Ethanol consumption, amino acid and glutathione blood levels in patients with and without chronic liver disease

Ethanol metabolism: The good, the bad, and the ugly

Throughout the world, ethanol is both an important commercial commodity and a source of major medical and social problems. Ethanol readily passes through biological membranes and distributes throughout the body. It is oxidized, first to acetaldehyde and then to acetate, and finally by the citric acid cycle in virtually all tissues. The oxidation of ethanol is irreversible and unregulated, making the rate dependent only on local concentration and enzyme activity. This unregulated input of reducing equivalents increases reduction of both cytoplasmic and intramitochondrial NAD and, through the latter, cellular energy state {[ATP]/([ADP][Pi])}. In brain, this increase in energy state stimulates dopaminergic neural activity signalling reward and a sense of well being, while suppressing glutamatergic neural activity signalling anxiety and unease. These positive responses to ethanol ingestion are important to social alcohol consumption. Importantly, decreased free [AMP] decreases AMP-dependent protein kinase (AMPK) activity, an important regulator of cellular energy metabolism. Oxidation of substrates used for energy metabolism in the absence of ethanol is down regulated to accommodate the input from ethanol. In liver, chronic ethanol metabolism results in fatty liver and general metabolic dysfunction. In brain, transport of other oxidizable metabolites through the blood-brain barrier and the enzymes for their oxidation are both down regulated. For exposures of short duration, ethanol induced regulatory changes are rapid and reversible, recovering completely when the concentrations of ethanol and acetate fall again. Longer periods of ethanol exposure and associated chronic suppression of AMPK activity activates regulatory mechanisms, including gene expression, that operate over longer time scales, both in onset and reversal. If chronic alcohol consumption is abruptly ended, metabolism is no longer able to respond rapidly enough to compensate. Glutamatergic neural activity adapts to chronic dysregulation of glutamate metabolism and suppression of glutamatergic neural activity by increasing excitatory and decreasing inhibitory amino acid receptors. A point is reached (ethanol dependence) where withdrawal of ethanol results in significant metabolic energy depletion in neurons and other brain cells as well as hyperexcitation of the glutamatergic system. The extent and regional specificity of energy depletion in the brain, combined with hyperactivity of the glutamatergic neuronal system, largely determines the severity of withdrawal symptoms.

Study of Fecal and Urinary Metabolite Perturbations Induced by Chronic Ethanol Treatment in Mice by UHPLC-MS/MS Targeted Profiling

Alcoholic liver disease (ALD) as a consequence of ethanol chronic consumption could lead to hepatic cirrhosis that is linked to high morbidity and mortality. Disease diagnosis is still very challenging and usually clear findings are obtained in the later stage of ALD. The profound effect of ethanol on metabolism can be depicted using metabolomics; thus, the discovery of novel biomarkers could shed light on the initiation and the progression of the ALD, serving diagnostic purposes. In the present study, Hydrophilic Interaction Liquid Chromatography tandem Mass Spectrometry HILIC-MS/MS based metabolomics analyisis of urine and fecal samples of C57BL/6 mice of both sexes at two sampling time points was performed, monitoring the effect of eight-week ethanol consumption. The altered hepatic metabolism caused by ethanol consumption induces extensive biochemical perturbations and changes in gut microbiota population on a great scale. Fecal samples were proven to be a suitable specimen for studying ALD since it was more vulnerable to the metabolic changes in comparison to urine samples. The metabolome of male mice was affected on a greater scale than the female metabolome due to ethanol exposure. Precursor small molecules of essential pathways of energy production responded to ethanol exposure. A meaningful correlation between the two studied specimens demonstrated the impact of ethanol in endogenous and symbiome metabolism.

Enhanced erythrocyte antioxidant status following an 8-week aerobic exercise training program in heavy drinkers

