Immune and inflammatory responses of human macrophages, dendritic cells, and T-cells in presence of micro- and nanoplastic of different types and sizes

Studying mercury and polymethyl methacrylate joint effects on endogenous hydrogen polysulfides via fluorescence imaging

Heavy metal ions and micro(nano)plastic pollution have attracted increasing attention. However, their toxicological effects on endogenous reactive species at molecular level are unclear, especially their joint effects. Hence, two typical environmental poisons, mercury (Hg2+) and polymethyl methacrylate (PMMA), posing significant risks to both human health and ecosystems, are selected as pollution models for studying joint effects. Hydrogen polysulfides (H2Sn, n > 1) play crucial roles in removing oxidants and intracellular electrophilic reagents, involved in regulating intracellular redox state. The understanding of its precise biological role and intricate mechanism action remains limited, especially suffering from exogenous environmental stress. Herein, we have developed a novel H2Sn- responsive fluorescence probe P-Y with outstanding performance. Moreover, probe P-Y could image endogenous H2Sn levels in cells, and was successfully applied for monitoring the fluctuations of endogenous H2Sn levels to investigate their effects on redox homeostasis under Hg2+ and PMMA single and combined exposure. This study provided imaging evidences and an absorbing insight for understanding H2Sn function under Hg2+ and PMMA single and joint effects in living organisms.

Short-term oral exposure to nanoplastics does not significantly impact the antiviral immune response of the mouse

The increasing prevalence of nanoplastics (NPs) in the environment, particularly polystyrene (PS) nanoparticles, raises concerns regarding their potential impact on human and animal health. Given their small size, NPs can cross biological barriers and accumulate in organs, including those critical for immune functions. This study investigates the effects of short-term oral exposure to 100 and 500 nm PS NPs on the adaptive immune responses during viral infections in vivo, using vesicular stomatitis virus (VSV) and lymphocytic choriomeningitis virus (LCMV) as models. Male and female C57BL/6 mice were orally exposed to PS NP for a period of 28 days, during which they were infected with either VSV or LCMV to study the humoral and cellular responses, respectively. The humoral responses were assessed by measuring total and VSV-specific antibody levels, and splenic immune populations. T cell phenotypes, activation, exhaustion and functionality towards LCMV epitopes were studied as readouts of the cellular responses. Our results demonstrate that short-term NP exposure does not significantly affect the generation or neutralizing capacity of antibodies against VSV, nor the cellular responses directed against LCMV. These findings indicate that, under these conditions, PS NP exposure does not significantly compromise the adaptive immune responses during viral infections, underscoring the value of in vivo models.

Nanoplastic-induced antibody liquid-liquid phase separation: Insights into potential immunotoxic implications

The increasing environmental prevalence of micro/nano plastics (MNPs) has raised significant concerns regarding their potential impact on human health, particularly in terms of immunotoxicity. However, the direct effects of MNPs on immune molecules, especially how they may influence protein liquid-liquid phase separation (LLPS)-a critical process implicated in various aspects of immune function-remain largely unexplored. This study addresses this gap by investigating the effects of polystyrene nanoparticles (PS NPs) with different surface modifications and sizes on LLPS in immunoglobulin Y (IgY) antibodies, critical components of the avian immune system. Our findings reveal that PS-COOH NPs uniquely induce LLPS in IgY in a size-dependent manner, while PS-NH2 and unmodified PS NPs do not. Furthermore, NP-induced LLPS disrupts IgY's antigen-binding capability, potentially impairing immune responses. Notably, the IgY-Fc fragment shows a greater tendency for LLPS than the full-length antibody, suggesting broader implications for immune receptor interactions. These findings underscore the significant roles of nanoparticle surface chemistry, size, and antigen interactions in modulating LLPS. This study pioneers the exploration of MNPs-induced LLPS as a potential mechanism of immunotoxicity, providing crucial insights into the health risks posed by environmental MNPs and informing strategies for mitigation.

Effects of microplastics on the immune system: How much should we worry?

