Simvastatin suppresses LPS-induced MMP-1 expression in U937 mononuclear cells by inhibiting protein isoprenylation-mediated ERK activation.

Matrix metalloproteinase (MMP) plays a crucial role in periodontal disease and is up-regulated by oral Gram-negative, pathogen-derived LPS. In this study, we reported that simvastatin, a 3-hydroxyl-3-methylglutaryl-CoA reductase inhibitor, effectively inhibited LPS-stimulated MMP-1 as well as MMP-8 and MMP-9 expression by U937 mononuclear cells. Our studies showed that the geranylgeranyl transferase inhibitor inhibited LPS-stimulated MMP-1 expression, and addition of isoprenoid intermediate geranylgeranyl pyrophosphate (GGPP) reduced the inhibitory effect of simvastatin on LPS-stimulated MMP-1 expression. We also demonstrated that simvastatin inhibited the activation of Ras and Rac, and the inhibition was abolished by addition of GGPP. The above results indicate that protein isoprenylation is involved in the regulation of MMP-1 expression by LPS and simvastatin. Moreover, we showed that simvastatin inhibited LPS-stimulated nuclear AP-1, but not NF-kappaB activity, and the inhibition was reversed by addition of GGPP. Simvastatin also inhibited LPS-stimulated ERK but not p38 MAPK and JNK. Finally, we showed that the inhibition of LPS-stimulated ERK activation by simvastatin was reversed by GGPP. Taken together, this study showed that simvastatin suppresses LPS-induced MMP-1 expression in U937 mononuclear cells by targeting protein isoprenylation-mediated ERK activation.

Periodontal disease status in gullah african americans with type 2 diabetes living in South Carolina.

BACKGROUND: African Americans have a disproportionate burden of diabetes. Gullah African Americans are the most genetically homogeneous population of African descent in the United States, with an estimated European admixture of only 3.5%. This study assessed the previously unknown prevalence of periodontal disease among a sample of Gullah African Americans with diabetes and investigated the association between diabetes control and the presence of periodontal disease. METHODS: Two hundred thirty-five Gullah African Americans with type 2 diabetes were included. Diabetes control was assessed by percentage of glycosylated hemoglobin (HbA1c) and divided into three categories: well controlled, <7%; moderately controlled, 7% to 8.5%; and poorly controlled, >8.5%. Participants were categorized as healthy (no clinical attachment loss [AL] or bleeding on probing) or as having early periodontitis (clinical AL > or =1 mm in at least two teeth), moderate periodontitis (three sites with clinical AL > or =4 mm and at least two sites with probing depth [PD] > or =3 mm), or severe periodontitis (clinical AL > or =6 mm in at least two teeth and PD > or =5 mm in at least one site). Observed prevalences of periodontitis were compared to rates reported for the National Health and Nutrition Examination Survey (NHANES) studies. RESULTS: All subjects had evidence of periodontal disease: 70.6% had moderate periodontitis and 28.5% had severe disease. Diabetes control was not associated with periodontal disease. The periodontal disease proportions were significantly higher than the reported national prevalence of 10.6% among African Americans without diabetes. CONCLUSION: Our sample of Gullah African Americans with type 2 diabetes exhibited a higher prevalence of periodontal disease compared to African Americans, with and without diabetes, as reported in NHANES III and NHANES 1999-2000.

Five-year prospective clinical evaluation of highly crystalline HA MP-1-coated dental implants.

Contemporary plasma-sprayed hydroxylapatite (HA) coatings with high crystalline content are much more resistant to in vivo degradation than HA coatings of a decade ago but reportedly exhibit reduced wettability, which could potentially negatively affect tissue adhesion and long-term clinical outcome. The present prospective study was undertaken to determine if highly crystalline HA MP-1-coated implants could meet a minimum 5-year implant success rate standard of 85% in view of their previously reported decreased wettability. Study subjects were consecutive patients with 1 or more missing teeth in the maxillary and/or mandibular jaw who presented in 3 university dental clinics and 1 private dental practice. A total of 120 patients were treated per protocol and successfully restored with implant-supported prostheses. Four implants failed in 3 patients and were withdrawn from the study. There were no other irresolvable adverse events. Cumulative implant success at 5 years was 97% (n = 184 implants in 88 patients), which exceeded the 85% standard for implant success after 5 years of clinical function.

Interleukin-6 released from fibroblasts is essential for up-regulation of matrix metalloproteinase-1 expression by U937 macrophages in coculture: cross-talking between fibroblasts and U937 macrophages exposed to high glucose.

Matrix metalloproteinases (MMPs) play a key role in periodontal disease. Although it is known that macrophages and fibroblasts are co-localized and express MMPs in the diseased periodontal tissue, the effect of interaction between these two cell types on MMP expression has not been well elucidated. Furthermore although it is known that diabetes is associated with accelerated periodontal tissue destruction, it remains unknown whether hyperglycemia, a major metabolic abnormality in diabetes, regulates MMP expression by affecting the cross-talking between fibroblasts and macrophages. In this study, human gingival fibroblasts and U937 macrophages were cocultured in a two-compartment transwell culture system, and the cells were treated with normal or high glucose. We found that coculture of fibroblasts and U937 macrophages led to an augmentation of MMP-1 expression by U937 macrophages, and high glucose further enhanced this augmentation. Similar observations were also made in the coculture of fibroblasts and human primary monocytes. We also found that interleukin 6 (IL-6) released by fibroblasts was essential for the augmentation of MMP-1 expression by U937 macrophages. Furthermore our results showed that high glucose, IL-6, and lipopolysaccharide had a synergistic effect on MMP-1 expression. Finally our study indicated that MAPK pathways and activator protein-1 transcription factor were involved in the coculture- and high glucose-augmented MMP-1 expression. In conclusion, this study demonstrates that IL-6 derived from fibroblasts is essential for MMP-1 up-regulation by cross-talking between fibroblasts and U937 macrophages exposed to high glucose, revealing an IL-6-dependent mechanism in MMP-1 up-regulation.

