Activation of the inducible nitric oxide synthase pathway contributes to inflammation-induced osteoporosis by suppressing bone formation and causing osteoblast apoptosis

K. J. Armour, K. E. Armour, Robert Jurgen Van T Hof, David M Reid, X. Wei, F. Y. Liew, S Ralston

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Abstract

Objective. Osteoporosis is a major clinical problem in chronic inflammatory diseases such as rheumatoid arthritis. The mechanism of bone loss in this condition remains unclear, but previous studies have indicated that depressed bone formation plays a causal role. Since cytokine-induced nitric oxide (NO) production has been shown to inhibit osteoblast growth and differentiation in vitro, this study was undertaken to investigate the role of the inducible NO synthase (iNOS) pathway in the pathogenesis of inflammation-mediated osteoporosis (IMO) by studying mice with targeted inactivation of the iNOS gene (iNOS knockout [iNOS KO] mice).

Methods. IMO was induced in wild-type (WT) and iNOS KO mice by subcutaneous injections of magnesium silicate. The skeletal response was assessed at the tibial metaphysis by measurements of bone mineral density, (BMD), using peripheral quantitative computed tomography, by bone histomorphometry, and by measurements of bone cell apoptosis.

Results. NO production increased 2.5-fold (P < 0.005) in WT mice with IMO, but did not change significantly in iNOS KO mice. Total BMD values decreased by, a mean +/- SEM of 14.4 +/- 2.0% in WT mice with IMO, compared with a decrease of 8.6 +/- 1.2% in iNOS KO mice with IMO (P < 0.01). Histomorphometric analysis confirmed that trabecular bone volume was lower in WT mice with IMO compared with iNOS KO mice with IMO (16.2 +/- 1.5% versus 23.4 +/- 2.6%; P < 0.05) and showed that IMO was associated with reduced bone formation and a 320% increase in osteoblast apoptosis (P < 0.005) in WT mice. In contrast, iNOS KO mice with IMO showed less inhibition of bone formation than WT mice and showed no significant increase in osteoblast apoptosis.

Conclusion. Inducible NOS-mediated osteoblast apoptosis and depressed bone formation play important roles in the pathogenesis of IMO.

Original languageEnglish
Pages (from-to)2790-2796
Number of pages6
JournalArthritis & Rheumatism
Volume44
Issue number12
DOIs
Publication statusPublished - 2001

Keywords

  • RHEUMATOID-ARTHRITIS
  • MECHANISMS

Cite this

Activation of the inducible nitric oxide synthase pathway contributes to inflammation-induced osteoporosis by suppressing bone formation and causing osteoblast apoptosis. / Armour, K. J.; Armour, K. E.; Van T Hof, Robert Jurgen; Reid, David M; Wei, X.; Liew, F. Y.; Ralston, S.

In: Arthritis & Rheumatism, Vol. 44, No. 12, 2001, p. 2790-2796.

Research output: Contribution to journalArticle

Armour, K. J. ; Armour, K. E. ; Van T Hof, Robert Jurgen ; Reid, David M ; Wei, X. ; Liew, F. Y. ; Ralston, S. / Activation of the inducible nitric oxide synthase pathway contributes to inflammation-induced osteoporosis by suppressing bone formation and causing osteoblast apoptosis. In: Arthritis & Rheumatism. 2001 ; Vol. 44, No. 12. pp. 2790-2796.
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title = "Activation of the inducible nitric oxide synthase pathway contributes to inflammation-induced osteoporosis by suppressing bone formation and causing osteoblast apoptosis",
abstract = "Objective. Osteoporosis is a major clinical problem in chronic inflammatory diseases such as rheumatoid arthritis. The mechanism of bone loss in this condition remains unclear, but previous studies have indicated that depressed bone formation plays a causal role. Since cytokine-induced nitric oxide (NO) production has been shown to inhibit osteoblast growth and differentiation in vitro, this study was undertaken to investigate the role of the inducible NO synthase (iNOS) pathway in the pathogenesis of inflammation-mediated osteoporosis (IMO) by studying mice with targeted inactivation of the iNOS gene (iNOS knockout [iNOS KO] mice).Methods. IMO was induced in wild-type (WT) and iNOS KO mice by subcutaneous injections of magnesium silicate. The skeletal response was assessed at the tibial metaphysis by measurements of bone mineral density, (BMD), using peripheral quantitative computed tomography, by bone histomorphometry, and by measurements of bone cell apoptosis.Results. NO production increased 2.5-fold (P < 0.005) in WT mice with IMO, but did not change significantly in iNOS KO mice. Total BMD values decreased by, a mean +/- SEM of 14.4 +/- 2.0{\%} in WT mice with IMO, compared with a decrease of 8.6 +/- 1.2{\%} in iNOS KO mice with IMO (P < 0.01). Histomorphometric analysis confirmed that trabecular bone volume was lower in WT mice with IMO compared with iNOS KO mice with IMO (16.2 +/- 1.5{\%} versus 23.4 +/- 2.6{\%}; P < 0.05) and showed that IMO was associated with reduced bone formation and a 320{\%} increase in osteoblast apoptosis (P < 0.005) in WT mice. In contrast, iNOS KO mice with IMO showed less inhibition of bone formation than WT mice and showed no significant increase in osteoblast apoptosis.Conclusion. Inducible NOS-mediated osteoblast apoptosis and depressed bone formation play important roles in the pathogenesis of IMO.",
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T1 - Activation of the inducible nitric oxide synthase pathway contributes to inflammation-induced osteoporosis by suppressing bone formation and causing osteoblast apoptosis

AU - Armour, K. J.

