Published
Inhibitory effect of luteolin on hepatocyte growth factor/scatter
factor -induced HepG2 cell invasion involving both MAPK/ERKs and
PI3K-Akt pathways
Abstract:
Hepatocyte growth factor (HGF), also known as scatter factor (SF), and its
receptor, the c-Met tyrosine kinase, play roles in cancer invasion and metastasis in a
wide variety of tumor cells.
Clinical observations suggest that HGF can promote
metastasis of hepatoma cells while stimulating tumor invasiveness.
We use HGF as
an invasive inducer of human hepatoma HepG2 cells to investigate the effect of
flavonoids on anti-invasion.
In our preliminary study, we investigated the effect of
flavonoids including luteolin, quercetin, baicalein, genistein, taxifolin, and catechin
on HGF-mediated migration and invasion of HepG2 cells.
We found that luteolin
presented the most potent potential on anti-migration and anti-invasion by Boyden
chamber assay.
Furthermore, luteolin inhibited HGF-induced cell scattering and
cytoskeleton change such as filopodia and lamellipodia was determined by both
phase-contrast and fluorescence microscopy studies.
In addition, Western blotting
and immunoprecipitation were performed to confirm luteolin suppressed the
phosphorylation of c-Met, the membrane receptor of HGF, as well as ERK1/2 and Akt,
but not JNK1/2, which is activated by HGF.
Our investigation demonstrated that
luteolin similar to PD98059, which acts as a specific inhibitor of MEK, an up stream
kinase regulating ERK1/2, and wortmannin, a PI3K inhibitor, inhibited the
invasiveness induced by HGF.
In conclusion, the luteolin inhibited HGF-induced
HepG2 cell invasion involving both MAPK/ERKs and PI3K-Akt pathways.
Anal. Chem., ASAP Article 10.1021/ac070675l S0003-2700(07)00675-0
Web Release Date: November 6, 2007
High-Throughput Automated Luminescent Magnetic Particle-Based
Immunoassay to Monitor Human Exposure to Pyrethroid
Insecticides
Ki Chang Ahn, Pete Lohstroh, # Shirley J. Gee, Nancy A. Gee, Bill Lasley,
and Bruce D. Hammock*
Department of Entomology and UCD Cancer Research Center, and Center for Health
and Environment, University of California, Davis, California 95616
Received for review April 5, 2007. Accepted September 18, 2007.
Abstract:
We have developed a sensitive, automated, competitive chemiluminescent
immunoassay for the detection of 3-phenoxybenzoic acid (3-PBA), a metabolite
common to many pyrethroid insecticides. The system uses a competitive
hapten-protein conjugate that has been labeled with an acridinium ester as the
chemiluminescent probe and secondary antibody-coated paramagnetic particles for
the separation. After the immunoassay reagents and samples are combined for the
competitive incubation step, a fully automated system is used to load the
postincubation mixture into a delivery cuvette, facilitating the subsequent magnetic
separation of the immunocomplex and the measurement of chemiluminescent signal
for quantification.
The immunoassay format described here supports the
requirement for high throughput necessary for monitoring large numbers of samples
in population-based studies. The optimized immunoassay was more sensitive than
the conventional enzyme immunoassay in buffer (IC50 = 0.1 and 2 g/L, respectively).
The mixed-mode solid-phase extraction used for sample preparation to reduce
possible urinary matrix effects allowed the accurate measurement of 3-PBA levels as
low as 1 g/L. The automated chemiluminescent immunoassay described here is
sensitive, simple to use, and more rapid than the previously reported standard
microplate assay.
Inorg. Chem., 46 (24), 10143 -10152.
