2-Hydroxyethyl methacrylate inflammatory effects in human gingival fibroblasts

Methacrylate Ester Monomers

The Expert Panel for Cosmetic Ingredient Safety reviewed newly available studies since their original assessment in 2005, along with updated information regarding product types and concentrations of use, and confirmed that these 22 methacrylate ester monomers are safe as used in nail enhancement products in the practices of use and concentration as described in this report, when skin contact is avoided.

The Effects of Thermocycling on the Physical Properties and Biocompatibilities of Various CAD/CAM Restorative Materials

The purpose of this study is to evaluate the changes in physical properties and biocompatibilities caused by thermocycling of CAD/CAM restorative materials (lithium disilicate, zirconia reinforced lithium silicate, polymer-infiltrated ceramic network, resin nanoceramic, highly translucent zirconia). A total of 225 specimens were prepared (12.0 × 10.0 × 1.5 mm) and divided into three groups subjected to water storage at 37 °C for 24 h (control group), 10,000 cycles in distilled water at 5-55 °C (first aged group), and 22,000 cycles in distilled water at 5-55 °C (second aged group) [(n= 15, each]). The nanoindentation hardness and Young's modulus (nanoindenter), surface roughness (atomic force microscopy (AFM)), surface texture (scanning electron microscopy (FE-SEM)), elemental concentration (energy dispersive spectroscopy (EDS)) and contact angle were evaluated. The morphology, proliferation and adhesion of cultured human gingival fibroblasts (HGFs) were analyzed. The data were analyzed using one-way ANOVA and Tukey's test (p < 0.05). The results showed that the nanoindentation hardness and Young's modulus were decreased after thermocycling aging. Cell viability and proliferation of the material decreased with aging except for the highly translucent zirconia. Zirconia-reinforced lithium silicate exhibited significantly lower cell viability compared to other materials. The surface roughnesses of all groups increased with aging. Cell viability and Cell adhesion were influenced by various factors, including the surface chemical composition, hydrophilicity, surface roughness, and topography.

Cytotoxicity and Apoptotic Mechanism of 2-Hydroxyethyl Methacrylate via Genotoxicity and the Mitochondrial-Dependent Intrinsic Caspase Pathway and Intracellular Reactive Oxygen Species Accumulation in Macrophages

Macrophages are mainly active cells of the immune system and play a role in the defense of pathogens. However, the overactivation of macrophages by fatal pathogens can result in toxic responses. 2-hydroxyethyl methacrylate (HEMA), which is a hydrophilic monomer, is used in dental adhesive reagents and composite resins as well as biocompatible hydrogels. The mechanisms underlying the genotoxicity engendered by HEMA-induced apoptosis that leads to cytotoxicity remain unclear. Accordingly, this study was conducted to clarify such mechanisms. The results showed that HEMA induced cell toxicity in RAW264.7 macrophages depending on the concentration. A higher HEMA concentration was associated with a higher level of apoptosis and genotoxicity. Moreover, HEMA induced a concentration-dependent increase in mitochondrial dysfunction and the intrinsic caspase pathway, including the activation of caspase-3 and caspase-9. HEMA was also found to upregulate intracellular reactive oxygen species generation and to decrease the activity of antioxidant enzymes, including superoxide dismutase and catalase. Taken together, the mitochondrial-dependent intrinsic caspase pathway and intracellular reactive oxygen species accumulation were found to mediate HEMA-induced genotoxicity and apoptosis, leading to cytotoxicity in RAW264.7 macrophages.

Iatrogenic acid-induced gingival recession during crown cementation: A case report

Accidental contact of various chemicals in dentistry may cause damage to the gingiva. A male patient presented for a full mouth rehabilitation with ceramic crowns. The patient underwent the steps of ceramic crown preparation uneventfully. At the time of crown delivery, cotton rolls were placed in several vestibular areas for isolation. They were regularly changed during different steps of etching and cementation process, which included the use of Multilink Primer B (Ivoclar Vivadent™). On removal of the cotton roll in the area of upper right canine, the gingival tissues appeared blanched and grayish white. The cotton roll was found to have absorbed some etching material in it. As the patient was asymptomatic, he was dismissed. Two weeks later, the patient presented with inflammation and gingival recession in the same area. Initially, he was treated palliatively, and subsequently, he received a connective tissue graft on the upper right canine. This case report showed that acid etching material used during the prosthodontic cementation may have caused a gingival recession, which was successfully treated with tunnel flap and connective tissue graft. Optimal isolation of the operative field should be performed to avoid this problem.

