5-Lipoxygenase (5-LOX), which is believed to be a major source of oxidative stress, participates in somatostatinreceptor transmembrane signaling in the central nervous system. We used the Tet-On inducible expression system in PC12 cells to obtain cell lines with reproducible, stable 5-LOX expression levels to study its function. Cell apoptosis rates induced by Ab 42 were determined using an apo-BrdDU kit. Lipid peroxide, antioxidant enzyme, and caspase-3 activities were evaluated with respective commercial kits. The expression of 5-LOX, bcl-2, and bax were detected by immunoblotting. A subclone of PC18 with Tet-On inducible expression of 5-LOX was selected from PC12 transfectants. Expression of 5-LOX had no signiˆcant inhibitory eŠect on the cell viability of the PC18 clone. In contrast, compared with the control group, the cell viability of clone PC18 was signiˆcantly reduced after the induction of 5-LOX during Ab exposure. The diŠerences in cell viability before and after the induction of 5-LOX during Ab insult were signiˆcantly oŠset by AA861. Overexpression of 5-LOX only slightly improved the activities of superoxide dismutase (SOD). The levels of intracellular peroxides, SOD and caspase-3 activity, and Bax expression were signiˆcantly upregulated, and the levels of glutathione peroxidase and catalase were downregulated correspondingly in clone PC18 during Ab exposure. These results indicate that constitutive expression of 5-LOX is not detrimental per se, but overexpression of 5-LOX may become problematic during Ab exposure.
