Analysis of PM2.5-induced cytotoxicity in human HaCaT cells based on a microfluidic system

Photoreactivity of polycyclic aromatic hydrocarbons (PAHs) and their mechanisms of phototoxicity against human immortalized keratinocytes (HaCaT)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic compounds in the environment. They are produced by many anthropogenic sources of different origins and are known for their toxicity, carcinogenicity, and mutagenicity. Sixteen PAHs have been identified as Priority Pollutants by the US EPA, which are often associated with particulate matter, facilitating their dispersion through air and water. When human skin is exposed to PAHs, it might occur simultaneously with solar radiation, potentially leading to phototoxic effects. Phototoxic mechanisms involve the generation of singlet oxygen and reactive oxygen species, DNA damage under specific light wavelengths, and the formation of charge transfer complexes. Despite predictions of phototoxic properties for some PAHs, there remains a paucity of experimental data. This study examined the photoreactive and phototoxic properties of the 16 PAHs enlisted in the Priority Pollutants list. Examined PAHs efficiently photogenerated singlet oxygen and superoxide anion in simple solutions. Furthermore, singlet oxygen phosphorescence was detected in PAH-loaded HaCaT cells. Phototoxicity against human keratinocytes was evaluated using various assays. At 5 nM concentration, examined PAHs significantly reduced viability and mitochondrial membrane potential of HaCaT cells following the exposure to solar simulated light. Analyzed compounds induced a substantial peroxidation of cellular proteins after light treatment. The results revealed that a majority of the examined PAHs exhibited substantial reactive oxygen species photoproduction under UVA and violet-blue light, with their phototoxicity corresponding to their photoreactive properties. These findings improve our comprehension of the interactions between PAHs and human skin cells under environmental conditions, particularly when exposed to solar radiation.

Biomimetic microfluidic chips for toxicity assessment of environmental pollutants

Various types of pollutants widely present in environmental media, including synthetic and natural chemicals, physical pollutants such as radioactive substances, ultraviolet rays, and noise, as well as biological organisms, pose a huge threat to public health. Therefore, it is crucial to accurately and effectively explore the human physiological responses and toxicity mechanisms of pollutants to prevent diseases caused by pollutants. The emerging toxicological testing method biomimetic microfluidic chips (BMCs) exhibit great potential in environmental pollutant toxicity assessment due to their superior biomimetic properties. The BMCs are divided into cell-on-chips and organ-on-chips based on the distinctions in bionic simulation levels. Herein, we first summarize the characteristics, emergence and development history, composition and structure, and application fields of BMCs. Then, with a focus on the toxicity mechanisms of pollutants, we review the applications and advances of the BMCs in the toxicity assessment of physical, chemical, and biological pollutants, respectively, highlighting its potential and development prospects in environmental toxicology testing. Finally, the opportunities and challenges for further use of BMCs are discussed.

Can l-ascorbic acid and trans-resveratrol protect HaCaT cells from fine particulate matter toxicity?

Continuous exposure of human skin to air pollution can result in a range of undesirable skin conditions. In our recent study, UV and visible light were found to increase cytotoxicity of fine particulate matter (PM2.5 ) against human keratinocytes. Since it is impossible to avoid exposure of human skin to PM2.5 , effective strategies are needed to reduce their damaging effects. l-ascorbic acid and resveratrol were tested as potential topical agents against pollution-related skin impairment. Although these agents were previously found to ameliorate PM-dependent damage, the effect of light and seasonal variation of particles were not previously studied. EPR spin-trapping, DPPH assay, and singlet oxygen phosphorescence were used to determine the scavenging activities of the antioxidants. MTT, JC-10 and iodometric assays were used to analyze the effect on PM2.5 -induced cytotoxicity, mitochondrial damage and oxidation of lipids. Live-cell imaging was employed to examine wound-healing properties of cells. Light-induced, PM2.5 -mediated oxidative damage was examined by immunofluorescent staining. Both antioxidants effectively scavenged free radicals and singlet oxygen produced by PM2.5 , reduced cell death and prevented oxidative damage to HaCaT cells. l-ascorbic acid and resveratrol, especially when applied in combination, can protect HaCaT cells against the dark and light induced toxicity of PM2.5 .

Pumped and pumpless microphysiological systems to study (nano)therapeutics

Fluidic microphysiological systems (MPS) are microfluidic cell culture devices that are designed to mimic the biochemical and biophysical in vivo microenvironments of human tissues better than conventional petri dishes or well-plates. MPS-grown tissue cultures can be used for probing new drugs for their potential primary and secondary toxicities as well as their efficacy. The systems can also be used for assessing the effects of environmental nanoparticles and nanotheranostics, including their rate of uptake, biodistribution, elimination, and toxicity. Pumpless MPS are a group of MPS that often utilize gravity to recirculate cell culture medium through their microfluidic networks, providing some advantages, but also presenting some challenges. They can be operated with near-physiological amounts of blood surrogate (i.e., cell culture medium) that can recirculate in bidirectional or unidirectional flow patterns depending on the device configuration. Here we discuss recent advances in the design and use of both pumped and pumpless MPS with a focus on where pumpless devices can contribute to realizing the potential future role of MPS in evaluating nanomaterials. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

3-Bromo-4,5-dihydroxybenzaldehyde Protects Keratinocytes from Particulate Matter 2.5-Induced Damages

