Gut-brain-immune interactions in neonatal hypoxic–ischemic brain injury

BACKGROUND: Neonatal hypoxia-ischemia (HI) is the leading cause of childhood mortality and neurodevelopmental disability. Despite therapeutic hypothermia as the only clinically established treatment to date, outcomes remain poor for a significant proportion of affected infants. Mechanistic understanding has been brain-oriented in the past, however the gut and immune system are increasingly recognized as active modulators of brain injury, recovery and neurodevelopment. MAIN BODY: Gut microbiota regulate microglial maturation, myelination and blood-brain barrier integrity. Neonatal HI induces gut dysbiosis and barrier failure, associated with neuroinflammation. First, faecal microbiota transplantation experiments in animal models suggest a causal relationship. Clinical data corroborate microbial perturbations in HIE infants, though antibiotic exposure and the NICU environment represent potential confounders. At the level of the immune system, dysregulated peripheral innate and adaptive immune responses are well documented in HI-affected neonates, with some alterations persisting into school age. The microbiota dimension of these immune responses remains largely unexplored, despite well-characterized microbiota-immune interactions in models of adult stroke. Therapeutic candidates include probiotics, human milk oligosaccharides and butyrate, each with preliminary preclinical support but no completed clinical trials in HIE. CONCLUSION: Reframing neonatal HI as a systemic gut-brain-immune disease opens up new possibilities for adjunctive therapy and biomarker discovery. Progress requires longitudinal multi-omic clinical cohorts, sex-stratified and disease-phase-resolved preclinical analyses and rigorous evaluation of microbiome-targeted interventions.