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Department of Physiology, the Department of Geriatrics, and the || Department of Disease-related Gene Regulation Research (Sandoz), Faculty of Medicine, The University of Tokyo, Tokyo 113, Japan; and the ¶ Pharmaceutical Basic Research Laboratories (Aobadai), Japan Tobacco Inc., Kanagawa 227, Japan
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Key Words: platelet-activating factor • platelet-activating factor receptor • anaphylaxis • endotoxic shock • gene targeting
Abbreviations used: ANOVA, analysis of variance; ES, embryonic stem; HR, heart rate; LTB4, leukotriene B4; MAP, mean arterial pressure; NO, nitric oxide; PAF, platelet-activating factor; RL, total lung resistance.
Platelet-activating factor (PAF1; 1-O-alkyl-2-acetyl- sn-glycero-3-phosphocholine) is a potent phospholipid mediator with various biological activities, including platelet activation, airway constriction, hypotension, and vascular permeation (1–4). PAF acts by binding to a G protein– coupled seven transmembrane receptor (5). Through G proteins, PAFR links to signal transduction mechanisms, including turnover of phosphatidylinositol, elevation in intracellular calcium concentration (6), and activation of many kinases, e.g., phosphatidylinositol-3 kinase (7), protein kinase C (8), and mitogen-activated protein kinase (9). We and others have cloned PAFR cDNAs of guinea pig (10), human (11–14), and rat (15) and a PAFR gene of mouse (16). A unique PAFR has been identified in each species by the molecular cloning technique, although possible existence of PAFR subtypes has been suggested by biochemical or pharmacologic methods (17, 18).
PAF is synthesized not only in various blood cells but also in many other tissues, e.g., early mammalian embryo (19), fetal lung (20), kidney (21), and brain (22) under physiological conditions. Thus, PAF, even at low concentrations, has been considered to constitutively regulate various physiological processes such as reproduction (19, 23), blood pressure (24), neural development (25), and hippocampal long-term potentiation (18). Despite extensive studies, the physiological importance of PAF in vivo remains largely unknown.
In addition to its role as a physiological mediator, PAF has been believed to be associated with the pathology of anaphylaxis and endotoxic shock. Systemic anaphylaxis is a rapid, often fatal type-I allergic reaction characterized by acute airway constriction, heart rate (HR) alteration, hypotension, and vascular leakage (26, 27); many anaphylactic symptoms can be mimicked by PAF injection in animals (4, 5). Indeed, PAF is released rapidly from antigen-stimulated mast cells (28) and basophils (29) in vitro. In studies in vivo, an increase in blood PAF level is also detected after antigen challenge to sensitized animals (30). PAFR antagonists, which inhibit the binding of PAF to the receptor, exert protective effects on anaphylaxis in animal models (30–32). However, the precise role of PAF among a lot of allergic mediators in the development of anaphylactic responses is unclear.
Endotoxic or septic shock is the result of activation of the immune system by endotoxin/LPS, a component of Gram-negative bacterial cell wall. In this state, macrophages produce large amounts of cytokines such as TNF-
To date, our ability to address the pathophysiological role of PAF has largely depended on the use of structurally diverse PAFR antagonists. However, pharmacologic studies often encounter problems related to the specificity of drugs. Indeed, several PAFR antagonists are demonstrated to have an inhibitory effect on the activity of intracellular PAF acetylhydrolase, an inactivating enzyme of PAF (42, 43). Some other antagonists inhibit histamine effects through the interaction with its G protein–coupled receptor (40, 44).
To clearly identify both the nonredundant physiological role of PAF and the pathophysiological role of PAF without the use of possibly nonspecific PAFR antagonists, we generated animals in which the PAFR signaling was congenitally declined by targeted disruption of the PAFR gene in murine embryonic stem (ES) cells. We report here that the resulting PAFR-deficient mice were fertile and developed normally. Furthermore, although these mice showed the markedly attenuated anaphylactic symptoms, the responses to endotoxin remained intact. Thus, our studies demonstrate that PAF plays a dominant role in eliciting anaphylaxis, and is not essential for reproduction, brain development, or endotoxic shock.
Targeted Disruption of Mouse PAFR Gene.
and IL-6, as well as other inflammatory mediators, including PAF, that are released into the circulation (33, 34). Thus, these events lead to hypotension, tissue injury, vascular leakage, and frequently, death. As is the case in anaphylaxis, PAF per se is capable of eliciting many symptoms associated with endotoxic shock (4, 5). Further, it has been reported that the blood PAF level increased during endotoxemia (30, 35) and the PAF acetylhydrolase activity decreased in plasma of patients with sepsis (36). The administration of PAFR antagonists to animals and humans protects them from the deleterious effects of endotoxin (30, 32, 37–40). Our recent demonstration that transgenic mice overexpressing PAFR are hypersensitive to endotoxin has suggested that PAF plays an exaggerating role in the in vivo response to endotoxin (41).
