Content and composition of lipoproteins of rat blood and liver and various parameters of oxidative stress during administration of cobalt chloride

Cobalt chloride effect on rat liver and serum blood lipoproteins content and composition and on some characteristics of lipid peroxidation and oxidative stress was investigated. The activation of free-radical oxidation and oxidative stress development were judged from the dynamics of lipid peroxidation products accumulation, from cathepsin D unsedimental activity and from the alteration of microsomal cytochrome P-450 content and from activity of a number antioxidative enzymes. In order to evaluate the state of glutathione-defence system the activities of glutathione peroxidase, glutathione S-transferase, glutathione reductase and some NADPH-generating enzymes and reduced glutathione level alteration were studied in liver. The data obtained show that the cobalt chloride injection leads to the development of the oxidative stress and to activation of some antioxidant defence system, namely, glutathione-depending enzymes, and of microsomal cytochrome P-450 catabolism. The system blood lipoproteins (liver lipoproteins was found to participate in metabolism adaptation under oxidative stress and in maintenance of biological membranes structure and functioning.     

Valproate treatment induces lipid globule accumulation with ultrastructural abnormalities of mitochondria in skeletal muscle

The association between an in vivo oxidative stress condition of the liver and hepatic porphyria during HCB intoxication is postulated. After 30 days of treatment, HCB (25 mg/kg b.w.) promotes an induction of microsomal cytochrome P450 system, increase in microsomal superoxide anion generation accompanied by increased levels of liver lipid peroxidation, as measured by the production of thiobarbituric acid reactants and by spontaneous visible chemiluminescence. Concomitantly, liver antioxidant defenses are slightly modified, with decreased activity of glutathione peroxidase, superoxide dismutase and glucose-6-phosphate dehydrogenase contributing to an oxidative stress condition of the liver. These liver biochemical alterations are closely related to increased levels of urinary coproporphyrin, plasma AST and ALT activities and to the onset of liver morphological lesions.     

Glutathione-dependent factors and inhibition of rat liver microsomal lipid peroxidation

The effects of reduced glutathione (GSH) and glutathione disulfide (GSSG) on lipid peroxidation were investigated in rat liver microsomes containing deficient or adequate amounts of alpha-tocopherol (alpha-TH). Rates of formation of thiobarbituric acid reactive substances (TBARS) as well as rates of consumption of alpha-TH and O2 were decreased by GSH and were more pronounced in the NADPH-dependent assay system than in the ascorbate-dependent system. The GSH-dependent inhibition of lipid peroxidation was potentiated by GSSG in the NADPH-dependent assay system, but it had no effect in the nonenzymatic system. Diphenyliodonium chloride, an inhibitor of NADPH cytochrome P-450 reductase, completely prevented lipid peroxidation in the NADPH-dependent assay system whereas it had no effect on the ascorbate-dependent system. This is further evidenced by the fact that purified rat liver microsomal NADPH cytochrome P-450 reductase (EC 1.6.2.4) was inhibited approximately 24% and 52% by 5 mM GSH and 5 mM GSH + 2.5 mM GSSG, respectively. Glutathione disulfide alone had no effect on reductase activity. Similarly, other disulfides such as cystine, cystamine and lipoic acid were without effect on reductase activity. These results clearly delineate different mechanisms underlying the combined effects of GSH and GSSG on microsomal lipid peroxidation in rat liver. One mechanism involves recycling of microsomal alpha-TH by GSH during oxidative stress via a labile protein, ostensibly associated with "free radical reductase" activity. A second glutathione-dependent mechanism appears to be mediated through the inhibition of NADPH cytochrome P-450 reductase. The enhanced inhibition by GSH + GSSG of microsomal lipid peroxidation in the NADPH-dependent assay system suggests suppression of the initiation phase at the level of NADPH cytochrome P-450 reductase which is independent of microsomal alpha-TH.     

