Vitamin D decreases Porphyromonas gingivalis internalized into macrophages by promoting autophagy

Objectives: This paper aims to study the effect of the active form of vitamin D (calcitriol) on the internalized Porphyromonas gingivalis in macrophages and to assess the role of Autophagy during this process.

Materials and methods: Quantitative RT-PCR and bacteria culture were used to quantify live P. gingivalis internalized into U937-derived macrophages. Western blot assays were performed to detect the effect of P. gingivalis and calcitriol on Autophagy in macrophages. Transmission electron microscope was used to observe the effect of calcitriol on the status of internalized P. gingivalis. Colocalization of P. gingivalis with the autophagosome and lysosome markers was observed by confocal laser scanning microscopy.

Results: Calcitriol caused a dose-dependent decrease in live P. gingivalis numbers and promoted both the endogenous and P. gingivalis-induced Autophagy in macrophages. Calcitriol significantly promoted the destruction of P. gingivalis and the colocalization of P. gingivalis with autophagosome and lysosome markers. Conversely, with 3-MA, live P. gingivalis numbers in macrophages increased significantly and inhibition effect of calcitriol on the number of live P. gingivalis was attenuated.

Conclusion: In U937-derived macrophages, calcitriol may promote colocalization of P. gingivalis with autophagosomes and lysosomes, namely Autophagy process, to degrade live P. gingivalis.