Effects of hydrogen peroxide (H2O2) on alkaline phosphatase activity and matrix mineralization of odontoblast and osteoblast cell lines

Dysfunctional stem and progenitor cells impair fracture healing with age

Successful fracture healing requires the simultaneous regeneration of both the bone and vasculature; mesenchymal stem cells (MSCs) are directed to replace the bone tissue, while endothelial progenitor cells (EPCs) form the new vasculature that supplies blood to the fracture site. In the elderly, the healing process is slowed, partly due to decreased regenerative function of these stem and progenitor cells. MSCs from older individuals are impaired with regard to cell number, proliferative capacity, ability to migrate, and osteochondrogenic differentiation potential. The proliferation, migration and function of EPCs are also compromised with advanced age. Although the reasons for cellular dysfunction with age are complex and multidimensional, reduced expression of growth factors, accumulation of oxidative damage from reactive oxygen species, and altered signaling of the Sirtuin-1 pathway are contributing factors to aging at the cellular level of both MSCs and EPCs. Because of these geriatric-specific issues, effective treatment for fracture repair may require new therapeutic techniques to restore cellular function. Some suggested directions for potential treatments include cellular therapies, pharmacological agents, treatments targeting age-related molecular mechanisms, and physical therapeutics. Advanced age is the primary risk factor for a fracture, due to the low bone mass and inferior bone quality associated with aging; a better understanding of the dysfunctional behavior of the aging cell will provide a foundation for new treatments to decrease healing time and reduce the development of complications during the extended recovery from fracture healing in the elderly.

Adverse Effects of Fine-Particle Exposure on Joints and Their Surrounding Cells and Microenvironment

Current understanding of the health risks and adverse effects upon exposure to fine particles is premised on the direct association of particles with target organs, particularly the lung; however, fine-particle exposure has also been found to have detrimental effects on sealed cavities distant to the portal-of-entry, such as joints. Moreover, the fundamental toxicological issues have been ascribed to the direct toxic mechanisms, in particular, oxidative stress and proinflammatory responses, without exploring the indirect mechanisms, such as compensated, adaptive, and secondary effects. In this Review, we recapitulate the current findings regarding the detrimental effects of fine-particle exposure on joints, the surrounding cells, and microenvironment, as well as their deteriorating impact on the progression of arthritis. We also elaborate the likely molecular mechanisms underlying the particle-induced detrimental influence on joints, not limited to direct toxicity, but also considering the other indirect mechanisms. Because of the similarities between fine air particles and engineered nanomaterials, we compare the toxicities of engineered nanomaterials to those of fine air particles. Arthritis and joint injuries are prevalent, particularly in the elderly population. Considering the severity of global exposure to fine particles and limited studies assessing the detrimental effects of fine-particle exposure on joints and arthritis, this Review aims to appeal to a broad interest and to promote more research efforts in this field.

Hydrogen peroxide-based products alter inflammatory and tissue damage-related proteins in the gingival crevicular fluid of healthy volunteers: a randomized trial

Hydrogen peroxide (H₂O₂)-based products are effective in tooth whitening; however, their safety is controversial as they may harm patient tissues/cells. These effects are suggested to be concentration-dependent; nonetheless, to date, there are no reports on H₂O₂-mediated oxidative damage in the gingival tissue, and neither whether this can be detected in gingival crevicular fluid (GCF) samples. We hypothesize that H₂O₂ whitening products may cause collateral oxidative tissue damage following in office application. Therefore, H₂O₂ and nitric oxide (NO) levels were investigated in GCF samples obtained from patients undergoing dental bleaching with H₂O₂ at different concentrations, in a randomized, double-blind, split-mouth clinical trial. A proteomic analysis of these samples was also performed. H₂O₂-based whitening products promoted inflammation which was detected in GCF samples and lasted for longer following 35% H₂O₂ bleaching. This included time-dependent changes in NO levels and in the abundance of proteins associated with NO synthesis, oxidative stress, neutrophil regulation, nucleic acid damage, cell survival and/or tissue regeneration. Overall, H₂O₂-based products used in office promote inflammation irrespective of their concentration. As the inflammation caused by 35% H₂O₂ is longer_, patients may benefit better from using lower concentrations of this bleaching product, as they may result in less tissue damage.

The presence of osteocalcin, osteopontin and reactive oxygen species-positive cells in pulp tissue after dental bleaching

AIM

To analyse the influence of H₂ O₂ on pulp repair through osteocalcin and osteopontin immunolabelling and in cellular defence by using the antireactive oxygen species (ROS) antibody.

METHODOLOGY

The maxillary molars of 50 rats were treated with 35% H₂ O₂ (Ble groups) or placebo gel (control groups). At 0 h and 2, 7, 15 and 30 days (n = 10 hemimaxillae), the rats were killed and pulp tissue was evaluated using inflammation and immunolabelling scores (osteocalcin/osteopontin); ROS-positive cells were counted. Paired t-test and Wilcoxon signed-rank test were used (P < 0.05).

RESULTS

The Ble group had necrosis in the coronal pulp at 0 h and in the occlusal third of the coronal pulp at 2 days; at 7, 15 and 30 days, no inflammation was noted similar to the controls (P > 0.05). Osteocalcin was absent in the Ble at 0 h, moderate at 2 days and increased thereafter, differing from the controls at all two periods (P < 0.05). Osteopontin was higher principally at 7 and 15 days in Ble groups, but differing with control groups from 2 days after bleaching (P < 0.05). The Ble group had more ROS-positive cells in the pulp at 7 and 15 days (P < 0.05). Tertiary dentine was observed at 7 days, increasing thereafter (P < 0.05).

CONCLUSIONS

Post-bleaching pulp repair was associated with increased osteocalcin over time. Osteopontin also participated in this process, and anti-ROS was involved in cellular defence against H₂ O₂ .

4-Hydroxyderricin inhibits osteoclast formation and accelerates osteoblast differentiation

4-Hydroxyderricin (4-HD) is a major polyphenol of Angelica keiskei (Japanese name Ashitaba), exhibiting anti-allergic, anti-diabetic, anti-oxidant, and antitumor effects. The present study was designed to evaluate the effects of 4-HD on bone formation and maintenance by using cultured osteoclasts and osteoblasts. 4-HD did not affect cell proliferation of stromal ST2 cells and preosteoblast MC3T3-E1 cells at concentrations of 1–10 μM. This compound inhibited the formation of multinucleated osteoclasts from mouse splenic cells, and we identified a molecular pathway of osteoclast differentiation mediated by 4-HD, which led to inhibition of the expression of receptor activator of nuclear factor-κB ligand and macrophage-colony stimulating factor in ST2 cells. By contrast, 4-HD enhanced indices of osteoblast differentiation, such as alkaline phosphatase activity and calcium deposition by osteoblastic MC3T3-E1 cells, at concentrations of 1–10 μM. Furthermore, we found that 4-HD at 1 μM attenuated H₂O₂ levels in MC3T3-E1 cells. Our findings indicate that 4-HD may have critical effects on bone formation and maintenance.

