Biological effect of food additive titanium dioxide nanoparticles on intestine: an in vitro study

Titanium dioxide nanoparticles (TiO₂ NPs) are widely found in food‐related consumer products. Understanding the effect of TiO₂ NPs on the intestinal barrier and absorption is essential and vital for the safety assessment of orally administrated TiO₂ NPs. In this study, the cytotoxicity and translocation of two native TiO₂ NPs, and these two TiO₂ NPs pretreated with the digestion simulation fluid or bovine serum albumin were investigated in undifferentiated Caco‐2 cells, differentiated Caco‐2 cells and Caco‐2 monolayer. TiO₂ NPs with a concentration less than 200 µg ml^–1 did not induce any toxicity in differentiated cells and Caco‐2 monolayer after 24 h exposure. However, TiO₂ NPs pretreated with digestion simulation fluids at 200 µg ml^–1 inhibited the growth of undifferentiated Caco‐2 cells. Undifferentiated Caco‐2 cells swallowed native TiO₂ NPs easily, but not pretreated NPs, implying the protein coating on NPs impeded the cellular uptake. Compared with undifferentiated cells, differentiated ones possessed much lower uptake ability of these TiO₂ NPs. Similarly, the traverse of TiO₂ NPs through the Caco‐2 monolayer was also negligible. Therefore, we infer the possibility of TiO₂ NPs traversing through the intestine of animal or human after oral intake is quite low. This study provides valuable information for the risk assessment of TiO₂ NPs in food. Copyright © 2015 John Wiley & Sons, Ltd.     

Influence of silver and titanium dioxide nanoparticles on in vitro blood-brain barrier permeability

An in vitro blood-brain barrier (BBB) model being composed of co-culture with endothelial (bEnd.3) and astrocyte-like (ALT) cells was established to evaluate the toxicity and permeability of Ag nanoparticles (AgNPs; 8 nm) and TiO₂ nanoparticles (TiO₂NPs; 6 nm and 35 nm) in normal and inflammatory central nervous system. Lipopolysaccharide (LPS) was pre-treated to simulate the inflammatory responses. Both AgNPs and Ag ions can decrease transendothelial electrical resistance (TEER) value, and cause discontinuous tight junction proteins (claudin-5 and zonula occludens-1) of BBB. However, only the Ag ions induced inflammatory cytokines to release, and had less cell-to-cell permeability than AgNPs, which indicated that the toxicity of AgNPs was distinct from Ag ions. LPS itself disrupted BBB, while co-treatment with AgNPs and LPS dramatically enhanced the disruption and permeability coefficient. On the other hand, TiO₂NPs exposure increased BBB penetration by size, and disrupted tight junction proteins without size dependence, and many of TiO₂NPs accumulated in the endothelial cells were observed. This study provided the new insight of toxic potency of AgNPs and TiO₂NPs in BBB.     

纳米二氧化钛神经毒性及其机制的研究进展

纳米二氧化钛（TiO2 NPs）作为一种新型纳米材料,已成为多个领域的研究热点。随着在日常生活中接触TiO2 NPs愈发容易,TiO2 NPs的毒性也逐渐受到关注。TiO2 NPs能够通过血脑屏障进入脑内并蓄积,引起脑组织、神经细胞的损伤,影响情感与认知,降低学习记忆能力。本文主要对近年来TiO2 NPs引起的体内、外神经毒性,以及其毒性机制如氧化应激、炎症反应、凋亡等的研究现状进行综述,旨在丰富TiO2 NPs的毒性研究数据库,为其日常安全使用提供科学依据。     

In vitro evaluation of the toxicity and underlying molecular mechanisms of Janus Fe3O4‐TiO2 nanoparticles in human liver cells

