ABSTRACT
Calcium phosphate (CaP) ceramics including hydroxyapatite (HA) and beta-tricalcium phosphate (ß-TCP) have been widely used for bone substitution in orthopedic, maxillofacial and dental surgery, as well as in tumor resections. CaP particles are also known to cause inflammatory responses, which are thought to be an unfavorable characteristic of prosthetic coating materials. On the other hand, the immunostimulatory effect of ß-TCP induces an anti-tumor effect in xenograft tumor models in athymic mice. To date, in depth analysis of the biological effects of ß-TCP has not been studied in mice. In the present study, in vivo biological effects of ß-TCP were investigated by subcutaneously injecting ß-TCP particles into mice. This induced extensive migration of immune cells to the area surrounding the injection. In addition, we found that in vitro treatment with ß-TCP in murine monocyte/macrophage cells (J774A.1) induced up-regulation of surface expression of CD86, and increased production of TNF-α, MIP-1α, and sICAM-1. Furthermore, conditioned medium from J774A.1 cells treated with ß-TCP facilitated migration of murine splenocytes in a transwell migration assay. These findings clarify that ß-TCP induces an immunostimulatory effect in mice, and suggest a potential for ß-TCP as a novel adjuvant for cancer therapy.
Subject(s)
Adjuvants, Immunologic/pharmacology , Calcium Phosphates/pharmacology , Animals , B7-2 Antigen/metabolism , Cell Line , Cell Movement/drug effects , Chemokine CCL3/metabolism , Intercellular Adhesion Molecule-1/metabolism , Macrophages/drug effects , Macrophages/physiology , Male , Mice , Mice, Inbred C57BL , Monocytes/drug effects , Monocytes/physiology , Phagocytosis/drug effects , Spleen/cytology , Tumor Necrosis Factor-alpha/metabolismABSTRACT
BACKGROUND: A cell-based assay system (Transfluor) has been developed for measurement of G-protein coupled receptor (GPCR) activity by using cells transfected to express a fusion protein of arrestin plus green fluorescent protein (GFP) and the target GPCR. Upon agonist stimulation, the arrestin-GFP translocates to and binds the activated GPCR at the plasma membrane. The receptor/arrestin-GFP complexes then localize in clathrin-coated pits and/or intracellular vesicles. This redistribution of arrestin-GFP into condensed fluorescent spots is useful for visually monitoring the active status of GPCRs and its quantitation is possible with certain types of digital image analysis systems. METHODS: We designed two lines of image processing algorithms to carry out quantitative measurement of the arrestin-GFP movement on an inverted version of laser scanning cytometry (iCyte) as an imaging platform. We used a cell line expressing arrestin-GFP and the wild-type beta2-adrenergic receptor or a modified version of this receptor with enhanced affinity for arrestin. Each cell line was challenged with various concentrations of agonist. RESULTS: A dose-dependent signal was measured and half-maximal effective concentration values were obtained that agreed well with results determined by other methods previously reported. CONCLUSIONS: The results indicate that the combination of Transfluor, iCyte, and our algorithms is suitable for robust and pharmacologically relevant GPCR ligand exploration.
