Lipopolysaccharide and D-galactosamine-induced hepatic injury is mediated by TNF-alpha and not by Fas ligand

The neuropeptide calcitonin gene-related peptide (CGRP) prevents inflammatory liver injury in mice

BACKGROUND/AIMS

Calcitonin gene-related peptide (CGRP) is a potent vasodilator and supposed to be responsible for neurogenic inflammation involved in migraine. Its role in inflammatory diseases of other organs is controversial and poorly investigated regarding liver inflammation, although the organ is innervated by CGRP containing primary sensory nerve fibers.

METHODS

Male Balb/c and IL-10(-/-) mice were pretreated with either alphaCGRP or the CGRP receptor antagonists CGRP(8-37) or BIBN4096BS. Immune-mediated liver injury was induced by administration of lipopolysaccharide (LPS) or tumor necrosis factor-alpha (TNFalpha) to galactosamine (GalN)-sensitized mice and evaluated by serum transaminase activities and cytokine levels. Furthermore, intrahepatic CGRP receptor expression and hepatic CGRP concentrations were examined.

RESULTS

CGRP receptor 1 was expressed by immune cells and hepatocytes in human and murine liver. During liver injury CGRP receptor expression was increased whereas hepatic CGRP concentrations concomitantly decreased. While CGRP receptor antagonists failed to affect liver damage, pretreatment with alphaCGRP protected mice from GalN/LPS-induced liver injury by suppression of the pro-inflammatory cytokine response independently from IL-10 but related to the induction of the transcriptional repressor inducible cAMP early repressor (ICER). In contrast, alphaCGRP failed to protect against GalN/TNFalpha-induced liver failure.

CONCLUSION

In the liver, CGRP exerts anti-inflammatory properties, which are characterized by a reduced production of pro-inflammatory cytokines.

Role of the perforin/granzyme cell death pathway in D-Gal/LPS-induced inflammatory liver injury

Cytotoxic T lymphocytes and their granule components, such as perforin and granzyme, play an important role in the defense of hepatic infections caused by different pathogens. Moreover, it has been shown in vitro that hepatocytes can initiate cell death via a perforin-dependent mechanism. Although it is well known that hepatocellular apoptosis in D-galactosamine/lipopolysaccharide (D-Gal/LPS)-associated liver failure is mediated by TNF-alpha-dependent Fas/FasL cytotoxicity, there is no information on the role of perforin-mediated mechanisms in vivo. Therefore, we studied whether the cytolytic perforin/granzyme pathway contributes to the D-Gal/LPS-associated hepatotoxicity. Perforin knockout (Pko) mice showed significantly higher hepatic TNF-alpha and IL-6 mRNA expression as well as plasma TNF-alpha and IL-6 concentrations within the first hour upon D-Gal/LPS challenge compared with perforin wild-type (Pwt) mice. At 6 h upon D-Gal/LPS challenge, Pko mice further presented with higher transaminase release and onconecrotic tissue damage, whereas hepatocellular apoptosis and caspase-3 cleavage remained unaffected by the perforin deficiency. Pretreatment with a recombinant human TNF-alpha receptor fusion protein attenuated necrotic and apoptotic tissue damage and reduced plasma transaminase activities as well as cytokine release, thereby preventing acute liver failure in Pko mice as effectively as in Pwt mice. These data do not only confirm the significance of TNF-alpha as distal mediator of hepatic injury in this model but simultaneously reveal a contribution of a perforin-dependent immunoregulation, limiting the D-Gal/LPS-induced overwhelming cytokine release and onconecrotic tissue injury.

Effects of endotoxin on liver Smac apoptosis channel

To study the effect of endotoxin on liver apoptosis, L02 liver cells were cultured and passaged in vitro, and then stimulated by endotoxin at 10 mg/mL for 4, 8, 16 and 24 h respectively. Liver apoptosis was flow cytometrically and fluorescently detected. Immunohistochemistry was used to detect the delivery of smac and caspase9. The delivery of liver cell smac and the activity of caspase3 were measured by caspase3 assay kit. The hepatic failure models of rats were established by using D-galactosamine. The blood serum and liver tissues were collected for the detection of the liver function, the level of endotoxin and the activity of caspase3 by using chromogenic substrate limulus amebocyte lysate method (LAL) and caspase3 active assay kit. The expression of smac and caspase9 in liver cells was detected by Western blotting. With in vitro study, the L02 cells stimulated by LPS condensed into conglobation and formed apoptotic bodies. After those cells were stained by hoechst, the apoptotic cells displayed blue color under the fluorescent microscope. The apoptosis rate was increased over time and the apoptosis was mainly of advanced stage. Meanwhile, the rate of smac delivery and activity of caspase9 and caspase3 were increased on L02 cell membrane. In vivo, hepatic failure and obvious endotoxemia were induced by injection of more than 200 mg/kg D-GalN. Hepatic mitochondria smac was reduced with dosage of D-GalN and, on the contrary, the activity of caspase3 was increased. D-GalN at 200 mg/kg increased Caspase9 while D-GalN at 300 mg/kg decreased caspase9. Mitochondria signal channel plays an important role in the endotoxin-induced apoptosis of hepatic cells by promoting the release of smac from mitochondria to cytoplasm and activating caspase9 and caspase3 in its low-level channel.

Contribution of hepatic stellate cells and matrix metalloproteinase 9 in acute liver failure

BACKGROUND/AIMS

Fulminant hepatitis or acute liver failure (ALF), initiated by viral infection or hepatic toxin, is a devastating medical complication without effective therapeutic treatment. In this study, we addressed the potential roles of hepatic stellate cells (HSCs) and their produced matrix metalloproteinases (MMPs) in development of ALF.

METHODS

Mice were given lipopolysaccharide (LPS) and beta-galactosamine (GA) or carbon tetrachloride to create ALF and establish the association of IL-1, MMP-9, and caspase-3 in acute liver failure.

RESULTS

In response to the hepatic toxin, IL-1 and MMP-9 were promptly induced within 1 hour, followed by caspase-3 activation at 2 hours, and dehiscence of sinusoids at 4 hours, and consequent lethality. In contrast, MMP-9 knockout mice were resistant to lethality and absent of caspase-3 activation, demonstrating an MMP-9-dependent activation of caspase in vivo. Further, IL-1-receptor knockout mice were resistant to lethality in MMP-9 dependent manner, indicating a causative relationship. Although many hepatic cells are capable to produce MMP-9 in vitro, HSCs were demonstrated here as the major hepatic cells to express MMP-9 in liver injury. To recapitulate the sinusoidal microenvironment we cultured primary HSCs in 3-dimensional ECM. In response to IL-1, massive MMP-9 was produced by the 3D culture concomitantly with degradation of type-IV collagen.

CONCLUSIONS

Based on these evidences, we propose a novel model to highlight the initiation of acute liver failure: IL-1-induced MMPs by HSCs within the space of Disse and thereafter ECM degradation may provoke the collapse of sinusoids, leading parenchymal cell death and loss of liver functions.

