Macrophage Depletion by Free Bisphosphonates and Zoledronate-Loaded Red Blood Cells

Abstract

Bisphosphonates, besides being important drugs for the treatment of various bone diseases, could also be used to induce apoptosis in macrophage-like and cancer cells. However, their activity in vivo is limited by a short plasma half-life and rapid uptake within bone. Therefore, several delivery systems have been proposed to modify their pharmacokinetic profile and biodistribution. Among these, red blood cells (RBCs) represent one of the most promising biological carriers. The aim of this study was to select the best performing compound among Clodronate, Pamidronate, Ibandronate and Zoledronate in killing macrophages and to investigate RBCs as innovative carrier system to selectively target bisphosphonates to macrophages. To this end, the encapsulation of the selected bisphosphonates in autologous RBCs as well as the effect on macrophages, both in vitro and in vivo were studied. This work shows that, among the tested bisphosphonates, Zoledronate has proven to be the most active molecule. Human and murine RBCs have been successfully loaded with Zoledronate by a procedure of hypotonic dialysis and isotonic resealing, obtaining a dose-dependent drug entrapment with a maximal loading of 7.96±2.03, 6.95±3.9 and 7.0±1.89 µmoles of Zoledronate/ml of packed RBCs for human, Swiss and Balb/C murine RBCs, respectively. Engineered RBCs were able to detach human and murine macrophages in vitro, leading to a detachment of 66±8%, 67±8% and 60.5±3.5% for human, Swiss and Balb/C RBCs, respectively. The in vivo efficacy of loaded RBCs was tested in Balb/C mice administering 59 µg/mouse of RBC-encapsulated Zoledronate. By a single administration, depletion of 29.0±16.38% hepatic macrophages and of 67.84±5.48% spleen macrophages was obtained, confirming the ability of encapsulated Zoledronate to deplete macrophages in vivo. In conclusion, RBCs loaded with Zoledronate should be considered a suitable system for targeted delivery to macrophages, both in vitro and in vivo.

Stereotaxic administrations of allogeneic human Vγ9Vδ2 T cells efficiently control the development of human glioblastoma brain tumors

“…42 The toxicity of such effective antitumor associations cannot be ruled out in GBM patients and will need to be extensively investigated. Some studies have described that zoledronate, like some other bisphophonate molecules, might induce the depletion of macrophages 43 and act on microglia, 44 the main brain myeloid-immune cells. Then, to avoid the use of zoledronate it might be interesting to select particular Vg9Vd2 T cells that could naturally and specifically react more efficiently against GBM cells.…”

Local application of alendronate controls bone formation and β‐tricalcium phosphate resorption induced by recombinant human bone morphogenetic protein‐2

“…Chappard et al recently shown that both osteoclasts and activated macrophages act together to resorb β-TCP. Furthermore, there are many studies that bisphosphonates are effective in macrophage depletion (Rogers et al, 2013;Sabatino et al, 2014). Furthermore, there are many studies that bisphosphonates are effective in macrophage depletion (Rogers et al, 2013;Sabatino et al, 2014).…”

Tumor-Associated Macrophage-Mediated Targeted Therapy of Triple-Negative Breast Cancer

“…Previously, using mice with subcutaneous B16-F10 tumors, we showed that the DOX-AS-M-PLGA-NPs can target tumors by interacting with TAMs, because depletion of mouse macrophages using zoledronic acid, a potent bisphosphonate known to induce macrophages to undergo apoptosis and is commonly used for the non-selective depletion of macrophages in mouse models [35, 36], decreases the distribution of DOX-AS-M-PLGA-NPs in tumors [26]. In addition, the DOX-AS-M-PLGA-NPs increase the uptake of the DOX by TAMs, as compared to DOX alone or DOX-AS-PLGA-NPs, which do not actively target TAMs due to the lack of surface-modification with mannose [26].…”