Dietary iron overload inhibits carbon tetrachloride-induced promotion in chemical hepatocarcinogenesis: effects on cell proliferation, apoptosis, and antioxidation

Contrasting Iron Metabolism in Undifferentiated Versus Differentiated MO3.13 Oligodendrocytes via IL-1β-Induced Iron Regulatory Protein 1

Parkinson's disease (PD) is a prevalent neurodegenerative disorder characterized by the loss of dopaminergic neurons and the accumulation of iron in the substantia nigra. While iron accumulation and inflammation are implicated in PD pathogenesis, their impact on oligodendrocytes, the brain's myelin-forming cells, remains elusive. This study investigated the influence of interleukin-1β (IL-1β), an elevated proinflammatory cytokine in PD, on iron-related proteins in MO3.13 oligodendrocytes. We found that IL-1β treatment in undifferentiated MO3.13 oligodendrocytes increased iron regulatory protein 1 and transferrin receptor 1 (TfR1) expression while decreasing ferroportin 1 (FPN1) expression. Consequently, iron uptake was enhanced, and iron release was reduced, leading to intracellular iron accumulation. Conversely, IL-1β treatment in differentiated MO3.13 oligodendrocytes exhibited the opposite effect, with decreased TfR1 expression, increased FPN1 expression, and reduced iron uptake. These findings suggest that IL-1β-induced dysregulation of iron metabolism in oligodendrocytes may contribute to the pathological processes observed in PD. IL-1β can increase the iron content in undifferentiated oligodendrocytes, thus facilitating the differentiation of undifferentiated MO3.13 oligodendrocytes. In differentiated oligodendrocytes, IL-1β may facilitate iron release, providing a potential source of iron for neighboring dopaminergic neurons, thereby initiating a cascade of deleterious events. This study provides valuable insights into the intricate interplay between inflammation, abnormal iron accumulation, and oligodendrocyte dysfunction in PD. Targeting the IL-1β-mediated alterations in iron metabolism may hold therapeutic potential for mitigating neurodegeneration and preserving dopaminergic function in PD.

Molecular alterations that precede the establishment of the hallmarks of cancer: An approach on the prevention of hepatocarcinogenesis

Chronic liver injury promotes the molecular alterations that precede the establishment of cancer. Usually, several decades of chronic insults are needed to develop the most common primary liver tumor known as hepatocellular carcinoma. As other cancer types, liver cancer cells are governed by a common set of rules collectively called the hallmarks of cancer. Although those rules have provided a conceptual framework for understanding the complex pathophysiology of established tumors, therapeutic options are still ineffective in advanced stages. Thus, the molecular alterations that precede the establishment of cancer remain an attractive target for therapeutic interventions. Here, we first summarize the chemopreventive interventions targeting the early liver carcinogenesis stages. After an integrative analysis on the plethora of molecular alterations regulated by anticancer agents, we then underline and discuss that two critical processes namely oxidative stress and genetic alterations, play the role of 'dirty work laborer' in the initial cell damage and drive the transformation of preneoplastic into neoplastic cells, respectively; besides, the activation of cellular senescence works as a key mechanism in attempting to prevent the onset and establishment of liver cancer. Whereas the detrimental effects of the binomial made up of oxidative stress and genetic alterations are either eliminated or reduced, senescence activation is promoted by anticancer agents. We argue that collectively, oxidative stress, genetic alterations, and senescence are key events that influence the fate of initiated cells and the establishment of the hallmarks of cancer.

Ferroptosis in a sarcopenia model of senescence accelerated mouse prone 8 (SAMP8)

As a systemic syndrome characterized by age-associated degenerative skeletal muscle atrophy, sarcopenia leads to a risk of adverse outcomes in the elderly. Age-related iron accumulation is found in the muscles of sarcopenia animal models and patients, but the role of iron in sarcopenia remains poorly understood. It has been recently found that iron overload in several diseases is involved in ferroptosis, an iron- dependent form of programmed cell death. However, whether this excess iron can result in ferroptosis in muscles is still unclear. In our present study, we found that ferric citrate induced ferroptosis in C2C12 cells, as well as impaired their differentiation from myoblasts to myotubes. Due to the decreased muscle mass and fiber size, 40-week-old senescence accelerated mouse prone 8 (SAMP8) mice were used as a sarcopenia model, in whose muscles the iron content and markers of ferroptosis were found to increase, compared to 8-week- old SAMP8 controls. Moreover, our results showed that iron overload upregulated the expression of P53, which subsequently repressed the protein level of Slc7a11 (solute carrier family 7, member 11), a known ferroptosis-related gene. The downregulation of Slc7a11 then induced the ferroptosis of muscle cells through the accumulation of lipid peroxidation products, which may be one of the causes of sarcopenia. The findings in this study indicate that iron plays a key role in triggering P53- Slc7a11-mediated ferroptosis in muscles, and suggest that targeting iron accumulation and ferroptosis might be a therapeutic strategy for treating sarcopenia.