Nicotine and Cotinine Inhibit Catalase and Glutathione Reductase Activity Contributing to the Impaired Osteogenesis of SCP-1 Cells Exposed to Cigarette Smoke

Cigarette smoking has been identified as a major risk factor for osteoporosis decades ago. Several studies have shown a direct relationship between cigarette smoking, decreased bone mineral density, and impaired fracture healing. However, the mechanisms behind impaired fracture healing and cigarette smoking are yet to be elucidated. Migration and osteogenesis of mesenchymal stem/stromal cells (MSCs) into the fracture site play a vital role in the process of fracture healing. In human nicotine, the most pharmacologically active and major addictive component present in tobacco gets rapidly metabolized to the more stable cotinine. This study demonstrates that physiological concentrations of both nicotine and cotinine do not affect the osteogenic differentiation of MSCs. However, cigarette smoke exposure induces oxidative stress by increasing superoxide radicals and reducing intracellular glutathione in MSCs, negatively affecting osteogenic differentiation. Although, not actively producing reactive oxygen species (ROS) nicotine and cotinine inhibit catalase and glutathione reductase activity, contributing to an accumulation of ROS by cigarette smoke exposure. Coincubation with N-acetylcysteine or L-ascorbate improves impaired osteogenesis caused by cigarette smoke exposure by both activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling and scavenging of ROS, which thus might represent therapeutic targets to support fracture healing in smokers.

Inflammation and Regeneration in the Dentin-pulp Complex: Net Gain or Net Loss?

The balance between the immune/inflammatory and regenerative responses in the diseased pulp is central to the clinical outcome, and this response is unique within the body because of its tissue site. Cariogenic bacteria invade the dentin and pulp tissues, triggering molecular and cellular events dependent on the disease stage. At the early onset, odontoblasts respond to bacterial components in an attempt to protect the tooth's hard and soft tissues and limit disease progression. However, as disease advances, the odontoblasts die, and cells central to the pulp core, including resident immune cells, pulpal fibroblasts, endothelial cells, and stem cells, respond to the bacterial challenge via their expression of a range of pattern recognition receptors that identify pathogen-associated molecular patterns. Subsequently, recruitment and activation occurs of a range of immune cell types, including neutrophils, macrophages, and T and B cells, which are attracted to the diseased site by cytokine/chemokine chemotactic gradients initially generated by resident pulpal cells. Although these cells aim to disinfect the tooth, their extravasation, migration, and antibacterial activity (eg, release of reactive oxygen species [ROS]) along with the bacterial toxins cause pulp damage and impede tissue regeneration processes. Recently, a novel bacterial killing mechanism termed neutrophil extracellular traps (NETs) has also been described that uses ROS signaling and results in cellular DNA extrusion. The NETs are decorated with antimicrobial peptides (AMPs), and their interaction with bacteria results in microbial entrapment and death. Recent data show that NETs can be stimulated by bacteria associated with endodontic infections, and they may be present in inflamed pulp tissue. Interestingly, some bacteria associated with pulpal infections express deoxyribonuclease enzymes, which may enable their evasion of NETs. Furthermore, although NETs aim to localize and kill invading bacteria using AMPs and histones, limiting the spread of the infection, data also indicate that NETs can exacerbate inflammation and their components are cytotoxic. This review considers the potential role of NETs within pulpal infections and how these structures may influence the pulp's vitality and regenerative responses.

Enhancement of Replication and Differentiation Potential of Human Bone Marrow Stem Cells by Nicotinamide Treatment

Background and Objectives

Therapies using mesenchymal stem cells (MSCs) generally require substantial expansion of cell populations. However, the replicative life span of MSCs is limited and their multipotency declines over continued passages, imposing a limitation on their application especially in aged individuals. In an effort to increase MSC life span, we tested the effects of nicotinamide (NAM), a precursor of NAD⁺ that has been shown to reduce reactive oxygen species generation and delay the onset of replicative senescence in fibroblasts.

Methods

Bone marrow stem cells (BMSCs) from healthy donors were cultivated in the presence of 5 mM NAM until the end of their life span. The levels of proliferation and differentiation to osteogenic, adipogenic, and chondrogenic lineages of BMSCs were compared between populations incubated in the absence or presence of NAM.

Results

The replicative life span was substantially increased with a significant delay in the onset of senescence, and differentiation to all tested lineages was increased. Furthermore, differentiation was sustained and the adipogenic switch from osteogenesis to adipogenesis was attenuated in late-passage BMSCs.

Conclusions

NAM could be considered as an important biological agent to expand and sustain the multipotency of BMSCs and thus broaden the application of stem cells in cell therapies.

Sources of free radicals and oxidative stress in the oral cavity

OBJECTIVE

An oral cavity is a place especially susceptible to oxidative damage. It is subjected to many environmental pro-oxidative factors or factors that have the ability to generate reactive oxygen species (ROS). The aim of this article is to present the main sources of ROS and oxidative stress in the oral environment.

DESIGN

A literature search was performed using the PubMed and Google Scholar databases.

RESULTS

One of the most important ROS sources in the oral cavity is periodontal inflammation. Other sources of ROS include: xenobiotics (ethanol, cigarette smoke, drugs), food (high-fat diet, high-protein diet, acrolein), dental treatment (ozone, ultrasound, non-thermal plasma, laser light, ultraviolet light), and dental materials (fluorides, dental composites, fixed orthodontic appliances, and titanium fixations). It has been shown that excessive production of ROS in the oral cavity may cause oxidative stress and oxidative damage to cellular DNA, lipids, and proteins, thus predisposing to many oral and systemic diseases.

CONCLUSIONS

Recognition of the exogenous sources of ROS and limitation of exposure to the ROS generating factors can be one of the prophylactic measures preventing oral and systemic diseases. It is suggested that antioxidant supplementation may be helpful in people exposed to excessive production of ROS in the oral cavity system.

Oleuropein and hydroxytyrosol protect rats' pups against bisphenol A induced hypothyroidism

Bisphenol A (BPA) can disturb the endocrine system and the organs that respond to endocrine signals in organisms, indirectly exposed during prenatal and/or early postnatal life. The present study was designed to assess the protective effect of phenolic compounds from olive leaves against BPA induced thyroid dysfunction and growth perturbation in young rats during lactation. The BPA disrupting effect on thyroid function was investigated by measuring changes in plasma levels of thyroid hormones. Free triiodothyronine (FT3) and thyroxine (FT4) were decreased in young rats breast-fed from mothers treated with bisphenol A. This effect was associated with an increase in the plasma level of thyroid-stimulating hormone (TSH). The histological and immunohistochemical study of the thyroid gland revealed a disturbance in morphological structure and thyroid cells function. Thyroid dysfunction led to a disruption in the skeletal bone growth of young rats. In fact, the infrared microspectroscopic analysis and histological examination of femoral bone showed significant changes in their histoarchitecture associated with a perturbation in the mechanism of bone tissue mineralization. The administration of oleuropein or hydroxytyrosol in BPA treated lactating mothers improved the thyroid cells function by enhancing thyroid hormone levels. Moreover, these phenolics increased the body growth characterized by an amelioration in the structure and the microstructure of femoral bone tissue. HPLC analysis of rats-breast milk indicated the presence of oleuropein and hydroxytyrosol, which could contribute to the protective effect against bisphenol A induced hypothyroidism in pups rats.

