Intranasal Tat-modified PEG-PCL nanomicelles delivering anti-RelA siRNA attenuate ischemia-reperfusion injury.

Inflammatory responses centered on microglial activation are deeply involved in the progression of cerebral ischemia-reperfusion injury, and RelA, a subunit of nuclear factor κB (NF-κB), acts as a central mediator of these responses. In this study, we evaluated the efficacy of a nose-to-brain drug delivery system that combines intranasal administration with polymeric nanomicelles modified with the cell-penetrating peptide Tat (polyethylene glycol [PEG]-polycaprolactone [PCL]-Tat) to deliver RelA-targeting small interfering RNA (siRNA), referred to as siRelA. The PEG-PCL-Tat-siRelA complex exhibited efficient intracellular uptake by BV-2 microglial cells and significantly suppressed RelA mRNA expression. No significant cytotoxicity was observed in BV-2 or primary cultured mouse hippocampal neurons. In addition, the complex showed high siRNA stability in the cerebrospinal fluid. Using a radiolabeled model siRNA, intranasal administration of PEG-PCL-Tat to mice subjected to transient middle cerebral artery occlusion (t-MCAO) significantly enhanced siRNA distribution in ischemic brain regions. Intranasal administration of PEG-PCL-Tat-siRelA significantly reduced the infarct volume in ischemic brain regions of the t-MCAO model mice. Furthermore, suppression of RelA mRNA expression in ischemic brain tissue was accompanied by significant reductions in the mRNA expression of NF-κB-downstream inflammatory cytokines. Taken together, these results suggest that intranasal delivery of siRelA using PEG-PCL-Tat represents a promising novel neuroprotective therapeutic strategy mediated by the modulation of inflammatory responses.