Drug
Metabolism Letters
ISSN: 1872-3128
Drug Metabolism Letters
Volume 4, Number 3, August 2010
Contents
Evaluation of Cytochrome P450 Inhibition
Assays Using Human Liver Microsomes by a Cassette Analysis
/LC-MS/MS Pp. 120-128
S. Zambon, S. Fontana and
M. Kajbaf
[Abstract] [Purchase
Article] [PMID:
20642444 PubMed - indexed for MEDLINE]
Induction of CYP2B6 and CYP3A4 Expression by 1-Aminobenzotriazole
(ABT) in Human Hepatocytes Pp. 129-133
K. Yang, K.H. Koh and
H. Jeong
[Abstract] [Purchase
Article] [PMID:
20642445 PubMed - indexed for MEDLINE]
Schistosoma mansoni Changes the Activity
of Phase II Drug-Metabolizing Enzymes: Role of Praziquantel
as Antibilharzial Drug Pp. 134-138
S.A. Sheweita, M. Hassan and
S.A. Bahashwan
[Abstract] [Purchase
Article] [PMID:
20642446 PubMed - indexed for MEDLINE]
L-4F Differentially Alters Plasma Levels of Oxidized
Fatty Acids Resulting in more Anti-Inflammatory HDL in Mice
Pp. 139-148
S. Imaizumi, V. Grijalva, M. Navab, B.J. Van Lenten,
A.C. Wagner, G.M. Anantharamiah, A.M. Fogelman and
S.T. Reddy
[Abstract]
[Supplementary Material]
[Full Text Article]
[PMID:
20642447 PubMed - indexed for MEDLINE]
Pharmacokinetics, Disposition, and Metabolism of [14C]-Nebicapone
in Humans Pp. 149-162
L.C. Wright, J. Maia, A.I. Loureiro,
L. Almeida and P. Soares-Da-Silva
[Abstract] [Purchase
Article] [PMID:
20642448 PubMed - indexed for MEDLINE]
Multiple Species Metabolism of PHA-568487, A Selective
α7 Nicotinic Acetylcholine Receptor Agonist Pp.
163-172
F.B. Shilliday, D.P. Walker, C. Gu,
X. Fang, B. Thornburgh, G.D. Fate and J.S.
Daniels
[Abstract] [Purchase
Article] [PMID:
20642449 PubMed - indexed for MEDLINE]
The Effect of Licorice Drink on the Systemic Exposure
of Verapamil in Rabbits Pp. 173-179
I.D. Al-Deeb, T.A. Arafat and
Y.M. Irshaid
[Abstract] [Purchase
Article] [PMID:
20642450 PubMed - indexed for MEDLINE]
Morphologic Characterization of PhoenixBio®
(uPA+/+/SCID) Humanized Liver
Chimeric Mouse Model Pp. 180-184
R.A. Peterson, D.L. Krull, H.R. Brown
and M. de Serres
[Abstract] [Purchase
Article] [PMID:
20642451 PubMed - indexed for MEDLINE]
Abstracts
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[Purchase
Article] [PMID:
20642444 PubMed - indexed for MEDLINE]
Evaluation of Cytochrome P450 Inhibition Assays Using Human
Liver Microsomes by a Cassette Analysis /LC-MS/MS
S. Zambon, S. Fontana and
M. Kajbaf
In vitro inhibition assays are used to screen
new chemical entities (NCEs) for inhibition studies by using
human liver microsomes. High-throughput inhibition assays
using pooling methods have been developed to keep pace with
screening requirements at the lead ADME stage. This method
can determine IC50 NCEs using
microsomes from various organs from any species. A cassette
analysis inhibition assay for five of the major CYP enzymes
(phenacetin for CYP1A2, diclofenac for CYP2C9, (S)-mephenytoin
for CYP2C19, bufurarol for CYP2D6 and midazolam, nifedipine
and atorvastatin for CYP3A4) in pooled human liver microsomes
using ultraperformance liquid chromatography tandem mass spectrometry
(LC/MS/MS) were developed. The major metabolites of seven
CYP-specific probe substrates for the five P450 isoforms were
monitored and quantified to determine IC50
values. Human liver microsomal incubation samples at each
test compound concentration were combined and analyzed simultaneously
by the LC/MS/MS method. The incubation was performed using
the selective CYP inhibitors for each isoform: fluvoxamine
(CYP1A2), sulphaphenazole (CYP2C9), ticlopidine (CYP2C19),
quinidine (CYP2D6), and Ketoconazole (CYP3A4). Similar IC50
results were obtained using the cassette analysis and discrete
analysis method. The IC50
values determined for typical CYP inhibitors were reproducible
and consistent with those reported in the literature. The
assay was fully automated in 96 well plate formats using Microlab
4000 series (Hamilton) coupled with two termomixer comfort
(Eppendorf). An overall 70% time savings was achieved by pooling
four isoforms samples (1A2, 2C9, 2C19 and 2D6) into one sample
and also by pooling three CYP 3A4 substrate
samples (MDZ, ATR, NIF) into one sample. Cassette analysis
minimized the number of injections on LC/MS/MS analysis which
results in a decrease in the LC/MS/MS analysis time.