Variations in dietary fat and cholesterol intakes modify antioxidant status of SHR and WKY rats

The effects of varying dietary fat saturation [butter (B), beef tallow (BT)] or polyunsaturation [(n-6) soybean oil (SBO), (n-3) menhaden oil (MO)] and cholesterol content (0.05 and 0.5 g/100 g) on systolic blood pressure (SBP), plasma lipids and tissue antioxidant status were investigated in 14-wk-old spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats. Varying dietary fat composition for 9 wk had no influence on SBP in either SHR or WKY rats. Rats fed MO diets exhibited smaller (P < 0.05) body weight gains, lower (P < 0.05) feed efficiency ratios and lower (P < 0.05) plasma cholesterol concentrations than those fed the B, BT and SBO diets. Significant (P < 0.05) interactions for animal strain x cholesterol intake and animal strain x fat source were noted for serum cholesterol concentrations. SHR exhibited higher (P < 0.05) RBC and liver catalase (CAT), and heart and liver superoxide dismutase (SOD) activities similar to those of WKY rats. The lower (P <0.01) RBC, heart and liver glutathione peroxidase (GSH-Px) activities observed in SHR coincided with higher (P <0.01) glutathione reductase (GSSG-Red), compared with WKY rats. Dietary cholesterol intake had no effect on RBC, heart and liver total sulfhydryl concentration or GSH-Px activities, but increased (P <0. 001) liver GSSG-Red. Feeding MO resulted in lower (P <0.001) RBC and heart GSH-Px activities. In contrast, feeding B and BT resulted in lower GSH-Px in liver. The significant (P < 0.01) animal strain x fat source interaction obtained for liver GSH-Px activity indicated that SHR responded differently to polyunsaturated fatty acid feeding than their WKY counterparts. Diet-induced changes in tissue antioxidant status were tissue specific and did not affect the development of hypertension in SHR.     

Heterogeneous expression of neurofilament proteins in forebrain and cerebellum during development: clinical implications for spinocerebellar ataxia

Previously it was shown that methylenedioxybenzenes (MDBs), particularly isosafrole, were highly effective at preventing CCl4-induced liver necrosis in vivo (Z.S. Zhao, P.J. O'Brien, The prevention of CCl4-induced liver necrosis in mice by naturally occurring methylenedioxybenzenes, Toxicol. Appl. Pharmacol., 140 (1996) 411-421), probably as a result of forming metabolic intermediate complexes with cytochrome P450. In the following it was shown that pretreatment of mice with isosafrole also completely prevented ferric nitrilotriacetate (FeNTA)-induced renal necrosis and lipid peroxidation, even though metabolic activation by cytochrome P450 is not involved. The naturally occurring or synthetic MDBs that prevented CCl4 hepatotoxicity also prevented hepatocyte lipid peroxidation. induced by FeNTA, but other cytochrome P450 inhibitors were ineffective. These compounds, in decreasing order of antioxidant effectiveness, were sesamol, 4-t-butyl-methylenedioxybenzene, isosafrole, piperonyl butoxide and 4-bromo-methylenedioxybenzene and safrole, whereas, benzodioxole, 3,4-(methylenedioxy)-toluene and 1,2-(methylenedioxy)-4-nitrobenzene were ineffective. Pre-incubating the hepatocytes with P450 inhibitors decreased the protective effects of isosafrole, suggesting that the catecholic metabolites of MDBs were responsible for the antioxidant activity. A greater inhibition of FeNTA-induced lipid peroxidation by catecholic metabolites was observed. Since cytochrome P450 did not participate in FeNTA-induced hepatocyte or microsomal lipid peroxidation, it is likely that the antioxidant properties of MDBs or their catecholic metabolites also contribute to their in vivo protection against CCl4 or FeNTA-induced hepato- or nephrotoxicity.     

