Inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) expression in fulminant hepatic failure

Selective PPARδ Agonist GW501516 Protects Against LPS-Induced Macrophage Inflammation and Acute Liver Failure in Mice via Suppressing Inflammatory Mediators

Inflammation is critical in the development of acute liver failure (ALF). Peroxisome proliferator-activated receptor delta (PPARδ) regulates anti-inflammatory responses and is protective in several diseases such as obesity and cancer. However, the beneficial effects and underlying mechanisms of PPARδ agonist GW501516 in ALF remain unclear. This study investigated the molecular mechanisms underlying the anti-inflammatory effects of GW501516 in macrophages and assessed its protective potential against lipopolysaccharide (LPS)/galactosamine (GalN)-induced ALF. In vivo administration of GW501516 significantly reduced LPS/GalN-induced hepatotoxicity, as evidenced by lower mortality, decreased liver damage, and attenuated secretion of IL-1β, IL-6, and TNF-α. GW501516 treatment also decreased LPS-induced nitric oxide synthase 2 (NOS2) expression and nitric oxide (NO) production in RAW264.7 cells, an effect reversed by PPARδ siRNA. Additionally, GW501516 inhibited LPS-induced phosphorylation of p38 and c-Jun N-terminal kinase (JNK), suggesting that inactivation of these MAPKs contributes to its effects. The secretion of IL-6, TNF-α, and NF-κB DNA-binding activity were also suppressed by GW501516, while the nuclear translocation of the NF-κB p65 subunit was unaffected. In conclusion, our findings suggest that GW501516 exerts protective effects in ALF by inhibiting the production of inflammatory mediators. Therefore, GW501516 may act as a potential agent for developing anti-inflammatory therapies for ALF.

Endothelial dysfunction in pathological processes of chronic liver disease during aging

Aging is associated with gradual changes in liver structure and physiological/pathological functions in hepatic cells including hepatocytes, cholangiocytes, Kupffer cells, hepatic stellate cells (HSCs), and liver sinusoidal endothelial cells (LSECs). LSECs are specialized hepatic endothelial cells that regulate liver homeostasis. These cells actively impact the hepatic microenvironment as they have fenestrations and a thin morphology to allow substance exchange between circulating blood and the liver tissue. As aging occurs, LSECs have a reduction in both the number and size of fenestrations, which is referred to as pseudocapillarization. This along with the aging of the liver leads to increased oxidative stress, decreased availability of nitric oxide, decreased hepatic blood flow, and increased inflammatory cytokines in LSECs. Vascular aging can also lead to hepatic hypoxia, HSC activation, and liver fibrosis. In this review, we described the basic structure of LSECs, and the effect of LSECs on hepatic inflammation and fibrosis during aging process. We briefly summarized the changes of hepatic microcirculation during liver inflammation, the effect of aging on the clearance function of LSECs, the interactions between LSECs and immunity, hepatocytes or other hepatic nonparenchymal cells, and the therapeutic intervention of liver diseases by targeting LSECs and vascular system. Since LSECs play an important role in the development of liver fibrosis and the changes of LSEC phenotype occur in the early stage of liver fibrosis, the study of LSECs in the fibrotic liver is valuable for the detection of early liver fibrosis and the early intervention of fibrotic response.

Retrospective Analysis of the Clinical Efficacy of N-Acetylcysteine in the Treatment of Hepatitis B Virus Related Acute-on-Chronic Liver Failure

Objective: HBV-related acute-on-chronic liver failure (HBV-ACLF) has a high mortality due to severe intrahepatic cholestasis and coagulation dysfunction, thus new treatment measures are urgently needed to improve the therapeutic effect. This study aimed to observe the efficacy of N-acetylcysteine (NAC) in the treatment of HBV-ACLF.

Methods: The data of patients with HBV-ACLF admitted to West China Hospital from October 2019 to August 2020 were collected retrospectively, and they were divided into treatment group and control group according to whether they had received additional NAC treatment. The improvement of biochemistry, coagulation function and disease severity score after 14 days of hospitalization were analyzed between two groups.

Results: A total of 90 HBV-ACLF patients were included, including 42 patients in treatment group and 48 patients in control group. Compared with baseline, serum TBil, DBil, TBA, GGT and ALP in two groups both decreased significantly, while PTA increased significantly. Interesting, the decrease of serum TBil, DBil and TBA and the increase of PTA in treatment group were all significantly than these in control group. Additionally, more patients in treatment group than control group changed from CTP grade C to grade B. Subgroup analysis of CTP grade C patients showed that the decrease of serum TBil, DBil and TBA and the increase of PTA in treatment group were significantly than these in control group.

Conclusion: The NAC treatment may help to improve intrahepatic cholestasis and coagulation dysfunction of HBV-ACLF.

Expression of immunoreactive inducible nitric oxide synthase in pancreatic islet cells from newly diagnosed and long-term type 1 diabetic donors is heterogeneous and not disease-associated

Exposure of isolated human islets to proinflammatory cytokines leads to up-regulation of inducible nitric oxide synthase (iNOS), raised NO, and beta cell toxicity. These findings have led to increasing interest in the clinical utility of iNOS blockade to mitigate beta cell destruction in human type 1 diabetes (T1D). However, recent studies show that iNOS-derived NO may also confer beta cell protection. To investigate this dichotomy, we compared islet cell distributions and intensity of iNOS immunostaining in pancreatic sections, co-stained for insulin and glucagon, from new-onset T1D donors (group 1), with non-diabetic autoantibody-negative (group 2), non-diabetic autoantibody-positive (group 3) and long-term diabetic donors (group 4). The cellular origins of iNOS, its frequency and graded intensities in islets and number in peri-islet, intra-islet and exocrine regions were determined. All donors showed iNOS positivity, irrespective of disease and presence of beta cells, had variable labelling intensities, without significant differences in the frequency of iNOS-positive islets among study groups. iNOS was co-localised in selective beta, alpha and other endocrine cells, and in beta cell-negative islets of diabetic donors. The number of peri- and intra-islet iNOS cells was low, being significantly higher in the peri-islet area. Exocrine iNOS cells also remained low, but were much lower in group 1. We demonstrate that iNOS expression in islet cells is variable, heterogeneous and independent of co-existing beta cells. Its distribution and staining intensities in islets and extra-islet areas do not correlate with T1D or its duration. Interventions to inactivate the enzyme to alleviate disease are currently not justified.

β-carotene inhibits NF-κB and restrains diethylnitrosamine-induced hepatic inflammation in Wistar rats

β-Carotene exhibits antioxidant and hepatoprotective activities via a multitude of biochemical mechanisms. However, the action mechanism involved in antioxidant and anti-inflammatory effects of this carotene in chronic liver diseases is not fully understood. In the present investigation, we have attempted to outline a plausible mechanism of β-carotene action against liver fibrosis in albino Wistar rats. To induce hepatic fibrosis, diethylnitrosamine (DEN) was administered in experimental rats for two weeks. DEN treated rats were divided into four groups, wherein each group comprised of five rats. β-Carotene supplement attenuated DEN-induced elevation in LFT markers (P < 0.05); averted depletion of glycogen (24%, P < 0.05) and, increased nitrite (P < 0.05), hydroxyproline (~67%, P < 0.05) and collagen levels (~65%, P < 0.05). Confocal microscopy of tissue sections stained with picrosirius red revealed accrued collagen in DEN-administered group, which was found to be reduced by β-carotene supplementation. Furthermore, β-carotene decreased the expression of iNOS/NOS-2 and NF-κB, as revealed by immunohistochemistry and Western immunoblotting. Collectively, these results demonstrate that β-carotene mitigates experimental liver fibrosis via inhibition of iNOS and NF-κB in-vivo. Thus, β-carotene may be suggested as a possible nutraceutical to curb experimental liver fibrosis.