Iron Overload-Induced Osteocyte Apoptosis Stimulates Osteoclast Differentiation Through Increasing Osteocytic RANKL Production In Vitro

Iron overload is closely associated with osteoporosis, the potential cellular mechanism involved in decreased osteoblast differentiation and increased osteoclast formation. However, the effect of iron overload on the biological behavior in osteocytes has not been reported. This study aims to investigate the changes of osteocytic activity, apoptosis, and its regulation on osteoclastogenesis in response to iron overload. MLO-Y4 osteocyte-like cells and primary osteocytes from mice were processed with ferric ammonium citrate (FAC) and deferoxamine (DFO), the conditioned medium (CM) was harvested and co-cultured with Raw264.7 cells and bone marrow-derived macrophages (BMDMs) to induce them to differentiate into osteoclasts. Osteocyte apoptosis, osteoclast differentiation, osteocytic gene expression and protein secretion of receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG) was examined. Excessive iron has a toxic effect on MLO-Y4 osteocyte-like cells. Increased cell apoptosis in MLO-Y4 cells and primary osteocytes was induced by iron overload. The osteoclastic formation, differentiation-related gene expression, and osteoclastic bone-resorption capability were significantly increased after treated with the CM from iron overload-exposed osteocytes. Excessive iron exposure significantly promoted the gene expression and protein secretion of the RANKL in MLO-Y4 cells. Addition of RANKL-blocking antibody completely abolished the increase of osteoclast formation and bone resorption capacity induced by the CM from osteocytes exposed to excessive iron. Moreover, the pan-caspase apoptosis inhibitor, QVD (quinolyl-valyl-O-methylaspartyl-[-2,6-difluorophenoxy]-methylketone) was used to inhibit osteocyte apoptosis. The results showed osteocyte apoptosis induced by iron overload was reduced by QVD and accompanied by the decrease of soluble RANKL (sRANKL) in supernatant. The increase of osteoclast formation and bone resorption capacity induced by the CM from osteocytes exposed to excessive iron was significantly decreased by QVD. These results indicated that iron overload-induced osteocyte apoptosis is required to regulate osteoclast differentiation by increasing osteocytic RANKL production. This study, for the first time, reveals the indirect effect of iron overload on osteoclast differentiation through regulating osteocytes.

Ferroptosis was more initial in cell death caused by iron overload and its underlying mechanism in Parkinson's disease

Ferroptosis, an iron-dependent nonapoptotic cell death, was referred in neurodegenerative diseases, but its role in Parkinson's disease remains unclear. Here, we used ferric ammonium citrate (FAC) to treat dopaminergic cell to mimic the iron overload during the progression of Parkinson's disease (PD). We found that the cell death types of iron-overloaded dopaminergic cells induced by concentrations of FAC were different. Ferroptosis firstly occurred in a relatively low concentration of FAC-treated group, and then apoptosis appeared in response to the increased iron doses. Moreover, both ferroptosis and apoptosis caused by iron overload could be rescued by inhibitors of ferroptosis, but inhibitors of apoptosis did not prevent the occurrence of ferroptosis. We verified that ferroptosis occurred before apoptosis in α-SynA53T homozygous PD mice model. The underlying mechanism might be associated with the p53 signaling pathway, but not MAPK signaling pathway. Collectively, our results revealed a previously unappreciated role of ferroptosis in the early stages of PD and indicated that ferroptosis could elicit apoptosis in cell death caused by iron overload.

Iron-Induced Liver Injury: A Critical Reappraisal

Iron is implicated in the pathogenesis of a number of human liver diseases. Hereditary hemochromatosis is the classical example of a liver disease caused by iron, but iron is commonly believed to contribute to the progression of other forms of chronic liver disease such as hepatitis C infection and nonalcoholic fatty liver disease. In this review, we present data from cell culture experiments, animal models, and clinical studies that address the hepatotoxicity of iron. These data demonstrate that iron overload is only weakly fibrogenic in animal models and rarely causes serious liver damage in humans, calling into question the concept that iron overload is an important cause of hepatotoxicity. In situations where iron is pathogenic, iron-induced liver damage may be potentiated by coexisting inflammation, with the resulting hepatocyte necrosis an important factor driving the fibrogenic response. Based on the foregoing evidence that iron is less hepatotoxic than is generally assumed, claims that assign a causal role to iron in liver injury in either animal models or human liver disease should be carefully evaluated.