Cellular senescence can be activated by several stimuli, including ultraviolet radiation and air pollutants. This study aimed to evaluate the protective effect of marine algae compound 3-bromo-4,5-dihydroxybenzaldehyde (3-BDB) on particulate matter 2.5 (PM_2.5)-induced skin cell damage in vitro and in vivo. The human HaCaT keratinocyte was pre-treated with 3-BDB and then with PM_2.5. PM_2.5-induced reactive oxygen species (ROS) generation, lipid peroxidation, mitochondrial dysfunction, DNA damage, cell cycle arrest, apoptotic protein expression, and cellular senescence were measured using confocal microscopy, flow cytometry, and Western blot. The present study exhibited PM_2.5-generated ROS, DNA damage, inflammation, and senescence. However, 3-BDB ameliorated PM_2.5-induced ROS generation, mitochondria dysfunction, and DNA damage. Furthermore, 3-BDB reversed the PM_2.5-induced cell cycle arrest and apoptosis, reduced cellular inflammation, and mitigated cellular senescence in vitro and in vivo. Moreover, the mitogen-activated protein kinase signaling pathway and activator protein 1 activated by PM_2.5 were inhibited by 3-BDB. Thus, 3-BDB suppressed skin damage induced by PM_2.5.

Ubiquitination as a key regulatory mechanism for O3-induced cutaneous redox inflammasome activation

NLRP1 is one of the major inflammasomes modulating the cutaneous inflammatory responses and therefore linked to a variety of cutaneous conditions. Although NLRP1 has been the first inflammasome to be discovered, only in the past years a significant progress was achieved in understanding the molecular mechanism and the stimuli behind its activation. In the past decades a crescent number of studies have highlighted the role of air pollutants as Particulate Matter (PM), Cigarette Smoke (CS) and Ozone (O3) as trigger stimuli for inflammasomes activation, especially via Reactive Oxygen Species (ROS) mediators. However, whether NLRP1 can be modulated by air pollutants via oxidative stress and the mechanism behind its activation is still poorly understood. Here we report for the first time that O3, one of the most toxic pollutants, activates the NLRP1 inflammasome in human keratinocytes via oxidative stress mediators as hydrogen peroxide (H2O2) and 4-hydroxy-nonenal (4HNE). Our data suggest that NLRP1 represents a target protein for 4HNE adduction that possibly leads to its proteasomal degradation and activation via the possible involvement of E3 ubiquitin ligase UBR2. Of note, Catalase (Cat) treatment prevented inflammasome assemble and inflammatory cytokines release as well as NLRP1 ubiquitination in human keratinocytes upon O3 exposure. The present work is a mechanistic study that follows our previous work where we have showed the ability of O3 to induce cutaneous inflammasome activation in humans exposed to this pollutant. In conclusion, our results suggest that O3 triggers the cutaneous NLRP1 inflammasome activation by ubiquitination and redox mechanism.

Integrative analysis to explore the biological association between environmental skin diseases and ambient particulate matter

Although numerous experimental studies have suggested a significant association between ambient particulate matter (PM) and respiratory damage, the etiological relationship between ambient PM and environmental skin diseases is not clearly understood. Here, we aimed to explore the association between PM and skin diseases through biological big data analysis. Differential gene expression profiles associated with PM and environmental skin diseases were retrieved from public genome databases. The co-expression among them was analyzed using a text-mining-based network analysis software. Activation/inhibition patterns from RNA-sequencing data performed with PM_2.5-treated normal human epidermal keratinocytes (NHEK) were overlapped to select key regulators of the analyzed pathways. We explored the adverse effects of PM on the skin and attempted to elucidate their relationships using public genome data. We found that changes in upstream regulators and inflammatory signaling networks mediated by MMP-1, MMP-9, PLAU, S100A9, IL-6, and S100A8 were predicted as the key pathways underlying PM-induced skin diseases. Our integrative approach using a literature-based co-expression analysis and experimental validation not only improves the reliability of prediction but also provides assistance to clarify underlying mechanisms of ambient PM-induced dermal toxicity that can be applied to screen the relationship between other chemicals and adverse effects.

Effects of <10-µm Particulate Matter on Cultured Human Sebocytes and Outer Root Sheath Cells and Usefulness of Siegesbeckia Herba Extract

Background

Particulate matter (PM) is one of the air pollutants that can damage human skin; the recent increase in the amount of PM may be detrimental to skin health.

Objective

We aimed to investigate the effects of PM on cultured human sebocytes and outer root sheath (ORS) cells and the effects of Siegesbeckia Herba extract (SHE) on PM-treated cultured cells.

Methods

Sebocytes and ORS cells were cultured. The cultured cells were treated with various concentrations of PM of <10 µm in size (PM10) (10 µg/ml, 25 µg/ml, 50 µg/ml, and 100 µg/ml) for 24 h. Real-time polymerase chain reaction, measurement of reactive oxygen species (ROS), small interfering (si) RNA transfection, Oil Red O and Nile red staining, and immunofluorescence staining were performed to analyze the presence of inflammatory cytokines, matrix metalloproteinases (MMPs), aryl hydrocarbon receptor (AhR), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), ROS, and lipid production. In addition, PM10 (100 µg/ml)-treated cultured cells were treated with 10 mg/ml of SHE.

