1
|
Drakos T, Giannakou M, Menikou G, Ioannides C, Damianou C. An improved method to estimate ultrasonic absorption in agar-based gel phantom using thermocouples and MR thermometry. Ultrasonics 2020; 103:106089. [PMID: 32045747 DOI: 10.1016/j.ultras.2020.106089] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 12/30/2019] [Accepted: 01/05/2020] [Indexed: 06/10/2023]
Abstract
In this paper, a novel experimental set-up was developed that measures the absorption coefficient. The proposed system was evaluated in an agar-based gel phantom. The new experimental system provides accurate and fast measurement of the rate of temperature change within the phantom. The rate of temperature change was measured using thermocouple and was confirmed using MR thermometry. An ultrasonic transducer with a broad beam was used in order to reduce the conduction effect. The absorption coefficient of the agar-based phantom was 0.26 dB/cm-MHz using 4% agar, 30% evaporated milk and 4% silica. The absorption coefficient increased by increasing the volume of the evaporated milk, and agar. The absorption coefficient increased at low silica concentration (<4%) and then decreased at higher concentration of silica (>4%). By proper selection of evaporated milk, agar and silica concentration, it is possible to achieve similar coefficient like in soft tissues. Acoustic absorption measurement is considered as a difficult measurement in ultrasonics because obtaining the precise temperature change in the focus is challenging. Due to the quick and accurate placement of the thermocouple at the ultrasonic beam, it is possible with the proposed system to perform absorption measurement is less than one minute.
Collapse
Affiliation(s)
- T Drakos
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
| | - M Giannakou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
| | - G Menikou
- Medical Physics Division, General Hospital of Nicosia, Nicosia, Cyprus
| | - C Ioannides
- Radiology Department, Ygia Polyclinic, Limassol, Cyprus
| | - C Damianou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
| |
Collapse
|
2
|
Hashemi E, Till C, Ioannides C. Stability of Phase II Conjugation Systems in Cultured Precision-cut Rat Hepatic Slices. Toxicol In Vitro 2012; 13:459-66. [PMID: 20654503 DOI: 10.1016/s0887-2333(99)00017-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/09/1999] [Indexed: 11/28/2022]
Abstract
The aim of the present study was to investigate the stability of Phase II conjugation enzymes in precision-cut rat liver slices that have been cultured, using the multiwell plate system, for various periods of time up to 72 hours. The enzyme activities monitored were epoxide hydrolase, glutathione S-transferase and the associated glutathione reductase, sulfotransferase and glucuronyl transferase. The activity of all enzymes studied declined with time when expressed per slice, but the rate of loss differed among the various enzymes. However, in most cases substantial Phase II activity was still present in the liver slices following a 24-hour incubation, and in some cases significant activity was even retained in slices cultured for 72 hours. These studies indicate that precision-cut liver slices maintain Phase II activity for long periods of time, thus allowing metabolic studies involving prolonged incubations to be performed.
Collapse
Affiliation(s)
- E Hashemi
- Drug Development, Hoechst Marion Roussel Ltd, Walton Manor, Walton, Milton Keynes, Bucks MK7 7AJ, UK
| | | | | |
Collapse
|
3
|
Konsue N, Ioannides C. Tissue differences in the modulation of rat cytochromes P450 and phase II conjugation systems by dietary doses of phenethyl isothiocyanate. Food Chem Toxicol 2008; 46:3677-83. [PMID: 18929617 DOI: 10.1016/j.fct.2008.09.046] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 09/03/2008] [Accepted: 09/22/2008] [Indexed: 01/30/2023]
Abstract
Rats were fed diets supplemented with phenethyl isothiocyanate (PEITC) at 0.06 (low dose, dietary intake level), 0.6 (medium dose) and 6.0 micromole/g (high dose), and xenobiotic-metabolising enzymes were monitored in liver, lung and kidney. At the low dose, inhibition of the hepatic O-dealkylation of ethoxy- and methoxyresorufin was noted, whereas at the high dose increases in the O-depentylation of pentoxyresorufin and O-debenzylation of benzyloxyquinoline were observed, whereas p-nitrophenol hydroxylase was inhibited. Hepatic bioactivation of 2-amino-3-methylimidazo-[4,5-f]quinoline to mutagens was not influenced by the PEITC-treatment. In the lung, at the high dose, ethoxyresorufin dealkylation was elevated and that of pentoxyresorufin suppressed; no significant changes were seen in the kidney. Quinone reductase was markedly elevated at all doses in liver, but the lung enzyme was refractive whereas in the kidney a modest rise was observed at the high dose. Hepatic glutathione S-transferase activity was stimulated by PEITC-treatment, but no effect was evident in the lung or kidney. It is concluded that the effects of PEITC on xenobiotic-metabolising systems are dose- and tissue-dependent, with the liver being the most sensitive and the lung generally resistant. Increased detoxication rather than cytochrome P450 inhibition is the likely mechanism of the chemopreventive activity of PEITC.
Collapse
Affiliation(s)
- N Konsue
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
| | | |
Collapse
|
4
|
Abstract
1. The principal objective was to evaluate the functional and structural integrity of precision-cut rat lung slices in culture over 72 h. 2. Lung slices metabolized 7-ethoxycoumarin in a time-dependent fashion, the major metabolites being the sulphate and glucuronide of 7-hydroxycoumarin with very low levels of the free compound. Prior treatment of rats with beta-naphthoflavone elevated markedly the rate of metabolism. The optimum slice thickness, as exemplified by the metabolism of 7-ethoxycoumarin, was about 600 microm. 3. Lung slices retained metabolic viability towards 7-ethoxycoumarin for 8 h, but after this point a marked decline in metabolic activity was noted. However, very low levels of activity were still evident following a 72 h incubation. 4. Morphological examination of lung slices revealed nuclear degeneration and loss of tissue architecture following 24h incubation. When cellular integrity was assessed using lactate dehydrogenase, a time-dependent leakage was evident with maximum loss occurring within 24h; longer incubations did not result in further leakage. 5. It is concluded that precision-cut rat lung slices, of 600 microm thickness, can be maintained metabolically viable in culture for some 8 h.
Collapse
Affiliation(s)
- M Umachandran
- Molecular Toxicology Group, School of Biomedical and Molecular Sciences, University of Surrey, Guildford GU2 7XH, UK
| | | | | |
Collapse
|
5
|
Pushparajah DS, Umachandran M, Plant KE, Plant N, Ioannides C. Up-regulation of the glutathione S-transferase system in human liver by polycyclic aromatic hydrocarbons; comparison with rat liver and lung. Mutagenesis 2008; 23:299-308. [DOI: 10.1093/mutage/gen012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
6
|
Myrianthefs P, Ioannides C, Fildissis G, Karatzas S, Baltopoulos G. Institution-specific guidelines for the management of ventilator-associated pneumonia. Crit Care 2007. [PMCID: PMC4095147 DOI: 10.1186/cc5253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
|
7
|
Abstract
Precision-cut bovine and cervine liver slices were incubated in RPMI 1640 media for up to 72 h, and cellular integrity was assessed utilizing the leakage of lactate dehydrogenase (LDH) and the formation of the formazan metabolite of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT). Leakage of LDH (80%) from the bovine and cervine slices was noted only following 10 h of culture, and similarly, the generation of MTT-formazan declined. Metabolic viability was determined using 7-ethoxycoumarin as the model substrate, which was metabolized by slices from both animal species in a time-dependent manner for at least 6 h to generate 7-hydroxycoumarin, which was secreted into the media primarily as glucuronide and sulphate conjugates. With both cervine and bovine slices metabolic activity decreased markedly after a 4-h preincubation as assessed following a further 2-h incubation in the presence of 7-ethoxycoumarin. Subsequently, ethoxycoumarin metabolism by bovine slices did not decrease further until 24 h and was still detectable at 72 h. In the case of cervine slices, activity declined gradually after 8 h, with no activity being detectable at 72 h. It may be concluded that cervine and bovine slices may be maintained metabolically active for 8-10 h, which should prove sufficient for xenobiotic metabolism studies to be performed.
