Abstract WP353: Inter-alpha Inhibitor Proteins (IAIPs) Reduce Astrocyte Activation and Gliosis in the Neonatal Brain After Hypoxic-ischemic (HI) Brain Injury

Abstract

Background: IAIPs are serine protease inhibitors that exert anti-inflammatory effects after HI brain injury. We have previously shown that IAIP administration after HI attenuates histopathological brain injury, apoptosis, and microglial activation and improves neurobehavioral outcomes in neonatal rats. Astrocytes are known to form glial scars, increase neuroinflammation, and exacerbate brain injury after stroke. Objective: To determine the effect of IAIPs on astrocytic GFAP expression in the neonatal rat brain after HI. Methods: HI was induced using the Rice-Vannucci method with right carotid ligation and exposure to 8% O 2 for 90 min. Post-natal day 7 rats were assigned to one of three groups: non-ischemic sham-control (Sham, n=12), HI exposed placebo-treated (HI-PL, n=13), or HI exposed IAIP-treated (HI-IAIP, n=14). Intraperitoneal injections of 30 mg/kg of IAIP or saline were given at 15 min, 24, and 48 h after HI. We recorded the sex of the rats. 72 h after HI, brains were collected, paraffin embedded, and sectioned. We performed immunohistochemical analysis by staining slides with GFAP, a marker of astrocyte activation. We performed stereological analysis by capturing images of the whole damaged hemisphere, cerebral cortex, hippocampus, and corpus callosum with the StereoInvestgator 10.0 Probe. We quantified GFAP expression levels using Image J software without knowledge of the group assignments. Results: Sham rats had significantly lower GFAP expression compared with the HI-PL group in the hemisphere (P<0.001), cortex (P<0.005), and hippocampus (P<0.005). IAIP treatment significantly reduced GFAP expression after HI in the hemisphere (P<0.05) compared with the HI-PL group. We also examined GFAP expression separately in male and female rats and found no differences in GFAP expression among the groups in females. However, we found that the Sham males had significantly lower GFAP expression compared to HI-PL in the hemisphere (P<0.005), cortex (P<0.005), and hippocampus (P<0.005), and that the IAIP treated HI exposed males had lower GFAP expression compared with the HI-PL group in the hemisphere (P<0.05) and cortex (P<0.05). Conclusion: IAIPs attenuate HI related astrogliosis in some brain regions particularly in male neonatal rats.