5-Lipoxygenase is required for proliferation of immature cerebellar granule neurons in vitro

Primary cultures of rat cerebellar granule neurons express 5-lipoxygenase, an enzyme from the inflammatory pathway of arachidonic acid. Outside the central nervous system (CNS) 5-lipoxygenase participates in cell proliferation. We hypothesized that 5-lipoxygenase is needed for proliferation of immature cerebellar granule neurons. Using cultures prepared from 7-day-old rat pups, we confirmed in vitro neurogenesis by immunocytolabeling with 2-bromo-5-deoxyuridine and beta-tubulin isotype III and quantified the rate of cell proliferation by assaying [3H]thymidine incorporation. We found that immature cerebellar granule neurons express large amounts of 5-lipoxygenase, and that treatment with a 5-lipoxygenase antisense, to reduce expression of this gene, decreased significantly (by 60%) the content of 5-lipoxygenase protein and effectively reduced cell proliferation. [3H]thymidine incorporation was significantly reduced by each of the three 5-lipoxygenase inhibitors we tested: AA-861 [2-(12-hydroxydodeca-5, 10-diynyl)-3,5,6-trimethyl-1,4-benzoquinone], MK-886 (C(27)H(33)ClNO(2)S.Na), and L-655,238 [alpha-penyl-3-(2-quinolinylmethoxy)-benzenemethanol]. Their anti-proliferative effect was reversible. We propose that neuronal expression of 5-lipoxygenase is crucial for neurogenesis in vitro, and possibly also in vivo.