Pazopanib-Induced Hepatotoxicity in an Experimental Rat Model

Pazopanib is an effective treatment for advanced renal cell carcinoma and soft tissue sarcoma. Besides classical adverse events of this drug class, hepatotoxicity has been described as a frequent side effect. The aim of the present study was to evaluate the effect of pazopanib on the liver in an experimental rat model. Sixteen Wistar albino rats were divided into 3 groups: experimental toxicity was induced with pazopanib (10 mg/kg) administered for 28 days (group 2) or 56 days (group 3) orally by gavage. Group 1 (control group) received only distilled water. Rats in groups 2 and 3 were sacrificed after the collection of blood and tissue samples on the 28th and 56th days, respectively. We found significant differences in bilirubin, alkaline phosphatase, lactate dehydrogenase, glucose, triglyceride, very-low-density lipoprotein, and iron values (p < 0.050 for all) but none in any other parameter (p > 0.050). All rats in the control group had normal histological features; however, none of the rats in groups 2 and 3 showed normal histology. In group 2, we observed mild sinusoidal dilatation, congestion, enlarged Kupffer cells, accumulation of yellow-brown-black pigment in the Kupffer cells and the accumulation of hemosiderin with Prussian blue reaction in the hepatocytes. In group 3, the findings mentioned above were more prominent, and besides these findings focal acinar transformation and macrovesicular steatosis were also observed. In group 3, mild inflammation within the portal areas was observed consisting of lymphocytes, neutrophils, and eosinophils. This study is the first that reports the biochemical and histopathological evaluation of pazopanib-related hepatic toxicity.

Characterization of ferroptosis in murine models of hemochromatosis

Ferroptosis is a recently identified iron-dependent form of nonapoptotic cell death implicated in brain, kidney, and heart pathology. However, the biological roles of iron and iron metabolism in ferroptosis remain poorly understood. Here, we studied the functional role of iron and iron metabolism in the pathogenesis of ferroptosis. We found that ferric citrate potently induces ferroptosis in murine primary hepatocytes and bone marrow-derived macrophages. Next, we screened for ferroptosis in mice fed a high-iron diet and in mouse models of hereditary hemochromatosis with iron overload. We found that ferroptosis occurred in mice fed a high-iron diet and in two knockout mouse lines that develop severe iron overload (Hjv^-/- and Smad4^Alb/Alb mice) but not in a third line that develops only mild iron overload (Hfe^-/- mice). Moreover, we found that iron overload-induced liver damage was rescued by the ferroptosis inhibitor ferrostatin-1. To identify the genes involved in iron-induced ferroptosis, we performed microarray analyses of iron-treated bone marrow-derived macrophages. Interestingly, solute carrier family 7, member 11 (Slc7a11), a known ferroptosis-related gene, was significantly up-regulated in iron-treated cells compared with untreated cells. However, genetically deleting Slc7a11 expression was not sufficient to induce ferroptosis in mice. Next, we studied iron-treated hepatocytes and bone marrow-derived macrophages isolated from Slc7a11^-/- mice fed a high-iron diet.

CONCLUSION

We found that iron treatment induced ferroptosis in Slc7a11^-/- cells, indicating that deleting Slc7a11 facilitates the onset of ferroptosis specifically under high-iron conditions; these results provide compelling evidence that iron plays a key role in triggering Slc7a11-mediated ferroptosis and suggest that ferroptosis may be a promising target for treating hemochromatosis-related tissue damage. (Hepatology 2017;66:449-465).

Hepatoprotective effects of Juglans regia extract against CCl4-induced oxidative damage in rats

CONTEXT

Different parts of the walnut [Juglans regia L. (Juglandaceae)] have been used in folk medicine for protection against liver injury, although its actual efficacy remains uncertain.

OBJECTIVE

The present study investigated the protective effect of walnut leaf extract against carbon tetrachloride (CCl4)-induced liver damage in rats.

MATERIALS AND METHODS

The rats were randomly divided into seven groups: control, CCl4 (i.p., 0.5 mL/kg b.w., 50% CCl4 in olive oil), walnut extract (at dose level of 0.2 g/kg b.w.) alone, walnut extract (at dose levels of 0.05, 0.1, 0.2 and 0.4 g/kg b.w.) with CCl4, and treatment was carried out accordingly. On the 28th day, rats were sacrificed and blood was withdrawn by cardiac puncture. Liver damage was assessed by serum biochemical parameters (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and albumin), antioxidant enzymes (superoxide dismutase and catalase) and histopathological observation.