Materials and Methods
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Abstract
Materials and Methods
Results and Discussion
References
Reagents.
Materials and chemicals were obtained from the following sources. -[32P]dCTP (111 TBq/mmol) and transfer membrane (Hybond-N+) were from Amersham (Tokyo, Japan); restriction enzymes and DNA-modifying enzymes were from Takara (Kyoto, Japan) or Toyobo (Kyoto, Japan); agaroses (Sea Kem and Nu Sieve) were from FMC (Rockland, ME); PAF (1- O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine) and leukotriene B4 (LTB4) were from Cayman Chemical (Ann Arbor, MI); [3H]WEB 2086 (499.5 GBq/mmol) and [3H]acetyl-PAF (370 GBq/mmol) were from Du Pont/New England Nuclear (Tokyo, Japan); fatty acid–free BSA, grade VI OVA, and endotoxin (LPS; Escherichia coli serotype O127:B8, code No. L-3129) were from Sigma Chemical Co. (St. Louis, MO); lyso-PAF was from Cascade Biochem (Berkshire, UK); pyrogen-free saline was from Otsuka Pharmaceuticals (Tokyo, Japan); RPMI 1640 medium was from Nissui (Tokyo, Japan). Other materials and reagents were of analytical grade. PAF and LTB4 were dissolved in pyrogen-free saline containing 0.25% BSA just before use. Endotoxin was suspended in saline. Unlabeled WEB 2086 was a gift from Boehringer Ingelheim (Ingelheim, Germany) and was dissolved in saline by sonication at a concentration of 0.5 mg/ml.
The murine PAFR genomic DNA was isolated by screening a 
FixII 129/Sv genomic library (Stratagene, La Jolla, CA) (16) with guinea pig PAFR cDNA (10). The targeting vector was constructed in pBluescript vector (Stratagene) using a 10.7-kb EcoRI fragment of the genomic DNA, a PGK-neo cassette, and an MC1-tk cassette (Fig. 1 a). The PGK-neo cassette was inserted into the PstI site in the exon. E14-1 cells were electroporated with NotI-linearized targeting vector and selected with G418 (225 µg active weight/ml) and fluoroiodoadenosyluracine (FIAU; 0.2 µM). The ES clones carrying the PAFR-targeted mutation on one allele through the homologous recombination event were screened by Southern blot analysis after ScaI digestion with a 5' flanking 0.6-kb SalI–EcoRI fragment (5' probe shown in Fig. 1 a). This fragment is located at the margin of the murine PAFR genomic DNA clone used; the SalI site derives from the polycloning sites of FixII vector. The 5' probe identified a 9.1-kb mutant band in addition to a 11.1-kb wild-type band (data not shown). Results were verified by hybridization of BamHI restriction digests with a 3' flanking 1.4-kb EcoRI–EcoRI fragment (3' probe shown in Fig. 1 a). Hybridization of ScaI restriction digests either with a 1.2-kb Eco47III–SpeI fragment containing the entire exon (PAFR probe shown in Fig. 1 a) or with a 1.1-kb AatI–BglII fragment of a neomycin resistance gene (Neo probe shown in Fig. 1 a) was also performed to ensure a single integration site. The former probe identified 9.1- and 3.5-kb mutant bands in addition to a 11.1-kb wild-type band (see Fig. 1 b), and the latter probe identified a 9.1-kb mutant band (data not shown).
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Northern Hybridization.
Total RNA was prepared from 2% casein-induced neutrophils as previously described (16). The RNA (1 µg) was electrophoresed, transferred to a nylon membrane, and hybridized (16) with either the PAFR probe shown in Fig. 1 a or a human glyceraldehyde-3-phosphate dehydrogenase (GAPDH) cDNA probe (Clontech, Palo Alto, CA).
Radioligand Binding Assay.
Lung membranes were prepared and used for ligand binding assay as described (41). Peritoneal exudate macrophages were obtained using thioglycollate as described in reference 16. The cells were cultured in 6-well dishes at 106 cells/well. After incubation for 2 h, nonadherent cells were washed away with RPMI 1640 medium containing 10% heat-inactivated FCS (GIBCO BRL, Rockville, MD). Adherent macrophages were then cultured for 1 or 2 d. Binding of [3H]WEB 2086 (20 nM) or [3H]acetyl-PAF (10 nM) was competed with unlabeled WEB 2086 (20 µM) in Hepes-Tyrode's buffer (pH 7.4) containing 0.1% BSA (Hepes-BSA buffer) at 20°C for 90 min or 25°C for 60 min, respectively. The cells were washed three times with cold Hepes-BSA buffer and lysed with 5% Triton X-100. The radioactivity associated with the cells was measured by liquid scintillation counting.
