title: Endothelin B receptor stimulation inhibits suicidal erythrocyte death.
abstract: Endothelins (ETs), potent endothelium-derived mediators, stimulate formation of nitric oxide, which, in turn, protects against suicidal erythrocyte death or eryptosis, characterized by phosphatidylserine exposure at the erythrocyte surface and triggered by increase in cytosolic Ca(2+) ([Ca(2+)](i)). The present study explored whether the ET1-receptor ETB influences suicidal erythrocyte death. To this end, [Ca(2+)](i) (Fluo3-fluorescence) and phosphatidylserine exposure (annexin V-binding) were determined utilizing FACS analysis. Energy depletion increased [Ca(2+)](i) and phosphatidylserine-exposure, effects significantly blunted by ET1 (IC(50) approximately 100 nM) and the ETB receptor-agonist sarafotoxin 6c (IC(50) approximately 10 nM) but not by ET2 and ET3. ET1 and sarafotoxin significantly delayed the kinetics of suicidal erythrocyte death following energy depletion. ETB stimulation did not blunt the effect of Ca(2+)-ionophore ionomycin (1 microM) on phosphatidylserine exposure. The in vivo significance was tested using rescued ETB-knockout (etb(-/-)) and wild-type (etb(+/+)) mice. The number of phosphatidylserine-exposing erythrocytes, of reticulocytes and spleen size were significantly larger in etb(-/-) mice than in etb(+/+)-mice. The etb(-/-) erythrocytes were more susceptible to the eryptotic effect of oxidative stress and more rapidly cleared from circulating blood than etb(+/+) erythrocytes. Finally, the spleens from etb(-/-) mice were enlarged and contained markedly more phosphatidylserine-exposing erythrocytes than spleens from etb(+/+) mice. The observations disclose a novel function of ET1, i.e., protection from suicidal erythrocyte death.
authors.affiliation: Department of Physiology, University of Tübingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Föller
authors.forename: Hasan
authors.initials: H
authors.lastname: Mahmud
authors.forename: Syed M
authors.initials: SM
authors.lastname: Qadri
authors.forename: Shuchen
authors.initials: S
authors.lastname: Gu
authors.forename: Manuel
authors.initials: M
authors.lastname: Braun
authors.forename: Diwakar
authors.initials: D
authors.lastname: Bobbala
authors.forename: Berthold
authors.initials: B
authors.lastname: Hocher
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000494:pharmacology; D004912:Erythrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D044023:Receptor, Endothelin B / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D014757:Viper Venoms / Q000494:pharmacology
chemical_list: D019332:Endothelin-1; D007476:Ionophores; D044023:Receptor, Endothelin B; D014757:Viper Venoms; C057354:sarafotoxins s6; D015759:Ionomycin; D002118:Calcium