Role of the Na/H antiport in pH-dependent cell death in pulmonary artery endothelial cells.
We investigated the role of intracellular pH (pH(i)) and Na/H exchange in cell death in human pulmonary artery endothelial cells (HPAEC) following a metabolic insult (inhibition-oxidative phosphorylation, glycolysis). Metabolic inhibition in medium at pH 7. 4 decreased viability (0-15% live cells) over 6 h. Cell death was attenuated by maneuvers that decreased pH(i) and inhibited Na/H exchange (acidosis, Na/H antiport inhibitors). In contrast, cell death was potentiated by maneuvers that elevated pH(i) or increased Na/H exchange (monensin, phorbol ester treatment) before the insult. HPAEC demonstrated a biphasic pH(i) response following a metabolic insult. An initial decrease in pH(i) was followed by a return to baseline over 60 min. Maneuvers that protected HPAEC and inhibited Na/H exchange (acidosis, Na(+)-free medium, antiport inhibitors) altered this pattern. pH(i) decreased, but no recovery was observed, suggesting that the return of pH(i) to normal was mediated by antiport activation. Although Na/H antiport activity was reduced (55-60% of control) following a metabolic insult, the cells still demonstrated active Na/H exchange despite significant ATP depletion. Phorbol ester pretreatment, which potentiated cell death, increased Na/H antiport activity above the level observed in monolayers subjected to a metabolic insult alone. These results demonstrate that HPAEC undergo a pH-dependent loss of viability linked to active Na/H exchange following a metabolic insult. Potentiation of cell death with phorbol ester treatment suggests that this cell death pathway involves protein kinase C-mediated phosphorylation events.
Cutaia
M
M
Pulmonary Disease Division, Department of Medicine, Veterans Affairs Medical Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
Tollefson
K
K
Kroczynski
J
J
Parks
N
N
Rounds
S
S
D000963:Antimetabolites / Q000494:pharmacology; D000968:Antimycin A / Q000031:analogs & derivatives / Q000494:pharmacology; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D003847:Deoxyglucose / Q000494:pharmacology; D004338:Drug Combinations; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000502:physiology*
D000963:Antimetabolites; D004338:Drug Combinations; D017923:Sodium-Hydrogen Exchangers; C032456:antimycin; D000968:Antimycin A; D006859:Hydrogen; D003847:Deoxyglucose