Oxidative stress-induced changes in pyridine nucleotides and chemoattractant 5-lipoxygenase products in aging neutrophils

Abstract

Neutrophils spontaneously undergo apoptosis, which is associated with increased oxidative stress. We found that there is a dramatic shift in the formation of 5-lipoxygenase products during this process. Freshly isolated neutrophils rapidly convert leukotriene B 4 (LTB 4) and 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) to their biologically inactive ω-oxidation products. However, ω-oxidation is impaired in neutrophils cultured for 24 h, when only 25% of the cells are nonapoptotic, resulting in the persistence of LTB 4 and a dramatic shift in 5-HETE metabolism to the potent granulocyte chemoattractant 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE). The reduced ω-oxidation activity seems to be due to a reduction in LTB 4 20-hydroxylase activity, whereas the increased 5-oxo-ETE formation is caused by a dramatic increase in the 5-hydroxyeicosanoid dehydrogenase cofactor NADP +. NAD +, but not NADPH, also increased, as did the GSSG/GSH ratio, indicative of oxidative stress. The changes in 5-HETE metabolism and pyridine nucleotides were inhibited by antiapoptotic agents (GM-CSF, forskolin) and antioxidants (diphenylene iodonium, catalase, deferoxamine), suggesting the involvement of H 2O 2 and possibly other reactive oxygen species. These results suggest that in severe inflammation, aging neutrophils that have evaded rapid uptake by macrophages may produce increased amounts of the chemoattractants 5-oxo-ETE and LTB 4, resulting in delayed resolution or exacerbation of the inflammatory process.