401 - Intranasal Insulin Decreases Persistent Neuronal Degeneration Following Neonatal Hypoxia-Ischemia In Juvenile Rats

Poster Number: 401
Publication Number: 401.236

Nilesh Dankhara, University of Mississippi School of Medicine, Jackson, MS, United States; Jonathan W. Lee, University of Mississippi School of Medicine, Jackson, MS, United States; Lu Silu, University of Mississippi Medical center, Jackson, MS, United States; Norma Ojeda, University of Mississippi School of Medicine, Brandon, MS, United States; Yi Pang, Univ. of Mississippi Med Ctr, JACKSON, MS, United States; Carolyn Glendye, University of Mississippi School of Medicine, Jackson, MS, United States; Abhay Bhatt, University of Mississippi School of Medicine, Jackson, MS, United States; Lir-Wan Fan, University of Mississippi Medical Center, Jackson, MS, United States

Background: Hypoxic-ischemic (HI) encephalopathy (HIE) remains a significant cause of morbidity and mortality in neonates. Despite therapeutic hypothermia, many infants develop cerebral palsy and long-term cognitive deficits. Our previous study has shown that intranasal insulin (InInsulin) administered immediately following HI exposure in P10 rats protects against HI-induced sensorimotor disturbances, long-term memory abnormality in P25 rats. Interestingly, we noted evidence of persistent inflammation in the form of an increase in microglia in the hippocampus at P25 following HI at P10, which InInsulin reduced.

Objective: The objective of the current project is to test the hypothesis that HI causes ongoing hippocampal damage at P25 following HI injury at P10, and InInsulin mitigates those changes.

Design/Methods: At postnatal day 10 (P10), Sprague-Dawley rat pups were randomly divided into four groups: HI+Insulin (Ins); HI+Vehicle (Veh); Sham+Insulin; Sham+Veh, with an equal male/female ratio. Pups either had HI exposure by ligation of the right carotid artery followed by 90 min of hypoxia or sham surgery followed by room air exposure. Immediately after HI or Sham, pups received either intranasal recombinant human insulin (25 μg) or an equivalent volume of Vehicle in each naris, followed by 2 more doses every 24 h. The hippocampal injury was examined by fluoro-Jade-c staining in the dorsal hippocampus area. We followed our Institutional Animal Care and Use Committee guidelines in accordance with the Guide 8 edition, for the Care and Use of Laboratory Animals published by the US National Institute of Health.

Results: Our results showed that HI decreased the numbers of mature neurons (NeuN+) in CA3 and immature neurons (DCX+) in DG regions and increased the numbers of degenerated neurons (Fluoro-Jade C+) in CA3 regions, as clearly evident in the image. InInsulin reduced HI-induced long-term hippocampal injury, as evidenced by increases in the numbers of mature neurons (NeuN+) in CA3 and immature neurons (DCX+) in DG regions and reduction in the numbers of degenerated neurons (FluoroJade C+) in CA3 regions.Conclusion(s): Our findings suggest that InInsulin provides long-lasting protective effects against neonatal (P10) hippocampal neuronal injury in juvenile rats, thus providing additional evidence supporting InInsulin as a promising non-invasive therapy to improve outcomes of newborns with HIE. Additionally, the novel findings of persistent inflammation and hippocampal injury this late following HI exposure suggest that the therapeutic window of anti-inflammatory therapy is more prolonged than currently known.
CV- DankharaNCV-DankharaN.pdf