Distinct cytokine patterns may regulate the severity of neonatal asphyxia-an observational study

Abstract

Background: Neuroinflammation and a systemic inflammatory reaction are important features of perinatal asphyxia. Neuroinflammation may have dual aspects being a hindrance, but also a significant help in the recovery of the CNS. We aimed to assess intracellular cytokine levels of T-lymphocytes and plasma cytokine levels in moderate and severe asphyxia in order to identify players of the inflammatory response that may influence patient outcome.

Methods: We analyzed the data of 28 term neonates requiring moderate systemic hypothermia in a single-center observational study. Blood samples were collected between 3 and 6 h of life, at 24 h, 72 h, 1 week, and 1 month of life. Neonates were divided into a moderate (n = 17) and a severe (n = 11) group based on neuroradiological and amplitude-integrated EEG characteristics. Peripheral blood mononuclear cells were assessed with flow cytometry. Cytokine plasma levels were measured using Bioplex immunoassays. Components of the kynurenine pathway were assessed by high-performance liquid chromatography.

Results: The prevalence and extravasation of IL-1b + CD4 cells were higher in severe than in moderate asphyxia at 6 h. Based on Receiver operator curve analysis, the assessment of the prevalence of CD4+ IL-1β+ and CD4+ IL-1β+ CD49d+ cells at 6 h appears to be able to predict the severity of the insult at an early stage in asphyxia. Intracellular levels of TNF-α in CD4 cells were increased at all time points compared to 6 h in both groups. At 1 month, intracellular levels of TNF-α were higher in the severe group. Plasma IL-6 levels were higher at 1 week in the severe group and decreased by 1 month in the moderate group. Intracellular levels of IL-6 peaked at 24 h in both groups. Intracellular TGF-β levels were increased from 24 h onwards in the moderate group.

Conclusions: IL-1β and IL-6 appear to play a key role in the early events of the inflammatory response, while TNF-α seems to be responsible for prolonged neuroinflammation, potentially contributing to a worse outcome. The assessment of the prevalence of CD4+ IL-1β+ and CD4+ IL-1β+ CD49d+ cells at 6 h appears to be able to predict the severity of the insult at an early stage in asphyxia.

Keywords: Cytokine network; Hypoxic ischemic encephalopathy; Neuroinflammation; Perinatal asphyxia.

Fig. 1

Intracellular cytokine level alterations in time represented by mean fluorescence intensity (MFI) values in moderate and severe asphyxia. Horizontal line, median; box, interquartile range; whisker, range. p < 0.05 a vs 6 h, b vs 24 h, c vs 72 h, d vs 1 week

Fig. 2

Plasma cytokine level alterations in time in moderate and severe asphyxia. Horizontal line, median; box, interquartile range; whisker, range. p < 0.05 a vs 6 h, b vs 24 h, c vs 72 h, d vs 1 week

Fig. 3

Cell prevalence data alterations in time in moderate and severe asphyxia. Horizontal line, median; box, interquartile range; whisker, range. p < 0.05 a vs 6 h, b vs 24 h, c vs 72 h, d vs 1 week

Fig. 4

Alterations in the components of the kynurenine pathway in time in moderate and severe asphyxia. Horizontal line, median; box, interquartile range; whisker, range. KYN kynurenine, KYNA kynurenic acid, TRP tryptophan, K/T kynurenine/tryptophan ratio. p < 0.05 a vs 6 h, b vs 24 h, c vs 72 h, d vs 1 week

Fig. 5

Receiver operator curve (ROC) analysis of the prevalence of CD4+ IL-1β+ and CD4+ IL-1β + CD49d+ cell subsets in moderate and severe neonatal asphyxia. AUC area under the curve