Exposure of U937 cells to an otherwise nontoxic concentration of peroxynitrite promotes a rapid necrotic response in the presence of pharmacological inhibitors of phospholipase A2. A 12-fold higher concentration of the oxidant, in the absence of additional treatments, caused remarkably greater DNA single-strand breakage, delayed formation of H 2O2, and depletion of reduced glutathione but an identical level of toxicity. Cell death was prevented in both circumstances by nanomolar levels of arachidonic acid or by cyclosporin A via mechanisms unrelated to elimination of the above effects and was causally linked to prevention of mitochondrial permeability transition. Treatment with a high dose of peroxynitrite for 30 min caused an approximately 40% decline in ATP, both in the absence and presence of arachidonate, whereas only a small, arachidonic acid-sensitive reduction of the ATP pool was detected in cells treated with the low dose of peroxynitrite and the phospholipase A2inhibitor. ATP-predepleted cells, however, were hypersensitive to peroxynitrite, and under these conditions, toxicity was not prevented by arachidonate. The above findings were reproduced in another promonocytic cell line, THP-1 cells. We concluded that the rapid necrotic response triggered by peroxynitrite in monocytes is mediated by a regulated process, not by ATP depletion, associated with reduced arachidonate availability. Supplementation of exogenous arachidonic acid always rescued cells via an ATP-dependent survival pathway.

U937 cell necrosis mediated by peroxynitrite is not caused by depletion of ATP and is prevented by arachidonate via an ATP-dependent mechanism.

CANTONI, ORAZIO;GUIDARELLI, ANDREA;PALOMBA, LETIZIA;FIORANI, MARA
2005

Abstract

Exposure of U937 cells to an otherwise nontoxic concentration of peroxynitrite promotes a rapid necrotic response in the presence of pharmacological inhibitors of phospholipase A2. A 12-fold higher concentration of the oxidant, in the absence of additional treatments, caused remarkably greater DNA single-strand breakage, delayed formation of H 2O2, and depletion of reduced glutathione but an identical level of toxicity. Cell death was prevented in both circumstances by nanomolar levels of arachidonic acid or by cyclosporin A via mechanisms unrelated to elimination of the above effects and was causally linked to prevention of mitochondrial permeability transition. Treatment with a high dose of peroxynitrite for 30 min caused an approximately 40% decline in ATP, both in the absence and presence of arachidonate, whereas only a small, arachidonic acid-sensitive reduction of the ATP pool was detected in cells treated with the low dose of peroxynitrite and the phospholipase A2inhibitor. ATP-predepleted cells, however, were hypersensitive to peroxynitrite, and under these conditions, toxicity was not prevented by arachidonate. The above findings were reproduced in another promonocytic cell line, THP-1 cells. We concluded that the rapid necrotic response triggered by peroxynitrite in monocytes is mediated by a regulated process, not by ATP depletion, associated with reduced arachidonate availability. Supplementation of exogenous arachidonic acid always rescued cells via an ATP-dependent survival pathway.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11576/1882152
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