Plastics are everywhere. It is widely recognized that they represent a global problem, the extent of which is yet to be defined. Humans are broadly exposed to plastics, whose effects and consequences are poorly characterized so far. The main route of exposure is via alimentary and respiratory intake. Plastics pollutions may come from both: water and food contamination itself, and their packaging. The smaller sizes (i.e. microplastics <150 µm - MPs) are considered to be the most pervasive of living organisms and, therefore, potentially the most harmful. As humans occupy one of the apex positions of the food chain, we are exposed to bioaccumulation and biomagnification effects of MPs. In fact, MPs are commonly found in human stools and blood. However, there are no data available yet on their ability to accumulate and to produce detrimental consequences on biological systems. Even though the effects of plastics pollution are poorly studied in mammals, including humans, they appear to have inflammatory effects, which is rather concerning as many etiologies of disease are based on a pro-inflammatory status.

Role of microplastics in the tumor microenvironment (Review)

Microplastics (MPs) are pervasive in several ecosystems and have the potential to infiltrate multiple aspects of human life through ingestion, inhalation and dermal exposure, thus eliciting substantial concerns regarding their potential implications for human health. Whilst initial research has documented the effects of MPs on disease development across multiple physiological systems, MPs may also facilitate tumor progression by influencing the tumor microenvironment (TME). This evolving focus underscores the growing interest in the role of MPs in tumorigenesis and their interactions within the TME. In the present review, the relationship between MPs and the TME is comprehensively assessed, providing a detailed analysis of their interactions with tumor cells, stromal cells (including macrophages, fibroblasts and endothelial cells), the extracellular matrix and inflammatory processes. Recommendations for future research directions and strategies to address and reduce microplastic pollution are proposed.

Micro-nanoplastic induced cardiovascular disease and dysfunction: a scoping review

BACKGROUND

The human bioaccumulation of micro- and nano-plastics (MNPs) is increasingly being recognised in the aetiology and pathophysiology of human disease.

OBJECTIVE

This systematic scoping review aims to provide a comprehensive investigation of studies examining the impacts of MNPs on the human cardiovascular system.

METHODS

Five databases (PubMed, SCOPUS, CINAHL, Web of Science and EMBASE) were systematically searched.

RESULTS

Forty-six articles were identified, 13 of which investigated the presence of MNPs within the human cardiovascular system, including atherosclerotic plaques, saphenous vein tissue, thrombi and venous blood. The effect of MNPs on cell lines suggest MNPs are cytotoxic, immunotoxic, and genotoxic.

SIGNIFICANCE

The findings of this review, when evaluated together with additional studies utilising animal models, suggest MNPs may contribute to global cardiovascular morbidity and mortality. In particular, the ability of MNPs to induce endothelial damage, oxy-LDL formation, foam cell development and apoptosis, as well as to alter the clotting cascade, has potential implications for vascular diseases. In addition, MNPs may play a role in the aetiology and progression of congenital heart abnormalities, infective pathologies and cardiomyopathies. Despite an increasing awareness of the ability for MNPs to result in cardiovascular disease and dysfunction, a limited amount of research has been conducted to date characterising the presence of MNPs in the human cardiovascular system. Reseach is required to understand the extent of this rapidly emerging issue and to develop strategies that will support clinicians to appropriately manage and educate their patients in the future.

Biological Effects of Micro-/Nano-Plastics in Macrophages

The environmental impact of plastics is worsened by their inadequate end-of-life disposal, leading to the ubiquitous presence of micro- (MPs) and nanosized (NPs) plastic particles. MPs and NPs are thus widely present in water and air and inevitably enter the food chain, with inhalation and ingestion as the main exposure routes for humans. Many recent studies have demonstrated that MPs and NPs gain access to several body compartments, where they are taken up by cells, increase the production of reactive oxygen species, and lead to inflammatory changes. In most tissues, resident macrophages engage in the first approach to foreign materials, and this interaction largely affects the subsequent fate of the material and the possible pathological outcomes. On the other hand, macrophages are the main organizers and controllers of both inflammatory responses and tissue repair. Here, we aim to summarize the available information on the interaction of macrophages with MPs and NPs. Particular attention will be devoted to the consequences of this interaction on macrophage viability and functions, as well as to possible implications in pathology.