Measurement of Intracellular Calcium Concentration.
Neutrophils were loaded with 3 µM Fura-2AM (Dojindo, Kumamoto, Japan) at 37°C for 1 h and resuspended in calcium-free Hepes-Tyrode's buffer (pH 7.4) at 2 x 106 cells/ml. Intracellular calcium concentrations were measured using a fluorometer (CAF-110; JASCO, Tokyo, Japan) as described previously (45).
Sensitization of Mice.
pafr+/+ and pafr–/– (18–22-wk-old) male mice were given an intraperitoneal injection of OVA (100 µg), aluminum hydroxide gel (1 mg), and pertussis toxin (300 ng; Kaken Pharmaceutical, Tokyo, Japan) (26). Elicitation of anaphylaxis or bleeding were performed 18–21 d after the immunization. Serum levels of OVA-specific IgE and IgG1 were determined by ELISA as described in the PharMingen (San Diego, CA) protocol. In brief, 96-well flat-bottomed plates (Corning Glass Works, Corning, NY) were coated with either rat anti– mouse IgE antibody (clone R35-72) or OVA. Bound IgE or IgG1 was detected with biotinylated OVA in combination with horseradish peroxidase–conjugated streptavidin or horseradish peroxidase–conjugated anti–mouse IgG1 (clone G1-6.5), respectively. 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (Sigma Chemical Co.) was used as a substrate to generate the color reaction, which was read at 405 nm. The Ig levels of the samples were estimated using serum of an OVA-immunized mouse as a standard, and were compared using the Mann-Whitney U test.
Measurement of Mean Arterial Pressure and HR.
Under urethane anesthesia (1.5 g/kg, intraperitoneal), mice were cannulated with PE-10 polyethylene tubing (Clay Adams, Parsippany, NJ) into the right femoral artery. The tubing was filled with heparinized saline and connected to a pressure transducer (TP-200T; Nihon Kohden, Tokyo, Japan). The blood pressure signals were amplified (AP-600G; Nihon Kohden) and stored into a tape recorder. HR was computed using a tachometer (AT-601G; Nihon Kohden) on the basis of an electrocardiogram. The data were fed into a computer (PC9801RX; NEC, Tokyo, Japan) to calculate the mean values. Body temperature was maintained at 37 ± 1°C with a heating pad by monitoring rectal temperature. The cannulated mice were injected with 200 µg/kg of PAF (10 ml/kg), 200 µg/kg of lyso-PAF (10 ml/kg), 15 mg/kg of endotoxin (1 ml/kg), or 150 µg of OVA (100 µl/head) via the right femoral vein.
Bronchopulmonary Responses.
Total lung resistance (RL) was measured as previously described (41, 46, 47). Mechanically ventilated mice were challenged with 500 µg OVA via the jugular vein in a 100-µl bolus. The lungs were removed intact 5 min after the challenge of OVA. For histological analysis, the lungs were frozen in liquid nitrogen, fixed in Carnoy's solution, and stained with hematoxylin and eosin (46). In other experiments, the dissected lungs were weighed and placed in a gravity convection oven at 90°C for 72 h to determine dry weights for calculation of wet weight/dry weight ratios (46).
Determination of Cytokine Levels.
Adherent peritoneal macrophages were prepared as described in reference 16 and were cultured on 48-well dishes at 2.5 x 105 cells/well in 250 µl of RPMI 1640 medium supplemented with 10% heat-inactivated FCS (Moregate, Melbourne, Australia). The cells were exposed to endotoxin (100 ng/ml) plus mouse rIFN-
(100 U/ml; Genzyme, Cambridge, MA) for 24 h. The supernatants were harvested and stored at –80°C. Concentrations of TNF- and IL-6 were determined in duplicate using murine ELISA kits obtained from Genzyme and Amersham, respectively. Limits of detection for TNF- and IL-6 were 35 and 40 pg/ml, respectively. Data shown are averages from two separate experiments. Unstimulated macrophages released undetectable levels of the cytokines.
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2 test). pafr–/– mouse lines were established from both clones. Inactivation of the PAFR gene was confirmed by genomic Southern analysis (Fig. 1 b) and by Northern analysis of RNA isolated from neutrophils (Fig. 1 c). Neither peritoneal macrophages nor lung tissues from pafr–/– mice displayed any detectable binding sites for the PAFR antagonist WEB 2086 (16, 48; data not shown), confirming the loss of surface receptors. In pafr–/– mice, challenge with PAF no longer induced an increase in intracellular calcium concentration in neutrophils (49) (Fig. 1 d) or a decrease in mean arterial pressure (MAP; reference 50; Fig. 1 e). These results provide compelling evidence that the PAFR plays an essential role in PAF-induced calcium mobilization in neutrophils and in systemic hypotension.