CpG DNA prevents liver injury and shock-mediated death by modulating expression of interleukin-1 receptor-associated kinases

Tumor necrosis factor-alpha (TNF-alpha) produced by macrophages in response to CpG DNA induces severe liver injury and subsequent death of D-galactosamine (D-GalN)-sensitized mice. In the present study we demonstrate that mice pre-exposed to CpG DNA are resistant to liver injury and death induced by CpG DNA/D-GalN. CpG DNA/D-GalN failed to induce TNF-alpha production and hepatocyte apoptosis in the mice pre-exposed to CpG DNA. In addition, macrophages isolated from the CpG DNA-pretreated mice showed suppressed activation of MAPKs and NF-kappaB and production of TNF-alpha in response to CpG DNA, indicating that the CpG DNA-mediated protection of CpG DNA/D-GalN-challenged mice is due to the hyporesponsiveness of macrophages to CpG DNA. CpG DNA pretreatment in vivo inhibited expression of interleukin-1 receptor-associated kinase (IRAK)-1 while inducing IRAK-M expression in macrophages. Suppressed expression of IRAK-1 was responsible for the macrophage hyporesponsiveness to CpG DNA. However, increased expression of IRAK-M was not sufficient to render macrophages hyporesponsive to CpG DNA but was required for induction of the optimal level of macrophage hyporesponsiveness. Taken together, reduced expression of IRAK-1 and increased expression of IRAK-M after CpG DNA pretreatment resulted in the hyporesponsiveness of macrophages that leads to the protection of mice from hepatic injury and death caused by CpG DNA/D-GalN.

Protective effects of amide constituents from the fruit of Piper chaba on D-galactosamine/TNF-alpha-induced cell death in mouse hepatocytes

The methanolic extract from the fruit of Piper chaba (Piperaceae) was found to have a hepatoprotective effect on D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced liver injury in mice. From the ethyl acetate-soluble fraction, a new amide constituent named piperchabamide E together with twenty known amide constituents (e.g., piperine, piperchabamides A-D, and piperanine) and two aromatic constituents were isolated as the hepatoprotective constituents. With regard to structure-activity relationships, the amide moiety and the 1,9-decadiene structure between the benzene ring and amide moiety were suggested to be important for strong inhibition of D-GalN/tumor necrosis factor-alpha (TNF-alpha)-induced death of hepatocytes. Furthermore, a principal amide constituent, piperine, dose-dependently inhibited increase in serum GPT and GOT levels at doses of 2.5-10 mg/kg (p.o.) in D-GalN/LPS-treated mice, and this inhibitory effect was suggested to depend on the reduced sensitivity of hepatocytes to TNF-alpha.

Sexual Dimorphism in Superantigen Shock Involves Elevated TNF-α and TNF-α–induced Hepatic Apoptosis

RATIONALE

There is conflicting evidence regarding sex differences in the outcome from severe sepsis and toxic shock. Superantigen-mediated toxic shock affects a higher proportion of female patients.

OBJECTIVES

The objective of the current study was to investigate sexual dimorphism in superantigen-associated sepsis and in superantigen-mediated shock and to identify the key mechanisms responsible for this sex difference.

METHODS

We measured mortality and serum cytokines after induction of sepsis with isogenic superantigen-positive and superantigen-negative Streptococcus pyogenes in HLA class II transgenics. During superantigen-mediated toxic shock, we measured mortality, T-cell responses, systemic tumor necrosis factor (TNF)-alpha and TNF receptors, TNF-alpha-induced hepatocyte apoptosis, and conditioning of these responses by tamoxifen treatment.

MEASUREMENTS AND MAIN RESULTS

In both superantigen-associated sepsis and in superantigen-mediated shock, serum TNF-alpha was increased in females compared with males. This was not attributable to a detectable difference in splenic TNF-alpha transcription; rather, serum soluble TNF receptors were higher in males. Pretreatment of females with the estrogen receptor modulator tamoxifen increased serum soluble TNF receptors, reduced the early serum TNF-alpha response, and improved mortality in females challenged with staphylococcal enterotoxin B. Lethal superantigen shock was characterized by hepatocyte apoptosis, and was reproduced by injection of TNF-alpha. Females had enhanced susceptibility to TNF-alpha-mediated lethality. TNF-alpha-induced hepatocyte apoptosis was greater in females, and was reduced by tamoxifen pretreatment.

CONCLUSIONS

Sexual dimorphism in experimental superantigen toxic shock results from increased systemic TNF-alpha in females, coupled with an increased susceptibility to TNF-alpha-induced hepatocyte apoptosis. Both processes are abrogated by estrogen receptor modulators.

Omega-3 fatty acids alleviate chemically induced acute hepatitis by suppression of cytokines

Cytokines such as tumor necrosis factor alpha (TNF-alpha) are key factors in liver inflammation. Supplementation with essential omega-3 polyunsaturated fatty acids (n-3 PUFA) has been demonstrated to lower TNF-alpha and IL-1 production in mononuclear cells. An inflammation-dampening effect has been observed with increased omega-3 fatty acid supplementation in several inflammatory diseases. In this study, we used the transgenic fat-1 mouse, expressing a Caenorhabditis elegans desaturase endogenously forming n-3 PUFA from n-6 PUFA, to analyze the effect of an increased n-3 PUFA tissue status in the macrophage-dependent acute D-galactosamine/lipopolysaccaride (D-GalN/LPS) hepatitis model. We show less severe inflammatory liver injury in fat-1 mice with a balanced n-6/n-3 PUFA ratio as evidenced by reduced serum alanine aminotransferase levels and less severe histological liver damage. This decreased inflammatory response was associated with decreased plasma TNF-alpha levels and with reduced hepatic gene expression of TNF-alpha, IL-1beta, IFN-gamma and IL-6 in fat-1 mice, leading to a decreased rate of apoptosis in livers from fat-1 animals, as measured by DAPI-staining.

CONCLUSION

The results of this study offer evidence for an inflammation dampening effect of omega-3 polyunsaturated fatty acids in the context of liver inflammation.

Treatment with Y-40138, a multiple cytokine production modulator, inhibits lipopolysaccharide- or tumour necrosis factor-alpha-induced production of pro-inflammatory cytokines and augments interleukin-10

N-[1-(4-[4-(pyrimidin-2-yl)piperazin-1-yl]methyl phenyl)cyclopropyl] acetamide . HCl (Y-40138) suppresses liver injury in concanavalin A- and D-galactosamine/lipopolysaccharide (LPS)-induced mouse hepatitis models. However, the mechanism of action of Y-40138 has not been fully investigated. In this study, we examined the effect of Y-40138 on cytokine production in mice. Cytokine production was induced by intraperitoneal injection of LPS (0.5 mg kg(-1)) or intravenous injection of recombinant mouse tumour necrosis factor (TNF)-alpha (10 mug mouse(-1)) in BALB/c mice. TNF-alpha and interleukin (IL)-10 reached maximum levels 1.5 h after the LPS injection. IL-12 and interferon-sigma (IFN-sigma) reached maximum levels 3 to 9 h after the injection. When Y-40138 was orally administered 30 min prior to the injection, it inhibited TNF-alpha, IL-12 and IFN-sigma production and augmented IL-10 production. Y-40138 also inhibited IL-12 production and augmented IL-10 production in TNF-alpha-stimulated mice. In IL-10 knockout mice, Y-40138 inhibited TNF-alpha and IL-12 production 1.5 h after the LPS injection but not after 3 h or later, unlike in wild mice. In addition, TNF-alpha production was inhibited by Y-40138 at concentrations that could not augment IL-10 production. These data suggest that Y-40138 modulates pro-inflammatory cytokine production by both IL-10-dependent and -independent mechanisms.