Plastic nanoparticle toxicity is accentuated in the immune-competent inflamed intestinal tri-culture cell model

Introduction: Important cell-based models of intestinal inflammation have been advanced in hopes of predicting the impact of nanoparticles on disease. We sought to determine whether a high level and extended exposure of nanoplastic might result in the added intestinal inflammation caused by nanoplastic reported in a mouse model of irritable bowel disease. Methods: The cell models consist of a Transwell©-type insert with a filter membrane upon which lies a biculture monolayer of Caco-2 and HT29-MTX-E12 made up the barrier cells (apical compartment). This monolayer was exposed to digested 40 nm diameter polymethacrylate (PMA) with surface-functionalized COOH (PMA-) or NH2 (PMA+) at a 'low level' (143 µg/cm2 monolayer surface area) or 'high level' (571 µg/cm2) for 24 or 48 h. Beyond the apical compartment in the well of the tissue culture plate, was a monolayer of macrophages, previously differentiated from THP-1 cells (basolateral compartment). Thus, the immune competent tri-cultures were examined as two models: healthy and inflamed. The inflamed model, the barrier cell monolayer having been previously activated with IFN-γ and the macrophages having been previously activated with IFN-γ and LPS expressed a greater secretion of pro-inflammation cytokines. Results: Sedimentation, Diffusion and Dosimetry model (ISDD) simulated that 8%-12% of the PMA was deposited onto the barrier cell monolayer in 24-48-h. The structure of the barrier cells in the inflamed model was disorganized for both PMA, high level, 48-h experiments. While neither the amount of PMA nor the exposure duration influenced the lactate dehydrogenase (LDH) secretion in the healthy model, only the high levels of both PMA- and PMA+ in 48-h exposure experiments resulted in a significantly increased LDH secreted by the barrier cells in the inflamed model, compared to inflamed control. This study is the first to show an additive inflammation of nanoplastic in an inflamed intestinal model of the intestine.

The microplastic-crisis: Role of bacteria in fighting microplastic-effects in the digestive system

Plastic particles smaller than 5 mm, referred to as Microplastics, pose health risks, like metabolic, immunological, neurological, reproductive, and carcinogenic effects, after being ingested. Smaller plastic particles are more likely to be absorbed by human cells, with nanoplastics showing higher potential for cellular damage, including DNA fragmentation and altered protein functions. Micro- and nanoplastics (MNPs) affect the gastrointestinal tract by altering the microbial composition, they could influence digestive enzymes, and possibly disrupt mucus layers. In the stomach, they potentially interfere with digestion and barrier functions, while in the intestines, they could increase permeability via inflammation and tissue disruption. MNPs can lead to microbial dysbiosis, leading to gastrointestinal symptoms. By activating inflammatory pathways, altering T cell functions and affecting dendritic cells and macrophages, immune system homeostasis could possibly be disrupted. Probiotics offer potential strategies to alleviate plastic effects, by either degrading plastic particles or directly countering health effects. We compared genetic sequences of probiotics to the genome of known plastic degraders and concluded that no probiotic bacteria could serve the role of plastic degradation. However, probiotics could directly mitigate MNP-health effects. They can restore microbial diversity, enhance the gut barrier, regulate bile acid metabolism, reduce inflammation, regulate insulin balance, and counteract metabolic disruptions. Antioxidative properties protect against lipid peroxidation and MNP-related reproductive system damage. Probiotics can also bind and degrade toxins, like heavy metals and bisphenol A. Additionally, bacteria could be used to aggregate MNPs and reduce their impact. Therefore, probiotics offer a variety of strategies to counter MNP-induced health effects.

The Emerging Threat of Micro- and Nanoplastics on the Maturation and Activity of Immune Cells

With the increasing use of plastics worldwide, the amount of plastic waste being discarded has also risen. This plastic waste undergoes physical and chemical processes, breaking down into smaller particles known as microplastics (MPs) or nanoplastics (NPs). Advances in technology have enhanced our ability to detect these smaller particles, and it has been confirmed that plastics can be found in marine organisms as well as within the human body. However, research on the effects of MPs or NPs on living organisms has only recently been started, and our understanding remains limited. Studies on the immunological impacts are still ongoing, revealing that MPs and NPs can differentially affect various immune cells based on the material, size, and shape of the plastic particles. In this review, we aim to provide a comprehensive understanding of the effects of MPs and NPs on the immune system. We will also explore the methods for plastic removal through physicochemical, microbial, or biological means.

