Asthma Research Group, Father Sean O'Sullivan Research Center, Firestone Institute for Respiratory Health, St. Joseph's Hospital; and Department of Medicine, McMaster University, Hamilton, Ontario, Canada L8N 4A6
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ABSTRACT |
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Using muscle bath techniques, we examined the inhibitory activities of several E- and F-ring isoprostanes in canine and porcine airway smooth muscle. 8-Isoprostaglandin E1 and 8-isoprostaglandin E2 (8-iso PGE2) reversed cholinergic tone in a concentration-dependent manner, whereas the F-ring isoprostanes were ineffective. Desensitization with 8-iso-PGE2 and PGE2 implicated isoprostane activity at the PGE2 receptor (EP). We found that the inhibitory E-ring isoprostane responses were significantly augmented by rolipram (a type IV phosphodiesterase inhibitor), while 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (a guanylate cyclase inhibitor) had no effect, suggesting a role for cAMP in isoprostane-mediated relaxations. 8-Iso-PGE2 did not reverse KCl tone, suggesting that voltage-dependent Ca2+ influx and myosin light chain kinase are not suppressed by isoprostanes. Patch-clamp studies showed marked suppression of K+ currents by 8-iso-PGE2. We conclude that E-ring isoprostanes exert PGE2 receptor-directed, cAMP-dependent relaxations in canine and porcine airway smooth muscle. This activity is not dependent on K+ channel activation or the direct inhibition of voltage-operated Ca2+ influx or myosin light chain kinase.
cyclic nucleotides; potassium channels; calcium channels; prostanoid receptors
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INTRODUCTION |
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IT HAS BEEN SUGGESTED THAT the bronchodilatory and contractile effects of free radicals in airways are mediated by isoprostanes (9), a large family of prostaglandin (PG)-like molecules, produced in a cyclooxygenase-independent manner via free radical-mediated peroxidation of the membrane phospholipid arachidonic acid (22-25). These molecules, which differ from PGs in the cis orientation of their side chains at the cyclopentane ring junction, are present at levels in the nanomolar range in normal human plasma and urine (23). Isoprostanes are present in even higher concentrations during periods of oxidative stress (20, 21, 23, 27), in such diseases as asthma (18), cystic fibrosis (19), chronic obstructive pulmonary disorder (17), and atherosclerosis (33), and may contribute to the pathology of these diseases (13, 23, 28).
Researchers have only recently begun to demonstrate the biological
responses elicited by isoprostanes in many tissue types. Most research
has focused solely on the excitatory activity of 8-iso-PGF2, a vasoconstrictor (16, 28,
40), bronchoconstrictor (9, 13), and inhibitor of
platelet aggregation (26).
Very little is known about the signaling pathways or receptors through which inhibitory isoprostanes act. It has been suggested that isoprostanes may act via prostanoid receptors (4, 37); isoprostanes and prostanoids differ only in the orientation of their side chain, thus allowing for many similar binding interactions with receptor active site residues (1, 38).
The prostanoid receptors are categorized as follows: DP, EP, FP, IP,
and TP receptors, one each for the five principal metabolites PGD2, PGE2, PGF2,
PGI2, and thromboxane A2, respectively (with
each receptor having an affinity of
1 order of magnitude greater for
one prostanoid over the other four) (2, 29). The EP
receptor can be further subdivided into the EP1,
EP2, EP3, and EP4 subtypes, all of
which bind PGE2 with high affinity but differ with regard
to physiological activity and/or the signaling pathway induced
(29). Evidence supporting subtypes of the EP1, EP3, FP, and TP receptors exists as well (7, 15,
32).
There is evidence to support 8-iso-PGF2
acting as an agonist at the vascular TP receptors (16, 28,
40) while conversely acting antagonistically at platelet TP
receptors to inhibit aggregation (26).
8-Iso-PGE2 may act at the TP receptor as well in
renal vasculature (25). There are also studies that
support a role for the FP (39) and the EP prostanoid
receptors (34, 38, 39) in excitatory
8-iso-PGE2 activity. It has also been argued that
isoprostanes may exert their effects through their own unique class of
receptor (28).
