Dental methacrylates may exert genotoxic effects via the oxidative induction of DNA double strand breaks and the inhibition of their repair

Methacrylate monomers used in dentistry have been shown to induce DNA double strand breaks (DSBs), one of the most serious DNA damage. In the present work we show that a model dental adhesive consisting of 45% 2-hydroxyethyl methacrylate (HEMA) and 55% bisphenol A-diglycidyl dimethacrylate (Bis-GMA) at concentrations up to 0.25 mM Bis-GMA induced oxidative DNA in cultured primary human gingival fibroblasts (HGFs) as evaluated by the comet assay and probed with human 8-hydroxyguanine DNA-glycosylase 1. HEMA/Bis-GMA induced DSBs in HGFs as assessed by the neutral comet assay and phosphorylation of the H2AX histone and sodium ascorbate or melatonin (5-methoxy-N-acetyltryptamine) both at 50 μM reduced the DSBs, they also inhibited apoptosis induced by HEMA/Bis-GMA. The adhesive slowed the kinetics of the repair of DNA damage induced by hydrogen peroxide in HGFs, while sodium ascorbate or melatonin improved the efficacy of H2O2-induced damage in the presence of the methacrylates. The adhesive induced a rise in the G2/M cell population, accompanied by a reduction in the S cell population and an increase in G0/G1 cell population. Sodium ascorbate or melatonin elevated the S population and reduced the G2/M population. In conclusion, HEMA/Bis-GMA induce DSBs through, at least in part, oxidative mechanisms, and these compounds may interfere with DSBs repair. Vitamin C or melatonin may reduce the detrimental effects induced by methacrylates applied in dentistry

Fluctuation of bone turnover markers' levels in samples of gingival crevicular fluid after orthodontic stimulus: a systematic review.

BACKGROUND The aim of the present study was to provide an overview of gingival crevicular fluid (GCF) bone turnover markers (BTMs) concerning the physiology of orthodontic tooth movement (OTM) and assess their potential contributions to regulating bone remodeling, that could prove useful in designing future approaches to modulating orthodontic tooth movement. METHODS Multiple electronic databases (MEDLINE/PubMed, Ovid MEDLINE, Ovid Embase, LILACS, and Cochrane Library) were searched up to October 1st, 2020. Randomized controlled trials (RCTs), controlled clinical trials, observational studies of prospective and retrospective designs, and cross-sectional studies reporting on levels of BTMs in GCF were eligible for inclusion. The quality of the included RCTs was assessed per the revised Cochrane risk of bias tool for randomized trials (RoB 2.0), whereas the risk of bias of the included cohort studies was assessed using the Risk Of Bias In Non-randomized Studies of Interventions tool. RESULTS Five RCTs, 9 prospective cohort studies, and 1 cross-sectional study fulfilled the inclusion criteria. The risk of bias was deemed as high for the RCTs and 4 of the prospective studies and moderate for the rest of the studies. The following biomarkers for bone formation were assessed: bone alcaline phosphatase (BALP), alcaline phosphatase (ALP), and osteocalcin (OC). For bone resorption, the following BTMs were assessed: deoxypyridinoline (DPD) and pyridinoline (PYD), N-terminal telopeptide (NTX), osteopontin (OPN), and tartrate-resistant acid phosphatase (TRAP). The follow-up period ranged mainly from baseline to 45 days, although one study had an expanded follow-up period of up to 16 months. The results of the included studies comparing different BTMs were heterogeneous and qualitatively reported. CONCLUSIONS Current evidence continues to support the potential for BTMs to provide clinically useful information particularly for adjusting or standardizing the orthodontic stimulus. The present systematic review has retrieved studies of high, overall, risk of bias, and has unveiled a substantial clinical and methodological heterogeneity among included studies. Further data of the relationships between the clinical assays and the physiological or pre-analytical factors contributing to variability in BTMs' concentrations are required. SYSTEMATIC REVIEW REGISTRATION CRD42020212056

Oxidative stress inhibits the proliferation, induces premature senescence and promotes a catabolic phenotype in human nucleus pulposus intervertebral disc cells