Microplastics as an Emerging Potential Threat: Toxicity, Life Cycle Assessment, and Management

The pervasiveness of microplastics (MPs) in terrestrial and aquatic ecosystems has become a significant environmental concern in recent years. Because of their slow rate of disposal, MPs are ubiquitous in the environment. As a consequence of indiscriminate use, landfill deposits, and inadequate recycling methods, MP production and environmental accumulation are expanding at an alarming rate, resulting in a range of economic, social, and environmental repercussions. Aquatic organisms, including fish and various crustaceans, consume MPs, which are ultimately consumed by humans at the tertiary level of the food chain. Blocking the digestive tracts, disrupting digestive behavior, and ultimately reducing the reproductive growth of entire living organisms are all consequences of this phenomenon. In order to assess the potential environmental impacts and the resources required for the life of a plastic product, the importance of life cycle assessment (LCA) and circularity is underscored. MPs-related ecosystem degradation has not yet been adequately incorporated into LCA, a tool for evaluating the environmental performance of product and technology life cycles. It is a technique that is designed to quantify the environmental effects of a product from its inception to its demise, and it is frequently employed in the context of plastics. The control of MPs is necessary due to the growing concern that MPs pose as a newly emergent potential threat. This is due to the consequences of their use. This paper provides a critical analysis of the formation, distribution, and methods used for detecting MPs. The effects of MPs on ecosystems and human health are also discussed, which posed a great challenge to conduct an LCA related to MPs. The socio-economic impacts of MPs and their management are also discussed. This paper paves the way for understanding the ecotoxicological impacts of the emerging MP threat and their associated issues to LCA and limits the environmental impact of plastic.

Identification and analysis of microplastic aggregation in CAR-T cells

Microplastics (MPs) are increasingly recognized as contaminants present in various environments and are widely acknowledged as potential hazards to the mammalian immune system. In our study of chimeric antigen receptor T cell (CAR-T) therapy, we observed the presence of MP in CAR-T cell products for the first time. It is worth exploring whether MP could enter CAR-T cells and how they might affect CAR-T cells' functionality. Therefore, we analyzed how MP affected CD19 and BCMA-CAR-T cells. Based on flow cytometry, ELISA, and cytotoxicity analysis of in vitro and in vivo experiments, MP suppressed the activity of CAR-T cells. Subsequent investigation revealed that the exposure of CAR-T cells to varying concentrations of MP resulted in a notable increase in apoptosis, ferroptosis, and exhaustion levels. Furthermore, the hyperactivation of the mTOR signaling pathway in MP-treated CAR-T cells was verified. The partial restoration of CAR-T cell function in MP was achieved by inhibiting the mTOR pathway. MP present a threat to CAR-T cell function due to their role in inducing CAR-T cell apoptosis, ferroptosis, and T-cell exhaustion through the hyperactivation of mTOR signaling pathways.

Effects of Polyvinyl Chloride (PVC) Microplastic Particles on Gut Microbiota Composition and Health Status in Rabbit Livestock

The widespread use of polyvinyl chloride (PVC) and its entry into humans and livestock is of serious concern. In our study, we investigated the impact of PVC treatments on physiological, pathological, hormonal, and microbiota changes in female rabbits. Trend-like alterations in weight were observed in the spleen, liver, and kidney in both low (P1) and high dose (P2) PVC treatment groups. Histopathological examination revealed exfoliation of the intestinal mucosa in the treated groups compared to the control, and microplastic particles were penetrated and embedded in the spleen. Furthermore, both P1 and P2 showed increased 17-beta-estradiol (E2) hormone levels, indicating early sexual maturation. Moreover, the elevated tumor necrosis factor alpha (TNF-α) levels suggest inflammatory reactions associated with PVC treatment. Genus-level analyses of the gut microbiota in group P2 showed several genera with increased or decreased abundance. In conclusion, significant or trend-like correlations were demonstrated between the PVC content of feed and physiological, pathological, and microbiota parameters. To our knowledge, this is the first study to investigate the broad-spectrum effects of PVC microplastic exposure in rabbits. These results highlight the potential health risks associated with PVC microplastic exposure, warranting further investigations in both animals and humans.

