Activation and damage of endothelial cells upon hypoxia/reoxygenation. Effect of extracellular pH.
Disturbances of blood flow upon vascular occlusions and spasms result in hypoxia and acidosis, while its subsequent restoration leads to reoxygenation and pH normalization (re-alkalization) in ischemic sites of the vascular bed. The effect of hypoxia/reoxygenation on activation and stimulation of apoptosis in cultured human endothelial cells was studied. The cells were subjected to hypoxia (2% O2, 5% CO2, 93% N(2)) for 24 h followed by reoxygenation (21% O2, 5% CO2, 74% N(2)) for 5 h. Reoxygenation was carried out at different pH-6.4 (preservation of acidosis after hypoxia), 7.0, and 7.4 (partial and complete re-alkalization, respectively). Hypoxia only slightly (by approximately 30%) increased the cell adhesion molecule ICAM-1 content on the cell surface, whereas reoxygenation more than doubled its expression. The reoxygenation effect depended on the medium acidity, and ICAM-1 increase was more pronounced at pH 7.0 compared to that at pH 6.4 and 7.4. Neither hypoxia nor reoxygenation induced expression of two other cell adhesion molecules, VCAM and E-selectin. Incubation of cells under hypoxic conditions but not reoxygenation stimulated secretion of von Willebrand factor and increased its concentration in the culture medium by more than 4 times. The percentage of cells containing apoptosis marker, activated caspase-3, was increased by approximately 1.5 times upon hypoxia as well as hypoxia/reoxygenation. Maximal values were achieved when reoxygenation was performed at pH 7.0. These data show that hypoxia/reoxygenation stimulate pro-inflammatory activation (ICAM-1 expression) and apoptosis (caspase-3 activation) of endothelial cells, and the extracellular pH influences both processes.
Antonova
O A
OA
Russian Cardiology Research and Production Complex, Moscow, 121552, Russia.
Loktionova
S A
SA
Romanov
Yu A
YA
Shustova
O N
ON
Khachikian
M V
MV
Mazurov
A V
AV
D000704:Analysis of Variance; D017209:Apoptosis / Q000502:physiology*; D001157:Arterial Occlusive Diseases; D053148:Caspase 3 / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000378:metabolism*; D015687:Cell Hypoxia; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D019040:E-Selectin / Q000737:chemistry / Q000378:metabolism; D042783:Endothelial Cells / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology; D005434:Flow Cytometry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D018799:Intercellular Adhesion Molecule-1 / Q000737:chemistry / Q000378:metabolism; D010100:Oxygen / Q000502:physiology*; D018709:Statistics, Nonparametric; D014471:Umbilical Veins; D019010:Vascular Cell Adhesion Molecule-1 / Q000737:chemistry / Q000378:metabolism; D014841:von Willebrand Factor / Q000378:metabolism*
D015815:Cell Adhesion Molecules; D017077:Culture Media, Conditioned; D019040:E-Selectin; D019010:Vascular Cell Adhesion Molecule-1; D014841:von Willebrand Factor; D018799:Intercellular Adhesion Molecule-1; D053148:Caspase 3; D010100:Oxygen