Characterization of prostaglandin (PG)-binding sites expressed on human basophils. Evidence for a prostaglandin E1, I2, and a D2 receptor.
Recent data suggest that prostaglandins (PGs) are involved in the regulation of basophil activation. The aim of this study was to characterize the basophil PG-binding sites by means of radioreceptor assays using 3H-labeled PGs. Scatchard analysis for pure (greater than 95%) chronic myeloid leukemia (CML) basophils revealed two classes of PGE1-binding sites differing in their affinity for the natural ligand (Bmax1 = 217 +/- 65 fmol/10(8) cells; Kd1 = 0.5 +/- 0.2 nM; Bmax2 = 2462 +/- 381 fmol/10(8) cells; Kd2 = 47 +/- 20 nM; IC50 = PGE1 less than PGI2 less than PGD2 less than PGE2 less than PGF2 alpha) as well as two classes of PGI2 (iloprost)-binding sites (Bmax1 = 324 +/- 145 fmol/10(8) cells; Kd1 = 0.5 +/- 0.3 nM; Bmax2 = 2541 +/- 381; Kd2 = 27 +/- 6 nM; IC50 = PGI2 less than PGE1 less than PGD2 less than PGE2 less than PGF2 alpha. In addition, CML basophils exhibited a single class of PGD2-binding sites (Bmax = 378 +/- 98 fmol/10(8) cells; Kd = 13 +/- 4 nM; IC50: PGD2 less than PGI2 less than PGE1 less than PGE2 less than PGF2 alpha). In contrast, we were unable to detect specific saturable PGE2-binding sites. Primary and immortalized (KU812) CML basophils revealed an identical pattern of PG receptor expression. Basophils (KU812) expressed significantly (p less than 0.001) lower number of PGE1 (PGI2)-binding sites (Bmax1: 9% (20%) of control; Bmax2: 36% (50%) of control) when cultured with recombinant interleukin 3 (rhIL-3), a basophil-activating cytokine, whereas rhIL-2 had no effect on PG receptor expression. Functional significance of binding of PGs to basophils was provided by the demonstration of a dose-dependent increase in cellular cAMP upon agonist activation, with PGE1 (ED50 = 1.7 +/- 1.1 nM) and PGI2 (ED50 = 2.8 +/- 2.3 nM) being the most potent compounds. These findings suggest that human basophils express specific receptors for PGE1, PGI2 as well as for PGD2.
Virgolini
I
I
Department of Nuclear Medicine, University of Vienna, Austria.
Li
S
S
Sillaber
C
C
Majdic
O
O
Sinzinger
H
H
Lechner
K
K
Bettelheim
P
P
Valent
P
P
D000527:Alprostadil / Q000378:metabolism; D001491:Basophils / Q000378:metabolism*; D001665:Binding Sites; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D011464:Epoprostenol / Q000378:metabolism; D006801:Humans; D016285:Iloprost / Q000378:metabolism; D007377:Interleukin-3 / Q000502:physiology; D007378:Interleukins / Q000502:physiology; D007700:Kinetics; D015230:Prostaglandin D2 / Q000378:metabolism; D011453:Prostaglandins / Q000378:metabolism*; D011863:Radioimmunoassay; D044006:Receptors, Epoprostenol; D011971:Receptors, Immunologic; D011982:Receptors, Prostaglandin / Q000378:metabolism*; D018078:Receptors, Prostaglandin E
D007377:Interleukin-3; D007378:Interleukins; D011453:Prostaglandins; D044006:Receptors, Epoprostenol; D011971:Receptors, Immunologic; D011982:Receptors, Prostaglandin; D018078:Receptors, Prostaglandin E; D011464:Epoprostenol; D000242:Cyclic AMP; D000527:Alprostadil; D016285:Iloprost; D015230:Prostaglandin D2; C036293:prostaglandin D2 receptor