Pathways of human exposure to microplastics, and estimation of the total burden

Altres ajuts: Acord transformatiu CRUE-CSICJ. Domenech was supported by a Predoctoral Fellowship (PIF) from the Universitat Autònoma de Barcelona.Plastic production is continuously growing and their wastes contaminate practically all environmental niches. In the environment, large plastics undergo continuous degradation processes generating a broad amount of microplastics and nanoplastics (MNPLs) that spread through air, land, and seas. Thus, humans suffer chronic exposures to MNPLs through different pathways: ingestion, inhalation, and dermal contact. Here, we have reviewed the recently published data regarding human exposure to MNPLs. The total load of plastic particles that humans are exposed to has been estimated based on these newly reported studies. This analysis of novel literature shows that despite ingestion is the most studied route of exposure, other routes of contact with MNPLs should not be underestimated. At the same time, gaps regarding the investigation of human exposures to environmental MNPLs have been detected, as well as the lack of robust and standardized protocols, operating procedures, and methodologies to detect/quantify MNPL in human/biological matrices

Analysis of glutathione and vitamin C effects

The alkaline single-cell gel electrophoresis (or Comet) assay was applied to evaluate the eventual DNA damage induced by the triphenolic metabolite of benzene, 1,2,4-benzenetriol (BT), in isolated human lymphocytes. Prior to BT treatment, ranging from 5 to 50 μM, a supplementation with glutathione (GSH, 350 μg/ml) was carried out to assess whether GSH may have a modulating effect on the Comet response. The effect of a fixed dose of BT was also evaluated in the presence of the exogenous antioxidant vitamin C (40 and 200 μM). Additionally, we investigated whether the polymorphism of glutathione S-transferase T1 (GSTT1) gene may affect the individual level of BT-induced DNA damage in vitro. For all donors included in the present study, BT produced a significant dose-response relationship. No clear effect of GSH preincubation was seen on the BT-induced response. On the contrary, a significant reduction of DNA damage was observed in the presence of vitamin C (at least at 200 μM). Although our data suggest some individual differences according to the GSTT1 genotype in the outcome of the Comet assay, a large number of individuals should be studied in further investigations to obtain reliable conclusions

Antagonistic in vivo interaction of polystyrene nanoplastics and silver compounds. A study using Drosophila

Acord transformatiu CRUE-CSICSince heavy metals and micro−/nanoplastics (MNPLs) can share common environmental niches, their potential interactions could modulate their hazard impacts. The current study was planned to evaluate the potential interactions between silver compounds (silver nanoparticles or silver nitrate) and two different sizes of polystyrene nanoplastics (PSNPLs) (PS-50 and PS-500 nm), administered via ingestion to Drosophila larvae. While egg-to-adult survival was not affected by the exposure to silver compounds, PSNPLs, or their coexposures, the combined treatments succeeded to restore the delay of fly emergence induced by silver compounds. Transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) showed the ability of PSNPLs to transport silver compounds (regardless of their form) across the intestinal barrier, delivering them into the hemolymph of Drosophila larvae in a concentration exceeding that mediated by the exposure to silver compounds alone. The molecular response (gene expression) of Drosophila larvae greatly fluctuated, accordingly if exposures were administered alone or in combination. Although PSNPLs produced some oxidative stress in the hemocytes of Drosophila, especially at the highest dose (1 mM), higher levels were observed after silver exposure, regardless of its form. Interestingly, the oxidative stress of silver, especially that produced by nano‑silver, drastically decreased when coexposed with PSNPLs. Similar effects were observed regarding the DNA damage induced in Drosophila hemocytes, where cotreatment decreased the genotoxicity induced by silver compounds. This antagonistic interaction could be attributed to the ability of tiny plastic specks to confine silver, avoiding its bioavailability, and diminishing their potential impacts

Genomic Instability in Newborn with Short Telomeres

Telomere length is considered to be a risk factor in adults due to its proved association with cancer incidence and mortality. Since newborn present a wide interindividual variation in mean telomere length, it is relevant to demonstrate if these differences in length can act also as an early risk indicator. To answer this question, we have measured the mean telomere length of 74 samples of cord blood from newborns and studied its association with the basal genetic damage, measured as the frequency of binucleated cells carrying micronuclei. In addition, we have challenged the cells of a subgroup of individuals (N = 35) against mitomycin-C (MMC) to establish their sensitivity to induced genomic instability. Results indicate that newborn with shorter telomeres present significantly higher levels of genetic damage when compared to those with longer telomeres. In addition, the cellular response to MMC was also significantly higher among those samples from subjects with shorter telomeres. Independently of the causal mechanisms involved, our results show for the first time that telomere length at delivery influence both the basal and induced genetic damage of the individual