Previously, we communicated the effects of seven different isoprostanes on airway smooth muscle, including the first description of relaxations evoked by E-ring isoprostanes (9). The aim of this study was to further enhance the present knowledge of isoprostanes and their inhibitory physiological responses. For this purpose, canine and porcine bronchial smooth muscle was used to examine the relaxant effects of several E- and F-ring isoprostanes as well as the signaling pathway(s) underlying these relaxations. Initial studies were also performed to assess the possibility that the relaxant isoprostanes act through the classic relaxant prostanoid receptors IP, DP, EP2, and EP4.
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METHODS |
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Tissue preparation. Adult mongrel dogs were euthanized with pentobarbital sodium (100 mg/kg), and lobes of lungs were excised; pig lungs were obtained from an abattoir. Trachea and lungs were placed in ice-cold Krebs solution (see Solutions and chemicals) and secured with dissection pins. The bronchus was carefully dissected by removal of the overlying connective tissue and pulmonary vasculature. Tracheal smooth muscle strips (~1 mm wide) and bronchial ring segments (3-5 mm OD, ~2-5 mm long) were excised and used immediately or stored at 4°C for use up to 48 h later.
Muscle bath studies. Tracheal strips and bronchial smooth muscle ring segments were hung in 4-ml baths. The tracheal strips were tied with silk thread (Ethicon 4-0), such that one end of the strip was anchored, while the other was fastened to a Grass FT.03 force transducer. Hooks inserted through the lumen, one of which was anchored and the other fastened to the transducer, were used to hang the bronchial rings. Changes in isometric force were digitized (at 2 Hz) and recorded on-line using the DigiMed System Integrator program (MicroMed, Louisville, KY).
Protocol.
Tissues were maintained in Krebs buffer containing 105 M
indomethacin (to prevent formation of endogenous PGs, which could cause
relaxation), gassed with 95% O2-5% CO2 to
give a final pH of 7.4, and maintained at 37°C. Preload tension was
applied and kept between 1.0 and 1.5 g (optimal resting tension)
to ensure maximal physiological responses. Tissues were equilibrated
for 1 h, during which time they were repeatedly washed with Krebs buffer. To establish a reference contraction for standardization of
contractile responses and to ensure tissue responsiveness, tissues were
challenged with 60 mM KCl. The KCl was then washed out, and tissues
were allowed to recover before the experiments were begun.
Patch-clamp studies.
Tracheal tissues were minced, transferred to dissociation buffer
containing collagenase (Sigma blend F; 0.9 U/ml) and elastase (type IV,
12.5 U/ml), incubated at 37°C for 1 h, and then gently triturated to liberate individual myocytes. These were allowed to
settle and adhere to the bottom of a recording chamber (1 ml volume)
and superfused with standard Ringer solution at room temperature. Electrophysiological responses were tested in cells that were phase
dense and appeared relaxed. Recordings were made using the nystatin
perforated-patch configuration of the conventional patch-clamp recording technique (8) and pipettes with tip resistances
of 3-5 M when filled with electrode solution. Membrane currents were filtered at 5 kHz and sampled at 2 Hz. Acquisition and analysis of
data were accomplished using Axopatch 200B and pCLAMP8 software (Axon
Instruments, Foster City, CA).
Solutions and chemicals.