Nicotine induces apoptosis in human osteoblasts via a novel mechanism driven by H2O2 and entailing Glyoxalase 1-dependent MG-H1 accumulation leading to TG2-mediated NF-kB desensitization: Implication for smokers-related osteoporosis

Nicotine contained in cigarette smoke contributes to the onset of several diseases, including osteoporosis, whose emerging pathogenic mechanism is associated with osteoblasts apoptosis. Scanty information is available on the molecular mechanisms of nicotine on osteoblasts apoptosis and, consequently, on an important aspect of the pathogenesis of smokers-related osteoporosis. Glyoxalase 1 (Glo1) is the detoxification enzyme of methylglyoxal (MG), a major precursor of advanced glycation end products (AGEs), potent pro-apoptotic agents. Hydroimidazolone (MG-H1) is the major AGE derived from the spontaneous MG adduction of arginine residues. The aim of this study was to investigate whether, and by means of which mechanism, the antiglycation defence Glo1 was involved in the apoptosis induced by 0.1 and 1µM nicotine in human primary osteoblasts chronically exposed for 11 and 21 days. By using gene overexpression/silencing and scavenging/inhibitory agents, we demonstrated that nicotine induces a significant intracellular accumulation of hydrogen peroxide (H₂O₂) that, by inhibiting Glo1, drives MG-H1 accumulation/release. MG-H1, in turn, triggers H₂O₂ overproduction via receptor for AGEs (RAGE) and, in parallel, an apoptotic mitochondrial pathway by inducing Transglutaminase 2 (TG2) downregulation-dependent NF-kB desensitization. Measurements of H₂O₂, Glo1 and MG-H1 circulating levels in smokers compared with non-smokers or in smokers with osteoporosis compared with those without this bone-related disease supported the results obtained in vitro. Our findings newly pose the antiglycation enzymatic defense Glo1 and MG-H1 among the molecular events involved in nicotine-induced reactive oxygen species-mediated osteoblasts apoptosis, a crucial event in smoker-related osteoporosis, and suggest novel exposure markers in health surveillance programmes related to smokers-associated osteoporosis.

1α,25-Dihydroxyvitamin D3 promotes bone formation by promoting nuclear exclusion of the FoxO1 transcription factor in diabetic mice

1α,25-Dihydroxyvitamin D3 (1,25(OH)2D3) is the active form of vitamin D, which is responsible for reducing the risk for diabetes mellitus (DM), decreasing insulin resistance, and improving insulin secretion. Previous studies have shown that 1,25(OH)2D3 inhibited the activity of FoxO1, which has been implicated in the regulation of glucose metabolism. However, its function and mechanism of action in DM-induced energy disorders and also in bone development remains unclear. Here, using in vitro and in vivo approaches including osteoblast-specific, conditional FoxO1-knock-out mice, we demonstrate that 1,25(OH)2D3 ameliorates abnormal osteoblast proliferation in DM-induced oxidative stress conditions and rescues the impaired glucose and bone metabolism through FoxO1 nuclear exclusion resulting from the activation of PI3K/Akt signaling. Using alizarin red staining, alkaline phosphatase assay, Western blot, and real-time qPCR techniques, we found that 1,25(OH)2D3 promotes osteoblast differentiation and expression of osteogenic phenotypic markers (i.e. alkaline phosphatase (1), collagen 1 (COL-1), osteocalcin (OCN), and osteopontin (OPN)) in a high-glucose environment. Moreover, 1,25(OH)2D3 increased both total OCN secretion and levels of uncarboxylated OCN (GluOC) by phosphorylating FoxO1 and promoting its nuclear exclusion, indicated by Western blot and cell immunofluorescence analyses. Taken together, our findings confirm that FoxO1 is a key mediator involved in glucose homeostasis and indicate that 1,25(OH)2D3 improves glucose metabolism and bone development via regulation of PI3K/Akt/FoxO1/OCN pathway.

Changes of mitochondrial respiratory function during odontogenic differentiation of rat dental papilla cells

Dental papilla cells (DPCs) belong to precursor cells differentiating to odontoblasts and play an important role in dentin formation and reproduction. This study aimed to explore the changes and and involvement of mitochondrial respiratory function during odontogenic differentiation. Primary DPCs were obtained from first molar dental papilla of neonatal rats and cultured in odontogenic medium for 7, 14, 21 days. DPCs, which expressed mesenchymal surface markers CD29, CD44 and CD90, had the capacity for self-renewal and multipotent differentiation. Odontoblastic induction increased mineralized matrix formation in a time-dependent manner, which was accompanied by elevated alkaline phosphatase (ALP), dentin sialophosphoprotein and dentin matrix protein 1 expression at mRNA and protein levels. Notably, odontogenic medium led to an increase in adenosine-5'-triphosphate content and mitochondrial membrane potential, whereas a decrease in intercellular reactive oxygen species production and NAD⁺/NADH ratio. Furthermore, odontogenic differentiation was significantly suppressed by treatment with rotenone, an inhibitor of mitochondrial respiratory chain. These results demonstrate that enhanced mitochondrial function is crucial for odontogenic differentiation of DPCs.

Extremely low frequency pulsed electromagnetic fields cause antioxidative defense mechanisms in human osteoblasts via induction of •O2- and H2O2

Recently, we identified a specific extremely low-frequency pulsed electromagnetic field (ELF-PEMF) that supports human osteoblast (hOBs) function in an ERK1/2-dependent manner, suggesting reactive oxygen species (ROS) being key regulators in this process. Thus, this study aimed at investigating how ELF-PEMF exposure can modulate hOBs function via ROS. Our results show that single exposure to ELF-PEMF induced ROS production in hOBs, without reducing intracellular glutathione. Repetitive exposure (>3) to ELF-PEMF however reduced ROS-levels, suggesting alterations in the cells antioxidative stress response. The main ROS induced by ELF-PEMF were •O₂⁻ and H₂O₂, therefore expression/activity of antioxidative enzymes related to these ROS were further investigated. ELF-PEMF exposure induced expression of GPX3, SOD2, CAT and GSR on mRNA, protein and enzyme activity level. Scavenging •O₂⁻ and H₂O₂ diminished the ELF-PEMF effect on hOBs function (AP activity and mineralization). Challenging the hOBs with low amounts of H₂O₂ on the other hand improved hOBs function. In summary, our data show that ELF-PEMF treatment favors differentiation of hOBs by producing non-toxic amounts of ROS, which induces antioxidative defense mechanisms in these cells. Thus, ELF-PEMF treatment might represent an interesting adjunct to conventional therapy supporting bone formation under oxidative stress conditions, e.g. during fracture healing.

Oxidative stress in bone remodeling: role of antioxidants

ROS are highly reactive molecules which consist of a number of diverse chemical species, including radical and non-radical oxygen species. Oxidative stress occurs as a result of an overproduction of ROS not balanced by an adequate level of antioxidants. The natural antioxidants are: thiol compounds among which GSH is the most representative, and non-thiol compounds such as polyphenols, vitamins and also various enzymes. Many diseases have been linked to oxidative stress including bone diseases among which one of the most important is the osteoporosis. The redox state changes are also related to the bone remodeling process which allows the continuous bone regeneration through the coordinated action of bone cells: osteoclasts, osteoblasts and osteocytes. Changes in ROS and/or antioxidant systems seem to be involved in the pathogenesis of bone loss. ROS induce the apoptosis of osteoblasts and osteocytes, and this favours osteoclastogenesis and inhibits the mineralization and osteogenesis. Excessive osteocyte apoptosis correlates with oxidative stress causing an imbalance in favor of osteoclastogenesis which leads to increased turnover of bone remodeling and bone loss. Antioxidants either directly or by counteracting the action of oxidants contribute to activate the differentiation of osteoblasts, mineralization process and the reduction of osteoclast activity. In fact, a marked decrease in plasma antioxidants was found in aged or osteoporotic women. Some evidence shows a link among nutrients, antioxidant intake and bone health. Recent data demonstrate the antioxidant properties of various nutrients and their influence on bone metabolism. Polyphenols and anthocyanins are the most abundant antioxidants in the diet, and nutritional approaches to antioxidant strategies, in animals or selected groups of patients with osteoporosis or inflammatory bone diseases, suggest the antioxidant use in anti-resorptive therapies for the treatment and prevention of bone loss.

