Assessing the in vitro toxicity of airborne (nano)particles to the human respiratory system: from basic to advanced models.

Several studies have been conducted to address the potential adverse health risks attributed to exposure to nanoscale materials. While in vivo studies are fundamental for identifying the relationship between dose and occurrence of adverse effects, in vitro model systems provide important information regarding the mechanism(s) of action at the molecular level. With a special focus on exposure to inhaled (nano)particulate material toxicity assessment, this review provides an overview of the available human respiratory models and exposure systems for in vitro testing, advantages, limitations, and existing investigations using models of different complexity. A brief overview of the human respiratory system, pathway and fate of inhaled (nano)particles is also presented.

Editorial of Special Issue: The Toxicity of Nanomaterials and Legacy Contaminants: Risks to the Environment and Human Health.

Nanotechnology and the incorporation of nanomaterials (NM) into everyday products help to solve problems in society and improve the quality of life, allowing for major advances in the technological, industrial, and medical fields [...].

Cell Model of Depression: Reduction of Cell Stress with Mirtazapine.

Depression is a very prevalent and complex disease. This condition is associated with a high rate of relapse, making its treatment a challenge. Thus, an intensive investigation of this disease and its treatment is necessary. In this work, through cell viability assays (MTT and neutral red assays) and alkaline comet assays, we aimed to test the induction of stress in human SH-SY5Y cells through the application of hydrocortisone and hydrogen peroxide and to test the reversal or attenuation of this stress through the application of mirtazapine to the cells. Our results demonstrated that hydrogen peroxide, and not hydrocortisone, can induce cellular stress, as evidenced by DNA damage and a global cellular viability reduction, which were alleviated by the antidepressant mirtazapine. The establishment of a cellular model of depression through stress induction is important to study new possibilities of treatment of this disease using cell cultures.

Unveiling the Toxicity of Fine and Nano-Sized Airborne Particles Generated from Industrial Thermal Spraying Processes in Human Alveolar Epithelial Cells.

High-energy industrial processes have been associated with particle release into workplace air that can adversely affect workers' health. The present study assessed the toxicity of incidental fine (PGFP) and nanoparticles (PGNP) emitted from atmospheric plasma (APS) and high-velocity oxy-fuel (HVOF) thermal spraying. Lactate dehydrogenase (LDH) release, 2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST-1) metabolisation, intracellular reactive oxygen species (ROS) levels, cell cycle changes, histone H2AX phosphorylation (γ-H2AX) and DNA damage were evaluated in human alveolar epithelial cells at 24 h after exposure. Overall, HVOF particles were the most cytotoxic to human alveolar cells, with cell viability half-maximal inhibitory concentration (IC50) values of 20.18 µg/cm2 and 1.79 µg/cm2 for PGFP and PGNP, respectively. Only the highest tested concentration of APS-PGFP caused a slight decrease in cell viability. Particle uptake, cell cycle arrest at S + G2/M and γ-H2AX augmentation were observed after exposure to all tested particles. However, higher levels of γ-H2AX were found in cells exposed to APS-derived particles (~16%), while cells exposed to HVOF particles exhibited increased levels of oxidative damage (~17% tail intensity) and ROS (~184%). Accordingly, APS and HVOF particles seem to exert their genotoxic effects by different mechanisms, highlighting that the health risks of these process-generated particles at industrial settings should not be underestimated.

Nanoparticle exposure and hazard in the ceramic industry: an overview of potential sources, toxicity and health effects.