Hepatic Lysosomal iNOS Activity Impairs Autophagy in Obesity

BACKGROUND & AIMS

The lysosome is an acidic organelle that is important for maintaining cellular and metabolic homeostasis in hepatocytes. Lysosomal dysfunction and chronic inflammation coexist, and both contribute to obesity-associated hepatic insulin resistance. However, in the context of obesity, the interplay between inflammatory signals and hepatic lysosomal function remains largely unknown. Inducible nitric oxide synthase (iNOS) is a hallmark for inflammation, and is activated in obesity. The aim of this study is to understand the molecular link between iNOS-mediated lysosomal nitric oxide (NO) production, hepatic lysosomal function, and autophagy in the context of obesity-associated insulin resistance.

METHODS

The role of iNOS in hepatic autophagy, as related to insulin and glucose homeostasis were studied in mice with diet-induced obesity (DIO). The effects and mechanisms of iNOS-mediated lysosomal NO production on lysosomal function and hepatic autophagy were studied in primary hepatocytes as well as in a mouse model of DIO.

RESULTS

We demonstrate that obesity promotes iNOS localization to the lysosome and decreases levels of lysosomal arginine, resulting in an accumulation of NO in hepatic lysosomes. This lysosomal NO production is attenuated by treatment with a NO scavenger, while co-overexpression of mTOR and a lysosomal arginine transporter (SLC38A9) enhances lysosomal NO production and suppresses autophagy. In addition, we show that deletion of iNOS ameliorates lysosomal nitrosative stress in the livers of DIO mice, promotes lysosomal biogenesis by activating transcription factor EB (TFEB), and enhances lysosomal function and autophagy. Lastly, deletion of iNOS in mice with DIO improves hepatic insulin sensitivity, which is diminished by suppression of TFEB or autophagy related 7 (Atg7).

CONCLUSIONS

Our studies suggest that lysosomal iNOS-mediated NO signaling disrupts hepatic lysosomal function, contributing to obesity-associated defective hepatic autophagy and insulin resistance.

NOS2 deficiency has no influence on the radiosensitivity of the hematopoietic system

OBJECTIVE

Previous studies have shown that inhibition of inducible NO synthase (NOS2 or iNOS) with an inhibitor can selectively protect several normal tissues against radiation during radiotherapy. However, the role of NOS2 in ionizing radiation (IR)-induced bone marrow (BM) suppression is unknown and thus was investigated in the present study using NOS2-/- and wild-type mice 14 days after they were exposed to a sublethal dose of total body irradiation (TBI).

METHODS

The effects of different doses of IR (1, 2 and 4 Gy) on the apoptosis and colony-forming ability of bone marrow cells from wild-type (WT) and NOS2-/- mice were investigated in vitro. In addition, we exposed NOS2-/- mice and WT mice to 6-Gy TBI or sham irradiation. They were euthanized 14 days after TBI for analysis of peripheral blood cell counts and bone marrow cellularity. Colony-forming unit-granulocyte and macrophage, burst-forming unit-erythroid and CFU-granulocyte, erythroid, macrophage in bone marrow cells from the mice were determined to evaluate the function of hematopoietic progenitor cells (HPCs), and the ability of hematopoietic stem cells (HSCs) to self-renew was analysed by the cobblestone area forming cell assay. The cell cycling of HPCs and HSCs were measured by flow cytometry.

RESULTS

Exposure to 2 and 4 Gy IR induced bone marrow cell apoptosis and inhibited the proliferation of HPCs in vitro. However, there was no difference between the cells from WT mice and NOS2-/- mice in response to IR exposure in vitro. Exposure of WT mice and NOS2-/- mice to 6 Gy TBI decreased the white blood cell, red blood cell, and platelet counts in the peripheral blood and bone marrow mononuclear cells, and reduced the colony-forming ability of HPCs (P < 0.05), damaged the clonogenic function of HSCs. However, these changes were not significantly different in WT and NOS2-/- mice.

CONCLUSION

These data suggest that IR induces BM suppression in a NOS2-independent manner.

Characterization and evaluation of nanoencapsulated diethylcarbamazine in model of acute hepatic inflammation

Previous studies from our laboratory have demonstrated that Diethylcarbamazine (DEC) is a potent anti-inflammatory drug. The aim of the present study was to characterize the nanoencapsulation of DEC and to evaluate its effectiveness in a model of inflammation for the first time. C57BL/6 mice were divided into six groups: 1) Control; 2) Carbon tetrachloride (CCl4); 3) DEC 25mg/kg+CCl4; 4) DEC 50mg/kg+CCl4; 5) DEC-NANO 05mg/kg+CCl4 and 6) DEC-NANO 12.5mg/kg+CCl4. Liver fragments were stained with hematoxylin-eosin, and processed for Western blot, ELISA and immunohistochemistry. Serum was also collected for biochemical measurements. Carbon tetrachloride induced hepatic injury, observed through increased inflammatory markers (TNF-α, IL-1β, PGE2, COX-2 and iNOS), changes in liver morphology, and increased serum levels of total cholesterol, triglycerides, TGO and TGP, LDL, as well as reduced HDL levels. Nanoparticles containing DEC were characterized by diameter, polydispersity index and zeta potential. Treatment with 12.5 nanoencapsulated DEC exhibited a superior anti-inflammatory action to the DEC traditional dose (50mg/kg) used in murine assays, restoring liver morphology, improving serological parameters and reducing the expression of inflammatory markers. The present formulation of nanoencapsulated DEC is therefore a potential therapeutic tool for the treatment of inflammatory hepatic disorders, permitting the use of smaller doses and reducing treatment time, while maintaining high efficacy.

Resveratrol protects late endothelial progenitor cells from TNF-α-induced inflammatory damage by upregulating Krüppel-like factor-2

Cardiovascular risk factors can negatively influence late endothelial progenitor cell (EPCs) number and functions, thus EPCs biology is a clinical implications for cardiovascular diseases. The present study aimed to investigate the potential protective effects of resveratrol (RES) on tumor necrosis factor (TNF)-α-induced inflammatory damage in late endothelial progenitor cells (EPCs) and to elucidate the underlying mechanisms. Late EPCs at passages 3–5 were pretreated with RES at a concentration of 20 µmol/l for 12 h and subsequently incubated with TNF-α (10 ng/ml) for 24 h. The adhesion, migration, proliferation and vasculogenesis of EPCs were subsequently detected. Furthermore, the mRNA expression levels of intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) were measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Nitric oxide (NO) levels in the supernatant were determined using a colorimetric assay kit. Additionally, the mRNA and protein expression of Krüppel-like factor-2 (KLF2) was determined by RT-qPCR and western blot analysis, respectively. The results indicated that TNF-α markedly inhibited the proliferation, adhesion, migration and vasculogenesis of late EPCs. However, RES ameliorated the effects induced by TNF-α. Furthermore, exposure of EPCs to TNF-α decreased the levels of NO secretion and KLF2 expression at the mRNA and protein levels, but upregulated the levels of inflammatory factors, including ICAM-1 and MCP-1, compared with the control group. RES significantly inhibited TNF-α-induced inflammatory damage through upregulation of KLF2 expression and downregulation of the expression of ICAM-1 and MCP-1. In conclusion, RES may exert protective effects on the cardiovascular system, as demonstrated by the amelioration of TNF-α-induced inflammation in EPCs following RES treatment, and may therefore be used in the future for the prevention of cardiovascular disease.

