Liposomal clodronate

Figure 3 Time response of CD14+ monocytes, expressed as percentage of total blood leukocytes, in LC-treated and control balloon-injured rabbits and control. Abbreviations. WBC, white blood cells LC, liposomal clodronate. Source From Ref. 52.

Jordan MB, Van Rooijen N, Izui S, Kappler J, Marrack P (2003) Liposomal clodronate as a novel agent for treating autoimmune hemolytic anemia in a mouse model. Blood 101 594... 

Figure 2 Effect of liposomal formulations BPs (alendronate and clodronate), empty and free drugs on RAW 264 cell survival. Curves represent percentage of cell inhibition with different BP concentrations. Cell count in buffer only was determined to be 100% (n = 3). Abbreviation BPs, bisphosphonates. Source From Ref 69.

The rat carotid artery injured by a balloon catheter has been widely used as a model of angioplasty. The rat model is a proliferation model without foam cells (93). This form of injury causes immediate coagulation and thrombosis cascade in which platelets adhere, spread, and degranulate on the denuded surface of the artery, and approximately 24 hours later SMC begin to proliferate. Liposomal BPs, clodronate, and alendronate were injected to male sabra rats, 15 and 3mg/kg, respectively (52,69,76). Marked neointimal formation and decreased luminal area were observed in control animals. Neointima/media (N/M) ratio was 1.3 0.2, and luminal stenosis was 44 3%. LC and LA suppressed intimal growth when administered intravenously on day -1 and day 6. N/M ratios were reduced by 60% and 69% for LC and LA, respectively. 

Danenberg HD, Fishbein 1, Gao J, et al. Macrophage depletion by clodronate-containing liposomes reduces neointimal formation after balloon injury in rats and rabbits. Circulation 2002 106 599-605. 

Monkkonen J, Liukkonen J, Taskinen M, Heath TD, Urtti A. Studies on liposome formulations for intraarticular delivery of clodronate. J Control Release 1995 35 145-154. 

Monkkonen J, Valjakka R, Hakasalo M, Urtti A. The effects of liposome surface-charge and size on the intracellular delivery of clodronate and gallium in-vitro. Int J Pharm 1994 107 189-197. 

Systemically administered liposome-encapsulated bisphosphonates (e.g., clodronate or alendronate) have been shown to be effective, in rat and rabbit models, in the prevention of restenosis. This complication frequently occurs following percutaneous coronary interventions. Thus, these compounds show considerable promise for clinical application in this area [31]. 

Frith JC, Monkkonen ), Blackburn GM, Russell RGG, Rogers M). Clodronate and liposome-encapsulated clodronate are metabolised to a toxic ATP analog, adenosine 5 -(/ / ,yy-dichloromethylene) triphosphate, by mammalian cells in vitro. J. Bone Miner. Res., 1997, 12, 1358-1367. 

Torres, P. F., Siegers, T. P., Peek, R., et al. (1999), Changes in cytokine mRNA levels in experimental corneal allografts after local clodronate-liposome treatment, Invest. Ophthalmol. Vis. Sci., 40,3194-3201. 

Key words Liposomes, Macrophages, Clodronate, Depletion of macrophages, Kupffer cells. 

Moreover, both liposomes and clodronate have already been introduced in the clinic and it may be anticipated that their combination in the transient suppression of macrophage activity for human application would be easier to achieve than for any of the other candidate effector molecules which are known until now (5, 6). 

Strong hydrophilic molecules such as the negatively charged bisphosphonate dichloromethylene-bisphosphonate (clodronate) and the positively charged diamidine propamidine can be solved in aqueous solutions in substantial concentrations. As a consequence such molecules can be encapsulated in multilamellar liposomes with a high efficacy (3). Once encapsulated, they cannot easily escape from the liposomes, since they are unable to cross their... 

The in vivo accessibility of various macrophages to liposomes is the main factor that determines the efficacy of the approach. The dose of clodronate liposomes required for depletion of... 

Stereotaxical injection of clodronate liposomes into the fourth ventricle of the central nervous system (CNS) of rats resulted in a complete depletion of perivascular and meningeal macrophages in the cerebellum, cerebrum, and spinal cord of these rats (20). These results confirm that, also, macrophages in the brain are accessible to liposomes if the latter are administered along the right route. 

In other recent studies, it was shown that microglia can be depleted from cultured slices of brain tissue using clodronate liposomes. This approach has been used to demonstrate that, in... 

Local injection of a suspension of liposomes can be performed in most organs. However, whether or not the liposomes will be able to diffuse from the injection site over the rest of the tissue will largely depend on the tissue structure. In the testis of rats, a loosely woven tissue structure allows the liposomes to reach most of the testicular macrophages, as demonstrated by the finding that at least 90% of the testicular macrophages can be depleted by clodronate liposomes (23). 

Normal dendritic cells (DC), localized in the T-cell areas in the spleen, will not be depleted by application of clodronate liposomes. However, a particular group of so called myeloid dendritic cells, localized at the border between marginal zone and red pulp, will be depleted as efficacious as macrophages (26). This is not surprising, since these cells are able to internalize particles of more than one micron. Since macrophages and dendritic cells show a considerable overlap in their activities, it remains an open question whether these cells should be considered as macrophages or dendritic cells. 

For some studies in the CNS, e.g. for research on the role of macrophages in experimental allergic encephalomyelitis (EAE), a rodent model for multiple sclerosis (MS), clodronate liposomes should be mannosylated (29, 30). 

Disperse the phospholipid film in 20 mL clodronate solution (for clodronate liposomes) or 20 mL PBS (for empty liposomes) by gentle rotation (max. 100 rpm) at room temperature. Development of foam should be avoided by reducing the speed of rotation. 

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