Collapse
Affiliation(s)
- S Sivapathasundaram
- Molecular Toxicology Group, School of Biomedical and Life Sciences, University of Surrey, Guildford GU2 7XH, Surrey, UK
| | | | | | | |
Collapse
|
8
|
Yoxall VR, Parker DA, Kentish PA, Ioannides C. Short-term black tea intake modulates the excretion of urinary mutagens in rats treated with 2-amino-3-methylimidazo-[4,5-f]quinoline (IQ): role of CYP1A2 upregulation. Arch Toxicol 2004; 78:477-82. [PMID: 15034640 DOI: 10.1007/s00204-004-0562-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2003] [Accepted: 02/13/2004] [Indexed: 11/30/2022]
Abstract
Rats were exposed to black tea (2.5% w/v) as their sole drinking liquid for either 1 day or 1 month, while controls were maintained on water. After this treatment period, all animals received a single oral dose IQ (2-amino-3-methylimidazo-[4,5-f]quinoline), and urine was collected for 48 h. Mutagenic activity of the urine was determined in the Ames test in the presence and absence of an activation system. The excretion of direct-acting mutagens was markedly reduced following tea intake, and was more pronounced after the 1-day treatment. Similarly, both tea treatments suppressed the excretion of indirect-acting mutagens. Furthermore, both tea treatments induced hepatic CYP1A2 activity and expression, but cytosolic glutathione S-transferase activity was only modestly induced in the group of animals receiving tea for 1 day, and only when DCNB (1,2-dichloro-4-nitrobenzene) was used as substrate; glucuronosyl activity was elevated modestly only in the animals receiving the tea for a month. It is concluded that even short-term exposure to black tea is capable of influencing the metabolic fate of IQ, and this is most likely related to the upregulation of CYP1A2.
Collapse
Affiliation(s)
- V R Yoxall
- Molecular Toxicology Group, School of Biomedical and Molecular Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK
| | | | | | | |
Collapse
|
9
|
Catterall F, McArdle NJ, Mitchell L, Papayanni A, Clifford MN, Ioannides C. Hepatic and intestinal cytochrome P450 and conjugase activities in rats treated with black tea theafulvins and theaflavins. Food Chem Toxicol 2003; 41:1141-7. [PMID: 12842182 DOI: 10.1016/s0278-6915(03)00073-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Theaflavins and theafulvins, a fraction of thearubigins, were isolated from aqueous infusions of black tea, and their effects on the hepatic and intestinal cytochrome P450 system, and on the glutathione S-transferase, epoxide hydrolase, glucuronosyl transferase and sulphotransferase enzyme systems were investigated in rats following oral intake for four weeks. Neither theafulvins nor theaflavins influenced cytochrome P450 activity in the liver as exemplified by the O-dealkylations of methoxy-, ethoxy- and pentoxyresorufin, the hydroxylations of lauric acid and p-nitrophenol, and the N-demethylation of erythromycin; similarly, hepatic xenobiotic conjugation systems were unaffected. In the intestine, both polyphenolic fractions markedly suppressed the O-deethylation of ethoxyresorufin and this was accompanied by a decrease in the CYP1A1 apoprotein levels. Probing intestinal microsomes with antibodies to CYP2E1 revealed the presence of a single band in the cytochrome P450 region whose intensity was lower in the polyphenol-treated animals. Immunoblot analysis utilising antibodies to CYP3A showed that the treatment with theafulvins and theaflavins reduced the apoprotein levels. A single band in the cytochrome P450 region was evident when the intestinal microsomes were probed with antibodies to CYP4A1 but the level of expression was not affected by the treatment with the black tea polyphenols. Finally, treatment of the rats with theaflavins had no effect on any of the intestinal conjugating enzymes studied, but treatment with theafulvins led to inhibition of glucuronosyl transferase activity.
Collapse
Affiliation(s)
- F Catterall
- School of Biomedical and Life Sciences, University of Surrey, Surrey, GU2 7XH, Guildford, UK
| | | | | | | | | | | |
Collapse
|
10
|
Catterall F, King LJ, Clifford MN, Ioannides C. Bioavailability of dietary doses of 3H-labelled tea antioxidants (+)-catechin and (-)-epicatechin in rat. Xenobiotica 2003; 33:743-53. [PMID: 12893523 DOI: 10.1080/0049825031000108315] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
1. The bioavailability and pharmacokinetic characteristics of the tea antioxidants (+)-catechin and (-)-epicatechin were investigated in the rat following intake of dietary doses. 2. To achieve this objective, tritiated derivatives (tritium was incorporated at the 3-position of the heterocyclic ring) of these compounds were administered to rats orally and intravenously at dose levels equivalent to human dietary levels of intake. 3. Following intravenous administration of both compounds, about one-third of the dose was excreted in the urine and two-thirds in the faeces, indicating extensive biliary excretion. When the same doses were administered orally, only about 5% of the dose of each compound was recovered in the urine. 4. Comparison of the areas under the curve following oral and intravenous administration revealed that the bioavailability of both compounds was less than 5%. 5. Exchange of tritium with water in the blood occurred 3 h after oral, but not after intravenous, administration of the flavanols to rat. This is believed to represent microbial degradation of the compounds by the gut flora. 6. It was established that the bioavailability of the tea antioxidants (+)-catechin and (-)-epicatechin in the rat following intake of dietary doses was poor.
Collapse
Affiliation(s)
- F Catterall
- School of Biomedical and Life Sciences, University of Surrey, Guildford, UK
| | | | | | | |
Collapse
|
11
|
Abstract
1. The use of herbal products to treat a wide range of conditions is rising rapidly, leading to increased intake of phytochemicals. Recent studies revealed potentially fatal interactions between herbal remedies and traditional drugs. 2. In transplant patients, self-medication with St John's wort (Hypericum perforatum) has led to a drop in plasma levels of the immunosuppressant drug cyclosporine, causing tissue rejection. 3. Intake of St John's wort increases the expression of intestinal P-glycoprotein and the expression of CYP3A4 in the liver and intestine. The combined up-regulation in intestinal P-glycoprotein and hepatic and intestinal CYP3A4 impairs the absorption and stimulates the metabolism of cyclosporine, leading to subtherapeutic plasma levels. The St John's wort component, hyperforin, contributes to the induction of CYP3A4. 4. St John's wort also enhances the metabolism of other CYP3A4 substrates including the protease inhibitors indinavir and nevirapine, oral contraceptives, and tricyclic antidepressants such as amitriptyline. 5. Other herbal remedies with the potential to modulate cytochrome P450 activity and thus participate in interactions with conventional drugs include Milk thistle, Angelica dahurica, ginseng, garlic preparations, Danshen and liquorice. 6. Herbal products are currently not subject to the rigorous testing indispensable for conventional drugs. However, if potential drug interactions are to be predicted, it is essential that the ability of herbal products to interfere with drug-metabolizing enzyme systems is fully established.
Collapse
Affiliation(s)
- C Ioannides
- Molecular Toxicology Group, School of Biomedical and Life Sciences, University of Surrey, Guildford GU2 7XH, UK.
| |
Collapse
|
12
|
Skene DJ, Papagiannidou E, Hashemi E, Snelling J, Lewis DF, Fernandez M, Ioannides C. Contribution of CYP1A2 in the hepatic metabolism of melatonin: studies with isolated microsomal preparations and liver slices. J Pineal Res 2001; 31:333-42. [PMID: 11703563 DOI: 10.1034/j.1600-079x.2001.310408.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The objective of the present studies was to define the enzyme systems catalysing the 6-hydroxylation of melatonin, by monitoring the levels of 6-sulphatoxymelatonin in rat hepatic postmitochondrial preparations and in precision-cut liver slices. Melatonin 6-hydroxylase activity was localized in microsomes and was supported by NADPH, but not NADH. Treatment of rats with beta-naphthoflavone more than tripled 6-sulphatoxymelatonin formation from melatonin, but gave rise only to a moderate increase (25%) in the sulphate conjugation of 6-hydroxymelatonin. Treatment of rats with phenobarbitone, acetone, dexamethasone and clofibrate did not increase 6-sulphatoxymelatonin generation when either melatonin or 6-hydroxymelatonin served as substrates. Of a number of cytochrome P450 inhibitors investigated, only furafylline inhibited markedly the conversion of melatonin to 6-sulphatoxymelatonin without any concomitant effect on the sulphoconjugation of 6-hydroxymelatonin. When liver slices were incubated with melatonin, treatment of rats with beta-naphthoflavone, and to a lesser extent phenobarbitone, elevated the levels of 6-sulphatoxymelatonin in the culture medium. No such increase was seen when slices from beta-naphthoflavone-treated rats were incubated with 6-hydroxymelatonin, whereas a modest increase was seen with slices from phenobarbitone-treated rats. Treatment of rats with acetone, dexamethasone or clofibrate failed to modulate the levels of 6-sulphatoxymelatonin generated from either melatonin or 6-hydroxymelatonin. Molecular modelling analysis revealed that melatonin had a high area/depth(2) ratio, displayed characteristics of CYP1A2 substrates and could be readily accommodated into the human CYP1A2 active site in a position favouring 6-hydroxylation. Collectively, all the above data provide strong experimental evidence that CYP1A2 is an important catalyst of the 6-hydroxylation of melatonin.