[Back to top] [Purchase
Article] [PMID:
20642445 PubMed - indexed for MEDLINE]
Induction of CYP2B6 and CYP3A4 Expression by 1-Aminobenzotriazole
(ABT) in Human Hepatocytes
K. Yang, K.H. Koh and
H. Jeong
1-Aminobenzotriazole (ABT) has been widely used in drug development
process as an irreversible inhibitor of CYP enzymes. One potential
use of ABT is to potentiate pharmacological effects of rapidly-metabolized
drugs on CYP expression by inhibiting their metabolism; however,
ABT’s own effects on CYP expression have been unknown.
In this study, we show that ABT up-regulates expression of
CYP2B6 and CYP3A4 potentially by activating nuclear receptor
CAR. In freshly isolated human hepatocytes, ABT increased
mRNA expression of CYP2B6 and CYP3A4 in a concentration-dependent
manner. ABT also modulated CYP-inducing actions of CITCO and
rifampin, the known inducers of CYP2B6 and CYP3A4. Results
from luciferase reporter assays confirmed that ABT increases
CYP2B6 promoter activity in CAR-expressing HepG2 cells. These
results suggest that the use of ABT as a potentiator of pharmacological
effects of rapidly-metabolized drugs is limited due to its
own pharmacological actions on CYP expression as a CAR activator.
[Back to top] [Purchase
Article] [PMID:
20642446 PubMed - indexed for MEDLINE]
Schistosoma mansoni Changes the Activity
of Phase II Drug-Metabolizing Enzymes: Role of Praziquantel
as Antibilharzial Drug
S.A. Sheweita, M. Hassan and
S.A. Bahashwan
Schistosomiasis is one of the major health problems in many
developing countries and causes liver damage. In addition,
under the influence of schistosomaisis, most of the endogenous
toxic compounds can be conjugated with glutathione via glutathione
S-transferase. Therefore, the present study showed the effect
of Schistosoma mansoni after 20, 30, 45, 60, and
75 days post-infection on the activity of glutathione-S-transferase
(GST) and glutathione reductase (GR), and on the levels of
glutathione [GSH] in the livers of male mice. In addition,
anti-schistosomal drug (praziquantel) was administered orally
[60 mg/kg body weight] for three consecutive days before decapitation
of the infected mice at each time point. In the present, depletion
of GSH levels was observed at 45, 60 and 75 days post-infection.
However, treatment of infected mice at 45, 60, and 75 days
post-infection with praziquantel for three consecutive days
before decapitation at each time point restored the increased
GSH levels to their normal values compared with control groups.
Inhibition of GST and induction of GR activities in the livers
of S. mansoni-infected mice at all time-points were
restored to their normal levels after praziquantel treatment.
It is concluded that S. mansoni infection changed
the activities of GST, GR and GSH levels. Moreover, it has
been found that praziquantel treatment of S. mansoni-infected
mice restored such alterations to their normal values and
this recovery could alleviate the deleterious effects of
S. mansoni infection. In addition, the present study
could provide new evidence to the damage occurred in livers
of S. mansoni-infected hosts. Also, it is suggested
that praziquantel is the best drug of choice for schistosoma
mansoni treatment.
