Labudzynskyi D. NF-κB-associated mechanisms involved in the implementation of osteoimmune interactions and systemic proinflammatory processes in experimental diabetes mellitus and the role of cholecalciferol in their correction.

Object: Structural-functional and molecular-cellular changes in the liver, immune system and bone tissue of mice in experimental diabetes mellitus. Methods: Biochemical and spectral (spectrophotometry, spectrofluorometry, cytometry, light and confocal microscopy), structural and histological (3-point bending test, μCT, H&E histology), physicochemical (gel electrophoresis for protein separation), molecular biology (PCR), immunochemical and cytological methods (immunoblotting, ELISA and immunocytochemistry), methods of working with the primary culture of eukaryotic cells (cultivating and evaluating their functional state), as well as methods of statistical analysis. We are the first who showed the close relationship between vitamin D3 deficiency and disorders of NF-κB-dependent regulatory processes in the bone tissue and immune system (osteoimmune interaction) in diabetes mellitus. These changes were associated with the impairment of the functional state of the cytokine system RANKL/RANK/OPG that led to the activation of NF-κB-mediated signaling pathways and caused disorders of bone tissue remodeling. It was found that diabetes-related abnormalities in the osteoimmune interaction were accompanied by changes in different segments of the immune system. In particular, we found a significant imbalance in the ratio of regulatory CD4+- and CD8+-lymphocytes, a decrease in the proliferative potential and an increase in the content of the activated p65 NF-κB subunit in splenocytes. The development of the associated structural and functional changes in liver tissue in the liver correlated with an increase in the expression of key pro-inflammatory cytokines (iNOS, VEGF-A, TNF-α) and elements of the RANKL/RANK/OPG axis. It was found out that the use of therapeutic doses of vitamin D3 in experimental diabetes normalized the level of 25OHD in serum and the expression of the vitamin D-endocrine system components in the liver of mice. By increasing the bioavailability of vitamin D, cholecalciferol contributed to a partial correction of the revealed alterations in the immune system, enzymatic activities of the pro-/antioxidant defense system, and the expression of NF-κB-mediated pro-/ anti-inflammatory factors in the liver tissue. These changes correlated with significant improvement of the biomechanical and biochemical parameters of the tibia and restoration of the disturbed balance of osteoimmune interaction in the process of bone tissue remodeling.