The Krebs buffer consisted of 116 mM NaCl, 4.6 mM KCl, 2.5 mM
CaCl2, 1.3 mM NaH2PO4, 1.2 mM
MgSO4, 23 mM NaHCO3, 11 mM
D-glucose, and 105 M indomethacin bubbled to
maintain pH 7.4. The composition of the dissociation buffer was as
follows (mM): 125 NaCl, 5 KCl, 1 CaCl2, 1 MgCl2, 10 HEPES, 0.25 EDTA, 10 D-glucose, and
10 L-taurine (pH 7.0). The composition of the electrode
solution was as follows: 140 mM KCl, 1 mM MgCl2, 0.4 mM
CaCl2, 20 mM HEPES, 1 mM EGTA, and 150 U/ml nystatin (pH
7.2). The composition of Ringer buffer was as follows (mM): 130 NaCl, 5 KCl, 1 CaCl2, 1 MgCl2, 20 HEPES, and 10 D-glucose (pH 7.4). The isoprostanes were dissolved in ethanol, with the exception of
8-iso-PGF3
, which was dissolved in
methyl acetate; these stock solutions were then diluted with Krebs
buffer. Aqueous dilutions were discarded after 24 h. ODQ, S-nitroso-N-acetylpenicillamine (SNAP), rolipram,
and ICI-192605 were dissolved in DMSO. All other compounds were
dissolved in Krebs buffer. The isoprostanes and PGE2 were
obtained from Cayman Chemical (Ann Arbor, MI) and rolipram from
Research Biochemicals. Cicaprost, iloprost, and BW-245C were gifts from
Dr. Denis Crankshaw (McMaster University). All other chemicals were
obtained from Sigma Chemical.
Data analysis.
Relaxations were expressed as percent reversal of precontractile tone
(minus preload tone). The concentration at which 50% reversal of tone
was achieved ([R50] values) was interpolated from the
concentration-response relationships. The log [R50] value (in M) is used to express the potency of the drug; %R is used to
describe the percentage of relaxation evoked for the highest drug
concentration used (i.e., the maximal response); n is the number of animals used.
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RESULTS |
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Relaxant responses to isoprostanes in canine and porcine bronchial
smooth muscle.
Cumulative concentration-response relationships were investigated for
various E- and F-ring isoprostanes (Fig.
1). In canine and porcine tissues,
8-iso-PGF1,
8-iso-PGF2
, and
8-iso-PGF2
had little or no effect on
cholinergic tone. In canine tissue, 8-iso-PGE1,
8-iso-PGE2, and
8-iso-PGF3
were quite effective as
bronchodilators, achieving 78 ± 5, 83 ± 4, and 88 ± 4% reversal of tone, respectively, when applied at 10
5 M
(Fig. 2A):
log
[R50] values were 5.4 ± 0.05, 5.6 ± 0.1, and 5.5 ± 0.04 M, respectively. In porcine tissue,
8-iso-PGE1 and 8-iso-PGE2 at 10
5 M
achieved 59 ± 13 and 59 ± 7% reversals at a concentration
of 10
5 M (Fig. 2B). The cost of these
compounds prevented us from testing at >10
5 M.
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Receptor identity.
It has been suggested that isoprostanes may act via the classic
prostanoid receptors (4, 37), three of which, DP, IP, and
EP (EP2 and EP4 subtypes), are generally
inhibitory in smooth muscle. We first sought to ascertain which
inhibitory prostanoid receptors are present in canine bronchial tissue.
Cumulative concentration-response relationships were investigated using
the receptor-selective agonists cicaprost and iloprost (IP selective),
BW-245C (DP selective), and PGE2 (EP selective, but does
not distinguish between EP2 and EP4). The
DP-selective agonist exerted only minor reversal (25 ± 6%) of
cholinergic tone at 105 M (Fig.
3), whereas the IP-selective agonists
were somewhat more efficacious, their effects beginning in the
submicromolar range, but still reversed cholinergic tone by <50% at
the highest concentration tested (%R = 51 ± 8% for
cicaprost and 37 ± 4% for iloprost). The EP-selective agonist,
however, markedly reversed tone (%R = 76 ± 13% at
10
5 M), with
log [R50] estimated to be
6.4 ± 0.1 M. These results indicate that the inhibitory
prostanoid receptors in canine bronchi are predominantly of the EP
type.
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Role of cyclic nucleotides. The EP2 and EP4 receptors generally couple to the Gs protein to induce adenylate cyclase activity, resulting in increased cAMP levels and subsequent activation of protein kinase A, which in turn phosphorylates various targets, leading to smooth muscle relaxation (14, 29). cAMP can also cause elevation of cGMP levels by various means, leading to powerful relaxations (31). We therefore investigated the role of cAMP vs. cGMP in isoprostane-induced relaxations.
The effects of ODQ, an inhibitor of soluble guanylate cyclase, on 8-iso-PGE2- and SNAP-evoked responses were compared. ODQ had essentially no effect on 8-iso-PGE2-induced reversal of tone evoked by 10
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Inhibition of Ca2+ channels or myosin
light chain kinase.