Post-Transcriptional Regulation of Hepatic DDAH1 with TNF Blockade Leads to Improved eNOS Function and Reduced Portal Pressure In Cirrhotic Rats

Portal hypertension (PH) is a major cause of morbidity and mortality in chronic liver disease. Infection and inflammation play a role in potentiating PH and pro-inflammatory cytokines, including TNF, are associated with severity of PH. In this study, cirrhotic bile duct ligated (BDL) rats with PH were treated with Infliximab (IFX, a monoclonal antibody against TNF) and its impact on modulation of vascular tone was assessed. BDL rats had increased TNF and NFkB compared to sham operated rats, and their reduction by IFX was associated with a reduction in portal pressure. IFX treatment also reduced hepatic oxidative stress, and biochemical markers of hepatic inflammation and injury. IFX treatment was associated with an improvement in eNOS activity and increased l-arginine/ADMA ratio and DDAH1 expression. In vitro analysis of HepG2 hepatocytes showed that DDAH1 protein expression is reduced by oxidative stress, and this is in part mediated by post-transcriptional regulation by the 3′UTR. This study supports a role for the DDAH1/ADMA axis on the effect of inflammation and oxidative stress in PH and provides insight for new therapies.

Altered glucose and lipid homeostasis in liver and adipose tissue pre-dispose inducible NOS knockout mice to insulin resistance

On the basis of diet induced obesity and KO mice models, nitric oxide is implied to play an important role in the initiation of dyslipidemia induced insulin resistance. However, outcomes using iNOS KO mice have so far remained inconclusive. The present study aimed to assess IR in iNOS KO mice after 5 weeks of LFD feeding by monitoring body composition, energy homeostasis, insulin sensitivity/signaling, nitrite content and gene expressions changes in the tissues. We found that body weight and fat content in KO mice were significantly higher while the respiratory exchange ratio (RER), volume of carbon dioxide (VCO₂), and heat production were lower as compared to WT mice. Furthermore, altered systemic glucose tolerance, tissue insulin signaling, hepatic gluconeogenesis, augmented hepatic lipids, adiposity, as well as gene expression regulating lipid synthesis, catabolism and efflux were evident in iNOS KO mice. Significant reduction in eNOS and nNOS gene expression, hepatic and adipose tissue nitrite content, circulatory nitrite was also observed. Oxygen consumption rate of mitochondrial respiration has remained unaltered in KO mice as measured using extracellular flux analyzer. Our findings establish a link between the NO status with systemic and tissue specific IR in iNOS KO mice at 5 weeks.

Increased intracellular Ca2+ decreases cisplatin resistance by regulating iNOS expression in human ovarian cancer cells

Previous studies have reported that intracellular Ca²⁺ signals and inducible nitric oxide synthase (iNOS) are involved in cell apoptosis. However, the role of iNOS in cisplatin resistance in ovarian cancer remains unclear. Here, we demonstrate that SKOV3/DDP ovarian cancer cells were more resistant to cisplatin than were SKOV3 ovarian cancer cells. The expression of intracellular Ca²⁺ and iNOS was more strongly induced by cisplatin in SKOV3 cells than in SKOV3/DDP cells. TAT-conjugated IP3R-derived peptide (TAT-IDP^S) increased cisplatin-induced iNOS expression and apoptosis in SKOV3/DDP cells. 2-Aminoethoxydiphenyl borate (2-APB) decreased cisplatin-induced iNOS expression and apoptosis in SKOV3 cells. Thus, iNOS induction may be a valuable strategy for improving the anti-tumor efficacy of cisplatin in ovarian cancer.

Hataedock Treatment Has Preventive Therapeutic Effects in Atopic Dermatitis-Induced NC/Nga Mice under High-Fat Diet Conditions

This study investigated the preventive therapeutic effects of Hataedock (HTD) treatment on inflammatory regulation and skin protection in AD-induced NC/Nga mice under high-fat diet conditions. Before inducing AD, the extract of Coptidis Rhizoma and Glycyrrhiza uralensis was administered orally to the 3-week-old mice. After that, AD-like skin lesions were induced by applying DNFB. All groups except the control group were fed a high-fat diet freely. We identified the effects of HTD on morphological changes, cytokine release and the induction of apoptosis through histochemistry, immunohistochemistry, and TUNEL assay. HTD downregulated the levels of IL-4 and PKC but increased the levels of LXR. HTD also suppressed the mast cell degranulation and release of MMP-9, Substance P. The levels of TNF-α, p-IκB, iNOS, and COX-2 were also decreased. The upregulation of inflammatory cell's apoptosis is confirmed by our results as increase of apoptotic body and cleaved caspase-3 and decrease of Bcl-2. HTD also reduced edema, angiogenesis, and skin lesion inflammation. Our results indicate HTD suppresses various inflammatory response on AD-induced mice with obesity through the regulation of Th2 differentiation and the protection of lipid barrier. Therefore, HTD could be used as an alternative and preventive therapeutic approach in the management of AD.

The therapeutic effect of CORM-3 on acute liver failure induced by lipopolysaccharide/D-galactosamine in mice

BACKGROUND

Acute liver failure (ALF) is a severe and life-threatening clinical syndrome resulting in a high mortality and extremely poor prognosis. Recently, a water-soluble CO-releasing molecule (CORM-3) has been shown to have anti-inflammatory effect. The present study was to investigate the effect of CORM-3 on ALF and elucidate its underlying mechanism.

METHODS

ALF was induced by a combination of LPS/D-GalN in mice which were treated with CORM-3 or inactive CORM-3 (iCORM-3). The efficacy of CORM-3 was evaluated based on survival, liver histopathology, serum aminotransferase activities (ALT and AST) and total bilirubin (TBiL). Serum levels of inflammatory cytokines (TNF-alpha, IL-6, IL-1beta and IL-10) and liver immunohistochemistry of NF-kappaB-p65 were determined; the expression of inflammatory mediators such as iNOS, COX-2 and TLR4 was measured using Western blotting.

RESULTS

The pretreatment with CORM-3 significantly improved the liver histology and the survival rate of mice compared with the controls; CORM-3 also decreased the levels of ALT, AST and TBiL. Furthermore, CORM-3 significantly inhibited the increased concentration of pro-inflammatory cytokines (TNF-alpha, IL-6 and IL-1beta) and increased the anti-inflammatory cytokine (IL-10) productions in ALF mice. Moreover, CORM-3 significantly reduced the increased expression of iNOS and TLR4 in liver tissues and inhibited the nuclear expression of NF-kappaB-p65. CORM-3 had no effect on the increased expression of COX-2 in the ALF mice. An iCORM-3 failed to prevent acute liver damage induced by LPS/D-GalN.