Alcohol-induced oxidative stress is involved in the development and progression of various pathological conditions and diseases. On the other hand, exercise training has been shown to improve redox status, thus attenuating oxidative stress-associated disease processes. The purpose of the present study was to evaluate the effect of an exercise training program that has been previously reported to decrease alcohol consumption on blood redox status in heavy drinkers. In a non-randomized within-subject design, 11 sedentary, heavily drinking men (age: 30.3 ± 3.5 years; BMI: 28.4 ± 0.86 kg/m²) participated first in a control condition for 4 weeks, and then in an intervention where they completed an 8-week supervised aerobic training program of moderate intensity (50-60% of the heart rate reserve). Blood samples were collected in the control condition (pre-, post-control) as well as before, during (week 4 of the training program), and after intervention (week 8 of the training program). Samples were analyzed for total antioxidant capacity (TAC), thiobarbituric acid reactive substances (TBARS), protein carbonyls (PC), uric acid (UA), bilirubin, reduced glutathione (GSH), and catalase activity. No significant change in indices of redox status in the pre- and post-control was observed. Catalase activity increased (p < 0.05) after 8 weeks of intervention compared to week 4. GSH increased (p < 0.05) after 8 weeks of intervention compared to the control condition and to week 4 of intervention. TAC, UA, bilirubin, TBARS, and PC did not significantly change at any time point. Moreover, concentrations of GSH, TBARS, and catalase activity negatively correlated with alcohol consumption. In conclusion, an 8-week aerobic training program enhanced erythrocyte antioxidant status in heavy drinkers, indicating that aerobic training may attenuate pathological processes caused by alcohol-induced oxidative stress.

Can saliva testing replace blood measurements for health monitoring? Insights from a correlation study of salivary and whole blood glutathione in humans

The feasibility of using saliva samples as diagnostic for health status is assessed.

Effects of acute exercise on liver function and blood redox status in heavy drinkers

Excessive alcohol consumption can induce oxidative stress, resulting in the development of several diseases. Exercise has been reported to prevent and/or improve a number of health issues through several mechanisms, including an improvement in redox status. It has also been previously suggested that exercise can help individuals with alcohol use disorders reduce their alcohol intake; however, research in this field is limited. The aim of the present study was to investigage the effects of acute exercise of moderate intensity on the liver function and blood redox status in heavy drinkers. For this purpose, a total of 17 heavy drinkers [age, 31.6±3.2 years; body mass index (BMI), 27.4±0.8 kg/m2; experimental group (EG)] and 17 controls [age, 33.5±1.3 years; BMI, 26.1±1.4 kg/m2; control group (CG), who did not exceed moderate alcohol consumption], underwent one trial of acute exercise of moderate intensity (50-60% of the heart rate reserve) for 30 min on a cycle ergometer, following an overnight fast, and abstaining from smoking and alcohol consumption. Blood samples were obtained before and immediately after exercise for later determination of the indices of liver function and blood redox status. The subjects in the EG had significantly higher (p<0.05) baseline γ-glutamyl transferase (γ-GT) levels compared to the subjects in the CG. Exercise thus resulted in significantly higher γ-GT levels (p<0.005) only in the EG. No significant differences in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) baseline levels were observed between the 2 groups. Following exercise, the AST levels increased significantly (p<0.001) in both groups, whereas the ALT levels increased significantly (p<0.01) only in the EG. The baseline glutathione (GSH) levels were significantly lower (p<0.05) and remained low following exercise in the EG. In addition, we observed a trend for higher (p=0.07) baseline levels of thiobarbituric acid-reactive substances (TBARS), which remained elevated post-exercise in the EG compared to the CG. Significantly increased post-exercise total antioxidant capacity (TAC; p<0.01) and uric acid (UA; p<0.05) levels were noted in the CG, whereas the TAC (p=0.06) and UA (p=0.08) levels increased and approached significance post-exercise in the EG. No significant differences in the baseline levels of total bilirubin and protein carbonyl were observed between the 2 groups, even post-exercise. Thus, the findings of the present study indicate that even though heavy drinkers may be prone to oxidative stress, their exercise-induced antioxidant response is similar to that of individuals who do not drink heavily.

Increased hepatocellular protein carbonylation in human end-stage alcoholic cirrhosis

OBJECTIVE

Oxidative stress is a significant contributing factor in the pathogenesis of alcoholic liver disease (ALD). In the murine models of chronic alcohol consumption, induction of oxidative stress results in increased peroxidation of polyunsaturated fatty acids to form highly reactive electrophilic α/β unsaturated aldehydes that post-translationally modify proteins altering activity. Data are presented here suggesting that oxidative stress and the resulting carbonylation of hepatic proteins is an ongoing process involved in alcohol-induced cirrhosis.

METHODS

Using age-matched pooled hepatic tissue obtained from healthy humans and patients with end stage cirrhotic ALD, overall carbonylation was assessed by immunohistochemistry and LC-MS/MS of streptavidin purified hepatic whole cell extracts treated with biotin hydrazide. Identified carbonylated proteins were further evaluated using bioinformatics analyses.

