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S Worrall

Publications and source records attributed to S Worrall.

At least 37 records · Page 2Linked to original sources
PubMed1995

Rat serum albumin modified by diflunisal acyl glucuronide is immunogenic in rats.

Acyl glucuronide metabolites of carboxylic acid drugs such as the salicylate derivative diflunisal (DF) have been shown to react with proteins in vitro and in vivo to produce covalent adducts. Such attachment of foreign compounds to endogenous molecules could be associated with toxic and/or immune consequences. In this study we have injected rats with rat serum albumin (RSA) modified (a) by DF using a carbodiimide reagent (-->DF-RSA-I, 4.9 micrograms DF/mg RSA) and (b) by incubation with DF acyl glucuronide (DAG) and its rearrangement isomers (iso-DAG) (-->DF-RSA-II, 0.34 micrograms DF/mg RSA). All of the six rats injected with DF-RSA-I produced antibodies reactive with DF-modified keyhole limpet hemocyanin (KLH), the coating protein used in the ELISA. Three out of six animals injected with DF-RSA-II generated similar antibodies. Cross-reactivity with other non-steroidal anti-inflammatory drugs (NSAIDs) such as naproxen and ketoprofen (as the free drugs) was not observed. This study shows that a self protein covalently modified by incubation with DAG and iso-DAG is immunogenic in rats. The data thus support the hypothesis that covalent modification of macromolecules by acyl glucuronide metabolites of acidic drugs in vivo can lead to the production of circulating antibodies which may be involved in aberrant immune responses such as drug hypersensitivity.

Animals↗
PubMed1994

Anti-acetaldehyde adduct antibodies generated by ethanol-fed rats react with reduced and unreduced acetaldehyde-modified proteins.

We have previously shown that rats fed ethanol for prolonged periods generate antibodies reactive with proteins modified by acetaldehyde in vitro. In this report we demonstrate that these antibodies react with two groups of adducts: those formed when acetaldehyde reacts with proteins at 37 degrees C for 24 hr ('unreduced' adducts) and those formed by a 1 hr incubation followed by the addition of sodium cyanoborohydride (a reducing agent specific for Schiff bases) to the reaction mixture ('reduced' adducts). These data suggest that adducts from both of these groups are formed in vivo as a result of ethanol ingestion by rats.

Acetaldehyde↗
PubMed1994

Distribution and turnover of acetaldehyde-modified proteins in liver and blood of ethanol-fed rats.

Previous studies have shown that acetaldehyde (AcH)-modified proteins are formed in the liver and blood of rats fed ethanol-containing diets. In this study we report the application of ELISA techniques to study the subcellular distribution and turnover of AcH-modified proteins in ethanol-fed and control rats. Modified proteins were found in liver mitochondrial, crude membrane and cytosolic fractions, as well as in plasma from ethanol-fed rats. No adducts were detected by our assay in haemolysates from the same animals. The rate of decline of AcH-modified proteins after cessation of ethanol feeding was also examined. Modified liver cytosolic proteins were shown to decline with a half-life of 2.3 weeks, whereas modified plasma adducts declined with a half-life of 4.8 weeks.

Acetaldehyde↗
PubMed1994

The effect of chronic ethanol feeding on cytokines in a rat model of alcoholic liver disease.

There is a growing body of evidence to suggest that cytokines may be involved in the aetiology of alcoholic hepatitis. To study the effects of chronic ethanol feeding on cytokine production we have maintained rats on the control and ethanol-containing forms of the Lieber-DeCarli liquid diet for six weeks. The animals were then given an i.v. injection of endotoxin to induce hepatitis. It was found that the ethanol-fed animals had biochemical and histological evidence of mild to severe liver damage whereas control-fed animals had minimal liver damage. When plasma levels of cytokines were measured, it was found that the ethanol-fed rats produced much higher levels of tumour necrosis factor and interleukin 6 bioactivity than the control-fed rats. However, elevated levels of interleukin 1 protein were not seen in the ethanol-fed animals.

Alcoholism↗
PubMed1994

Studies on the usefulness of acetaldehyde-modified proteins and associated antibodies as markers of alcohol abuse.

Acetaldehyde, an intermediate in ethanol metabolism, has been shown to react with proteins to produce both stable and unstable adducts. These modified proteins are immunogenic, leading to the production of anti-adduct antibodies. In this report we describe studies carried out to determine whether anti-adduct antibodies could be used as a marker of alcohol abuse. We have used ELISAs to measure plasma immunoreactivity with unmodified and acetaldehyde-modified bovine serum albumin in groups of female and male social drinkers, heavy drinkers and alcoholics. When total immunoreactivity with the unmodified and acetaldehyde-modified proteins was measured it was found that each of the groups exhibited elevated reactivity with the modified protein as compared to the unmodified. Similar results were obtained when IgM immunoreactivity was measured. However, when IgA immunoreactivity was measured the reactivity with the modified protein was more greatly elevated in the heavy drinking and alcoholic groups than in the social drinking groups. There was no evidence of IgG reactivity with modified protein in any of the groups. These data suggest that elevated IgA reactivity with acetaldehyde-modified proteins may be a marker for high alcohol intake.