Development, Reproduction, and Cardiac Homeostasis.
pafr–/– mice were healthy in appearance and grew normally up to 1 yr of age. There were no changes in blood cell populations, differential leukocyte counts, or serum biochemical parameters (data not shown). Light microscopic examination of major organs (brain, heart, lung, liver, kidney, pituitary, thyroid, adrenal, thymus, spleen, gastrointestinal tract, bone, bone marrow, and skin) revealed no differences in morphology between pafr+/+ and pafr–/– mice at 13–16 wk old (data not shown). A requirement for PAF in neural cell migration had previously been proposed based on the finding that mutation in the LIS1 gene encoding a subunit of brain PAF acetylhydrolase causes Miller-Dieker lissencephaly (25). The apparent lack of brain malformation in pafr–/– mice suggests, however, that the LIS1 subunit may have other function(s) relevant to brain development that are unrelated to PAF. This is consistent with a recent report that LIS1 reduces microtubule catastrophe events by interacting with tubulin (51).
PAF has also been proposed to play significant roles in reproductive functions such as implantation and parturition in various species (52–54). In fact, human preembryos produced by in vitro fertilization show an increased rate of implantation after exposure to PAF (53) and transgenic mice that overproduce PAFR display reproductive disorders (41). Hence, there existed a possibility that pafr–/– mice might be infertile. Contrary to this expectation, however, the homozygous pafr–/– mice were fertile and produced healthy litters of normal size (6.2 ± 1.2 [pafr–/– x pafr–/–; n = 5] versus 8.0 ± 0.7 [pafr+/– x pafr+/–; n = 7]; mean litter size ± SEM, P 
0.2, the unpaired t test [two-tailed]). These results suggest that PAF is not essential for normal development and reproduction of mice, although we cannot rule out the possible existence of additional PAFR subtypes as previously suggested by biochemical and pharmacologic experiments (17, 18). Furthermore, it is also possible that there may be receptor-independent actions of PAF.
MAP was measured through a catheter placed in the femoral artery. There were no significant differences in the baseline of both parameters between pafr+/+ and pafr–/– mice (101 ± 5 versus 107 ± 4 mmHg; mean ± SEM, n = 5 each, P 0.4, the unpaired t test [two-tailed]). Although intravenously administered PAF has a potent hypotensive effect, as shown in Fig. 1 e, the lack of difference in MAP between pafr+/+ and pafr–/– mice suggests that PAF may not be a mediator involved in setting the basal tone of vascular smooth muscle. HR of pafr+/+ and pafr–/– mice were also indistinguishable (586 ± 22 versus 560 ± 28 beats/ min; mean ± SEM, n = 5 each, P 0.5, the unpaired t test [two-tailed]). However, on the contrary, we observed in OVA-sensitized mice (see below) that HR of pafr–/– mice (648 ± 7 beats/min; mean ± SEM, n = 10) was significantly higher than that of pafr+/+ mice (570 ± 18 beats/ min; n = 12, P = 0.003, the Mann-Whitney U test), whereas MAPs were comparable between pafr+/+ and pafr–/– mice. Sensitization for active anaphylaxis may be associated with many changes, e.g., in levels of antigen-specific Igs of different isotypes, numbers of various effector cells, and local concentrations of immunomodulatory cytokines. It is possible that some of these changes cause the observed increase in the basal HR.
Active Systemic Anaphylaxis.
To directly evaluate the pathophysiological role of PAF in systemic anaphylaxis, pafr+/+ and pafr–/– mice were sensitized with OVA in the presence of adjuvants (26). This treatment caused mice of both genotypes to develop comparable and significant levels of OVA-specific IgE and IgG1 (data not shown), which mediate systemic anaphylaxis (27). The sensitized animals were injected intravenously with OVA to elicit systemic anaphylaxis. Cardiovascular or bronchopulmonary parameters were measured to assess the severity of the shock. Soon after challenge with OVA, all pafr+/+ mice developed severe and irreversible hypotension (Fig. 2 a). In this shock state, HR response to OVA was biphasic. OVA caused a rapid onset of tachycardia that reached a maximal increase of 
20% after 10 min, followed by bradycardia (Fig. 2 b). The tachycardia may be a compensatory response due to baroreceptor reflex. Five of six pafr+/+ mice died within 25 min (Fig. 2), and the remaining mouse died after 48 min. In contrast, the fall in MAP was much milder in pafr–/– mice compared with pafr+/+ mice (Fig. 2 a). Furthermore, HR remained stable upon the administration of OVA (Fig. 2 b). Only one of seven pafr–/– mice died after 36 min. Lethality among pafr–/– mice monitored 50 min after the antigen challenge was significantly lower than that of pafr+/+ mice (P <0.005, as determined by Fisher's exact test).
