Synthesis and preliminary pharmacological characterisation of a new class of nitrogen-containing bisphosphonates (N-BPs)

Abstract

a new series of bisphosphonates bearing either the nitrogen containing NO-donor furoxan (1,2,5-oxadiazole 2-oxide) system or the related furazan (1,2,5-oxadiazole) in lateral chain has been developed. pK a values and affinity for hydroxyapatite were determined for all the compounds. The products were able to inhibit osteoclastogenesis on RAW 246.7 cells at 10 M concentration. The most active compounds were further assayed on human PBMC cells and on rat microsomes. Unlike most nitrogen-containing bisphosphonates which target farnesyl pyrophosphate synthase, experimental and theoretical investigations suggest that the activity of our derivatives may be related to different mechanisms. The furoxan derivatives were also tested for their ability to relax rat aorta strips in view of their potential NO-dependent vasodilator properties.

Local delivery of nitric oxide: Targeted delivery of therapeutics to bone and connective tissues

“…Due to their ability to reduce bone turnover, bisphosphonates represent an effective treatment for disorders that are characterized by excessive bone resorption such as post-menopausal osteoporosis [83]. Recently, bisphosphonates have been functionalized with organic nitrate NO donors to target NO to bone more effectively (Figure 4) [83, 90]. The nitrobisphosphonates (i.e.…”

“…The ability of the compounds to be taken up selectively into bone tissue (over blood and muscle) was studied using a radioactive labeling technique [83]. Bisphosphonates containing furoxans, an additional NO donor classes, were also examined for their ability to inhibit osteoclastogenesis [90]. Nitric oxide release from these compounds was demonstrated by their ability to relax rat aorta strips.…”

Effects of bisphosphonates on osteoclastogenesis in RAW264.7 cells

“…For osteoclast differentiation, RAW cells were transferred to 48-well culture plates (Falcon) at a density of 0.5x10 4 cells/ well with α-minimum essential medium (α-MEM; Wako Pure Chemical Industries, Ltd.) supplemented with 10% heatinactivated FBS, 50 ng/ml RANKL (Oriental Yeast, Japan), 284 µM L-ascorbic acid 2-phosphate (Sigma-Aldrich), 2 mM L-alanyl-L-glutamine (Sigma-Aldrich) and 66.7 µg/ ml kanamycin-sulfate at 37˚C in a humidified atmosphere of 95% air and 5% CO 2 prior to treatment with different reagents. Medium containing these reagents was replaced every other day.…”

“…Bisphosphonates are a class of compounds that contain the P-C-P substructure instead of the P-O-P moiety present in pyrophosphate (4), and to this P-C-P backbone, two side chains are attached (Fig. 1).…”

“…Non-nitrogen-containing bisphosphonates, which lack nitrogen and contain short R 1 and R 2 side chains, are incorporated into non-hydrolysable ATP analogues. These metabolites accumulate in the cell cytoplasm, consequently inhibiting numerous (4). Via both of these mechanisms, osteoclast signaling is disrupted.…”