Plasmatic profiles of cytokines/chemokines, glial fibrillary acidic protein (GFAP) and MRI brain damage in neonates with hypoxic ischemic encephalopathy (HIE)

Abstract

Background: Perinatal hypoxia triggers the release of cytokines and chemokines by neurons, astrocytes and microglia. In response to hypoxia-ischemia resting/ramified microglia proliferate and undergo activation, producing proinflammatory molecules. The brain damage extension seems to be related to both the severity of hypoxia and the balance between pro and anti-inflammatory response and can be explored with neuroimaging.

Aims: The aim of this preliminary study was to explore possible relationships between plasma levels of inflammatory cytokines/chemokines and the severe brain damage detectable by Magnetic Resonance Imaging (MRI), performed during the hospitalization.

Methods: In 10 full terms neonates with hypoxic ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH), divided into cases and controls, according to MRI results, we measured and compared the plasma levels of CCL2/MCP-1, CXCL8, GFAP, IFN y, IL-10, IL-18, IL-6, CCL3, ENOLASE2, GM-CSF, IL-1b, IL-12p70, IL-33, TNFα, collected at four different time points during TH (24, 25-48, 49-72 h of life, and 7-10 days from birth). Five of enrolled babies had pathological brain MRI (cases) and 5 had a normal MRI examination (controls). Cytokines were measured by Magnetic Luminex Assay. MRI images were classified according to Barkovich's score.

Results: Mean levels of all cytokines and molecules at time T1 were not significantly different in the two groups. Comparing samples paired by day of collection, the greatest differences between cases and controls were found at times T2 and T3, during TH. At T4, levels tended to get closer again (except for IL-6, IL10 and IL18). Infants with worse MRI showed higher plasmatic GFAP levels than those with normal MRI, while their IL-18 was lower. The mean levels of CCL3MIP1alpha, GMCSF, IL1BETA overlapped throughout the observation period in both groups.

Conclusion: In a small number of infants with worse brain MRI, we found higher levels of GFAP and of IL-10 at T4 and a trend toward low IL-18 levels than in infants with normal MRI, considered early biomarker of brain damage and a predictor of adverse outcome, respectively. The greatest, although not significant, difference between the levels of molecules was found in cases and controls at time points T2 and T3, during TH.

Keywords: Asphyxia; Cytokines; Glial fibrillary acidic protein (GFAP); Neuroinflammation; Therapeutic hypothermia.