Down-regulation of the hepatic cytochrome P450 by an acute inflammatory reaction: implication of mediators in human and animal serum and in the liver

1. Infection and inflammation trigger a cascade of mediators that eventually will down-regulate the hepatic cytochrome P450 (P450). The present study aimed to characterize the mediators contained in the serum of rabbits with an acute inflammatory reaction (AIR) induced by the s.c. injection of turpentine (5 ml), and in the serum of humans with an acute upper respiratory tract viral infection. 2. Hepatocytes from control (H(CONT)) rabbits and rabbits with an AIR (H(INFLA)) were isolated and cultured. Compared with H(CONT) in H(INFLA) the production of theophylline metabolites, 3-methylxanthine (3MX), 1-methyluric acid (1MU), and 1,3-dimethyluric acid (1,3DMU) was reduced as was the amount of total P450, while lipid peroxidation was increased. Incubation of H(INFLA) with serum of rabbits with an AIR (RS(INFLA)) for 4 h further reduced the formation of the metabolites of theophylline as well as the amount of P450, and enhanced the lipid peroxidation. RS(INFLA) obtained 6, 12 and 24 h after the injection of turpentine showed the same ability to down-regulate hepatic P450 as the serum obtained at 48 h. 3. The efficacy (Emax) of RS(INFLA) to inhibit the formation of theophylline metabolites differed, i.e. 1,3DMU > 1MU > 3MX, and the potency of serum mediators (IC50) was similar for 3MX and 1MU, but lower for 1,3DMU. 4. Incubation of serum of human volunteers (HS(INFLA)) with a viral infection with H(CONT) or H(INFLA) reduced the production of theophylline metabolites, as well as the amount of P450, and increased the lipid peroxidation. HS(INFLA) depressed 1,3DMU more efficiently than 3MX and 1MU. HS(INFLA) reduced 3MX with greater efficacy than did RS(INFLA). Potency was very variable but not different from rabbits. 5. It is concluded that the serum of rabbits with an AIR or of humans with a viral infection contain several mediators that inhibit noncompetitively various isoenzymes of the hepatic P450. The decrease in P450 induced by HS(INFLA) or RS(INFLA) is closely associated with the increase in lipid peroxidation (r2= 0.8870) suggesting that lipid peroxidation could directly or indirectly be involved in the P450 down-regulation.     

RNA extraction from virus-diseased sweet potato for reverse transcriptase polymerase chain reaction analysis

Apoptosis occurs in both clinical and experimental alcoholic liver disease. The mechanisms involved in alcohol-induced apoptosis of liver cells are not completely understood. Induction of cytochrome P450 2E1, the alcohol-inducible cytochrome P450, is one of the proposed mechanisms. Exposure of Hep G2 cells expressing cytochrome P450 2E1 to arachidonic acid leads to increased lipid peroxidation and apoptosis. Increased levels of iron in the liver also promote lipid peroxidation and are associated with increased numbers of apoptotic hepatocytes. Tumor necrosis factor (TNF) acting through its receptors can induce apoptosis in hepatocytes. Increased levels of tumor necrosis factor and its receptors have been described in alcoholic liver disease. The liver is also CD95 receptor positive and in liver tissue from patients with alcoholic hepatitis, the CD95 ligand is expressed at high levels in hepatocytes. Cytotoxic T lymphocytes could, through the CD95 receptor-ligand interaction, promote apoptosis.     

Epidemiology of childhood asthma

The objective of the present study was to investigate the expression of major xenobiotic-metabolising cytochrome P450 proteins, and of other enzyme systems, in hepatic and extrahepatic tissues of rabbits rendered atherosclerotic by the dietary administration of 1% cholesterol diets for 8 weeks. Individual cytochrome P450 proteins were monitored using diagnostic substrates and immunologically in Western blot analysis. The activity of all hepatic isoforms studied was depressed in the atherosclerotic animals; when, however, apoprotein levels were determined immunologically, no major differences were evident between the control and the atherosclerotic rabbits. In vitro studies indicated that neither cholesterol nor palm oil inhibited cytochrome P450 activity. The effects of cholesterol treatment leading to atherosclerosis on kidney, heart and lung cytochrome P450 activities were isoform- and tissue-specific; no change was evident in the heart activities, but in the lung and kidney cytochrome P450 activities were clearly modulated by the treatment with cholesterol. Apoprotein levels did not always parallel the changes in activities. Western blot analysis of aortic cytochromes P450 revealed that administration of cholesterol-rich diets enhanced CYP2B and CYP3A apoprotein levels. Cholesterol feeding to rabbits gave rise to a marked decrease in hepatic glutathione S-transferase activity but did not influence glutathione reductase or total glutathione levels. The same treatment had no effect on catalase, glutathione peroxidase and superoxide dismutase. It is concluded that treatment of rabbits with cholesterol-rich diets leading to atherosclerosis gives rise to profound changes in the expression of cytochrome P450 proteins in the liver and other tissues; possible mechanisms are discussed.     