Enhancement of mite allergen-induced eosinophil infiltration in the murine airway and local cytokine/chemokine expression by Asian sand dust

Data on the effects of sand dust toward allergic asthma produced by indoor allergens, such as house dust mites, are not currently available. This study was undertaken to clarify the role of Asian sand dust on mite allergen, Dermatophagoides farinae (D. farinae)-induced eosinophilic inflammation in the murine lung, using sand dusts from the Maowusu Desert (Inner Mongolia) (SD-1) and the Tengger Desert (China) (SD-2). ICR mice were intratracheally administered saline; SD-1 alone; SD-2 alone; D. farinae alone; D. farinae + SD-1; and D. farinae + SD-2, 4 times at 2-wk intervals. The two sand dusts enhanced infiltration of eosinophil in the airway, along with goblet-cell proliferation related to D. farinae. The degree of eosinophil infiltration induced with SD-2 was greater than with SD-1. The SD-1, which contained higher amounts of beta-glucan, increased the expression of interferon (IFN)-gamma in bronchoalveolar lavage fluids (BALF) with or without D. farinae, but SD-2 did not. Synergistically or cumulatively elevated levels of interleukin (IL)-5, eotaxin, and monocyte chemotactic protein in BALF related to D. farinae were higher with D. farinae + SD-2 than with D. farinae + SD-1. These results suggest that increased cytokine and chemokines in BALF play an important role in the enhancement of eosinophil infiltration in the airway induced by D. farinae + sand dusts. The reduced eosinophil infiltration in the SD-1-treated mice could be due to suppression of Th-2 cytokine and eotaxin via interferon-gamma induced by microbial materials, such as beta-glucan.

Protective effect of fasudil, a Rho-kinase inhibitor, on chemokine expression, leukocyte recruitment, and hepatocellular apoptosis in septic liver injury

Rho-kinase signaling regulates important features of inflammatory reactions. Herein, we investigated the effect and mechanisms of action of the Rho-kinase inhibitor fasudil in endotoxemic liver injury. C57/BL/6 mice were challenged with lipopolysaccharide (LPS) and D-galactosamine, with or without pretreatment with the Rho-kinase inhibitor fasudil. Six hours after endotoxin challenge, leukocyte-endothelium interactions in the hepatic microvasculature were studied by use of intravital fluorescence microscopy and tumor necrosis factor alpha (TNF-alpha); CXC chemokines as well as liver enzymes and apoptosis were determined. Administration of fasudil reduced LPS-induced leukocyte adhesion in postsinusoidal venules and sequestration in sinusoids. Moreover, we found that fasudil abolished extravascular infiltration of leukocytes as well as production of TNF-alpha and CXC chemokines in the liver of endotoxemic mice. Liver enzymes and hepatocellular apoptosis were markedly reduced, and sinusoidal perfusion was improved significantly in endotoxemic mice pretreated with fasudil. Our novel data document that fasudil is a potent inhibitor of endotoxin-induced expression of TNF-alpha and CXC chemokines as well as leukocyte infiltration and hepatocellular apoptosis in the liver. Based on the present findings, it is suggested that inhibition of the Rho-kinase signaling pathway may be a useful target in the treatment of septic liver injury.

Defective innate antibacterial host responses during murine Klebsiella pneumoniae bacteremia: tumor necrosis factor (TNF) receptor 1 deficiency versus therapy with anti-TNF-alpha

Klebsiella pneumoniae is a leading cause of pneumonia due to gram-negative bacteria. A significant clinical complication of pulmonary infection with K. pneumoniae is peripheral blood dissemination, which results in a systemic infection coincident with the localized pulmonary infection. This study describes the critical importance of tumor necrosis factor (TNF) receptor 1 (TNFR1)-mediated signaling during K. pneumoniae bacteremia. TNFR1-deficient mice displayed a significantly increased mortality rate after intravenous inoculation. Unexpectedly, this increased mortality occurred in the absence of either increased bacterial burden or increased liver injury. However, excessive production of proinflammatory cytokines, including TNF-alpha , was observed in TNFR1-deficient mice, compared with that observed in infected C57BL/6 mice, which suggests that production was dysregulated in the absence of TNFR1 signaling. In contrast, other experiments examined the effect of immunotherapy with anti-TNF-alpha during K. pneumoniae bacteremia. Administration of a neutralizing anti-TNF-alpha antibody completely ablated K. pneumoniae-induced liver injury. This reduction in liver injury failed to translate into an improved survival rate, because mice died of the infection as late as 10 days after infection. Bacterial clearance after neutralization of TNF-alpha was significantly impaired at later time points during infection. Diminished production of liver-associated cytokines and chemokines correlated with impaired bacterial clearance, which suggests that antibacterial immune responses were dampened. These data indicate that the antibacterial host response is dysregulated in mice lacking TNFR1 or TNF-alpha bioactivity.

Soluble human p55 and p75 tumor necrosis factor receptors reverse spontaneous arthritis in transgenic mice expressing transmembrane tumor necrosis factor α

OBJECTIVE

The roles of the transmembrane and secreted forms of tumor necrosis factor alpha (TNFalpha) in rheumatoid arthritis (RA) remain unclear. Agents used to inhibit TNFalpha have shown varying efficacy in RA patients, suggesting that anti-TNFalpha agents possess dissimilar mechanisms of action, including the ability to neutralize transmembrane (tmTNFalpha) and secreted TNFalpha. In this study, TNFalpha-knockout (TNFalpha-KO) mice that were genetically altered to express elevated levels of tmTNFalpha were constructed to further understand the roles of the 17-kd secreted, trimeric, and 26-kd transmembrane forms of TNFalpha.

METHODS

A speed-congenic mating scheme was used to generate 3 unique strains of mice: 1) transgenic tmTgA86 mice overexpressing 26-kd tmTNFalpha and also secreting 17-kd trimeric TNFalpha (tmTNFalpha-transgenic), 2) TNFalpha-/- mice (TNFalpha-KO), and 3) transgenic mice overexpressing tmTNFalpha backcrossed to TNFalpha-KO mice (tmTNFalpha-transgenic/TNFalpha-KO). Mice were treated with phosphate buffered saline (as vehicle control), dexamethasone (as positive control), or modified recombinant human soluble TNF receptor (sTNFR) p55 or p75, and were assessed clinically and histopathologically for signs of inflammation and development of arthritis.

RESULTS

The tmTNFalpha-transgenic/TNFalpha-KO mice were born with crinkled tails and spinal deformities similar to those in ankylosing spondylitis. By 2-4 weeks, these mice developed symmetric inflammatory arthritis, characterized by tissue swelling, pannus formation, and bone deformities. The tmTNFalpha-transgenic mice also developed spontaneous-onset arthritis, but at a slower rate (100% incidence by 10-12 weeks). Clinical and histologic progression of arthritis in the tmTNFalpha-transgenic/TNFalpha-KO mice was reduced by treatment with dexamethasone or with the p55 or p75 sTNFR (69% and 63% reduction in total histologic score, respectively).

CONCLUSION

These data show that arthritis is sufficiently initiated and maintained in tmTNFalpha-transgenic/TNFalpha-KO mice, and that it can be neutralized by recombinant human p55 or p75 sTNFR, resulting in amelioration of the biologic and subsequent histologic destructive effects of tmTNFalpha.

