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D Mantle

Publications and source records attributed to D Mantle.

At least 55 records · Page 3Linked to original sources
PubMed1999

Quantification of protease activities in synovial fluid from rheumatoid and osteoarthritis cases: comparison with antioxidant and free radical damage markers.

We have compared (using the same series of experimental samples) the levels of activity of a comprehensive range of cytoplasmic, lysosomal and matrix protease types, together with the levels of free radical-induced protein damage (determined as protein carbonyl derivative) in synovial fluid from rheumatoid (RA) and osteoarthritis (OA) cases. Many protease types showed significantly increased activity (typically by a factor of 2-3-fold) in RA compared to OA cases. Protease activity levels (including those enzyme types putatively involved in the immune response, such as dipeptidyl aminopeptidase IV) in plasma were not significantly different in RA and control cases. The level of free radical induced damage to synovial fluid proteins was approximately 2-fold higher in RA compared to OA, although there was no significant difference in total antioxidant status in synovial fluid or plasma between RA, OA or control cases. We conclude from the above that activation of proteolytic enzymes and free radicals (occurring specifically within synovial tissues) are likely to be of equal potential importance as protein damaging agents in the pathogenesis of RA, and the development of novel therapeutic strategies for the latter disorder should include both protease inhibitory and free radical scavenging elements. In addition, the protease inhibitory element should be designed to inhibit the action of a broad range of enzymic mechanistic types (cysteine, serine, metallo proteinases and peptidases).

Antioxidants↗
PubMed1999

Effect of ethanol and acetaldehyde on intracellular protease activities in human liver, brain and muscle tissues in vitro.

The effect of ethanol and acetaldehyde on the activity of a range of intracellular cytoplasmic and lysosomal proteolytic enzymes has been determined in human brain, liver and skeletal muscle tissues in vitro. There was a substantial degree of inhibition for most protease types in all tissues if sufficiently high concentrations of ethanol (10%, v/v; 1.7 mol/L) or acetaldehyde (1%, v/v; 0.17 mol/L) were used in the assay media. However, it was concluded that direct inhibition of proteases in vivo by ethanol or acetaldehyde is improbable, at the concentrations of these agents likely to pertain in vivo, and that any effect of these agents on intracellular protein catabolism must occur via a more subtle biochemical mechanism.

Acetaldehyde↗
PubMed1999

Effect of flavonoids on protease activities in human skeletal muscle tissue in vitro.

The effect of a representative range of flavonoid compounds on the activities of a range of proteolytic enzyme types in human skeletal muscle tissue was determined in vitro. All of the proteases showed some degree of inhibition by all of the flavonoid compounds investigated, with IC50 values (concentration of flavonoid required to inhibit initial activity of muscle proteases by 50%) for various enzyme/flavonoid combinations ranging from approx. 50 micromol/l to 2 mmol/l. These data demonstrate that in addition to their well described antioxidant characteristics, flavonoids also possess novel antiproteolytic inhibitory activity in vitro, which may in part explain some of the beneficial effects of these plant derived compounds in vivo.

Endopeptidases↗
PubMed1999

Comparative effect of fenitrothion treatment on intracellular protease activities in insecticide-resistant and susceptible strains of Musca domestica L.

In order to further elucidate the biochemical mechanisms responsible for insecticide resistance in insects, we have determined changes in the activity levels of a comprehensive range of proteolytic enzymes (cytoplasmic and lysosomal proteinases and peptidases, which play a key role in normal cell functioning) in fenitrothion-resistant (571ab) and susceptible (Cooper) strains of Musca domestica following in vivo exposure to the insecticide fenitrothion. Untreated insects of the resistant strain had significantly higher levels (20-100%) of activity for many protease types compared to the susceptible strain (whole body analysis). Exposure to fenitrothion resulted in further activity increases for most proteases at some point during the subsequent 24 h period in resistant strain insects; susceptible strain insects were also capable of similar increases in protease activities. We therefore suggest that it must be the combination of intrinsically higher protease levels (prior to pesticide exposure), together with the capacity to further increase protease activities following insecticide exposure, which is important in the mechanism by which proteases may confer survival advantages in insecticide resistant insects. We further speculate that this mechanism may involve increased supply of precursor amino acids from proteolytic degradation products to the intracellular pool, prior to de novo synthesis of detoxifying enzymes following insecticide exposure.