Exposure to polystyrene microplastics during lactational period alters immune status in both male mice and their offspring

The widespread use of microplastics and their harmful effects on the environment have emerged as serious concerns. However, the effect of microplastics on the immune system of mammals, particularly their offspring, has received little attention. In this study, polystyrene microplastics (PS-MPs) were orally administered to male mice during lactation. Flow cytometry was used to assess the immune cells in the spleens of both adult male mice and their offspring. The results showed that mice exposed to PS-MPs exhibited an increase in spleen weight and an elevated number of B and regulatory T cells (Tregs), irrespective of dosage. Furthermore, the F1 male offspring of the PS-MPs-exposed group had enlarged spleens; an increased number of B cells, T helper cells (Th cells), and Tregs; and an elevated ratio of T helper cells 17 (Th17 cells) to Tregs and T helper cells 1 (Th1 cells) to T helper cells 2 (Th2 cells). These results suggested a pro-inflammatory state in the spleen. In contrast, in the F1 female offspring exposed to PS-MPs, the changes in splenic immune cells were less pronounced. In the F2 generation of mice with exposed to PS-MPs, minimal alterations were observed in spleen immune cells and morphology. In conclusion, our study demonstrated that exposure to real human doses of PS-MPs during lactation in male mice altered the immune status, which can be passed on to F1 offspring but is not inherited across generations.

Microplastics in the Human Body: Exposure, Detection, and Risk of Carcinogenesis: A State-of-the-Art Review

Background: Humans cannot avoid plastic exposure due to its ubiquitous presence in the natural environment. The waste generated is poorly biodegradable and exists in the form of MPs, which can enter the human body primarily through the digestive tract, respiratory tract, or damaged skin and accumulate in various tissues by crossing biological membrane barriers. There is an increasing amount of research on the health effects of MPs. Most literature reports focus on the impact of plastics on the respiratory, digestive, reproductive, hormonal, nervous, and immune systems, as well as the metabolic effects of MPs accumulation leading to epidemics of obesity, diabetes, hypertension, and non-alcoholic fatty liver disease. MPs, as xenobiotics, undergo ADMET processes in the body, i.e., absorption, distribution, metabolism, and excretion, which are not fully understood. Of particular concern are the carcinogenic chemicals added to plastics during manufacturing or adsorbed from the environment, such as chlorinated paraffins, phthalates, phenols, and bisphenols, which can be released when absorbed by the body. The continuous increase in NMP exposure has accelerated during the SARS-CoV-2 pandemic when there was a need to use single-use plastic products in daily life. Therefore, there is an urgent need to diagnose problems related to the health effects of MP exposure and detection. Methods: We collected eligible publications mainly from PubMed published between 2017 and 2024. Results: In this review, we summarize the current knowledge on potential sources and routes of exposure, translocation pathways, identification methods, and carcinogenic potential confirmed by in vitro and in vivo studies. Additionally, we discuss the limitations of studies such as contamination during sample preparation and instrumental limitations constraints affecting imaging quality and MPs detection sensitivity. Conclusions: The assessment of MP content in samples should be performed according to the appropriate procedure and analytical technique to ensure Quality and Control (QA/QC). It was confirmed that MPs can be absorbed and accumulated in distant tissues, leading to an inflammatory response and initiation of signaling pathways responsible for malignant transformation.

Molecular and Cellular Effects of Microplastics and Nanoplastics: Focus on Inflammation and Senescence

Microplastics and nanoplastics (MNPs) are ubiquitous environmental contaminants. Their prevalence, persistence, and increasing industrial production have led to questions about their long-term impact on human and animal health. This narrative review describes the effects of MNPs on oxidative stress, inflammation, and aging. Exposure to MNPs leads to increased production of reactive oxygen species (ROS) across multiple experimental models, including cell lines, organoids, and animal systems. ROS can cause damage to cellular macromolecules such as DNA, proteins, and lipids. Direct interaction between MNPs and immune cells or an indirect result of oxidative stress-mediated cellular damage may lead to increased production of pro-inflammatory cytokines throughout different MNP-exposure conditions. This inflammatory response is a common feature in the pathogenesis of neurodegenerative, cardiovascular, and other age-related diseases. MNPs also act as cell senescence inducers by promoting mitochondrial dysfunction, impairing autophagy, and activating DNA damage responses, exacerbating cellular aging altogether. Increased senescence of reproductive cells and transfer of MNPs/induced damages from parents to offspring in animals further corroborates the transgenerational health risks of the tiny particles. This review aims to provoke a deeper investigation into the notorious effects these pervasive particles may have on human well-being and longevity.

