Gadolinium chloride pretreatment ameliorates acute cadmium-induced hepatotoxicity.

Cadmium is a known industrial and environmental pollutant. It causes hepatotoxicity upon acute administration. Features of cadmium-induced acute hepatoxicity encompass necrosis, apoptosis, peliosis and inflammatory infiltration. Gadolinium chloride (GdCl3) may prevent cadmium-induced hepatotoxicity by suppressing Kupffer cells. The effect of GdCl3 pretreatment on a model of acute cadmium-induced liver injury was investigated. Male Wistar rats 4-5 months old were injected intraperitoneally with normal saline followed by cadmium chloride (CdCl2; 6.5 mg/kg) or GdCl3 (10 mg/kg) followed by CdCl2 (6.5 mg/kg; groups I and II, respectively). Rats of both the groups were killed at 9, 12, 16, 24, 48 and 60 h after cadmium intoxication. Liver sections were analyzed for necrosis, apoptosis, peliosis and mitoses. Liver regeneration was also evaluated by tritiated thymidine incorporation into hepatic DNA. Serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were also determined. Hepatic necrosis, hepatocyte and nonparenchymal cell apoptosis and macroscopic and microscopic types of peliosis hepatis were minimized by gadolinium pretreatment. Serum levels of AST and ALT were also greatly diminished in rats of group II. Tritiated thymidine incorporation into hepatic DNA was increased in gadolinium pretreatment rats. Kupffer cell activation was minimal in both the groups of rats. Gadolinium pretreatment attenuates acute cadmium-induced liver injury in young Wistar rats, with mechanisms other than Kupffer cell elimination.

The emerging role of serotonin in liver regeneration.

Serotonin has a multifunctional role in many different organs serving either as a neurotransmitter in the central nervous system or a paracrine factor in the gastrointestinal tract. Over 90% of serotonin is synthesised in the enterochromaffin cells of the intestine and subsequently taken up by platelets. The involvement of platelet-derived serotonin in liver mass restoration after partial hepatectomy or toxic injury has been greatly investigated during the last decade. There is a growing body of evidence implicating serotonin in hepatic regeneration through altered expression of serotonin receptor subtypes in the liver. This review article provides a brief overview on the current knowledge about the actions of serotonin in liver regeneration.

Acetaminophen-induced liver injury and oxidative stress: protective effect of propofol.

BACKGROUND AND OBJECTIVE: We evaluated the effects of propofol on oxidative stress and acute liver injury and regeneration produced by acetaminophen administration in rats. METHODS: Acetaminophen (3.5 g kg(-1)) was administered by gastric tube to 50 adult male Wistar rats. One minute before acetaminophen, propofol was administered intraperitoneally (60 mg kg(-1)) to 25 rats and diethyl ether to the other 25 animals. All rats were sacrificed. Markers of oxidative stress (malondialdehyde levels, cholesterol/high-density lipoprotein cholesterol fraction and glutathione-S-transferase-pi activity), liver injury (aspartate aminotransferase alanine aminotransferase and alkaline phosphatase and histological signs of inflammation and in-situ apoptosis) and liver regeneration (rate of [3H]thymidine incorporation into hepatic DNA, activity of liver thymidine kinase and mitotic index in hepatocytes) were determined. Unpaired Student's t-test and one-way analysis of variance were used for statistical analysis and a P value of 0.05 or less was considered significant. RESULTS: All markers of oxidative stress were significantly decreased in propofol-treated animals. Biochemical and histological markers of liver injury and regeneration in propofol-treated animals did not show any significant decrease compared with those observed in the control group. CONCLUSION: The antioxidant capacity of propofol, verified in our study, did not manage to prevent liver injury and accelerate regeneration after acetaminophen administration in rats.

VEGF isoforms and receptors expression throughout acute acetaminophen-induced liver injury and regeneration.