Hazard assessment of ingested polystyrene nanoplastics in Drosophila larvae

Micro- and nanoplastics (MNPLs) are intentionally produced for commercial uses (primary MNPLs) or are formed from environmentally aged plastics (secondary MNPLs). Independent of their origin, all of them will finally end up in the environment constituting some of the known emergent pollutants. Despite the inert nature of plastics, questions about their potential biological effects on human health need to find sound answers. In addition, the association between the potentially induced effects and the MNPL size is also required to be known. In this context, we have used our in vivo model of Drosophila larvae and three nanopolystyrene plastics (PSNPLs) sized 50, 200, and 500 nm (PS-50, PS-200, and PS-500) to add new data to better understand the potential health risks of MNPLs. Our model has permitted us to visualize (via transmission electron microscopy, TEM) the journey of the PSNPLs administered via ingestion, their interaction with gut lumen components (including symbiotic microbiota), their uptake by gut enterocytes, their translocation through the intestinal barrier to the hemolymph, and their uptake by hemocytes. This behavior was observed for the three analyzed sizes and, for the largest sizes, changes in size/shape were observed in ingested PSNPLs. Although no relevant toxicity, as measured by the egg-to-adult viability, was observed, exposure induced a wide molecular response altering the expression of genes involved in the general stress response, in the antioxidant response and even in the genotoxicity response, as well as in genes related to the intestinal damage response. Furthermore, a general induction of ROS production and DNA damage was also detected. Interestingly, these types of responses were size-dependent with the small PSNPL size inducing a higher response

Nanoplastics and arsenic co-exposures exacerbate oncogenic biomarkers under an in vitro long-term exposure scenario

The increasing accumulation of plastic waste and the widespread presence of its derivatives, micro- and nanoplastics (MNPLs), call for an urgent evaluation of their potential health risks. In the environment, MNPLs coexist with other known hazardous contaminants and, thus, an interesting question arises as to whether MNPLs can act as carriers of such pollutants, modulating their uptake and their harmful effects. In this context, we have examined the interaction and joint effects of two relevant water contaminants: arsenic and polystyrene nanoplastics (PSNPLs), the latter being a model of nanoplastics. Since both agents are persistent pollutants, their potential effects have been evaluated under a chronic exposure scenario and measuring different effect biomarkers involved in the cell transformation process. Mouse embryonic fibroblasts deficient for oxidative DNA damage repair mechanisms, and showing a cell transformation status, were used as a sensitive cell model. Such cells were exposed to PSNPLs, arsenic, and a combination PSNPLs/arsenic for 12 weeks. Interestingly, a physical interaction between both pollutants was demonstrated by using TEM/EDX methodologies. Results also indicate that the continuous co-exposure enhances the DNA damage and the aggressive features of the initially transformed phenotype. Remarkably, co-exposed cells present a higher proportion of spindle-like cells within the population, an increased capacity to grow independently of anchorage, as well as enhanced migrating and invading potential when compared to cells exposed to arsenic or PSNPLs alone. This study highlights the need for further studies exploring the long-term effects of contaminants of emerging concern, such as MNPLs, and the importance of considering the behavior of mixtures as part of the hazard and human risk assessment approaches

