NADPH oxidase-derived free radicals are key oxidants in alcohol-induced liver disease.

In North America, liver disease due to alcohol consumption is an important cause of death in adults, although its pathogenesis remains obscure. Despite the fact that resident hepatic macrophages are known to contribute to early alcohol-induced liver injury via oxidative stress, the exact source of free radicals has remained a mystery. To test the hypothesis that NADPH oxidase is the major source of oxidants due to ethanol, we used p47(phox) knockout mice, which lack a critical subunit of this major source of reactive oxygen species in activated phagocytes. Mice were treated with ethanol chronically, using a Tsukamoto-French protocol, for 4 weeks. In wild-type mice, ethanol caused severe liver injury via a mechanism involving gut-derived endotoxin, CD14 receptor, production of electron spin resonance-detectable free radicals, activation of the transcription factor NF-kappaB, and release of cytotoxic TNF-alpha from activated Kupffer cells. In NADPH oxidase-deficient mice, neither an increase in free radical production, activation of NF-kappaB, an increase in TNF-alpha mRNA, nor liver pathology was observed. These data strongly support the hypothesis that free radicals from NADPH oxidase in hepatic Kupffer cells play a predominant role in the pathogenesis of early alcohol-induced hepatitis by activating NF-kappaB, which activates production of cytotoxic TNF-alpha.

New reactive oxidizing species causes formation of carbon-centered radical adducts in organic extracts of blood following liver transplantation.

alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (4-POBN) radical adducts from Folch (chloroform:methanol) extraction of blood of transplanted livers exhibited a large 6-line electron paramagnetic resonance (EPR) spectrum. Slow EPR sample preparation involving freezing and thawing prior to extraction over 15 min yielded a spectrum assigned as a lipid-derived free radical species, whereas rapid (< 1 min) extraction without a freeze-thaw cycle yielded a mixture of radicals, one with coupling constants similar to the alpha-hydroxymethyl-4-POBN adduct (4-POBN/.CH2OH). Extraction with purified chloroform, however, yielded a much weaker, probably lipid-derived signal. Use of 13C-methanol in the Folch extracting solution yielded a 12-line EPR spectrum, indicating that a new, highly reactive oxidant species from blood following liver transplantation can convert organic solvents used in tissue extractions to free radicals. This hypothesis was supported by simulation of EPR spectra of free radicals extracted rapidly with Folch, which indicated that the spectrum contained two carbon-centered species, one with hyperfine coupling constants similar to the alpha-methylhydroxyl-4-POBN adduct, the other probably lipid-derived. Because the former originates from methanol in the Folch, extraction of samples with alcohol-free organic solvent is most likely superior when the potential for formation of stable oxidant species exists, such as after liver transplantation.

Clarification of the relationship between free radical spin trapping and carbon tetrachloride metabolism in microsomal systems.

It has been proposed that the C-phenyl-N-tert-butylnitrone/trichloromethyl radical adduct (PBN/.CCl3) is metabolized to either the C-phenyl-N-tert-butylnitrone/carbon dioxide anion radical adduct (PBN/.CO2-) or the glutathione (GSH) and CCl4-dependent PBN radical adduct (PBN/[GSH-.CCl3]). Inclusion of PBN/.CCl3 in microsomal incubations containing GSH, nicotinamide adenine dinucleotide phosphate (NADPH), or GSH plus NADPH produced no electron spin resonance (ESR) spectral data indicative of the formation of either the PBN/[GSH-.CCl3] or PBN/.CO2- radical adducts. Microsomes alone or with GSH had no effect on the PBN/.CCl3 radical adduct. Addition of NADPH to a microsomal system containing PBN/.CCl3 presumably reduced the radical adduct to its ESR-silent hydroxylamine because no ESR signal was observed. The Folch extract of this system produced an ESR spectrum that was a composite of two radicals, one of which had hyperfine coupling constants identical to those of PBN/.CCl3. We conclude that PBN/.CCl3 is not metabolized into either PBN/[GSH-.CCl3] or PBN/.CO2- in microsomal systems.

