Antidotal effects of deferrioxamine in experimental liver injury--role of lipid peroxidation

Oxidant Stress and Acetaminophen Hepatotoxicity: Mechanism-Based Drug Development

Significance: Acetaminophen (APAP) is one of the quantitively most consumed drugs worldwide. Although safe at therapeutic doses, intentional or unintentional overdosing occurs frequently causing severe liver injury and even liver failure. In the United States, 50% of all acute liver failure cases are caused by APAP overdose. However, only one antidote with a limited therapeutic window, N-acetylcysteine, is clinically approved. Thus, more effective therapeutic interventions are urgently needed. Recent Advances: Although APAP hepatotoxicity has been extensively studied for almost 50 years, particular progress has been made recently in two areas. First, there is now a detailed understanding of involvement of oxidative and nitrosative stress in the pathophysiology, with identification of the reactive species involved, their initial generation in mitochondria, amplification through the c-Jun N-terminal kinase pathway, and the mechanisms of cell death. Second, it was demonstrated in human hepatocytes and through biomarkers in vivo that the mechanisms of liver injury in animals accurately reflect the human pathophysiology, which allows the translation of therapeutic targets identified in animals to patients. Critical Issues: For progress, solid understanding of the pathophysiology of APAP hepatotoxicity and of a drug's targets is needed to identify promising new therapeutic intervention strategies and drugs, which may be applied to humans. Future Directions: In addition to further refine the mechanistic understanding of APAP hepatotoxicity and identify additional drugs with complementary mechanisms of action to prevent cell death, more insight into the mechanisms of regeneration and developing of drugs, which promote recovery, remains a future challenge. Antioxid. Redox Signal. 35, 718-733.

Ferroptosis and Acetaminophen Hepatotoxicity: Are We Going Down Another Rabbit Hole?

Acetaminophen (APAP) hepatotoxicity is the most frequent cause of acute liver failure in the US. The mechanisms of APAP-induced liver injury have been under extensive investigations for decades, and many key events of this necrotic cell death are known today. Initially, two opposing hypotheses for cell death were proposed: reactive metabolite and protein adduct formation versus reactive oxygen and lipid peroxidation (LPO). In the end, both mechanisms were reconciled, and it is now generally accepted that the toxicity starts with formation of reactive metabolites that, after glutathione depletion, bind to cellular proteins, especially on mitochondria. This results in a mitochondrial oxidant stress, which requires amplification through a mitogen-activated protein kinase cascade, leading ultimately to enough reactive oxygen and peroxynitrite formation to trigger the mitochondrial membrane permeability transition and cell death. However, the earlier rejected LPO hypothesis seems to make a comeback recently under a different name: ferroptosis. Therefore, the objective of this review was to critically evaluate the available information about intracellular signaling mechanisms of APAP-induced cell death and those of ferroptosis. Under pathophysiologically relevant conditions, there is no evidence for quantitatively enough LPO to cause cell death, and thus APAP hepatotoxicity is not caused by ferroptosis. However, the role of mitochondria-localized minor LPO remains to be further investigated.

Iron chelation attenuates intracranial pressure and improves survival in a swine model of acute liver failure

Oxidative mechanisms have been implicated in the pathogenesis of brain edema in acute liver failure (ALF). The aim of this study was to test the hypothesis that inhibition of iron-catalyzed oxidative reactions through iron chelation using deferoxamine could attenuate brain edema in a swine model of ischemic ALF. Following ALF induction (end-to-side portacaval anastomosis and ligation of the hepatoduodenal ligament), 14 animals were randomized to a study group that received an intravenous infusion of 150 mg/kg deferoxamine (group DF; n = 7) or a control group (group C; n = 7). Six sham-operated animals were also assigned to a deferoxamine-treated group (n = 3) or a control group (n = 3). Hemodynamic, neurological, and hematological parameters were monitored postoperatively. All sham animals maintained normal hemodynamics and intracranial pressure. At 18 hours, group DF animals had higher mean arterial pressure (mean +/- standard deviation: 98.0 +/- 15.9 versus 69.9 +/- 15.8 mmHg, P < 0.004), lower intracranial pressure (18.1 +/- 8.6 versus 32.7 +/- 13.4 mmHg, P < 0.032), and higher cerebral perfusion pressure (76.4 +/- 16.4 versus 37.1 +/- 25.6 mmHg, P < 0.006) in comparison with group C. Similar differences were recorded up to the 24th postoperative hour, leading to a significant difference in animal survival (88% in group DF versus 17% in group C, P < 0.001). Furthermore, group DF exhibited an attenuated increase of serum malondialdehyde from the baseline (16% versus 74%, P < 0.05) and lower brain malondialdehyde concentrations (3.7 +/- 1.3 versus 5.7 +/- 2.0 microM/mg of protein, P < 0.05) in comparison with controls. In conclusion, deferoxamine delayed the development of intracranial hypertension and improved survival in pigs with ischemic ALF.

