Neuroprotective Effects Of Pioglitazone Is Associated With PPARγ-mediated Inhibition Of NF-κB Signaling Pathway In Rat Model Of Permanent Focal Cerebral Ischemia

Aim: To investigate the neuroprotective actions of pioliotazone (Piog) and the effects of Piog-mediated PPAR_γactivation on NF-κB signaling pathway in rat model of permanent focal cerebral ischemia.Methods: Permanent middle cerebral artery occlusion (pMCAO) model was induced by using intraluminal filament technique in rats. Piog (0.5, 1 and 2mg/kg) was administrated intraperitoneally (i.p.) twice at 24h before and at the time of ischemia, or administrated intraperitoneally (i.p.) only once 10 min after the onset of ischemia. The neuroprotection of Piog was analyzed by scoring neurological deficits, assessing brain infarction volume with 2,3,5-triphenyltetrazolium chloride (TTC) and determining the brain water content at 24 h after ischemia. A selective PPAR_γantagonist GW9662 150, 300 and 600 nmol/kg was administrated intra-cerebral ventricularly (i.c.v.) 30 min before ischemia. Piog (1mg/kg) was administrated intraperitoneally (i.p.) 10 min after the onset of ischemia. Infarction volume was assessed with 2,3,5-triphenyltetrazolium chloride (TTC) at 24 h after ischemia. Western blot analysis was employed to determine alterations in IκBα, p-ERK in ischemic striatum at the indicated time. Brain sections were immunostained for NF-κB p65 in ischemic striatum. RT-PCR was used to measure p53 mRNA levels in ischemic striatum.Results: Piog (0.5, 1 and 2mg/kg) reduced infarction volume in a dose-dependent manner (P＜0.05, P＜0.01) when administered twice at 24h before and at the time of ischemia, or only once at 10 min after the onset of ischemia. Piog 0.5, 1 and 2mg/kg also significantly ameliorated motor behavior deficits, diminished the increase in brain water content (P＜0.01). Pretreatment with the irreversible PPAR_γantagonist GW9662 300 and 600nmol/kg abolished piog's neuroprotection against ischemia (P＜0.01). Western blot analysis revealed that Piog (0.5, 1 and 2mg/kg) markedly up-regulated the levels of IκBαin ischemic striatum at 12 h after ischemia (P＜0.01). GW9662 significantly decreased the increased levels of IκBαinduced by Piog in ischemic striatum at 12 h after ischemia (P ＜0.01). Western blot analysis revealed that the levels of p-ERK significantly decreased at 12 h in ischemic striatum after ischemia (P＜0.01),Piog 0.5, 1 and 2mg/kg strongly increased the levels of p-ERK, GW9662 markedly decreased levels of p-ERK mediated by Piog in ischemic striatum at 12 h after ischemia (P＜0.01). Immunohistochemical staining demonstrated that cytoplasm staining was seen in ischemic striatum in sham-operated rats, and nuclear staining was increased in the ischemic striatal cells in model rats at 12 h after ischemia, Nuclear translocation of NF-κB was reduced in ischemic striatal cells in Piog-treated rats. GW9662 could antagonize the inhibition of nuclear translocation of NF-κB induced by Piog. Piog (1,2mg/kg) repressed the expression of NF-κB target gene p53 mRNA in ischemic striatum at 12 h after ischemia (P＜0.05), GW9662 up-regulated the decreased expression of p53 mRNA mediated by Piog in ischemic striatum at 12 h after ischemia.Conclusion: The present findings provide the evidence that pioglitazone has neuroprotective activity on cerebral ischemic injury, and this effect may be mediated by PPAR_γ-dependent inhibition of NF-κB signaling pathway.