title: Aryl hydrocarbon receptor mediates indoxyl sulfate-induced cellular senescence in human umbilical vein endothelial cells.
abstract: OBJECTIVE
  Vascular senescence, which is accelerated in individuals with chronic kidney disease (CKD), contributes to the development of cardio-renal syndrome, and various uremic toxins may play important roles in the mechanisms underlying this phenomenon. We recently reported that indoxyl sulfate (IS), a uremic toxin, directly activates aryl hydrocarbon receptor (AhR) and generates oxidative stress through NADPH oxidase-4 in human umbilical vein endothelial cells (HUVECs). In the current study, we sought to examine whether IS regulates sirtuin 1 (Sirt1) and affects endothelial senescence via AhR activation.
  
  
  METHODS
  HUVECs were incubated with 500 μmol/L of IS for the indicated time periods. In order to evaluate changes in the senescence of the HUVECs, the number of senescence-associated β-galactosidase (SA β-gal)-positive cells was determined using an image analysis software program. The intracellular nicotinamide phosphoribosyltransferase (iNampt) activity, cellular NAD(＋)/NADPH ratio and Sirt1 activity were analyzed according to a colorimetric assay to determine the mechanism of cellular senescence. Furthermore, we evaluated the involvement of AhR in the senescence-related changes induced by IS using AhR antagonists.
  
  
  RESULTS
  IS decreased the iNampt activity, NAD(＋)/NADPH ratio and Sirt1 activity, resulting in an increase in the percentage of SA β-gal-positive cells. On the other hand, the AhR antagonists restored the IS-induced decrease in the NAD(＋) content in association with an improvement in the iNampt activity and ameliorated the senescence-related changes. Taken together, these results indicate that IS impairs the iNampt-NAD(＋)-Sirt1 system via AhR activation, which in turn promotes endothelial senescence.
  
  
  CONCLUSIONS
  The IS-AhR pathway induces endothelial senescence. Therefore, blocking the effects of AhR in the endothelium may provide a new therapeutic tool for treating cardio-renal syndrome.
authors.affiliation: Department of Cardiovascular Medicine, Toho University Faculty of Medicine.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Koizumi
authors.forename: Junko
authors.initials: J
authors.lastname: Tatebe
authors.forename: Ippei
authors.initials: I
authors.lastname: Watanabe
authors.forename: Junichi
authors.initials: J
authors.lastname: Yamazaki
authors.forename: Takanori
authors.initials: T
authors.lastname: Ikeda
authors.forename: Toshisuke
authors.initials: T
authors.lastname: Morita
mesh_terms: D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects*; D016207:Cytokines / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007200:Indican / Q000494:pharmacology*; D009243:NAD / Q000378:metabolism; D054409:Nicotinamide Phosphoribosyltransferase / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism*; D056564:Sirtuin 1 / Q000378:metabolism*
chemical_list: D016207:Cytokines; D018336:Receptors, Aryl Hydrocarbon; D009243:NAD; D054409:Nicotinamide Phosphoribosyltransferase; C085455:nicotinamide phosphoribosyltransferase, human; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D007200:Indican