In vitro and in vivo protective effects of proteoglycan isolated from mycelia of Ganoderma lucidum on carbon tetrachloride-induced liver injury

AIM: To investigate the possible mechanism of the protective effects of a bioactive fraction, Ganoderma lucidum proteoglycan (GLPG) isolated from Ganoderma lucidum mycelia, against carbon tetrachloride-induced liver injury.

METHODS: A liver injury model was induced by carbon tetrachloride. Cytotoxicity was measured by MTT assay. The activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined with an automatic multifunction-biochemical analyzer and the levels of superoxide dismutase (SOD) and TNF-α were determined following the instructions of SOD kit and TNF radioimmunoassay kit. Liver sections were stained with hematoxylin and eosin (H&E) for histological evaluation and examined under light microscope.

RESULTS: We found that GLPG can alleviate the L-02 liver cells injury induced by carbon tetrachloride (CCl₄) through the measurements of ALT and AST activities and the administration of GLPG to L-02 cells did not display any toxicity. Furthermore, histological analysis of mice liver injury induced by CCl₄ with or without GLPG pretreatment indicated that GLPG can significantly suppress the toxicity induced by CCl₄ in mice liver. We also found that GLPG reduced TNF-α level induced by CCl₄ in the plasma of mice, whereas increased SOD activity in the rat serum.

CONCLUSION: GLPG has hepatic protective activity against CCl₄-induced injury both in vitro and in vivo. The possible anti-hepatotoxic mechanisms may be related to the suppression of TNF-α level and the free radical scavenging activity.

Curcumin ameliorates acute thioacetamide-induced hepatotoxicity

BACKGROUND AND AIM

Increased production of reactive oxygen species and nitric oxide and activation of nuclear factor kappa B are implicated in the pathogenesis of various liver diseases, including fulminant hepatic failure. Curcumin is a naturally occurring anti-oxidant that reduces oxidative stress and inhibits nuclear factor kappa B and nitric oxide formation. The aim of the present study is to assess curcumin's therapeutic potential in acute thioacetamide hepatotoxicity, a rat model of fulminant hepatic failure.

METHODS

Fulminant hepatic failure was induced by two intraperitoneal (i.p.) injections of 300 mg/kg thioacetamide (TAA) at 24-h intervals. The experimental groups received a low-dose (200 mg/kg per day, i.p.) or a high-dose (400 mg/kg per day) of curcumin, initiated 48 h prior to the first TAA injection. A fourth group was administered neither TAA nor curcumin and served as a control.

RESULTS

The survival rate was higher in both curcumin-treated groups compared to the TAA only treated group. Biochemical parameters of liver injury, blood ammonia and hepatic necroinflammation were lower in the low-dose curcumin group compared to TAA controls, and were further reduced in the high-dose group (P < 0.05 and P < 0.01, respectively). Curcumin treatment also reduced the TAA-induced elevated hepatic levels of thiobarbituric acid-reactive substances (TBARS), and inhibited the nuclear binding of nuclear factor kappa B (NFkappaB) and inducible nitric oxide (iNOS) protein expression.

CONCLUSIONS

Curcumin improved survival and minimized oxidative stress, hepatocellular injury and hepatic necroinflammation, NFkappaB binding and iNOS expression in a rat model of FHF. These findings support the role of ROS, NFkappaB and iNOS in mediating liver insult due to TAA, and that of curcumin as a hepato-protectant.