Inhibitory effects of coumarin and acetylene constituents from the roots of Angelica furcijuga on d-galactosamine/lipopolysaccharide-induced liver injury in mice and on nitric oxide production in lipopolysaccharide-activated mouse peritoneal macrophages

The methanolic extract (200 mg/kg, p.o. and i.p.), principal coumarin constituents (isoepoxypteryxin, anomalin, and praeroside IV), and a polyacetylene constituent (falcarindiol) (25 mg/kg, i.p.) from the roots of Angelica furcijuga protected the liver injury induced by D-galactosamine (D-GalN)/lipopolysaccharide (LPS) in mice. In in vitro experiments, coumarin constituents (hyuganins A-D, anomalin, pteryxin, isopteryxin, and suksdorfin) and polyacetylene constituents [(-)-falcarinol and falcarindiol] substantially inhibited LPS-induced NO and/or TNF-alpha production in mouse peritoneal macrophages, and isoepoxypteryxin inhibited D-GalN-induced cytotoxicity in primary cultured rat hepatocytes. Furthermore, hyuganin A, anomalin, and isopteryxin inhibited the decrease in cell viability by TNF-alpha in L929 cells.

p38 mitogen-activated protein kinase-dependent chemokine production, leukocyte recruitment, and hepatocellular apoptosis in endotoxemic liver injury

OBJECTIVE

To determine the role of p38 mitogen-activated protein kinase (MAPK) signaling in endotoxin-induced liver injury.

BACKGROUND

MAPKs have been reported to play a potential role in regulating inflammatory responses, but the role of p38 MAPK signaling in chemokine production, leukocyte recruitment, and hepatocellular apoptosis in the liver of endotoxemic mice is not known.

METHODS

Endotoxin-induced leukocyte-endothelium interactions were studied by use of intravital fluorescence microscopy in the mouse liver. Tumor necrosis factor-alpha (TNF-alpha) and CXC chemokines, liver enzymes, and apoptosis were determined 6 hours after endotoxin challenge. The specific p38 MAPK inhibitor SB 239063 was given immediately prior to endotoxin exposure. Phosphorylation and activity of p38 MAPK were determined by immunoprecipitation and Western blot.

RESULTS

Endotoxin increased phosphorylation and activity of p38 MAPK in the liver, which was markedly inhibited by SB 239063. Inhibition of p38 MAPK signaling dose-dependently decreased endotoxin-induced leukocyte rolling, adhesion, and sinusoidal sequestration of leukocytes. SB 239063 markedly reduced endotoxin-induced formation of TNF-alpha and CXC chemokines in the liver. Indeed, the endotoxin-provoked increase of liver enzymes and hepatocellular apoptosis were abolished and sinusoidal perfusion was restored in endotoxemic mice treated with SB 239063.

CONCLUSIONS

This study demonstrates that p38 MAPK signaling plays an important role in regulating TNF-alpha and CXC chemokine production in endotoxemic liver injury and that inhibition of p38 MAPK activity abolishes endotoxin-induced leukocyte infiltration as well as hepatocellular apoptosis. These novel findings suggest that interference with the p38 MAPK pathway may constitute a therapeutic strategy against septic liver damage.

Staphylococcal enterotoxin A-induced hepatotoxicity is predominantly mediated by Fas ligand (CD95L)

OBJECTIVE

To determine the role of tumor necrosis factor alpha (TNF-alpha) and Fas ligand (FasL, CD95L) in superantigen-induced and endotoxin-induced liver injury.

SUMMARY BACKGROUND DATA

Gram-positive bacteria are increasingly common causes of sepsis and multiorgan failure, but the pathophysiologic mechanisms of superantigen-provoked hepatotoxicity remain elusive.

METHODS

Intravital fluorescence microscopy was used to study the liver microcirculation in mice challenged with superantigen (staphylococcal enterotoxin A, SEA) or endotoxin (lipopolysaccharide, LPS) combined with D-galactosamine.

RESULTS

Administration of 10 microg LPS and 50 microg SEA caused similar hepatocellular damage as determined by liver enzymes and apoptosis. Notably, TNF-alpha-deficient mice were completely protected against hepatic injury provoked by LPS, whereas no protection was observed in response to SEA. On the other hand, FasL-deficient mice were protected against liver injury induced by SEA, but no protection was found when challenged with LPS. LPS increased clear-cut leukocyte recruitment, whereas SEA had no significant effect on leukocyte responses in the liver microcirculation. Leukocyte responses to LPS were decreased by >56% in TNF-alpha gene-targeted animals. Moreover, antiadhesive therapy, ie, immunoneutralization of P-selectin, which is an effective inhibitor of leukocyte recruitment, protected against LPS-induced but not against SEA-induced hepatic damage.

CONCLUSIONS

These novel findings demonstrate that the mechanisms of hepatic injury in endotoxin-induced and superantigen-induced sepsis are principally different. On one hand, SEA-provoked hepatotoxicity is mediated by FasL and is not associated with leukocyte recruitment. On the other hand, liver damage provoked by LPS is mediated by TNF-alpha and characterized by prominent leukocyte responses. These data may facilitate development of more specific therapies against sepsis of different origins.

Magnetic resonance imaging of inflammation with a specific selectin-targeted contrast agent

E-selectin-targeted contrast enhancement of blood vessels in inflamed tissues was investigated with a new contrast agent, Gd-DTPA-B(sLe(x))A, which was recently obtained by grafting a synthetic mimetic of sialyl-Lewis(x), an E-selectin ligand, onto Gd-DTPA. The pharmacokinetics, biodistribution, and potential to image inflammation by MRI of this E-selectin-targeted contrast agent were evaluated. The inhibition (by 15-34%) produced by Gd-DTPA-B(sLe(x))A on Sialyl Le(x)-PAA-biotin binding to E-selectin confirmed the specific interaction of the new contrast agent with this adhesion molecule. Gd-DTPA-B(sLe(x))A was tested at a dose of 0.1 mmol/kg b.w. on mice and rats in a fulminant hepatitis model induced by the co-administration of D-galactosamine and E. coli lipopolysaccharide. A significant and prolonged contrast enhancement between blood vessels and liver parenchyma was obtained in pathological conditions, which attests to the specificity of the agent for E-selectin. The prolonged vascular residence (48.9 min in hepatitis vs. 29.8 min in healthy animals), as evidenced by the pharmacokinetic characterization, suggests that Gd-DTPA-B(sLe(x))A interacts with the specific receptors expressed during inflammation. The biodistribution of the compound indicates its retention in inflamed liver by both specific mechanisms and nonspecific accumulation due to the necrotic lesions. The same mechanisms are invoked to account for its retention in the spleen.

Dynamic movement of cytochrome c from mitochondria into cytosol and peripheral circulation in massive hepatic cell injury

BACKGROUND

In the process of apoptosis, it is known that the transition of cytochrome c from mitochondria into the cytosol occurs, and tumor necrosis factor (TNF)-alpha is one of the molecules responsible for this event. But in the state of hypercytokine induced by D-galactosamine (D-GaIN)/Lipopolysaccharide (LPS), the localization of cytochrome c is little known.

METHODS

Rats were administrated with D-GaIN(700 mg/kg)/LPS(200 microg/kg). Blood and tissue samples were collected and examined for levels of pro-inflammatory cytokines, the apoptosis of liver cells, and the localization of cytochrome c.

RESULT

Before administration of D-GaIN/LPS, cytochrome c was definitely localized in the mitochondria. At 2 h after simultaneous administration of D-GaIN/LPS, cytochrome c had accumulated in the cytosol following abrupt increases of plasma TNF-alpha. Massive cell destruction due to apoptosis proved by Terminal deoxynucleo-tidyl transferase-mediated dUTP nick end labeling staining was observed in liver tissue 4 h later and markedly increased levels of cytochrome c were detected in the plasma 12 h after D-GaIN/LPS administration.

