Hepatoprotective effect of electrolyzed reduced water against carbon tetrachloride-induced liver damage in mice

The study investigated the protective effect of electrolyzed reduced water (ERW) against carbon tetrachloride (CCl₄)-induced liver damage. Male ICR mice were randomly divided into control, CCl₄, CCl₄ + silymarin, and CCl₄ + ERW groups. CCl₄-induced liver lesions include leukocytes infiltration, hepatocyte necrosis, ballooning degeneration, mitosis, calcification, fibrosis and an increase of serum alanine aminotransferase (ALT), and aminotransferase (AST) activity. In addition, CCl₄ also significantly decreased the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). By contrast, ERW or silymarin supplement significantly ameliorated the CCl₄-induced liver lesions, lowered the serum levels of hepatic enzyme markers (ALT and AST) and increased the activities of SOD, catalase, and GSH-Px in liver. Therefore, the results of this study show that ERW can be proposed to protect the liver against CCl₄-induced oxidative damage in mice, and the hepatoprotective effect might be correlated with its antioxidant and free radical scavenging effect.     

Protective effects of Dunaliella salina – A carotenoids-rich alga,against carbon tetrachloride-induced hepatotoxicity in mice

The protective effects of Dunaliella salina (D. salina) on liver damage were evaluated by carbon tetrachloride (CCl₄)-induced hepatotoxicity in mice. Male ICR mice were orally treated with D. salina or silymairn daily with administration of CCl₄ twice a week for 8 weeks. CCl₄ induced liver damage and significantly (p < 0.05) increased the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) in serum and decreased the activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px), and GSH content in liver whereas increased hepatic malondialdehyde (MDA) content as compared with control group. Treatment with D. salina or silymarin could significantly (p < 0.05) decrease the ALT, AST, and ALP levels in serum and increase the activities of SOD, catalase, GSH-Px, glutathione reductase, and GSH content and decrease the MDA content in liver when compared with CCl₄-treated group. Liver histopathology also showed that D. salina reduced the incidence of liver lesions induced by CCl₄. The results suggest that D. salina exhibits potent hepatoprotective effects on CCl₄-induced liver damages in mice, and that the hepatoprotective effects of D. salina may be due to both the increase of antioxidant enzymes activities and inhibition of lipid peroxidation.     

Antioxidant and hepatoprotective activities of phenolic rich fraction of Seabuckthorn (Hippophae rhamnoides L.) leaves

Present study was aimed to investigate antioxidant and hepatoprotective activities of phenolic rich fraction (PRF) of Seabuckthorn leaves on CCl₄ induced oxidative stress in Sprague Dawley rats. Total phenolic content was found to be 319.33 mg gallic acid equivalent (GAE)/g PRF and some of its phenolic constituents, such as gallic acid, myricetin, quercetin, kaempferol and isorhamnetin were found to be in the range of 1.935-196.89 mg/g of PRF as determined by reverse-phase high-performance liquid chromatography (RP-HPLC).Oral administration of PRF at dose of 25-75 mg/kg body weight significantly protected from CCl₄ induced elevation in aspartate aminotransferase (AST), alanine aminotransferase (ALT), γ-glutamyl transpeptidase (GGT) and bilirubin in serum, elevation in hepatic lipid peroxidation, hydroperoxides, protein carbonyls, depletion of hepatic reduced glutathione (GSH) and decrease in the activities of hepatic antioxidant enzymes; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione-S-transferase (GST). The PRF also protected against histopathological changes produced by CCl₄ such as hepatocytic necrosis, fatty changes, vacuolation, etc. The data obtained in the present study suggests that PRF has potent antioxidant activity, prevent oxidative damage to major biomolecules and afford significant protection against CCl₄ induced oxidative damage in the liver.     

Carbon tetrachloride-induced liver damage in asialoglycoprotein receptor-deficient mice