The role of Kupffer cell oxidant production in early ethanol-induced liver disease.

Considerable evidence for a role of Kupffer cells in alcoholic liver disease has accumulated and they have recently been shown to be a predominant source of free radicals. Several approaches including pharmacological agents, knockout mice, and viral gene transfer have been used to fill critical gaps in understanding key mechanisms by which Kupffer cell activation, oxidant formation, and cytokine production lead to liver damage and subsequent pathogenesis. This review highlights new data in support of the hypothesis that Kupffer cells play a pivotal role in hepatotoxicity due to ethanol by producing oxidants via NADPH oxidase.

Mechanisms of alcohol-induced hepatotoxicity: studies in rats.

Alcohol treatment results in increases in the release of endotoxin from gut bacteria and membrane permeability of the gut to endotoxin, or both. Females are more sensitive to these changes. Elevated levels of endotoxin activate Kupffer cells to release substances such as eicosanoids, TNF-alpha and free radicals. Prostaglandins increase oxygen uptake and most likely are responsible for the hypermetabolic state in the liver. The increase in oxygen demand leads to hypoxia in the liver, and on reperfusion, alpha-hydroxyethyl free radicals are formed which lead to tissue damage in oxygen-poor pericentral regions of the liver lobule.

Evidence that free radicals are involved in graft failure following orthotopic liver transplantation in the rat--an electron paramagnetic resonance spin trapping study.

The purpose of these studies was to determine whether free radicals were formed as a consequence of reperfusion during orthotopic liver transplantation and whether their formation was related to graft failure. Grafts were stored for 18 hr in Euro-Collins solution or for 48 hr in University of Wisconsin solution (nonsurvival conditions) and reperfused with blood containing the spin trap alpha-phenyl N-tert-butylnitrone (PBN). Venous blood samples (4-5 ml) were collected, and serum was extracted with chloroform and methanol (2:1) and analyzed for radical adducts by electron paramagnetic resonance (EPR) spectroscopy. In samples from livers stored under nonsurvival conditions, EPR spectra were detected indicating the presence of PBN radical adducts. In contrast, radical adduct formation was 3- to 4-fold lower in similar experiments performed with untransplanted livers or with livers stored under survival conditions (1 hr in Ringer's solution or 24 hr in UW solution). Oxygen radicals are more likely involved in the production of radical adducts because formation was nearly completely prevented by superoxide dismutase plus catalase or Carolina rinse, which contains glutathione, desferrioxamine mesylate, and allopurinol. Radical adduct formation was much greater in a blood-free perfusion system where oxygen delivery was high, suggesting that blood elements are not necessary for radical adduct formation. An inverse correlation between survival of livers stored in UW solution and radical adduct signal was observed in this study. Thus, it is concluded that free radicals formed during reperfusion are involved in the mechanism of graft failure following liver transplantation in the rat.

Primary nonfunction of fatty livers produced by alcohol is associated with a new, antioxidant-insensitive free radical species.

The formation of free radicals after orthotopic liver transplantation in the rat correlates with graft failure. Fatty livers from alcoholics transplant poorly, so these studies were designed to examine the effect of alcohol on free radical formation in a rearterialized rat liver transplantation model. Treatment of rats for 3-5 weeks with either a high-fat or an ethanol-containing liquid diet caused characteristic pericentral lipid accumulation. After storage in University of Wisconsin cold storage solution (UW) and transplantation, a reperfusion injury characterized by increased postoperative AST levels (greater than 1500 U/l in about 3 hours) was observed in rats fed high-fat or alcohol-containing diets, whereas parenchymal cell injury was seen much less in low-fat controls. Survival was around 63% in the low-fat group but decreased to 12 and 18% in the high-fat and alcohol groups, respectively. Furthermore, intracellular lipid content correlated inversely with survival. In untransplanted livers, the spin trap alpha-phenyl N-tert-butylnitrone (PBN) was infused, and blood samples were collected and extracted with chloroform:methanol. Signals indicative of carbon-centered PBN radical adducts were barely detectable in all untransplanted groups studied by electron paramagnetic resonance. In contrast, a robust 6-line complex spectrum was obtained from all groups studied immediately after 48 hours of cold storage in UW solution and transplantation. A mixture of 3 radical species was identified. Two had coupling constants similar to lipid-derived free radicals, whereas the third is a new species with unique coupling constants and is most likely oxygen derived. In low-fat controls, the signal was reduced significantly by superoxide dismutase (SOD)/catalase; however, SOD/catalase had no effect on free radicals in lipid-loaded livers. Thus, both dietary high fat and alcohol exposure produce a unique SOD/catalase-insensitive free radical species that may be involved in the mechanism of failure of fatty livers after orthotopic liver transplantation.

