Activation of Nrf2-Antioxidant Signaling by 1,25-Dihydroxycholecalciferol Prevents Leptin-Induced Oxidative Stress and Inflammation in Human Endothelial Cells

Background: Obesity is associated with hyperleptinemia and endothelial dysfunction. Hyperleptinemia has been reported to induce both oxidative stress and inflammation by increasing reactive oxygen species production. Objective: The objective of this study was to determine the effects of 1,25-dihydroxycholecalciferol [1,25(OH) 2 D 3 ] against leptin-induced oxidative stress and inflammation in human endothelial cells. Methods: Small interfering RNA (siRNA) were used to knock down the expression of vitamin D receptor (VDR) in human umbilical vein endothelial cells (HUVECs). HUVECs were pretreated for 4 h with physiologic (10 -10 M) or supraphysiologic (10 -7 M) concentrations of 1,25(OH) 2 D 3 and exposed to leptin (10 ng/mL). Superoxide anion production and translocation of nuclear factor (erythroid-derived 2)-like 2 (NRF2) and nuclear transcription factor κB (NF-κB) subunit p65 to the nucleus and the activation of their target genes were quantified. Results: Pretreatment of HUVECs with 1,25(OH) 2 D 3 prevented the leptin-induced increase in superoxide anion production ( P < 0.05). Pretreatment with 1,25(OH) 2 D 3 further increased NRF2 translocation to the nucleus (by 3-fold; P < 0.05) and increased mRNA expression of superoxide dismutase 2 ( SOD2 ; by 2-fold), glutathione peroxidase ( GPX ; by 3-fold), NAD(P)H dehydrogenase (quinone) 1 ( NQO1 ; by 4-fold), and heme oxygenase 1 ( HMOX1 ; by 2-fold) ( P < 0.05). Leptin doubled the translocation of NF-κB ( P < 0.05) to the nucleus and increased ( P < 0.05) the upregulation of vascular inflammatory mediators such as monocyte chemoattractant protein 1 ( MCP1 ; by 1-fold), transforming growth factor β ( TGF β by 1-fold), and vascular cell adhesion molecule 1 ( VCAM1 ; by 4-fold) ( P < 0.05), which were prevented ( P < 0.05) by pretreatment with 1,25(OH) 2 D 3 Protective effects of 1,25(OH) 2 D 3 were confirmed to be VDR dependent by using VDR siRNA. Conclusion: Pretreatment with 1,25(OH) 2 D 3 in the presence of a high concentration of leptin has a beneficial effect on HUVECs through the regulation of mediators of antioxidant activity and inflammation.