Dexamethasone prevents acute cadmium-induced hepatic injury but exacerbates kidney dysfunction in rabbits

Cadmium is a potent hepatotoxicant for which neither effective preventive methods nor the mechanism of toxicity has been established. We investigated the preventive effect of dexamethasone against cadmium toxicity on cadmium-induced liver injury in rabbits. Pretreatment with dexamethasone at 1 mg/kg increased the rate of survival in rabbits administered 2.5 mg/kg iv cadmium. Cadmium induced acute severe liver injury characterized by hepatocellular necrosis, infiltration by inflammatory cells, and increases of plasma GOT, GPT, LDH, and LDH5. Dexamethasone mitigated the acute hepatotoxic effect of cadmium, but exacerbated cadmium-induced kidney dysfunction, with destruction of renal tubular cells and increases in excretion of protein, glucose, and amino acids into urine. The cadmium concentration in liver and kidney of rabbits administered cadmium was not changed by dexamethasone pretreatment. Although metallothionein mRNA expression induced by cadmium was not affected by dexamethasone in liver or kidney, cadmium-induced metallothionein protein production was augmented at the early phase in liver and decreased at the later phase in kidney. Neutrophilia observed after cadmium administration was enhanced initially by dexamethasone pretreatment. These results indicate that dexamethasone pretreatment potently prevented cadmium-induced liver injury, but exacerbated renal tubular dysfunction.     

Pathophysiological role of the acute inflammatory response during acetaminophen hepatotoxicity

Neutrophils are recruited into the liver after acetaminophen (AAP) overdose but the pathophysiological relevance of this acute inflammatory response remains unclear. To address this question, we compared the time course of liver injury, hepatic neutrophil accumulation and inflammatory gene mRNA expression for up to 24 h after treatment with 300 mg/kg AAP in C3Heb/FeJ and C57BL/6 mice. Although there was no relevant difference in liver injury (assessed by the increase of plasma alanine aminotransferase activities and the areas of necrosis), the number of neutrophils and the expression of several pro-inflammatory genes (e.g., tumor necrosis factor-alpha, interleukin-1beta and macrophage inflammatory protein-2) was higher in C3Heb/FeJ than in C57BL/6 mice. In contrast, the expression of the anti-inflammatory genes interleukin-10 and heme oxygenase-1 was higher in C57BL/6 mice. Despite substantial hepatic neutrophil accumulation, none of the liver sections from both strains stained positive for hypochlorite-modified proteins, a specific marker for a neutrophil-induced oxidant stress. In addition, treatment with the NADPH oxidase inhibitors diphenyleneiodonium chloride or apocynin or the anti-neutrophil antibody Gr-1 did not protect against AAP hepatotoxicity. Furthermore, although intercellular adhesion molecule-1 (ICAM-1) was previously shown to be important for neutrophil extravasation and tissue injury in several models, ICAM-1-deficient mice were not protected against AAP-mediated liver injury. Together, these data do not support the hypothesis that neutrophils aggravate liver injury induced by AAP overdose.     

Analysis of chemokines and reactive oxygen species formation by rat and human neutrophils induced by microcystin-LA, -YR and -LR.

Microcystins (MC), a family of heptapeptide toxins produced by some genera of Cyanobacteria, have potent hepatotoxicity and tumor-promoting activity. Leukocyte infiltration in the liver was observed in MC-induced acute intoxication. Although the mechanisms of hepatotoxicity are still unclear, neutrophil infiltration in the liver may play an important role in triggering toxic injury and tumor development. The present study reports the effects of MC-LA, MC-YR and MC-LR (1 and 1000 nM) on human and rat neutrophils functions in vitro. Cell viability, DNA fragmentation, mitochondrial membrane depolarization and intracellular reactive oxygen species (ROS) levels were measured by flow cytometry. Extracellular ROS content was measured by lucigenin-amplified chemiluminescence, and cytokines were determined by ELISA. We found that these MC increased interleukin-8 (IL-8), cytokine-induced neutrophil chemoattractant-2alphabeta (CINC-2alphabeta) and extracellular ROS levels in human and rat neutrophils. Apart from neutrophil presence during the inflammatory process of MC-induced injury, our results suggest that hepatic neutrophil accumulation is further increased by MC-induced neutrophil-derived chemokine.     

