Figure 4: Impaired APEX1 contributes to DNMT1 upregulation and DNA hypermethylation induced by high glucose treatment in dental epithelial stem cells (DESCs).

(A) Western blot analysis of DNMT1 and DNMT3a levels in the cervical loops of offspring from control and diabetic dams; *P < 0.05 vs. control. (B) Global DNA methylation levels in the cervical loop of offspring from control and diabetic dams; *P < 0.05 vs. control. (C) DESCs treated with high glucose showed significant upregulation of DNMT1 and overexpression of APEX1WT, whereas redox-deficient APEX1C65A attenuated the DNMT1 upregulation induced by high-glucose treatment; *P < 0.05 vs. control; #P < 0.05 vs. high glucose. (D) High glucose treatment induced a significant increase in global DNA methylation levels and overexpression of APEX1WT, whereas redox-deficient APEX1C65A attenuated global DNA hypermethylation induced by high glucose treatment; *P < 0.05 vs. control; #P < 0.05 vs. high glucose. (E) Western blotting showed that Apex1 knockdown or inhibition of redox activity by the inhibitor E3330 enhanced DNMT1 expression, but did not affect DNMT3a expression; *P < 0.05 vs. control. (F) Apex1 knockdown or inhibition of redox activity by the inhibitor E3330 significantly increased global DNA methylation levels; *P < 0.05 vs. control.