Mononuclear and Polynuclear Copper(I) Complexes with a New
N,N',S-Donor Ligand and with Structural Analogies to the Copper
Thionein Core
Abstract:
The N,N',S-donor ligand 4-methoxy-3,5-dimethyl-2-((3-(2-(methylthio)phenyl)-1H
-pyrazol-1-yl)methyl)pyridine (L) was prepared from 2-(chloromethyl)-4-methoxy3,5-dimethylpyridine hydrochloride and 3-(2-(methylthio)phenyl)-1H-pyrazole. The
Cu(I) complexes [Cu2(L)2CH3CN] [Cu(L)CH3CN](BF4)3 (1), [Cu(L)PPh3]BF4 (2),
and [Cu6(L)2(C6F5S)6] (3) were prepared and characterized by X-ray crystallography
(PPh3 = triphenylphosphine, C6F5S- = pentafluorothiophenolate). The unit cell of
compound 1 consists of cocrystallized mononuclear and dinuclear entities in which all
of the copper atoms exhibit distorted tetrahedral coordination. Compound 2 is
monomeric with L bound in the 3-N,N',S mode and a PPh3 molecule that completes
the coordination environment. Compound 2 presents a fluxional behavior in CDCl3
solution due to the boat inversion of the six-membered N,N' chelate ring ( H =
+43.6(3) kJ mol-1, S = -16(1) J mol-1 K-1). Crystallization of 3 in acetonitrile
leads to a polynuclear structure that contains a CH3CN molecule coordinated to one of
the copper atoms: [Cu6(L)2(C6F5S)6CH3CN] (3a). The core of 3a partially resembles
a {Cu4S6} adamantane-like moiety, the only difference being that the Cu-NCCH3
interaction leads to the opening of the cluster by disrupting a Cu-Cu interaction. Part
of this assembly is found in the yeast metallothionein copper(I)-cysteinate core whose
crystal structure has recently been reported. Two additional [Cu(L)]+ peripheral
moieties interact with the cluster by means of bridging thiolates. ESI-mass
spectrometry, conductivity measurements, and 1H/19F pulsed gradient spin echo
(PGSE) NMR experiments suggest that 3a dissociates in acetonitrile solution: 3a +
CH3CN [Cu4(C6F5S)6]2- + 2[Cu(L)CH3CN]+. The stability of the cluster with
respect to the hypothetical mononuclear species, [Cu(L)(C6F5S)], is confirmed by
DFT calculations (B3LYP), which illustrate the exergonic character of the reaction:
6[Cu(L')(C6H5S)] [Cu6(L')2(C6H5S)6] + 4L' ( G298 = -58.6 kJ mol-1, where L' and
C6H5S- are simplified models for L and C6F5S-, respectively). The energetics pertinent
to the ionic dissociation of the cluster in acetonitrile is computed using the polarizable
continuum model (PCM) approach.
J. Org. Chem., 72 (24), 9060 -9066, 2007
Synthesis of -Functionalized Porphyrins via Palladium-Catalyzed
Carbon-Heteroatom Bond Formations: Expedient Entry into 
-Chiral Porphyrins
Abstract
A procedure was developed for the preparation of -monobromo-tetraphenylporphyrin
(BrTPP) in a greatly improved yield from the selective bromination of
tetraphenylpor-phyrin (TPP) by NBS.
BrTPP was successfully employed as a
versatile synthon for convenient synthesis of a wide range of -monofunctionalized
porphyrins
with
various
heteroatom
carbon-heteroatom bond formations.
functionalities
via
palladium-mediated
Examples include -amino, -amido, -oxo, and
-mercaptoporphyrins from reactions with amines, amides, alcohols, and thiols,
respectively.
Applying the synthetic approach to chiral amides, -chiral porphyrins
were effectively constructed.
Org. Lett., 9 (20), 4033 -4036, 2007.
Synthesis of the Acutumine Spirocycle via a Radical-Polar Crossover
Reaction
Abstract
A new radical-polar crossover reaction was developed that consists of intramolecular
conjugate addition of an aryl radical followed by enolate formation and hydroxylation.
A C-C bond, a C-O bond, and two congested stereocenters are created in the process.
The product is obtained as a single isomer. The method was used to synthesize the
spirocyclic subunit of the alkaloid acutumine.
Journal of Chemical Physics; 11/14/2007, Vol. 127 Issue 18
Random-phase-approximation-based correlation energy functionals:
Benchmark results for atoms.
