Pentoxifylline attenuates bacterial lipopolysaccharide-induced enhancement of allyl alcohol hepatotoxicity.

Small amounts of exogenous lipopolysaccharide (LPS) (10 ng/kg-100 microg/kg) enhance the hepatotoxicity of allyl alcohol in male Sprague-Dawley rats. This augmentation of allyl alcohol hepatotoxicity appears to be linked to Kupffer cell function, but the mechanism of Kupffer cell involvement is unknown. Since Kupffer cells produce tumor necrosis factor-alpha (TNF alpha) upon exposure to LPS, and this cytokine has been implicated in liver injury from large doses of LPS, we tested the hypothesis that TNF alpha contributes to LPS enhancement of allyl alcohol hepatotoxicity. Rats were treated with LPS (10-100 microg/kg iv) 2 h before allyl alcohol (30 mg/kg ip). Co-treatment with LPS and allyl alcohol caused liver injury as assessed by an increase in activity of alanine aminotransferase in plasma. Treatment with LPS caused an increase in plasma TNF alpha concentration, which was prevented by administration of either pentoxifylline (PTX) (100 mg/kg iv) or anti-TNF alpha serum (1 ml/rat iv) one h prior to LPS. Only PTX protected rats from LPS-induced enhancement of allyl alcohol hepatotoxicity; anti-TNF alpha serum had no effect. Exposure of cultured hepatocytes to LPS (1-10 microg/ml) or to TNF alpha (15-150 ng/ml) for 2 h did not increase the cytotoxicity of allyl alcohol (0.01-200 microM). These data suggest that neither LPS nor TNF alpha alone was sufficient to increase the sensitivity of isolated hepatocytes to allyl alcohol. Furthermore, hepatocytes isolated from rats treated 2 h earlier with LPS (i.e., hepatocytes which were exposed in vivo to TNF alpha and other inflammatory mediators) were no more sensitive to allyl alcohol-induced cytotoxicity than hepatocytes from na?ve rats. These data suggest that circulating TNF alpha is not involved in the mechanism by which LPS enhances hepatotoxicity of allyl alcohol and that the protective effect of PTX may be due to another of its biological effects.     

Enhancement of allyl alcohol hepatotoxicity by endotoxin requires extrahepatic factors.

Noninjurious doses of bacterial endotoxin (lipopolysaccharide; LPS) enhance allyl alcohol-induced liver damage in rats in a Kupffer cell (KC)-dependent fashion. To investigate the mechanism by which KCs contribute to liver injury in this model, isolated KCs and hepatocytes (HCs) were cocultured. Addition of LPS to the cocultured cells did not enhance allyl alcohol-induced cytotoxicity. In addition, recirculating perfusion of isolated livers from na?ve rats with LPS for 2 h did not significantly enhance allyl alcohol-induced toxicity as measured by release of alanine aminotransferase (ALT). These results suggest an extrahepatic factor is required for LPS potentiation of allyl alcohol hepatotoxicity. To examine whether the coagulation cascade contributes to injury in this model, rats were given either warfarin at 42 and 18 h before LPS, or heparin at 1 h before LPS, and were treated with allyl alcohol 2 h after LPS. Warfarin and heparin each significantly blocked the decrease in plasma fibrinogen levels and attenuated the increase in plasma ALT activity in rats treated with LPS and allyl alcohol. To assess the role of thrombin in this injury, isolated livers from rats pretreated with LPS were perfused with thrombin or vehicle and allyl alcohol. Though LPS pretreatment enhanced the toxicity of allyl alcohol compared with livers from na?ve rats, perfusion with thrombin did not increase sensitivity to allyl alcohol. In summary, LPS augments the hepatotoxicity of allyl alcohol through a mechanism involving extrahepatic factors, one of which may be a component of the coagulation cascade.     