Acetaldehyde↗
PubMed1993

Antibodies from alcoholics, ethanol-fed rats and a rabbit immunised with proteins modified by acetaldehyde in vitro react with liver cytosolic proteins from ethanol-fed rats.

In previous studies we have shown that ethanol-fed rats generate antibodies reactive with proteins modified by acetaldehyde in vitro and that their livers contain proteins modified by acetaldehyde. In this study we demonstrate that the antibodies from these animals react with the modified proteins found in their livers. Furthermore, when the antibodies reactive with specific proteins were isolated, they were found to react with all of the modified proteins detected by the whole serum. This suggests that all of the proteins modified by acetaldehyde in vivo carry the same or similar epitope(s). In addition, antibodies from alcoholics and a rabbit immunised with proteins modified by acetaldehyde in vitro also reacted with the liver cytosolic proteins from ethanol-fed rats. Therefore it appears that similar epitopes are generated in alcoholics as a result of ethanol misuse, in rat liver due to prolonged ethanol feeding and by the in vitro modification procedure used to produce the immunogen for the rabbit.

Acetaldehyde↗
PubMed1992

Studies on the reactivity of acyl glucuronides--III. Glucuronide-derived adducts of valproic acid and plasma protein and anti-adduct antibodies in humans.

The major metabolite of the anti-epileptic agent valproic acid (VPA) is its acyl glucuronide conjugate (VPA-G), which undergoes non-enzymic, pH-dependent rearrangement via acyl migration to a mixture of beta-glucuronidase-resistant forms (collectively VPA-G-R). We have compared the reactivity of VPA-G and VPA-G-R towards covalent VPA-protein adduct formation by incubation in buffer, human serum albumin (HSA) and fresh human plasma at pH 7.4 and 37 degrees. In all three media, the predominant reaction of VPA-G over 30 hr was rearrangement to VPA-G-R (ca. 24%). Hydrolysis was quite minor (ca. 2%) and covalent adduct formation negligible (when protein was present). On the other hand, both hydrolysis (ca. 27%) and adduct formation (ca. 7%) were extensive when VPA-G-R was incubated with HSA or plasma. These data do not support a transacylation mechanism for VPA-protein adduct formation, since this pathway should be much more highly favoured by VPA-G (an acyl-substituted acetal) than VPA-G-R (simple esters). VPA-protein adducts were found in the plasma of epileptic patients taking VPA chronically (mean 0.77 +/- SD 0.63 microgram VPA equivalents/mL, N = 17). An enzyme linked immunosorbent assay was developed, using HSA modified by incubation with VPA-G-R, to test the immunoreactivity of the patients' plasma. Of 57 patients tested, nine showed measurable levels of antibodies to these adducts, but the titres were very low, with no difference in response to modified and unmodified protein detectable at plasma dilutions of 1:16 or greater. These results suggest that the VPA-protein adducts have little immunogenicity, and are in agreement with clinical observations that drug hypersensitivity responses have not been associated with VPA therapy. Thus, although the in vitro data show that VPA-G is an example of a relatively unreactive acyl glucuronide, covalent VPA-plasma protein adducts and anti-adduct antibodies are nonetheless formed in vivo, at least in some patients on chronic therapy with the drug.

Adult↗
PubMed1992

Modification of proteins and other biological molecules by acetaldehyde: adduct structure and functional significance.

1. Chronic ethanol consumption is a major cause of liver disease. The modification of hepatic proteins by acetaldehyde (AcH), the primary metabolite of ethanol, has for some time been suggested as one of the major events initiating alcoholic liver disease. 2. These alterations in protein structure are believed to affect liver cell function, and may serve to activate the immune system. 3. This review considers the interaction between AcH and macromolecules and its functional implications.

Acetaldehyde↗
PubMed1991

Detection of stable acetaldehyde-modified proteins in the livers of ethanol-fed rats.

Liver cytosolic fractions, obtained from rats pair-fed diets supplemented with either ethanol or an isocaloric amount of sucrose for periods from 3 weeks to 27 months, were tested for the presence of acetaldehyde-modified proteins by immunoblotting, using a partially purified antiserum raised in rabbits against proteins modified by acetaldehyde in vitro. The antiserum reacted with a large number of proteins in cytosolic fractions from ethanol-fed rats but did not react with any proteins in the same fraction from control animals. The duration of the ethanol-containing diet did not appear to influence the number of proteins modified or the total amount of modification within the time range tested. These results indicate that many proteins in rat liver cytosol are targets for modification by acetaldehyde in vivo.

Acetaldehyde↗
PubMed1991

Antibodies against acetaldehyde-modified epitopes: an elevated IgA response in alcoholics.