Biochemical and morphological studies on the effects of anthocyans and vitamin E on carbon tetrachloride induced liver injury

The effects of the natural antioxidants-anthocyans and vitamin E (in a solubilized pharmaceutical form) on carbon tetrachloride-induced liver injury in rats are studied. The changes in the activity of serum transaminases (ALAT and ASAT), the content of the reduced glutathione and cytochrome P-450 as well as the intensity of the processes of lipid peroxidation are assessed. The anthocyans exert a protective effect comparable to that of vitamin E on liver cells. The favorable effects of the combination of the antioxidants on the content of the reduced glutathione and on the processes of lipid peroxidation are more intensely expressed. The morphological changes occurring in hepatocytes correlate with the results of the biochemical studies. It is evident that both substances have a marked hepatoprotective activity.     

Abdominal hysterectomy practice patterns in the United States

Diets rich in polyunsaturated fatty acids (PUFA) are well known to suppress hepatic lipogenic enzymes compared to fat-free diets or diets rich in saturated fatty acids. However, the mechanism underlying suppression of lipogenic enzymes is not quite clear. The present study was undertaken to investigate whether lipid peroxidation products are involved in suppression of lipogenic enzymes. Therefore, an experiment with growing male rats assigned to six groups over a period of 40 d was carried out. Rats received semisynthetic diets containing 9.5% coconut oil and 0.5% fresh soybean oil (coconut oil diet, peroxide value 5.1 meq O2/kg oil), 10% fresh soybean oil (fresh soybean oil diet, peroxide value 9.5 meq O2/kg oil), or 10% thermally treated soybean oil (oxidized soybean oil diet, peroxide value 74 meq O2/kg oil). To modify the antioxidant state of the rats, we varied the vitamin E supply (11 and 511 mg alpha-tocopherol equivalents per kg of diet) according to a bi-factorial design. Food intake and body weight gain were not influenced by dietary fat and vitamin E supply. Activities of hepatic lipogenic enzymes were markedly influenced by the dietary fat. Feeding either fresh or oxidized soybean oil diets markedly reduced activities of fatty acid synthase, (FAS), acetyl CoA-carboxylase, (AcCX), glucose-6-phosphate dehydrogenase, (G6PDH), 6-phosphogluconate dehydrogenase, and ATP citrate lyase (ACL) relative to feeding the coconut oil diet. Moreover, feeding oxidized soybean oil slightly, but significantly, lowered activities of FAS, AcCX, and ACL compared to feeding fresh soybean oil. Activities of hepatic lipogenic enzymes were reflected by concentrations of triglycerides in liver and plasma. Rats fed the coconut oil diet had markedly higher triglyceride concentrations in liver and plasma than rats consuming fresh or oxidized soybean oil diets, and rats fed oxidized soybean oil had lower concentrations than rats fed fresh soybean oil. The vitamin E supply of the rats markedly influenced concentrations of thiobarbituric acid-reactive substances in liver, but it did not influence activities of hepatic lipogenic enzymes. Because the vitamin E supply had no effect, and ingestion of an oxidized oil had only a minor effect, on activities of hepatic lipogenic enzymes, it is strongly suggested that neither exogenous nor endogenous lipid peroxidation products play a significant role in the suppression of hepatic lipogenic enzymes by diets rich in PUFA. Therefore, we assumed that dietary PUFA themselves are involved in regulation of hepatic lipogenic enzymes. Nevertheless, the study shows that ingestion of oxidized oils, regardless of the vitamin E supply, also affects hepatic lipogenesis, and hence influences triglyceride levels in liver and plasma.     