RESULTS

Administration of walnut leaf extract (ranging from 0.2 to 0.4 g/kg b.w.) significantly lowered serum alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase levels in CCl4-treated rats. Walnut leaf extract increased antioxidant enzymes, including superoxide dismutase and catalase. Histopathological examination of livers showed that walnut leaves extract reduced fatty degeneration, cytoplasmic vacuolization and necrosis in CCl4-treated rats.

DISCUSSION AND CONCLUSION

These results suggest that walnut extract has a protective effect over CCl4-induced oxidative damage in rat liver. These results demonstrate that walnut extract acts as a good hepatoprotective and antioxidant agent in attenuating hepatocellular damage.

Accelerated CCl4-induced liver fibrosis in Hjv-/- mice, associated with an oxidative burst and precocious profibrogenic gene expression

Hereditary hemochromatosis is commonly associated with liver fibrosis. Likewise, hepatic iron overload secondary to chronic liver diseases aggravates liver injury. To uncover underlying molecular mechanisms, hemochromatotic hemojuvelin knockout (Hjv-/-) mice and wild type (wt) controls were intoxicated with CCl(4). Hjv-/- mice developed earlier (by 2-4 weeks) and more acute liver damage, reflected in dramatic levels of serum transaminases and ferritin and the development of severe coagulative necrosis and fibrosis. These responses were associated with an oxidative burst and early upregulation of mRNAs encoding α1-(I)-collagen, the profibrogenic cytokines TGF-β1, endothelin-1 and PDGF and, notably, the iron-regulatory hormone hepcidin. Hence, CCl4-induced liver fibrogenesis was exacerbated and progressed precociously in Hjv-/- animals. Even though livers of naïve Hjv-/- mice were devoid of apparent pathology, they exhibited oxidative stress and immunoreactivity towards α-SMA antibodies, a marker of hepatic stellate cells activation. Furthermore, they expressed significantly higher (2-3 fold vs. wt, p<0.05) levels of α1-(I)-collagen, TGF-β1, endothelin-1 and PDGF mRNAs, indicative of early fibrogenesis. Our data suggest that hepatic iron overload in parenchymal cells promotes oxidative stress and triggers premature profibrogenic gene expression, contributing to accelerated onset and precipitous progression of liver fibrogenesis.

Hepcidin expression in the liver of rats fed a magnesium-deficient diet

Mg deficiency accelerates Fe accumulation in the liver, which may induce various metabolic disturbances. In the present study, we examined the gene expression of Hepcidin, a peptide hormone produced in the liver to regulate intestinal Fe absorption negatively, in Mg-deficient rats. Although liver Fe concentration was significantly higher in rats fed an Mg-deficient diet for 4 weeks than in rats fed a control diet, Hepcidin expression in the liver was comparable between the dietary groups. Previous studies revealed that Fe overload up-regulated Hepcidin expression through transcriptional activation by Fe-induced bone morphogenetic protein (Bmp) 6, a growth/differentiation factor belonging to the transforming growth factor-β family, in the liver. Mg deficiency up-regulated the expression of Bmp6 but did not affect the expression of inhibition of DNA binding 1, a sensitive Bmp-responsive gene. In addition, the expression of Bmp receptors such as activin receptor-like kinase 2 (Alk2), activin receptor type IIA (Actr2a), activin receptor type IIB (Actr2b) and Bmp type II receptor (Bmpr2) was lower in the liver of Mg-deficient rats than in that of control rats. The present study indicates that accumulation of hepatic Fe by Mg deficiency is a stimulant inducing Bmp6 expression but not Hepcidin expression by blunting Bmp signalling possibly resulting from down-regulation of the receptor expression. Unresponsive Hepcidin expression may have a role in Mg deficiency-induced changes related to increased liver Fe.

Beneficial effects of yam on carbon tetrachloride-induced hepatic fibrosis in rats

BACKGROUND

In a previous study, lyophilised yam reduced brain amyloid beta-protein (Abeta) accumulation and improved the antioxidative defence system in senescence-accelerated (SAMP8) mice. Therefore, the aim of this study was to investigate the hepatic protection of yam in the carbon tetrachloride-induced hepatic fibrosis of rats. Hepatic fibrosis was induced in rats via intraperitoneal injections of CCl(4) at a dose of 1 mL kg(-1) body weight (BW) twice weekly for 8 weeks. Three groups of rats were gavaged daily with yams at doses of 0.5, 1 and 2 g kg(-1) BW for 8 weeks, respectively.

RESULTS

Yam treatments significantly decreased the ratio of liver/body weight, levels of gamma-glutaminotranspeptidase (GGT), low-density lipoprotein, and triglyceride in serum when compared with those administered CCl(4) alone. Treatment with yams significantly elevated antioxidant activities of glutathione peroxidase (GSH-Px) and superoxidase dismutase (SOD) in livers. Microscopically, yam-treated groups presented with low histoscores of CCl(4)-induced liver injury and fibrosis. Additionally, yam treatment reduced the area of GGT-positive foci and the index of proliferating cell nuclear antigen (PCNA) in liver.