Relaxant agonists may act by inhibiting Ca2+ influx and/or
suppressing myosin light chain kinase (MLCK) activity
(36). To test whether isoprostanes exert either of these
effects, we used tissues preconstricted with KCl (60 mM), which evokes
contractions that are entirely dependent on both of these processes.
Tissues were pretreated with atropine and propranolol to eliminate the contributions of cholinergic and adrenergic nerves stimulated by KCl.
8-Iso-PGE2 did not substantially reverse KCl tone, inducing <15% relaxation, compared with the complete reversal of tone in matching tissues preconstricted with 107 M CCh (Fig.
8). The relative lack of effect of the
isoprostane on KCl-evoked tone indicates that
8-iso-PGE2 does not have a major inhibitory
effect on voltage-gated Ca2+ channels or MLCK.
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Activation of K+ channels.
It is often suggested that bronchodilators mediate their effects in
part by opening K+ channels, leading to membrane
hyperpolarization and cessation of voltage-dependent Ca2+
influx. We used the patch-clamp electrophysiological technique to test
directly whether isoprostanes activate K+ currents. Figure
9A shows representative traces
of currents evoked using depolarizing step commands from a holding
potential of 60 mV; the current-voltage relationship is given in Fig.
9B. 8-Iso-PGE2 (10
5 M) in the
application pipette caused a marked suppression of these K+
currents: on average, currents evoked by pulses to +10 mV were reduced
72 ± 13% (n = 8). Clearly, then, isoprostanes do
not mediate their relaxant effects via activation of K+
channels.
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DISCUSSION |
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Researchers have only begun to characterize the biological effects
of isoprostanes. Most studies of isoprostane-elicited responses have
focused solely on the excitatory activity of 8-iso-PGF2 on various types of tissues. Only recently has attention been focused
on their potential inhibitory effects.
Previously, we reported the effects of seven different isoprostanes on airway smooth muscle, including the first description of relaxations evoked by E-ring isoprostanes (9). The results of this study demonstrate that 8-iso-PGE1 and 8-iso-PGE2 induce relaxations in canine and porcine bronchial smooth muscle with similar potencies, whereas F-ring isoprostanes are relatively ineffective in this respect. E-ring isoprostane-induced relaxations were conserved in epithelium-denuded porcine tracheal tissues as well as in N-nitro-L-arginine- and indomethacin-treated, epithelium-intact bronchial tissues (data not shown). This finding is consistent with isoprostanes acting directly on smooth muscle tissues, although a role for epithelium-derived relaxant mediators cannot be entirely discounted.
Isoprostanes and prostanoids share a similar structure, differing only
in the orientation of their side chains; thus it is reasonable to
assume that they are capable of forming similar binding interactions
with receptor active site residues (23). Indeed, Breyer
(1) and Ungrin et al. (38) shed some light on
the structural features of PGE2 required for binding to the EP1 prostanoid receptor, including the hydroxyl group on
the cyclopentane ring and the side chain, both of which are present
on the isoprostanes tested in this study. There is evidence to support
8-iso-PGF2
(16, 26, 28, 40) and
8-iso-PGE2 (25) activity at the TP
prostanoid receptor. There are also studies supporting the role of FP
(39) and EP excitatory prostanoid receptors (34, 38,
39) in 8-iso-PGE2 activity. On the other hand,
others argue for the existence of a unique class of isoprostane
receptors (28).
The EP2 prostanoid receptor, along with the IP and, to a lesser extent, the DP receptor, is known to be involved in human bronchial smooth muscle relaxations, whereas EP4 is not (30). EP2 was also shown to mediate airway smooth muscle relaxations in mice (6, 35). Our data suggest that IP and DP receptors are largely unimportant with respect to prostanoid relaxations in canine bronchial tissue, since only partial responses to the IP- and DP-selective agonists are seen and only at relatively high concentrations. Instead, these IP- and DP-selective agonists may be exerting nonspecific actions at inhibitory EP receptors, which are present and are likely to be involved in isoprostane-induced relaxations, as was demonstrated using receptor desensitization techniques. Using this approach, we determined that PGE2 desensitization of the 8-iso-PGE2 response and vice versa were due to homologous desensitization, inasmuch as neither 8-iso-PGE2 nor PGE2 induced heterologous desensitization of the isoproterenol response.