Ethanol, not fat accumulation per se, increases free radical production in a low-flow, reflow liver perfusion model.

BACKGROUND: Ethanol increases primary graft failure after liver transplantation, yet whether it acts via mechanisms involving fat accumulation remains unclear. METHODS: Rats were pair-fed a modified Lieber-DeCarli liquid diet containing 35% (high-fat) or 12% (low-fat) of calories as fat combined with 36% of calories as ethanol or isocaloric maltose-dextrin for 4-5 weeks. Reperfusion injury to the liver was studied using a low-flow, reflow perfusion model and a liver transplantation model, and free radicals were detected using electron spin resonance and the spin trapping technique. RESULTS: As expected, basal hepatic triglycerides were similar in livers from rats fed low- and high-fat control diets. Ethanol did not alter triglyceride levels significantly in rats fed a low-fat diet, but increased values about 2.4-fold in rats fed a high-fat diet. Ethanol increased lactate dehydrogenase release during reperfusion from 10 to 26 IU/g/h in rats fed a low-fat diet and from 17 to 34 IU/g/h in rats fed a high-fat diet, respectively. Portal pressure increased from about 3 to 10.5 cm H2O upon reperfusion in livers from high-fat, ethanol-fed rats, but only reached values of 9.1 in the low-fat, ethanol-fed group. A free radical adduct signal was detected in the bile of livers from ethanol-treated rats, and the magnitude of this signal was similar in livers of ethanol-treated rats fed high- or low-fat diets. However, radical adducts could not be detected in either group in the absence of dietary ethanol. Moreover, 67-77% rats given low-fat or high-fat control diets survived after liver transplantation, but only 11% survived if treated with ethanol. CONCLUSIONS: It is concluded that ethanol plays a major role in hepatic reperfusion injury, most likely via mechanisms involving free radicals. Increased hepatic fat content alone plays only a minor role, probably by causing slight disturbances in the hepatic microcirculation.

Glycine improves survival after hemorrhagic shock in the rat.

This study investigated the effect of glycine on hemorrhagic shock in the rat. Rats were bled to maintain mean arterial pressure at 30-35 mm Hg for 1 h and subsequently resuscitated with 60% shed blood and lactated Ringer's solution. Only 20% of rats receiving saline just prior to resuscitation survived 72 h after shock. Survival was increased by glycine (11.2-90.0 mg/kg, i.v.) in a dose-dependent manner (half-maximal effect = 25 mg/kg) and reached maximal values of 78% at 45 mg/kg. Eighteen hours after resuscitation, creatinine phosphokinase increased 23-fold, transaminases increased 33-fold, and creatinine was elevated 2.4-fold, indicating injury to the heart, liver, and kidney, respectively. Pulmonary edema, leukocyte infiltration, and hemorrhage were also observed. In the kidney, proximal tubular necrosis, leukocyte infiltration, and severe hemorrhage in the outer medullary area occurred in rats receiving saline. Glycine reduced these pathological alterations significantly. It has been reported that oxidative stress and tumor necrosis factor(TNF)-alpha-production are involved in the pathophysiology of multiple-organ injury after shock. In this study, free radical production was increased 4-fold during shock, an effect blocked largely by glycine. Increases in intracellular calcium and production of TNF-alpha by isolated Kupffer cells stimulated by endotoxin were elevated significantly by hemorrhagic shock, alterations which were totally prevented by glycine. Taken together, it is concluded that glycine reduces organ injury and mortality caused by hemorrhagic shock by preventing free radical production and TNF-alpha formation.