Generation and Role of Reactive Oxygen and Nitrogen Species Induced by Plasma, Lasers, Chemical Agents, and Other Systems in Dentistry

The generation of reactive oxygen and nitrogen species (RONS) has been found to occur during inflammatory procedures, during cell ischemia, and in various crucial developmental processes such as cell differentiation and along cell signaling pathways. The most common sources of intracellular RONS are the mitochondrial electron transport system, NADH oxidase, and cytochrome P450. In this review, we analyzed the extracellular and intracellular sources of reactive species, their cell signaling pathways, the mechanisms of action, and their positive and negative effects in the dental field. In dentistry, ROS can be found—in lasers, photosensitizers, bleaching agents, cold plasma, and even resin cements, all of which contribute to the generation and prevalence of ROS. Nonthermal plasma has been used as a source of ROS for biomedical applications and has the potential for use with dental stem cells as well. There are different types of dental stem cells, but their therapeutic use remains largely untapped, with the focus currently on only periodontal ligament stem cells. More research is necessary in this area, including studies about ROS mechanisms with dental cells, along with the utilization of reactive species in redox medicine. Such studies will help to provide successful treatment modalities for various diseases.

Insulin-like growth factor-1 promotes the proliferation and odontoblastic differentiation of human dental pulp cells under high glucose conditions

Insulin-like growth factor-1 (IGF-1) promotes human dental pulp stem cell proliferation and osteogenic differentiation. However, the effects of IGF-1 on the proliferation, apoptosis and odontoblastic differentiation (mineralization) of dental pulp cells (DPCs) under high glucose (GLU) conditions remain unclear. In this study, isolated primary human DPCs were treated with various concentrations of high GLU. Cell proliferation and apoptosis were determined by Cell Counting Kit-8 and Annexin V-FITC/PI assays, respectively. The cells were cultured in odontoblastic induction medium containing various concentrations of high GLU. Odontoblastic differentiation was determined by alkaline phosphatase (ALP) activity assay. Mineralization formation was evaluated by von Kossa staining. The expression levels of IGF family members were measured by western blot analysis and RT-qPCR during proliferation and differentiation. The cells were then exposed to 25 mM GLU and various concentrations of IGF-1. Cell proliferation, apoptosis, ALP activity, mineralization formation and the levels of mineralization-related proteins were then evaluated. Our results revealed that high GLU significantly inhibited cell proliferation and promoted cell apoptosis. GLU (25 and 50 mM) markedly reduced ALP activity and mineralization on days 7 and 14 after differentiation. The levels of IGF family members were markedly decreased by high GLU during proliferation and differentiation. However, IGF-1 significantly reversed the effects of high GLU on cell proliferation and apoptosis. Additionally, IGF-1 markedly restored the reduction of ALP activity and mineralization induced by high GLU. Our findings thus indicate that IGF-1 attenuates the high GLU-induced inhibition of DPC proliferation, differentiation and mineralization.

The role of mitochondria in osteogenic, adipogenic and chondrogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are progenitors of connective tissues, which have emerged as important tools for tissue engineering due to their differentiation potential along various cell types. In recent years, accumulating evidence has suggested that the regulation of mitochondria dynamics and function is essential for successful differentiation of MSCs. In this paper, we review and provide an integrated view on the role of mitochondria in MSC differentiation. The mitochondria are maintained at a relatively low activity level in MSCs, and upon induction, mtDNA copy number, protein levels of respiratory enzymes, the oxygen consumption rate, mRNA levels of mitochondrial biogenesis-associated genes, and intracellular ATP content are increased. The regulated level of mitochondrial ROS is found not only to influence differentiation but also to contribute to the direction determination of differentiation. Understanding the roles of mitochondrial dynamics during MSC differentiation will facilitate the optimization of differentiation protocols by adjusting biochemical properties, such as energy production or the redox status of stem cells, and ultimately, benefit the development of new pharmacologic strategies in regenerative medicine.

Selenium- and Tellurium-Based Antioxidants for Modulating Inflammation and Effects on Osteoblastic Activity

Increased oxidative stress plays a significant role in the etiology of bone diseases. Heightened levels of H₂O₂ disrupt bone homeostasis, leading to greater bone resorption than bone formation. Organochalcogen compounds could act as free radical trapping agents or glutathione peroxidase mimetics, reducing oxidative stress in inflammatory diseases. In this report, we synthesized and screened a library of organoselenium and organotellurium compounds for hydrogen peroxide scavenging activity, using macrophagic cell lines RAW264.7 and THP-1, as well as human mono- and poly-nuclear cells. These cells were stimulated to release H₂O₂, using phorbol 12-myristate 13-acetate, with and without organochalogens. Released H₂O₂ was then measured using a chemiluminescent assay over a period of 2 h. The screening identified an organoselenium compound which scavenged H₂O₂ more effectively than the vitamin E analog, Trolox. We also found that this organoselenium compound protected MC3T3 cells against H₂O₂-induced toxicity, whereas Trolox did not. The organoselenium compound exhibited no cytotoxicity to the cells and had no deleterious effects on cell proliferation, viability, or alkaline phosphatase activity. The rapidity of H₂O₂ scavenging and protection suggests that the mechanism of protection is due to the direct scavenging of extracellular H₂O₂. This compound is a promising modulators of inflammation and could potentially treat diseases involving high levels of oxidative stress.

Biological characteristic effects of human dental pulp stem cells on poly-ε-caprolactone-biphasic calcium phosphate fabricated scaffolds using modified melt stretching and multilayer deposition

Craniofacial bone defects such as alveolar cleft affect the esthetics and functions that need bone reconstruction. The advanced techniques of biomaterials combined with stem cells have been a challenging role for maxillofacial surgeons and scientists. PCL-coated biphasic calcium phosphate (PCL-BCP) scaffolds were created with the modified melt stretching and multilayer deposition (mMSMD) technique and merged with human dental pulp stem cells (hDPSCs) to fulfill the component of tissue engineering for bone substitution. In the present study, the objective was to test the biocompatibility and biofunctionalities that included cell proliferation, cell viability, alkaline phosphatase activity, osteocalcin, alizarin red staining for mineralization, and histological analysis. The results showed that mMSMD PCL-BCP scaffolds were suitable for hDPSCs viability since the cells attached and spread onto the scaffold. Furthermore, the constructs of induced hDPSCs and scaffolds performed ALP activity and produced osteocalcin and mineralized nodules. The results indicated that mMSMD PCL-BCP scaffolds with hDPSCs showed promise in bone regeneration for treatment of osseous defects.

Effects of phosphatidylserine-containing liposomes on odontogenic differentiation of human dental pulp cells

Phosphatidylserine (PS) is known to enhance biomineralization due to the ability to accumulate calcium ions. In this study, the effects of PS on odontogenic differentiation and mineralization of human dental pulp cells (HDPCs) were investigated using phosphatidylserine-containing liposomes (PSLs). PSL was slightly cytotoxic at 125 µM in growth medium, and ALP activity was up-regulated in the PSL-treated HDPCs at non-cytotoxic concentrations. Mineralization was also enhanced by PSL, while mRNA expressions of DSPP and OCN genes were slightly attenuated. The mRNA expression of Runx2 was not altered by PSL. It is thus likely that PSL selectively affected odontogenic differentiation processes of HDPC. Finally, the interaction between PSL and HDPC was investigated by staining with annexin V-FITC in PSL-treated HDPC. It was found that PS was gradually incorporated into HDPC cytoplasm for several days. The results of this study suggest that PSL is able to stimulate dentin formation in dental pulps.

Influence of enamel/dentin thickness on the toxic and esthetic effects of experimental in-office bleaching protocols

OBJECTIVES

This paper aims to assess the whitening effectiveness and toxicity of tooth-bleaching protocols applied to enamel/dentin disks simulating mandibular incisors (ICs) and premolars (PMs).

