Inhibition of NF-κB activation by 5-lipoxygenase inhibitors protects brain against injury in a rat model of focal cerebral ischemia

BACKGROUND: Stroke is one of the leading causes of death worldwide and a major cause of morbidity and mortality in the United States of America. Brain ischemia-reperfusion (IR) triggers a complex series of biochemical events including inflammation. Leukotrienes derived from 5-lipoxygenase (5-LOX) cause inflammation and are thus involved in the pathobiology of stroke injury. METHODS: To test the neuroprotective efficacy of 5-LOX inhibition in a rat model of focal cerebral IR, ischemic animals were either pre- or post-treated with a potent selective 5-LOX inhibitor, (N- [3-[3-(-fluorophenoxy) phenyl]-1-methyl-2-propenyl]-N-hydroxyurea (BW-B 70C). They were evaluated at 24 h after reperfusion for brain infarction, neurological deficit score, and the expression of 5-LOX. Furthermore, the mechanism and the anti-inflammatory potential of BW-B 70C in the regulation of nuclear factor kappa B (NF-κB) and inflammatory inducible nitric oxide synthase (iNOS) were investigated both in vivo and in vitro. RESULTS AND DISCUSSION: Both pre- and post-treatment with BW-B 70C reduced infarctions and improved neurological deficit scores. Immunohistochemical study of brain sections showed IR-mediated increased expression of 5-LOX in the neurons and microglia. BW-B 70C down-regulated 5-LOX and inhibited iNOS expression by preventing NF-κB activation. Two other structurally different 5-LOX inhibitors were also administered post IR: caffeic acid and 2, 3, 5-trimethyl-6- [12-hydroxy-5, 10-dodecadiynyl]-1, 4-benzoquinone (AA-861). As with BW-B 70C, they provided remarkable neuroprotection. Furthermore, in vitro, BW-B 70C inhibited lipopolysaccharide (LPS) mediated nitric oxide production, iNOS induction and NF-κB activation in the BV2 microglial cell line. Treating rat primary microglia with BW-B70C confirmed blockage of LPS-mediated translocation of the p65 subunit of NF-κB from cytosol to nucleus. CONCLUSION: The study demonstrates the neuroprotective potential of 5-LOX inhibition through down-regulation of NF-κB in a rat model of experimental stroke.