Bilirubin Activates Transcription of HIF-1alpha in Human Proximal Tubular Cells Cultured in the Physiologic Oxygen Content.
10.3346/jkms.2014.29.S2.S146
- Author:
Sung Gyun KIM
1
;
Shin Young AHN
;
Eun Seong LEE
;
Sejoong KIM
;
Ki Young NA
;
Dong Wan CHAE
;
Ho Jun CHIN
Author Information
1. Department of Internal Medicine, Hallym University College of Medicine, Seoul, Korea.
- Publication Type:Original Article
- Keywords:
Proximal Tubular Cell;
Bilirubin;
HIF-1;
ROS
- MeSH:
Bilirubin/*pharmacology;
Cell Line;
Epithelial Cells/cytology/metabolism;
Humans;
Hydrogen Peroxide/toxicity;
Hypoxia-Inducible Factor 1, alpha Subunit/genetics/*metabolism;
Kidney Tubules, Proximal/cytology;
Mitogen-Activated Protein Kinase 1/metabolism;
Mitogen-Activated Protein Kinase 3/metabolism;
NADPH Oxidase/antagonists & inhibitors/genetics/metabolism;
Oxygen/*pharmacology;
Phosphatidylinositol 3-Kinases/metabolism;
Phosphorylation/drug effects;
Proto-Oncogene Proteins c-akt/metabolism;
RNA Interference;
Ribosomal Protein S6 Kinases, 70-kDa/metabolism;
Signal Transduction/drug effects;
TOR Serine-Threonine Kinases/metabolism;
Transcriptional Activation/*drug effects;
Up-Regulation/drug effects
- From:Journal of Korean Medical Science
2014;29(Suppl 2):S146-S154
- CountryRepublic of Korea
- Language:English
-
Abstract:
The expression of hypoxia-inducible factor (HIF) is influenced by reactive oxygen species (ROS). Effect of bilirubin on HIF-1 expression in proximal tubular cells was investigated under physiological oxygen concentration, which is relative hypoxic condition mimicking oxygen content in the medulla of renal tissue. The human kidney (HK2) cells were cultured in 5% oxygen with or without bilirubin. HIF-1alpha protein expression was increased by bilirubin treatment at 0.01-0.2 mg/dL concentration. The messenger RNA expression of HIF-1alpha was increased by 1.69+/-0.05 folds in the cells cultured with 0.1 mg/dL bilirubin, compared to the control cells. The inhibitors of PI3K/mTOR, PI3K/AKT, and ERK 1/2 pathways did not attenuate increased HIF-1alpha expression by bilirubin. HIF-1alpha expression decreased by 10 microM exogenous hydrogen peroxide (H2O2); scavenger of ROS with or without bilirubin in the HK2 cells increased HIF-1alpha concentration more than that in the cells without bilirubin. Exogenous H2O2 decreased the phosphorylation of P70S6 kinase, which was completely reversed by bilirubin treatment. Knockdown of NOX4 gene by small interfering RNA (siRNA) increased HIF-1alpha mRNA expression. In coonclusion, bilirubin enhances HIF-1alpha transcription as well as the up-regulation of HIF-1alpha protein translation through the attenuation of ROS and subunits of NADPH oxidase.
