Allopregnanolone is neuroprotective in hypoxic-ischemic injury of the immature brain

Hypoxic-ischemic (HI) brain injury in premature infants causes major cognitive deficits and cerebral palsy (CP). Premature infants are devoid of a placental supply of Allopregnanolone (ALLO). ALLO is essential for brain growth and neuronal and glial cell survival. Goals and objectives: To assess whether ALLO supplementation mitigates hypoxic-ischemic (HI) brain injury. To conduct a comparative analysis of RNA sequencing between ALLO-treated HI mice and untreated HI mice. To elucidate the mechanism of action of ALLO in the context of HI brain injury.Methods: A neonate mouse model of HI was treated with 3 doses of ALLO (10mg/kg/dose IP) on P5, P8, and P11 or saline. Molecular, biochemical, histopathological, and transcriptome studies were done on P12-P14. Others were examined at P60 for neurobehavioral analysis. Results: ALLO-treated HI mice showed significant improvement in neuro-regeneration, myelination, motor function, coordination, learning, and memory, along with significant attenuation of neuro-inflammation. RNA sequencing analysis showed that the ALLO-treated HI group had a significant downregulation of inflammatory responsive genes, reduced glutamate excitotoxicity, improved neurogenesis, and improved neural repair, restoring neural integrity and cognitive function. Using electron microscopy, mitochondrial ultrastructure in hippocampal neurons showed small, fragmented mitochondria, with loss of mitochondrial membrane and cristae in HI group, while ALLO protected mitochondrial ultrastructure after HI exposure. Conclusion: ALLO is a unique natural neurotherapeutic steroid in HI injury through promoting neurogenesis, neurodegeneration, and oligodendrogenesis, reducing neuroinflammation and glutamate excitotoxicity, and preserving mitochondrial structure and function.