Pathogenesis of carbon tetrachloride-induced hepatocyte injury bioactivation of CCI4 by cytochrome P450 and effects on lipid homeostasis

Association of resveratrol with the suppression of TNF-α/NF-kB/iNOS/HIF-1α axis-mediated fibrosis and systemic hypertension in thioacetamide-induced liver injury

Chronic liver injury can lead to hepatic failure and the only available method of treatment would be liver transplantation. The link between inflammation (TNF-α), nuclear factor-kappa B (NF-kB), nitrosative stress (iNOS) and hypoxia-inducible factor-1α (HIF-1α) in thioacetamide (TAA) induced liver fibrosis, and hypertension with and without the incorporation of the anti-inflammatory and antioxidant resveratrol (RES) has not been investigated before. Consequently, we injected rats with either 200 mg/kg TAA for 8 weeks starting at week 2 (model group) or pretreated them before TAA injections with RES (20 mg/kg) for 2 weeks and continued them on RES and TAA until being culled at week 10 (protective group). In the model group, we documented the induction of hepatic fibrosis and upregulation of tumor necrosis factor-α (TNF-α), NF-kB, inducible nitric oxide synthase (iNOS), HIF-1α and the profibrotic biomarkers alpha-smooth muscle actin (α-SMA) and matrix metalloproteinase-9 (MMP-9) that was significantly (p ≤ 0.0014) ameliorated by RES. RES also significantly (p ≤ 0.0232) reduced triglycerides (TG), cholesterol (CHOL), very low-density lipoprotein (vLDL-C), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure, and heart rate (HR) induction by TAA. Also, a significant (p < 0.0001) positive correlation between TNF-α/NF-kB/iNOS/HIF-1α axis-mediated fibrosis and hypertension and liver injury biomarkers was observed. These findings suggest that in the hepatotoxic compound, TAA is associated with TNF-α/NF-kB/iNOS/HIF-1α-mediated fibrosis and hypertension, whilst being inhibited by RES.

Protective Effects of Chlorogenic Acid against Carbon Tetrachloride-Induced Hepatotoxicity in Mice

The protective effects of chlorogenic acid (CGA) against liver injury were evaluated by its reduction in carbon tetrachloride (CCl4)-induced hepatic damage in ICR mice. The animals were orally given CGA (60, 100, and 200 mg/kg, respectively) or silymairn (200 mg/kg) daily with 0.3% CCl4 administration (3 mL/kg, dissolved in olive oil) after medicament treatment on the 7th day. Compared with the normal group, CCl4 caused severe impairment in liver according to the evidence of significant reduction in the level of total albumin and expansion (p < 0.05) of the activities in aspartate aminotransferase (AST) and alanine aminotransferase (ALT), cholesterol, triglyceride (TG), and total albumin in serum, decreased the level of glutathione (GSH), and diminished the activities of catalase, superoxide dismutase (SOD), glutathione reductase (GSH-Rd), and glutathione peroxidase (GSH-Px) in liver while increasing the level of hepatic thiobarbituric acid-reactive substances (TBARS). However, oral administration of CGA or silymarin could significantly (p < 0.05) decrease the serum levels of AST, ALT, cholesterol, TG, and total albumin and elevated the serum total albumin and the activities of GSH, catalase, SOD, GSH-Rd, and GSH-Px while leading to decline the TBARS in liver compared with CCl4-intoxicated group. Moreover, histopathology displayed that CGA decreased the formation of lesions in liver resulted from CCl4. The outcomes indicate that CGA shows the efficiency hepatoprotective consequences for CCl4-incited liver injuries in mice by the elevation of the activities of antioxidant enzymes and hindrance of lipid peroxidation.

Medicinal plants with hepatoprotective potentials against carbon tetrachloride-induced toxicity: a review

Background

Carbon tetrachloride (CCl4) is a well-characterized hepatotoxic agent. With rising cases of liver diseases, the identification, assessment, and development of hepatoprotective agents from plants source has become imperative.

Main body

With arrays of literature on plants with hepatoprotective potentials, this review sourced published literatures between 1998 and 2020 and systematically highlighted about 92 medicinal plants that have been reported to protect against CCl4-induced liver injury in animal models. The results show that herbal plants provide protection for the liver against CCl4 by downregulation of the liver marker enzymes and activation of antioxidant capacity of the liver cells with the restoration of liver architecture. We also provided the traditional and accompanying pharmacological uses of the plants. A variety of phytochemicals mostly flavonoids and polyphenols compounds were suggested to offer protection against liver injuries.

Conclusion

It can be concluded that there are a variety of phytochemicals in plant products with hepatoprotective activity against CCl4-induced toxicity in animal models.

