TiO2 nanoparticles induce endothelial cell activation in a pneumocyte-endothelial co-culture model

Current Challenges to Align Inflammatory Key Events in Animals and Lung Cell Models In Vitro

With numerous novel and innovative in vitro models emerging every year to reduce or replace animal testing, there is an urgent need to align the design, harmonization, and validation of such systems using in vitro-in vivo extrapolation (IVIVE) approaches. In particular, in inhalation toxicology, there is a lack of predictive and prevalidated in vitro lung models that can be considered a valid alternative for animal testing. The predictive power of such models can be enhanced by applying the Adverse Outcome Pathways (AOP) framework, which casually links key events (KE) relevant to IVIVE. However, one of the difficulties identified is that the endpoint analysis and readouts of specific assays in in vitro and animal models for specific toxicants are currently not harmonized, making the alignment challenging. We summarize the current state of the art in endpoint analysis in the two systems, focusing on inflammatory-induced effects and providing guidance for future research directions to improve the alignment.

Pro-inflammatory effects of crystalline- and nano-sized non-crystalline silica particles in a 3D alveolar model

BACKGROUND

Silica nanoparticles (SiNPs) are among the most widely manufactured and used nanoparticles. Concerns about potential health effects of SiNPs have therefore risen. Using a 3D tri-culture model of the alveolar lung barrier we examined effects of exposure to SiNPs (Si10) and crystalline silica (quartz; Min-U-Sil) in the apical compartment consisting of human alveolar epithelial A549 cells and THP-1-derived macrophages, as well as in the basolateral compartment with Ea.hy926 endothelial cells. Inflammation-related responses were measured by ELISA and gene expression.

RESULTS

Exposure to both Si10 and Min-U-Sil induced gene expression and release of CXCL8, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α) and interleukin-1β (IL-1β) in a concentration-dependent manner. Cytokine/chemokine expression and protein levels were highest in the apical compartment. Si10 and Min-U-Sil also induced expression of adhesion molecules ICAM-1 and E-selectin in the apical compartment. In the basolateral endothelial compartment we observed marked, but postponed effects on expression of all these genes, but only at the highest particle concentrations. Geneexpressions of heme oxygenase-1 (HO-1) and the metalloproteases (MMP-1 and MMP-9) were less affected. The IL-1 receptor antagonist (IL-1RA), markedly reduced effects of Si10 and Min-U-Sil exposures on gene expression of cytokines and adhesion molecules, as well as cytokine-release in both compartments.

CONCLUSIONS

Si10 and Min-U-Sil induced gene expression and release of pro-inflammatory cytokines/adhesion molecules at both the epithelial/macrophage and endothelial side of a 3D tri-culture. Responses in the basolateral endothelial cells were only induced at high concentrations, and seemed to be mediated by IL-1α/β released from the apical epithelial cells and macrophages.

Titanium dioxide nanoparticles induce endothelial cell apoptosis via cell membrane oxidative damage and p38, PI3K/Akt, NF-κB signaling pathways modulation

BACKGROUND

Titanium dioxide nanoparticles (TiO₂ NPs) are widely used nanoparticles. Despite, several studies investigated the toxic effects of TiO₂ NPs on HUVECs, the results are contradictory and the possible underlying mechanisms remain unclear.

METHODS

In the present study, we conducted an in vitro study to re-evaluate the possible toxic effects of TiO₂ NPs on HUVECs including cell viability, lipids peroxidation, intracellular signaling pathways and nitric oxide syntheses enzymes.

RESULTS

Our results demonstrated that, TiO₂ NPs were internalized to HUVECs and induce intracellular reactive oxygen species production and cell membrane oxidative damage at the higher concentration. TiO₂ NPs induce IKKα/β and Akt phosphorylation and p38 dephosphorylation. After 24 h treatment, pro-inflammatory cytokines, adhesion molecules and chemokine upregulated significantly. TiO₂ NPs have no significant effects on eNOS enzymatic activation and iNOS gene expression. At cellular level, apoptosis is the main process that occur in response to TiO2 NPs treatment. HUVECs pretreatment with N-acetyl-l-cysteine (NAC) ameliorate the toxic effects of TiO₂ NPs that indicate the oxidative stress is essential in TiO₂ NPs -induced toxicity. Total antioxidant capacity show a trend to increase in response to TiO₂ NPs exposure.

CONCLUSIONS

Taken together, this study confirmed the effects of TiO₂ NPs on endothelial cells and proposed multiple underlying mechanisms including cell membrane oxidative damage and intracellular processes.