The asialoglycoprotein (ASGP) receptor is an abundant hepatocyte-specific receptor involved in receptor-mediated endocytosis. This receptor's abundance and function is decreased by chronic ethanol administration prior to the appearance of pathology such as necrosis or inflammation. Hence, this study aimed to determine if ASGP receptor function is required to protect against liver injury by utilizing a knockout mouse model lacking functional ASGP receptor in the setting of carbon tetrachloride (CCl₄) hepatotoxicity. Briefly, ASGP receptor-deficient (RD) mice and wild-type (WT) mice were injected with 1 ml/kg body weight of CCl₄. In the subsequent week, mice were monitored for liver damage and pathology (aspartate transaminase (AST), alanine transaminase (ALT) and light microscopy). The consequences of CCl₄ injection were examined by measuring α-smooth muscle actin (α-SMA) deposition, contents of malondialdehyde and the percentage of apoptotic hepatocytes. After CCl₄ injection, RD mice showed increased liver pathology together with significantly increased activities of AST and ALT compared to that in WT mice. There were also significantly more apoptotic bodies, lipid peroxidation and deposition of α-SMA in RD mice versus WT mice following CCl₄ injection. Since these two mouse strains only differ in whether or not they have the ASGP receptor, it can be concluded that proper ASGP receptor function exerted a protective effect against CCl₄ toxicity. Thus, receptor-mediated endocytosis by the ASGP receptor could represent a novel molecular mechanism that is responsible for subsequent liver health or injury.     

Aminotriazole attenuated carbon tetrachloride-induced oxidative liver injury in mice

Carbon tetrachloride (CCl₄) has been used extensively to study xenobiotic-induced oxidative liver injury. Catalase (CAT) is a major antioxidant enzyme while aminotriazole (ATZ) is commonly used as a CAT inhibitor. In the present study, the effects of ATZ on CCl₄-induced liver injury were investigated. Our experimental data showed that pretreatment with ATZ significantly decreased CCl₄-induced elevation of serum aspartate transaminase (AST) and alanine transaminase (ALT) and improved hepatic histopathological abnormality. ATZ dose-dependently inhibited the activity of CAT, but it reduced the content of H₂O₂ and the levels of malondialdehyde (MDA) in liver tissues. ATZ decreased plasma level of pro-inflammatory cytokines (TNF-α and IL-6) and reduced hepatic levels of myeloperoxidase (MPO). In addition, posttreatment with ATZ also decreased the level of ALT and AST. These data indicated that ATZ effectively alleviated CCl₄-induced oxidative liver damage. These findings suggested that ATZ might have potential value in preventing oxidative liver injury.     

Medium optimization and potential hepatoprotective effect of mycelial polysaccharides from Pholiota dinghuensis Bi against carbon tetrachloride-induced acute liver injury in mice

Response surface methodology was employed to optimize the medium compositions for the production of mycelial polysaccharide from Pholiota dinghuensis Bi (PDP). As a result, the optimal medium for crude PDP production was determined as follows (g/L): glucose 36.0, corn flour 11.8, peptone 3.0, yeast extract 5.4, KH₂PO₄ 1.0, and MgSO₄ 1.5. In a verification experiment, a yield of 756 ± 38 mg/L crude PDP was obtained. Furthermore, biochemical assay and histopathological analysis showed that crude PDP exerted significant hepatoprotective effect in a dose-dependent manner against carbon tetrachloride (CCl₄)-induced acute liver injury. Crude PDP prevented the increase of activities of serum alanine aminotransferase and aspartate aminotransferase, reduced the formation of malondialdehyde and enhanced the activities of superoxide dismutase and glutathione peroxidase in CCl₄-induced hepatotoxicity in mice.     

Protective effects of seabuckthorn (Hippophae rhamnoides L.) seed oil against carbon tetrachloride-induced hepatotoxicity in mice

The present study examined the protective effects of seabuckthorn (Hippophae rhamnoides L., SBT) seed oil on carbon tetrachloride (CCl₄)-induced hepatic damage in male ICR mice. Our results showed that oral administration of SBT seed oil at doses of 0.26, 1.30, and 2.60 mg/kg for 8 weeks significantly reduced the elevated levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), triglyceride (TG), and cholesterol at least 13% in serum, and the level of malondialdehyde (MDA) in liver at least 22%, that was induced by CCl₄ (1 mL/kg) in mice. Moreover, the treatment of SBT seed oil was also found to significantly increase the activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px), glutathione reductase (GSH-Rd), and GSH content in liver up to 134%. Our study found that the optimal dose of SBT seed oil was 0.26 mg/kg, as the minimum amount exhibiting the greatest hepatoprotective effects on CCl₄-induced liver injury. Overall, the hepatoprotective effect of SBT seed oil at all tested doses was found to be comparable to that of silymarin (200 mg/kg) and have been supported by the evaluation of the liver histopathology in mice.     