High glucose enhances lipopolysaccharide-stimulated CD14 expression in U937 mononuclear cells by increasing nuclear factor kappaB and AP-1 activities.

We have demonstrated recently that high glucose augments lipopolysaccharide (LPS)-stimulated matrix metalloproteinase (MMP) and cytokine expression by U937 mononuclear cells and human monocyte-derived macrophages. Since CD14 is a receptor for LPS, one potential underlying mechanism is that high glucose enhances CD14 expression. In the present study, we determined the effect of high glucose on CD14 expression by U937 mononuclear cells. After being chronically exposed to normal or high glucose for 2 weeks or longer, cells were treated with LPS for 24 h. Real-time PCR showed that although high glucose by itself did not increase CD14 expression significantly, it augmented LPS-stimulated CD14 expression by 15-fold. Immunoassay showed a marked enhancement of both membrane-associated and soluble CD14 protein levels by high glucose. Further investigations using transcription factor activity assays and gel shift assays revealed that high glucose augmented LPS-stimulated CD14 expression by enhancing transcription factor nuclear factor kappaB (NFkappaB) and activator protein-1 (AP-1) activities. Finally, studies using anti-CD14 neutralizing antibody showed that CD14 expression is essential for the enhancement of LPS-stimulated MMP-1 expression by high glucose. Taken together, this study has demonstrated a robust augmentation by high glucose of LPS-stimulated CD14 expression through AP-1 and NFkappaB transcriptional activity enhancement, elucidating a new mechanism by which hyperglycemia boosts LPS-elicited gene expression involved in inflammation and tissue destruction.

Sodium lactate increases LPS-stimulated MMP and cytokine expression in U937 histiocytes by enhancing AP-1 and NF-kappaB transcriptional activities.

The plasma lactate concentration in patients with obesity and type 2 diabetes is often higher than that in nondiabetic individuals. Although it is known that increased lactate concentration is an independent risk factor for developing type 2 diabetes, the underlying mechanisms are not well understood. Because inflammation plays an important role in the development of type 2 diabetes, we postulated that increased lactate level might contribute to the pathogenesis of type 2 diabetes by enhancing inflammation. In the present study, we demonstrated that preexposure of U937 macrophage-like cells to sodium lactate increased LPS-stimulated matrix metalloproteinase (MMP)-1, IL-1beta, and IL-6 secretion. Augmentation of LPS-stimulated MMP-1 secretion was diminished when sodium lactate was replaced by lactic acid that reduced pH in the culture medium. Furthermore, quantitative real-time PCR indicated that the increased secretion of MMP-1, IL-1beta, and IL-6 was due to increased mRNA expression. To explore the underlying signaling mechanism, blocking studies using specific inhibitors for NF-kappaB and MAPK cascades were performed. Results showed that blocking of either NF-kappaB or MAPK pathways led to the inhibition of MMP-1, IL-1beta, and IL-6 expression stimulated by sodium lactate, LPS, or both. Finally, electrophoretic mobility shift assays showed a synergy between sodium lactate and LPS on AP-1 and NF-kappaB transcriptional activities. In conclusion, this study has demonstrated for the first time that sodium lactate and LPS exert synergistic effect on MMP and cytokine expression through NF-kappaB and MAPK pathways and revealed a novel mechanism potentially involved in the development of type 2 diabetes and its complications.

Pre-exposure to high glucose augments lipopolysaccharide-stimulated matrix metalloproteinase-1 expression by human U937 histiocytes.

BACKGROUND AND OBJECTIVES: It has been well established that patients with diabetes have increased prevalence and severity of periodontal diseases. However, the underlying mechanisms are not well understood. Given that bacterial infection is the primary cause of periodontal disease, we postulated that hyperglycemia may interplay with bacterial virulence factors such as lipopolysaccharide to up-regulate matrix metalloproteinase (MMP), leading to increased periodontal tissue destruction. METHODS AND RESULTS: We showed that prolonged pre-exposure of U937 histiocytes to high glucose markedly increased lipopolysaccharide-stimulated MMP-1 secretion and mRNA expression. Our results also showed that the effect of high glucose on lipopolysaccharide-induced MMP-1 expression is cell type-specific because no similar response was observed in human gingival fibroblasts. In addition to MMP-1, high glucose also augments lipopolysaccharide-stimulated MMP-7, -8, and -9 mRNA expression. In the investigation of the signaling pathways involved in the enhancement of lipopolysaccharide-induced MMP-1 expression by high glucose, we found that both high glucose and lipopolysaccharide regulate MMP-1 expression through the nuclear factor kappaB (NFkappaB) and mitogen-activated protein kinase (MAPK) cascades. CONCLUSIONS: The present study has shown that pre-exposure to high glucose and subsequent lipopolysaccharide treatment synergistically stimulates MMP-1 expression by mononuclear phagocytes through the NFkappaB and MAPK signaling pathways. This study has thus delineated a pathogenic mechanism that may be involved in the exacerbated periodontal disease in diabetic patients.