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Br J Pharmacol. 2009 Jun;157(3):427-35. doi: 10.1111/j.1476-5381.2009.00160.x. Epub 2009 Apr 3.

Zoledronic acid induces formation of a pro-apoptotic ATP analogue and isopentenyl pyrophosphate in osteoclasts in vivo and in MCF-7 cells in vitro.

Author information

1
Department of Pharmaceutics, University of Kuopio, Yliopistonranta 1 B, P.O. Box 1627, Kuopio FIN-70211, Finland. Johanna.Raikkonen@uku.fi

Abstract

BACKGROUND AND PURPOSE:

Bisphosphonates (BPs) are highly effective inhibitors of bone resorption. Nitrogen-containing bisphosphonates (N-BPs), such as zoledronic acid, induce the formation of a novel ATP analogue (1-adenosin-5'-yl ester 3-(3-methylbut-3-enyl) ester triphosphoric acid; ApppI), as a consequence of the inhibition of farnesyl pyrophosphate synthase and the accumulation of isopentenyl pyrophosphate (IPP). ApppI induces apoptosis, as do comparable metabolites of non-nitrogen-containing bisphosphonates (non-N-BPs). In order to further evaluate a pharmacological role for ApppI, we obtained more detailed data on IPP/ApppI formation in vivo and in vitro. Additionally, zoledronic acid-induced ApppI formation from IPP was compared with the metabolism of clodronate (a non-N-BP) to adenosine 5'(beta,gamma-dichloromethylene) triphosphate (AppCCl2p).

EXPERIMENTAL APPROACH:

After giving zoledronic acid in vivo to rabbits, IPP/ApppI formation and accumulation was assessed in isolated osteoclasts. The formation of ApppI from IPP was compared with the metabolism of clodronate in MCF-7 cells in vitro. IPP/ApppI and AppCCl2p levels in cell extracts were analysed by mass spectrometry.

KEY RESULTS:

Isopentenyl pyrophosphate/ApppI were formed in osteoclasts in vivo, after a single, clinically relevant dose of zoledronic acid. Furthermore, exposure of MCF-7 cells in vitro to zoledronic acid at varying times and concentrations induced time- and dose-dependent accumulation of IPP/ApppI. One hour pulse treatment was sufficient to cause IPP accumulation and subsequent ApppI formation, or the metabolism of clodronate into AppCCl2p.

CONCLUSIONS AND IMPLICATIONS:

This study provided the first conclusive evidence that pro-apoptotic ApppI is a biologically significant molecule, and demonstrated that IPP/ApppI analysis is a sensitive tool for investigating pathways involved in BP action.

PMID:
19371349
PMCID:
PMC2707989
DOI:
10.1111/j.1476-5381.2009.00160.x
[Indexed for MEDLINE]
Free PMC Article

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