CONCLUSION

These findings provided evidence that CORM-3 may offer a novel alternative approach for the management of ALF through anti-inflammatory functions.

Adiponectin attenuates liver fibrosis by inducing nitric oxide production of hepatic stellate cells

Adiponectin protects against liver fibrosis, but the mechanisms have not been fully elucidated. Here, we showed that adiponectin upregulated inducible nitric oxide synthase (iNOS) messenger RNA (mRNA) and protein expression in hepatic non-parenchymal cells, particularly in hepatic stellate cells (HSCs), and increased nitric oxide (NO2-/NO3-) concentration in HSC-conditioned medium. Adiponectin attenuated HSC proliferation and migration but promoted apoptosis in a NO-dependent manner. More advanced liver fibrosis with decreased iNOS/NO levels was observed in adiponectin knockout mice comparing to wide-type mice when administered with CCI4 while NO donor supplementation rescued the phenotype. Further experiments demonstrated that adiponectin-induced iNOS/NO system activation is mediated through adipoR2-AMPK-JNK/Erk1/2-NF-κB signaling. These data suggest that adiponectin inhibits HSC function, further limiting the development of liver fibrosis at least in part through adiponectin-induced NO release. Therefore, adiponectin-mediated NO signaling may be a novel target for the treatment of liver fibrosis.

KEY MESSAGES

• Adiponectin activates HSC iNOS/NO and SEC eNOS/NO systems. • Adiponectin inhibits HSC proliferation and migration but promotes its apoptosis. • Adiponectin inhibits CCL4-induced liver fibrosis by modulation of liver iNOS/NO. • Adiponectin stimulates HSC iNOS/NO via adipoR2-AMPK-JNK/ErK1/2-NF-κB pathway.

Protective role of cannabinoid receptor 2 activation in galactosamine/lipopolysaccharide-induced acute liver failure through regulation of macrophage polarization and microRNAs

Acute liver failure (ALF) is a potentially life-threatening disorder without any effective treatment strategies. d-Galactosamine (GalN)/lipopolysaccharide (LPS)-induced ALF is a widely used animal model to identify novel hepato-protective agents. In the present study, we investigated the potential of a cannabinoid receptor 2 (CB2) agonist, JWH-133 [(6aR,10aR)-3-(1,1-dimethylbutyl)-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran], in the amelioration of GalN/LPS-induced ALF. JWH-133 treatment protected the mice from ALF-associated mortality, mitigated alanine transaminase and proinflammatory cytokines, suppressed histopathological and apoptotic liver damage, and reduced liver infiltration of mononuclear cells (MNCs). Furthermore, JWH-133 pretreatment of M1/M2-polarized macrophages significantly increased the secretion of anti-inflammatory cytokine interleukin-10 (IL-10) in M1 macrophages and potentiated the expression of M2 markers in M2-polarized macrophages. In vivo, JWH-133 treatment also suppressed ALF-triggered expression of M1 markers in liver MNCs, while increasing the expression of M2 markers such as Arg1 and IL-10. microRNA (miR) microarray analysis revealed that JWH-133 treatment altered the expression of only a few miRs in the liver MNCs. Gene ontology analysis of the targets of miRs suggested that Toll-like receptor (TLR) signaling was among the most significantly targeted cellular pathways. Among the altered miRs, miR-145 was found to be the most significantly decreased. This finding correlated with concurrent upregulated expression of its predicted target gene, interleukin-1 receptor-associated kinase 3, a negative regulator of TLR4 signaling. Together, these data are the first to demonstrate that CB2 activation attenuates GalN/LPS-induced ALF by inducing an M1 to M2 shift in macrophages and by regulating the expression of unique miRs that target key molecules involved in the TLR4 pathway.

Hepatic inducible nitric oxide synthase expression increases upon exposure to hypergravity

Stimulation by a number of conditions, including infection, cytokines, mechanical injury, and hypoxia, can upregulate inducible nitric oxide synthase (iNOS) in hepatocytes. We observed that exposure to hypergravity significantly upregulated the transcription of the hepatic iNOS gene. The aim of this study was to confirm our preliminary data, and to further investigate the distribution of the iNOS protein in the livers of mice exposed to hypergravity. ICR mice were exposed to +3 Gz for 1 h. We investigated the time course of change in the iNOS expression. Hepatic iNOS mRNA expression progressively increased in centrifuged mice from 0 to 12 h, and then decreased rapidly by 18 h. iNOS mRNA levels in the livers of centrifuged mice was significantly higher at 3, 6, and 12 h than in uncentrifuged control mice. The pattern of iNOS protein expression paralleled that of the mRNA expression. At 0 and 1 h, weak cytoplasmic iNOS immunoreactivity was found in some hepatocytes surrounding terminal hepatic venules. It was noted that at 6 h there was an increase in the number of perivenular hepatocytes with moderate to strong cytoplasmic immunoreactivity. The number of iNOS-positive hepatocytes was maximally increased at 12 h. The majority of positively stained cells showed a strong intensity of iNOS expression. The expression levels of iNOS mRNA and protein were significantly increased in the livers of mice exposed to hypergravity. These results suggest that exposure to hypergravity significantly upregulates iNOS at both transcriptional and translational levels.

Reduced hepatic eNOS phosphorylation is associated with NAFLD and type 2 diabetes progression and is prevented by daily exercise in hyperphagic OLETF rats

We tested the hypothesis that nonalcoholic fatty liver disease (NAFLD) is associated with reduced hepatic endothelial nitric oxide synthase (eNOS) activation status via S1177 phosphorylation (p-eNOS) and is prevented by daily voluntary wheel running (VWR). Hyperphagic Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an established model of obesity, type 2 diabetes (T2D) and NAFLD, and normophagic controls [Long-Evans Tokushima Otsuka (LETO)] were studied at 8, 20, and 40 wk of age. Basal hepatic eNOS phosphorylation (p-eNOS/eNOS) was similar between LETO and OLETFs with early hepatic steatosis (8 wk of age) and advanced steatosis, hyperinsulinemia, and hyperglycemia (20 wk of age). In contrast, hepatic p-eNOS/eNOS was significantly lower (P < 0.05) in OLETF rats with T2D advancement and the transition to more advanced NAFLD with inflammation and fibrosis [increased tumor necrosis factor-α (TNF-α), CD68, and CD163 mRNA expression; 40 wk of age]. Reduced hepatic eNOS activation status in 40-wk OLETF rats was significantly correlated with reduced p-Akt/Akt (r = 0.73, P < 0.05), reduced serum insulin (r = 0.59, P < 0.05), and elevated serum glucose (r = -0.78, P < 0.05), suggesting a link between impaired glycemic control and altered hepatic nitric oxide metabolism. VWR by OLETF rats, in conjunction with NAFLD and T2D prevention, normalized p-eNOS/eNOS and p-Akt/Akt to LETO levels. Basal activation of hepatic eNOS and Akt are maintained until advanced NAFLD and T2D development in obese OLETF rats. The prevention of this reduction by VWR may result from maintained insulin sensitivity and glycemic control.