Treatment failure and methadone dose in a public methadone maintenance treatment programme in Geneva

PURPOSE: To determine the effect of an anaesthetic with antioxidant potential, propofol, on red blood cell (RBC) antioxidant enzyme activities and RBC susceptibility to peroxidative challenge. METHODS: Propofol was administered by intravenous bolus (2.5 mg.kg-1) and continuous infusion (36 and 72 ml.hr-1 in nine swine; 216 ml.hr-1 in two swine), to achieve serum concentrations between 5 and 30 micrograms.ml-1 for two hours at each rate. Arterial blood sampling was at 0, 10, 30, 60, and 120 min for each rate of infusion, for measurement of plasma propofol concentration, activities of plasma and RBC superoxide dismutase, glutathione peroxidase, glutathione reductase, RBC catalase, and RBC malondialdehyde (MDA) formation in response to ex vivo oxidative challenge with t-butyl hydrogen peroxide (tBHP; 1.5 mM). Antioxidant mechanisms were determined by in vitro study of MDA formation, GSH depletion, and oxidation of haemoglobin to methaemoglobin in human erythrocytes exposed to propofol 0-75 microM. The antioxidant potential of propofol was compared with that of alpha-tocopherol utilising the reaction with 2,4,6-tripyridyl-s-triazine (TPTZ). RESULTS: Propofol had no effect on plasma or RBC antioxidant enzyme activities. It inhibited RBC MDA production over the range of 0-20 micrograms.ml-1 (y = -18.683x + 85.431; R2 = 0.8174). Effective propofol concentrations for 25% and 50% reductions in MDA levels were 7-12 and 12-20 micrograms.ml-1, respectively. Propofol has a similar effect on human erythrocytes in vitro (R2 = 0.98). CONCLUSION: Propofol antagonises the effects of forced peroxidation of red cells at anaesthetic and sub-anaesthetic concentrations in swine. Its actions include scavenging of oxygen derived free radicals in a tocopherol-like manner.     

Effect of nifedipine on the elimination of theophylline in the rabbit subjected to hypoxia or to an inflammatory reaction

This study was performed to assess whether nifedipine could prevent the decrease in hepatic cytochrome P450 induced by acute moderate hypoxia or an inflammatory reaction. Rabbits were subjected to acute moderate hypoxia (PaO2 > 37 mmHg), with or without pretreatment with nifedipine (0.5 mg kg-1 subcutaneously every 8 h, for 48 h). Another group received 5 mL of turpentine subcutaneously with or without pretreatment with nifedipine (0.5 mg kg-1 s.c. every 8 h, for 72 h). The kinetics of 2.5 mg kg-1 of theophylline were studied in all rabbits up to 8 h, at which time total cytochrome P450 and malondialdehyde were assessed in the liver. Compared with control rabbits, hypoxia and an inflammatory reaction increased theophylline plasma concentrations, as a result of 3 decrease in theophylline systemic clearance. Both experimental conditions reduced hepatic cytochrome P450 by 40 to 50% and increased hepatic malondialdehyde by approximately 50% (P < 0.05). In control animals, pretreatment with nifedipine did not influence theophylline kinetics, the liver content in cytochrome P450 or malondialdehyde. Pretreatment with nifedipine partially prevented the hypoxia- and the inflammation-induced decrease in liver cytochrome P450; however, nifedipine did not prevent the decrease in theophylline clearance or the increase in liver malondialdehyde. It is concluded that nifedipine affords a partial protection against hypoxia- or inflammation-induced hepatic cellular injury.     

Quantitation of T2 lesion load in multiple sclerosis with magnetic resonance imaging: a pilot study of a probabilistic neural network approach

