Anti-Inflammatory Effects of Epoxyeicosatrienoic Acids

Article (PDF Available)inInternational journal of vascular medicine 2012(1):605101 · July 2012with40 Reads
DOI: 10.1155/2012/605101 · Source: PubMed
Abstract
Epoxyeicosatrienoic acids (EETs) are generated by the activity of both selective and also more general cytochrome p450 (CYP) enzymes on arachidonic acid and inactivated largely by soluble epoxide hydrolase (sEH), which converts them to their corresponding dihydroxyeicosatrienoic acids (DHETs). EETs have been shown to have a diverse range of effects on the vasculature including relaxation of vascular tone, cellular proliferation, and angiogenesis as well as the migration of smooth muscle cells. This paper will highlight the growing evidence that EETs also mediate a number of anti-inflammatory effects in the cardiovascular system. In particular, numerous studies have demonstrated that potentiation of EET activity using different methods can inhibit inflammatory gene expression and signalling pathways in endothelial cells and monocytes and in models of cardiovascular diseases. The mechanisms by which EETs mediate their effects are largely unknown but may include direct binding to peroxisome proliferator-activated receptors (PPARs), G-protein coupled receptors (GPCRs), or transient receptor potential (TRP) channels, which initiate anti-inflammatory signalling cascades.
Hindawi Publishing Corporation
International Journal of Vascular Medicine
Volume 2012, Article ID 605101, 7 pages
doi:10.1155/2012/605101
Review A rticle
Anti-Inflammatory Effects of Epoxyeicosatrienoic Acids
Scott J. Thomson, Ara Askari, and David Bishop-Bailey
Translational Medicine and Therapeutics, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry,
Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
Correspondence should be addressed to Scott J. Thomson, s.j.thomson@qmul.ac.uk
Received 30 May 2012; Accepted 20 June 2012
Academic Editor: Ken-ichi Aihara
Copyright © 2012 Scott J. Thomson et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Epoxyeicosatrienoic acids (EETs) are generated by the activity of both selective and also more general cytochrome p450
(CYP) enzymes on arachidonic acid and inactivated largely by soluble epoxide hydrolase (sEH), which converts them to their
corresponding dihydroxyeicosatrienoic acids (DHETs). EETs have been shown to have a diverse range of eects on the vasculature
including relaxation of vascular tone, cellular proliferation, and angiogenesis as well as the migration of smooth muscle cells. This
paper will highlight the growing evidence that EETs also mediate a number of anti-inflammatory eects in the cardiovascular
system. In par ticular, numerous studies have demonstrated t hat potentiation of EET activity using dierent methods can inhibit
inflammatory gene expression and signalling pathways in endothelial cells and monocytes and in models of cardiovascular
diseases. The mechanisms by which EETs mediate their eects are largely unknown but may include direct binding to peroxisome
proliferator-activated receptors (PPARs), G-protein coupled receptors (GPCRs), or transient receptor potential (TRP) channels,
which initiate anti-inflammatory signalling cascades.
1. Introduction
Cardiovascular diseases such as atherosclerosis have a strong
inflammatory component. Inflammation in the vascular
wall may be initiated by endothelial dysfunction and
the accumulation of toxic oxidised circulating lipids [1].
Inflammatory mediators such as TNFα and IL-1β secreted,
which induces the upregulation of cell adhesion molecules,
facilitates leukocyte recruitment in to the vascular wall [2, 3]
and stimulates vascular smooth muscle cell migration and
proliferation [4]. Circulating monocytes not only respond
to inflammatory stimuli by producing large amounts of
inflammatory mediators but they are also crucial for eective
activation of lymphocytes and adaptive immunity. The hall-
mark of advanced unstable atherosclerotic lesions is that they
are monocyte/macrophage rich and highly inflammatory.
Inflammatory responses are normally promptly termi-
nated since excessive or prolonged inflammation can lead
to chronic pathological conditions such as cardiovascular
diseases, Crohns disease, rheumatoid ar thritis, or cancer.
Although there have been many new treatments recently
developed to combat inflammatory diseases, some of these
treatments are either very expensive and/or not eective
in subsets of patients. Therefore, it is important to con-
tinue to investigate mechanisms that regulate inflammatory
responses as they may open up novel therapeutic targets.
There is a growing list of evidence that the epoxygenase
pathway of arachidonic acid metabolism, which generates
epoxyeicosatrienoic acids (EETs), exerts anti-inflammatory
eects that may be harnessed to treat disease. This paper
will summarise that evidence and highlight outstanding
questions that remain to be answered.
2. Overview of the Epoxygenase Pathway of
Arachidonic Acid Metabolism
Arachidonic acid is an omega-6 polyunsaturated long chain
fatty acid that contains 20 carbon atoms and four cis-
double bonds and possesses a carboxyl group and a methyl
group at respective ends of the molecule. The double bonds
are located between carbons 5-6, 8-9, 11-12, and 14-15
relative to the carboxyl group. Therefore, its chemical name
is all-cis-5,8,11,14-eicosatetraenoic acid and its lipid name
2 International Journal of Vascular Medicine
is 20 : 4 (n-6). The cis-configuration of the four double
bonds causes the arachidonic acid backbone to significantly
bend. In contrast, double bonds in the trans-configuration
or saturated arachidonic acid result in structurally unbent or
flexible backbones.
Experiments performed more than 30 years ago showed
that incubations of radio-labelled arachidonic acid with
microsomal preparations derived from a variety of tissues
including liver [5, 6], kidney [7], hypothalamus [8], and
anterior pituitary [9] resulted in the for m ation of EETs.
This epoxygenase reaction required cytochrome p450
(CYP) enzymes and utilised NADPH and oxygen in a 1 : 1
stoichiometric ratio [5]. One atom of molecular oxygen
is incorporated into one of the four double bonds of
arachidonic acid retaining the cis-geometry and yielding
four potential EETs, that is, 5,6-EET, 8,9-EET, 11,12-EET,
or 14,15-EET, respectively. Furthermore, each EET can be
present in either the S/R or R/S stereoconfiguration, thus
eight potential EETs can be formed.
2.1. Epoxygenation of Arachidonic Acid Performed by Spe-
cific CYPs. CYP enzymes catalyze the oxidation of organic
substances, as well as xenobiotics. Altogether, 57 putative
CYP genes have been identified in man (by comparison
mice have 103 and rat 89 CYP, resp.) that are divided into
15 subfamilies [10]. Attempts have been made to classify
human CYP genes by substrate; however, a more systematic
nomenclature is generally used since the true physiological
roles of many of these genes are still unknown [11]. To
date, at least 12 human CYP genes have been reported to
possess epoxygenase activity, although most studies have
been focussed on the CYP2C and CYP2J families, which are
considered the major epoxygenase enzymes.