Effect of ghrelin on chronic liver injury and fibrogenesis in male rats: possible role of nitric oxide

Recent studies have revealed that ghrelin may be an antioxidant and anti-inflammatory agent in many organs, however its role in chronic liver injury (CLI) remains unclear. The role of nitric oxide (NO) in CLI is controversial as evidence suggests that NO is either a primary mediator of liver cell injury or exhibits a protective effect against injurious stimuli. Recent evidence demonstrated that the therapeutic potential for ghrelin was through eNOS activation and increase in NO production. However, its role on NO production in the liver has not been previously investigated. The aim of this study was to investigate the role of ghrelin in treatment of CLI, and whether this action is mediated through NO. Forty male rats were divided into four groups: Group I: Control; Group II: chronic liver injury (CLI); Group III: CLI+Ghrelin; and Group IV: CLI+Ghrelin+l-NAME. Liver enzymes and tumor necrosis factor alpha (TNF-α), were measured to assess hepatocellular injury. Liver tissue collagen content, malondialdehyde (MDA), gene expression of Bax, Bcl-2, and eNOS were assessed to determine the mechanism of ghrelin action. Results showed that ghrelin decreased serum liver enzymes and TNF-α levels. Ghrelin also reduced liver tissue collagen, MDA, and Bax gene expression, and increased Bcl-2 and eNOS gene expression. The effects on TNF-α, collagen, MDA, Bax, and eNOS were partially reversed in Group IV, suggesting that ghrelin's action could be through modulation of NO levels. Therefore, ghrelin's hepatoprotective effect is partially mediated by NO release.

Role of nitric oxide synthase genes in hepatitis E virus infection

Hepatitis E virus (HEV) is the most common cause of endemic and epidemic acute hepatitis. A correlation between iNOS, eNOS polymorphisms, levels and severity of disease has been reported, and here, we examined the role of iNOS and eNOS gene polymorphisms and their levels in HEV-related acute viral hepatitis and acute liver failure. Hepatitis E virus-related cases of acute hepatitis (294 patients) and liver failure (82 patients) and age- and sex-matched healthy controls (331 subjects) were included in the study. PCR-RFLP was performed to identify the polymorphisms in the iNOS and eNOS genes. iNOS and eNOS levels were studied using ELISA assays and HEV viral load, genotype and combined effects of iNOS genotype, levels and parameters for disease severity were examined. The frequency of iNOS (CT + TT) and eNOS (GT + TT) genotypes was higher in subjects with liver failure compared with controls. iNOS and eNOS levels in patients with acute liver failure (55.51 ± 6.33 IU/mL, 60.2 ± 3.69) cases were significantly increased as compared to patients with acute viral hepatitis (17.8 ± 6.08 IU/mL, 23.7 ± 6.57) and controls (P < 0.05). A significant positive correlation was observed between the iNOS and eNOS levels in our study population when compared with the severity of disease parameters. Hence, the iNOS C150T polymorphism and the eNOS G894T polymorphism and high levels of iNOS and eNOS are associated with an increased risk of HEV-related acute hepatitis and liver failure. This study supports the possible role of nitric oxide synthase genes (iNOS and eNOS) in determining the severity of HEV infection.

Investigation of the expression of mediators of neovascularization from mononuclear leukocytes in thromboangiitis obliterans

The aim of this study was to investigate the expression of the cytokines, chemokines and effective molecules of peripheral blood mononuclear cells (PBMCs) that play a role in neovascularization in thromboangiitis obliterans (TAO). Lymphocytes from TAO patients ( n = 20) and control subjects (healthy smokers [ n = 16] and non-smokers [ n = 17]) were evaluated using realtime polymerase chain reaction in order to examine the mRNA expression of CXCL1 and interleukin 8 (IL-8; inducers of collateral development by recruitment of circulating progenitor cells [CPCs]), endothelial cell growth factor A (VEGF-A) and inducible nitric oxide synthase (iNOS; inducers of angiogenesis) and interferon gamma (IFN- γ) and vascular endothelial growth factor receptor 1 (VEGFR-1; inhibitors of angiogenesis). CXCL1 expression was significantly higher in the TAO patients than control subjects. The expressions of IL-8, VEGFR-1 and IFN- γ were significantly higher in the TAO patients and smokers than in non-smokers. However, no differences in iNOS and VEGF-A expression were noted. In conclusion, PBMCs from TAO patients expressed cytokines that potentially recruit CPCs and promote arteriogenesis. However, TAO patients typically have low CPC levels, perhaps due to high oxidative stress. Further studies are recommended in order to investigate the efficacy of antioxidant therapy on the outcome of TAO before administration of angiogenic factors.

Current concepts on the role of nitric oxide in portal hypertension

Portal hypertension (PHT) is defined as a pathological increase in portal venous pressure and frequently accompanies cirrhosis. Portal pressure can be increased by a rise in portal blood flow, an increase in vascular resistance, or the combination. In cirrhosis, the primary factor leading to PHT is an increase in intra-hepatic resistance to blood flow. Although much of this increase is a mechanical consequence of architectural disturbances, there is a dynamic and reversible component that represents up to a third of the increased vascular resistance in cirrhosis. Many vasoactive substances contribute to the development of PHT. Among these, nitric oxide (NO) is the key mediator that paradoxically regulates the sinusoidal (intra-hepatic) and systemic/splanchnic circulations. NO deficiency in the liver leads to increased intra-hepatic resistance while increased NO in the circulation contributes to the hyperdynamic systemic/splanchnic circulation. NO mediated-angiogenesis also plays a role in splanchnic vasodilation and collateral circulation formation. NO donors reduce PHT in animals models but the key clinical challenge is the development of an NO donor or drug delivery system that selectively targets the liver.

Eosinophils involved in fulminant hepatic failure are associated with high interleukin-6 expression and absence of interleukin-5 in liver and peripheral blood

BACKGROUND/AIMS

Although eosinophils are considered to play an important role in the pathogenesis of various parasitic, allergic and autoimmune digestive diseases, their role in fulminant hepatic failure (FHF) is unknown. Our contribution was to identify and quantify eosinophils and cytokine levels [interleukin (IL)-6, IL-5 and macrophage inflammatory protein (MIP)-1alpha] in liver parenchyma and peripheral blood from FHF patients at pre- and post-transplantation steps.

METHODS

Histochemical methods were used to identify/quantify eosinophils in liver samples. Liver and plasma cytokine levels were quantified using immunofluorescence methods.

RESULTS

Fulminant hepatic failure patients showed a high number of intrahepatic eosinophils concomitant with an increased expression of IL-6, besides the IL-6-positive eosinophils associated with the lack of IL-5. Also, an increased number of eosinophils and soluble IL-6 and MIP-1alpha with a low expression of IL-5 in peripheral blood at the pretransplantation step was observed.

CONCLUSIONS

The increased number of intrahepatic eosinophils, besides the high production of IL-6, may be involved in liver dysfunction. In addition, the low presence of IL-5 in liver and peripheral blood may represent a particular pattern of eosinophil behaviour in human liver failure, which may also involve MIP-1alpha. Further ex vivo studies are necessary to evaluate the specific role of eosinophils in FHF.

Overexpression of hepatic inducible nitric oxide synthase in biliary atresia

AIMS

Biliary atresia (BA) is a rare and serious liver disease in infants characterized by progressive inflammatory cholangiopathy. The aims of this study were to investigate hepatic expression of inducible nitric oxide synthase (iNOS) in BA and to associate the iNOS expression with their early therapeutic outcome.