Results

PM10 upregulates the expression of inflammatory cytokines, MMPs, AhR, NF-κB, and ROS in cultured human sebocytes and ORS cells. The production of ROS was dramatically reduced in AhR siRNA-transfected cells. In addition, PM10 upregulates sebum production in cultured sebocytes. SHE inhibited the upregulation of inflammatory cytokines, MMPs, AhR, NF-κB, ROS, and sebum production in cultured human sebocytes and/or ORS cells by PM10.

Conclusion

Effects of PM10 on cultured human sebocytes and ORS cells can be regulated by SH.

Implementing organ-on-chip in a next-generation risk assessment of chemicals: a review

Organ-on-chip (OoC) technology is full of engineering and biological challenges, but it has the potential to revolutionize the Next-Generation Risk Assessment of novel ingredients for consumer products and chemicals. A successful incorporation of OoC technology into the Next-Generation Risk Assessment toolbox depends on the robustness of the microfluidic devices and the organ tissue models used. Recent advances in standardized device manufacturing, organ tissue cultivation and growth protocols offer the ability to bridge the gaps towards the implementation of organ-on-chip technology. Next-Generation Risk Assessment is an exposure-led and hypothesis-driven tiered approach to risk assessment using detailed human exposure information and the application of appropriate new (non-animal) toxicological testing approaches. Organ-on-chip presents a promising in vitro approach by combining human cell culturing with dynamic microfluidics to improve physiological emulation. Here, we critically review commercial organ-on-chip devices, as well as recent tissue culture model studies of the skin, intestinal barrier and liver as the main metabolic organ to be used on-chip for Next-Generation Risk Assessment. Finally, microfluidically linked tissue combinations such as skin-liver and intestine-liver in organ-on-chip devices are reviewed as they form a relevant aspect for advancing toxicokinetic and toxicodynamic studies. We point to recent achievements and challenges to overcome, to advance non-animal, human-relevant safety studies.

Anti-Adhesive Properties of Calcium Alginate from Sargassum fusiforme against Particulate Matter-Induced Inflammation

Fine dust generated by particulate matter (PM) pollution is a serious ecological issue in industrialized countries and causes disorders of the respiratory system and skin in humans. In the previous study, Sargassum fusiforme was treated with citric acid to remove heavy metals. In this study, the transfer of PM-mediated inflammatory responses through the skin to macrophages was evaluated. Moreover, the anti-adhesive effects of calcium alginate isolated from S. fusiforme (SFCA) against PM-induced inflammation were investigated. The structures of processing and unprocessing SFCA were then analyzed by Fourier-transform infrared spectroscopy (FT-IR), revealing minimal change after acid-processing. SFCA had protective effects both in PM-stimulated HaCaT keratinocytes and RAW 264.7 macrophages. In cellular environments, it was found that SFCA attenuated signal protein expressions such as inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, prostaglandin E₂ (PGE₂), and pro-inflammatory cytokines. Furthermore, macrophages were added to the culture medium of PM-stimulated keratinocytes to induce inflammation. SFCA was observed to significantly inhibit inflammatory responses; additionally, SFCA showed an in vivo anti-adhesive effect in zebrafish embryos.

Effect of GNWs/NiO-WO3/GNWs Heterostructure for NO2 Gas Sensing at Room Temperature

Recently, as air pollution and particulate matter worsen, the importance of a platform that can monitor the air environment is emerging. Especially, among air pollutants, nitrogen dioxide (NO₂) is a toxic gas that can not only generate secondary particulate matter, but can also derive numerous toxic gases. To detect such NO₂ gas at low concentration, we fabricated a GNWs/NiO-WO₃/GNWs heterostructure-based gas sensor using microwave plasma-enhanced chemical vapor deposition (MPECVD) and sputter, and we confirmed the NO₂ detection characteristics between 10 and 50 ppm at room temperature. The morphology and carbon lattice characteristics of the sensing layer were investigated using field emission scanning electron microscopy (FESEM) and Raman spectroscopy. In the gas detection measurement, the resistance negative change according to the NO₂ gas concentration was recorded. Moreover, it reacted even at low concentrations such as 5–7 ppm, and showed excellent recovery characteristics of more than 98%. Furthermore, it also showed a change in which the reactivity decreased with respect to humidity of 33% and 66%.

SH-29 and SK-119 Attenuates Air-Pollution Induced Damage by Activating Nrf2 in HaCaT Cells

Air pollution has been repeatedly linked to numerous health-related disorders, including skin sensitization, oxidative imbalance, premature extrinsic aging, skin inflammation, and increased cancer prevalence. Nrf2 is a key player in the endogenous protective mechanism of the skin. We hypothesized that pharmacological activation of Nrf2 might reduce the deleterious action of diesel particulate matter (DPM), evaluated in HaCaT cells. SK-119, a recently synthesized pharmacological agent as well as 2,2′-((1E,1′E)-(1,4-phenylenebis(azaneylylidene))bis(methaneylylidene))bis(benzene-1,3,5-triol) (SH-29) were first evaluated in silico, suggesting a potent Nrf2 activation capacity that was validated in vitro. In addition, both compounds were able to attenuate key pathways underlying DPM damage, including cytosolic and mitochondrial reactive oxygen species (ROS) generation, tested by DC-FDA and MitoSOX fluorescent dye, respectively. This effect was independent of the low direct scavenging ability of the compounds. In addition, both SK-119 and SH-29 were able to reduce DPM-induced IL-8 hypersecretion in pharmacologically relevant concentrations. Lastly, the safety of both compounds was evaluated and demonstrated in the ex vivo human skin organ culture model. Collectively, these results suggest that Nrf2 activation by SK-119 and SH-29 can revert the deleterious action of air pollution.

