ETA and ETB receptors cooperate in DNA synthesis via opposing regulations of cAMP in human lung cell line.
We investigated the contribution of endothelin type A (ETA) and ETB receptors on ET-induced DNA synthesis in CCD-18Lu cells, a human lung cell line possessing both ETA and ETB (ETA/ETB ratio: 9:1). ET-1 (0.05-2 nM) potently induced [3H]thymidine incorporation by 2- to 14-fold over the basal level. An ETA-selective antagonist, FR139317, inhibited 0.2 nM ET-1-induced DNA synthesis dose dependently, showing complete inhibition at 1 microM. ET-3 was inactive up to 2 nM. In contrast, ETB-selective antagonists, 100 nM of BQ-788 or IRL 2500, partially (30-60%) inhibited 0.2 nM ET-1-induced DNA synthesis. Stimulation of either ETA or ETB evoked the increases in intracellular Ca2+ concentration ([Ca2+]i). ETB-mediated but not ET-1-induced [Ca2+]i increase was pertussis toxin (PTX) sensitive. Adenosine 3',5'-cyclic monophosphate (cAMP) formation via ETA was observed in PTX-treated cells, whereas the inhibition of isoproterenol-stimulated cAMP formation via ETB was observed in PTX-untreated cells. Like the ETB-selective antagonists, PTX treatment or dibutyryl cAMP partially (50-70%) inhibited ET-1-induced DNA synthesis. These data suggest that 1) ET-1 induces DNA synthesis predominantly through ETA, via PTX-insensitive G protein; 2) ETA-mediated cAMP formation inhibits DNA synthesis; and 3) stimulation of ETB coupling to Gi protein modulates ETA-mediated DNA synthesis by inhibiting cAMP formation.
Takimoto
M
M
International Research Laboratories, Ciba-Geigy Japan, Takarazuka, Japan.
Oda
K
K
Früh
T
T
Takai
M
M
Okada
T
T
Sasaki
Y
Y
D002455:Cell Division; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis*; D019332:Endothelin-1 / Q000378:metabolism*; D019333:Endothelin-2 / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000378:metabolism*; D017466:Receptors, Endothelin / Q000378:metabolism*; D015398:Signal Transduction
D019332:Endothelin-1; D019333:Endothelin-2; D017466:Receptors, Endothelin; D004247:DNA; D000242:Cyclic AMP