Hypothermia is not therapeutic in a neonatal piglet model of inflammation-sensitized hypoxia–ischemia

Kathryn Martinello ,Christopher Meehan,Boris W Kramer,Xavier Golay,Henrik Hagberg,Donald Peebles,David L Price ,Nigel Klein,Magdalena Sokolska,Ilias Tachtsidis,Tatenda Mutshiya,Qin Yang,Mariya Hristova,Cally J Tann ,Tim G A M Wolfs,Adnan Avdic-Belltheus,Pierre Gressèns ,Bobbi Fleiss,Alan Bainbridge,Mustafa Ali Akın ,Ingran Lingam,Nicola J Robertson

doi:10.1038/s41390-021-01584-6

Abstract

BackgroundPerinatal inflammation combined with hypoxia–ischemia (HI) exacerbates injury in the developing brain. Therapeutic hypothermia (HT) is standard care for neonatal encephalopathy; however, its benefit in inflammation-sensitized HI (IS-HI) is unknown.MethodsTwelve newborn piglets received a 2 µg/kg bolus and 1 µg/kg/h infusion over 52 h of Escherichia coli lipopolysaccharide (LPS). HI was induced 4 h after LPS bolus. After HI, piglets were randomized to HT (33.5 °C 1–25 h after HI, n = 6) or normothermia (NT, n = 6). Amplitude-integrated electroencephalogram (aEEG) was recorded and magnetic resonance spectroscopy (MRS) was acquired at 24 and 48 h. At 48 h, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive brain cell death, microglial activation/proliferation, astrogliosis, and cleaved caspase-3 (CC3) were quantified. Hematology and plasma cytokines were serially measured.ResultsTwo HT piglets died. aEEG recovery, thalamic and white matter MRS lactate/N-acetylaspartate, and TUNEL-positive cell death were similar between groups. HT increased microglial activation in the caudate, but had no other effect on glial activation/proliferation. HT reduced CC3 overall. HT suppressed platelet count and attenuated leukocytosis. Cytokine profile was unchanged by HT.ConclusionsWe did not observe protection with HT in this piglet IS-HI model based on aEEG, MRS, and immunohistochemistry. Immunosuppressive effects of HT and countering neuroinflammation by LPS may contribute to the observed lack of HT efficacy. Other immunomodulatory strategies may be more effective in IS-HI.ImpactAcute infection/inflammation is known to exacerbate perinatal brain injury and can worsen the outcomes in neonatal encephalopathy.Therapeutic HT is the current standard of care for all infants with NE, but the benefit in infants with coinfection/inflammation is unknown.In a piglet model of inflammation (LPS)-sensitized HI, we observed no evidence of neuroprotection with cooling for 24 h, based on our primary outcome measures: aEEG, MRS Lac/NAA, and histological brain cell death.Additional neuroprotective agents, with beneficial immunomodulatory effects, require exploration in IS-HI models.

Highlights

Therapeutic hypothermia (HT) is standard care for neonates with intrapartum-related neonatal encephalopathy (NE) under intensive care settings
We have recently demonstrated an increase in mortality arterial catheter (Vygon) for intermittent blood sampling (Abbot and brain cell death in Escherichia coli (E. coli) LPS-sensitized Laboratories, UK) and continuous monitoring of heart rate and hypoxic brain injury in the piglet model, compared with either E. coli LPS or hypoxia alone.[10]
Plasma and Cerebrospinal fluid (CSF) cytokine response to LPS and HI was largely unchanged with HT

Summary

Introduction

Therapeutic hypothermia (HT) is standard care for neonates with intrapartum-related neonatal encephalopathy (NE) under intensive care settings. Attenuated efficacy of HT may be due to severity of illness, timing Male large white piglets aged ≤36 h were sedated with of insult in relation to initiation of HT, or sensitization with intramuscular midazolam (150 μg) and anesthetized with 2–3%. METHODS: Twelve newborn piglets received a 2 μg/kg bolus and 1 μg/kg/h infusion over 52 h of Escherichia coli lipopolysaccharide (LPS). At 48 h, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive brain cell death, microglial activation/proliferation, astrogliosis, and cleaved caspase-3 (CC3) were quantified. AEEG recovery, thalamic and white matter MRS lactate/N-acetylaspartate, and TUNEL-positive cell death were similar between groups. CONCLUSIONS: We did not observe protection with HT in this piglet IS-HI model based on aEEG, MRS, and immunohistochemistry. Immunosuppressive effects of HT and countering neuroinflammation by LPS may contribute to the observed lack of HT efficacy. Other immunomodulatory strategies may be more effective in IS-HI

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