Microplastics: an often-overlooked issue in the transition from chronic inflammation to cancer

The presence of microplastics within the human body has raised significant concerns about their potential health implications. Numerous studies have supported the hypothesis that the accumulation of microplastics can trigger inflammatory responses, disrupt the microbiome, and provoke immune reactions due to their physicochemical properties. Chronic inflammation, characterized by tissue damage, angiogenesis, and fibrosis, plays a crucial role in cancer development. It influences cancer progression by altering the tumor microenvironment and impairing immune surveillance, thus promoting tumorigenesis and metastasis. This review explores the fundamental properties and bioaccumulation of microplastics, as well as their potential role in the transition from chronic inflammation to carcinogenesis. Additionally, it provides a comprehensive overview of the associated alterations in signaling pathways, microbiota disturbances, and immune responses. Despite this, the current understanding of the toxicity and biological impacts of microplastics remains limited. To mitigate their harmful effects on human health, there is an urgent need to improve the detection and removal methods for microplastics, necessitating further research and elucidation.

Detection and quantification of microplastics in various types of human tumor tissues

Microplastics (MPs) have been detected in various human tissues. However, whether MPs can accumulate within tumors and how they affect the tumor immune microenvironment (TIME) and therapeutic responses remains unclear. This study aimed to determine the presence of MPs in tumors and their potential effects on the TIME. Sixty-one tumor samples were collected for analysis. The presence of MPs in tumors was qualitatively and quantitatively assessed using pyrolysis-gas chromatography-mass spectrometry. MPs were detected in 26 of the samples examined. Three types of MPs were identified: polystyrene, polyvinyl chloride, and polyethylene. In lung, gastric, colorectal, and cervical tumors, the MP detection rates were 80 %, 40 %, 50 %, and 17 % (7.1-545.9 ng/g), respectively. MPs were detected in 70 % of pancreatic tumors (18.4-427.1 ng/g) but not detected in esophageal tumors. In pancreatic cancer, the MP-infiltrated TIME exhibited a reduction in CD8+ T, natural killer, and dendritic cell counts, accompanied by substantial neutrophil infiltration. This study illustrates the potential presence of MPs in diverse tumors; varying adhesive affinities were observed among different tumor types. MPs may lead to a more adverse TIME in pancreatic tumors. Further investigations are warranted to assess whether MPs promote tumor progression and affect the efficacy of immunotherapy.

Micro/nano-plastics impacts in cardiovascular systems across species

The widespread presence of microplastics and nanoplastics (MPs/NPs) in the environment has become a critical public health issue due to their potential to infiltrate and affect various biological systems. Our review is crucial as it consolidates current data and provides a comprehensive analysis of the cardiovascular impacts of MPs/NPs across species, highlighting significant implications for human health. By synthesizing findings from studies on aquatic and terrestrial organisms, including humans, this review offers insights into the ubiquity of MPs/NPs and their pathophysiological roles in cardiovascular systems. We demonstrated that exposure to MPs/NPs is linked to various cardiovascular ailments such as thrombogenesis, vascular damage, and cardiac impairments in model organisms, which likely extrapolate to humans. Our review critically evaluated methods for detecting MPs/NPs in biological tissues, assessing their toxicity, and understanding their behaviour within the vasculature. These findings emphasise the urgent need for targeted public health strategies and enhanced regulatory measures to mitigate the impacts of MP/NP pollution. Furthermore, the review underlined the necessity of advancing research methodologies to explore long-term effects and potential intergenerational consequences of MP/NP exposure. By mapping out the intricate links between environmental exposure and cardiovascular risks, our work served as a pivotal reference for future research and policymaking aimed at curbing the burgeoning threat of plastic pollution.