The ceramic industry is an industrial sector of great impact in the global economy that has been benefiting from advances in materials and processing technologies. Ceramic manufacturing has a strong potential for airborne particle formation and emission, namely of ultrafine particles (UFP) and nanoparticles (NP), meaning that workers of those industries are at risk of potential exposure to these particles. At present, little is known on the impact of engineered nanoparticles (ENP) on the environment and human health and no established Occupational Exposure Limits (OEL) or specific regulations to airborne nanoparticles (ANP) exposure exist raising concerns about the possible consequences of such exposure. In this paper, we provide an overview of the current knowledge on occupational exposure to NP in the ceramic industry and their impact on human health. Possible sources and exposure scenarios, a summary of the existing methods for evaluation and monitoring of ANP in the workplace environment and proposed Nano Reference Values (NRV) for different classes of NP are presented. Case studies on occupational exposure to ANP generated at different stages of the ceramic manufacturing process are described. Finally, the toxicological potential of intentional and unintentional ANP that have been identified in the ceramic industry workplace environment is discussed based on the existing evidence from in vitro and in vivo inhalation toxicity studies.

l-proline supplementation improves nitric oxide bioavailability and counteracts the blood pressure rise induced by angiotensin II in rats.

We evaluated whether l-proline (Pro) supplementation improves redox status and nitric oxide (NO) bioavailability and prevents or delays angiotensin II (AngII)-induced hypertension. Male Sprague-Dawley rats were distributed to four experimental groups: Pro + AngII (Pro-Ang), Pro + Saline (Pro-Sal), Vehicle + AngII (Veh-Ang) and Veh + Saline (Veh-Sal). Pro solution (2 g.kg-1·day-1) or water (vehicle) were orally administered, from day 0 to day 21. AngII (200 ng.kg-1.min-1) or saline were infused (s.c.) from day 7 to day 21. Systolic blood pressure (SBP) was measured by the tail-cuff method. From day 20-21, animals were kept on metabolic cages for 24h-urine collection. On day 21, urine and blood were collected for further quantification of redox status biomarkers, NO-related markers (urinary nitrates and nitrites, U-NOx; plasma asymmetric dimethylarginine, P-ADMA), metabolic and renal parameters. Pro prevented the AngII-induced SBP rise [mean (95% CI), Day 19: Pro-AngII, 137 (131; 143) vs. Veh-AngII, 157 (151; 163) mm Hg, P < 0.001]. Pro-AngII rats also had increased values of U-NOx, systemic and urinary total antioxidant status (TAS), urinary H2O2 and plasma urea, as well as reduced P-ADMA and unaltered urinary isoprostanes. Plasma Pro was inversely correlated with P-ADMA (r = -0.52, p = 0.0009) and positively correlated with urinary TAS (r = 0.55, p = 0.0005) which, in turn, was inversely correlated with P-ADMA (r = -0.56, p = 0.0004). Furthermore, urinary H2O2 values decreased across P-ADMA tertiles (p for linear trend = 0.023). These results suggest that Pro reduces P-ADMA levels and improves redox status, thereby increasing NO bioavailability and counteracting the AngII-induced SBP rise. H2O2 and TAS modulation by Pro may contribute to the reduced P-ADMA concentration.

In vitro genotoxicity assessment of an oxidized dextrin-based hydrogel for biomedical applications.

Hydrogels are three-dimensional, crosslinked networks of hydrophilic polymers swollen with a large amount of water or biological fluids, without dissolving. Dextrin, a low-molecular-weight carbohydrate composed by glucose residues, has been used to develop an injectable hydrogel for biomedical applications. Dextrin was first oxidized to introduce aldehyde groups, which then reticulate with adipic acid dihydrazide, forming the dextrin-based hydrogel (HG). The HG and its components were tested for cyto- and genotoxicity according to the International Standard ISO 10993-3 on the biological evaluation of medical devices. To assess genotoxicity, a battery of in vitro genotoxicity tests employing both eukaryotic and prokaryotic models was performed: comet assay, cytokinesis-block micronucleus assay and Ames test. Our data revealed that the HG (IC50  = 2.8 mg/mL) and oxidized dextrin by itself (IC50  = 1.2 mg/mL) caused a concentration-dependent decrease in cellular viability of human lymphoblastoid TK6 cells after 24 hours of exposure to the test agents. However, these concentrations are unlikely to be reached in vivo. In addition, no significant increase in the DNA and chromosomal damage of TK6 cells exposed to non-cytotoxic concentrations of the HG and its isolated components was detected. Furthermore, neither the HG nor its metabolites exerted a mutagenic effect in different of Salmonella typhimurium strains and in an Escherichia coli mix. Our data demonstrated the genocompatibility of the HG (up to 3.5 mg/mL) for biomedical applications. To our best acknowledge, this is the first report with a detailed genotoxicity assessment of an aldehyde-modified polysaccharide/adipic acid dihydrazide hydrogel.