Berberine in combination with yohimbine attenuates sepsis-induced neutrophil tissue infiltration and multiorgan dysfunction partly via IL-10-mediated inhibition of CCR2 expression in neutrophils

Infiltration of activated neutrophils into the vital organs contributes to the multiple organ dysfunctions in sepsis. In the present study, we investigated the effects of berberine in combination with yohimbine (BY) on neutrophil tissue infiltration and multiple organ damage during sepsis, and further elucidated the involved mechanisms. Sepsis was induced in mice by cecal ligation and puncture (CLP). BY or CCR2 antagonist was administered 2 h after CLP, and anti-IL-10 antibody (IL-10 Ab) or control IgG was injected intraperitoneally just before BY treatment. We found that IL-10 production was enhanced by BY therapy in septic mice. BY significantly attenuated neutrophil tissue infiltration and multiple organ injury in CLP-challenged mice, all of which were completely reversed by IL-10 Ab pretreatment. The levels of KC, MCP-1, MIP-1α and MIP-2 in the lung, liver and kidney were markedly increased 6 h after CLP. BY reduced the tissue concentrations of these chemokines in septic mice, but IL-10 Ab pretreatment did not completely eliminate these inhibitory effects of BY. Particularly, dramatically increased CCR2 expression in circulating neutrophils of septic mice was reduced by BY and this effect was completely abolished by IL-10 Ab pretreatment. Furthermore, CCR2 antagonist also inhibited lung and renal injury and neutrophil infiltration in septic mice. Taken together, our data strongly suggest that BY therapy attenuates neutrophil tissue infiltration and multiple organ injury in septic mice, at least in part, via IL-10-mediated inhibition of CCR2 expression in circulating neutrophils.     

Tumor necrosis factor-alpha-null mice are not resistant to cadmium chloride-induced hepatotoxicity

Acute administration of cadmium results in hepatotoxicity. Recent reports indicate that Kupffer cells, the resident macrophages of the liver, participate in the manifestation of chemical-induced hepatotoxicity. Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine that is a major product of Kupffer cells and mediates the hepatotoxic effects of lipopolysaccharide (LPS). It has been speculated that cadmium also may exert its hepatotoxicity via the production of TNF-alpha by the Kupffer cells. Therefore, this study was undertaken to determine whether mice deficient in TNF-alpha are resistant to Cd-induced hepatotoxicity. TNF-alpha-null (TNF-KO) and wild-type (WT) mice were dosed ip with saline, LPS (0.1 mg/kg)/Gln (d-galactosamine, 700 mg/kg), or CdCl2 (2.2, 2.8, 3.4, and 3.9 mg Cd/kg). Serum alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) activities were quantified to assess liver injury. Caspase-3 activity was quantified to assess hepatocellular apoptosis. LPS/Gln treatment increased ALT (17-fold) and SDH (21-fold) in WT mice. In contrast, LPS/Gln-treatment did not significantly increase ALT or SDH in TNF-KO mice. LPS/Gln-treatment caused a 7.8-fold increase in caspase-3 activity in WT mice but did not increase caspase-3 in TNF-KO mice. Cadmium caused a dose-dependent increase in liver injury in both WT and TNF-KO mice. However, the liver injury produced by Cd in the TNF-KO mice was not different from that in WT at any dose. No significant increase in caspase-3 activity was detected in any of the Cd-treated mice. These data indicate that, in contrast to LPS/Gln-induced hepatotoxicity, TNF-alpha does not appear to mediate Cd-induced hepatotoxicity.     