Jiang, Hong; Engel, Eberhard
The random phase approximation for the correlation energy functional of the density
functional theory has recently attracted renewed interest. Formulated in terms of the
Kohn-Sham orbitals and eigenvalues, it promises to resolve some of the fundamental
limitations of the local density and generalized gradient approximations, as, for
instance, their inability to account for dispersion forces. First results for atoms,
however, indicate that the random phase approximation overestimates correlation
effects as much as the orbital-dependent functional obtained by a second order
perturbation expansion on the basis of the Kohn-Sham Hamiltonian. In this
contribution, three simple extensions of the random phase approximation are
examined; (a) its augmentation by a local density approximation for short-range
correlation, (b) its combination with the second order exchange term, and (c) its
combination with a partial resummation of the perturbation series including the
second order exchange. It is found that the ground state and correlation energies as
well as the ionization potentials resulting from the extensions (a) and (c) for closed
subshell atoms are clearly superior to those obtained with the unmodified random
phase approximation. Quite some effort is made to ensure highly converged data, so
that the results may serve as benchmark data. The numerical techniques developed
in this context, in particular, for the inherent frequency integration, should also be
useful for applications of random phase approximation-type functionals to more
complex systems.
Journal of Chemical Physics; 11/14/2007, Vol. 127 Issue 18
Adsorption, desorption, and diffusion of nitrogen in a model
nanoporous material. II. Diffusion limited kinetics in amorphous
solid water.
By: Zubkov, Tykhon; Smith, R. Scott; Engstrom, Todd R.; Kay, Bruce D.
The adsorption, desorption, and diffusion kinetics of N2 on thick (up to ∼9 μm)
porous films of amorphous solid water (ASW) films were studied using molecular
beam techniques and temperature programmed desorption. Porous ASW films were
grown on Pt (111) at low temperature (<30 K) from a collimated H2O beam at
glancing incident angles. In thin films (<1 μm), the desorption kinetics are well
described by a model that assumes rapid and uniform N2 distribution throughout the
film. In thicker films (>1 μm), N2 adsorption at 27 K results in a nonuniform
distribution, where most of N2 is trapped in the outer region of the film.
Redistribution of N2 can be induced by thermal annealing. The apparent activation
energy for this process is ∼7 kJ/mol, which is approximately half of the desorption
activation energy at the corresponding coverage. Preadsorption of Kr preferentially
adsorbs onto the highest energy binding sites, thereby preventing N2 from trapping in
the outer region of the film which facilitates N2 transport deeper into the porous film.
Despite the onset of limited diffusion, the adsorption kinetics are efficient, precursor
mediated, and independent of film thickness. An adsorption mechanism is proposed,
in which a high-coverage N₂ front propagates into a pore by the rapid
transport of physisorbed second layer N2 species on top of the first surface bound
layer.
Inorg. Chem., 46 (24), 10229 -10240.
Influence of Steric Hindrance on the Core Geometry and
Sulfoxidation Chemistry of Carboxylate-Rich Diiron(II) Complexes
Abstract:
The
asymmetric
terphenyl-2'-carboxylate
ligand
3,5-dimethyl-1,1':3',1'
Ph,Xyl
'-terphenyl-2'-carboxylate, O2CAr , was prepared in high yield. This ligand facilitates
the assembly of the diiron(II) complexes [Fe2( -O2CArTol)2(O2CArPh,Xyl)2(THF)2] [2, -O2CArTol
= 2,6-di-p-tolylbenzoate], [Fe2(
-O2CArTol)2(O2CArPh,Xyl)2(pyridine)2] (5), [Fe2(
-O2CArPh,Xyl)2-(O2CArPh,Xyl)2(THF)2] (3), and [Fe2( -O2CArPh,Xyl)2(O2CArPh,Xyl)2(pyridine)2] (6),
all of which have a windmill geometry. The iron-iron distance of 3.355[10] Å in 6 is ~1
Å shorter than that in the analogue [Fe2( -O2CArTol)2(O2CArTol)2(pyridine)2] (4) and similar
to the ~3.3 Å metal-metal separation at the active site of the reduced diiron(II) form of the
soluble methane monooxygenase hydroxylase enzyme (MMOHred).