A search for oxygen-centered free radicals in the lipoxygenase/linoleic acid system.

Studies of the oxygenation of linoleic acid by soybean lipoxygenase utilizing electron spin resonance spectroscopy and oxygen uptake have been undertaken. The spin trap, alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (4-POBN) was included in the lipoxygenase system to capture short-lived free radicals. Correlation of radical adduct formation rates with oxygen uptake studies indicated that the major portion of radical adduct formation occurred when the system was nearly anaerobic. Incubations containing [17O]oxygen with nuclear spin of 5/2 did not have additional ESR lines as would be expected if an oxygen-centered 4-POBN-lipid peroxyl radical adduct were formed indicating that the trapped radical must be reassigned as a carbon-centered species. To establish the presence of [17O2]oxygen in our incubations, a portion of the gas from the lipoxygenase/linoleate experiments was used to prepare the 4-POBN-superoxide radical adduct utilizing a superoxide producing microsomal/paraquat/NADPH system.

[17O]oxygen hyperfine structure for the hydroxyl and superoxide radical adducts of the spin traps DMPO, PBN and 4-POBN.

[17O]oxygen hyperfine coupling constants are reported for the superoxide and hydroxyl radical adducts with the spin traps 5,5-dimethyl-1-pyrroline N-oxide, N-t-butyl-alpha-phenylnitrone and alpha-(4-pyridyl 1-oxide)-N-t-butylnitrone. These couplings provide spectroscopic evidence that the spin adducts have been correctly identified.

The carbon dioxide anion radical adduct in the perfused rat liver: relationship to halocarbon-induced toxicity.

CCl4 has been shown previously to be metabolized to the trichloromethyl radical (.CCl3) and to a novel oxygen-containing carbon dioxide anion radical (.CO2-) in the perfused rat liver and in vivo. Since the role of free radicals in CCl4-induced hepatotoxicity is unclear, these studies were designed to determine if a relationship between .CO2- formation and halocarbon-induced hepatotoxicity exists. CCl4 or bromotrichloromethane (CBrCl3) was infused into livers from control or phenobarbital-treated rats perfused with either nitrogen- or oxygen-saturated Krebs-Henseleit bicarbonate buffer. Samples of effluent perfusate and chloroform/methanol extracts of liver were analyzed by ESR spectroscopy for free radical adducts following infusion of halocarbon and the spin trap, phenyl-t-butylnitrone (PBN). Hyperfine coupling constants and 13C-isotope effects observed in the ESR spectra of organic extracts of liver demonstrated the presence of the PBN radical adduct of .CCl3 from both halocarbons. Radical adducts in aqueous extracts of liver and effluent perfusate had hyperfine coupling constants and 13C-isotope effects identical to those of PBN/.CO2- generated chemically from formate. The PBN/.CO2- radical adduct was also observed in urine following the intragastric administration of CBrCl3 and PBN. Detection of PBN/.CO2- adducts in the effluent perfusate was decreased 3- to 4-fold by DIDS (0.2 mM), an inhibitor of the plasma membrane anion transport system. The rate of formation of PBN/.CO2- was decreased 2- to 3-fold following inhibition of cytochrome P-450-dependent monooxygenases by metyrapone (0.5 mM) and was increased about 2-fold by induction of cytochrome P-450 by phenobarbital pretreatment. Toxicity of halocarbons in the perfused liver was assessed by measuring the release of lactate dehydrogenase (LDH) into the effluent perfusate in livers from phenobarbital-treated rats under conditions identical to those employed to detect radical adducts (i.e., during the infusion of CCl4 or CBrCl3 into livers perfused with either nitrogen- or oxygen-saturated perfusate). Under all conditions studied, PBN/.CO2- was detected in the effluent perfusate within 2-4 min. Metabolism of halocarbons to PBN/.CO2- was 6- to 8-fold faster during perfusion with nitrogen-saturated rather than with oxygen-saturated perfusate. Concomitantly, liver damage detected from LDH release occurred much sooner during halocarbon infusion in the presence of nitrogen-saturated rather than oxygen-saturated perfusate. A good correlation between the rate of formation of PBN/.CO2- and the time of onset of LDH release following halocarbon infusion was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