TOP1 and 2, polysaccharides from Taraxacum officinale, attenuate CCl4-induced hepatic damage through the modulation of NF-κB and its regulatory mediators

In this work, we estimate the inhibitory effect of two polysaccharides from Taraxacum officinale (TOP) on CCl₄-induced oxidative stress and inflammation in Sprague–Dawley rats. TOP1 and 2 (304, 92 mg/kg bw) were administered for 7 days via a stomach sonde, and hepatitis was induced by a single dose of CCl₄ (50% CCl₄/olive oil; 0.5 mL/kg bw) administration. CCl₄ significantly elevated serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities. Histopathological observation further revealed that CCl₄-induced moderate levels of inflammatory cell infiltration, centrilobular fatty change, apoptosis, and necrosis. However, TOPs pretreatment markedly decreased AST and ALT activities as well as hepatic lesions. TOPs also increased free radical scavenging activity, as exhibited by a lowered TBARS concentration. TOPs pretreatment also reversed other hepatitis-associated symptoms, including GSH depletion, inhibited anti-oxidative enzyme activities, up-regulation of NF-κB and increased expression of its regulatory inflammatory mediators, such as inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β. These results suggest that TOPs have a hepatoprotective effect by modulating inflammatory responses and ameliorating oxidative stress.     

Effects of standardized bilberry fruit extract (Mirtoselect®) on resolution of CCl4-induced liver fibrosis in mice

Bilberry (Vaccinium myrtillus L) has been traditionally used in the treatment of various liver disorders. The aim of this study was to investigate the effects of bilberry fruit extract (BE) on carbon tetrachloride (CCl₄)-induced hepatic fibrosis. Male Balb/C mice were treated with CCl₄ dissolved in olive oil (20% v/v, 2 ml/kg) intraperitoneally (i.p.), twice a week for 7 weeks. BE (1, 5, and 10 mg/kg) was given to mice for next 15 days, 72 h after the last dose of CCl₄. The CCl₄ administration increased oxidative stress as well as the expression of tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β1) in the liver. Furthermore, increased α-smooth muscle actin (α-SMA) expression and hydroxyproline levels indicated activation of hepatic stellate cells (HSCs) and enhanced collagen production. BE 10 mg/kg markedly attenuated oxidative stress, decreased TNF-α, TGF-β1, and α-SMA expression, and eliminated hepatic collagen deposits. These results indicate that BE, in a dose dependent manner, induces the resolution of liver fibrosis by decreasing oxidative stress and inactivating HSCs via down-regulation of fibrogenic cytokines, TGF-β1 and TNF-α.     

Protective effect of fermented sea tangle against ethanol and carbon tetrachloride-induced hepatic damage in Sprague–Dawley rats

Sea tangle has long been used as Korean folk remedy to promote material health, and is one of the popular dietary supplement. This study was designed to evaluate the protective effect of fermented sea tangle (FST) against ethanol and carbon tetrachloride (CCl₄)-induced hepatotoxicity in rats. Sprague–Dawley rats were orally treated with FST (25, 250, 2500 mg/kg/day) with administration of ethanol (5 mL/kg) for 13 weeks and the single intraperitoneal (i.p.) dose of 50% CCl₄ (5 mL/kg/day, CCl₄ in olive oil) at 12 week, and repeated i.p. dose of 20% CCl₄ (2 mL/kg/day) for 1 week. Hepatotoxicity was evaluated by measuring the serum levels of glutamic pyruvate transaminase (GPT), gamma glutamyl transpeptidase (γ-GT) and malondialdehyde (MDA) as well as the tissue levels of antioxidant enzyme such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Ethanol and CCl₄-induced the rat liver damage, and significantly increased (p < 0.05) the GPT, γ-GT and MDA levels, and decreased the SOD, CAT and GPx levels. However, treatment with FST could decrease serum GPT, γ-GT, and MDA levels significantly in plasma, and increase the activities of SOD, CAT, and GPx in liver tissues compared with ethanol and CCl₄-treated group.     

Silica nanoparticles as hepatotoxicants

Nano-size materials are increasingly used in cosmetics, diagnosis, imaging and drug delivery, but the toxicity of the nano-size materials has never been fully investigated. Here, we investigated the relationship between particle size and toxicity using silica particles with diameters of 70, 300 and 1000 nm (SP70, SP300, and SP1000) as a model material. To evaluate acute toxicity, we first performed histological analysis of liver, spleen, kidney and lung by intravenous administration of silica particles. SP70-induced liver injury at 30 mg/kg body weight, while SP300 or 1000 had no effect even at 100 mg/kg. Administration of SP70 dose-dependently increased serum markers of liver injury, serum aminotransferase and inflammatory cytokines. Repeated administration of SP70 twice a week for 4 weeks, even at 10 mg/kg, caused hepatic fibrosis. Taken together, nano-size materials may be hepatotoxic, and these findings will be useful for future development in nanotechnology-based drug delivery system.     

