Influence of aminoguanidine on parameters of liver injury and regeneration induced in rats by a necrogenic dose of thioacetamide

Synergistic effect of aminoguanidine and l-carnosine against thioacetamide-induced hepatic encephalopathy in rats: behavioral, biochemical, and ultrastructural evidence

Hepatic encephalopathy depicts the cluster of neurological alterations that occur during acute or chronic hepatic injury. Hyperammonemia, inflammatory injury, and oxidative stress are the main predisposing factors for the direct and indirect changes in cerebral metabolism causing encephalopathy. The aim of this study was to evaluate the possible synergistic effect between aminoguanidine (AG; 100 mg/kg, p.o.) and l-carnosine (CAR; 200 mg/kg, p.o.) on hepatic encephalopathy that was induced by thioacetamide (TAA; 100 mg/kg, i.p.) administered three times weekly for six weeks. Behavioral changes, biochemical parameters, histopathological analysis, and immunohistochemical and ultrastructural studies were conducted 24 h after the last treatment. Combining AG with CAR improved TAA-induced locomotor impairment and motor incoordination evidenced by reduced locomotor activity and decline in motor skill performance, as well as ameliorated cognitive deficits. Moreover, both drugs restored the levels of serum hepatic enzymes and serum and brain levels of ammonia. In addition, the combination significantly modulated hepatic and brain oxidative stress biomarkers, inflammatory cytokines, and cleaved caspase-3 expression. Furthermore, they succeeded in activating nuclear erythroid 2-related factor 2 (Nrf2) expression and heme oxygenase-1 (HO-1) activity and ameliorating markers of hepatic encephalopathy, including hepatic necrosis and brain astrocyte swelling. This study shows that combining AG with CAR exerted a new intervention for hepatic and brain damage in hepatic encephalopathy due to their complementary antioxidant, anti-inflammatory effects and hypoammonemic effects via Nrf2/HO-1 activation and NO inhibition.

Thioacetamide-induced liver injury: protective role of genistein

This study aimed to investigate the possible protective effects of genistein (GEN), a phytoestrogen, on the liver injury induced in rats by thioacetamide (TTA; 200.0 mg·(kg body mass)(-1); administered 3 times a week by intraperitoneal injection). GEN (0.5, 1.0, or 2.0 mg·(kg body mass)(-1); by subcutaneous injection) was concurrently administered on a daily basis for 8 weeks, and its effects were evaluated 24 h after the administration of the last dose. The results from this study revealed that TTA-induced liver injury was associated with massive changes in the serum levels of liver biomarkers, oxidative stress markers, and liver inflammatory cytokines. Treatment of TAA-induced liver injury in rats with GEN decreased the elevated serum levels of aspartate aminotransferase, alanine aminotransferase, and total and direct bilirubin, and increased the serum level of albumin. GEN also restored the liver levels of malondialdehyde and reduced glutathione, as well as tumor necrosis factor-alpha, interleukin-6, and their modulator nuclear factor kappa-light-chain-enhancer of activated B cells. From our results, it can be concluded that GEN attenuates the liver injury-induced in rats with TAA, and this hepatoprotective role is attributed to its anti-inflammatory and antioxidant properties.

Polyploidization in liver tissue

Polyploidy (alias whole genome amplification) refers to organisms containing more than two basic sets of chromosomes. Polyploidy was first observed in plants more than a century ago, and it is known that such processes occur in many eukaryotes under a variety of circumstances. In mammals, the development of polyploid cells can contribute to tissue differentiation and, therefore, possibly a gain of function; alternately, it can be associated with development of disease, such as cancer. Polyploidy can occur because of cell fusion or abnormal cell division (endoreplication, mitotic slippage, or cytokinesis failure). Polyploidy is a common characteristic of the mammalian liver. Polyploidization occurs mainly during liver development, but also in adults with increasing age or because of cellular stress (eg, surgical resection, toxic exposure, or viral infections). This review will explore the mechanisms that lead to the development of polyploid cells, our current state of understanding of how polyploidization is regulated during liver growth, and its consequence on liver function.

Curcumin protects against thioacetamide-induced hepatic fibrosis by attenuating the inflammatory response and inducing apoptosis of damaged hepatocytes

Inflammation and hepatic stellate cell (HSC) activation are the most crucial steps in the formation of hepatic fibrosis. Hepatocytes damaged by viral or bacterial infection, alcohol or toxic chemicals initiate an inflammatory response that activates collagen production by HSCs. Recent studies indicate curcumin has liver-protective effects due to its anti-inflammatory, antioxidant and anticancer activities; however, the mechanisms are not well understood. In this study, we show that curcumin protected against hepatic fibrosis in BALB/c mice in vivo by inhibiting HSC activation, inflammatory responses and inducing apoptosis of damaged hepatocytes. Using the thioacetamide (TAA)-induced hepatic fibrosis animal model, we found that curcumin treatment up-regulated P53 protein expression and Bax messenger RNA (mRNA) expression and down-regulated Bcl-2 mRNA expression. Together, these responses increased hepatocyte sensitivity to TAA-induced cytotoxicity and forced the damaged cells to undergo apoptosis. Enhancing the tendency of damaged hepatocytes to undergo apoptosis may be the protective mechanism whereby curcumin suppresses inflammatory responses and hepatic fibrogenesis. These results provide a novel insight into the cause of hepatic fibrosis and the cytoprotective effects curcumin has on hepatic fibrosis suppression.

Hepatocytes polyploidization and cell cycle control in liver physiopathology

Most cells in mammalian tissues usually contain a diploid complement of chromosomes. However, numerous studies have demonstrated a major role of "diploid-polyploid conversion" during physiopathological processes in several tissues. In the liver parenchyma, progressive polyploidization of hepatocytes takes place during postnatal growth. Indeed, at the suckling-weaning transition, cytokinesis failure events induce the genesis of binucleated tetraploid liver cells. Insulin signalling, through regulation of the PI3K/Akt signalling pathway, is essential in the establishment of liver tetraploidization by controlling cytoskeletal organisation and consequently mitosis progression. Liver cell polyploidy is generally considered to indicate terminal differentiation and senescence, and both lead to a progressive loss of cell pluripotency associated to a markedly decreased replication capacity. Although adult liver is a quiescent organ, it retains a capacity to proliferate and to modulate its ploidy in response to various stimuli or aggression (partial hepatectomy, metabolic overload (i.e., high copper and iron hepatic levels), oxidative stress, toxic insult, and chronic hepatitis etc.). Here we review the mechanisms and functional consequences of hepatocytes polyploidization during normal and pathological liver growth.