The Effect of Selected Dental Materials Used in Conservative Dentistry, Endodontics, Surgery, and Orthodontics as Well as during the Periodontal Treatment on the Redox Balance in the Oral Cavity

Oxidative stress (OS) is a redox homeostasis disorder that results in oxidation of cell components and thus disturbs cell metabolism. OS is induced by numerous internal as well as external factors. According to recent studies, dental treatment may also be one of them. The aim of our work was to assess the effect of dental treatment on the redox balance of the oral cavity. We reviewed literature available in PubMed, Medline, and Scopus databases, including the results from 2010 to 2020. Publications were searched according to the keywords: oxidative stress and dental monomers; oxidative stress and amalgam; oxidative stress and periodontitis, oxidative stress and braces, oxidative stress and titanium; oxidative stress and dental implants, oxidative stress and endodontics treatment, oxidative stress and dental treatment; and oxidative stress and dental composite. It was found that dental treatment with the use of composites, amalgams, glass-ionomers, materials for root canal filling/rinsing, orthodontic braces (made of various metal alloys), titanium implants, or whitening agents can disturb oral redox homeostasis by affecting the antioxidant barrier and increasing oxidative damage to salivary proteins, lipids, and DNA. Abnormal saliva secretion/composition was also observed in dental patients in the course of OS. It is suggested that the addition of antioxidants to dental materials or antioxidant therapy applied during dental treatment could protect the patient against harmful effects of OS in the oral cavity.

Organic Eluates Derived from Intermediate Restorative Dental Materials

A great number of different types of materials have been used in dentistry as intermediate restoratives. Among them, new resin-based bases have been released in the dental market. The present study focuses on the identification of the organic eluates released from such materials and the study of their surface microstructure in combination with their corresponding elemental composition. For this purpose, the following materials were used:ACTIVA™BioACTIVE-BASE/LINER™, Ketac™Bond Glass Ionomer, SDR™ and Vitrebond™Light Cure Glass Ionomer Liner/Base. Methanolic leachates derived from polymerized materials were analyzed by means of gas chromatography-mass spectrometry (GC-MS). Scanning electron microscopy(SEM) was used for the surface monitoring of suitably prepared specimens. The GC-MS analysis revealed the elution of twenty different substances from the three resin-based materials, while none was eluted from the glass ionomer base. The SEM analysis for Vitrebond™ presented small pits, the one for Ketac™Bond presented elongated cracks, while no voids were present for ACTIVA™BioACTIVE-BASE/LINER™ and SDR™. Moreover, the resin matrix of some dental materials may inhibit elements' accumulation on the surface layers. Particularly, the detected organic eluents may be related to potential toxic effects.

Oleic acid and hydroxytyrosol present in olive oil promote ROS and inflammatory response in normal cultures of murine dermal fibroblasts through the NF-κB and NRF2 pathways