Insights into the potential carcinogenicity of micro- and nano-plastics

There is a growing concern regarding the potential health effects that continuous exposure to environmental micro- and nano-plastics (MNPLs) may cause on humans. Due to their persistent nature, MNPLs may accumulate in different organs and tissues and may induce in the long term the development of cancer. The present study aimed to review the existing literature on the carcinogenic potential of MNPLs. As studies directly assessing carcinogenicity were expected to be scarce, studies dealing with indirect outcomes associated with the carcinogenic process were considered in the literature search. Of the 126 studies screened, 19 satisfied the inclusion criteria. Besides, 7 additional cross-referenced articles, identified through a careful reading of the previously selected papers, also met the inclusion criteria and, consequently, were included in the review. Most of the selected studies were performed using in vitro models whereas about 40% of the studies were done in rodents, although none of them included a 2-year carcinogenicity assay. Most of the reviewed studies pointed out the potential of MNPLs to induce inflammation and genotoxicity, the latter being recognized as a strong predictor of carcinogenicity. These, along with other important findings such as the MNPLs' ability to accumulate into cells and tissues, or their capacity to induce fibrosis, may suggest an association between MNPLs exposures and the carcinogenic potential. Nevertheless, the limited number of available studies precludes reaching clear conclusions. Therefore, this review also provides several recommendations to cover the current knowledge gaps and address the future evaluation of the MNPLs' carcinogenic risk

Effects of true-to-life PET nanoplastics using primary human nasal epithelial cells

Altres ajuts: acords transformatius de la UABSince inhalation is a relevant exposure route, studies using appropriate micro/nanoplastic (MNPLs) models, representative targeted cells, and relevant biomarkers of effect are required. We have used lab-made polyethylene terephthalate (PET)NPLs obtained from PET plastic water bottles. Human primary nasal epithelial cells (HNEpCs) were used as a model of the first barrier of the respiratory system. Cell internalization and intracellular reactive oxygen species (iROS) induction, as well as the effects on mitochondria functionality and in the modulation of the autophagy pathway, were evaluated. The data indicated significant cellular uptake and increased levels of iROS. Furthermore, a loss of mitochondrial membrane potential was observed in the exposed cells. Regarding the effects on the autophagy pathway, PETNPLs exposure significantly increases LC3-II protein expression levels. PETNPLs exposure also induced significant increases in the expression of p62. This is the first study showing that true-to-life PETNPLs can alter the autophagy pathway in HNEpCs

Long-term exposure to nanoplastics alters molecular and functional traits related to the carcinogenic process

Acord transformatiu CRUE-CSICMicro/nanoplastics (MNPLs) are considered emergent pollutants widely spread over all environmental compartments. Although their potential biological effects are being intensively evaluated, many doubts remain about their potential health effects in humans. One of the most underdeveloped fields is the determination of the potential tumorigenic risk of MNPLs exposure. To shed light on this topic, we have designed a wide battery of different hallmarks of cancer applied to prone-to-transformed progress MEF cells exposed to polystyrene nanoplastics (PSNPLs) in the long term (6 months). Interestingly, most of the evaluated hallmarks of cancer are exacerbated after exposure, independently if they are associated with an early tumoral phenotype (changes in stress-related genes, or microRNA deregulation), advanced tumoral phenotype (growing independently of anchorage ability, and migration capacity), or an aggressive tumoral phenotype (invasion potential, changes in pluripotency markers, and ability to grow to form tumorspheres). This set of obtained data constitutes a relevant warning on the potential carcinogenic risk associated with long-term exposures to MNPLs, specifically that induced by the PSNPLs evaluated in this study

Effects of titanium dioxide nanoparticles on the Hprt gene mutations in V79 hamster cells

The genotoxicity of anatase/rutile TiO nanoparticles (TiO NPs, NM105 at 3, 15 and 75 µg/cm 2) was assessed with the mammalian in-vitro Hypoxanthine guanine phosphoribosyl transferase (Hprt) gene mutation test in Chinese hamster lung (V79) fibroblasts after 24 h exposure. Two dispersion procedures giving different size distribution and dispersion stability were used to investigate whether the effects of TiO NPs depend on the state of agglomeration. TiO NPs were fully characterised in the previous European FP7 projects NanoTEST and NanoREG2. Uptake of TiO NPs was measured by transmission electron microscopy (TEM). TiO NPs were found in cytoplasmic vesicles, as well as close to the nucleus. The internalisation of TiO NPs did not depend on the state of agglomeration and dispersion used. The cytotoxicity of TiO NPs was measured by determining both the relative growth activity (RGA) and the plating efficiency (PE). There were no substantial effects of exposure time (24, 48 and 72 h), although a tendency to lower RGA at longer exposure was observed. No significant difference in PE values and no increases in the Hprt gene mutant frequency were found in exposed relative to unexposed cultures in spite of evidence of uptake of NPs by cells