Interleukin-33 and Soluble ST2 Levels in Infants with Hypoxic-Ischemic Encephalopathy.

INTRODUCTION: Interleukin (IL)-33 and its receptor ST2L play key roles in the IL-33/ST2 signaling pathway. Soluble ST2 (sST2) inhibits the proper function of IL-33. sST2 levels are increased in patients with several neurological diseases, but in infants with hypoxic-ischemic encephalopathy (HIE), IL-33 and sST2 levels have not been studied. This study aimed to investigate whether serum levels of IL-33 and sST2 are useful as biomarkers of HIE severity and prognostic factors for infants with HIE. METHODS: Twenty-three infants with HIE and 16 controls (gestational age ≥36 weeks and ≥1,800 g birth weight) were enrolled in this study. Serum levels of IL-33 and sST2 were measured at <6 h, 1-2, 3, and 7 days of age. Hydrogen-1 magnetic resonance spectroscopy was performed, and ratios of peak integrals of lactate/N-acetylaspartate (Lac/NAA) were calculated as objective indicators of brain damage. RESULTS: In the moderate and severe HIE, serum sST2 concentrations were increased and there was a good correlation between serum sST2 and HIE severity on days 1-2, whereas no variation was observed in serum IL-33. Serum sST2 levels were positively correlated with Lac/NAA ratios (Kendall's rank correlation coefficient = 0.527, p = 0.024), and both sST2 and Lac/NAA ratios were significantly higher in HIE infants with neurological impairment (p = 0.020 and <0.001, respectively). CONCLUSIONS: sST2 may be a useful predictor of severity and later neurological outcomes in infants with HIE. Further investigation is required to elucidate the relationship between the IL-33/ST2 axis and HIE.