MATERIALS AND METHODS

A 10% hydrogen peroxide (H₂O₂) gel was applied for 3 × 15, 1 × 15, or 1 × 5 min to enamel/dentin disks simulating mandibular ICs and PMs, and the trans-enamel and trans-dentinal diffusion products were applied to human dental pulp cells (1 h). Professional therapy (35% H₂O₂-3 × 15 min) was used as positive control, and non-bleached samples were used as negative control. Cell viability and morphology, oxidative stress generation, and odontoblastic marker expression were assessed. The H₂O₂ diffusion and enamel color change (ΔE) were also analyzed.

RESULTS

The 10% H₂O₂ gel induced significant cell viability reduction only when applied 3 × 15 min, with the intensity of oxidative stress and down-regulation of odontoblastic markers being higher in the IC group. The other experimental bleaching protocols caused slight alterations regarding the cell parameters evaluated, with intensity being related to enamel/dentin thickness. These effects were also correlated with higher H₂O₂ diffusion in the IC group. ΔE values similar as positive control were found for the 10% 3 × 15 and 1 × 15 protocols on IC group, after 4 and 6 sessions.

CONCLUSION

Application of a 10% H₂O₂ bleaching gel for 15 or 45 min to thin dental substrate significantly minimizes cell toxicity in comparison with highly concentrated gels associated with similar esthetic outcomes by increasing the number of bleaching sessions.

CLINICAL RELEVANCE

Bleaching gels with 10% H₂O₂ applied in small teeth for short periods may be an interesting alternative to obtain whitening effectiveness without causing toxicity to pulp cells, which may be able to reduce the tooth hypersensitivity claimed by patients.

Regulation of Adipogenesis Through Differential Modulation of ROS and Kinase Signaling Pathways by 3,4'-Dihydroxyflavone Treatment

Studies on adipogenesis may be important for regulating human and/or animal obesity, which causes several complications such as, type II diabetes, hypertension, and cardiovascular disease, thus giving rise to increased economic burden in many countries. Previous reports revealed that various flavonoids have anti-apoptotic, antioxidant, and cell differentiation-regulating activities with a number of physiological benefits, including protection from cardiovascular disease, cancers, and oxidative stress. As we found that the hydroxylation patterns of the flavonoid B ring are known to play a critical role in their function, we screened several flavonoids containing different numbers and positions of OH substitutions in B ring for their modulatory property on adipogenesis. In this study, we revealed the anti-adipogenic activity of the naturally derived flavonoid, 3,4'-dihydroxyflavone (3,4'-DHF) in murine 3T3-L1 pre-adipocytes and equine adipose-derived stromal cells (eADSCs). We found that treatment with 3,4'-dihydroxyflavone (3,4'-DHF) led to decreased expression of adipogenic markers and lipid deposition with differential modulation of ROS and kinase signaling pathways. Regulation of ROS generation through the differential modulation of ROS-regulating gene expression was revealed to have an important role in the suppression of adipogenesis and increase of osteogenesis in eADSCs following 3,4'-DHF treatment. These results suggest that the flavonoid 3,4'-DHF can be used to regulate adipogenesis in ADSCs, which has potential therapeutic application in regenerative medicine or health care for humans and many sport or companion animals. J. Cell. Biochem. 118: 1065-1077, 2017. © 2016 Wiley Periodicals, Inc.

Selective antitumoural action of pressurized mango leaf extracts against minimally and highly invasive breast cancer

Mango leaves, traditionally used to reduce inflammation, have been proved to possess antitumoral action against different types of breast cancer (hormone receptor-positive or negative).

Cerium Oxide-Incorporated Calcium Silicate Coating Protects MC3T3-E1 Osteoblastic Cells from H2O2-Induced Oxidative Stress

Oxidative stress regulates cellular functions in multiple pathological conditions, including bone formation by osteoblastic cells. In this work, the protective effects of cerium oxide (CeO₂)-incorporated calcium silicate (CeO₂-CS) coating on the response of osteoblasts to H₂O₂-induced oxidative stress and the related mechanism were examined. CeO₂ incorporation significantly improved osteoblast viability and reduced cell apoptosis caused by H₂O₂ when compared with the control. H₂O₂-induced reduction of differentiation marker alkaline phosphatase (ALP) was recovered in the presence of the CeO₂-CS coating. The above effects were mediated by the antioxidant effect of CeO₂. The CeO₂-CS coating immersed in 0.1 mM H₂O₂ aqueous solution was able to degrade 64 % of it in 1 week. In addition, CeO₂ incorporation decreased reactive oxygen species (ROS) production and suppressed malondialdehyde (MDA) formation in H₂O₂-treated osteoblasts. Taken together, CeO₂-CS biomedical coatings with antioxidant property would be promising for bone regeneration under oxidative stress.

Mechanisms underlying the antiapoptotic and anti-inflammatory effects of monotropein in hydrogen peroxide-treated osteoblasts

Monotropein, the primary iridoid glycoside isolated from Morindacitrifolia, has been previously reported to possess potent antioxidant and antiosteoporotic properties. However, there is no direct evidence correlating the antiosteoporotic effect of monotropein with its observed antioxidant capacity, and the molecular mechanisms involved in mediating these processes remain unclear. Therefore, the aim of the present study was to investigate the protective effects of monotropein against oxidative stress in osteoblasts and the mechanisms involved in mediating this process. Osteoblast viability was evaluated using the MTT assay. The mitochondrial membrane potential and reactive oxygen species were detected by flow cytometry analyses. Western blotting and enzyme‑linked immunosorbent assays were performed to detect protein expression levels. A significant reduction in osteoblast viability was observed at 24 h following exposure to various concentrations (100‑1,000 µM) of H2O2 compared with untreated osteoblasts. The cytotoxic effect of H2O2 was notably reversed when osteoblasts were pretreated with 1‑10 µg/ml monotropein. Pretreatment with 1-10 µg/ml monotropein increased the mitochondrial membrane potential and reduced the generation of reactive oxygen species in osteoblasts following exposure to H2O2. In addition, the H2O2‑induced increase in apoptotic markers (caspase-3 and caspase-9) and H2O2-induced reduction in sirtuin 1 levels were significantly reversed following pretreatment of cells with monotropein. Furthermore, monotropein significantly reduced H2O2‑induced stimulation of NF‑κB expression, in addition to the expression of a number of proinflammatory mediators. These results indicate that monotropein suppresses apoptosis and the inflammatory response in H2O2‑induced osteoblasts through the activation of the mitochondrial apoptotic signaling pathway and inhibition of the NF‑κB signaling pathway.

Phytoestrogen (+)-pinoresinol exerts antitumor activity in breast cancer cells with different oestrogen receptor statuses

Background

Consumption of virgin olive oil (VOO) has been associated with a low breast cancer incidence. Pinoresinol is a phytoestrogen that is typically found in VOO. Considering the role of oestrogen in breast cancer development and progression, we investigated the potential antitumor activity of pinoresinol in breast cancer cells.

Methods

To address this question, we treated MDA-MB-231 (oestrogen receptor [ER] negative) and MCF7 (ER+) human breast tumour cells and MCF10A human mammary epithelial cells (ER-) with different concentrations of pinoresinol. The cytotoxic activity, cell proliferation, cell cycle profile, apoptosis induction, reactive oxygen species production and DNA damage were assessed.

Results

Pinoresinol showed cytotoxic, anti-proliferative and pro-oxidant activity in human breast tumour cells, independent of their oestrogen receptor status. In addition, pinoresinol exerted antioxidant activity and prevented DNA damage associated with oxidative stress in human mammary epithelial cells.