Aged and degenerated intervertebral discs are characterised by a significant increase in the number of senescent cells, which may be associated with the deterioration of this tissue due to their catabolic phenotype. On the other hand, carboxymethyl-lysine has been found to be accumulated with ageing in the proteins of the disc, evidencing the existence of oxidative stress in this tissue. Accordingly, here we investigated the effect of oxidative stress on the physiology of human nucleus pulposus cells. Hydrogen peroxide (H2O2) at subcytotoxic concentrations transiently increased the intracellular levels of reactive oxygen species, activated the p38 MAPK, ERKs, JNKs and Akt signalling pathways and induced the nuclear translocation of NF-κΒ and Nrf2. It also provoked DNA damage and triggered a DNA repair response by activating the ATM-Chk2-p53-p21WAF1-pRb pathway, ultimately resulting in a G1 cell cycle delay and the decrease of cells’ proliferation. Prolonged exposure to H2O2 led to premature cellular senescence, as characterised by the inhibition of proliferation, the enhanced senescence-associated β galactosidase staining and the over-expression of known molecular markers, without though a significant decrease in the chromosome telomere length. H2O2-senescent cells were found to possess a catabolic phenotype, mainly characterised by the up-regulation of extracellular matrix-degrading enzymes (MMP-1, -2, -9 and ADAMTS-5) and the down-regulation of their inhibitors (TIMPs), as well as of several proteoglycans, including aggrecan, the major component of the nucleus pulposus. The senescent phenotype could be reversed by N-acetyl-L-cysteine, supporting the use of antioxidants for the improvement of disc physiology and the deceleration of disc degeneration

The effect of triethylene glycol dimethacrylate on p53-dependent G2 arrest in human gingival fibroblasts

Dental resin composites have been reported to exert adverse effects on cells of the oral cavity. In this study, we demonstrate that a non-cytotoxic concentration of the resin co-monomer triethylene glycol dimethacrylate (TEGDMA) results in the reduction of the proliferation rate of human gingival fibroblasts (HGFs), by delaying them at the G2 phase of the cell cycle, and in the sustained production of reactive oxygen species. These phenomena are accompanied by an early transient de-phosphorylation of ERK1/2 and JNKs and a late activation of the p53-p21WAF1-pRb molecular pathway. By using siRNA-mediated knocking down of the human p53 gene, we present evidence that the onco-suppressive protein p53 controls the TEGDMA-activated G2 checkpoint in HGFs and prevents their entry into mitosis, possibly in order to protect them from the detrimental genotoxic effects of the compound. © 2010 Elsevier Ltd

Mesenchymal stromal cells derived from whole human umbilical cord exhibit similar properties to those derived from Wharton’s jelly and bone marrow

Mesenchymal stromal cells (MSC) can be isolated from several regions of human umbilical cords, including Wharton's jelly (WJ), artery, vein or cord lining. These MSC appear to be immune privileged and are promising candidates for cell therapy. However, isolating MSC from WJ, artery, vein or cord lining requires time‐consuming tissue dissection. MSC can be obtained easily via briefly digesting complete segments of the umbilical cord, likely containing heterogenous or mixed populations of MSC (MC‐MSC). MC‐MSC are generally less well characterized than WJ‐MSC, but nevertheless represent a potentially valuable population of MSC. This study aimed to further characterize MC‐MSC in comparison to WJ‐MSC and also the better‐characterized bone marrow‐derived MSC (BM‐MSC). MC‐MSC proliferated faster, with significantly faster doubling times reaching passage one 8.8 days sooner and surviving longer in culture than WJ‐MSC. All MSC retained the safety aspect of reducing telomere length with increasing passage number. MSC were also assessed for their ability to suppress T‐cell proliferation and for the production of key markers of pluripotency, embryonic stem cells, tolerogenicity (CD40, CD80, CD86 and HLA‐DR) and immunomodulation (indoleamine 2,3‐dioxygenase [IDO] and HLA‐G). The MC‐MSC population displayed all of the positive attributes of WJ‐MSC and BM‐MSC, but they were more efficient to obtain and underwent more population doublings than from WJ, suggesting that MC‐MSC are promising candidates for allogeneic cell therapy in regenerative medicine