2.2. CYP2C. One of the earliest studies using recombinant
human CYP compared the metabolic profiles of the CYP2C8
and CYP2C9 enzymes [12], which are 77% identical at the
amino acid level. Despite their high similarity, CYP2C8 and
CYP2C9 exhibit both regio- and stereoselective dierences
in their epoxygenation of arachidonic acid. For instance,
CYP2C8 produced only 14,15-EET and 11,12-EET at a
1.25 : 1 ratio, which represented 68% of the total metabolites
measured. By contrast, CYP2C9 produced 14,15-EET 11,12-
EET and 8,9-EET at a ratio of 2.3 : 1 : 0.5, which represented
69% of total metabolites. Furthermore, with respect to stere-
oselectivity, CYP2C8 was 81% selective for the 11(R),12(S)-
EET configuration, whereas CYP2C9 was 70% selective for
the 11(S),12(R)-EET configuration [12]. These CYP enzymes
also carry out other reactions including allylic hydroxylation
on arachidonic acid and other fatty acids.
2.3. CYP2J2. Epoxygenase activity of human CYP2J2 was
first demonstrated by the Zeldin lab, who initially cloned
and characterised the gene [13]. Recombinant CYP2J2
metabolised arachidonic acid to all four potential epoxy-
genase products, with 14,15-EET being the predominant
metabolite formed. CYP2J2 was found to be highly expressed
in the heart, and EETs were produced in similar proportions
as recombinant CYP2J2 suggesting that CYP2J2 played a
major role in EET generation in the heart in vivo [13].
CYP2J2 expression is also seen in kidney, liver and muscle
tissues [13], and, to a lesser extent, in the gut [14].
2.4. Other CYPs. A comprehensive comparison study by
Rifkind and colleagues examined the epoxygenase activity of
a panel of 10 CYP proteins by overexpressing them in HepG2
cells and measuring metabolic products. CYP 2C8, 2C9,
1A2, and 2E1 principally produced epoxygenase products. By
contrast, CYP2D6 was inactive, while CYPs 2A6, 3A3, 3A4,
and 3A5 had minimal epoxygenase activity [15]. CYP3A4
has also been shown to make the epoxygenase products 8,9-
EET, 11,12-EET, and 14,15-EET, respectively, in several breast
cancer cell lines [16]. Other CYPs that have been shown
to possess epoxygenase activity include CYP1A, CYP2B1
and CYP2B2 [17] and CYP2B12 [18], CYP2C8, CYP2C9,
CYP2D18 [19], CYP2N1 and CYP2N2 [20], and rat CYP4A2
and 4A3 [21]. The full extent of the epoxygenase activity
of these enzymes and the physiological consequences of any
activity is, however, poorly understood.
3. Soluble Epoxide Hydrolase
Once formed, EETs are unstable because the y are rapidly
metabolised. The main catabolic pathway is the conversion of
EETs into dihydroxyeicosatrienoic acid (DHETs), catalysed
by soluble epoxide hydrolase (sEH) [22]. DHETs are gen-
erally considered to be less active; however, they have been
shown to exert vasodilatory eects on coronary arteries [23].
DHETS are far more polar than their corresponding EETs
and quickly diuse out of tissues as the 1, diols or conjugates
of them. Other pathways of EET metabolism include chain
elongation, β-oxidation, and ω-oxidation [24]. 5,6 EET and
8,9 EET are substrates for COX enzymes [25] and can also be
incorporated into membrane phospholipids. DHETs have a
lower binding anity for phospholipids which may account
for its relatively increased plasma levels [26].
Recently, the damaging cardiovascular risk factor homo-
cysteine has been shown to upregulate sEH in endothelial
cells and promote a proinflammatory environment [27]. In
contrast, elevating the levels of endogenous CYP products by
removing (sEH knockout mice) or inhibiting soluble epoxide
hydrolase (sEH-1) has been shown to reduce neointima for-
mation [28], atherosclerosis and abdominal aortic aneurysm
development, dyslipidaemia in hyperlipidaemic mice [29],
and reduce hypertension [30] and diabetes [31]indierent
mouse models. A number of sEH inhibitors have now been
developed and are moving towards clinical trials for a variety
of disorders related to cardiovascular disease.
4. Epoxygenases in Vascular and
Inflammatory Cells
CYP2C mediated generation of 11,12 EET has also been
documented in porcine coronary arteries [32], and CYP2C
enzymes have been found expressed in endothelial cells [33],
International Journal of Vascular Medicine 3
and in primary human monocytes and M1 (CYP2C8) and
M2 macrophages (CYP2C8 and CYP2C9) [34].
CYP2J2 immunoreactivity is seen in the endothelial and
smooth muscle cell layers of human coronary arteries [35], as
well as in the human monocytic cell lines THP-1 and U937,
primary monocytes and M1 and M2 macrophages [34],
and the endothelial cell line EA hy.926s [36]. Interestingly,
neither CYP2J2 nor CYP2C8 mRNA expression was detected
in human polymorphonuclear cells [34]. More recently, the
increased risk of coronary artery disease was shown to be
associated with a polymorphism in the promoter of CYP2J2
gene in some populations, which decreases the expression of
the enzyme [37].
5. Epoxygenases and EETs
Suppress Inflammation
EETs have been shown to exert multiple biological eects
on the vasculature including proproliferation and angio-
genic eects [38]. EETs have also been hypothesized as
endothelium-derived hyperpolarizing factors, as they hyper-
polarize and relax vascular smooth muscle cells by activat-
ing calcium-activated potassium channels [32]. However,
a number of the anti-inflammator y activities of EETs on
inflammatory cells, as discussed below, appear independent
of any cellular hyper polarisation [35].
5.1. Endothelial Cells. Overexpression of CYP2J2 in human
and bovine endothelial cells inhibits TNFα-induced
VCAM-1 [39] and VCAM-1 promoter activity in reporter
assays [35]. Treatment with the epoxygenase inhibitor
SKF525A reversed the eects of CYP2J2 overexpression on
VCAM-1 promoter activity [35]. Exogenous EETs also exert
the same eects as CYP2J2 overexpression, although dierent
EETs can have dierent selectivities. In human endothelial
cells, 11,12-EET significantly inhibited VCAM-1 expression
in response to TNFα,IL-1α, or LPS. By contrast, 14,15-EET
had negligible eect, while 5,6-EET, 8,9-EET, and 11,12-
DHET all inhibited to varying degrees but to a lesser extent
than 11,12-EET. 11,12-EET also inhibited TNFα-induced
E-selectin and ICAM-1 expression [35]. Mice engineered
to overexpress the human epoxygenase genes CYP2J2 or
CYP2C8, respectively, were generated to investigate their
roles in endothelial cells. Primary pulmonary endothelial
cells derived from these mice showed reduced levels of LPS-
induced adhesion molecule and chemokine gene expression.