Animals↗
PubMed1999

Free radicals as mediators of alcohol toxicity.

In this article we have reviewed recent evidence in support of the hypothesis that acute/chronic alcohol toxicity is mediated primarily via the generation of damaging free radical species in various tissues. Studies in man, animal model or in vitro experimental systems have shown: (1) the demonstration of alcohol-induced free radical species directly via esr spectroscopic analysis; (2) increases in indirect markers of ethanol-induced free radical damage in tissues, such as lipid peroxides and protein carbonyl; (3) ethanol-induced alterations in the levels of endogenous tissue antioxidants. These data show the induction of free radicals by ethanol to be a complex interactive process. The classical pathway for ethanol metabolism, catalysed by alcohol dehydrogenase to form acetaldehyde, results in the formation of free radicals, resulting from concomitant changes in NADH levels and NADH/NAD+ redox ratios, which in turn modulate the activity of the free radical generating enzyme xanthine oxidase. The induction of CYP 2E1 in the microsomes results in the generation of HER, another major route by which ethanol induces free radical formation. In addition to the above, ethanol may also induce free radical formation via the reaction of aldehyde oxidase with acetaldehyde or NADH to generate oxyradicals via disturbance in the metabolism of the pro-oxidant iron, or via increased efflux from mitochondria following altered mitochondrial oxidative metabolism.

Alcoholism↗
PubMed1998

Differential protein oxidation in Duchenne and Becker muscular dystrophy.

We describe the use of an immunoblotting technique to investigate the potential role of reaction oxygen species in the pathogenesis of Duchenne muscular dystrophy. Quadriceps femoris muscle biopsy samples were obtained from six patients with Duchenne and six with Becker muscular dystrophy, and from six control subjects. These were analysed for the presence of protein carbonyl moieties (indicative of oxidation to protein) by SDS-polyacrylamide gel electrophoresis and Western blotting, using a commercially available antibody. In all Duchenne and Becker patient samples analysed, a heavily oxidized protein species was identified migrating at 125 kDa. This oxidized species was not present (or was present at very low levels) in normal control samples. Use of the present technique also identified that the various muscle proteins in Duchenne and Becker muscular dystrophy muscle are oxidized to varying degrees, supporting the hypothesis of a differential susceptibility of proteins to oxidation in these disorders. Work from the present study further supports the hypothesis that reactive oxygen species play a role in dystrophic muscle cell pathogenesis.

Amino Acids↗
PubMed1998

Comparison of proteolytic enzyme activities in adults of insecticide resistant and susceptible strains of the housefly M. domestica L.

Intracellular proteolytic activity in a DDT-resistant and a susceptible strain of M. domestica was determined by assaying a comprehensive range of cytoplasmic and lysosomal enzymes. The resistant strain showed significantly higher protease activities in whole body, head, thorax, abdomen and gut homogenates compared to the susceptible strain. The activity of alanyl- and arginyl aminopeptidase from both strains increased substantially after topical treatment with DDT at 1, 2 and 3 h, suggesting an involvement of proteolytic enzymes in the induction of detoxifying enzymes, thus indicating a possible role of the intracellular proteolytic activities in the resistance mechanism.

Aminopeptidases↗
PubMed1998

Effect of Tri-O-cresyl phosphate (TOCP) on proteolytic enzyme activities in mouse liver in vivo.

To develop a clearer understanding of the biochemical mechanisms of toxicity in higher animals, we determined the effect of four sublethal dosages (0.25 to 1.0 g/Kg) of organophosphate (OP), and of tri-ortho-cresyl phosphate (TOCP) on the activities of a representative range of cytoplasmic and lysosomal proteolytic enzymes in mouse liver in vivo. Administration of the lowest sublethal dosage of TOCP (0.25g/1Kg, 24 hours) resulted in significant inhibition (10 to 30% of control activity) of the cytoplasmic proteases tripeptidyl aminopeptidase and proline endopeptidase only. An increasing dosage of TOCP (1g/Kg for 7 days) resulted in significant inhibition (10 to 50% of control activity) of the cytoplasmic proteases alanyl aminopeptidase, leucyl aminopeptidase, tripeptidyl aminopeptidase, and proline endopeptidase, as well as the lysosomal proteases dipeptidyl aminopeptidase I and cathepsins B, D, and L. The activities of the cytoplasmic proteases arginyl aminopeptidase and dipeptidyl aminopeptidase IV, and of lysosomal proteases dipeptidyl aminopeptidase II and cathepsin H were not significantly altered following TOCP administration at this higher dosage. All of the above proteases are involved in the general process of intracellular protein turnover (common to all tissues), and may also have more specialized functions such as the processing of physiologically active hormonal peptides, and the processing of antigenic proteins in the immune response. Data obtained in the present study suggest that inhibition of the above enzymes by OP such as TOCP may represent a previously unrecognized toxicity hazard induced by the latter compound in higher animals.