Recent studies show that Janus Fe₃O₄‐TiO₂ nanoparticles (NPs) have potential applications as a multifunctional agent of magnetic resonance imaging (MRI) and photodynamic therapy (PDT) for the diagnosis and therapy of cancer. However, little work has been done on their biological effects. To evaluate the toxicity and underlying molecular mechanisms of Janus Fe₃O₄‐TiO₂ nanoparticles, an in vitro study using a human liver cell line HL‐7702 cells was conducted. For comparison, the Janus Fe₃O₄‐TiO₂ NPs parent material TiO₂ NPs was also evaluated. Results showed that both Fe₃O₄‐TiO₂ NPs and TiO₂ NPs decreased cell viability and ATP levels when applied in treatment, but increased malonaldehyde (MDA) and reactive oxygen species (ROS) generation. Mitochondria JC‐1 staining assay showed that mitochondrial membrane permeability injury occurred in both NPs treated cells. Cell viability analysis showed that TiO₂ NPs induced slightly higher cytotoxicity than Fe₃O₄‐TiO₂ NPs in HL7702 cells. Western blotting indicated that both TiO₂ NPs and Fe₃O₄‐TiO₂ NPs could induce apoptosis, inflammation, and carcinogenesis related signal protein alterations. Comparatively, Fe₃O₄‐TiO₂ NPs induced higher signal protein expressions than TiO₂ NPs under a high treatment dose. However, under a low dose (6.25 μg/cm²), neither NPs had any significant toxicity on HL7702 cells. In addition, our results suggest both Fe₃O₄‐TiO₂ NPs and TiO₂ NPs could induce oxidative stress and have a potential carcinogenetic effect in vitro. Further studies are needed to elaborate the detailed mechanisms of toxicity induced by a high dose of Fe₃O₄‐TiO₂ NPs.     

Nanoparticle (NP) uptake by type I alveolar epithelial cells and their oxidant stress response

Abstract

Mammalian cells take up nanoparticles (NPs) and some NPs increase ROS. We used imaging and measure ROS in parallel to evaluate NP-cell interactions with type I-like alveolar epithelial cells exposed to NPs at 1.2 µg/cm². Titanium dioxide (Ti0₂), gold (Au), silver (Ag), and manganese (Mn) were internalized by R3-1 cells; copper (Cu) NPs were observed at the cell surface only. TiO₂ and Au did not increase cell death but Mn and Cu did, with surviving cells recovering after initial Cu exposure. Ag NPs caused 80% of R3-1 cells to lift off the slides within 1 h. Amplex Red was used to report H₂O₂ production after exposure to 0.4 µg/cm² TiO₂, Au, Cu, Mn and Ag. TiO₂, Au, and Ag caused no significant increase in H₂O₂ while Cu and Mn increased H₂O₂. NPs that give up electrons, increase ROS production and cause cell death in R3-1 cells.     

Cytotoxic and inflammatory responses of TiO2 nanoparticles on human peripheral blood mononuclear cells

Titanium dioxide nanoparticles (TiO₂‐NPs) have been widely used in many applications. Owing to their nanoscale size, interactions between cells and NPs have been expansively investigated. With the health concerns raised regarding the adverse effects of these interactions, closer examination of whether TiO₂‐NPs can induce toxicity towards human cells is greatly needed. Therefore, in this study, we investigated the cytotoxicity of TiO₂‐NPs towards human blood cells (peripheral blood mononuclear cells [PBMCs]) in serum‐free medium, for which there is little information regarding the cytotoxic effects of TiO₂‐NPs. Our results provide evidence that PBMCs treated with TiO₂‐NPs (at concentrations ≥25 μg ml^?1) for 24 h significantly reduced cell viability and significantly increased production of toxic mediators such as reactive oxygen species and inflammatory response cytokines such as interleukin‐6 and tumor necrosis factor‐α (P < 0.05). Cell apoptosis induction also occurred at these concentrations. Significant expressions of cyclooxygenase‐2 and interleukin‐1β were also observed in PBMCs treated with TiO₂‐NPs at concentrations ≥125 μg ml^?1. Our data presented here clearly indicate that the concentration of TiO₂‐NPs (at size ~26.4 ± 1.2 nm) applied to human blood cells has a strong impact on cytotoxic induction. Copyright © 2016 John Wiley & Sons, Ltd.     