Effect of micro- and nanoplastic particles on human macrophages

Micro- and nanoplastics (MNPs) are ubiquitous in the environment, resulting in the uptake of MNPs by a variety of organisms, including humans, leading to particle-cell interaction. Human macrophages derived from THP-1 cell lines take up Polystyrene (PS), a widespread plastic. The question therefore arises whether primary human macrophages also take up PS micro- and nanobeads (MNBs) and how they react to this stimulation. Major aim of this study is to visualize this uptake and to validate the isolation of macrophages from peripheral blood mononuclear cells (PBMCs) to assess the impact of MNPs on human macrophages. Uptake of macrophages from THP-1 cell lines and PBMCs was examined by transmission electron microscopy (TEM), scanning electron microscopy and live cell imaging. In addition, the reaction of the macrophages was analyzed in terms of metabolic activity, cytotoxicity, production of reactive oxygen species (ROS) and macrophage polarization. This study is the first to visualize PS MNBs in primary human cells using TEM and live cell imaging. Metabolic activity was size- and concentration-dependent, necrosis and ROS were increased. The methods demonstrated in this study outline an approach to assess the influence of MNP exposure on human macrophages and help investigating the consequences of worldwide plastic pollution.

Pollutants, microbiota and immune system: frenemies within the gut

Pollution is a critical concern of modern society for its heterogeneous effects on human health, despite a widespread lack of awareness. Environmental pollutants promote several pathologies through different molecular mechanisms. Pollutants can affect the immune system and related pathways, perturbing its regulation and triggering pro-inflammatory responses. The exposure to several pollutants also leads to alterations in gut microbiota with a decreasing abundance of beneficial microbes, such as short-chain fatty acid-producing bacteria, and an overgrowth of pro-inflammatory species. The subsequent intestinal barrier dysfunction, together with oxidative stress and increased inflammatory responses, plays a role in the pathogenesis of gastrointestinal inflammatory diseases. Moreover, pollutants encourage the inflammation-dysplasia-carcinoma sequence through various mechanisms, such as oxidative stress, dysregulation of cellular signalling pathways, cell cycle impairment and genomic instability. In this narrative review, we will describe the interplay between pollutants, gut microbiota, and the immune system, focusing on their relationship with inflammatory bowel diseases and colorectal cancer. Understanding the biological mechanisms underlying the health-to-disease transition may allow the design of public health policies aimed at reducing the burden of disease related to pollutants.

Harmful effects of true-to-life nanoplastics derived from PET water bottles in human alveolar macrophages

The increasing presence of secondary micro/nanoplastics (MNPLs) in the environment requires knowing if they represent a real health concern. To such end, an important point is to test representative MNPLs such as the denominated true-to-life MNPLs, resulting from the degradation of plastic goods in lab conditions. In this study, we have used polyethylene terephthalate (PET) NPLs resulting from the degradation of PET water bottles. Since inhalation is an important exposure route to environmental MNPLS, we have used mouse alveolar macrophages (MH-S) as a target cell, and the study focused only on the cells that have internalized them. This type of approach is novel as it may capture the realistic adverse effects of PETNPLs only in the internalized cells, thereby mitigating any biases while assessing the risk of these MNPLs. Furthermore, the study utilized a set of biomarkers including intracellular reactive oxygen species (ROS) levels, variations on the mitochondrial membrane potential values, and the macrophage polarization to M1 (pro-inflammatory response) and M2 (anti-proinflammatory response) as possible cellular effects due to PETNPLs in only the cells that internalized PETNPLs. After exposures lasting for 3 and 24 h to a range of concentrations (0, 25, 50, and 100 μg/mL) the results indicate that no toxicity was induced despite the 100% internalization observed at the highest concentration. Significant intracellular levels of ROS were observed, mainly at exposures lasting for 24 h, in an indirect concentration-effect relationship. Interestingly, a reduction in the mitochondrial membrane potential was observed, but only at exposures lasting for 24 h, but without a clear concentration-effect relationship. Finally, PETNPL exposure shows a significant polarization from M0 to M1 and M2 subtypes. Polarization to M1 (pro-inflammatory stage) was more marked and occurred at both exposure times. Polarization to M2 (anti-inflammatory stage) was only observed after exposures lasting for 24 h. Due to the relevance of the described biomarkers, our results underscore the need for further research, to better understand the health implications associated with MNPL exposure.

