Endothelial dysfunction in rats with ligature-induced periodontitis: Participation of nitric oxide and cycloxygenase-2-derived products.

OBJECTIVES: Considering the evident relationship between periodontitis and cardiovascular diseases in humans, we aimed to study the in vitro vascular reactivity of aorta rings prepared from rats with ligature-induced periodontitis. METHODS: Seven days after the induction of unilateral periodontitis, the animals were euthanised; rings were prepared from the descending abdominal aortas and mounted in tissue baths for the in vitro measurement of the isometric force responses to norepinephrine (NE) and acetylcholine (ACh), as well as in the presence of inhibitors of nitric oxide synthase (NOS) and cycloxygenase (COX) isoenzymes. Aortic COX and NOS gene expressions were analysed by RT-PCR, as well as protein COX-2 expression by Western blot. RESULTS: Periodontitis resulted in significant alveolar bone loss and did not affect arterial pressure. However, both NE-induced contraction and ACh-induced relaxation were significantly decreased and related to the presence of endothelium. Diminished eNOS and augmented COX-2 and iNOS expressions were found in the aortas from rats with periodontitis, and the pharmacological inhibition of COX-2 or iNOS improved the observed vasomotor deficiencies. CONCLUSIONS: We can thus conclude that periodontitis induces significant endothelial dysfunction in rat aorta which is characterized by decreased eNOS expression and mediated by upregulated iNOS and COX-2 products.

The H2S-releasing naproxen derivative, ATB-346, inhibits alveolar bone loss and inflammation in rats with ligature-induced periodontitis.

BACKGROUND: In experimental periodontitis, non-steroidal antiinflammatory drugs (NSAIDs) effectively inhibit the resultant alveolar bone loss. However, their deleterious gastric effects, observed in both animals and humans, dramatically limit their long-term use. It has been proven that the addition of a hydrogen sulfide (H2S)-releasing moiety to classical NSAID structures results in antiinflammatory compounds with improved gastric safeness. In this way, we decided to compare the effects of naproxen with its H2S-releasing derivative ATB-346 on ligature-induced periodontitis in rats. METHODS: Male Holtzman rats had a cotton ligature placed subgingivally around the lower right first molar during 7 days. During this period, groups of animals were daily treated with Na2S (a spontaneous H2S donor) or equimolar oral doses of naproxen (10 mg/kg) or ATB-346 (16 mg/kg). The mandibles were finally collected for histological analysis, radiographical measurements of alveolar bone loss and micro-computed tomography (µCT) analysis. Interleukin (IL)-1ß, IL-6 and IL-10 were quantified in gingiva samples, and the stomachs were also collected for scoring of tissue damage and measurement of myeloperoxidase (MPO, a marker of granulocyte infiltration). RESULTS: Ligature-induced bone loss was significantly inhibited by all the treatments, although only ATB-346 treatment resulted in significant inhibition of bone defect and other histological characteristics (such as flatness of the gingival epithelium, chronic inflammatory cell infiltration and loss of connective tissue in the gingival papillae). Both naproxen and ATB-346 inhibited the increase of gingival IL-1ß and IL-6 secondary to periodontitis, but IL-10 was unaffected. Significant damage and increased MPO contents were only found in the stomachs of the naproxen-treated animals. CONCLUSION: The H2S-releasing moiety in the ATB-346 compound not only does not impair the effects of the parent naproxen on periodontitis, but also improves bone quality and prevents the gastric mucosa damage due to prostaglandin inhibition, thus configuring a potentially new adjuvant therapy for periodontal diseases.

Correction: A critical role for suppressors of cytokine signaling 3 in regulating LPS-induced transcriptional activation of matrix metalloproteinase-13 in osteoblasts.

[This corrects the article DOI: 10.7717/peerj.51.].

A critical role for suppressors of cytokine signaling 3 in regulating LPS-induced transcriptional activation of matrix metalloproteinase-13 in osteoblasts.

