Cell shrinkage, or apoptotic volume decrease (AVD), is a ubiquitous characteristic of programmed cell death that is independent of the death stimulus and occurs in all examples of apoptosis. Here we distinguished two specific stages of AVD based on cell size and a unique early reversal of intracellular ions that occurs in response to activation of both intrinsic and extrinsic cell death signal pathways. The primary stage of AVD is characterized by an early exchange of the normal intracellular ion distribution for sodium from 12 to 113.6 mM and potassium from 139.5 to 30 mM. This early ionic reversal is associated with a 20 -40% decrease in cell volume, externalization of phosphatidylserine, loss of mitochondrial membrane potential, and caspase activation and activity along with nuclear condensation that occurs independent of actin cytoskeleton disruption. Disruption of the actin cytoskeleton, however, prevents a secondary stage of AVD in apoptotic cells, characterized by a loss of both potassium and sodium that results in an 80 -85% loss in cell volume, DNA degradation, and apoptotic body formation. Together these studies demonstrate that AVD occurs in two distinct stages with the earliest stage reflecting a cellular cationic gradient reversal.Apoptosis, or programmed cell death, is a fundamental process in which activation of specific biochemical and morphological events results in death. Cell volume loss, chromatin condensation, and internucleosomal DNA fragmentation are all defining characteristics of this mode of cell death (1, 2). Externalization of phosphatidylserine, depolarization of the mitochondrial membrane potential along with release of various mitochondrial components, and caspase activity have also been used to identify apoptosis (3-5). The interplay of these catabolic events in the cell death program in relation to the loss of cell volume is not well understood.Apoptotic volume decrease (AVD 2 (6)) or the loss of cell volume during apoptosis is thought to result primarily from changes in the intracellular ionic environment. The movement of monovalent ions, particularly sodium and potassium, has been shown to play a pivotal role in both the activation and execution of apoptosis (7-9). Loss of intracellular sodium and potassium has been shown to occur in the shrunken population of apoptotic cells as part of AVD (6, 10, 11). However, earlier studies have shown that an increase in intracellular sodium also occurs during apoptosis (12, 13). Studies with sodium-substituted media revealed that sodium influx is a necessary requirement for AVD during apoptosis in cells treated with Fas ligand, since apoptotic stimulation in the absence of extracellular sodium resulted in cellular swelling rather than shrinkage (13). Despite this swelling of cells, other well defined characteristics of apoptosis including chromatin condensation, externalization of the phosphatidylserine, caspase activity, and DNA degradation persisted. Furthermore, maintenance of normal physiologic intracellular ion concentrations has been...

Genistein's effects are concentration-dependent in both cell lines. Lower concentrations elicit proliferative effects on UtLM cells only; whereas, higher concentrations alter morphology, inhibit proliferation, and increase caspase activity and apoptosis in both cell types, with the latter two effects being more extensive in UtSMCs.

Intracellular glutathione (GSH) depletion is an important hallmark of apoptosis. We have recently shown that GSH depletion by its extrusion regulates apoptosis independently of excessive reactive oxygen species accumulation. However, the mechanisms by which GSH depletion regulates apoptosis are still unclear. Because disruption of intracellular ionic homeostasis, associated with apoptotic volume decrease (AVD), is necessary for the progression of apoptotic cell death, we sought to evaluate the relationship between GSH transport and ionic homeostasis during Fas ligand (FasL)-induced apoptosis in Jurkat cells. GSH depletion in response to FasL was paralleled by distinct degrees of AVD identified by differences in cellular forward scatter and electronic impedance analysis. Inhibition of GSH efflux prevented AVD, K ؉ loss, and the activation of two distinct ionic conductances, mediated by Kv1.3 and outward rectifying Cl Apoptosis or programmed cell death is a ubiquitous energydependent, evolutionary conserved process. Under physiological conditions it is important not only in the constant turnover of cells in all tissues, but also during the normal development and senescence of the organism. Moreover, its deregulation has been observed to occur as either a cause or consequence of distinct pathologies (1, 2). A clear example is apoptosis mediated by Fas ligand (FasL) 2 receptor (Fas/CD95/Apo-1) activation, which is necessary for immune system homeostasis because of its role in the rapid clearance of immunoreactive T cells maintaining the immune balance and reducing the risk of autoimmune diseases (3). Apoptosis is a highly ordered process characterized by the progressive activation of precise pathways leading to specific biochemical and morphological alterations. Initial stages of apoptosis are characterized by activation of initiator caspases, changes in the cellular redox potential, intracellular ionic homeostasis, cell shrinkage or apoptotic volume decrease (AVD), loss of membrane lipid asymmetry, and chromatin condensation. Later stages associated with the execution phase of apoptosis are characterized by execution caspase and endonuclease activation, apoptotic body formation, and cell fragmentation (4, 5). Reduced glutathione (GSH) is the most abundant low molecular weight thiol in animal cells and is the major determinant in the redox potential of the cell. It is involved in many cellular processes, including antioxidant defense, drug detoxification, signaling, and proliferation (6 -10). Glutathione loss is an early hallmark in the progression of cell death in response to different apoptotic stimuli (11)(12)(13)(14)(15)(16)(17)(18)(19). Death receptor (including Fas)-induced GSH depletion has been clearly associated with the activation of a plasma membrane transport mechanism and not to its oxidation by reactive oxygen species (ROS) (20 -23). Several studies have shown a correlation between GSH efflux and the progression of apoptosis, and inhibition of GSH loss is able to rescue cells from cell death progress...