Oxidative Stress, Inflammation, and Cancer: How Are They Linked?

The molecular details of mammalian stress-activated signal transduction pathways have only begun to be dissected. This, despite the fact that the impact of these pathways on the pathology of chroni...

Mammalian Mitogen-Activated Protein Kinase Signal Transduction Pathways Activated by Stress and Inflammation

Different types of cell death are often defined by morphological criteria, without a clear reference to precise biochemical mechanisms. The Nomenclature Committee on Cell Death (NCCD) proposes unified criteria for the definition of cell death and of its different morphologies, while formulating several caveats against the misuse of words and concepts that slow down progress in the area of cell death research. Authors, reviewers and editors of scientific periodicals are invited to abandon expressions like 'percentage apoptosis' and to replace them with more accurate descriptions of the biochemical and cellular parameters that are actually measured. Moreover, at the present stage, it should be accepted that caspase-independent mechanisms can cooperate with (or substitute for) caspases in the execution of lethal signaling pathways and that 'autophagic cell death' is a type of cell death occurring together with (but not necessarily by) autophagic vacuolization. This study details the 2009 recommendations of the NCCD on the use of cell death-related terminology including 'entosis', 'mitotic catastrophe', 'necrosis', 'necroptosis' and 'pyroptosis'.

/pdf/classification-of-cell-death-recommendations-of-the-1yur9psysd.pdf

Classification of cell death: recommendations of the Nomenclature Committee on Cell Death

This review is directed at understanding how neuronal death occurs in two distinct insults, global ischemia and focal ischemia. These are the two principal rodent models for human disease. Cell dea...

Ischemic Cell Death in Brain Neurons

Reactive oxygen species (ROS) are generated as by-products of cellular metabolism, primarily in the mitochondria. When cellular production of ROS overwhelms its antioxidant capacity, damage to cellular macromolecules such as lipids, protein, and DNA may ensue. Such a state of “oxidative stress” is thought to contribute to the pathogenesis of a number of human diseases including those of the lung. Recent studies have also implicated ROS that are generated by specialized plasma membrane oxidases in normal physiological signaling by growth factors and cytokines. In this review, we examine the evidence for ligand-induced generation of ROS, its cellular sources, and the signaling pathways that are activated. Emerging concepts on the mechanisms of signal transduction by ROS that involve alterations in cellular redox state and oxidative modifications of proteins are also discussed.

Reactive oxygen species in cell signaling

Murine L929 fibrosarcoma cells treated with tumor necrosis factor (TNF) rapidly die in a necrotic way, due to excessive formation of reactive oxygen intermediates. We investigated the role of caspases in the necrotic cell death pathway. When the cytokine response modifier A (CrmA), a serpin-like caspase inhibitor of viral origin, was stably overexpressed in L929 cells, the latter became 1,000-fold more sensitive to TNF-mediated cell death. In addition, TNF sensitization was also observed when the cells were pretreated with Ac-YVAD-cmk or zDEVD-fmk, which inhibits caspase-1– and caspase-3–like proteases, respectively. zVAD-fmk and zD-fmk, two broad-spectrum inhibitors of caspases, also rendered the cells more sensitive, since the half-maximal dose for TNF-mediated necrosis decreased by a factor of 1,000. The presence of zVAD-fmk also resulted in a more rapid increase of TNF-mediated production of oxygen radicals. zVAD-fmk–dependent sensitization of TNF cytotoxicity could be completely inhibited by the oxygen radical scavenger butylated hydroxyanisole. These results indicate an involvement of caspases in protection against TNF-induced formation of oxygen radicals and necrosis.

https://rupress.org/jem/article-pdf/187/9/1477/1115555/97-2150.pdf

Inhibition of Caspases Increases the Sensitivity of L929 Cells to Necrosis Mediated by Tumor Necrosis Factor

Tumor necrosis factor (TNF) is selectively cytotoxic to some types of tumor cells in vitro and exerts antitumor activity in vivo. Reactive oxygen intermediates (ROIs) have been implicated in the direct cytotoxic activity of TNF. By using confocal microscopy, flow cytometry, and the ROI-specific probe dihydrorhodamine 123, we directly demonstrate that intracellular ROIs are formed after TNF stimulation. These ROIs are observed exclusively under conditions where cells are sensitive to the cytotoxic activity of TNF, suggesting a direct link between both phenomena. ROI scavengers, such as butylated hydroxyanisole, effectively blocked the formation of free radicals and arrested the cytotoxic response, confirming that the observed ROIs are cytocidal. The mitochondrial glutathione system scavenges the major part of the produced ROIs, an activity that could be blocked by diethyl maleate; under these conditions, TNF-induced ROIs detectable by dihydrorhodamine 123 oxidation were 5- to 20-fold higher.