Collapse
Affiliation(s)
- D J Skene
- School of Biological Sciences, University of Surrey, Guildford, Surrey, GU2 5XH, UK
| | | | | | | | | | | | | |
Collapse
|
13
|
Sivapathasundaram S, Magnisali P, Coldham NG, Howells LC, Sauer MJ, Ioannides C. A study of the expression of the xenobiotic-metabolising cytochrome P450 proteins and of testosterone metabolism in bovine liver. Biochem Pharmacol 2001; 62:635-45. [PMID: 11585060 DOI: 10.1016/s0006-2952(01)00710-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The expression of xenobiotic-metabolising cytochrome P450 proteins in the liver of cattle was determined using substrate probes and immunologically by Western blot analysis. Compared to the rat, cattle displayed much higher coumarin 7-hydroxylase (CYP2A) and ethoxyresorufin O-deethylase (CYP1) activity but, in contrast, it exhibited much lower debrisoquine 4-hydroxylase (CYP2D) and lauric acid hydroxylase activities (CYP4A). The ethoxyresorufin O-deethylase activity was markedly inhibited by furafylline and a-naphthoflavone, and coumarin 7-hydroxylase by 8-methoxypsoralen. Immunoblot analysis employing antibodies to rat CYP1A1 recognised two immunorelated proteins in bovine liver whose expression appeared to be higher compared with rat. Kinetic studies indicated that a single enzyme is likely to be responsible for the O-deethylation of 7-ethoxyresorufin in bovine liver. When bovine microsomes were probed with antibodies to rat CYP2A2, a single protein was detected in cattle liver. Kinetic analysis followed by construction of Eadie-Hofstee plots indicated that more than one enzyme contributes to the 7-hydroxylation of coumarin. Immunoblot analysis employing antibodies to human CYP2D6 and rat CYP4A1 revealed in both cases a single, poorly expressed immunoreacting band in bovine microsomes. Similar immunoblot studies detected proteins in cattle liver immunorelated to the CYP2B, CYP2C, CYP2E, and CYP3A subfamilies. Bovine microsomes metabolised testosterone but, in contrast to the rat, failed to produce 2alpha- and 16alpha-hydroxytestosterone. On the other hand, bovine microsomes produced levels of another hydroxylated metabolite, possibly 12-hydroxytestosterone. In conclusion, results emanating from this study indicate the presence of proteins in the cattle liver belonging to all the xenobiotic-metabolising families of cytochrome P450.
Collapse
Affiliation(s)
- S Sivapathasundaram
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | | | | | |
Collapse
|
14
|
Anderson D, Dhawan A, Yardley-Jones A, Ioannides C, Webb J. Effect of antioxidant flavonoids and a food mutagen on lymphocytes of a thalassemia patient without chelation therapy in the Comet assay. Teratog Carcinog Mutagen 2001; 21:165-74. [PMID: 11223893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Thalassemia remains a significant health problem in Europe, the Middle East, and Asia. In such patients, generally high iron levels make free oxygen radicals accessible, for example, through Fenton-type chemistry, and generate superoxide and hydroxyl radicals. Increased oxygen radical capacity is known to be associated with cancer and ageing. It was shown in previous studies that peripheral blood lymphocytes from a sickle/beta thal double heterozygote-sickle phenotype, thalassemia patient, not yet on chelation therapy, were more sensitive to the effects of oxygen radicals and iron salts than lymphocytes from normal controls. Iron overload in thalassemia patients can result from dietary absorption. It was considered that with other dietary agents, such as food mutagens and flavonoids, the thalassemia patient might also show increased sensitivity to the effects of these agents. The present study, therefore, compared the effects of the food mutagen/carcinogen, 3-amino-1-methyl-5H-pyrido(4,3-b)indole (Trp-P-2), in fresh or frozen normal human peripheral lymphocytes with frozen lymphocytes from the same thalassemia patient. The lymphocytes from the thalassemia patient showed an approximately two-fold increase in sensitivity. When a combination of Tryp-P-2, with either quercitin or kaempferol, was compared in frozen lymphocytes and lymphocytes from the thalassemia patient, a two-fold increase in sensitivity was also maintained. Responses to Trp-P-2 were reduced to untreated control levels at the highest doses of quercitin and kaempferol, and were highly significantly different by comparison with Trp-P-2 alone (P<0.001). The flavonoids acted in an antigenotoxic/antioxidant manner. Sensitivity was slightly increased with kaempferol by comparison with quercitin. At low concentrations of the flavonoids there was some evidence of an exacerbation of response, perhaps due to a switch to pro-oxidant status. This exacerbation of response at low doses of flavonoids has been seen in earlier studies with normal lymphocytes. Teratogenesis Carcinog. Mutagen. 21:165-174, 2001.
Collapse
Affiliation(s)
- D Anderson
- TNO-BIBRA International Ltd., Woodmansterene Road, Carshalton SM54DS, Surrey, United Kingdom.
| | | | | | | | | |
Collapse
|
15
|
Abstract
The fate of the mushroom hydrazine [14C]agaritine was investigated in the mouse and rat strains previously employed in carcinogenicity studies with the edible mushroom Agaricus bisporus. Agaritine was rapidly absorbed in both species, achieving higher blood levels in the mouse, but with similar area under the curve. Covalent binding of agaritine material to proteins was detected only in the liver and kidney, but the extent of binding was the same in the rat and mouse. Most of the radioactivity was excreted during the first 24 hours in both animal species: in the rat it was distributed equally between urine and feces, whereas in the mouse more of the radioactivity was excreted in the urine. No qualitative differences in the metabolic profile were evident, but quantitative differences were observed. Treatment of the urine with deconjugating enzymes did not reveal the presence of any conjugates. Agaritine, N'-acetyl-4-(hydroxymethyl)phenylhydrazine, and 4-(hydroxymethyl)benzene diazonium ion were not detected in the urine or in the plasma of either species. No mutagens or promutagens were detected by the Ames mutagenicity assay in the urine of either species after exposure to agaritine. Repeated administration of agaritine to rats and mice did not alter the urinary metabolic profile and excretion of radioactivity. Similarly, feeding mice a raw mushroom diet, according to the protocol employed in the carcinogenicity studies, did not modulate the excretion of radioactivity or the urinary metabolic pattern. No major species differences in the fate of agaritine in rat and mouse were noted that could provide a rationale for the carcinogenicity of A. bisporus in the mouse, but not in the rat.
