A class of 5-benzylidene-2-phenylthiazolinones with high potency as direct 5-lipoxygenase inhibitors

Article abstract of DOI:10.1021/jm101165z

A novel class of potent direct 5-lipoxygenase (5-LO) inhibitors bearing a thiazolinone-scaffold identified by virtual screening is presented. A range of substitutions and the importance of the 2-phenyl moiety were evaluated. This series is characterized by high potency in intact polymorphonuclear leukocytes and a cell-free system, exemplified by (Z)-2-(4-chlorophenyl)-5-(4- methoxybenzylidene)-5H-thiazol-4-one (18, IC₅₀ = 0.28 and 0.09 μ-M). These disubstituted thiazolinones may possess potential for intervention with inflammatory and allergic diseases and certain cancer types.

Full text of DOI:10.1021/jm101165z

BRIEF ARTICLE
pubs.acs.org/jmc
A Class of 5-Benzylidene-2-phenylthiazolinones with High Potency as
Direct 5-Lipoxygenase Inhibitors
Bettina Hofmann,*,†,‡ Sebastian Barzen,† Carmen B. R€odl,† Andreas Kiehl,† Julia Borig,†
†
†
§,‡
†
ꢀ
Aleksandra Zivkoviꢁc, Holger Stark, Gisbert Schneider, and Dieter Steinhilber
†Institute of Pharmaceutical Chemistry, Goethe University Frankfurt, Max-von-Laue-Strasse 9, D-60438 Frankfurt, Germany
‡Institute of Organic Chemistry and Chemical Biology, ZAFES/CMP, Goethe University Frankfurt, Siesmayerstrasse 70, D-60323
Frankfurt, Germany
S Supporting Information
b
ABSTRACT: A novel class of potent direct 5-lipoxygenase (5-LO) inhibitors bearing a thiazolinone-scaffold identified by virtual
screening is presented. A range of substitutions and the importance of the 2-phenyl moiety were evaluated. This series is
characterized by high potency in intact polymorphonuclear leukocytes and a cell-free system, exemplified by (Z)-2-(4-
chlorophenyl)-5-(4-methoxybenzylidene)-5H-thiazol-4-one (18, IC50 = 0.28 and 0.09 μM). These disubstituted thiazolinones
may possess potential for intervention with inflammatory and allergic diseases and certain cancer types.
’ INTRODUCTION
thiazolinone. Our strategy was aimed at exploring the influence
of different substituents at these phenyl residues (Figure 1B) and
assessing the role of the 2-phenyl residue on 5-LO activity.
5-Lipoxygenase (5-LO), a non-heme-iron-containing dioxy-
genase, catalyzes the biosynthesis of leukotrienes (LTs), which
are lipid mediators of inflammatory and allergic responses and
play a key role in host defense reactions. LTs exert their biological
effects via specific G-protein-coupled receptors and play a pivotal
role in inflammatory and allergic disorders and cardiovascular
diseases and cancer.1,2 5-LO catalyzes the first steps in the
conversion of arachidonic acid (AA) into LTA4 under the aid
of the nuclear membrane-bound 5-LO-activating protein
(FLAP).3 LTA4 is further converted by LTA4 hydrolase into
LTB4 which is a potent chemotactic agent and activator for
phagocytes. Alternatively, conjugation of LTA4 with reduced
glutathione by LTC4 synthases yields the cysteinyl-containing
LTs C4, D4, and E4 that cause bronchoconstriction and vascular
permeability.1 Because of the key role of 5-LO in LT biosynth-
esis, 5-LO inhibitors are supposed to be of therapeutic value for
the treatment of asthma, allergic rhinitis, atherosclerosis, and
certain types of cancer.2,4 Also, some novel indications came up,
e.g., chronic myeloid leukemia (CML),5 malaria,6a,6b and cancer
chemoprevention.7
’ RESULTS AND DISCUSSION
In our previous report, we presented the 5-benzylidene-2-
phenyl-5H-thiazol-4-one 1 (Figure 1A) as an inhibitor of 5-LO
product formation with low micromolar activity.8 The thiazoli-
none core by itself is known in 5-LO inhibitors; in 1994 Unangst
et al. reported dual 5-LO/COX inhibition by 5-[[3,5-bis(1,
1-dimethylethyl)-4-hydroxyphenyl]-methylene]-2-imino-4-thia-
zolidinone (Figure 2A).10a Recently, Geronikaki et al. identified
2-thiazolylimino-5-arylidene-4-thiazolidinones (Figure 2B) with
moderate activity against dual soybean 13-LO/COX-1.10b
Nevertheless, theses structures differ from our class in the
2-phenyl moiety and the substitution pattern at both phenyl
rings that is unique to our compound class. Notably, for 1 no
inhibition of COX-2 was observed.8 Thus, it is possible that the
2-phenyl substituent in this scaffold class is responsible for the
selective 5-LO activity. To our knowledge, this moiety has not
been described as a 5-LO/COX dual inhibitor.
