In vitro inhibition of CYP2B1 monooxygenase by myrcene and other monoterpenoid compounds
Department of Biological Sciences, The National School for Public Health, Oswaldo Cruz foundation, Rio de Janeiro, Brazil. Toxicology Letters
(Impact Factor: 3.26).
06/1997; 92(1):39-46. DOI: 10.1016/S0378-4274(97)00034-9
beta-myrcene (MYR) is an acyclic monoterpene found in the essential oils of several useful plants such as lemongrass (Cymbopogon citratus), hop, bay, verbena and others. Recently it has been reported that MYR as well as lemongrass oil blocked the metabolic activation of some promutagens (e.g., cyclophosphamide and aflatoxin B1) in in vitro genotoxicity assays. The present study was performed to evaluate the inhibitory effects of MYR and some other monoterpenoid compounds on microsomal enzymes involved in the activation of genotoxic substances. The effects of MYR and other monoterpenes on the activity of pentoxyresorufin-O-depenthylase (PROD), a selective marker for CYP2B1, was determined in a pool of liver microsomes prepared from phenobarbital-treated rats. The effect of MYR on the activity of ethoxyresorufin-O-deethylase (EROD), a marker for CYP4501A1, was investigated in liver microsomes of untreated rats. Results revealed that MYR had almost no effect on EROD (IC50 > 50 microM), but produced a concentration-dependent inhibition of PROD activity (IC50 =0.14 microM). The analysis of alterations produced by MYR on PROD kinetic parameters (Lineweaver-Burk plot) suggested that inhibition is competitive (Ki = 0.14 microM). The inhibitory effects of seven other monoterpenes on PROD activity (pentoxyresorufin 5 microM) were also studied and the IC50 were as follows: (-)-alpha-pinene, 0.087 microM; (+)-alpha-pinene, 0.089 microM; d-limonene, 0.19 microM; alpha-terpinene, 0.76 microM; citral, 1.19 microM; citronellal, 1.56 microM, and (+/-) camphor, 7.89 microM. The potent inhibitory effects on CYP4502B1 suggest that MYR, and other monoterpenes, interfere with the metabolism of xenobiotics which are substrates for this isoenzyme.
Available from: Efrosini Katsanou
- "To investigate enzyme activity of CYP1A1, relevant enzyme activities were assessed through the CYP1A1-specific deethylation of ethoxyresorufin , as shown in Fig. 2. Microsomes from hepatic tissues of rats exposed to high dose of caffeine (100 mg/kg b.w./day) showed a statistically significant increase in EROD activity in relation to control (3.1-fold). In contrast, high dose of CMGE (2000 mg/kg b.w./day) did not cause a similar induction of activity in relation to control. "
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ABSTRACT: Chios mastic gum (CMG), a resin derived from Pistacia lentiscus var. chia, is known since ancient times for its pharmacological activities. CYP1A1 and CYP1A2 enzymes are among the most involved in the biotransformation of chemicals and the metabolic activation of pro-carcinogens. Previous studies referring to the modulation of these enzymes by CMG have revealed findings of unclear biological and toxicological significance. For this purpose, the modulation of CYP1A1 and CYP1A2 enzymes in the liver of male Wistar rats following oral administration of CMG extract (CMGE), at the levels of mRNA and CYP1A1 enzyme activity, was compared to respective enzyme modulation following oral administration of a well-known bioactive natural product, caffeine, as control compound known to involve hepatic enzymes in its metabolism. mRNA levels of Cyp1a1 and Cyp1a2 were measured by reverse transcription real-time polymerase chain reaction and their relative quantification was calculated. CYP1A1 enzyme induction was measured through the activity of ethoxyresorufin-O-deethylase (EROD). The results indicated that administration of CMGE at the recommended pharmaceutical dose does not induce significant transcriptional modulation of Cyp1a1/2 and subsequent enzyme activity induction of CYP1A1 while effects of the same order of magnitude were observed in the same test system following the administration of caffeine at the mean daily consumed levels. The outcome of this study further confirms the lack of any toxicological or biological significance of the specific findings on liver following the administration of CMGE.