Aminoguanidine impedes human pancreatic tumor growth and metastasis development in nude mice

AIM: To study the action of aminoguanidine on pancreatic cancer xenografts in relation to cell proliferation, apoptosis, redox status and vascularization.

METHODS: Xenografts of PANC-1 cells were developed in nude mice. The animals were separated into two groups: control and aminoguanidine treated. Tumor growth, survival and appearance of metastases were determined in vivo in both groups. Tumors were excised and ex vivo histochemical studies were performed. Cell growth was assessed by Ki-67 expression. Apoptosis was studied by intratumoral expression of B cell lymphoma-2 protein (Bcl-2) family proteins and Terminal deoxynucleotidyl transferase biotin-dUTP Nick End Labeling (Tunel). Redox status was evaluated by the expression of endothelial nitric oxide synthase (eNOS), catalase, copper-zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD) and glutathione peroxidase (GPx). Finally, vascularization was determined by Massons trichromic staining, and by VEGF and CD34 expression.

RESULTS: Tumor volumes after 32 d of treatment by aminoguanidine (AG) were significantly lower than in control mice (P < 0.01). Median survival of AG mice was significantly greater than control animals (P < 0.01). The appearance of both homolateral and contralateral palpable metastases was significantly delayed in AG group. Apoptotic cells, intratumoral vascularization (trichromic stain) and the expression of Ki-67, Bax, eNOS, CD34, VEGF, catalase, CuZnSOD and MnSOD were diminished in AG treated mice (P < 0.01), while the expression of Bcl-2 and GPx did not change.

CONCLUSION: The antitumoral action of aminoguanidine is associated with decreased cell proliferation, reduced angiogenesis, and reduced expression of antioxidant enzymes.

A toxicogenomics approach for early assessment of potential non-genotoxic hepatocarcinogenicity of chemicals in rats

For assessing carcinogenicity in animals, it is difficult and costly, an alternative strategy has been desired. We explored the possibility of applying a toxicogenomics approach by using comprehensive gene expression data in rat liver treated with various compounds. As prototypic non-genotoxic hepatocarcinogens, thioacetamide (TAA) and methapyrilene (MP) were selected and 349 commonly changed genes were extracted by statistical analysis. Taking both compounds as positive with six compounds, acetaminophen, aspirin, phenylbutazone, rifampicin, alpha-naphthylisothiocyanate, and amiodarone as negative, prediction analysis of microarray (PAM) was performed. By training and 10-fold cross validation, a classifier containing 112 probe sets that gave an overall success rate of 95% was obtained. The validity of the present discriminator was checked for 30 chemicals. The PAM score showed characteristic time-dependent increases by treatment with several non-genotoxic hepatocarcinogens, including TAA, MP, coumarin, ethionine and WY-14643, while almost all of the non-carcinogenic samples were correctly predicted. Measurement of hepatic glutathione content suggested that MP and TAA cause glutathione depletion followed by a protective increase, but the protective response is exhausted during repeated administration. Therefore, the presently obtained PAM classifier could predict potential non-genotoxic hepatocarcinogenesis within 24 h after single dose and the inevitable pseudo-positives could be eliminated by checking data of repeated administrations up to 28 days. Tests for carcinogenicity using rats takes at least 2 years, while the present work suggests the possibility of lowering the time to 28 days with high precision, at least for a category of non-genotoxic hepatocarcinogens causing oxidative stress.

Hepatocytes are protected by herb Phyllanthus niruri protein isolate against thioacetamide toxicity

The herb, Phyllanthus niruri has been known to possess protective activity against various drugs and toxins induced hepatic disorders. Present study was conducted to evaluate the role of the protein isolate of the herb against thioacetamide (TAA)-induced cytotoxicity in mice hepatocytes. In vitro cell viability, lactate dehydrogenase (LDH) and alanine amino transferase (ALT) leakage were measured as the indicators of cell damage. In addition, measurement of the level of non-protein thiol, glutathione (GSH); activities of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) as well as the extent of lipid peroxidation were carried out to evaluate the prooxidant-antioxidant status of the cell. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay was performed to determine the radical scavenging activity of the protein isolate. Results showed that the administration of the protein isolate prior to TAA exposure significantly reduced the release of LDH and ALT leakage and enhanced the cell viability in a dose-dependent manner in hepatocytes. Besides, the protein isolate appeared to prevent the alterations in GSH levels and activities of the anti-oxidant enzymes related to prooxidant-antioxidant status of hepatocytes. It also reduced the TAA-induced lipid peroxidation significantly as demonstrated by the reduction of malondialdehyde (MDA) production. DPPH radical scavenging assay showed that the protein isolate possessed radical scavenging activity. Combining, the data suggest that the protein isolate could protect hepatocytes from TAA-induced cellular injury probably by its antioxidative and radical scavenging properties.

Enteral nutrition affects nitric oxide production in peripheral blood and liver after a postoperative lipopolysaccharide-induced endotoxemia in rats

OBJECTIVES

Sepsis is a common complication in the early postoperative period, leading to the augmentation of oxidative and nitrosative stresses. The present study investigated the role of enteral nutrition on nitric oxide (NO) production after a lipopolysaccharide (LPS)-induced endotoxemia as an index of nitrosative stress.

METHODS

Fifty rats were subjected to midline laparotomy and feeding gastrostomy. Ten rats served as controls after recovering from operative stress. The remaining rats received, through gastrostomy, enteral nutrition or placebo feeding for 24 h, after which they were injected intraperitoneally with LPS or equal volume of saline. Two hours later blood and liver tissue were collected. NO production was quantified in serum samples and homogenates of liver tissue by a modification of Griess's reaction. NO synthase (NOS) mRNA expression was examined in homogenate of liver tissue by reverse transcription-polymerase chain reaction.

RESULTS

The operation significantly increased basal NO production in rat serum. LPS induced a further significant increase of NO levels. Enteral feeding of rats significantly decreased NO levels in both groups. In contrast, enteral nutrition was found to increase significantly NO levels in liver homogenates from rats treated with LPS. A constitutive endothelial NOS mRNA expression was found in liver tissue, whereas LPS administration induced inducible NOS mRNA expression in liver tissue regardless of enteral feeding.