CONCLUSION

Liver injury induced by simultaneous administration of D-GaIN/LPS was closely associated with the production of TNF-alpha, and also with the dynamic movement of cytochrome c from the mitochondria into the cytosol, and then into the systemic circulation. The detection of plasma cytochrome c levels may be a useful clinical tool for the detection of apoptosis in vivo.

Cooperative effect of biliverdin and carbon monoxide on survival of mice in immune-mediated liver injury

Induction of the heme-degrading enzyme heme oxygenase-1 (HO-1) has been shown to be beneficial in terms of improvement of liver allograft survival and prevention of CD95-mediated apoptosis in the liver. In the present study, we investigated the effects of HO-1, and its products carbon monoxide (CO), biliverdin (BV), and iron/ferritin, in a mouse model of inflammatory liver damage inducible by lipopolysaccharide (LPS) in mice sensitized with the hepatocyte-specific transcription inhibitor D-galactosamine (GalN). Our results show that HO-1 induction by cobalt-protoporphyrin-IX (CoPP) reduced cytokine expression, protected mice from liver injury, and prolonged survival. While in contrast to ferritin overexpression, single administration of the CO donor methylene chloride (MC) or of BV also protected mice from liver damage, only coadministration of both HO products prolonged survival and reduced the expression of cytokines, e.g., tumor necrosis factor (TNF) and interferon gamma (IFN-gamma). In conclusion, HO-1-induced prolongation of survival, but not the protection from liver damage, seems to be dependent on down-regulation of cytokine synthesis.

Fibronectin suppresses apoptosis and protects mice from endotoxic shock

Multiple-organ failure related to septicemia is a common cause of early mortality after liver transplantation. Endotoxemia following living donor hepatectomy may be a cause of postoperative death. Plasma fibronectin (Fn) exerts a broad range of biological effects on cellular adhesion, motility, differentiation, apoptosis, hemostasis, wound healing, reticuloendothelial system function, and ischemic injury. We studied the therapeutic effect of plasma Fn in mice after an intraperitoneal injection of lipopolysaccharide (LPS) and d-galactosamine (GalN). Female Balb/c mice received simultaneous intraperitoneal injection of LPS (50 microg/kg) and GalN (400 mg/kg). Thirty minutes prior to GalN/LPS administration, plasma Fn or bovine serum albumin was given intravenously. A single administration of plasma Fn (500 mg/kg) protected in dose-dependent fashion against lethal shock after GalN/LPS challenge. Plasma Fn significantly reduced the serum tumor necrosis factor-alpha, interferon-gamma, and interleukin-6 levels and significantly increased the serum interleukin-10 levels after GalN/LPS administration. Furthermore, plasma Fn significantly inhibited liver necrosis at 9 hours after GalN/LPS injection. The fraction of apoptotic-positive cells in these plasma Fn-treated mice was significantly lower than in the control group. These results support the protective treatment of endotoxin-induced liver injury by plasma Fn.

Proapoptotic effect of proteolytic activation of matrix metalloproteinases by Streptococcus pyogenes thiol proteinase (Streptococcus pyrogenic exotoxin B)

Streptococcus pyogenes thiol proteinase, also known as streptococcal pyrogenic exotoxin B (SpeB), has been suggested to be a major virulence factor in S. pyogenes infection. SpeB was reported to induce apoptosis of host cells, but its mechanism of action is not yet fully understood. In this study, we examined the involvement of matrix metalloproteinases (MMPs) in SpeB-induced apoptosis. We first developed a large-scale preparation of recombinant SpeB and precursors of human MMP-9 and -2 (proMMPs) by using Escherichia coli Rosetta (DE3)pLysS and baculovirus-insect cell expression systems, respectively. Treatment with SpeB induced effective proteolytic activation of both proMMP-9 and -2. When RAW264 murine macrophages were incubated with SpeB-activated proMMP-9, the level of tumor necrosis factor alpha (TNF-alpha) in conditioned medium (CM), assessed by an enzyme immunoassay, was elevated. This increase was completely inhibited by addition of the MMP inhibitor SI-27 to the cell culture. The CM also produced marked induction of apoptosis of U937 human monocytic cells. Similarly, soluble Fas ligand (sFasL) was detected in CM of cultures of SW480 cells expressing FasL after treatment with SpeB-activated proMMPs; this CM also induced apoptosis in U937 cells. SpeB had a direct effect as well and caused the release of TNF-alpha and sFasL from the cells. SpeB-dependent production of MMP-9 and -2 and proapoptotic molecules (TNF-alpha and sFasL) was evident in a murine model of severe invasive S. pyogenes infection. These results suggest that SpeB or SpeB-activated MMPs contribute to tissue damage and streptococcal invasion in the host via extracellular release of TNF-alpha and sFasL.

Anti-tumor necrosis factor-alpha therapy during murine Klebsiella pneumoniae bacteremia: increased mortality in the absence of liver injury

Klebsiella pneumoniae is a leading cause of gram-negative bacterial pneumonia, often resulting in bacteremia concurrent with the localized pulmonary infection. The beneficial role of tumor necrosis factor (TNF)-alpha during pulmonary infection has been well documented; however, consequences of TNF-alpha production during systemic bacterial infection are controversial. A murine model of K. pneumoniae was developed to address this important issue. Liver-associated TNF-alpha mRNA was induced within 30 min after intravenous bacterial inoculation and remained elevated through 6 h before returning to near-baseline at 24 h postinfection. Intravenous K. pneumoniae infection induced liver cellular injury that was completely ablated when mice were pretreated with a neutralizing anti-TNF-alpha antibody. Interestingly, this reduction in liver injury failed to translate into improved survival. Mice receiving anti-TNF-alpha continued to succumb to the infection even out to day 10 postinfection. Bacterial clearance after TNF-alpha neutralization was significantly impaired at later time points during infection. Correlating with impaired bacterial clearance was diminished production of liver-associated MIP-2, MIP-1alpha, MCP-1, and interferon-gamma. Further evidence of diminished antibacterial immune responses was noted when the activational status of splenic natural killer cells in anti-TNF-alpha-treated mice was examined 24 h postinfection. Natural killer cells displayed decreased CD69 expression. Combined, these data indicate that the beneficial effects of TNF-alpha during systemic K. pneumoniae infection outweigh the detrimental effects of TNF-alpha-mediated hepatocyte cellular injury. Anti-TNF-alpha therapy, although preventing liver injury during blood-borne bacterial infection, results in a dampened anti-bacterial host response, resulting in decreased bacterial clearance and overall survival.

Protective Effect of Protocatechuic Acid Isopropyl Ester against Murine Models of Sepsis: Inhibition of TNF-α and Nitric Oxide Production and Augmentation of IL-10

Antioxidants have been shown to be effective in murine models of sepsis. Protocatechuic acid has antioxidant activity. In the present study, the protective effects of protocatechuic acid and its derivatives were investigated in a mouse model of septic shock induced by lipopolysaccharide (LPS)/D-galactosamine (GalN). Pretreatment of animals with protocatechuic acid effectively suppressed LPS/GalN-induced lethality; protocatechuic acid isopropyl ester was the most effective among the various derivatives of protocatechuic acid. Protocatechuic acid isopropyl ester was also effective in protection against the high-dose LPS-induced shock. Pretreatment with protocatechuic acid isopropyl ester effectively suppressed the LPS/GalN-induced increase in plasma tumor necrosis factor (TNF)-alpha alanine aminotransferase (ALT), nitrite/nitrate levels, and hepatic malondialdehyde levels. In contrast, it markedly enhanced the LPS/GalN-induced increase in plasma interleukin (IL)-10 levels, without any changes in IL-6 plasma levels. These results suggest that protocatechuic acid isopropyl ester could be useful for the prevention of sepsis.