Furthermore, these anti-inflammatory eects were inhibited
by treatment with the epoxygenase inhibitor MS-PPOH and
a putative EET receptor antagonist 14,15-EEZE [40].
5.2. Monocytic Cells. Similar to endothelial cells, EET activity
has also been shown to antagonise inflammatory signals in
monocytic cells. Phorbol ester treatment of THP-1 led to
a 4-fold increase in CYP2J2 expression between 3–7 days
after stimulation, suggesting that endogenous expression
of CYP2J2 may regulate inflammatory responses in these
cells [36]. Addition of 8,9-EET or 11,12-EET inhibited
basal TNF secretion from THP1 cells by about 90% and
40%, respect ively [34]. Similarly, the epoxygenase inhibitor
SKF525A led to a concentration-dependent superinduc tion
of LPS-induced PGE
2
in rat monocytes and COX-2 in mouse
and human monocytes [41]. Consistent with these find-
ings, exogenous 11,12-EET dose dependently inhibited LPS-
induced PGE
2
and attenuated SKF-mediated superinduc-
tion. 11,12-EET also inhibited LPS-induced COX-2 activity
and expression [41]. EETs can, therefore, both compete with
arachidonic acid for the binding site in COX enzymes as
well as inhibit the inflammation induced induction of COX-
2 expression. A study found that EETs were detected in
human peritoneal macrophages under basal conditions, but
not following zymosan treatment, which caused a shift to
prostaglandin synthesis [42].
5.3. Leukocyte Endothelial Cell Interactions. Several studies
have demonstrated that EETs can regulate functional inter-
action between leukocytes and endothelial cells. Treatment
of endothelial cells with 14,15-EET significantly enhanced
attachment of the monocytic cell line U937 [ 43]. Pretreat-
ment of endothelial cells with EETs alone or in combi-
nation with PMA had neglig ible eects on adherence of
PMNs. However, cotreatment of EETs and PMA led to a
concentration-dependent decrease in adherence of PMNs
when cocultured with endothelial cells [44]. 11,12-EET, but
not 14,15-EET, was shown to inhibit adherence of monocytic
cells in an ex vivo model. Mice were treated with TNFα
alone or in combination with either 11,12-EET or 14,15-EET,
and carotid arteries were remove d and incubated with U937
cells. The l evel of inhibition of adherent cells was comparable
to that of treatment with a blocking VCAM-1 antibody
[35]. PBMCs derived from mice systemically overexpressing
human CYP2J2 via in vivo gene delivery were significantly
less adherent to TNFα-treated HUVECs compared to control
PBMCs [39].
5.4. In Vivo Models. There have been conflicting reports
on the eects of EETs i n acute models of inflammation in
vivo. Rats injected with TNFα showed elevated plasma levels
of adhesion molecules and inflammatory cytokines, and
decreased levels of the anti-inflammatory mediator IL-10.
However, these eects were sig nificantly reduced by systemic
overexpression of human CYP2J2 [39], suggesting that EETs
act as anti-inflammatory mediators. Similarly, TNFα-treated
human bronchi also showed reduced inflammation when
treated with 14,15-EET [45]. LPS responses of wild-ty pe
mice have also been compared to sEH
/ null mice or mice
that had endothelial-specific overexpression of the human
CYP2J2 or CYP2C8. All three genetically modified mice
had reduced levels of inflammatory gene expression and
neutrophil recruitment in the lung following LPS injection.
Moreover, these eects correlated with decreased ac tivation
of the key transcription factor NF-κB[40]. By contrast,
another study found that to sEH
/ null mice were not
protected from LPS-induced inflammatory gene expression
or neutrophil recruitment in the liver, and that treatment
with the sEH inhibitor AUDA also had minimal eect liver
inflammation, despite higher levels of endogenous EETs [46].
4 International Journal of Vascular Medicine
This suggests that either the eects of EETs are organ specific,
or that liver is more susceptible to endotoxin shock.
6. Mechanisms of EET Action
6.1. NF-κB Inhibition. The mechanisms by which EETs
mediate their anti-inflammatory eects remain ill-defined,
but there are several reports that they can inhibit activation
of NF-κB, a key transcription factor for inflammatory gene
induction. In mammals NF-κB comprises five subunits, with
the RelA (p65) subunit being expressed in most cell types.
Under basal conditions, NF-κB dimers are localised in the
cytoplasm due to interactions with IκB (inhibitor of NF-
κB) proteins. Signalling cascades induced by inflammator y
descend on the IKK (inhibitor of NF-κB kinase) complex,
which phosphorylates IκB. This tags IκBforsubsequent
ubiquitination and degradation by the proteosome, which, in
turn, facilitates NF-κB nuclear t ranslocation where it binds
to its cognate binding elements to activate transcription
[47, 48].
11,12-EET inhibits NF-κBreporteractivityinboth
HEK293 cells [34] a nd human endothelial cells [35]fol-
lowing stimulation. Furthermore, 11,12-EET also inhibited
TNFα-induced RelA nuclear translocation, IκBα degrada-
tion, and IKKα activity, respectively [35], indicating that
EET-mediated inhibition of NF-κB occurs upstream of IKK.
Interestingly, 14,15-EET was also shown to inhibit the
TNFα-induced degradation of IκBα in primary human lung
tissue [45]buthadnoeect on NF-κBreporteractivity
in HEK293s, suggesting that 14,15-EET may act in a cell
type-specific manner. Similarly, 8,9-EET and 11,12-EET
inhibited NF-κB reporter gene activity in HEK293 cells [34].
In contrast to CYP2J2, CYP2C9 increased NF-κBactivity
in human vascular endothelium via sup eroxide generation,
potentially giving this CYP a proinflammatory profile [49].