RESULTS

Using immunohistochemistry and Western blotting, protein carbonylation was increased in end stage ALD occurring primarily in hepatocytes. Mass spectrometric analysis revealed a total of 1224 carbonylated proteins in normal hepatic and end-stage alcoholic cirrhosis tissue. Of these, 411 were unique to cirrhotic ALD, 261 unique to normal hepatic tissue and 552 common to both groups. Bioinformatic pathway analysis of hepatic carbonylated proteins revealed a propensity of long term EtOH consumption to increase post-translational carbonylation of proteins involved in glutathione homeostatic, glycolytic and cytoskeletal pathways. Western analysis revealed increased expression of GSTA4 and GSTπ in human ALD. Using LC-MS/MS analysis, a nonenaldehyde post-translational modification was identified on Lysine 235 of the cytoskeletal protein vimentin in whole cell extracts prepared from human end stage ALD hepatic tissue.

CONCLUSIONS

These studies are the first to use LC-MS/MS analysis of carbonylated proteins in human ALD and begin exploring possible mechanistic links with end-stage alcoholic cirrhosis and oxidative stress.

Protective effect of a cysteine prodrug and antioxidant, L-2-oxothiazolidine-4-carboxylate, against ethanol-induced gastric lesions in rats

Earlier studies have suggested an important role of glutathione (GSH) in cytoprotection against free radicals induced oxidative damage. This study reports gastroprotective effects of a cysteine precursor, L-2-oxothiazolidine-4-carboxylate (OTC), in experimental models of gastric secretion and ulceration. Acid secretion studies (volume and acidity) were undertaken in pylorus-ligated rats whereas the gastric lesions were induced by ethanol. Different groups of animals were treated with OTC (0, 100, 200 and 400 mg/kg). The levels of gastric wall mucus, nonprotein sulfhydryls (NP-SH) and myeloperoxidase (MPO) were measured in the glandular stomach of rats following ethanol-induced gastric lesions. Both medium and high doses of OTC significantly reduced the volume and acidity of gastric secretion in pylorus-ligated rats. Pretreatment with OTC significantly and dose-dependently attenuated the formation of ethanol-induced gastric lesion. OTC significantly protected the gastric mucosa against ethanol-induced depletion of gastric wall mucus, NP-SH and MPO. The gastroprotective effects of OTC may be attributed to its ability to inhibit neutrophils activity and replenish GSH demand.

Acetaminophen usage patterns and concentrations of glutathione and gamma-glutamyl transferase in alcoholic subjects

STUDY OBJECTIVES

To determine if subjects with chronic alcoholism are predisposed to acetaminophen-induced hepatotoxicity, and to determine the contributing factors.

DESIGN

Prospective cohort study.

SETTING

Community-based crisis intervention center.

SUBJECTS

One hundred eighty-eight subjects who answered "yes" to at least one of the four questions on the CAGE (Cut down-Annoyed-Guilty-Eye-opener) questionnaire for identifying alcoholism, and 10 healthy volunteers (controls).

INTERVENTION

A history, physical examination, urine toxicologic analysis, ethanol and drug therapy history, and venous blood samples were collected on all subjects.

MEASUREMENTS AND MAIN RESULTS

Venous blood was analyzed for a liver profile, prothrombin time, and total and oxidized glutathione concentrations. A significantly higher proportion of daily drinkers were regular daily users (29.2% [45/154] vs 11.8% [4/34], p=0.0497) as well as abusers (35.7% [55/154] vs 14.7% [5/34], p=0.0237) of acetaminophen compared with non daily drinkers. Alcoholic subjects with elevated gamma-glutamyl transferase (GGT >or= 51 U/L) levels had significantly lower median plasma glutathione concentrations (2.33 micromol/L, 95% confidence interval [CI] 1.74-2.69 micromol/L) compared with those of alcoholic subjects with normal GGT concentrations (5.97 micromol/L, 95% CI 4.39-7.03 micromol/L, p<0.0001) and healthy volunteers (6.59 micromol/L, 95% CI 4.79-9.65 micromol/L, p=0.0002). A significant inverse correlation was also noted between the GGT concentration and the plasma total glutathione concentration (r = -0.62, p<0.0001). None of the 188 subjects met all preset criteria for hepatotoxicity.

