Lectin-type oxidized LDL receptor 1 modulates matrix metalloproteinase 2 production in peri-implantitis

Abstract

Peri-implantitis is a disease in which inflammatory lesions that affect the surrounding soft and hard tissues develop. Matrix metalloproteinase 2 (MMP2) is hypothesized to be involved in this destructive process. However, the regulatory mechanism of action of MMP2 in the peripheral tissues of the implant are not fully understood. To determine the expression of MMP2 in peri-implantitis, peri-implant crevicular fluid (PICF) was collected from patients with peri-implantitis. The healthy volunteers' peripheral blood human macrophages infected with Porphyromonas gingivalis (P. gingivalis) were used as a cell model to explore the regulatory mechanism of MMP2 regarding dental implants. Western blotting, reverse transcription-quantitative PCR and immunofluorescence staining were used to measure the expression of MMP2 in the present study. MMP2 expression was increased in the PICF of the patients with peri-implantitis and in human macrophages infected with P. gingivalis. Lectin-type oxidized LDL receptor 1 (LOX-1) mediated the expression of MMP2 in human macrophages upon infection of P. gingivalis, whereas dendritic cell-associated c-type lectin-1 did not appear to be involved in this regulatory process. However, JNK and ERK1/2 were involved in P. gingivalis induced MMP2 expression. The results of this study showed that MMP2 was involved in peri-implantitis. MMP2 was upregulated by LOX-1 in a JNK and ERKk1/2 signaling dependent manner in the cell model. The LOX-1/MMP2 signaling pathway may thus be a potential target for management of peri-implantitis.

Keywords: Porphyromonas gingivalis; lectin-type oxidized LDL receptor 1; matrix metalloproteinase 2; peri-implantitis.

Figure 1

MMP2 expression is increased in patients with peri-implantitis. (A) In patients with peri-implant inflammation (n=10/group), the protein levels of MMP2 in PICF were higher than that in healthy patients. (B) Immunofluorescence staining showed expression of MMP2 (green) in the peri-implantitis patients' gingival surface (magnification, x400). ^*P<0.05. MMP2, matrix metalloproteinase 2; PICF, peri-implant crevicular fluid.

Figure 2

MMP2 expression is increased in P. gingivalis infected human macrophages. (A) MMP2 mRNA expression was elevated 4 and 16 h after infection of human macrophages with P. gingivalis. (B) MMP2 protein levels were higher 16 h after infection with P. gingivalis bacteria. ^***P<0.001. MMP2, matrix metalloproteinase 2; P. gingivalis/P. g, Porphyromonas gingivalis; NC, negative control.

Figure 3

MMP2 production in P. gingivalis infected human macrophages is mediated by LOX-1. The MMP2 (A) mRNA and (B) protein expression levels were lower when pre-treated with the LOX-1 neutralizing antibody. The MMP2 (C) mRNA and (D) protein levels were lower when pre-treated with the LOX-1 inhibitor. ^*P<0.05, ^**P<0.01, ^***P<0.001. ns, not significant; MMP2, matrix metalloproteinase 2; P. gingivalis, Porphyromonas gingivalis; LOX-1, Lectin-type oxidized LDL receptor 1; IgG, immunoglobulin; Poly (I), polyinosinic acid; Ab, antibody.

Figure 4

MMP2 production in P. gingivalis infected human macrophages was independent of dectin-1. Pre-treatment with dectin-1 neutralizing antibody did not significantly affect the (A) mRNA and (B) protein expression levels of MMP2. Similarly, the MMP2 (C) mRNA and (D) protein expression levels were not significantly affected with dectin-1 inhibitor pre-treatment either. ^***P<0.001. ns, not significant; MMP2, matrix metalloproteinase 2; P. gingivalis, Porphyromonas gingivalis; IgG, immunoglobulin; Ab, antibody.

Figure 5

JNK and Erk1/2 are responsible for P. gingivalis induced MMP2 production. The upregulated expression of MMP2 at the (A) mRNA and (B) protein level in human macrophages infected P. gingivalis bacteria decreased when pre-treated with the JNK inhibitor before infection. The upregulated MMP2 (C) mRNA and (D) protein levels in response to infection with live P. gingivalis bacteria decreased when pre-treated with the Erk1/2 inhibitor. ^*P<0.05, ^**P<0.01, ^***P<0.001. ns, not significant; MMP2, matrix metalloproteinase 2; P. gingivalis, Porphyromonas gingivalis; IgG, immunoglobulin; Ab, antibody.