Abstract 3475: A Plasminogen Activator Inhibitor-based Therapy of Infection-Sensitized Hypoxia-Ischemia Injury in Newborn Rodent Brains

Abstract

Introduction: The combination of intrauterine infection and hypoxia-ischemia (HI) is a severe threat to immature brains. Further, infection may alter the response to HI in immature brains, but key steps of the switch are unclear. Better understanding these differential responses may suggest new therapeutic targets in neonatal care. This is particular urgent for premature infants who have a high incidence of chorioamnionitis and HI insults, but are unfit for hypothermia therapy. Hypothesis: (1) Infection pre-exposure significantly amplifies the nuclear factor-kappa B (NF-κB) signaling activity following HI in a tissue-plasminogen activator (tPA)-dependant manner. (2) CPAI, a stable-mutant form of plasminogen activator inhibitor-1 (PAI-1) that resists pure HI, also confers significant protection against infection-sensitized HI brain injury in newborns. Methods: Seven-day-old Wistar rat pups were injected with a low-dose lipopolysaccharide (LPS, 0.3 mg/kg, IP) 4 h before imposing cerebral HI using the Rice-Vannucci model, followed by post-hypoxia injection of CPAI or saline into cerebral ventricles. The brains were collected between 4-24 h recovery for biochemical and histological analyses, at 7 d to measure damage, or at 2 months of age for behavioral testing and diffusion tensor imaging of the white-matter (WM). Results: LPS mitigated HI-induced parenchymal tPA activity, but intensified NF-kB signaling, microglia activation, synthesis of chemoattractive cytokines, damage to blood-brain-barrier, and brain tissue loss, which were all significantly ameliorated by the CPAI treatment. The therapeutic window of CPAI was at least 4 h after the LPS/HI insult. CPAI-treated pups also developed near-normal motor and WM functions at 2 months of age. Conclusions: Infection alters the immature brain response to HI by activating tPA-dependent NF-_B signaling but diminishing the tPA proteolytic activity. Because CPAI effectively inhibits both proteolytic and pro-inflammatory functions of tPA, it may be a promising therapeutic of infection-sensitized neonatal HI brain injury.