We studied the effect of prostaglandin F2 alpha on parameters related to microsomal metabolism (free radical production and lipid peroxidation, glutathione content and activity of microsomal oxidases) after an induction by ethanol or acetone combined with starvation. Long-term ethanol administration led to a significant increase in lipid peroxide formation and NADPH-dependent chemiluminescence amplified by luminol and lucigenin. At the same time hydrogen peroxide production and NADPH-stimulated lipid peroxidation were enhanced although the effect did not reach the level of statistical significance. The concentration of reduced glutathione (GSH) in the liver was decreased 2-fold, whereas oxidized glutathione (GSSG) content remained unaltered. Ethanol intoxication resulted in an increase in 7-ethoxycoumarin-O-deethylase (ECOD), 7-benzyloxycoumarin-O-deethylase (BCOD) and 7-ethoxy-resorufin-O-deethylase (EROD) activities, whereas 7-pentoxyresorufin-O-deethylase (PROD) and ethylmorphin-N-demethylase (EMND) activities were unaltered. The combination of acetone treatment with starvation resulted in a significant increase in lipid and hydrogen peroxide formation, NADPH-dependent lipid peroxidation and chemiluminescence. GSH and GSSG concentration in the liver dramatically decreased 5- and 3-fold, respectively. The acetone treatment led to significant increase in EROD, ECOD, BCOD, PROD and EMND activities. The treatment of ethanol-intoxicated rats with prostaglandin F2 alpha (PGF2 alpha) exerted more pronounced prooxidant effect on liver than action of alcohol itself. At the same time, PGF2 alpha improved most of parameters changed by acetone treatment combined with starvation, decreasing lipid peroxide and radical formation and enhancing GSH and GSSG contents.     

Depression of the hepatic cytochrome P450 by an acute inflammatory reaction: characterization of the nature of mediators in human and rabbit serum, and in the liver

There is increasing evidence suggesting that several mediators are involved in the cascade of events leading to the depression of the cytochrome P450 (P450) by an inflammatory reaction. The present study aimed to confirm the presence of mediators in the serum (RS(INFLA)) and hepatocytes (H(INFLA)) of rabbits with an acute inflammatory reaction, and in the serum of humans with an acute upper respiratory tract viral infection (HS(URTVI)). The inflammatory reaction was induced by the s.c. injection of 5 ml of turpentine. Incubation of RS(INFLA) or HS(URTVI) with H(INFLA) depressed the P450, diminished the formation of theophylline metabolites (3-methylxanthine, 1-methyluric acid, and 1,3-dimethyluric acid), and increased lipid peroxidation. The addition of preheated RS(INFLA) or HS(URTVI) to H(INFLA) did not diminish the amount of P450 or theophylline metabolites, and prevented the increase in lipid peroxidation. Incubating the filtrate of RS(INFLA) or HS(URTVI) dialyzed through membranes with cut-off of 10, 30, 50 and 100 kd, with H(INFLA) showed that rabbit and human mediators have molecular weights ranging from 10 to 30 kd. Incubation of H(INFLA) with hepatocytes from control rabbits (H(CONT)) did not decrease further the P450. However, when RS(INFLA) was added to co-cultured H(CONT) + H(INFLA), the depression of P450 was 37% greater (p<0.05), and the amount of theophylline metabolites generated was around 30% (p<0.05) smaller than that observed when H(CONT) or H(INFLA) were incubated with RS(INFLA). Based on the present results we may speculate that human and rabbit serum mediators are proteins of molecular weights ranging from 10 to 30 kd, and in addition, primed hepatocytes once exposed to the serum mediators release mediators able to depress the P450 in H(CONT).     

Hepatotoxicity of diisopropyl ester of malonic acid and chloromalonic acids, disinfection by-products of the fungicide isoprothiolane

The fungicide isoprothiolane (diisopropyl 1,3-dithiolane-2-ylidenemalonate) decomposes to the diisopropyl esters of malonic acid (DM), chloromalonic acid (DCM) and dichloromalonic acid (DDCM) upon aqueous chlorination. In this study, the cytotoxicity of these compounds was examined using rat hepatocytes cultured on Matrigel. DCM and DDCM caused hepatocellular death at concentrations > 0.5 mM, while DM had no effect on the cell viability even at the maximum concentration examined (4 mM). Significant lipid peroxidation, measured as 2-thiobarbituric acid reactive substances, was observed in both DCM- and DDCM-treated hepatocyte cultures, and was significantly enhanced by pretreatment with 0.1 mM bis(p-nitrophenyl)phosphate (BNPP), a carboxylesterase inhibitor. When both BNPP and SKF-525A, a cytochrome P450 inhibitor, were present in the medium, DCM-induced cytotoxicity and lipid peroxidation were significantly suppressed compared to cultures with BNPP-treatment alone. By contrast, the DDCM-induced cytotoxicity was not affected by the combined pretreatment of SKF-525A and BNPP. These results indicate that DCM is metabolically activated by cytochrome P450 in an ester form, while DDCM is activated by a mechanism other than one involving cytochrome P450. To further elucidate the cytochrome P450 isozyme involved in the metabolic activation of DCM, microsomal lipid peroxidation was studied in vitro using microsomes from rats treated with beta-naphthoflavone, musk xylene, phenobarbital, pyrazole, or dexamethasone. Among these preparations, the microsomes from dexamethasone-treated rats showed the most extensive lipid peroxidation in the presence of DCM, and the lipid peroxidation was enhanced by BNPP as observed in hepatocyte cultures. These findings suggest the possible involvement of cytochrome P450 3A in the metabolic activation of DCM.     

