title: Oxidative stress and cell senescence combine to cause maximal renal tubular epithelial cell dysfunction and loss in an in vitro model of kidney disease.
abstract: BACKGROUND
  The incidence and cost of chronic kidney disease (CKD) are increasing. Renal tubular epithelial cell dysfunction and attrition, involving increased apoptosis and cell senescence, are central to the pathogenesis of CKD. The aim here was to use an in vitro model to investigate the separate and cumulative effects of oxidative stress, mitochondrial dysfunction and cell senescence in promoting loss of renal mass.
  
  
  METHODS
  Human kidney tubular epithelial cells (HK2) were treated with moderate hydrogen peroxide (H2O2) for oxidative stress, with or without cell cycle inhibition (apigenin, API) for cell senescence. Adenosine triphosphate (ATP) and oxidative stress were measured by ATP assay, lipid peroxidation, total antioxidant capacity, mitochondrial function with confocal microscopy, MitoTracker Red CMXRos and live cell imaging with JC-1. In parallel, cell death and injury (i.e. apoptosis and Bax/Bcl-XL expression, lactate dehydrogenase), cell senescence (SA-β-galactosidase) and renal regenerative ability (cell proliferation), and their modulation with the anti-oxidant N-acetyl-cysteine (NAC) were investigated.
  
  
  RESULTS
  H2O2 and API, separately, increased oxidative stress and mitochondrial dysfunction, apoptosis and cell senescence. Although API caused cell senescence, it also induced oxidative stress at levels similar to H2O2 treatment alone, indicating that senescence and oxidative stress may be intrinsically linked. When H2O2 and API were delivered concurrently, their detrimental effects on renal cell loss were compounded. The antioxidant NAC attenuated apoptosis and senescence, and restored regenerative potential to the kidney.
  
  
  CONCLUSIONS
  Oxidative stress and cell senescence both cause mitochondrial destabilization and cell loss and contribute to the development of the cellular characteristics of CKD.
authors.affiliation: Centre for Kidney Disease Research, School of Medicine, The University of Queensland, Princess Alexandra Hospital, Brisbane, Qld., Australia.
authors.forename: David M
authors.initials: DM
authors.lastname: Small
authors.forename: Nigel C
authors.initials: NC
authors.lastname: Bennett
authors.forename: Sandrine
authors.initials: S
authors.lastname: Roy
authors.forename: Brian G
authors.initials: BG
authors.lastname: Gabrielli
authors.forename: David W
authors.initials: DW
authors.lastname: Johnson
authors.forename: Glenda C
authors.initials: GC
authors.lastname: Gobe
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D047310:Apigenin / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D016922:Cellular Senescence / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007668:Kidney / Q000503:physiopathology; D007684:Kidney Tubules / Q000166:cytology / Q000503:physiopathology*; D015227:Lipid Peroxidation / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D012038:Regeneration; D051436:Renal Insufficiency, Chronic / Q000503:physiopathology*
chemical_list: D047310:Apigenin; D006861:Hydrogen Peroxide; D000111:Acetylcysteine