Collapse
Affiliation(s)
- K Walton
- School of Physical Sciences, University of Surrey, Guildford, UK
| | | | | | | | | |
Collapse
|
16
|
Catterall FS, Coombs MM, Ioannides C, Sepiol JJ, Wilson J. Mutagenicity of bay-region amino-substituted cyclopenta[a]phenanthrenes and 2- and 5-aminochrysene. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 2001; 492:7-11. [PMID: 11377239 DOI: 10.1016/s1383-5718(01)00144-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The relative mutagenic potentials of 11-amino-16,17-dihydro-15H-cyclopenta[a]phenanthrene, its 17-keto derivative, and 2- and 5-aminochrysene have been compared in Salmonella typhimurium TA98 and TA100 in the presence of a postmitochondrial liver preparation from Aroclor 1254 induced rats. The 11-amino hydrocarbon is a very weak mutagen (0.27 revertants/nmol), whereas the 11-amino-17-ketone is much more active (129 revertants/nmol). 2-Aminochrysene is the most mutagenic arylamine ( approximately 500 revertants/nmol) among these compounds, but its 5-amino isomer is much less active (0.9 revertants/nmol). Possible reasons for these marked differences are suggested. Use of TA98 with over-expressing O-acetyltransferase (YG 1024) and deficient in this enzyme (TA98/l,8-DNP(6)) with the 11-amino-17-ketone and with 5-aminochrysene clearly indicates the importance of this enzyme in their bioactivation, implying oxidation of the amino group to the hydroxylamine in both these compounds.
Collapse
Affiliation(s)
- F S Catterall
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, GU2 7XH, Surrey, UK
| | | | | | | | | |
Collapse
|
17
|
Walton K, Coombs MM, Walker R, Ioannides C. The metabolism and bioactivation of agaritine and of other mushroom hydrazines by whole mushroom homogenate and by mushroom tyrosinase. Toxicology 2001; 161:165-77. [PMID: 11297805 DOI: 10.1016/s0300-483x(00)00430-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Whole homogenates of Agaricus bisporus metabolised the mushroom hydrazine agaritine [beta-N-(gamma-L(+)glutamyl)-4-(hydroxymethyl) phenylhydrazine] to generate at least three metabolites. None of these metabolites, however, was the free hydrazine [4-(hydroxymethyl)phenylhydrazine], the postulated metabolite of agaritine believed to be formed as a result of the loss of the gamma-glutamyl group, the reaction being catalysed by gamma-glutamyltransferase. The three metabolites of agaritine displayed weak mutagenic activity towards Salmonella typhimurium strain TA104. 4-(Hydroxymethyl)phenylhydrazine, as the N'-acetyl derivative, was metabolised by mushroom tyrosinase to yield a number of metabolites that induced a mutagenic response in S. typhimurium TA104. Similar to N'-acetyl-4-(hydroxymethyl)phenylhydrazine, agaritine was extensively metabolised by the mushroom tyrosinase but, in contrast, the structurally related N'-acetyl-4-hydrazinobenzoic acid did not serve as substrate of this enzyme, implying a critical role for the hydroxymethyl group at the para-position. In conclusion, the current studies have demonstrated for the first time that: (a) whole mushroom homogenates readily metabolise agaritine but not to the postulated 4-(hydroxymethyl)phenylhydrazine; and (b) mushroom tyrosinase metabolises agaritine and N'-acetyl-4-(hydroxymethyl)phenylhydrazine, in the latter case forming genotoxic metabolites.
Collapse
Affiliation(s)
- K Walton
- School of Biological Sciences, Molecular Toxicology Group, University of Surrey, Guildford GU2 5XH UK
| | | | | | | |
Collapse
|
18
|
Lewis DF, Ioannides C, Parke DV, Schulte-Hermann R. Quantitative structure-activity relationships in a series of endogenous and synthetic steroids exhibiting induction of CYP3A activity and hepatomegaly associated with increased DNA synthesis. J Steroid Biochem Mol Biol 2000; 74:179-85. [PMID: 11162923 DOI: 10.1016/s0960-0760(00)00121-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The results of a quantitative structure-activity relationship (QSAR) study on a total of 14 steroids exhibiting induction of a CYP3A-associated activity and increase in liver weight/DNA synthesis is reported. It is found that different, but related, structural descriptors correlate with increase in ethylmorphine N-demethylase activity (r=0.92) and with the increase in liver weight (r=0.78) and DNA synthesis (r=0.78). Although there is a strong correlation between increase in liver weight and DNA content (r=0.999), neither of these correlated with ethylmorphine N-demethylase activity. These findings are discussed in the light of CYP3A induction, substrate specificity and inhibition; a proposed model of human CYP3A4 based on sequence homology with CYP102, a bacterial P450 of known crystal structure, demonstrates the possible mode of interaction between substrates and inhibitors within the putative active site.
Collapse
Affiliation(s)
- D F Lewis
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Surrey GU2 7XH, Guildford, UK
| | | | | | | |
Collapse
|
19
|
Abstract
The objective of this study was to evaluate the stability of individual, xenobiotic-metabolising, cytochrome P450 proteins in precision-cut rat liver slices cultured for up to 72 h using the multiwell plate system. This was achieved using established diagnostic probes (O-dealkylation of methoxy-, ethoxy- and pentoxy-resorufin, testosterone 2alpha-hydroxylase, debrisoquine 4-hydroxylase, aniline p-hydroxylase and lauric acid hydroxylase) and immunologically using Western blotting. All cytochrome P450 activities declined in culture, the most rapid loss occurring at about 8-12 h of culture; in all cases no detectable activity was present in the 72-h cultured slices. Isoform-specific differences in the stability of various cytochrome P450 proteins were observed, with CYP2E1 being the most stable. When cytochrome P450 expression was determined immunologically, a different picture emerged. High levels of apoprotein were retained in the slices even when activity was very low. In the case of CYP2B, apoprotein levels even increased following the culture of hepatic slices. It is concluded, that for tissue slices to become an acceptable in vitro alternative system for long-term incubations, the culturing conditions must be improved to ensure that cytochrome P450 activities are better maintained.
Collapse
Affiliation(s)
- E Hashemi
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, GU2 5XH, UK
| | | | | |
Collapse
|
20
|
Affiliation(s)
- R A Blouin
- Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington 40536-0082, USA
| | | | | | | | | |
Collapse
|
21
|
Abstract
The title compound is a more potent carcinogen than would be anticipated from its simple phenanthrene structure lacking further D-ring conjugation. In vitro it undergoes microsomal metabolism to yield as major metabolites its 15- and 17-alcohols and its 16, 17-diol; other minor metabolites are also derived from attack at the 5-membered ring, but no evidence of aromatic oxidation is apparent. The title compound is a weak mutagen in the Ames' test with Salmonella typhimurium TA100, but only with microsomal bio-activation. The 17-ol and 16,17-diol are inactive, with or without biological activation. By contrast the 15-alcohol, a rather reactive compound, is a strong mutagen both in the presence and absence of the bio-activation system. This, therefore, may be the proximate carcinogen, and its structural analogy to the naturally occurring hepato-carcinogen safrole is noted.
Collapse
Affiliation(s)
- F S Catterall
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | |
Collapse
|
22
|
Barnett CR, Ioannides C. Xenobiotic-metabolizing enzyme systems and aging. Methods Mol Med 2000; 38:119-130. [PMID: 22351269 DOI: 10.1385/1-59259-070-5:119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The human body is continuously exposed to a wide array of structurally diverse chemicals. Such exposure occurs even at the fetal stage as almost all chemicals that are present in the mother's blood can readily cross the placenta and reach the fetus. Some of these chemicals are ingested voluntarily, for example, medicines and food additives, but the vast majority are taken involuntarily, as environmental contaminants present in the air or in the occupational environment. Undoubtedly, the most important source of such chemicals is the diet, and many dietary constituents have been shown to induce many forms of toxicity including cancer (1). Exposure to chemicals is thus inevitable and unavoidable. The body cannot exploit these chemicals either to generate energy or transform them to building blocks and consequently its response is to rid itself of their presence. This chapter discusses the role of drug-metabolizing enzyme systems in this process and the effects of age. The measurement of drug-metabolizing activities is of increasing importance in the safety evaluation of drugs in humans. This chapter describes the use of alkylphenoxazone derivatives for investigating selected activities of drug-metabolizing enzymes.