Adenoviral infection decreases mortality from lipopolysaccharide-induced liver failure via induction of TNF-alpha tolerance

Effects of adenoviral infection on in vivo responses to LPS mediated by TNF-alpha were evaluated in a murine model. Adenovirus-infected mice showed decreased mortality from fulminant hepatitis induced by administration of LPS or staphylococcal enterotoxin B in the presence of D-galactosamine. Importantly, TNF-alpha resistance genes within adenoviral E3 region were not required, because E1,E3-deleted vectors showed similar effects. Adenovirus-infected mice exhibited higher TNF-alpha levels after LPS stimulation, no difference in TNFR1 expression, and similar mortality from Fas-induced fulminant hepatitis. Decreased production of IL-6 and KC in response to exogenous TNF-alpha, in addition to protection from TNF-alpha, suggested that adenoviral infection results in TNF-alpha tolerance.

Anti-TNF-alpha therapies: the next generation

The functioning of the immune system is finely balanced by the activities of pro-inflammatory and anti-inflammatory mediators or cytokines. Unregulated activities of these mediators can lead to the development of serious inflammatory diseases. In particular, enhanced tumour-necrosis factor-alpha (TNF-alpha) synthesis is associated with the development of rheumatoid arthritis, psoriatic arthritis and inflammatory bowel disease. Inhibiting TNF-alpha activities in these diseases has been remarkably successful. However, the current injectable protein therapies have associated risks and limitations. An oral, small molecule that regulates TNF-alpha biology could either replace the injectables or provide better disease control when used alone or in conjunction with existing therapies. In this review, we discuss briefly the present understanding of TNF-alpha-mediated biology and the current injectable therapies in clinical use, and focus on some of the new therapeutic approaches with oral, small-molecule inhibitors.

Increased mortality and dysregulated cytokine production in tumor necrosis factor receptor 1-deficient mice following systemic Klebsiella pneumoniae infection

A significant clinical complication of pulmonary infections with Klebsiella pneumoniae is peripheral blood dissemination, resulting in a systemic infection concurrent with the localized pulmonary infection. In this context, little is known about the role of tumor necrosis factor receptor 1 (TNFR1)-mediated innate immune responses during systemic Klebsiella infections. Mice lacking TNFR1 were significantly more susceptible to Klebsiella-induced mortality following intravenous inoculation. Bacterial clearance was impaired in TNFR1-deficient mice at early times following infection. Unexpectedly, bacterial burdens at the onset of mortality (days 2 to 3 postinfection) were not higher in mice lacking TNFR1. However, elevated production of liver-associated proinflammatory cytokines (interleukin-12, tumor necrosis factor alpha [TNF-alpha[, and gamma interferon [IFN-gamma]) and chemokines (MIP-1 alpha, MIP-2, and MCP-1) was observed within the first 24 h of infection. Additionally, excessive plasma-associated IFN-gamma was also observed late in the course of infection (day 3). Spleen cells from day-3 infected TNFR1-deficient mice secreted markedly enhanced levels of IFN-gamma when cultured in vitro. Additionally, there was a marked increase in the total number of activated lymphocyte subsets as indicated by CD69 upregulation. A notable exception was the sharp decrease in the frequency of splenic NK T cells in infected TNFR1 knockout (KO) mice. Anti-TNF-alpha therapy in TNFR1 KO mice significantly reduced chemokine production and liver injury. Combined, these data indicate a dysregulated antibacterial host response following intravenous Klebsiella infection in the absence of TNFR1 signaling, resulting in heightened cytokine production and hyperactivation of specific splenic lymphocyte subsets.

Lack of gp130 expression in hepatocytes promotes liver injury

BACKGROUND & AIMS

Interleukin 6 (IL-6) contributes via its signal transducer gp130 to the acute phase response (APR) in hepatocytes. Recent studies indicated that IL-6 is involved in the regulation of different pathophysiologic conditions of the liver. To define the IL-6-dependent intracellular pathways more specifically, we generated a hepatocyte-specific gp130 knockout mouse.

METHODS

Hepatocyte-specific gp130-deficient mice were generated using the Cre-loxP system. Expression of the Cre recombinase was under the control of a hepatocyte-specific control element. Adult mice were challenged with IL-6, oncostatin M (OSM), and LPS.

RESULTS

Cre expression started at day 10.5 postconception, and a complete deletion of gp130 in hepatocytes was found at day 14 during liver development. The adult liver of these mice showed no abnormalities; however, after IL-6 and OSM stimulation, gp130-dependent pathways (STAT3, APR gene expression) were completely blocked in the liver of these animals. Additionally, challenging hepatocyte-specific gp130 knockout animals with lipopolysaccharides (LPS) lead to an onset of acute liver injury with an increase of hepatocyte apoptosis associated with elevated tumor necrosis factor alpha (TNF-alpha) serum levels and reduced nuclear factor kappaB (NF-kappaB) activation in hepatocytes.

CONCLUSIONS

Our findings demonstrate that gp130 is of minor relevance for embryonal development of hepatocytes. However, the molecule has an essential role in controlling acute phase gene expression and provides hepatocellular protection after LPS challenge.

Induction of apoptosis by 2,3,7,8-tetrachlorodibenzo-p-dioxin following endotoxin exposure

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent and persistent environmental toxin that induces hepatotoxicity and increases endotoxin-induced liver injury. The objective of this study was to evaluate whether TCDD could modulate apoptosis and cytokine-controlled apoptotic signaling pathways following lipopolysaccharide (LPS) exposure in female B6C3F1 mice. The effects of TCDD treatment were most dramatic late in the time course (10-14 days posttreatment). Serum enzyme activities were elevated at day 10 (100 microg TCDD/40 microg LPS treatment) and day 14 (100 microg TCDD/saline treatment), indicating peak liver damage occurred at those times. Histological examination of perfused livers showed an increase in apoptotic cells at day 14 in animals treated with 10 microg TCDD. Caspase-1 activity was suppressed at 14 days in mice treated with 100 microg TCDD/40 microg LPS and 100 microg TCDD/4 microg LPS compared to the respective corn oil (CO)/LPS-treated controls. Caspase-3 activity was suppressed at 14 days in 100 microg TCDD/saline-100 microg TCDD/40 microg LPS- and 100 microg TCDD/4 microg LPS-treated mice compared to respective CO/saline- or CO/LPS-treated control mice. At 40 microg LPS, caspase activity was stimulated in TCDD (100 microg)-exposed mice at 3 and 7 days and then suppressed at 10 and 14 days. Western blot analysis, electrophoretic mobility shift assay, and ELISA did not show any effect by TCDD (100 microg) on IkappaB-beta and IkappaB-alpha protein expression or on DNA binding activity of the nuclear NFkappaB protein. These data indicate that TCDD induces apoptosis 14 days posttreatment; however, we found no evidence of suppression of the antiapoptotic transcription factor NFkappaB.