Fine Particulate Matter-Induced Oxidative Stress Mediated by UVA-Visible Light Leads to Keratinocyte Damage

The human skin is exposed to various environmental factors including solar radiation and ambient air pollutants. Although, due to its physical and biological properties, the skin efficiently protects the body against the harm of environmental factors, their excessive levels and possible synergistic action may lead to harmful effects. Among particulate matter present in ambient air pollutants, PM2.5 is of particular importance for it can penetrate both disrupted and intact skin, causing adverse effects to skin tissue. Although certain components of PM2.5 can exhibit photochemical activity, only a limited amount of data regarding the interaction of PM2.5 with light and its effect on skin tissue are available. This study focused on light-induced toxicity in cultured human keratinocytes, which was mediated by PM2.5 obtained in different seasons. Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM) were employed to determine sizes of the particles. The ability of PM2.5 to photogenerate free radicals and singlet oxygen was studied using EPR spin-trapping and time-resolved singlet oxygen phosphorescence, respectively. Solar simulator with selected filters was used as light source for cell treatment to model environmental lightning conditions. Cytotoxicity of photoexcited PM2.5 was analyzed using MTT assay, PI staining and flow cytometry, and the apoptotic pathway was further examined using Caspase-3/7 assay and RT-PCR. Iodometric assay and JC-10 assay were used to investigate damage to cell lipids and mitochondria. Light-excited PM2.5 were found to generate free radicals and singlet oxygen in season-dependent manner. HaCaT cells containing PM2.5 and irradiated with UV-Vis exhibited oxidative stress features-increased peroxidation of intracellular lipids, decrease of mitochondrial membrane potential, enhanced expression of oxidative stress related genes and apoptotic cell death. The data indicate that sunlight can significantly increase PM2.5-mediated toxicity in skin cells.

Genomic Approach to the Assessment of Adverse Effects of Particulate Matters on Skin Cancer and Other Disorders and Underlying Molecular Mechanisms

Air pollutants are in the spotlight because the human body can easily be exposed to them. Among air pollutants, the particulate matter (PM) represents one of the most serious toxicants that can enter the human body through various exposure routes. PMs have various adverse effects and classified as severe carcinogen by International Agency for Research on Cancer. Their physical and chemical characteristics are distinguished by their size. In this review, we summarized the published information on the physicochemical characteristics and adverse effects of PMs on the skin, including carcinogenicity. Through comparisons of biological networks constructed from relationships discussed in the previous scientific publications, we show it is possible to predict skin cancers and other disorders from particle-size-specific signaling alterations of PM-responsive genes. Our review not only helps to grasp the biological association between ambient PMs and skin diseases including cancer, but also provides new approaches to interpret chemical-gene-disease associations regarding the adverse effects of these heterogeneous particles.

Skin biological responses to urban pollution in an ex vivo model

The skin epidermis is continuously exposed to external aggressions, including environmental pollution. The cosmetic industry must be able to offer dedicated products to fight the effects of pollutants on the skin. We set up an experimental model that exposed skin explants maintained in culture to a pollutant mixture. This mixture P representing urban pollution was designed on the basis of the French organization 'Air Parif' database. A chamber, called Pollubox®, was built to allow a controlled nebulization of P on the cultured human skin explants. We investigated ultrastructural morphology by transmission electron microscopy of high pressure frozen skin explants. A global transcriptomic analysis indicated that the pollutant mixture was able to induce relevant xenobiotic and antioxidant responses. Modulated detoxifying genes were further investigated by laser micro-dissection coupled to qPCR, and immunochemistry. Both approaches showed that P exposure correlated with overexpression of detoxifying genes and provoked skin physiological alterations down to the stratum basale. The model developed herein might be an efficient tool to study the effects of pollutants on skin as well as a powerful testing method to evaluate the efficacy of cosmetic products against pollution.

Natural compounds protect the skin from airborne particulate matter by attenuating oxidative stress

Particulate matter (PM) is a common indirect indicator of air pollution and threatens public health upon prolonged exposure, leading to oxidative stress, increasing the risk of develop respiratory and cardiovascular, as well as several autoimmune diseases and cancer. Nowadays, as a first line defense against PM, skin health attracted much attention. Our review summarized the skin damage mechanism induced by PM, including damage skin barrier directly, reactive oxygen species (ROS) accumulation, autophagy, and two canonical signaling pathways. Furthermore, ROS and oxidative stress have been considered pathogenesis centers, with essential skin damage roles. Extracts from plants and natural compounds which present high antioxidant capacity could be used to treat or protect against air pollution-related skin damage. We conclude the extracts reported in recent studies with protective effects on PM-mediated skin damage. Besides, the mechanism of extracts' positive effects has been revealed partially.