The EP2 and EP4 receptors couple to the Gs protein to induce adenylate cyclase activity, resulting in increased cAMP levels (14, 29). Inhibition of type IV phosphodiesterase activity with rolipram enhanced the relaxations to 8-iso-PGE1 and 8-iso-PGE2 in porcine and canine tissues. These results suggest that the two E-ring isoprostanes may induce relaxations through the accumulation of cAMP and that type IV phosphodiesterase opposes this. Further studies involving the inhibition of adenylate cyclase and protein kinase A would lend additional support to this conclusion. In contrast, the guanylate cyclase inhibitor ODQ had no effect on 8-iso-PGE2-induced relaxations, thus ruling out the involvement of cGMP in these responses.
Isoprostanes may induce relaxations by downregulating MLCK activity directly or indirectly via inhibition of Ca2+ influx from voltage-gated Ca2+ channels. KCl was employed to elicit contractions via membrane depolarization, promoting the opening of voltage-gated Ca2+ channels. The resulting influx of cytosolic Ca2+ activates MLCK, which phosphorylates myosin, thus allowing for interaction with actin filaments (36). Essentially no reversal of KCl tone was observed for 8-iso-PGE2, thus implying no direct inhibition of the voltage-gated Ca2+ channels or MLCK by 8-iso-PGE2 occured. However, no direct measurements of MLCK activity were performed.
Alternatively, 8-iso-PGE2 may activate K+
channels in the membrane. Bronchodilators such as -adrenergic
agonists and nitric oxide are proposed to induce relaxations in airways
via activation of large-conductance Ca2+-dependent
K+ channels (3, 10-12). We tested this
directly using patch-clamp techniques and found that K+
currents were rapidly and markedly suppressed by isoprostanes.
Other signaling pathways by which isoprostanes might exert a relaxant effect include 1) inhibition of the Rho A-Rho kinase pathway, which increases the Ca2+ sensitivity of the contractile apparatus by inhibiting myosin light chain phosphatase, 2) inhibition of the phosphoinositide pathway, which increases cytosolic Ca2+ by activating sarcoplasmic reticulum inositol trisphosphate Ca2+ channels, 3) activation of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase, which decreases cytosolic Ca2+, or 4) activation of myosin light chain phosphatase, which dephosphorylates and deactivates myosin.
Most of the experiments in this study involved the use of CCh, a cholinergic agonist that acts at the M2 and M3 muscarinic receptors present on airway smooth muscle to induce contraction. Activation of M3 receptors leads to the induction of phosphoinositide turnover, whereas M2 receptor activation results in the inhibition of adenylate cyclase and thus a decreased level of cAMP. Because inhibitory isoprostanes appear to act through induction of adenylate cyclase activity, the use of CCh as the precontractile agent confounds the results, leading to an attenuation of isoprostane-induced relaxation. We have demonstrated that this functional antagonism could be overcome using the M2 receptor-selective inhibitor AFDX-116.
Isoprostanes are present in the nanomolar range in normal human plasma (23) and increase up to 100- to 200-fold during periods of oxidative stress, which characterize a variety of disease states (20, 21, 23, 27). The physiological responses of isoprostanes commence in the submicromolar range and are thus clinically relevant. Therefore, a better understanding of the mechanisms of action of isoprostanes may provide further insight into the pathology of oxidative stress.
In conclusion, it was found that 8-iso-PGE2 and 8-iso-PGE1 induce relaxations in canine and porcine bronchial smooth muscle, likely because of activity at the EP prostanoid receptor. The relaxant responses to the E-ring compounds appear to be mediated by the second messenger cAMP. Although the downstream effector(s) is unclear, we have ruled out activation of K+ channels and have evidence to suggest that there is no direct inhibition of voltage-gated Ca2+ channels or of MLCK.