Neutrophils contribute to endotoxin enhancement of allyl alcohol hepatotoxicity

Nontoxic doses of endotoxin (lipopolysaccharide, LPS) enhance the hepatotoxicity of many xenobiotic agents, including allyl alcohol. Systemic LPS exposure induces an inflammatory response, including accumulation and activation of neutrophils (PMNs) in the liver. The hypothesis that PMNs play a causal role in LPS enhancement of allyl alcohol hepatotoxicity was tested. Rats were pretreated with an anti-neutrophil antibody (anti-PMN immunoglobulin [lg]) to deplete circulating PMNs. Subsequently, they were given LPS or its vehicle, and 2 h later allyl alcohol was administered. The numbers of circulating and hepatic PMNs were decreased in rats pretreated with anti-PMN lg, and liver toxicity induced by cotreatment with LPS and allyl alcohol was attenuated. Treatment with allyl alcohol diminishes the concentration of reduced glutathione (GSH) in liver, raising the possibility that antioxidant defense was compromised in these livers. Accordingly, the hypothesis was tested that allyl alcohol-induced reduction in GSH renders liver cells more sensitive to reactive oxygen species produced by activated PMNs. Isolated hepatocytes were incubated with allyl alcohol in the presence and absence of isolated PMNs stimulated to produce reactive oxygen species. Allyl alcohol produced a concentration-dependent increase in ALT release from hepatocytes. Activated PMNs produced a statistically significant increase in cell killing that was so small it is unlikely to explain the role of PMNs in liver injury in vivo. To test the hypothesis that proteases released from activated PMNs increase the sensitivity of liver cells to allyl alcohol, isolated hepatocytes were incubated with medium from PMNs activated to undergo degranulation. Protease-containing medium from PMNs did not affect allyl alcohol-induced release of ALT from hepatocytes. Taken together, these results indicate that PMNs play a role in the potentiation of allyl alcohol toxicity by LPS. It is unlikely that PMNs contribute to this injury through release of reactive oxygen species or proteases, and other mechanisms must be involved.     

Effects of iron overload and lindane intoxication in relation to oxidative stress, Kupffer cell function, and liver injury in the rat

Parameters related to liver oxidative stress, Kupffer cell function, and hepatocellular injury were assessed in control rats and in animals subjected to lindane (40 mg/kg; 24 h) and/or iron (200 mg/kg; 4 h) administration. Independently of lindane treatment, iron overload enhanced the levels of iron in serum and liver. Biliary efflux of glutathione disulfide increased by 140, 160, or 335% by lindane, iron, or their combined administration, respectively, and the hepatic content of protein carbonyls was elevated by 5.84-, 2.95-, and 10-fold. Colloidal carbon uptake by perfused livers was not modified by lindane and/or iron, whereas gadolinium chloride (GdCl(3)) pretreatment diminished uptake by 60-72%. Carbon-induced liver O(2) uptake was not altered by lindane, whereas iron produced a 61% increase and the combined treatment led to a 72% decrease over control values. Pretreatment with GdCl(3) abolished these effects in all groups. Lindane-treated rats showed acidophilic hepatocytes in periportal areas and some hepatic cells with nuclear pyknosis, whereas iron overload led to moderate hyperplasia and hypertrophy of Kupffer cells and moderate inflammatory cell infiltration. Combined lindane-iron treatment led to hepatocytes with pyknotic nuclei, significant acidophilia, and extensive lymphatic and neutrophil infiltration in the portal space. Hepatic myeloperoxidase activity increased by 1.1-, 2.1-, or 6.7-fold by lindane, iron, or their combined administration, respectively. Liver sinusoidal lactate dehydrogenase efflux increased by 2.2-fold (basal conditions) and 9.7-fold (carbon infusion) in the lindane-iron treated rats, effects that were diminished by 35 and 78% by GdCl(3) pretreatment, respectively. These data support the contention that lindane sensitizes the liver to the damaging effects of iron overload by providing an added enhancement to the oxidative stress status in the tissue, and this may contribute to the alteration of the respiratory activity of Kupffer cells and the development of an inflammatory response.     

