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P Clot

Publications and source records attributed to P Clot.

At least 19 recordsLinked to original sources
PubMed1996

Role of cytochrome P4502E1-dependent formation of hydroxyethyl free radical in the development of liver damage in rats intragastrically fed with ethanol.

We have previously shown that the treatment with diallyl sulfide (DAS) and phenylethyl isothiocyanate (PIC) of rats receiving ethanol in the alcohol tube-feeding model effectively suppressed the induction of cytochrome P4502E1 (CYP2E1) by ethanol. Here we report that rat treatment with DAS and PIC significantly decreased the trapping of hydroxyethyl free radicals in liver microsomes incubated in vitro with ethanol. Furthermore, these inhibitors also greatly reduced the production of hydroxyethyl radical-derived epitopes detectable in vivo in the liver of ethanol-fed rats. The action of DAS and PIC on the formation of hydroxyethyl radicals paralleled their inhibitory effect on lipid peroxidation as monitored using, respectively, liver malonildialdehyde (MDA) and plasma lipid hydroperoxide levels as well as by the titers of antibodies versus MDA adducts to proteins. Thus, these results indicated a link between the induction of CYP2E1 by ethanol, the formation of hydroxyethyl radicals and the stimulation of lipid peroxidation. The pathological scores in the livers of rats fed with ethanol plus or minus DAS and PIC also correlated with levels of hydroxyethyl radical-derived epitopes. Rats fed intragastrically with ethanol developed antibodies and the formation of these antibodies was greatly reduced by DAS and PIC. Taken together these results suggest that CYP2E1 plays an important role in the generation of hydroxyethyl radicals during chronic alcohol feeding and that ethanol-derived free radicals might play a role in the onset of liver injury in this model of alcohol administration.

Allyl Compounds↗
PubMed1995

Activation of alkylhydrazines to free radical intermediates by ethanol-inducible cytochrome P-4502E1 (CYP2E1).

Electron spin resonance (EPR) spectroscopy analysis using the spin trapping agent 4-pyridyl-1-oxide-t-butyl nitrone (4-POBN) was used to measure the formation of free radical intermediates during NADPH-dependent oxidation of 1-methyl-, 1-ethyl-, and 1-isopropylhydrazine in rat liver microsomes and in reconstituted enzyme systems. The experiments in microsomes revealed that the specific activation of the hydrazines, as measured by the EPR signal intensities, was about two-fold higher, when expressed per nmol of P-450, in microsomes from rats treated with ethanol (EtOH) as compared to membranes isolated from either phenobarbital (PB)-, beta-naphthoflavone (beta-NF)-treated or control rats. Furthermore, kinetic experiments revealed that EtOH-microsomes had an apparent affinity for 1-ethylhydrazine about one order of magnitude higher than PB-microsomes. In reconstituted vesicular systems composed of phospholipids, NADPH cytochrome P-450 reductase and P-450, the intensities of EPR signals produced by the formation of the methyl-, ethyl- and isopropyl-free radicals, were 3- to 5-fold more intense in membrane vesicles containing ethanol-inducible CYP2E1 than phenobarbital-inducible CYP2B1. By contrast, CYP1A2, CYP2B4 and CYP2C4 were inefficient catalysts of radical formation. Desferrioxamine, catalase and superoxide dismutase did not influence the extent of ethyl radicals formed in EtOH-microsomes, indicating that hydroxyl radicals are not involved in the CYP2E1-dependent activation of 1-ethylhydrazine. Addition of cytochrome b5, an efficient donor of the second electron to P-450 and hence an inhibitor of the formation of the oxy-cytochrome P-450 complex, increased to be consistent with the results, did not influence the amount of ethyl radicals trapped. In liver microsomes from untreated rats selective substrates of CYP2E1, such as diethyl-dithiocarbamate and p-nitrophenol, as well as anti-CYP2E1-IgG, inhibited the free radical formation from 1-ethylhydrazine by about 60%. The anti-CYP2E1 IgG used significantly inhibited ethyl radical production also in human liver microsomes incubated with 1-ethylhydrazine and 4-POBN. Taken together, these results indicate that CYP2E1, as compared to other rat liver cytochromes P-450, is an efficient catalyst of transformation of alkylhydrazines to free radical intermediates, a finding that might be of importance in the development of the toxicity of these compounds.

Animals↗
PubMed1995

Detection of antibodies against proteins modified by hydroxyethyl free radicals in patients with alcoholic cirrhosis.