To further evaluate the potential of 1, we assessed its effec-
tiveness in a cell-free assay. For LT biosynthesis, AA is released by
cPLA2 and converted by activated 5-LO after the transfer by
FLAP.3 Activation of 5-LO in the cell requires Ca2þ mobilization
and/or 5-LO phosphorylation by protein kinases that causes
translocation of 5-LO from soluble cellular compartments to the
nuclear membrane close to FLAP.3 For conclusive analysis of the
effectiveness of the test compounds, a cell-based test system
using isolated human polymorphonuclear leukocytes (PMNL)
and a cell-free assay utilizing the 100000g supernatant (S100) of
PMNL homogenates were applied. In the cell-based assays, many
Recently, we presented the use of ligand-based virtual screen-
ing to identify new inhibitors of 5-LO product formation.8
Briefly, two similarity search methods, “Charge3D”9a,9b and
“TripleCharge3D”,9a,9c were applied for virtual screening. With
these methods, two molecules are compared based on their
three-dimensional distribution of partial atom charges. This led
among others to the discovery of a thiazolinone structure series,
represented by 1 (5-(4-ethoxybenzylidene)-2-phenyl-5H-thia-
zol-4-one, Figure 1A and Table 1), having low micromolar
5-LO inhibitory activity in a cellular assay. Here, we describe a
structure-activity relationship (SAR) of this class of direct 5-LO
inhibitors based on the scaffold of 1. Characteristic structural
features of 1 are two phenyl residues connected to the central
Received: September 8, 2010
Published: February 22, 2011
r
2011 American Chemical Society
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Journal of Medicinal Chemistry
BRIEF ARTICLE
possibilities aside from direct interference with 5-LO exist (e.g.,
FLAP or cPLA2 inhibition, suppression of 5-LO kinases or Ca2þ
mobilization, inhibition of 5-LO translocation) eventually sup-
pressing LT synthesis.11 To evaluate the compounds in intact
PMNL, the 5-LO products 5(S)-hydro(pero)xy-6-trans-8,11,14-
cis-eicosatetraenoic acid (5-H(P)ETE) and the trans- and epi-
trans-isomers of LTB4, as well as LTB4 were analyzed. Cells were
preincubated with the compounds, and subsequently 5-LO
product formation was elicited by 2.5 μM ionophore A23187.
Exogenous AA (20 μM) was supplemented to circumvent the
necessity of cPLA2-mediated endogenous substrate supply. For
evaluation of the effectiveness of the test compounds in the cell-
free assay, 5-LO products were analyzed in PMNL S100 after
preincubation with the compounds and subsequent stimulation
of 5-LO product formation by addition of 1 mM CaCl2 and 20
μM AA. The 5-LO inhibitor 35 (BWA4C)12 was taken as
reference compound showing IC50 of 0.05 μM in PMNL S100
and IC50 of 0.08 μM in intact PMNL (Table 1), which is similar
to the literature.12 Because we were mainly interested in SARs
regarding the direct interaction with 5-LO, the following discus-
sion is focused on the activity of the compounds in cell-free S100.
Nevertheless, all inhibitors were active in the whole cell assay
even though slightly less potent. Their potency in intact PMNL is
given for completeness.
Compound 1 caused potent inhibition of 5-LO product
formation in intact PMNL and in cell-free PMNL S100 with
IC50 of 2 and 0.5 μM, respectively (Table 1), which identifies the
compound as a direct 5-LO inhibitor. As the first hit, 1 served as
the structural template for a follow-up virtual screening round to
identify analogues bearing the thiazolinone scaffold. Our study
aimed at exploring the influence of different substituents at both
phenyl residues (Figure 1 B) and assessing the role of the 2-phenyl
residue on 5-LO inhibitory activity. Thus, we screened the ASINEX
(Moscow, Russia) and SPECS (Delft, The Netherlands) com-
pound collections for 5-benzylidene-2-phenylthiazolinones
Figure 1. Structures of parent compound 1 (A) and herein reported
active compounds (B, best hits).