Genotoxic evaluation of titanium dioxide nanoparticles in vivo and in vitro

With the extensive application of titanium dioxide (TiO₂) nanoparticles (NPs) in food industry, there is a rising debate concerning the possible risk associated with exposure to TiO₂ NPs. The purpose of this study is to evaluate the genotoxicity of TiO₂ NPs using in vivo and in vitro test systems. In vivo study, the adult male Sprague-Dawley rats were exposed to anatase TiO₂ NPs (75 ± 15 nm) through intragastric administration at 0, 10, 50 and 200 mg/kg body weight every day for 30 days. The γ-H₂AX assay showed TiO₂ NPs could induce DNA double strand breaks in bone marrow cells after oral administration. However, the micronucleus test revealed that the oral-exposed TiO₂ NPs did not cause damage to chromosomes or mitotic apparatus observably in rat bone marrow cells. In vitro study, Chinese hamster lung fibroblasts (V79 cells) were exposed to TiO₂ NPs at the dose of 0, 5, 10, 20, 50 and 100 μg/mL. Significant decreases in cell viability were detected in all the treated groups after 24 h and 48 h exposure. Significant DNA damage was only observed at the concentration of 100 μg/mL after 24 h treatment using the comet assay. The obvious gene mutation was observed at the concentration of 20 and 100 μg/mL after 2 h treatment using hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene mutation assay. This study presented a comprehensive genotoxic evaluation of TiO₂ NPs, and TiO₂ NPs were shown to be genotoxic both in vivo and in vitro tests. The gene mutation and DNA strand breaks seem to be more sensitive genetic endpoints for the detection of TiO₂ NPs induced genotoxic effects.     

The effect of airborne Palladium nanoparticles on human lung cells,endothelium and blood – A combinatory approach using three in vitro models

A better understanding of the mechanisms behind adverse health effects caused by airborne fine particles and nanoparticles (NP) is essential to improve risk assessment and identification the most critical particle exposures. While the use of automobile catalytic converters is decreasing the exhausts of harmful gases, concentrations of fine airborne particles and nanoparticles (NPs) from catalytic metals such as Palladium (Pd) are reaching their upper safe level. Here we used a combinatory approach with three in vitro model systems to study the toxicity of Pd particles, to infer their potential effects on human health upon inhalation. The three model systems are 1) a lung system with human lung cells (ALI), 2) an endothelial cell system and 3) a human whole blood loop system. All three model systems were exposed to the exact same type of Pd NPs. The ALI lung cell exposure system showed a clear reduction in cell growth from 24 h onwards and the effect persisted over a longer period of time. In the endothelial cell model, Pd NPs induced apoptosis, but not to the same extent as the most aggressive types of NPs such as TiO₂. Similarly, Pd triggered clear coagulation and contact system activation but not as forcefully as the highly thrombogenic TiO₂ NPs. In summary, we show that our 3-step in vitro model of the human lung and surrounding vessels can be a useful tool for studying pathological events triggered by airborne fine particles and NPs.     

Titanium dioxide nanoparticles translocate through differentiated Caco‐2 cell monolayers,without disrupting the barrier functionality or inducing genotoxic damage

The widespread use of titanium dioxide nanoparticles (TiO₂NPs) in commercial food products makes intestinal cells a suitable target. Accordingly, we have used the human colon adenocarcinoma Caco‐2 cells to detect their potential harmful effects. Caco‐2 cells can differentiate in to enterocytic‐like cells, forming consistent cell monolayers and are used as a model of the intestinal barrier. Using both undifferentiated and differentiated Caco‐2 cells, we have explored a set of biomarkers, aiming to evaluate undesirable effects associated to TiO₂NP exposure. Results indicate non‐toxic effects in exposures ranging 1‐200 μg ml^?1. Significant differences were observed in cell uptake, with a higher amount of incorporated TiO₂NPs in undifferentiated cells, as visualized using confocal microscopy. In well‐established monolayers, translocation was detected using both confocal microscopy and transmission electron microscopy with energy‐dispersive X‐ray spectroscopy. In spite of the observed uptake and translocation, TiO₂NP exposures did not modify the integrity of the monolayer, as measured using the transepithelial electrical resistance and Lucifer yellow methods. The potential genotoxic effects in differentiated cells were evaluated in the comet assay, with and without formamidopyrimidine DNA glycosylase enzyme to detect oxidatively the damaged DNA bases. Although some changes were detected at the lower dose (10 μg ml^?1), no effects were observed at higher doses.     

