Glucocorticoids Stimulate Inflammatory 5-Lipoxygenase Gene Expression and Protein Translocation in the Brain


  • Abbreviations used : cyc, cyclophilin ; FLAP, 5-lipoxygenase-activating protein ; 5-LO, 5-lipoxygenase ; TBST buffer, 10 mM Tris base, 0.15 M NaCl, and 0.05% Tween 20.

Address correspondence and reprint requests to Dr. H. Manev at Psychiatric Institute, University of Illinois at Chicago, 1601 West Taylor Street, MC 912, Chicago, IL 60612, U.S.A.


Abstract : In the brain, the expression of 5-lipoxygenase (5-LO), the enzyme responsible for the synthesis of inflammatory leukotrienes, increases during aging. Antiinflammatory drugs are currently being evaluated for the treatment of aging-associated neurodegenerative diseases such as Alzheimer's disease. Although generally considered antiinflammatory, glucocorticoids, whose production also increases during aging, are not particularly effective in this disease. In human monocytes, 5-LO mRNA content increases on exposure to the synthetic glucocorticoid dexamethasone, which prompted us to hypothesize that glucocorticoids might increase 5-LO expression in the brain as well. We treated rats for 10 days either with corticosterone (implanted subcutaneously) or with dexamethasone (injected daily) ; they were killed on day 10 after pellet implantation or 24 h after the 10th dexamethasone injection. We found increased levels of 5-LO mRNA and protein in hippocampus and cerebellum of glucocorticoid-treated rats ; 5-LO-activating protein (FLAP) mRNA content was not affected. Using western immunobloting, we also observed the concurrent translocation of 5-LO protein from cytosol to membrane, an indication of its activation. Thus, glucocorticoid-mediated up-regulation of the neuronal 5-LO pathway may contribute to rendering an aging brain vulnerable to degeneration.