Development of sensor cells using NF-κB pathway activation for detection of nanoparticle-induced inflammation

Emerging factors affecting peri-implant bone metabolism

Implant dentistry has evolved to the point that standard implant osseointegration is predictable. This is attributed in part to the advancements in material sciences that have led toward improvements in implant surface technology and characteristics. Nonetheless, there remain several cases where implant therapy fails (specifically at early time points), most commonly attributed to factors affecting bone metabolism. Among these patients, smokers are known to have impaired bone metabolism and thus be subject to higher risks of early implant failure and/or late complications related to the stability of the peri-implant bone and mucosal tissues. Notably, however, emerging data have unveiled other critical factors affecting osseointegration, namely, those related to the metabolism of bone tissues. The aim of this review is to shed light on the effects of implant-related factors, like implant surface or titanium particle release; surgical-related factors, like osseodensification or implanted biomaterials; various drugs, like selective serotonin reuptake inhibitors, proton pump inhibitors, anti-hypertensives, nonsteroidal anti-inflammatory medication, and statins, and host-related factors, like smoking, diet, and metabolic syndrome on bone metabolism, and aseptic peri-implant bone loss. Despite the infectious nature of peri-implant biological complications, these factors must be surveyed for the effective prevention and management of peri-implantitis.

Dental implant material related changes in molecular signatures in peri-implantitis - A systematic review of omics in-vivo studies

OBJECTIVE

Titanium particles have been shown in in-vitro studies to lead to the activation of specific pathways, this work aims to systematically review in- vivo studies examining peri-implant and periodontal tissues at the transcriptome, proteome, epigenome and genome level to reveal implant material-related processes favoring peri-implantitis development investigated in animal and human trials.

METHODS

Inquiring three literature databases (Medline, Embase, Cochrane) a systematic search based on a priori defined PICOs was conducted: '-omics' studies comparing molecular signatures in healthy and infected peri-implant sites and/or healthy and periodontitis-affected teeth in animals/humans. After risk of bias assessments, lists of differentially expressed genes and results of functional enrichment analyses were compiled whenever possible.

RESULTS

Out of 2187 screened articles 9 publications were deemed eligible. Both healthy and inflamed peri-implant tissues showed distinct gene expression patterns compared to healthy/diseased periodontal tissues in animal (n = 4) or human studies (n = 5), with immune response, bone metabolism and oxidative stress being affected the most. Due to the lack of available re-analyzable data and inconsistency in methodology of the eligible studies, integrative analyses on differential gene expression were not applicable CONCLUSION: The differences of transcriptomic signatures in between peri-implant lesions compared to periodontal tissue might be related to titanium particles arising from dental implants and are in line with the in-vitro data recently published by our group. Nevertheless, limitations emerge from small sample sizes of included studies and insufficient publication of re-analyzable data.

Dental implant material related changes in molecular signatures in peri-implantitis - A systematic review and integrative analysis of omics in-vitro studies

OBJECTIVE

Since peri-implantitis differs clinically and histopathologically from periodontitis, implant wear debris is considered to play a role in the destructive processes. This work aims to systematically review if titanium particles affect oral-related cells through changes in molecular signatures (e.g., transcriptome, proteome, epigenome), thereby promoting peri-implantitis.

METHODS

Leveraging three literature databases (Medline, Embase, Cochrane) a systematic search based on a priori defined PICOs was conducted: '-omics' studies examining titanium exposure in oral-related cells. After risk of bias assessments, lists of differentially expressed genes, proteins, and results of functional enrichment analyses were compiled. The significance of overlapping genes across multiple studies was assessed via Monte Carlo simulation and their ranking was verified using rank aggregation.

RESULTS

Out of 2104 screened articles we found 12 eligible publications. A significant overlap of gene expression in oral-related cells exposed to titanium particles was found in four studies. Furthermore, changes in biological processes like immune/inflammatory or stress response as well as toll-like receptor (TLR) and mitogen-activated protein kinase (MAPK) signaling pathways were linked to titanium in transcriptome and proteome studies. Epigenetic changes caused by titanium were detected but inconsistent.

CONCLUSION

An influence of titanium implant wear debris on the development and progression of peri-implantitis is plausible but needs to be proven in further studies. Limitations arise from small sample sizes of included studies and insufficient publication of re-analyzable data.