Role of kupffer cells in cold/warm ischemia-reperfusion injury of rat liver

The mechanisms of liver injury from cold storage and reperfusion are not completely understood. The aim of the present study was to investigate whether the inactivation of Kupffer cells (KCs) by gadolinium chloride (GdCl3) modulates ischemia-reperfusion injury in the rat liver. Hepatic function was assessed using an isolated perfused rat liver model. In livers subjected to cold storage at 4 degees C in University of Wisconsin solution for 24 hrs and to 20 min rewarm-ing ischemia, oxygen uptake was markedly decreased, Kupffer cell phagocytosis was stimulated, releases of purine nucleoside phosphorylase and lactate dehydrogenase were increased as compared with control livers. Pretreatment of rats with GdCl3, a selective KC toxicant, suppressed Kupffer cell activity, and reduced the grade of hepatic injury induced by ischemia-reperfusion. While the initial mixed function oxidation of 7-ethoxycoumarin was not different from that found in the control livers, the subsequent conjugation of its meta-bolite to sulfate and glucuronide esters was suppressed by ischemia-reperfusion. GdCl3 restored sulfation and glucuronidation capacities to the level of the control liver. Our findings suggest that Kupffer cells could play an important role in cold/warm ischemia-reperfusion hepatic injury.     

Gadolinium chloride, a Kupffer cell inhibitor, attenuates hepatic injury in a rat model of chronic cholestasis

The aim of the current study was to elucidate the effect of Kupffer cells inhibition on hepatic injury induced by chronic cholestasis. Sprague-Dawley rats underwent bile duct ligation (BDL) or sham operation and were treated with either saline solution or gadolinium chloride (GdCl(3), a specific Kupffer cell inhibitor, 20 mg/kg i.p. daily). Serum and liver samples were collected after 28 days. Direct and total bilirubin concentrations and serum enzyme activities of alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and γ-glutamyl transpeptidase (GGT) increased following BDL (p < 0.01). On the contrary to bilirubin concentrations and AST activity, GdCl(3) partially prevented the elevation in ALP, ALT and GGT enzyme activities (p < 0.05). GdCl(3) alleviated lipid peroxidation (reflected by malondialdehyde [MDA] concentration) and increased the activities of antioxidant enzymes (i.e. catalase and glutathione peroxidase) in liver samples after BDL (p < 0.05). Fibrosis, ductular proliferation and portal inflammation were also scored in liver samples. Among morphological changes appeared following BDL (i.e. marked fibrosis, portal inflammation and ductular proliferation); only ductular proliferation was not alleviated by GdCl(3). Therefore, Kupffer cells inhibition has beneficial effects against the development of hepatic injury induced by chronic cholestasis.     

Effect of hepatotoxic chemicals and hypoxia on hepatic nonparenchymal cells: impairment of phagocytosis by Kupffer cells and disruption of the endothelium in rat livers perfused with colloidal carbon

Kupffer cells play an important role in liver function and phagocytosis of foreign particles in the hepatic portal tract. Therefore, the purpose of this study was to investigate the influence of several hepatotoxic chemicals (allyl alcohol, ethylhexanol, and menadione) and hypoxia on phagocytic activity of Kupffer cells in perfused rat liver. A recently developed optical method was used to determine rates of phagocytosis of carbon particles by Kupffer cells in periportal and pericentral regions of the liver lobule based on changes in reflected light from the liver surface (te Koppele, J.M., and Thurman, R.G. 1990. Am. J. Physiol. 259, G814-G821). With all chemicals studied, a rapid (10-30 min) decline in the rate of phagocytosis preceded parenchymal cell death as assessed from release of lactate dehydrogenase. These chemicals impaired parenchymal cell energy status as indicated by inhibition of O2 uptake and bile flow prior to cell death. Livers swell when they are damaged, a process which increases perfusion pressure and could theoretically damage the endothelium and lead to nonspecific uptake of carbon. In perfusions with a hepatotoxic concentration of allyl alcohol (350 microM), carbon particles accumulated in swollen livers after 70 min of perfusion. Histological studies revealed that carbon particles were localized predominantly in periportal regions of the liver lobule in perfusions with all hepatotoxicants studied. When perfusion pressure was elevated to 20 cm H2O in the absence of hepatotoxicants, carbon particles detected optically accumulated in upstream regions of the liver lobule (periportal or pericentral regions in perfusions in the anterograde or retrograde directions, respectively). In scanning electron microscopy of nonswollen livers, the endothelium remained intact. In swollen livers, however, the endothelium was disrupted and carbon was detected bound nonspecifically to parenchymal cells. Fifteen minutes after addition of allyl alcohol, bile canaliculi were dilated and endothelial fenestrations were enlarged. After 2 hr of perfusion with allyl alcohol, hepatic ultrastructure was severely disrupted. Thus, it is concluded that perfusion with hepatotoxic chemicals or hypoxia results in a rapid decrease of particle phagocytosis by Kupffer cells followed by changes in endothelial cell ultrastructure.     