BACKGROUND/AIMS: We have previously shown that hydroxyethyl free radicals produced during cytochrome P4502E1-mediated oxidation of ethanol covalently bind to microsomal proteins. The present study examined whether alkylation of proteins by hydroxyethyl radicals induces an immunologic response in alcoholic patients. METHODS: A microplate enzyme-linked immunosorbent assay was developed using as antigen human serum albumin or bovine fibrinogen reacted with chemically produced hydroxyethyl radicals. RESULTS: This assay showed that the sera of alcoholic cirrhotics contained both immunoglobulin (Ig) Gs and IgAs that recognized proteins modified by hydroxyethyl radicals, whereas practically no reaction was observed in the sera of healthy controls or cirrhotics without evidence of alcohol abuse. The reactivity of the sera from alcoholic patients was not influenced by the protein to which hydroxyethyl radicals were bound. The sera of alcoholic cirrhotics also contained antibodies directed against acetaldehyde-modified albumin. However, the reaction of alcoholic sera with hydroxyethyl radical epitopes was not inhibited by increasing concentrations of acetaldehyde-modified albumin produced under either reducing or nonreducing conditions. CONCLUSIONS: The results indicate that a new group of antigens that do not cross-react with antibodies against acetaldehyde-derived epitopes is formed by the alkylation of protein by hydroxyethyl radicals and is involved in the development of immunologic reactions in alcoholic patients.

Adult↗
PubMed1995

Modulation of experimental alcohol-induced liver disease by cytochrome P450 2E1 inhibitors.

This study was done to determine if a relationship exists between CYP2E1 induction by ethanol, lipid peroxidation, and liver pathology in experimental alcohol-induced liver disease in the rat. Rats were fed ethanol with or without diallyl sulfide (DAS) or phenethyl isothiocyanate (PIC) intragastrically for 1 month. CYP2E1 induction by ethanol was correlated with lipid peroxidation, liver microsomal CYP2E1 hydroxylation of paranitrophenol, and the liver pathology score using the data from the PIC-fed rats. Some of the data from the ethanol and DAS-fed rats were not included here because they have been reported elsewhere. Microsomal CYP2E1 protein levels induction by ethanol was decreased by PIC ingestion. Similarly, PIC reduced the increase microsomal reduced form of nicotinamide-adenine dinucleotide (NADPH)-dependent lipid peroxidation and p-nitrophenol hydroxylase (PNPH) activity, induced by ethanol feeding. The lipid peroxidation was reduced to below control levels; however, the pathology score was partially but not significantly reduced by isothiocyanate feeding. CYP2E1 messenger RNA (mRNA) was decreased by both inhibitors of CYP2E1. Immunohistochemical staining of liver for CYP2E1 protein showed that the lobular distribution of the isozyme changed from the centrilobular to a diffuse pattern, with an increase in the periportal region when the CYP2E1 inhibitors were fed with ethanol, and that this change correlated with the change in the distribution of fat in the lobule. The data support the idea that there is a link between CYP2E1 induction by ethanol and the early phase of ethanol-induced liver injury in this rat model. This link may involve lipid peroxidation, but other factors related to CYP2E1 induction must also be involved.

Administration, Oral↗
PubMed1994

Free radical activation of acetaldehyde and its role in protein alkylation.

The formation of carbon centered free radicals, identified as methylcarbonyl species, was observed using ESR spectroscopy and the spin trapping agent 4-pyridyl-1-oxide-N-t-butyl nitrone (4-POBN) during the oxidation of acetaldehyde by xanthine oxidase. The reaction was dependent upon the presence of OH. radicals and was inhibited by the addition of superoxide dismutase, catalase or OH. radical scavengers. The generation of methylcarbonyl radicals was associated with a doubling of stable acetaldehyde adducts with serum albumin, and 4-POBN or superoxide dismutase and catalase, completely blocked this effect. Thus, methylcarbonyl radicals contributed to acetaldehyde-mediated protein alkylation which is involved in causing toxic as well as immunological reactions ascribed to acetaldehyde.

Acetaldehyde↗
PubMed1994

Monitoring oxidative damage in patients with liver cirrhosis and different daily alcohol intake.

This study looked at the possible association between alcohol abuse and free radical mediated oxidative injury by examining the presence of oxidative damage, as monitored by erythrocyte malonildialdehyde and plasma lipid hydroperoxides, in patients with liver cirrhosis and different lifetime daily alcohol intake. All patients with an alcohol intake above 100 g/day (ALC) showed concentrations of malonildialdehyde and lipid hydroperoxide on average four to fivefold higher than cirrhotic patients with alcohol intake below 100 g/day (NAC) or healthy controls. Further subgrouping of ALC patients showed that those with alcohol intake ranging between 100 and 200 g/day (ALC1) had malonildialdehyde and lipid hydroperoxide concentrations significantly lower than those with an intake higher than 200 g/day (ALC2). These differences were not related to the extent of liver injury or to the liver derangement as assessed by Child's classification. The increase in lipid peroxidation markers in ALC cirrhotic patients was associated with a decrease in, respectively, plasma alpha-tocopherol and erythrocyte glutathione concentrations. Significant differences were also seen between ALC1 and ALC2 groups in plasma alpha-tocopherol, but not in erythrocyte glutathione concentrations. The concentrations of alpha-tocopherol and glutathione in the blood of NAC patients were in contrast not substantially different from those of healthy controls. The close association between oxidative damage and alcohol abuse suggested that free radical intermediates produced during ethanol metabolism might be responsible for causing oxidative damage.

