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Biotecnologia Aplicada
Elfos Scientiae
ISSN: 0684-4551
Vol. 18, Num. 2, 2001, pp. 88-90
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Biotecnología Aplicada
Biotecnología Aplicada, Vol. 18, No. 2, April 2001, pp. 88-90
D-002: Effects on Hepatic Drug Metabolizing Enzyme Activities in Rats
Idania Rodeiro*, Celia Alemán, Rosa Más, Caridad P Acosta, Rafael Gámez
Department of Toxicology. Center of Natural Products. National Center
for Scientific Research. Ave 25. and 158, Playa, Ciudad de La Habana, Cuba.
*Autor de correspondencia
Recibido en agosto del 2000. Aprobado en febrero del 2001
Code Number: BA01013
ABSTRACT
D-002 is a new natural drug from beeswax with anti-inflammatory
and anti-ulcer effects proved in different experimental animal models. Pre-clinical
toxicology of D-002 showed no drug-related toxicity. The present study was performed
to evaluate the effects of D-002 on drug-metabolizing enzymes (Fase I) in male
Sprague Dawley rats. The content of P-450 and b5 cytochromes and the activities
of the NADPH cytochrome c reductase, aminopyrine N-demethylase,
N-dimethylnitrosamine dealkylase, were determined. The biotransformation
of benzo(a)pyrene was evaluated by using the Ames test. The results demonstrate
that D-002 administered orally at dosis of 50 to 1000 mg/kg/day for one
month does not affect the activities of the hepatic drug-metabolizing enzymes
investigated. Positive controls treated with phenobarbital and b-naphthoflavone
showed significant differences.
Keywords: D-002, hepatic drug-metabolizing enzymes, Sprague Dawley rats
RESUMEN
D-002: efectos sobre la actividad de las enzimas hepáticas metabolizadoras
de medicamentos en ratas. En este trabajo se evaluaron los posibles efectos
de D-002, un nuevo producto natural aislado y purificado de la cera de las abejas
que presenta actividad antiinflamatoria y antiulcerosa en diferentes modelos
animales experimentales. El estudio toxicológico preclínico no mostró toxicidad
relacionada con el medicamento. El presente trabajo se realizó con el objetivo
de estudiar los posibles efectos del producto sobre algunas enzimas microsomales
hepáticas de fase I en ratas macho Sprague Dawley. Se evaluaron los efectos
sobre el contenido total de citocromo P-450, citocromo b5 y sobre las actividades
de las enzimas citocromo c-reductasa dependiente de NADPH, aminopirina-desmetilasa
y N-dimetilnitrosamina-desalquilasa. Además, se evaluaron los efectos
del producto sobre la biotransformación del benzo(a)pireno mediante la prueba
de Ames. Los resultados demuestran que la administración de dosis orales de
D-002 (50-1 000 mg/kg/día) durante 30 días no modifica el contenido de
los citocromos P-450 y b5, ni la actividad enzimática de los sistemas estudiados.
Sin embargo, las fracciones microsomales procedentes de los animales del grupo
utilizado como control positivo que fue tratado con fenobarbital y b-benzoflavona,
sí mostraron los cambios esperados en todos los casos.
Palabras claves: D-002, enzimas hepáticas metabolizadoras de medicamentos,
ratas Sprague Dawley
Introduction
D-002 is a mixture of primary aliphatic alcohols of high molecular
weight isolated and purified from beeswax (Apis mellifera). It contains
triacontanol followed by octacosanol, dotriacontanol, hexacosanol and tetracontanol,
and tetratriacontanol as a minor component. D-002 has shown mild anti-inflammatory
activity [1] and effective anti-ulcer effects in different experimental animal
models [2, 3]. D-002 administered orally at 5 to 50 mg/kg prevented ulcers experimentally
induced by ethanol (60%), HCl (0.6 M) and indometacin. It also inhibits
ulcers induced in pylorus-ligated rats [2]. These anti-ulcer effects seem to
be mediated by a reinforcement of the gastric mucosa defensive mechanisms [3].
Acute, subchronic and chronic toxicity studies in rats did not show
any drug-related toxicity [4, 5]. Likewise, in vitro and in vivo mutagenicity
studies did not show genotoxic effects on somatic or germinal cells [6]. Some
anti-ulcer drugs like H2 antagonists and the Na+/K+ pump inhibitors act as inductors
or inhibitors of different families of the hepatic mixed-function oxidase system
[7. 9], which implies that the study of drug-metabolizing enzyme activities
of new drugs with anti-ulcer effects is still justified.
The aim of this research was to study whether D-002 administered
orally at 50. 1000 mg/kg/day for one month affects the activity of this
oxidase system in male Sprague Dawley rats.
Materials and Methods
Chemicals
All chemicals were of analytical reagent grade. Phenobarbital,
NADP and NADH (sodium salts) were obtained from BDH (UK). Acacia gum, b-naphthoflavone,
glucose-6-phosphate, glucose-6-phosphate dehydrogenase, cytochrome c, NADPH,
aminopyrine, dimethylnitrosamine, benzo(a)pyrene and sodium dithionite were
purchased from Sigma (St. Louis, MO, USA).
