The orphan nuclear receptor NR4A1 attenuates oxidative stress-induced β cells apoptosis via up-regulation of glutathione peroxidase 1

Aims: Our previous study showed that NR4A1 protects against oxidative stress-induced cell Apoptosis. However, the targets downstream of NR4A1 are incompletely known. Glutathione Peroxidase 1 (GPX1) is the most common antioxidant enzyme in the Glutathione Peroxidase class. In this study, we aimed to investigate whether GPX1 is a mediator of the protective effects of NR4A1 in pancreatic β cells.

Main methods: A pancreatic β cell line, MIN6, was used to generate NR4A1 over-expression cell line. GPX1 expression and GPX1 promoter trans-activation in these cells was determined. These cells were then treated with H₂O₂, and the active caspase3 level was determined.

Key findings: NR4A1 over-expression in MIN6 cells resulted in increased GPX1 expression at both mRNA and protein levels. Dual luciferase assay showed that NR4A1 over-expression was able to enhance the trans-activation of GPX1 promoter, and the critical regulatory elements were narrowed down between 0 to -2000 bp in GPX1 promoter with a putative NR4A1 binding site (-273 to -268). ChIP assays demonstrated that NR4A1 physically associates with the GPX1 promoter. Over-expression of GPX1 reduced the active level of Caspase3 after H₂O₂ treatment.

Significance: NR4A1 increases the expression of GPX1 by enhancing the trans-activation of GPX1 promoter through binding to the putative binding site on GPX1 promoter. NR4A1 potentially protects pancreatic β cells against oxidative stress-induced Apoptosis by increasing GPX1 expression.