Few studies have evaluated the effects of olive oil on normal tissues like skin and its components. Hence, we investigated whether olive oil could increase the production of ROS and oxidative damage in murine dermal fibroblast cultures in a short-term exposition. In addition, we evaluated the role of oleic acid and hydroxytyrosol, which are the two most important components of olive oil, in the associated mechanisms of action, and the metabolism of long-chain fatty acids from olive oil. To study this, neonatal murine dermal fibroblasts (NMDF) were incubated with olive oil, oleic acid, or hydroxytyrosol for 24 or 72 h. The NMDF incubated with olive oil or oleic acid showed an increase in the production of ROS after 24 h, lipid peroxidation, and protein carbonylation after 72 h, as well as increased expression of nuclear factor-kappa B (NF-κB) p65 and cyclooxygenase-2 (COX-2) after 72 h. However, NMDF treated with olive oil or hydroxytyrosol demonstrated an increase in the expression of nuclear factor-erythroid2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1) after 72 h. In addition, NMDF treated with olive oil also showed an increase in the protein expression of diacylglycerol acyltransferase1 (DGAT1), which promotes triacylglycerol synthesis, and in the levels of triacylglycerols. The microscopic analysis showed Nile red-positive lipid droplets inside olive oil-treated NMDF after 72 h. Moreover, gas chromatography-mass spectrometry demonstrated high levels of oleic acid in the olive oil-treated NMDF after 72 h. In conclusion, oleic acid present in the olive oil promotes the production of ROS and oxidative damage in murine dermal fibroblasts, which leads to NF-κB p65 and COX-2 expression, while hydroxytyrosol promotes NRF2 and HO-1 expression. In addition, NMDF area capable of absorbing long-chain fatty acids derived from olive oil, which promotes the synthesis and the accumulation of triacylglycerols into cytoplasm of NMDF through DGAT1 activation.

Establishing a macrophage model with relevance for oral methacrylate monomer exposures: Attenuated Staphylococcus aureus-induced cytokine release from human macrophages

BACKGROUND

Leakage of unpolymerized methacrylate monomers after placement of methacrylate-containing polymeric dental materials leads to human exposure. Based on studies using murine macrophages and LPS from Escherichia coli (E. coli), dental monomers like 2-hydroxyethyl methacrylate (HEMA) are known to inhibit lipopolysaccharide (LPS) induced cytokine release. The aim of this study was to establish a model system with relevance for human oral monomer exposure using exposure to live gram-positive bacteria, and to confirm the HEMA-induced effects on cytokine release in this model.

METHODS

The human THP-1 monocyte cell line was differentiated to macrophages using phorbol 12-myristate 13-acetate (PMA), before exposure to 0.5-2mM HEMA and live Staphylococcus aureus (S. aureus) in various multiplicity of infections (MOI). Cytokine release and cytotoxicity were determined after (i) 2-24h pre-exposure to HEMA followed by 2-4h S. aureus exposure and (ii) 2-4h simultaneous exposure. The 24h pre-exposure regime was also tested in primary human airway macrophages and for phagocytosis of S. aureus in THP-1 macrophages.

RESULTS

HEMA attenuated the cytokine release more strongly in the pre-exposure than combined exposure regime, with a maximal reduction of 95% in the S. aureus-induced cytokine release. A MOI of 0.1 (corresponding to a bacteria-macrophage ratio of 1:10) was determined to be optimal in the THP-1 macrophages as it induced sufficient cytokine release and negligible cytotoxicity. Attenuated release of S. aureus-induced interleukin (IL)-1β after HEMA exposure was confirmed in primary airway macrophages, while HEMA increased the phagocytosis of S. aureus in THP-1 cells.

CONCLUSION

The model was successfully established and attenuated bacteria-induced cytokine release after HEMA exposure confirmed.

Pulp Fibroblast Cell Apoptosis After Application of Hema Dentine Bonding Material with Ethanol and Water Solvent

The most common main materials for dentin bonding for composite resin restoration is 2-hydroxyethyl methacrylate (HEMA). HEMA has beneficial physical and chemical properties, and stable, yet toxic. The addition of ethanol or water, may reduce the toxic effect of HEMA. Ethanol solvent has lower H-bonding capacity compared to water solvent, so it can bind less free radicals from the residual monomer. This study aimed to analyze apoptosis due to dentine bonding application with ethanol and water solvent. Fibroblast culture cells were obtained from extracted third molar, by means of tripsinasion method. The cells were divided into 4 groups as reached confluent: cell culture without treatment as control, cell culture with scaffold chitosan, cell culture with scaffold and polymerized dentin bonding with ethanol or water solvent. Apoptosis observation was conducted using immunohistochemistry method with ethidium bromide acridin orange staining, under fluorescent microscope with 40´ magnification. There was a significant difference among groups (p=0.0001), yet no differences found between different solvent. Apoptosis rate in fibroblast cells culture exposed to HEMA bonding with ethanol solvent was 67%, while the cells exposed to HEMA bonding with water solvent was 44%. The effect of dentin bonding with ethanol solvent and water solvent towards apoptosis rate of pulp fibroblast cells is not different.