Complete genome sequence of the dairy isolate Streptococcus macedonicus ACA-DC 198

The species Streptococcus macedonicus is associated with the food environment, especially with fermented dairy products. Here we present the complete 2.1-Mb genome sequence of strain ACA-DC 198, which was isolated from naturally fermented Greek kasseri cheese

Effect of blue light on the proliferation of human gingival fibroblasts

Objectives: Previous studies have reported that blue light, under conditions similar to those used for orthodontic bonding, influences several aspects of cellular physiology. The purpose of this study was to investigate the effect of the exposure to blue light curing sources, i.e. halogen, light emitting diode (LED) and plasma arc irradiation, on the proliferation of human gingival fibroblasts. Methods: Primary cultures of human gingival fibroblasts were exposed to halogen, LED and plasma arc irradiation for 240, 180 and 120 s, respectively. The effect of blue light on DNA synthesis and cell proliferation was estimated by tritiated thymidine incorporation and direct cell counting, respectively. The possible involvement of an oxidative stress on the effect of blue light irradiation was studied by using N-acetyl-cysteine. Finally the formation of DNA double-strand breaks after irradiation was studied by immunofluorescence with an antibody against histone H2A.x phosphorylated in Ser139. Results: Blue light showed no immediate effect on the regulation of DNA synthesis. However, exposure of cells to these light sources inhibits cell proliferation measured one week after irradiation. This phenomenon is not attributed to the formation of DNA double strand breaks and cannot be annulled by N-acetyl-cysteine. Significance: The results presented here indicate a mild inhibition of gingival fibroblasts' proliferation after exposure to blue light and necessitate further study to clarify the exact mechanism underlying this effect. © 2007 Academy of Dental Materials

Fluctuation of bone turnover markers' levels in samples of gingival crevicular fluid after orthodontic stimulus: a systematic review

Background: The aim of the present study was to provide an overview of gingival crevicular fluid (GCF) bone turnover markers (BTMs) concerning the physiology of orthodontic tooth movement (OTM) and assess their potential contributions to regulating bone remodeling, that could prove useful in designing future approaches to modulating orthodontic tooth movement. Methods: Multiple electronic databases (MEDLINE/PubMed, Ovid MEDLINE, Ovid Embase, LILACS, and Cochrane Library) were searched up to October 1st, 2020. Randomized controlled trials (RCTs), controlled clinical trials, observational studies of prospective and retrospective designs, and cross-sectional studies reporting on levels of BTMs in GCF were eligible for inclusion. The quality of the included RCTs was assessed per the revised Cochrane risk of bias tool for randomized trials (RoB 2.0), whereas the risk of bias of the included cohort studies was assessed using the Risk Of Bias In Non-randomized Studies of Interventions tool. Results: Five RCTs, 9 prospective cohort studies, and 1 cross-sectional study fulfilled the inclusion criteria. The risk of bias was deemed as high for the RCTs and 4 of the prospective studies and moderate for the rest of the studies. The following biomarkers for bone formation were assessed: bone alcaline phosphatase (BALP), alcaline phosphatase (ALP), and osteocalcin (OC). For bone resorption, the following BTMs were assessed: deoxypyridinoline (DPD) and pyridinoline (PYD), N-terminal telopeptide (NTX), osteopontin (OPN), and tartrate-resistant acid phosphatase (TRAP). The follow-up period ranged mainly from baseline to 45 days, although one study had an expanded follow-up period of up to 16 months. The results of the included studies comparing different BTMs were heterogeneous and qualitatively reported. Conclusions: Current evidence continues to support the potential for BTMs to provide clinically useful information particularly for adjusting or standardizing the orthodontic stimulus. The present systematic review has retrieved studies of high, overall, risk of bias, and has unveiled a substantial clinical and methodological heterogeneity among included studies. Further data of the relationships between the clinical assays and the physiological or pre-analytical factors contributing to variability in BTMs' concentrations are required