CONCLUSIONS

Daily drinkers were more than twice as likely as non daily drinkers to be regular daily acetaminophen users and abusers. Alcoholic subjects with elevated GGT concentrations had significantly lower plasma total glutathione concentrations, and plasma total glutathione concentrations inversely correlated with GGT concentrations. Elevated GGT concentrations may be a clinical marker of depleted glutathione in alcoholic subjects. Acetaminophen-induced hepatotoxicity appears to be uncommon in alcoholic subjects, despite the 31.9% (60/188 patients) who took doses that are potentially hepatotoxic.

Platelet aggregation is affected by nitrosothiols in patients with chronic hepatitis: In vivo and in vitro studies

AIM: To investigate the relationship among the number of platelets and plasma levels of S-nitrosothiols (S-NO), nitrite, total non-protein SH (NPSH), glutathione (GSH), cysteine (CYS), malondialdehyde (MDA), 4-hydroxininenal (4HNE), tumor necrosis factor-alpha (TNFα) and interleukin (IL)-6 in patients with chronic hepatitis C (CH).

METHODS: In vitro the aggregation of platelets derived from controls and CH patients was evaluated before and after the addition of adenosine diphosphate (ADP) and collagen, both in basal conditions and after incubation with nitrosoglutathione (GSNO).

RESULTS: In vivo, S-NO plasma levels increased significantly in CH patients and they were significantly directly correlated with platelet numbers. Patients with platelet counts < 150 000/μL, had a smaller increase in S-NO, lower levels of GSH, CYS, NPSH, TNFα, and IL-6, and higher levels of nitrite, MDA, and 4-HNE relative to those of patients with platelet counts > 150 000/μL. In vitro, the ADP and collagen aggregation time was increased in platelets from patients and not from controls; in addition, platelets from CH patients but not from controls also showed a latency time after exposure to collagen.

CONCLUSION: The incubation of platelets with GSNO improved the percentage aggregation and abolished the latency time.

Protective effects of green tea polyphenol extracts against ethanol-induced gastric mucosal damages in rats: stress-responsive transcription factors and MAP kinases as potential targets

There are multiple lines of compelling evidence from epidemiologic and laboratory studies supporting that frequent consumption of green tea is inversely associated with the risk of chronic human diseases including cancer. The chemopreventive and chemoprotective effects of green tea have been largely attributed to antioxidative and anti-inflammatory activities of its polyphenolic constituents, such as epigallocatechin gallate. The present study was designed to evaluate the efficacy of green tea polyphenols in protecting against alcohol-induced gastric damage and to elucidate the underlying mechanisms. Intragastric administration of ethanol to male Sprague-Dawley rats caused significant gastric mucosal damage, which was accompanied by elevated expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) as well as transient activation of redox-sensitive transcription factors, such as NF-kappaB and AP-1, and mitogen-activated protein kinases (MAPKs). Oral administration of the green tea polyphenolic extract (GTE) significantly ameliorated mucosal damages induced by ethanol and also attenuated the ethanol-induced expression of COX-2 and iNOS. Inactivation of MAPKs, especially p38 and ERKl/2, by GTE might be responsible for inhibition of ethanol-induced expression of COX-2 and iNOS.

Genetic polymorphisms of GSTT1, GSTM1, GSTP1, MnSOD, and catalase in nonhereditary chronic pancreatitis: evidence of xenobiotic stress and impaired antioxidant capacity

Epidemiological studies have demonstrated a variety of potential environmental factors that may alter susceptibility to chronic pancreatitis (CP) through oxidative/xenobiotic stress; however, a direct causal and mechanistic role has not been established. We aimed (1) to determine the prevalence of functional genetic polymorphisms in the antioxidant enzymes, glutathione S-transferase GSTM-1, GSTP-1, and GSTT-1, manganese superoxide dismutase, and catalase in CP and (2) to reveal evidence of oxidative stress in patients with CP by measuring whole-blood glutathione redox status. In total, 122 patients with CP (75 alcohol-induced [A1CP], 33 idiopathic [ICP], and 13 hereditary) and 245 age- and sex-matched controls were recruited. The prevalence of the functional GSTT-1 genotype (GSTT-1*A) was significantly higher in CP (88.5%) compared to healthy controls (76%; chi2 = 7.26, P = 0.007). Stratification to disease etiology demonstrated that the GSTT-1*A genotype was also significantly more prevalent among patients with ICP (94%; P = 0.02; 95% CI, 0.04-9.16) but not in those with A1CP. In 22 patients with stable CP, the whole-blood glutathione concentration (median [IQR]: 72 micromol/L [21-181 micromol/L]) and the glutathione redox ratio (GSH/GSSG) (median [IQR]: 9 (3-77]) were significantly reduced compared to those in 20 healthy volunteers (median [IQR]: 815 micromol/L [679-1148 micromol/L], P < 0.001, and 96 [52-347], P = 0.005, respectively). We conclude that the GSTT-1 functional genotype is associated with ICP. Evidence of altered glutathione redox status suggests that this disease modification may be a consequence of oxidative stress or the bioactivation of xenobiotics.