Hepatoprotective effect of piceatannol against carbon tetrachloride-induced liver fibrosis in mice

Piceatannol (3,5,3',4'-trans-tetrahydroxystilbene) is a natural analog and a metabolite of resveratrol present in grapes and red wine. Previous studies have reported that piceatannol exerts a broad spectrum of health benefits including antioxidant, anti-inflammatory, chemopreventive, and neuroprotective effects. However, little is known about the hepatoprotective effect of piceatannol against toxin-induced liver fibrosis. Therefore, the objective of this study is to evaluate the protective effect of piceatannol in a mouse model of CCl₄-induced hepatic fibrosis. Oral administration of piceatannol significantly improved the hepatic functions of CCl₄-treated mice in both therapeutic and preventive models. Additionally, the immunohistochemical staining results revealed that collagen deposition in CCl₄-injected mice was significantly reduced by treatment with piceatannol. Moreover, piceatannol remarkably suppressed the expressions of collagen I, α-smooth muscle protein (α-SMA), and tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) induced by CCl₄. The anti-fibrotic mechanism of piceatannol was associated with the regulation of the transforming growth factor-β (TGF-β)/Smad signaling pathway. Finally, piceatannol also profoundly alleviated CCl₄-induced hepatic oxidative damage by elevating the level of glutathione and catalase activity. Altogether, our current findings suggest that piceatannol may serve as a bioactive agent that inhibits or alleviates toxic-induced fibroproliferative diseases, especially in the prevention of liver fibrosis.

Chronic cadmium exposure at environmental-relevant level accelerates the development of hepatotoxicity to hepatocarcinogenesis

Cadmium (Cd) is an environmental heavy metal with long biological half-time and adverse health effects. The long-term toxicity of Cd at low levels remains to be elucidated. Here, we investigated the impact of dietary Cd intake at environmental doses in the full disease cycle from liver injury, fibrosis, inflammation to cancer progression in mouse models and in vitro. We found that chronic low-dose Cd exposure promoted the hepatotoxicity and hepato-pathogenesis in normal and CCl₄ mouse models. Cd enhanced liver injury and accelerated liver fibrosis, a key risk factor for cirrhosis and liver cancer, featured as up-regulation of fibrosis-related markers (TGF-β1, collagen-1, and TIMP1) and activation of hepatic stellate cells. Consistently, Cd increased the inflammation and the infiltration of macrophages and dendritic cells in liver. At late stage, the angiogenetic factors, VEGF and CD34, were elevated, indicating abnormal angiogenesis. At the end of treatment, Cd promoted CCl₄-induced liver cancer formation, including incidence, tumor number and size. These effects were more pronounced in male mice than that in females. The promoting-effects of Cd on fibrosis and angiogenesis were further validated in hepatic stellate cells and liver sinusoidal endothelial cells. PPAR and ERBB signaling pathways were identified as the potential pathways to promote the toxicity of chronic Cd exposure. These findings provide a better understanding about the long-term influence of environmental Cd spanning the entire precancerous lesions-to-cancer formation cycle.

Isotschimgine alleviates nonalcoholic steatohepatitis and fibrosis via FXR agonism in mice

Farnesoid X receptor (FXR) agonist obeticholic acid (OCA) has emerged as a potential therapy for nonalcoholic fatty liver disease (NAFLD). However, the side effects of OCA may limit its application in clinics. We identified previously that isotschimgine (ITG) is a non-steroidal FXR selective agonist and has potent therapeutic effects on NAFLD in mice. Here, we aimed to evaluate the therapeutic effects of ITG on nonalcoholic steatohepatitis (NASH) and fibrosis in mice. We used methionine and choline deficient (MCD) diet-induced NASH mice, bile duct ligation (BDL), and carbon tetrachloride (CCl₄ )-treated hepatic fibrosis mice to investigate the effects of ITG on NASH, fibrosis, and cholestatic liver injury. Our results showed that ITG improved steatosis and inflammation in the liver of MCD diet-fed mice, as well as alleviated fibrosis and inflammation in the liver of CCl₄ -treated mice. Furthermore, ITG attenuated serum bile acid levels, and reduced vacuolization, inflammatory infiltration, hepatic parenchymal necrosis, and collagen accumulation in the liver of BDL mice. Mechanistically, ITG increased the expression of FXR target genes. These data suggest that ITG is an FXR agonist and may be developed as a novel therapy for NASH, hepatic fibrosis, or primary biliary cholangitis.

Effects of aqueous leaf extract of avocado (Persea americana) on total cholesterol, triacylglycerols, protein and haematological parameters in CCl4-intoxicated rats

Background

Avocado (Persea americana) is one of the plants widely used in ethnomedicine in Nigeria. The present study was aimed at investigating effects of aqueous Avocado (Persea americana) leaf extract on total cholesterol, triacylglycerols, protein and haematological parameters in carbon tetrachloride (CCl4)-intoxicated rats.

Methods

We evaluated the possible effects of pre-treatment with aqueous extract of Persea americana (AEPA) on protein, total cholesterol (T-CHOL), triacylglycerols (TAGs) and haematological parameters in Wistar male albino rats intoxicated with CCl4. Group 1 was the healthy control; group 2 rats were pre-treated with Reducdyn® (100 mg/kg/day) as a standard drug, groups 4 and 5 rats were pre-treated with AEPA at a dose of 100 mg/kg and 200 mg/kg per day respectively, the treatments were administered orally for 7 days. On the seventh day, rats in the treatment groups were injected with a fresh mixture of CCl4 and olive oil (3 ml/kg, 1:1; sc).

Results

Pre-treatment of rats with AEPA resulted in marked increase (p < 0.05) in total protein and reduction in T-CHOL (19–34%) compared to CCl4 alone. Also, there was significant decrease (p < 0.05) in serum TAG concentration when rats were pre-treated with 100 mg and 200 mg kg− 1 b. wt. AEPA. Similarly, AEPA provoked (p < 0.05) a lowering of T-CHOL and TAG levels and an increase in liver protein concentration in the rats. Administration of AEPA at both concentrations restored (p < 0.05) WBC count and ameliorated neutropenia and lymphocytosis caused by CCl4 intoxication.