Moving into advanced nanomaterials. Toxicity of rutile TiO2 nanoparticles immobilized in nanokaolin nanocomposites on HepG2 cell line.

Immobilization of nanoparticles on inorganic supports has been recently developed, resulting in the creation of nanocomposites. Concerning titanium dioxide nanoparticles (TiO2 NPs1), these have already been developed in conjugation with clays, but so far there are no available toxicological studies on these nanocomposites. The present work intended to evaluate the hepatic toxicity of nanocomposites (C-TiO22), constituted by rutile TiO2 NPs immobilized in nanokaolin (NK3) clay, and its individual components. These nanomaterials were analysed by means of FE-SEM4 and DLS5 analysis for physicochemical characterization. HepG2 cells were exposed to rutile TiO2 NPs, NK clay and C-TiO2 nanocomposite, in the presence and absence of serum for different exposure periods. Possible interferences with the methodological procedures were determined for MTT,6 neutral red uptake, alamar blue (AB), LDH,7 and comet assays, for all studied nanomaterials. Results showed that MTT, AB and alkaline comet assay were suitable for toxicity analysis of the present materials after slight modifications to the protocol. Significant decreases in cell viability were observed after exposure to all studied nanomaterials. Furthermore, an increase in HepG2 DNA damage was observed after shorter periods of exposure in the absence of serum proteins and longer periods of exposure in their presence. Although the immobilization of nanoparticles in micron-sized supports could, in theory, decrease the toxicity of single nanoparticles, the selection of a suitable support is essential. The present results suggest that NK clay is not the appropriate substrate to decrease TiO2 NPs toxicity. Therefore, for future studies, it is critical to select a more appropriate substrate for the immobilization of TiO2 NPs.

Assessment of DNA damage in a group of professional dancers during a 10-month dancing season.

Despite the numerous health benefits of physical activity, some studies reported that increased intensity and duration may induce oxidative stress in several cellular components including DNA. The aim of this study was to assess the level of basal DNA damage as well as oxidative DNA damage in a group of professional dancers before and after a 10-month dancing season. A group of individuals from general population was also assessed as a control. The alkaline version of the comet assay was the method selected to measure both basal DNA damage and oxidative stress, since this method quantifies both endpoints. In order to measure oxidative stress, the comet assay was coupled with a lesion-specific endonuclease (formamidopyrimidine glycosylase) to detect oxidized purines. The levels of oxidative DNA damage in dancers were significantly increased after the dancing season. Pre-season levels of oxidative DNA damage were lower in dancers than those obtained from the general population, suggesting an adaptation of antioxidant system in dancers. Results of the present biomonitoring study indicate the need for more effective measures to protect ballet dancers from potentially occupational health risks related to regular intensive physical exercise.

Gold nanorods induce early embryonic developmental delay and lethality in zebrafish (Danio rerio).