The Role of Phospholipase Activity of Peroxiredoxin 6 in Its Transmembrane Transport and Protective Properties

Peroxiredoxin 6 (Prdx6) is a multifunctional eukaryotic antioxidant enzyme. Mammalian Prdx6 possesses peroxidase activity against a wide range of organic and inorganic hydroperoxides, as well as exhibits phospholipase A2 (aiPLA2) activity, which plays an important role in the reduction of oxidized phospholipids and cell membrane remodeling. Exogenous Prdx6 has recently been shown to be able to penetrate inside the cell. We hypothesized that this entry may be due to the phospholipase activity of Prdx6. Experiments using exogenous Prdx6 in three cell lines (3T3, A549, RAW 264.7) demonstrated that it is the phospholipase activity that promotes its penetration into the cell. Overoxidation of Prdx6 led to a suppression of the peroxidase activity and a 3-to-4-fold growth of aiPLA2, which enhanced the efficiency of its transmembrane transport into the cells by up to 15 times. A mutant form of Prdx6-S32A with an inactivated phospholipase center turned out to be unable to enter the cells in both the reduced and oxidized state of the peroxidase active center. Previously, we have shown that exogenous Prdx6 has a significant radioprotective action. However, the role of phospholipase activity in the radioprotective effects of Prdx6 remained unstudied. Trials with the mutant Prdx6-S32A form, with the use of a total irradiation model in mice, showed a nearly 50% reduction of the radioprotective effect upon aiPLA2 loss. Such a significant decrease in the radioprotective action may be due to the inability of Prdx6-S32A to penetrate animal cells, which prevents its reduction by the natural intracellular reducing agent glutathione S-transferase (πGST) and lowers the efficiency of elimination of peroxides formed from the effect of ionizing radiation. Thus, phospholipase activity may play an important role in the reduction of oxidized Prdx6 and manifestation of its antioxidant properties.

Current research progress of mammalian cell-based biosensors on the detection of foodborne pathogens and toxins

Foodborne diseases caused by pathogens and toxins are a serious threat to food safety and human health; thus, they are major concern to society. Existing conventional foodborne pathogen or toxin detection methods, including microbiological assay, nucleic acid-based assays, immunological assays, and instrumental analytical method, are time-consuming, labor-intensive and expensive. Because of the fast response and high sensitivity, cell-based biosensors are promising novel tools for food safety risk assessment and monitoring. This review focuses on the properties of mammalian cell-based biosensors and applications in the detection of foodborne pathogens (bacteria and viruses) and toxins (bacterial toxins, mycotoxins and marine toxins). We discuss mammalian cell adhesion and how it is involved in the establishment of 3D cell culture models for mammalian cell-based biosensors, as well as evaluate their limitations for commercialization and further development prospects.

A Cell Model of Human Small Intestinal Wall Based on Genetically Modified Caco-2 Cells

We propose a cell model of the human small intestinal wall based on genetically modified Caco-2 cells that allows visualization and quantitative assessment of activation of NF-κB factor and related intracellular pathway by using fluorescence microscopy. A dose-dependent increase in fluorescence intensity of the obtained cells in response to TNFα exposure in concentrations of 1-100 ng/ml was demonstrated. It was found that this parameter correlates with a decrease in the transepithelial resistance of the cell monolayer in response to TNFα and can be used to assess the toxic effects of substances on epithelial cells of the human small intestine.

Screening Method for Anti-Colon Cancer Drugs Using Two Sensor Cell Lines with Human β4-Galactosyltransferase 4 Gene Promoters

The increased expression of β4-galactosyltransferase (β4GalT) 4 is closely associated with poor prognosis of colon cancer. Recently, we showed that the expression of the β4GalT4 gene is regulated by the 0.17 kb core promoter region containing one binding site for Specificity protein 1 (Sp1). To develop a screening method for anti-colon cancer drugs, two sensor cell lines having the luciferase gene under the control of two β4GalT4 gene promoters that differed in length were established from SW480 human colon cancer cells. The hGT4-0.17-sensor cells possessed the luciferase reporter driven by the 0.17 kb promoter, while the hGT4-0.3-sensor cells possessed the luciferase reporter driven by the 0.3 kb promoter containing one binding site each for colon cancer-related transcription factors including activator protein 2, E2F, caudal-related homeobox transcription factors, and Runt-related transcription factors besides Sp1. Upon treatment with mitogen-activated protein kinase signaling inhibitor U0126, the promoter activities of the hGT4-0.3-sensor cells decreased significantly, while those of the hGT4-0.17-sensor cells remained unchanged. These results suggest that the responsiveness to U0126 differs between two sensor cell lines due to the different regulation of the luciferase reporters. This study provides the screening method for anti-colon cancer drugs by the combination of two sensor cell lines.