Collapse
Affiliation(s)
- C R Barnett
- School of Biomedical Sciences, University of Ulster, Cromore, Road, Coleraine, County Londonderry, Northern Ireland
| | | |
Collapse
|
23
|
Ioannides C. Apron flap incision for neck dissection. Plast Reconstr Surg 2000; 105:470-1. [PMID: 10627021 DOI: 10.1097/00006534-200001000-00084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
24
|
Catterall F, Souquet JM, Cheynier V, de Pascual-Teresa S, Santos-Buelga C, Clifford MN, Ioannides C. Differential modulation of the genotoxicity of food carcinogens by naturally occurring monomeric and dimeric polyphenolics. Environ Mol Mutagen 2000; 35:86-98. [PMID: 10712742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Naturally occurring dimeric polyphenolics and their gallate esters were isolated from grape seeds, almond fruits, and apple skin, and their ability to modulate the mutagenicity of food carcinogens was studied in the Ames test, and compared to that of the monomeric green tea flavonols, (+)-catechin and (-)-epicatechin. Neither the monomeric nor the dimeric polyphenols and their galloylated derivatives influenced the mutagenic activity elicited by the indirectly acting food carcinogens benzo[a]pyrene and 2-amino-3-methylimidazo-[4,5-f]quinoline (IQ), in the presence of a hepatic activation system derived from Aroclor 1254-treated rats; the only exception was the B7 dimer, which, at concentrations above 1 microM, suppressed the mutagenicity of IQ. None of the polyphenolics modulated the mutagenic activity elicited by the directly acting carcinogen N'-methyl-N'-nitro-nitrosoguanidine (MNNG). In contrast, all the dimeric polyphenols and the galloylated metabolites, at concentrations over 1 microM, potentiated the mutagenic activity induced by the indirectly acting carcinogen N-nitrosopyrrolidine, in the presence of an activation system derived from isoniazid-treated rats. In conclusion, dimeric polyphenols and galloylated derivatives of plant origin are unlikely to influence the initiation stage of the carcinogenicity of chemicals through mechanisms that involve inhibition of their cytochrome P450-mediated bioactivation or scavenging of the reactive, genotoxic intermediates.
Collapse
Affiliation(s)
- F Catterall
- School of Biological Sciences, University of Surrey, Guilford, Surrey, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
25
|
Bu-Abbas A, Dobrota M, Copeland E, Clifford MN, Walker R, Ioannides C. Proliferation of hepatic peroxisomes in rats following the intake of green or black tea. Toxicol Lett 1999; 109:69-76. [PMID: 10514032 DOI: 10.1016/s0378-4274(99)00119-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Rats maintained on green, black or decaffeinated black tea (2.5%, w/v) as their sole drinking fluid displayed higher hepatic CN- insensitive palmitoyl CoA oxidase activity than controls; the extent of increase was similar with the three types of tea. Morphological examination of the liver using electron microscopy revealed an increase in the number of peroxisomes in the tea-treated animals. The same treatment of the animals with green and black tea resulted in a similar rise in hepatic microsomal lauric acid hydroxylation. Analysis by HPLC of the aqueous tea extracts employed in the current study showed that the total flavanol content of the green variety was much higher than the black varieties, and confirmed the absence of caffeine in the decaffeinated black tea. It may be concluded from the present studies that neither caffeine nor flavanoids are likely to be responsible for the proliferation of peroxisomes observed in rats treated with tea.
Collapse
Affiliation(s)
- A Bu-Abbas
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | | | | | |
Collapse
|
26
|
Abstract
PURPOSE To propose a clinical classification of fractures of the frontal sinus and discuss the implications on treatment. PATIENTS AND METHODS One hundred patients with fractures of the frontal sinus seen and operated on in two University hospital units (Leuven and Nijmegen). The majority of the patients were surgically treated according to a protocol based on the proposed classification. Fractures were classified according to their location, extent, involvement of the nasofrontal duct, and injury to the dura. Fragments were reduced and fixed, defects were reconstructed with autologous bone grafts, and the sinus cavity was drained, obliterated, or cranialized. In the latter cases, the sinus mucosa was thoroughly removed before obliteration or cranialization. RESULTS The follow-up ranged from 6 months to 12 years. There were functional complications in 4% of patients. Minor aesthetic sequelae were noticed in 14% of the patients. CONCLUSION A detailed classification of fractures of the frontal sinus is proposed. It has helped the authors set up a treatment protocol. Optimally, if used by clinicians, it will contribute to a more standardized method of surgical care of patients with such injuries.
Collapse
Affiliation(s)
- C Ioannides
- Department of Plastic and Reconstructive Surgery, Middlesex Hospital, University College Hospitals, London, England
| | | |
Collapse
|
27
|
Marczylo T, Ioannides C. Evidence for the presence of a microsomal NADH-dependent enzyme system that can bioactivate aromatic amines in the liver of rats and mice. Toxicology 1999; 134:127-41. [PMID: 10403632 DOI: 10.1016/s0300-483x(99)00034-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Experimental evidence is presented for the presence in the liver of rats and mice of an Aroclor 1254-inducible, NADH-dependent enzyme system that can catalyse the bioactivation of aromatic and heterocyclic amines to genotoxic metabolites. It differs from the established microsomal cytochrome P450 and flavin monooxygenase systems in its response to treatment with cytochrome P450 inducing agents, optimum protein concentration and in vitro modulation by DMSO. The mutagenic metabolites generated by the NADH-supported system appear to be similar to those generated by the NADPH-mediated systems. Mutagenicity of the aminocompounds in the presence of either cosubstrate was less pronounced in an O-acetyltransferase-deficient bacterial strain, implying the presence of hydroxylamines. Moreover, glutathione potentiated the mutagenic response of both the NADH- and NADPH-generated metabolites. Cytochrome c suppressed markedly the NADPH-dependent mutagenicity of aromatic amines but had no such effect in the presence of NADH. Similarly, antibodies to cytochrome P450 reductase markedly inhibited the NADPH-, but not the NADH-dependent bioactivation of the aromatic amine 2-aminoanthracene. The cytochrome P450 suicide inhibitor, 1-aminobenzotriazole, decreased the mutagenicity of both, the NADH- and NADPH-mediated bioactivation of the aminocompounds. The above findings raise the possibility that a cytochrome P450-like protein, that can receive electrons from NADH, possibly through cytochrome b5 reductase, is present in the hepatic microsomes of rats and mice, and is capable of catalysing the bioactivation of aromatic amines through N-hydroxylation. Such a hypothesis is supported by the findings that NADH could support the O-dealkylation of 7-methoxy- and 7-ethoxy-resorufin, in the absence of NADPH. Finally the NADH-dependent bioactivation of aromatic amines was induced markedly by Aroclor 1254 and benzo(a)pyrene in Ah responsive, but not Ah nonresponsive, mice indicating that it is associated with the Ah locus.
Collapse
Affiliation(s)
- T Marczylo
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK
| | | |
Collapse
|
28
|
Abstract
Thirty-one patients with large scalp and cranium defects were reconstructed with free tissue transfer and scalp flaps. Twenty-eight of the defects resulted after tumour resection, two after infection and one after an extensive burn. Thirty-one free flaps (mainly the latissimus dorsi myocutaneous and the radial forearm fasciocutaneous) and five large (> 200 cm2) scalp flaps were used. Major complications occurred in one patient who developed meningitis and finally died (3.2%), and in one patient who lost a latissimus dorsi flap (3.2%). There were no other significant problems with the remaining patients. All other free flaps and scalp flaps survived. Primary reconstruction with free tissue transfer was our first choice of treatment because of the wide spectrum of advantages of free flaps. However, in a limited number of cases there was an indication for large scalp flaps, which, when properly designed, gave satisfactory results.
Collapse
Affiliation(s)
- C Ioannides
- Department of Surgery, University Hospitals, Leuven, Belgium
| | | | | |
Collapse
|
29
|
Abstract
The present study was undertaken to investigate whether the consumption of green tea and black tea influences the excretion of mutagens and promutagens in rats treated orally with the food carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Rats were maintained on aqueous extracts (2.5%, w/v) of green tea, black tea or decaffeinated black tea as their sole drinking liquid. After 4 weeks, the animals received, by gastric intubation, a single dose of IQ (5 mg/kg), and urine was collected for 48 h. Direct and indirect mutagenicity, in the presence of an activation system derived from Aroclor 1254-treated rats, was determined in the urine samples using the Ames mutagenicity assay. Consumption of green tea and black tea, but not of decaffeinated black tea, markedly decreased the urinary excretion of mutagens and promutagens. In a further study, supplementation of decaffeinated black tea with caffeine suppressed the excretion of mutagens and promutagens in the urine of rats pretreated with IQ. It is concluded that both green tea and black tea modulate the bioactivation and metabolism of IQ, and that caffeine is largely responsible for this effect.