6.2. STAT3. EETs can also activate STAT3 in human breast
cancer cell lines, with 14,15-EET promoting STAT3 tyrosine-
705 phosphorylation and nuclear translocation [16]. Acti-
vation of STAT3 was shown to be dependent on cell
proliferation, which led the authors to conclude that 14,15-
EET may be involved in an autocrine/paracrine pathway
driving cell growth. Interestingly, the anti-inflammatory
eects of IL-10 in macrophages are also dependent on STAT3
tyrosine-705 phosphorylation [50]. Taken together, these
results suggest that the anti-inflammatory eects of EETs
may be mediated by activation of STAT3, in addition to the
inhibition of NF-κB.
6.3. EETs as PPAR Agonists. PPARs are a subfamily of the
nuclear receptor superfamily that comprises three ligand-
activated tr anscription factors: PPARα (NR1C1), PPARβ/δ
(NR1C2), and PPARγ (NR1C3). Upon ligand binding, they
form heterodimers with the retinoid X receptor and bind to
specific response elements in gene promoters to upregulate
gene transcription [51]. PPARs have been show n to regulate
diverse physiological processes such a s fatty acid and glucose
metabolism, angiogenesis, and cellular proliferation and
dierentiation, in addition to inflammation. PPAR ligands
include a variety of fatty acids, and there has been recent
evidence that metabolites of the epoxygenase pathway can
activate PPAR receptors.
The omega -alcohol of 14,15-EET, 20,14,15-HEET, or a
1 : 4 mixture of the omega-alcohols of 8,9- and 11,12-EETs
activated human and mouse PPARα in transient transfection
assays, suggesting a role for them as endogenous ligands
for these orphan nuclear receptors [52]. Overexpression of
human CYP2J2 in HEK293 cells resulted in a synergistic
activation of PPARα,-β/δ and, -γ reporter gene activity .
8,9-EET and 11,12-EET, but not 14,15-EET, (in contrast to
its hydroxy metabolite 20,14,15-HEET) were able to induce
PPARα reporter activity [53]. Furthermore, IL-1β-induced
NF-κB reporter ac tivity and COX-2 mRNA induction in
HEK293 cells was significantly inhibited cells expressing of
CYP2J2 and PPARα.
Competition and direct binding assays subsequently
revealed that EETs bind to the ligand-binding domain of
PPARγ with K(d) in the μM range. In the presence of the
sEH inhibitor AUDA, EETs increased PPARγ transcription
activity in endothelial cells and 3T3-L1 preadipocytes. In
endothelial cells, AUDA enhanced, but overexpression of
sEH reduced laminar flow-induced PPARγ activity, EET
generation, and the inhibition of VCAM-1 expression [54].
PPARs, therefore, represent a viable receptor target for the
anti-inflammatory eects of EETs. However, it should be
noted that AUDA may exert multiple eects in addition to
sEH inhibition. It has b een shown to act both as a PPAR
agonist [55] and a EET mimetic [56]; therefore, results using
AUDA should be cautiously interpreted.
6.4. GPCRs. ForsometimeithasbeensuggestedthatEETs
might mediate many of their eects v ia binding to a putative
G-protein coupled receptor(s) (GPCRs). For example, 11,12-
EET produced a 0.5- to 10-fold increase in the activity of the
KCa channels in smooth muscle cells derived from bovine
coronary arteries, which was dependent on the presence of
GTP [57]. Furthermore, blocking antibodies against GSα,
but not Gβγ or anti-Giα, were able to inhibit the activation
induced by 11,12-EET [57]. Using radio-ligand binding,
14,15-EET has been shown to have a high a
nity for a
receptor expressed on guinea pig-derived mononuclear cells,
which was purported to be a G-protein coupled receptor
that stimulated cAMP production [58]. This putative GPCR-
cAMP pathway remains elusive but may represent a novel
anti-inflammatory pathway by which EETs act.
6.5. TRPV1 and EETs. TRPV4 is a cation channel of the
“transient receptor potential” (TRP) family that functions
as a Ca
2+
entry channel, that is expressed in smooth muscle
cells, endothelial cells, as well as in perivascular nerves.
CYP-dependent generation of 5,6-EET can activate TRPV4
in murine endothelial cells and is a possible contributing
mechanism to the hyperpolarising eects of EETs [59].
Additionally, 11,12-EET can ac tivate TRPV4 channels in
smooth muscle cells from rat cerebral arteries [60], and 5,6-
EET and 8,9-EET can a ctivate TRPV4 in human endothelial
International Journal of Vascular Medicine 5
cells [61]. Although activated by EETs, there is little evidence
that ac tivation of TRPV4 is anti-inflammatory, though it
does lead to vasodilation via nitric oxide, prostacyclin,
and intermediate/small conductance K+ channel-dependent
pathways, and in vascular smooth muscle, large conductance
K+ channel activation, and hyperpolarization [62].
7. Summary and Outlook
More than 100 metabolites der ived from arachidonic acid
have been described, with the best characterised com-
ing from the COX and LOX pathways which generate
prostanoids and leukotrienes, respectively [63]. Knowledge
of these pathways has led to several important therapeutic
breakthroughs such as COX inhibitors which are used to
treat pain and inflammation and leukotriene antagonists
that have been used to treat asthma. By contrast, much less
is known about the epoxygenase pathway of arachidonic
acid metabolism, although as outlined in this paper, EETs
can exert a number of cardio-protective anti-inflammatory
eects on vascular cells such as endothelial cells and
monocytes. These include inhibition of proinflammatory
mediators and cell adhesion molecules. Indeed, a recent
study has measured epoxygenase products in atherosclerotic
patients [64]. Compared to healthy volunteers, both obese
and nonobese CAD patients had significantly higher plasma
EETs [64], suggesting that this is a compensation mechanism
to protect against ongoing vascular inflammation.
Although elevating epoxygenase products via sEH inhi-
bition have been shown to be beneficial in a wide variety
of animal models of cardiovascular disease, the mecha-
nisms through which these eects are mediated are still
largely unknown, although NF-κBandSTAT3haveboth
been implicated. However, several fundamental question
regarding the role of EETs in vascular inflammation remain
unanswered. Firstly, it is clear that CYP epoxygenases can act
on substrates other than arachidonic acid, such as cardio-
protective fish oils. Eicosapentaenoic acid for example is an
omega-3 long chain fatty acid that diers from arachidonic
acid by the addition of one extra double bond at the 17-
18 carbon position. Epoxygenation of eicosapentaenoic acid
by CYP enzymes generates 17,18-epoxyeicosatrienoic acid,
which has a hyperpolarising eect on bronchial smooth
muscle cells in vitro and in vivo [65]. Similarly, linoleic
acid, which is the major dietary fat, can be epoxygenated
by CYP enzymes resulting in potent metabolites which
are probably proinflammatory in nature. However, little is
known regarding the function of many of these alternative
epoxygenase metabolites have on the cardiovascular system
during inflammation. Secondly, the full range of epoxy-
genase ac tivity by CYP enzymes in healthy and diseased
physiological settings is still not completely understood and
remains a significant barrier to progress in the field. Thirdly,
and probably most importantly, definitive identification of
a specific receptor that mediates the activities of EETs
is essential to fully understand the epoxygenase pathway,
and will help to elucidate new therapies for cardiovascular
diseases in the future.