The formation of a novel free radical metabolite from CCl4 in the perfused rat liver and in vivo.

Electron spin resonance spectroscopy has been used to monitor free radicals formed during CCl4 metabolism by perfused livers from phenobarbital-treated rats. Livers were perfused simultaneously with the spin trap phenyl N-t-butylnitrone and with either 12CCl4 or 13CCl4. Perfusate samples and CHCl3:CH3OH extracts of perfusate and liver samples were analyzed for phenyl N-t-butylnitrone radical adducts of reactive free radicals. In the organic extracts, hyperfine coupling constants and 13C isotope effects observed in the ESR spectra indicated the presence of the radical adduct of the trichloromethyl radical. Surprisingly, an additional free radical signal about two orders of magnitude more intense than that of the phenyl N-t-butylnitrone/CCl.3 radical adduct was observed in the aqueous liver perfusate. This adduct was also detected by ESR in rat urine 2 h after intragastric addition of spin trap and CCl4. This radical adduct had hyperfine coupling constants and 13C isotope effects identical with the radical adduct of the carbon dioxide anion radical (CO2-.). Analysis of the pH dependence of the coupling constants yielded a pK alpha of 2.8 for the CO2-. radical adduct formed either in the perfused liver or chemically. Carbon tetrachloride is converted into CCl.3 by cytochrome P-450 through a reductive dehalogenation. The trichloromethyl free radical reacts with oxygen to form the trichloromethyl peroxyl radical, CCl3OO., which may be converted into .COCl and then trapped. This radical adduct would hydrolyze to the carboxylic acid form, which is detected spectroscopically. Alternatively, the carbon dioxide anion free radical could form through complete dechlorination and then react with the spin trap to give the CO2-. radical adduct directly.

Reaction of glutathione with a free radical metabolite of carbon tetrachloride.

Carbon tetrachloride and bromotrichloromethane are both metabolized by cytochrome P-450 in the presence of phenyl-N-t-butyl nitrone PBN) to the PBN/trichloromethyl (PBN/.CCl3) and the PBN carbon dioxide anion (PBN/.CO2-) radical adducts in the liver. The formation of the latter but not the former species in perfused liver was reduced markedly by prior depletion of hepatic glutathione with either diethyl maleate or buthionine sulfoximine treatments. In microsomal incubations, the PBN/.CO2- radical adduct was detected only upon the addition of cytosol. In microsomal incubations containing PBN, CCl4, and GSH, but no added cytosol, a novel radical adduct with distinctive coupling constants was detected. This radical adduct's ESR spectrum exhibited 13C isotope effects when it was formed in an incubation containing 13CCl4 or Br13CCl3. The presence of GSH in the radical adduct is postulated based on the radical adduct's hydrophilicity and slow rate of rotation in solution. The detection of this new radical adduct, PBN/[GSH-.CCl3], establishes the reaction of GSH with a CCl4-derived free radical as a significant event in the metabolism of CBrCl3 and CCl4. The cytosolic conversion of PBN/[GSH-.CCl3] into PBN/.CO2- has been demonstrated and characterizes the PBN/.CO2- radical adduct as the product of metabolism of PBN/[GSH-.CCl3], a primary radical adduct. Thus, it is concluded that GSH rather than oxygen is obligatory for the formation of PBN/.CO2- from .CCl3 in intact cells.