Hepatoprotective and antioxidant activity of Melaleuca styphelioides on carbon tetrachloride-induced hepatotoxicity in mice

Context: Liver disease is a serious problem. Polyphenolic compounds have marked antioxidant effect and can prevent the liver damage caused by free radicals. In vitro studies have revealed the strong antioxidant activity of an ellagitannin-rich plant, namely, Melaleuca styphelioides Sm. (Myrtaceae).

Objective: In view of the limited therapeutic options available for the treatment of liver diseases, the hepatoprotective potential of the methanol extract of M. styphelioides leaves (MSE) was investigated against CCl₄-induced liver injury in mice.

Materials and methods: MSE was administered (500 and 1000?mg/kg/d p.o.) along with CCl₄ for 6 weeks. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were determined in the serum. Glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione transferase (GST), and malondialdehyde (MDA) were estimated in the liver homogenate. The bioactive components of MSE were identified by NMR, UV and HRESI-MS/MS data.

Results: MSE treatment (500 and 1000?mg/kg/d) markedly inhibited the CCl₄-induced increase in the levels of AST (31 and 38%), ALT (29 and 32%), ALP (13 and 19%), and MDA (22 and 37%) at the tested doses, respectively. MSE treatment markedly increased the levels of GSH (29 and 57%) and antioxidant enzymes compared with the CCl₄-treated group. MSE was more effective than silymarin in restoring the liver architecture and reducing the fatty changes, central vein congestion, Kupffer cell hyperplasia, inflammatory infiltration, and necrosis induced by CCl₄. The LD₅₀ of MSE was more than 5000?mg/kg.

Conclusion: MSE confers potent antioxidant and hepatoprotective effects against CCl₄-induced toxicity.     

Differential hepatoprotective mechanisms of rutin and quercetin in CCl4-intoxicated BALB/cN mice

Aim:

To investigate the mechanisms underlying the protective effects of quercetin-rutinoside (rutin) and its aglycone quercetin against CCl₄-induced liver damage in mice.

Methods:

BALB/cN mice were intraperitoneally administered rutin (10, 50, and 150 mg/kg) or quercetin (50 mg/kg) once daily for 5 consecutive days, followed by the intraperitoneal injection of CCl₄ in olive oil (2 mL/kg, 10% v/v). The animals were sacrificed 24 h later. Blood was collected for measuring the activities of ALT and AST, and the liver was excised for assessing Cu/Zn superoxide dismutase (SOD) activity, GSH and protein concentrations and also for immunoblotting. Portions of the livers were used for histology and immunohistochemistry.

Results:

Pretreatment with rutin and, to a lesser extent, with quercetin significantly reduced the activity of plasma transaminases and improved the histological signs of acute liver damage in CCl₄-intoxicated mice. Quercetin prevented the decrease in Cu/Zn SOD activity in CCl₄-intoxicated mice more potently than rutin. However, it was less effective in the suppression of nitrotyrosine formation. Quercetin and, to a lesser extent, rutin attenuated the inflammation in the liver by down-regulating the CCl₄-induced activation of nuclear factor-kappa B (NF-κB), tumor necrosis factor-α (TNF-α) and cyclooxygenase (COX-2). The expression of inducible nitric oxide synthase (iNOS) was more potently suppressed by rutin than by quercetin. Treatment with both flavonoids significantly increased NF-E2-related factor 2 (Nrf2) and heme oxygenase (HO-1) expression in injured livers, although quercetin was less effective than rutin at an equivalent dose. Quercetin more potently suppressed the expression of transforming growth factor-β1 (TGF-β1) than rutin.

Conclusion:

Rutin exerts stronger protection against nitrosative stress and hepatocellular damage but has weaker antioxidant and anti-inflammatory activities and antifibrotic potential than quercetin, which may be attributed to the presence of a rutinoside moiety in position 3 of the C ring.     

