Peroxynitrite damages U937 cell DNA via the intermediate formation of mitochondrial oxidants

Abstract

SummaryEight years ago, we published in this journal the first evidence that peroxynitrite does not directly produce DNA singlestrand breakage in intact U937 cells (Guidarelli et al., IUBMB Life, 50,(195)(196)(197)(198)(199)(200)(201). This event was rather attributed to the secondary reactive species produced at the mitochondrial level via a Ca 2+ -dependent reaction, in which ubisemiquinone serves as an electron donor. Under these conditions, electrons are directly transferred to molecular oxygen and superoxide/H 2 O 2 , and the ensuing DNA damage can therefore be produced in a timedependent manner for at least 30 min. Formation of H 2 O 2 and DNA single-strand breaks was therefore dependent on interference with electron transport at the complex III level as well as on mitochondrial Ca 2+ accumulation. Further studies led to the demonstrations that peroxynitrite mobilizes Ca 2+ from the ryanodine receptor. Finally, in U937 cells, a pro-monocytic cell line sharing with monocytes/macrophages the same signaling events to survive to peroxynitrite, mitochondrial H 2 O 2 promotes inhibition of survival via tyrosine phosphatase activation, leading to ERK1/2 dephosphorylation and thus to upstream inhibition of the survival signaling.2008 IUBMB IUBMB Life, 60(11): 753-756, 2008

Characterization of the pattern of the nongenomic signaling pathway through which TCDD-induces early inflammatory responses in U937 human macrophages

“…It is known that in U937 macrophages, PKC-alpha is abundantly expressed and rapidly activated in response to stressors that initiate pro-inflammatory and pro-survival cell signaling. In the case of this early induction of COX-2 mRNA by TCDD, PKC-alpha is the most likely suspect due to its association with cPLA2 activation and pro-inflammatory signaling in U937 macrophages (Cantoni and Guidarelli, 2008). Furthermore, we could obtain some supporting data that nifedipine and 2-APB, which are so effective in antagonizing this nongenomic action of TCDD are also effective inhibitors of PKCα mRNA expression under the identical test condition.…”

Melatonin: A Versatile Protector against Oxidative DNA Damage

“…Nitric oxide ( • NO) and superoxide radical anion (O 2 −• ) are also produced as a consequence of immune responses to inflammation [ 92 ]. Albeit they do not directly damage DNA, their reaction yields peroxynitrite (ONOO − ) [ 93 ], which reacts with DNA [ 94 , 95 , 96 ]. Guanine residues seems to be the main target of ONOO − , since its reaction with these residues is significantly faster than those involving other nucleosides, and its reactions with 8-oxo-dG is even more favorable than with the parent molecule [ 97 ].…”

Cytotoxic and Antitumor Activity of Sulforaphane: The Role of Reactive Oxygen Species

“…Its efficacy indirectly demonstrates that SFR (at least up to 30 μ M, the highest concentration tested in this study) does not affect electron flow through the respiratory chain upstream to Complex III since, if electrons do not reach this site, myxothiazol would not prevent SFR-caused ROS formation. Notably, chemical inhibition of Complex III by agents acting as antimycin A (i.e., differently from myxothiazol) is known to represent a common and toxicologically relevant mechanism capable of boosting ROS generation within mitochondria [ 65 – 68 ]. Indeed, this latter mode of inhibiting Complex III, which is likely shared by SFR, causes an accumulation of ubisemiquinone which starts serving as an electron donor for molecular oxygen in a reaction producing superoxide anion and its dismutation product H 2 O 2 , which undergoes Fenton reaction and finally attacks sensitive cellular targets.…”