Acknowledgment
This work was supported by the British Heart Foundation
(PG/11/39/28890).
References
[1] G. Leonarduzzi, P. Gamba, S. Gargiulo, F. Biasi, and G. Poli,
“Inflammation-related gene expression by lipid oxidation-
derived products in the progression of atherosclerosis, Free
Radical Biology and Medicine, vol. 52, no. 1, pp. 19–34.
[2] P. He, “Leucocyte/endothelium interactions and microves-
sel permeability: coupled or uncoupled?” Cardiovascular
Research, vol. 87, no. 2, pp. 281–290, 2010.
[3] C. H. Y. Wong, B. Heit, and P. Kubes, “Molecular regulators
of leucocyte chemotaxis during inflammation, Cardiovascular
Research, vol. 86, no. 2, pp. 183–191, 2010.
[4] P. Libby, G. Sukhova, R. T. Lee, and Z. S. Galis, “Cytokines reg-
ulate vascular functions related to stability of the atheroscle-
rotic plaque, Journal of Cardiovascular Pharmacology, vol. 25,
supplement 2, pp. S9–S12, 1995.
[5] J. Capdevila, N. Chacos, and J. Werringloer, “Liver microsomal
cytochrome P-450 and the oxidative metabolism of arachi-
donic acid, Proceedings of the National Academy of Sciences
of the United States of America, vol. 78, no. 9, pp. 5362–5366,
1981.
[6] E. H. Oliw and J. A. Oates, “Oxygenation of arachidonic
acid by hepatic microsomes of the rabbit; mechanism of
biosynthesis of two vicinal dihydroxyeicosatrienoic acids,
Biochimica et Biophysica Acta, vol. 666, no. 3, pp. 327–340,
1981.
[7] E. H. Oliw and P. Moldeus, “Metabolism of arachidonic acid
by isolated rat hepatocytes, renal cells and by some rabbit
tissues. Detection of vicinal diols by mass fragmentogr aphy,
Biochimica et Biophysica Acta, vol. 721, no. 2, pp. 135–143,
1982.
[8] J.Capdevila,N.Chacos,andJ.R.Falck,“Novelhypothalamic
arachidonate products stimulate somatostatin release from the
median eminence, Endocrinology, vol. 113, no. 1, pp. 421–423,
1983.
[9]J.Capdevila,G.D.Snijder,andJ.R.Falck,“Epoxygenation
of arachidonic acid by rat anterior pituitary microsomal
fractions, FEBS Letters, vol. 178, no. 2, pp. 319–322, 1984.
[10] D. R. Nelson, D. C. Zeldin, S. M. G. Homan, L. J. Maltais, H.
M. Wain, and D. W. Nebert, “Comparison of cytochrome P450
(CYP) genes from the mouse and human genomes, including
nomenclature recommendations for genes, pseudogenes and
alternative-splice variants, Pharmacogenetics, vol. 14, no. 1,
pp. 1–18, 2004.
[11] F. Peter Guengerich and Q. Cheng, “Orphans in the human
cytochrome P450 superfamily: approaches to discovering
functions and relevance in pharmacology, Pharmacological
Reviews, vol. 63, no. 3, pp. 684–699, 2011.
[12] B. E. Daikh, J. M. Lasker, J. L. Raucy, and D. R. Koop, “Regio-
and stereoselective epoxidation of arachidonic acid by human
cytochromes P450 2C8 and 2C9, JournalofPharmacology
and Experimental Therapeutics, vol. 271, no. 3, pp. 1427–1433,
1994.
[13] S. Wu, C. R. Moomaw, K. B. Tomer, J. R. Falck, and D.
C. Zeldin, “Molecular cloning and expression of CYP2J2, a
human cytochrome P450 arachidonic acid epoxygenase highly
expressedinheart,The Journal of Biological Chemistry, vol.
271, no. 7, pp. 3460–3468, 1996.
6 International Journal of Vascular Medicine
[14] A. Gaedigk, D. W. Baker, R. A. Totah et al., “Variability
of CYP2J2 expression in human fetal tissues, Journal of
Pharmacology and Experimental Therapeutics, vol. 319, no. 2,
pp. 523–532, 2006.
[15] A. B. Rifkind, C. Lee, T. K. H. Chang, and D. J. Waxman,
Arachidonic acid metabolism by human cytochrome P450s
2C8, 2C9, 2E1, and 1A2: regioselective oxygenation and
evidence for a role for CYP2C enzymes in arachidonic
acid epoxygenation in human liver microsomes, Archives of
Biochemistry and Biophysics, vol. 320, no. 2, pp. 380–389, 1995.
[16] R. Mitr a, Z. Guo, M. Milani et al., “CYP3A4 mediates growth
of estrogen receptor-positive breast cancer cells in part by
inducing nuclear translocation of phospho-Stat3 through
biosynthesis of (
±)-14,15-epoxyeicosatrienoic acid (EET),
The Journal of Biological Chemistry, vol. 286, no. 20, pp.
17543–17559, 2011.
[17] J. H. Capdevila, A. Karara, D. J. Waxman, M. V. Martin, J.
R. Falck, and F. P. Guenguerich, “Cytochrome P-450 enzyme-
specific control of the regio- and enantiofacial selectivity of
the microsomal arachidonic acid epoxygenase, The Journal of
Biological Chemistry, vol. 265, no. 19, pp. 10865–10871, 1990.
[18] D. S. Keeney, C . Skinner, S. Wei, T. Friedberg, and M. R.
Waterman, A keratinocyte-specific epoxygenase, CYP2B12,
metabolizes arachidonic acid with unusual selectivity, produc-
ing a single major epoxyeicosatrienoic acid, The Journal of
Biological Chemistry, vol. 273, no. 15, pp. 9279–9284, 1998.
[19] C. M. Thompson, J. H. Capdevila, and H. W. Strobel, “Recom-
binant cytochrome P450 2D18 metabolism of dopamine and
arachidonic acid, Journal of Pharmacology and Expe rimental
Therapeutics, vol. 294, no. 3, pp. 1120–1130, 2000.