Collapse
Affiliation(s)
- N J McArdle
- School of Biological Sciences, University of Surrey, Guildford, Surrey, GU2 5XH, UK
| | | | | |
Collapse
|
30
|
Bu-Abbas A, Clifford MN, Walker R, Ioannides C. Modulation of hepatic cytochrome P450 activity and carcinogen bioactivation by black and decaffeinated black tea. Environ Toxicol Pharmacol 1999; 7:41-47. [PMID: 21781908 DOI: 10.1016/s1382-6689(98)00049-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/1998] [Revised: 11/25/1998] [Accepted: 11/30/1998] [Indexed: 05/31/2023]
Abstract
The principal objective of this study was to compare the ability of green, black and decaffeinated black tea to modulate hepatic expression of cytochromes P450 in the rat, and the consequences on the bioactivation of some food-borne carcinogens. Furthermore, these studies allow inferences to be drawn as to the contribution of caffeine and flavanols in the tea-mediated changes in cytochrome P450 expression. Black tea is prepared from fresh tea leaf following oxidation of flavanols by polyphenol oxidases and consequently has a low content of these compounds. All three types of tea enhanced lauric acid hydroxylation but in the case of decaffeinated black tea no statistical significance was attained. Green tea and black tea, but not decaffeinated black tea, stimulated the O-dealkylations of methoxy-, ethoxy- and pentoxy-resorufin indicating upregulation of CYP1A and CYP2B. Immunoblot analysis revealed that green and black tea, but not decaffeinated black tea, elevated the hepatic CYP1A2 apoprotein levels. Hepatic microsomes from green and black tea-treated rats, but not those from the decaffeinated black tea-treated rats, were more effective than controls in converting IQ into mutagenic species in the Ames test. It is concluded that flavanols are not responsible for the effects of tea on the cytochrome P450 system, but caffeine could account for the increase in CYP1A2 and the consequent increase in the bioactivation of IQ.
Collapse
Affiliation(s)
- A Bu-Abbas
- School of Biological Sciences, University of Surrey, Guildford, Surrey, GU2 5XH, UK
| | | | | | | |
Collapse
|
31
|
Affiliation(s)
- C Ioannides
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK
| |
Collapse
|
32
|
Hashemi E, Dobrota M, Till C, Ioannides C. Structural and functional integrity of precision-cut liver slices in xenobiotic metabolism: a comparison of the dynamic organ and multiwell plate culture procedures. Xenobiotica 1999; 29:11-25. [PMID: 10078837 DOI: 10.1080/004982599238786] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
1. Objectives were two-fold: (1) to compare the viability of precision-cut liver slices in two culture systems, namely the dynamic organ and the multiwell plate; and (2) to evaluate whether increasing the number of slices per incubation results in a proportional increase in the extent of metabolism. 2. With both culturing systems, the major products of 7-ethoxycoumarin metabolism were the sulphate and glucuronide conjugates of 7-hydroxycoumarin with very low levels of the free compound. When the multiwell plate procedure was used, metabolism increased linearly for at least 10 h, whereas it tended to plateau after 6 h in the dynamic organ culture system. At preincubations > 10 h, significantly more metabolism of 7-ethoxycoumarin was seen in the slices cultured using the multiwell system compared with the dynamic organ system. 3. Morphological evaluation employing light and electron microscopy revealed that liver slices incubated using the multiwell system were structurally better preserved compared with those incubated using the dynamic organ system. 4. Using the multiwell system, increasing the number of slices per incubation from one to two resulted in only a modest increase in the metabolism of 7-ethoxycoumarin. The rate of metabolism of this substrate was much higher with one liver slice when expressed per mg homogenate protein. 5. It is concluded that (1) the multiwell plate culture system for culturing slices is superior to the dynamic organ system in studying the metabolism of xenobiotics following long-term incubations, (2) increasing the number of slices per incubation does not result in a corresponding increase in the rate of metabolism, and (3) in both culture systems optimal viability appears to be within 24 h of incubation.
Collapse
Affiliation(s)
- E Hashemi
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | |
Collapse
|
33
|
Catterall F, Copeland E, Clifford MN, Ioannides C. Contribution of theafulvins to the antimutagenicity of black tea: their mechanism of action. Mutagenesis 1998; 13:631-6. [PMID: 9862196 DOI: 10.1093/mutage/13.6.631] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Theafulvins were isolated from black tea aqueous infusions and their antimutagenic activity was evaluated against a number of food carcinogens. Theafulvins gave rise to a concentration-dependent inhibition of the mutagenicity of 2-amino-3-methylimidazo-[4,5-f]quinoline, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, benzo[a]pyrene, 7,12-dimethylbenz[a]anthracene, nitrosopyrrolidine and nitrosopiperidine, but, in contrast, the mutagenicity of aflatoxin B1 was enhanced. The mutagenicity exhibited by N'-methyl-N'-nitro-N-nitrosoguanidine and 9-aminoacridine was not influenced and weakly inhibited by theafulvins, respectively. The p-hydroxylation of aniline and the O-dealkylations of methoxy-, ethoxy- and, to a lesser extent, pentoxyresorufin were inhibited by theafulvins in a concentration-dependent manner. When microsomal metabolism was terminated after metabolic activation of the promutagens, incorporation of the theafulvins into the activation system did not modulate the mutagenic response. It is concluded that theafulvins play an important role in the antimutagenic activity of black tea by inhibiting cytochrome P450-dependent bioactivation of the carcinogens.
Collapse
Affiliation(s)
- F Catterall
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | |
Collapse
|
34
|
Lewis DF, Ioannides C, Parke DV. An improved and updated version of the compact procedure for the evaluation of P450-mediated chemical activation. Drug Metab Rev 1998; 30:709-37. [PMID: 9844807 DOI: 10.3109/03602539808996328] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- D F Lewis
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | |
Collapse
|
35
|
|
36
|
Pride MW, Shuey S, Grillo-Lopez A, Braslawsky G, Ross M, Legha SS, Eton O, Buzaid A, Ioannides C, Murray JL. Enhancement of cell-mediated immunity in melanoma patients immunized with murine anti-idiotypic monoclonal antibodies (MELIMMUNE) that mimic the high molecular weight proteoglycan antigen. Clin Cancer Res 1998; 4:2363-70. [PMID: 9796966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The purpose of this study was to determine whether a combination of two anti-idiotypic antibodies that mimic the high molecular weight proteoglycan antigen found on most melanoma tumors was capable of enhancing cellular immunity in vaccinated high-risk patients with melanoma. Twenty-eight stage I-IV high-risk patients with melanoma were immunized with a mixture of variable concentrations of MELIMMUNE-1 and MELIMMUNE-2, along with the adjuvant SAF-m, using two immunization schedules. Peripheral blood mononuclear cells were collected before the first immunization and 4 weeks after the final immunization and tested for in vitro proliferation to MELIMMUNE-1 and MELIMMUNE-2 and for cytotoxicity against 51Cr-labeled target cell lines. Additionally, supernatants from in vitro proliferation cultures were tested for interleukin 10 and IFN-gamma levels. Significant in vitro proliferation to MELIMMUNE-1 and MELIMMUNE-2 were observed in postimmunization samples but not in prevaccination samples. The mean stimulation index for MELIMMUNE-2 (33.7 +/- 0.6) was significantly higher than that for MELIMMUNE-1 (13.9 +/- 0.3; P < 0.025). Supernatants obtained from 78% of the in vitro stimulated cultures pre- or postvaccination contained significant levels of interleukin 10 (range, 0.43-142 pg/ml), whereas IFN-gamma levels were elevated in 53% of postvaccination samples (range, 3-245 pg/ml) but not prevaccination samples. More importantly, we were able to generate specific CTL responses in 43% of the patients, which correlated with elevated IFN-gamma levels. These results indicate that MELIMMUNE enhances cell-mediated immunity in patients with melanoma.