Nanoparticle size and combined toxicity of TiO2 and DSLS (surfactant) contribute to lysosomal responses in digestive cells of mussels exposed to TiO2 nanoparticles

The aim of this investigation was to understand the bioaccumulation, cell and tissue distribution and biological effects of disodium laureth sulfosuccinate (DSLS)-stabilised TiO₂ nanoparticles (NPs) in marine mussels, Mytilus galloprovincialis. Mussels were exposed in vivo to 0.1, 1 and 10?mg Ti/L either as TiO₂ NPs (60 and 180?nm) or bulk TiO₂, as well as to DSLS alone. A significant Ti accumulation was observed in mussels exposed to TiO₂ NPs, which were localised in endosomes, lysosomes and residual bodies of digestive cells, and in the lumen of digestive tubules, as demonstrated by ultrastructural observations and electron probe X-ray microanalysis. TiO₂ NPs of 60?nm were internalised within digestive cell lysosomes to a higher extent than TiO₂ NPs of 180?nm, as confirmed by the quantification of black silver deposits after autometallography. The latter were localised mainly forming large aggregates in the lumen of the gut. Consequently, lysosomal membrane stability (LMS) was significantly reduced upon exposure to both TiO₂ NPs although more markedly after exposure to TiO₂-60 NPs. Exposure to bulk TiO₂ and to DSLS also affected the stability of the lysosomal membrane. Thus, effects on the lysosomal membrane depended on the nanoparticle size and on the combined biological effects of TiO₂ and DSLS.     

Cell cooperation and role of the P2X7 receptor in pulmonary inflammation induced by nanoparticles

Abstract

Macrophages and alveolar epithelial cells are the first targets of inhaled nanoparticles (NPs) reaching the alveoli. Mono- or co-cultures of lung epithelial (A549 or NCI-H441) and macrophage (THP-1) cell lines were used to study the cell cooperation and the involvement of the P2X₇ cell death receptor during the inflammation caused by SiO₂ and TiO₂ NPs. Here we show that, secretion of pro-inflammatory cytokines (IL-1β, IL-6 and IL-8) in response to NPs exposure was higher in co-cultures than in mono-cultures. A functional P2X₇ receptor was found in all the cell lines studied. Its involvement in IL-1β secretion in co-cultures was demonstrated using a specific antagonist, the brilliant blue G. Furthermore, mono and co-cultures exhibited distinct secretion patterns of pro-inflammatory cytokines in response to NPs exposure, and we provide the first evidence that the P2X₇ receptor is involved in the inflammation triggered by SiO₂ and TiO₂ NPs, by increasing IL-1β secretion, and likely through the inflammasome pathway. Altogether, our data indicate that cell co-cultures used in this study represent valid models to study the inflammatory mechanisms of NPs within the alveoli.     

Genotoxicity evaluation of titanium dioxide nanoparticles using the Ames test and Comet assay

Titanium dioxide nanoparticles (TiO₂‐NPs) are being used increasingly for various industrial and consumer products, including cosmetics and sunscreens because of their photoactive properties. Therefore, the toxicity of TiO₂‐NPs needs to be thoroughly understood. In the present study, the genotoxicity of 10nm uncoated sphere TiO₂‐NPs with an anatase crystalline structure, which has been well characterized in a previous study, was assessed using the Salmonella reverse mutation assay (Ames test) and the single‐cell gel electrophoresis (Comet) assay. For the Ames test, Salmonella strains TA102, TA100, TA1537, TA98 and TA1535 were preincubated with eight different concentrations of the TiO₂‐NPs for 4 h at 37 °C, ranging from 0 to 4915.2 µg per plate. No mutation induction was found. Analyses with transmission electron microscopy (TEM) and energy‐dispersive X‐ray spectroscopy (EDS) showed that the TiO₂‐NPs were not able to enter the bacterial cell. For the Comet assay, TK6 cells were treated with 0–200 µg ml^–1 TiO₂‐NPs for 24 h at 37 °C to detect DNA damage. Although the TK6 cells did take up TiO₂‐NPs, no significant induction of DNA breakage or oxidative DNA damage was observed in the treated cells using the standard alkaline Comet assay and the endonuclease III (EndoIII) and human 8‐hydroxyguanine DNA‐glycosylase (hOGG1)‐modified Comet assay, respectively. These results suggest that TiO₂‐NPs are not genotoxic under the conditions of the Ames test and Comet assay. Published 2012. This article is a US Government work and is in the public domain in the USA.     