[20] M. F. Oleksiak, S. Wu, C. Parker, S. I. Karchner, J. J. Stegeman,
and D. C. Zeldin, “Identification, functional characterization,
and regulation of a new cytochrome P450 subfamily, the
CYP2Ns, The Journal of Biological Chemistry, vol. 275, no. 4,
pp. 2312–2321, 2000.
[21] X. Nguyen, M. H. Wang, K. M. Reddy, J. R. Falck, and M.
L. Schwartzman, “Kinetic profile of the rat CYP4A isoforms:
arachidonic acid metabolism and i soform-specific inhibitors,
American Journal of Physiology, vol. 276, no. 6, part 2, pp.
R1691–R1700, 1999.
[22] J. D. Imig, “Epoxides and soluble epoxide hydrolase in
cardiovascular physiology, Physiological Reviews, vol. 92, no.
1, pp. 101–130.
[23]B.T.Larsen,H.Miura,O.A.Hatoumetal.,“Epoxye-
icosatrienoic and dihydroxyeicosatrienoic acids dilate human
coronary arterioles via BKCa channels: implications for
soluble epoxide hydrolase inhibition, American Journal of
Physiology, vol. 290, no. 2, pp. H491–H499, 2006.
[24]A.A.Spector,X.Fang,G.D.Snyder,andN.L.Weintraub,
“Epoxyeicosatrienoic acids (EETs): metabolism and biochem-
ical function, Progress in Lipid Research, vol. 43, no. 1, pp. 55–
90, 2004.
[25] J. D. Imig, “Eicosanoid regulation of the renal vasculature,
American Journal of Physiology, vol. 279, no. 6, pp. F965–F981,
2000.
[26] N. L. Weintraub, X. Fang, T. L. Kaduce, M. VanRollins,
P. Chatterjee, and A. A. Spector, “Epoxide hydrolases reg-
ulate epoxyeicosatrienoic acid incorporation into coronary
endothelial phospholipids, American Journal of Physiology,
vol. 277, no. 5, part 2, pp. H2098–H2108, 1999.
[27] D. Zhang, X. Xie, Y. Chen, B. D. Hammock, W. Kong, and
Y. Zhu, “Homocysteine upregulates soluble epoxide hydrolase
in vascular endothelium in vitro and in vivo, Circulation
Research, vol. 110, no. 6, pp. 808–817.
[28] M. Revermann, M. Schloss, E. Barbosa-Sicard et al., “Soluble
epoxide hydrolase deficiency attenuates neointima formation
in the femoral cumodel of hyperlipidemic mice, Arterioscle-
rosis, Thrombosis, and Vascular Biology, vol. 30, no. 5, pp. 909–
914, 2010.
[29] L. N. Zhang, J. Vincelette, Y. Cheng et al., “Inhibition of sol-
uble epoxide hydrolase attenuated atherosclerosis, abdominal
aortic aneurysm formation, and dyslipidemia, Arteriosclero-
sis, Thrombosis, and Vascular Biology, vol. 29, no. 9, pp. 1265–
1270, 2009.
[30] C. R. Lee, J. D. Imig, M. L. Edin et al., “Endothelial
expression of human cytochrome P450 epoxygenases lowers
blood pressure and attenuates hypertension-induced renal
injur y in mice, The FASEB Journal, vol. 24, no. 10, pp. 3770–
3781, 2010.
[31] P. Luo, H. H. Chang, Y. Zhou et al., “Inhibition or deletion of
soluble epoxide hydrolase prevents hyperglycemia, promotes
insulin secretion, and reduces islet apoptosis, Journal of
Pharmacology and Experimental Therapeutics, vol. 334, no. 2,
pp. 430–438, 2010.
[32] B. Fissithaler, R. Popp, L. Kiss et al., “Cytochrome P450 2C is
an EDHF synthasein coronary arteries, Nature, vol. 401, no.
6752, pp. 493–497, 1999.
[33] B. Fisslthaler, I. Fleming, and R. Busse, “EDHF: a cytochrome
P450 metabolite in coronary arteries, Seminars in Perinatol-
ogy, vol. 24, no. 1, pp. 15–19, 2000.
[34] J. Bystrom, J. A. Wray, M. C. Sugden et al., “Endogenous
epoxygenases are modulators of monocyte/macrophage activ-
ity, PLoS ONE, vol. 6, no. 10, Article ID e26591, 2011.
[35] K. Node, Y. Huo, X. Ruan et al., Anti-inflammatory prop-
erties of cytochrome P450 epoxygenase-derived eicosanoids,
Science, vol. 285, no. 5431, pp. 1276–1279, 1999.
[36] K. Nakayama, T. Nitto, T. Inoue, and K. Node, “Expression
of the cytochrome P450 epoxygenase CYP2J2 in human
monocytic leukocytes, Life Sciences, vol. 83, no. 9-10, pp. 339–
345, 2008.
[37] M. Spiecker, H. Darius, T. Hankeln et al., “Risk of coro-
nary artery disease associated with polymorphism of the
cytochrome P450 epoxygenase CYP2J2, Circulation, vol. 110,
no. 15, pp. 2132–2136, 2004.
[38] U. R. Michaelis, B. Fisslthaler, M. Medhora, D. Harder,
I. Fleming, and R. Busse, “Cytochrome P450 2C9-derived
epoxyeicosatrienoic acids induce angiogenesis via cross-talk
with the epidermal growth factor receptor (EGFR), The
FASEB Journal, vol. 17, no. 6, pp. 770–772, 2003.
[39] G. Zhao, L. Tu, X. Li et al., “Delivery of AAV2-CYP2J2 protects
remnant kidney in the 5/6-nephrectomized rat via inhibition
of apoptosis andfibrosis, Human Gene Therapy. In press.
[40] Y. Deng, M. L. Edin, K. N. Theken et al., “Endothelial CYP
epoxygenase overexpression and soluble epoxide hydrolase
disruption attenuate acute vascular inflammatory responses in
mice, The FASEB Journal, vol. 25, no. 2, pp. 703–713, 2011.
[41] W. Kozak, D. M. Arono, O. Boutaud, and A. Kozak, “11,12-
Epoxyeicosatrienoic acid attenuates synthesis of prostaglandin
E2 in rat monocytes stimulated with lipopolysaccharide,
Experimental Biology and Medicine, vol. 228, no. 7, pp. 786–
794, 2003.
[42] K. Werner, W. R. Schaefer, H. Schweer, W. R. Deppert, U.
