5-LOX Inhibitor Zileuton Reduces Inflammatory Reaction and Ischemic Brain Damage Through the Activation of PI3K/Akt Signaling Pathway

Abstract

Previous studies from our laboratories showed that an anti-inflammatory drug, 5-lipoxygenase inhibitor zileuton, attenuates ischemic brain damage via inhibiting inflammatory reaction. However, it was elusive whether zileuton attenuates inflammatory reaction and ischemic brain damage through the modulation of PI3K/Akt signaling pathway. In the present study, we, for the first time, investigated whether PI3K/Akt pathway was involved in zileuton's anti-inflammatory and neuroprotective properties against brain damage following experimental ischemic stroke. Adult male Sprague-Dawley rats underwent middle cerebral artery occlusion (MCAO), then received treatment with zileuton or vehicle after the onset of ischemia. LY294002 was injected intracerebroventricularly to inhibit the activation of PI3K/Akt signaling pathway selectively. Neurological deficit scores, cerebral infarct volume, morphological characteristic and cerebral water content were assessed 24 h after cerebral ischemia. The enzymatic activity of myeloperoxidase (MPO) was measured 24 h after cerebral ischemia. Expression of p-Akt, t-Akt and COX-2 in ischemic brain were determined by western blot. NF-κB p65 immuno-positive cells in ischemic brain were detected 24 h after cerebral ischemia. The content of TNF-α in blood was examined by ELISA. 5-LOX inhibitor zileuton significantly reduces neurological deficit scores, cerebral infarct volume, cerebral water content, ischemic neuronal injury and the enzymatic activity of MPO, all of which were abolished by LY294002 administration. Zileuton significantly up-regulates the expression of p-Akt, which was inhibited by LY294002 administration. Zileuton significantly down-regulates the over-expression of NF-κB p65 and COX-2, and attenuates the release of TNF-α, all of which were disminished by LY294002 administration. These results suggest that zileuton attenuates ischemic brain damage by inhibiting inflammatory reaction through the activation of PI3K/Akt signaling pathway.

Keywords: 5-Lipoxygenase; Cerebral ischemia; Inflammation; LY294002; PI3K/Akt; Zileuton.