Protective effect of N-acetylcysteine and deferoxamine on carbon tetrachloride-induced acute hepatic failure in rats

OBJECTIVE

Carbon tetrachloride (CCl4) is a lipid-soluble potent hepatotoxic; thus, it widely is used as an animal model of severe hepatic failure. Treatment with antioxidants may modulate the toxic effects of CCl4 on liver, generally with drug administration before CCl4, which can restrict its use in the clinical setting. We here describe the effects of N-acetylcysteine, deferoxamine, or both in the treatment of CCl4-induced hepatic failure.

DESIGN

Prospective, randomized, controlled experiment.

SETTING

Animal basic science laboratory.

SUBJECTS

Male Wistar rats, weighing 200-250 g.

INTERVENTIONS

Rats exposed to CCl4 were treated with N-acetylcysteine and/or deferoxamine or vehicle.

MEASUREMENTS AND MAIN RESULTS

N-acetylcysteine plus deferoxamine treatment significantly attenuated hepatic and central nervous system oxidative damage after acute hepatic failure induced by CCl4. In addition, the serum levels of alanine aminotransferase, total bilirubin, and prothrombin time in the N-acetylcysteine plus deferoxamine group were significantly lower than those in the N-acetylcysteine or deferoxamine and saline groups. After N-acetylcysteine plus deferoxamine treatment, hepatocellular necrosis and inflammatory infiltration induced by carbon tetrachloride were greatly decreased. Survival in untreated rats was 5%. Survival increased to 25% and 35%, respectively, with N-acetylcysteine and deferoxamine treatment. In rats treated with N-acetylcysteine plus deferoxamine, survival was 80%.

CONCLUSIONS

Our data provide the first experimental demonstration that N-acetylcysteine plus deferoxamine reduces mortality rate, decreases oxidative stress, and limits inflammatory infiltration and hepatocyte necrosis induced by CCl4 in the rat.

The antioxidant and antifibrogenic effects of the glycosaminoglycans hyaluronic acid and chondroitin-4-sulphate in a subchronic rat model of carbon tetrachloride-induced liver fibrogenesis

Hepatic fibrosis involves the interplay of many factors including reactive oxygen species. Recent reports described antioxidant properties of glycosaminoglycans (GAGs). Since several findings have shown that hyaluronic acid (HYA) and chondroitin-4-sulphate (C4S) may act as antioxidant molecules, the aim of this research was to evaluate the antioxidant effects of HYA and C4S treatment in a rat model of liver fibrosis. The effect on tissue inhibitors of metalloproteinases (TIMPs) was also studied. Liver fibrosis was induced in rats by eight intraperitoneal injections of CCl4, twice a week for 6 weeks. HYA or C4S alone (25 mg/kg) or HYA and C4S in combination (12.5 + 12.5 mg/kg) were administered daily by the same route during the 6 weeks. At the end of the 6-week treatment period (24 h after the last dose of GAGs), the following parameters were evaluated: (1) serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, as index of hepatic cell disruption; (2) hepatic conjugated dienes (CD), as index of lipid peroxidation; (3) hepatic TIMPs activity and expression; (4) hepatic superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, as index of endogenous defences; (5) hepatic hydroxyproline, as index of collagen deposition. CCl4-induced liver fibrosis enhanced lipid peroxidation and TIMPs activation, increased ALT and AST, depleted antioxidants SOD and GPx, and caused collagen deposition in liver tissue. Treatment with GAGs, especially when in combination, successfully reduced ALT and AST rise, lipid peroxidation by evaluating conjugated dienes, TIMPs activation and mRNA expression, partially restored SOD and GPx activities, and limited collagen deposition in the hepatic tissue. The data obtained showed that these molecules were able to limit hepatic injury induced by chronic CCl4 intoxication and especially limited liver fibrosis. They also confirm that HYA and C4S may exert antioxidant mechanism, while reduction of TIMPs expression suggests that GAGs may influence MMPs and TIMPs imbalance in liver fibrosis.

