Pleiotrophin ameliorates white matter injury of neonatal rats by activating the mTOR/YY1/Id4 signaling pathway.

Brain white matter injury (WMI) is a serious disease of the central nervous system. Pleiotrophin (PTN) promotes the differentiation and myelination of oligodendrocytes (OLs) in vitro. However, the role of PTN in WMI remains unknown. Therefore, this study aimed to investigate the neuroprotective role and potential mechanisms of PTN function in neonatal rats with WMI. The PTN and mammalian target of rapamycin (mTOR) inhibitor everolimus was used to treat a WMI model in postnatal day 3 Sprague-Dawley rats, in which the right common carotid arteries of these rats were isolated, ligated, and exposed to a hypoxic environment (6% O 2  + 94% N 2 ) for 2 h. OL differentiation and myelination, as well as the spatial learning and memory abilities of the rats were evaluated to examine the effects of PTN. Two proteins of the mTOR signaling pathway, YingYang1 (YY1) and inhibitor of DNA binding 4 (Id4), were detected and were used to explore the potential mechanisms of PTN in rat WMI experiment and oxygen glucose deprivation (OGD) model. We found that the differentiation and myelination of OLs were impaired after WMI. PTN administration rescued this injury by activating mTOR/YY1 and inhibiting Id4. Everolimus administration inhibited mTOR/YY1 and activated Id4, which blocked the neuroprotective role of PTN in WMI. PTN plays a neuroprotective role in neonatal rats with WMI, which could be involved in the mTOR/YY1/Id4 signaling pathway.