Advanced glycation end products promote human aortic smooth muscle cell calcification in vitro via activating NF-κB and down-regulating IGF1R expression
Abstract
Yi WANG*, Zhen-yu ZHANG, Xiao-qing CHEN, Xiang WANG, Heng CAO, Shao-wen LIU
Department of Cardiology, Shanghai First People’s Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
Aim: To investigate the effects of advanced glycation end products (AGEs) on calcification in human aortic smooth muscle cells (HASMCs) in vitro and the underlying mechanisms.
Methods: AGEs were artificially prepared. Calcification of HASMCs was induced by adding inorganic phosphate (Pi, 2 mmol/L) in the media, and observed with Alizarin red staining. The calcium content in the supernatant was measured using QuantiChrome Calcium Assay Kit. Expression of the related mRNAs and proteins was analyzed using real-time PCR and Western blot, respectively. Chromatin immunoprecipitation (ChIP) assay was used to detect the binding of NF-κB to the putative IGF1R promoter.
Results: AGEs (100 µg/mL) significantly enhanced Pi-induced calcification and the levels of osteocalcin and Cbfα1 in HASMCs. Furthermore, the treatment decreased the expression of insulin-like growth factor 1 receptor (IGF1R). Over-expression of IGF1R in HASMCs suppressed the AGEs-induced increase in calcium deposition. When IGF1R expression was knocked down in HASMCs, AGEs did not enhance the calcium deposition. Meanwhile, AGEs time-dependently decreased the amounts of IκBα and Flag-tagged p65 in the cytoplasmic extracts, and increased the amount of nuclear p65 in HASMCs. In the presence of NF-κB inhibitor PDTC (50 μmol/L), the AGEs-induced increase in calcium deposition was blocked. Over-expression of p65 significantly enhanced Pi-induced mineralization, but suppressed IGF1R mRNA level. Knockdown of p65 suppressed the AGEs-induced increase in calcium deposition, and rescued the IGF1R expression. The ChIP analysis revealed that NF-κB bound the putative IGF1R promoter at position -230 to -219 bp. The inhibition of IGF1R by NF-κB was abolished when IGF1R reporter plasmid contained mutated binding sequence for NF-κB or an NF-κB reporter vector.
Conclusion: The results demonstrate that AGEs promote calcification of human aortic smooth muscle cells in vitro via activation of NF-κB and down-regulation of IGF1R expression.
Keywords: vascular calcification; advanced glycation end products; human aortic smooth muscle cell; osteocalcin; Cbfα1; insulin-like growth factor 1 receptor (IGF1R); nuclear factor-kappa B; PDTC
The present study was supported by the Natural Science Foundation of Shanghai, China (No 09ZR1425200).
* To whom correspondence should be addressed.
E-mail wangyikxy2008@126.com
Received 2012-08-04 Accepted 2012-11-14
Keywords:
Department of Cardiology, Shanghai First People’s Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200080, China
Aim: To investigate the effects of advanced glycation end products (AGEs) on calcification in human aortic smooth muscle cells (HASMCs) in vitro and the underlying mechanisms.
Methods: AGEs were artificially prepared. Calcification of HASMCs was induced by adding inorganic phosphate (Pi, 2 mmol/L) in the media, and observed with Alizarin red staining. The calcium content in the supernatant was measured using QuantiChrome Calcium Assay Kit. Expression of the related mRNAs and proteins was analyzed using real-time PCR and Western blot, respectively. Chromatin immunoprecipitation (ChIP) assay was used to detect the binding of NF-κB to the putative IGF1R promoter.
Results: AGEs (100 µg/mL) significantly enhanced Pi-induced calcification and the levels of osteocalcin and Cbfα1 in HASMCs. Furthermore, the treatment decreased the expression of insulin-like growth factor 1 receptor (IGF1R). Over-expression of IGF1R in HASMCs suppressed the AGEs-induced increase in calcium deposition. When IGF1R expression was knocked down in HASMCs, AGEs did not enhance the calcium deposition. Meanwhile, AGEs time-dependently decreased the amounts of IκBα and Flag-tagged p65 in the cytoplasmic extracts, and increased the amount of nuclear p65 in HASMCs. In the presence of NF-κB inhibitor PDTC (50 μmol/L), the AGEs-induced increase in calcium deposition was blocked. Over-expression of p65 significantly enhanced Pi-induced mineralization, but suppressed IGF1R mRNA level. Knockdown of p65 suppressed the AGEs-induced increase in calcium deposition, and rescued the IGF1R expression. The ChIP analysis revealed that NF-κB bound the putative IGF1R promoter at position -230 to -219 bp. The inhibition of IGF1R by NF-κB was abolished when IGF1R reporter plasmid contained mutated binding sequence for NF-κB or an NF-κB reporter vector.
Conclusion: The results demonstrate that AGEs promote calcification of human aortic smooth muscle cells in vitro via activation of NF-κB and down-regulation of IGF1R expression.
Keywords: vascular calcification; advanced glycation end products; human aortic smooth muscle cell; osteocalcin; Cbfα1; insulin-like growth factor 1 receptor (IGF1R); nuclear factor-kappa B; PDTC
The present study was supported by the Natural Science Foundation of Shanghai, China (No 09ZR1425200).
* To whom correspondence should be addressed.
E-mail wangyikxy2008@126.com
Received 2012-08-04 Accepted 2012-11-14