Effects of HEMA on Nrf2-related gene expression using a newly developed 3D co-culture model of the oral mucosa

OBJECTIVE

2-Hydroxyethyl methacrylate (HEMA) is a component of many resin-modified materials and elutes from dental restorations into the oral cavity. Objective of our investigation was to determine the impact of HEMA on oral keratinocytes (OKF6/TERT2) and gingival fibroblasts (HGFs) in a newly established 3D co-culture model (3D-CCM) and to analyze the permeability of OKF6/TERT2 cells for HEMA.

METHODS

Well-characterized 3D-CCMs, consisting of confluent OKF6/TERT2 cells on cell culture inserts above HGF-containing collagen gels, were treated supra-epithelial with HEMA. Mass spectrometry was used to measure the supra- and sub-epithelial distribution of HEMA after 24 h. The impact of HEMA on nuclear factor erythroid 2-related factor 2 (Nrf2) target genes was measured by qRT-PCR and western blot analysis.

RESULTS

Mass spectrometry showed that HEMA was evenly distributed above and below the keratinocyte layer after 24 h. Analyzed target genes of Nrf2 were induced in both cell types on the mRNA-level but less pronounced in HGFs. On the protein-level, both cell types showed similar effects: At 5 mM HEMA, heme oxygenase-1 was induced 5.1-fold in OKF6/TERT2 cells and 4.1-fold in HGFs. NAD(P)H quinone dehydrogenase-1 was approximately induced 1.85-fold in both cell types.

SIGNIFICANCE

Our 3D-CCM is suitable to analyze the biocompatibility of dental materials due to an improved simulation of the oral mucosa compared to monolayer cultures. Our results indicate that HEMA is able to penetrate a dense layer of keratinocytes and to activate the cellular oxidative defense response. This may be due to the activation of the Nrf2-pathway in both cell types.

Functions of transcription factors NF-κB and Nrf2 in the inhibition of LPS-stimulated cytokine release by the resin monomer HEMA

OBJECTIVE

Resin monomers like 2-hydroxyethyl methacrylate (HEMA) interfere with effects induced by stressors such as lipopolysaccharide (LPS) released from cariogenic microorganisms. In this study, mechanisms underlying monomer-induced inhibition of the LPS-stimulated secretion of inflammatory cytokines from immunocompetent cells were investigated.

METHODS

Secretion of pro-inflammatory cytokines TNF-α, IL-6 and the anti-inflammatory IL-10 from RAW264.7 mouse macrophages exposed to LPS and HEMA (0-6-8mM) was determined by ELISA. The formation of reactive oxygen (ROS) and nitrogen species (RNS) was determined by flow cytometry (FACS) after staining of cells with specific fluorescent dyes. Cell viability was analyzed by FACS, and protein expression was detected by Western blotting.

RESULTS

Secretion of TNF-α, IL-6 and IL-10 from LPS-stimulated cells increased after a 24h exposure. A HEMA-induced decrease in cytokine secretion resulted from the inhibition of LPS-stimulated NF-κB activation. Nuclear translocation of NF-κB was inhibited possibly as a result of enhanced levels of hydrogen peroxide (H₂O₂) and nitric oxide (NO) in HEMA-exposed cells. Oxidative stress caused by HEMA-induced formation of H₂O₂ and LPS-stimulated peroxynitrite (ONOO) also enhanced nuclear expression of Nrf2 as the major regulator of redox homeostasis, as well as Nrf2-controlled stress protein HO-1 to inhibit NF-κB activity. HEMA inhibited the LPS-stimulated expression of NOS (nitric oxide synthase) to produce NO but counteracted the expression of Nox2, which forms superoxide anions that combine with NO to peroxynitrite.