Acetaminophen (APAP) is a widely-used analgesic and a known hepatotoxic agent. Vascular endothelial growth factor (VEGF) is a growth factor with multiple functional roles. VEGF plays an important role in angiogenesis and hepatic regeneration. The aim of this study was to determine the expression of VEGF isoforms and its receptors throughout liver regeneration after the administration of a toxic dose of APAP in rats. Ten groups of adult male rats received a dose of 3.5 g/kg b.w. of APAP per os. The rats were killed post administration at 0-288 h. Blood and liver tissue were extracted. Determination of serum transaminases and alkaline phosphatase activities was performed. Liver injury and regeneration were assessed with hematoxylin-eosin specimens, morphometric analysis, hepatic thymidine kinase assay and Ki-67 expression. Reverse transcription-polymerase chain reaction and immunohistochemical methods were used for assessment of VEGF isoforms and receptors differential expression. High activities of aspartate aminotransferase were observed at 24 and 36 h with another peak of activity at 192 h post administration. Alanine aminotransferase was highest at 36 h. Alkaline phosphatase was increased post 24 h being higher at 72,192 and 240 h. Centrilobular necrosis was observed at 48-72 h and thorough restoration of the liver microarchitecture was observed at 288 h. Liver regeneration lasted from 24-192 h according to the results from thymidine kinase activity and Ki-67 expression. VEGF and VEGF receptor-2 m-RNA levels presented with a three-peak pattern of expression at 12-24, 72-96 and 192-240 h post administration. Significant difference was noted between periportal and centrilobular immunohistochemical expression. VEGF proves to play a critical role during APAP-induced liver regeneration as it presents with three points of higher expression. The first two time points are associated with the initial inflammatory reaction to the noxious stimulus and the hepatocyte regenerative process where as the third one is indicative of the potential involvement of VEGF in processes of remodeling.

Effect of 5-HT(2) receptor blockade on cadmium-induced acute toxicity.

The protective effect of 5-HT(2) receptor blockade with ketanserin or ritanserin against cadmium liver injury was investigated. Male Wistar rats were injected intraperitoneally with a sublethal dose of cadmium (3.5 mg/kg body weight). Rats were treated with normal saline (group I), ketanserin (3 mg/kg body weight; group II), or ritanserin (3 mg/kg body weight; group III) 2 hr prior and 4 hr after cadmium administration and killed at different time points. Hematoxylin/eosin-stained liver sections were assessed for necrosis, apoptosis, peliosis, mitoses, and inflammatory infiltration. Apoptosis was also quantified by the TUNEL assay. Nonparenchymal liver cells and activated Kupffer cells were identified histochemically. Necrosis, hepatocyte apoptosis, nonparenchymal cell apoptosis, and macroscopic and microscopic peliosis were markedly reduced or minimized in ketanserin- or ritanserin-treated rats. The observed protective effect was almost identical for both ketanserin and ritanserin administration. 5-HT(2) receptor blockade exerts a protective effect against acute cadmium-induced hepatotoxicity.

Peliosis hepatis: microscopic and macroscopic type, time pattern, and correlation with liver cell apoptosis in a model of toxic liver injury.

Macroscopic and microscopic types of peliosis hepatis, time pattern, and correlation with hepatocyte and sinusoidal cell apoptosis were investigated. Male Wistar rats were injected with a dose of cadmium (6.5 mg CdCl(2)/kg body weight, intraperitoneally; group I). Putrescine (300 micromol/kg body weight, intraperitoneally; group II) was injected at 2, 5, and 8 hours and vascular endothelial growth factor (VEGF; 400 ng/animal, intravenously; group III) at 2 hours. Animals from each group were humanely killed 0, 6, 12, 24, 48, or 60 hours after cadmium intoxication. Liver tissue was histologically assessed for necrosis, apoptosis, and peliosis. Apoptosis was also quantified by the TUNEL assay for hepatocytes and nonparenchymal liver cells. The discrimination between hepatic cell subpopulations was done histochemically. Sinusoidal cell apoptosis and macroscopic peliosis hepatis evolved in a monophasic pattern and correlated closely. Putrescine or VEGF administration totally reversed macroscopic peliosis. Putrescine exerted a major protective effect on hepatocytes, whereas the protective effect of VEGF was more pronounced for nonparenchymal liver cells. Microscopic peliosis also evolved in a monophasic pattern preceding macroscopic type. The extent of the lesion was reduced by putrescine and almost totally reversed by VEGF. Macroscopic peliosis progresses as a compound lesion closely correlating with nonparenchymal cell apoptosis. Both hepatocyte and nonparenchymal cell injury are prerequisites for the genesis of the lesion. Microscopic peliosis precedes macroscopic peliosis and up to a degree seems to be independent of initial hepatocyte injury, but it seems to depend on nonparenchymal cell injury.

Effect of serotonin receptor 2 blockage on liver regeneration after partial hepatectomy in the rat liver.

