Cytotoxicity and Genotoxicity of Root Canal Sealers Based on Mineral Trioxide Aggregate

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

TEGDMA-induced oxidative DNA damage and activation of ATM and MAP kinases

The development of strategies for the protection of oral tissues against the adverse effects of resin monomers is primarily based on the elucidation of underlying molecular mechanisms. The generation of reactive oxygen species beyond the capacity of a balanced redox regulation in cells is probably a cause of cell damage. This study was designed to investigate oxidative DNA damage, the activation of ATM, a reporter of DNA damage, and redox-sensitive signal transduction through mitogen-activated protein kinases (MAPKs) by the monomer triethylene glycol dimethacrylate (TEGDMA). TEGDMA concentrations as high as 3-5 mm decreased THP-1 cell viability after a 24 h and 48 h exposure, and levels of 8-oxoguanine (8-oxoG) increased about 3- to 5-fold. The cells were partially protected from toxicity in the presence of N-acetylcysteine (NAC). TEGDMA also induced a delay in the cell cycle. The number of THP-1 cells increased about 2-fold in G1 phase and 5-fold in G2 phase in cultures treated with 3-5 mm TEGDMA. ATM was activated in THP-1 cells by TEGDMA. Likewise, the amounts of phospho-p38 were increased about 3-fold by 3 mm TEGDMA compared to untreated controls after a 24 h and 48 h exposure period, and phospho-ERK1/2 was induced in a very similar way. The activation of both MAPKs was inhibited by NAC. Our findings suggest that the activation of various signal transduction pathways is related to oxidative stress caused by a resin monomer. Signaling through ATM indicates oxidative DNA damage and the activation of MAPK pathways indicates oxidative stress-induced regulation of cell survival and apoptosis. (C) 2008 Elsevier Ltd. All rights reserved.

In vitro cytotoxicity of some natural and semi-synthetic isocoumarins from Paepalanthus bromelioides

Numerous natural compounds have a potential for therapeutic applications, but may have to be chemically modified to alter toxic side effects. We investigated structural parameters that could affect the cytotoxicity of isocoumarins similar to 9,10-dihydroxy-5,7-dimethoxy-1H-naphtho(2,3c)pyran-1-one (paepalantine 1). Paepalantine 1 has antimicrobial activity, as well as significant in vitro cytotoxic effects in the McCoy cell line. Two other natural and two semi-synthetic isocoumarins with similar structures obtained from the capitula of Paepalanthus bromelioides were tested on the same cell line by the neutral red assay. Substitution of the 9 and/or 10-OH group made these compounds less cytotoxic.

A complexa fisiopatologia dos episódios vasooclusivos na anemia falciforme

Hemolytic anemia and vasoocclusion are the cardinal clinical features of sickle cell anemia. Vasoocclusion is a complex process involving not only the polymerization of deoxygenated sickle hemoglobin tetramers, but also interactions between sickle erythrocytes, vascular endothelium, platelets, leukocytes, and plasma proteins. The increased adherence of sickle erythrocytes to endothelium has been implicated as an early step in vasoocclusion. Other researchers have focused on leukocytes and platelets which might also contribute to disturbed blood flow. Microvascular occlusion results in acute painful crises, whereas macrovascular occlusion seems to be the cause of organ failure. The anemia results from the markedly shortened circulatory survival of sickle erythrocytes, together with a limited erythropoietic response. The erythropoiesis increases intensively, but it is not enough to balance the increased rate of erythrocytes destruction to maintain normal levels of total erythrocytes and hemoglobin concentrations; mainly by the low oxygen affinity of hemoglobin S and increased 2,3-Diphosphoglycerate. It is very difficult to separate processes leading to anemia or to vasoocclusion. Understanding the involvement of multiple blood componentes in vasoocclusion may elucidate the clinical manifestations and complications of sickle cell anemia, and may give new insights into the preventive and curative therapy.

Apoptose em otorrinolaringologia e cabeça e pescoço

This paper intend to review recent advances in our understanding of programmed cell death, or apoptosis, and discuss implications of these basic science advances in the development of causes and potential treatments of a variety of diseases of the head and neck. Conclusions: apoptosis is now understood to be important in the normal development and survival of all multicellular organism. Deregulation of this normally tighly controlled process underlies a variety of disease states, including neoplasia, autoimmune disease, and disorders of the central nervous system. A better understanding of this process and regulation may help otolaryngologists better understand diseases relevant to this specialty and will lead to improved therapeutic interventions.

