Use of Fluorescent Probes to Assess the Early Sulfhydryl Depletion and Oxidative Stress Induced by Mechlorethamine in Human Bronchial Epithelial Cells

Fanconi anemia (FA) and crosslinker sensitivity: Re-appraising the origins of FA definition

The commonly accepted definition of Fanconi anemia (FA) relying on DNA repair deficiency is submitted to a critical review starting from the early reports pointing to mitomycin C bioactivation and to the toxicity mechanisms of diepoxybutane and a group of nitrogen mustards causing DNA crosslinks in FA cells. A critical analysis of the literature prompts revisiting the FA phenotype and crosslinker sensitivity in terms of an oxidative stress (OS) background, redox-related anomalies of FA (FANC) proteins, and mitochondrial dysfunction. This re-appraisal of FA basic defect might lead to innovative approaches both in elucidating FA phenotypes and in clinical management.

Differential responses of proliferative and non-proliferative leukemia cells to oxidative stress

The response of three human leukemia cell lines, the proliferative promonocyte THP-1 and the promyeloid HL60 cells and the non-proliferative phorbol ester-treated HL60 cells (HL60/PMA), to oxidative stress induced by tert-butylhydroperoxide (t-BHP) treatment was analyzed by fluorescence microplate assay, anti-oxidant enzyme activity measurements, high performance liquid chromatography, yopro-1/PI incorporation, poly (ADP-ribose) polymerase and caspase 3 cleavages. After t-BHP treatment, the non-proliferative HL60/PMA cells exhibited a weak increase in reactive oxygen species (ROS) production, a better preservation of thiol content, a decrease of glutathione peroxidase activity and a high ability to undergo necrosis rather than apoptosis. Submitted to the same treatment, the proliferative HL60 and THP-1 cells exhibited a high increase of ROS production, a moderate thiol depletion and a high percentage of apoptosis. Under thiol depleting conditions, the oxidative treatment of the HL60/PMA cells resulted in a high ROS production that reached levels similar to those of the two other cell lines and in cell death mainly by necrosis. In conclusion, these results that show proliferative phenotype is essential for cell response towards oxidative stress, are of particular interest in chemotherapy involving an oxidative mechanism.

Molecular targets against mustard toxicity: implication of cell surface receptors, peroxynitrite production, and PARP activation

Despite many years of research into chemical warfare agents, cytotoxic mechanisms induced by mustards are not well understood. Reactive oxygen and nitrogen species (ROS and RNS) are likely to be involved in chemical warfare agents induced toxicity. These species lead to lipid peroxidation, protein oxidation, and DNA injury, and trigger many pathophysiological processes that harm the organism. In this article, several steps of pathophysiological mechanisms and possible ways of protection against chemical warfare agents have been discussed. In summary, pathogenesis of mustard toxicity is explained by three steps: (1) mustard binds target cell surface receptor, (2) activates intracellular ROS and RNS leading to peroxynitrite (ONOO(-)) production, and (3) the increased ONOO(-) level damages organic molecules (lipids, proteins, and DNA) leading to poly(adenosine diphosphate-ribose) polymerase (PARP) activation. Therefore, protection against mustard toxicity could also be performed in these ways: (1) blocking of cell surface receptor, (2) inhibiting the ONOO(-) production or scavenging the ONOO(-) produced, and (3) inhibiting the PARP, activated by ONOO(-) and hydroxyl radical (OH(*)) induced DNA damage. As conclusion, to be really effective, treatment against mustards must take all molecular mechanisms of cytotoxicity into account. Combination of several individual potent agents, each blocking one of the toxic mechanisms induced by mustards, would be interesting. Therefore, variations of combination of cell membrane receptor blockers, antioxidants, nitric oxide synthase inhibitors, ONOO(-) scavengers, and PARP inhibitors should be investigated.

Metformin decreases intracellular production of reactive oxygen species in aortic endothelial cells

Beyond its antidiabetic activity justifying its use in the treatment of the type 2 diabetes, metformin (MET [dimethylguanidine, Glucophage]) has been shown to exhibit antioxidant properties in vitro, which could contribute to limit the deleterious vascular complications of diabetes. We investigated whether MET, at the pharmacological level of 10 -5 mol/L, was able to modulate intracellular production of reactive oxygen species (ROS) both in quiescent bovine aortic endothelial cells (BAECs) and in BAECs stimulated by a short incubation with high levels of glucose (30 mmol/L, 2 hours) or angiotensin II (10 -7 mol/L, 1 hour). Intracellular ROS production was measured by fluorescence of the DCF (2,7-dichlorodihydrofluorescein) probe. Our results showed that MET was able to reduce the intracellular production of ROS in both nonstimulated BAECs (-20%, P < .05) and BAEC stimulated by high levels of glucose or angiotensin II (-28% and -72%, respectively, P < .01). Experiments performed in the presence of the nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase inhibitor apocynin or the respiratory mitochondrial chain inhibitor rotenone indicated that MET exerted its effect partly through an inhibition of the formation of ROS produced mainly by NAD(P)H oxidase and also, to a lesser extent, by the respiratory mitochondrial chain.

Sulfur mustard induces the formation of keratin aggregates in human epidermal keratinocytes☆1Current address: University of Texas at Austin, Cell & Molecular Biology, 1 University Station C0930, Austin, TX 78712-0253, USA

The vesicant sulfur mustard is an alkylating agent that has the capacity to cross-link biological molecules. We are interested in identifying specific proteins that are altered upon sulfur mustard exposure. Keratins are particularly important for the structural integrity of skin, and several genetically inherited blistering diseases have been linked to mutations in keratin 5 and keratin 14. We examined whether sulfur mustard exposure alters keratin biochemistry in cultured human epidermal keratinocytes. Western blotting with specific monoclonal antibodies revealed the formation of stable high-molecular-weight "aggregates" containing keratin 14 and/or keratin 5. These aggregates begin to form within 15 min after sulfur mustard exposure. These aggregates display a complex gel electrophoresis pattern between approximately 100 and approximately 200 kDa. Purification and analysis of these aggregates by one- and two-dimensional gel electrophoresis and mass spectrometry confirmed the presence of keratin 14 and keratin 5 and indicate that at least some of the aggregates are composed of keratin 14-keratin 14, keratin 14-keratin 5, or keratin 5-keratin 5 dimers. These studies demonstrate that sulfur mustard induces keratin aggregation in keratinocytes and support further investigation into the role of keratin aggregation in sulfur mustard-induced vesication.