Glutathione Depletion and Disruption of Intracellular Ionic Homeostasis Regulate Lymphoid Cell Apoptosis

Abstract

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...

Life and Death of Lymphocytes: A Volume Regulation Affair

“…In the apoptotic model of Fas ligand treated Jurkat cells, GSH depletion was paralleled by distinct degrees (or stages) of cell shrinkage [46]. These stages of AVD were similar to those defined in a previous study on the effects of cytoskeleton disruption and apoptosis [24].…”

Ochratoxin A induces apoptosis in neuronal cells

“…Importantly, OTA significantly decreased gamma-glutamylcysteinyl synthetase levels in kidney tubulus cells via a Nrf2 dependent mechanism [6]. Gamma-glutamylcysteinyl synthetase is the rate limiting enzyme of glutathione synthesis and depletion of cellular glutathione often leads to apoptosis [11].…”

Apoptosis and glutathione: beyond an antioxidant

“…Alterations in the intracellular ionic homeostasis of the cell have been clearly linked to the progression of apoptosis. 107 Recent reports show that during apoptosis, cell shrinkage or apoptotic volume decrease, associated with the impairment in the Na þ -K þ -ATPase activity, 108 and activation of K þ and Cl À conductances 109,110 are also regulated by alterations in GSH homeostasis. A wide variety of ion channels and transporters have been shown to be regulated by ROS.…”