Table 1. IC50 for Inhibition of 5-LO and 5-LO Product Formation by Test Compounds in Cell-Free S100 and Intact PMNLc
a Residual activity (percentage of control) is >60% at 10 μM . b Residual activity (percentage of control) is >60% at 30 μM. c The asterisk (/) indicates
synthesized compounds.
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BRIEF ARTICLE
Figure 2. Sample structures of known thiazolinone-based 5-LO inhi-
bitors (A,10a B10b): best (A, R3 = Ph, R4 = H; B, m-NO2) and worst
derivative (A, R3, R4 = H; B, p-NO2) of each series is shown.
Figure 3. General synthetic procedure for synthesized compounds.15
using MACCS substructure keys.13a,13b This involved the gen-
eration of MACCS keys from a given set of 166 predefined
substructures. A bit is set whenever one of these substructures is
present in a molecule. Bit strings of the query and the database
compounds were compared using the Tanimoto coefficient
T.14a,14b T ranges from 0 to 1, where 1 indicates bit string
identity. Molecules were retained with a Tanimoto coefficient
of >0.69 (indicating structural similarity to 1). From this list, 19
commercially available substances (2-17, 30, 31, and 33,
Table 1) were selected and tested with three compounds derived
from our previous screening8 (29, 32, and 34) to obtain a
preliminary SAR. We selected compounds bearing different
substitution patterns at the 5-benzylidene and compounds hav-
ing the 2-phenyl substituted to examine the role of these
moieties. Substances with substitutions at the 5-benzylidene
residue all bear p-methyl or no substitution at the 2-phenyl
residue (2-13). The direct 5-LO inhibitory activity determined
in S100 varied about an order of magnitude (0.13 μM (8) and 3
μM (5 and 6)) despite the variation in substitution pattern
performed (2-13). Within this series, o-OH seems to be more
potent than p-OH, which is most prominent if there is no
substitution at R2 present (5 and 3), enhancing the inhibitory
activity from 3 to 0.3 μM. Replacement of m-chloro of 5 by
another electron-withdrawing but less lipophilic group, nitro
(6), did not alter efficiency (IC50 = 3 μM for both). The
chloride substitution alone (2) produced one of the most
potent compounds of this series but did not significantly alter
the potency compared to the unsubstituted derivative 14
(IC50 = 0.35 μM). Elongation with a vinyl group (15) was
also well tolerated (IC50 = 0.23 μM). Different groups are
accepted at the 5-position of the thiazolinone, notably also
slight decrease of inhibitory activity (IC50 = 0.63 μM). p- and m-
acetaldehyde (25 and 26) were equipotent (IC50 = 0.11 and
0.13 μM), whereas a p-hydroxy group (22) led to a somewhat
decreased potency (IC50 = 0.65 μM). Exchange of the p-methoxy
residue of 18 by a hydroxyl group (28) was without effect (IC50
=
0.09 and 0.11 μM). Addition of a hydrophilic methyl ester at R1
(20) and R2 (21) was also well tolerated with IC50 of 0.19 and
0.58 μM. The only exception was a methoxy substitution at R2
(23), which was surprisingly less potent in S100 (IC50 = 4 μM)
but highly potent in intact PMNL (IC50 = 0.32 μM).
To examine the role of the 2-phenyl substituent for 5-LO
inhibitory activity, we evaluated the potency of compounds
having this moiety replaced by different aliphatic heterocyles
(pyrrolidine, piperidine, or azepane) or by an N-linker (29-34).
These structural changes were detrimental with an almost total
loss of activity, e.g., 33. Only the replacement of the 2-phenyl by
an azepane (with a propoxy substituent at R1, 34) preserved
moderate activity (IC50 = 14 μM). This highlights the directly
coupled 2-phenyl residue as being superior to the examined
heterocycles and N-linkers for the tested compounds regarding
5-LO inhibitory activity.
Taken together, we found that by keeping the core scaffold,
different substituents cause only small changes in the compounds
potencies. Different groups were tolerated at the 5-position,
notably also lipophilic voluminous ones (e.g., 17). High overall
lipophilicity is known as a general determinant for many potent
5-LO inhibitors.16 In contrast, changes in the scaffold to aliphatic
cyclic amines (pyrrolidine, piperidine or azepane) or N-contain-
ing linkers instead of the 2-phenyl residue (29-34) showed
impaired (34 and 29) or no 5-LO inhibitory activity (30-33).