Collapse
Affiliation(s)
- M W Pride
- Department of Bioimmunotherapy, The University of Texas M. D. Anderson Cancer Center, Houston 77030, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Lewis DF, Ioannides C, Parke DV. A combined COMPACT and HazardExpert study of 40 chemicals for which information on mutagenicity and carcinogenicity is known, including the results of human epidemiological studies. Hum Exp Toxicol 1998; 17:577-86. [PMID: 9821022 DOI: 10.1177/096032719801701009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The COMPACT approach for defining structural criteria for substrates and inducers of cytochrome P450 (CYP) enzymes which mediate the formation of reactive intermediates is discussed in the context of prediction of potential carcinogenicity. This is broadened to encompass structural studies on mammalian P450s, including those relevant to genetic polymorphism in man. The use of the COMPACT system, in parallel with the structure alert program HazardExpert (now incorporated into the Pallas system), for evaluating human carcinogenicity data is reported, as an example of the possible employment of a battery of short-term test procedures for safety evaluation. In particular, the importance of using the log P value (as a measure of compound lipophilicity) to assess the likelihood of a potentially toxic compound reaching the site of activation, is emphasized by the finding that most procarcinogens requiring metabolic activation by P450s are lipophilic in nature.
Collapse
Affiliation(s)
- D F Lewis
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | |
Collapse
|
38
|
|
39
|
Lewis DF, Ioannides C, Parke DV. Cytochromes P450 and species differences in xenobiotic metabolism and activation of carcinogen. Environ Health Perspect 1998; 106:633-641. [PMID: 9755138 PMCID: PMC1533178 DOI: 10.1289/ehp.98106633] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The importance of cytochrome P450 isoforms to species differences in the metabolism of foreign compounds and activation of procarcinogens has been identified. The possible range of P450 isozymes in significant variations in toxicity exhibited by experimental rodent species may have a relevance to chemical risk assessment, especially as human P450s are likely to show changes in the way they metabolize xenobiotics. Consequently, in the safety evaluation of chemicals, we should be cautious in extrapolating results from experimental animal models to humans. This paper focuses on examples in which species differences in P450s lead to significant alterations in carcinogenic response, and includes a discussion of the current procedures for toxicity screening, with an emphasis on short-term tests.
Collapse
Affiliation(s)
- D F Lewis
- School of Biological Sciences, University of Surrey, Guildford, Surrey, GU2 5XH, United Kingdom
| | | | | |
Collapse
|
40
|
Lewis D, Ioannides C, Parke D. A combined COMPACT and HazardExpert study of 40 chemicals for which information on mutagenicity and carcinogenicity is known, including the results of human epidemiological studies. Hum Exp Toxicol 1998. [DOI: 10.1191/096032798678907919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
41
|
Bu-Abbas A, Clifford MN, Walker R, Ioannides C. Contribution of caffeine and flavanols in the induction of hepatic Phase II activities by green tea. Food Chem Toxicol 1998; 36:617-21. [PMID: 9734711 DOI: 10.1016/s0278-6915(98)00019-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Aqueous extracts of green tea, at concentrations of 2.5. 5.0 and 7.5%, were administered to rats as the sole drinking fluid for 4 weeks. Hepatic glutathione S-transferase (GST) activity, determined using 1-chloro-2,4-dinitrobenzene (CDNB) and 3,4-dichloronitrobenzene (DCNB) as substrates, and UDP-glucuronosyl transferase activity, determined using 2-aminophenol as substrate, were induced but the effect was not always dose dependent. At the two highest doses, hepatic catalase activity was inhibited. In a second study, animals were exposed for 4 weeks to aqueous extracts (2.5%, v/v) of green tea, black tea (which has a much lower content of flavanols compared with green tea) and decaffeinated black tea. Treatment with the black tea enhanced GST activity, whether monitored using CDNB or DCNB, and the glucuronidation of 2-aminophenol. Treatment with decaffeinated black tea failed to modulate any of these activities, whereas treatment with green tea only enhanced the glucuronidation of 2-aminophenol. Finally, at this concentration of tea extract administration, black and decaffeinated black tea, but not green tea, suppressed catalase activity. It is concluded that neither flavanols nor caffeine are responsible for the induction of hepatic Phase II activities and inhibition of catalase activity in the rat.
Collapse
Affiliation(s)
- A Bu-Abbas
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | |
Collapse
|
42
|
Abstract
The ability of the cytosolic arylamine oxidase to convert structurally diverse aromatic and heterocyclic amines to mutagens in the Ames test was investigated using hepatic cytosol from Aroclor 1254-treated rats as the activation system. Using this system, only amino compounds containing at least three fused aromatic rings elicited a strong mutagenic effect; heterocyclic amines failed to exhibit mutagenicity. In contrast, when Aroclor 1254-induced rat hepatic microsomal preparations served as the activation system, monocyclic, bicyclic as well as larger amino compounds induced a clear mutagenic response; moreover, heterocyclic amines were potent mutagens. Nitrosamines displayed mutagenicity in the presence of only the microsomal activation system. In the presence of the cytosol, the mutagenic response of aromatic amines was much lower in the bacterial strain TA98-1,8-DNP6, which is deficient in O-acetyltransferase activity, compared to the normal TA98 strain. This finding implies that the cytosolic activation of aromatic amines involves N-hydroxylation.
Collapse
Affiliation(s)
- T Marczylo
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK
| | | |
Collapse
|
43
|
Abstract
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.
Collapse
Affiliation(s)
- A Irizar
- Molecular Toxicology Group, School of Biological Sciences, University of Surrey, Guildford, UK
| | | |
Collapse
|
44
|
Walton K, Walker R, Ioannides C. Effect of baking and freeze-drying on the direct and indirect mutagenicity of extracts from the edible mushroom Agaricus bisporus. Food Chem Toxicol 1998; 36:315-20. [PMID: 9651048 DOI: 10.1016/s0278-6915(97)00161-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The objectives of the study were to evaluate the effect of baking and freeze-drying on the direct and indirect mutagenicity in the Ames test of ethanolic extracts from the edible mushroom Agaricus bisporus. Direct mutagenicity was not influenced by baking for 10 min at 225 degrees C, but more prolonged baking, for example 4 hr at 100 degrees C reduced mutagenicity. Hepatic cytosol from Aroclor 1254-induced rats and mushroom tyrosinase potentiated the mutagenic response elicited by the mushroom extracts. Baking did not influence either of these processes. Finally, freeze-drying influenced neither the direct nor the indirect mutagenicity of the mushroom extracts. It is concluded that mutagenic and premutagenic compounds present in mushroom are generally not heat labile.
Collapse
Affiliation(s)
- K Walton
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | |
Collapse
|
45
|
Di Bello MG, Masini E, Ioannides C, Ndisang JF, Fomusi Ndisang J, Raspanti S, Bani Sacchi T, Mannaioni PF. Histamine release from rat mast cells induced by the metabolic activation of drugs of abuse into free radicals. Inflamm Res 1998; 47:122-30. [PMID: 9562337 DOI: 10.1007/s000110050299] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The metabolic activation of morphine, cocaine and methadone into free radicals could have pathophysiological relevance in the organic injuries of drug addiction. METHODS Isolated purified rat serosal mast cells were incubated with morphine, cocaine and methadone (10(-7) M-10(-4) M) with oxidative enzymes (prostaglandin-H-synthetase, 25 mU; rat liver homogenate fraction S 10-mix, 400 microl), and with the drugs of abuse in the presence of oxidative enzymes. Histamine and lactate dehydrogenase (LDH) were analysed with a fluorimetric and spectrophotometric assay, respectively; the generation of malonyldialdehyde (MDA) was measured by a spectrophotometric assay. RESULTS The release of mast cell histamine and the generation of MDA are present only when mast cells were incubated with the drugs of abuse in the presence of oxidative enzymes. This release was dependent on the concentration of the drug in question and showed a maximum value at 10(-4) M. Moreover, in parallel experiments we demonstrated that, under the same experimental conditions, the release of LDH was always less than 20% of the total, suggesting that this effect is due to a selective exocytotic process. Histamine release and MDA generation were abated by the free radical scavengers: reduced glutathione, 10(-4) M GSH and alpha-tocopherol, 10(-4) M and by the spin trapper 5.5-dimethyl-1-pyrroline-N-oxide, 10(-4) M DMPO. The light and electron microscopic features are consistent with exocytotic secretion in the cases of morphine and methadone and with cell lysis in the case of cocaine. CONCLUSION These results suggest that morphine, cocaine and methadone are activated into free radicals which produce membrane lipid perturbation and histamine release, suggesting that a massive release of mast cell histamine could be an additional risk factor in heroin and cocaine overdoses.