Karck, and H. P. Zahradnik, “Characterization and identifi-
cation of cytochrome P450 metabolites of arachidonic acid
released by human peritoneal macrophages obtained from the
International Journal of Vascular Medicine 7
pouch of Doug las, Prostaglandins Leukotrienes and Essential
Fatty Acids, vol. 67, no. 6, pp. 397–404, 2002.
[43] K. A. Pritchard Jr., R. R. Tota, M. B. Stemerman, and P. Y. K.
Wong, “14,15-Epoxyeicosatrienoic acid promotes endothelial
cell dependent adhesion of human monocytic tumor U937
cells, Biochemical and Biophysical Research Communications,
vol. 167, no. 1, pp. 137–142, 1990.
[44] P. F. Pratt, M. Rosolowsky, and W. B. Campbell, “Eects of
epoxyeicosatrienoic acids on polymorphonuclear leukocyte
function, Life Sciences, vol. 70, no. 21, pp. 2521–2533, 2002.
[45] C. Morin, M. Sirois, V. Echave, M. M. Gomes, and E.
Rousseau, “EET displays anti-inflammatory eects in TNF-α-
stimulated human bronchi: putative role of CPI-17, American
Journal of Respiratory Cell and Molecular Biology, vol. 38, no. 2,
pp. 192–201, 2008.
[46] K. L. Fife, Y. Liu, K . R. Schmelzer et al., “Inhibition of
soluble epoxide hydrolase does not protect against endotoxin-
mediated hepatic inflammation, Journal of Pharmacology and
Exper imental Therapeutics, vol. 327, no. 3, pp. 707–715, 2008.
[47] M. S. Hayden and S. Ghosh, “Shared principles in NF-κB
signaling, Cell, vol. 132, no. 3, pp. 344–362, 2008.
[48] M. S. Hayden and S. Ghosh, “NF-κB, the first quarter-century:
remarkable progress and outstanding questions, Genes &
Development, vol. 26, no. 3, pp. 203–234, 2012.
[49] I. Fleming, U. R. Michaelis, D. Bredenk
¨
otter et al.,
“Endothelium-derived hyperpolarizing factor synthase
(cytochrome P450 2C9) is a functionally significant source
of reactive oxygen species in coronary arteries, Circulation
Research, vol. 88, no. 1, pp. 44–51, 2001.
[50] L. Williams, L. Bradley, A. Smith, and B. Foxwell, “Signal
transducer and activator of transcription 3 is the dominant
mediator of the anti-inflammatory eects of IL-10 in human
macrophages, Journal of Immunology, vol. 172, no. 1, pp. 567–
576, 2004.
[51] J. Berger and D. E. Moller, The mechanisms of action of
PPARs, Annual Review of Medicine, vol. 53, pp. 409–435,
2002.
[52]L.A.Cowart,S.Wei,M.H.Hsuetal.,“TheCYP4A
isoforms hydroxylate epoxyeicosatrienoic acids to form high
anity peroxisome proliferator-activated receptor ligands,
The Journal of Biological Chemistry, vol. 277, no. 38, pp.
35105–35112, 2002.
[53] J. A. Wray, M. C. Sugden, D. C. Zeldin et al., “The epoxyge-
nases CYP2J2 activates the nuclear receptor PPARα in vit ro
and in vivo, PLoS ONE, vol. 4, no. 10, Article ID e7421, 2009.
[54] Y. Liu, Y. Zhang, K. Schmelzer et al., The antiinflammatory
eect of laminar flow: the role of PPARγ, epoxyeicosatrienoic
acids, and soluble epoxide hydrolase, Proceedings of the
National Academy of Sciences of the United States of America,
vol. 102, no. 46, pp. 16747–16752, 2005.
[55] X. Fang, S. Hu, B. Xu et al., “14,15-Dihydroxyeicosatrienoic
acid activates peroxisome proliferator-activated receptor-α,”
American Journal of P hysiology, vol. 290, no. 1, pp. H55–H63,
2006.
[56] J. J. Olearczyk, M. B. Field, I. H. Kim, C. Morisseau, B.
D. Hammock, and J. D. Imig, “Substituted adamantyl-urea
inhibitors of the soluble epoxide hydrolase dilate mesenteric
resistance vessels, Journal of Pharmacology and Experimental
Therapeutics, vol. 318, no. 3, pp. 1307–1314, 2006.
[57] P. L. Li and W. B. Campbell, “Epoxyeicosatrienoic acids
activate K
+
channels in coronary smooth muscle through a
guanine nucleotide binding protein, Circulation Research, vol.
80, no. 6, pp. 877–884, 1997.
[58] P. Y. K. Wong, K. T. Lin, Y. T. Yan et al., “14(R),15(S)-
epoxyeicosatrienoic acid (14(R),15(S)-EET) receptor in
guinea pig mononuclear cell membranes, Journal of Lipid
Mediators, vol. 6, no. 1–3, pp. 199–208, 1992.
[59]H.Watanabe,J.Vriens,J.Prenen,G.Droogmans,T.Voets,
and B. Nillus, Anandamide and arachidonic acid use epoxye-
icosatrienoic acids to activate TRPV4 channels, Nature, vol.
424, no. 6947, pp. 434–438, 2003.
[60]S.Earley,T.J.Heppner,M.T.Nelson,andJ.E.Brayden,
“TRPV4 forms a novel Ca
2+
signaling complex with ryanodine
receptors and BKCa channels, Circulation Research, vol. 97,
no. 12, pp. 1270–1279, 2005.
[61] J. Vriens, G. Owsianik, B. Fisslthaler et al., “Modulation of the
Ca
2+
permeable cation channel TRPV4 by cytochrome P450
epoxygenases in vascular endothelium, Circulation Research,
vol. 97, no. 9, pp. 908–915, 2005.
[62] R. L. Baylie and J. E. Brayden, “TRPV channels and vascular
function, Acta Physiologica, vol. 203, no. 1, pp. 99–116.
[63] M. W. Buczynski, D. S. Dumlao, and E. A. Dennis, An
integrated omics analysis of eicosanoid biology, Journal of
Lipid Research, vol. 50, no. 6, pp. 1015–1038, 2009.
[64] K. N. Theken, R. N. Schuck, M. L. Edin et al., “Evaluation
of cytochrome P450-derived eicosanoids in humans w i th
stable atherosclerotic cardiovascular disease, Atherosclerosis,
vol. 222, no. 2, pp. 530–536.