CONCLUSION

Daily administration of yam attenuates CCl(4)-induced hepatic fibrosis in rats in a dose-dependent manner; this attenuation may be related to the antioxidant properties of yams.

Participation of Functionally Different Macrophage Populations and Monocyte Chemoattractant Protein-1 in Early Stages of Thioacetamide-induced Rat Hepatic Injury

Macrophages are crucial in hepatic fibrogenesis. In acute hepatic necrosis induced in rats by a single injection of 300 mg/kg body weight (BW) of thioacetamide (TAA), macrophage properties were investigated using single or double immunohistochemistry. Macrophages reacting with anti-CD68, anti-CD163, or major histocompatibility complex (anti-MHC) class II antibody appeared in injured centrilobular areas on days 1-5 after injection. Increased expression of CD68 and CD163 reflect phagocytosis and production of pro-inflammatory factors, respectively. There were also macrophages double-positive to CD68/CD163, CD68/MHC class II, or CD163/MHC class II; of these, macrophages double-positive to CD68/MHC class II were most frequent, indicating that macrophages with enhanced phagocytic activity came to express MHC class II. The appearance of these macrophages corresponded to increased expression of mRNAs of monocyte chemoattractant protein-1 (MCP-1), a chemokine, on day 1, and TGF-β1, a fibrogenic factor, on day 3. Some hepatic stellate cells (HSCs) in injured areas reacted with anti-MCP-1 antibody. To investigate the effects of MCP-1, we added MCP-1 to HS-P, a rat macrophage line. Addition of MCP-1 increased immunoexpression for CD68 and CD163 and up-regulated TGF-β1 mRNA expression. Collectively, macrophages in acute hepatic necrosis may express different properties such as phagocytosis, MHC class II expression, and TGF-β1 production; such expression may be influenced by MCP-1 produced by HSCs.

Iron deposition and fat accumulation in dimethylnitrosamine-induced liver fibrosis in rat

AIM: To investigate if iron deposition and fat accumulation in the liver play a pathogenetic role in dimethylnitrosamine (DMN)-induced liver fibrosis in rat.

METHODS: Thirty rats were treated with DMN at does consecutive days of 10 μL/kg daily, i.p., for 3 consecutive day each week for 4 wk. Rats (n = 30) were sacrificed on the first day (model group A) and 21^st d (model group B) after cessation of DMN injection. The control group (n = 10) received an equivalent amount of saline. Liver tissues were stained with hematoxylin & eosin (HE) and Masson and Prussian blue assay and oberserved under electron microscopy. Serum alanine aminotransferase (ALT) and liver tissue hydroxyproline (Hyp) content were tested.

RESULTS: The liver fibrosis did not automatically reverse, which was similar to previous reports, the perilobular deposition of iron accompanied with collagen showed marked characteristics at both the first and 21^st d after cessation of DMN injection. However, fat accumulation in hepatocytes occurred only at the 21^st d after cessation of DMN injection.

CONCLUSION: Iron deposition and fat accumulation may play important roles in pathological changes in DMN-induced rat liver fibrosis. The detailed mechanisms of these characteristics need further research.

Increased iron deposition in rat liver fibrosis induced by a high-dose injection of dimethylnitrosamine

Using a developed rat model of hepatic necrosis and subsequent fibrosis induced by a high-dose intraperitoneal injection of dimethylnitrosamine (DMN), we studied iron deposition and expression of transforming growth factor-beta(1) (TGF-beta(1)) during the development of persistent liver fibrosis. Rats were sacrificed at several timepoints from 6 h to 10 months post-injection and the livers were examined for iron content and distribution, and for expression of alpha-smooth muscle actin, ED-1, TGF-beta(1), and collagen (alpha(2))I. Morphologic evidence of acute submassive hemorrhagic necrosis peaked at 36 h; on day 3 the residual parenchyma contained activated hepatic stellate cells (HSCs) and necrotic areas contained numerous macrophages; and on day 5, necrotic tissues and erythrocytes had been phagocytosed and macrophages contained abundant iron deposits. From days 7 to 10, iron-laden macrophages and activated HSCs (myofibroblasts) populated the fibrous septa in parallel. From week 2 to month 10, closely arranged macrophages and myofibroblasts were found in central-to-central bridging fibrotic tissue. TGF-beta(1) was strongly detected in both macrophages and HSCs during development of liver fibrosis. Our data suggest that increased iron deposition may be involved in the initiation and perpetuation of rat liver fibrosis. Iron-laden macrophages may influence HSCs through the action of TGF-beta(1) in DMN-induced liver fibrosis.