Hyaluronic acid and chondroitin-4-sulphate treatment reduces damage in carbon tetrachloride-induced acute rat liver injury

Oxidative stress is involved in the pathogenesis of chemically mediated liver injury. Since glycosaminoglycans possess antioxidant activity, the aim of this work was to assess the protective effects of hyaluronic acid and chondroitin-4-sulphate treatment in a model of carbon tetrachloride-induced liver injury. Liver damage was induced in male rats by an intraperitoneal injection of carbon tetrachloride (1 ml/kg in vegetal oil). Serum alanine aminotransferase and aspartate aminotransferase, hepatic malondialdehyde, plasma TNF-alpha, hepatic reduced glutathione and catalase, and myeloperoxidase, an index of polymorphonuclear infiltration in the jeopardised hepatic tissue, were evaluated 24 h after carbon tetrachloride administration. Carbon tetrachloride produced a marked increase in serum alanine aminotransferase and aspartate aminotransferase activities, primed lipid peroxidation, enhanced plasma TNF-alpha levels, induced a severe depletion of reduced glutathione and catalase, and promoted neutrophil accumulation. Intraperitoneal treatment of rats with hyaluronic acid (25 mg/kg) or chondroitin-4-sulphate (25 mg/kg) failed to exert any effect in the considered parameter, while the combination treatment with both glycosaminoglycans (12,5 + 12,5 mg/kg) decreased the serum levels of alanine aminotransferase and aspartate aminotransferase, inhibited lipid peroxidation by reducing hepatic malondialdehyde, reduced plasma TNF-alpha, restored the endogenous antioxidants, and finally decreased myeloperoxidase activity. These results suggest that hyaluronic acid and chondroitin-4-sulphate possess a different antioxidant mechanism and consequently the combined administration of both glycosaminoglycans exerts a synergistic effect with respect to the single treatment.

Dolichol content in isolated sinusoidal liver cells after in vivo chronic treatment with thioacetamide

The content of dolichol, an isoprenoid present in all biological membranes, was determined in isolated sinusoidal liver cells after treatment of rats for 2 and 4 months with a low dosage of the hepatotoxin thioacetamide. The significant decrease in dolichol observed in hepatocytes after 2 months might be explained by peroxidation of the isoprenoid. At the same time point, retinol was retained, and decreased only after 4 months of treatment. After 4 months of treatment therefore both lipids decreased. In a subfraction of hepatic stellate cells, Ito-1 cells, the main storage site of vitamin A, dolichol decreased significantly only after 4 months. A remarkable difference from hepatocytes is that in Ito-1 cells retinol content significantly decreased after 2 months of treatment. In another subfraction, Ito-2 cells, the content of the two isoprenoids decreased in parallel. This heterogeneous subfraction might represent those transitional hepatic stellate cells that, while losing retinol, are in the process of differentiating into myofibroblasts secreting extracellular matrix components. In Kupffer cells and sinusoidal endothelial cells, impairment of dolichol might be observed later, only after 4 months of treatment, while retinol decreases uniformly over time. Starting after two months of treatment, the decrease of dolichol and the increase of retinol in hepatocytes, at the same time as retinol decreases in hepatic stellate cells, might be taken as an early index of incipient liver injury due to thioacetamide. This hypothesis is discussed with regard to a role of dolichol in the modulation of membrane fluidity for intracellular and intercellular retinol transport.

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.

Protective effects of thymoquinone and desferrioxamine against hepatotoxicity of carbon tetrachloride in mice

The effects of thymoquinone (TQ) and desferrioxamine (DFO) against carbon tetrachloride (CCl4)-induced hepatotoxicity were investigated. A single dose of CCl4 (20 microl/kg, i.p.) induced hepatotoxicity, manifested biochemically by significant elevation of activities of serum enzymes, such as alanine transaminase (ALT, EC: 2.6.1.2) , aspartate transaminase (AST, EC: 2.6.1.1) and lactate dehydrogenase (LDH, EC: 1.1.1.27). Hepatotoxicity was further evidenced by significant decrease of total sulfhydryl (-SH) content, and catalase (EC: 1.11.1.6) activity in hepatic tissues and significant increase in hepatic lipid peroxidation measured as malondialdhyde (MDA). Pretreatment of mice with DFO (200 mg/kg i.p.) 1 h before CCl4 injection or administration of TQ (16 mg/kg/day, p.o.) in drinking water, starting 5 days before CCl4 injection and continuing during the experimental period, ameliorated the hepatotoxicity induced by CCl4, as evidenced by a significant reduction in the elevated levels of serum enzymes as well as a significant decrease in the hepatic MDA content and a significant increase in the total sulfhydryl content 24 h after CCl4 administration. In a separate in vitro assay, TQ and DFO inhibited the non-enzymatic lipid peroxidation of normal mice liver homogenate induced by Fe3+/ascorbate in a dose-dependent manner. These results indicate that TQ and DFO are efficient cytoprotective agents against CCl4-induced hepotoxicity, possibly through inhibition of the production of oxygen free radicals that cause lipid peroxidation.

