Iron citrate reduces high phosphate-induced vascular calcification by inhibiting apoptosis

Paola Ciceri, Francesca Elli, Paola Braidotti, Monica Falleni, Delfina Tosi, Gaetano Bulfamante, Geoffrey A. Block, Mario Cozzolino

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Abstract

Background and aims High phosphate-induced vascular calcification (VC) and iron deficiency-induced anemia are two major contributors of cardiovascular morbidity and mortality in patients affected by chronic kidney disease (CKD). Since phosphate (Pi) control and iron replacement are common therapies in CKD, the aim of our study was to investigate the effect of iron on high Pi-induced VC in rat vascular smooth muscle cells (VSMCs). Methods We treated VSMCs with 5 mM Pi and iron citrate (Fe3+) to evaluate Ca deposition by Alizarin Red destaining, DNA fragmentation by ELISA, gene expression by RT-PCR and protein expression by Western blot. Results Pretreatment with Fe3+ prevents high Pi-induced calcium (Ca) deposition concentration-dependently, with 90.1% inhibition at 50 μM (0.716 ± 0.04 vs. 0.071 ± 0.01, OD/mg protein; Pi vs. Pi + Fe3+, p < 0.01). We found that 50 μM Fe3+ completely prevents high Pi-induced apoptosis measured as DNA fragmentation (1.51 ± 0.08 vs. 1.03 ± 0.06, Pi vs. Pi + Fe3+; p < 0.01), through the prevention of the downregulation of the pro-survival pathway GAS6/AXL. Moreover, Fe3+ stimulates autophagy, a protective phenomenon in VC, as demonstrated by electron microscopy and by autophagy flux detected by LC3IIβ protein expression. Finally, high Pi-induced osteoblastic differentiation is partially affected by Fe3+, since BMP2 increase is prevented and OPN is enhanced, but RUNX2 increase and α-actin and SM22α decrease are not modified. Interestingly, the addition of Fe3+ at different time points after Pi challenge completely blocks the progression of Ca deposition. Conclusions In conclusion, iron citrate inhibits high Pi-induced Ca deposition by prevention of apoptosis, induction of autophagy, and partially affecting osteoblastic differentiation.

Original languageEnglish
Pages (from-to)93-101
Number of pages9
JournalAtherosclerosis
Volume254
DOIs
Publication statusPublished - Nov 1 2016

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Keywords

  • Apoptosis
  • Iron
  • Phosphate
  • Vascular calcification
  • VSMC

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

Cite this

Ciceri, P., Elli, F., Braidotti, P., Falleni, M., Tosi, D., Bulfamante, G., Block, G. A., & Cozzolino, M. (2016). Iron citrate reduces high phosphate-induced vascular calcification by inhibiting apoptosis. Atherosclerosis, 254, 93-101. https://doi.org/10.1016/j.atherosclerosis.2016.09.071