Alteration of macrophage viability, differentiation, and function by bisphosphonates.

BACKGROUND: A serious adverse effect of long-term bisphosphonate (BP) administration is bisphosphonate-related osteonecrosis of the jaw (BRONJ). Among different proposed pathogenesis, suppression of immune cells is gaining interest. Because monocytes/macrophages could get access to BP since residing in the blood and bone microenvironment, the aim of this study was to analyze the behaviors of macrophages after BP treatments in vitro. METHODS: THP-1 cell, an established human monocytic cell model, was used in this study. The effects of BPs, alendronate (ALN) and zoledronic acid (ZA), on macrophage viability, differentiation, and function were investigated. MTT, morphological analysis, flow cytometry, quantitative PCR, and gelatin zymography assay were performed. RESULTS: BPs impaired macrophage viability at almost all concentration tested (1-100 µM). Cell morphology was altered in the presence of 100 µM BPs. Furthermore, differentiating macrophage viability was also affected by both ALN and ZA at 100 and 10-100 µM, respectively. At high concentration (100 µM), ZA caused a reduction in cell differentiation. On the contrary, ALN and ZA increased matrix metalloproteinase mRNA expressions and activities at low doses (1-10 µM). CONCLUSION: BPs directly acted on macrophage by reducing macrophage survival, inducing morphological alterations, impairing differentiation from monocytes to macrophages, and affecting macrophage function at both mRNA and activity levels.

Differential inflammasome activation by Porphyromonas gingivalis and cholesterol crystals in human macrophages and coronary artery endothelial cells.

OBJECTIVE: Observational evidence suggests association between periodontitis and atherosclerotic vascular disease (ASVD), however the cause-effect remains unclear. In this study, we investigated the mechanistic link of the two diseases by measuring production of interleukin (IL)-1ß, a potent inflammatory cytokine, induced via inflammasome activation by a key periodontal pathogen--Porphyromonas gingivalis LPS and cholesterol crystals (CC). METHODS: An in vitro model of primary human monocyte-derived macrophages (M1 and M2 macrophages) and coronary artery endothelial cells (HCAEC) was employed as a source of inflammasome product-IL-1ß. Both cell types are essential in initial inflammatory process of ASVD. As inflammasome activation requires 2 signals, P. gingivalis LPS was used as a signal1 and CC as a signal2. RESULTS: We found markedly release of IL-1ß from P. gingivalis LPS-primed M1 and M2 macrophages treated with CC. Unlike macrophages, HCAEC showed no release of IL-1ß in response to P. gingivalis LPS priming and subsequent treatment with either CC or extracellular danger molecule adenosine-5'-triphosphate (signal2). However, HCAEC, which were primed with pro-inflammatory cytokine TNF-α (signal1) and treated with adenosine-5'-triphosphate, consistently secreted minimal IL-1ß. The amount of IL-1ß released from activated HCAEC was much lower than that from M1 or M2 macrophages. CONCLUSIONS: P. gingivalis LPS and CC induced a differential activation of the inflammasome between human macrophages and HCAEC. The mechanistic role of periodontal infection in inflammasome activation as a cause of ASVD requires further investigation.