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ACKNOWLEDGEMENTS |
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We thank Dr. D. Crankshaw (McMaster University) for the kind gift of cicaprost, iloprost, and BW-245C.
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FOOTNOTES |
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These studies were supported by operating grants from the Canadian Institutes of Health Research and the Ontario Thoracic Society, a studentship from the National Science and Engineering Research Council (A. Catalli), and a Medical Research Council of Canada Scientist Award (L. J. Janssen).
Address for reprint requests and other correspondence: A. Catalli, Dept. of Medicine, McMaster University, St. Joseph's Hospital, 50 Charlton Ave. East, Hamilton, ON, Canada L8N 4A6 (E-mail: janssenl{at}mcmaster.ca).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
June 28, 2002;10.1152/ajplung.00038.2002
Received 24 January 2002; accepted in final form 13 June 2002.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Breyer, RM.
Prostaglandin EP1 receptor subtype selectivity takes shape.
Mol Pharmacol
59:
1357-1359,
2001
2.
Coleman, RA,
Smith WL,
and
Narumiya S.
International Union of Pharmacology classification of prostanoid receptors: properties, distribution, and structure of the receptors and their subtypes.
Pharmacol Rev
46:
205-229,
1994[ISI][Medline].
3.
Corompt, E,
Bessard G,
Lantuejoul S,
Naline E,
Advenier C,
and
Devillier P.
Inhibitory effects of large Ca2+-activated K+ channel blockers on -adrenergic- and NO-donor-mediated relaxations of human and guinea-pig airway smooth muscles.
Naunyn Schmiedebergs Arch Pharmacol
357:
77-86,
1998[ISI][Medline].
4.
Elmhurst, JL,
Betti PA,
and
Rangachari PK.
Intestinal effects of isoprostanes: evidence for the involvement of prostanoid EP and TP receptors.
J Pharmacol Exp Ther
282:
1198-1205,
1997
5.
Fernandes, LB,
Fryer AD,
and
Hirshman CA.
M2 muscarinic receptors inhibit isoproterenol-induced relaxation of canine airway smooth muscle.
J Pharmacol Exp Ther
262:
119-126,
1992[Abstract].
6.
Fortner, CN,
Breyer RM,
and
Paul RJ.
EP2 receptors mediate airway relaxation to substance P, ATP, and PGE2.
Am J Physiol Lung Cell Mol Physiol
281:
L469-L474,
2001
7.
Hirata, T,
Ushikubi F,
Kakizuka A,
Okuma M,
and
Narumiya S.
Two thromboxane A2 receptor isoforms in human platelets. Opposite coupling to adenylyl cyclase with different sensitivity to Arg60-to-Leu mutation.
J Clin Invest
97:
949-956,
1996
8.
Horn, R,
and
Marty A.
Muscarinic activation of ionic currents measured by a new whole-cell recording method.
J Gen Physiol
92:
145-159,
1988[Abstract].
9.
Janssen, LJ,
Premji M,
Netherton S,
Catalli A,
Cox G,
Keshavjee S,
and
Crankshaw DJ.
Excitatory and inhibitory actions of isoprostanes in human and canine airway smooth muscle.
J Pharmacol Exp Ther
295:
506-511,
2000
10.
Jones, TR,
Charette L,
Garcia ML,
and
Kaczorowski GJ.
Selective inhibition of relaxation of guinea-pig trachea by charybdotoxin, a potent Ca++-activated K+ channel inhibitor.
J Pharmacol Exp Ther
255:
697-706,
1990[Abstract].
11.
Jones, TR,
Charette L,
Garcia ML,
and
Kaczorowski GJ.
Interaction of iberiotoxin with -adrenoceptor agonists and sodium nitroprusside on guinea pig trachea.
J Appl Physiol
74:
1879-1884,
1993[Abstract].
12.
Kannan, MS,
and
Johnson DE.
Modulation of nitric oxide-dependent relaxation of pig tracheal smooth muscle by inhibitors of guanylyl cyclase and calcium-activated potassium channels.
Life Sci
56:
2229-2238,
1995[ISI][Medline].
13.
