In multicellular organisms, homeostasis is maintained through a balance between cell proliferation and cell death. Although much is known about the control of cell proliferation, less is known about the control of cell death. Physiologic cell death occurs primarily through an evolutionarily conserved form of cell suicide termed apoptosis. The decision of a cell to undergo apoptosis can be influenced by a wide variety of regulatory stimuli. Recent evidence suggests that alterations in cell survival contribute to the pathogenesis of a number of human diseases, including cancer, viral infections, autoimmune diseases, neurodegenerative disorders, and AIDS (acquired immunodeficiency syndrome). Treatments designed to specifically alter the apoptotic threshold may have the potential to change the natural progression of some of these diseases.

https://science.sciencemag.org/content/sci/267/5203/1456.full.pdf

Apoptosis in the pathogenesis and treatment of disease

http://www.healthcare.uiowa.edu/corefacilities/esr/publications/buettnerpubs/pdf/FRBM-2001-30-1191-FQS-Redox.pdf

Redox environment of the cell as viewed through the redox state of the glutathione disulfide/glutathione couple.

https://www.cell.com/cell/pdf/0092-8674(94)90544-4.pdf

H2O2 from the oxidative burst orchestrates the plant hypersensitive disease resistance response

Stimulation of rat vascular smooth muscle cells (VSMCs) by platelet-derived growth factor (PDGF) transiently increased the intracellular concentration of hydrogen peroxide (H2O2). This increase could be blunted by increasing the intracellular concentration of the scavenging enzyme catalase or by the chemical antioxidant N-acetylcysteine. The response of VSMCs to PDGF, which includes tyrosine phosphorylation, mitogen-activated protein kinase stimulation, DNA synthesis, and chemotaxis, was inhibited when the growth factor-stimulated rise in H2O2 concentration was blocked. These results suggest that H2O2 may act as a signal-transducing molecule, and they suggest a potential mechanism for the cardioprotective effects of antioxidants.

/pdf/requirement-for-generation-of-h2o2-for-platelet-derived-v74u1jl5ys.pdf

Requirement for Generation of H2O2 for Platelet-Derived Growth Factor Signal Transduction

Apoptosis signal‐regulating kinase (ASK) 1 was recently identified as a mitogen‐activated protein (MAP) kinase kinase kinase which activates the c‐Jun N‐terminal kinase (JNK) and p38 MAP kinase pathways and is required for tumor necrosis factor (TNF)‐α‐induced apoptosis; however, the mechanism regulating ASK1 activity is unknown. Through genetic screening for ASK1‐binding proteins, thioredoxin (Trx), a reduction/oxidation (redox)‐regulatory protein thought to have anti‐apoptotic effects, was identified as an interacting partner of ASK1. Trx associated with the N‐terminal portion of ASK1 in vitro and in vivo . Expression of Trx inhibited ASK1 kinase activity and the subsequent ASK1‐dependent apoptosis. Treatment of cells with N ‐acetyl‐l‐cysteine also inhibited serum withdrawal‐, TNF‐α‐ and hydrogen peroxide‐induced activation of ASK1 as well as apoptosis. The interaction between Trx and ASK1 was found to be highly dependent on the redox status of Trx. Moreover, inhibition of Trx resulted in activation of endogenous ASK1 activity, suggesting that Trx is a physiological inhibitor of ASK1. The evidence that Trx is a negative regulator of ASK1 suggests possible mechanisms for redox regulation of the apoptosis signal transduction pathway as well as the effects of antioxidants against cytokine‐ and stress‐induced apoptosis.

Mammalian thioredoxin is a direct inhibitor of apoptosis signal-regulating kinase (ASK) 1.

https://www.cell.com/immunology/pdf/0167-5699(94)90018-3.pdf

Oxidative stress as a mediator of apoptosis

Use of an aqueous soluble tetrazolium/formazan assay to measure viability and proliferation of lymphokine-dependent cell lines

N-Acetylcysteine (NAC) is a well established thiol antioxidant which, after uptake, deacylation and conversion to glutathione functions as both a redox buffer and a reactive oxygen intermediate scavenger. We report here that NAC completely blocks activation induced death and associated DNA fragmentation of myelin basic protein (MBP) specific T cell hybridomas. Conversely, NAC had very little effect on the antigen driven proliferation of a MBP specific T cell line similar to that from which the hybridomas were derived. NAC displayed an analogous absolute inhibition of mitogen mediated activation induced death, even if added up to 3 h post activation. Although glutathione was as efficient as NAC at blocking activation induced death, dithiothreitol displayed minimal inhibition while L-cysteine had no effect at all. The observation that certain thiol antioxidants such as NAC and glutathione can completely block the activation induced death of T cell hybridomas implicates redox regulation in this process.

Inhibition of activation-induced death in T cell hybridomas by thiol antioxidants: oxidative stress as a mediator of apoptosis.

Lipid hydroperoxides induce apoptosis in T cells displaying a HIV-associated glutathione peroxidase deficiency.

CCRF-CEM is a human T-cell line originally isolated from a child with acute lymphoblastic leukemia. At cell densities > 2 x 10(5) cells per ml, CEM cells grow in serum-free medium, but at lower cell densities the cultures rapidly undergo apoptosis, or programmed cell death. The viability of low-density CEM cells could be preserved by supplementing the serum-free medium with "conditioned" medium from high-density CEM cultures, but a variety of known growth factors and lymphokines were ineffective. Fractionation of conditioned medium by sequential chromatography on DEAE-cellulose, propyl agarose, chromatofocusing, and hydrophobic-interaction HPLC resulted in the isolation of a 60-kDa protein capable of sustaining CEM growth in the absence of serum. The active protein was identified as human catalase based on its amino acid sequence and composition and was subsequently shown to exhibit catalase activity and to be replaceable by human erythrocyte catalase or bovine liver catalase. Comparison of the level of intracellular catalase activity with the amount released into the culture medium demonstrated that the latter accounted for < 3% of the total catalase activity present in the cell culture. These findings show that, despite its low amount, the catalase released by CEM cells, and perhaps by T cells in general, provides a critical first line of defense against hydrogen peroxide (H2O2) present in the extracellular milieu.

https://www.pnas.org/content/pnas/90/10/4708.full.pdf

Thomas M. Buttke

Papers

Oxidative stress as a mediator of apoptosis

Use of an aqueous soluble tetrazolium/formazan assay to measure viability and proliferation of lymphokine-dependent cell lines

Inhibition of activation-induced death in T cell hybridomas by thiol antioxidants: oxidative stress as a mediator of apoptosis.

Lipid hydroperoxides induce apoptosis in T cells displaying a HIV-associated glutathione peroxidase deficiency.

Autocrine production of extracellular catalase prevents apoptosis of the human CEM T-cell line in serum-free medium