Protection against hepatotoxicity by a single dose of amphetamine: the potential role of heat shock protein induction

Amphetamine has been shown previously to increase levels of the inducible 70-kDa heat shock protein (hsp70i) in mouse liver. In the present study, the hepatic concentrations of a variety of hsps in livers of mice pretreated with amphetamine (15 mg/kg, i.p.) were evaluated, and the time course of hsp induction was examined. Amphetamine treatment caused an acute rise in core body temperature to 40 degrees C for at least 1 hr and increased hsp25 and hsp70i levels, as measured by Western blotting, at 6, 24, 48, and 72 hr with no apparent induction of other hsps (hsp60, hsc70, or hsp90). A 72-hr amphetamine pretreatment lowered the hepatotoxicity of an acute dose of acetaminophen (350 mg/kg, i.p.) or bromobenzene (0.45 ml/kg, i.p.), but had no effect on the toxicity of carbon tetrachloride (0.04 ml/kg, i.p.) or cocaine (50 mg/kg, i.p.), as measured by serum alanine aminotransferase activity and histopathological analysis. No protection from acetaminophen or bromobenzene hepatotoxicity was observed when hepatotoxicant administration was delayed until hsp levels had returned to control values (144 hr after amphetamine pretreatment). Amphetamine pretreatment did not reduce in vivo covalent binding to proteins of radiolabeled [3H]acetaminophen, [14C]bromobenzene, [14C]carbon tetrachloride, or [3H]cocaine, indicating that the protective effects were not due to inhibition of reactive metabolite formation from these toxicants. These results suggest that elevated levels of hsp25 and hsp70i provide protection against acetaminophen and bromobenzene hepatotoxicity.

Assessment of lipid peroxidation associated with lung damage induced by oxidative stress. In vivo and in vitro studies

The lung thiobarbituric acid-reactive substances (TBA-RS) content and the amount of ethane exhaled, two potential markers of the lipid peroxidation process, were measured in rats following intratracheal administration of chemicals stimulating the production of free radicals, i.e. paraquat, phorbol myristate acetate and ferrous ions. Five hours after treatment, autopsy revealed gross pulmonary damage but the lung TBA-RS and the ethane exhalation were not different from control animals. On the contrary, a large increase in ethane production was observed 2 hr after intraperitoneal administration of the hepatotoxic carbon tetrachloride. In vitro, incubation of lung and liver homogenates from control rats with ferrous iron led to the development of a lipid peroxidation process in both tissues but the accumulation of TBA-RS and ethane was much lower with homogenates from lung as compared to liver tissue. Those results suggest that the lung may be more resistant than the liver to the initiation and/or propagation of a lipid peroxidation process. The possibility that others markers than ethane and TBA-RS are more appropriate to detect this process in the lung must also be considered.

Superoxide dismutase amplifies dye photosensitized production of desferal free radical: an electron spin resonance study

Desferal free radical (DFFR) photogenerated from dye sensitization was studied by electron spin resonance. When irradiated at the visible maximum in the presence of O2, both rose bengal and riboflavin sensitized the oxidation of Desferal (DF) and generated the DFFR. The yield of DFFR was amplified by superoxide dismutase (SOD). The SOD enhancement was attributed to the inhibition of superoxide-induced DFFR destruction. Similar SOD enhancement was observed with dyes Rhodamine 123 and Gentian Violet. Our studies suggest that when Desferal is used as a chelating agent in the presence of SOD, systems involving O2- could face interference from DFFR even at concentrations as low as 10 microM DF. DFFR may interfere with the chain reaction of lipid peroxidation resulting in an apparent protective action which, in fact, has very little to do with chelating the catalytic iron.