subcutaneously injected with indomethacin (10 mg/kg BW) 1 h later (DIN); and v) mice subcutaneously injected with indomethacin (10 mg/kg BW), then gastrically intubated with 12 mg DMG‑Na/0.3 ml sterile saline solution once after 1 h (IND). The present study was evaluated the effects of DMG‑Na on mice intestinal damage induced by indomethacin injection. The histological morphology of the small intestine improved (P<0.05) in the DIN and IND groups, compared with the IN group. The antioxidant system was enhanced, oxidative damage was reduced, and the expression of antioxidant‑associated genes was increased in the small intestine and its mitochondria in the DIN and IND groups, compared with the IN group. The above results suggested that pretreatment and treatment with DMG‑Na reduced oxidative damage by enhancing antioxidant capacity, increasing the expression of antioxidant‑associated genes, ameliorating mitochondrial dysfunction and suppressing apoptosis. Further study is required to determine the specific mechanism by which pretreatment and treatment with DMG‑Na reduced small intestinal damage.

Chemical induction of hepatic apoptosis in rodents

The urge of identifying new pharmacological interventions to prevent or attenuate liver injury is of critical importance and needs an expanded experimental toolbox. Hepatocyte injury and cellular death is a prominent feature behind the pathology of liver diseases. Several research activities focused on identifying chemicals and hepatotoxicants that induce cell death by apoptosis, in addition to presenting its corresponding signaling pathway. Although such efforts provided further understanding of the mechanisms of cell death, it has also raised confusion concerning identifying the involvement of several modes of cell death including apoptosis, necrosis and fibrosis. The current review highlights the ability of several chemicals and potential hepatotoxicants to induce liver damage in rodents by means of apoptosis while the probable involvement of other modes of cell death is also exposed. Thus, several chemical substances including hepatotoxins, mycotoxins, hyperglycemia inducers, metallic nanoparticles and immunosuppressant drugs are reviewed to explore the hepatic cytotoxic spectrum they could exert on hepatocytes of rodents. In addition, the current review address the mechanism by which hepatotoxicity is initiated in hepatocytes in different rodents aiding the researcher in choosing the right animal model for a better research outcome.

Activatable probes for diagnosing and positioning liver injury and metastatic tumors by multispectral optoacoustic tomography

Optoacoustic tomography (photoacoustic tomography) is an emerging imaging technology displaying great potential for medical diagnosis and preclinical research. Rationally designing activatable optoacoustic probes capable of diagnosing diseases and locating their foci can bring into full play the role of optoacoustic tomography (OAT) as a promising noninvasive imaging modality. Here we report two xanthene-based optoacoustic probes (C1X-OR1 and C2X-OR2) for temporospatial imaging of hepatic alkaline phosphatase (or β-galactosidase) for evaluating and locating drug-induced liver injury (or metastatic tumor). The probes rapidly respond to the disease-specific biomarkers by displaying red-shifted NIR absorption bands and generate prominent optoacoustic signals. Using multispectral optoacoustic tomography (MSOT), we can precisely localize the focus of drug-induced liver injury in mice using C1X-OR1, and the metastatic tumors using C2X-OR2. This work suggests that the activatable optoacoustic chromophores may potentially be applied for diagnosing and localizing disease foci, especially smaller and deeper ones.

Compound Ammonium Glycyrrhizin Protects Hepatocytes from Injury Induced by Lipopolysaccharide/Florfenicol through a Mitochondrial Pathway

Florfenicol (FFC), a widely used drug for chicken diseases, can aggravate lipopolysaccharide (LPS) damage to the liver. For this condition, natural or synthetic products displaying strong antioxidant capacity are expected to prevent LPS/FFC from inducing liver injury, so in our study, the compound ammonium glycyrrhizin (CAG) is used as the protective drug to decrease the injury to liver. The research aims to illustrate the underlying mechanism of combining LPS with FFC-induced liver injury and the protective role of CAG by using primary chicken hepatocytes as an in vitro model. The results show that LPS/FFC induced cell apoptosis and CAG protected hepatocytes from injury. The permeability of the cell membrane is elevated by LPS/FFC, leading to the efflux of enzymes (ALT, AST). Flow cytometry analysis indicates that LPS/FFC treatment increased the apoptosis rate significantly. Furthermore, with the up-regulation of apoptosis genes bax, cytochrome c and the down-regulation of bcl-2, caspase-3 and caspase-9 are activated at the gene level. LPS/FFC-induced mitochondrial damage is accompanied by a significant decrease in mitochondrial membrane potential (MMP) and severe mitochondrial damage. However, CAG improves the situation for the purpose of protecting the liver. In conclusion, it is speculated that LPS/FFC induces severe liver injury through apoptosis and the CAG protects hepatocytes from injury via the mitochondria-mediated apoptosis pathway.

TNFα sensitizes hepatocytes to FasL-induced apoptosis by NFκB-mediated Fas upregulation

Although it is well established that TNFα contributes to hepatitis, liver failure and associated hepatocarcinogenesis via the regulation of inflammation, its pro-apoptotic role in the liver has remained enigmatic. On its own, TNFα is unable to trigger apoptosis. However, when combined with the transcriptional inhibitor GaLN, it can cause hepatocyte apoptosis and liver failure in mice. Moreover, along with others, we have shown that TNFα is capable of sensitizing cells to FasL- or drug-induced cell death via c-Jun N-terminal kinase (JNK) activation and phosphorylation/activation of the BH3-only protein Bim. In this context, TNFα could exacerbate hepatocyte cell death during simultaneous inflammatory and T-cell-mediated immune responses in the liver. Here we show that TNFα sensitizes primary hepatocytes, established hepatocyte cell lines and mouse embryo fibroblasts to FasL-induced apoptosis by the transcriptional induction and higher surface expression of Fas via the NFκB pathway. Genetic deletion, diminished expression or dominant-negative inhibition of the NFκB subunit p65 resulted in lower Fas expression and inhibited TNFα-induced Fas upregulation and sensitization to FasL-induced cell death. By hydrodynamic injection of p65 shRNA into the tail vein of mice, we confirm that Fas upregulation by TNFα is also NFκB-mediated in the liver. In conclusion, TNFα sensitization of FasL-induced apoptosis in the liver proceeds via two parallel signaling pathways, activation of JNK and Bim phosphorylation and NFκB-mediated Fas upregulation.