CONCLUSION

These findings indicate that early enteral feeding leads to a reduction in circulating NO levels induced by operation and endotoxemia, but increases hepatic NO levels in endotoxemia probably by the effect of LPS-induced inducible NOS on the increased L-arginine uptake.

Attenuation of cadmium chloride induced cytotoxicity in murine hepatocytes by a protein isolated from the leaves of the herb Cajanus indicus L

Cadmium has been recognized as a strong environmental pollutant. Exposure to this heavy metal occurs through the intake of foodstuffs, drinking water and also via the inhalation of air. Present study was conducted to evaluate the protective effect of a 43 kDa protein, isolated from the leaves of the herb Cajanus indicus, against cadmium-induced cytotoxicity in hepatocytes. For this study, cadmium chloride (CdCl(2)) has been used as the source of cadmium. Treatment of hepatocytes with 800 microM CdCl(2) for 3 h caused significant reduction in cell viability in association with the increased levels of glutamate pyruvate transaminase (GPT) and alkaline phosphatase (ALP) leakage. The activities of the antioxidant enzymes, superoxide dismutase, catalase (CAT), glutathione-S-transferase and glutathione reductase, and the levels of cellular metabolites, reduced glutathione (GSH) as well as total thiols have also been decreased under the same treatment. In addition, the toxin enhanced the levels of the lipid peroxidation end products and oxidized glutathione (GSSG). Incubation of hepatocytes with the protein at a dose of 0.1 mg/ml for 3 h prior to the toxin treatment (at a dose of 800 microM for 3 h) restored the activities of all the antioxidant enzymes, the levels of GSH, total thiols, cell viability and also attenuated the increased levels of GPT, ALP, lipid peroxidation and GSSG. In addition, the protein resisted CdCl(2) induced alterations of all the parameters when applied in combination with CdCl(2). Effects of a known antioxidant, vitamin E, and a non-relevant protein, bovine serum albumin against CdCl(2) induced cytotoxicity have also been included in the study. Combining all, we would like to say that the protein possessed protective activity against CdCl(2) induced cytotoxicity in mouse hepatocytes probably via its antioxidant property.

Role of hepatic nitric oxide synthases in rats with thioacetamide-induced acute liver failure and encephalopathy

BACKGROUND

Hepatic encephalopathy is neuropsychiatric derangement secondary to hepatic decompensation or portal-systemic shunting. Nitric oxide (NO) synthase inhibition aggravates encephalopathy and increases mortality in rats with thioacetamide (TAA)-induced acute liver failure, suggesting a protective role of NO. This study investigated the roles of endothelium-derived constitutive NO synthase (eNOS) and inducible NOS (iNOS) in the liver of rats with fulminant hepatic failure and encephalopathy.

METHODS

Male Sprague-Dawley rats (300-350 g) were randomized to receive TAA 350 mg/kg/day, by intraperitoneal injection or normal saline for 3 days. Severity of encephalopathy was assessed with the Opto-Varimex animal activity meter. Plasma levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, and bilirubin were measured. Hepatic iNOS and eNOS RNA and protein expressions were assessed by reverse transcription-polymerase chain reaction and Western blot analyses, respectively.

RESULTS

The TAA group showed lower motor activity counts than the normal saline group. Hepatic eNOS, but not iNOS, mRNA and protein expressions were enhanced in the TAA group. In addition, hepatic eNOS mRNA expression was negatively correlated with total movement but positively correlated with ALT and AST. Protein expression of hepatic eNOS was positively correlated with ALT, AST and bilirubin.

CONCLUSION

Upregulation of hepatic eNOS was observed in rats with TAA-induced fulminant hepatic failure and encephalopathy, which might play a regulatory role.

Involvement of P53 and Bax/Bad triggering apoptosis in thioacetamide-induced hepatic epithelial cells

AIM: Thioacetamide (TAA) has been used in studying liver fibrosis and cirrhosis, however, the mechanisms of TAA-induced apoptosis in liver are still unclear. The hepatic epithelial cell line clone 9 was cultured and treated with TAA to investigate the causes of cell death.

METHODS: The cell viability of TAA-induced clone 9 cells was determined using MTT assay. Total cellular GSH in TAA-induced clone 9 cells was measured using a slight modification of the Tietze assay. The activity of caspase 3 in TAA-induced clone 9 cells was monitored by the cleavage of DEVD-p-nitroanaline. TUNEL assay and flow cytometry were applied for the determination of DNA fragmentation and the proportion of apoptosis in TAA-induced clone 9 cells, respectively. The alterations of caspase 3, Bad, Bax and Phospho-P53 contents in TAA-induced clone 9 cells were measured by Western blot.

RESULTS: The experimental data indicated that TAA caused rat hepatic epithelial cell line clone 9 cell death in a dose-and time-dependent manner; 60% of the cells died (MTT assay) within 24 h after 100 mg/L TAA was applied. Apoptotic cell percentage (TUNEL assay) and caspase 3 activities were highest after 100 mg/L TAA was added for 8 h. The release of GSH and the elevation in caspase content after TAA treatment resulted in clone 9 cell apoptosis via oxidative stress and a caspase-dependent mechanism. The phospho-p53, Bax and Bad protein expressions in clone 9 cells were increased after TAA treatment.

CONCLUSION: These results reveal that TAA activates p53, increases caspase 3, Bax and Bad protein contents, perhaps causing the release of cytochrome c from mitochondria and the disintegration of membranes, leading to apoptosis of cells.

