Effects of tiludronate and ibandronate on the secretion of proinflammatory cytokines and nitric oxide from macrophages in vitro.

Bisphosphonates inhibit osteoclastic bone resorption and are used for the treatment of bone diseases. Some bisphosphonates, such as clodronate and tiludronate, can be incorporated into non-hydrolysable ATP analogues in cells, whereas the more potent anti-resorptive aminoalkylbisphosphonates are not metabolised. Furthermore, clodronate inhibits proinflammatory cytokine and nitric oxide (NO) secretion from activated macrophages in vitro and has anti-inflammatory properties in vivo, especially when delivered into cells by liposomes. By contrast, aminobisphosphonates can induce an acute phase response and fever in vivo, which appears to involve the induction of cytokine secretion. In this study we examined the effect of liposome-mediated intracellular delivery of one aminobisphosphonate, ibandronate, and one metabolizable bisphosphonate, tiludronate, on the secretion of inflammatory mediators. The intracellular uptake of bisphosphonates by macrophages was enhanced by a factor of 20-200 by using liposomes. Tiludronate dose-dependently inhibited both cytokine and NO secretion from activated macrophages, and liposomal tiludronate was more potent than the free drug. By contrast, ibandronate enhanced LPS-induced secretion of IL-1beta and IL-6 but did not affect TNFalpha or NO secretion at non-cytotoxic concentrations. The present results, together with our previous studies, strongly suggest that bisphosphonates can be grouped into those that are metabolised by cells and that are capable of inhibiting cytokine and NO secretion from macrophages, thus having potential anti-inflammatory properties, and those that are not metabolised but can actually enhance the production of cytokines following macrophage activation.

In vitro and in vivo effects of tetrakisphosphonates on bone resorption, tumor osteolysis, ectopic calcification, and macrophages.

The biological effects of bisphosphonates in calcium-related disorders are attributed to the incorporation of the bisphosphonates in bone, enabling direct interaction with osteoclasts and/or osteoblasts. The high accumulation of bisphosphonates in bone, due to their high affinity to hydroxyapatite (HAP), is essential for mediating in vitro and in vivo activity. In this study we examined the activity of tetrakisphosphonates, molecules containing two P-C-P type bisphosphonate moieties connected by a carbon chain. The novel compounds were examined in a battery of in vitro and in vivo models including HAP formation and dissolution, ectopic calcification, bone resorption, tumor osteolysis, and of macrophage-like cells (anti- or pro-inflammatory properties). The inhibition of ectopic calcification was ranked as follows: geminal bisphosphonates > bisacylphosphonates > tetrakisphosphonates. Pamidronate, but not the tetrakisphosphonates, was an effective antiosteolytic agent. Neither DNTP (tetrasodium 1,9-dihydroxynonane 1,1,9,9-tetrakisphosphonate) nor the bisacylphosphonate, PiBP (pimeloylbisphosphonate) seem to possess strong macrophage suppressive or inductive effects and can be considered to be relatively inactive in terms of anti- or pro-inflammatory action. A significant anticalcification effect was caused by various phosphonates, such as the tetrakisphosphonates, but DNTP, a tetrakisphosphonate, was found toxic as it impeded somatic growth and bone development.