Necrostatin-1 Protects Against D-Galactosamine and Lipopolysaccharide-Induced Hepatic Injury by Preventing TLR4 and RAGE Signaling

Fulminant hepatic failure (FHF) is a life-threatening clinical syndrome results in massive inflammation and hepatocyte death. Necroptosis is a regulated form of necrotic cell death that is emerging as a crucial control point for inflammatory diseases. The kinases receptor interacting protein (RIP) 1 and RIP3 are known as key modulators of necroptosis. In this study, we investigated the impact of necroptosis in the pathogenesis of FHF and molecular mechanisms, particularly its linkage to damage-associated molecular pattern (DAMP)-mediated pattern recognition receptor (PRR) signaling pathways. Male C57BL/6 mice were given an intraperitoneal injection of necrostatin-1 (Nec-1, RIP1 inhibitor; 1.8 mg/kg; dissolved in 2% dimethyl sulfoxide in phosphate-buffered saline) 1 h before receiving D-galactosamine (GalN; 800 mg/kg)/lipopolysaccharide (LPS; 40 μg/kg). Hepatic RIP1, RIP3 protein expression, their phosphorylation, and RIP1/RIP3 complex formation upregulated in the GalN/LPS group were attenuated by Nec-1. Nec-1 markedly reduced the increases in mortality and serum alanine aminotransferase activity induced by GalN/LPS. Increased serum high mobility group box 1 (HMGB1) and interleukin (IL)-33 release, HMGB1-toll-like receptor 4 and HMGB1-receptor for advanced glycation end products (RAGE) interaction, and nuclear protein expressions of NF-κB and early growth response protein-1 (egr-1) were attenuated by Nec-1. Our finding suggests that necroptosis is responsible for GalN/LPS-induced liver injury through DAMP-activated PRR signaling.

Anti-inflammatory properties of ursodeoxycholyl lysophosphatidylethanolamide in endotoxin-mediated inflammatory liver injury

AIM

Endotoxin-mediated liver inflammation is a key component of many acute and chronic liver diseases contributing to liver damage, fibrosis and eventually organ failure. Here, we investigated ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE), a synthetic bile acid-phospholipid conjugate regarding its anti-inflammatory and anti-fibrogenic properties.

METHODS

Anti-inflammatory properties of UDCA-LPE were evaluated in a mouse model of D-galactosamine/lipopolysaccharide (GalN/LPS)-induced acute liver injury, LPS treated RAW264.7 macrophages and murine primary Kupffer cells. Furthermore, anti-inflammatory and anti-fibrotic effects of UDCA-LPE were studied on primary hepatic stellate cells (HSC) incubated with supernatant from LPS±UDCA-LPE treated RAW264.7 cells.

RESULTS

UDCA-LPE ameliorated LPS-induced increase of IL-6, TNF-α, TGF-β, NOX-2 in the GalN/LPS model by up to 80.2% for IL-6. Similarly, UDCA-LPE markedly decreased the expression of inflammatory cytokines IL-6, TNF-α and TGF-β as well as the chemokines MCP1 and RANTES in LPS-stimulated RAW 264.7 cells. Anti-inflammatory effects were also observed in primary murine Kupffer cells. Mechanistic evaluation revealed a reversion of LPS-activated pro-inflammatory TLR4 pathway by UDCA-LPE. Moreover, UDCA-LPE inhibited iNOS and NOX-2 expression while activating eNOS via phosphorylation of AKT and pERK1/2 in RAW264.7 cells. HSC treated with conditioned medium from LPS±UDCA-LPE RAW264.7 cells showed lower fibrogenic activation due to less SMAD2/3 phosphorylation, reduced expression of profibrogenic CTGF and reduced pro-inflammatory chemokine expression.

CONCLUSION

In the setting of endotoxin-mediated liver inflammation, UDCA-LPE exerts profound anti-inflammatory and anti-fibrotic effect implying a promising potential for the drug candidate as an experimental approach for the treatment of acute and chronic liver diseases.

Elental® amino acid component has protective effects on primary cultured hepatocytes and a rat model of acute liver injury

Amino acids can exert protective effects on the liver either when administered as a medication or following an operation. In this study, we examined the protective effects of amino acids on the liver using in vitro and in vivo models by studying their influence on the induction of inducible nitric oxide synthase (iNOS) and nitric oxide production as a liver injury marker in cultured hepatocytes and liver-protective effects in d-galactosamine and lipopolysaccharide (GalN/LPS)-treated rats, respectively. Primary cultured rat hepatocytes were treated with interleukin (IL)-1β in the presence or absence of Elental® amino acid component (EleAA; 17 amino acids). Rats were pretreated with either EleAA or a diet containing selected amino acids followed by GalN/LPS injection. Survival rate and mRNA expression were analyzed. EleAA inhibited iNOS induction through reduction of mRNA synthesis and stability in cultured hepatocytes, indicating prevention of liver injury, but did not show a liver-protective effect in GalN/LPS rats. Among EleAA, Lys, Trp, His, and Arg (4AA) markedly decreased nitric oxide production and inhibited nuclear factor-κB (NF-κB) activation. In GalN/LPS rats, 4AA (3% of each amino acid in diet) increased survival rate by 50% and decreased mRNA expression of iNOS, tumor necrosis factor-α, and cytokine-induced neutrophil chemoattractant-1 in the liver. 4AA reduced NF-κB activation induced by GalN/LPS. 4AA inhibited the expression of inflammatory mediators, in part through inhibition of NF-κB activation in cultured hepatocytes and GalN/LPS-treated rats. The results suggest that EleAA has therapeutic potential for organ injuries including liver.

