The influence of titanium dioxide nanoparticles on their cellular response to macrophage cells

Broccoli extracellular vesicles enhance the therapeutic effects and restore the chemosensitivity of 5-fluorouracil on colon cancer

Broccoli contains an amount of biologically active substances, which bring beneficial effects on human health. Plant extracellular vesicles have been shown to be novel key factors in cancer diagnosis and tumor therapy. To date, the challenge of overcoming chemoresistance to 5-fluorouracil (5-FU) to facilitate the clinical management of colorectal cancer (CRC) has not been successful. Nevertheless, the functions of broccoli extracellular vesicles (BEVs) in the progression of CRC and 5-FU resistance are predominantly unclear. Herein, we showed that BEVs isolated from broccoli juice were effectively taken up by colorectal cancer HT-29 cells. The co-administration of BEVs and 5-FU significantly inhibited the proliferation and migration of colorectal cancer HT-29 cells, effectively blocking cell cycle progression. Furthermore, the co-administration of BEVs and 5-FU induced apoptosis by stimulating ROS production and disrupting mitochondrial function. Importantly, we found that BEVs reversed 5-FU resistance in HT-29 cells by suppressing the abnormal activation of the PI3K/Akt/mTOR signaling pathway. Collectively, our findings represent a novel strategy for utilizing BEVs to improve the efficacy of colorectal cancer treatment and enhance 5-FU chemosensitivity.

Toxicity mechanism of engineered nanomaterials: Focus on mitochondria

With the rapid development of nanotechnology, engineered nanomaterials (ENMs) are widely used in various fields. This has exacerbated the environmental pollution and human exposure of ENMs. The study of toxicity of ENMs and its mechanism has become a hot research topic in recent years. Mitochondrial damage plays an important role in the toxicity of ENMs. This paper reviews the structural damage, dysfunction, and molecular level perturbations caused by different ENMs to mitochondria, including ZnO NPs, Ag NPs, TiO2 NPs, iron oxide NPs, cadmium-based quantum dots, CuO NPs, silica NPs, carbon-based nanomaterials. Among them, mitochondrial quality control plays an important role in mitochondrial damage. We further summarize the cellular level outcomes caused by mitochondrial damage, mainly including, apoptosis, ferroptosis, pyroptosis and inflammation response. In addition, we concluded that reducing mitochondrial damage at source as well as accelerating recovery from mitochondrial damage through ENMs modification and pharmacological intervention are two feasible strategies. This review further provides new insights into the mitochondrial toxicity mechanisms of ENMs and provides a new foothold for predicting human health and environmental risks of ENMs.

Titanium dioxide nanoparticles: revealing the mechanisms underlying hepatotoxicity and effects in the gut microbiota

Numerous studies in recent years have questioned the safety of oral exposure to titanium dioxide nanoparticles (TiO2 NPs). TiO2 NPs are not only likely to accumulate in the gastrointestinal tract, but they are also found to penetrate the body circulation and reach distant organs. The liver, which is considered to be a target organ for nanoparticles, is of particular concern. TiO2 NPs accumulate in the liver and cause oxidative stress and inflammatory reactions, resulting in pathological damage. The impact of TiO2 NPs on liver aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was studied using a meta-analysis. According to the findings, TiO2 NPs exposure can cause an elevation in AST and ALT levels in the blood. Furthermore, TiO2 NPs are eliminated mostly through feces, and their lengthy residence in the gut exposes them to microbiota. The gut microbiota is also dysbiotic due to titanium dioxide's antibacterial capabilities. This further leads to changes in the amount of microbiota metabolites, which can reach the liver with blood circulation and trigger hepatotoxicity through the gut-liver axis. This review examines the gut-liver axis to assess the effects of gut microbiota dysbiosis on the liver to provide suggestions for assessing the gut-hepatotoxicity of TiO2 NPs.