Fermented blueberry and black rice containing Lactobacillus plantarum MG4221: a novel functional food for particulate matter (PM2.5)/dinitrochlorobenzene (DNCB)-induced atopic dermatitis

Particulate matter (PM_2.5) is a risk factor for the deterioration of atopic dermatitis (AD) and certain constituents of PM_2.5 can induce inflammation via oxidative stress. Natural functional foods, including antioxidative blueberry and black rice, can be the best alternative for the development of AD therapy. Thus, we investigated whether PM_2.5 regulated the expression of proinflammatory cytokines involved in the progression of AD and further investigated the improvement effect of fermented blueberry and black rice extract (FBBBR) containing Lactobacillus plantarum MG4221 in vitro and in vivo. The FBBBR treatment significantly ameliorated skin inflammation compared with the control treatments via regulation of the mitogen-activated protein kinase (MAPK)/nuclear factor-κB (NF-κB) pathways in PM_2.5-treated HaCaT cells. In PM_2.5/dinitrochlorobenzene (DNCB)-treated NC/Nga mice, the oral administration of FBBBR significantly decreased transepidermal water loss and erythema, the incidence of scratching behavior, and the production of serum immunoglobin E and T helper 2-associated cytokine and, similar to dexamethasone treatment, up-regulated the protein expression of filaggrin and involucrin in skin tissue. Syringic acid and kuromanin, standard compounds found in FBBBR, significantly decreased the interleukin (IL)-1β, IL-6 and IL-8 levels in PM_2.5-treated HaCaT cells. Therefore, we can suggest that FBBBR may serve as an important functional food for AD.

Novel podophyllotoxin and benzothiazole derivative induces transitional morphological and functional changes in HaCaT cells

Podophyllotoxin (PPT) is an antimitotic drug used topically in the treatment of anogenital warts. Due to its toxicity it cannot be administered systemically as an anticancer agent. However, modified PPT derivatives such as etoposide and teniposide are used clinically as systemic agents. Thus, we invented novel PPT derivative KL3 that was synthesized by photocyclization. Earlier we have shown that KL3 has an anticancer effect in various cell lines. Here we compared the toxicity of KL3 vs PPT on non-cancerous normal human keratinocytes (HaCaT) and peripheral blood mononuclear cells (PBMC) showing that KL3 is less toxic than PPT to non-cancerous cells. At concentrations that neither induced cell death, nor affected cell cycle, KL3 in HaCaT cells evoked transient ultrastructural features of ER stress, swelling of mitochondria and elongation of cytoplasmic processes. Those changes partially reversed with prolonged incubation while features of autophagy were induced. PPT in equivalent concentrations induced HaCaT cell death by cell cycle arrest, intrinsic apoptosis and finally disintegration of cell membranes followed by secondary necrosis. In conclusion, we show that the KL3 derivative of PPT in contrast to PPT allows repair of normal keratinocytes and triggers mechanisms that restore non-tumor cell homeostasis.

Fucoxanthin-rich fraction from Sargassum fusiformis alleviates particulate matter-induced inflammation in vitro and in vivo

Particulate matter (PM) contributes to air pollution and primarily originates from unregulated industrial emissions and seasonal natural dust emissions. Fucoxanthin (Fx) is a marine natural pigment from brown macroalgae that has been shown to have various beneficial effects on health. However, the effects of Fx on PM-induced toxicities in cells and animals have not been assessed. In this study, we investigated the anti-inflammatory potential of the Fx-rich fraction (FxRF) of Sargassum fusiformis against PM-mediated inflammatory responses. The FxRF composition was analyzed by rapid-resolution liquid chromatography mass spectrometry. Fx and other main pigments were identified. FxRF attenuated the production of inflammatory components, including prostaglandin E2 (PGE2), cyclooxygenase-2, interleukin (IL)-1β, and IL-6 from PM-exposed HaCaT keratinocytes. PM exposure also reduced the levels of nitric oxide (NO), tumor necrosis factor-α, inducible nitric oxide synthase (iNOS), and PGE2 in PM-exposed RAW264.7 macrophages. Additionally, the culture medium from PM-exposed HaCaT cells induced upregulation of NO, iNOS, PGE2, and pro-inflammatory cytokines in RAW264.7 macrophages. FxRF also significantly decreased the expression levels of factors involved in inflammatory responses, such as NO, reactive oxygen species, and cell death, in PM-exposed zebrafish embryos. These results demonstrated the potential protective effects of FxRF against PM-induced inflammation both in vitro and in a zebrafish model.

A Membrane-free Liver-Gut-on-Chip Platform for the Assessment on Dysregulated Mechanisms of Cholesterol and Bile Acid Metabolism Induced by PM2.5

Fine particulate matter (PM_2.5)-induced metabolic diseases have attracted a great deal of attention recently. However, the relevant metabolic mechanisms of PM_2.5 in vivo have not yet been fully described due to the lack of reliable platforms. Herein, a membrane-free liver-gut-on-chip (L-GOC) platform was developed to investigate metabolism dysregulation induced by PM_2.5. A multiple organ system with a liver-gut structure and two circulation paths (L-G and G-L circulation paths) was created, and then cells were exposed to PM_2.5 on this platform. Secreted high-density lipoprotein (HDL) levels were detected, which demonstrates that this multiple organ system functioned with normal physiological metabolism at the organ level. Untargeted metabolomic analysis showed that there were 364 metabolites of LO2 cells dysregulated after exposure to PM_2.5 at a concentration of 200 μg/mL. Moreover, cholesterol and bile acid metabolism were significantly dysregulated. Further immunofluorescence and ELISA assays confirmed that signal transduction pathways related to cholesterol metabolism (LCAT-CE, PON1-HDL, and SRB1-HDL metabolic pathways) and bile acid metabolism (CYP7A1-CA/CDCA/DCA metabolic pathways) were disturbed. These results indicate that PM_2.5 primarily disturbed cholesterol metabolism of the liver and then disrupted bile acid metabolism of the liver (primary bile acid biosynthesis) and gut (secondary bile acid biosynthesis) via related metabolic pathways. These findings may partially explain the metabolic mechanisms of cells triggered by PM_2.5 exposure.