Influence of Kupffer cell inactivation on cycloheximide-induced hepatic injury

In our previous study, we found that cycloheximide (CHX) induces hepatocellular necrosis as well as hepatocellular apoptosis. This article evaluates the role of Kupffer cells on cycloheximide-induced hepatic injury using gadolinium chloride (GdCl(3)) for the inhibition of Kupffer cells. One group of rats was treated with CHX (CHX group), and another was treated with GdCl(3) before being treated with the same dose of CHX (GdCl(3)/CHX group). The necrotic change in the GdCl(3)/CHX group was exacerbated under the induction of hepatocellular apoptosis by the CHX treatment. A substantial diminution of the number of ED1- or ED2-positive cells was demonstrated in the GdCl(3)/CHX group compared to the CHX group. In addition, the degree of decrease in ED2-positive cells was more apparent than that in ED1-positive cells. Increases in the mRNA levels of IL-10 and Stat3 were observed in the CHX group, but not in the GdCl(3)/CHX group. On the other hand, the hepatic mRNA levels of chemokines and adhesion molecules such as Ccl20, LOX-1, and E-selectin were significantly increased only in the GdCl(3)/CHX group. Thus, Kupffer cell inactivation by the GdCl(3) treatment leads to a loss of the capacity to produce IL-10, supposedly resulting in the enhancement of pro-inflammatory cytokine activities such as tumor necrosis factor (TNF) signaling. These events are suggested to be a factor of the inflammatory exacerbation in the livers of the GdCl(3)/CHX group. In conclusion, Kupffer cells may play a role in protecting hepatic necroinflammatory changes by releasing anti-inflammatory cytokines following the hepatocellular apoptosis resulting from CHX treatment.     

Enhanced Effectiveness of Dimethyl-4,4‘-dimethoxy-5,6,5’,6‘-dimethylene dioxybiphenyl-2,2’-dicarboxylate in Combination with Garlic Oil against Experimental Hepatic Injury in Rats and Mice

The present study was designed to evaluate the effects of dimethyl-4,4′-dimethoxy-5,6,5′,6′-dimethylene dioxybiphenyl-2,2′-dicarboxylate (PMC) in combination with garlic oil against chemical-induced hepatic injury in rats and mice. Rats insulted with carbon tetrachloride were concomitantly treated with PMC and/or garlic oil (50 and 100 mg kg^?1, respectively) for four weeks. Whereas treatment of animals with garlic oil alone was ineffective in suppressing carbon tetrachloride-induced hepatotoxicity, administration of PMC in combination with garlic oil more effectively protected the liver against the carbon tetrachloride-induced insult than PMC alone, as monitored by serum aminotransferase activity. Hepatoprotective effects of the formulation were further supported by the changes in the numbers of Kupffer cells and dead hepatocytes. Although prior treatment of rats with PMC for three days failed to protect hepatotoxicity elicited by allyl alcohol, the formulation of PMC and garlic oil was capable of blocking allyl alcohol-induced hepatotoxicity by ～ 40%. To further examine the effect of the agents on lipid metabolism in the liver, hepatic triglycerides and cholesterol contents were assessed in mice after a diet containing PMC and/or garlic oil for one week followed by a single dose of carbon tetrachloride. Garlic oil appeared to be more effective in bringing hepatic lipid levels to those of control than PMC alone. Treatment of animals with PMC in combination with garlic oil synergistically improved chemical-induced impairment of hepatic triglycerides and cholesterol. These results demonstrated that PMC in combination with garlic oil is effective in protecting (or treating) chemical-induced hepatic injury and that the formulation may be effective against chemical-induced fat-infiltration of the liver.     