Ammonium glycyrrhizin counteracts liver injury caused by lipopolysaccharide/amoxicillin-clavulanate potassium

We treated isolated chicken primary hepatocytes with lipopolysaccharide/amoxicillin clavulanate potassium (LPS/AC) to model liver injury and investigate its underlying mechanisms. We also used this model to assess the cytoprotective effects of compound ammonium glycyrrhizin (CAG) in vitro. LPS/AC-induced injury decreased cell viability and increased the activity of serum aspartate transaminase and alanine transaminase. Levels of superoxide dismutase, glutathione, and glutathione peroxidase were lower than control, while levels of the oxidative product malondialdehyde and reactive oxygen species were higher. Treatment with CAG for 24 h ameliorated these changes. Caspase-3 activity assays and flow cytometry revealed increased apoptosis in the model group. However, apoptosis decreased after CAG treatment, as confirmed by Hoechst 33342 staining. We also observed changes in mitochondrial ultrastructure. Real-time PCR and western blot analyses showed that CAG treatment downregulated LPS/AC-induced RNA expression of caspase-3, caspase-9, bax, cytochrome c, and fas, and upregulated the expression of bcl-2. Mitochondrial cytochrome c was released into the cytosol and the inner mitochondrial membrane potential (ΔΨm) was decreased. Our results highlight CAG as a potential therapeutic agent to counteract LPS/AC-induced liver injury.

Halobacterial nano vesicles displaying murine bactericidal permeability-increasing protein rescue mice from lethal endotoxic shock

Bactericidal/permeability-increasing protein (BPI) had been shown to possess anti-inflammatory and endotoxin neutralizing activity by interacting with LPS of Gram-negative bacteria. The current study examines the feasibility of using murine BPI (mBPI) expressed on halophilic Archaeal gas vesicle nanoparticles (GVNPs) for the treatment of endotoxemia in high-risk patients, using a murine model of D-galactosamine-induced endotoxic shock. Halobacterium sp. NRC-1was used to express the N-terminal 199 amino acid residues of mBPI fused to the GVNP GvpC protein, and bound to the surface of the haloarchaeal GVNPs. Our results indicate that delivery of mBPIN-GVNPs increase the survival rate of mice challenged with lethal concentrations of lipopolysaccharide (LPS) and D-galactosamine. Additionally, the mBPIN-GVNP-treated mice displayed reduced symptoms of inflammation, including inflammatory anemia, recruitment of neutrophils, liver apoptosis as well as increased pro-inflammatory serum cytokine levels.

The mechanism of LPS-induced vascular endothelial cell and renal tubular cell injury in experimental disseminated intravascular coagulation (DIC)

The mechanism of LPS-induced tissue injury in experimental disseminated intravascular coagulation (DIC) was investigated. The generalized Shwartzman reaction (GSR) was used for an experimental murine DIC model. GSR was induced in mice by two consecutive injections of LPS. Vascular endothelial cells in various organs of those mice were stained positively by the in situ nick end labeling specific for fragmented DNA. Renal tubular cells were also stained with the nick end labeling. Fragmented nuclei were histologically detected on vascular endothelial cells and renal tubular cells in GSR-induced mice. It was suggested that apoptotic cell death might participate in development of vascular endothelial cell and renal tubular cell injury in GSR. Interferon-γ and ICAM-1 seemed to play an important role in the apoptosis of vascular endothelial cells. On the other hand, Fas and Fas ligand system seemed to be involved in the apoptosis of renal tubular cells. The detailed mechanism of vascular endothelial cell and renal tubular cell injury is discussed.

Sphingosine kinase 1 inhibition improves lipopolysaccharide/D-galactosamine-induced acute liver failure by inhibiting mitogen-activated protein kinases pathway

BACKGROUND

Sphingosine kinase 1 (SphK1)/sphingosine-1-phosphate (S1P)/sphingosine-1-phosphate receptors (S1PRs) signaling plays a key role in inflammatory responses. Lei et al. showed that SphK1 inhibition presented a hepatoprotective effect on acute liver damage via decreasing hepatic high-mobility group box 1 (HMGB1) cytoplasmic translocation.

OBJECTIVE

We aim to determine whether SphK1 or S1PRs inhibition improves lipopolysaccharide (LPS)/D-galactosamine (GalN)-induced acute liver failure by inhibiting the mitogen-activated protein kinases (MAPKs) pathway.

METHODS

A mouse model of acute liver failure was induced by LPS/GalN. Male C57BL/6J mice (6-8 weeks) were randomly distributed into five groups: control group, LPS/GalN group, SphK1 inhibition group (LPS/GalN+SKI-5c), S1PR1 inhibition group (LPS/GalN+W146), and S1PR3 inhibition group (LPS/GalN+CAY10444).

RESULTS

We confirmed the findings of Lei et al. that hepatic SphK1 expression was upregulated; serum transaminase activity (AST, ALT), as well as serum TNF-α and IL-6, were decreased by SphK1 inhibition. We further showed that the expression of S1PR1 and S1PR3 was augmented in response to LPS/GalN. SphK1 inhibition improves hepatic hemorrhage, and the activities of hepatic caspase-3 and myeloperoxidase (MPO). Furthermore, the activation of the MAPKs family (JNK, ERK and p38) was suppressed by SphK1 inhibition. However, S1PR1 or S1PR3 inhibition did not protect the mouse against liver damage, though S1PR1 or S1PR3 inhibition reduced serum TNF-α and IL-6, and partially attenuated the phosphorylation of the MAPKs signaling.

CONCLUSIONS

SphK1 inhibition improves LPS/GalN-induced liver injury by inhibiting activation of MAPKs signaling.

Propofol reduces liver dysfunction caused by tumor necrosis factor-α production in Kupffer cells

PURPOSE

The present study, conducted in rats, investigated whether propofol attenuates lipopolysaccharide (LPS)-triggered liver dysfunction via regulation of tumor necrosis factor (TNF)-α production in activated Kupffer cells.

METHODS

Rats received LPS (500 μg/kg) under Urethane™ sedation (1 g/kg) in combination with propofol (5 mg/kg/h) or Intralipid™ from 1 h before to 6 h after LPS administration. Some rats were treated with 10 mg/kg gadolinium chloride (GdCl3) to induce Kupffer cell depletion. The serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), TNF-α mRNA and protein expression, caspase-3 activation and apoptosis were evaluated in hepatocytes. Immunofluorescence staining revealed expression of the pan-macrophage marker CD68 as well as TNF-α in Kupffer cells.