Anthocyanins and metabolites resolve TNF-α-mediated production of E-selectin and adhesion of monocytes to endothelial cells

This study investigated the capacity of an anthocyanin-rich fraction (ACN-RF) from blueberry, single anthocyanins (cyanidin, delphinidin and malvidin-3-glucoside; Cy, Dp and Mv-3-glc) and related metabolites (protocatechuic, gallic and syringic acid; PrA, GA and SA) to resolve an inflammation-driven adhesion of monocytes (THP-1) on endothelial cell (HUVECs) and secretion of cell adhesion molecules E-selectin and vascular cell adhesion molecule 1 (VCAM-1). The adhesion of THP-1 to HUVECs was induced by tumour necrosis factor α (TNF-α, 100 ng mL^-1). Subsequently, ACN-RF, single ACNs and metabolites (from 0.01 to 10 μg mL^-1) were incubated for 24 h. The adhesion was measured in a fluorescence spectrophotometer. E-selectin and VCAM-1 were quantified by ELISA. No toxicological effects were observed for the compounds and the doses tested. ACN-RF and Mv-3-glc reducedTHP-1 adhesion at all the concentrations with the maximum effect at 10 μg/ml (-60.2% for ACNs and-33.9% for Mv-3-glc). Cy-3-glc decreased the adhesion by about 41.8% at 10 μg mL^-1, while PrA and GA reduced the adhesion of THP-1 to HUVECs both at 1 and at 10 μg mL^-1 (-29.5% and -44.3% for PrA, respectively, and -18.0%and -59.3% for GA, respectively). At the same concentrations a significant reduction of E-selectin, but notVCAM-1 levels, was documented. No effect was observed following Dp-3-glc and SA supplementation. Overall, ACNs and metabolites seem to resolve, in a dose-dependent manner, the inflammation-driven adhesion of THP-1 to HUVECs by decreasing E-selectin concentrations. Interestingly, Mv-3-glc was active at physiologically relevant concentrations.

Bio-Effects of TiO2 Nanoparticles on Human Colorectal Cancer and Umbilical Vein Endothelial Cell Lines

Background: Due to the possible biomedical potential of nanoparticles, titanium dioxide nanoparticles (TiO2 NPs) have received great attention in cancer research. Although selectivity of cytotoxicity with TiO2 NPs in various cells is clinically significant comparisons of cancer and non-cancer cells have been limited. Therefore, we here studied exposure to TiO2 NPs in colorectal cancer cells (CRCs) and human umbilical vein endothelial cells (HUVECs). Methods: After characterization of TiO2 NPs, culture and treatment of cells (HCT116, HT29 and HUVEC), viability was assessed by MTT assay and in terms of morphological features. Acridine orange (AO) and propidium iodide (PI) assays were carried out to estimate the incidence of apoptosis. The RT-PCR method was also employed to evaluate the expression of P53, Bax, Bcl-2 and Caspase 3. Results: Exposure to increasing concentrations of TiO2 NPs enhanced overall cell survival of HCT116 cells and reduced the Bcl-2 and Caspase 3 expression while the ratio of Bax/Bcl-2 was down-regulated. TiO2 NPs at 400 and 50 μg/ml concentrations suppressed cell proliferation and induced apoptosis of HT29 cells and also up-regulated P53 and Bax at the mRNA level, enhanced the Bax/Bcl-2 ratio and eventually up-regulated Caspase 3 mRNA. Although, inhibition of cell proliferation in HUVECs was seen at 200 and 400 μg/ml TiO2 NPs, it was not marked. Conclusion: TiO2 NPs have selective bio-effects on exposed cells with dose- and cell-dependent influence on viability. Cell proliferation in HCT116 as a metastatic colorectal cancer cell line appeared to be stimulated via multiple signaling pathways, with promotion of apoptosis in less metastatic cells at 50 and 400 μg/ml concentrations. This was associated with elevated P53, Bax and Caspase 3 mRNA and reduced Bcl-2 expression. However, TiO2 NPs did not exert any apparent significant effects on HUVECs as hyperproliferative angiogenic cells.

Engineering an aligned endothelial monolayer on a topologically modified nanofibrous platform with a micropatterned structure produced by femtosecond laser ablation

Laser ablated nanofibers with micropattern regulated adhesion and orientation of HUVEC and also contributed to generate an aligned endothelial monolayer.

Titanium dioxide nanoparticles induce the expression of early and late receptors for adhesion molecules on monocytes

BACKGROUND

There is growing evidence that exposure to titanium dioxide nanoparticles (TiO2 NPs) could be harmful. Previously, we have shown that TiO2 NPs induces endothelial cell dysfunction and damage in glial cells. Considering that inhaled particles can induce systemic effects and the evidence that nanoparticles may translocate out of the lungs, we evaluated whether different types of TiO2 NPs can induce the expression of receptors for adhesion molecules on monocytes (U937 cell line). We evaluated the role of reactive oxygen spices (ROS) on these effects.

