Phosphorus and uremic serum up-regulate osteopontin expression in vascular smooth muscle cells

Neal X. Chen, Kalisha D. O'Neill, Danxia Duan, Sharon M. Moe

Research output: Contribution to journalArticle

275 Citations (Scopus)

Abstract

Background. Dialysis patients have accelerated atherosclerosis, with extensive calcification of both the intima and media. Cross-sectional studies have implicated hyperphosphatemia in this process, but the mechanism is unclear. Methods. To test the hypothesis that hyperphosphatemia and/or uremia induces vascular calcification, bovine vascular smooth muscle cells (BVSMC) were treated with increasing concentrations of β-glycerophosphate, a phosphate donor, in the presence or absence of inhibitors for sodium/phosphate (Na/Pi) co-transport (foscarnet) or alkaline phosphatase (levamisole) for 48 hours. BVSMC also were incubated for various times with DMEM plus 15% pooled uremic sera from patients with low (LP) or high serum phosphorus (HP), or from pooled healthy control serum. Calcification in BVSMC was examined by quantitation of calcium deposition. Osteopontin expression and alkaline phosphatase activity were assessed by Western blotting and a colorimetric assay. Results. β-glycerophosphate increased osteopontin expression and alkaline phosphatase activity in BVSMC. Inhibition of either alkaline phosphatase activity or Na/Pi co-transport abolished this effect. Compared to incubation with control human serum, BVSMC cultured with uremic sera had increased mineral deposition. Uremic sera also increased alkaline phosphatase activity and osteopontin expression in BVSMC. The addition of β-glycerophosphate to uremic HP or LP sera did not further augment osteopontin expression. Blocking Na/Pi co-transport or alkaline phosphatase activity only partially inhibited uremic sera-induced osteopontin expression, indicating that other non-Na/Pi co-transport dependent mechanisms also are involved. Conclusion. β-glycerophosphate and uremic sera induce calcification and osteopontin expression in BVSMC. The uremic sera-induced osteopontin expression in BVSMC is partially mediated through alkaline phosphatase activity and a Na/Pi co-transporter dependent mechanism. However, other non-Na/Pi dependent mechanisms also contribute to accelerated vascular calcification in patients with ESRD.

Original languageEnglish (US)
Pages (from-to)1724-1731
Number of pages8
JournalKidney international
Volume62
Issue number5
DOIs
StatePublished - Jan 1 2002

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Osteopontin
Vascular Smooth Muscle
Phosphorus
Smooth Muscle Myocytes
Up-Regulation
Alkaline Phosphatase
Serum
Glycerophosphates
Hyperphosphatemia
Vascular Calcification
Foscarnet
Symporters
Levamisole
Uremia
Chronic Kidney Failure
Minerals
Dialysis
Atherosclerosis
Cross-Sectional Studies
Western Blotting

Keywords

  • Atherosclerotic placques
  • Calcification
  • End-stage renal disease
  • Hyperphosphatemia
  • Intima and media
  • Uremia

ASJC Scopus subject areas

  • Nephrology

Cite this

Phosphorus and uremic serum up-regulate osteopontin expression in vascular smooth muscle cells. / Chen, Neal X.; O'Neill, Kalisha D.; Duan, Danxia; Moe, Sharon M.

In: Kidney international, Vol. 62, No. 5, 01.01.2002, p. 1724-1731.

Research output: Contribution to journalArticle

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abstract = "Background. Dialysis patients have accelerated atherosclerosis, with extensive calcification of both the intima and media. Cross-sectional studies have implicated hyperphosphatemia in this process, but the mechanism is unclear. Methods. To test the hypothesis that hyperphosphatemia and/or uremia induces vascular calcification, bovine vascular smooth muscle cells (BVSMC) were treated with increasing concentrations of β-glycerophosphate, a phosphate donor, in the presence or absence of inhibitors for sodium/phosphate (Na/Pi) co-transport (foscarnet) or alkaline phosphatase (levamisole) for 48 hours. BVSMC also were incubated for various times with DMEM plus 15{\%} pooled uremic sera from patients with low (LP) or high serum phosphorus (HP), or from pooled healthy control serum. Calcification in BVSMC was examined by quantitation of calcium deposition. Osteopontin expression and alkaline phosphatase activity were assessed by Western blotting and a colorimetric assay. Results. β-glycerophosphate increased osteopontin expression and alkaline phosphatase activity in BVSMC. Inhibition of either alkaline phosphatase activity or Na/Pi co-transport abolished this effect. Compared to incubation with control human serum, BVSMC cultured with uremic sera had increased mineral deposition. Uremic sera also increased alkaline phosphatase activity and osteopontin expression in BVSMC. The addition of β-glycerophosphate to uremic HP or LP sera did not further augment osteopontin expression. Blocking Na/Pi co-transport or alkaline phosphatase activity only partially inhibited uremic sera-induced osteopontin expression, indicating that other non-Na/Pi co-transport dependent mechanisms also are involved. Conclusion. β-glycerophosphate and uremic sera induce calcification and osteopontin expression in BVSMC. The uremic sera-induced osteopontin expression in BVSMC is partially mediated through alkaline phosphatase activity and a Na/Pi co-transporter dependent mechanism. However, other non-Na/Pi dependent mechanisms also contribute to accelerated vascular calcification in patients with ESRD.",
keywords = "Atherosclerotic placques, Calcification, End-stage renal disease, Hyperphosphatemia, Intima and media, Uremia",
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T1 - Phosphorus and uremic serum up-regulate osteopontin expression in vascular smooth muscle cells

AU - Chen, Neal X.

