4 research outputs found
Determination of Pharmacokinetics of Chrysin and Its Conjugates in Wild-Type FVB and Bcrp1 Knockout Mice Using a Validated LC-MS/MS Method
Chrysin, a flavone found in many
plants, is also available as a
dietary supplement because of its reported anticancer activities.
However, its bioavailability is very poor due to extensive phase II
metabolism. The purpose of this study was to develop an UPLC-MS/MS
method to simultaneously quantify chrysin and its phase II metabolites,
and to determine its pharmacokinetics in FVB wild-type and Bcrp knockout
(Bcrp1 ā/ā) mice. In addition, the role of BCRP in chrysin
phase II disposition was further investigated in Caco-2 cells. The
results showed that our sensitive and reproducible UPLC-MS/MS method
was successfully applied to the pharmacokinetic study of chrysin in
wild-type and Bcrp1 (ā/ā) FVB mice after oral administration
(20 mg/kg). Although there was no significant change in systemic exposure
of chrysin and its metabolites, it was found that the <i>T</i><sub>max</sub> for chrysin glucuronide was significantly shorter
(<i>p</i> < 0.01) in Bcrp1-deficient mice. Furthermore,
it was shown that inhibition of BCRP by Ko143 significantly reduced
the efflux of chrysin sulfate in Caco-2 cells. In conclusion, BCRP
had significant but less than expected impact on pharmacokinetics
of chrysin and its conjugates, which were determined using a newly
developed and validated LC-MS/MS method
TransportāGlucuronidation Classification System and PBPK Modeling: New Approach To Predict the Impact of Transporters on Disposition of Glucuronides
Glucuronide
metabolites require the action of efflux transporters
to exit cells due to their hydrophilic properties. In this study,
we proposed a transportāglucuronidation classification system
and developed a PBPK model to predict the impact of BCRP on systemic
exposure of glucuronides. The clearance by UGTs in S9 fractions and
the efflux clearance of glucuronides by BCRP in human UGT1A9-overexpressing
HeLa cells were incorporated in the classification system and PBPK
model. Based on simulations for glucuronide AUC for theoretical compounds
in the classification system, it was indicated that BCRP was more
important for compounds with greater efflux clearance of their glucuronides
by BCRP regardless of differences in clearance by UGTs. Pharmacokinetic
studies were performed in WT and Bcrp1 (ā/ā) mice for
8 compounds to verify our predictions. Among eight compounds, the
glucuronide AUC of daidzein and genistein increased significantly
in Bcrp1 (ā/ā) mice, while only slight increases in
systemic exposure were observed for other glucuronides. The results
from pharmacokinetic studies were in agreement with the predictions
except for resveratrol, which was effluxed predominantly by transporters
other than BCRP. Therefore, for glucuronides that were predominantly
mediated by BCRP, this study provided a useful approach in predicting
the impact of BCRP on its disposition and the potential DDIs involving
BCRP
SULT1A3-Mediated Regiospecific 7-O-Sulfation of Flavonoids in Caco-2 Cells Can Be Explained by the Relevant Molecular Docking Studies
Flavonoids are polyphenolic compounds with various claimed
health
benefits, but the extensive metabolism by uridine-5ā²-diphospho-glucuronosyltransferases
(UGTs) and sulfotransferases (SULTs) in liver and intestine led to
poor oral bioavailabilities. The effects of structural changes on
the sulfonation of flavonoids have not been systemically determined,
although relevant effects of structural changes on the glucuronidation
of flavonoids had. We performed the regiospecific sulfonation of sixteen
flavonoids from five different subclasses of flavonoids, which are
represented by apigenin (flavone), genistein (isoflavone), naringenin
(flavanone), kaempherol (flavonol), and phloretin (chalcone). Additional
studies were performed using 4 monohydroxyl flavonoids with a āOH
group at the 3, 4ā², 5 or 7 position, followed by 5 dihydroxyl
flavonoids, and 2 trihydroxyl flavonoids by using expressed human
SULT1A3 and Caco-2 cell lysates. We found that these compounds were
exclusively sulfated at the 7-OH position by SULT1A3 and primarily
sulfated at the 7-OH position in Caco-2 cell lysates with minor amounts
of 4ā²-<i>O</i>-sulfates formed as well. Sulfonation
rates measured using SULT1A3 and Caco-2 cell lysates were highly correlated
at substrate concentrations of 2.5 and 10 Ī¼M. Molecular docking
studies provided structural explanations as to why sulfonation only
occurred at the 7-OH position of flavones, flavonols and flavanones.
In conclusion, molecular docking studies explain why SULT1A3 exclusively
mediates sulfonation at the 7-OH position of flavones/flavonols, and
correlation studies indicate that SULT1A3 is the main isoform responsible
for flavonoid sulfonation in the Caco-2 cells
Revolving Door Action of Breast Cancer Resistance Protein (BCRP) Facilitates or Controls the Efflux of Flavone Glucuronides from UGT1A9-Overexpressing HeLa Cells
Cellular
production of flavonoid glucuronides requires the action
of both UDP-glucuronosyltransferases (UGT) and efflux transporters
since glucuronides are too hydrophilic to diffuse across the cellular
membrane. We determined the kinetics of efflux of 13 flavonoid glucuronides
using the newly developed HeLa-UGT1A9 cells and correlated them with
kinetic parameters derived using expressed UGT1A9. The results indicated
that, among the seven monohydroxylflavones (HFs), there was moderately
good correlation (<i>r</i><sup>2</sup> ā„ 0.65) between
the fraction metabolized (<i>f</i><sub>met</sub>) derived
from HeLa-UGT1A9 cells and CL<sub>int</sub> derived from the UGT1A9-mediated
metabolism. However, there was weak or no correlation between these
two parameters for six dihydroxylflavones (DHFs). Furthermore, there
was weak or no correlation between various kinetic parameters (<i>K</i><sub>m</sub>, <i>V</i><sub>max</sub>, or CL<sub>int</sub>) for the efflux and the metabolism regardless of whether
we were using seven HFs, six DHFs, or a combination thereof. Instead,
the cellular excretion of many flavonoid glucuronides appears to be
controlled by the efflux transporter, and the poor affinity of glucuronide
to the efflux transporter resulted in major intracellular accumulation
of glucuronides to a level that is above the dosing concentration
of its aglycone. Hence, the efflux transporters appear to act as the
āRevolving Doorā to control the cellular excretion of
glucuronides. In conclusion, the determination of a flavonoidās
susceptibility to glucuronidation must be based on both its susceptibility
to glucuronidation by the enzyme and resulting glucuronideās
affinity to the relevant efflux transporters, which act as the āRevolving
Door(s)ā to facilitate or control its removal from the cells