Porphyromonas gingivalis Suppresses Differentiation and Increases Apoptosis of Osteoblasts From New Zealand Obese Mice

Abstract

Background: Metabolic syndrome (MetS), a complex cluster of risk factors for chronic diseases such as cardiovascular disease, is observed to be increasingly associated with periodontal disease. However, the fundamental contribution of periodontal bacteria to periodontal bone loss in patients with MetS remains unclear. The aim of the present study is to analyze the effect of Porphyromonas gingivalis on differentiation of primary osteoblasts from New Zealand obese (NZO) mice, a model for MetS, compared with C57 Black 6 JAX (C57BL/6J) mice osteoblasts. Methods: Primary calvarial osteoblasts, isolated from 3‐day‐old NZO and control C57BL/6J mice, were stimulated with P. gingivalis. Proliferation was quantified by 5‐bromo‐2′‐deoxyuridine incorporation. Cell cycle and early and late apoptosis were measured by flow cytometry. Gene expression was determined by real‐time polymerase chain reaction (RT‐PCR). Results: Twelve hours after P. gingivalis stimulation, NZO osteoblasts showed significantly decreased proliferation (P ≤0.01) with increased G2 cell cycle phase compared with normal osteoblasts. Flow cytometry analysis demonstrated significant (P ≤0.01) increase of early apoptotic cells (annexin V positive) and late apoptosis (caspase 3 activity) in NZO cells compared with control cells at 3 and 6 hours after stimulation. No significant lactate dehydrogenase release was found after P. gingivalis stimulation. RT‐PCR data showed significantly suppressed expression (P ≤0.01) of collagen 1, osteocalcin, and Runt‐related transcription factor 2 in NZO cells compared with normal osteoblasts. Conclusions: The present data demonstrate that P. gingivalis downregulates proliferation and promotes apoptosis in primary NZO osteoblasts, unlike C57BL/6J osteoblasts. Also, suppressed osteoblastic marker expression in NZO cells may contribute to pathogenesis of periodontitis, suggesting a similar process in patients with MetS.

Effect of the three Enterococcus faecalis strains on apoptosis in MC3T3 cells

“…We found that the three strains of E. faecalis can induce the apoptosis of the MC3T3 cells. We observed an apoptosis peak in the MC3T3 cells at 6 hr postinfection, which was also found in the study of live Porphyromonas gingivalis on apoptosis in osteoblasts in New Zealand obese mice (Dittmann et al., ). To further provide insight into the effect of E. faecalis on osteoblast apoptosis, the expression of members in the Bcl‐2 family was measured at 6 hr postinfection.…”

A20 Restricts Inflammatory Response and Desensitizes Gingival Keratinocytes to Apoptosis

“…It is noteworthy that the impact of P. gingivalis on cell death has been controversial where studies reporting either apoptotic or anti-apoptotic effects. These differences have been attributed to the response being cell type and host resistance specific and/or associated with the length and amount of bacterial exposure and differences in the virulence of different bacterial strains (12,44,45,49,(70)(71)(72). Here we consistently demonstrated that A20 competent cells exhibit minimal to no apoptosis upon P. gingivalis exposure consistent with previous reports.…”

Diet-Induced Obesity and Its Differential Impact on Periodontal Bone Loss

“…We also used relatively low PA levels and only 6 h of P. gingivalis exposure in our cell culture models to complement our animal model and to investigate the early effects of infection. This may explain why we saw minimal differences in our osteoblast cultures, whereas another study demonstrated that osteoblasts from obese mice exhibited significantly reduced proliferation and increased apoptosis compared with those from control mice, when assessed 8 d after bacterial exposure (Dittmann et al 2015). The osteoclast preparations were not 100% pure, being obtained from bone marrow flushings, which contain stromal cell populations in addition to osteoclasts.…”