AU - O'Neill, Kalisha D.

AU - Duan, Danxia

AU - Moe, Sharon M.

PY - 2002/1/1

Y1 - 2002/1/1

N2 - Background. Dialysis patients have accelerated atherosclerosis, with extensive calcification of both the intima and media. Cross-sectional studies have implicated hyperphosphatemia in this process, but the mechanism is unclear. Methods. To test the hypothesis that hyperphosphatemia and/or uremia induces vascular calcification, bovine vascular smooth muscle cells (BVSMC) were treated with increasing concentrations of β-glycerophosphate, a phosphate donor, in the presence or absence of inhibitors for sodium/phosphate (Na/Pi) co-transport (foscarnet) or alkaline phosphatase (levamisole) for 48 hours. BVSMC also were incubated for various times with DMEM plus 15% pooled uremic sera from patients with low (LP) or high serum phosphorus (HP), or from pooled healthy control serum. Calcification in BVSMC was examined by quantitation of calcium deposition. Osteopontin expression and alkaline phosphatase activity were assessed by Western blotting and a colorimetric assay. Results. β-glycerophosphate increased osteopontin expression and alkaline phosphatase activity in BVSMC. Inhibition of either alkaline phosphatase activity or Na/Pi co-transport abolished this effect. Compared to incubation with control human serum, BVSMC cultured with uremic sera had increased mineral deposition. Uremic sera also increased alkaline phosphatase activity and osteopontin expression in BVSMC. The addition of β-glycerophosphate to uremic HP or LP sera did not further augment osteopontin expression. Blocking Na/Pi co-transport or alkaline phosphatase activity only partially inhibited uremic sera-induced osteopontin expression, indicating that other non-Na/Pi co-transport dependent mechanisms also are involved. Conclusion. β-glycerophosphate and uremic sera induce calcification and osteopontin expression in BVSMC. The uremic sera-induced osteopontin expression in BVSMC is partially mediated through alkaline phosphatase activity and a Na/Pi co-transporter dependent mechanism. However, other non-Na/Pi dependent mechanisms also contribute to accelerated vascular calcification in patients with ESRD.

AB - Background. Dialysis patients have accelerated atherosclerosis, with extensive calcification of both the intima and media. Cross-sectional studies have implicated hyperphosphatemia in this process, but the mechanism is unclear. Methods. To test the hypothesis that hyperphosphatemia and/or uremia induces vascular calcification, bovine vascular smooth muscle cells (BVSMC) were treated with increasing concentrations of β-glycerophosphate, a phosphate donor, in the presence or absence of inhibitors for sodium/phosphate (Na/Pi) co-transport (foscarnet) or alkaline phosphatase (levamisole) for 48 hours. BVSMC also were incubated for various times with DMEM plus 15% pooled uremic sera from patients with low (LP) or high serum phosphorus (HP), or from pooled healthy control serum. Calcification in BVSMC was examined by quantitation of calcium deposition. Osteopontin expression and alkaline phosphatase activity were assessed by Western blotting and a colorimetric assay. Results. β-glycerophosphate increased osteopontin expression and alkaline phosphatase activity in BVSMC. Inhibition of either alkaline phosphatase activity or Na/Pi co-transport abolished this effect. Compared to incubation with control human serum, BVSMC cultured with uremic sera had increased mineral deposition. Uremic sera also increased alkaline phosphatase activity and osteopontin expression in BVSMC. The addition of β-glycerophosphate to uremic HP or LP sera did not further augment osteopontin expression. Blocking Na/Pi co-transport or alkaline phosphatase activity only partially inhibited uremic sera-induced osteopontin expression, indicating that other non-Na/Pi co-transport dependent mechanisms also are involved. Conclusion. β-glycerophosphate and uremic sera induce calcification and osteopontin expression in BVSMC. The uremic sera-induced osteopontin expression in BVSMC is partially mediated through alkaline phosphatase activity and a Na/Pi co-transporter dependent mechanism. However, other non-Na/Pi dependent mechanisms also contribute to accelerated vascular calcification in patients with ESRD.

KW - Atherosclerotic placques

KW - Calcification

KW - End-stage renal disease

KW - Hyperphosphatemia

KW - Intima and media

KW - Uremia

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