Regulation of lipopolysaccharide sensitivity by IFN regulatory factor-2

IFN regulatory factors (IRFs) are a family of transcription factors and include several members that regulate expression of pro- and anti-inflammatory genes. Mice with a targeted mutation in IRF-2 (IRF-2(-/-)) were studied after injection of LPS to evaluate the importance of IRF-2 in the regulation of endotoxicity. IRF-2(-/-) mice were highly refractory to LPS-induced lethality. Although hepatic TNF-alpha mRNA and circulating TNF-alpha were significantly elevated in LPS-challenged IRF-2(-/-) mice, levels of IL-1, IL-12, and IFN-gamma mRNA and protein, as well as IL-6 protein, were significantly lower than levels seen in LPS-challenged IRF-2(+/+) mice. IRF-2(-/-) mice were also more refractory to TNF-alpha challenge than were control mice, which was consistent with their diminished sensitivity to LPS, yet no significant difference in the mRNA expression of TNFRs was observed. IL-12R beta 2 mRNA levels from LPS-challenged IRF-2(-/-) mice were significantly different after 1, 6, and 8 h, suggesting that both diminished IL-12 and altered IL-12R expression contribute to the paucity of IFN-gamma produced. IRF-2 knockout mice also failed to sustain LPS-inducible levels of IRF-1 and IFN consensus sequence binding protein mRNA expression, two transacting factors required for IL-12 transcription, perhaps as a result of diminished IL-1 beta, IL-6, and IFN-gamma levels. Liver sections from IRF-2(+/+) and IRF-2(-/-) mice were analyzed 6 h after a typically lethal injection of LPS. IRF-2(-/-) mice exhibited greater numbers of apoptotic Kupffer cells than did wild-type mice, suggesting a novel anti-apoptotic role for IRF-2. Collectively, these findings reveal a critical role for IRF-2 in endotoxicity, and point to a previously unappreciated role for IRF-2 in the regulation of apoptosis.

The role of cytokines in liver failure and regeneration: potential new molecular therapies

The liver is a unique organ, and first in line, the hepatocytes encounter the potential to proliferate during cell mass loss. This phenomenon is tightly controlled and resembles in some way the embryonal co-inhabitant cell lineage of the liver, the embryonic hematopoietic system. Interestingly, both the liver and hematopoietic cell proliferation and growth are controlled by various growth factors and cytokines. IL-6 and its signaling cascade inside the cells through STAT3 are both significantly important for liver regeneration as well as for hematopoietic cell proliferation. The process of liver regeneration is very complex and is dependent on the etiology and extent of liver damage and the genetic background. In this review we will initially describe the clinical relevant condition, portraying a number of available animal models with an emphasis on the relevance of each one to the human condition of fulminant hepatic failure (FHF). The discussion will then be focused on the role of cytokines in liver failure and regeneration, and suggest potential new therapeutic modalities for FHF. The recent findings on the role of IL-6 in liver regeneration and the activity of the designer IL-6/sIL-6R fusion protein, hyper-IL-6, in particular, suggest that this molecule could significantly enhance liver regeneration in humans, and as such could be a useful treatment for FHF in patients.

Rosmarinic acid, a major polyphenolic component of Perilla frutescens, reduces lipopolysaccharide (LPS)-induced liver injury in D-galactosamine (D-GalN)-sensitized mice

The protective activity of rosmarinic acid from Perilla frutescens on liver injury induced by LPS in D-GalN-sensitized mice was examined. We also investigated the effects of antitumor necrosis factor-alpha antibody (anti-TNF), superoxide dismutase (SOD), and aminoguanidine (AG) on this model in order to elucidate the mechanism of rosmarinic acid protection. Perilla extract (PE) and rosmarinic acid (RA) treatments significantly reduced the elevation of plasma asparatate aminotransferase levels, as well as anti-TNF and SOD treatment, compared with controls, but this reduction was not seen in the AG group. These results were confirmed by histological examination using hematoxylin-eosin and in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. Increases in tumor necrosis factor-alpha (TNF-alpha) mRNA expression in liver and in plasma TNF-alpha levels, which were observed in control mice, were not significantly reduced by PE or RA. PE and RA treatments also did not significantly diminish iNOS mRNA expression or plasma nitrate/nitrite levels. Nitrotyrosine and N(epsilon)-(hexanonyl)lysine (HEL) production, the residue of oxidative stress, was observed in livers from controls, but not in those mice pretreated with PE or RA. These results suggest that the liver protection of RA is due to the scavenging or reducing activities-superoxide or peroxynitirite rather than to inhibition of TNF-alpha production.

Involvement of endogenous CRF in carbon tetrachloride-induced acute liver injury in rats

Central neuropeptides play important roles in many physiological and pathophysiological regulation mediated through the autonomic nervous system. In regard to the hepatobiliary system, several neuropeptides act in the brain to regulate bile secretion, hepatic blood flow, and hepatic proliferation. Central injection of corticotropin-releasing factor (CRF) aggravates carbon tetrachloride (CCl4)-induced acute liver injury through the sympathetic nervous pathway in rats. However, still nothing is known about a role of endogenous neuropeptides in the brain in hepatic pathophysiological regulations. Involvement of endogenous CRF in the brain in CCl4-induced acute liver injury was investigated by centrally injecting a CRF receptor antagonist in rats. Male fasted Wistar rats were injected with CRF receptor antagonist alpha-helical CRF-(9-41) (0.125-5 microg) intracisternally just before and 6 h after CCl4 (2 ml/kg) administration, and blood samples were obtained before and 24 h after CCl4 injection for measurement of hepatic enzymes. The liver sample was removed 24 h after CCl4 injection, and histological changes were examined. Intracisternal alpha-helical CRF-(9-41) dose dependently (0.25-2 microg) reduced the elevation of alanine aminotransferase and aspartate aminotransferase levels induced by CCl4. Intracisternal alpha-helical CRF-(9-41) reduced CCl4-induced liver histological changes, such as centrilobular necrosis. The effect of central CRF receptor antagonist on CCl4-induced liver injury was abolished by sympathectomy and 6-hydroxydopamine pretreatment but not by hepatic branch vagotomy or atropine pretreatment. These findings suggest the regulatory role of endogenous CRF in the brain in experimental liver injury in rats.

Medicinal foodstuffs. XXIX. Potent protective effects of sesquiterpenes and curcumin from Zedoariae Rhizoma on liver injury induced by D-galactosamine/lipopolysaccharide or tumor necrosis factor-alpha

The 80% aqueous acetone extract of Zedoariae Rhizoma was found to show a protective effect against D-galactosamine (D-GalN)/lipopolysaccharide-induced acute liver injury in mice. To clarify the active compounds, the principal constituents were examined and 11 sesquiterpenes (furanodiene, curdione, neocurdrione, dehydrocurdione, germacrone, 13-hydroxygermacrone, curcumenol, isocurcumenol, aerugidiol, zedoarondiol, and curcumenone) and a diarylheptanoid (curcumin) were found to inhibit the increase in serum aspartate aminotransaminase and alanine aminotransaminase at a dose of 50 mg/kg p.o. in agreement with the previous in vitro studies, except for dehydrocurdione, aerugidiol, and zedoarondiol. In particular, curdione, neocurdione, curcumenol, and isocurcumenol potently inhibited the increase at a dose of 12.5 mg/kg p.o. Furthermore, the eight sesquiterpenes, furanodiene, curdione, neocurdione, dehydrocurdione, germacrone, 13-hydroxygermacrone, curcumenol, and curcumenone, also showed a protective effect against D-GalN/tumor necrosis factor-alpha-induced liver injury in mice at a dose of 50 mg/kg p.o.