Conclusions

Overall, the results suggest that pinoresinol may have antitumor activity in human breast cancer cells independently of oestrogen receptor status. Furthermore, the results show that the pinoresinol has the typical characteristics of a chemopreventive compound.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1233-7) contains supplementary material, which is available to authorized users.

Novel antioxidant capability of titanium induced by UV light treatment

The intracellular production of reactive oxygen species (ROS) is a representative form of cellular oxidative stress and plays an important role in triggering adverse cellular events, such as the inflammatory reaction and delayed or compromised differentiation. Osteoblastic reaction to titanium with particular focus on ROS production remains unknown. Ultraviolet (UV) light treatment improves the physicochemical properties of titanium, specifically the induction of super hydrophilicity and removal of hydrocarbon, and eventually enhances its osteoconductivity. We hypothesized that there is a favorable regulatory change of ROS production within osteoblasts in contact with UV-treated titanium. Osteoblasts were cultured on titanium disks with or without UV-pretreatment. The intracellular production of ROS was higher on acid-etch-created rough titanium surfaces than on machine-prepared smooth ones. The ROS production was reduced by 40-50% by UV pretreatment of titanium regardless of the surface roughness. Oxidative DNA damage, as detected by 8-OHdG expression, was alleviated by 50% on UV-treated titanium surfaces. The expression of inflammatory cytokines was consistently lower in osteoblasts cultured on UV-treated titanium. ROS scavenger, glutathione, remained more without being depleted in osteoblasts on UV-treated titanium. Bio-burden test further showed that culturing osteoblasts on UV-treated titanium can significantly reduce the ROS production even with the presence of hydrogen peroxide, an oxidative stress inducer. These data suggest that the intracellular production of ROS and relevant inflammatory reaction, which unavoidably occurs in osteoblasts in contact with titanium, can be significantly reduced by UV pretreatment of titanium, implying a novel antioxidant capability of the particular titanium.

Toxicity and efficiency study of plant extracts-based bleaching agents

OBJECTIVES

Tooth bleaching is one of the most required dental esthetic treatments. However, it can generate side effects like oral irritation, enamel alteration, tooth sensitivity, especially caused by hydrogen peroxide, the main bleaching component of the commercial products. Therefore, development of new tooth bleaching agents, based on natural products, with comparable esthetic results and lower side effects is needed. The aim of this study was to evaluate the biological effects and bleaching efficacy of four experimental bleaching agents, derived from fruit juices, against the commercially available Opalescence (Ultradent, USA).

MATERIALS AND METHODS

Organic acid composition of the gels was characterized by HPLC. Bleaching efficiency was tested by spectrophotometry on composite restorative materials. Biological testing was done in vitro, on human fibroblasts. Cells were exposed to dilutions of the bleaching gel-conditioned medium. Viability was measured by MTS, apoptosis by FACS-AnnexinV FITC/Propidium iodide, NF-kB activation by western blot, malondyaldehide, and superoxide dismutase activity by spectrophotometry.

RESULTS

All gels exhibited physical stability and dental bleaching capabilities. Experimental gels induced significantly better viability and apoptosis rates, lower lipid peroxidation, and increased antioxidant defense, compared to Opalescence.

CONCLUSIONS

The studied experimental gel formulations exhibited a good safety profile in vitro, as well as bleaching efficiency on restorative composite materials.

CLINICAL RELEVANCE

These data open new possibilities for the use of new natural products in dental bleaching treatments that can insure significant esthetic results and lower side effects.

Plasma sprayed cerium oxide coating inhibits H2O2-induced oxidative stress and supports cell viability

Oxidative stress is a risk factor in the pathogenesis of osteoporosis, and plays a major role in bone regeneration of osteoporotic patients. Cerium oxide (CeO2) ceramics have the unique ability to protect various types of cells from oxidative damage, making them attractive for biomedical applications. In this study, we developed a plasma sprayed CeO2 coating with a hierarchical topography where ceria nanoparticles were superimposed in the micro-rough coating surface. The protective effects of the CeO2 coating on the response of osteoblasts to H2O2-induced oxidative stress have been demonstrated in terms of cell viability, apoptosis and differentiation. The CeO2 coating reversed the reduced superoxide dismutase activity, decreased reactive oxygen species production and suppressed malondialdehyde formation in H2O2-treated osteoblasts. It indicated that the CeO2 coating can preserve the intracellular antioxidant defense system. The cytocompatibility of the CeO2 coating was further assessed in vitro by cell viability assay and scanning electron microscopy analysis. Taken together, the CeO2 coating could provide an opportunity to be utilized as a potential candidate for bone regeneration under oxidative stress.

Culturing on decellularized extracellular matrix enhances antioxidant properties of human umbilical cord-derived mesenchymal stem cells

Human umbilical cord-derived mesenchymal stem cells (UC-MSCs) have attracted great interest in clinical application because of their regenerative potential and their lack of ethical issues. Our previous studies showed that decellularized cell-deposited extracellular matrix (ECM) provided an in vivo-mimicking microenvironment for MSCs and facilitated in vitro cell expansion. This study was conducted to analyze the cellular response of UC-MSCs when culturing on the ECM, including reactive oxygen species (ROS), intracellular antioxidative enzymes, and the resistance to exogenous oxidative stress. After decellularization, the architecture of cell-deposited ECM was characterized as nanofibrous, collagen fibrils and the matrix components were identified as type I and III collagens, fibronectin, and laminin. Compared to tissue culture polystyrene (TCPS) plates, culturing on ECM yielded a 2-fold increase of UC-MSC proliferation and improved the percentage of cells in the S phase by 2.4-fold. The levels of intracellular ROS and hydrogen peroxide (H2O2) in ECM-cultured cells were reduced by 41.7% and 82.9%, respectively. More importantly, ECM-cultured UC-MSCs showed enhanced expression and activity of intracellular antioxidative enzymes such as superoxide dismutase and catalase, up-regulated expression of silent information regulator type 1, and suppressed phosphorylation of p38 mitogen-activated protein kinase. Furthermore, a continuous treatment with exogenous 100μM H2O2 dramatically inhibited osteogenic differentiation of UC-MSCs cultured on TCPS, but culturing on ECM retained the differentiation capacity for matrix mineralization and osteoblast-specific marker gene expression. Collectively, by providing sufficient cell amounts and enhancing antioxidant capacity, decellularized ECM can be a promising cell culture platform for in vitro expansion of UC-MSCs.

Dietary zinc deficiency induces oxidative stress and promotes tumor necrosis factor-α- and interleukin-1β-induced RANKL expression in rat bone

We investigated the effects of dietary zinc deficiency on oxidative stress and bone metabolism. Four-week-old male Wistar rats were randomly assigned to one of three groups for 4 weeks: a zinc-adequate group (30 ppm); a zinc-deficient group (1 ppm); and a pair-fed group (30 ppm) that was pair-fed to the zinc-deficient group. The iron content and the thiobarbituric acid reactive substance level in bone were higher in the zinc-deficient group than in the zinc-adequate and pair-fed groups. The mRNA expression level of osteoblastogenesis-related genes such as bone morphogenetic protein 2 and runt-related transcription factor 2 was lower in the zinc-deficient group than in the zinc-adequate and pair-fed groups. In contrast, the mRNA expression levels of tumor necrosis factor-α, interleukin-1β and osteoclastogenesis-related genes such as receptor activator of nuclear factor-κB ligand and nuclear factor of activated T cells cytoplasmic 1 were higher in the zinc-deficient group than in the zinc-adequate and pair-fed groups.