Potential effects of L-NAME on alcohol-induced oxidative stress

AIM: Nitric oxide (NO) is a highly reactive oxidant synthesized from L-arginine by nitric oxide synthase (NOS). NO may cause injury through the generation of potent radicals. Nw- nitro-L-arginine methyl ester (L-NAME) is a non-selective inhibitor of NOS. We aimed to evaluate whether L-NAME treatment had protective effects against oxidative stress in rats intragastrically fed with ethanol during a 4 wk-period.

METHODS: Thirty-six male Wistar rats were divided into 3 equal groups: group 1 (control group-isocaloric dextrose was given), group 2 (6 g/kg·d ethanol-induced group) and group 3 (both ethanol 6 g/kg·d and L-NAME 500 mg/L in drinking water-given group). Animals were sacrificed at the end of 4 wk-experimental period, and intracardiac blood and liver tissues were obtained. Biochemical measurements were performed both in plasma and in homogenized liver tissues. Alanine amino transferase (ALT), aspartate amino transferase (AST), malondialdehyde (MDA), NO, superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) levels were measured by spectrophotometry.

RESULTS: ALT and AST in group 2 (62 U/L and 128 U/L, respectively) were higher than those in group 1 (24 U/L and 38 U/L) and group 3 (37 U/L and 81 U/L) (P<0.001 for both). Plasma and tissue levels of MDA in group 2 (4.66 μmol/L and 0.55 nmol/mg protein) were higher than in group 1 (2.65 μmol/L and 0.34 nmol/mg protein) and group 3 (3.43 μmol/L and 0.36 nmol/mg protein) (P<0.001 for both). Plasma and liver tissue levels of NO in group 2 (54.67 μmol/L and 586.50 nmol/mg protein) were higher than in group 1 (34.67 μmol/L and 435.33 nmol/mg protein) and group 3 (27.50 μmol/L and 412.75 nmol/mg protein ) (P<0.001 for both). Plasma and liver tissue SOD activities in group 2 (15.25 U/mL and 5.38 U/ mg protein, respectively) were lower than in group 1 (20.00 U/mL and 8.13 U/ mg protein) and group 3 (19.00 U/mL and 6.93 U/ mg protein) (P<0.001 for both). Plasma and liver tissue CAT activities in group 2 (145 U/mL and 37 U/ mg protein, respectively) were lower than in group 1 (176 U/mL and 73 U/mg protein) and group 3 (167 U/mL and 61 U/mg protein) (P<0.001 for both). Meanwhile, erythrocytes and liver tissue levels of GSH in group 2 (4.12 mg/g Hb and 5.38 nmol/mg protein, respectively) were lower than in group 1 (5.52 mg/g Hb and 4.49 nmol/mg protein) and group 3 (5.64 mg/g Hb and 4.18 nmol/mg protein) (P<0.001 for both).

CONCLUSION: Our findings show that L-NAME may produce a restorative effect on ethanol-induced liver damage via decreasing oxidative stress and increasing antioxidant status.

Lipid peroxide levels and antioxidant status in alcoholic liver disease

The present study was conducted to evaluate some of the components of antioxidant defense system and oxidative damage in 20 male patients of alcoholic liver disease (ALD). The results were compared with 20 healthy male smokers and 20 healthy male non-smokers volunteers. Patients were subjected to detailed clinical examination and laboratory investigations. Blood samples were collected for estimating reduced glutathione (GSH), total thiols (T-SH) malondialdehyde (MDA), transaminases (AST, ALT), glutathione-S-transferease (GST) and gammaglutamyl transferase (GGT). Serum aspartate amino transferase (AST)/alanine amino transferase (ALT) ratio was significantly (p<0.01) reduced in ALD patients as compared to the controls. However, the core of utility of MDA and GST was found to be significantly (p<0.01) increased in ALD patients compared to controls. There was a significant negative correlation of MDA with both GSH and TSH. Plasma GGT levels were significantly (p<0.01) increased in alcoholics and the enzyme showed a significant positive correlation with MDA. These results give enough evidence of increased oxidative stress and compromised antioxidant defense system in patients with ALD.