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The results of this study elucidated a large contribution of PAF to allergen-induced airway obstruction. As for the effects of PAF on the bronchopulmonary system, we reported that PAFR overexpressing mice show a remarkable airway hypersensitivity to methacholine (41). Thus, PAF is likely to play an important role in the pathophysiology of the bronchopulmonary system. However, the murine airways are somehow unresponsive to the intravenously administered PAF (41, 50, 56), whereas PAF given in the same manner elicited severe hypotension in mice (Fig. 1 e; reference 50). This is in contrast to our present data from immunologically stimulated mice which shows that PAF is deeply involved in both hypotension and bronchoconstriction. The murine airways, therefore, do not appear to respond to the blood-released PAF, which exerts deleterious effects on the cardiovascular system. Only PAF produced in the lung may act on the airways in a paracrine fashion.
Endotoxic Shock.
To assess the importance of PAF and PAFR in the development of endotoxic shock, PAFR-deficient mice were examined for their sensitivity to endotoxin using three kinds of assays. First, pafr+/+ and pafr–/– mice were treated with endotoxin given intravenously at a dose range of 7.5–30 mg/kg. As shown in Table 1, there was no significant difference in lethality in this model between pafr+/+ and pafr–/– mice. At each dose, mice of both genotypes exhibited apparently equivalent symptoms of endotoxic shock: lethargy, piloerection, and diarrhea. We next measured MAP of anesthetized mice in endotoxemia for 100 min as shown in Fig. 2 a. pafr–/– mice showed hypotensive responses to endotoxin that were indistinguishable from those of pafr+/+ mice (Fig. 4). The drop in MAP during endotoxic shock was slow but progressive, in contrast to the rapid drop observed during anaphylactic shock (Fig. 2 a). Finally, the ability of pafr–/– macrophages to respond to endotoxin was evaluated. Thioglycollate-stimulated peritoneal macrophages were exposed to endotoxin to induce expression of TNF- and IL-6. Levels of these cytokines in the culture medium were measured by ELISA. In pafr+/+ and pafr–/– macrophages, endotoxin induced equivalent levels of TNF- (10,250 and 10,544 pg/ml, respectively) and IL-6 (4,352 and 4,314 pg/ml, respectively).
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and IL-6, the inflammatory cytokines induced by endotoxin, to the same extent as those from wild-type mice. Since we have previously reported an increased susceptibility to endotoxin in PAFR overexpressing mice (41), it is very intriguing that PAFR-deficient mice show normal sensitivity to endotoxin. It may be that PAF functions in vivo not as an essential, but as an exaggerating factor for endotoxic shock. There are noteworthy pharmacologic reports exhibiting that ID50 values of various PAF antagonists for death due to anaphylaxis are nearly equal to those for PAF-induced death (32), whereas the doses of PAFR antagonists for inhibiting endotoxin-induced death are usually >10 times higher than those for inhibiting PAF-induced death (39). These data may suggest that PAFR antagonists attenuate the symptoms of anaphylaxis and endotoxic shock in different ways. The latter might be PAFR independent.
Concluding Remarks.
Although PAF has pleiotropic biological activities in vitro, the effects of deleting the PAFR gene were restricted to anaphylactic responses, i.e., PAFR-deficient mice were fertile and grew normally and were as sensitive to endotoxin as the wild-type mice. Thus, we conclude that although PAF is a dominant anaphylactic mediator, it may not be required for reproduction, neural development, or endotoxic shock. PAFR antagonists should, therefore, be useful in preventing anaphylactic responses in humans without causing serious mechanism-based side effects. Recent mouse models demonstrated that neither IgE (26) nor its high-affinity receptor, Fc
RI (27), is required for active systemic anaphylaxis, further supporting the validity of PAF as a target mediator for preventing and treating the disorder.
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Acknowledgments |
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This work was supported in part by grants-in-aid from the Ministry of Education, Science, Sports and Culture and the Ministry of Health and Welfare of Japan, by grants from Human Science Foundation, Senri Life Science Foundation and the Program for Promotion of Fundamental Studies in Health Sciences of the Organization for Drug ADR Relief, R&D Promotion and Product Review of Japan, and by Toyota Physical and Chemical Research Institute (to S. Ishii).