These findings suggested that dietary zinc deficiency reduced osteoblastogenesis via a decrease in the expression of bone morphogenetic protein 2 and increased osteoclastogenesis via enhancement of the expression of receptor for activator of nuclear factor-κB ligand induced by oxidative stress-stimulated tumor necrosis factor-α and interleukin-1β.

Effect of Different Light Sources and Enamel Preconditioning on Color Change, H2O2 Penetration, and Cytotoxicity in Bleached Teeth

This study evaluated the effects of acid etching of the enamel and the combination of different light sources (halogen light, light-emitting diodes [LEDs], and LED/Laser) and the bleaching product on color change, penetration of hydrogen peroxide (H2O2), and cytotoxicity over time. The color change (ΔE) and the amount of H2O2 that permeated the tooth tissue were analyzed using a spectrophotometer. Cell metabolism and morphology were evaluated using the methylthiazol tetrazolium assay and scanning electron microscopy, respectively. The ΔE values and H2O2 permeation were not significantly different under any of the experimental conditions. Tooth whitening significantly reduced cell metabolism, regardless of whether a light source was used. Preconditioning the enamel did not influence the cellular metabolism in any group. In conclusion, combining the bleaching product with different light sources and/or preconditioning the enamel resulted in few significant changes in color, transenamel and transdentinal penetration of H2O2, or cytotoxicity and cell morphology.

Antiosteoporotic effects of Alpinia officinarum Hance through stimulation of osteoblasts associated with antioxidant effects

BACKGROUND/OBJECTIVE

Alpinia officinarum Hance (AOH) is a traditional herbal medicine specific to south China and serves as a civil medication application of an antioxidant. Growing evidence demonstrates that antioxidants are beneficial for the treatment of osteoporosis. This study was designed to investigate the antiosteoporotic effects of total extracts from AOH in ovariectomised (OVX) rats and the different fractions in AOH on primary osteoblasts activities.

METHODS

The total extract of AOH was extracted by refluxing using 95% ethanol, then the five fractions (F1-F5) were separated from AOH using thin-layer chromatography according to polarity from high to low, and the galangin content was determined using high performance liquid chromatography. In an in vivo study, 36 4-month-old female Sprague-Dawley rats were used as a Sham-operated group, OVX with vehicle (OVX), OVX with epimedium flavonoids (EF, 150 mg/kg/d), and OVX with AOH (AOH, 300 mg/kg/d), respectively. Daily oral administration started on Day 3 after OVX and lasted for 12 weeks. In the in vitro study, primary osteoblasts were incubated with AOH, galangin, and five different fractions (F1-F5) with or without hydrogen peroxide (H2O2), respectively.

RESULTS

Treatment with AOH significantly attenuated osteopenia accompanied by a decreased percentage of osteoclast perimeter and bone formation rate per unit of bone surface, enhanced the bone strength, and prevented the deterioration of trabecular microarchitecture associated with a decrease in biochemical parameters of oxidative stress. Furthermore, treatment with AOH, F3, F4, and galangin increased cell viability, differentiation, and mineralisation in osteoblasts with or without H2O2 and rescued the deleterious effects of H2O2 on cell apoptosis and intracellular reactive oxygen species level. The effects on osteoblast formation were highly aligned with the amounts of flavonoids within AOH.

CONCLUSION

These data demonstrate that ethanol extracts from AOH significantly reverse bone loss, partially by increasing bone formation, and by suppressing bone resorption associated with antioxidant effects, suggesting that AOH can be developed as a promising agent for the prevention and treatment of osteoporosis.

Comparison of the Effects of In-office Bleaching Times on Whitening and Tooth Sensitivity: A Single Blind, Randomized Clinical Trial

OBJECTIVES

The objective of the present study was to compare the bleaching efficacy (BE) and tooth sensitivity (TS) of in-office bleaching applied under different time protocols.

METHODS AND MATERIALS

Fifty-three patients were randomly distributed into three groups: the bleaching agent was applied in one (1×15), two (2×15), or three (3×15) 15-minute applications. The labial surfaces of the anterior teeth were bleached using a 35% hydrogen peroxide gel. Two bleaching sessions with a one-week interval between were performed. The shade evaluation was performed with a visual shade guide and spectrophotometer before and 30 days after bleaching. Participants recorded TS with a five-point verbal scale. Color change was analyzed by one-way analysis of variance and Tukey tests. The absolute risk of TS and TS intensity were evaluated by the Fisher exact and Friedman/Kruskal-Wallis tests, respectively (α= 0.05).

RESULTS

Significant whitening was observed in all groups, with statistically lower BE for the 1×15 group (p<0.05). The absolute risk of TS (95% confidence interval) was lower for the 1×15 group than for the other groups (p<0.05). The TS intensity of the 3×15 group was statistically higher than that associated with the other protocols (p<0.05).

CONCLUSIONS

A single 15-minute application produced less TS but reduced BE. The protocol with 2×15 produced a degree of BE similar to that of the 3×15 group, but with reduced overall TS intensity.

Dental Pulp Defence and Repair Mechanisms in Dental Caries

Dental caries is a chronic infectious disease resulting from the penetration of oral bacteria into the enamel and dentin. Microorganisms subsequently trigger inflammatory responses in the dental pulp. These events can lead to pulp healing if the infection is not too severe following the removal of diseased enamel and dentin tissues and clinical restoration of the tooth. However, chronic inflammation often persists in the pulp despite treatment, inducing permanent loss of normal tissue and reducing innate repair capacities. For complete tooth healing the formation of a reactionary/reparative dentin barrier to distance and protect the pulp from infectious agents and restorative materials is required. Clinical and in vitro experimental data clearly indicate that dentin barrier formation only occurs when pulp inflammation and infection are minimised, thus enabling reestablishment of tissue homeostasis and health. Therefore, promoting the resolution of pulp inflammation may provide a valuable therapeutic opportunity to ensure the sustainability of dental treatments. This paper focusses on key cellular and molecular mechanisms involved in pulp responses to bacteria and in the pulpal transition between caries-induced inflammation and dentinogenic-based repair. We report, using selected examples, different strategies potentially used by odontoblasts and specialized immune cells to combat dentin-invading bacteria in vivo.

17β-Estradiol induces odontoblastic differentiation via activation of the c-Src/MAPK pathway in human dental pulp cells

The present study is aimed at investigating the effects of the exogenous estrogen 17β-estradiol (E2) on odontoblastic differentiation in human dental pulp cells (HDPCs) immotalized with hTERT gene and their molecular mechanism. Proliferation was detected by BrdU assay, and odontoblast differentiation induction was evaluated by the expression of dentin sialophosphoprotein (DSPP), dentin sialoprotein (DSP) and dentin matrix protein1 (DMP1), and alkaline phosphatase (ALP) activity and mineralization. Estrogen receptor-α (ER-α), c-Src, and mitogen-activated protein kinases (MAPKs) were examined and their inhibitors were used to determine the roles on odontogenic induction. E2 significantly promoted the HDPC proliferation, which was mediated by extracellular signal-related kinase 1/2. E2 upregulated DSPP, DSP, and DMP1 as the odontogenic differentiation markers and enhanced ALP activity and mineralization. E2 increased phosphorylation of ER-α and fulvestrant, an ER downregulator, significantly downregulated DSPP, DMP1, and DSP induced by E2. Moreover, E2 treatment activated c-Src and MAPKs upon odontogenic induction, whereas chemical inhibition of c-Src and MAPKs decreased expression of DSPP, DMP1, and DSP and mineralization augmented by E2. Moreover, fulvestrant reduced E2-induced phosphorylation of c-Src and MAPK and inhibition of c-Src by PP2 attenuated activation of MAPKs during E2-induced odontoblastic differentiation. Taken together, these results indicated that E2 stimulates odontoblastic differentiation of HDPCs via coordinated regulation of ER-α, c-Src, and MAPK signaling pathways, which may play a key role in the regeneration of dentin.

