Human umbilical vein endothelial cells (HUVECs) show Ca(2+) mobilization as well as Ca(2+) influx upon hypoxia.
Bleb formation is an early event of cellular damage observed in a variety of cell types upon hypoxia. Although we previously found that the [Ca(2+)](i) rise before bleb formation only at the same loci of HUVECs upon hypoxia (localized [Ca(2+)](i) rise), the mode of the [Ca(2+)](i) rise remains ill-defined. In order to clarify the mechanisms causing the localized [Ca(2+)](i) rise in hypoxia challenged HUVECs, we studied the effects of several Ca(2+) channel blockers or a Ca(2+) chelator, EGTA, which reduces extracellular Ca(2+) concentration on the hypoxia-induced localized [Ca(2+)](i) rise and bleb formation by employing a confocal laser scanning microscopy (CLSM). After the initiation of hypoxia, [Ca(2+)](i) rose gradually in a localized fashion up to 15 min, which was associated with bleb formation at the same loci. The maximal [Ca(2+)](i) rise was 435 +/- 84 nM at the loci of bleb formation. Ca(2+) channel blockers including Ni(2+) (non-specific, 1 mM), nifedipine (L type, 10 microM), nicardipine (L + T type, 10 microM), and cilnidipine (L + N type, 10 microM) did not inhibit either the localized [Ca(2+)](i) rise or bleb formation. Although both the localized [Ca(2+)](i) rise and bleb formation were inhibited by lowering extracellular Ca(2+) concentration below 100 nM, a diffuse [Ca(2+)](i) rise through the cytoplasm remained without bleb formation, which was inhibited by a phospholipase C (PLC) inhibitor, U73122. In conclusion, hypoxia causes both the Ca(2+) mobilization and the Ca(2+) influx in HUVECs and the Ca(2+) influx through unknown Ca(2+) channels is responsible for the localized [Ca(2+)](i) rise integral to bleb formation.
Aono
Y
Y
Department of Surgery II, Osaka University Medical School, Suita, Japan. yaono@surg2.med.osaka-u.ac.jp
Ariyoshi
H
H
Sakon
M
M
Ueda
A
A
Tsuji
Y
Y
Kawasaki
T
T
Monden
M
M
D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004533:Egtazic Acid / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004963:Estrenes / Q000494:pharmacology; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D018613:Microscopy, Confocal / Q000379:methods; D009529:Nicardipine / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004963:Estrenes; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D004533:Egtazic Acid; D009538:Nicotine; D009529:Nicardipine; D010738:Type C Phospholipases; D009543:Nifedipine; D002118:Calcium