Data from: Thyroid hormone protects primary cortical neurons exposed to hypoxia by reducing DNA methylation and apoptosis

Traumatic Brain Injury (TBI) is associated with disruption of cerebral
blood flow leading to localized brain hypoxia. Thyroid hormone (TH)
treatment, administered shortly after injury, has been shown to promote
neural protection in rodent TBI models. The mechanism of TH protection,
however, is not established. We used mouse primary cortical neurons to
investigate the effectiveness and possible pathways of T3-promoted cell
survival after exposure to hypoxic injury. Cultured primary cortical
neurons were exposed to hypoxia (0.2% oxygen) for 7 hours with or without
T3 (5 nM). T3 treatment enhanced DNA 5-hydroxymethylcytosine (5-hmc)
levels and attenuated the hypoxia-induced increase in DNA 5-methylcytosine
(5-mc). In the presence of T3, mRNA expression of Tet family genes was
increased and DNA methyltransferases, (Dnmt) 3a and Dnmt3b, were
downregulated, compared to conditions in the absence of T3. These
T3-induced changes decreased hypoxia-induced DNA de novo methylation,
which reduced hypoxia-induced neuronal damage and apoptosis. We utilized
RNA-seq to characterize T3-regulated genes in cortical neurons under
hypoxic conditions and identified 22 genes that were upregulated and 15
genes that were downregulated. Krupple-like factor 9 (KLF9), a
multifunctional transcription factor that plays a key role in CNS
development, was highly upregulated by T3 treatment in hypoxic conditions.
Knockdown of the KLF9 gene resulted in early apoptosis and abolished the
beneficial role of T3 in neuronal survival. KLF9 mediates, in part, the
neuronal protective role of T3. T3 treatment reduces hypoxic damage,
although pathways that reduce DNA methylation and apoptosis, remains to be
elucidated.