Targeting oxidant-dependent mechanisms for the treatment of COPD and its comorbidities

Chronic obstructive pulmonary disease (COPD) is an incurable global health burden and is characterised by progressive airflow limitation and loss of lung function. In addition to the pulmonary impact of the disease, COPD patients often develop comorbid diseases such as cardiovascular disease, skeletal muscle wasting, lung cancer and osteoporosis. One key feature of COPD, yet often underappreciated, is the contribution of oxidative stress in the onset and development of the disease. Patients experience an increased burden of oxidative stress due to the combined effects of excess reactive oxygen species (ROS) and nitrogen species (RNS) generation, antioxidant depletion and reduced antioxidant enzyme activity. Currently, there is a lack of effective treatments for COPD, and an even greater lack of research regarding interventions that treat both COPD and its comorbidities. Due to the involvement of oxidative stress in the pathogenesis of COPD and many of its comorbidities, a unique therapeutic opportunity arises where the treatment of a multitude of diseases may be possible with only one therapeutic target. In this review, oxidative stress and the roles of ROS/RNS in the context of COPD and comorbid cardiovascular disease, skeletal muscle wasting, lung cancer, and osteoporosis are discussed and the potential for therapeutic benefit of anti-oxidative treatment in these conditions is outlined. Because of the unique interplay between oxidative stress and these diseases, oxidative stress represents a novel target for the treatment of COPD and its comorbidities.

Oleanolic Acid, a Compound Present in Grapes and Olives, Protects against Genotoxicity in Human Mammary Epithelial Cells

Oleanolic acid (AO) and maslinic acid (MA) are constituents of the skins of different fruits, including olives and white or red grapes. Although both compounds are known to have beneficial properties against different types of cancers, thus far, there are no studies about their chemopreventive effects in human breast cancer. Thus, we sought to elucidate whether both compounds possess chemopreventive activity. Two cell lines of human breast cancer cells and one noncancerous human mammary epithelial cells were used to determine the effects of OA and MA. The results showed that OA inhibited the proliferation and increased the oxidative stress of highly invasive cells. Additionally, OA decreased oxidative stress and oxidative damage to the DNA in human mammary epithelial cells. These results suggest that OA could act as a chemopreventive agent in human breast cancer and could inhibit the proliferation of highly invasive breast cancer cells.

Plumbagin protects against glucocorticoid-induced osteoporosis through Nrf-2 pathway

Long-term and high-dose glucocorticoids (GCs) supplementation has been linked to osteoporosis. In this study, we studied the protective role of plumbagin against GC-induced cell damage in MC3T3-E1 cells. The effect of dexamethasone (DEX) and plumbagin on cell viability was determined. DEX showed as IC-50 value of 95 μM. Further, 10 μM plumbagin treatment effectively ameliorated DEX-induced cell death by increasing the cell viability to 92 %. A further effect of plumbagin on DEX-induced oxidative stress was determined through reactive oxygen species (ROS) level, lipid peroxide content, and antioxidant status. Nrf-2 nuclear localization was analyzed through immunofluorescence. Protein expression of redox regulator Nrf-2 and their target genes HO-1 and NQO1 and osteogenic markers (OCN, OPN Runx-2) were determined by Western blot. Apoptotic effect was analyzed by mitochondrial membrane potential and caspase activities (3, 8, and 9). The results showed that DEX treatment showed a significant increase in oxidative stress through increased ROS levels and downregulation of cytoprotective antioxidant proteins and antioxidant enzyme activities. Further DEX treatment downregulated the osteogenic markers and upregulated apoptosis through decreased mitochondrial membrane potential and upregulation of caspase activities. Plumbagin treatment significantly reversed the levels of oxidative stress and apoptotic markers and protected against DEX-induced cell damage. Further, plumbagin treatment significantly improved the expression of osteogenic markers compared to DEX treatment. In conclusion, the present study shows that plumbagin offers significant protective role against DEX-induced cellular damage via regulating oxidative stress, apoptosis, and osteogenic markers.

Hydrogen peroxide induces apoptosis in human dental pulp cells via caspase-9 dependent pathway

INTRODUCTION

Reactive oxygen species are a group of metabolic intermediates produced during oxidative metabolism in eukaryotic cells. They include superoxide anion (O2(-)), hydrogen peroxide (H2O2), hydroxyl radical (·OH), and (1)O2. Of these intermediates, H2O2 is the most stable. Dental pulp cells can be invaded by tooth bleaching, laser radiation, and dental materials. This can influence the intracellular level of reactive oxygen species. Apoptosis, which is the best-known form of programmed cell death, is pivotal to tissue development and regeneration. Little information is available regarding the relationship between H2O2 and apoptosis of human dental pulp cells (hDPCs). The purpose of this study was to investigate whether H2O2 can induce apoptosis in hDPCs and its signaling way.

METHODS

HDPCs were obtained by using a modified tissue explant technique in vitro and cultured at 37°C, 20% O2 (5% CO2, 95% air) in Dulbecco modified Eagle medium. Cell viability was investigated by methyl-thiazol-tetrazolium assay. Cell apoptosis was detected by using the annexin V-fluorescein isothiocyanate/propidium iodide apoptosis assay and flow cytometry. Expression of activated caspase-3, cleaved caspase-9, and β-actin was analyzed by using Western blot.

RESULTS

Cell viability of hDPCs decreased more in treated groups than in the control group from days 1 to 7. The relative number of apoptotic cells and the expression of activated caspase-3 and cleaved caspase-9 were much higher in groups exposed to 20 and 50 μmol/L H2O2.

CONCLUSIONS

These results imply that low concentrations of H2O2 are cytotoxic to hDPCs and induce apoptosis in hDPCs in a caspase-9-dependent way.

Indirect cytocompatibility of a low-concentration hydrogen peroxide bleaching gel to odontoblast-like cells

AIM

To assess the initial cytotoxicity and the late phenotype marker expression of odontoblast-like cells (MDPC-23) subjected to less aggressive in-office bleaching therapies.

METHODOLOGY

A 17.5% hydrogen peroxide (H2O2) gel was applied for 45, 15 or 5 min to enamel/dentine discs adapted to trans-wells positioned over cultured MDPC-23 cells. No treatment was performed on the negative control. Immediately after bleaching, the cell viability, gene expression of inflammatory mediators and quantification of H2O2 diffusion were evaluated. The ALP activity, DSPP and DMP-1 gene expression and mineralized nodule deposition (MND) were assessed at 7, 14 or 21 days post-bleaching and analysed statistically with Mann-Whitney U-tests (α = 5%).

RESULTS

H2O2 diffusion, proportional to treatment time, was observed in all bleached groups. Reductions of approximately 31%, 21% and 13% in cell viability were observed for the 45-, 15- and 5-min groups, respectively. This reduction was significant (P < 0.05) for the 45- and 15-min groups, which also presented significant (P < 0.05) over-expression of inflammatory mediators. The 45-min group was associated with significant (P < 0.05) reductions in DMP-1/DSPP expression at all periods, relative to control. The ALP activity and MND were reduced only in initial periods. The 15-min group had less intense reduction of all markers, with no difference to control at 21 days.

CONCLUSIONS

The 17.5% H2O2 applied to tooth specimens for 5 min caused no alteration in the odontoblast-like cells. When this gel was applied for 45 or 15 min, a slight cytotoxicity, associated with alterations in phenotypic markers, was observed. However, cells were able to recover their functions up to 21 days post-bleaching.