CONCLUSIONS

Resin monomers like HEMA inhibit LPS-stimulated NF-κB activation essential for cytokine release as a crucial response of immunocompetent cells of the dental pulp to invading cariogenic pathogens.

Biological Activities and Potential Oral Applications of N-Acetylcysteine: Progress and Prospects

N-Acetylcysteine (NAC), a cysteine prodrug and glutathione (GSH) precursor, has been used for several decades in clinical therapeutic practices as a mucolytic agent and for the treatment of disorders associated with GSH deficiency. Other therapeutic activities of NAC include inhibition of inflammation/NF-κB signaling and expression of proinflammatory cytokines. N-Acetylcysteine is also a nonantibiotic compound possessing antimicrobial property and exerts anticarcinogenic and antimutagenic effects against certain types of cancer. Recently, studies describing potentially important biological and pharmacological activities of NAC have stimulated interests in using NAC-based therapeutics for oral health care. The present review focused on the biological activities of NAC and its potential oral applications. The potential side effects of NAC and formulations for drug delivery were also discussed, with the intent of advancing NAC-associated treatment modalities in oral medicine.

Transcriptome modifications in human gingival fibroblasts exposed to 2-hydroxyethyl methacrylate

2-Hydroxyethyl methacrylate (HEMA),a tooth filling material, was proven to have toxic effects on different cell types, including human gingival fibroblasts (HGFs), and to be able to influence odontoblast vitality. The aim of the present study was to assess the differential transcriptome modulation induced by low HEMA concentration in cultured HGFs. RNA extracted from cultured HGFs exposed to 3 mmol/l HEMA for 24 or 96 h underwent a whole genome microarray analysis. Data analysis showed the presence of two gene clusters, composed by 310 transcripts differentially expressed after 24- and 96-h HEMA treatment compared to controls. Functional analysis demonstrated that these transcripts are mainly involved in cellular survival and death, and inflammatory response. The study highlighted an overall damage induced by HEMA exposure at both 24 and 96 h, mainly leading to a proliferation impairment. Interestingly, 24-h HEMA treatment seems to induce the cells to trigger repair mechanisms, evidencing an early compensatory response, whereas 96-h incubation appears to cause the occurrence of apoptosis as a consequence of the chronic damage.

Psychological stress-induced catecholamines accelerates cutaneous aging in mice

Psychological stress may be an important extrinsic factor which influences aging process. However, neither study demonstrated the mechanism by which chronic stress participates in skin aging. Aim of this study was to investigate the effects of chronic psychological stress on mice skin. Mice were daily submitted to rotational stress, for 28 days, until euthanasia. After 28 days, mice were killed and normal skin was analyzed. Macroscopically, dorsum skin of chronically stressed mice presented more wrinkled when compared to that of nonstressed mice. In mice skin, chronic stress increased lipid peroxidation, carbonyl protein content, nitrotyrosine levels, neutrophil infiltration, neutrophil elastase, tissue inhibitor of metalloproteinase-1 and metalloproteinase-8 levels. Nevertheless, chronic stress reduced dermis thickness, collagen type I, fibrilin-1 and elastin protein levels in mice skin. In in vitro assays, murine skin fibroblasts were exposed to elevated epinephrine levels plus inhibitors of reactive oxygen species (ROS) and reactive nitrogen species (RNS), fibroblast activity was evaluated in a short time. In skin fibroblast culture, treatment with inhibitors of ROS and RNS synthesis abolished the increase in carbonyl protein content and lipid peroxide accumulation induced by epinephrine. In conclusion, chronic psychological stress may be an important extrinsic factor, which contributes to skin aging in mice.