Adult↗
PubMed1994

Risks and benefits of splenectomy in myelofibrosis: an analysis of 39 cases.

From 1980 to 1993, 39 splenectomies were performed in the Department of Visceral Surgery of Saint-Louis Hospital, in patients referred for myelofibrosis associated with myeloid splenomegaly. The short term morbidity was considerable: 33 serious haemorrhagic, infectious or thrombotic complications including 5 fatal accidents were observed in 18 patients. Severe thrombotic or infectious complications leading to 6 further deaths occurred in 8 patients over the two years following splenectomy, while six cases of acute leukaemia appeared between 6 months and 3 years after splenectomy. In 40% of cases with regular follow-up, the operation did not provide any haematological improvement and all these patients died. Only patients with minimally progressive or stable myelofibrosis and residual marrow activity in isotope studies showed an amelioration of general status with relief of pain and reduction of transfusional requirements. The indication for splenectomy should therefore probably be limited to such cases.

Adult↗
PubMed1993

Splenectomy in human immunodeficiency virus-related thrombocytopenia.

To evaluate the efficacy and safety of splenectomy in patients with human immunodeficiency virus (HIV)-related thrombocytopenia, 30 HIV-infected patients with thrombocytopenia (platelet count < 50 x 10(9)/l) who underwent splenectomy were followed prospectively for a mean period of 42 months. There were no perioperative deaths and morbidity was minimal. Twenty-one patients had a persistent complete response, six had a partial response and were asymptomatic after splenectomy, and only three showed no response. Three patients developed acquired immune deficiency syndrome during follow-up, an incidence that was no different from that expected. Splenectomy is a safe and effective treatment in HIV-infected patients with severe symptomatic thrombocytopenic purpura resistant to medical therapy.

Adolescent↗
PubMed1993

Specificity of autoantibodies against oxidized LDL as an additional marker for atherosclerotic risk.

BACKGROUND: LDL oxidation is a crucial step in the development and progression of atherosclerotic lesions. The detection of an increase in the anti-oxidized LDL antibody titre may thus represent a biological marker of enhanced LDL oxidation in vivo. METHODS: The occurrence of anti-oxidized LDL autoantibodies was investigated in control patients, in patients with atherosclerotic coronary artery disease, in those without clinically relevant signs of atherosclerosis, but considered at risk, and in patients with chronic alcohol-related liver disease. RESULTS: Anti-oxidized LDL autoantibodies were present in the plasma of the majority of patients with overt coronary atherosclerosis. An increased antibody titre can also be detected well before the onset of clinically relevant signs of the atherosclerotic disease in patients classically considered at risk, indicating the occurrence of in-vivo LDL oxidation during atherosclerosis development. The specificity of molecular targets (LDL) for oxidative modifications is supported by the demonstration that anti-oxidized LDL autoantibodies are absent in the plasma of alcoholic patients who exhibit a marked increase in biological markers of oxidative stress but do not classically develop atherosclerosis. CONCLUSION: These data demonstrate that the occurrence of anti-oxidized LDL autoantibodies could be specifically related to the promotion and progression of atherosclerosis and is not a simple epiphenomenon of any oxidative process occurring in vivo.

Adult↗
PubMed1991

[Splenectomy for chronic thrombocytopenic purpura].

During the period 1985-1989, 49 patients underwent splenectomy for chronic idiopathic thrombocytopenic purpura in our department. A correct follow-up was available for 39 patients. All patients had been previously treated with corticosteroids. We evaluated the platelet count one year after the operation and the relation between this count and several preoperative and postoperative factors. We observed a favourable prognosis when the preoperative study of platelet sequestration showed splenic destruction, when the duration of symptoms was less than one year and when there was a rapid increase in the platelet count during the first week after the operation.

Adrenal Cortex Hormones↗
PubMed1987

Splenectomy performed upon thirty-seven patients with hairy cell leukemia.

Thirty-seven patients with hairy cell leukemia underwent splenectomy. The postoperative course was uneventful for 34 patients. Improvement of peripheral cytopenia was obtained in the majority of patients. Survival time of patients who underwent splenectomy was significantly longer than for patients who did not undergo this procedure. Splenectomy is a habitually effective form of treatment for hairy cell leukemia, although not completely free of risks.

Adult↗