AU - Armour, K. E.

AU - Van T Hof, Robert Jurgen

AU - Reid, David M

AU - Wei, X.

AU - Liew, F. Y.

AU - Ralston, S

PY - 2001

Y1 - 2001

N2 - Objective. Osteoporosis is a major clinical problem in chronic inflammatory diseases such as rheumatoid arthritis. The mechanism of bone loss in this condition remains unclear, but previous studies have indicated that depressed bone formation plays a causal role. Since cytokine-induced nitric oxide (NO) production has been shown to inhibit osteoblast growth and differentiation in vitro, this study was undertaken to investigate the role of the inducible NO synthase (iNOS) pathway in the pathogenesis of inflammation-mediated osteoporosis (IMO) by studying mice with targeted inactivation of the iNOS gene (iNOS knockout [iNOS KO] mice).Methods. IMO was induced in wild-type (WT) and iNOS KO mice by subcutaneous injections of magnesium silicate. The skeletal response was assessed at the tibial metaphysis by measurements of bone mineral density, (BMD), using peripheral quantitative computed tomography, by bone histomorphometry, and by measurements of bone cell apoptosis.Results. NO production increased 2.5-fold (P < 0.005) in WT mice with IMO, but did not change significantly in iNOS KO mice. Total BMD values decreased by, a mean +/- SEM of 14.4 +/- 2.0% in WT mice with IMO, compared with a decrease of 8.6 +/- 1.2% in iNOS KO mice with IMO (P < 0.01). Histomorphometric analysis confirmed that trabecular bone volume was lower in WT mice with IMO compared with iNOS KO mice with IMO (16.2 +/- 1.5% versus 23.4 +/- 2.6%; P < 0.05) and showed that IMO was associated with reduced bone formation and a 320% increase in osteoblast apoptosis (P < 0.005) in WT mice. In contrast, iNOS KO mice with IMO showed less inhibition of bone formation than WT mice and showed no significant increase in osteoblast apoptosis.Conclusion. Inducible NOS-mediated osteoblast apoptosis and depressed bone formation play important roles in the pathogenesis of IMO.

AB - Objective. Osteoporosis is a major clinical problem in chronic inflammatory diseases such as rheumatoid arthritis. The mechanism of bone loss in this condition remains unclear, but previous studies have indicated that depressed bone formation plays a causal role. Since cytokine-induced nitric oxide (NO) production has been shown to inhibit osteoblast growth and differentiation in vitro, this study was undertaken to investigate the role of the inducible NO synthase (iNOS) pathway in the pathogenesis of inflammation-mediated osteoporosis (IMO) by studying mice with targeted inactivation of the iNOS gene (iNOS knockout [iNOS KO] mice).Methods. IMO was induced in wild-type (WT) and iNOS KO mice by subcutaneous injections of magnesium silicate. The skeletal response was assessed at the tibial metaphysis by measurements of bone mineral density, (BMD), using peripheral quantitative computed tomography, by bone histomorphometry, and by measurements of bone cell apoptosis.Results. NO production increased 2.5-fold (P < 0.005) in WT mice with IMO, but did not change significantly in iNOS KO mice. Total BMD values decreased by, a mean +/- SEM of 14.4 +/- 2.0% in WT mice with IMO, compared with a decrease of 8.6 +/- 1.2% in iNOS KO mice with IMO (P < 0.01). Histomorphometric analysis confirmed that trabecular bone volume was lower in WT mice with IMO compared with iNOS KO mice with IMO (16.2 +/- 1.5% versus 23.4 +/- 2.6%; P < 0.05) and showed that IMO was associated with reduced bone formation and a 320% increase in osteoblast apoptosis (P < 0.005) in WT mice. In contrast, iNOS KO mice with IMO showed less inhibition of bone formation than WT mice and showed no significant increase in osteoblast apoptosis.Conclusion. Inducible NOS-mediated osteoblast apoptosis and depressed bone formation play important roles in the pathogenesis of IMO.

KW - RHEUMATOID-ARTHRITIS

KW - MECHANISMS

U2 - 10.1002/1529-0131(200112)44:12<2790::AID-ART466>3.0.CO;2-X

DO - 10.1002/1529-0131(200112)44:12<2790::AID-ART466>3.0.CO;2-X

M3 - Article

VL - 44

SP - 2790

EP - 2796

JO - Arthritis & Rheumatism

JF - Arthritis & Rheumatism

SN - 0004-3591

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ER -