RESULTS

ALT and AST serum levels increased approximately four-fold in LPS-exposed rats compared with Intralipid™-treated rats at 6 h after LPS administration, whereas propofol and GdCl3 reduced the LPS-induced increases. LPS simultaneously augmented TNF-α expression in Kupffer cells, followed by increased caspase-3 activity and apoptosis in hepatocytes. Immunofluorescence staining and immunoblotting assay showed that TNF-α expression in Kupffer cells was inhibited by propofol and GdCl3, resulting in a reduction of caspase-3 activity and apoptosis in LPS-treated rat hepatocytes.

CONCLUSIONS

Propofol (5 mg/kg/h) attenuated LPS-triggered liver dysfunction via inhibition of TNF-α production in activated Kupffer cells. These results suggest that propofol is capable of inhibiting inflammation-induced liver dysfunction in vivo.

Antagonistic interaction between cordyceps sinensis and exercise on protection in fulminant hepatic failure

Herb supplements are widely used by Asian athletes; however, there are no studies evaluated the co-effects of exercise and herb supplements on hepatic failure. In this study, D-GalN/LPS-induced fulminant hepatic failure was used to examine whether there are synergistic or antagonistic effects of exercise and Cordyceps sinensis (CS). Mice were randomly divided into eight groups: control, swimming exercise for four weeks, D-GalN/LPS challenge, swimming exercise plus D-GalN/LPS, 20 mg/kg or 40 mg/kg CS pretreated for four weeks plus D-GalN/LPS, and swimming exercise combined with 20 mg/kg or 40 mg/kg CS pretreatment plus D-GalN/LPS. Either exercise or 40 mg/kg CS pretreatment alone significantly decreased D-GalN/LPS-induced TNF-α, AST, NO, apoptotic-related proteins, and hepatocyte apoptosis. Exercise or 40 mg/kg CS alone increased the IL-10 and D-GalN/LPS-suppressed Superoxide Dismutase (SOD) level. However, no protective or worse effect was observed in the mice treated with exercise preconditioning combined 40 mg/kg CS compared to those receive exercise alone or CS alone. TNF-α, AST, NO level, caspase-3 activity, and hepatocytes apoptosis were not significantly different in the exercise combined with 40 mg/kg CS compared to mice challenged with D-GalN/LPS. The IL-10 level was significantly decreased after D-GalN/LPS stimulation in the mice received exercise combined with 40 mg/kg CS, indicating the combination strongly reduced the anti-inflammatory effect. In summary, preconditioning exercise or CS pretreatment alone can protect mice from septic liver damage, but in contrast, the combination of exercise and CS does not produce any benefit. The antagonistic interactions between exercise and CS imply taking CS is not recommended for people who undertake regular exercise.

Anti-apoptotic therapeutic approaches in liver diseases: do they really make sense?

A variety of data suggesting apoptotic cell death as a key feature of liver injury stimulated researchers to investigate the therapeutic potential of anti-apoptotic strategies in experimental models. However, the overestimated role of apoptotic cell death in liver injury has tempered the clinical translation of the protection afforded by anti-apoptotic regimes in experimental models. Thus, the hope for apoptosis modulation as potential treatment strategy for injured liver in humans could not be confirmed. Herein, we evaluated the degree of apoptosis in different hepatic stress models which are relevant for the human pathophysiology. Using morphological criteria of apoptosis, caspase-3 activation as well as TUNEL assay in combination with a positive control of apoptosis in liver injury, we quantified apoptotic cell death discriminating between parenchymal and non-parenchymal cells and confirmed these results by cleaved caspase-3 and PARP-1 protein expression. Discussing our findings and relating them to the existing literature on the potential role of apoptotic cell death, we strongly recommend reconsidering anti-apoptotic strategies to ameliorate liver injury efficiently.

Curcumin attenuates D-galactosamine/lipopolysaccharide-induced liver injury and mitochondrial dysfunction in mice

Curcumin, a naturally occurring antioxidant, has various beneficial effects in the treatment of human diseases. However, little information regarding the protection it provides against acute liver injury is available. The present study investigated the protective effects of curcumin against D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced acute liver injury in mice. A total of 40 male Kunming mice were randomly assigned to 5 groups: 1) mice administered saline vehicle injection (control), 2) mice administered 200 mg/kg body weight (BW) curcumin by i.p. injection (CUR), 3) mice administered D-GalN/LPS (700 mg and 5 μg/kg BW) via i.p. injection (GL), 4) mice administered 200 mg/kg BW curcumin i.p. 1 h before D-GalN/LPS injection (CUR-GL), and 5) mice administered 200 mg/kg BW curcumin i.p. 1 h after D-GalN/LPS injection (GL-CUR). Twenty h after D-GalN/LPS injection, serum alanine aminotransferase activities were 18.5% and 13.5% lower (P < 0.05) and aspartate aminotransferase (AST) activities were 26.6% and 9.6% lower (P < 0.05) in the CUR-GL and GL-CUR groups, respectively, than in the GL group. The CUR-GL and GL-CUR groups had 64.4% and 15.0% higher (P < 0.05) mitochondrial membrane potentials, respectively, and the CUR-GL group had a 44.7% lower reactive oxygen species concentration than the GL group (P < 0.05). Mitochondrial manganese superoxide dismutase activities were 111% and 77.9% higher (P < 0.05) and the percentages of necrotic cells were 47.0% and 32.4% lower (P < 0.05) in the CUR-GL and GL-CUR groups, respectively, than in the GL group. Liver mRNA levels of sirtuin 1 (Sirt1) were 56.4% lower (P < 0.05) in the CUR-GL group than in the GL group. Moreover, compared with the GL-CUR group, the CUR-GL group had an 18.7% lower serum AST activity, a 31.7% lower mitochondrial malondialdehyde concentration, a 36.0% lower hepatic reactive oxygen species concentration, and a 43.0% higher mitochondrial membrane potential. These results suggested that curcumin protects against D-GalN/LPS-induced liver damage by the enhancing antioxidant defense system, attenuating mitochondrial dysfunction and inhibiting apoptosis. This was especially true for curcumin pretreatment, which highlighted its promise as a preventive treatment for acute liver injury in clinical settings.

