Vitamin D-Dimer: A Possible Biomolecule Modulator in Cytotoxic and Phagocytosis Processes?

Background: Vitamin D-3 complexed to deglycosylated vitamin D binding protein (VitDdgVDBP) is a water-soluble vitamin D dimeric compound (VitD-dgVDBP). It is not clear how VitD-dgVDBP affects circulating monocytes, macrophages, other immune cell systems, including phagocytosis and apoptosis, and the generation of reactive oxygen species (ROS) compared to dgVDBP. Methods: Flow cytometry was used to measure superoxide anion radical (O-2*(-)) levels and macrophage activity in the presence of VitD-dgVDBP or dgVDBP. VitD-dgVDBP was incubated with normal human lymphocytes (nPBMCs), and several clusters of determination (CDs) were estimated. dgVDBP and VitD-dgVDBP apoptosis was estimated on malignant prostatic cells. Results: The macrophage activity was 2.8-fold higher using VitD-dgVDBP (19.8.10(6) counts) compared to dgVDBP (7.0.10(6) counts), but O-2*(- )production was 1.8-fold lower in favor of VitD-dgVDBP (355.10(3) counts) compared to dgVDBP (630.10(6) counts). The calculated ratio of the radical/macrophage activity was 5-fold lower compared to that of dgVDBP. Only VitD-dgVDBP activated caspase-3 (8%), caspase-9 (13%), and cytochrome-C (11%) on prostatic cancer cells. PE-Cy7-labeled VitD-dgVDBP was found to bind to cytotoxic suppressor cells, monocytes/macrophages, dendritic and natural killer cells (CD8+), and helper cells (CD4+). After 12 h of co-incubation of nPBMCs with VitD-dgVDBP, significant activation and expression were measured for CD16++/CD16 (0.6 +/- 0.1% vs. 0.4 +/- 0.1%, p < 0.05), CD45k+ (96.0 +/- 6.0% vs. 84.7 +/- 9.5%, p < 0.05), CD85k+ (24.3 +/- 13.2% vs. 3.8 +/- 3.2%, p < 0.05), and CD85k /CD123 (46.8 +/- 8.1% vs. 3.5 +/- 3.7%, p < 0.001) compared to the control experiment. No significant difference was found using CD3+, CD4+, CD8+, CD4/CD8, CD4/CD8, CD16+, CD16++, CD14+, or CD123+. A significant decline in CD14+/CD16+ was obtained in the presence of VitDdgVDBP (0.7 +/- 0.2% vs. 3.1 +/- 1.7%; p < 0.01). Conclusion: The newly developed water-soluble VitD(3) form VitD-dgVDBP affected cytotoxic suppressor cells by activating the low radical-dependent CD16 pathway and seemed to induce apoptosis in malignant prostatic cells.