A series of
t
ortho-substituted picolyl-based ligands, 2-picSMe, 2-picSEt, 2-picS Bu, 2-picSPh,
2-picSPh(Me3) (Ph(Me3) = mesityl), and 2-picSPh(iPr3) (Ph(iPr3) = 2,4,6-triisopropylphenyl),
were prepared and allowed to react with [Fe2( -O2CAr)2(O2CAr)2(THF)2] to produce [Fe2(
-O2CAr)3(O2CAr)(picSR)] (7-13, Ar = ArTol or ArPh,Xyl) complexes in 45-87% yields. The
substrates tethered to the pyridine N-donor ligands picSR, where R = Me, Et, tBu, or Ph,
coordinate to one iron atom of the diiron(II) center by the nitrogen and sulfur atoms to
form a five-membered chelate ring. The Fe-S distance becomes elongated with
increasing steric hindrance imparted by the R group. The most sterically hindered ligands,
2-picSPh(Me3) and 2-picSPh(iPr3), bind to the metal only through the pyridine nitrogen
atom. The reactions of several of these complexes with dioxygen were investigated, and
the oxygenated products were analyzed by 1H NMR spectroscopy and GC/MS
measurements following decomposition on a Chelex resin. The amount of sulfoxidation
product is correlated with the Fe···S distance. The ratio of oxidized to unoxidized
thioether substrate varies from 3.5, obtained upon oxygenation of the weakly coordinated
2-picSPh ligand in 10, to 1.0, obtained for the bulky 2-picSPh(iPr3) ligand in 12, for which
the iron-sulfur distance is >4 Å. External thioether substrates were not oxidized when
present in oxygenated solutions of paddlewheel and windmill diiron(II) complexes
containing 1-methylimidazole or pyridine ligands, respectively.
biochemical pharmacology 71 ( 2006 ) 540 – 549
Structure activity and molecular modeling analyses of ribose- and
base-modified uridine 50-triphosphate analogues at the human P2Y2
and P2Y4 receptors
Kenneth A. Jacobson a,*, Stefano Costanzi b, Andrei A. Ivanov a, Susanna Tchilibon a,
Pedro Besada a, Zhan-Guo Gao a, Savitri Maddileti c, T. Kendall Harden c
a Molecular
Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and
Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
b Computational
Chemistry Core Laboratory, National Institute of Diabetes and Digestive and
Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
c Department
of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
abstract
With the long-term goal of developing receptor subtype-selective high affinity
agonists for the uracil nucleotide-activated P2Y receptors, we have carried out a series
of structure activity and molecular modeling studies of the human P2Y2 and P2Y4
receptors. UTP analogues with substitutions in the 20-position of the ribose moiety
retained capacity to activate both P2Y2 and P2Y4 receptors. Certain of these
analogues were equieffective for activation of both receptors whereas
20-amino-20-deoxy-UTP exhibited higher potency for the P2Y2 receptor and
20-azido-UTP exhibited higher potency for the P2Y4 receptor. 4-Thio substitution
of the uracil base resulted in a UTP analogue with increased potency relative to UTP
for activation of both the P2Y2 and P2Y4 receptors. In contrast, 2-thio substitution
and halo- or alkyl substitution in the 5-position of the uracil base resulted in
molecules that were 3–30-fold more potent at the P2Y2 receptor than P2Y4 receptor.
6-Aza-UTP was a P2Y2 receptor agonist that exhibited no activity at the P2Y4
receptor. Stereoisomers of UTPaS and 20-deoxy-UTPaS were more potent at the
P2Y2 than P2Y4 receptor, and the R-configuration was favored at both receptors.