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[Supplementary Material]
[Full Text Article]
[PMID:
20642447 PubMed - indexed for MEDLINE]
L-4F Differentially Alters Plasma Levels of Oxidized
Fatty Acids Resulting in more Anti-Inflammatory HDL in Mice
S. Imaizumi, V. Grijalva, M. Navab, B.J. Van Lenten,
A.C. Wagner, G.M. Anantharamiah, A.M. Fogelman and
S.T. Reddy
To determine in vivo if L-4F differentially alters
plasma levels of oxidized fatty acids resulting in more anti-inflammatory
HDL. Injecting L-4F into apoE null mice resulted in a significant
reduction in plasma levels of 15-HETE, 5-HETE, 13-HODE and
9-HODE. In contrast, plasma levels of 20-HETE were not reduced
and plasma levels of 14,15-EET, which are derived from the
cytochrome P450 pathway, were elevated after injection of
L-4F. Injection of 13(S)-HPODE into wild-type C57BL/6J
mice caused an increase in plasma levels of 13-HODE and 9-HODE
and was accompanied by a significant loss in the anti-inflammatory
properties of HDL. The response of atherosclerosis resistant
C3H/HeJ mice to injection of 13(S)-HPODE was similar
but much more blunted. Injection of L-4F at a site different
from that at which the 13(S)-HPODE was injected resulted
in significantly lower plasma levels of 13-HODE and 9-HODE
and significantly less loss of HDL anti-inflammatory properties
in both strains. i) L-4F differentially alters
plasma levels of oxidized fatty acids in vivo. ii)
The resistance of the C3H/HeJ strain to atherosclerosis may
in part be mediated by a reduced reaction of this strain to
these potent lipid oxidants. L-4F differentially alters plasma
levels of oxidized fatty acids in mice and the resistance
of C3H/HeJ mice to atherosclerosis may be mediated by a reduced
reaction of this strain to these potent lipid oxidants.
[Back to top] [Purchase
Article] [PMID:
20642448 PubMed - indexed for MEDLINE]
Pharmacokinetics, Disposition, and Metabolism of [14C]-Nebicapone
in Humans
L.C. Wright, J. Maia, A.I. Loureiro,
L. Almeida and P. Soares-Da-Silva
Objective: This study investigated
the absorption, distribution, metabolism and excretion (ADME)
of nebicapone [BIA 3-202; 1-(3,4-dihydroxy-5-nitrophenyl)-2-phenyl-ethanone],
a reversible catechol-O-methyltransferase (COMT)
inhibitor, in 4 healthy male subjects. Methods; This was a
single center, open, non-placebo-controlled, single-group,
and a single 200 mg dose study of [14C]-nebicapone
(2.5 MBq). Blood, urine and faeces were collected up to 264
hours post-dose. Results: Collectively more
than 22 metabolites were identified in plasma, urine and faeces,
with 3-O-nebicapone-glucuronide (BIA 3-476) identified as
the major metabolite. Plasma concentration-time profiles of
[14C]-nebicapone demonstrated
Tmax (h) 1.25±0.65,
t1/2 (h) 134.55±25.67,
Cmax (ng-eq/g) 19647.02±4930.20,
AUC0-t (h.ng-eq/g) 161735.51±9224.66,
AUC0-∞ (h.ng-eq/g)
199603.30±16854.08, and for whole blood Tmax
1.00±0.41, t1/2
32.98±22.82, AUC0-t
35539.23±13664.87, AUC0-∞
36970.64±14559.17. Plasma pharmacokinetics of nebicapone
demonstrated Tmax
(h) 1.00±0.41, t1/2
(h) 2.34±0.51; Cmax
(ng-eq/g) 12650.00±2898.85, AUC0-t
(h.ng-eq/g) 18719.96±734.18, AUC0-∞
(h.ng-eq/g) 18392.12±753.81; BIA 3-476 demonstrated
Tmax 1.25±0.50,
t1/2 3.47±0.68;
Cmax 15250±2563.20,
AUC0-t 53810.61±7358.81,
AUC0-∞ 54541.21±7135.70;
3-O-methyl-nebicapone (BIA 3-270) demonstrated Tmax
21.01±6.01 , t1/2
103.43±6.01; Cmax
286.25±20.48, AUC0-t
27641.89±4569.99, AUC0-∞
36968.12±4294.42. Conclusions: Nebicapone
and BIA 3-476 accounted for most early phase circulating nebicapone-derived
moieties, have limited circulating cell association, peak
concentrations shortly after dosing, and short body residence.
In longer terminal half-life phases low concentrations of
BIA 3-270 predominate. While about 70% of the dose was eliminated
in the urine as BIA 3-476, < 1% of the dose was excreted
as unchanged nebicapone. Faecal excretion accounted
for 17.3% administered dose. On average, the total recovery
of 88.6% of the radioactivity suggested no worrisome retention
of drug derived material following a single 200 mg administration
of nebicapone to healthy volunteers. The treatment was
very well tolerated with no reported adverse events.