Chronic iron overload stimulates hepatocyte proliferation and cyclin D1 expression in rodent liver

Hepatomegaly is commonly observed in hepatic iron overload due to human hemochromatosis and in animal models of iron loading, but the mechanisms underlying liver enlargement in these conditions have received scant attention. In this study, male rats were treated with iron dextran or dextran alone for 6 months. Chronic iron loading resulted in a > 50-fold increase in hepatic iron concentration. Both liver weights and liver/body weight ratios were increased approximately 2-fold in the iron-loaded rats (P < 0.001 for both). Hepatocyte nuclei expressing proliferating cell nuclear antigen (PCNA), a marker of S phase, were significantly increased in the iron-loaded livers, suggesting enhanced proliferation. To assess the mechanisms by which iron promotes proliferation, the expression of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, hepatocyte growth factor (HGF), and transforming growth factor-alpha (TGF-alpha) were assessed by reverse transcription-polymerase chain reaction (RT-PCR). Of these growth-associated factors, only TNF-alpha messenger RNA (mRNA) was significantly increased by iron loading (about 3-fold; P = 0.005). Because cyclin D1 is required for entry of hepatocytes into the cell cycle after partial hepatectomy or treatment with direct mitogens, levels of immunoreactive cyclin D1 were examined and found to be significantly increased in the iron-loaded livers. The increase in cyclin D1 protein in the iron-loaded livers was paralleled by an increase in the abundance of its transcript as measured by real-time PCR. Taken together, these results suggest that iron is a direct mitogen in the liver and raise the possibility that chronic stimulation of hepatocyte proliferation may play a role in the pathophysiology of iron overload states.

Modulation of apoptosis as a target for liver disease

Apoptosis mediated via extrinsic or intrinsic pathways is essential for maintaining cellular homeostasis in the liver. The extrinsic pathway is triggered from the cell surface by engagement of death receptors as CD95, TRAIL (TNF-related apoptosis inducing ligand) and TNF (tumour necrosis factor) or TGF-beta (transforming growth factor beta) receptors. The intrinsic pathway is initiated from the mitochondria and can be influenced by Bcl-2 family members. Both pathways are intertwined and play a physiological role in the liver. Dysregulation of apoptosis pathways contributes to diseases as hepatocellular carcinoma, viral hepatitis, autoimmune hepatitis, ischaemia-reperfusion injury, iron or copper deposition disorders, toxic liver damage and acute liver failure. The apoptosis defects are often central pathogenetic events; hence molecular mechanisms of apoptosis give not only insight into disease mechanisms but also provide potential corresponding therapeutic candidates in liver disease. The focus of this review is the identification of apoptotic signalling components in the liver as therapeutic targets.

Early induction of TGF-beta1 through a fasting-re-feeding regimen promotes liver carcinogenesis by a sub-initiating dose of diethylnitrosamine

We previously reported that a sub-necrogenic dose (20 mg/kg) of diethylnitrosamine (DENA) can induce the development of liver cancer when rats undergo a fasting-re-feeding regimen. The present study was undertaken to establish whether fasting followed by re-feeding builds up mechanisms able to trigger liver fibrosis, eventually leading to cirrhosis and cancer. Adult male rats, for fasted 4 days, were given 20 mg/kg of DENA after 1 day of re-feeding; in parallel, consistently fed animals receiving 20 mg/kg (sub-necrogenic) or 200 mg/kg (necrogenic dose) of DENA were used as negative and positive controls, respectively. All three groups were then subjected to the 2-acetylaminofluorene/carbon tetrachloride promoting regimen. Fasting induced moderate apoptosis in liver tissue, as evidenced by increased levels of transforming growth factor-beta1 (TGF-beta1) and Bax proteins and by a dramatic drop in the level of Bcl-2. Subsequent re-feeding caused all changes to revert except TGF-beta1 up-regulation. Histological findings of inflammation and fibrosis were consistently associated with increased production of TGF-beta1, the inflammatory cytokine with the most pronounced profibrogenic action. Thus, up-regulation of TGF-beta1 expression appears as a major mechanism by which the fasting-re-feeding regimen predisposes to initiation and promotion of liver carcinogenesis in rats. Avoiding fasting-re-feeding could be considered in the nutritional status of patients with liver fibrosis.