Dieckol, an algae-derived phenolic compound, suppresses airborne particulate matter-induced skin aging by inhibiting the expressions of pro-inflammatory cytokines and matrix metalloproteinases through regulating NF-κB, AP-1, and MAPKs signaling pathways

Exposure to particulate matter causes skin aging. In the present study, we investigated the effect of an algae-derived phenolic compound, dieckol (DK), against Chinese particulate matter (CPM)-stimulated aging in vitro in human dermal fibroblasts (HDF cells) and in vivo in zebrafish. DK effectively protected HDF cells against CPM-induced oxidative stress by scavenging intracellular reactive oxygen species. Moreover, DK significantly improved collagen synthesis and inhibited intracellular collagenase activity in CPM-stimulated HDF cells. In addition, DK remarkably reduced the expression of pro-inflammatory cytokines and matrix metalloproteinases via regulating the nuclear factor kappa B, activator protein 1, and mitogen-activated protein kinases signaling pathways in CPM-stimulated HDF cells. Furthermore, the in vivo test results demonstrated that DK effectively improved the survival rate of CPM-stimulated zebrafish via suppressing oxidative stress and inflammatory response. In conclusion, this study suggests that DK is a potential anti-aging compound that can be used as a therapeutic agent to improve CPM-induced skin aging, or as an ingredient to develop a cosmetic or medicine in the cosmeceutical and pharmaceutical industries.

Ambient particulate matter attenuates Sirtuin1 and augments SREBP1-PIR axis to induce human pulmonary fibroblast inflammation: molecular mechanism of microenvironment associated with COPD

Evidences have shown a strong link between particulate matter (PM) and increased risk in human mortality and morbidity, including asthma, chronic obstructive pulmonary disease (COPD), respiratory infection, and lung cancer. However, the underlying toxicologic mechanisms remain largely unknown. Utilizing PM-treated human pulmonary fibroblasts (HPF) models, we analyzed gene expression microarray data and Ingenuity Pathway Analysis (IPA) to identify that the transcription factor sterol regulatory element-binding protein 1 (SREBP1) was the main downstream regulator of Sirtuin1 (SIRT1). Quantitative PCR and western blot results showed that SIRT1 inhibited SREBP1 and further downregulated Pirin (PIR) and Nod-like receptor protein 3 (NLRP3) inflammasome after PM exposure. Inhibitors of SIRT1, SREBP1, and PIR could reverse PM-induced inflammation. An in silico analysis revealed that PIR correlated with smoke exposure and early COPD. Immunohistochemical analysis of tissue microarrays from PM-fed mouse models was used to determine the association of PIR with PM. These data demonstrate that the SIRT1-SREBP1-PIR/ NLRP3 inflammasome axis may be associated with PM-induced adverse health issues. SIRT1 functions as a protector from PM exposure, whereas PIR acts as a predictor of PM-induced pulmonary disease. The SIRT1-SREBP1-PIR/ NLRP3 inflammasome axis may present several potential therapeutic targets for PM-related adverse health events.

Assessment of Air Pollutant PM2.5 Pulmonary Exposure Using a 3D Lung-on-Chip Model

Airborne particulate matters have posed significant risk to human health worldwide. Fine particulate matters (PM2.5, aerodynamic diameter <2.5 μm) are associated with increased morbidity and mortality attributed to pulmonary diseases. An advanced in vitro model would benefit the assessment of PM2.5 induced pulmonary injuries and drug development. In this work, we present a PM2.5 exposure model to evaluate the pulmonary risk of fine particulate matter exposure in an organotypic manner with the help of 3D human lung-on-a-chip. By compartmentalized co-culturing of human endothelial cells, epithelial cells, and extra cellular matrix, our lung-on-a-chip recapitulated the structural features of the alveolar-blood barrier, which is pivotal for exogenous hazard toxicity evaluation. PM2.5 was applied to the channel lined with lung epithelial cells to model the pulmonary exposure of fine particulate matter. The results indicated acute high dose PM2.5 exposure would lead to various malfunctions of the alveolar-capillary barrier, including adheren junction disruption, increased ROS generation, apoptosis, inflammatory biofactor expression in epithelial cells and endothelial cells, elevated permeability, and monocyte attachments. Collectively, our lung-on-a-chip model provides a simple platform to investigate the complex responses after PM2.5 exposure in a physiologically relevant level, which could be of great potential in environmental risk assessment and therapeutic treatment development.