A 43 kDa protein from the herb Cajanus indicus L. protects thioacetamide induced cytotoxicity in hepatocytes

The aim of this study was to investigate the role of a hepatoprotective protein isolated from the herb Cajanus indicus L. on thioacetamide (TAA) induced toxicity in isolated mouse hepatocytes. In vitro cell viability, lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and total protein leakage were measured as the indicator of cell damage. The amount of glutathione (GSH) and lipid peroxidation were also measured to determine the oxidative status of the cells. The reduced cell viability in TAA treated hepatocytes was almost completely recovered upon protein treatment. LDH, ALT and total protein secretion outside the cells after TAA treatment confirmed the cell membrane damage. Incubation of hepatocytes with the protein prior to TAA administration significantly prevented the cell membrane damage as revealed from less LDH, ALT and total protein leakage. TAA depleted endogenous antioxidant GSH and increased membrane lipid peroxidation in hepatocytes. The protein had very prominent effect in altering the GSH level and lipid peroxidation. The protein exhibited all these cytoprotective effects in a dose-dependent manner. Besides, measurement of DPPH radical scavenging activity showed that the protein could scavenge free radicals. In addition, the protein resisted TAA induced alterations of various effects when applied in combination with TAA. The cytoprotective activity of the protein was found to be comparable with alpha-tocopherol, a well-known antioxidant. Results suggest that the protein from C. indicus can act as a hepatoprotector and primary antioxidant against TAA-induced cytotoxicity in mouse hepatocytes.

Acetaldehyde does not inhibit glutathione peroxidase and glutathione reductase from mouse liver in vitro

Acetaldehyde, the primary ethanol metabolite, has been implicated in the pathogenesis of alcoholic liver disease, but the mechanism involved is still under investigation. This study aims at the search for direct in vitro effects of different concentrations of acetaldehyde (30, 100 and 300microM) on the activities of glutathione reductase (GR), glutathione peroxidase (GPx) from liver supernatants, and the thiol-peroxidase activity of ebselen. They did not change after pre-incubation with acetaldehyde, which suggests that acetaldehyde does not have any direct effect. Nor were direct effects of acetaldehyde toward thiols, such as dithioerythritol and glutathione (GSH), observed either, even though GSH - measured as non-protein thiols from liver supernatants - were oxidized in the presence of acetaldehyde. In addition, acetaldehyde (up to 300microM) significantly oxidized GSH when incubated in the presence of commercially available gamma-glutamyltranspeptidase (GGT), but not in the presence of glutathione-S-transferase. The interaction between ebselen and GSH was also evaluated in an attempt to better understand the possible link between acetaldehyde and nucleophilic selenol groups. The formation and stability of ebselen intermediaries, produced in the chemical interaction between GSH and ebselen, were not affected by acetaldehyde either. Overall, the acetaldehyde oxidation of hepatic low-molecular thiols depends on mouse liver constituents and GGT is proposed as an important enzyme involved in this phenomenon. Thiol depletion, a phenomenon usually observed in the livers of alcoholic patients, can be related to GSH metabolism, and the involvement of GGT may reflect a molecular mechanism involved in thiol oxidation.

A 43-kDa protein from the leaves of the herb Cajanus indicus L. modulates chloroform induced hepatotoxicity in vitro

A 43-kDa protein isolated from the leaves of the herb Cajanus indicus L. has been shown to possess a protective role against drug- and toxin- induced hepatotoxicity both in vivo and in vitro. The current study was conducted to evaluate its protective action against chloroform (CHCl3)-induced cytotoxicity in hepatocytes. Cellular viability and biochemical parameters such as glutamate pyruvate transaminase (GPT) and lactate dehydrogenase (LDH) release from the cells were measured. In addition, the antioxidant effect of the protein was investigated from the DPPH radical scavenging assay and by determining the levels of the antioxidant enzyme catalase (CAT), cellular reserves of reduced glutathione (GSH), and lipid peroxidation end products (measured as TBARS). Treatment of the cells with CHCl3 decreased cellular viability and increased GPT and LDH. Cells treated with the protein before and immediately after CHCl3 application showed a marked improvement in their viability and reduced leakage of GPT and LDH. The levels of CAT and GSH, which were diminished in cells treated with CHCl3, were restored by protein treatment. CHCl3 induced enhancement of lipid peroxidation in hepatocytes was significantly reduced by protein treatment. Results of the DPPH assay with the protein showed its radical scavenging activity. This data suggests that the protein possesses protective activity against CHCl3-induced cytotoxicity in hepatocytes and protects against CHCl3-induced hepatic damage.

Effects of TVE application during 70% hepatectomy on regeneration capacity of rats1

BACKGROUND

For adequate control of excess bleeding during liver resection, total vascular exclusion (TVE) is preferred by surgeons, especially when the tumor is located in the posterior liver lobes or near the cava. To the authors' knowledge, the effects of TVE technique on the postoperative liver regeneration process have not thus far been evaluated yet in the literature. This study was planned to compare the effects of liver resections performed either with portal pedicle clamping or with TVE on the regeneration process.

MATERIALS AND METHODS

Seventy percent hepatectomy was performed with portal pedicle clamping (n=10, Group A) or with TVE (n=10, Group B) in rats. At 48 h after resection, sampling was performed for the measurement of serum transaminase, alkaline phosphatase (ALP), tissue malondialdehyde (MDA), and glutathione (GSH) levels. Liver regeneration rate, proliferating cell nuclear antigen (PCNA) labeling, and mitotic indices were also evaluated.

RESULTS

Liver injury determinants (serum transaminases, ALP, and tissue MDA levels) were found significantly higher in group B than in group A. Liver regeneration rate, liver GSH levels, PCNA labeling index, and mitotic index were significantly lower in group B than in group A.

CONCLUSIONS

The injury during TVE seems to be greater than during resection with portal pedicle clamping. The negative effect of this oxidative damage may influence the regenerative capacity of the remnant liver tissue.

The effects of selective nitric oxide synthase blocker on survival, mesenteric blood flow and multiple organ failure induced by zymosan

BACKGROUND

Circulatory failure in multiple organ dysfunction syndromes (MODS) is characterized with systemic vasodilation, diminished blood flow to various vascular beds. The aim of this study was to investigate the effects of selective inhibition of nitric oxide on the mesenteric arterial blood flow (MABF), survival and organ injury of the liver, kidney, lung and spleen in zymosan-induced MODS.

MATERIALS AND METHODS

Forty Swiss albino mice (20-40 g), 7 to 9 weeks old, were obtained. Animals were randomly divided into four groups. The first group were treated intraperitoneally (i.p) with vehicle (saline) and served as a sham group for aminoguanidine (AG) (n=10). The second group was treated with zymosan (500 mg/kg, suspended in saline solution, i.p). The mice in the third and fourth group received AG (15 mg/kg) 1 h and 6 h after zymosan or saline administration, respectively. Eighteen hours after the administration of zymosan, animals were assessed for MODS described subsequently. The signals from the flowmeter were also recorded on mesenteric arterial blood flow values.