Due to their unique electronic and optical features, gold nanoparticles (AuNP) have received a great deal of attention for application in different fields such as catalysis, electronics, and biomedicine. The large-volume manufacturing predicted for future decades and the inevitable release of these substances into the environment necessitated an assessment of potential adverse human and ecological risks due to exposure to AuNP. Accordingly, this study aimed to examine the acute and developmental toxicity attributed to a commercial suspension of Au nanorods stabilized with cetyltrimethylammonium bromide (CTAB-AuNR) using early embryonic stages of zebrafish (Danio rerio), a well-established model in ecotoxicology. Zebrafish embryos were exposed to CTAB-AuNR (0-150 µg/L) to determine for developmental assessment until 96 hr post fertilization (hpf) and lethality. Uptake of CTAB-AuNR by embryos and nanoparticles potential to induce DNA damage was also measured at 48 and 96 hpf. Analysis of the concentration-response curves with cumulative mortality at 96 hpf revealed a median lethal concentration (LC50,96h) of 110.2 µg/L. At sublethal concentrations, CTAB-AuNR suspensions were found to produce developmental abnormalities such as tail deformities, pericardial edema, decreased body length, and delayed eye, head, and tail elongation development. Further, less than 1% of the initial concentration of CTAB-AuNR present in the exposure media was internalized by zebrafish embryos prior to (48 hpf) and after hatching (96 hpf). In addition, no marked DNA damage was detected in embryos after exposure to CTAB-AuNR. Overall, CTAB-AuNR suspensions produced lethal and sublethal effects on zebrafish embryos with possible repercussions in fitness of adult stages. However, these results foresee a low risk for fish since the observed effects occurred at concentrations above the levels expected to find in the aquatic environment.

Amine neurotransmitters, inflammation and epithelial sodium transport.

NEW FINDINGS: What is the topic of this review? The present work reviews the roles of renal and intestinal dopamine and 5-HT in the maintenance of fluid and electrolyte homeostasis. The role of inflammatory agents at the intestinal level that affect fluid and electrolyte homeostasis is also addressed. What advances does it highlight? General mechanisms of epithelial cell ion transport in the gastrointestinal tract and kidney share considerable similarities, particularly with regard to basolateral Na(+) ,K(+-) ATPase as a driving force for the movement of numerous substrates across the cell membrane. The physiological importance of the renal actions of monoamines (dopamine, noradrenaline and 5-HT) mainly depends on the sources of the amines in the kidney and on their availability to activate the amine-specific receptors. Dopamine and 5-HT are also relatively abundant in the mucosal cell layer of the intestine, and recent evidence suggests their physiological relevance in regulating electrolyte transport. The gastrointestinal tract can be an important site for the loss of water and electrolytes, in the presence of intestinal inflammation. General mechanisms of epithelial cell ion transport in the gastrointestinal tract and kidney share considerable similarities with regard to basolateral Na(+) ,K(+) -ATPase as a driving force for the movement of numerous substrates across the cell membrane. The present work reviews the roles of renal and intestinal dopamine and 5-HT in the maintenance of fluid and electrolyte homeostasis. The role of inflammatory agents at the intestinal level that affect fluid and electrolyte homeostasis is also addressed.

Short- and long-term distribution and toxicity of gold nanoparticles in the rat after a single-dose intravenous administration.

Surface chemistry plays an important role in gold nanoparticles (AuNPs) stability and biocompatibility, which are crucial for their implementation into the clinical setting. We evaluated short- (30 min) and long-term (28 days) biodistribution and toxicity of ~20 nm citrate- and pentapeptide CALNN-coated AuNPs after a single intravenous injection in rats. The pattern of AuNPs distribution in Cit- and CALNN-AuNPs-injected rats was very similar in the assessed time-points. Both AuNPs were quickly removed from the bloodstream and preferentially accumulated in the liver. At 28 days liver remained the main accumulation site but at significantly lower levels compared to those found at 30 min. Spleen atrophy and hematological findings compatible with mild anemia were observed in CALNN-AuNPs-administered rats. Under our experimental conditions, surface coating had more impact on toxicity rather than on biodistribution of the AuNPs. Improvements in the design of capping peptides need to be done to increase biomedical applicability of peptide-coated AuNPs. FROM THE CLINICAL EDITOR: The biodistribution and toxicity of ~ 20 nm citrate- and pentapeptide CALNN-coated gold nanoparticles was investigated after a single intravenous injection in rats. Rapid clearance and hepatic accumulation was found at 30-minutes, whereas mild anemia and spleen atrophy was seen 28 days post injection. The authors also concluded that the toxicity was related to the capping proteins as opposed to the biodistribution of the particles, providing important suggestion for future design of gold nanoparticles.

