Lipoxygenase inhibitors protect brain cortex macromolecules against oxidation evoked by nitrosative stress.

Lipoxygenases (LOX) are a family of enzymes that are responsible for the metabolism of arachidonic and docosahexaenoic acid and for the formation of several eicosanoids and docosanoids, including leukotrienes, lipoxins and neuroprotectins. Depending on cells' redox state and other milieu conditions, these enzymes are engaged in oxidative stress and cell death mechanisms or in cell protection. In this study the antioxidative properties of several inhibitors of LOX isoforms were evaluated. We investigated the effect of a non-selective inhibitor of all LOXs and selective inhibitors of 5-LOX and 12-LOX on lipid and protein oxidation in brain cortex subjected to nitrosative stress, on dityrosine formation and on survival of an immortalized clonal mouse hippocampal cell line (HT22). The nitrosative stress was induced by nitric oxide (NO) donor, 0.5 mM sodium nitroprusside (SNP) and peroxynitrite (0.03 mM). Our data showed that nitrosative stress led to significant enhancement of lipid peroxidation and carbonyl group formation in brain cortex homogenate compared to control. Inhibitor of all LOXs nordihydroguaiaretic acid, 5-LOX inhibitors (zileuton, BWB70C), and inhibitors of 12/15-LOX baicalein and AA-861 (also an inhibitor of 5-LOX) significantly reduced, in a concentration dependent manner (1-10 μM), the level of lipid and protein oxidation. However, AA-861 and zileuton had no effect on carbonyl group formation. Moreover, we observed that LOX inhibitors protected a significant pool of HT22 cells against death evoked by 0.5 mM SNP. In summary, our results indicate that all LOX inhibitors in concentrations above 1-2.5 M demonstrated antioxidative properties. These results should be taken into consideration during evaluation of experimental and clinical effects of LOX inhibitors.