Reperfusion rather than storage injury predominates following long-term (48 h) cold storage of grafts in UW solution: studies with Carolina Rinse in transplanted rat liver.

Both storage injury and reperfusion injury have been reported in association with liver transplantation; however, which predominates is not clear. Therefore, these studies were designed to evaluate whether Carolina Rinse, which minimizes reperfusion injury following orthotopic liver transplantation in the rat, would be effective after long-term (48 h) storage of grafts in University of Wisconsin (UW) cold storage solution where sufficient time for development of storage injury exists. Livers were rinsed with either Ringer's solution or Carolina Rinse solution immediately prior to completion of implantation surgery. In the Ringer's group, 30-day survival was high following 24 h of cold storage (4/5) but was very low after 48 h (1/16). Importantly, survival was increased significantly (5/14) when grafts were rinsed with Carolina Rinse following 48 h of cold storage. In both groups, parenchymal cells appeared normal by scanning electron microscopy, excluded trypan blue, and released SGOT at values only slightly above the normal range immediately (i.e., less than 5 min) after 48 h of cold storage. However, SGOT values rose steadily during the 1st hour postoperatively following reperfusion in the Ringer's rinse group and reached levels around 1,000 U/l. In addition, nonparenchymal cells were not labelled with trypan blue following storage, but significant labelling occurred within 1 h. Both SGOT release and nonparenchymal cell injury were reduced significantly when grafts were rinsed with Carolina Rinse prior to completion of surgery. Liver injury assessed histologically 24 h postoperatively was also reduced about 50% by Carolina Rinse. Oxidative stress appeared to be involved, since radical adducts, most likely of lipid origin, were trapped during the first 5 min after reperfusion with the spin trapping technique and detected by electron paramagnetic resonance spectroscopy. Lipid radical formation was reduced nearly completely on reperfusion by Carolina Rinse. Since Carolina Rinse improved survival of liver grafts following long periods of cold storage and reduced lipid radical formation and hepatocellular injury, we concluded that a reperfusion injury rather than a storage injury predominates following orthotopic transplantation of livers stored for long periods of time in cold UW solution.

Viral delivery of superoxide dismutase gene reduces cyclosporine A-induced nephrotoxicity.

BACKGROUND: Cyclosporine A (CsA) increases free radical formation in the kidney. Accordingly, this study investigated whether gene delivery of superoxide dismutase (SOD) reduced radical production and nephrotoxicity caused by CsA. METHODS: Rats were given adenovirus (Ad) carrying lacZ or Cu/Zn-SOD genes three days prior to CsA treatment. Histology, glomerular filtration rates (GFRs) and free radical adducts in urine were assessed. RESULTS: SOD activity was increased 2.5-fold three days after viral infection and remained at 2- and 1.6-fold higher 10 and 17 days later. Treatment with CsA for seven days decreased GFR by 70% in rats infected with Ad-lacZ as expected; however, the decrease was diminished significantly in rats receiving Ad-SOD. CsA treatment for two weeks caused a loss of brush border and dilation of proximal tubules, necrosis, and increased leukocyte infiltration into the kidney; these effects were minimized by SOD. Dimethyl sulfoxide (DMSO) was attacked by the hydroxyl radical to produce a methyl radical. Indeed, administration of CsA with 12C-DMSO in rats infected with Ad-lacZ produced a radical adduct with hyperfine coupling constants similar to 4-POBN/methyl radical adduct and another unknown radical adduct. CsA given with 13C-DMSO produced a 12-line spectrum, confirming the involvement of hydroxyl radicals. Free radical adducts detected in urine were increased approximately fivefold by CsA, an effect blocked completely by SOD. CONCLUSIONS: CsA increases free radical formation. Gene delivery of SOD blocks formation of free radicals, thereby minimizing nephrotoxicity caused by CsA.