The involvement of cytochrome P450 peroxidase in the metabolic bioactivation of cumene hydroperoxide by isolated rat hepatocytes

Organic hydroperoxides are believed to be primarily detoxified in cells by the GSH peroxidase/GSSG reductase system and activated to cytotoxic radical species by non-heme iron. However, organic hydroperoxides seem to be bioactivated by cytochrome P450 (P450) in isolated hepatocytes as various P450 (particularly P450 2E1) inhibitors inhibited cumene hydroperoxide (CumOOH) metabolism and attenuated subsequent cytotoxic effects including antimycin A-resistant respiration, lipid peroxidation, iron mobilization, ATP depletion, and cell membrane disruption. CumOOH metabolism was also faster in P450 1A-induced hepatocytes and was inhibited by the P450 1A inhibitor alpha-naphthoflavone. The ferric chelator deferoxamine also prevented cytotoxicity even after CumOOH had been metabolized but had no effect on CumOOH metabolism. This emphasizes the toxicological significance of the iron released following hydroperoxide metabolic activation by cytochrome P450. The radical trap, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), had no effect on CumOOH metabolism but prevented CumOOH-induced antimycin A-resistant respiration, lipid peroxidation, iron mobilization, and loss of membrane integrity. These results suggest that CumOOH is metabolically activated by some P450 enzymes (e.g., P450 2E1) in hepatocytes to form reactive radical metabolites or oxidants that cause lipid peroxidation and cytotoxicity.     

Aspects of evolving urogenital tuberculosis. 60 cases

In the present study, the effects of thymosin alpha1 on lipid peroxidation were studied in an in vivo model of experimental hypercholesterolemia. In groups II-IV, rabbits were fed a high-cholesterol diet 2% (w/w) for 10 weeks. Thereafter, rabbits in group III were fed a normal diet for another 14 days and those in group IV were given a normal diet plus 25 microg/kg thymosin alpha1 intraperitoneally every other day for the same period. At the end of this period, plasma and erythrocyte lipid levels and susceptibility of erythrocytes to lipid peroxidation were determined in all groups. Hypercholesterolemic rabbits had high plasma and erythrocyte lipid peroxide (TBARS) levels compared to control animals fed a normal diet. Plasma and erythrocyte TBARS levels significantly decreased in the thymosin-alpha1-injected rabbits. In thymosin-alpha1-treated animals (group IV), most of the lipid plaques were replaced by fibrous tissue. These findings suggest that thymosin alpha1 may have some beneficial effects on the treatment of atherosclerosis by normalizing blood lipid levels and by substantially protecting endothelial cells against free radical injury.     

Bronchoalveolar lavage studies in children without parenchymal lung disease: cellular constituents and protein levels

