Abstract
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 (AppCCl(2)p).
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 AppCCl(2)p levels in cell extracts were analysed by mass spectrometry.
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 AppCCl(2)p.
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.
Original language | English |
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Pages (from-to) | 427-435 |
Number of pages | 9 |
Journal | British Journal of Pharmacology |
Volume | 157 |
Issue number | 3 |
Early online date | 3 Apr 2009 |
DOIs | |
Publication status | Published - Jun 2009 |
Keywords
- AppCCl(2)p
- ApppI
- bisphosphonate
- cellular uptake
- clodronate
- IPP
- osteoclast
- zoledronic acid
- nitrogen-containing bisphosphonates
- HMG-COA reductase
- bone-resorption
- breast-cancer
- inhibition
- prenylation
- mechanism
- drugs
- localization