PM2.5 induces apoptosis, oxidative stress injury and melanin metabolic disorder in human melanocytes

Recent growing evidence suggested that particulate matter 2.5 (PM2.5) has strong toxic effects on skin systems. However, the possible effects and the mechanisms of PM2.5 on vitiligo remain poorly understood. Therefore, the present study aimed to further investigate the effects and possible mechanisms of PM2.5 on vitiligo. Human keratinocytes (HaCaT cells) and human melanocytes (PIG1 cells and PIG3V cells) were exposed to PM2.5 (0-200 µg/ml) for 24 h. The cell viability of the three cell lines was measured by a Cell Counting Kit-8 assay. The secretions of stem cell factor (SCF) and basic fibroblast growth factor (bFGF) in HaCaT cells were evaluated by ELISA. The melanin contents, cellular tyrosinase activity, apoptosis, cell migration, malondialdehyde (MDA) contents, superoxide dismutase (SOD) levels, glutathione peroxidase (GSH-Px) levels and related protein expressions in PIG1 cells and PIG3V cells were evaluated by a NaOH assay, DOPA assay, Annexin V-FITC/Propidium Iodide staining, MDA assay, SOD assay, GSH-Px assay and western blotting, respectively. It was demonstrated that PM2.5 exposure inhibited cell viability of all three cell lines (HaCaT, PIG1 and PIG3V cells). PM2.5 exposure attenuated the secretions of SCF and bFGF in HaCaT cells. Moreover, PM2.5 exposure attenuated the activation of tyrosinase and melanogenesis, inhibited cell migration, and induced apoptosis and oxidative stress injury in PIG1 cells and PIG3V cells. In addition, PM2.5 exposure caused upregulated cytosolic cytochrome C and activated caspase-3 in PIG1 cells and PIG3V cells. Furthermore, PM2.5 exposure activated the nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 signaling pathway. The present results suggested that PM2.5 exposure could inhibit the secretions of SCF and bFGF in keratinocytes, and cause oxidative stress injury and melanin metabolic disorder in melanocytes. Therefore, PM2.5 could be a new risk factor for vitiligo.

Skin inflammation induced by ambient particulate matter in China

Most published studies on particulate matter (PM) concerning PM_2.5 and PM₁₀ have focused on PM-induced effects on the respiratory system (particularly lung) and cardiovascular system effects. However, epidemiological and mechanistic studies suggest that PM_2.5 and PM₁₀ also affects the skin, which is a key health issue. In this study, we first reviewed the current status of PM_2.5 and PM₁₀ in China, including relevant regulations, concentration levels, chemical components, and emission sources. Next, we summarized the association between PM_2.5 and PM₁₀ or its representative components, in relation to skin inflammation as well as inflammatory skin diseases, such as atopic dermatitis, acne, eczema, and skin aging. Finally, we determined the mechanism of oxidative stress or programmed cell death induced through PM, which can provide useful information for future research on PM-induced skin inflammation.

Cytotoxicity analysis of ambient fine particle in BEAS-2B cells on an air-liquid interface (ALI) microfluidics system

Ambient fine particle is a crucial indicator of air pollution brought into the air by sundry natural and public events. However, a comprehensive understanding of the PM_2.5-induced cytotoxicity especially the contribution of bioaerosol part is still undiscovered. Herein, an ALI microfluidics system integrated multi-omics (iTRAQ & RNA-seq) was successfully utilized to recognize the molecular mechanisms induced by microorganisms carried bioaerosol in human lung epithelial cells. The cells viability was above 98% within 21 days on this system. Moreover, the results showed that eight microorganisms-related pathways (e.g., Salmonella, amoebiasis, HTLV-1) were activated after exposure to PM_2.5 for 24 h, which played a certain proportion in contributing to inflammation reaction. In addition, multi-omics demonstrated that three inflammation-related signal transduction cascades including MAPK signaling pathway, TNF signaling pathway, and TGF signaling pathway were triggered by fine particles, ultimately leading to apoptosis-related process disorder by associated cytokines like TNF, IL6, and TGF-β. Furthermore, flow cytometry analysis showed that the cell apoptosis rate increased from 3.8% to 66.7% between the cells exposed to PM_2.5 (10 μg/cm²) for 24 h and untreated control cells, which indicated that the fine particles had the ability to activate apoptosis-related signal cascades and result in apoptosis. ELISA assay and western blot indicated that HO-1, JNK, IL6, TNF, NF-κB, and FGF14 were significantly increased after exposure to PM_2.5 while Casp3 and FGFR were decreased, which were consistent with the multi-omics. Moreover, PM_2.5 components (OC, EC, 16PAHs, As, Cu, Mn, Cl^-, and NO₃^-) were significantly correlated to the inflammation related proteins and cytokines, which played a vital role in the inflammation and apoptosis related signaling pathways. These findings pointed to strong links among microorganisms infection, inflammation, and apoptosis in cell response to PM_2.5 carried microorganisms. It also provided a new approach for understanding PM_2.5-induced cytotoxicity and health risks.

Environmental Stressors on Skin Aging. Mechanistic Insights

The skin is the main barrier that protects us against environmental stressors (physical, chemical, and biological). These stressors, combined with internal factors, are responsible for cutaneous aging. Furthermore, they negatively affect the skin and increase the risk of cutaneous diseases, particularly skin cancer. This review addresses the impact of environmental stressors on skin aging, especially those related to general and specific external factors (lifestyle, occupation, pollutants, and light exposure). More specifically, we have evaluated ambient air pollution, household air pollutants from non-combustion sources, and exposure to light (ultraviolet radiation and blue and red light). We approach the molecular pathways involved in skin aging and pathology as a result of exposure to these external environmental stressors. Finally, we reflect on how components of environmental stress can interact with ultraviolet radiation to cause cell damage and the critical importance of knowing the mechanisms to develop new therapies to maintain the skin without damage in old age and to repair its diseases.