Influence of the surface coating on the cytotoxicity, genotoxicity and uptake of gold nanoparticles in human HepG2 cells.

The toxicological profile of gold nanoparticles (AuNPs) remains controversial. Significant efforts to develop surface coatings to improve biocompatibility have been carried out. In vivo biodistribution studies have shown that the liver is a target for AuNPs accumulation. Therefore, we investigated the effects induced by ~20 nm spherical AuNPs (0-200 µM Au) with two surface coatings, citrate (Cit) compared with 11-mercaptoundecanoic acid (11-MUA), in human liver HepG2 cells. Cytotoxicity was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction and lactate dehydrogenase (LDH) release assays after 24 to 72 h of incubation. DNA damage was assessed by the comet assay, 24 h after incubation with the capped AuNPs. Uptake and subcellular distribution of the tested AuNPs was evaluated by quantifying the gold intracellular content by graphite furnace atomic absorption spectrometry (GFAAS) and transmission electron microscopy (TEM), respectively. The obtained results indicate that both differently coated AuNPs did not induce significant cytotoxicity. An inverse concentration-dependent increase in comet tail intensity and tail moment was observed in Cit-AuNPs- but not in MUA-AuNPs-exposed cells. Both AuNPs were internalized in a concentration-dependent manner. However, no differences were found in the extent of the internalization between the two types of NPs. Electron-dense deposits of agglomerates of Cit- and MUA-AuNPs were observed either inside endosomes or in the intercellular spaces. In spite of the absence of cytotoxicity, DNA damage was observed after exposure to the lower concentrations of Cit- but not to MUA-AuNPs. Thus, our data supports the importance of the surface properties to increase the biocompatibility and safety of AuNPs.

Multiparametric in vitro genotoxicity assessment of different variants of amorphous silica nanomaterials in rat alveolar epithelial cells.

The hazard posed to human health by inhaled amorphous silica nanomaterials (aSiO2 NM) remains uncertain. Herein, we assessed the cyto- and genotoxicity of aSiO2 NM variants covering different sizes (7, 15, and 40 nm) and surface modifications (unmodified, phosphonate-, amino- and trimethylsilyl-modified) on rat alveolar epithelial (RLE-6TN) cells. Cytotoxicity was evaluated at 24 h after exposure to the aSiO2 NM variants by the lactate dehydrogenase (LDH) release and WST-1 reduction assays, while genotoxicity was assessed using different endpoints: DNA damage (single- and double-strand breaks [SSB and DSB]) by the comet assay for all aSiO2 NM variants; cell cycle progression and γ-H2AX levels (DSB) by flow cytometry for those variants that presented higher cytotoxic and DNA damaging potential. The variants with higher surface area demonstrated a higher cytotoxic potential (SiO2_7, SiO2_15_Unmod, SiO2_15_Amino, and SiO2_15_Phospho). SiO2_40 was the only variant that induced significant DNA damage on RLE-6TN cells. On the other hand, all tested variants (SiO2_7, SiO2_15_Unmod, SiO2_15_Amino, and SiO2_40) significantly increased total γ-H2AX levels. At high concentrations (28 µg/cm2), a decrease in G0/G1 subpopulation was accompanied by a significant increase in S and G2/M sub-populations after exposure to all tested materials except for SiO2_40 which did not affect cell cycle progression. Based on the obtained data, the tested variants can be ranked for its genotoxic DNA damage potential as follows: SiO2_7 = SiO2_40 = SiO2_15_Unmod > SiO2_15_Amino. Our study supports the usefulness of multiparametric approaches to improve the understanding on NM mechanisms of action and hazard prediction.

Suitability of salivary leucocytes to assess DNA repair ability in human biomonitoring studies by the challenge-comet assay.