Thus, it can be deduced that the 2-phenyl residue is crucial for the
5-LO inhibitory activity among this compound class. Regarding
different substitutions at the 5-benzylidene moiety, inhibitory
activity of these thiazolinones seems to be robust against altera-
tions at that residue. Obviously, these compounds presented here
show a flat, so-called “continuous structure-activity relationship”.17
LO inhibitors are already known to show a continuous SAR:18 In
a systematic analysis of SARs over different compound classes,
Wawer et al. identified that LO inhibitors, taken from the
molecular drug data report (MDDR, version 2005.2, Symyx
Software, San Ramon, CA, U.S.), display a “continuous” SAR.18
Continuous SARs are characterized by tolerance against struc-
tural variations.17 The spectrum of active compounds for a
given target thereby includes similar structures that show
similar activity and structures with different scaffolds having
nearly the same biological activity. The latter could (in the case
of 5-LO) be ascribed to the well-known three types of 5-LO
inhibitors (iron ligand, redox type, and nonredox type).16 On
the basis of their structures, for the compounds reported herein
iron-chelating or reducing properties are unlikely. Thus, they
lipophilic, voluminous ones like tert-butylphenyl (16, IC50
=
0.3 μM) or anthracene (17, IC50 = 0.3 μM), even though 17
may get trapped in highly lipophilic areas in the cell, as it is less
potent in intact PMNL.
To explore the influence of substitutions at the 2-phenyl
moiety, we synthesized several thiazolinones with substitutions
at R2 (18-28), as only derivatives with substitutions at the
5-benzylidene were available commercially. The starting point
was 7 bearing a p-methoxy group at the 5-benzylidene which
was kept for all compounds except 20 and 28. The following
general synthetic procedure was applied (Figure 3): a solution
of the corresponding benzonitrile (1 equiv, 0.07-0.5 mmoL),
thioglycolic acid (1-1.1 equiv), the corresponding benzalde-
hyde (1 equiv), and TEA in methanol was refluxed overnight.
The reaction mixture was evaporated under reduced pressure,
and the pure product was recrystallized from ethanol and
washed with acetone.15
The introduction of electron-withdrawing halogens at the
2-phenyl, p-chloride (18), or m-fluoride (27) did not alter the
inhibitory potency (IC50 = 0.09 and 0.12 μM, respectively).
Another electron withdrawing group, p-amino (24), led to a
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BRIEF ARTICLE
’ CONCLUSIONS
We show that 5-benzylidene-2-phenylthiazolinones act as
novel and potent direct 5-LO inhibitors, exemplified by 18 with
IC50 in intact PMNL and cell-free S100 of 0.28 and 0.09 μM,
respectively. The high effectiveness in whole cells and cell-free
systems encourages further investigations of this compound
class. Future experiments to resolve the binding mode will allow
for structure-based lead optimization to further increase their
inhibitory activity at 5-LO. Furthermore, studies addressing the
effectiveness in vivo using animal models of inflammation are
necessary and may reveal the therapeutic potential of these
thiazolinone derivatives.
Figure 4. Inhibition of 5-LO product formation by 18 in intact PMNL
(b) and in PMNL 100000g supernatants (O). Error bars give the
standard error of the mean (n = 3-5).
’ MATERIALS AND METHODS
Compounds and Chemistry. Compounds 1-6, 8-17, and
29-34 were purchased from Asinex (Moscow, Russia) or SPECS
(Delft, The Netherlands) and exhibit g95% purity determined by
supplier using 1H NMR and LC-MS. Compounds 7 and 18-28 were
not found to be commercially available and thus synthesized according
to Zayed et al.15 (By now, 19 is commercially available.) Melting points
for synthesized compounds were determined on a Buchi 510 melting
might be designated nonredox type inhibitors or even belong to
a novel class.
Comparison with the known thiazolinone 5-LO inhibitors10a,10b
(Figures 1 and 2) revealed the 2-phenyl moiety as a major
structural difference of the compounds presented herein. Both
already published inhibitor classes have the 5-benzylidene-2-
phenyl-5H-thiazol-4-one core in common but apart from this
have a quite distinct scaffold. Furthermore, only limited struc-
tures are available. Thus, comparison to other SARs of thiazoli-
none based 5-LO inhibitors is quite difficult. The structures
published by Geronikaki et al.10b exhibit weaker 5-LO inhibitory
potency (IC50 ≈ 90 μM) than those by Unangt et al.10a and by us
(both IC50 < 1 μM). Moreover, the least active compound by
Unangst et al. (Figure 2A, IC50 > 10 μM10a) resembles 28 except
the 2-chlorophenyl. Thus, it can be hypothesized that the
2-phenyl of our scaffold class is important for 5-LO inhibitory
activity in this structural context.