http://www.pnas.org/content/92/18/8115.full.pdf

Direct evidence for tumor necrosis factor-induced mitochondrial reactive oxygen intermediates and their involvement in cytotoxicity.

Generation and biological characterization of membrane-bound, uncleavable murine tumor necrosis factor.

We investigated the biological role of the human tumor necrosis factor p75 (hTNF-R75), making use of the species specificity of TNF responses in murine (m) T cell lines. Several TNF-mediated activities on mouse T cells, such as cytokine induction or proliferation, showed a 100-500-fold difference in specific biological activity between mTNF and hTNF. After transfection of hTNF-R75 cDNA in a rat/mouse T cell hybridoma (PC60), however, the 100-fold lower specific biological activity of hTNF was converted to the same specific biological activity as mTNF. The TNF-mediated induction of granulocyte/macrophage colony-stimulating factor was strongly synergized by the addition of interleukin 1. In the presence of the latter cytokine, ligand-competing monoclonal antibodies against hTNF-R75 (utr-1, utr-2, utr-3) were agonistic on transfected PC60 cells. This agonistic activity was further enhanced by crosslinking with sheep anti-murine immunoglobulin antibodies. These data provide direct evidence for a functional role of TNF-R75, without ligand-dependent TNF-R55 involvement, in the induction of cytokine secretion in T cells.

/pdf/functional-characterization-of-the-human-tumor-necrosis-1jau4df0j6.pdf

Functional characterization of the human tumor necrosis factor receptor p75 in a transfected rat/mouse T cell hybridoma.

Introduction and expression of the proto-oncogene bcl-2 (B-cell lymphoma/leukemia 2) has been shown to extend the survival of certain hematopoietic cell lines after growth factor deprivation, by blocking apoptosis or programmed cell death. We investigated the effect of bcl-2 expression on cellular sensitivity to lysis by tumor necrosis factor (TNF), a cytokine capable of inducing apoptosis in several tumor cell lines. Introduction of the human bcl-2 gene in the highly TNF-sensitive L929 mouse fibrosarcoma cell line did not result in altered TNF sensitivity. Likewise, NIH3T3 and REF cells, which are resistant to TNF cytotoxicity but become TNF sensitive upon cotreatment with actinomycin D or upon expression of the adenovirus E1A gene, did not show altered TNF sensitivity upon bcl-2 transfection. Despite constitutive expression of the endogenous bcl-2 gene, human MCF7 breast carcinoma cells, as well as HL60 promyelocytic leukemia and U937 histiocytic lymphoma cell lines were found to be TNF sensitive. bcl-2-overexpressing derivatives of these cell lines did not acquire reduced TNF sensitivity and still exhibited the characteristic pattern of internucleosomal DNA fragmentation of TNF-induced apoptosis. Moreover, bcl-2 expression in the interleukin 3 (IL-3)-dependent myeloid cell line 32D protected these cells from apoptosis resulting from growth factor deprivation, but not from apoptosis induced by TNF. These data clearly establish the absence of a correlation between bcl-2 gene expression and cellular sensitivity to TNF-induced cell lysis. These findings are discussed in the context of the hypothesis of different pathways for induction of apoptosis, only some of which are affected by bcl-2 expression.

J. Grooten

Papers

Inhibition of Caspases Increases the Sensitivity of L929 Cells to Necrosis Mediated by Tumor Necrosis Factor

Direct evidence for tumor necrosis factor-induced mitochondrial reactive oxygen intermediates and their involvement in cytotoxicity.

Generation and biological characterization of membrane-bound, uncleavable murine tumor necrosis factor.

Functional characterization of the human tumor necrosis factor receptor p75 in a transfected rat/mouse T cell hybridoma.

Effect of bcl-2 proto-oncogene expression on cellular sensitivity to tumor necrosis factor-mediated cytotoxicity.