Recent insights into autophagy and metals/nanoparticles exposure

Some anthropogenic pollutants, such as heavy metals and nanoparticles (NPs), are widely distributed and a major threat to environmental safety and public health. In particular, lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg) have systemic toxicity even at extremely low concentrations, so they are listed as priority metals in relation to their significant public health burden. Aluminum (Al) is also toxic to multiple organs and is linked to Alzheimer's disease. As the utilization of many metal nanoparticles (MNPs) gradually gain traction in industrial and medical applications, they are increasingly being investigated to address potential toxicity by impairing certain biological barriers. The dominant toxic mechanism of these metals and MNPs is the induction of oxidative stress, which subsequently triggers lipid peroxidation, protein modification, and DNA damage. Notably, a growing body of research has revealed the linkage between dysregulated autophagy and some diseases, including neurodegenerative diseases and cancers. Among them, some metals or metal mixtures can act as environmental stimuli and disturb basal autophagic activity, which has an underlying adverse health effect. Some studies also revealed that specific autophagy inhibitors or activators could modify the abnormal autophagic flux attributed to continuous exposure to metals. In this review, we have gathered recent data about the contribution of the autophagy/mitophagy mediated toxic effects and focused on the involvement of some key regulatory factors of autophagic signaling during exposure to selected metals, metal mixtures, as well as MNPs in the real world. Besides this, we summarized the potential significance of interactions between autophagy and excessive reactive oxygen species (ROS)-mediated oxidative damage in the regulation of cell survival response to metals/NPs. A critical view is given on the application of autophagy activators/inhibitors to modulate the systematic toxicity of various metals/MNPs.

Ti Ions Induce IL-1β Release by Activation of the NLRP3 Inflammasome in a Human Macrophage Cell Line

The aim of the present study was to investigate whether titanium (Ti)-induced release of interleukin (IL)-1β acts through the assembly of the NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome. In addition, we examined whether particulate Ti or TiO₂ activates the same intracellular pathways with the assembly of the NLRP3 inflammasome as Ti ions. Ti ions are known to induce IL-1β maturation and release by the formation of metal-protein aggregates. Wild-type THP-1 (wt.) cells and NLRP3^- and ASC^- (apoptosis-associated speck-like protein containing caspase recruitment domain (CARD)) knockdown cells were used in the experimental analyses. Macro- and nanoparticles (NPs) of both Ti and TiO₂ were used as test agents. IL-1β release as a biomarker for inflammasome activation and cell viability was also analyzed. Periodate-oxidized adenosine triphosphate (oATP) was used to attenuate downstream signaling in NLRP3 inflammasome activation. Cellular uptake of Ti was examined using transmission electron microscopy. Cells exposed to the Ti-ion solution showed a dose-dependent increase in the release of IL-1β; conversely, exposure to particulate Ti did not result in increased IL-1β release. Cell viability was not affected by particulate Ti. Knockdown cells exposed to Ti showed a statistically significant reduction in the release of IL-1β compared with wt. cells (p < 0.001). Cellular uptake was detected in all Ti mixtures, and aggregates with various structures were observed. Ti ion-induced release of bioactive IL-1β in THP-1 cells involves the assembly of the NLRP3 inflammasome.

Graphene oxide and mineralized collagen-functionalized dental implant abutment with effective soft tissue seal and romotely repeatable photodisinfection

Grasping the boundary of antibacterial function may be better for the sealing of soft tissue around dental implant abutment. Inspired by ‘overdone is worse than undone’, we prepared a sandwich-structured dental implant coating on the percutaneous part using graphene oxide (GO) wrapped under mineralized collagen. Our unique coating structure ensured the high photothermal conversion capability and good photothermal stability of GO. The prepared coating not only achieved suitable inhibition on colonizing bacteria growth of Streptococcus sanguinis, Fusobacterium nucleatum and Porphyromonas gingivalis but also disrupted the wall/membrane permeability of free bacteria. Further enhancements on the antibacterial property were generally observed through the additional incorporation of dimethylaminododecyl methacrylate. Additionally, the coating with sandwich structure significantly enhanced the adhesion, cytoskeleton organization and proliferation of human gingival fibroblasts, which was effective to improve soft tissue sealing. Furthermore, cell viability was preserved when cells and bacteria were cultivated in the same environment by a coculture assay. This was attributed to the sandwich structure and mineralized collagen as the outmost layer, which would protect tissue cells from photothermal therapy and GO, as well as accelerate the recovery of cell activity. Overall, the coating design would provide a useful alternative method for dental implant abutment surface modification and functionalization.

Titanium Nanoparticles Enhance Production and Suppress Stabilin-1-Mediated Clearance of GDF-15 in Human Primary Macrophages