The challenge-comet assay is a simple but effective approach that provides a quantitative and functional determination of DNA repair ability, and allows to monitor the kinetics of repair process. Peripheral blood mononuclear cells (PBMC) are the cells most frequently employed in human biomonitoring studies using the challenge-comet assay, but having a validated alternative of non-invasive biomatrix would be highly convenient for certain population groups and circumstances. The objective of this study was to validate the use of salivary leucocytes in the challenge-comet assay. Leucocytes were isolated from saliva samples and challenged (either in fresh or after cryopreservation) with three genotoxic agents acting by different action mechanisms: bleomycin, methyl methanesulfonate, and ultraviolet radiation. Comet assay was performed just after treatment and at other three additional time points, in order to study repair kinetics. The results obtained demonstrated that saliva leucocytes were as suitable as PBMC for assessing DNA damage of different nature that was efficiently repaired over the evaluated time points, even after 5 months of cryopreservation (after a 24 h stimulation with PHA). Furthermore, a new parameter to determine the efficacy of the repair process, independent of the initial amount of damage induced, is proposed, and recommendations to perform the challenge-comet assay with salivary leucocytes depending on the type of DNA repair to be assessed are suggested. Validation studies are needed to verify whether the method is reproducible and results reliable and comparable among laboratories and studies.

P2Y receptors on astrocytes and microglia mediate opposite effects in astroglial proliferation.

Nucleotides released upon brain injury signal to astrocytes and microglia playing an important role in astrogliosis, but the participation of microglia in the purinergic modulation of astrogliosis is still unclear. Highly enriched astroglial cultures and co-cultures of astrocytes and microglia were used to investigate the influence of microglia in the modulation of astroglial proliferation mediated by nucleotides. In highly enriched astroglial cultures, adenosine-5'-triphosphate (ATP), adenosine 5'-O-(3-thio)-triphosphate (ATPγS), adenosine 5'-O-(3-thio)-diphosphate (ADPßS; 0.01-1 mM), and adenosine-5'-diphosphate (ADP; 0.1-1 mM) increased proliferation up to 382%, an effect abolished in co-cultures containing 8% of microglia. The loss of ATP proliferative effect in co-cultures is supported by its fast metabolism and reduced ADP accumulation, an agonist of P2Y(1,12) receptors that mediate astroglial proliferation. No differences in ADPßS and ATPγS metabolism or P2Y(1,12) receptors expression were found in co-cultures that could explain the loss of their proliferative effect. However, conditioned medium from microglia cultures or co-cultures treated with ADPßS, when tested in highly enriched astroglial cultures, also prevented ADPßS proliferative effect. None of the uracil nucleotides tested had any effect in proliferation of highly enriched astroglial cultures, but uridine-5'-triphosphate (UTP; 0.1-1 mM) inhibited proliferation up to 66% in co-cultures, an effect that was dependent on uridine-5'-diphosphate (UDP) accumulation, coincident with a co-localization of P2Y(6) receptors in microglia and due to cell apoptosis. The results indicate that microglia control astroglial proliferation by preventing the proliferative response to adenine nucleotides and favouring an inhibitory effect of UTP/UDP. Several microglial P2Y receptors may be involved by inducing the release of messengers that restrain astrogliosis, a beneficial effect for neuronal repair mechanisms following brain injury.

How can exposure to engineered nanomaterials influence our epigenetic code? A review of the mechanisms and molecular targets.

Evidence suggests that engineered nanomaterials (ENM) can induce epigenetic modifications. In this review, we provide an overview of the epigenetic modulation of gene expression induced by ENM used in a variety of applications: titanium dioxide (TiO2), silver (Ag), gold (Au), silica (SiO2) nanoparticles and carbon-based nanomaterials (CNM). Exposure to these ENM can trigger alterations in cell patterns of DNA methylation, post-transcriptional histone modifications and expression of non-coding RNA. Such effects are dependent on ENM dose and physicochemical properties including size, shape and surface chemistry, as well as on the cell/organism sensitivity. The genes affected are mostly involved in the regulation of the epigenetic machinery itself, as well as in apoptosis, cell cycle, DNA repair and inflammation related pathways, whose long-term alterations might lead to the onset or progression of certain pathologies. In addition, some DNA methylation patterns may be retained as a form of epigenetic memory. Prenatal exposure to ENM may impair the normal development of the offspring by transplacental effects and/or putative transmission of epimutations in imprinting genes. Thus, understanding the impact of ENM on the epigenome is of paramount importance and epigenetic evaluation must be considered when assessing the risk of ENM to human health.