Collapse
Affiliation(s)
- M G Di Bello
- Department of Preclinical and Clinical Pharmacology, University of Florence, Italy
| | | | | | | | | | | | | | | |
Collapse
|
46
|
Abstract
There are two forms of diabetes, insulin-dependent Diabetes mellitus (IDDM) and non-insulin dependent Diabetes mellitus (NIDDM). There is evidence to suggest that reactive oxygen is involved in the pathogenicity and complications arising from IDDM, but there is little to suggest a role of oxidative stress in the pathogenesis of NIDDM. In order to investigate this hypothesis further, peripheral blood samples were taken from control individuals and IDDM and NIDDM patients and examined for antioxidant capacity and in the Comet assay for DNA strand breakage. The individuals answered a questionnaire to provide information relating to lifestyle factors in case such factors might have a confounding effect. There were 20 controls, 22 IDDM patients and 23 NIDDM patients. No differences could be detected in control and diabetic patient groups in terms of creatinine levels and antioxidant capacity. DNA damage in the Comet assay was at a lower level than in the control in the IDDM patients and a slightly lower level in the NIDDM patients, which might indicate that these cells are handling more oxidative damage on a regular basis. As expected, there were differences in glycosylated haemoglobin (HbA(1C)) levels. The confounding factors (smoking, drinking and vitamin intakes, etc.) appeared to have no effect.
Collapse
Affiliation(s)
- D Anderson
- BIBRA International, Carshalton, Surrey, UK
| | | | | | | |
Collapse
|
47
|
Abstract
The molecular dimensions and electronic structures of the first group of 100 US NCI/NTP miscellaneous chemicals, evaluated for potential carcinogenicity by computer-optimized molecular parametric analysis for chemical toxicity (COMPACT) have been re-determined. Using improved criteria for cytochrome P450 (CYP) substrate specificity, re-defined for CYP1 as having a COMPACT radius [square root of (deltaE - 9.5)2 + (a/d(2) - 7.8)2] of < 6.5, and for CYP2E as having a collision diameter of 6.5 angstroms or less and deltaE < 15.5, the likely substrates of CYP1 and CYP2E, which are regarded as potential carcinogens, have been identified. In addition, log P values have been taken into account; those chemicals with log P < 0 are non-lipophilic substrates unlikely to reach the activating cytochrome enzymes, and have been regarded as non-carcinogens. The second group of 100 US NCI/NTP chemicals have also now been categorized by COMPACT into CYP1 and CYP2E substrates, and their potential carcinogenicities evaluated. Of the 203 chemicals in the 2 groups, those positive in the rodent two-species life-span carcinogenicity study (rodent assay) were 53%, those positive in the Ames test (mutagenicity) were 48%, and those positive in the COMPACT programme (carcinogenicity, mutagenicity, cytotoxicity) were 54%. Concordance between the COMPACT prediction of carcinogenicity/cytotoxicity and rodent two species life-span carcinogenicity data for the 203 chemicals is 69%, and correlation of COMPACT with Ames test data is 61%. The sensitivity of COMPACT for predicting rodent carcinogenicity is 72%, whereas the sensitivity of the Ames test for predicting carcinogenicity for the 203 chemicals was only 57%. The degree (severity) of rodent carcinogenicity also showed correlation with the COMPACT predictive evaluations of the chemicals.
Collapse
Affiliation(s)
- D F Lewis
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | |
Collapse
|
48
|
Abstract
Agaritine (N2-[L-(+)-glutamyl]-4-(hydroxymethylphenyl)hydrazine), the principal hydrazine found in the edible mushroom Agaricus bisporus, as well as the N'-acetyl derivative of 4-(hydroxymethyl)phenylhydrazine and 4-(hydroxymethyl)benzene diazonium ion, as the tetraborate salt, considered as the putative proximate and ultimate carcinogens of agaritine, were all synthesised chemically. The mutagenicity of these compounds and of 4-hydrazinobenzoic acid, a precursor of agaritine biosynthesis in mushroom, was investigated in the Ames test, using Salmonella typhimurium strain TA104, in the absence and in the presence of either mushroom tyrosinase or rat hepatic cytosol as activation systems. In the absence of an activation system the diazonium ion was clearly the most mutagenic of the four compounds studied. When tyrosinase was used as activation system, the mutagenicity of N'-acetyl-4-(hydroxymethyl)phenylhydrazine was enhanced; glutathione and superoxide dismutase markedly suppressed the mutagenic response. When the mutagenicity of the four compounds was evaluated in the presence of rat hepatic cytosol, an increase was seen only in the case of N'-acetyl-4-(hydroxymethyl)phenylhydrazine; this was shown to be due to deacetylation releasing the more mutagenic free hydrazine. Collectively, the above data are compatible with an activation of agaritine that involves an initial loss of the gamma-glutamyl group followed by microsomal oxidation of the free hydrazine to generate the diazonium ion. Also of interest is the observation that mushroom tyrosinase can convert N'-acetyl-4-(hydroxymethyl)phenylhydrazine to mutagenic product(s); whether these products contribute to the mutagenicity of mushroom extracts remains to be established.
Collapse
Affiliation(s)
- K Walton
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | |
Collapse
|
49
|
Lewis DF, Brantom PG, Ioannides C, Walker R, Parke DV. Nitrosamine carcinogenesis: rodent assays, quantitative structure-activity relationships, and human risk assessment. Drug Metab Rev 1997; 29:1055-78. [PMID: 9421685 DOI: 10.3109/03602539709002243] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- D F Lewis
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | | | |
Collapse
|
50
|
Walton K, Coombs MM, Catterall FS, Walker R, Ioannides C. Bioactivation of the mushroom hydrazine, agaritine, to intermediates that bind covalently to proteins and induce mutations in the Ames test. Carcinogenesis 1997; 18:1603-8. [PMID: 9276636 DOI: 10.1093/carcin/18.8.1603] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The present study was undertaken to establish whether liver and kidney enzyme systems, from rat and mouse, have the potential to metabolise and bioactivate agaritine, beta-N-(gamma-L(+)glutamyl)-4-(hydroxymethyl)phenylhydrazine, the most abundant hydrazine present in the edible mushroom Agaricus bisporus. Agaritine was weakly mutagenic, in the absence of an activation system, in Salmonella typhimurium strain TA104. Rat kidney homogenates, characterised by high gamma-glutamyl transpeptidase activity, enhanced the mutagenic response. In contrast, hepatic microsomes, having very low gamma-glutamyl transpeptidase activity, did not influence the mutagenicity of agaritine. However, hepatic microsomes could further potentiate the mutagenic response induced by the kidney. Agaritine was a good substrate for purified gamma-glutamyl transpeptidase, being converted to a major metabolite, 4-(hydroxymethyl)phenylhydrazine, formed as a result of the loss of the glutamyl moiety. Kidney homogenates from the rat and mouse also catalysed this reaction, the former being the more effective. Metabolism of agaritine was suppressed by serine-borate, an inhibitor of gamma-glutamyl transpeptidase. Kidney homogenates from rat and mouse could metabolise agaritine to intermediate(s) that bound covalently to proteins, with the rat preparations being the more effective; covalent binding was inhibited by glutathione. In contrast, hepatic preparations alone were ineffective in producing such covalent binding but did further increase the covalent binding mediated by the kidney preparations. It is concluded that rat and mouse kidney homogenates catalyse the removal of the glutamyl group from agaritine to yield the reactive free hydrazine, which is further converted to the highly reactive diazonium ion by hepatic microsomes.
Collapse
Affiliation(s)
- K Walton
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | | | | | | | |
Collapse
|