Effect of aging on liver glutathione levels and hepatocellular injury from carbon tetrachloride, allyl alcohol or galactosamine

Severity of liver damage 24 hr after i.p. administration of carbon tetrachloride (0.2 ml/kg), allyl alcohol (0.036 ml/kg) or galactosamine (400 mg/kg) was evaluated in male rats at 4-5, 14-15 or 24-25 months of age. Allyl alcohol hepatotoxicity, as judged by light microscopy and serum alanine aminotransferase levels, increased markedly as a function of age. In contrast, carbon tetrachloride and galactosamine toxicities were unchanged or slightly diminished in old rats. Hepatic glutathione (GSH) concentrations were unaffected by aging; thus, the age-dependent increase in susceptibility to allyl alcohol toxicity was not a result of diminished GSH availability in old age. Hepatotoxicant-induced changes in GSH were observed in allyl alcohol-treated old rats (20% increase) and in galactosamine-treated young-adult and middle-aged rats (30% decrease).     

Mechanism of allyl alcohol toxicity and protective effects of low-molecular-weight thiols studied with isolated rat hepatocytes

Freshly isolated hepatocytes from male rats were incubated with allyl alcohol at concentrations up to 2 mM. Allyl alcohol exerted a dose-dependent toxicity on the cells which was inversely related to cellular glutathione (GSH) content and accordingly influenced by stimulation as well as inhibition of GSH synthesis. The toxicity was prevented by inhibitors of alcohol dehydrogenase and augmented by the aldehyde dehydrogenase inhibitor disulfiram, suggesting that the toxic metabolite was the reactive aldehyde acrolein. The pattern of hepatocellular metabolism of allyl alcohol was monitored by high-pressure liquid chromatography (HPLC) analysis. The results suggest that acrolein, which is formed by the activity of alcohol dehydrogenase, preferentially reacts with cellular GSH to form an aldehyde-GSH adduct which subsequently is metabolized to the corresponding acid. In addition, a thiohemiacetal may be produced and subsequently degraded. In cells depleted of GSH, acrolein may react with essential macromolecules and thereby lead to structural and functional derangement and, eventually, irreversible injury.     

氯化钆减轻肝脏缺血再灌注损伤的实验研究

目的:探讨氯化钆(Gadolinium Chloride,GdCl3)抑制肝脏枯否细胞对大鼠肝脏缺血再灌注损伤的保护作用。方法:雌性Wistar大鼠30只随机分为3组,对照组只开腹和关腹,术前24h、48h经鼠尾静脉注射生理盐水,每次7mL/kg;肝脏缺血再灌注(I/R)组术前24h、48h经鼠尾静脉注射生理盐水,每次7mL/kg;氯化钆 肝脏缺血再灌注(GdCl3 I/R)组,术前24h、48h经鼠尾静脉注射0.2%氯化钆溶液,每次7mL/kg。第3天进行肝脏部分缺血再灌注手术(10%水合氯醛麻醉,上腹正中开口)。缺血30min后,原位血液再灌注2h。取肝中叶组织,制备10%组织匀浆用于乳酸脱氢酶(LDH)活力的测定;分离肝细胞,进行细胞凋亡与坏死检验;抽提肝组织细胞总RNA,利用RT-PCR法检测IL-10mRNA表达。结果:部分肝脏缺血再灌注后,I/R组LDH活力明显低于对照组(P<0.05),也低于GdCl3 I/R组(P<0.05);I/R组肝细胞大量死亡,GdCl3 I/R组中有早期凋亡肝细胞和晚期凋亡肝细胞,死亡肝细胞大大减少;I/R组IL-10表达量明显增多,GdCl3 I/R组IL-10表达量相对较少,对照组IL-10基本不表达。结论:氯化钆能够抑制枯否细胞吞噬、分泌功能,具有减轻肝脏缺血再灌注的损伤作用。     

Kupffer cells are responsible for liver cirrhosis induced by carbon tetrachloride

Inhibition of Kupffer cells could disrupt the sequence of events leading to organ injury by damping down the fibrogenic stimulus. To elucidate the role of Kupffer cells in liver fibrosis and cirrhosis, rats were treated with gadolinium chloride (GdCl(3)) and cirrhosis was induced by subchronic carbon tetrachoride (CCl(4)) administration. Carbon tetrachloride was administered three times per week for 8 weeks to male Wistar rats treated simultaneously with GdCl(3) (20 mg kg(-1), i.p. daily); appropriate controls were performed. Serum enzyme activities of alkaline phosphatase (ALP), gamma-glutamyl transpeptidase (gamma-GTP) and alanine aminotransferase (ALT) and bilirubin concentration increased significantly by CCl(4), whereas GdCl(3) prevented completely the increase in gamma-GTP and partially prevented the increase in ALP, ALT and bilirubins (P < 0.05). Liver glycogen was depleted by CCl(4), an effect that GdCl(3) was not capable of preventing. Moreover, gadolinium by itself depleted it. Lipid peroxidation increased about 2.5-fold by administration with CCl(4), whereas GdCl(3) preserved lipid peroxidation within normal values. Hepatic collagen increased threefold after subchronic intoxication with CCl(4) (P < 0.05) whereas GdCl(3) prevented partially (P < 0.05) the increase in collagen content, as evidenced by the liver hydroxyproline content and by the histopathological analysis. The present results suggest that Kupffer cells are needed for the production of CCl(4)-induced cirrhosis, because their inactivation with GdCl(3) prevents the disease.     

