11 research outputs found
Nonquaternary Reactivators for Organophosphate-Inhibited Cholinesterases
A new class of amidine-oxime reactivators of organophosphate
(OP)-inhibited
cholinesterases (ChE) was synthesized and tested in vitro and in vivo.
Compared with 2-PAM, the most promising cyclic amidine-oxime (i.e., <b>12e</b>) showed comparable or greater reactivation of OP-inactivated
AChE and OP-inactivated BChE. To the best of our knowledge, this is
the first report of a nonquaternary oxime that has, comparable to
2-PAM, in vitro potency for reactivation of Sarin (GB)-inhibited AChE
and BChE. Amidine-oximes were tested in vitro, and reactivation rates
for OP-inactivated butyrylcholinesterase (BChE) were greater than
those for 2-PAM or MINA. Amidine-oxime reactivation rates for OP-inactivated
acetylcholinesterase (AChE) were lower compared to 2-PAM but greater
compared with MINA. Amidine-oximes were tested in vivo for protection
against the toxicity of nerve agent model compounds. (i.e., a model
of Sarin). Post-treatment (i.e., 5 min after OP exposure, i.p,) with
amidine oximes <b>7a</b>–<b>c</b> and <b>12a</b>, <b>12c</b>, <b>12e</b>, <b>12f</b>, and <b>15b</b> (145 μmol/kg, i.p.) protected 100% of the mice challenged
with the sarin model compound. Even at 25% of the initial dose of
amidine-oxime (i.e., a dose of 36 μmol/kg, i.p.), <b>7b</b> and <b>12e</b> protected 100% of the animals challenged with
the sarin nerve agent model compound that caused lethality in 6/11
animals without amidine-oxime
Wnt Inhibition Correlates with Human Embryonic Stem Cell Cardiomyogenesis: A Structure–Activity Relationship Study Based on Inhibitors for the Wnt Response
Human embryonic stem cell-based high-content screening
of 550 known
signal transduction modulators showed that one “lead”
(<b>1</b>, a recently described inhibitor of the proteolytic
degradation of Axin) stimulated cardiomyogenesis. Because Axin controls
canonical Wnt signaling, we conducted an investigation to determine
whether the cardiogenic activity of <b>1</b> is Wnt-dependent,
and we developed a structure–activity relationship to optimize
the cardiogenic properties of <b>1</b>. We prepared analogues
with a range of potencies (low nanomolar to inactive) for Wnt/β-catenin
inhibition and for cardiogenic induction. Both functional activities
correlated positively (<i>r</i><sup>2</sup> = 0.72). The
optimal compounds induced cardiogenesis 1.5-fold greater than <b>1</b> at 30-fold lower concentrations. In contrast, no correlation
was observed for cardiogenesis and modulation of transforming growth
factor β (TGFβ)/Smad signaling that prominently influences
cardiogenesis. Taken together, these data show that Wnt signaling
inhibition is essential for cardiogenic activity and that the pathway
can be targeted for the design of druglike cardiogenic molecules
Synthesis and SAR of <i>b</i>‑Annulated 1,4-Dihydropyridines Define Cardiomyogenic Compounds as Novel Inhibitors of TGFβ Signaling
A medium-throughput murine embryonic stem cell (mESC)-based
high-content
screening of 17000 small molecules for cardiogenesis led to the identification
of a <i>b</i>-annulated 1,4-dihydropyridine (1,4-DHP) that
inhibited transforming growth factor β (TGFβ)/Smad signaling
by clearing the type II TGFβ receptor from the cell surface.
Because this is an unprecedented mechanism of action, we explored
the series’ structure–activity relationship (SAR) based
on TGFβ inhibition, and evaluated SAR aspects for cell-surface
clearance of TGFβ receptor II (TGFBR2) and for biological activity
in mESCs. We determined a pharmacophore and generated 1,4-DHPs with
IC<sub>50</sub>s for TGFβ inhibition in the nanomolar range
(e.g., compound <b>28</b>, 170 nM). Stereochemical consequences
of a chiral center at the 4-position was evaluated, revealing 10-
to 15-fold more potent TGFβ inhibition for the (+)- than the
(−) enantiomer. This stereopreference was not observed for
the low level inhibition against Activin A signaling and was reversed
for effects on calcium handling in HL-1 cells
Inhibition of Protein Kinase C-Driven Nuclear Factor-κB Activation: Synthesis, Structure−Activity Relationship, and Pharmacological Profiling of Pathway Specific Benzimidazole Probe Molecules
A unique series of biologically active chemical probes that selectively inhibit NF-κB activation induced by protein kinase C (PKC) pathway activators have been identified through a cell-based phenotypic reporter gene assay. These 2-aminobenzimidazoles represent initial chemical tools to be used in gaining further understanding on the cellular mechanisms driven by B and T cell antigen receptors. Starting from the founding member of this chemical series <b>1a</b> (notated in PubChem as CID-2858522), we report the chemical synthesis, SAR studies, and pharmacological profiling of this pathway-selective inhibitor of NF-κB activation
Human carboxylesterase 1 active site structure.
<p>Active site of human carboxylesterase 1 covalently inhibited via S221 with cyclosarin (magenta) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0017441#pone.0017441-Hemmert1" target="_blank">[8]</a>. The other catalytic residues, in addition to S221, are H468 and E354 (yellow), and are surrounded by hydrophobic residues (grey surface) including V146 and L363 (light blue), as well as the oxyanion hole (white).</p
Bimolecular rates of inhibition, Michaelis-Menten constants, and rates of reactivation for wild-type and V146H/L363E hCE1 against racemic cyclosarin and stereoisomers of cyclosarin model compounds.
<p>N = 3, s.d., N.D. is not determined, N.R. is no reactivation, pH 7.4, 25°C.</p>a<p>Racemic <i>bona fide</i> cyclosarin,</p>b<p>stereoisomers of cyclosarin model compounds,</p>c<p>(8).</p
Organophosphate (OP) inhibition of human carboxylesterase 1 (hCE1).
<p><b>A</b>. Three G-type OP nerve agents and OP model compound (R represents respective <i>O</i>-alkoxy groups). Wild-type hCE1 preferentially binds the stereoisomers shown (7). <b>B</b>. Schematic mechanism of OP hydrolysis by hCE1. X represents the leaving group and * denotes a non-reactive state.</p
Catalytic efficiencies (<i>k</i><sub>cat</sub>/<i>K</i><sub>m</sub>) of engineered enzymes towards hemisubstrates.
a<p>(16).</p>b<p>(32).</p>c<p>(32).</p
Mechanism of reactivation by V146H/L363E hCE1 after cyclosarin binding.
<p><b>A</b>. Model of V146H/L363E (cyan) hCE1 with P<i><sub>R</sub></i> cyclosarin (magenta) including a water molecule (red) between E363 and the central phosphorus. <b>B</b>. Proposed mechanism for enhanced reactivation following cyclosarin inhibition. <b>C</b>. pH dependence of V146H/L363E (black) and L363E (grey) hCE1 dephosphonylation following cyclosarin inhibition.</p
Reactivation of hCE1 following nerve agent exposure.
<p><b>A</b>. Spontaneous reactivation of V146H/L363E hCE1 following inhibition by racemic sarin (blue), soman (green), or cyclosarin (red). Wild type hCE1 (grey) only reactivates following sarin inhibition (7). n = 6, s.d. <b>B</b>. Rates of dephosphonylation for hCE1 variants in the presence of sarin (blue), soman (green) and cyclosarin (red). n = 3, s.d.</p