Dendritic Cell Protection from Cisplatin Nephrotoxicity Is Independent of Neutrophils

Cisplatin is a very effective chemotherapeutic agent used against a wide range of solid tumors. A major adverse effect of cisplatin therapy is acute kidney injury (AKI). Neutrophils are reported to infiltrate and exacerbate injury in a wide range of sterile inflammatory models of tissue injury. Here, we studied the kinetics of neutrophil infiltration into kidneys and their role in cisplatin-mediated AKI. Mice treated with cisplatin showed an increase in circulating neutrophils 24 and 48 h after cisplatin administration. Cisplatin treatment caused an increase in kidney leukocytes with neutrophils accounting for the majority of the infiltrating leukocytes. The extent of neutrophil infiltration coincided with the severity of kidney injury and renal dysfunction. To examine the functional relevance of infiltrating neutrophils in cisplatin nephrotoxicity, we depleted neutrophils using a neutrophil-specific antibody (anti-Ly-6G). This antibody resulted in greater than 90% depletion of neutrophils in both the blood and kidney. Of note, depletion of neutrophils had no impact on the extent of cisplatin-induced AKI as compared to non-depleted mice. Earlier, we reported that dendritic cell depletion in CD11c-DTRtg mice causes exacerbation of AKI and a dramatic increase in renal neutrophils. Thus, we also examined the role of neutrophils in dendritic cell-depleted mice treated with cisplatin. Dendritic cell depletion exacerbated AKI in spite of neutrophil depletion. These data demonstrate that cisplatin nephrotoxicity is not mediated by neutrophils and that dendritic cells protect kidneys via neutrophil-independent mechanisms.     

Protective effects of nicotinamide against acetaminophen-induced acute liver injury

Nicotinamide (NAM), the amide form of vitamin B3, is involved in a wide range of biological processes. Recent evidence revealed the anti-inflammatory and anti-oxidant properties of NAM and suggests it may be used as a novel strategy in the prevention of acute liver injury. In the present study, we investigated the potential protective effects of NAM on acetaminophen (APAP)-induced acute liver injury in mice. Mice were treated with NAM at 400 mg/kg 30 min before or after administration of APAP at a hepatotoxic dose of 400 mg/kg body weight via intraperitoneal injection. Liver injury and the expression of inflammation-related molecules were determined by histological examination and biochemical analysis, respectively. In addition, the survival rate of mice was assessed after APAP administration. Pretreatment with NAM for 30 min significantly decreased plasma levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and malondialdehyde (MDA), and diminished histopathologic evidence of hepatic toxicity in mice following APAP administration. Similarly, posttreatment with NAM also decreased plasma ALT and AST levels in APAP-administrated mice. Furthermore, both pretreatment and posttreatment with NAM prolonged the survival rate of acute liver injury mice, accompanied by a significant reduction in the plasma levels of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interferon-γ (INF-γ), and interleukin-6 (IL-6). Together, these findings suggest that NAM possesses protective effects on APAP-induced liver injury, which may involve the anti-inflammatory action.     

Inhibition of neutrophil migration by a protein kinase inhibitor for the treatment of ischemic brain infarction.

This study investigated the therapeutic potential of agents that inhibited neutrophil infiltration in cerebral ischemic infarction. The migration of neutrophils elicited by N-formyl-methionyl-leucyl-phenylalanine, tumor necrosis factor, C5a or platelet-activating factor was potently inhibited by fasudil, an inhibitor of protein kinases including rho kinase, protein kinase C and myosin light chain kinase, and hydroxy fasudil, a metabolite of fasudil, in vitro. In a microembolism model in rats, myeloperoxidase-quantified neutrophil accumulation in the ischemic brain was observed 24 hr after embolization. Intravenous administration of fasudil prevented the accumulation of neutrophils. In rats given fasudil, myeloperoxidase activity in the ipsilateral hemisphere (0.04+/-0.01 unit/g wet tissue) was significantly lower than that in ischemic rats (0.11+/-0.02 unit/g wet tissue). Fasudil also significantly reduced the size of the infarct area and improved neurological functions. These results suggest that neutrophil infiltration into the ischemic brain is involved in the pathogenesis of ischemic injury and that inhibiting neutrophil infiltration may provide an effective therapeutic intervention to reduce ischemic injury.     