UNLABELLED: The effect of serotonin receptor 2 blockade (5-HT(2)) on liver regeneration after 30-34% and 60-70% partial hepatectomy in the rat liver was investigated. MATERIALS AND METHODS: Male Wistar rats were subjected to 60-70% (group I) and 30-34% (group II) partial hepatectomy. Serotonin receptor 2 blockade was exerted by intraperitoneal administration of ketanserin at different doses and time points after partial hepatectomy. The rats of all groups were killed at different time points until 96 h after partial hepatectomy. The rate of liver regeneration was evaluated by the mitotic index in hematoxylin and eosin sections, the immunochemical detection of Ki67 and proliferating cell nuclear antigens, the rate of [(3)H]-thymidine incorporation into hepatic DNA and liver thymidine kinase enzymatic activity. RESULTS: Liver regeneration peaked at 24 and 32 h after partial hepatectomy in 60-70% hepatectomized rats. In 30-34% hepatectomized rats liver regeneration peaked at 60 h, whereas low rates of regenerative activity were observed between 24 and 72 h after partial hepatectomy. Ketanserin administration arrested liver regeneration only when administered at 16 h after 60-70% partial hepatectomy. Ketanserin also abrogated the observed peak of regenerative activity at 60 h in 30-34% hepatectomized rats when administered at 52 h after partial hepatectomy. All indices of liver regeneration were affected by ketanserin administration. CONCLUSIONS: Serotonin receptor 2 blockade can arrest liver regeneration only when administered close to G1/S transition point, and that while serotonin may be a cofactor for DNA synthesis, it does not play a role in initiation of liver regeneration.

The effect of hepatic stimulator substance (HSS) on liver regeneration arrest induced by 5-HT2 receptor blockade.

BACKGROUND: The restorative effect of hepatic stimulator substance (HSS) against hepatic regeneration arrest induced by 5-HT2 receptor blockade was investigated. MATERIALS AND METHODS: Male Wistar rats were subjected to 60-70% partial hepatectomy and to 5-HT2 receptor blockade at 16 h after partial hepatectomy by ketanserin administration (6 mg/kg bodyweight intraperitoneally; group I). HSS at the dose of 100 mg protein/kg bodyweight was administered at 10 or 17 h after partial hepatectomy in ketanserin-treated rats (groups II and III). The mitotic index in hematoxylin-eosin-stained liver sections, immunochemical detection of PCNA and Ki 67 nuclear antigens and the rate of [3H]-thymidine incorporation into hepatic DNA were used as indices of liver regeneration. RESULTS: Liver regeneration, as evaluated by [3H]-thymidine incorporation into hepatic DNA, mitotic index, PCNA and Ki67 nuclear antigens, peaked at 40 h in groups I, II and III of rats and no significant differences were observed between the studied groups. CONCLUSION: HSS administration is not capable of reversing the liver regeneration arrest induced by 5-HT2 receptor blockade.

Effect of hepatic stimulator substance (HSS) on cadmium-induced acute hepatotoxicity in the rat liver.

The hepatoprotective effect of HSS against cadmium-induced liver injury was investigated. Rats were intoxicated with a dose of cadmium (3.5 mg/kg b.w.). The rats were treated with normal saline (group I) or HSS (100 mg protein/kg b.w.; group II) 2 hr later and killed at different time points. Hematoxylin-eosin (HE) sections were assessed for necrosis, apoptosis, peliosis, mitoses, and inflammatory infiltration. Serum enzyme activities were assayed. Apoptosis was quantified by the Tunel technique. Thymidine kinase activity and the rate of [3H]thymidine incorporation into DNA were also assayed. Necrosis, hepatocyte apoptosis, and peliosis were minimized in HSS-treated rats (group II). Nonparenchymal cell apoptosis and liver regeneration were not quantitively altered in the HSS-treated group, though the time profile was different. HSS protects hepatocytes against cadmium-induced necrosis, apoptosis, and peliosis. Apoptosis was the major type of cell death for nonparenchymal liver cells and strongly correlated with the extent of peliosis. Interactions between hepatocytes and nonparenchymal liver cells seem to be important for the genesis of hepatic trauma in acute cadmium hepatotoxicity.

The hepatoprotective effect of putrescine against cadmium-induced acute liver injury.