The hepatotoxicity of acetaminophen overdose depends on the metabolic activation to a toxic reactive metabolite by the hepatic mixed function oxidases. There is evidence that an increase in cytosolic Ca2+ is involved in acetaminophen hepatotoxicity. The effects of the Ca2+-antagonists nifedipine (NF), verapamil (V), diltiazem (DL) and of the calmodulin antagonist trifluoperazine (TFP) on the activity of some drug-metabolizing enzyme systems, lipid peroxidation and acute acetaminophen toxicity were studied in male albino mice. No changes in the drug-metabolizing enzyme activities studied and in the cytochrome P-450 and b5 contents were observed 1 h after oral administration of V (20 mg/kg). DL (70 mg/kg) and TFP (3 mg/kg). NF (50 mg/kg) increased cytochrome P-450 content, NADPH-cytochrome c reductase and ethylmorphine-N-demethylase activities. DL and TFP significantly decreased lipid peroxidation. NF, V, DL and TFP administered 1 h before acetaminophen (700 mg/kg orally) increased the mean survival time of animals. A large increase of serum aspartate aminotransferase(AST), and liver weight and depletion of liver reduced glutathione (GSH) occurred in animals receiving toxic acetaminophen dose. NF, V and DL prevented and TFP decreased the acetaminophen-induced hepatic damage measured both by plasma AST and by liver weight. NF, V, DL and TFP changed neither the hepatic GSH level nor the GSH depletion provoked by the toxic dose of acetaminophen. This suggests that V, DL and TFP do not influence the amount of the acetaminophen toxic metabolite formed in the liver. The possible mechanism of the protective effect of NF, V, DL and TFP on the acetaminophen-induced toxicity is discussed.     

Effect of silibinin on oxidative damage of blood constituents

Silibinin (SDH) is a flavonoid with ascertained hepatoprotective effects, which have been partially attributed to its antioxidant properties. Oxidation of blood constituents could have a role in atherogenesis and interfere with the rheologic properties of the blood. In this study we investigated, whether SDH could protect some blood constituents against oxidative modification. In human plasma we measured TBARS and fluorescence generation as indicators of copper or azobis amidinopropane hydrochloride (AAPH) at 760 mm Hg PO2-induced lipid peroxidation. SDH at 50 microM inhibited copper-induced TBARS formation by 25% and fluorescence by 47%. SDH also inhibited AAPH-induced lipid peroxidation, but at 175 microM concentration only. Oxidative modification of albumine was evaluated by fluorescence generation. SDH at 50 microM inhibited copper/hydrogen peroxide fluorescence generation by 54% and at 2.5 microM it inhibited EDTA-Fe (II)/hydrogen peroxide fluorescence generation by 31%. The protection of albumin by SDH was confirmed by SDS-PAGE electrophoresis. Copper-induced red-cell lipid peroxidation was evaluated by TBARS formation. SDH at 250 microM inhibited copper-induced lipid peroxidation and hemolysis by 45% and 94%, respectively. SDH also inhibited hemolysis in red-cell suspensions exposed to hydrogen peroxide, but not lipid peroxidation. Our results show that SDH may protect blood constituents from oxidative damage.     

Inclusion of oxidized vegetable oil in broiler diets. Its influence on nutrient balance and on the antioxidative status of broilers

Over a period of 4 wk, 24 10-d-old broiler hens were fed diets containing 11% vegetable oil (9% rapeseed oil, 2% soybean oil), which was added either fresh (1 meq O2/kg oil) or oxidized (156 meq O2/kg oil). The effects of the dietary treatments on nutrient digestibility were examined in a balance experiment. The antioxidative status of the animals was evaluated using plasma concentrations of thiobarbituric acid-reactive substances (TBARS), erythrocyte hemolysis in vitro, selenium-dependent and selenium-independent activity of glutathione peroxidase in liver cell cytosolic fractions, and concentrations of tocopherols and other fat-soluble compounds with antioxidative properties (lutein, beta-carotene, and retinol) in plasma and various tissues (skeletal muscle, cardiac muscle, liver, and abdominal fat). Compared to the fresh oil, the concentrations of linoleic and linolenic acid were slightly lower in oxidized oil. The concentration of alpha-tocopherol in the diet with fresh oil was an average of 80.8 mg/kg diet, whereas the diet with oxidized oil only provided 44 mg/kg. The dietary selenium content averaged 0.48 mg/kg in both diets. During the experiment, none of the animals showed symptoms of diarrhea or vitamin E deficiency. The intake of oxidized oil caused a growth depression after 2 wk. The retention of fat (P = 0.07), energy (P = 0.09), and alpha-tocopherol (P < 0.01) was lower in the group fed oxidized fat. Furthermore, these animals showed significantly higher plasma concentrations of TBARS (P < 0.01), and lower concentrations of tocopherols, lutein, beta-carotene, and retinol in plasma and tissues.