Contrasting effects of alendronate and clodronate on RAW 264 macrophages: the role of a bisphosphonate metabolite

Clodronate (dichloromerhylidene-bisphosphonate), a halogen-containing bisph osphonate, can inhibit the release of cytokines from RAW 264 macrophages an d has anti-inflammatory properties in rheumatoid arthritis, whilst amino-co ntaining bisphosphonates such as alendronate (4-amino-1-hydroxybutylidene-b isphosphonate), have pro-inflammatory properties and can cause an acute pha se response. The basis for these pharmacological properties is unclear. Rec ently, it was demonstrated that clodronate is metabolised by certain cell l ines in vitro to an analogue of ATP, whereas amino-bisphosphonates are not. We therefore investigated whether clodronate can also be metabolised by RA W 264 macrophages and whether intracellular accumulation of the metabolite (AppCCl(2)p) could account for the anti-inflammatory properties of clodrona te. The effect of alendronate and AppCCl(2)p on the release of cytokines (I L-1 beta, IL-6, and TNF alpha) from RAW 264 cells was compared, and the eff ect of the bisphosphonates and AppCCl(2)p on the DNA binding activities of transcription factors, NF-kappa B and AP-1, was investigated. Pretreatment of RAW 264 macrophages with alendronate augmented the LPS-stimulated releas e of IL-1 beta and increased the binding of NF-kappa B to DNA in an electro phoretic mobility shift assay. Without LPS-induction, alendronate did not a ffect cytokine release or NF-kappa B binding. Clodronate was metabolised by RAW 264 cells to AppCCl(2)p. Like clodronate, AppCCl(2)p inhibited the LPS -induced release of cytokines and NO from RAW 264 macrophages. Both clodron ate and its metabolite also inhibited the LPS-stimulated binding of NF-kapp a B to DNA. in conclusion, these results suggest that the metabolite of clo dronate may be responsible for the anti-inflammatory properties of clodrona te, and that the contrasting effects of different bisphosphonates on the re lease of cytokines could be mediated partly through changes in the DNA bind ing activity of NF-kappa B. (C) 1999 Elsevier Science B.V. All rights reser ved.