1
point apparatus (Buchi, Switzerland) and are uncorrected. H NMR
spectra were recorded on a Bruker DPX 250 (250 MHz) spectrometer
(Bruker, Germany). 1H NMR data are reported in the following order:
chemical shift (d) in ppm downfield from tetramethylsilane as internal
reference; multiplicity (br, broad; s, singlet; d, doublet; dd, double
doublet; t, triplet; m, multiplet); approximate coupling constant (J) in
hertz (Hz); number and assignment of protons. 13C NMR spectra were
recorded on a Bruker DPX 250 (63 or 75 MHz) spectrometer (Bruker,
Germany). ESI-MS was performed on a Fisons Instruments VG Plat-
form II (Manchester, Great Britain) in positive polarity. Data are listed as
mass number ([M þ H]þ) and relative intensity (%). Elemental analysis
results (C, H, N) were measured on a CHN-Rapid (Heraeus, Germany)
and were within (0.4% of the theoretical values for all final compounds,
which corresponds to g95% purity. Educts and all other reactants were
commercially obtained from Sigma-Aldrich, ABCR, Alfa Aesar, and
Acros Organics and were used without further purification unless otherwise
stated. Analytical TLC (thin layer chromatography) was performed with
TLC plates (F254, Merck) with detection using a UV lamp. For the
Knoevenagel condensation, only the Z-isomer was obtained.
General Procedure. A solution of the corresponding benzonitrile
(1 equiv, 0.001-0.05 mol), thioglycolic acid (1-1.1 equiv), the
corresponding benzaldehyde (1 equiv), and TEA in methanol was
refluxed for at least 12 h (Figure 3). The mixture was evaporated under
reduced pressure. The pure product was recrystallized from ethanol and
washed with acetone.15 Detailed synthesis and analytical data of all
synthesized compounds are provided in the Supporting Information.
Assay Systems. Materials. Arachidonic acid and calcium iono-
phore A23187 were from Sigma (Deisenhofen, Germany). HPLC
solvents were from Merck (Darmstadt, Germany).
To compare our compounds with already known 5-LO
inhibitors, we performed a MACCS keys similarity search against
publicly available 5-LO inhibitors. We screened the ChEMBLdb
(https://www.ebi.ac.uk/chembldb), a database of bioactive
druglike small molecules with annotated bioactivities abstracted
from the literature, using 1 as query. Among the 20 most similar
unique structures bearing no thiazolinone moiety (Supporting
Information Table S1), scaffolds comprising diverse heterocycles
and phenyl rings are found. The potencies (determined in
comparable cell based assays) range from IC50 = 2 nM to
IC50 = 9200 nM. Therewith our structures are well situated in
the activity range of known 5-LO inhibitors. Our structures
presented herein are characterized by direct, selective, stimulus
independent, and noncytotoxic 5-LO inhibitory mechanisms
(personal communication), which might be advantageous over
other inhibitors.
With substitutions at R1 position we were able to slightly
improve the activity of the lead structure, exemplified by 18
which concentration-dependently inhibited 5-LO in the cell-free
assay and in intact PMNL with IC50 of 0.09 and 0.28 μM,
respectively (Figure 4). Our SAR studies revealed a clear SAR in
the 2-position of the thiazolinone, where replacement of benzene
by aliphatic heterocycles or introduction of an N-linker led to a
complete loss of activity. In contrast, the 5-benzylidene showed
high tolerance toward structural modifications in terms of
introduced substituents. Taken together, this series represents
the first class of 5-benzylidene-2-phenylthiazolinones with po-
tent direct 5-LO inhibitory activity.
Determination of 5-LO Product Formation. Determination
of 5-LO product formation was performed as previously described.19 A
detailed description is provided in the Supporting Information. For
calculation of IC50, samples were treated with three increasing concen-
trations of each compound in three to five independent experiments and
the mean and standard error of the mean were calculated. Measurements
from each drug concentration were normalized to DMSO control
condition. IC50 values are approximations determined by graphical
analysis (linear interpolation between points between 50% activity)
using SigmaPlot2004 (SSI Inc.).