Available from: Edson L. L. Baldin
- "Enan (2001) suggested that the toxicity of essential oil constituents is related to the octopaminergic nervous system of the insects. On the other hand, De Oliveira et al. (1997) mentioned that some monoterpenes may inhibit cytochrome P-450-dependent monooxygenases (De Oliveira et al. 1997 "
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ABSTRACT: The sweet potato whitefly, Bemisia tabaci Gennadius biotype B (Hemiptera: Aleyrodidae), causes high economic losses in vegetables, beans, soybeans, peanuts, cotton, and several ornamental plants. Repeated spray applications of synthetic pesticides has led B. tabaci to develop resistance to numerous conventional insecticides, besides polluting the environment. In this work, we investigated the bioactivity of the essential oil of Pelargonium graveolens L’Her (Geraniaceae) (PG-EO) and some related monoterpenes against the sweet potato whitefly Bemisia tabaci Gennadius biotype B (Homoptera: Aleyrodidae) in tomato. This oil significantly reduced the number of B. tabaci adults on tomato leaflets. The deterrence experiments showed similar results for PG-EO, geraniol, and citronellol; however, citronellol was more effective than PG-EO. In fumigation tests, the essential oil of P. graveolens caused 100 % mortality of adults of B. tabaci biotype B at concentrations from 0.5 μL L−1 in air. The vapor toxicity of geraniol, linalool, and citronellol, the main chemical constituents of the essential oil of P. graveolens (PG-EO), was similar to that of PG-EO. These results suggest that PG-EO and its related monoterpenes are potentially applicable to develop effective natural product-based pest-management compounds.
Available from: Renato Carvalho
- "Liver microsomal fraction I (MF I) was prepared as described previously , except for the use of 100 mM Tris 150 mM KCl buffer solution pH 7.4 instead of the sucrose solution. Aliquots of MF I were stored at -80°C until further use. "
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ABSTRACT: The mechanisms by which malaria up and down-regulates CYP activities are not understood yet. It is also unclear whether CYP activities are modulated during non-lethal malaria infections. This study was undertaken to evaluate the time course of CYP alterations in lethal (Plasmodium berghei ANKA) and non-lethal (Plasmodium chabaudi chabaudi) murine malaria. Additionally, hypotheses on the association of CYP depression with enhanced nitric oxide (NO) production, and of CYP2a5 induction with endoplasmic reticulum dysfunction, enhanced haem metabolism and oxidative stress were examined as well.
Female DBA-2 and C57BL/6 mice were infected with P.berghei ANKA or P. chabaudi and killed at different post-infection days. Infection was monitored by parasitaemia rates and clinical signs. NO levels were measured in the serum. Activities of CYP1a (ethoxyresorufin-O-deethylase), 2b (benzyloxyresorufin-O-debenzylase), 2a5 (coumarin-7-hydroxylase) and uridine-diphosphoglucuronyl-transferase (UGT) were determined in liver microsomes. Glutathione-S-transferase (GST) activity and concentrations of gluthatione (GSH) and thiobarbituric acid-reactive substances (TBARS) were determined in the liver. Levels of glucose-regulated protein 78 (GRP78) were evaluated by immunoblotting, while mRNAs of haemoxygenase-1 (HO-1) and inducible nitric oxide synthase (iNOS) were determined by quantitative RT-PCR.
Plasmodium berghei depressed CYP1a and 2b and induced 2a5 in DBA-2 mice. In P.berghei-infected C57BL/6 mice CYP activities remained unaltered. In both strains, GST and UGT were not affected by P.berghei. Plasmodium c. chabaudi depressed CYP1a and 2b and induced 2a5 activities on the day of peak parasitaemia or near this day. CYP2a5 induction was associated with over-expression of HO-1 and enhanced oxidative stress, but it was not associated with GRP78 induction, a marker of endoplasmic reticulum stress. Plasmodium chabaudi increased serum NO on days near the parasitaemia peak in both strains. Although not elevating serum NO, P.berghei enhanced iNOS mRNA expression in the liver.
Down-regulation of CYP1a and 2b and induction of 2a5 occurred in lethal and non-lethal infections when parasitaemia rates were high. A contribution of NO for depression of CYP2b cannot be ruled out. Results were consistent with the view that CYP2a5 and HO-1 are concurrently up-regulated and suggested that CYP2a5 induction may occur in the absence of enhanced endoplasmic reticulum stress.
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