Submitted: 20 January 1998
Revised: 10 March 1998
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References |
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1 Hanahan DJ. Platelet activating factor: a biologically active phosphoglyceride, Annu Rev Biochem, 1986, 55, 483–509.[Medline]
2 Prescott SM, Zimmerman GA & McIntyre TM. Platelet-activating factor, J Biol Chem, 1990, 265, 17381–17384.
3 Barnes PJ. Platelet activating factor and asthma, Ann NY Acad Sci, 1991, 629, 193–204.[Medline]
4 Imaizumi T-a, Stafforini DM, Yamada Y, McIntyre TM, Prescott SM & Zimmerman GA. Platelet-activating factor: a mediator for clinicians, J Intern Med, 1995, 238, 5–20.[Medline]
5 Izumi T & Shimizu T. Platelet-activating factor receptor: gene expression and signal transduction, Biochim Biophys Acta, 1995, 1259, 317–333.[Medline]
6 Prpic, V., R.J. Uhing, J.E. Weiel, L. Jakoi, G. Gawdi, B. Herman, and D.O. Adams. 1988. Biochemical and functional responses stimulated by platelet-activating factor in murine peritoneal macrophages. J. Cell Biol. 107:363–372 (see published erratum 107:1260).
7 Stephens L, Jackson T & Hawkins PT. Synthesis of phosphatidylinositol 3,4,5-trisphosphate in permeabilized neutrophils regulated by receptors and G-proteins, J Biol Chem, 1993, 268, 17162–17172.
8 Liu B, Nakashima S, Takano T, Shimizu T & Nozawa Y. Implication of protein kinase C alpha in PAF-stimulated phospholipase D activation in Chinese hamster ovary (CHO) cells expressing PAF receptor, Biochem Biophys Res Commun, 1995, 214, 418–423.[Medline]
9 Honda Z-i, Takano T, Gotoh Y, Nishida E, Ito K & Shimizu T. Transfected platelet-activating factor receptor activates mitogen-activated protein (MAP) kinase and MAP kinase kinase in Chinese hamster ovary cells, J Biol Chem, 1994, 269, 2307–2315.
10 Honda Z-i, Nakamura M, Miki I, Minami M, Watanabe T, Seyama Y, Okado H, Toh H, Ito K, Miyamoto T & Shimizu T. Cloning by functional expression of platelet-activating factor receptor from guinea-pig lung, Nature, 1991, 349, 342–346.[Medline]
11 Nakamura M, Honda Z-i, Izumi T, Sakanaka C, Mutoh H, Minami M, Bito H, Seyama Y, Matsumoto T, Noma M & Shimizu T. Molecular cloning and expression of platelet-activating factor receptor from human leukocytes, J Biol Chem, 1991, 266, 20400–20405.
12 Ye RD, Prossnitz ER, Zou AH & Cochrane CG. Characterization of a human cDNA that encodes a functional receptor for platelet activating factor, Biochem Biophys Res Commun, 1991, 180, 105–111.[Medline]
13 Kunz D, Gerard NP & Gerard C. The human leukocyte platelet-activating factor receptor. cDNA cloning, cell surface expression, and construction of a novel epitope-bearing analog, J Biol Chem, 1992, 267, 9101–9106.
14 Sugimoto T, Tsuchimochi H, McGregor CG, Mutoh H, Shimizu T & Kurachi Y. Molecular cloning and characterization of the platelet-activating factor receptor gene expressed in the human heart, Biochem Biophys Res Commun, 1992, 189, 617–624.[Medline]
15 Bito H, Honda Z-i, Nakamura M & Shimizu T. Cloning, expression and tissue distribution of rat platelet-activating-factor–receptor cDNA, Eur J Biochem, 1994, 221, 211–218.[Medline]
16 Ishii S, Matsuda Y, Nakamura M, Waga I, Kume K, Izumi T & Shimizu T. A murine platelet-activating factor receptor gene: cloning, chromosomal localization and up-regulation of expression by lipopolysaccharide in peritoneal resident macrophages, Biochem J, 1996, 314, 671–678.[Medline]
17 Hwang SB. High affinity receptor binding of platelet-activating factor in rat peritoneal polymorphonuclear leukocytes, Eur J Pharmacol, 1991, 196, 169–175.[Medline]
18 Kato K, Clark GD, Bazan NG & Zorumski CF. Platelet-activating factor as a potential retrograde messenger in CA1 hippocampal long-term potentiation, Nature, 1994, 367, 175–179.[Medline]
19 O'Neill C. Embryo-derived platelet activating factor, Reprod Fertil Dev, 1992, 4, 283–288.[Medline]
20 Hoffman, D.R., C.T. Truong, and J.M. Johnston. 1986. Metabolism and function of platelet-activating factor in fetal rabbit lung development. Biochim. Biophys. Acta. 879:88–96 (see published erratum 919:311).