Lack of genotoxicity of formocresol, paramonochlorophenol, and calcium hydroxide on mammalian cells by comet assay

Formocresol, paramonochlorophenol, and calcium hydroxide are widely used in dentistry because of their antibacterial activities in root canal disinfection. However, the results of genotoxicity studies using these materials are inconsistent in literature. The goal of this study was to examine the genotoxic potential of formocresol, paramonochlorophenol, and calcium hydroxide using mouse lymphoma cells and human fibroblasts cells in vitro by the comet assay. Data were assessed by Kruskal-Wallis nonparametric test. The results showed that all compounds tested did not cause DNA damage for the tail moment or tail intensity parameters. These findings suggest that formocresol, paramonochlorophenol, and calcium hydroxide do not promote DNA damage in mammalian cells and that the comet assay is a suitable tool to investigate genotoxicity.

Benzopyrans from Curvularia sp., an endophytic fungus associated with Ocotea corymbosa (Lauraceae)

An isolate of Curvularia sp. was obtained from the leaves of Ocotea corymbosa, a native plant of the Brazilian Cerrado. The ethyl acetate extract from culture of this fungus afforded two benzopyran derivatives: (2′S)-2-(propan-2′-ol)-5-hydroxy-benzopyran-4-one (2) and 2,3-dihydro-2-methyl-benzopyran-4,5-diol (4); and two known benzopyrans: 2-methyl-5-methoxy-benzopyran-4-one (1) and (2R)-2,3-dihydro-2-methyl-5-methoxy- benzopyran-4-one (3). The structures of 2 and 4 were established on the basis of comprehensive spectroscopic analysis, mainly using 1D and 2D NMR experiments. The benzopyrans 1 and 2 showed weak in vitro antifungal activity against Cladosporium sphaerospermum and C. cladosporioides. Analyses of the biological activities were also carried out on HeLa (human cervix tumor) and CHO (Chinese hamster ovary) cells, aiming to evaluate their potential effects on mammalian cell line proliferation. Results from both cell lines indicated that compound 2 was able to induce cell proliferation: 70% on HeLa cells and 25% on CHO cells. © 2005 Elsevier Ltd. All rights reserved.

Immune Response to the Rhodococcus equi infection in high and low antibody-producing mice (selection IV-A)

Rhodococcus equi is a Gram-positive, facultative intracellular bacterium which infects macrophages and causes rhodococcal pneumonia and enteritis in foals. Recently, this agent has been recognized as an opportunistic pathogen for immunocompromised humans. Several murine experimental models have been used to study R. equi infection. High (H IV-A) and Low (L IV-A) antibody (Ab)-producers mice were obtained by bi-directional genetic selections for their ability to produce antibodies against sheep and human erythrocytes (Selection IV-A). These lines maintain their phenotypes of high and low responders also for other antigens than those of selection (multispeciflc effect). A higher macrophage activity in L IV-A mice has been described for several intracellular infectious agents, which could be responsible for their intense macrophage antigens (Ag)-handling and low Ab production. Due to these differences, L IV-A mice were found to exhibit a better performance to trigger an effective immune response towards intracellular pathogens. The objective of this work was to characterize the immune response of Selection IV-A against R. equi. H IV-A and L IV-A mice were infected with 2.0 × 10 6 CFU of ATCC 33701 +R. equi by intravenous route. With regards to bacterial clearance and survival assays, L IV-A mice were more resistant than H IV-A mice to virulent R. equi. L IV-A mice presented a higher hydrogen peroxide (H 2O 2) and nitric oxide (NO) endogenous production by splenic macrophages than H IV-A mice. L IV-A expressed the most intense cellular response, available by the Delayed-Type Hypersensitivity (DTH) reaction, which activated macrophages and produced more H 2O 2 and NO. The three times higher specific antibodies titres in H IV-A indicated that Selection IV-A maintained the multispecific effect and the polygenic control of humoral and cellular responses also to R. equi.

Effects of acetylsalicylic acid and acetic acid solutions in VX2 carcinoma cells. In vitro analysis

Purpose: To analyze, in vitro, the effects of acetylsalicylic acid (aspirin) and acetic acid solutions on VX2 carcinoma cells in suspension and to examine the correlation between these effects and neoplastic cell death. Methods: The VX2 tumor cells (107 cells/ml) were incubated in solutions containing differing concentrations (2.5% and 5%) of either acetylsalicylic acid or acetic acid, or in saline solution (controls). Every five minutes, cell viability was tested (using the trypan blue test) and analyzed under light microscopy. Results: Tumor cell viability (in %) decreased progressively and, by 30 minutes, neoplastic cell death had occurred in all solutions. Conclusion: Based on this experimental model and the methodology employed, we conclude that these solutions cause neoplastic cell death in vitro.

