Extending the vitamin D pathway to vitamin D3and CYP27A1 in periodontal ligament cells

In periodontal connective tissue cells, the vitamin D pathway has been elucidated, and vitamin D3 in the main storage form, 25-hydroxy vitamin D3 (25[OH]D3 ), and the functional form, 1,25-dihydroxy vitamin D3 (1,25[OH]2 D3 ), have been found to induce the expression of human cationic antimicrobial protein (hCAP-18)/LL-37. Moreover, synergistic effects between Toll-like receptor agonists and 25(OH)D3 have been reported. This research aimed at extending the vitamin D pathway to vitamin D3 and CYP27A1 in human periodontal ligament cells (hPDLCs) to further explore its function in periodontal inflammatory reaction.Vitamin D3 was used to stimulate hPDLCs in the presence or absence of Porphyromonas gingivalis lipopolysaccharide (Pg-LPS). Conversely, CYP27A1 RNA interference was performed to further validate the findings. The mRNA expression of hCAP-18 was determined with real-time polymerase chain reaction. Monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) were also detected. The cell supernatant levels of LL-37 were detected with enzyme-linked immunosorbent assay.Vitamin D3 significantly enhanced the generation of hCAP-18/LL-37. A combination of Pg-LPS and vitamin D3 significantly promoted hCAP-18/LL-37 expression. When the expression of CYP27A1 was knocked down with RNA interference, the induction of hCAP-18/LL-37 expression was significantly inhibited. Therefore, the mRNA levels of MCP-1 and IL-8 in hPDLCs were significantly decreased through the vitamin D pathway.The vitamin D pathway from vitamin D3 to hCAP-18/LL-37 exists in hPDLCs, and CYP27A1 might be involved in periodontal immune defense.