Bioluminescence imaging of caspase-3 activity in mouse liver

Apoptosis is an essential process for the maintenance of liver physiology. The ability to noninvasively image apoptosis in livers would provide unique insights into its role in liver disease processes. In the present work, we established a stable mouse model by hydrodynamics methods to study the activity of caspase-3 and evaluate the effect of the apoptosis inhibitors in mouse livers under true physiological conditions by bioluminescence imaging. The reporter plasmid attB-ANLuc(DEVD)BCLuc that contains fragment of attB and ANLuc(DEVD)BCLuc was codelivered with the mouse-codon optimized φC31 (φC31o) integrase plasmids specifically to mouse liver by hydrodynamic injection procedure. Then, φC31o integrase mediated intramolecular recombination between wild-type attB and attP site in mice, and thus the reporter expression cassette attB-ANLuc(DEVD)BCLuc was integrated permanently into mouse liver chromosome. We used these mice to characterize in vivo activation of caspase-3 upon treatment with LPS/D-GalN. Our data show that liver apoptosis could be reflected by the activity of luciferase. The shRNA targeting caspase-3 protein or apoptosis inhibitors could effectively downregulate luciferase activity in vivo. Also, this model could be used to measure caspase-3 activation during inflammatory and infectious events in vivo as verified by infected with MHV-3. This model could be used for screening anti-apoptosis compounds target mouse livers.

The protective role of the transmembrane thioredoxin-related protein TMX in inflammatory liver injury

AIMS

Accumulating evidence indicates that oxidative stress is associated with inflammation, and the cellular redox status can determine the sensitivity and the final outcome in response to inflammatory stimuli. To control the redox balance, mammalian cells contain a variety of oxidoreductases belonging to the thioredoxin superfamily. The large number of these enzymes suggests a complex mechanism of redox regulation in mammals, but the precise function of each family member awaits further investigations.

RESULTS

We generated mice deficient in transmembrane thioredoxin-related protein (TMX), a transmembrane oxidoreductase in the endoplasmic reticulum (ER). When exposed to lipopolysaccharide (LPS) and d-(+)-galactosamine (GalN) to induce inflammatory liver injury, mutant mice were highly susceptible to the toxicants and developed severe liver damage. LPS-induced production of inflammatory mediators was equivalent in both wild-type and TMX(-/-) mice, whereas neutralization of the proinflammatory cytokine tumor necrosis factor-α suppressed the toxic effects of LPS/GalN in the mutant mice. Liver transcriptional profiles revealed enhanced activation of the p53-signaling pathway in the TMX(-/-) mice after LPS/GalN treatment. Furthermore, TMX deficiency also caused increased sensitivity to thioacetamide, which exerts its hepatotoxicity through the generation of reactive oxygen species.

INNOVATION

The present study is the first to address the role of the oxidoreductase TMX in inflammatory liver injury. The phenotype of mice deficient in TMX suggests a functional link between redox regulation in the ER and susceptibility to oxidative tissue damage.

CONCLUSION

We conclude that TMX plays a major role in host defense under the type of inflammatory conditions associated with oxidative stress.

Beta-catenin-NF-κB interactions in murine hepatocytes: a complex to die for

Wnt/β-catenin signaling plays an important role in hepatic homeostasis, especially in liver development, regeneration, and cancer, and loss of β-catenin signaling is often associated with increased apoptosis. To elucidate how β-catenin may be regulating hepatocyte survival, we investigated the susceptibility of β-catenin conditional knockout (KO) mice and their wild-type (WT) littermates to Fas and tumor necrosis factor-α (TNF-α), two common pathways of hepatocyte apoptosis. While comparable detrimental effects from Fas activation were observed in WT and KO, a paradoxical survival benefit was observed in KO mice challenged with D-galactosamine/lipopolysaccharide. KO mice showed significantly lower morbidity and liver injury due to early, robust, and protracted activation of NF-κB in the absence of β-catenin. Enhanced NF-κB activation in KO mice was associated with increased basal inflammation and Toll-like receptor 4 expression and lack of the p65/β-catenin complex in hepatocytes. The p65/β-catenin complex in WT livers underwent temporal dissociation allowing for NF-κB activation to regulate hepatocyte survival following TNF-α-induced hepatic injury. Decrease of total β-catenin protein but not its inactivation induced p65 activity, whereas β-catenin stabilization either chemically or due to mutations repressed it in hepatomas in a dose-dependent manner, whereas β-catenin stabilization repressed it either chemically or due to mutations.

CONCLUSION

The p65/β-catenin complex in hepatocytes undergoes dynamic changes during TNF-α-induced hepatic injury and plays a critical role in NF-κB activation and cell survival. Modulation of β-catenin levels is a unique mode of regulating NF-κB activity and thus may present novel opportunities in devising therapeutics in specific hepatic injuries.

Role of naofen in apoptosis of hepatocytes induced by lipopolysaccharide through mitochondrial signaling in rats

AIM

  Lipopolysaccharide (LPS) causes apoptosis of hepatocytes, which is probably mediated by inflammatory substances released from Kupffer cells (KCs). Recently, we have reported that naofen, a newly found intracellular WD40-repeat protein, has a role in inducing the apoptosis in HEK293 cells. Hence, the present study was undertaken to investigate a role of naofen in the LPS-induced apoptosis of rat hepatocytes.

METHODS

  Rats were treated with i.v. injections of LPS, and livers were extirpated to evaluate expression of naofen and apoptosis. In in vitro experiments, hepatocytes and KCs were separately isolated from rat livers. The incubation medium for KCs treated with LPS (KC-CM) was used for hepatocyte culture.