Association of antioxidant enzyme gene polymorphisms and glutathione status with severe acute pancreatitis

BACKGROUND & AIMS

Genetic variations in antioxidant metabolism may explain varying biological responses to acute pancreatitis (AP). We studied the contribution of oxidative stress to the pathogenesis of severe pancreatitis by examining the prevalence of functional gene polymorphisms of antioxidant enzymes and evidence of heightened oxidative stress.

METHODS

DNA from 320 patients with AP (90 severe) and 263 controls was genotyped for glutathione S-transferase (Mu-1 [M-1], theta-1 [T-1], and pi-1 [P-1: Ile-105Val]), manganese superoxide dismutase (Ala-9Val), and catalase (C-260T) polymorphisms. Erythrocyte reduced glutathione (GSH) concentration was determined 24 and 72 hours after the onset of pain in 46 patients (11 severe). Disease severity was assessed using Atlanta clinical criteria, Acute Physiology Scores (APS), and peak serum C-reactive protein levels.

RESULTS

The functional GSTT-1*A genotype was more prevalent in severe (96%) compared with mild attacks of AP (78%; odds ratio [OR], 5.9; 95% confidence interval [CI ], 2-17; P < 0.0001) and controls (76%; OR, 6.6; 95% CI, 2.3-18.7; P < 0.0001). Compared with null genotype, GSTT-1*A was associated with higher peak C-reactive protein levels (184 vs. 94 g/dL; P = 0.0005) and APS (24 hours, P = 0.04; 48 hours, P = 0.015). Reduced glutathione (GSH) at 24 hours was lower in mild (median, 382 nmol/g) and severe attacks (median, 407 nmol/g) compared with controls (median, 3685 nmol/g; P < 0.001). Levels increased at 72 hours in mild (P = 0.012) but not severe attacks and inversely correlated with APS (r = -0.49; P = 0.04).

CONCLUSIONS

The functional GSTT-1*A genotype was associated with severe attacks of pancreatitis. Heightened oxidative stress characterized by glutathione depletion may be of importance in mediating the progression from mild to severe pancreatitis.

Inflammatory cytokine response to Vibrio vulnificus elicited by peripheral blood mononuclear cells from chronic alcohol users is associated with biomarkers of cellular oxidative stress

Vibrio vulnificus is the leading cause of death in the United States associated with the consumption of raw seafood, particularly oysters. In epidemiological studies, primary septicemia and inflammation-mediated septic shock caused by V. vulnificus is strongly associated with liver disease, often in the context of chronic alcohol abuse. The present study was undertaken to determine whether clinical biomarkers of liver function or cellular oxidative stress are associated with peripheral blood mononuclear cell inflammatory cytokine responses to V. vulnificus. Levels of interleukin-1 beta (IL-1 beta), IL-6, IL-8, and tumor necrosis factor alpha elicited in response to V. vulnificus and measured in cell supernatants were not associated with the liver biomarkers aspartate aminotransferase (AST) or alanine aminotransferase (ALT) or the AST/ALT ratio. In contrast, reduced glutathione (GSH) levels were associated with the release of all four cytokines (IL-1 beta [R(2) = 0.382; P = 0.006], IL-6 [R(2) = 0.393; P = 0.005], IL-8 [R(2) = 0.487; P = 0.001], and TNF-alpha [R(2) = 0.292; P = 0.021]). Those individuals with below-normal GSH levels produced significantly less proinflammatory cytokines in response to V. vulnificus. We hypothesize that persons with markers for cellular oxidative stress have increased susceptibility to V. vulnificus septicemia.

Glutathione depletion increases nitric oxide-induced oxidative stress in primary rat hepatocyte cultures: involvement of low-molecular-weight iron

Various drugs and chemicals can cause a glutathione (GSH) depletion in the liver. Moreover, nitric oxide (NO) can be generated in response to physiological and pathological situations such as inflammation. The aim of this study was to estimate oxidative stress when primary rat hepatocytes were exposed to GSH depletion after NO production. For this purpose, cells were preincubated with lipopolysaccharide (LPS) and gamma-interferon (IFN) for 18 h in order to induce NO production by NO synthase and then L-buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, was added for 5 h. In hepatocyte cultures preincubated with LPS and IFN before BSO addition, an increase in lipid peroxidation was noted. In those cells, an elevation of iron-bound NO and a decrease in free NO led us to suggest the involvement of low-molecular-weight iron (LMW iron) in the enhancement of oxidative stress. Indeed, addition of deferiprone, a chelator of LMW iron, reduced iron-bound NO levels and the extent of oxidative stress. Moreover, an important elevation of LMW iron levels was also observed. As both, N-acetylcysteine, a GSH precursor, and N(G)-monomethyl-L-arginine, a NO synthase inhibitor, totally inhibited the elevation of LMW iron and oxidative stress, a cooperative role could be attributed to NO production and GSH depletion.