[Back to top] [Purchase
Article] [PMID:
20642449 PubMed - indexed for MEDLINE]
Multiple Species Metabolism of PHA-568487, A Selective
α7 Nicotinic Acetylcholine Receptor Agonist
F.B. Shilliday, D.P. Walker, C. Gu,
X. Fang, B. Thornburgh, G.D. Fate and J.S.
Daniels
The quinuclidine PHA-0568487(1) is an agonist
of the alpha7 nicotinic acetylcholine receptor that was designed
to mitigate the bioactivation associated with the core scaffold
and subsequently remove associated liabilities with in
vivo tolerability. The drug metabolites of 1
in nonclinical species were identified in plasma and urine
of rats, dogs and monkeys receiving oral administrations of
1. The in vitro biotransformation
of 1 was subsequently investigated in multiple
species employing cryopreserved hepatocytes, hepatic subcellular
fractions and recombinantly-expressed human P450 enzymes.
In addition, in vitro metabolism of synthetically
prepared metabolite precursors were instrumental in the elucidation
of several secondary metabolites. The results indicated
that the principal biotransformation of 1
was oxidation of the benzo[1,4]dioxane moiety (M8, M10) followed
by subsequent oxidation to a range of secondary metabolites
(M1-7, M9,M11,M13-15, and M17-18). The carboxylic acids
M1 and M2 resulting from the oxidative cleavage of the dioxane
ring were the principal metabolites observed in the plasma,
urine and hepatocyte incubations across all species (M1 &
M2). Quinuclidine oxidation was another pathway of importance,
yielding an N-oxide (M12) which was also observed
in all species.P450 2D6 and FMO1 catalyze the oxidation of
the quinuclidine nitrogen. The N‑oxidation
of the quinuclidine moiety is consistent with previously published
accounts of this scaffold’s metabolism and, interestingly,
may implicate the uncommon quinuclidine moiety as an entity
directing the metabolism of this scaffold (e.g., 1)
via FMO1 and P450 2D6 oxidation.
[Back to top] [Purchase
Article] [PMID:
20642450 PubMed - indexed for MEDLINE]
The Effect of Licorice Drink on the Systemic Exposure
of Verapamil in Rabbits
I.D. Al-Deeb, T.A. Arafat and
Y.M. Irshaid
The effect of licorice root drink (aqueous extract of Glycyrrhiza
glabra Fabaceae) on plasma concentration of verapamil,
using rabbits as animal model, was investigated. Two groups
of locally inbred Newzeland male rabbits were used. The first
group was given a single dose of licorice drink (4 ml/kg body
weight) concomitantly with 30 mg/kg verapamil, and the second
group was given a daily dose of licorice drink (4 ml/kg body
weight) for two weeks, with single doses of verapamil on days,
7 and 14. Single dose treatment resulted in a nonsignificant
decrease in mean Cmax by
33.2% (P = 0.41), but in a significant decrease of AUC0-24
and AUC0-∞ by 60.5%
and 63.6%, respectively (P = 0.01). First period of multiple
dose treatment study (7 days), resulted in a significant reduction
in mean Cmax, AUC0-24
and AUC0-∞ by 55.0%,
47.0% and 45.7%, respectively (P = 0.02, 0.03 and 0.03, respectively).
A more pronounced effect was seen at second period of multiple
dose treatment study (14 days), where the corresponding decrease
was, 85.4%, 76.8% and 73.3%, respectively (P < 0.01). Mean
Tmax was significantly increased
4.2-fold over control period at day 14 of multiple dose study
(P = 0.02). In conclusion, licorice root drink decreased verapamil
systemic exposure both after single dose and after daily doses
for 14 days.
[Back to top] [Purchase
Article] [PMID:
20642451 PubMed - indexed for MEDLINE]
Morphologic Characterization of PhoenixBio®
(uPA+/+/SCID) Humanized Liver
Chimeric Mouse Model
R.A. Peterson, D.L. Krull, H.R. Brown
and M. de Serres
Morphological evaluation of humanized chimeric mouse livers
from the PhoenixBio® (uPA+/+/SCID)
mouse model show robust replacement and expansion with human
hepatocytes, however areas of human hepatocytes had prominent
steatosis and a variable lack of sinusoids which was consistent
with decreased hepatocellular perfusion and lacked bile canalicular
formation between human and mouse hepatocytes. |