Ameliorative effects of Moringa oleifera Lam seed extract on liver fibrosis in rats

This study was carried out to evaluate the effect of Moringa oleifera Lam (Moringa) seed extract on liver fibrosis. Liver fibrosis was induced by the oral administration of 20% carbon tetrachloride (CCl₄), twice weekly and for 8 weeks. Simultaneously, M.oleifera Lam seed extract (1 g/kg) was orally administered daily. The biochemical and histological results showed that Moringa reduced liver damage as well as symptoms of liver fibrosis. The administration of Moringa seed extract decreased the CCl₄-induced elevation of serum aminotransferase activities and globulin level. The elevations of hepatic hydroxyproline content and myeloperoxidase activity were also reduced by Moringa treatment. Furthermore, the immunohistochemical study showed that Moringa markedly reduced the numbers of smooth muscle α-actin-positive cells and the accumulation of collagens I and III in liver. Moringa seed extract showed significant inhibitory effect on 1,1-diphenyl-2-picrylhydrazyl free radical, as well as strong reducing antioxidant power. The activity of superoxide dismutase as well as the content of both malondialdehyde and protein carbonyl, which are oxidative stress markers, were reversed after treatment with Moringa. Finally, these results suggested that Moringa seed extract can act against CCl₄-induced liver injury and fibrosis in rats by a mechanism related to its antioxidant properties, anti-inflammatory effect and its ability to attenuate the hepatic stellate cells activation.     

Protective potential of Royal Jelly against carbon tetrachloride induced-toxicity and changes in the serum sialic acid levels

Royal Jelly (RJ) is used in the Turkish folk medicine for the treatment of number of disorders. The present study describes the hepatoprotective and antioxidant activities of the RJ against carbon tetrachloride (CCl₄)-induced acute liver damage. Sprague–Dawley rats were used for the experiment. CCl₄ (0.8 ml/kg; s.c.) and RJ (50, 100, 200 mg/kg; orally) were given every other day, for 20 days. Malondialdehyde, reduced glutathione in whole blood and tissues; ceruloplasmin, sialic acid, ascorbic acid, retinol, β-carotene and liver enzymes levels in serum were measured. Additionally, histopathological alterations in the liver were examined. RJ exerted the significant protective effect on liver damage as well as on oxidative stress induced by CCl₄, resulting in reduced lipid peroxidation and improved endogenous antioxidant defence systems. It also reduced the elevated levels of liver enzymes. Histopathological study further confirmed the hepatoprotective effect of RJ, when compared with the CCl₄ treated control groups. In conclusion, present study reveals biological evidence that supports the use of RJ in the treatment of chemical-induced hepatotoxicity.     

Antifibrotic effects of ZK14, a novel nitric oxidedonating biphenyldicarboxylate derivative, on rat HSC-T6 cells and CCI4-induced hepatic fibrosis

Aim:

To study the pharmacologic effect of ZK₁₄, a novel nitric oxide-donating biphenyldicarboxylate (DDB) derivative, on HSC-T6 cells and on CCl₄-induced hepatic fibrosis.

Methods:

Inhibition of HSC-T6 cell growth by ZK₁₄ was evaluated by MTT assay. The effect of ZK₁₄ on the percentage of HSC-T6 cells undergoing apoptosis was measured using Annexin-V/PI double-staining and TUNEL assay. Mitochondrial membrane potential (MMP) and caspase activities were tested. Hepatic fibrosis was induced in Sprague-Dawley rats by intraperitoneal injection with 14% CCl₄. Rats with hepatic fibrosis were randomly divided into four groups: model control, ZK₁₄ (20 mg/kg), ZK₁₄ (10 mg/kg) and DDB (5 mg/kg). Levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), hyaluronic acid (HA), type III collagen (PCIII), and nitric oxide (NO) were assessed, and liver samples were stained with hematoxylin-eosin. The NO level in cells treated with ZK₁₄ in vitro was also measured.

Results:

The effect of ZK₁₄ on HSC-T6 cell apoptosis was concentration- and time-dependent, with up to 50% of cells becoming apoptotic when exposed to 100 μmol/L ZK₁₄ for 18 h. ZK₁₄ treatment resulted in mitochondrial membrane depolarization and activation of caspases 3 and 9. At a dose of 20 mg/kg, ZK₁₄ significantly decreased serum transaminase (AST, ALT) activities and fibrotic index (HA, PCIII) levels and significantly inhibited fibrogenesis.

Conclusion:

These data indicate that ZK₁₄, a novel NO-donating DDB derivative, promotes HSC-T6 apoptosis in vitro through a signaling mechanism involving mitochondria and caspase activation and it inhibits CCl₄-induced hepatic fibrosis in vivo. The results suggest that ZK₁₄ has potential therapeutic value in the treatment of hepatic fibrosis.     