Tissue influx of neutrophils and monocytes is delayed during development of trovafloxacin‐induced tumor necrosis factor‐dependent liver injury in mice

Idiosyncratic drug‐induced liver injury (iDILI) has a poorly understood pathogenesis. However, iDILI is often associated with inflammatory stress signals in human patients as well as animal models. Tumor necrosis factor (TNF) and neutrophils play a key role in onset of trovafloxacin (TVX)‐induced iDILI, but the exact role of neutrophils and other leukocytes remains to be defined. We therefore set out to study the kinetics of immunological changes during the development of TVX‐induced iDILI in the established murine model of acute liver injury induced by administration of TVX and TNF. Initially, TNF stimulated the appearance of leukocytes, in particular neutrophils, into the liver of TVX‐treated mice, but even more so in control mice treated with the non‐DILI inducing analogue levofloxacin (LVX) or saline as vehicle (Veh). This difference was apparent at 2 hours after TNF administration, but at 4 hours, the relative neutrophil amounts were reduced again in Veh‐ and LVX‐treated mice whereas the amounts in TVX‐treated mice remained at the same increased level as at 2 hours. The influx of monocytes/macrophages, which was unaffected in Veh‐ and LVX‐treated mice was markedly reduced or even absent in TVX‐treated mice. Unlike controls, mice receiving TVX + TNF display severe hepatotoxicity with clear pathology and apoptosis, coagulated hepatic vessels and increased alanine aminotransferase levels and interleukin 6/10 ratios. Findings indicate that TVX delays the acute influx of neutrophils and monocytes/macrophages. Considering their known anti‐inflammatory functions, the disruption of influx of these innate immune cells may hamper the resolution of initial cytotoxic effects of TVX and thus contribute to liver injury development.     

Role of the Nalp3 inflammasome in acetaminophen-induced sterile inflammation and liver injury

Acetaminophen (APAP) overdose is the leading cause of acute liver failure in the US and UK. Recent studies implied that APAP-induced injury is partially mediated by interleukin-1β (IL-1β), which can activate and recruit neutrophils, exacerbating injury. Mature IL-1β is formed by caspase-1, dependent on inflammasome activation. The objective of this invetstigation was to evaluate the role of the Nalp3 inflammasome on release of damage associated molecular patterns (DAMPs), hepatic neutrophil accumulation and liver injury (ALT, necrosis) after APAP overdose. Mice deficient for each component of the Nalp3 inflammasome (caspase-1, ASC and Nalp3) were treated with 300 mg/kg APAP for 24 h; these mice had similar neutrophil recruitment and liver injury as APAP-treated C57Bl/6 wildtype animals. In addition, plasma levels of DAMPs (DNA fragments, keratin-18, hypo- and hyper-acetylated forms of high mobility group box-1 protein) were similarly elevated with no significant difference between wildtype and gene knockout mice. In addition, aspirin treatment, which has been postulated to attenuate cytokine formation and the activation of the Nalp3 inflammasome after APAP, had no effect on release of DAMPs, hepatic neutrophil accumulation or liver injury. Together, these data confirm the release of DAMPs and a sterile inflammatory response after APAP overdose. However, as previously reported minor endogenous formation of IL-1β and the activation of the Nalp3 inflammasome have little impact on APAP hepatotoxicity. It appears that the Nalp3 inflammasome is not a promising therapeutic target to treat APAP overdose.     

Inhalation of activated protein C inhibits endotoxin-induced pulmonary inflammation in mice independent of neutrophil recruitment