METHODS

Hepatic iNOS expression was determined using immunohistochemistry from liver biopsies of 24 BA patients, and 16 non-BA patients whose liver tissues were needed in the treatment process. Six months after surgery, the BA patients were categorized into two groups;good and poor outcome. The iNOS expression of hepatocyte areas was evaluated based on its intensity using ImageJ software. Unpaired t-tests were used for the comparisons of iNOS expression between groups.

RESULTS

Hepatic iNOS expression of BA patients was significantly stronger than that of non-BA patients (P < 0.0001). The largest area of hepatic iNOS expression was the area of hepatocytes. Subgroup analysis of BA patients at 6 months post-op revealed that there was no difference in iNOS expression between the patients with good outcome and those with poor outcome (P = 0.732).

CONCLUSIONS

Overexpression of hepatic iNOS in BA patients was demonstrated. Within liver tissues, hepatocytes were the major source of hepatic iNOS production. However, the expression was not associated with the early therapeutic outcome. These results suggest that iNOS plays a role in the liver pathology of BA but its expression cannot be used as a predictor for therapeutic outcome.

Expression of interleukin-16 in sciatic nerves, spinal roots and spinal cords of experimental autoimmune neuritis rats

Experimental autoimmune neuritis (EAN) is a well-known animal model of Guillain-Barré Syndrome. In this study, we studied the spatiotemporal expression of interleukin-16 (IL-16) in the nervous system of EAN rats and pharmacological effects of minocycline on IL-16 expressions in EAN rats. In sciatic nerves and dorsal/ventral roots of EAN rats, IL-16+ cells, identified as macrophages and T cells, were mainly found to concentrate around blood vessels. However, in spinal cords, IL-16+ microglial cells were mainly found in lumbar dorsal horns. Massive IL-16+ cell accumulation in sciatic nerves and spinal roots was temporally correlated with severity of neurological signs of EAN. Furthermore, a strong correlation of IL-16+ cell accumulation with local demyelination in perivascular areas of sciatic nerves, and significant reduction of IL-16+ cell numbers in sciatic nerves and spinal cords by minocycline suggested a pathological contribution of IL-16+ cells in EAN. Taken together, robust IL-16+ cell accumulation in the nervous system and its temporal correlation with severity of neurological signs in EAN might suggest a pathological role of IL-16 in EAN, which makes IL-16 a potential pharmacological target.

Endothelial nitric oxide synthase is a critical factor in experimental liver fibrosis

Reduced expression of endothelial nitric oxide synthase (eNOS) in chronic liver disease can reduce hepatic perfusion and accelerate fibrosis. The relationship between eNOS expression and liver fibrogenesis remains unclear. We investigated whether L-arginine attenuated chronic liver fibrosis through eNOS expression. Chronic liver injury was induced by administration of carbon tetrachloride (CCl(4)) to mice for 8 weeks. 5-Methylisothiourea hemisulphate (SMT), an iNOS inhibitor, or L-arginine, a NOS substrate were injected subcutaneously. CCl(4)-induced hepatotoxicity, oxidative stress and accumulation of collagen were detected in the liver. The expression levels of inducible NOS (iNOS) and nuclear factor kappa-B (NF-kappaB) activity in the liver after CCl(4) treatment were increased but eNOS expression and activator protein-1 (AP-1) activity were decreased. Both SMT and L-arginine effectively reduced CCl(4) induced oxidative stress and collagen formation, but L-arginine showed a significantly greater suppression of collagen formation, iNOS expression and NF-kappaB activity. L-arginine also restored the level of eNOS and AP-1 activity. L-arginine was more effective than SMT in suppressing liver fibrosis. L-arginine might improve NO production which facilitates hepatic blood flow and thus retards liver fibrogenesis. Our results showed that the reduced eNOS expression in CCl(4)-treated mice was reversed by L-arginine. Furthermore, L-arginine also reversed the reduced AP-1 activity, an eNOS promoter.

Improved outcome of EAN, an animal model of GBS, through amelioration of peripheral and central inflammation by minocycline

Experimental autoimmune neuritis (EAN) is a widely used animal model of the human acute inflammatory demyelinating polyradiculoneuropathy, which is the most common subtype of Guillain-Barré Syndrome. EAN is pathologically characterized by breakdown of the blood-nerve barrier, infiltration of reactive immune cells, local inflammation, demyelination in the peripheral nervous system and mechanical allodynia. Minocycline is known to have neuroprotective and anti-inflammatory effects. Furthermore, relieve of neuropathic pain following minocycline administration was observed in a variety of animal models. Here, we investigated the effects of minocycline on rat EAN. Suppressive treatment with minocycline (50 mg/kg body weight daily immediately after immunization) significantly attenuated the severity and duration of EAN. Macrophage and T-cell infiltration and demyelination in sciatic nerves of EAN rats treated with minocycline were significantly reduced compared to phosphate-buffered saline (PBS)-treated EAN rats. mRNA expressions of matrix metallopeptidase-9, inducible nitric oxide synthase and pro-inflammatory cytokines interleukin-1 β and tumour necrosis factor-α in EAN sciatic nerves were greatly decreased by administration of minocycline as well. Furthermore, minocycline attenuated mechanical allodynia in EAN rats and greatly suppressed spinal microglial activation. All together, our data showed that minocycline could effectively suppress the peripheral and spinal inflammation (immune activation) to improve outcome in EAN rats, which suggests that minocycline may be considered as a potential candidate of pharmacological treatment for autoimmune-mediated neuropathies.

Hepatocyte survival in acute hepatitis is due to c-Jun/AP-1-dependent expression of inducible nitric oxide synthase

Analysis of the molecular factors determining hepatocyte survival or death in response to inflammatory stimuli is essential for understanding the pathogenesis of inflammatory liver disease and for identifying novel therapeutic approaches. c-Jun N-terminal kinase (JNK) is a major mediator of cytokine-induced cell death during hepatitis, but the signaling pathways downstream of JNK remain less well defined. Here we show that the transcription factor c-Jun/AP-1, a prototypic target of JNK, is strongly expressed in the liver of patients with acute liver injury. The molecular function of c-Jun in inflammatory liver disease was analyzed in mice by using the Con A model of T cell-mediated hepatitis. Mice lacking c-Jun in hepatocytes display increased liver cell death and mortality upon Con A injection. This phenotype is caused by impaired expression of inducible nitric oxide synthase (nos2), a direct transcriptional target of c-Jun, and reduced production of hepatoprotective nitric oxide (NO). Moreover, increased hepatotoxicity in mutant mice is likely caused by hypoxia and oxidative stress and can be rescued pharmacologically by liver-specific NO delivery. These findings demonstrate that c-Jun/AP-1 is hepatoprotective during acute hepatitis by regulating nos2/NO expression and thus functionally antagonizes the cell death-promoting functions of JNK.

Dexamethasone transiently attenuates up-regulation of endostatin/collagen XVIII following traumatic brain injury

Endostatin/collagen XVIII is a specific inhibitor of endothelial proliferation and migration in vitro. It has also been shown to have anti-angiogenic activity and tumor growth inhibitory activity in vivo and in vitro. Here we studied expression of endostatin/collagen XVIII in a rat traumatic brain injury (TBI) model, focusing on the early phase. A significant up-regulation of endostatin/collagen XVIII in TBI began as early as 24 h post-TBI. Double-staining experiment revealed that the major resource of endostatin/collagen XVIII(+) cells in our TBI rat model was a subpopulation of reactivated microglia/macrophages. Our data further showed that dexamethasone attenuated up-regulation of endostatin/collagen XVIII expression at days 1 and 2, but not at day 4, post-TBI, indicating that dexamethasone might possess an early and transient influence to the angiogenesis following TBI.