Conclusion

These results suggest that AEPA could be protective against the development of fatty liver and might also be exhibiting the potential to prevent alterations in haematological parameters caused by CCl4 intoxication in rats.

A single pretreatment with clofibric acid attenuates carbon tetrachloride-induced necrosis, but not steatosis, in rat liver

The present study investigated whether a single pretreatment with clofibric acid suppresses liver injury in rats after CCl₄ intoxication. Rats received a single pretreatment with clofibric acid (100 mg/kg, i.p.) 1 h prior to a CCl₄ (1 mL/kg, p.o.) challenge, and were euthanized 24 h after the CCl₄ administration. A single pretreatment with clofibric acid effectively suppressed increases in the serum aminotransferase activities and the severity of necrosis following the CCl₄ challenge, whereas the pretreatment did not protect against CCl₄-induced fatty liver. The clofibric acid pretreatment did not affect blood concentrations of CCl₄ in the early stage after CCl₄ dosing, or the level of the CCl₄ reaching the liver 1 h after the CCl₄ challenge. Moreover, the clofibric acid pretreatment did not affect the intensity of the covalent binding of the [¹⁴C]CCl₄ metabolite to microsomal proteins and lipids. The clofibric acid pretreatment did not alter microsomal cytochrome P450 2E1 activity. Based on these results, we conclude that protection against CCl₄-induced hepatocellular necrosis by a clofibric acid pretreatment does not require its repeated administration, and that a single and brief pre-exposure to clofibric acid prior to CCl₄ dosing markedly suppresses necrosis without affecting the development and progression of steatosis.

Tribulus terrestris ameliorates carbon tetrachloride-induced hepatotoxicity in male rats through suppression of oxidative stress and inflammation

Hepatoprotection is a goal for the harmful effect of several hepatotoxic agents. The present study has been executed to assess the useful impacts of Tribulus terrestris (TT) and silymarin (SLM) against carbon tetrachloride (CCL₄)-induced hepatotoxicity. Forty-two male rats were partitioned into six groups: group I: received 0.3% CMC-Na in distilled water, group II: TT (500 mg/kg BW, orally), group III: SLM (200 mg/kg, orally) for 14 consecutive days (on days 11 and 12 intraperitoneal corn oil), group IV: CCL₄, group V: TT (500 mg/kg BW) plus CCL₄, and group VI: SLM (200 mg/kg orally) plus CCL₄. The CCL₄ was administered (2.0 ml/kg BW) intraperitoneal on days 11 and 12. Sera were collected for assessment of hepatic injury markers and pro-inflammatory cytokines. Additionally, liver tissue oxidative stress, lipid peroxidation, histopathological examination, and immunohistochemical analysis (Bax and bcl-2) were done. CCL₄ injection induced significant reductions in hepatic antioxidants while increased hepatic lipid peroxidation as well as serum hepatic injury biomarkers and pro-inflammatory cytokines. The histopathological examination showed necrotic and degenerative changes in the hepatic tissue, while immunohistochemical analysis revealed marked hepatic expression of activated Bax, and bcl-2, following CCL₄ injection. TT pretreatment significantly improved all examined parameters and restored the hepatic architecture. The current study illustrated that TT effectively alleviates hepatic oxidative damage, apoptosis, and inflammation, induced by acute CCL₄ intoxication. In this manner, TT has promising cytoprotective powers against hepatotoxicity induced by CCL₄.

The Cumulative Risk Assessment of Hepatotoxic Chemicals: A Hepatic Histopathology Perspective

The increased concern on the consequence of exposure to multiple chemical combinations has led national regulatory authorities to develop different concepts to conduct risk assessments on chemical mixtures. Pesticide residues were identified as "problem formulation" in the respective European regulations and in this context, the European Food and Safety Authority has suggested to group pesticidal active ingredients (AIs) into cumulative assessment groups (CAGs) based on the toxicological properties of each AI. One proposed CAG, on the liver, currently consists of 15 subgroups, each representing a specific hepatotoxic effect observed in toxicity studies. Dietary cumulative risk assessments would then have to be conducted assuming dose additivity of all members of each CAG subgroup. The purpose of this publication is to group AIs based upon the knowledge of the pathogenesis of liver effects to discriminate between primary end points (direct consequence of chemical interaction with a biological target) and secondary end points (which are a consequence of, or that arise out of, a previous pathological change). Focusing on the relevant primary end points strengthens and simplifies the selection of compounds for cumulative risk assessment regarding the liver and better rationalizes the basis for chemical grouping. Relevant dose additivity is to be expected at the level of the primary/leading pathological end points and not at the level of the secondary end points. We recognize, however, that special consideration is needed for substances provoking neoplasia, and this category is included in the group of primary end points for which chemicals inducing them are grouped for risk assessment. Using the pathological basis for defining the respective CAGs, 6 liver subgroups and 2 gallbladder/bile duct groups are proposed. This approach simplifies the cumulative assessment calculation without obviously affecting consumer safety.

