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

Intervention with extracellular matrix metalloproteinase inducer in osteoclasts attenuates periodontitis-induced bone resorption

Extracellular matrix metalloproteinase inducer (EMMPRIN) plays critical roles in the regulation of inflammation and bone metabolism. The roles of EMMPRIN signaling in osteoclasts are worthy of deep study. The present study aimed to investigate bone resorption in periodontitis through the intervention of EMMPRIN signaling. The distribution of EMMPRIN in human periodontitis was observed. RANKL-induced osteoclast differentiation of mouse bone marrow-derived macrophages (BMMs) were treated with EMMPRIN inhibitor in vitro. Rats with ligation-induced periodontitis were treated with EMMPRIN inhibitor and harvested for microcomputed tomography scanning, histologic observation, immunohistochemistry, and double immunofluorescence analysis. Positive expressions of EMMPRIN could be found in the CD68+-infiltrating cells. Downregulated EMMPRIN restrained osteoclast differentiation of BMMs in vitro, which also inhibited MMP-9 expression (*P < 0.05). In vivo, EMMPRIN inhibitor restrained ligation-induced bone resorption by decreasing tartrate-resistant acid phosphatase-positive osteoclasts. Both EMMPRIN-positive and MMP-9-positive osteoclasts were less common in the EMMPRIN inhibitor groups than in the control groups. Intervention of EMMPRIN signaling in osteoclasts could probably provide a potential therapeutic target for attenuating ligation-induced bone resorption.

Lipopolysaccharide induces inflammatory microglial activation through CD147-mediated matrix metalloproteinase expression

Microglia-mediated neuroinflammation plays a vital role in the pathophysiological processes of multiple neurodegenerative diseases. Lipopolysaccharide (LPS) is an environmental poison that can induce inflammatory microglial activation. Matrix metalloproteinases (MMPs) are vital factors regulating microglial activation, and CD147 is a key MMP inducer, which can induce inflammation by inducing MMPs. However, whether it is involved in the regulation of microglial activation has not been reported. In this study, the role of CD147 in LPS-induced microglial inflammatory activation was investigated by establishing in vivo and in vitro models. The results suggested that LPS-induced microglial activation was accompanied by the induction of CD147 expression while the inhibition of CD147 expression could inhibit LPS-induced microglial inflammatory activation. In addition, the results also indicated that the role of CD147 in LPS-induced pro-inflammatory activation of microglia was related to its downstream MMP-3, MMP-8, and autophagy. Furthermore, the inhibition of MMP-3, MMP-8, and autophagy attenuated LPS-induced inflammatory activation of microglia. At the same time, there was a certain interaction between MMPs and autophagy, which is shown that inhibiting the expression of MMPs could inhibit autophagy, whereas inhibiting autophagy could inhibit the expression of MMPs. Taken together, we provided the first evidence that CD147/MMPs can be involved in LPS-induced inflammatory activation of microglia through an autophagy-dependent manner.

Cyclophilin A causes severe fever with thrombocytopenia syndrome virus-induced cytokine storm by regulating mitogen-activated protein kinase pathway

Introduction

Severe fever with thrombocytopenia syndrome (SFTS) has become a global threat to public health since its first report in China in 2009. However, the pathogenesis of SFTS virus (SFTSV) in humans remains unclear. Also, there are no effective therapeutics for SFTS. Cyclophilin A (CyPA) regulates protein folding and trafficking involved in various viral infectious diseases, but its role in SFTSV infection has not been elucidated.

Methods

We detected plasma CyPA levels in 29 healthy subjects and 30 SFTS patients by ELISA. In THP-1 cells and normal human peripheral blood mononuclear cells (PBMCs), SFTSV-induced extracellular CyPA (eCyPA) was also detected by ELISA. In THP-1, the effects of CyPA on Mitogen-activated protein kinase (MAPK) pathway and NF-κB were determined by Western blot. We validated the interaction between CypA and CD147 by human recombinant CyPA (hrCyPA) and the CD147 inhibitor. Effects of CyPA inhibitor Cyclosporine A (CsA) on cytokines and SFTSV replication in THP-1 cells was also detected. 8-week-old Interferon-α/β Receptor (IFNAR) knockout (IFNAR-/-) C57BL/6 mice were divided into mock group, 10⁶TCID₅₀ SFTSV (Untreated) group and 10⁶TCID₅₀ SFTSV+CsA (CsA-treated) group. The changes of body weight, animal behavior and survival time of each group were recorded. Blood samples were collected from tail vein regularly. After death, the liver, spleen, lung, kidney and brain were collected for pathological HE staining and SFTSV-NP immunohistochemical staining.

Results

Compared to healthy subjects and SFTS patients in the febrile phase of the disease, plasma CyPA levels in SFTS patients at the multi-organ dysfunction (MOD) phase showed significantly elevated (P < 0.01). Extracellular CyPA activates the MAPK pathway by binding to CD147 in THP-1 infected with SFTSV. CsA inhibits the pro-inflammatory and promoting replication effects of CyPA after SFTSV infection in vitro. In vivo, CsA can prolong the survival time and delay the weight loss of SFTSV mice. CsA reduces multi-organ dysfunction in IFNAR-/- mice infected with SFTSV.