Animals
Male Sprague Dawley rats weighing 150 to 200 g were obtained from
the Centro Nacional para la Producción de Animales de Laboratorio (CENPALAB,
Havana, Cuba). Animals were adapted to experimental conditions.
The water and food (rat standard chow, supplied by CENPALAB) were
supplied ad libitum.
Administration, dosage and experimental
groups
Relative concentrations of each alcohol in the D-002 batch were:
triacontanol (26.63%), octacosanol (17.49%), dotriacontanol (16.95%), hexacosanol
(15.39%), tetracosanol (13.24%) and tetratriacontanol (2.23%). All the suspensions
were prepared daily in acacia gum-water vehicle (10 mg/kg). The drugs were
administered daily for a month by oral gavage.
Three experimental groups of 12 animals each were treated with 50,
500 and 1 000 mg/kg/day of D-002. Control rats received by gavage similar
volumes of the vehicle used in the preparation of the suspensions. Other two
animal groups were administered in the study: one was used as positive control
and was administered with phenobarbital and b-naphthoflavone according to INVITTOX
Protocol [10]; the other was used as negative control and received no treatment.
Twenty-four hours after the last dose, each rat was weighed, sacrificed
by cervical dislocation, bled and placed on its back on an autopsy board. Livers
were removed, weighed and used for microsome preparation. The weight of the
liver was used to obtain the percent of organ weight relative to body weight
(%).
It was calculated as follows:
% = weight of liver/body weight x 100
Preparation of microsomes
Liver samples (5 g) from three animals were homogenized in three
volumes of ice-cold 1.15% KCl using a Polytron homogenizer. The cell debris,
nuclei and mitochondria were removed by centrifugation at 9 000 xg
for 20 min at 0. 4 ºC. The supernatant was ultracentrifuged at 100 000
xg for 60 min at 0. 4 ºC. The pellet was resuspended in ice-cold
0.1 mol/L Tris-HCl buffer, pH 7.4 containing 0.175 mmol/L KCL and
0.2 mmol/L EDTA. Aliquots of 1 mL of microsomal fractions were quickly
stored at -80 ºC until usage. Sterility of the preparation was determined
by plating 0.1 mL on minimal agar containing histidine and biotin.
Microsomal proteins were determined according to the method of Lowry
et al. [11]. P-450 and b5 cytochromes were determined by the method of
Omura and Sato [12], and NADPH cytochrome c reductase activity as described
by Williams and Kamin [13]. Aminopyrine demethylase activity was measured through
formaldehyde formation according to the method of Nash [14] and dimethylnitrosamine
N-demethylase according to Weibel et al. [15].
Ames mutagenicity test was used as indicator of the benzo(a)pyrenohydroxilase
activity. The bacteria (Salmonella typhimurium, TA38 strain), the benzo(a)pyrene
(10 and 20 mL/plate), the cofactors and the activation system (containing 20%
v/v liver microsomes) were incubated at 37 ºC for 48 h [16].
Statistical analysis
Data are presented as mean values ± standard deviations of the
mean. Comparisons between groups were performed using the Mann-Whitney test,
with a= 0.05 selected a priori for statistical significance.
Results and Discussion
In this study, the effects of a new mixture of higher primary aliphatic
alcohols on the microsomal mixed-funtion oxidase system in rats were investigated.
The effects of repeated oral doses of D-002 during a month on the parameters
measured are shown in Tables 1 and 2. As it can be observed,
D-002 did not affect liver weight, which is in agreement with the results of
previous toxicological studies conducted in Sprague Dawley rats [5]. No differences
were observed between treated and control groups relating to the rest of the
parameters measured. These results show that D-002 did not affect hepatic microsomal
drug-metabolizing enzyme activity even at 1 000 mg/kg/day.
Table 1. Effects of oral administration of D-002 during a month
to male Sprague Dawley rats on hepatic microsomal drug metabolizing enzyme activity.
