Combined pharmacotherapy suppress ferroptosis and inflammation after neonatal intraventricular hemorrhage
Neonatal intraventricular hemorrhage (IVH) is a common complication of extremely premature newborns, and results in reduced neurogenesis, white matter injury, cortical atrophy, and subsequent cerebral palsy, learning and memory disabilities. However, the impact of IVH on the hippocampus, an area critical for memory and learning capabilities throughout life, remains relatively unexplored. Using a preterm rabbit pup model that structurally resembles human perinatal brain development, we report, widespread hematoma and iron accumulation in the hippocampal dentate gyrus (DG) following IVH. This accumulation is facilitated by the anatomical positioning of the hippocampus within the unidirectional CSF flow pathway and the vulnerability of the immature dentate gyrus vasculature. Sulforaphane (SFN; an activator of nuclear factor erythroid 2 related factor 2 [Nrf2] transcriptional factor and anti-inflammatory pathways) and deferoxamine (DFN; an iron chelator) reduced iron deposition, free hemoglobin, and activated glial cells (sp. astrocytes and microglia), particularly in the DG molecular layer and hilar regions. The attenuated inflammatory responses correlate with decreased ferroptosis-mediated neuronal death, and substantial restoration of the dysregulated gene pathways associated with inflammation, immune activation, and neuronal cell death in the developing hippocampal/DG region. This was associated with a gene profile favoring ferroptotic cell death rather than apoptosis or autophagy pathways. Moreover, we also identified a regional specificity to certain effects as no astrogliosis was observed in hippocampal CA1 to CA4 regions after IVH or when compared with healthy controls. Our study is the first to demonstrate hippocampal hematoma and iron accumulation associated pathologic mechanisms following neonatal IVH. The results provide mechanistic insights into hippocampal injury as well as a therapeutic proof-of-concept for targeting iron toxicity and inflammation in the developing brain to mitigate injury. These results justify extending analyses of injury reversal to long-term postnatal ages and behavior studies to assess therapeutic potential. The study illustrates novel therapeutic interventions that attenuate early mediators of injury that improves recovery of hippocampal/DG formation/maturation and neuroprotection after neonatal IVH. We speculate that these protective effects may prolong donor stem cell survival thus, potentiating benefits of living cellular therapy in the future.