Differential hepatotoxicity induced by cadmium in Fischer 344 and Sprague-Dawley rats.

A number of reports document that Fischer 344 (F344) rats are more susceptible to chemically induced liver injury than Sprague-Dawley (SD) rats. Cadmium (CdCl2), a hepatotoxicant that does not require bioactivation, was used to better define the biological events that are responsible for the differences in liver injury between F344 and SD rats. CdCl2 (3 mg/kg) produced hepatotoxicity in both rat strains, but the hepatic injury was 18-fold greater in F344 rats as assessed by plasma alanine aminotransferase (ALT) activity. This difference in toxicity was not observed when isolated hepatocytes were incubated with CdCl2 in vitro, indicating that other cell types contribute to Cd-induced hepatotoxicity in vivo. Indeed, the sieve plates of hepatic endothelial cells (EC) in F344 rats were damaged to a greater degree than EC in SD rats. Additionally, Kupffer cell (KC) inhibition reduced hepatotoxicity in both strains, suggesting that this cell type is involved in the progression of CdCl2-induced hepatotoxicity. Moreover, enhanced synthesis of heat shock protein 72 occurred earlier in the SD rat. Maximal levels of hepatic metallothionein (MT), a protein associated with cadmium tolerance, were greater in SD rats. These protective factors may limit CdCl2-induced hepatocellular injury in SD compared with F344 rats by reducing KC activation and the subsequent inflammatory response that allows for the progression of hepatic injury.     

The roles of Kupffer cells in hepatocellular dysfunction after femur fracture trauma in rats

The aim of this study was to investigate the effects of trauma on alterations in cytochrome P450 (CYP 450)-dependent drug metabolizing function and to determine the role of Kupffer cells in hepatocellular dysfunction. Rats underwent closed femur fracture (FFx) with associated soft-tissue injury under anesthesia, while control animals received only anesthesia. To deplete Kupffer cells in vivo, gadolinium chloride (GdCl3) was injected intravenously via the tail vein at 7.5 mg/kg body wt., 1 and 2 days prior to FFx surgery. At 72 h after FFx, serum alanine aminotransferase (ALT) activity was increased, and this increase was attenuated by GdCl3 pretreatment. Serum aspartate aminotransferase (AST) and lipid peroxidation levels were not changed by FFx. Hepatic microsomal CYP 450 content and aniline p-hydroxylase (CYP 2E1) activity were significantly decreased; decreases that were not prevented by GdCl3. The level of CYP 2B1 activity was decreased by Kupffer cell inactivation, but not by FFx. There were no significant differences in the activities of CYP 1A1, CYP 1A2 and NADPH-CYP 450 reductase among any of the experimental groups. Our findings suggest that FFx trauma causes mild alterations of hepatic CYP 450-dependent drug metabolism, and that Kupffer cells are not essential for the initiation of such injury.     

Attenuation of cadmium-induced liver injury in senescent male fischer 344 rats: role of Kupffer cells and inflammatory cytokines