RESULTS

In zymosan-treated animals, the MABF was significantly lower than that of solvent (saline)-treated controls (ml min(-1), controls: 4.6 +/- 0.6; zymosan: 1.6 +/- 0.9, P <0.05). When animals were treated with AG, there were no significant differences in MABF values between AG group and solvent (saline)-treated control group. However AG prevented zymosan-induced mesenteric MABF decrease. Treatment with aminoguanidine also decreased mortality.

CONCLUSION

AG is capable of inhibiting both the induction and the activity of the already iNOS; it remains a potential therapeutic agent in patients with MODS.

Emblica officinalis reverses thioacetamide-induced oxidative stress and early promotional events of primary hepatocarcinogenesis

Emblica officinalis is widely used in Indian medicine for the treatment of various diseases. In the present study, it was found that fruits of E. officinalis inhibit thioacetamide-induced oxidative stress and hyper-proliferation in rat liver. The administration of a single necrotic dose of thioacetamide(6.6 mM kg(-1)) resulted in a significant (P < 0.001) increase in serum glutamic oxaloacetic transaminase(SGOT), serum glutamic pyruvic transaminase (SGPT) and gamma-glutamyl transpeptidase (GGT) levels compared with saline-treated control values. Thioacetamide caused hepatic glutathione (GSH) depletion and a concomitant increase in malanodialdehyde (MDA) content. It also resulted in an increase(P < 0.001) in the activity of glutathione-S-transferase (GST), glutathione reductase (GR), glucose 6-phosphate dehydrogenase (G6PD) and a decrease in glutathione peroxidase (GPx) activity (P < 0.001). Hepatic ornithine decarboxylase activity and thymidine incorporation in DNA were increased bythioacetamide administration. Prophylactic treatment with E. officinalis for 7 consecutive days before thioacetamide administration inhibited SGOT, SGPT and GGT release in serum compared with treated control values. It also modulated the hepatic GSH content and MDA formation. The plant extract caused a marked reduction in levels of GSH content and simultaneous inhibition of MDA formation. E. officinalis also caused a reduction in the activity of GST, GR and G6PD. GPx activity was increased after treatment with the plant extract at doses of 100 mg kg(-1) and 200 mg kg(-1). Prophylactic treatment with the plant caused a significant down-regulation of ornithine decarboxylase activity (P < 0.001) and profound inhibition in the rate of DNA synthesis (P < 0.001). In conclusion, the acute effects of thioacetamide in rat liver can be prevented by pre-treatment with E. officinalis extract.

Changes to hepatocyte ploidy and binuclearity profiles during human chronic viral hepatitis

BACKGROUND AND AIMS

The importance of the hepatocyte ploidisation pattern to the control of cell proliferation and differentiation has been well established. However, there are no data that have characterised hepatocyte ploidy at various stages of chronic liver inflammation and fibrosis in vivo.

METHODS

We therefore investigated hepatocyte ploidy/binuclearity patterns in 57 patients with chronic hepatitis, using a recently developed methodology which allows simultaneous hepatocyte ploidy and binuclearity analyses on the same liver section.

RESULTS

The percentage of mononuclear diploid hepatocytes was significantly reduced in patients with high hepatitis activity and marked fibrosis (low activity: 75.1 (18.8)% v high activity: 61.8 (21.6)%, p=0.0111, and low fibrosis: 77.3 (13.8)% v high fibrosis: 57.4 (23.3)%, p=0.0002). Accordingly, the percentage of mononuclear polyploid hepatocytes increased in patients with high hepatitis activity and marked fibrosis (low activity: 11.9 (15.5)% v high activity: 22.2 (20.1)%, p=0.0166, and low fibrosis: 9.4 (10.7)% v high fibrosis: 26.4 (21.6)%, p=0.0001). In addition, the fraction of binuclear hepatocytes was significantly higher in patients with hepatitis B virus (HBV) than in those with hepatitis C virus (HCV) infections (HBV: 18.2 (7.6)% v HCV: 12.0 (4.8)%; p=0.0020). Under multivariate analysis, HBV infection was an independent factor accounting for the larger binuclear hepatocyte fraction (p=0.0294).

CONCLUSION

Our results revealed an increase in the polyploid hepatocyte fraction which correlates with the severity of chronic hepatitis; moreover, we demonstrated that HBV and HCV related chronic hepatitis exhibited distinctive hepatocyte ploidy patterns, thus allowing the suggestion that these two viral infections may modulate liver ploidy through different mechanisms.

Potential effects of L-NAME on alcohol-induced oxidative stress

AIM: Nitric oxide (NO) is a highly reactive oxidant synthesized from L-arginine by nitric oxide synthase (NOS). NO may cause injury through the generation of potent radicals. Nw- nitro-L-arginine methyl ester (L-NAME) is a non-selective inhibitor of NOS. We aimed to evaluate whether L-NAME treatment had protective effects against oxidative stress in rats intragastrically fed with ethanol during a 4 wk-period.

METHODS: Thirty-six male Wistar rats were divided into 3 equal groups: group 1 (control group-isocaloric dextrose was given), group 2 (6 g/kg·d ethanol-induced group) and group 3 (both ethanol 6 g/kg·d and L-NAME 500 mg/L in drinking water-given group). Animals were sacrificed at the end of 4 wk-experimental period, and intracardiac blood and liver tissues were obtained. Biochemical measurements were performed both in plasma and in homogenized liver tissues. Alanine amino transferase (ALT), aspartate amino transferase (AST), malondialdehyde (MDA), NO, superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) levels were measured by spectrophotometry.

