Caffeine’s Effects with Enolase as a Biomarker in a Preterm Rat Model for Hypoxic Ischemic Encephalopathy

Rachel R. Koski, University of Minnesota Medical School, Edina, MN, United States; Madison Heidelberger, University of Minnesota Medical School, Minneapolis, MN, United States; Phu Tran, University of Minnesota, Minneapolis, MN, United States

Background: Approximately 5-9 of 1000 preterm infants ( < 35 weeks gestational age) experience hypoxic ischemic encephalopathy (HIE). Yet, there is no routine use of diagnostic biomarkers or approved treatment therapy for them. Biomarkers offer an objective way to identify HIE. MRI imaging is used to diagnose HIE presence and severity in term infants, but not in preterm infants. Neuron specific enolase (NSE), a plasma protein specific to neuron damage, can aid in early detection of HIE leading to treatment. Caffeine, a non-selective adenosine receptor antagonist, is used to treat apnea of prematurity in infants and has potential neuroprotective effects. In animal models of term HIE, caffeine shows anti-inflammatory properties and improved neurobehavioral outcomes. It remains unknown if caffeine has similar neuroprotective effects in preterm HIE neonates.

Objectives: Determine neuroprotective effects of caffeine therapy and investigate NSE as a potential biomarker for both detecting HIE and testing the efficacy of caffeine in an established preterm HIE rat model.

Design/Methods: Rat litters were culled to 4 males & 4 females. Pups were randomly assigned within litters to: sham+saline (S), sham+caffeine (C), hypoxic-ischemic (HI)+S, and HI+C. At postnatal day (P)7, (~34weeks GA preterm infant), HI was induced by carotid ligation + 8% O2 (90min hypoxia). Control (sham) pups underwent similar surgical procedure without ligation or hypoxia. S or C was given (IP injection) at 0, 24 & 48hrs post-HI. Brain (cortex) and plasma samples were collected at 24 & 72hrs post-HI. Brain-IL1b (known marker for brain injury) and plasma-NSE levels were assayed using ELISA. Spearman correlation was computed for IL1b and NSE. 2-way ANOVA with post hoc Tukey comparison tests were used to analyze changes among treatment groups.

Results: Preliminary data shows an increase in NSE with HI compared to sham groups at 24hr post-HI(p= 0.017), but not at 72hr post-HI(p=0.2). There is a trend of decrease in NSE concentration with caffeine treated groups, but no statistically significant difference. IL1b assessment is ongoing. Sex differences will be reported.

Conclusion: The findings suggest NSE as a potential diagnostic biomarker for brain injury and monitoring for efficacy of caffeine treatment in preterm HIE. More studies are ongoing to establish NSE as an objective measure of HIE injury. Thus, NSE provides a potentially novel blood-based opportunity to monitor the efficacy of treatment for premature HIE model in brain development.