The hepatoprotective effect of putrescine against cadmium liver injury was investigated. Male Wistar rats were injected with a dose of cadmium (6.5 mg CdCl(2)/kg bodyweight, intraperitoneally). Normal saline (group I) or putrescine (300 micro mol/kg bodyweight; group II) were injected 2, 5 and 8 h later. A number of animals of both groups were killed 0, 12, 16, 24, 48 or 60 h after cadmium intoxication. Liver tissue was histologically assessed for necrosis, apoptosis, peliosis, mitoses, and inflammatory infiltration. Apoptosis was also quantified by the TUNEL assay for hepatocytes and nonparenchymal liver cells. The discrimination between hepatic cell subpopulations was achieved histochemically. The mitotic index in hematoxylin-eosin-stained sections and by the immunochemical detection of Ki67 nuclear antigen, (3)H-thymidine incorporation into hepatic DNA, and hepatic thymidine kinase activity were all used as indices of liver regeneration. Both hepatocyte apoptosis and liver necrosis evolved in a biphasic temporal pattern. Nonparenchymal cell apoptosis and peliosis hepatis evolved in a monophasic pattern and were correlated closely. Putrescine administration totally reversed liver necrosis and hepatocyte apoptosis. The time profile of nonparenchymal apoptosis was altered and peliosis hepatis was also totally attenuated. In conclusion, putrescine protected hepatocytes and modulated the mechanism of cadmium-induced acute hepatotoxicity.

Effect of acute ethanol exposure on hepatic stimulator substance (HSS) levels during liver regeneration: protective function of HSS.

Ethanol administration in rats induces liver damage and suppression of liver regeneration. To further understand the underlying mechanism, we investigated the effects of ethanol on hepatic stimulator substance (HSS) levels during liver regeneration caused by partial hepatectomy. The hepatotrophic action of HSS to ethanol-treated partially hepatectomized rats was also examined. Rats received repetitive ethanol or saline doses beginning 1 hr prior to 70% partial hepatectomy (PH), and the animals were killed at 16, 24, 32, 40, 48, and 60 hr after PH. Our results showed that ethanol inhibited hepatic regenerative capacity and prolonged liver regenerative process. HSS biological activity in ethanol-administered rats peaked at 48 hr after PH, in contrast to saline-treated ones where activity peaked at 24 hr. Additionally, exogenous HSS administration to ethanol-treated partially hepatectomized rats increased liver proliferating capacity and suppressed the elevation of serum ALT activity. These results showed that ethanol modifies the time course of HSS biological activity during the regenerating process. The observed suppression of HSS activity at 24 hr after PH was in relation with a reduction of DNA synthesis. Exogenous administration of HSS to ethanol-treated partially hepatectomized rats restored DNA synthesis and ameliorated serum AST levels, indicating that HSS could be used in the treatment of ethanol-induced hepatic failures.

Time-course of cadmium-induced acute hepatotoxicity in the rat liver: the role of apoptosis.

Exposure to toxic metals and pollutants is a major environmental problem. Cadmium is a metal causing acute hepatic injury but the mechanism of this phenomenon is poorly understood. In the present study, we investigated the mechanism and time-course of cadmium-induced liver injury in rats, with emphasis being placed on apoptosis in parenchymal and nonparenchymal liver cells. Cadmium (3.5 mg/kg body weight) was injected intraperitoneally and the rats were killed 0, 9, 12, 16, 24, 48 and 60 h later. The extent of liver injury was evaluated for necrosis, apoptosis, peliosis, mitoses and inflammatory infiltration in hematoxylin-eosin-stained liver sections, and by assaying serum enzyme activities. The number of cells that died via apoptosis was quantified by TUNEL assay. The identification of nonparenchymal liver cells and activated Kupffer cells was performed histochemically. Liver regeneration was evaluated by assaying the activity of liver thymidine kinase and by the rate of 3H-thymidine incorporation into DNA. Both cadmium-induced necrotic cell death and parenchymal cell apoptosis showed a biphasic elevation at 12 and 48 h and peaked at 48 and 12 h, respectively. Nonparenchymal cell apoptosis peaked at 48 h. Peliosis hepatis, another characteristic form of liver injury, was first observed at 16 h and, at all time points, closely correlated with the apoptotic index of nonparenchymal liver cells, where the lesion was also maximial at 48 h. Kupffer cell activation and neutrophil infiltration were minimal for all time points examined. Based on thymidine kinase activity, liver regeneration was found to discern a classic biphasic peak pattern at 12 and 48 h. It was very interesting to observe that cadmium-induced liver injury did not involve inflammation at any time point. Apoptosis seems to be a major mechanism for the removal of damaged cells, and constitutes the major type of cell death in nonparenchymal liver cells. Apoptosis of nonparenchymal cells is the basis of the pathogenesis of peliosis hepatis. The first peaks of necrosis and parenchymal cell apoptosis seem to evolve as a result of direct cadmium effects whereas the latter ones result from ischemia.

Hepatic stimulator substance administration ameliorates liver regeneration in an animal model of fulminant hepatic failure and encephalopathy.