21 Blank ML, Snyder F, Byers LW, Brooks B & Muirhead EE. Antihypertensive activity of an alkyl ether analog of phosphatidylcholine, Biochem Biophys Res Commun, 1979, 90, 1194–1200.[Medline]
22 Kunievsky B & Yavin E. Production and metabolism of platelet-activating factor in the normal and ischemic fetal rat brain, J Neurochem, 1994, 63, 2144–2151.[Medline]
23 Toyoshima K, Narahara H, Furukawa M, Frenkel RA & Johnston JM. Platelet-activating factor. Role in fetal lung development and relationship to normal and premature labor, Clin Perinatol, 1995, 22, 263–280.[Medline]
24 Masugi F, Ogihara T, Saeki S, Otsuka A & Kumahara Y. Role of acetyl glyceryl ether phosphorylcholine in blood pressure regulation in rats, Hypertension (Dallas), 1985, 7, 742–746.
25 Hattori M, Adachi H, Tsujimoto M, Arai H & Inoue K. Miller-Dieker lissencephaly gene encodes a subunit of brain platelet-activating factor acetylhydrolase, Nature, 1994, 370, 216–218.[Medline]
26 Oettgen HC, Martin TR, Wynshaw-Boris A, Deng C, Drazen JM & Leder P. Active anaphylaxis in IgE-deficient mice, Nature, 1994, 370, 367–370.[Medline]
27 Miyajima I, Dombrowicz D, Martin TR, Ravetch JV, Kinet JP & Galli SJ. Systemic anaphylaxis in the mouse can be mediated largely through IgG1 and FcRIII. Assessment of the cardiopulmonary changes, mast cell degranulation, and death associated with active or IgE- or IgG1-dependent passive anaphylaxis, J Clin Invest, 1997, 99, 901–914.[Medline]
28 Mencia-Huerta J-M, Lewis RA, Razin E & Austen KF. Antigen-initiated release of platelet-activating factor (PAF-acether) from mouse bone marrow–derived mast cells sensitized with monoclonal IgE, J Immunol, 1983, 131, 2958–2964.[Abstract]
29 Hanahan DJ, Demopoulos CA, Liehr J & Pinckard RN. Identification of platelet activating factor isolated from rabbit basophils as acetyl glyceryl ether phosphocholine, J Biol Chem, 1980, 255, 5514–5516.
30 Nagaoka, J., K. Harada, A. Kimura, S. Kobayashi, M. Murakami, T. Yoshimura, K. Yamada, O. Asano, K. Katayama, and I. Yamatsu. 1991. Inhibitory effects of the novel platelet activating factor receptor antagonist, 1-ethyl-2-[N-(2-methoxy) benzoyl-N-[(2R)-2-methoxy-3-(4-octadecylcarbamoyloxy) piperidinocarbonyloxypropyloxy]carbonyl] aminomethyl-pyridinium chloride, in several experimentally induced shock models. Arzneim.-Forsch./Drug Res. 41:719–724.
31 Casals-Stenzel J. Effects of WEB 2086, a novel antagonist of platelet activating factor, in active and passive anaphylaxis, Immunopharmacology, 1987, 13, 117–124.[Medline]
32 Terashita Z, Kawamura M, Takatani M, Tsushima S, Imura Y & Nishikawa K. Beneficial effects of TCV-309, a novel potent and selective platelet activating factor antagonist in endotoxin and anaphylactic shock in rodents, J Pharmacol Exp Ther, 1992, 260, 748–755.
33 Morrison DC & Ryan JL. Endotoxins and disease mechanisms, Annu Rev Med, 1987, 38, 417–432.[Medline]
34 Bone RC. The pathogenesis of sepsis, Ann Intern Med, 1991, 115, 457–469.
35 Chang TW, Wu MH & Yang YJ. Blood levels of platelet-activating factor in endotoxin-sensitive and endotoxin-resistant mice during endotoxemia, J Formosan Med Assoc, 1992, 91, 1133–1137.[Medline]
36 Graham RM, Stephens CJ, Silvester W, Leong LL, Sturm MJ & Taylor RR. Plasma degradation of platelet-activating factor in severely ill patients with clinical sepsis, Crit Care Med, 1994, 22, 204–212.[Medline]
37 Casals-Stenzel J. Protective effect of WEB 2086, a novel antagonist of platelet activating factor, in endotoxin shock, Eur J Pharmacol, 1987, 135, 117–122.[Medline]
38 Guinot P & Braquet P. Effects of the PAF antagonists, ginkgolides (BN-52063, BN-52021), in various clinical indications, J Lipid Mediat Cell Signal, 1994, 10, 144–146.
39 Giral M, Balsa D, Ferrando R, Merlos M, Garcia RJ & Forn J. Effects of UR-12633, a new antagonist of platelet-activating factor, in rodent models of endotoxic shock, Br J Pharmacol, 1996, 118, 1223–1231.[Medline]
40 Merlos M, Giral M, Balsa D, Ferrando R, Queralt M, Puigdemont A, Garcia RJ & Forn J. Rupatadine, a new potent, orally active dual antagonist of histamine and platelet-activating factor (PAF), J Pharmacol Exp Ther, 1997, 280, 114–121.
