Protective effect of Ginkgolids (A + B) is associated with inhibition of NIK/IKK/IκB/NF-κB signaling pathway in a rat model of permanent focal cerebral ischemia

Abstract

Background and purpose: We have previously reported that Ginkgolids which contain Ginkgolids A and B (Ginkgolids (A + B), GKAB) reduce infarct size in a rat model of focal ischemia. NF-κB-inducing kinase (NIK)–IκBα kinase (IKK) pathway plays an important role in activation of nuclear factor kappaB (NF-κB). A previous study demonstrated that Ginkgolid B inhibited lipopolysaccharide (LPS)- and platelet activating factor (PAF)-induced NF-κB activation in rat pleural polymorphonuclear granulocytes. However, little is known about the inhibitory mechanisms of Ginkgolids on the activation of NF-κB. The present study evaluated the effects of GKAB on NIK/IKK/IκB/NF-κB signaling pathway in a rat model of permanent focal cerebral ischemia. Methods: Rats were subjected to permanent middle cerebral artery occlusion (pMCAO) by intraluminal suture blockade. GKAB was injected intravenously (iv) immediately after ischemic onset. Western blot analysis was employed to determine alterations in IκBα, phosphorylated NIK (p-NIK) and phosphorylated IKKα (p-IKKα). Immunohistochemistry was used to confirm the nuclear translocation of NF-κB p65. RT-PCR was used to detect induction of NF-κB target gene c-Myc mRNA. Results: The results showed a brief increase in p-NIK levels after ischemia. GKAB blocked ischemia-induced increases in p-NIK and p-IKKα levels, and reversed the decline in IκBα levels. Ischemia-induced nuclear translocation of NF-κB p65 was attenuated by GKAB . GKAB also repressed the ischemia-induced increase in expression of NF-κB target gene c-Myc mRNA. Conclusions: These findings suggest that GKAB-mediated neuroprotective effect against ischemia appears to be associated with blocking NF-κB activation by suppressing the NIK–IKK pathway.