Abstract

Aims: Reduced expression of human equilibrative nucleoside transporter 1 (hENT1) results from nitric oxide (NO)-dependent reduced SLC29A1 transcriptional activity in human umbilical vein endothelial cells (HUVECs) from gestational diabetes. As expression of the transcription factor C/EBP homologous protein 10 (hCHOP, which forms heterodimers with C/EBPα transcription factor) is activated by NO and induced in diabetes mellitus, we hypothesize that hCHOP plays a role in the gestational diabetes-reduced hENT1 expression in HUVECs. Methods and results: HUVEC primary cultures from 42 normal and 42 gestational diabetic pregnancies were used for adenosine uptake assays. Real-time PCR (mRNA quantification), western blotting (protein abundance), and luciferase activity (SLC29A1 promoter activity) were used. hCHOP-C/EBPα activity was assayed by chromatin immunoprecipitation. Overlap extension mutagenesis was used to generate a mutated hCHOP-C/EBPα consensus site at the SLC29A1 promoter, and endothelial NO synthase (eNOS) siRNA recombinant adenovirus was used to knock down eNOS. hCHOP nuclear protein abundance and binding to DNA were higher in gestational diabetes, paralleled by reduced SLC29A1 promoter activity, hENT1 expression, and transport activity. These changes were blocked by hCHOP consensus sequence mutation (-1845G > T and -1844C > A), eNOS-siRNA-induced knockdown, and NG-nitro-l-arginine methyl ester (NOS inhibitor), and were mimicked by S-nitroso-N-acetyl-l, d-penicillamine (NO donor) in cells from normal pregnancies. hCHOP and C/EBPα overexpression mimicked gestational diabetes effects in cells from normal pregnancies, but did not alter SLC29A1 promoter activity or hENT1-adenosine transport in cells from gestational diabetes. Conclusion: The hCHOP-C/EBPα complex down-regulates SLC29A1 expression in an NO-dependent manner in HUVECs from gestational diabetes. © The Author 2009.