AIMS/BACKGROUND: Hepatic stimulator substance (HSS) is a liver-specific growth factor implicated in hepatocellular proliferation and hepatoprotection in models of acute liver injury. In the present study, we examined the effect of exogenous HSS administration on liver proliferating capacity and survival outcome in an experimental animal model of fulminant hepatic failure (FHF) and encephalopathy, induced by repeated injections of thioacetamide (TAA) in rats. METHODS: Fulminant hepatic failure was induced in adult male Wistar rats by three consecutive intraperitoneal injections of TAA (400 mg/kg of body weight), at 24 h time intervals. The animals received intraperitoneally either a saline solution or HSS (50 mg protein/kg of body weight), 2 h after the second and third TAA injections. The animals were killed at 6, 12 and 18 h post the last injection of TAA. RESULTS: Levels of liver enzymes and urea in serum, blood ammonia values, liver histology, stage of hepatic encephalopathy and survival were statistically significantly improved in TAA-intoxicated and HSS-treated rats compared to TAA-intoxicated and saline-treated ones. Furthermore, HSS ameliorated liver regenerative indices--DNA biosynthesis, thymidine kinase activity and hepatocyte mitotic activity--in a statistically significant manner. CONCLUSIONS: Our data suggest the beneficial effect of HSS administration in this animal model of FHF and encephalopathy, supporting evidence for a possible use of HSS as supportive therapy, by increasing hepatocellular proliferation, in management of FHF.

The effect of co-administration of simvastatin and alcohol in rats.

INTRODUCTION: The effect of chronic co-administration of alcohol (Alc) and lipid-lowering drugs on hepatic function has not been extensively evaluated. We studied the effects of administering Alc together with a 3-hydroxy-3 methylglutaryl coenzyme A reductase inhibitor [simvastatin (S)]. MATERIALS AND METHODS: Male Wistar rats (8 weeks old) were randomized and divided into 4 groups of 10 each. They were fed (once a day) via a stomach tube with: 1) 2 ml of olive oil; group Oil, 2) with Oil + 2 ml of 25% v/v pure Alc in water; group Alc + Oil, 3) with Oil + S (65 micrograms/100 g body weight); group S + Oil, 4) with Oil + Alc + S; group S + Alc + Oil. Another 13 male Wistar rats were only fed a standard laboratory diet (control group). After 8 weeks blood samples were drawn and the livers were removed. Blood glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AP), total protein, albumin, total cholesterol (TC) and triglycerides (TG) were measured. Liver histopathology was also assessed. RESULTS: Differences were found between the control group and tube-fed groups in glucose (p < 0.001). No differences were found among tube-fed groups in blood glucose, ALT, total protein, albumin, AP and TC. AST activity was significantly higher in the Alc + Oil than in the Oil or S + Oil groups (p < 0.001 for both comparisons) demonstrating the effect of Alc on AST. The AST did not differ significantly in the Oil or S + Oil groups indicating a lack of effect of S. Furthermore, S significantly reduced the Alc-induced increase in AST (Alc + Oil vs S + Alc + Oil; p = 0.042). The TG concentration was significantly higher in the Alc + Oil group compared to the Oil, S + Oil and S + Alc + Oil groups (p = 0.02). Therefore, S significantly decreased the alcoholinduced increase in TG. Liver histopathology was similar in all groups and within the normal range. CONCLUSION: A moderate amount of Alc daily together with S is safe in rats. Additionally, S administration in Wistar rats diminishes the Alc-induced TG and AST rises.

Hepatic stimulator substance activity in animal model of fulminant hepatic failure and encephalopathy.

Hepatic stimulator substance (HSS) is a known liver-specific but species-nonspecific growth factor. In the present study we examined the activity of the endogenously produced HSS in an established experimental model of fulminant hepatic failure (FHF) and encephalopathy, induced by repeated injections of thioacetamide (TAA). FHF was induced by three consecutive intraperitoneal injections of TAA (400 mg/kg body weight) in rats, at time intervals of 24 hr. The animals were killed at 0, 6, 12, or 18 hr following the last injection of TAA. The rate of tritiated thymidine incorporation into hepatic DNA, the enzymatic activity of liver thymidine kinase (EC 2.7.1.21), and the assessment of mitotic index in hepatocytes were used to estimate liver regeneration. HSS extract obtained from the livers of TAA-treated rats, sacrificed at the above-mentioned time points was tested for its activity. Increased HSS activity was noted in all TAA-treated animals, presenting a peak at 12 hr following the third TAA dose, suggesting active participation of this growth factor in hepatocyte replication in this animal model of FHF and encephalopathy. It may also be suggested that up-regulation of HSS activity could be used in future as a therapeutic approach in FHF.