Effect of the HDAC Inhibitor, Sodium Butyrate, on Neurogenesis in a Rat Model of Neonatal Hypoxia-Ischemia: Potential Mechanism of Action

Neonatal hypoxic-ischemic (HI) brain injury likely represents the major cause of long-term neurodevelopmental disabilities in surviving babies. Despite significant investigations, there is not yet any known reliable treatment to reduce brain damage in suffering infants. Our recent studies in an animal model of HI revealed the therapeutic potential of a histone deacetylase inhibitor (HDACi). The neuroprotective action was connected with the stimulation of neurogenesis in the dentate gyrus subgranular zone. In the current study, we investigated whether HDACi-sodium butyrate (SB)-would also lead to neurogenesis in the subventricular zone (SVZ). By using a neonatal rat model of hypoxia-ischemia, we found that SB treatment stimulated neurogenesis in the damaged ipsilateral side, based on increased DCX labeling, and restored the number of neuronal cells in the SVZ ipsilateral to lesioning. The neurogenic effect was associated with inhibition of inflammation, expressed by a transition of microglia to the anti-inflammatory phenotype (M2). In addition, the administration of SB increased the activation of the TrkB receptor and the phosphorylation of the transcription factor-CREB-in the ipsilateral hemisphere. In contrast, SB administration reduced the level of HI-induced p75(NTR). Together, these results suggest that BDNF-TrkB signaling plays an important role in SB-induced neurogenesis after HI. These findings provide the basis for clinical approaches targeted at protecting the newborn brain damage, which may prove beneficial for treating neonatal hypoxia-ischemia.