Gestational arsenic exposure induces anxiety-like behaviors in adult offspring by reducing DNA hydroxymethylation in the developing brain

Abstract

Several studies found that reduction of 5-hydroxymethylcytosine (5hmC), a marker of DNA hydroxymethylation highly enriched in developing brain, is associated with anxiety-like behaviors. This study aimed to investigate whether gestational arsenic (As) exposure induces anxiety-like behaviors in adult offspring by reducing DNA hydroxymethylation in the developing brain. The dams drank ultrapure water containing NaAsO2 (15 mg/L) throughout pregnancy. Anxiety-like behaviors were evaluated and developing brain 5hmC was detected. Results showed that anxiety-like behaviors were observed in As-exposed adult offspring. In addition, 5hmC content was reduced in As-exposed fetal brain. Despite no difference on Tet1, Tet2 and Tet3 expression, TET activity was suppressed in As-exposed fetal brain. Mechanistically, alpha-ketoglutarate (α-KG), a cofactor for TET dioxygenases, was reduced and Idh2, a key enzymatic gene for mitochondrial α-KG synthesis, was downregulated in As-exposed fetal brain. Of interest, ascorbic acid, a cofactor for TET dioxygenases, reversed As-induced suppression of TET activity. Moreover, ascorbic acid attenuated As-induced reduction of 5hmC in fetal brain. In addition, ascorbic acid alleviated As-induced anxiety-like behaviors in adult offspring. Taken together, these results suggest that gestational As exposure induces anxiety-like behaviors in adult offspring, possibly at part, by inhibiting DNA hydroxymethylation in developing brain.

Keywords

• Arsenic
• Brain development
• Anxiety-like behavior
• Ten-eleven translocation (TET) activity
• DNA hydroxymethylation