Development and characterization of a new model of tacrine-induced hepatotoxicity: role of the sympathetic nervous system and hypoxia-reoxygenation.

Tacrine is an acetylcholinesterase inhibitor approved for the treatment of Alzheimer's disease. Unfortunately, reversible hepatotoxicity in about 30% of patients at therapeutic doses limits clinical use. The purpose of this study was to develop and characterize a model of tacrine hepatotoxicity to begin to understand the mechanisms of injury. Rats were given tacrine (10-50 mg/kg, intragatrically) and killed 24 hr later. An increase in serum aspartate aminotransferase was observed up to 35 mg/kg and histology revealed pericentral necrosis and fatty changes. Aspartate aminotransferase was increased from 12 to 24 hr and returned to control values by 32 hr. Livers were perfused in a nonrecirculating system to measure oxygen uptake and trypan blue was infused at the end of each experiment to evaluate tissue perfusion. Time for trypan blue to distribute evenly throughout the liver 3 hr after tacrine treatment was significantly increased (6.9 +/- 1.3 min) compared to controls (1.0 +/- 0.3 min) reflecting decreased tissue perfusion. Tacrine also significantly increased the binding of a hypoxia marker, pimonidazole, in pericentral regions almost 3-fold, and increased portal pressure in vivo significantly. It is hypothesized that tacrine, by inhibiting acetylcholine breakdown in the celiac ganglion, increases sympathetic activity in the liver leading to vascular constriction, hypoxia and liver injury. To test this hypothesis, the hepatic nerve was severed and animals were allowed to recover before tacrine treatment. This procedure significantly reduced serum aspartate aminotransferase, time of dye distribution, pimonidazole binding and portal pressure. Furthermore, a free radical adduct was detected with spin trapping and electron spin resonance spectroscopy 8 hr after tacrine treatment, providing evidence for reoxygenation. When catechin (100 mg/kg, i.p.), a free radical scavenger, was given before tacrine, injury was decreased by about 45%. Furthermore, feeding 5% arginine in the diet significantly reduced portal pressure and time of dye distribution. These data are consistent with the hypothesis that tacrine hepatotoxicity is a hypoxia-reoxygenation injury mediated through the sympathetic nervous system.

Allopurinol prevents early alcohol-induced liver injury in rats.

Free radical formation caused by chronic ethanol administration could activate transcription factors such as nuclear factor-kappaB (NF-kappaB), which regulates production of inflammatory cytokines. Xanthine oxidase is one potential source of reactive oxygen species. Therefore, the purpose of this study is to determine whether allopurinol, a xanthine oxidase inhibitor and scavenger of free radicals, would affect free radical formation, NF-kappaB activation, and early alcohol-induced liver injury in rats. Male Wistar rats were fed a high-fat diet with or without ethanol (10-16 g/kg/day) continuously for up to 4 weeks with the Tsukamoto-French enteral protocol. Either allopurinol or saline vehicle was administered daily. Allopurinol had no effect on body weight or the cyclic pattern of ethanol in urine. Mean urine ethanol concentrations were 271 +/- 38 and 252 +/- 33 mg/dl in ethanol- and ethanol + allopurinol-treated rats, respectively. In the control group, serum aspartate aminotransferase and alanine aminotransferase levels were approximately 40 I.U./l and 25 U/l, respectively. Administration of enteral ethanol for 4 weeks increased serum transaminases approximately 5-fold. Allopurinol blunted these increases significantly by approximately 50%. Ethanol treatment also caused severe fatty infiltration, mild inflammation, and necrosis. These pathological changes also were blunted significantly by allopurinol. Furthermore, enteral ethanol caused free radical adduct formation, values that were reduced by approximately 40% by allopurinol. NF-kappaB binding was minimal in the control group but was increased significantly nearly 2.5-fold by ethanol. This increase was blunted to similar values as control by allopurinol. These results indicate that allopurinol prevents early alcohol-induced liver injury, most likely by preventing oxidant-dependent activation of NF-kappaB.