Robust Neuroprotection by NEMO (IKKγ)-binding Domain Peptide via Anti-inflammatory Effects in the Post-ischemic Brain

Microglia exhibit a complex and context-dependent role in the post-ischemic brain, performing both neuroprotective and neurotoxic functions. Among the many factors contributing to pro-inflammatory microglia activation, NF-κB signaling plays a pivotal role. The NEMO (IKKγ)-binding domain (NBD) peptide, an 11-amino-acids cell-permeable peptide spanning the NBD of IKKα and IKKβ, acts as a highly specific inhibitor by preventing NEMO-IKKα/IKKβ complex formation. We investigated the neuroprotective effects of the NBD peptide in a post-ischemic brain using a transient middle cerebral artery occlusion (MCAO) animal model. In in vitro experiments, pre-treatment of BV2 cells (a microglia cell line) with NBD peptide significantly suppressed LPS-induced NEMO-IKKα/IKKβ complex formation, nuclear translocation of p65, and upregulation of numerous pro-inflammatory cytokines expressions. The anti-inflammatory effect was further confirmed in reporter gene assay following reporter plasmid transfection, demonstrating a NBD peptide dose-dependent response. In the post-ischemic brain, intranasal delivery of NBD peptide significantly suppressed NEMO-IKKα/IKKβ complex formation, IκB-α phosphorylation, microglial activation, and cytokine induction. Notably, intranasal administration of NBD peptide 3 h post-MCAO significantly reduced infarct volumes in a dose-dependent manner. A significant reduction in infarct volume was observed by 6 h post-administration, suggesting an extended therapeutic window for the NBD peptide. These neuroprotective effects were accompanied by the attenuation of neurological deficits and motor function impairment, as assessed by rota-rod, beam balance, and corner turn tests. Collectively, these results highlight a robust neuroprotective effect along with long-term outcomes of NBD peptide in the post-ischemic brain, with NBD peptide-mediated blocking of NEMO-IKKα/IKKβ complex formation serving as a key underlying molecular mechanism.