Endothelium-derived hyperpolarization factor (EDHF) is up-regulated in a pig model of acute liver failure

BACKGROUND

Acute liver failure (ALF) is hemodynamically characterized by hyperdynamic circulation, but the pathophysiologic mechanisms underlying these disturbances are not known. The purposes of the present experiments were: to study systemic and peripheral hemodynamics in vivo, to measure changes in vascular reactivity in vitro, and to determine the role of endothelium-dependent vasodilator pathways in a well-validated porcine model of ALF.

METHODS

Landrace pigs (24-29 kg) were allocated to sham operation (n=8) or ALF induced by hepatic devascularization (n=9). Systemic and regional hemodynamics were monitored. Femoral artery rings were prepared for isometric tension recordings 8 h after ALF induction. Contractile responses to phenylephrine were assessed in ring segments of endothelium-intact femoral arteries in the absence or presence of inhibitors of endothelium-derived hyperpolarizing factor, nitric oxide synthase, cyclooxygenase and heme oxygenase pathways.

RESULTS

Pigs with ALF developed a hyperdynamic circulation. Cardiac index increased (PGT<0.001), while mean arterial pressure (PGT=0.012) and systemic vascular resistance decreased (PGT<0.001) in this group. Femoral artery blood flow decreased in controls, while it remained unchanged in ALF (PGT=0.010). Accordingly, vascular resistance across the hind leg was significantly decreased (PGT<0.001) in ALF. The combination of Ca2+-activated potassium channel inhibitors charybdotoxin and apamin, which block the release of endothelium-derived hyperpolarizing factor, increased the contraction force (ANOVA, PGT=0.05) and Emax (P=0.01) to phenylephrine in ALF. In contrast, inhibitors of nitric oxide synthase, cyclooxygenase and heme oxygenase pathways did not increase isometric contraction force.

CONCLUSIONS

Endothelium dependent hyperpolarization of vascular smooth muscle contributes to the development of hyperdynamic circulation in ALF.

Curcumin ameliorates acute thioacetamide-induced hepatotoxicity

BACKGROUND AND AIM

Increased production of reactive oxygen species and nitric oxide and activation of nuclear factor kappa B are implicated in the pathogenesis of various liver diseases, including fulminant hepatic failure. Curcumin is a naturally occurring anti-oxidant that reduces oxidative stress and inhibits nuclear factor kappa B and nitric oxide formation. The aim of the present study is to assess curcumin's therapeutic potential in acute thioacetamide hepatotoxicity, a rat model of fulminant hepatic failure.

METHODS

Fulminant hepatic failure was induced by two intraperitoneal (i.p.) injections of 300 mg/kg thioacetamide (TAA) at 24-h intervals. The experimental groups received a low-dose (200 mg/kg per day, i.p.) or a high-dose (400 mg/kg per day) of curcumin, initiated 48 h prior to the first TAA injection. A fourth group was administered neither TAA nor curcumin and served as a control.

RESULTS

The survival rate was higher in both curcumin-treated groups compared to the TAA only treated group. Biochemical parameters of liver injury, blood ammonia and hepatic necroinflammation were lower in the low-dose curcumin group compared to TAA controls, and were further reduced in the high-dose group (P < 0.05 and P < 0.01, respectively). Curcumin treatment also reduced the TAA-induced elevated hepatic levels of thiobarbituric acid-reactive substances (TBARS), and inhibited the nuclear binding of nuclear factor kappa B (NFkappaB) and inducible nitric oxide (iNOS) protein expression.

CONCLUSIONS

Curcumin improved survival and minimized oxidative stress, hepatocellular injury and hepatic necroinflammation, NFkappaB binding and iNOS expression in a rat model of FHF. These findings support the role of ROS, NFkappaB and iNOS in mediating liver insult due to TAA, and that of curcumin as a hepato-protectant.

Morphology and regulatory mechanism of hepatocyte apoptosis in experimental fulminant hepatic failure

AIM: To study the morphological changes and the regulation of nitric oxide (NO), Fasand Bcl-2 on hepatocyte apoptosis in mouse model of experimental fulminant hepatic failure (FHF)..

METHODS: Mouse model of experimental FHF was established by combination of lipopolysaccharide (LPS) and D-galactosamin (D-GalN). The expression of Fas and Bcl-2 in the liver tissues was tested by immunohistochemistry. The level of serum NO and iNOS mRNA expression in liver were tested by nitrate reductase method and reverse transcription polymerase chain reaction (RT-PCR), respectively. The hepatocyte apoptosis was examined by TUNEL method. In addition, the changes of the above items were observed after pretreatment with L-NMMA, an inhibitor of iNOS.

RESULTS: The level of serum NO and expression of iNOS mRNA in the liver tissues were increased at 2 h in model group, reaching the peak at 4 h. There was a little Fas expression at 2 h in model group. The expression of Fas was increased significantly at 8 and 12 h, which was distinctly higher than that at 2 h (100% vs 20%, P < 0.01) and 4 h (100% vs 40%, P < 0.05). The expression of Bcl-2 started to increase at 2 h, reaching the peak at 4 h, which was markedly higher than that at 2 h (90% vs 60%, P < 0.05). The expression of Bcl-2 at 4 h was also significantly higher than that at 8 or 12 h (90% vs 20%, both P < 0.01). Typical features of hepatocyte apoptosis were observed at 8 h. The level of serum NO and liver iNOS mRNA expression were normal and the Fas, Bcl-2 expression did not change notably after L-NMMA administration in comparison with those in model group (P > 0.05). Typical hepatocyte apoptosis was also observed at 8 h after L-NMMA administration, and the pathological changes of the liver tissues were more severe.

CONCLUSION: Both expression of Fas and Bcl-2 are increased in FHF. Fas expression is consistent with hepatocyte apoptosis, while Bcl-2 expression is negatively correlated with hepatocyte apoptosis. Single administration of iNOS inhibitor can not protect hepatocytes against apoptosis and injury.

Pathogenic molecular mechanisms in an animal model of fulminant hepatic failure: rabbit hemorrhagic viral disease

In this study we sought to determine whether molecular mechanisms involved in the pathogenesis of fulminant hepatic failure are present in rabbits experimentally infected with rabbit hemorrhagic disease virus (RHDV). The activities of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase, as well as bilirubin concentration, were found to be significantly increased 36 hours after infection. Infected animals also demonstrated significant decreases in factor VII activity, in the Fischer index, and in the deterioration of prothrombin time. The concentration of reduced glutathione was significantly decreased 36 hours after infection, and we noted a marked increase in the ratio of oxidized to reduced glutathione. Infected animals showed progressive decreases in liver activity of the antioxidant enzyme superoxide dismutase. Expression of hepatocyte growth factor and c-met was found to be progressively reduced from 24 hours after infection, during which time we detected no modification in messenger RNA (mRNA) levels of transforming growth factor (TGF)-alpha. TFG-beta 1 was overexpressed 24 and 36 hours after infection, and 36 hours after infection we detected a significant increase in TNF-alpha mRNA levels. Experimental RHDV infection also induced marked activation of nuclear factor-kappaB and a significant increase in inducible nitric oxide synthase mRNA levels from 24 hours after infection. Data obtained from this animal model support its usefulness in the investigation of potential novel therapeutical modalities aimed at neutralizing reactive oxygen species and hepatocyte growth inhibitors or enhancing hepatocyte responsiveness to mitogens.