Macrophages are key innate immune cells that mediate implant acceptance or rejection. Titanium implants degrade over time inside the body, which results in the release of implant wear-off particles. Titanium nanoparticles (TiNPs) favor pro-inflammatory macrophage polarization (M1) and lower tolerogenic activation (M2). GDF-15 regulates immune tolerance and fibrosis and is endocytosed by stabilin-1. How TiNPs affect the healing activities of macrophages and their release of circulating cytokines is an open question in regenerative medicine. In this study for the first time, we identified the transcriptional program induced and suppressed by TiNPs in human pro-inflammatory and healing macrophages. Microarray analysis revealed that TiNPs altered the expression of 5098 genes in M1 (IFN-γ-stimulated) and 4380 genes in M2 (IL-4–stimulated) macrophages. 1980 genes were differentially regulated in both M1 and M2. Affymetrix analysis, confirmed by RT-PCR, demonstrated that TiNPs upregulate expression of GDF-15 and suppress stabilin-1, scavenger receptor of GDF-15. TiNPs also significantly stimulated GDF-15 protein secretion in inflammatory and healing macrophages. Flow cytometry demonstrated, that scavenging activity of stabilin-1 was significantly suppressed by TiNPs. Confocal microscopy analysis showed that TiNPs impair internalization of stabilin-1 ligand acLDL and its transport to the endocytic pathway. Our data demonstrate that TiNPs have a dual effect on the GDF-15/stabilin-1 interaction in macrophage system, by increasing the production of GDF-15 and suppressing stabilin-1-mediated clearance function. In summary, this process can result in a significant increase of GDF-15 in the extracellular space and in circulation leading to unbalanced pro-fibrotic reactions and implant complications.

Silica nanoparticles induce mitochondrial pathway-dependent apoptosis by activating unfolded protein response in human neuroblastoma cells

The application of silica nanoparticles (SiNPs) in areas of agriculture and medicine has raised great concerns for the potential adverse effects of SiNPs. The increasing toxicological studies focused mainly on the lung and cardiovascular system, but the adverse effects of SiNPs on nervous system have not been well explored. This study aimed to evaluate the role and mechanism of unfolded protein reaction (UPR) in SiNPs-induced cell injury on nerve cells in vitro. We investigated the UPR-mediated apoptosis caused by SiNPs in human neuroblastoma (SH-SY5Y) cell line. The size of SiNPs and its effect on cell ultrastructure were observed by transmission electron microscopy (TEM). Cell growth, mitochondrial membrane potential (MMP), calcium ion (Ca²⁺ ), apoptosis rate, and the expression level of related proteins were evaluated using MTT, flow cytometry, and western blot in SH-SY5Y cells exposed to SiNPs. The results showed that with the increase of SiNPs concentration, cell viability decreased, MMP decreased, active oxygen (ROS), and Ca²⁺ levels increased in a dose-dependent manner. In addition, protein expression of PERK, GRP78, and other related proteins in the unfolded protein response increased in a dose-response manner together with the expression of apoptosis proteins. Conclusively, this study confirmed that SiNPs can affect the neural system by interfering structure and functional and inducing apoptosis in nerve cells through unfolded protein response.

Titanium Dioxide Presents a Different Profile in Dextran Sodium Sulphate-Induced Experimental Colitis in Mice Lacking the IBD Risk Gene Ptpn2 in Myeloid Cells

Environmental and genetic factors have been demonstrated to contribute to the development of inflammatory bowel disease (IBD). Recent studies suggested that the food additive; titanium dioxide (TiO2) might play a causative role in the disease. Therefore, in the present study we aimed to explore the interaction between the food additive TiO2 and the well-characterized IBD risk gene protein tyrosine phosphatase non-receptor type 2 (Ptpn2) and their role in the development of intestinal inflammation. Dextran sodium sulphate (DSS)-induced acute colitis was performed in mice lacking the expression of Ptpn2 in myeloid cells (Ptpn2LysMCre) or their wild type littermates (Ptpn2fl/fl) and exposed to the microparticle TiO2. The impact of Ptpn2 on TiO2 signalling pathways and TiO2-induced IL-1β and IL-10 levels were studied using bone marrow-derived macrophages (BMDMs). Ptpn2LysMCre exposed to TiO2 exhibited more severe intestinal inflammation than their wild type counterparts. This effect was likely due to the impact of TiO2 on the differentiation of intestinal macrophages, suppressing the number of anti-inflammatory macrophages in Ptpn2 deficient mice. Moreover, we also found that TiO2 was able to induce the secretion of IL-1β via mitogen-activated proteins kinases (MAPKs) and to repress the expression of IL-10 in bone marrow-derived macrophages via MAPK-independent pathways. This is the first evidence of the cooperation between the genetic risk factor Ptpn2 and the environmental factor TiO2 in the regulation of intestinal inflammation. The results presented here suggest that the ingestion of certain industrial compounds should be taken into account, especially in individuals with increased genetic risk.