Effects of Olive Leaf Extract on Prevention of Molecular, Histopathological, and Enzymatic Changes in Chicken Carbon Tetrachloride-Induced Liver Damage

BACKGROUND

Today, the use of additives such as antibiotics and growth hormones that increase production efficiency in breeding broiler chickens has become inevitable. However, the use of such additives and antibiotics associated with side effects such as liver damage. Oxidative stress occurs due to an imbalance between oxidants and antioxidants. Studies have shown that olive leaves have an antioxidant effect on free radicals. This study was to evaluate the possible effect of olive leaf extract on carbon tetrachloride (CCL4)-induced liver damage (molecular and tissue) and changes of enzymes in chickens.

MATERIALS AND METHODS

A total of 50 chickens were used and classified into5 groups. Treatment groups received 0.5, 1, and 1.5 mg/kg of the olive leaf extract from day 21 of the experiment. Two control groups-healthy and poisoned-did not receive any extract. On the day 35 of the experiment, 1cc of CCL4 was dissolved with olive oil and injected intraperitoneally into the experimental and poisoned control groups. Blood and liver tissue sampling were performed.

RESULTS

The histopathology results showed that at high doses of olive leaf extract, the cells and vessels were regularly curable, and sinusoids were healthy. The expression of B-cell lymphoma 2 (BCL2) increased, and that of BH3 interacting domain death agonist (BID )decreased. Enzymatic tests, including serum glutamic-oxaloacetic transaminase, serum glutamic-pyruvic transaminase, alkaline phosphatase, gamma-glutamyl transpeptidase, showed a reduction in BID expression in the experimental group compared with the control group(P<0.005).

CONCLUSION

We concluded that olive leaf extract boosts the BCL2 -an antiapoptotic gene-and reduces BID -an apoptosis gene-in the liver of chicken. It prevents the liver cells from disintegrating and destroys sinusoids and liver blood vessels. The high doses of the olive leaf extract caused liver resistance to CCL4 toxicity in chicken.

Protective Effects of Ammannia baccifera Against CCl4-Induced Oxidative Stress in Rats

Ammannia baccifera Linn. is commonly used as a traditional medicine in India and China. The antioxidant potential of an ethanolic extract of A. baccifera (EEAB; 250 mg/kg and 500 mg/kg) was evaluated against CCL4-induced toxicity in rats. Antioxidant activity was assessed by measuring the enzymatic and non-enzymatic antioxidants. Phytochemical constituents of EEAB were also analyzed by using UHPLC-QTOF-MS. EEAB treatment markedly reduced CCl4 effects on lipid peroxidation, cholesterol, triacylglycerides, and protein carbonyls. It increased the levels of phospholipids, total sulfhydryl, and antioxidant enzymes, which were reduced by CCl4 intoxication. Treatment with EEAB significantly alleviated the CCl4 effect on non-enzymatic antioxidants. Isoenzyme pattern analyses revealed that significant alterations in superoxide dismutase (SOD1), glutathione peroxidase (GPx2, GPx3), and catalase (CAT) occurred in rats that were exposed to CCl4 and restored post EEAB treatment. Moreover, CCl4-induced down regulation of SOD, CAT, and GPx gene expression was conversely counteracted by EEAB. Its bioactivity may be due to its incorporation of major compounds, such as chlorogenic acid, quercetin, protocatechuic acid, lamioside, crocetin, and khayasin C. These results suggest that EEAB may be used as a potent antioxidant and hepatoprotective agent since it is a rich source of flavonoids and phenolic compounds.

Role of the sympathetic nervous system in carbon tetrachloride-induced hepatotoxicity and systemic inflammation

Carbon tetrachloride (CCl₄) is widely used as an animal model of hepatotoxicity and the mechanisms have been arduously studied, however, the contribution of the sympathetic nervous system (SNS) in CCl₄-induced acute hepatotoxicity remains controversial. It is also known that either CCl₄ or SNS can affect systemic inflammatory responses. The aim of this study was to establish the effect of chemical sympathectomy with 6-hydroxydopamine (6-OHDA) in a mouse model of CCl₄-induced acute hepatotoxicity and systemic inflammatory response. Mice exposed to CCl₄ or vehicle were pretreated with 6-OHDA or saline. The serum levels of aminotransferases and alkaline phosphatase in the CCl₄-poisoning mice with sympathetic denervation were significantly lower than those without sympathetic denervation. With sympathetic denervation, hepatocellular necrosis and fat infiltration induced by CCl₄ were greatly decreased. Sympathetic denervation significantly attenuated CCl₄-induced lipid peroxidation in liver and serum. Acute CCl₄ intoxication showed increased expression of inflammatory cytokines/chemokines [eotaxin-2/CCL24, Fas ligand, interleukin (IL)-1α, IL-6, IL-12p40p70, monocyte chemoattractant protein-1 (MCP-1/CCL2), and tumor necrosis factor-α (TNF-α)], as well as decreased expression of granulocyte colony-stimulating factor and keratinocyte-derived chemokine. The overexpressed levels of IL-1α, IL-6, IL-12p40p70, MCP-1/CCL2, and TNF-α were attenuated by sympathetic denervation. Pretreatment with dexamethasone significantly reduced CCl₄-induced hepatic injury. Collectively, this study demonstrates that the SNS plays an important role in CCl₄-induced acute hepatotoxicity and systemic inflammation and the effect may be connected with chemical- or drug-induced hepatotoxicity and circulating immune response.