Titanium dioxide nanoparticles prime a specific activation state of macrophages

Titanium dioxide nanoparticles (TiO₂ NPs) are widely used in foods, cosmetics, and medicine. Although the inhalation toxicity of TiO₂ NPs has been studied, the potential adverse effects of oral exposure of low-dose TiO₂ NPs are largely unclear. Herein, with macrophage cell lines, primary cells, and mouse models, we show that TiO₂ NPs prime macrophages into a specific activation state characterized by excessive inflammation and suppressed innate immune function. After a month of dietary exposure in mice or exposure in vitro to TiO₂ NPs (10 and 50?nm), the expressions of pro-inflammatory genes in macrophages were increased, and the expressions of anti-inflammatory genes were decreased. In addition, for macrophages exposed to TiO₂ NPs in vitro and in vivo, their chemotactic, phagocytic, and bactericidal activities were lower. This imbalance in the immune system could enhance the susceptibility to infections. In mice, after a month of dietary exposure to low doses of TiO₂ NPs, an aggravated septic shock occurred in response to lipopolysaccharide challenge, leading to elevated levels of inflammatory cytokines in serum and reduced overall survival. Moreover, TLR4-deficient mice and primary macrophages, or TLR4-independent stimuli, showed less response to TiO₂ NPs. These results demonstrate that TiO₂ NPs induce an abnormal state of macrophages characterized by excessive inflammation and suppressed innate immune function in a TLR4-dependent manner, which may suggest a potential health risk, particularly for those with additional complications, such as bacterial infections.     

Distinct toxic interactions of TiO2 nanoparticles with four coexisting organochlorine contaminants on algae

Engineered nanoparticles are increasingly discharged into the environment. After discharge, these nanoparticles can interact with co-existing organic contaminants, resulting in a phenomena referred to as ‘joint toxicity’. This study evaluated joint toxicities of TiO₂ nanoparticles (TiO₂NPs) with four different (atrazine, hexachlorobenzene, pentachlorobenzene, and 3,3′,4,4′-tetrachlorobiphenyl) organochlorine contaminants (OCs) toward algae (Chlorella pyrenoidosa). The potential mechanisms underlying the joint toxicity were discussed, including TiO₂NPs–OC interactions, effects of TiO₂NPs and OCs on biophysicochemical properties of algae and effects of TiO₂NPs and OCs on each other’s bioaccumulation in algae. The results indicate that coexposure led to a synergistic effect on the joint toxicity for TiO₂NPs–atrazine, antagonistic effect for TiO₂NPs–hexachlorobenzene and TiO₂NPs–3,3',4,4'-tetrachlorobiphenyl, and an additive effect for TiO₂NPs–pentachlorobenzene. There was nearly no adsorption of OCs by TiO₂NPs, and the physicochemical properties of TiO₂NPs were largely unaltered by the presence of OCs. However, both OCs and NPs affected the biophysicochemical properties of algal cells and thereby influenced the cell surface binding and/or internalization. TiO₂NPs significantly increased the bioaccumulation of each OC. However, with the exception of atrazine, the bioaccumulation of TiO₂NPs decreased when used with each OC. The distinct joint toxicity outcomes were a result of the balance between the increased toxicities of OCs (increased bioaccumulations) and the altered toxicity of TiO₂NPs (bioaccumulation can either increase or decrease). These results can significantly improve our understanding of the potential environmental risks associated with NPs.     

The effects of endoplasmic reticulum stress inducer thapsigargin on the toxicity of ZnO or TiO2 nanoparticles to human endothelial cells

It was recently shown that ZnO nanoparticles (NPs) could induce endoplasmic reticulum (ER) stress in human umbilical vein endothelial cells (HUVECs). If ER stress is associated the toxicity of ZnO NPs, the presence of ER stress inducer thapsigargin (TG) should alter the response of HUVECs to ZnO NP exposure. In this study, we addressed this issue by assessing cytotoxicity, oxidative stress and inflammatory responses in ZnO NP exposed HUVECs with or without the presence of TG. Moreover, TiO₂ NPs were used to compare the effects. Exposure to 32?μg/mL ZnO NPs (p?2 NPs (p?>?0.05), significantly induced cytotoxicity as assessed by WST-1 and neutral red uptake assay, as well as intracellular ROS. ZnO NPs dose-dependently increased the accumulation of intracellular Zn ions, and ZnSO₄ induced similar cytotoxic effects as ZnO NPs, which indicated a role of Zn ions. The release of inflammatory proteins tumor necrosis factor α (TNFα) and interleukin-6 (IL-6) or the adhesion of THP-1 monocytes to HUVECs was not significantly affected by ZnO or TiO₂ NP exposure (p?>?0.05). The presence of 250?nM TG significantly induced cytotoxicity, release of IL-6 and THP-1 monocyte adhesion (p?p?>?0.05). ANOVA analysis indicated no interaction between exposure to ZnO NPs and the presence of TG on almost all the endpoints (p?>?0.05) except neutral red uptake assay (p?相似文献   

