Acidification Prevents Endothelial Cell Apoptosis by Axl Activation

ABSTRACT—Prior studies have shown that acidification due to hypercarbia protects endothelial cells from serum deprivation–induced apoptosis. However, the mechanism(s) responsible for the antiapoptotic effect of acidification is still unclear. cDNA array screening was performed on human umbilical vein endothelial cells cultured in a bicarbonate medium equilibrated either with 5% CO2 (pH 7.4) or with 20% CO2 (pH 7.0). Tyrosine kinase receptor Axl expression was 3.3-fold higher after 6 hours at pH 7.0 compared with pH 7.4; this modulation was confirmed by reverse transcriptase–polymerase chain reaction (3.0±0.9-fold, P