Molecular docking studies revealed that the binding mode of UTP is similar for both
the P2Y2 and P2Y4 receptor binding pockets with the most prominent dissimilarities
of the two receptors located in the second transmembrane domain (V90 in the P2Y2
receptor and I92 in the P2Y4 receptor) and the second extracellular loop (T182 in the
P2Y2 receptor and L184 in the P2Y4 receptor). In summary, this work reveals
substitutions in UTP that differentially affect agonist activity at P2Y2 versus P2Y4
receptors and in combination with molecular modeling studies should lead to
chemical synthesis of new receptor subtype-selective drugs.
Free Radical Research, July 2007; 41(7): 812–822
Cell adhesion and integrin expression are modulated by oxidative
stress in EA.hy 926 cells
Abstract
The effects of oxidative stress on integrin-mediated cell adhesion to the extracellular
matrix (ECM) and related apoptosis were investigated using the EA.hy926 endothelial
cells treated (or not) with two oxidants: the hypoxanthine/xanthine oxidase system
(HX/XO) or the tert-butyl hydroperoxide (t-BHP) which both increased cell apoptosis.
Cell adhesion onto vitronectin (Vn) and fibronectin (Fn) was increased at low
concentrations of HX/XO (up to 5 mU/ml) or t-BHP (up to 125mM) and prevented
ROS-induced apoptosis. Flow cytometry analysis of integrin expression showed that
the expression of integrin av and a5 subunits was, respectively, increased and
decreased. Cell adhesion inhibition experiments using function-blocking monoclonal
antibodies against integrin subunits indicated that avb1 and avb3 integrins were
involved in adhesion of cells to Vn, and avb3 integrin played a major role in
oxidant-treated cells. For adhesion to Fn, a5b1 and avb1 integrins were required for
oxidant-treated cells. Taken together, the results suggest that reactive oxygen
species (ROS) produced either by HX/XO or t-BHP could affect expression and/or
activation of specific integrins in the interaction of EA.hy926 cells with ECM.
Keywords: Reactive oxygen species, apoptosis, endothelial cell adhesion,
extracellular matrix, integrins
J. Agric. Food Chem. 2007, 55, 36863691
Reactivity Relationships of Flavan-3-ols on Product
Generation in Aqueous Glucose/Glycine Model Systems
YUKO NODA AND DEVIN G. PETERSON*
Department of Food Science, The Pennsylvania State University, 327 Food Science Building, University Park,
Pennsylvania 16802-2504
Abstract
Ring structure-reactivity relationships of three flavan-3-ols [epicatechin (EC),
epicatechin gallate (ECG), and epigallocatechin gallate (EGCG)] and three simple
phenolic compounds (1,3,5-trihydroxybenzene, 1,2,3-trihydroxybenzene, and
methylgallate as the analogous individual A, B, and C benzene rings of EGCG) on
product generation in an aqueous glucose-glycine reaction model system (125 °C and
30 min) were investigated. The addition of EC, ECG, or EGCG to a glucoseglycine
model was reported to similarly significantly reduce the formation of pyrazine,
methylsubstituted pyrazines, and cyclotene. All three flavan-3-ols were also
reported to generate phenolic-C2, C3, C4, and C6 sugar fragment adducts and to
statistically reduce the concentration of glyoxal, glycolaldehyde, methylglyoxal,
hydroxyacetone, diacetyl, acetoin, and 3-deoxyglucosone during the reaction time
course, except for the EGCG reaction where 3-deoxyglucosone was not statistically
different from the control after 20 min. For the simple phenolic compounds,
methylgallate followed by 1,2,3-trihydroxybenzene was the least reactive, while
1,3,5-trihydroxybenzene was reported as the most reactive phenolic structure for
quenching or reducing the concentration of the R-hydroxyand R-dicarbonyl sugar
fragments during the reaction time course. These results imply that the main
mechanism flavan-3-ols reduced product generation was phenolic-sugar fragment
carbonyl trapping reactions primarily on the A ring (the meta-polyhydroxylated
benzene ring) or not due to the alteration of the reaction reduction potential.
KEYWORDS: Carbonyl reactions; flavan-3-ols; Maillard reaction; sugar fragments;
structure-reactivity; trapping; aroma generation; polyhydroxybenzene