Ginseng extract and ginsenoside Rb1 attenuate carbon tetrachloride-induced liver fibrosis in rats

Background

Ginsenosides, the major bioactive compounds in ginseng root, have been found to have antioxidant, immunomodulatory and anti-inflammatory activities. This study investigated the effects of ginsenosides on carbon tetrachloride (CCl₄)-induced hepatitis and liver fibrosis in rats.

Methods

Male Sprague–Dawley rats were randomly divided into four groups: control, CCl₄, CCl₄ + 0.5 g/kg Panax ginseng extract and CCl₄ + 0.05 g/kg ginsenoside Rb1 groups. The treated groups were orally given Panax ginseng extract or ginsenoside Rb1 two weeks before the induction of liver injury for successive 9 weeks. Liver injury was induced by intraperitoneally injected with 400 ml/l CCl₄ at a dose of 0.75 ml/kg body weight weekly for 7 weeks. The control group was intraperitoneally injected with olive oil.

Results

The pathological results showed that ginsenoside Rb1 decreased hepatic fat deposition (2.65 ± 0.82 vs 3.50 ± 0.75, p <0.05) and Panax ginseng extract lowered hepatic reticular fiber accumulation (1.05 ± 0.44 vs 1.60 ± 0.39, p <0.01) increased by CCl₄. Plasma alanine aminotransferase and aspartate aminotransferase activities were increased by CCl₄ (p <0.01)_, and aspartate aminotransferase activity was decreased by Panax ginseng extract at week 9 (p <0.05). Exposure to CCl₄ for 7 weeks, the levels of plasma and hepatic triglycerides (p <0.01), hepatic cholesterol (p <0.01), interleukin-1β (p <0.01), prostaglandin E₂ (p <0.05), soluble intercellular adhesion molecule-1 (p <0.05), hydroxyproline (p <0.05), matrix metalloproteinase-2 (p <0.05) and tissue inhibitor of metalloproteinase-1 (TIMP-1) (p <0.01) were elevated, however, hepatic interleukin-10 level was lowered (p <0.05). Both Panax ginseng extract and ginsenoside Rb1 decreased plasma and hepatic triglyceride, hepatic prostaglandin E₂, hydroxyproline and TIMP-1 levels, and Panax ginseng extract further inhibited interleukin-1β concentrations (p <0.05).

Conclusions

Panax ginseng extract and ginsenoside Rb1 attenuate plasma aminotransferase activities and liver inflammation to inhibit CCl₄-induced liver fibrosis through down-regulation of hepatic prostaglandin E₂ and TIMP-1.

Urinary metabonomics study on toxicity biomarker discovery in rats treated with Xanthii Fructus

ETHNOPHARMACOLOGICAL RELEVANCE

Xanthii Fructus (XF) is commonly called "Cang-Erzi" in traditional Chinese medicine (TCM) and widely used for the treatment of sinusitis, headache, rheumatism, and skin itching. However, the clinical utilization of XF is relatively restricted owing to its toxicity.

AIM OF THE STUDY

To discover the characteristic potential biomarkers in rats treated with XF by urinary metabonomics.

MATERIALS AND METHODS

Ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was applied in the study. The total ion chromatograms obtained from control and different dosage groups were distinguishable by a multivariate statistical analysis method.

RESULTS

The greatest difference in metabolic profile was observed between high dosage group and control group, and the metabolic characters in rats treated with XF were perturbed in a dose-dependent manner. The metabolic changes in response for XF treatment were observed in urinary samples, which were revealed by orthogonal projection to latent structures discriminate analysis (OPLS-DA), and 10 metabolites could be served as the potential toxicity biomarkers. In addition, the mechanism associated with the damages of lipid per-oxidation and the metabolic disturbances of fatty acid oxidation were investigated.

CONCLUSIONS

These results indicate that metabonomics analysis in urinary samples may be useful for predicting the toxicity induced by XF.

Electron attachment to antipyretics: possible implications of their metabolic pathways

The empty-level structures and formation of negative ion states via resonance attachment of low-energy (0-15 eV) electrons into vacant molecular orbitals in a series of non-steroidal anti-inflammatory drugs (NSAIDs), namely aspirin, paracetamol, phenacetin, and ibuprofen, were investigated in vacuo by electron transmission and dissociative electron attachment (DEA) spectroscopies, with the aim to model the behavior of these antipyretic agents under reductive conditions in vivo. The experimental findings are interpreted with the support of density functional theory calculations. The negative and neutral fragments formed by DEA in the gas phase display similarities with the main metabolites of these commonly used NSAIDs generated in vivo by the action of cytochrome P450 enzymes, as well as with several known active agents. It is concluded that xenobiotic molecules which possess pronounced electron-accepting properties could in principle follow metabolic pathways which parallel the gas-phase dissociative decay channels observed in the DEA spectra at incident electron energies below 1 eV. Unwanted side effects as, e.g., hepatoxicity or carcinogenicity produced by the NSAIDs under study in human organism are discussed within the "free radical model" framework, reported earlier to describe the toxic action of the well-known model toxicant carbon tetrachloride.