Sonicated polyethylene terephthalate nano- and micro-plastic-induced inflammation, oxidative stress, and autophagy in vitro

The environmental presence of nano- and micro-plastic particles (NMPs) is suspected to have a negative impact on human health. Environmental NMPs are difficult to sample and use in life science research, while commercially available plastic particles are too morphologically uniform. Additionally, this NMPs exposure exhibited biological effects, including cell internalization, oxidative stress, inflammation, cellular adaptation, and genotoxicity. Therefore, developing new methods for producing heterogenous NMPs as observed in the environment is important as reference materials for research. Thus, we aimed to generate and characterize NMPs suspensions using a modified ultrasonic protocol and to investigate their biological effects after exposure to different human cell lines. To this end, we produced polyethylene terephthalate (PET) NMPs suspensions and characterized the particles by dynamic light scattering and scanning electron microscopy. Ultrasound treatment induced polymer degradation into smaller and heterogeneous PET NMPs shape fragments with similar surface chemistry before and after treatment. A polydisperse suspension of PET NMPs with 781 nm in average size and negative surface charge was generated. Then, the PET NMPs were cultured with two human cell lines, A549 (lung) and HaCaT (skin), addressing inhalation and topical exposure routes. Both cell lines interacted with and have taken up PET NMPs as quantified via cellular granularity assay. A549 but not HaCaT cell metabolism, viability, and cell death were affected by PET NMPs. In HaCaT keratinocytes, large PET NMPs provoked genotoxic effects. In both cell lines, PET NMPs exposure affected oxidative stress, cytokine release, and cell morphology, independently of concentration, which we could relate mechanistically to Nrf2 and autophagy activation. Collectively, we present a new PET NMP generation model suitable for studying the environmental and biological consequences of exposure to this polymer.

Micro and nano plastics release from a single absorbable suture into simulated body fluid

Synthetic polymers are widely used in medical devices and implants where biocompatibility and mechanical strength are key enablers of emerging technologies. One concern that has not been widely studied is the potential of their microplastics (MPs) release. Here we studied the levels of MP debris released following 8-week in vitro tests on three typical polyglycolic acid (PGA) based absorbable sutures (PGA 100, PGA 90 and PGA 75) and two nonabsorbable sutures (polypropylene-PP and polyamide-PA) in simulated body fluid. The MP release levels ranked from PGA 100 > > PGA 90 > PGA 75 > > PP ∼ PA. A typical PGA 100 suture released 0.63 ± 0.087 million micro (MPs > 1 µm) and 1.96 ± 0.04 million nano (NPs, 200-1000 nm) plastic particles per centimeter. In contrast, no MPs were released from the nonabsorbable sutures under the same conditions. PGA that was co-blended with 10-25% L-lactide or epsilon-caprolactone resulted in a two orders of magnitude lower level of MP release. These results underscore the need to assess the release of nano- and microplastics from medical polymers while applied in the human body and to evaluate possible risks to human health.

Enhancement of Macrophage Immunity against Chlamydial Infection by Natural Killer T Cells

Lung macrophage (LM) is vital in host defence against bacterial infections. However, the influence of other innate immune cells on its function, including the polarisation of different subpopulations, remains poorly understood. This study examined the polarisation of LM subpopulations (monocytes/undifferentiated macrophages (Mo/Mφ), interstitial macrophages (IM), and alveolar macrophages (AM)). We further assessed the effect of invariant natural killer T cells (iNKT) on LM polarisation in a protective function against Chlamydia muridarum, an obligate intracellular bacterium, and respiratory tract infection. We found a preferentially increased local Mo/Mφ and IMs with a significant shift to a type-1 macrophage (M1) phenotype and higher expression of iNOS and TNF-α. Interestingly, during the same infection, the alteration of macrophage subpopulations and the shift towards M1 was much less in iNKT KO mice. More importantly, functional testing by adoptively transferring LMs isolated from iNKT KO mice (iNKT KO-Mφ) conferred less protection than those isolated from wild-type mice (WT-Mφ). Further analyses showed significantly reduced gene expression of the JAK/STAT signalling pathway molecules in iNKT KO-Mφ. The data show an important role of iNKT in promoting LM polarisation to the M1 direction, which is functionally relevant to host defence against a human intracellular bacterial infection. The alteration of JAK/STAT signalling molecule gene expression in iNKT KO-Mφ suggests the modulating effect of iNKT is likely through the JAK/STAT pathway.