Kawikova, I,
Barnes PJ,
Takahashi T,
Tadjkarimi S,
Yacoub MH,
and
Belvisi MG.
8-Epi-PGF2, a novel noncyclooxygenase-derived prostaglandin, constricts airways in vitro.
Am J Respir Crit Care Med
153:
590-596,
1996[Abstract].
14.
Knox, AJ,
and
Tattersfield AE.
Airway smooth muscle relaxation.
Thorax
50:
894-901,
1995[ISI][Medline].
15.
Kotani, M,
Tanaka I,
Ogawa Y,
Usui T,
Mori K,
Ichikawa A,
Narumiya S,
Yoshimi T,
and
Nakao K.
Molecular cloning and expression of multiple isoforms of human prostaglandin E receptor EP3 subtype generated by alternative messenger RNA splicing: multiple second messenger systems and tissue-specific distributions.
Mol Pharmacol
48:
869-879,
1995[Abstract].
16.
Lahaie, I,
Hardy P,
Hou X,
Hassessian H,
Asselin P,
Lachapelle P,
Almazan G,
Varma DR,
Morrow JD,
Roberts LJ,
and
Chemtob S.
A novel mechanism for vasoconstrictor action of 8-isoprostaglandin F2 on retinal vessels.
Am J Physiol Regul Integr Comp Physiol
274:
R1406-R1416,
1998
17.
Montuschi, P,
Collins JV,
Ciabattoni G,
Lazzeri N,
Corradi M,
Kharitonov SA,
and
Barnes PJ.
Exhaled 8-isoprostane as an in vivo biomarker of lung oxidative stress in patients with COPD and healthy smokers.
Am J Respir Crit Care Med
162:
1175-1177,
2000
18.
Montuschi, P,
Corradi M,
Ciabattoni G,
Nightingale J,
Kharitonov SA,
and
Barnes PJ.
Increased 8-isoprostane, a marker of oxidative stress, in exhaled condensate of asthma patients.
Am J Respir Crit Care Med
160:
216-220,
1999
19.
Montuschi, P,
Kharitonov SA,
Ciabattoni G,
Corradi M,
van Rensen L,
Geddes DM,
Hodson ME,
and
Barnes PJ.
Exhaled 8-isoprostane as a new non-invasive biomarker of oxidative stress in cystic fibrosis.
Thorax
55:
205-209,
2000
20.
Morrow, JD,
Awad JA,
Boss HJ,
Blair IA,
and
Roberts LJ.
Non-cyclooxygenase-derived prostanoids (F2-isoprostanes) are formed in situ on phospholipids.
Proc Natl Acad Sci USA
89:
10721-10725,
1992[Abstract].
21.
Morrow, JD,
Awad JA,
Kato T,
Takahashi K,
Badr KF,
Roberts LJ,
and
Burk RF.
Formation of novel non-cyclooxygenase-derived prostanoids (F2-isoprostanes) in carbon tetrachloride hepatotoxicity. An animal model of lipid peroxidation.
J Clin Invest
90:
2502-2507,
1992[ISI][Medline].
22.
Morrow, JD,
Harris TM,
and
Roberts LJ.
Noncyclooxygenase oxidative formation of a series of novel prostaglandins: analytical ramifications for measurement of eicosanoids.
Anal Biochem
184:
1-10,
1990[ISI][Medline].
23.
Morrow, JD,
Hill KE,
Burk RF,
Nammour TM,
Badr KF,
and
Roberts LJ.
A series of prostaglandin F2-like compounds are produced in vivo in humans by a non-cyclooxygenase, free radical-catalyzed mechanism.
Proc Natl Acad Sci USA
87:
9383-9387,
1990[Abstract].
24.
Morrow, JD,
Minton TA,
Badr KF,
and
Roberts LJ.
Evidence that the F2-isoprostane, 8-epi-prostaglandin F2, is formed in vivo.
Biochim Biophys Acta
1210:
244-248,
1994[ISI][Medline].
25.
Morrow, JD,
Minton TA,
Mukundan CR,
Campbell MD,
Zackert WE,
Daniel VC,
Badr KF,
Blair IA,
and
Roberts LJ.
