Porphyromonas gingivalis Infection Accelerates Atherosclerosis Mediated by Oxidative Stress and Inflammatory Responses in ApoE-/- Mice.

BACKGROUND: The periodontal pathogen Porphyromonas gingivalis (P. gingivalis) has been proven to accelerate the development of atherosclerosis in apolipoprotein E (ApoE)-deficient mice. In this study, we used an ApoE knockout (ApoE-/-) mouse model with chronic intravenous infection with P. gingivalis to investigate the possible mechanisms of P. gingivalis-induced atherosclerosis. METHODS: Eight-week-old ApoE-/- mice were randomly assigned to two groups: (a) ApoE-/- + PBS (n = 8); (b) ApoE-/- + P. gingivalis (n = 8). Both of the groups received intravenous injections 3 times per week. After 4 weeks, oxidative stress mediators in serum, heart, aorta, and liver tissues were analyzed by using histology, ELISA, realtime PCR, and Western blot. RESULTS: Development of atherosclerosis as plaque formation in the aorta has been confirmed upon P. gingivalis infection. An abnormal lipid profile was found in the serum (increased amounts of very low-density lipoprotein [vLDL] and oxidized low-density lipoprotein [oxLDL], and decreased amount of HDL) and in some organs including heart, aorta or liver (increased mRNA levels of oxidized low-density lipoprotein receptor-1 [LOX-1] or fatty acid synthase [FAS]). Meanwhile, aggravated oxidative stress (higher level of reactive oxygen species [ROS] in the serum, and increased mRNA levels of nicotinamide adenine dinucleotide phosphate oxidase [NOX]-2 and/or NOX-4 in the three organs) was observed, as well as enhanced inflammatory responses (increased expression and secretion of C-reactive protein [CRP] in the liver and serum, and increased mRNA levels of cyclooxygenase-2 [NOX-2] and/or inducible nitric oxide synthase [iNOS] in the three organs). Besides, inflammatory mediators including nuclear factor of kappa B (NF-κB) and iNOS showed increased protein levels in the three organs after P. gingivalis infection. CONCLUSIONS: These results suggest that chronic intravenous infection with P. gingivalis in ApoE-/- mice could accelerate the development of atherosclerosis, possibly associated with mediating oxidative stress as well as inflammatory responses and disturbing the lipid profile.

Positive Correlation between Activated CypA/CD147 Signaling and MMP-9 Expression in Mice Inflammatory Periapical Lesion.

AIM: Cyclophilin A (CypA)/CD147 signaling plays critical roles in the regulation of inflammation and bone metabolism. This study aimed to investigate the participation of CypA/CD147 in mice periapical lesions progression and its relationship with bone resorption. METHODOLOGY: Periapical lesions were induced by pulp exposure in the first lower molars of 40 C57BL/6J mice. The mice were sacrificed on days 0, 7, 14, 21, 28, 35, 42, and 49. Mandibles were harvested for X-ray imaging, microcomputed tomography scanning, histologic observation, immunohistochemistry, enzyme histochemistry, and double immunofluorescence analysis. Western blot was employed to further detect the related molecular signaling pathways in LPS-stimulated RAW 264.7 cells treated with CypA inhibitor. RESULTS: The volume and area of the periapical lesions increased from day 0 to day 35 and remained comparably stable until day 49. Immunohistochemistry demonstrated that the CypA expression levels also increased from day 0 to day 35 and decreased until day 49, similar to CD147 expression (R 2 = 0.4423, P < 0.05), osteoclast number (R 2 = 0.5101, P < 0.01), and the expression of osteoclastogenesis-related matrix metalloproteinase 9 (MMP-9) (R 2 = 0.4715, P < 0.05). Serial sections further confirmed the colocalization of CypA and CD147 on osteoclasts with immunohistochemistry. And the distribution of CypA-positive or CD147-positive cells was positively correlated with the dynamics of MMP-9-positive cells by using immunofluorescence analysis. Furthermore, CD147 and MMP-9 expression in RAW 264.7 cells were both downregulated with CypA inhibitor treatment (P < 0.05). CONCLUSIONS: The present study reveals the positive correlation of CypA/CD147 signaling and osteoclast-related MMP-9 expression in mice inflammatory periapical lesions progression. Therefore, intervention of CypA/CD147 signaling could probably provide a potential therapeutic target for attenuating inflammatory bone resorption.

From the Cover: Activation of NF-κB-Autophagy Axis by 2-Hydroxyethyl Methacrylate Commits Dental Mesenchymal Cells to Apoptosis.

2-hydroxyethyl methacrylate (HEMA) is the major resin monomer that is released from incomplete polymerized dental restorative and adhesive biomaterials during dental therapy. Autophagy and apoptosis are biologically connected and the relationship between autophagy and apoptosis is complex under various circumstances. This study aimed to determine whether autophagy is activated by HEMA and further explore the function of autophagy during the HEMA-induced apoptosis of dental mesenchymal cells (DMCs). We exposed DMCs to different concentrations of HEMA. Cell viability showed a time- and concentration-dependent decrease when exposed to HEMA. We showed that HEMA exposure increased autophagic vacuoles and the expression of autophagic biomarkers (Beclin1, Atg5 and LC3). Pre-incubated with autophagy inhibitors (3-methyladenine and chloroquine) significantly prevented HEMA-induced apoptosis. Interestingly, HEMA initiated nuclear factor-κB (NF-κB) expression and nuclear translocation, whereas the NF-κB inhibitor (Bay 11-7082) markedly suppressed HEMA-induced autophagic activation and apoptosis. As is consistent with the in vitro results, HEMA treatment resulted in dental pulp tissue toxicity and activation of typical autophagic vacuoles in the tooth slice organ culture model ex vivo. In summary, we demonstrated that NF-κB signaling functioned upstream of HEMA-inducecd autophagy in DMCs and that the activation of NF-κB-autophagy axis was responsible for HEMA-induced apoptosis. Our findings provide novel insights into the mechanisms of resin monomer-mediated dental pulp damage during dental treatment, highlighting the activation of NF-κB-autophagy axis as an important mechanism of HEMA-mediated apoptosis.