The role of salt-inducible kinases on the modulation of renal and intestinal Na+,K+-ATPase activity during short- and long-term high-salt intake.

Type 1 salt-inducible kinases (SIK1) has been shown to act as a mediator during the cellular adaptation to variations in intracellular sodium in a variety of cell types. Type 2 SIK (SIK2) modulates various biological functions and acts as a signal transmitter in various pathways. To evaluate the role of both SIK isoforms in renal and intestinal Na+,K+-ATPase (NKA) activity, we made use of constitutive sik1-/- (SIK1-KO), sik2-/- (SIK2-KO), double sik1-/-sik2-/- (double SIK1*2-KO) knockout and wild-type (WT) mice challenged to a standard (0.3% NaCl) or chronic high-salt (HS, 8% NaCl) diet intake for 48 h or 12 weeks. Long-term HS intake in WT was accompanied by 2-fold increase in jejunal NKA activity and slight (~30% reduction) decreases in NKA in the ileum and cecum; none of these changes was accompanied by changes in the expression of α1-NKA. The ablation of SIK1 and SIK2 prevented the marked increase in jejunal NKA activity following the long-term HS intake. The ablation of SIK1 and SIK2 in mice on a long-term HS intake impacted differently in the ileum and cecum. The most interesting finding is that in SIK2-KO mice marked reductions in NKA activity were observed in the ileum and cecum when compared to WT mice, both on normal and long-term HS intake. In summary, SIK1 or SIK2 ablation on chronic high-salt intake is accompanied by modulation of NKA along the intestinal tract, which differ from those after an acute high-salt intake, and this may represent an absorptive compensatory mechanism to keep electrolyte homeostasis.

Toxicity assessment of industrial engineered and airborne process-generated nanoparticles in a 3D human airway epithelial in vitro model.

The advanced ceramic technology has been pointed out as a potentially relevant case of occupational exposure to nanoparticles (NP). Not only when nanoscale powders are being used for production, but also in the high-temperature processing of ceramic materials there is also a high potential for NP release into the workplace environment. In vitro toxicity of engineered NP (ENP) [antimony tin oxide (Sb2O3•SnO2; ATO); zirconium oxide (ZrO2)], as well as process-generated NP (PGNP), and fine particles (PGFP), was assessed in MucilAir™ cultures at air-liquid interface (ALI). Cultures were exposed during three consecutive days to varying doses of the aerosolized NP. General cytotoxicity [lactate dehydrogenase (LDH) release, WST-1 metabolization], (oxidative) DNA damage, and the levels of pro-inflammatory mediators (IL-8 and MCP-1) were assessed. Data revealed that ENP (5.56 µg ATO/cm2 and 10.98 µg ZrO2/cm2) only caused mild cytotoxicity at early timepoints (24 h), whereas cells seemed to recover quickly since no significant changes in cytotoxicity were observed at late timepoints (72 h). No meaningful effects of the ENP were observed regarding DNA damage and cytokine levels. PGFP affected cell viability at dose levels as low as ∼9 µg/cm2, which was not seen for PGNP. However, exposure to PGNP (∼4.5 µg/cm2) caused an increase in oxidative DNA damage. These results indicated that PGFP and PGNP exhibit higher toxicity potential than ENP in mass per area unit. However, the presence of a mucociliary apparatus, as it occurs in vivo as a defense mechanism, seems to considerably attenuate the observed toxic effects. Our findings highlight the potential hazard associated with exposure to incidental NP in industrial settings.