BACKGROUND AND PURPOSE: Intravenous administration of recombinant human activated protein C (rhAPC) is known to reduce lipopolysaccharide (LPS)-induced pulmonary inflammation by attenuating neutrophil chemotaxis towards the alveolar compartment. Ideally, one would administer rhAPC in pulmonary inflammation at the site of infection to minimize the risk of systemic bleeding complications. In this study, we therefore assessed the effect of inhaled rhAPC in a murine model of acute lung injury. EXPERIMENTAL APPROACH: Mice were exposed to LPS (0.5 mg kg(-1): intranasally) to induce acute lung injury. 30 minutes before and 3 hours after LPS exposure mice were subjected to vehicle or rhAPC inhalation (25 or 100 microg per mouse in each nebulization). In order to establish whether rhAPC inhalation affects neutrophil recruitment, neutrophil migration was determined in vitro using a trans-well migration assay. KEY RESULTS: rhAPC inhalation dose-dependently decreased LPS-induced coagulation and inflammation markers in bronchoalveolar lavage fluid (BALF), reduced protein leakage into the alveolar space and improved lung function. In contrast, rhAPC did not prevent LPS-induced neutrophil recruitment into the alveolar space.Neutrophil migration in vitro towards FCS or interleukin (IL)-8 was significantly inhibited by pretreatment with rhAPC (0.01-10 microg ml(-1)], whereas rhAPC (10 microg ml(-1)) added to the chemoattractant (modelling for topical rhAPC administration) did not affect neutrophil migration towards FCS or IL-8. CONCLUSIONS AND IMPLICATIONS: rhAPC inhalation significantly diminished LPS-induced pulmonary inflammation. The benefit of inhaled rhAPC appeared not to involve attenuation of neutrophil recruitment, in contrast to its effects after intravenous administration.     

Exaggerated hepatotoxicity of acetaminophen in mice lacking tumor necrosis factor receptor-1. Potential role of inflammatory mediators

Transgenic mice with a targeted disruption of the tumor necrosis factor receptor 1 (TNFR1) gene were used to analyze the role of TNF-alpha in pro- and anti-inflammatory mediator production and liver injury induced by acetaminophen. Treatment of wild-type mice with acetaminophen (300 mg/kg) resulted in centrilobular hepatic necrosis. This was correlated with expression of inducible nitric oxide synthase (NOS II) and nitrotyrosine staining of the liver. Expression of macrophage chemotactic protein-1 (MCP-1), KC/gro, interleukin-1beta (IL-1beta), matrix metalloproteinase-9 (MMP-9), and connective tissue growth factor (CTGF), inflammatory mediators known to participate in tissue repair, as well as the anti-inflammatory cytokine, interleukin-10 (IL-10), also increased in the liver following acetaminophen administration. TNFR1(-/-) mice were found to be significantly more sensitive to the hepatotoxic effects of acetaminophen than wild-type mice. This was correlated with more rapid and prolonged induction of NOS II in the liver and changes in the pattern of nitrotyrosine staining. Acetaminophen-induced expression of MCP-1, IL-1beta, CTGF, and MMP-9 mRNA was also delayed or reduced in TNFR1(-/-) mice relative to wild-type mice. In contrast, increases in IL-10 were more rapid and more pronounced. These data demonstrate that signaling through TNFR1 is important in inflammatory mediator production and toxicity induced by acetaminophen.     

山豆根不同组分多次给药肝毒性损伤实验研究

目的研究山豆根不同组分多次给药对小鼠肝毒性损伤的作用程度。方法连续7天给小鼠灌胃不同剂量的山豆根水提、醇提组分,观察小鼠一般状况,于给药后第7天检测小鼠血清丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)、碱性磷酸酶(AKP)的活性和总胆红素(TBI)、白蛋白(ALB)的含量,计算肝脏指数,并观察肝组织形态变化。结果山豆根水提、醇提组分高、中剂量组在药后第7天可致小鼠体重增长缓慢,血清中ALT、AST、AKP活性升高,TBI含量升高,ALB含量下降,肝脏指数增大,并出现肝细胞病理组织学变化,水提组分对上述指标的影响比醇提组分明显。结论多次给小鼠高、中剂量的山豆根水提组分和醇提组分均可造成明显的肝损伤,既可致肝功能指标的改变,又可致肝细胞器质性病变,且水提组分的肝毒性大于醇提组分。     

