title: NFAT2 mediates high glucose-induced glomerular podocyte apoptosis through increased Bax expression.
abstract: BACKGROUND
  Hyperglycemia promotes podocyte apoptosis and plays a key role in the pathogenesis of diabetic nephropathy. However, the mechanisms that mediate hyperglycemia-induced podocyte apoptosis is still far from being fully understood. Recent studies reported that high glucose activate nuclear factor of activated T cells (NFAT) in vascular smooth muscle or pancreatic β-cells. Here, we sought to determine if hyperglycemia activates NFAT2 in cultured podocyte and whether this leads to podocyte apoptosis. Meanwhile, we also further explore the mechanisms of NFAT2 activation and NFAT2 mediates high glucose-induced podocyte apoptosis.
  
  
  METHODS
  Immortalized mouse podocytes were cultured in media containing normal glucose (NG), or high glucose (HG) or HG plus cyclosporine A (a pharmacological inhibitor of calcinerin) or 11R-VIVIT (a special inhibitor of NFAT2). The activation of NFAT2 in podocytes was detected by western blotting and immunofluorescence assay. The role of NFAT2 in hyperglycemia-induced podocyte apoptosis was further evaluated by observing the inhibition of NFAT2 activation by 11R-VIVIT using flow cytometer. Intracellular Ca(2+) was monitored in HG-treated podcocytes using Fluo-3/AM. The mRNA and protein expression of apoptosis gene Bax were measured by real time-qPCR and western blotting.
  
  
  RESULTS
  HG stimulation activated NFAT2 in a time- and dose-dependent manner in cultured podocytes. Pretreatment with cyclosporine A (500nM) or 11R-VIVIT (100nM) completely blocked NFAT2 nuclear accumulation. Meanwhile, the apoptosis effects induced by HG were also abrogated by concomitant treatment with 11R-VIVIT in cultured podocytes. We further found that HG also increased [Ca(2+)]i, leading to activation of calcineurin, and subsequent increased nuclear accumulation of NFAT2 and Bax expression in cultured podocytes.
  
  
  CONCLUSIONS
  Our results identify a new finding that HG-induced podocyte apoptosis is mediated by calcineurin/NFAT2/Bax signaling pathway, which may present a promising target for therapeutic intervention.
authors: Department of Nephrology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, 106 Zhongshan No. 2 Road, Guangzhou 510080, People's Republic of China. liruizhao1979@126.com
authors: Ruizhao
authors: R
authors: Li
authors: Li
authors: L
authors: Zhang
authors: Wei
authors: W
authors: Shi
authors: Bin
authors: B
authors: Zhang
authors: Xinling
authors: X
authors: Liang
authors: Shuangxin
authors: S
authors: Liu
authors: Wenjian
authors: W
authors: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D019703:Calcineurin / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003928:Diabetic Nephropathies / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D050778:NFATC Transcription Factors / Q000378:metabolism*; D050199:Podocytes / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: C494827:Bax protein, mouse; D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D051028:bcl-2-Associated X Protein; D019703:Calcineurin; D005947:Glucose; D002118:Calcium