Discussion

Our results indicate that CyPA is associated with SFTSV-induced cytokine storm, which can be a potential target for SFTS therapy.

Characterizations of alveolar repair after mandibular second molar extraction: an experimental study in rats

BACKGROUND

Characterizations of rat mandibular second molar extraction socket with significantly different buccal and lingual alveolar ridge width remain unclear.

OBJECTIVE

To observe alterations in the alveolar ridge after extraction of mandibular second molars, and to examine processes of alveolar socket healing in an experimental model of alveolar ridge absorption and preservation.

METHODOLOGY

Eighteen Wistar rats were included and divided into six groups regarding healing time in the study. Bilateral mandibular second molars were extracted. The rats with tooth extraction sockets took 0, 1.5, 2, 3, 4 and 8 weeks of healing. Histological observation, tartrate-resistant acidic phosphatase (TRAP) staining, Masson's trichrome staining, immunohistochemical staining and micro-computed tomography (micro-CT) were applied to estimate alterations in the alveolar ridge.

RESULTS

Different buccal and lingual alveolar ridge width led to different height loss. Lingual wall height (LH) decreased significantly two weeks after tooth extraction. Buccal wall height rarely reduced its higher ridge width. From two to eight weeks after extraction, bone volume (BV/TV), density (BMD), and trabecular thickness (Tb.Th) progressively increased in the alveolar socket, which gradually decreased in Tb.Sp and Tb.N. LH showed no significant change during the same period. Osteogenic marker OCN and OPN increased during bone repair from two to eight weeks. The reduced height of the lingual wall of the tooth extraction socket was rarely repaired in the later repair stage. Osteoclast activity led to absorption of the alveolar ridge of the alveolar bone wall within two weeks after operation. We observed positive expression of EMMPRIN and MMP-9 in osteoclasts that participated in the absorption of the spire region.

CONCLUSION

Extraction of rat mandibular second molars may help the study of alveolar ridge absorption and preservation. The EMMPRIN-MMP-9 pathway may be a candidate for further study on attenuating bone resorption after tooth extraction.

Mycoplasma genitalium Protein of Adhesion Induces Inflammatory Cytokines via Cyclophilin A-CD147 Activating the ERK-NF-κB Pathway in Human Urothelial Cells

Mycoplasma genitalium protein of adhesion (MgPa) plays an important role in the process of adhesion and invasion of host cells by M. genitalium, and is thus significant for its pathogenic mechanisms in host cells. Our previous study has demonstrated that cyclophilin A (CypA) is the receptor for MgPa in human urothelial cells (SV-HUC-1) and can, therefore, mediate the adherence and invasion of M. genitalium into host cells by interacting with MgPa. However, the specific pathogenesis of M. genitalium to host cells and the possible pathogenic mechanism involved in the interaction of MgPa and CypA have never been clarified. The study aimed to elucidate the mechanism involved in the pathogenicity of MgPa. Recombinant MgPa (rMgPa) induced extracellular CypA (eCypA) was detected in SV-HUC-1 cells by ELISA, and the interaction between CypA and CD147 was validated using co-localization and co-immunoprecipitation assay. In addition, both extracellular signal-regulated kinases (ERK) phosphorylation and NF-κB activation evoked by rMgPa-induced eCypA were also demonstrated. The findings of this study verified that rMgPa could induce the secretion of eCypA in SV-HUC-1 cells and thus promote the protein and mRNA expression of IL-1β, IL-6, TNF-α and MMP-9 via CypA-CD147 interaction and thus activating ERK-NF-κB pathway, which is beneficial to elucidate the pathogenesis and possible pathogenic mechanism of M. genitalium to host cells.

High Mobility Group Box 1 Expression in Oral Inflammation and Regeneration

High mobility group box 1 (HMGB1) is a non-histone DNA-binding protein of about 30 kDa. It is released from a variety of cells into the extracellular milieu in response to inflammatory stimuli and acts on specific cell-surface receptors, such as receptors for advanced glycation end-products (RAGE), Toll-like receptor (TLR)2, TLR4, with or without forming a complex with other molecules. HMGB1 mediates various mechanisms such as inflammation, cell migration, proliferation, and differentiation. On the other hand, HMGB1 enhances chemotaxis acting through the C-X-C motif chemokine ligand (CXCL)12/C-X-C chemokine receptor (CXCR)4 axis and is involved in regeneration. In the oral cavity, high levels of HMGB1 have been detected in the gingival tissue from periodontitis and peri-implantitis patients, and it has been shown that secreted HMGB1 induces pro-inflammatory cytokine expression, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, which prolong inflammation. In contrast, wound healing after tooth extraction or titanium dental implant osseointegration requires an initial acute inflammation, which is regulated by secreted HMGB1. This indicates that secreted HMGB1 regulates angiogenesis and bone remodeling by osteoclast and osteoblast activation and promotes bone healing in oral tissue repair. Therefore, HMGB1 can prolong inflammation in the periodontal tissue and, conversely, can regenerate or repair damaged tissues in the oral cavity. In this review, we highlight the role of HMGB1 in the oral cavity by comparing its function and regulation with its function in other diseases. We also discuss the necessity for further studies in this field to provide more specific scientific evidence for dentistry.