A Key Major Guideline for Engineering Bioactive Multicomponent Nanofunctionalization for Biomedicine and Other Applications: Fundamental Models Confirmed by Both Direct and Indirect Evidence

This paper deals with the engineering multicomponent nanofunctionalization process considering fundamental physicochemical features of nanostructures such as surface energy, chemical bonds, and electrostatic interactions. It is pursued by modeling the surface nanopatterning and evaluating the proposed technique and the models. To this end, the effects of surface modifications of nanoclay on surface interactions, orientations, and final features of TiO₂/Mt nanocolloidal textiles functionalization have been investigated. Various properties of cross-linkable polysiloxanes (XPs) treated samples as well as untreated samples with XPs have been compared to one another. The complete series of samples have been examined in terms of bioactivity and some physical properties, given to provide indirect evidence on the surface nanopatterning. The results disclosed a key role of the selected factors on the final features of treated surfaces. The effects have been thoroughly explained and modeled according to the fundamental physicochemical features. The developed models and associated hypotheses interestingly demonstrated a full agreement with all measured properties and were appreciably confirmed by FESEM evidence (direct evidence). Accordingly, a guideline has been developed to facilitate engineering and optimizing the pre-, main, and post-multicomponent nanofunctionalization procedures in terms of fundamental features of nanostructures and substrates for biomedical applications and other approaches.

Cellular Response to Titanium Dioxide Nanoparticles in Intestinal Epithelial Caco-2 Cells is Dependent on Endocytosis-Associated Structures and Mediated by EGFR

Titanium dioxide (TiO₂) is one of the most applied nanomaterials and widely used in food and non-food industries as an additive or coating material (E171). It has been shown that E171 contains up to 37% particles which are smaller than 100 nm and that TiO₂ nanoparticles (NPs) induce cytotoxicity and inflammation. Using a nuclear factor Kappa-light-chain enhancer of activated B cells (NF-κB) reporter cell line (Caco-2^nfkb-RE), Real time polymerase chain reaction (PCR), and inhibition of dynamin and clathrin, it was shown that cellular responses induced by 5 nm and 10 nm TiO₂ NPs (nominal size) depends on endocytic processes. As endocytosis is often dependent on the epithelial growth factor receptor (EGFR), further investigations focused on the involvement of EGFR in the uptake of TiO₂ NPs: (1) inhibition of EGFR reduced inflammatory markers of the cell (i.e., nuclear factor (NF)-κB activity, mRNA of IL8, CCL20, and CXCL10); and (2) exposure of Caco-2 cells to TiO₂ NPs activated the intracellular EGFR cascade beginning with EGFR-mediated extracellular signal-regulated kinases (ERK)1/2, and including transcription factor ELK1. This was followed by the expression of ERK1/2 target genes CCL2 and CXCL3. We concluded that TiO₂ NPs enter the cell via EGFR-associated endocytosis, followed by activation of the EGFR/ERK/ELK signaling pathway, which finally induces NF-κB. No changes in inflammatory response are observed in Caco-2 cells exposed to 32 nm and 490 nm TiO₂ particles.