Free radical-induced generation of isoprostanes in vivo. Evidence for the formation of D-ring and E-ring isoprostanes.
J Biol Chem
269:
4317-4326,
1994
26.
Morrow, JD,
Minton TA,
and
Roberts LJ.
The F2-isoprostane, 8-epi-prostaglandin F2, a potent agonist of the vascular thromboxane/endoperoxide receptor, is a platelet thromboxane/endoperoxide receptor antagonist.
Prostaglandins
44:
155-163,
1992[Medline].
27.
Morrow, JD,
and
Roberts LJ.
Mass spectrometry of prostanoids: F2-isoprostanes produced by non-cyclooxygenase free radical-catalyzed mechanism.
Methods Enzymol
233:
163-174,
1994[ISI][Medline].
28.
Morrow, JD,
and
Roberts LJ.
The isoprostanes. Current knowledge and directions for future research.
Biochem Pharmacol
51:
1-9,
1996[ISI][Medline].
29.
Narumiya, S,
Sugimoto Y,
and
Ushikubi F.
Prostanoid receptors: structures, properties, and functions.
Physiol Rev
79:
1193-1226,
1999
30.
Norel, X,
Walch L,
Labat C,
Gascard JP,
Dulmet E,
and
Brink C.
Prostanoid receptors involved in the relaxation of human bronchial preparations.
Br J Pharmacol
126:
867-872,
1999
31.
Pelligrino, DA,
and
Wang Q.
Cyclic nucleotide crosstalk and the regulation of cerebral vasodilation.
Prog Neurobiol
56:
1-18,
1998[ISI][Medline].
32.
Pierce, KL,
and
Regan JW.
Prostanoid receptor heterogeneity through alternative mRNA splicing.
Life Sci
62:
1479-1483,
1998[ISI][Medline].
33.
Pratico, D,
Iuliano L,
Mauriello A,
Spagnoli L,
Lawson JA,
Rokach J,
Maclouf J,
Violi F,
and
FitzGerald GA.
Localization of distinct F2-isoprostanes in human atherosclerotic lesions.
J Clin Invest
100:
2028-2034,
1997
34.
Sametz, W,
Hennerbichler S,
Glaser S,
Wintersteiger R,
and
Juan H.
Characterization of prostanoid receptors mediating actions of the isoprostanes, 8-iso-PGE2 and 8-iso-PGF2, in some isolated smooth muscle preparations.
Br J Pharmacol
130:
1903-1910,
2000
35.
Sheller, JR,
Mitchell D,
Meyrick B,
Oates J,
and
Breyer R.
EP2 receptor mediates bronchodilation by PGE2 in mice.
J Appl Physiol
88:
2214-2218,
2000
36.
Somlyo, AP,
and
Somlyo AV.
Signal transduction and regulation in smooth muscle.
Nature
372:
231-236,
1994[ISI][Medline].
37.
Takahashi, K,
Nammour TM,
Fukunaga M,
Ebert J,
Morrow JD,
Roberts LJ,
Hoover RL,
and
Badr KF.
Glomerular actions of a free radical-generated novel prostaglandin, 8-epi-prostaglandin F2, in the rat: evidence for interaction with thromboxane A2 receptors.
J Clin Invest
90:
136-141,
1992[ISI][Medline].
38.
Ungrin, MD,
Carriere MC,
Denis D,
Lamontagne S,
Sawyer N,
Stocco R,
Tremblay N,
Metters KM,
and
Abramovitz M.
Key structural features of prostaglandin E2 and prostanoid analogs involved in binding and activation of the human EP1 prostanoid receptor.
Mol Pharmacol
59:
1446-1456,
2001
39.
Unmack, MA,
Rangachari PK,
and
Skadhauge E.
Effects of isoprostanes and prostanoids on porcine small intestine.
J Pharmacol Exp Ther
296:
434-441,
2001
40.
Wagner, RS,
Weare C,
Jin N,
Mohler ER,
and
Rhoades RA.
Characterization of signal transduction events stimulated by 8-epi-prostaglandin (PG) F2 in rat aortic rings.
Prostaglandins
54:
581-599,
1997[Medline].