Previous studies have shown that angiotensinogen (AGT) synthesis is enhanced by high glucose (HG) in rat renal proximal tubular cells. We aimed to investigate the glucose-responsive elements within human AGT (hAGT) promoter in human immortalized proximal tubular HK-2 cells.Design and Method:
HK-2 cells were treated with normal glucose (NG: 5.5 mmol/L) and high glucose (HG: 15 mmol/L). Human AGT promoter region was cloned from -4358 to +122. Consecutive 5’-end deletion mutant constructs and different site-direct mutagenesis products were transfected into HK-2, followed by promoter activity measurement by dual luciferase assay. Chromatin immunoprecipitation (CHIP) assay was used to confirm protein-DNA binding.Results:
Compared to NG, hAGT mRNA and protein levels were significantly increased by HG treatment for 48 hours. Region from -22 to -1,896, whose deletion attenuated the effects of HG on hAGT promoter activity, was selected as glucose-responsive region. Among corresponding transcriptional factors of glucose-responsive regions, hepatocyte nuclear factor (HNF)-5 is involved in glucose metabolism and AGT regulation. Compared to NG, HG effect on promoter activity was negligible in HK-2 transfected with HNF-5 point mutated hAGT promoter, while significantly displayed with intact hAGT promoter transfection. Reduced protein level after HNF-5 point mutation was confirmed by CHIP assay.Conclusions:
These data suggest that HG enhances human proximal tubular AGT through the activation of HNF-5.