Suppressor of cytokine signaling 3 (SOCS3) is a key regulator of cytokine signaling in macrophages and T cells. Although SOCS3 seems to contribute to the balance between the pro-inflammatory actions of IL-6 family of cytokines and anti-inflammatory signaling of IL-10 by negatively regulating gp130/Jak/Stat3 signal transduction, how and the molecular mechanisms whereby SOCS3 controls the downstream impact of TLR4 are largely unknown and current data are controversial. Furthermore, very little is known regarding SOCS3 function in cells other than myeloid cells and T cells. Our previous study demonstrates that SOCS3 is expressed in osteoblasts and functions as a critical inhibitor of LPS-induced IL-6 expression. However, the function of SOCS3 in osteoblasts remains largely unknown. In the current study, we report for the first time that LPS stimulation of osteoblasts induces the transcriptional activation of matrix metalloproteinase (MMP)-13, a central regulator of bone resorption. Importantly, we demonstrate that SOCS3 overexpression leads to a significant decrease of LPS-induced MMP-13 expression in both primary murine calvariae osteoblasts and a mouse osteoblast-like cell line, MC3T3-E1. Our findings implicate SOCS3 as an important regulatory mediator in bone inflammatory diseases by targeting MMP-13.

Mineral trioxide aggregate-based endodontic sealer stimulates hydroxyapatite nucleation in human osteoblast-like cell culture.

INTRODUCTION: The main purpose of this study was to evaluate the biocompatibility and bioactivity of a new mineral trioxide aggregate (MTA)-based endodontic sealer, MTA Fillapex (MTA-F; Angelus, Londrina, Brazil), in human cell culture. METHODS: Human osteoblast-like cells (Saos-2) were exposed for 1, 2, 3, and 7 days to MTA-F, Epiphany SE (EP-SE; SybronEndo, Orange, CA), and zinc oxide-eugenol sealer (ZOE). Unexposed cultures were the control group (CT). The viability of the cells was assessed by MTT assay and the morphology by scanning electron microscopy (SEM). The bioactivity of MTA-F was evaluated by alkaline phosphatase activity (ALP) and the detection of calcium deposits in the culture with alizarin red stain (ARS). Energy-dispersive X-ray spectroscopy (EDS) was used to chemically characterize the hydroxyapatite crystallites (HAP). Saos-2 cells were cultured for 21 days for ARS and SEM/EDS. ARS results were expressed as the number of stained nodules per area. Statistical analysis was performed with analysis of variance and Bonferroni tests (P < .01). RESULTS: MTA-F exposure for 1, 2, and 3 days resulted in increased cytotoxicity. In contrast, viability increased after 7 days of exposure to MTA-F. Exposure to EP-SE and ZOE was cytotoxic at all time points. At day 7, ALP activity increase was significant in the MTA-F group. MTA-F presented the highest percentage of ARS-stained nodules (MTA-F > CT > EP-SE > ZOE). SEM/EDS analysis showed hydroxyapatite crystals only in the MTA-F and CT groups. In the MTA-F group, crystallite morphology and chemical composition were different from CT. CONCLUSIONS: After setting, the cytotoxicity of MTA-F decreases and the sealer presents suitable bioactivity to stimulate HAP crystal nucleation.

Efeitos de drogas antiplaquetárias na doença periodontal / Effects of antiplatelet drugs in periodontal disease

A associação entre plaquetas, angiogênese e progressão ou reparo da doença periodontal tem sido pouco explorada e, consequentemente, os resultados são inconclusivos. As bactérias patogênicas presentes no sítio periodontal liberam endotoxinas que afetam a integridade endotelial e são capazes de induzir a produção de mediadores químicos derivados de proteínas plasmáticas e da coagulação sanguínea e ao mesmo tempo altera a função plaquetária. Há grande interesse na modulação da atividade das plaquetas nas alterações vasculares, especialmente cardiovasculares. Para isso, drogas antiplaquetárias que são comumente usadas na prevenção da doença tromboembólica, tais como infarto do miocárdio, isquemia cerebral e insuficiência arterial periférica, têm sido utilizadas. A aspirina é o único anti-inflamatório não esteroidal com atividade antiplaquetária. No periodonto, além de reduzir os níveis de citocinas inflamatórias, afeta significativamente o sangramento a sondagem, sugerindo uma modulação dose-dependente da periodontite. Em contrapartida, clopidogrel e ticlopidina são drogas derivadas da tienopiridina, sem ação anti-inflamatória conhecida, sugerindo-se que este benefício esteja relacionado a um efeito anti-inflamatório indireto correlacionado a sua atividade antiplaquetária já estabelecida. Na literatura, são escassas as informações a cerca do efeito destas drogas sobre o periodonto e desenvolvimento da doença periodontal. O uso de drogas antiplaquetárias hipoteticamente pode alterar a patogênese da periodontite e consequente reparação dos tecidos periodontais através do bloqueio da secreção de mediadores químicos que, de modo geral, são importantes na modulação do processo inflamatório e de reparo tecidual.