RESULTS: ALT and AST in group 2 (62 U/L and 128 U/L, respectively) were higher than those in group 1 (24 U/L and 38 U/L) and group 3 (37 U/L and 81 U/L) (P<0.001 for both). Plasma and tissue levels of MDA in group 2 (4.66 μmol/L and 0.55 nmol/mg protein) were higher than in group 1 (2.65 μmol/L and 0.34 nmol/mg protein) and group 3 (3.43 μmol/L and 0.36 nmol/mg protein) (P<0.001 for both). Plasma and liver tissue levels of NO in group 2 (54.67 μmol/L and 586.50 nmol/mg protein) were higher than in group 1 (34.67 μmol/L and 435.33 nmol/mg protein) and group 3 (27.50 μmol/L and 412.75 nmol/mg protein ) (P<0.001 for both). Plasma and liver tissue SOD activities in group 2 (15.25 U/mL and 5.38 U/ mg protein, respectively) were lower than in group 1 (20.00 U/mL and 8.13 U/ mg protein) and group 3 (19.00 U/mL and 6.93 U/ mg protein) (P<0.001 for both). Plasma and liver tissue CAT activities in group 2 (145 U/mL and 37 U/ mg protein, respectively) were lower than in group 1 (176 U/mL and 73 U/mg protein) and group 3 (167 U/mL and 61 U/mg protein) (P<0.001 for both). Meanwhile, erythrocytes and liver tissue levels of GSH in group 2 (4.12 mg/g Hb and 5.38 nmol/mg protein, respectively) were lower than in group 1 (5.52 mg/g Hb and 4.49 nmol/mg protein) and group 3 (5.64 mg/g Hb and 4.18 nmol/mg protein) (P<0.001 for both).

CONCLUSION: Our findings show that L-NAME may produce a restorative effect on ethanol-induced liver damage via decreasing oxidative stress and increasing antioxidant status.

Effects of thioacetamide on pancreatic islet B-cell function

Thioacetamide (0.01-1.3 mM) fails to exert any significant immediate effect upon insulin release from rat isolated islets. However, when administered (4 micromol/g body wt) intraperitoneally 24 h before sacrifice, it reduced food intake and body weight and affected the secretory response of isolated islets to several secretagogues, despite unaltered insulin content of such islets. This coincided with a decrease in D-[U-14C]glucose oxidation, total islet calcium content and the ionized calcium content of secretory granules in islet B-cells, and changes in both 133Ba and 45Ca net uptake. Likewise, in islets prepared from thioacetamide-injected rats and prelabeled with 45Ca before perifusion, the cationic and insulin secretory responses to D-glucose or gliclazide, but not to the association of Ba2+ and theophylline in the absence of extracellular Ca2+, often differed from that otherwise found in islets prepared from control rats. These findings are interpreted as indicative of an impaired capacity of Ca2+ sequestration by intracellular organelles in the islet B-cells of thioacetamide-treated rats.

The effects of early and late administration of inhibitors of inducible nitric oxide synthase in a thioacetamide-induced model of acute hepatic failure in the rat

BACKGROUND/AIMS

Nitric oxide (NO) is a pivotal mediator of inflammation. Its role in acute hepatic failure (AHF) is controversial. We investigated the role of NO, and the hypothesis that inhibition of inducible NO synthase (iNOS) activity would improve outcome in liver failure in rats, using the iNOS inhibitors L-NAME and aminoguanidine (AMG).

METHODS

AHF was induced by two intraperitoneal injections of thioacetamide (TAA). Seven groups (n=10) were studied. Group I: TAA alone. Groups II, III and IV were additionally pre-treated with the NO precursor L-arginine (300 mg/kg i.p.), or iNOS inhibitors AMG (100 mg/kg s.c.), or N(G)-nitro-L-arginine methyl ester (L-NAME) (100 mg/kg s.c.) for 5 days, respectively. Groups V, VI and VII received L-arginine, AMG or L-NAME commencing immediately after TAA administration. Clinical and biochemical parameters were assessed serially, and mortality investigated in further similar cohorts for each regime.

RESULTS

AMG, pre-treatment but not post-treatment, significantly improved outcome including mortality (10 vs. 70%, P<0.005). The less selective iNOS inhibitor L-NAME was not beneficial. Arginine pre-and post-treatment, and iNOS inhibition post-treatment, worsened clinical parameters of TAA-induced liver failure.

CONCLUSIONS

Administration of the iNOS inhibitor AMG prior to insult reduces the severity of damage and improves mortality.

A comparison of hepatoprotective activities of aminoguanidine and N-acetylcysteine in rat against the toxic damage induced by azathioprine

Azathioprine (AZA) is an important drug used in the therapy of autoimmune system disorders. It induces hepatotoxicity that restricts its use. The rationale behind this study was the proven efficacy of N-acetylcysteine (NAC; a replenisher of sulfhydryls) and reports on the antioxidant potential of aminoguanidine (AG; an iNOS inhibitor), that might be useful to protect against the toxic implications of AZA. AG (100 mg/kg; i.p.) or NAC (100 mg/kg; i.p.) were administered to the Wistar male rats for 7 days and after that AZA (15 mg/kg, i.p.) was given as a single dose. This caused an increase in the activity of hepatic aminotransferases (AST and ALT) in the serum 24 h after AZA treatment. AZA (7.5 or 15 mg/kg, i.p.) also caused an increase in rat liver lipid peroxides and a lowering of reduced glutathione (GSH) contents. In the other part of experiment, protective effects of AG and NAC were observed on AZA induced hepatotoxicity. NAC significantly protected against the toxic effects produced by AZA. Pretreatment with NAC prevented any change in the activities of both the aminotransferases after AZA. This pretreatment also resulted in a significant decline in the contents of lipid peroxides and a significant elevation in GSH level was evident after AZA treatment. In the group with AG pretreatment the activities of AST and ALT did not increase significantly after AZA when compared to control. However, the lipid peroxides and GSH levels did not have any significant difference when compared to AZA group. These observations also indicate that the improvement in the GSH levels by NAC is the most significant protective mechanism rather than any other mechanistic profile. The protective effect of AG against the enzyme leakage seems to be through the liver cell membrane permeability restoration and is independent of any effects on liver GSH contents.

