Endothelin generating pathway through endothelin1-31 in human cultured bronchial smooth muscle cells.
The effects of endothelin (ET)-1(1-31) and ET-2(1-31), human chymase products of the corresponding big ETs, on the intracellular free Ca2+ concentration ([Ca2+]i) and [125I]-ET-1 binding were investigated using human cultured bronchial smooth muscle cells (BSMC). ET-1(1-31) (10(-8)M - 3 x 10(-7)M) and ET-2(1-31) (3 x 10(-8)M - 3 x 10(-6) M) caused an increase in [Ca2+]i in a concentration-dependent manner. Big ET-1 (3 x 10(-8)M - 10(-6)M) also caused this increase, but not big ET-2 at concentrations up to 10(-6)M. The [Ca2+]i increase induced by ET-1 was inhibited by both BQ123, an ET(A)-receptor antagonist, and BQ788, an ET(B)-receptor antagonist, whereas that induced by ET-3 was inhibited by BQ788 but not by BQ123. Increases in [Ca2+]i caused by ET-1(1-31), big ET-1 and ET-2(1-31) were completely inhibited by 10(-4)M phosphoramidon, a dual neutral endopeptidase (NEP)/endothelin-converting enzyme (ECE) inhibitor, and 10(-5)M thiorphan, a NEP inhibitor. Scatchard plot analyses of the saturation curves of [125I]-ET-1 and [125I]-ET-3 showed that both ET(A)- and ET(B)- receptors at the ratio of 4:1 were expressed on BSMC. ET-1(1-31), big ET-1 and ET-2(1-31) inhibited [125I]-ET-1 binding in a concentration-dependent manner, and these effects were attenuated by treatment with thiorphan. On the other hand, big ET-2 slightly inhibited the binding at a high concentration and this was not affected by thiorphan. These results suggest that ET-1(1-31), big ET-1 and ET-2(1-31) cause an increase in [Ca2+]i by being converted into the corresponding ET-1 and ET-2 by NEP, but this did not occur with big ET-2 in human BSMC. ET-2(1-31), produced by human chymase from big ET-2 might be important for the generation of ET-2 in human bronchial tissue.
Hayasaki-Kajiwara
Y
Y
Discovery Research Laboratories, Shionogi & Co., Ltd., Toyonaka, Osaka, Japan.
Naya
N
N
Shimamura
T
T
Iwasaki
T
T
Nakajima
M
M
D000328:Adult; D001667:Binding, Competitive; D001980:Bronchi / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000378:metabolism / Q000494:pharmacology / Q000031:analogs & derivatives; D019334:Endothelin-3 / Q000378:metabolism / Q000494:pharmacology; D016232:Endothelins / Q000737:chemistry / Q000494:pharmacology*; D006020:Glycopeptides / Q000494:pharmacology; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D011869:Radioligand Assay; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000096:biosynthesis / Q000187:drug effects
D019332:Endothelin-1; D019334:Endothelin-3; D016232:Endothelins; D006020:Glycopeptides; D007457:Iodine Radioisotopes; D009842:Oligopeptides; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D010880:Piperidines; D011480:Protease Inhibitors; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; C114932:endothelin-1 (1-31); C086539:BQ 788; C072247:cyclo(Trp-Asp-Pro-Val-Leu); D002118:Calcium; C008890:phosphoramidon