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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(s) -
Räikkönen Johanna,
Crockett Julie C,
Rogers Michael J,
Mönkkönen Hannu,
Auriola Seppo,
Mönkkönen Jukka
Publication year - 2009
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2009.00160.x
Subject(s) - isopentenyl pyrophosphate , zoledronic acid , in vivo , farnesyl pyrophosphate , chemistry , bone resorption , in vitro , biochemistry , pyrophosphate , diphosphonates , pharmacology , atp synthase , medicine , biology , enzyme , microbiology and biotechnology
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′(β,γ‐dichloromethylene) triphosphate (AppCCl 2 p). 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 AppCCl 2 p 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 AppCCl 2 p. 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.