Arachidonic acid induces calcium-dependent mitochondrial formation of species promoting strand scission of genomic DNA

Both the phospholipase A2 activator melittin and reagent arachidonic acid (AA) are poor inducers of DNA single strand breaks in U937 cells. These responses, however, were dramatically increased by the calcium-mobilizing agent caffeine (Cf) or by the respiratory substrate pyruvate via a mechanism that involved enforced mitochondrial Ca2+ accumulation and that was sensitive to lipoxygenase inhibitors. In permeabilized cells, the DNA damage generated by AA in combination with either Cf, L-malate or CaCl2 was blunted by catalase. AA generated DNA strand scission also in HeLa cells supplemented with pyruvate via a mechanism identical to that observed in U937 cells. This response was associated with an enforced formation of free radical species. These results demonstrate that mitochondria play a pivotal role in the DNA-damaging response evoked by AA and provide the bases for a calcium-dependent mechanism whereby the AA produced during inflammatory processes may affect various pathologic conditions, including carcinogenesis.