METHODS

The expression of receptors for early (sLe(x) and PSGL-1) and late (LFA-1, VLA-4 and αVβ3) adhesion molecules was evaluated in U937 cells on a time course (3-24 h) using a wide range of concentrations (0.001-100 μg/mL) of three types of TiO2 NPs (<25 nm anatase, 50 nm anatase-rutile or < 100 nm anatase). Cells exposed to TNFα were considered positive controls, and unexposed cells, negative controls. In some experiments we added 10 μmolar of N-acetylcysteine (NAC) to evaluate the role of ROS.

RESULTS

All tested particles, starting at a concentration of 0.03 μg/mL, induced the expression of receptors for early and late adhesion molecules. The largest increases were induced by the different molecules after 3 h of exposure for sLe(x) and PSGL-1 (up to 3-fold of the positive controls) and after 18 h of exposure for LFA-1, VLA-4 and αVβ3 (up to 2.5-fold of the positive controls). Oxidative stress was observed as early as 10 min after exposure, but the maximum peak was found after 4 h of exposure. Adhesion of exposed or unexposed monocytes to unexposed or exposed endothelial cells was tested, and we observed that monocytes cells adhere in similar amounts to endothelial cells if one of the two cell types, or both were exposed. When NAC was added, the expression of the receptors was inhibited.

CONCLUSIONS

These results show that small concentrations of particles may activate monocytes that attach to endothelial cells. These results suggest that distal effects can be induced by small amounts of particles that may translocate from the lungs. ROS play a central role in the induction of the expression of these receptors.

Predilection of contralateral upper lung metastasis in upper lobe lung adenocarcinoma patients

BACKGROUND

Lung cancer with lung to lung metastasis is common. The objective of this study was to investigate the association among the distribution of contralateral lung metastases versus primary lung tumor location, clinical characteristics, and epidermal growth factor receptor (EGFR) mutations status.

METHODS

The study included treatment-naïve stage IV lung adenocarcinoma with contralateral lung metastases from 2012 through 2013.

RESULTS

In total, 103 patients were enrolled after excluding lung cancer with histology other than adenocarcinoma, synchronous multiple primary lung cancers, or other active malignancy. The median age was 65 years (range, 28-93 years); 47 male patients (45.6%); 69 non-smoker (NS) patients (67.0%); 68 Eastern Cooperative Oncology Group performance status (ECOG PS) 0-1 patients (66.0%); 38 M1a patients (38.9%); and 60 EGFR mutation patients (58.3%). There were 51 cases (49.5%) with primary lung cancer located over upper lobes. Among them, 36 (70.6%) had contralateral upper lung predominance metastasis, 9 (17.6%) had lower lung predominance, and 6 (11.8%) had equal distribution. Among the 52 lower lobe tumors, 17 (32.7%), 19 (36.5%), and 16 (30.8%) had upper, lower lung predominance, and equal distribution metastasis, respectively. Univariate analysis showed only male gender and primary tumor location over upper lobes were significantly associated with contralateral upper lung predominance metastases. After multivariate analysis, only primary tumor location over upper lobes was significantly associated with contralateral upper lung predominance metastases (adjusted OR 5.49, 95% CI, 2.15-14.03, P<0.001).

CONCLUSIONS

Upper lobe lung adenocarcinoma was significantly associated with contralateral upper lung predominance metastases. Further research is needed to elucidate the mechanisms underlying this phenomenon.

The influence of flow, shear stress and adhesion molecule targeting on gold nanoparticle uptake in human endothelial cells

The uptake of nanoparticles by endothelial cells is dependent on shear stress adaptation and flow exposure conditions. Adaptation of primary human umbilical vein endothelial cells (HUVECs) to shear stress for 24 h was associated with reduced internalisation of unmodified 80 nm spherical gold nanoparticles (AuNPs) (mean hydrodynamic size of 99 nm in culture medium) after exposure to flow conditions compared with cells that were cultured and exposed to static conditions. Under static conditions, targeting of 80 nm AuNPs conjugated with antibodies against the intracellular adhesion molecule 1 (ICAM-1) (mean hydrodynamic size of 109 nm in culture medium) markedly increased the internalisation of AuNPs in HUVECs that were activated with the tumour necrosis factor (TNF), a treatment that markedly increased the surface expression of ICAM-1. Shear stress-adapted and TNF-activated HUVECs, which were exposed to flow conditions, had higher association with anti-ICAM-1 AuNPs than cells that were not TNF-activated or exposed to particles under static conditions. Hence, shear stress adaptation reduces the uptake of unmodified AuNPs and increases the association between anti-ICAM-1 AuNPs and TNF-activated HUVECs.

