Abstract
Perinatal infection aggravates neonatal hypoxic-ischemic (HI) brain injury and may interfere with therapeutic hypothermia. While the NF-κB signaling pathway has been implicated in microglia activation in infection-sensitized HI, the current therapeutic strategies rely on systemic intervention, which could impair neonatal immunity and increase the risk of severe infection. To devise a brain-targeted anti-NF-κB strategy, we examined the effects of intranasal delivery of tat-NBD peptides in two animal models of neonatal infection-sensitized HI. Kinetic experiments showed that tat-NBD peptides entered the olfactory bulbs rapidly (10-30 min) and peaked in the cerebral cortex around 60 min after intranasal application in P7 rats. Further, intranasal delivery of 1.4 mg/kg tat-NBD, which is only 7% of the intravenous dose in past studies, markedly attenuated NF-κB signaling, microglia activation, and brain damage triggered by HI with 4 or 72 h pre-exposure to the bacterial endotoxin lipopolysaccharide (LPS). In contrast, intranasal delivery of mutant tat-NBD peptides or systemic application of minocycline failed to block LPS-sensitized HI injury. Yet, intranasal delivery of up to 5.6 mg/kg tat-NBD peptides immediately after pure-HI insult showed little protection, likely due to its rapid clearance from the brain and inability to inhibit parenchymal plasminogen activators. Together, these results suggest a novel therapy of infection-sensitized HI brain injury in newborns.