Several recent reports have shown that antibodies reactive with acetaldehyde (AcH)-modified epitopes are present in alcoholics. However, similar antibodies have also been found in patients with non-alcoholic liver disease and control subjects. In each of these studies total immunoglobulin binding to the AcH-modified proteins was measured, with no attempt being made to identify the classes of immunoglobulin involved. In the present study we employed an enzyme-linked immunosorbent assay (ELISA) to assess the classes of immunoglobulin involved in this response, using plasma samples from 97 alcoholics with varying degrees of liver disease, 35 patients with non-alcoholic liver disease and 33 control subjects. All three groups exhibited a large IgM response and a negligible IgG response. However, the alcoholics exhibited a significantly higher IgA response than either of the other groups. This suggests that the measurement of the IgA response to AcH-modified epitopes may be a specific marker of ethanol abuse.

Acetaldehyde↗
PubMed1991

Acetaldehyde-modified proteins and associated antibodies in ethanol-fed rats.

Rats fed ethanol for periods of 3-27 months were found to produce an immune response to acetaldehyde-modified proteins, whereas treatment for a shorter period (3 weeks) did not lead to such a response. The antibodies from the ethanol-fed animals were shown to be reactive with a series of proteins modified by acetaldehyde in vitro. This suggests that reactivity towards the modified proteins is independent of the carrier protein, with antibodies being raised which interact solely with the acetaldehyde-containing adduct and not the protein itself. We have also been able to demonstrate the presence of modified proteins in the liver cytosol of these ethanol-fed rats. However, unlike previous reports which suggested that only one protein was modified, we found that many cytosolic proteins were modified. This suggests that the modification of proteins by acetaldehyde is less specific than was previously thought.

Acetaldehyde↗
PubMed1991

Alcohol abusers exhibit a higher IgA response to acetaldehyde-modified proteins.

In the present study we have used an enzyme-linked immunosorbent assay to measure the immunoreactivity towards acetaldehyde-modified proteins in plasma from alcoholics, patients with non-alcoholic liver disease and control social drinkers. All three groups showed a response to modified proteins when total immunoglobulin binding was measured. However, when the assay was modified such that class-specific immunoglobulin binding was measured, it was found that the alcoholic response had a significantly greater immunoglobulin A component than patients with non-alcoholic liver disease or controls who were social drinkers. Thus measurement of IgA binding to acetaldehyde-modified proteins may be a marker for alcohol abuse.

Acetaldehyde↗
PubMed1990

Antibodies against acetaldehyde-modified epitopes: presence in alcoholic, non-alcoholic liver disease and control subjects.

Several studies have recently shown the presence of antibodies against acetaldehyde-modifications in the sera of alcoholic patients. To assess the specificity of this immune response, plasma immunoreactivity with proteins modified in vitro by acetaldehyde was measured using an enzyme-linked immunosorbent assay in 97 alcoholic patients with varying degrees of alcoholic liver disease, in 35 patients with non-alcoholic liver diseases and in 33 control subjects who were social drinkers. All three groups showed some response against acetaldehyde-modified epitopes. The highest plasma reactivities were found in alcoholics, especially those with steatosis and alcoholic hepatitis. Plasma from patients with non-alcoholic liver disease and control subjects also reacted with the acetaldehyde conjugates, but to a lesser extent than plasma from alcoholics. The reliability of these antibodies as markers of either alcohol abuse or alcoholic liver disease therefore appears to be low. However, further studies using more precisely modified proteins or elucidation of the classes of immunoglobulin involved in the immune response against the modified proteins may give clearer differences between the three groups.

Acetaldehyde↗
PubMed1989

Ethanol induces the production of antibodies to acetaldehyde-modified epitopes in rats.

Rats treated with ethanol for periods of 3-27 months were found to produce an immune response to acetaldehyde-modified proteins, whereas treatment for a shorter period (3 weeks) did not lead to such a response. The reactivity towards the modified proteins was shown to be independent of the carrier protein as antibodies were reactive with modified human plasma proteins and modified bovine haemoglobin. The data presented here support the hypothesis that acetaldehyde-modified proteins may act as neoantigens in alcoholics and may play a role in the aetiology of alcoholic liver disease.

Acetaldehyde↗
PubMed1988

Purification of brain D2 dopamine receptor.

D2 dopamine receptors have been extracted from bovine brain using the detergent cholate and purified approximately 20,000-fold by affinity chromatography on haloperidol-sepharose and wheat germ agglutinin-agarose columns. The purified preparation contains D2 dopamine receptors as judged by the pharmacological specificity of [3H]spiperone binding to the purified material. The sp. act. of [3H]spiperone binding in the purified preparation is 2.5 nmol/mg protein. The purified preparation shows a major diffuse band at Mr 95,000 upon SDS-polyacrylamide gel electrophoresis and there is evidence for microheterogeneity either at the protein or glycosylation level. Photoaffinity labelling of D2 dopamine receptors also shows a species of Mr 95,000. The D2 dopamine receptor therefore is a glycoprotein of Mr 95,000.

Affinity Labels↗