Expression of retinol binding protein 4 and nuclear factor-κB in diabetic rats with atherosclerosis and the intervention effect of pioglitazone

This study aims to investigate the expression of retinol binding protein 4 (RBP4) and the activity of nuclear factor-kappa B (NF-κB) in diabetic rats with atherosclerosis, and to evaluate the intervention effect of pioglitazone. A total of 75 Wistar rats were randomly divided into four groups: Normal control (NC), diabetic rats (DM1), diabetic rats with atherosclerosis (DM2) and diabetic rats treated with pioglitazone (DM + Pio). The activity of NF-κB, the levels of serum and adipose tissue RBP4, fasting plasma glucose (FPG), fasting insulin (FINS), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), triglycerides (TG) and arteria caudilis systolic blood pressure (SBP) were measured. Percentage of fat mass (PFM), atherogenic index of plasma (AIP) and homeostasis model assessment of insulin resistance (HOMA-IR) were calculated. Compared with the NC and DM + Pio groups, all the parameters mentioned above increased significantly in the DM1 and DM2 groups, with the exception that HDL-c decreased. Pearson analysis showed that RBP4 in serum and adipose tissue were positively associated with TG, LDL-c, FINS, PFM, AIP, HOMA-IR, NF-κB, SBP and negatively associated with HDL-c. Multivariable logistic regression analysis showed that serum RBP4 and TG were predictors for the presence of diabetic atherosclerosis. In conclusion, RBP4 may be an effective predictor for diabetic atherosclerosis; pioglitazone is able to decrease RBP4 and NF-κB, which may partly contribute to its protective effect against diabetic atherosclerosis.

Titanium dioxide nanoparticles stimulate sea urchin immune cell phagocytic activity involving TLR/p38 MAPK-mediated signalling pathway

Titanium dioxide nanoparticles (TiO2NPs) are one of the most widespread-engineered particles in use for drug delivery, cosmetics, and electronics. However, TiO2NP safety is still an open issue, even for ethical reasons. In this work, we investigated the sea urchin Paracentrotus lividus immune cell model as a proxy to humans, to elucidate a potential pathway that can be involved in the persistent TiO2NP-immune cell interaction in vivo. Morphology, phagocytic ability, changes in activation/inactivation of a few mitogen-activated protein kinases (p38 MAPK, ERK), variations of other key proteins triggering immune response (Toll-like receptor 4-like, Heat shock protein 70, Interleukin-6) and modifications in the expression of related immune response genes were investigated. Our findings indicate that TiO2NPs influence the signal transduction downstream targets of p38 MAPK without eliciting an inflammatory response or other harmful effects on biological functions. We strongly recommend sea urchin immune cells as a new powerful model for nano-safety/nano-toxicity investigations without the ethical normative issue.

Release of titanium ions from an implant surface and their effect on cytokine production related to alveolar bone resorption

Although interest in peri-implant mucositis and peri-implantitis has recently been increasing, the mechanisms driving these diseases remain unknown. Here, the effects of titanium ions on the inflammation and bone resorption around an implant were investigated. First, the accumulated amount of Ti ions released into gingival and bone tissues from an implant exposed to sodium fluoride solution was measured using inductively coupled plasma mass spectrometry. Next, the cellular responses in gingival and bone tissues to Ti ions and/or Porphyromonas gingivalis-lipopolysaccharide (P. gingivalis-LPS) were assessed using a rat model. More Ti ions were detected in the gingival tissues around an implant after treatment with sodium fluoride (pH 4.2) than in its absence, which suggests that the fluoride corroded the implant surface under salivary buffering capacity. The injection of Ti ions (9ppm) significantly increased the mRNA expression and protein accumulation of chemokine (C-C motif) ligand 2, as well as the ratio of receptor activator of nuclear factor-κB ligand to osteoprotegerin, in rat gingival tissues exposed to P. gingivalis-LPS in a synergistic manner. In addition, the enhanced localization of toll-like receptor 4, which is an LPS receptor, was observed in gingival epithelium loaded with Ti ions (9ppm). These data suggest that Ti ions may be partly responsible for the infiltration of monocytes and osteoclast differentiation by increasing the sensitivity of gingival epithelial cells to microorganisms in the oral cavity. Therefore, Ti ions may be involved in the deteriorating effects of peri-implant mucositis, which can develop into peri-implantitis accompanied by alveolar bone resorption.

