Bronchial hyperreactivity, increased endotoxin lethality and melanocytic tumorigenesis in transgenic mice overexpressing platelet-activating factor receptor

Abstract

Although platelet-activating factor (PAF) has been shown to exert pleiotropic effects on isolated cells or tissues, controversy still exists as to whether it plays significant pathophysiological roles in vivo. To answer this question, we established transgenic mice over-expressing a guinea-pig PAF receptor (PAFR). The transgenic mice showed a bronchial hyperreactivity to methacholine and an increased mortality when exposed to bacterial endotoxin. An aberrant melanogenesis and proliferative abnormalities in the skin were also observed in the transgenic mice, some of which spontaneously bore melanocytic tumors in the dermis after aging. Thus, PAFR transgenic mice proved to be a useful model for studying the basic pathophysiology of bronchial asthma and endotoxin-induced death, and screening of therapeutics for these disorders. Furthermore, our findings provide new insights regarding the role of PAF in the morphogenesis of dermal tissues as well as the mitogenic activity of PAF and PAFR in vivo.

Platelet-activating Factor (PAF) Induces Growth Stimulation, Inhibition, and Suppression of Oncogenic Transformation in NRK Cells Overexpressing the PAF Receptor

“…Transgenic mice overexpressing PAFR develop skin tumors (29), an event further supporting its role in control of cell growth.…”

“…PAFR expression plasmid was constructed by inserting guinea pig PAFR cDNA into pCXN2 expression vector (32), which contains cytomegalovirus enhancer, ␤-actin promoter, and ␤-globin polyadenylation signal for cDNA expression and neomycin resistant gene for selection (29). NRK cells were transfected with pCXN2-PAFR, using a LipofectAMINE reagent (Life Technologies, Inc.).…”

A Single Enzyme Catalyzes Both Platelet-activating Factor Production and Membrane Biogenesis of Inflammatory Cells

“…Radioligand Binding Assay-The method of PAF-PAF receptor (PAFR) binding assay was described previously (7,33). Briefly, the membrane fraction containing 158 fmol of PAFR from hearts and skeletal muscles of PAFR transgenic mice (7,34) were mixed with 25 nM [ 3 H]WEB 2086 and the lipid extract in a 96-well plate. After incubation at 25°C for 90 min, receptor-bound [ 3 H]WEB 2086 was collected by filtration through a UniFilter-GF/C (PerkinElmer Life Sciences) using a MicroMate 196 simultaneous 96-well harvester (PerkinElmer Life Sciences), and the filter was washed and dried.…”

“…The acetyltransferase activity of mLysoPAFAT/LPCAT2 was linear for the first 40 min at 37°C, and the enzyme exhibited calcium-dependent activity with a pH optimum around 7.4 (data not shown). To confirm whether the product of the acetyltransferase reaction is PAF, we first performed a competitive receptor binding assay using PAFR prepared from PAFR-transgenic mice (7,34). Lipid extracts from the acetyltransferase reaction of mLysoPAFAT/LPCAT2 with lyso-PAF competed for binding of [ 3 H]WEB2086 to PAFR, indicating that the enzyme indeed produced PAF (supplemental Fig.…”

Oxidized glycerophosphocholines as biologically active mediators for ultraviolet radiation-mediated effects

“…Moreover, the epidermal PAF-R can transactivate the epidermal growth factor receptor which can induce a mild proliferative response 25 . It should be noted that the phenotype of a transgenic mouse which overexpressed the PAF-R (by using an actin promoter) included a hyperproliferative dermatitis 26 .…”