RESULTS

  Intravenous injections of LPS enhanced the expression of naofen in the livers. Livers showed terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive staining, and elevated caspase-3 activity. In isolated KCs or hepatocytes, LPS hardly affected naofen expression and caspase-3 activity, whereas incubation of hepatocytes with KC-CM enhanced both naofen expression and caspase-3 activation. Transfection of hepatocyte with naofen siRNA prevented such effects of KC-CM, and clearly eliminated KC-CM-induced reduction of Bcl-2 and Bcl-xL. In contrast, overexpression of naofen in hepatocytes downregulated Bcl-2 and Bcl-xL, released cytochrome c from mitochondria, and activated caspase-3.

CONCLUSION

  These results indicate that LPS may induce the hepatic apoptosis in association with enhanced naofen expression, and that naofen may mediate the activation of caspase-3 through downregulating the Bcl-2 and Bcl-xL expression, and releasing cytochrome c from mitochondria to cytoplasm.

Ecto-5'-nucleotidase (CD73) decreases mortality and organ injury in sepsis

The extracellular concentrations of adenosine are increased during sepsis, and adenosine receptors regulate the host's response to sepsis. In this study, we investigated the role of the adenosine-generating ectoenzyme, ecto-5'-nucleotidase (CD73), in regulating immune and organ function during sepsis. Polymicrobial sepsis was induced by subjecting CD73 knockout (KO) and wild type (WT) mice to cecal ligation and puncture. CD73 KO mice showed increased mortality in comparison with WT mice, which was associated with increased bacterial counts and elevated inflammatory cytokine and chemokine concentrations in the blood and peritoneum. CD73 deficiency promoted lung injury, as indicated by increased myeloperoxidase activity and neutrophil infiltration, and elevated pulmonary cytokine levels. CD73 KO mice had increased apoptosis in the thymus, as evidenced by increased cleavage of caspase-3 and poly(ADP-ribose) polymerase and increased activation of NF-κB. Septic CD73 KO mice had higher blood urea nitrogen levels and increased cytokine levels in the kidney, indicating increased renal dysfunction. The increased kidney injury of CD73 KO mice was associated with augmented activation of p38 MAPK and decreased phosphorylation of Akt. Pharmacological inactivation of CD73 in WT mice using α, β-methylene ADP augmented cytokine levels in the blood and peritoneal lavage fluid. These findings suggest that CD73-derived adenosine may be beneficial in sepsis.

Toll-like receptors in acute liver injury and regeneration

Liver is the lymphoid organ with an overwhelming innate immune system, which functions as a filter organ at the first line between the digestive tract and the rest of the body, with receiving 80% of the blood supply through portal vein. TLRs are widely expressed on parenchymal and non-parenchymal cells in the liver, which play critical roles for the liver health. Recent studies indicate that TLR-medicated signals have been involved in almost all liver diseases such as acute and chronic hepatitis, liver fibrosis and cirrhosis, alcoholic and non-alcoholic liver disease, ischemia/reperfusion liver injury, liver regeneration and hepatocellular carcinoma. In this review, the expressions of TLRs in hepatic cell populations including hepatocytes, LSECs, Kupffer cells, lymphocytes, DCs, biliary epithelial cells and HSCs, and TLR ligands and signaling in the liver are summarized. Further, recent advances in the roles of TLRs in acute liver injury and regeneration as mediator and regulator, and their potential therapeutic targets are discussed.

HMGB1 cytoplasmic translocation in patients with acute liver failure

Background

High-mobility group box 1 (HMGB1) is a late mediator of lethal systemic inflammation. Acute liver failure (ALF) has been shown to trigger systemic inflammation in clinical and animal studies. To evaluate the possibility of HMGB1 cytoplasmic translocation in ALF, we determined whether HMGB1 is released in hepatocytes and end organ in patients with liver failure/injury.

Methods

HepG2 cell were stimulated with LPS or TNF-α, the increase of HMGB1 extracellularly in the culture medium and intracellularly in various cellular fractions were determined by western blot or immunocytochemistry. To observe sub-cellular location of HMGB1 in hepatocytes, liver specimens were obtained from 6 patients with ALF caused by HBV infection, 10 patients with chronic viral hepatitis B, 6 healthy controls, as well as animals model of ALF by intraperitoneal administration of D-GalN (600 mg/kg) and LPS (0.5 mg/kg).

Results

In HepG2 cell culture, LPS or TNF actively induced HMGB1 cytoplasmic translocation and release in a time- and dose-dependent fashion. In animal model of ALF, cytoplasmic HMGB1 translocation was observed in hepatocyts as early as 3 hours post onset of ALF. In patients with ALF caused by HBV infection, cytoplasmic HMGB1 translocation was similarly observed in some hepatocytes of the liver specimen.

Conclusions

Cytoplasmic HMGB1 translocation may occur during ALF, which may potentially contribute to the pathogenesis of liver inflammatory diseases.

Mutation of mitochondrial ATP8 gene improves hepatic energy status in a murine model of acute endotoxemic liver failure

AIMS

Mitochondria not only generate and modulate bioenergy but also serve as biosensors for oxidative stress, and eventually become effector organelles for cell viability. Therefore, the implications of mitochondrial (dys)function in the development of multiple organ failure are profound. We investigated whether a mutation in the ATPase subunit-8 gene affects the course of endotoxemic acute liver failure.

MAIN METHODS

C57BL/6J (ATP8 wild type) and C57BL/6J-mt(FVB/N) (ATP8 mutant) mice were challenged with d-galactosamine (GalN) and Escherichia coli lipopolysaccharide (LPS) for induction of acute liver failure, and studied 6 h thereafter. Control mice received physiological saline only. Analysis included in vivo fluorescence microscopy of hepatic microcirculation and levels of hepatocellular apoptosis, hepatic adenosine nucleotides and oxidative stress. Additionally, survival rates were assessed.

KEY FINDINGS

Induction of endotoxemic liver failure provoked marked liver damage, which was coexistent with a drop of total adenosine nucleotide levels and increased oxidative stress. Of interest, oxidative stress was higher in the GalN/LPS challenged ATP8 mutants compared to wild types. Concomitantly, adenosine triphosphate (ATP) levels in livers of mice carrying the ATP8 mutation remained higher than those in wild type mice. As net result, ATP8 mutants showed lower transaminase release and a tendency to better survival rate upon GalN/LPS exposure compared to wild types.