PGE1-induced NO reduces apoptosis by D-galactosamine through attenuation of NF-kappaB and NOS-2 expression in rat hepatocytes

Prostaglandin E1 (PGE1) reduces cell death in experimental and clinical liver dysfunction. We have previously shown that PGE1 preadministration protects against NO-dependent cell death induced by D-galactosamine (D-GalN) through a rapid increase of nuclear factor kappaB (NF-kappaB) activity, inducible NO synthase (NOS-2) expression, and NO production. The present study investigates whether PGE1-induced NO was able to abolish NF-kappaB activation, NOS-2 expression, and apoptosis elicited by D-GalN. Rat hepatocytes were isolated following the classical method of collagenase perfusion of liver. PGE1 (1 micromol/L) was administered 2 hours before D-GalN (5 mmol/L) in primary culture rat hepatocytes. PGE1 reduced inhibitor kappaBalpha degradation, NF-kappaB activation, NOS-2 expression, and apoptosis induced by D-GalN. The administration of an inhibitor of NOS-2 abolished the inhibitory effect of PGE1 on NF-kappaB activation and NOS-2 expression in D-GalN-treated hepatocytes. Transfection studies using different plasmids corresponding to the NOS-2 promoter region showed that D-GalN and PGE1 regulate NOS-2 expression through NF-kappaB during the initial stage of hepatocyte treatment. PGE1 was able to reduce the promoter activity induced by D-GalN. In addition, a NO donor reduced NOS-2 promoter activity in transfected hepatocytes. In conclusion, administration of PGE1 to hepatocytes produces low levels of NO, which inhibits its own formation during D-GalN-induced cell death through the attenuation of NF-kappaB-dependent NOS-2 expression. Therefore, a dual role for NO in PGE1-treated D-GalN-induced toxicity in hepatocytes is characterized by a rapid NO release that attenuates the late and proapoptotic NOS-2 expression.

Inhibition of inducible nitric oxide synthase protects against liver injury induced by mycobacterial infection and endotoxins

BACKGROUND/AIMS

Bacillus Calmette Guerin (BCG) infection causes hepatic injury following granuloma formation and secretion of cytokines which render mice highly sensitive to endotoxin-mediated hepatotoxicity. This work investigates the role of inducible nitric oxide synthase (iNOS) in liver damage induced by BCG and endotoxins in BCG-infected mice.

METHODS

Liver injury and cytokine activation induced by BCG and by LPS upon BCG infection (BCG/LPS) were compared in wild-type and iNOS-/- mice.

RESULTS

iNOS-/- mice infected with living BCG are protected from hepatic injury when compared to wild-type mice which express iNOS protein in macrophages forming hepatic granulomas. In addition, iNOS-/- mice show a decrease in BCG-induced IFN-gamma serum levels. LPS challenge in BCG-infected mice strongly activates iNOS in the liver and spleen of wild-type mice which show important liver damage associated with a dramatic increase in TNF and IL-6 and also Th1 type cytokines. In contrast, iNOS-/- mice are protected from liver injury after BCG/LPS challenge and their TNF, IL-6 and Th1 type cytokine serum levels raise moderately.

CONCLUSIONS

These results demonstrate that nitric oxide (NO) from iNOS is involved in hepatotoxicity induced by both mycobacterial infection and endotoxin effects upon BCG infection and that inhibition of NO from iNOS protects from liver injuries.

Protective effect of MDL28170 against thioacetamide-induced acute liver failure in mice

Liver injury is known to often progress even after the hepatotoxicant is dissipated. The hydrolytic enzyme calpain, which is released from dying hepatocytes, destroys the surrounding cells and results in progression of injury. Therefore, control of calpain activation may be a suitable therapeutic intervention in cases of fulminant hepatic failure. This study evaluated the effects of a potent cell-permeable calpain inhibitor, MDL28170, and its mechanisms of action on thioacetamide (TAA)-induced hepatotoxicity in mice. We found that MDL28170 significantly decreased mortality and change in serum transaminase after TAA administration. The necroinflammatory response in the liver was also suppressed. Furthermore, a significant suppression of hepatocyte apoptosis could be found by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay. The upregulation of inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha), both of which are known to mediate the propagation of inflammation, was abolished. MDL2810 also effectively blocked hepatic stellate cell activation, which is assumed to be the early step in liver fibrosis. These results demonstrated that MDL28170 attenuated TAA-induced acute liver failure by inhibiting hepatocyte apoptosis, abrogating iNOS and TNF-alpha mRNA upregulation and blocking hepatic stellate cell activation.

Nitric oxide synthase inhibitors modulate lipopolysaccharide-induced hepatocyte injury: dissociation between in vivo and in vitro effects

Effects of endotoxemia-induced NO production on rat liver and hepatocytes in culture were investigated. Rats were treated intraperitoneally with saline, lipopolysaccharide (LPS, 10 mg/kg), L-nitroarginine methyl ester (L-NAME)+LPS, aminoguanidine (AG)+LPS, FK 506+LPS, S-nitroso-N-acetyl penicillamine (SNAP)+L-NAME+LPS and SNAP+FK 506+LPS. Mortality, hepatocyte viability and liver function test were estimated. Liver morphology was observed by light and electron microscopy. Hepatocyte cultures were treated with LPS, cytokine mixture (CM) with or without FK 506, L-NAME or AG. Hepatocyte function and inducible form of NOS (iNOS) expression were evaluated. Twenty-four hours after treatments with saline, LPS, L-NAME+LPS, AG+LPS, FK 506+LPS, SNAP+L-NAME+LPS and SNAP+FK 506+LPS, rat mortalities were 0%, 10%, 48%, 8%, 20%, 38% and 0%, and hepatocyte viabilities were 93+/-3%, 80+/-3%, 52+/-8%, 88+/-1%, 70+/-3%, 80+/-4% and 82+/-3%, respectively. AG+LPS or L-NAME+LPS administration was followed by excessive vacuolization of hepatocytes with lesions in the intermediary lobule zone characterized by features of secondary necrosis as a continuation of apoptotic processes. SNAP+L-NAME+LPS resulted in a well-preserved structure of central vein lobules with sparse signs of apoptosis. Treatment with LPS or CM increased iNOS expression in hepatocyte culture, which was inhibited by L-NAME, FK 506 or AG. AG reduced LPS-induced rise in alanine aminotransferase leakage. LPS-induced NO exerts cytoprotective effects in vivo, while LPS-induced NO in vitro appears to be toxic. Based on the data of this report, one cannot use in vitro results to predict in vivo responses to LPS-induced NO production. The pharmacological modulation of iNOS expression or NO production in vivo or in vitro, therefore, by the development of specific NO donors or inhibitors is promising for improvement of hepatocyte functions under the two experimental conditions, respectively.