TiO2 nanoparticles induced hippocampal neuroinflammation in mice

Titanium dioxide nanoparticles (TiO2 NPs) have been used in various medical and industrial areas. However, the impacts of these nanoparticles on neuroinflammation in the brain are poorly understood. In this study, mice were exposed to 2.5, 5, or 10 mg/kg body weight TiO2 NPs for 90 consecutive days, and the TLRs/TNF-α/NF-κB signaling pathway associated with the hippocampal neuroinflammation was investigated. Our findings showed titanium accumulation in the hippocampus, neuroinflammation and impairment of spatial memory in mice following exposure to TiO2 NPs. Furthermore, TiO2 NPs significantly activated the expression of Toll-like receptors (TLR2, TLR4), tumor necrosis factor-α, nucleic IκB kinase, NF-κB-inducible kinase, nucleic factor-κB, NF-κB2(p52), RelA(p65), and significantly suppressed the expression of IκB and interleukin-2. These findings suggest that neuroinflammation may be involved in TiO2 NP-induced alterations of cytokine expression in mouse hippocampus. Therefore, more attention should be focused on the application of TiO2 NPs in the food industry and their long-term exposure effects, especially in the human central nervous system.

Comparison of cellular uptake and inflammatory response via toll-like receptor 4 to lipopolysaccharide and titanium dioxide nanoparticles

The innate immune response is the earliest cellular response to infectious agents and mediates the interactions between microbes and cells. Toll-like receptors (TLRs) play an important role in these interactions. We have already shown that TLRs are involved with the uptake of titanium dioxide nanoparticles (TiO₂ NPs) and promote inflammatory responses. In this paper, we compared role of cellular uptake and inflammatory response via TLR 4 to lipopolysaccharide (LPS) and TiO₂ NPs. In the case of LPS, LPS binds to LPS binding protein (LBP) and CD 14, and then this complex binds to TLR 4. In the case of TiO₂ NPs, the necessity of LBP and CD 14 to induce the inflammatory response and for uptake by cells was investigated using over-expression, antibody blocking, and siRNA knockdown experiments. Our results suggested that for cellular uptake of TiO₂ NPs, TLR 4 did not form a complex with LBP and CD 14. In the TiO₂ NP-mediated inflammatory response, TLR 4 acted as the signaling receptor without protein complex of LPS, LBP and CD 14. The results suggested that character of TiO₂ NPs might be similar to the complex of LPS, LBP and CD 14. These results are important for development of safer nanomaterials.

Role of the Toll Like receptor (TLR) radical cycle in chronic inflammation: possible treatments targeting the TLR4 pathway

Activation of the Toll-like receptor 4 (TLR4) complex, a receptor of the innate immune system, may underpin the pathophysiology of many human diseases, including asthma, cardiovascular disorder, diabetes, obesity, metabolic syndrome, autoimmune disorders, neuroinflammatory disorders, schizophrenia, bipolar disorder, autism, clinical depression, chronic fatigue syndrome, alcohol abuse, and toluene inhalation. TLRs are pattern recognition receptors that recognize damage-associated molecular patterns and pathogen-associated molecular patterns, including lipopolysaccharide (LPS) from gram-negative bacteria. Here we focus on the environmental factors, which are known to trigger TLR4, e.g., ozone, atmosphere particulate matter, long-lived reactive oxygen intermediate, pentachlorophenol, ionizing radiation, and toluene. Activation of the TLR4 pathways may cause chronic inflammation and increased production of reactive oxygen and nitrogen species (ROS/RNS) and oxidative and nitrosative stress and therefore TLR-related diseases. This implies that drugs or substances that modify these pathways may prevent or improve the abovementioned diseases. Here we review some of the most promising drugs and agents that have the potential to attenuate TLR-mediated inflammation, e.g., anti-LPS strategies that aim to neutralize LPS (synthetic anti-LPS peptides and recombinant factor C) and TLR4/MyD88 antagonists, including eritoran, CyP, EM-163, epigallocatechin-3-gallate, 6-shogaol, cinnamon extract, N-acetylcysteine, melatonin, and molecular hydrogen. The authors posit that activation of the TLR radical (ROS/RNS) cycle is a common pathway underpinning many "civilization" disorders and that targeting the TLR radical cycle may be an effective method to treat many inflammatory disorders.