Mushroom insoluble polysaccharides prevent carbon tetrachloride-induced hepatotoxicity in rat

The aim of the present study was to investigate the effect of mushroom insoluble non-starch polysaccharides (MINSP) on the carbon tetrachloride (CCl₄)-induced hepatic damage in rat. MINSP (100 and 200 mg/kg) administered daily orally for 15 days before CCl₄ (1.5 ml/kg). The effect of MINSP treatment was also examined in normal rats. Normal groups treated with MINSP showed significant decrease in serum activities of the liver enzymes, lipid peroxides and nitric oxide (NO) in the liver. Reduced glutathione (GSH) and total proteins (TP) contents in liver homogenate also increased after treatment with only MINSP for 15 days. In CCl₄-treated rats, significant elevation in serum liver enzymes, increased lipid peroxides and NO in the liver, and depletion of hepatic-GSH level were observed. Pre-treatment with MINSP significantly ameliorated the tested parameters when compared with CCl₄-treated group. It improved the antioxidant activity of the liver in a dose-dependent manner. Histopathological examination of hepatic tissue revealed that MINSP administration alone protected hepatocytes from the damage induced by CCl₄. Conclusion: MINSP are safe; it could be used as fat replacer in processing low fat diet. MINSP represents a good functional food and liver supporter for patient suffering from various liver diseases.     

A possible mechanism for the decrease in serum thyroxine level by phenobarbital in rodents

Effects of phenobarbital (PB) on the levels of serum thyroid hormones such as total thyroxine (T₄) and triiodothyronine were examined in male mice, hamsters, rats, and guinea pigs. One day after the final administration of PB (80 mg/kg, intraperitoneal, once daily for 4 days), significant decreases in the levels of the serum total T₄ and free T₄ occurred in mice, hamsters, and rats, while a significant decrease in the level of serum triiodothyronine was observed in hamsters and rats among the animals examined. In addition, a significant decrease in the level of serum thyroid-stimulating hormone was observed in only hamsters among the rodents examined. Significant increases in the level and activity of hepatic T₄-UDP-glucuronosyltransferase (UGT1A) after the PB administration occurred in mice, hamsters, and rats, while the increase in the amount of biliary [¹²⁵I]T₄-glucuronide after an intravenous injection of [¹²⁵I]T₄ to the PB-pretreated animals occurred only in rats. In mice, rats, and hamsters, but not guinea pigs, PB pretreatment promoted the clearance of [¹²⁵I]T₄ from the serum, led to a significant increase in the steady-state distribution volumes of [¹²⁵I]T₄, and raised the concentration ratio (Kp value) of the liver to serum and the liver distribution of [¹²⁵I]T₄. The present findings indicate that the PB-mediated decreases in the serum T₄ level in mice, hamsters, and rats, but not guinea pigs, occur mainly through an increase in the accumulation level of T₄ in the liver.     

Secretory phospholipase A₂-mediated progression of hepatotoxicity initiated by acetaminophen is exacerbated in the absence of hepatic COX-2

We have previously reported that among the other death proteins, hepatic secretory phospholipase A₂ (sPLA₂) is a leading mediator of progression of liver injury initiated by CCl₄ in rats. The aim of our present study was to test the hypothesis that increased hepatic sPLA₂ released after acetaminophen (APAP) challenge mediates progression of liver injury in wild type (WT) and COX-2 knockout (KO) mice. COX-2 WT and KO mice were administered a normally non lethal dose (400 mg/kg) of acetaminophen. The COX-2 KO mice suffered 60% mortality compared to 100% survival of the WT mice, suggesting higher susceptibility of COX-2 KO mice to sPLA₂-mediated progression of acetaminophen hepatotoxicity. Liver injury was significantly higher at later time points in the KO mice compared to the WT mice indicating that the abatement of progression of injury requires the presence of COX-2. This difference in hepatotoxicity was not due to increased bioactivation of acetaminophen as indicated by unchanged cyp2E1 protein and covalently bound ¹⁴C-APAP in the livers of KO mice. Hepatic sPLA₂ activity and plasma TNF-α were significantly higher after APAP administration in the KO mice. This was accompanied by a corresponding fall in hepatic PGE₂ and lower compensatory liver regeneration and repair (³H-thymidine incorporation) in the KO mice. These results suggest that hindered compensatory tissue repair and poor resolution of inflammation for want of beneficial prostaglandins render the liver very vulnerable to sPLA₂-mediated progression of liver injury. These findings are consistent with the destructive role of sPLA₂ in the progression and expansion of tissue injury as a result of continued hydrolytic breakdown of plasma membrane phospholipids of perinecrotic hepatocytes unless mitigated by sufficient co-induction of COX-2.