In the previous study we showed that senescent male Fischer 344 rats were resistant to Cd-induced hepatotoxicity compared with young-adult rats. In the present study we investigated the role of Kupffer cells and inflammatory cytokines in this effect of aging. The phagocytic activity of Kupffer cells, determined as the removal of carbon from blood, was stimulated by the administration of a hepatotoxic dose of Cd (3 mg/kg sc) in young-adult (5 months) rats but not in old (28 months) rats. Hepatic concentrations of interleukin (IL)-1beta and cytokine-induced neutrophil chemoattractant (CINC), but not of tumor necrosis factor-alpha or IL-6, were elevated in young rats treated with Cd. In old rats, however, the increase in IL-1beta produced by Cd was not statistically significant and the increase in CINC was much lower than in young-adult rats. Pretreatment with gadolinium chloride or cyclosporin A inhibited the elevations in hepatic cytokines and attenuated Cd-induced liver damage, assessed on the basis of serum alanine aminotransferase and sorbitol dehydrogenase activities. Cd-induced hepatotoxicity in the different treatment groups correlated well with hepatic levels of CINC (r = 0.98, p < 0.001) but not with those of IL-1beta. The results suggest that (1) Kupffer cell activation is essential for inflammatory liver damage from Cd, (2) IL-1beta and CINC are important mediators of the inflammatory response induced by Cd, and (3) the attenuation of Cd-induced liver injury in senescent rats is caused by an impairment in Kupffer cell activation, leading to a lower production of CINC and less inflammatory liver injury.     

Effect of carboxylesterase inhibitors on the acute hepatotoxicity of esters of allyl alcohol

Inhibitors of carboxylesterases were used to determine the importance of enzymatic hydrolysis in the production of liver injury by esters of allyl alcohol. Hydrolysis of the esters allyl acetate, allyl cinnamate, and allyl phenoxyacetate by homogenates of liver from rats treated with 125 mg/kg triorthotolyl phosphate (TOTP) was almost completely inhibited compared to that of control livers. Allyl acetate, allyl cinnamate, and allyl phenoxyacetate were administered orally to rats 18 hr after pretreatment with 125 mg/kg TOTP or 0.5 to 10 mg/kg of the defoliant S,S,S-tributylphosphorotrithioate (DEF). TOTP pretreatment significantly inhibited the rise in plasma alanine-α-ketoglutarate transaminase (AKT) activity and prevented changes in liver morphology produced by 60 to 150 mg/kg allyl acetate. DEF pretreatment protected against the hepatotoxicity of 60 mg/kg allyl acetate. This protective effect was maximal after treatment with 1 mg/kg DEF, which inhibited liver esterase 56%. TOTP prevented the elevation of plasma AKT activity induced by 250, 400, or 600 mg/kg allyl cinnamate. TOTP exerted only a slight protective effect against allyl phenoxyacetate hepatic necrosis, in that it prevented the injury produced by 200 mg/kg but not that produced by 250 or 400 mg/kg allyl phenoxyacetate. Pretreatment of rats with 375 mg/kg pyrazole, an inhibitor of alcohol dehydrogenase, completely prevented the elevation of plasma AKT activity after 90 mg/kg allyl acetate or 250 mg/kg allyl cinnamate. These studies demonstrate that, while it is likely that all three allyl esters share a common mechanism of hepatotoxic action, enzymatic hydrolysis is a necessary step in the activation of allyl acetate and allyl cinnamate to hepatotoxins but is less important in the activation of allyl phenoxyacetate.     

Methoxyflurane enhances allyl alcohol hepatotoxicity in rats. Possible involvement of increased acrolein formation

The effect of methoxyflurane anesthesia on allyl alcohol-induced hepatotoxicity and the metabolism of allyl alcohol was studied in male rats. Hepatotoxicity was assessed by the measurement of serum alanine aminotransferase activity and histopathological examination. Allyl alcohol-induced hepatotoxicity was enhanced when allyl alcohol (32 mg/kg) was administered 4 hr before or up to 8 days after a single 10-min exposure to methoxyflurane vapors. The possibility that methoxyflurane increases alcohol dehydrogenase-dependent oxidation of allyl alcohol to acrolein, the proposed toxic metabolite, was evaluated by measuring the rate of acrolein formation in the presence of allyl alcohol and liver cytosol. The effect of methoxyflurane on alcohol dehydrogenase activity in liver cytosol was also assessed by measuring the rate of NAD+ utilization in the presence of ethyl alcohol or allyl alcohol. Alcohol dehydrogenase activity and rate of acrolein formation were elevated in methoxyflurane-pretreated rats. The results suggest that a modest increase in alcohol dehydrogenase activity and rate of acrolein formation markedly enhances allyl alcohol-induced hepatotoxicity.