Hot Water ExtractedLycium BarbarumandRehmannia GlutinosaInhibit Liver Inflammation and Fibrosis in Rats

Polysaccharide-rich Lycium barbarum and Rehmannia glutinosa have been considered to have immune-modulating activity. This study investigated the effects of water extracted Lycium barbarum and Rehmannia glutinosa (HE) on carbon tetrachloride ( CCl4)-induced liver injury in rats. Male Sprague-Dawley rats were randomly divided into: normal diet + peritoneal injection of olive oil (control), normal diet + CCl4injection ( CCl4), 1 × HE (0.05% HE for each) + CCl4(1 × HE), and 3 × HE (0.15% HE for each) + CCl4(3 × HE) groups. Rats were injected with 40% CCl4at a dose of 0.75 ml/kg body weight once a week for seven weeks, one week after herbal extract treatment. After eight week herbal extract treatment, pathohistological examination showed that both 1× and 3 × HE treatments diminished necrotic hepatocytes, chemoattraction of inflammatory cells, and liver fibrosis. Both 1× and 3 × HE treatments decreased plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, and reduced hepatic levels of pro-inflammatory cytokines — tumor necrosis factor-α and interleukin-1β — compared to CCl4treatment alone. The 1 × HE treatment increased hepatic anti-inflammatory cytokine IL-10 levels. Both the 1× and 3 × HE treatments suppressed liver fibrosis biomarkers — transforming growth factor-β1 and hydroxyproline. Therefore, treatment with water extracted Lycium barbarum and Rehmannia glutinosa (0.05% and 0.15% for each) for eight weeks protects against necrotic damage, indicated by decreases in plasma ALT and AST activities, and suppresses liver fibrosis by down-regulation of liver inflammation in rats with CCl4-induced liver injury.

Curcumin or saikosaponin a improves hepatic antioxidant capacity and protects against CCl4-induced liver injury in rats

Curcumin and saikosaponin a, the bioactive phytochemicals of turmeric and Bupleurum, act as antioxidants. This study investigated the effects of supplementation with curcumin and/or saikosaponin a on hepatic lipids and antioxidant status in rats with CCl(4)-induced liver injury. Male Sprague-Dawley rats were randomly divided into control, CCl(4), CCl(4) + curcumin (0.005%; CU), CCl(4) + saikosaponin a (0.004%; SS), and CCl(4) + curcumin + saikosaponin a (0.005% + 0.004%; CU+SS) groups. CCl(4) (40% in olive oil) was injected intraperitoneally at a dose of 0.75 mL/kg once a week. Curcumin and/or saikosaponin a was administered orally 1 week before CCl(4) injection for 8 weeks. The pathological results showed that liver fibrosis was ameliorated in the SS and CU+SS groups. After 8 weeks, supplementation with curcumin and/or saikosaponin a significantly decreased plasma alanine aminotransferase and aspartate aminotransferase activities, as well as plasma and hepatic cholesterol and triglyceride levels. The CU+SS group showed reversal of the impaired hepatic superoxide dismutase activity and an increase in total glutathione level. Supplementation with curcumin and/or saikosaponin a significantly improved hepatic antioxidant status and suppressed malondialdehyde formation. Therefore, supplementation with curcumin and/or saikosaponin a protects against CCl(4)-induced liver injury by attenuating hepatic lipids and lipid peroxidation and enhancing antioxidant defense. Curcumin and saikosaponin a had no additive effects on hepatoprotection except for greater improvement in the total glutathione level and antioxidant status.

Protective effects of Ginkgo biloba, Panax ginseng, and Schizandra chinensis extract on liver injury in rats

This study investigated the effects of the combined extracts of Ginkgo biloba, Panax ginseng, and Schizandra chinensis at different doses on hepatic antioxidant status and fibrosis in rats with carbon tetrachloride (CCl4)-induced liver injury. Male Sprague-Dawley rats (n = 8-12 per group) were divided into the control, CCl4, CCl4 + silymarin (0.35%), CCl4 + low-dose herbal extract (0.24% of Ginkgo biloba, Panax ginseng, and Schizandra chinensis extract at 1:1:1; LE), and CCl4 + high-dose herbal extract (1.20% of the same herbal extract; HE) groups. Silymarin or herbal extract was orally given to rats a week before chronic intraperitoneal injection with CCl4 for 6 weeks. The pathological results showed that herbal extract suppressed hepatic bile duct proliferation, and low-dose herbal extract inhibited liver fibrosis. Hepatic superoxide dismutase (SOD) activity was lower in the CCl4 group, but there was no difference in the silymarin or herbal extract treated groups compared to the control group. Hepatic catalase activity and the ratio of reduced to oxidized glutathione were significantly higher (p < 0.05) in the HE group than those in the CCl4 group. Silymarin and herbal extract reversed the impaired hepatic total antioxidant status (p < 0.05). Herbal extract partially reduced the elevated hepatic lipid peroxides. Hepatic transforming growth factor-beta1 (TGF-beta1) level decreased significantly (p < 0.05) in the LE group. Therefore, high-dose herbal extract improved hepatic antioxidant capacity through enhancing catalase activity and glutathione redox status, whereas low-dose herbal extract inhibited liver fibrosis through decreasing hepatic TGF-beta1 level in rats with CCl4-induced liver injury.