Monitoring autophagy immunohistochemically and ultrastructurally during human head and neck carcinogenesis. Relationship with the DNA damage response pathway

Autophagy is a catabolic process that preserves cellular homeostasis. Its exact role during carcinogenesis is not completely defined. Specifically in head and neck cancer, such information from clinical settings that comprise the whole spectrum of human carcinogenesis is very limited. Towards this direction, we examined the in situ status of the autophagy-related factors, Beclin-1, microtubule-associated protein 1 light chain 3, member B (LC3B) and sequestosome 1/p62 (p62) in clinical material covering all histopathological stages of human head and neck carcinogenesis. This material is unique as each panel of lesions is derived from the same patient and moreover we have previously assessed it for the DNA damage response (DDR) activation status. Since Beclin-1, LC3B and p62 reflect the nucleation, elongation and degradation stages of autophagy, respectively, their combined immunohistochemical (IHC) expression profiles could grossly mirror the autophagic flux. This experimental approach was further corroborated by ultrastructural analysis, applying transmission electron microscopy (TEM). The observed Beclin-1/LC3B/p62 IHC patterns, obtained from serial sections analysis, along with TEM findings are suggestive of a declined authophagic activity in preneoplastic lesions that was restored in full blown cancers. Correlating these findings with DDR status in the same pathological stages are indicative of: (i) an antitumor function of autophagy in support to that of DDR, possibly through energy deprivation in preneoplastic stages, thus preventing incipient cancer cells from evolving; and (ii) a tumor-supporting role in the cancerous stage. © 2017 by the authors. Licensee MDPI, Basel, Switzerland

Comparative genomics of the dairy isolate Streptococcus macedonicus ACA-DC 198 against related members of the Streptococcus bovis/Streptococcus equinus complex

Background: Within the genus Streptococcus, only Streptococcus thermophilus is used as a starter culture in food fermentations. Streptococcus macedonicus though, which belongs to the Streptococcus bovis/Streptococcus equinus complex (SBSEC), is also frequently isolated from fermented foods mainly of dairy origin. Members of the SBSEC have been implicated in human endocarditis and colon cancer. Here we compare the genome sequence of the dairy isolate S. macedonicus ACA-DC 198 to the other SBSEC genomes in order to assess in silico its potential adaptation to milk and its pathogenicity status.Results: Despite the fact that the SBSEC species were found tightly related based on whole genome phylogeny of streptococci, two distinct patterns of evolution were identified among them. Streptococcus macedonicus, Streptococcus infantarius CJ18 and Streptococcus pasteurianus ATCC 43144 seem to have undergone reductive evolution resulting in significantly diminished genome sizes and increased percentages of potential pseudogenes when compared to Streptococcus gallolyticus subsp. gallolyticus. In addition, the three species seem to have lost genes for catabolizing complex plant carbohydrates and for detoxifying toxic substances previously linked to the ability of S. gallolyticus to survive in the rumen. Analysis of the S. macedonicus genome revealed features that could support adaptation to milk, including an extra gene cluster for lactose and galactose metabolism, a proteolytic system for casein hydrolysis, auxotrophy for several vitamins, an increased ability to resist bacteriophages and horizontal gene transfer events with the dairy Lactococcus lactis and S. thermophilus as potential donors. In addition, S. macedonicus lacks several pathogenicity-related genes found in S. gallolyticus. For example, S. macedonicus has retained only one (i.e. the pil3) of the three pilus gene clusters which may mediate the binding of S. gallolyticus to the extracellular matrix. Unexpectedly, similar findings were obtained not only for the dairy S. infantarius CJ18, but also for the blood isolate S. pasteurianus ATCC 43144.Conclusions: Our whole genome analyses suggest traits of adaptation of S. macedonicus to the nutrient-rich dairy environment. During this process the bacterium gained genes presumably important for this new ecological niche. Finally, S. macedonicus carries a reduced number of putative SBSEC virulence factors, which suggests a diminished pathogenic potential. © 2014 Papadimitriou et al.; licensee BioMed Central Ltd