Paraoxonase-1, an Aggressive-Periodontitis-Related Gene In a Japanese Population

Objectives: One of the characteristics of Aggressive Periodontitis (AgP) is familial aggregation. Therefore, the disease susceptibility is thought to be influenced by genetic risk factors. However, specific genetic variants have not been fully clarified yet. To determine genetic risk factors of AgP, we conducted whole-exome sequencing on 44 Japanese AgP patients and identified a disease-related gene, Paraoxonase-1 (PON-1) SNP rs854560. There are previous reports that PON-1 SNP affects the onset of osteoporosis, but there are no reports about the involvement of PON-1 in homeostasis of periodontal tissue. In this study, we aimed to analyze the functions of PON-1 in human periodontal ligament (HPDL) cells.
Methods: We cultured HPDL cells in a presence or absence of PON-1 specific inhibitor 2-hydroxyquinoline (2-HQ). We assessed the mRNA expression of calcification-related genes by real-time PCR, Alkaline-Phosphatase (ALP) activity, and formation of calcified-nodule by Alizarin-Red staining. We then generated PON-1 expressing vectors and transfected into HPDL cells. We used empty vector as a control. We cultured them with mineralization-inducing medium, and assessed the mRNA expression of calcification-related genes by real-time PCR, and ALP activity.
Results: In the course of the cytodifferentiation of HPDL cells, real-time PCR and ALP activity assay showed that 2-HQ significantly downregulated the mRNA expression of calcification-related genes and ALP activity, respectively. Alizarin-Red staining showed that 2-HQ also downregulated the formation of calcified-nodule. Real-time PCR and ALP activity assay showed that PON-1 plasmid-transfected HPDL cells upregulated the mRNA expression of calcification-related genes and ALP activity respectively, compared to the control HPDL cells.
Conclusions: AgP-related gene PON-1 is involved in cytodifferentiation of HPDL cells. It is suggested that PON-1 plays an important role in homeostasis of periodontal tissue.