Aryl hydrocarbon receptor mediates indoxyl sulfate-induced cellular senescence in human umbilical vein endothelial cells

J Atheroscler Thromb. 2014;21(9):904-16. doi: 10.5551/jat.23663. Epub 2014 Apr 12.

Abstract

Aim: 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.

MeSH terms

  • Cells, Cultured
  • Cellular Senescence / drug effects*
  • Cytokines / metabolism
  • Human Umbilical Vein Endothelial Cells / cytology*
  • Human Umbilical Vein Endothelial Cells / drug effects*
  • Human Umbilical Vein Endothelial Cells / metabolism
  • Humans
  • Immunoblotting
  • Indican / pharmacology*
  • NAD / metabolism
  • Nicotinamide Phosphoribosyltransferase / metabolism
  • Oxidative Stress / drug effects
  • Receptors, Aryl Hydrocarbon / metabolism*
  • Sirtuin 1 / metabolism*

Substances

  • Cytokines
  • Receptors, Aryl Hydrocarbon
  • NAD
  • Nicotinamide Phosphoribosyltransferase
  • nicotinamide phosphoribosyltransferase, human
  • SIRT1 protein, human
  • Sirtuin 1
  • Indican