Computational Methods. Similarity Searching Using
MACCS Keys. The similarity search for commercially available
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Journal of Medicinal Chemistry
BRIEF ARTICLE
structural similar derivatives of compound 1 was performed with MOE
(version 2006.08, Chemical Computing Group Ltd., Montreal, Canada)
using MACCS substructure keys13a,13b and the Tanimoto coefficient.14a,14b
The ASINEX Gold (version Nov 05; 231812 molecules, ASINEX,
Moscow, Russia) and SPECS compound collections (version Feb 08;
~200000 molecules, SPECS, Delft, The Netherlands) were screened.
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’ ASSOCIATED CONTENT
1
S
Supporting Information. Chemical synthesis; H and
b
13C NMR, MS, and elemental analysis data of synthesized
compounds; X-ray structure of 7; 5-LO activity assay; and data
of MACCS keys similarity search against known 5-LO inhibitors.
This material is available free of charge via the Internet at http://
pubs.acs.org.
’ AUTHOR INFORMATION
(10) (a) Unangst, P. C.; Connor, D. T.; Cetenko, W. A.; Sorenson,
R. J.; Kostlan, C. R.; Sircar, J. C.; Wright, C. D.; Schrier, D. J.; Dyer, R. D.
Synthesis and biological evaluation of 5-[[3,5-bis(1,1-dimethylethyl)-4-
hydroxyphenyl]methylene]oxazoles, -thiazoles, and -imidazoles: novel
dual 5-lipoxygenase and cyclooxygenase inhibitors with antiinflamma-
tory activity. J. Med. Chem. 1994, 37, 322–328. (b) Geronikaki, A. A.;
Lagunin, A. A.; Hadjipavlou-Litina, D. I.; Eleftheriou, P. T.; Filimonov,
D. A.; Poroikov, V. V.; Alam, I.; Saxena, A. K. Computer-aided discovery
of anti-inflammatory thiazolidinones with dual cyclooxygenase/lipoxy-
genase inhibition. J. Med. Chem. 2008, 51, 1601–1609.
Corresponding Author
*Phone: þþ49-69-798-29343. Fax: þþ49-69-798-29323; E-mail:
hofmann@pharmchem.uni-frankfurt.de.
Present Addresses
§Institute of Pharmaceutical Sciences, ETH Z€urich, Wolfgang-
Pauli-Street 10, 8093 Z€urich, Switzerland.
’ ACKNOWLEDGMENT
(11) Werz, O. Inhibition of 5-lipoxygenase product synthesis by
natural compounds of plant origin. Planta Med. 2007, 73, 1331–1357.
(12) Tateson, J. E.; Randall, R. W.; Reynolds, C. H.; Jackson, W. P.;
Bhattacherjee, P.; Salmon, J. A.; Garland, L. G. Selective inhibition of
arachidonate 5-lipoxygenase by novel acetohydroxamic acids: biochem-
ical assessment in vitro and ex vivo. Br. J. Pharmacol. 1988, 94, 528–539.
(13) (a) Willett, P.; Barnard, J. M.; Downs, G. M. Chemical
similarity searching. J. Chem. Inf. Comput. Sci. 1998, 38, 983–996. (b)
Durant, J. L.; Leland, B. A.; Henry, D. R.; Nourse, J. G. Reoptimization of
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(14) (a) Martin, Y. C.; Kofron, J. L.; Traphagen, L. M. Do structu-
rally similar molecules have similar biological activity?. J. Med. Chem.
2002, 45, 4350–4358. (b) Muchmore, S. W.; Debe, D. A.; Metz, J. T.;
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The study was supported by the EU (Grant LSHM-CT-2004-
0050333), the LOEWE Lipid Signaling Forschungszentrum
Frankfurt (LiFF), and LOEWE OSF. The authors are grateful
Chemical Computing Group Ltd., Montreal, Canada, for a MOE
research license.
’ ABBREVIATIONS USED
5-LO, 5-lipoxygenase; AA, arachidonic acid; cPLA2, cytosolic
phospholipase A2; FLAP, 5-lipoxygenase-activating protein; 5-
H(P)ETE, 5(S)-hydro(pero)xy-6-trans-8,11,14-cis-eicosatetrae-
noic acid; LT(B4), leukotriene (B4); PMNL, polymorphonuclear
leukocyte; S100, 100000g supernatant; SAR, structure-activity
relationship
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