| Popis: |
Epigenetic regulation plays an important role in both physiological and pathological conditions. Among them, the ten-eleven translocation (TET) methyl cytosine dioxygenase is key to oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), subsequent 5-formylcytosine (5fC), 5-carboxylcytosine (5caC), and eventually to unmodified cytosine. However, few studies have investigated the role of Tet2 in regulating expression of tight junction proteins of the blood brain barrier. In the present study, we found that the level of 5hmC decreased in endothelial cells of aging brains. It was even weaker in endothelial cells of 8-week and 12-month old Tet2 knockout (KO) mice. Similar phenomenon was observed in zonula occludens-1 (ZO-1) expression by endothelial cells. Simultaneously, it was found there was an increased number of microglia in the Tet2 KO mouse. In vascular endothelial cell experiments, we found that H2O2 significantly decreased expression of 5hmC and ZO-1. Tet2 knock-down using siRNA significantly decreased the level of ZO-1 in endothelial cells. MeChip-PCR showed that the level of 5hmC in the ZO-1 promoter region was significantly decreased by H2O2, which was significantly rescued by N-acetyl cysteine (NAC). These findings were also observed in human brains where decreased levels of 5hmC in brain endothelial cells were accompanied by reduced levels of ZO-1. These findings indicate that DNA methylation and demethylation is essential in regulating the integrity of blood brain barrier. This might be a potential target for neuroprotection during aging and in diverse neurological conditions. |