SIGNIFICANCE

Our findings demonstrate that mutation in the ATPase subunit-8 partially protects mice against endotoxemic stress, most probably due to better hepatic energy status despite elevated oxidative stress. Thus, modulating mitochondrial function to preserve bioenergetic status may be an effective strategy to protect against sepsis-induced multiorgan dysfunction.

Low susceptibility of NC/Nga mice to the lipopolysaccharide-mediated lethality with D-galactosamine sensitization and the involvement of fewer natural killer T cells

The LPS-mediated lethality of NC/Nga mice, having fewer NKT cells, was examined by using d-galactosamine (d-GalN)-sensitization. The NC/Nga mice were not killed by a simultaneous administration of d-GalN and LPS whereas all C57BL/6 (B6) control mice were killed. The injection of d-GalN and LPS failed to elevate the levels of serum alanine aminotransferase and caspase 3 in the liver tissues of NC/Nga mice. Further, the nitric oxide (NO) level of the d-GalN- and LPS-injected NC/Nga mice was much lower than those of the B6 mice. The expression of an inducible NO synthase (iNOS) was significantly reduced in the livers of NC/Nga mice. However, there was no significant difference in LPS-induced TNF-α production between B6 mice and NC/Nga mice. The NC/Nga mice had an impaired expression of IFN-γ protein and mRNA in response to d-GalN and LPS. The pretreatment with α-galactosylceramide (α-GalCer), which activates Vα14(+) NKT cells and induces the production of IFN-γ, rendered NC/Nga mice more susceptible to the LPS-mediated lethality. The livers of NC/Nga mice had fewer NKT cells compared to B6 mice. Taken together, it is suggested that the resistance of NC/Nga mice to the LPS-mediated lethality with d-GalN sensitization depended on the impaired IFN-γ production caused by fewer NKT cells and reduced NO production that followed.

Thrombopoietin limits IL-6 release but fails to attenuate liver injury in two hepatic stress models

OBJECTIVE

Various pleiotropic substances have been suggested as candidates that directly reduce the severity of liver injury after hepatic ischemia/reperfusion (I/R) and upon acute liver failure (ALF). Herein, we studied whether thrombopoietin (TPO), the main regulator of megakaryopoiesis and thrombopoiesis, showed hepatoprotective effects and might mediate an antiapoptotic function in liver tissue under stress.

METHODS/RESULTS

In livers with ALF or undergoing warm hepatic I/R, injury was quantified by intravital fluorescence microscopy, chemical, and immunohistochemical analysis as well as western immunoblot. Induction of both ALF and I/R injury led to hepatocellular expression of c-mpl, the receptor of TPO. Exogenous application of recombinant TPO in a low (12.5 microg/kg) as well as a high (75 microg/kg) dose, however, did not ameliorate postischemic perfusion and leukocyte endothelial cell interaction, but slightly aggravated transaminase release upon I/R. Similarly, TPO was unable to dampen hepatic microcirculatory deteriorations after the induction of ALF, but caused an increase of leukocyte accumulation and transaminase activity when applied in high dose. Low dose of TPO did not influence the amount of hepatocellular apoptosis, whereas high-dose TPO slightly diminished the activation of caspase 3. Interestingly, exogenous TPO application completely reversed the stress-induced increase of plasma IL-6 levels, suggesting a negative feedback of TPO on IL-6 release.

CONCLUSION

Although the existence of the TPO-receptor on target liver cells TPO plays only a minor role in mediating hepatocyte apoptosis and does not provide protection against hepatic injury, contrasting the efficacy of the related hematopoietic growth factor erythropoietin.

Bach1 deficiency ameliorates hepatic injury in a mouse model

Bach1 is a basic region-leucine zipper (bZip) protein that forms heterodimers with the small Maf proteins and functions as a repressor of gene expression. One of the target genes of Bach1 is Hmox-1 that encodes heme oxygenase-1 (HO-1). HO-1 degrades heme into carbon monoxide (CO), biliverdin, and iron. HO-1 is strongly induced by various stresses as well as its substrate heme, and protects cells and tissues against insults through diverse cytoprotective functions of the reaction products CO and biliverdin. Bach1-deficiency in mice leads to higher expression of Hmox-1 in various tissues. Here we investigated the effects of Bach1-deficiency in mice on tissue injuries: hepatic injury induced by D-galactosamine (GalN) and lipopolysaccharide (LPS), and mouse paw edema induced by carrageenin, polysaccharide derived from various seaweeds. Bach1-deficiency suppressed induction of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities in response to the GalN/LPS-treatment. However, production of tumor necrosis factor alpha (TNF-alpha) and nitric oxide (NO), both being cytotoxic mediators in LPS-induced hepatic injury, in Bach1-deficient mice and their peritoneal macrophages was similar to wild type controls. In contrast, Bach1-deficiency did not affect extent of mouse paw edema induced by carrageenin, which enhances vascular permeability by activating kinin release. These results indicate that Bach1 plays an inhibitory role in the cytoprotection of LPS-induced liver injury but not in the kinin-mediated inflammatory edema. The inhibitory role for Bach1 may stem from its activity to repress gene expression including HO-1.

Uncoupling protein-2 deficiency provides protection in a murine model of endotoxemic acute liver failure

OBJECTIVE

Liver injury and cell death are prominent features in the pathogenesis of acute liver failure. Mitochondrial uncoupling protein 2 plays a controversial role in liver cell death through its involvement in the production of reactive oxygen species and adenosine triphosphate.

DESIGN

This randomized controlled animal study was designed to investigate the exact role of uncoupling protein 2 in the pathogenesis of endotoxemic acute liver failure.

SETTING

Research laboratory of an academic institution. SUBJECTS, INTERVENTIONS, AND MEASUREMENTS: Uncoupling protein 2+/+ and uncoupling protein 2-/- mice were challenged with D-galactosamine (Gal, 720 mg/kg intraperitoneally) and Escherichia coli lipopolysaccharide (10 microg/kg intraperitoneally) and studied 6 hrs thereafter (n = 5 per group). Control mice received physiologic saline (n = 5 per group). Analysis included in vivo fluorescence microscopy of hepatic microcirculation and hepatocellular apoptosis as well as plasma malondialdehyde concentrations as reactive oxygen species-dependent lipid peroxidation product and hepatic adenosine triphosphate levels.