Aminopeptidases↗
PubMed1997

Effect of pirimiphos-methyl on proteolytic enzyme activities in rat heart, kidney, brain and liver tissues in vivo.

To elucidate whether pesticide toxicity in higher animals involves pesticide-induced dysfunction of the intracellular protein catabolic process, we have determined the effect in vivo of the organophosphate insecticide pirimiphos-methyl on the activities of representative protein catabolising cytoplasmic and lysosomal proteases (responsible for the various stages of the protein degradation cascade and essential for normal cell functioning) in heart, kidney, brain and liver target tissues in the rat. In liver tissue (the major site of pesticide metabolism), the activities of all of the cytoplasmic proteases investigated (alanyl-, arginyl-, leucyl aminopeptidases, dipeptidyl aminopeptidase IV, tripeptidyl aminopeptidase, proline endopeptidase) were significantly inhibited (by 20-40% of control activity) following administration of 10 mg pirimiphos-methyl/kg bodyweight, whereas of the lysosomal proteases investigated, only the activities of dipeptidyl aminopeptidase I and cathepsin D were significantly reduced (by 15-20% of control activity). In contrast, there was no insecticide-induced inhibition of protease activities in heart, kidney or brain tissues; some lysosomal enzymes (dipeptidyl aminopeptidase I, cathepsins L and D) showed significantly increased activities in these tissues (the reason for which remains to be determined). We conclude that the effect of pirimiphos-methyl on proteolytic enzyme activities differs in different target tissues, and that pirimiphos-methyl induced inhibition of proteases in liver tissue may represent a previously unrecognised toxicity hazard in higher animals.

Animals↗
PubMed1997

Studies on the time-course of ethanol's acute effects on skeletal muscle protein synthesis: comparison with acute changes in proteolytic activity.

A study of the effects of ethanol on skeletal muscle protein synthesis and protease activities was carried out in young male Wistar rats (150 g) for up to 24 hr after a single intraperitoneal dose of 75 mmol of ethanol/kg of body weight. At 20 min, the mean blood ethanol levels were 448 mg/dl. This level dropped steadily to zero through the following 24 hr. Compared with pair-fed controls, significant reductions in total protein, RNA, and DNA contents were seen only after 24 hr in all skeletal muscles studied: changes were more marked in the muscles containing large proportions of type II fibers. In plantaris muscle, the fractional rate of protein synthesis (ks, %/day) did not fall 20 min after dosage but was reduced after 1 hr by 23% (p < 0.001), and by 63% after 24 hr, compared with control saline-injected rats (p < 0.001). This effect was independent of dietary intake because, compared with the pair-fed group, the 24-hr ethanol-treated rats still showed a 52% decrease in fractional rates of protein synthesis (p < 0.001). Smaller reductions in ks were seen in soleus muscles in response to ethanol at 24 hr (-39%, p < 0.001). The activities of a variety of lysosomal and nonlysosomal proteases in plantaris muscle of 24-hr treated rats were not significantly affected by ethanol. Only alanyl- and tripeptidyl-aminopeptidase activities were reduced significantly (26%, p < 0.05 and 39%, p < 0.01, respectively). These results suggest that the muscle compositional changes seen over acute periods of ethanol toxicity are predominantly associated with impaired synthesis of protein and that the contribution of cellular proteolytic systems may be minimal. The effects of ethanol on skeletal muscle protein metabolism are greater in muscles containing a predominance of type II fibers than in those containing mainly type I fibers. Ethanol's effects on muscle may be influenced by hormonal changes after 24 hr, because protein synthesis is still compromised and free plasma T3 and corticosterone are altered at this time-point.

Alcoholism↗