Alkaline stress-induced apoptosis in human pulmonary artery endothelial cells

Abstract

The effect of alkaline stress, or an increase in extracellular pH (pHext), on cell viability is poorly defined. Human pulmonary artery endothelial cells (HPAEC) were subjected to alkaline stress using different methods of increasing pHext. Viability and mode of cell death following alkaline stress were determined by assessing nuclear morphology, ultrastructural features, and caspase-3 activity. Incubation of monolayers in media set to different pHext values (7.4-8.4) for 24-h induced morphological changes suggesting apoptosis (35-45% apoptotic cells) following severe alkaline stress. The magnitude of apoptosis was related to the severity of alkaline stress. These findings were confirmed with an assessment of ultrastructural changes and caspase-3 activation. While there was no difference in the intracellular calcium level ([Ca(2+)](i)) in monolayers set to pHext 7.4 versus 8.4 following the first hour of alkaline stress, blockade of calcium uptake with the chelator, EGTA, potentiated the magnitude of apoptosis under these conditions. Potentiation of apoptosis was reduced by calcium supplementation of the media. Finally, alkaline stress was associated with an increase in intracellular pH. This is the first report of apoptosis following alkaline stress in endothelial cells in the absence of other cell death stimuli.

Viability of Human Blood Leukocytes Compared with Their Respective Cell Lines after Plasma Treatment

“…20 The elevated pH level of the culture medium may contribute to apoptosis induction since it is known that alkaline stress can cause apoptosis in human cells. 21 Moreover, it is already known that reactive species such as superoxide anions and hydroxyl radicals are formed by plasma treatment of liquids. 22 Therefore, it has to be further investigated what effects these molecules and the pH have on cellular level.…”

Extracellular Acidic pH Inhibits Oligodendrocyte Precursor Viability, Migration, and Differentiation

“…A possible link between acidic environment and OPC death has been suggested by Feldman et al [43], through involvement of acid-sensing channel-1a (ASIC1a) expressed in OPCs and increased Ca +2 influx. Extracellular alkaline pH effects on cell survival have been generally less studied than acidification effects [133]–[136]. However, in the CNS, transient alkalization may follow ischemic acidification events [136]; This alkaline-induced increase in cell death has also been reported for several cell types including human endothelial cells [133], in association with increased activation of caspase-3 pathway and subsequent apoptosis; and a murine fibrosarcoma cell line, in association with elevated Ca +2 and mitochondrial damage [135].…”

Adeno-associated virus induces apoptosis during coinfection with adenovirus

“…Numerous studies correlate cell death with alterations in extracellular and intracellular pH. For example, increased extracellular pH in the absence of any other cytotoxic agents was sufficient to induce caspase-dependent apoptosis in cultured endothelial cells, and this increase in pH was accompanied by a corresponding increase in intracellular pH (Cutaia et al, 2005). In another report, elevated intracellular pH was associated with increased mitochondrial membrane potential, reactive oxygen species, DNA fragmentation, and cell death (Majima et al, 1998).…”