Genotoxicity in primary human peripheral lymphocytes after exposure to regular and white mineral trioxide aggregate

Objective: Taking into consideration that DNA damage plays an important role in carcinogenesis, the purpose of this study was to evaluate whether regular and white mineral trioxide aggregate (MTA) are able to induce genetic damage in primary human cells. Study design: Human peripheral lymphocytes obtained from 10 healthy volunteers were exposed to 2 presentation forms of MTA at final concentrations ranging from 1 to 1000 μg/mL for 1 hour at 37°C. The negative control group was treated with vehicle control (phosphate buffer solution, PBS) for 1 hour at 37°C and the positive control group was treated with hydrogen peroxide (at 100 μM) for 5 minutes on ice. Results were analyzed by the Friedman nonparametric test. Results: The results pointed out that either regular or white MTA in all concentrations tested did not induce DNA breakage in human peripheral lymphocytes as depicted by the mean tail moment. Conclusion: In summary, our results indicate that exposure to MTA may not be a factor that increases the level of DNA lesions in human peripheral lymphocytes as detected by single cell gel (comet) assay. © 2006 Mosby, Inc. All rights reserved.

Inhibition of eukaryotic translation initiation factor 5A (eIF5A) hypusination impairs melanoma growth

The eukaryotic translation initiation factor 5A (eIF5A) undergoes a specific post-translational modification called hypusination. This modification is required for the functionality of this protein. The compound N1-guanyl-1,7-diaminoheptane (GC7) is a potent and selective inhibitor of deoxyhypusine synthase, which catalyses the first step of eIF5A hypusination process. In the present study, the effects of GC7 on cell death were investigated using two cell lines: melan-a murine melanocytes and Tm5 marine melanoma. In vitro treatment with GC7 increased by 3-fold the number of cells presenting DNA fragmentation in Tm5 cells. Exposure to GC7 also decreased viability to both cell lines. This study also describes, for the first time, the in vivo antitumour effect of GC7, as indicated by impaired melanoma growth in C57BL/6 mice. Copyright © 2006 John Wiley & Sons, Ltd.

Induction of chromosome aberrations in the Allium cepa test system caused by the exposure of seeds to industrial effluents contaminated with azo dyes

Numerous potentially mutagenic chemicals have been studied mainly because they can cause damaging and inheritable changes in the genetic material. Several tests are commonly used for biomonitoring pollution levels and to evaluate the effects of toxic and mutagenic agents present in the natural environment. This study aimed at assessing the potential of a textile effluent contaminated with azo dyes to induce chromosomal and nuclear aberrations in Allium cepa test systems. A continuous exposure of seeds in samples of the textile effluent in different concentrations was carried out (0.3%, 3%, 10%, and 100%). Cells in interphase and undergoing division were examined to assess the presence of chromosome aberrations, nuclear changes, and micronuclei. Our results revealed a mutagenic effect of the effluent at concentrations of 10% and 100%. At lower concentrations, the effluent (3% and 0.3%) did not induce mutagenic alterations in the test organism A. cepa. These findings are of concern, since cell damage may be transmitted to subsequent generations, possibly affecting the organism as a whole, as well as the local biota exposed to the effluent discharge. If the damage results in cell death, the development of the organism may be affected, which could also lead to its death. © 2008 Elsevier Ltd. All rights reserved.

Identification of ellagic acid derivatives in methanolic extracts from Qualea species

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Inhibition of human neutrophil apoptosis by Paracoccidioides brasiliensis: Role of interleukin-8

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by Paracoccidiodes brasiliensis that presents a wide spectrum of clinical manifestations. Because of the great number of neutrophils polymorphonuclear neutrophils (PMN) found in the P. brasiliensis granuloma, studies have been done to evaluate the role of these cells during the development of the infection. This fungus is found intracellularly in PMN and monocytes/macrophages, suggesting that it is capable of evading damage and surviving inside these cells. Thus, in the present study, we investigated whether P. brasiliensis can prolong the lifetime of PMN, and if this process would be related with IL-8 levels. PMN apoptosis and intracellular levels of IL-8 were analysed by flow cytometry and culture supernatants IL-8 levels were evaluated by enzyme-linked immunosorbent assay. We found that coincubation with P. brasiliensis yeast cells results in an inhibition of PMN apoptosis, which was associated with increase in IL-8 production by these cells. Cocultures treatment with monoclonal antibody anti-IL-8 reversed the inhibitory effect of P. brasiliensis on PMN apoptosis, besides to increase spontaneous apoptosis of these cells. These data show that, in contrast to other microbial pathogens that drive phagocytes into apoptosis to escape killing, P. brasiliensis can extend the lifetime of normal human PMN by inducing autocrine IL-8 production. © 2008 The Authors.