酒精对HBV转基因小鼠肝脏的损伤作用及其机制

目的探讨在肝损伤早期酒精和HBV协同作用的分子机制。方法20只HBV转基因小鼠和20只普通小鼠随机分为4组:转基因小鼠酒精组(alcohol-fed Tg mice)和普通小鼠酒精组(alcohol-fed Wt mice),以白酒灌胃;转基因小鼠对照组(control Tg mice)和普通小鼠对照组(control Wtmice),以生理盐水灌胃。连续处理10wk后检测各组小鼠血清ALT、AST水平,肝组织转化生长因子-β1(TGF-β1)、Smad3、Smad7、结缔组织生长因子(CTGF)mRNA表达水平及TGF-β1、CTGF、α-平滑肌肌动蛋白(α-SMA)蛋白表达水平。结果酒精可升高转基因小鼠血清ALT、AST水平,诱发其肝脏病理损伤,但纤维化不明显;肝组织TGF-β1、Smad3、Smad7、CTGF mRNA及TGF-β1、CTGF、α-SMA蛋白表达增加。结论酒精和HBV对肝损伤协同作用的机制可能与TGF-β1、Smad3、CTGF、α-SMA表达增加以及TGF-β1/Smads通路信号分子表达比例失调有关。     

Neutrophil activation during acetaminophen hepatotoxicity and repair in mice and humans

Following acetaminophen (APAP) overdose there is an inflammatory response triggered by the release of cellular contents from necrotic hepatocytes into the systemic circulation which initiates the recruitment of neutrophils into the liver. It has been demonstrated that neutrophils do not contribute to APAP-induced liver injury, but their role and the role of NADPH oxidase in injury resolution are controversial. C57BL/6 mice were subjected to APAP overdose and neutrophil activation status was determined during liver injury and liver regeneration. Additionally, human APAP overdose patients (ALT: > 800 U/L) had serial blood draws during the injury and recovery phases for the determination of neutrophil activation. Neutrophils in the peripheral blood of mice showed an increasing activation status (CD11b expression and ROS priming) during and after the peak of injury but returned to baseline levels prior to complete injury resolution. Hepatic sequestered neutrophils showed an increased and sustained CD11b expression, but no ROS priming was observed. Confirming that NADPH oxidase is not critical to injury resolution, gp91^phox−/− mice following APAP overdose displayed no alteration in injury resolution. Peripheral blood from APAP overdose patients also showed increased neutrophil activation status after the peak of liver injury and remained elevated until discharge from the hospital. In mice and humans, markers of activation, like ROS priming, were increased and sustained well after active liver injury had subsided. The similar findings between surviving patients and mice indicate that neutrophil activation may be a critical event for host defense or injury resolution following APAP overdose, but not a contributing factor to APAP-induced injury.     

Ghrelin ameliorates bleomycin-induced acute lung injury by protecting alveolar epithelial cells and suppressing lung inflammation

Acute lung injury is a critical illness syndrome consisting of acute respiratory failure with bilateral pulmonary infiltrates that is refractory to current therapies. Acute lung injury is characterized by injury of the alveolar capillary barrier, neutrophil accumulation, and induction of pro-inflammatory cytokines followed by devastating lung fibrosis. Ghrelin, an acylated peptide produced in the stomach, increases food intake and growth hormone secretion, suppresses inflammation, and promotes cell survival. We investigated the pharmacological potential of ghrelin in the treatment of acute lung injury by using a bleomycin-induced acute lung injury model in mice. Ghrelin or saline was given to mice daily starting 1 day after bleomycin administration. Ghrelin-treated mice showed a definitively higher survival rate than saline-treated ones. They also had smaller reductions in body weight and food intake. The amelioration of neutrophil alveolar infiltration, pulmonary vascular permeability, induction of pro-inflammatory cytokines, and subsequent lung fibrosis were notable in ghrelin-treated mice. Additionally, ghrelin administration reduced the injury-induced apoptosis of alveolar epithelial cells. Our results indicate that ghrelin administration exerts a protective effect against acute lung injury by protecting the alveolar epithelial cells and regulating lung inflammation, and highlight ghrelin as a promising therapeutic agent for the management of this intractable disease.     