Du-Zhong (Eucommia ulmoides Oliv.) leaves inhibits CCl4-induced hepatic damage in rats

The protective effects of water extract of Du-Zhong (Eucommia ulmoides Oliv.) leaves (WEDZ) and its active compound (protocatechuic acid; PCA) on liver damage were evaluated by carbon tetrachloride (CCl4)-induced chronic hepatotoxicity in rats. Wistar rats were orally treated with WEDZ (0.1, 0.5, and 1.0 g/kg bw) or PCA (0.1 g/kg bw) with administration of CCl4 (0.5 ml/rat, 20% CCl4 in olive oil) for 28 consecutive days. It showed that CCl4-treated rats increased the relative organ weights of liver and kidney. CCl4-induced rats liver damage and significantly (p<0.05) increased the GOT, GPT, LDH and ALP levels in serum as compared with the control group. Treatment with WEDZ or PCA could decrease the GOT, GPT, LDH and ALP levels in serum when compared with CCl4-treated group. CCl4-treated rats also significantly (p<0.05) decreased the GSH content in liver and trolox equivalent antioxidant capacity (TEAC) in serum whereas increased (p<0.05) MDA content in liver as compared with the control group. Treatment with WEDZ or PCA also significantly (p<0.05) increased the GSH content and significantly (p<0.05) decreased the MDA content in liver. Administration of WEDZ or PCA could increase the activities of GPx, GRd and GST in liver. Liver histopathology showed that WEDZ or PCA reduced the incidence of liver lesions including hepatic cells cloudy swelling, lymphocytes infiltration, cytoplasmic vacuolization, hepatic necrosis and fibrous connective tissue proliferated induced by CCl4 in rats. The data suggest that oral administration with WEDZ for 28 consecutive days significantly decrease the intensity of hepatic damage induced by CCl4 in rats.

Protective effects of caffeic acid phenethyl ester (CAPE) on carbon tetrachloride-induced hepatotoxicity in rats

In the present study, protective effects of caffeic acid phenethyl ester (CAPE) have been evaluated on carbon tetrachloride (CCl4)-induced hepatotoxicity in rat. Twenty-four male Wistar rats were divided in three groups. Group I was used as control. Rats in group II were injected every other day with CCl4 for 1 month, whereas rats in group III were injected every other day with CCl4 and CAPE for 1 month. At the end of the experiment, all animals were killed by decapitation and blood samples were obtained. Serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total and conjugated bilirubin levels and hepatic malondialdehyde (MDA) contents were determined. For histopathological evaluation, livers of all rats were removed and processed for light microscopy. All biochemical parameters in serum and the hepatic MDA content were significantly higher in animals treated with CCl4 than in the controls. Rats treated with CCl4 and CAPE showed a significant reduction in biochemical parameters in serum and hepatic MDA content. Livers of rats treated with CCl4 showed classic histology of cirrhosis, whereas the histopathological changes were reduced after administration of CCl4 and CAPE. A normal lobular appearance was observed in livers in this group except for fatty degeneration. The results of our study indicate that CAPE treatment prevents CCl4-induced liver damage in rats.

Protective effects of melatonin against carbon tetrachloride-induced hepatotoxicity in rats: a light microscopic and biochemical study

The aim of this study was to examine the protective effects of melatonin against CCl4-induced hepatotoxicity in the rat. Twenty-four male Wistar rats were divided into three groups. Group I was used as a control. Rats in group II were injected every other day with CCl4 for 1 month, whereas rats in group III were injected every other day with CCl4 and melatonin for 1 month. At the end of the experiment, all animals were killed by decapitation and blood samples were obtained. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total and conjugated bilirubin levels were determined. For histopathological evaluation, livers of all rats were removed and processed for light microscopy. All serum biochemical parameters were significantly higher in animals treated with CCl4 than in the controls. When rats injected with CCl4 were treated with melatonin, significantly reduced elevations in serum biochemical parameters were found. In liver sections of the CCl4-injected group, necrosis, fibrosis, mononuclear cell infiltration, haemorrhage, fatty degeneration and formation of regenerative nodules were observed. Additionally, apoptotic figures, microvesicular steatosis and hydropic degeneration in hepatocytes were seen in this group. In contrast, the histopathological changes observed after administration of CCl4 were lost from rats treated with CCl4 and melatonin. Except for mild hydropic degeneration of the hepatocytes, a normal lobular appearance was seen in the livers of this group. The results of our study indicate that melatonin treatment prevents CCl4-induced liver damage in rats.