Proliferation and adhesion capability of human gingival fibroblasts onto zirconia, lithium disilicate and feldspathic veneering ceramic in vitro

Human gingival fibroblasts (HGFs) were cultured onto CAD/CAM zirconia (Group A), CAD/CAM zirconia after polishing (Group B), CAD/CAM lithium disilicate after polishing (Group C), and feldspathic ceramic (Group D) to evaluate their proliferation and adhesion potential. After 3 h, HGF adhesion was similar in all groups. Later, HGFs closely adhered to surfaces, particularly onto groups B, C and D, acquiring an elongated shape. Proliferation assay showed no differences in cell viability among the groups after 24 h, while significant increase was shown after 72 h in Groups B and C. After 24 h, similar Collagen I levels were found in all groups, while after 72 h Groups B and C revealed a deep reduction in respect to the 24 h level. In vitro, HGF behavior may reflect variability in soft tissue response to different surface materials for prosthetic restorations, and support that polished zirconia is able to achieve a better integration in vivo in respect to the other materials.

NF-kB mediated down-regulation of collagen synthesis upon HEMA (2-hydroxyethyl methacrylate) treatment of primary human gingival fibroblast/Streptococcus mutans co-cultured cells

PURPOSE

In vitro studies have evidenced the cytotoxic effect of HEMA (2-hydroxyethyl methacrylate), the most common component of dental resin-based restorative material, which is released within the oral cavity, on eukaryotic cells such as gingival fibroblast and epithelial cells. However, since the presence of microorganisms within the oral cavity cannot be excluded and little is known about the interactions occurring between eukaryotic cells and the human oral microbiota, our attention has been addressed to investigate the effect of 3 mM HEMA on the molecular mechanisms driving the response of human gingival fibroblasts (HGFs) co-cultured with Streptococcus mutans.

METHODOLOGY

HGF/S. mutans co-culture has been set up in our lab, and upon HEMA treatment, S.mutans and HGF cells' viability and adhesion along with type I collagen gene and pro-collagen I, Bax, Bcl2, nuclear factor kB (NF-kB), IkBα, pIkBα protein expression by PCR, Western blotting and ELISA assays have been investigated.

RESULTS

HEMA treatment determines a significant decrease of type I collagen protein production, even in the presence of S. mutans, in parallel to a decrease of cell viability and adhesion, which seem to be regulated by NF-kB activation. In fact, when SN50, NF-kB-specific pharmacological inhibitor, is added to the culture, cell proliferation along with collagen synthesis is restored.

CONCLUSION

The modulation exerted by S. mutans on the cytotoxic effect of HEMA suggests that within the oral cavity, the eukaryotic/prokaryotic cell interactions, maintaining the balance of the environment, allow HEMA to perform its adhesive and bonding function and that the use of a co-culture system, which simulates the oral cavity organization, improves the knowledge concerning the biocompatibility of this dental material.

A dual role for β1 integrin in an in vitro Streptococcus mitis/human gingival fibroblasts co-culture model in response to TEGDMA

AIM

To evaluate the effect of TEGDMA on human gingival fibroblasts (HGFs) in vitro co-cultured with Streptococcus mitis, focusing on the signalling pathways underlying cell tissue remodelling and inflammatory response processes.

METHODOLOGY

β1 integrin expression was evaluated by means of imaging flow cytometry. The Western blot technique was used to investigate the expression of protein kinase C (PKC), extracellular signal-regulated kinase (ERK), matrix metalloproteinase 9 (MMP9) and 3 (MMP3). RT-PCR was performed to quantify nuclear factor-kb subunits (Nf-kb1, ReLa), IkB kinase β (IkBkB), cyclooxygenase II (COX-2) and tumour necrosis factor-α (TNF-α) mRNA levels. Statistical analysis was performed using the analysis of variance (anova).

RESULTS

When HGFs are co-cultured with S. mitis, β1 integrin intensity, phosphorylated PKC (p-PKC), activated ERK (p-ERK), IkBkB mRNA level and MMP9 expression increased (for all molecules P < 0.05 HGFs versus HGFs co-cultured with S. mitis). A higher level of MMP3 in HGFs treated with TEGDMA was recorded (P < 0.05 HGFs versus HGFs exposed to TEGDMA). COX-2 inflammatory factor mRNA level appeared higher in HGFs exposed to 1 mmol L(-1) TEGDMA (P < 0.01 HGFs versus HGFs exposed to TEGDMA), whereas TNF-α gene expression was higher in HGFs co-cultured with S. mitis (P < 0.05 HGFs versus HGFs co-cultured with S. mitis).