Role of toll-like receptors 3, 4 and 7 in cellular uptake and response to titanium dioxide nanoparticles

Innate immune response is believed to be among the earliest provisional cellular responses, and mediates the interactions between microbes and cells. Toll-like receptors (TLRs) are critical to these interactions. We hypothesize that TLRs also play an important role in interactions between nanoparticles (NPs) and cells, although little information has been reported concerning such an interaction. In this study, we investigated the role of TLR3, TLR4 and TLR7 in cellular uptake of titanium dioxide NP (TiO2 NP) agglomerates and the resulting inflammatory responses to these NPs. Our data indicate that TLR4 is involved in the uptake of TiO2 NPs and promotes the associated inflammatory responses. The data also suggest that TLR3, which has a subcellular location distinct from that of TLR4, inhibits the denaturation of cellular protein caused by TiO2 NPs. In contrast, the unique cellular localization of TLR7 has middle-ground functional roles in cellular response after TiO2 NP exposure. These findings are important for understanding the molecular interaction mechanisms between NPs and cells.

Detection of cellular response to titanium dioxide nanoparticle agglomerates by sensor cells using heat shock protein promoter

Nanotechnology is becoming increasingly important for products used in our daily lives, such as the masses of titanium dioxide nanoparticle agglomerates (TiO(2) NPs) used in the pharmaceutical industry, for cosmetic products, or for pigments. Meanwhile, a serious lack of detailed information concerning the interaction between the nanomaterials and cells limits their biological and medical applications. Sensing technology is very important for understanding these interactions. We have shown that TiO(2) NPs induce heat shock protein 70B' (HSP70B') mRNA [Okuda-Shimazaki et al., 2010. Int J Mol Sci 11:2383-2392]. In the current work, sensor cells for detection of cellular responses to NPs were prepared by transfecting an HSP70B' promoter-reporter plasmid. First, to find suitable cells for detection, five different mammalian cell lines were chosen as potential sensor cells. The results showed TiO(2) NP response in some cell lines, although different sensor cells had different TiO(2) NP response levels, as heat shock response ability is important for the detection. Then, we studied the TiO(2) NP time-course response and dose response. The results indicated that our sensor cells can detect TiO(2) NP cellular responses. Our work should aid in understanding the interactions between bio-nanomaterials and cells.

Effect of polyethylene glycol modification of TiO₂nanoparticles on cytotoxicity and gene expressions in human cell lines

Nanoparticles (NPs) are tiny materials used in a wide range of industrial and medical applications. Titanium dioxide (TiO(2)) is a type of nanoparticle that is widely used in paints, pigments, and cosmetics; however, little is known about the impact of TiO(2) on human health and the environment. Therefore, considerable research has focused on characterizing the potential toxicity of nanoparticles such as TiO(2) and on understanding the mechanism of TiO(2) NP-induced nanotoxicity through the evaluation of biomarkers. Uncoated TiO(2) NPs tend to aggregate in aqueous media, and these aggregates decrease cell viability and induce expression of stress-related genes, such as those encoding interleukin-6 (IL-6) and heat shock protein 70B' (HSP70B'), indicating that TiO(2) NPs induce inflammatory and heat shock responses. In order to reduce their toxicity, we conjugated TiO(2) NPs with polyethylene glycol (PEG) to eliminate aggregation. Our findings indicate that modifying TiO(2) NPs with PEG reduces their cytotoxicity and reduces the induction of stress-related genes. Our results also suggest that TiO(2) NP-induced effects on cytotoxicity and gene expression vary depending upon the cell type and surface modification.

Distinct immunomodulatory effects of a panel of nanomaterials in human dermal fibroblasts

There are many efforts in understanding the effects of nanoparticles on cell viability and metabolism, however, not much is known regarding the distinct molecular mechanisms of inflammation and cellular stress using low dosing concentrations. To address this gap in the literature, we utilized a novel experimental design that specifically probes the effects of a panel of commonly studied engineered nanomaterials along immunomodulatory pathways, including NF-κB. The panel of particles selected for this study included quantum dot nanocrystals, titanium dioxide, hydroxylated fullerenes, and silver nanoparticles. Cell viability, antioxidant activity, select messenger RNA, and protein modulation were studied in primary human dermal fibroblasts (HDF) and NF-κB knockdown HDF cells. Inflammatory and non-inflammatory immune responses were measured using protein and real-time PCR array analysis from HDF cells exposed to sub-lethal concentrations of nanoparticles. Differences in cellular response to nanoparticles in protein and antioxidant experiments were evident in NF-κB knockdown cells. The methods used in the study, along with the resultant data sets, serve as a potential model for studying the complex pathway-specific biochemical responses in cell and tissue systems associated with nanoparticle exposures.