Abrogation of bleomycin-induced lung fibrosis by nitric oxide synthase inhibitor, aminoguanidine in mice

The effects of aminoguanidine (AG), a specific inhibitor of inducible nitric oxide synthase, on the bleomycin (BL)-induced lung fibrosis was evaluated in mice. The animals were placed into five groups: saline (SA)-instilled drinking water (SA+H(2)O), saline-instilled drinking water containing 0.5%AG (SA+0.5%AG), BL-instilled drinking water (BL+H(2)O), BL-instilled drinking water containing 0.2%AG (BL+0.2%AG), and BL-instilled drinking water containing 0.5%AG (BL+0.5%AG). The mice had free access to H(2)O or H(2)O containing AG and lab chow ad lib 2 days prior to intratracheal (IT) instillation of BL (0.07U/mouse/100 microL) or an equivalent volume of sterile isotonic saline. The mice in the SA+0.5%AG group consumed the greatest amount of AG without any ill effects than the mice in any other group. There were no differences in any of the measured biochemical determinants between the SA+H(2)O and SA+0.5%AG control groups. The IT instillation of BL in the BL+H(2)O group caused significant increases in the lipid peroxidation, hydroxyproline content, and prolyl hydroxylase activity of lungs and influx of inflammatory cells in the broncheoalveolar lavage fluid (BALF) as compared to both control groups. The intake of aminoguanidine by mice in the BL+0.5%AG group caused significant reductions in the BL-induced increases in all measured biochemical indices of lung fibrosis without any effects on the influx of inflammatory cells in the BALF. In fact, AG in both BL-treated groups additionally increased the total cell counts in the BALF from mice in the BL+0.2%AG and BL+0.5%AG groups as compared to the BL+H(2)O group. Histopathological evaluation of the lungs revealed that the mice in the BL+0.5%AG group had markedly fewer fibrotic lesions than mice in the BL+H(2)O group. These results demonstrate that aminoguanidine minimizes the BL-induced lung fibrosis at both the biochemical and the morphological level and support our earlier hypothesis that the production of nitric oxide plays a significant role in the pathogenesis lung fibrosis caused by BL.

Nitric oxide in liver diseases: friend, foe, or just passerby?

Research on the free radical gas, nitric oxide (NO), during the past twenty years is one of the most rapid growing areas in biology. NO seems to play a part in almost every organ and tissue. However, there is considerable controversy and confusion in understanding its role. The liver is one organ that is clearly influenced by NO. Acute versus chronic exposure to NO has been associated with distinct patterns of liver disease. In this paper we review and discuss the involvement of NO in various liver diseases collated from observations by various researchers. Overall, the important factors in determining the beneficial versus harmful effects of NO are the amount, duration, and site of NO production. A low dose of NO serves to maximize blood perfusion, prevent platelet aggregation and thrombosis, and neutralize toxic oxygen radicals in the liver during acute sepsis and reperfusion events. NO also demonstrates antimicrobial and antiapoptosis properties during acute hepatitis infection and other inflammatory processes. However, in the setting of chronic liver inflammation, when a large sustained amount of NO is present, NO might become genotoxic and lead to the development of liver cancer. Additionally, during prolonged ischemia, high levels of NO may have cytotoxic effects leading to severe liver injury. In view of the various possible roles that NO plays, the pharmacologic modulation of NO synthesis is promising in the future treatment of liver diseases, especially with the emergence of selective NO synthase inhibitors and cell-specific NO donors.

Beneficial effect of nitric oxide synthase inhibitor on hepatotoxicity induced by allyl alcohol

The effect of aminoguanidine (a selective inhibitor of inducible nitric oxide synthase) on allyl alcohol-induced liver injury was assessed by the measurement of serum ALT and AST activities and histopathological examination. When aminoguanidine (50-300 mg/kg, i.p.) was administered to mice 30 min before a toxic dose of allyl alcohol (75 microL/kg, i.p.), significant changes related to liver injury were observed. In the presence of aminoguanidine the level of ALT and AST enzymes were significantly decreased. All symptoms of liver necrosis produced by allyl alcohol toxicity almost completely disappeared when animals were pretreated with aminoguanidine at 300 mg/kg. Depletion of hepatic glutathione as a consequence of allyl alcohol metabolism was minimal in mice pretreated with aminoguanidine at 300 mg/kg. It was found that the inhibition of toxicity was not due to alteration in allyl alcohol metabolism since aminoguanidine did not effect alcohol dehydrogenase activity both in vivo and in vitro.

Pyrrolidine dithiocarbamate protects against thioacetamide-induced fulminant hepatic failure in rats

BACKGROUND/AIMS

Reactive oxygen species and nuclear factor kappa B (NF-kappaB) activation have been implicated in the pathogenesis of cell injury in experimental models of liver damage. The aim of the present study was to examine whether pyrrolidine dithiocarbamate (PDTC), an anti oxidant and inhibitor of NF-kappaB activation, would prevent hepatic damage induced in a rat model of thioacetamide (TAA)-induced liver failure.

METHODS

Fulminant hepatic failure was induced in the control and treatment groups by two intraperitoneal injections of TAA (either 300 or 400 mg/kg) at 24-h intervals. In the treatment groups, rats were treated also with PDTC (60 mg/kg/24 h, i.p.), initiated 24 h prior to TAA.

RESULTS

Liver enzymes, blood ammonia, and hepatic levels of thiobarbituric acid reactive substances (P<0.001) and protein carbonyls (P<0.05) were significantly lower in rats treated with PDTC compared to TAA only. Liver histology and the survival rate in the PDTC-treated rats were also improved (P<0.01 compared to TAA only). NF-kappaB activation, 2 and 6 h after TAA administration, was inhibited by PDTC.

CONCLUSIONS

In a rat model of fulminant hepatic failure, the administration of PDTC attenuated liver damage and improved survival. This effect may be due to decreased oxidative stress and inhibition of NF-kappaB activation.

Polyploidy associated with oxidative injury attenuates proliferative potential of cells

Polyploid cells are encountered ubiquitously but the biological significance of polyploidy is unclear. In view of their extensive capacity for regeneration, hepatocytes offer excellent systems for analyzing growth control mechanisms. We isolated hepatocytes from adult rats with and without two-third partial hepatectomy, which induces hepatic polyploidy. Polyploid hepatocytes showed evidence for oxidative injury with antioxidant depletion, lipid peroxidation and 8-hydroxy-adducts of guanine in nuclear DNA. Liver repopulation assays in intact animals showed markedly decreased replication capacity in polyploid hepatocytes. Recapitulation of polyploidy in cultured hepatocytes established that mitogenic stimulation in the presence of oxidative DNA injury was capable of inducing polyploidy. The findings provide novel frameworks in the context of polyploidy for understanding tissue development, regeneration and oncogenesis.