Vascular toxicity of ultra-small TiO2 nanoparticles and single walled carbon nanotubes in vitro and in vivo

Ultra-small nanoparticles (USNPs) at 1-3 nm are a subset of nanoparticles (NPs) that exhibit intermediate physicochemical properties between molecular dispersions and larger NPs. Despite interest in their utilization in applications such as theranostics, limited data about their toxicity exist. Here the effect of TiO2-USNPs on endothelial cells in vitro, and zebrafish embryos in vivo, was studied and compared to larger TiO2-NPs (30 nm) and to single walled carbon nanotubes (SWCNTs). In vitro exposure showed that TiO2-USNPs were neither cytotoxic, nor had oxidative ability, nevertheless were genotoxic. In vivo experiment in early developing zebrafish embryos in water at high concentrations of TiO2-USNPs caused mortality possibly by acidifying the water and caused malformations in the form of pericardial edema when injected. Myo1C involved in glomerular development of zebrafish embryos was upregulated in embryos exposed to TiO2-USNPs. They also exhibited anti-angiogenic effects both in vitro and in vivo plus decreased nitric oxide concentration. The larger TiO2-NPs were genotoxic but not cytotoxic. SWCNTs were cytotoxic in vitro and had the highest oxidative ability. Neither of these NPs had significant effects in vivo. To our knowledge this is the first study evaluating the effects of TiO2-USNPs on vascular toxicity in vitro and in vivo and this strategy could unravel USNPs potential applications.

An improved 3D tetraculture system mimicking the cellular organisation at the alveolar barrier to study the potential toxic effects of particles on the lung

Background

Exposure to fine and ultra-fine ambient particles is still a problem of concern in many industrialised parts of the world and the intensified use of nanotechnology may further increase exposure to small particles. Complex in vitro coculture systems may be valuable tools to study particle-induced processes and to extrapolate effects of particles on the lung. A system consisting of four different human cell lines which mimics the cell response of the alveolar surface in vitro was developed to study native aerosol exposure (Vitrocell™ chamber). The system is composed of an alveolar type-II cell line (A549), differentiated macrophage-like cells (THP-1), mast cells (HMC-1) and endothelial cells (EA.hy 926), seeded in a 3D-orientation on a microporous membrane.

Results

The spatial distribution of the cells in the tetraculture was analysed by confocal laser scanning microscopy (CLSM), showing a confluent layer of endothelial and epithelial cells on both sides of the transwell. Macrophage-like cells and mast cells can be found on top of the epithelial cells. The cells formed colonies under submerged conditions, which disappeared at the ALI. To evaluate the response to oxidative stress, the dichlorodihydrofluorescein diacetate (DCFH-DA) assay was used together with 2,2’-azobis-2-methyl-propanimidamide-dihydrochloride (AAPH) as inducer of oxidative stress. The tetraculture showed less induction of reactive oxygen species (ROS) production after being treated with a positive control compared to the monocultures of EA.hy 926, THP-1 and HMC-1. Submerged cultures showed elevated ROS and IL-8 levels compared to ALI cultures. The Vitrocell™ aerosol exposure system was not significantly influencing the viability. Using this system, cells were exposed to an aerosol of 50 nm SiO₂-Rhodamine NPs in PBS. The distribution of the NPs in the tetraculture after exposure was evaluated by CLSM. Fluorescence from internalized particles was detected in CD11b-positive THP-1 cells only.

Conclusion

The system can be used in conjunction with a native aerosol exposure system and may finally lead to a more realistic judgement regarding the hazard of new compounds and/or new nano-scaled materials in the future. The results for the ROS production and IL-8 secretion suggest that submerged exposure may lead to an overestimation of observed effects.

Recent advances in particulate matter and nanoparticle toxicology: a review of the in vivo and in vitro studies

Epidemiological and clinical studies have linked exposure to particulate matter (PM) to adverse health effects, which may be registered as increased mortality and morbidity from various cardiopulmonary diseases. Despite the evidence relating PM to health effects, the physiological, cellular, and molecular mechanisms causing such effects are still not fully characterized. Two main approaches are used to elucidate the mechanisms of toxicity. One is the use of in vivo experimental models, where various effects of PM on respiratory, cardiovascular, and nervous systems can be evaluated. To more closely examine the molecular and cellular mechanisms behind the different physiological effects, the use of various in vitro models has proven to be valuable. In the present review, we discuss the current advances on the toxicology of particulate matter and nanoparticles based on these techniques.