41 Ishii S, Nagase T, Tashiro F, Ikuta K, Sato S, Waga I, Kume K, Miyazaki J-i & Shimizu T. Bronchial hyperreactivity, increased endotoxin lethality and melanocytic tumorigenesis in transgenic mice overexpressing platelet-activating factor receptor, EMBO (Eur Mol Biol Organ) J, 1997, 16, 133–142.[Medline]
42 Svetlov SI, Howard KM, Miwa M, Flickinger BD & Olson MS. Interaction of platelet-activating factor with rat hepatocytes: uptake, translocation, metabolism, and effects on PAF-acetylhydrolase secretion and protein tyrosine phosphorylation, Arch Biochem Biophys, 1996, 327, 113–122.[Medline]
43 Adachi T, Aoki J, Manya H, Asou H, Arai H & Inoue K. PAF analogues capable of inhibiting PAF acetylhydrolase activity suppress migration of isolated rat cerebellar granule cells, Neurosci Lett, 1997, 235, 133–136.[Medline]
44 Carceller E, Merlos M, Giral M, Balsa D, Almansa C, Bartroli J, Garcia RJ & Forn J. [(3-Pyridylalkyl)piperidylidene]benzocycloheptapyridine derivatives as dual antagonists of PAF and histamine, J Med Chem, 1994, 37, 2697–2703.[Medline]
45 Nakamura M, Honda Z-i, Waga I, Matsumoto T, Noma M & Shimizu T. Endotoxin transduces Ca2+signaling via platelet-activating factor receptor, FEBS Lett, 1992, 314, 125–129.[Medline]
46 Nagase T, Ohga E, Sudo E, Katayama H, Uejima Y, Matsuse T & Fukuchi Y. Intercellular adhesion molecule-1 mediates acid aspiration–induced lung injury, Am J Respir Crit Care Med, 1996, 154, 504–510.[Abstract]
47 Uozumi N, Kume K, Nagase T, Nakatani N, Ishii S, Tashiro F, Komagata Y, Maki K, Ikuta K, Ouchi Y et al.. Role of cytosolic phospholipase A2in allergic response and parturition, Nature, 1997, 390, 618–622.[Medline]
48 Casals-Stenzel J, Muacevic G & Weber K. Pharmacological actions of WEB 2086, a new specific antagonist of platelet activating factor, J Pharmacol Exp Ther, 1987, 241, 974–981.
49 Ferby IM, Waga I, Sakanaka C, Kume K & Shimizu T. Wortmannin inhibits mitogen-activated protein kinase activation induced by platelet-activating factor in guinea pig neutrophils, J Biol Chem, 1994, 269, 30485–30488.
50 Chen X-S, Sheller JR, Johnson EN & Funk CD. Role of leukotrienes revealed by targeted disruption of the 5-lipoxygenase gene, Nature, 1994, 372, 179–182.[Medline]
51 Sapir T, Elbaum M & Reiner O. Reduction of microtubule catastrophe events by LIS1, platelet-activating factor acetylhydrolase subunit, EMBO (Eur Mol Biol Organ) J, 1997, 16, 6977–6984.[Medline]
52 Maki N, Hoffman DR & Johnston JM. Platelet-activating factor acetylhydrolase activity in maternal, fetal, and newborn rabbit plasma during pregnancy and lactation, Proc Natl Acad Sci USA, 1988, 85, 728–732.
53 O'Neill C, Ryan JP, Collier M, Saunders DM, Ammit AJ & Pike IL. Supplementation of in-vitro fertilisation culture medium with platelet activating factor, Lancet, 1989, 2, 769–772.[Medline]
54 Ryan JP, Spinks NR, O'Neill C & Wales RG. Implantation potential and fetal viability of mouse embryos cultured in media supplemented with platelet-activating factor, J Reprod Fertil, 1990, 89, 309–315.
55 Serhan CN, Haeggstrom JZ & Leslie CC. Lipid mediator networks in cell signaling: update and impact of cytokines, FASEB J, 1996, 10, 1147–1158.[Abstract]
56 Martin TR, Gerard NP, Galli SJ & Drazen JM. Pulmonary responses to bronchoconstrictor agonists in the mouse, J Appl Physiol, 1988, 64, 2318–2323.
57 Szabo C, Wu CC, Mitchell JA, Gross SS, Thiemermann C & Vane JR. Platelet-activating factor contributes to the induction of nitric oxide synthase by bacterial lipopolysaccharide, Circ Res, 1993, 73, 991–999.
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P <0.05 versus the pafr–/– saline group, as determined by analysis of variance (ANOVA) with Scheffe's test for pair-wise comparisons. OVA had no effects on MAP or HR in unsensitized mice (data not shown).