Taurine has a protective effect against thioacetamide-induced liver cirrhosis by decreasing oxidative stress

Thioacetamide (TAA) administration (0.3 g/l of tap water for a period of 3 months) to rats resulted in hepatic cirrhosis as assessed by biochemical and histopathological findings. This treatment caused an increase in the levels of malondialdehyde (MDA) and diene conjugates (DCs) and a decrease in the levels of glutathione (GSH), vitamin E, vitamin C and the activities of glutathione peroxidase (GSH-Px) in the liver of rats. Superoxide dismutase (SOD) activities were unchanged. Taurine (2% w/w, added to the chow diet) was administered together with TAA (0.3 g/l of drinking water) for 3 months. Taurine was found to decrease TAA-induced hepatic lipid peroxidation and to increase TAA-depleted vitamin E levels and GSH-Px activities. Histopathological findings also suggested that taurine has an inhibitive effect on TAA-induced hepatic cirrhosis. These results indicate that taurine treatment has a protective effect against TAA-induced liver cirrhosis by decreasing oxidative stress.

The protective effect of taurine against thioacetamide hepatotoxicity of rats

Thioacetamide (TAA) administration (three consecutive intraperitoneal injections of 400 mg/kg at 24-h interval) to rats resulted in hepatic injury as assessed by the measurement of serum transaminase activities and histopathological findings. This treatment caused an increase in the levels of malondialdehyde (MDA), diene conjugates (DCs) and glutathione (GSH) and the activity of superoxide dismutase SOD ), and a decrease in the levels of vitamins E and C and the activity of glutathione peroxidase (GSH-Px) in the liver of rats. Taurine administration (400 mg/kg, i.p., every 12 h and started 24 h prior to the first TAA injection) was found to decrease serum transaminase activities and hepatic lipid peroxidation without any significant change in hepatic antioxidant system. Histopathological findings also suggested that taurine has ameliorated effect on TAA-induced hepatic necrosis. These results indicate that taurine treatment, together with TAA administration, diminished the severity of the liver injury by decreasing oxidative stress due to its possible scavenger effect.

Hepatic polyploidy and liver growth control

The onset of cellular polyploidy is recognized in all differentiated mammalian tissues. Polyploidy has been noted frequently in the normal liver, as well as in pathophysiological states of the liver. As insights into the significance of polyploidy accumulate gradually, it is becoming clear that cells belonging to high ploidy classes exhibit advancement toward terminal differentiation and cellular senescence with greater probabilities of apoptosis. Involvement of specific genetic abnormalities, such as impaired DNA repair, may lead to hepatocellular polyploidy. Working models indicate that extensive polyploidy could lead to organ failure, as well as to oncogenesis with activation of precancerous cell clones.

Aminoguanidine attenuates endotoxin-induced mesenteric vascular hyporeactivity

BACKGROUND

The aim of this study was to investigate the effects of inducible nitric oxide synthase inhibition by aminoguanidine on endotoxin-induced reduction in mesenteric blood flow.

METHODS

Twenty Sprague-Dawley rats (180-230 g) allocated into four groups were administered either Escherichia coli endotoxin 1 mg/kg intraperitoneally or its solvent saline and were pretreated with either aminoguanidine (15 mg/kg intraperitoneally 20 min before and 2 h after endotoxin injection) or saline. Some 4 h after endotoxin injection, animals were anaesthetized, arterial blood pressure and mesenteric blood flow were measured and the resistance in the mesenteric vascular beds was then calculated. The effect of phenylephrine (1-30 microg/kg intravenously) on these parameters was also investigated.

RESULTS

Endotoxin did not significantly modify the mean arterial blood pressure but decreased mesenteric blood flow by increasing the vascular resistance (mean(s.e.m.) 7.8(1.0) versus 13.7(1.2) mmHg per min per ml for control versus endotoxin groups; n = 5, P = 0.0099). Aminoguanidine alone had no effect on either the mean arterial blood pressure or mesenteric blood flow, but it completely blocked the effects of endotoxin. On the other hand, endotoxin significantly attenuated the responsiveness to phenylephrine which was restored by aminoguanidine.

CONCLUSION

The present results indicate that endotoxin decreases the mesenteric vascular blood flow by increasing vascular resistance and decreases responsiveness to phenylephrine. The effects of endotoxin were inhibited by aminoguanidine. The mesenteric vasoconstriction in response to endotoxin might not be explained by the overproduction of nitric oxide; other actions of aminoguanidine may explain its inhibitory effect. Presented in part to the 10th Annual Meeting of the Surgical Infection Society - Europe, Istanbul, Turkey, May 1997

Evaluation of oxidative stress based on lipid hydroperoxide, vitamin C and vitamin E during apoptosis and necrosis caused by thioacetamide in rat liver

After 12 h of thioacetamide (500 mg/kg body weight) administration to rats, the activity of caspase-3-like protease in the liver increased significantly compared to that in the control group. In plasma, the activity of caspase-3 was barely detectable in the control rat, but had increased significantly after 24 h of drug administration along with a dramatic increase in GOT. These results indicate that thioacetamide causes apoptosis in the liver by activating caspase-3, which is released to plasma by successive necrosis. At 24 h, the concentration of liver lipid hydroperoxides, a mediator of radical reaction, was 2.2 times as high as that of control rats. After 12 and 24 h of thioacetamide administration, the liver concentrations of vitamins C and E decreased significantly. The decrease of antioxidants and formation of lipid hydroperoxides 24 h after thioacetamide administration support the view that extensive radical reactions occur in the liver during the necrotic process.

Protective effect of aminoguanidine, a nitric oxide synthase inhibitor, against carbon tetrachloride induced hepatotoxicity in mice

The present study was undertaken to evaluate the effect of aminoguanidine (AG) on carbon tetrachloride (CCl4)-induced hepatotoxicity. Treatment of mice with CCl4 (20 microl/kg, i.p.) resulted in damage to centrilobular regions of the liver, increase in serum aminotransferase and rise in lipid peroxides level 24 hours after CCl4 administration. Pretreatment of mice with AG (50 mg/kg, i.p.) 30 minutes before CCl4 was found to protect mice from the CCl4-induced hepatic toxicity. This protection was evident from the significant reduction in serum aminotransferase, inhibition of lipid peroxidation and prevention of CCl4-induced hepatic necrosis revealed by histopathology. Aminoguanidine, a relatively specific inhibitor of inducible nitric oxide synthase, did not inhibit the in vitro lipid peroxidation. Taken together, these data suggest a potential role of nitric oxide as an important mediator of CCl4-induced hepatotoxicity.