Moderate iron overload enhances lipid peroxidation in livers of rats, but does not affect NF-kappaB activation induced by the peroxisome proliferator, Wy-14,643

It has been hypothesized that high concentrations of tissue iron may enhance carcinogenesis induced by free radical mechanisms. Wy-14,643 is a peroxisome proliferator that is hepatocarcinogenic in rats. Tumor induction may result in part from excessive production of reactive oxygen species, particularly H(2)O(2). The purpose of this study was to examine the effect of iron status on oxidative stress and NF-kappaB activation in livers of rats treated with Wy-14,643. Forty-eight male Sprague-Dawley rats were fed one of four diets (20, 45, 650, 1500 mg Fe/kg diet) for 28 d. At the time of tissue collection, liver iron ranged from 1.4 to 9.9 micro mol/g wet tissue in the diet groups. Wy-14,643 (0 or 0.1 g/100 g diet) was added to the diet for the final 10 d of the study. Wy-14,643 doubled the liver weight/body weight ratio (P = 0.0001), which was also increased by iron supplementation (P < 0.01). Iron supplementation increased thiobarbituric acid reactive substances and/or conjugated dienes, but there was no synergism between Wy 14,643 and iron on lipid peroxidation measures. The hepatic DNA binding activity of NF-kappaB was increased in rats administered Wy-14,643. However, differences in liver iron concentration did not alter activation of NF-kappaB in untreated rats or in those treated with Wy-14,643. DNA double-strand breakage was not affected by iron or Wy-14,643. In summary, although moderate changes in iron status altered liver lipid peroxidation, iron did not significantly increase oxidative stress induced by a hepatocarcinogenic peroxisome proliferator.

Reduction of carbon tetrachloride-induced rat liver injury by IRFI 042, a novel dual vitamin E-like antioxidant

Carbon tetrachloride (CCl4 )-induced hepatotoxicity is likely the result of a CCl4 -induced free radical production which causes membrane lipid peroxidation and activation of transcription factors regulating both the TNF-alpha gene and the early-immediate genes involved in tissue regeneration. IRFI 042 is a novel vitamin E-like compound having a masked sulphydryl group in the aliphatic side chain. We studied the effect of IRFI 042 on CCl4 -induced liver injury. Liver damage was induced in male rats by an intraperitoneal injection of CCl4 (1 ml/kg in vegetal oil). Serum alanine aminotransferase (ALT) activity, liver malondialdehyde (MAL), hydroxyl radical formation (OH*), calculated indirectly by a trapping agent, hepatic reduced glutathione (GSH) concentration, plasma TNF-alpha, liver histology and hepatic mRNA levels for TNF-alpha were evaluated 48 h after CCl4 administration. Hepatic vitamin E (VE) levels were evaluated, in a separate group of animals, 2 h after CCl4 injection. A control group with vitamin E (100 mg/kg) was also treated in order to evaluate the differences versus the analogue treated groups. Intraperitoneal injection of carbon tetrachloride produced a marked increase in serum ALT activity (CCl4 = 404.61 +/- 10.33 U/L; Controls= 28.54 +/- 4.25 U/L), liver MAL (CCl4 = 0.67 +/- 0.16 nmol/mg protein; Controls= 0.13 +/- 0.06 nmol/mg protein), OH(7) levels assayed as 2,3-DHBA (CCl4 = 8.73 +/- 1.46 microM; Controls= 0.45 +/- 0.15 microM) and 2,5-DHBA (CCl4 = 24.61 +/- 3.32 microM; Controls= 2.75 +/- 0.93 microM), induced a severe depletion of GSH (CCl4 = 3.26 +/- 1.85 micromol/g protein; Controls= 17.82 +/- 3.13 micromol/g protein) and a marked decrease in VE levels (CCl4 = 5.67 +/- 1.22 nmol/g tissue; Controls= 13.47 +/- 3.21 nmol/g tissue), caused liver necrosis, increased plasma TNF-alpha levels (CCl4 = 57.36 +/- 13.24 IU/ml; Controls= 7.26 +/- 2.31 IU/ml) and enhanced hepatic mRNA for TNF-alpha (CCl4 = 19.22 +/- 4.38 a.u.; Controls= 0.76 +/- 0.36 a.u.). IRFI 042 (100 mg/kg, 30 min after CCl4 injection) blunted liver MAL (0.32 +/- 0.17 nmol/mg protein), decreased the serum levels of ALT (128.71 +/- 13.23 U/L), and restored the hepatic concentrations of VE (9.52 +/- 3.21 nmol/g tissue), inhibited OH* production (2,3-DHBA= 3.54 +/- 1.31 microM; 2,5-DHBA= 7.37 +/- 2.46 microM), restored the endogenous antioxidant GSH (12.77 +/- 3.73 mmol/g protein) and improved histology. Furthermore IRFI 042 treatment suppressed plasma TNF-alpha concentrations (31.47 +/- 18.25 IU/ml) and hepatic TNF-alpha mRNA levels (11.65 +/- 3.21 a.u.). The acute treatment with vitamin E failed to exert any protective effect against CCl4 -induced hepatotoxicity. These investigations suggest that IRFI 042 treatment may be of benefit during free radical-mediated liver injury.