Group
|
Liver weight (%)
|
Protein (mg/kg)
|
Cytochrome
P-450 (nmol/mg)
|
Cytochrome b5 (nmol/mg)
|
Control (-)
|
2.52 ± 0.28
|
25.6 ± 0.8
|
0.41 ± 0.05
|
0.43 ± 0.07
|
Control (+)
|
3.82 ± 0.24*
|
31.2 ± 2.1*
|
1.76 ± 0.15*
|
0.73 ± 0.08*
|
Control vehicle
|
2.52 ± 0.15
|
26.7 ± 2.9
|
0.47 ± 0.13
|
0.50 ± 0.10
|
D-002
|
|
|
|
|
50 mg/kg
|
2.62 ± 0.20
|
26.8 ± 0.8
|
0.47 ± 0.10
|
0.52 ± 0.11
|
500 mg/kg
|
2.60 ± 0.21
|
28.6 ± 2.1
|
0.51 ± 0.10
|
0.52 ± 0.09
|
1000 mg/kg
|
2.69 ± 0.29
|
29.0 ± 2.1
|
0.46 ± 0.05
|
0.49 ± 0.10
|
|
NADPH cyt c reductase (nmol/mg/min)
|
Aminopyrine demethylase
(nmol/g liver)
|
Dimethylnitrosamine dealkylase (nmol/mg/min)
|
Control (-)
|
15.6 ± 2.8
|
0.12 ± 0.03
|
0.08 ± 0.01
|
Control (+)
|
26.7 ± 9.4*
|
0.46 ± 0.10*
|
0.15 ± 0.03*
|
Control vehicle
|
14.5 ± 2.1
|
0.11 ± 0.05
|
0.09 ± 0.01
|
D-002
|
|
|
|
50 mg/kg
|
14.8 ± 3.1
|
0.09 ± 0.02
|
0.08 ± 0.02
|
500 mg/kg
|
15.7 ± 1.6
|
0.12 ± 0.02
|
0.08 ± 0.01
|
1000 mg/kg
|
14.6 ± 3.6
|
0.14 ± 0.03
|
0.09 ± 0.03
|
Control (-): microsomal fraction obtained from non-treated animals.
Control (+): microsomal fraction obtained from animals treated with phenobarbital
and b -napthoflavone. %: percent of the liver weight relative to body weight.
Results as mean ± SD, Mann Whitney U test, *p < 0.05.
Table 2. Results of oral administration of D-002 during a month
to male Sprague Dawley rats on the benzo(a)pyrene biotransformation using the
Ames test.
|
Concentration
of benzo(a)pyrene
|
10 µL/plate
|
20 µL/plate
|
S9 mix from non-treated animals
|
25.3 ± 2.5
|
24.6 ± 0.6
|
S9 mix from induced animals
|
47.0 ± 6.2*
|
77.3 ± 2.1*
|
S9 mix from vehicle treated animals
|
22.0 ± 1.7
|
24.6 ± 1.5
|
S9 mix from 50 mg/kg treated animals
|
22.6 ± 1.7
|
23.7 ± 0.6
|
S9 mix from 500 mg/kg treated animals
|
20.3 ± 6.5
|
22.3 ± 0.6
|
S9 mix from 1000 mg/kg treated animals
|
22.6 ± 2.3
|
24.3 ± 1.5
|
The data represent the number of revertant colonies/plate of almost
three independent experiments (3 plates/dose), (x ± SD). The strain of Salmonella
typhimurium used was TA38, S9 mix contained 20% v/v liver microsomes
and cofactors. Mann Whitney U test, *p < 0.05.
The total content of the cytochromes P-450 and b5 was not modified
indicating that D-002 did not act through a direct interaction with them. No
significant difference in the NADPH-dependent reduction of cytochrome c was
detected, which indicates that D-002 did not interfere with the electron flow
to the cytochromes. Likewise, the forms of the cytochromes P-450 responsible
for the biotransformation of the substrates used were not increased nor decreased.
In this case, we determined the activity of CYP3A, CYP2E and CYP1A enzymes through
the biotransformation of benzo(a)pyrene using the Ames test. These represent
some of the main isoenzymes of this superfamily of proteins with toxicological
or clinical implications [17].
By contrast, the expected increase in these parameters in rats
treated with phenobarbital and b-benzoflavona was observed. These findings support
the validity of the methodologies and conditions used in this work.
Few studies have been performed to gain insight into the biotransformation
of these very long chain aliphatic alcohols. Nevertheless, results of pharmacokinetic
and metabolic studies have suggested that they may be partly oxidized and degraded
to fatty acids through b-oxidation, although no strong evidences are available
[18, 19]. Previous studies performed with policosanol (another mixture of very
long chain aliphatic alcohols) demonstrated that treatment with this drug does
not interfere with the activity of the drug-metabolizing enzymes in rats nor
in dogs [20, 21]. These premises and the results of this work suggest that the
metabolism of this kind of chemicals does not induce changes on the hepatic
microsomal system.
On the other hand, H2 antagonists and Na+/K+ pump inhibitors affect
the content of cytochrome P-450 and the several enzymatic activities of these
monooxygenase systems in rat liver microsomes [7, 9]. However, D-002 did not
affect hepatic microsomal drug-metabolizing enzyme activities, which is not
surprising because the anti-ulcer action mechanism of D-002 differs from that
of these drugs.
The microsomal cytochrome P-450 dependent mixed-function oxidase
system comprises a superfamily of protein with one or more isoenzymes each [22,
23]. Many chemicals may lead to selective increase or decrease of the activities
of one or more families. This is very important in pre-clinical assays of new
drugs because it could be relevant for clinical use [24]. Drug interactions
during therapy may lead to significant toxicity or treatment failure and one
of the primary mechanisms for the development of interactions is the perturbation
of one or multiple hepatic enzymes that make up the cytochrome P-450 detoxifying
system. In addition, the information on whether the drug can adversely affect
an enzyme pathway will also help to anticipate potential drug interactions.
The results of this study indicate that D-002 does not induce
any changes on the hepatic drug-metabolizing activities measured.
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