Cytokine-mediated downregulation of vasopressin V(1A) receptors during acute endotoxemia in rats

The reduced pressure response to vasopressin during acute sepsis has directed our interest to the regulation of vasopressin V(1A) receptors. Rats were injected with lipopolysaccharide for induction of experimental gram-negative sepsis. V(1A) receptor gene expression was downregulated in the liver, lung, kidney, and heart during endotoxemia. Inasmuch as the concentrations of proinflammatory cytokines such as interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma were highly increased during sepsis, the influence of these cytokines on V(1A) receptor expression was investigated in primary cultures of hepatocytes and in the aortic vascular smooth muscle cell line A7r5. V(1A) receptor expression was downregulated by the cytokines in a nitric oxide-independent manner. Blood pressure dose-response studies after injection of endotoxin showed a diminished responsiveness to the selective V(1) receptor agonist Phe(2),Ile(3),Orn(8)-vasopressin. Our data show that sepsis causes a downregulation of V(1A) receptors and suggest that this effect is likely mediated by proinflammatory cytokines. We propose that this downregulation of V(1A) receptors contributes to the attenuated responsiveness of blood pressure in response to vasopressin and, therefore, contributes to the circulatory failure in septic shock.

Hepatoprotective principles from the flowers of Tilia argentea (linden): structure requirements of tiliroside and mechanisms of action

The methanolic extract from the flowers of Tilia argentea (linden) was found to show a hepatoprotective effect against D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced liver injury in mice. By bioassay-guided separation using in vitro D-GalN-induced damage to hepatocytes, five flavonol glycosides were isolated as the hepatoprotective constituents of the methanolic extract. Tiliroside, the principal flavonol glycoside, strongly inhibited serum GPT and GOT elevations at doses of 25-100 mg/kg (p.o.) in D-GalN/LPS-treated mice. By comparing the inhibitory effects of tiliroside with those of its components alone, the kaempferol 3-O-beta-D-glucopyranoside moiety was found to be essential for the activity, and its effect was suggested to depend on the inhibition of tumor necrosis factor-alpha (TNF-alpha) production, decreased sensitivity of hepatocytes to TNF-alpha, and on the protection of hepatocytes against D-GalN.

Involvement of cyclooxygenase-2 in the potentiation of allyl alcohol-induced liver injury by bacterial lipopolysaccharide

Bacterial endotoxin (lipopolysaccharide; LPS) augments the hepatotoxicity of a number of xenobiotics including allyl alcohol. The mechanism for this effect is known to involve the inflammatory response elicited by LPS. Upregulation of cyclooxygenase-2 (COX-2) and production of eicosanoids are important aspects of inflammation, therefore studies were undertaken to investigate the role of COX-2 in LPS-induced enhancement of liver injury from allyl alcohol. Rats were pretreated (iv) with a noninjurious dose of LPS or sterile saline vehicle and 2 h later were treated (ip) with a noninjurious dose of allyl alcohol or saline vehicle. COX-2 mRNA was determined by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), and liver injury was assessed from activities in serum of alanine and aspartate aminotransferases (ALT and AST, respectively) and from histology. Liver injury was observed only in rats cotreated with LPS and allyl alcohol. Serum ALT activity was increased by 4 h after administration of LPS and continued to increase through 8 h. COX-2 mRNA was detectable at low levels in livers from rats receiving only the vehicles at any time up to 8 h. Expression of COX-2 mRNA was increased by 30 min after administration of LPS and remained elevated through 6 h. Allyl alcohol treatment alone caused an increase in COX-2 mRNA at 4 h (2 h after allyl alcohol) that lasted less than 2 h. In livers from rats cotreated with LPS and allyl alcohol, levels of COX-2 mRNA were greater than levels seen with either LPS or allyl alcohol alone. The increased expression of COX-2 mRNA was accompanied by an increase in the concentration of prostaglandin (PG) D(2) in plasma. Plasma PGD(2) concentration was increased to a greater extent in rats treated with LPS plus allyl alcohol compared to allyl alcohol or LPS alone. Pretreatment with the COX-2 selective inhibitor, NS-398, abolished the increase in plasma PGD(2) and reduced the increase in ALT and AST activities observed in rats cotreated with LPS and allyl alcohol. NS-398 did not affect liver injury from allyl alcohol alone administered at a larger, hepatotoxic dose. In addition, ibuprofen, a nonselective inhibitor of cyclooxygenases, did not protect against liver injury from LPS plus allyl alcohol. In isolated hepatocytes PGD(2), but not PGE(2), reduced the concentration of allyl alcohol required to cause half-maximal cytotoxicity. These results suggest that products of COX-2 play a role in the augmentation of allyl alcohol-induced liver injury by LPS.

1,8-cineole protects against liver failure in an in-vivo murine model of endotoxemic shock

The effects of 1,8-cineole on D-galactosamine/lipopolysaccharide (GalN/LPS)-induced shock model of liver injury was investigated in mice. The co-administration of GalN (700 mg kg(-1), i.p.) and LPS (5 microg kg(-1), i.p.) greatly elevated serum concentrations of tumour necrosis factor-alpha (TNF-alpha), alanine aminotransferase and aspartate aminotransferase, and induced massive hepatic necrosis and lethality in 100% of control mice. Pretreatment with 1,8-cineole (400 mg kg(-1), p.o.) and dexamethasone (1 mg kg(-1), s.c.), 60 min before GalN/LPS, offered complete protection (100%) against the lethal shock and acute elevation in serum TNF-alpha and serum transaminases. Hepatic necrosis induced by GalN/LPS was also greatly reduced by both 1,8-cineole and dexamethasone treatment. The results indicate that 1,8-cineole protects mice against GalN/LPS-induced liver injury through the inhibition of TNF-alpha production, and suggest that 1,8-cineole may be a promising agent to combat septic-shock-associated pathologies.

Reduced susceptibility of nonobese diabetic mice to TNF-alpha and D-galactosamine-mediated hepatocellular apoptosis and lethality

Nonobese diabetic (NOD/LtJ or NOD) mice are resistant to doses of LPS and D-galactosamine that uniformly produce lethality in C57BL/6J (B6) mice (p < 0.01). Liver caspase-3-like activity, serum transaminase levels (both p < 0.05), and the numbers of apoptotic liver nuclei were also reduced in NOD compared with B6 mice treated with LPS (100 ng) and D-galactosamine (8 mg). NOD mice were also at least 100-fold more resistant to recombinant human TNF-alpha and D-galactosamine treatment than B6 mice (p < 0.001). Binding of recombinant human TNF-alpha to splenocytes from NOD mice was similar to that seen in B6 mice, suggesting that the defect in responsiveness was not due to an inability of recombinant human TNF-alpha to bind the NOD TNF type 1 (p55) receptor. Because the TNF type 1 (p55) receptor shares a common signaling pathway with Fas (CD95), NOD and B6 mice were treated with the Fas agonist antibody, Jo-2. Surprisingly, NOD mice were as sensitive as B6 mice to Fas-induced lethality and hepatic injury. In addition, primary hepatocytes isolated from NOD mice and cultured in vitro in the presence of D-galactosamine with or without TNF-alpha were found to be resistant to apoptosis and cytotoxicity when compared with B6 mice. In contrast, Jo-2 treatment produced similar increases in caspase-3 activity and cytotoxicity in primary hepatocytes from NOD and B6 mice. The resistance to LPS- and TNF-alpha-mediated lethality and hepatic injury in D-galactosamine-sensitized NOD mice is apparently due to a post-TNFR binding defect, and independent of signaling pathways shared with Fas.