[65] C. Morin, M. Sirois, V. Echave, E. Rizcallah, and E. Rousseau,
“Relaxing eects of 17(18)-EpETE on arterial and airway
smooth muscles in human lung, American Journal of Physi-
ology, vol. 296, no. 1, pp. L130–L139, 2009.
    • "The correlation of DAS28 and its improvement with the anti-inflammatory CYP-450 dihydroxy-fatty acids metabolites and the LOX derived LXA 4 possibly reflects the intact innate anti-inflammatory pathways in these patients still trying to lessen the RA disease burden. The dihydroxy-fatty acids, 14,15-DiHETE, 11,12- EpETrE and 14,15-DiHETrE are able to attenuate proinflammatory pathways through activating and signalling via the PPAR-gamma pathway [42]. The urinary oxidised lipid profile of RA patients indicates the complex nature of the disease with oxidative stress and inflammation having an intimate relationship with clinically measured parameters. "
    [Show abstract] [Hide abstract] ABSTRACT: Oxidised lipids, covering enzymatic and auto-oxidation-synthesised mediators, are important signalling metabolites in inflammation while also providing a readout for oxidative stress, both of which are prominent physiological processes in a plethora of diseases. Excretion of these metabolites via urine is enhanced through the phase-II conjugation with glucuronic acid, resulting in increased hydrophilicity of these lipid mediators. Here, we developed a bovine liver-β-glucuronidase hydrolysing sample preparation method, using liquid chromatography coupled to tandem mass spectrometry to analyse the total urinary oxidised lipid profile including the prostaglandins, isoprostanes, dihydroxy-fatty acids, hydroxy-fatty acids and the nitro-fatty acids. Our method detected more than 70 oxidised lipids biosynthesised from two non-enzymatic and three enzymatic pathways in urine samples. The total oxidised lipid profiling method was developed and validated for human urine and was demonstrated for urine samples from patients with rheumatoid arthritis. Pro-inflammatory mediators PGF2α and PGF3α and oxidative stress markers iPF2α- IV, 11-HETE and 14-HDoHE were positively associated with improvement of disease activity score. Furthermore, the anti-inflammatory nitro-fatty acids were negatively associated with baseline disease activity. In conclusion, the developed methodology expands the current metabolic profiling of oxidised lipids in urine, and its application will enhance our understanding of the role these bioactive metabolites play in health and disease.
    Full-text · Article · Jul 2016
    • "Although the existence and biological relevance of prostaglandins have been known for over half a century , the contribution of EETs to the regulation of these processes has only been realized within the past two decades (Morisseau and Hammock, 2013). Compared to the pro-inflammatory prostaglandins, EETs are potently anti-inflammatory (Thomson et al., 2012 ), antihypertensive (Jiang et al., 2011), anticonvulsive (Inceoglu et al., 2013 ) and analgesic (Inceoglu et al., 2008; Inceoglu et al., 2006). Concentrations of EETs are reported to be regulated both by their synthesis by P450s, particularly −2J2 and −2C8 in addition to others, and by their hydrolysis by sEH (Chacos et al., 1983; Imig, 2012; Morisseau and Hammock, 2013). "
    [Show abstract] [Hide abstract] ABSTRACT: Epoxyeicosatrienoic acids (EETs) are potent endogenous analgesic metabolites produced from arachidonic acid by cytochrome P450s (P450s). Metabolism of EETs by soluble epoxide hydrolase (sEH) reduces their activity, while their stabilization by sEH inhibition decreases both inflammatory and neuropathic pain. Here, we tested the complementary hypothesis that increasing the level of EETs through induction of P450s by omeprazole (OME), can influence pain related signaling by itself, and potentiate the anti-hyperalgesic effect of sEH inhibitor. Rats were treated with OME (100mg/kg/day, p.o., 7days), sEH inhibitor TPPU (3mg/kg/day, p.o.) and OME (100mg/kg/day, p.o., 7days)+TPPU (3mg/kg/day, p.o., last 3days of OME dose) dissolved in vehicle PEG400, and their effect on hyperalgesia (increased sensitivity to pain) induced by PGE2 was monitored. While OME treatment by itself exhibited variable effects on PGE2 induced hyperalgesia, it strongly potentiated the effect of TPPU in the same assay. The significant decrease in pain with OME+TPPU treatment correlated with the increased levels of EETs in plasma and increased activities of P450 1A1 and P450 1A2 in liver microsomes. The results show that reducing catabolism of EETs with a sEH inhibitor yielded a stronger analgesic effect than increasing generation of EETs by OME, and combination of both yielded the strongest pain reducing effect under the condition of this study.
    Full-text · Article · Nov 2015
    • "Despite the use of enabling formulations, increases in exposure following oral delivery are often not achieved. IT has been studied that (EETs) can affect vasodilatation and vasoconstriction in several vascular beds1234. According to their research, anti-inflammatory, anti-hypertensive, and other therapeutic benefitscan be achieved with increasing the levels of EETs567891011. "
    [Show abstract] [Hide abstract] ABSTRACT: Hypertension is a common medical condition in the general population. Researchers are constantly looking for new medications to control this disease. Recently, soluble epoxide hydrolase (sEH) was identified as possible new drug target for hypertension. 1, 3-dicyclohexylurea (1,3-DCU) was reported to inhibit the sEH at nM range. However, due to the poor oral bioavailability (BA) of 1,3-DCU (even at low dose), utilizing1,3 –DCU in this target research become problematic. It is believed that the key ADME issues of 1,3-DCU are poor aqueous solubility, poor dissolution rate, and high systemic clearance. Formerly, ananosuspension/crystalline nanoparticle formulation has been used in the rats and observed higherBA. Despite the improvement, the mechanism ofhow crystalline nanoparticleimproves the BA has not been fully understood. The prediction of howcrystalline nanoparticleperforms in vivoremains uncertain. Therefore, a tool needs to be developed to better understand the enhanced BA of 1,3-DCUcrystalline nanoparticle. In this study, the limitation of the oral delivery of 1, 3-DCU was assessed by a dynamic model combines measured intrinsic dissolution rate, particle size, gastrointestinal transit (GI), and diffusion through unstirred water layer to estimate the amount of drug absorbed and then followed by multi-compartmental pharmacokinetic analysis. It was found that this modeling approach adequately captures the effect of a crystalline nanoparticle formulation and mimicking the oral BA. The ultimate goal for this study is to assess the suitability of using a new dynamic modeling approach to predict in vivo performance of the crystalline nanoparticle. This work may aid in future investigations of similar compounds.
    Full-text · Article · Jul 2015 · Toxicology and Applied Pharmacology
Show more