MAIN RESULTS

Administration of Gal-lipopolysaccharide in uncoupling protein 2+/+ mice caused systemic cytokine release and malondialdehyde production. Further, it provoked marked hepatic damage, characterized by intrahepatic leukocyte recruitment (10.5 +/- 1.3 n/mm2 vs. 3.3 +/- 0.5 n/mm2), microvascular perfusion failure (33.1% +/- 1.6% vs. 2.3% +/- 0.4%), and adenosine triphosphate depletion (3.4 +/- 0.9 micromol/g vs. 6.4 +/- 0.9 micromol/g). Furthermore, uncoupling protein +/+ mice revealed a huge rise in cell apoptosis, given by high numbers of hepatocytes exhibiting nuclear chromatin fragmentation (44.9 +/- 11.5 n/mm2 vs. 0.0 +/- 0.0 n/mm2) and cleaved caspase-3 expression (1.24 +/- 0.24 vs. 0.06 +/- 0.04). Liver injury was coexistent with enzyme release (alanine aminotransferase 442 +/- 126 U/L vs. 57 +/- 12 U/L) and necrotic cell death. Of interest, Gal-lipopolysaccharide-exposed uncoupling protein 2-/- mice exhibited higher rates of hepatocellular apoptosis (135.6 +/- 46.0 n/mm2) as well as cleaved caspase-3 expression (1.75 +/- 0.25), however, preserved hepatic adenosine triphosphate (6.4 +/- 1.7), milder perfusion failure (24.5 +/- 2.4) and decreased leukocyte recruitment (2.7 +/- 0.2), less necrotic injury, lower transaminase levels (340 +/- 91), and finally better survival rates.

CONCLUSION

The higher adenosine triphosphate availability in uncoupling protein 2-deficient mice might allow hepatocytes to undergo apoptosis as an energy-consuming mode of cell death, while at the same time cellular adenosine triphosphate levels seem to increase hepatic resistance against harmful effects upon Gal-lipopolysaccharide exposure. As net result, uncoupling protein 2 deficiency provided protection under endotoxemic stress conditions, underlining the significant role of the bioenergetic status in critical illness.

Glycyrrhizin prevents of lipopolysaccharide/D-galactosamine-induced liver injury through down-regulation of matrix metalloproteinase-9 in mice

Glycyrrhizin, a biological active compound isolated from the liquorice root, has been used as a treatment for chronic hepatitis. We have examined the involvement of matrix metalloproteinase (MMP)‐9 in the development of lipopolysaccharide (LPS) and D‐galactosamine (GalN)‐induced liver injury in mice. We also investigated the effect of glycyrrhizin on expression of MMP‐9 in this model. Levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increased after LPS/GalN treatment. Expression of MMP‐9 mRNA and protein was markedly up‐regulated in liver tissues 6–8 h after LPS/GalN treatment. Pretreatment with glycyrrhizin (50 mg kg⁻¹) and the MMP inhibitor (5 mg kg⁻¹) suppressed increases in serum levels of ALT and AST in mice treated with LPS/GalN. Furthermore, glycyrrhizin inhibited levels of both mRNA and protein for MMP‐9. Immunohistochemical reaction for MMP‐9 was observed in macrophages/monocytes infiltrated in the inflammatory area of liver injury. Glycyrrhizin reduced the infiltration of inflammatory cells and immunoreactive MMP‐9 in liver injury. The results indicated that MMP‐9 played a role in the development of LPS/GalN‐induced mouse liver injury, and suggested that an inhibition by glycyrrhizin of the acute liver injury may have been due to a down‐regulation of MMP‐9.

A role of cell apoptosis in lipopolysaccharide (LPS)-induced nonlethal liver injury in D-galactosamine (D-GalN)-sensitized rats

Lipopolysaccharide (LPS) is implicated in the pathology of acute liver injury and can induce lethal liver failure when simultaneously administered with D-galactosamine (D-GalN). At the present time, nonlethal liver failure, the liver injury of clinical implication, is incompletely understood following challenge by low-dose LPS/D-GalN. We report here our investigation of the effects of liver injury following a nonlethal dose LPS/D-GalN and the role of apoptosis in this disorder. Blood biochemistry indexes, including those of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBIL), had risen by 6 h post-LPS/D-GalN injection, reached a peak at 24 h and sustained high levels at 48 h. An abnormal liver appearance was found at 24 and 48 h post-injection. Histopathological changes of hepatic injuries accompanied by hepatocellular death, inflammatory infiltration and hemorrhage began to appear at 6 h and were markedly aggravated at 24 and 48 h. Cell apoptosis was significantly induced by the nonlethal dose LPS/D-GalN challenge, and the apoptotic indexes (AIs) in 24 h- and 48 h-treated rats were approximately 70%, as estimated by the terminal transferase dUTP nick end labeling (TUNEL) assay. The mRNA levels of the inflammatory cytokine IL-1beta rose markedly at 6 h and maintained high levels at 24 and 48 h; however, TNF-alpha levels were normal in the liver tissues of 6-, 24- and 48-h-treated rats. mRNA expression of the damage gene nitric oxide synthase (NOS) was also induced early by the LPS/D-GalN challenge, reaching a peak at 6 h, then gradually decreasing in a stepwise manner; conversely, high expression levels of the apoptosis-inducing gene p53 mRNA were not found in the early post-injection period (6 h) but emerged in the crest-time of liver apoptosis (24 h) and were maintained at this level until the late stage (48 h). We also observed that in 24 h-treated rats, caspase-3, -8, -9 and -12 were markedly activated by LPS/D-GalN challenge. These results suggest that a challenge with low-dose LPS in conjunction with D-GalN can induce nonlethal but marked liver failure, the main morphological feature of which is hepatic apoptosis, which may be associated with a high expression of inducible (i)NOS (early post-injection period) and p53 genes (in the mid and late stages) and at least three apoptosis pathways participate in the pathogenesis.