Oral exposure of titanium oxide nanoparticles induce ileum physical barrier dysfunction via Th1/Th2 imbalance

In this work, we aimed to evaluate the adverse effects and the mechanism of intestinal barrier caused by titanium dioxide nanoparticles (TiO₂ NPs). Here, the effects of two different dosages (300 and 1200 mg/kg) of TiO₂ NPs on female mice (n = 5) were investigated. After 28-day oral exposure, the results of Ti content were significantly increased in the ileum in comparison with the control. The histopathological structure index of the ileum was significantly changed after TiO₂ NPs exposure; villi height and crypt depth were decreased and increased, respectively. Meanwhile, TiO₂ NPs treatment also significantly altered the transcription levels of genes. First, the GATA-3 and STAT-4 were upregulation and downregulation, respectively. Second, gene expressions of the Zonula Occludens-1, claudin (CLDN)-12, occludin, and myosin light chain kinase were significantly upregulated, while the CLDN-3 was decreased. Finally, the caspase-3, caspase-9, and caspase-12 were upregulated. The results of TUNEL staining indicated apoptosis in the ileum. In general, TiO₂ NPs treatment significantly changed the intestine physical barrier in a dose-dependent manner. The toxicity of TiO₂ NPs could be through the imbalance in the Th1/Th2.

Bone loss around implants-is it metallosis?

Most would agree that the etiology of dental implant failure is related to oral biofilm. At present one group of scientists and clinicians feel that biofilm is solely responsible for bone loss around the devices. However, there is strong evidence that particles and ions of titanium released into the surrounding tissues by the action of biofilm and/or mechanical forces, a process termed metallosis, can be responsible for bone loss around some dental implants. These findings are reinforced by similar responses found around failed metal on metal joint prostheses. Both possible etiologies are discussed in detail in this commentary.

Targeting of Hepatic Macrophages by Therapeutic Nanoparticles

Hepatic macrophage populations include different types of cells with plastic properties that can differentiate into diverse phenotypes to modulate their properties in response to different stimuli. They often regulate the activity of other cells and play an important role in many hepatic diseases. In response to those pathological situations, they are activated, releasing cytokines and chemokines; they may attract circulating monocytes and exert functions that can aggravate the symptoms or drive reparation processes. As a result, liver macrophages are potential therapeutic targets that can be oriented toward a variety of aims, with emergent nanotechnology platforms potentially offering new perspectives for macrophage vectorization. Macrophages play an essential role in the final destination of nanoparticles (NPs) in the organism, as they are involved in their uptake and trafficking in vivo. Different types of delivery nanosystems for macrophage recognition and targeting, such as liposomes, solid-lipid, polymeric, or metallic nanoparticles, have been developed. Passive targeting promotes the accumulation of the NPs in the liver due to their anatomical and physiological features. This process is modulated by NP characteristics such as size, charge, and surface modifications. Active targeting approaches with specific ligands may also be used to reach liver macrophages. In order to design new systems, the NP recognition mechanism of macrophages must be understood, taking into account that variations in local microenvironment may change the phenotype of macrophages in a way that will affect the uptake and toxicity of NPs. This kind of information may be applied to diseases where macrophages play a pathogenic role, such as metabolic disorders, infections, or cancer. The kinetics of nanoparticles strongly affects their therapeutic efficacy when administered in vivo. Release kinetics could predict the behavior of nanosystems targeting macrophages and be applied to improve their characteristics. PBPK models have been developed to characterize nanoparticle biodistribution in organs of the reticuloendothelial system (RES) such as liver or spleen. Another controversial issue is the possible toxicity of non-degradable nanoparticles, which in many cases accumulate in high percentages in macrophage clearance organs such as the liver, spleen, and kidney.

Metal Oxide Nanoparticles in Therapeutic Regulation of Macrophage Functions

Macrophages are components of the innate immune system that control a plethora of biological processes. Macrophages can be activated towards pro-inflammatory (M1) or anti-inflammatory (M2) phenotypes depending on the cue; however, polarization may be altered in bacterial and viral infections, cancer, or autoimmune diseases. Metal (zinc, iron, titanium, copper, etc.) oxide nanoparticles are widely used in therapeutic applications as drugs, nanocarriers, and diagnostic tools. Macrophages can recognize and engulf nanoparticles, while the influence of macrophage-nanoparticle interaction on cell polarization remains unclear. In this review, we summarize the molecular mechanisms that drive macrophage activation phenotypes and functions upon interaction with nanoparticles in an inflammatory microenvironment. The manifold effects of metal oxide nanoparticles on macrophages depend on the type of metal and the route of synthesis. While largely considered as drug transporters, metal oxide nanoparticles nevertheless have an immunotherapeutic potential, as they can evoke pro- or anti-inflammatory effects on macrophages and become essential for macrophage profiling in cancer, wound healing, infections, and autoimmunity.