Oxidative stress in viral and alcoholic hepatitis

Liver damage ranges from acute hepatitis to hepatocellular carcinoma, through apoptosis, necrosis, inflammation, immune response, fibrosis, ischemia, altered gene expression and regeneration, all processes that involve hepatocyte, Kupffer, stellate, and endothelial cells. Reactive oxygen and nitrogen species (ROS, RNS) play a crucial role in the induction and in the progression of liver disease, independently from its etiology. They are involved in the transcription and activation of a large series of cytokines and growth factors that, in turn, can contribute to further production of ROS and RNS. The main sources of free radicals are represented by hepatocyte mitochondria and cytochrome p450 enzymes, by endotoxin-activated macrophages (Kupffer cells), and by neutrophils. The consequent alteration of cellular redox state is potentiated by the correlated decrease of antioxidant and energetic reserves. Indices of free radical-mediated damage, such as the increase of malondialdehyde, 4-hydroxynonenal, protein-adducts, peroxynitrite, nitrotyrosine, etc., and/or decrease of glutathione, vitamin E, vitamin C, selenium, etc., have been documented in patients with viral or alcoholic liver disease. These markers may contribute to the monitoring the degree of liver damage, the response to antiviral therapies and to the design of new therapeutic strategies. In fact, increasing attention is now paid to a possible "redox gene therapy." By enhancing the antioxidant ability of hepatocytes, through transgene vectors, one could counteract oxidative/nitrosative stress and, in this way, contribute to blocking the progression of liver disease.

Red blood cell antioxidant and iron status in alcoholic and nonalcoholic cirrhosis

BACKGROUND

Iron overload has been reported in alcoholic liver cirrhosis but it remains to be established whether iron is involved in inducing oxidative damage to erythrocytes in alcoholic cirrhosis. The aim of this study was to assess oxidative damage and red cell indicators of antioxidant defences in alcoholics with mild-to-severe liver cirrhosis, taking into account the iron status.

MATERIALS AND METHODS

Twenty-nine patients with alcoholic liver cirrhosis (AC) and 27 with nonalcoholic cirrhosis (NAC) were studied. Serum lipid peroxides (LPO) were assayed by a colourimetric method. Serum-free malonyldialdehyde (MDA) was assayed by selected ion monitoring in positive chemical ionization; serum 4-hydroxy-2(E)-nonenal (4-HNE) was determined by a colorimetric method. Reduced (GSH) and oxidized glutathione (GSSG), adenine and pyridine cofactors were assayed in whole blood extracts by HPLC. Hexose-monophosphate shunt (HMPS), glycolytic pathway (EMP) and antioxidant enzyme activities were determined by standard methods. Iron status was evaluated by standard clinical chemistry and by histological grading of liver iron. Nontransferrin-bound iron (NTBI) was measured in serum by HPLC.

RESULTS

GSH progressively decreased with increasing severity of liver involvement in AC and NAC. MDA, 4-HNE and NTBI were significantly higher in AC serum. Stimulation of red cell HMPS and reducing potential, in terms of NADPH production, were more pronounced in AC.

CONCLUSIONS

These results suggest that NTBI is more important than the decrease of antioxidant defences in inducing lipid peroxidation. NTBI may play a catalytic role in free radical reactions in the presence of cellular reductants such as NADPH.