Role of osteopontin in regulating hepatic inflammatory responses and toxic liver injury

Osteopontin (OPN) produced by cells of the immune system, epithelial tissue, smooth muscle cells, osteoblasts and tumor cells has been implicated in various pathophysiological functions such as cell binding, spreading and migration, and tumor metastasis. OPN is known to bind to integrins expressed on macrophages through the arginine-glycine-aspartic acid (RGD) motif and promote migration of cells resulting in granuloma. In the liver, it has been reported that hepatic Kupffer cells secrete OPN facilitating macrophage infiltration in necrotic areas following carbon tetrachloride liver toxicity. Recent work has underlined the importance of OPN as a pivotal cytokine/chemokine in the generated hepatic neutrophil response during early phase alcoholic liver injury. Increased hepatobiliary OPN expression correlated well with higher neutrophil infiltration in a rat model of alcoholic steatohepatitis. In the same model of alcoholic steatohepatitis, higher hepatic expression of OPN in females was attributed to the higher neutrophil infiltration and consequent higher female sensitivity to liver damage. OPN as a potential biomarker for inflammatory liver disease has also been recently assessed. This review will focus on studies demonstrating the role of OPN in mediating hepatic inflammation (neutrophils, monocytes/macrophages and lymphocytes) and the ensuing liver toxicity.     

Inhibitory effect of glycyrrhizin on lipopolysaccharide and d-galactosamine-induced mouse liver injury

The effects of glycyrrhizin isolated from licorice root were investigated on acute hepatitis induced by lipopolysaccharide (LPS) and d-galactosamine in mice. Serum alanine aminotransferase (ALT) activity was markedly increased 6 h to 8 h after administration of LPS/d-galactosamine. Levels in serum of cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10 and IL-12 reached a maximum by 2 h, whereas levels of IL-18, as well as of ALT, were maximal at 8 h. Glycyrrhizin (ED(50): 14.3 mg/kg) inhibited the increase in ALT levels when it was given to mice at 30 min before administration of LPS/d-galactosamine. Inflammatory responses, including infiltration of neutrophils and macrophages in the liver injury, were modulated by glycyrrhizin. Increases in ALT levels were reduced by an administration of glycyrrhizin at 10 min and 60 min but not 3 h, even after LPS/d-galactosamine treatment. However, glycyrrhizin had no effect on the production of TNF-alpha, IL-6, IL-10 and IL-12, whereas it significantly inhibited IL-18 production. Exogenous IL-18 further increased the elevation in ALT levels in mice treated with LPS/d-galactosamine. Glycyrrhizin completely suppressed the effect of IL-18 of increasing ALT levels. IL-18 was detected by immunohistochemistry in inflammatory cells such neutrophils and macrophages in liver injury. Glycyrrhizin reduced the responsiveness of cells to IL-18 in the liver injury. These results suggest that glycyrrhizin inhibits the LPS/d-galactosamine-induced liver injury through preventing inflammatory responses and IL-18 production. Furthermore, it seems that glycyrrhizin prevents IL-18-mediated inflammation in liver injury.     

Reduced hepatotoxicity of acetaminophen in mice lacking inducible nitric oxide synthase: potential role of tumor necrosis factor-alpha and interleukin-10

Macrophage-derived inflammatory mediators have been implicated in tissue injury induced by a number of hepatotoxicants. In the present studies, we used transgenic mice with a targeted disruption of the gene for inducible nitric oxide synthase (NOS II) to analyze the role of nitric oxide in inflammatory mediator production in the liver and in tissue injury induced by acetaminophen. Treatment of wild-type mice with acetaminophen (300 mg/kg) resulted in centrilobular hepatic necrosis, which was evident within 3 h and reached a maximum at 18 h. This was correlated with NOS II expression and nitrotyrosine staining of the liver, which was most prominent after 6 h. Expression of mRNA for tumor necrosis factor-alpha (TNF-alpha), interleukin-10 (IL-10), matrix metalloproteinase-9, and connective tissue growth factor (CTGF) also increased in the liver following acetaminophen treatment of wild-type mice. NOS II knockout mice were found to be less sensitive to the hepatotoxic effects of acetaminophen than wild-type mice. This did not appear to be due to differences in acetaminophen-induced glutathione depletion or adduct formation. In NOS II knockout mice treated with acetaminophen, hepatic expression of TNF-alpha, as well as CTGF, was significantly increased compared to wild-type mice. In contrast, IL-10 expression was reduced. These data demonstrate that nitric oxide is important in hepatotoxicity induced by acetaminophen. Moreover, some of its effects may be mediated by altering production of pro- and antiinflammatory cytokines and proteins important in tissue repair.