Transport of saquinavir across human brain-microvascular endothelial cells by poly(lactide-co-glycolide) nanoparticles with surface poly-(γ-glutamic acid)

Poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) with surface poly-(γ-glutamic acid) (γ-PGA) were applied to enhance the transport of saquinavir (SQV) across the blood-brain barrier (BBB). PLGA NPs encapsulated SQV and grafted with γ-PGA to form drug carriers (γ-PGA/SQV-PLGA NPs) for crossing through a monolayer of human brain-microvascular endothelial cells (HBMECs) regulated with human astrocytes. The results revealed that a lower molecular weight of γ-PGA yielded a higher grafting efficiency of γ-PGA on PLGA NPs. In addition, γ-PGA with a low molecular weight accelerated the dissolution of SQV from γ-PGA/SQV-PLGA NPs. A higher grafting efficiency (more didecyl dimethylammonium bromide) and a lower molecular weight of γ-PGA increased the permeability of SQV across the BBB, in general. When the grafting efficiency was 85.2% at 6 kDa of γ-PGA, γ-PGA/SQV-PLGA NPs reached about 6 times the permeability of free SQV (the maximal permeability). γ-PGA could also promote the endocytosis of NPs and expression of ornithine decarboxylase by HBMECs. γ-PGA/SQV-PLGA NPs are efficacious nanoparticulate carriers in delivering antiretroviral drug across the BBB.     

Internalisation of hybrid titanium dioxide/para-amino benzoic acid nanoparticles in human dendritic cells did not induce toxicity and changes in their functions

Nanoparticles (NPs) have been reported to penetrate into human skin through lesional skin or follicular structures. Therefore, their ability to interact with dendritic cell (DC) was investigated using DCs generated from monocytes (mono-DCs). Hybrid titanium dioxide/para-amino benzoic acid (TiO₂/PABA) NPs did not induce any cell toxicity. NPs were internalised into DCs through macropinocytosis and not by a receptor-mediated mechanism. Confocal microscopy showed that NPs were not detected in the nucleus. These data are confirmed by electronic microscopy which demonstrated that hybrid NPs were rapidly in contact with cellular membrane and localised into cytoplasmic vesicles without colocalisation with clathrin-coated vesicles. Hybrid NPs did not induce CD86 or HLA-DR overexpression or cytokine secretion (IL-8 and TNF-α) indicating no DC activation. Internalisation of hybrid NPs did not modify DC response towards sensitisers such as nickel and thimerosal or LPS used as positive controls. Moreover, hybrid NPs did not induce any oxidative stress implicated in DC activation process. After mono-DC irradiation by ultraviolet A (UVA), hybrid NP-treated cells did not produce UVA-induced reactive oxygen species (ROS) and exhibited a better cell viability compared with UVA-irradiated control cells, suggesting a protecting effect of hybrid TiO₂/PABA NPs against UVA-induced ROS.     

Inflammatory response in human alveolar epithelial cells after TiO2 NPs or ZnO NPs exposure: Inhibition of surfactant protein A expression as an indicator for loss of lung function

The increasing use of metal oxide nanoparticles (MONPs) as TiO₂ NPs or ZnO NPs has led to environmental release and human exposure. The respiratory system, effects on lamellar bodies and surfactant protein A (SP-A) of pneumocytes, can be importantly affected. Exposure of human alveolar epithelial cells (A549) induced differential responses; a higher persistence of TiO₂ in cell surface and uptake (measured by Atomic Force Microscopy) and sustained inflammatory response (by means of TNF-α, IL-10, and IL-6 release) and ROS generation were observed, whereas ZnO showed a modest response and low numbers in cell surface. A reduction in SP-A levels at 24 h of exposure to TiO₂ NPs (concentration-dependent) or ZnO NPs (the higher concentration) was also observed, reversed by blocking the inflammatory response (by the inhibition of IL-6). Loss of SP-A represents a relevant target of MONPs-induced inflammatory response that could contribute to cellular damage and loss of lung function.