CONCLUSIONS

β1 integrin triggered the signalling pathway, transduced by p-PKCα and involving ERK 1 and 2 and MMPs. This pathway resulted in an unbalanced equilibrium in tissue remodelling process, along with inflammatory response when HGFs are exposed to bacteria or biomaterial alone. On the contrary, the TEGDMA/S. mitis combination restored the balance between extracellular matrix deposition and degradation and prevented an inflammatory response.

Biological responses of human gingival fibroblasts (HGFs) in an innovative co-culture model with Streptococcus mitis to thermosets coated with a silver polysaccharide antimicrobial system

This study sought to evaluate the in vitro biological response of human gingival fibroblasts (HGFs) co-coltured with Streptococcus mitis to bisphenol A glycidylmethacrylate/triethylene glycol dimethacrylate (BisGMA/TEGDMA) thermosets coated with Chitlac-nAg, a nanocomposite system with antimicrobial properties. To avoid bacterial adhesion to dental devices and to reduce cytotoxicity against eukaryotic cells, we coated BisGMA/TEGDMA methacrylic thermosets with a new material, Chitlac-nAg, formed by stabilizing silver nanoparticles, which have well-known antimicrobial properties, with a polyelectrolyte solution containing Chitlac. Cytotoxicity, cell morphology, cell migration and inflammatory interleukine-6 (IL-6) and prostaglandin E2 (PGE2) secretion were evaluated. Our results showed that the cytotoxicity exerted on HGFs by our nanocomposite material was absent in our co-culture model, where fibroblasts are able to adhere and migrate. After 24 h thermosets coated with Chitlac as well as those coated with Chitlac-nAg exerted a minimal cytotoxic effect on HGFs, while after 48 h LDH release rises up 20%. Moreover the presence of S. mitis reduced this release in a greater amount with Chitlac-nAg coated thermosets. The secretion of IL-6 was significant in both Chitlac and Chitlac-nAg coated thermosets, but PGE2 production was minimal, suggesting that the IL-6 production was not related to an inflammatory response. Co-culture and the addiction of saliva did not influence IL-6 and PGE2 secretion. Data obtained in the present work suggest that Chitlac n-Ag coated thermosets could significantly improve the success rates of restorative dentistry, since they limit bacterial adhesion and are not toxic to HGFs.

The regulation of cytotoxicity and cyclooxygenase-2 expression by 2-hydroxy-ethyl methacrylate in human osteoblasts are related to intracellular glutathione levels

AIM

To investigate the effects of 2-hydroxy-ethyl methacrylate (HEMA) on cytotoxicity and cyclooxygenase-2 (COX-2) protein expression in human osteoblasts.

METHODOLOGY

Cytotoxicity was judged using an Alamar Blue reduction assay on human osteoblast cell line U2OS. Western blot was used to evaluate the expression of COX-2 protein by HEMA. To determine whether glutathione (GSH) levels were important in cytotoxicity and COX-2 expression of HEMA, cells were pre-treated with the GSH precursor, 2-oxothiazolidine-4-carboxylic acid (OTZ), to boost thiol levels, or buthionine sulfoximine (BSO) to deplete GSH. Paired Student's t-tests were applied for the statistical analysis of the results.

RESULTS

HEMA demonstrated a cytotoxic effect to U2OS cells in a dose-dependent manner (P < 0.05). The 50% inhibition concentration of HEMA was approximately 3 mmol L(-1) . HEMA was found to induce COX-2 protein expression in U2OS cells (P < 0.05). The addition of OTZ acted as a protective effect on HEMA-induced cytotoxicity and COX-2 expression (P < 0.05). In contrast, the addition of BSO enhanced HEMA-induced cytotoxicity and COX-2 expression (P < 0.05).

CONCLUSION

Taken together, the levels of HEMA that were tested inhibited cell growth on U2OS cells. HEMA has a significant potential for periapical toxicity. The activation of COX-2 protein expression may be one of the mechanisms of HEMA-induced periapical inflammation. These inhibitory effects were associated with intracellular GSH levels.