Protective effect of diphenylmethyl selenocyanate against CCl4-induced hepatic injury

Organoselenocyanates represent an important class of chemopreventive agent, which possess antioxidative, antimutagenic as well as cancer chemopreventive properties. The present study is an attempt to evaluate the protective effect of diphenylmethyl selenocyanate -- a synthetic organoselenocyanate against carbon tetrachloride (CCl(4))-induced hepatic damage in Swiss albino mice in vivo. Mice were pretreated with the Se-compound orally in a duration dependent manner (7 and 15 days) to observe its protective action against an acute toxic dose (24 h) of CCl(4) (single injection at a dose of 20 microl and 50 microl kg(-1) b.w.) that induced hepatic necrosis and caused DNA damage (strand breaks) in the hepatocytes. This study revealed that pretreatment with the Se-compound reduced the extent of massive hepatic necrosis in a duration dependent manner, but it had no modulatory effect on hepatocellular apoptosis caused by acute toxic doses of CCl(4). It was also found that the Se-compound could significantly (P < 0.01) prevent the CCl(4)-induced elevation of DNA damage in hepatocytes measured by comet assay in a duration dependent manner. So these findings will further strengthen the view that organoselenocyanate is an effective chemopreventive agent against acute hepatic damage, caused by halogenated alkanes such as CCl(4).

Inhibiting proteasomal degradation of microsomal triglyceride transfer protein prevents CCl4-induced steatosis

Carbon tetrachloride (CCl(4)) interferes with triglyceride secretion and causes steatosis, fibrosis, and necrosis. In mice, CCl(4) decreased plasma triglyceride-rich lipoproteins, increased cellular lipids, and reduced microsomal triglyceride transfer protein (MTP) without diminishing mRNA levels. Similarly, CCl(4) decreased apoB-lipoprotein production and MTP activity but had no effect on mRNA levels in primary enterocytes and colon carcinoma and hepatoma cells. CCl(4) did not affect MTP synthesis but induced post-translational degradation involving ubiquitinylation and proteasomes in McA-RH7777 cells. By contrast, MTP inhibitor increased cellular lipids without affecting MTP protein. MTP was covalently modified when cells were incubated with (14)CCl(4). This modification was prevented by the inhibition of P450 oxygenases, indicating that CCl(3)(.) generated by these enzymes targets MTP for degradation. To determine whether inhibition of proteolysis could prevent CCl(4) toxicity, mice were fed with CCl(4) with or without lactacystin. Lactacystin increased ubiquitinylated MTP and prevented lipid accumulation in tissues. Thus, CCl(4) induces post-translational degradation without affecting lipid transfer activity, whereas MTP antagonist inhibits lipid transfer activity without causing its destruction. These studies identify MTP as a major target of CCl(4) and its degradation as a novel mechanism involved in the onset of steatosis, suggesting that inhibition of proteolysis may prevent some forms of steatosis.

A temporal study on the histopathological, biochemical and molecular responses of CCl(4)-induced hepatotoxicity in Cyp2e1-null mice

Previous study using Cyp2e1-null mice showed that Cyp2e1 is required in CCl(4)-induced liver injury at 24h, what remains unclear are the temporal changes in liver damage and the spectrum of genes involved in this process. We investigated the time-dependent liver changes that occurred at morphological, histopathological, biochemical and molecular levels in both Cyp2e1(+/+) and Cyp2e1(-/-) mice after treating with either corn oil or CCl(4) (1 ml/kg) for 2, 6, 12, 24 and 48 h. A pale orange colored liver, indicative of fatty infiltration, was observed in Cyp2e1(+/+) mice treated with CCl(4) for 24 and 48 h, while the Cyp2e1(+/+) mice treated with corn oil and Cyp2e1(-/-) mice treated with either corn oil or CCl(4) showed normal reddish brown colored liver. Ballooned hepatocytes with multiple vacuoles in their cytoplasm were observed in the livers of Cyp2e1(+/+) mice 24 and 48 h after treating with CCl(4). The levels of serum alanine aminotransferase and aspartate aminotransferase, markers for liver injury, were significantly higher at 12h, peaked at 24h and gradually decreased at 48 h after CCl(4) intoxication. In contrast, this kind of damage was not apparent in the Cyp2e1(-/-) mice treated with CCl(4). Altered expressions of genes related to liver cirrhosis, apoptosis, oxidative stress, xenobiotic detoxification, lipid metabolism, chemsensory signaling or tumorigenesis, structural organization, regeneration and inflammatory response were identified, and the time-dependent changes in expression of these genes were varied. Overall, the present study provides insights into the mechanism of CCl(4)-induced hepatotoxicity in animal models.

Role of cytochrome P450 in phospholipase A2- and arachidonic acid-mediated cytotoxicity

Phospholipases A2 (PLA2) comprise a set of extracellular and intracellular enzymes that catalyze the hydrolysis of the sn-2 fatty acyl bond of phospholipids to yield fatty acids and lysophospholipids. The PLA2 reaction is the primary pathway through which arachidonic acid (AA) is released from phospholipids. PLA2s have an important role in cellular death that occurs via necrosis or apoptosis. Several reports support the hypothesis that unesterified arachidonic acid in cells is a signal for the induction of apoptosis. However, most of the biological effects of arachidonic acid are attributable to its metabolism by mainly three different groups of enzymes: cytochromes P450, cyclooxygenases, and lipoxygenases. In this review we will focus on the role of cytochrome P450 in AA metabolism and toxicity. The major pathways of arachidonic acid metabolism catalyzed by cytochrome P450 generate metabolites that are subdivided into two groups: the epoxyeicosatrienoic acids, formed by CYP epoxygenases, and the arachidonic acid derivatives that are hydroxylated at or near the omega-terminus by CYP omega-oxidases. In addition, autoxidation of AA by cytochrome P450-derived reactive oxygen species produces lipid hydroperoxides as primary oxidation products. In some cellular models of toxicity, cytochrome P450 activity exacerbates PLA2- and AA-dependent injury, mainly through the production of oxygen radicals that promote lipid peroxidation or production of metabolites that alter Ca2+ homeostasis. In contrast, in other situations, cytochrome P450 metabolism of AA is protective, mainly by lowering levels of unesterified AA and by production of metabolites that activate antiapoptotic pathways. Several lines of evidence point to the combined action of phospholipase A2 and cytochrome P450 as central in the mechanism of cellular injury in several human diseases, such as alcoholic liver disease and myocardial reperfusion injury. Inhibition of specific PLA2 and cytochrome P450 isoforms may represent novel therapeutic strategies against these diseases.

