High Glucose Induced Podocyte Apoptosis Through Sp1-Bax Pathway

Hyperglycaemia promotes podocyte apoptosis and plays a key role in the pathogenesis of diabetic nephropathy. However, the mechanism that mediates hyperglycaemia-induced podocyte apoptosis is still remains unknown. Recent studies showed that transcription factor Sp1 has been implicated in glucose-mediated expression of genes involved in diabetic nephropathy. Here, we sought to determine if hyperglycemia activates Sp1 in cultured podocyte and whether this leads to podocyte apoptosis. Meanwhile, we also further explore the mechanisms of Sp1 mediates high glucose induced podocyte apoptosis. Immortalized mouse podocytes were cultured in media containing normal glucose (NG), or high glucose (HG) or Sp1 siRNA. The expression of Sp1 in podocytes was detected by real-time RCR, western blotting and immunofluorescence assay. The role of Sp1 in hyperglycaemia-induced podocyte apoptosis was further evaluated by observing the inhibition of Sp1 expression by Sp1 siRNA using flow cytometer. The mRNA and protein expression of apoptosis gene Bax were measured by real-time RCR and western blotting. Our results demonstrated that HG stimulation increased Sp1 expression in a time-and dose-dependent manner in cultured podocytes. Pretreatment with Sp1 siRNA (50 nM) markedly decreased nuclear Sp1 expression. Meanwhile, the apoptosis effects induced by HG were also abrogated by Sp1 knock down in cultured podocytes. In addition, we further found that HG also increased Bax expression in cultured podocytes, and this effect was blocked by Sp1 siRNA. In Conclusion, our results identify a new founding that HG induced podocyte apoptosis is mediated by Sp1/Bax signaling pathway, which may present a promising target for therapeutic intervention.