Normotonic cell shrinkage induced by Na+ deprivation results in apoptotic cell death in human epithelial HeLa cells.
Apoptosis is a major form of cell death that occurs in response to a variety of signals in both physiological and pathological situations. A hallmark of apoptosis is normotonic cell shrinkage, called apoptotic volume decrease (AVD), the process of which involves fluxes of K(+), Cl(-), and Na(+). Na(+) influx was suggested to be required in Fas-induced apoptosis in human Jurkat T cells, whereas Na(+) efflux was found to be associated with AVD and apoptosis in human HL-60 cells. Here we examined the effects of extracellular Na(+) deprivation on cell volume and viability in human epithelial HeLa cells. The incubation of HeLa cells in normotonic Na(+)-free Ringer solution resulted in persistent cell shrinkage after > or = 30 min and reduction in cell viability after > or = 1 h. After exposure to Na(+)-free solution for 5 h, a marked reduction in cell viability was found to be associated with an activation of caspase-3 without showing significant LDH release, indicating that the cells underwent apoptosis but not necrosis. Na(+) deprivation-induced cell shrinkage and apoptotic cell death were significantly inhibited by a blocker of Na(+)-K(+)-2Cl(-) cotransporter (NKCC) or of the reverse-mode operation of Na(+)/Ca(2+) exchanger (NCX), but not by a blocker of Na(+)/H(+) exchanger (NHE). Therefore it is concluded that Na(+) deprivation causes persistent cell shrinkage resulting from Na(+) efflux mainly via NKCC and NCX and thereafter leads to apoptotic death of HeLa cells. It is also suggested that normotonic cell shrinkage per se, if persistent, provides a sufficient condition for apoptosis induction.
Nukui
Miho
M
Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 445-8585 Japan.
Shimizu
Takahiro
T
Okada
Yasunobu
Y
D017209:Apoptosis / Q000187:drug effects*; D048429:Cell Size / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D012964:Sodium / Q000172:deficiency* / Q000494:pharmacology; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism
D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers; D028021:Sodium-Potassium-Chloride Symporters; D012964:Sodium