Differential gene expression profiles in the steatosis/fibrosis model of rat liver by chronic administration of carbon tetrachloride

Global gene expression profile was analyzed by microarray analysis of rat liver RNA after chronic carbon tetrachloride (CCl(4)) administration. Rats received 0.5 ml CCl(4)/kg three times a week, and the liver samples were obtained after 0, 30, 60, and 90 days of injection. Histopathologic studies of liver tissues enabled the classification of the CCl(4) effect into mild and severe fatty liver/steatosis (30 and 60 days, respectively) and fibrosis/cirrhosis (90 days) stages. The expression levels of 4,900 clones on a custom rat gene microarray were analyzed and the results were confirmed by semi-quantitative RT-PCR. Four hundred thirty-eight clones were differentially expressed with more than a 1.625-fold difference (which equals 0.7 in log2 scale) at one or more time points. Multiple genes involved in lipid metabolism and ribosome biogenesis showed differential transcript levels upon chronic CCl(4) administration, which was previously seen in acute rat model as well. In addition, a total of 149 clones were identified as fibrosis/cirrhosis-specific genes by either fold changes or Significance Analysis of Microarrays. In conclusion, we report microarray analysis results in rat liver upon chronic CCl(4) administration with a full chronological profile that not only covered fatty liver/steatosis but also later points of fibrosis/cirrhosis. These data will provide the insight of specific gene expression profiles that is implicated in the multistep process of fatty liver/steatosis and fibrosis/cirrhosis after chronic hepatotoxin exposure.

Comprehensive analysis of differential gene expression profiles on carbon tetrachloride-induced rat liver injury and regeneration

Microarray analysis of RNA from carbon tetrachloride (CCl4)-administered rat livers was performed at various time points to establish a global gene expression profile during injury and regeneration stages. A single dose of 1 ml/kg of CCl4 was given by ip injection, and the liver samples were obtained after 6, 24, 48 h, and 2 weeks. Histopathologic, biochemical, and immunohistochemical studies enabled the classification of the CCl4 effect into injury (6 and 24 h) and regeneration (48 h and 2 weeks) stages. The expression levels of 5180 clones on a custom rat gene microarray were analyzed and 587 clones yielded changeable gene expression on at least single time point. One hundred seventy-nine clones were classified as injury-specific clones, while 38 clones as regeneration-specific clones. Characteristic gene expression profiles could be associated with CCl4-induced gene expression with the disruption of lipid metabolism, which is known to cause the fatty liver induced by CCl4 treatment. In addition, induction of the transcripts for many ribosomal proteins was detected during the injury stage, particularly at the 24-h time point, despite the previous report of decreased protein synthesis rate upon CCl4 treatment. Several genes with known functions were also identified as CCl4-regulated genes. In conclusion, we established a global gene expression profile utilizing microarray analysis in rat liver upon acute CCl4 administration with a full chronological profile that not only covers injury stage but also later points of regeneration stage.

Albumin-expressing hepatocyte-like cells develop in the livers of immune-deficient mice that received transplants of highly purified human hematopoietic stem cells

Rodent bone marrow cells can contribute to liver. If these findings are applicable to humans, marrow stem cells could theoretically be harvested from a patient and used to repair his/her damaged liver. To explore this potential, CD34(+) or highly purified CD34(+)CD38(-)CD7(-) human hematopoietic stem cells from umbilical cord blood and bone marrow were transplanted into immunodeficient mice. One month after transplantation, carbon tetrachloride (CCl(4)) was administered into the mice to induce liver damage and hepatocyte proliferation. Mice were analyzed in comparison with CCl(4)-injured mice that did not receive transplants and noninjured controls that received transplants with the same stem cell populations, one month after liver damage. Human-specific albumin mRNA and protein were expressed in the mouse liver and human albumin was detected in the serum of mice that had received CCl(4) injury. Human alpha-fetoprotein was never expressed, but in some mice, human cytokeratin 19 was expressed, which may indicate bile duct development in addition to the albumin-secreting hepatocyte-like cells. Human albumin was not expressed in the starting stem cell populations in injured mice that did not receive transplants nor in noninjured mice that had received transplants of human stem cells. Human albumin expression was detected only in CCl(4)-treated mice that received transplants of human stem cells, and recovery was increased by administration of human hepatocyte growth factor 48 hours after the CCl(4)-mediated liver injury. Our studies provide evidence that human "hematopoietic" stem/progenitor cell populations have the capacity to respond to the injured liver microenvironment by inducing albumin expression.