Nutritional modulation of immune function

The inflammatory response to injury and infection, although an essential part of immune function, carries the risk of severe tissue depletion and immunosuppression. These outcomes increase morbidity and delay recovery. Evidence is accumulating that single-nucleotide polymorphisms in the genes controlling pro-inflammatory cytokine production adversely influence the response. Immunonutrition provides a means of modulating the inflammatory response to injury and infection, and thereby improves clinical outcome. n-3 Polyunsaturated fatty acids (n-3 PUFA), glutamine, arginine, S amino acids and nucleotides are important components of immunonutrient mixes. While animal model studies suggest that all these components may exert a beneficial effect in patients, the number of large randomized placebo-controlled trials utilizing immunonutrition is fairly limited and the observed effects are relatively small. Meta-analyses suggest that while immunonutrition may not reduce mortality rates, a reduction in hospital length of stay, decreased requirements for ventilation and lower infection rates are achieved by this mode of nutrition. The present paper discusses some underlying reasons for the difficulty in demonstrating the clinical efficacy of immunonutrition. Paramount among these reasons is the antioxidant status and genetic background of the patient. A number of studies suggest that there is an inverse relationship between inflammation and T-cell function. Immuno-enhancive effects have been shown in a number of studies in which n-3 PUFA, glutamine and N-acetyl cysteine have been employed. All these nutrients may exert their effects by suppressing inflammation; n-3 PUFA by direct suppression of the process and glutamine and N-acetyl cysteine by acting indirectly on antioxidant status. Glutamine and nucleotides exert a direct effect on lymphocyte proliferation. Preliminary data suggests that not all genotypes are equally sensitive to the effects of immunonutrition. When further studies have been conducted to discern the precise interaction between each individual's genotype of relevance to the response to injury and infection, and immunonutrients, the level of precision in the application of immunonutrition will undoubtedly improve.

Can dietary intake influence plasma levels of amino acids in liver cirrhosis?

BACKGROUND

Modifications in plasma amino acid patterns in cirrhotics are attributed to impaired liver function, being more evident in alcoholic than in viral cirrhosis.

AIM

To evaluate whether diet influences plasma amino acid concentrations in different aetiological groups of cirrhotics.

PATIENTS

Study population comprised 40 patients with cirrhosis (25 virus- and 15 alcohol-related], all Child A, and 30 healthy subjects (controls).

METHOD

A food frequency and quality questionnaire was utilized to determine dietary history and alcohol intake. Nutritional status was evaluated by anthropometric method. Amino acids were determined, on venous blood samples, using a specific analyzer while cysteine was evaluated by fluorescent high power liquid chromatography

RESULTS

The total daily intake of calories, proteins, lipids, and carbohydrates was similar in all individuals. Food quality distinguished the cirrhotics from the controls, but not the different aetiological groups of cirrhotics. Plasma cysteine levels were significantly lower, while aromatic amino acids and methionine were significantly higher, in all cirrhotics (p<0.001 and p<0.01, respectively, versus controls). The decrease in cysteine and the increase in other amino acids were more marked in alcoholics (p<0.01).

CONCLUSIONS

Ethanol intake, but not diet, further enhances the changes in plasma aromatic amino acids, methionine and cysteine induced by impaired liver function in patients with cirrhosis, suggesting a direct interference of alcohol in their metabolism.

Accumulation of docosahexaenoic acid in phosphatidylserine is selectively inhibited by chronic ethanol exposure in C-6 glioma cells

Neuronal membranes are highly enriched with docosahexaenoic acid (22:6n-3), and its content can be altered by ethanol consumption. We have previously reported that the 22:6n-3 status in membrane affects the biosynthesis of phosphatidylserine (PS), a phospholipid class which contains an exceptionally high proportion of 22:6n-3. The aim of the present study is to investigate the effect of chronic ethanol exposure on PS accumulation in relation to the 22:6n-3 status. C-6 glioma cells were enriched with 25 microM 22:6n-3 for 48 h and the PS accumulation was first evaluated in comparison to nonenriched cells as well as cells enriched with arachidonic acid (20:4n-6). Electrospray liquid chromatography-mass spectrometry analysis revealed that cells treated with 22:6n-3 showed significantly higher accumulation of PS in comparison to nonenriched or 20:4n-6-enriched cells, primarily due to an increase of 1-stearoyl-2-docosahexaenoyl-glycerophosphoserine (18:0,22:6-PS). Chronic ethanol exposure selectively affected the accumulation of PS in 22:6n-3-enriched cells. After cells were exposed to 20 or 50 mM ethanol for 4 wk, accumulation of 18:0,22:6-PS upon 22:6n-3 supplementation was significantly lower, resulting in a drastic reduction of total PS. Concomitantly, ethanol-treated cells showed lower incorporation of serine in comparison to control cells. From these data, it was concluded that supplementation of cells with 22:6n-3 promotes the accumulation of PS and chronic ethanol treatment diminishes this effect at least in part through impaired serine incorporation processes. Attenuated accumulation of 22:6n-3 in PS and the reduction of PS thus may have significant implications in pathophysiological effects of ethanol, especially in tissues with abundant 22:6n-3.