An Air-Liquid Interface Organ-Level Lung Microfluidics Platform for Analysis on Molecular Mechanisms of Cytotoxicity Induced by Cancer-Causing Fine Particles

Fine particulate matter less than 2.5 μm in diameter (PM_2.5) is regarded as a carcinogenic factor, but the mechanism has been left unexplored. Our goal was to reveal the carcinogenic mechanism at the gene and protein level under the inhalational air-liquid interface (ALI) condition. Herein, we developed an ALI organ-level lung microfluidic platform (ALI-OLMP) carrying lung epithelial cell line BEAS-2B and human pulmonary microvascular endothelial cells (HPMEC); the cell viability was above 98% within 14 days on this system, which was used to mimic the practical alveolar microenvironment for the multiomics analysis, to identify the global gene and protein expression after exposure to PM_2.5 in Shanghai, China from 2014 to 2015. The combined RNA-Seq and iTRAQ analysis indicated that the unique set was 2532 genes at 10 μg/cm² of PM_2.5, and there were also at least 25 identical activated signal transduction cascades including bladder cancer, transcriptional dysregulation in cancer, the TP53 (p53) signaling pathway, Jak-STAT signaling pathway, and PI3K-Akt signaling pathway, which could lead to blocking of differentiation, cell proliferation and survival, and sustained angiogenesis. The images obtained by the transmission electron microscopy (TEM) showed that the particles could enter the mitochondria, and even get into the nucleus. The Pearson's correlation coefficient test elucidated that inorganics (EC), organics (OC, PAHs, and alkane), and metals (Cr, Mn, and Sb) were significantly correlated to the dysregulated oncoproteins (VEGF, IL6, MDM2, AKT1, STAT, and P53). The findings may to some extent explain the molecular mechanism of carcinogenicity caused by fine-particle exposure.

Autophagy Activation by Crepidiastrum Denticulatum Extract Attenuates Environmental Pollutant-Induced Damage in Dermal Fibroblasts

Pollution-induced skin damage results in oxidative stress; cellular toxicity; inflammation; and, ultimately, premature skin aging. Previous studies suggest that the activation of autophagy can protect oxidation-induced cellular damage and aging-like changes in skin. In order to develop new anti-pollution ingredients, this study screened various kinds of natural extracts to measure their autophagy activation efficacy in cultured dermal fibroblast. The stimulation of autophagy flux by the selected extracts was further confirmed both by the expression of proteins associated with the autophagy signals and by electron microscope. Crepidiastrum denticulatum (CD) extract treated cells showed the highest autophagic vacuole formation in the non-cytotoxic range. The phosphorylation of adenosine monophosphate kinase (AMPK), but not the inhibition of mammalian target of rapamycin (mTOR), was observed by CD-extract treatment. Its anti-pollution effects were further evaluated with model compounds, benzo[a]pyrene (BaP) and cadmium chloride (CdCl₂), and a CD extract treatment resulted in both the protection of cytotoxicity and a reduction of proinflammatory cytokines. These results suggest that the autophagy activators can be a new protection regimen for anti-pollution. Therefore, CD extract can be used for anti-inflammatory and anti-pollution cosmetic ingredients.

Evaluating nanomedicine with microfluidics

Nanomedicines are engineered nanoscale structures that have an extensive range of application in the diagnosis and therapy of many diseases. Despite the rapid progress in and tremendous potential of nanomedicines, their clinical translational process is still slow, owing to the difficulty in understanding, evaluating, and predicting their behavior in complex living organisms. Microfluidic techniques offer a promising way to resolve these challenges. Carefully designed microfluidic chips enable in vivo microenvironment simulation and high-throughput analysis, thus providing robust platforms for nanomedicine evaluation. Here, we summarize the recent developments and achievements in microfluidic methods for nanomedicine evaluation, categorized into four sections based on their target systems: single cell, multicellular system, organ, and organism levels. Finally, we provide our perspectives on the challenges and future directions of microfluidics-based nanomedicine evaluation.

PM2.5 exposure aggravates oligomeric amyloid beta-induced neuronal injury and promotes NLRP3 inflammasome activation in an in vitro model of Alzheimer's disease

Background

Numerous studies suggested that PM2.5 exposure was associated with increased risk of Alzheimer’s disease (AD). But the precise mechanisms by which PM2.5 contributed to AD pathogenesis have not been clarified.

Methods

In the presence or absence of neurons, oligomeric amyloid beta (oAβ)-primed microglia were stimulated with PM2.5. Firstly, we determined the effects of PM2.5 exposure on neuronal injury and inflammation in neurons-microglia co-cultures. Then, we examined whether NLRP3 inflammasome activation was involved in PM2.5-induced inflammation. After that, we investigated whether PM2.5 exposure increased ROS level in oAβ-stimulated microglia. At last, we examined whether ROS and NLRP3 inflammasome activation was required for PM2.5-induced neuronal injury in neurons-microglia co-cultures.

Results

In the present study, we showed that PM2.5 exposure aggravated oAβ-induced neuronal injury and inflammation in neurons-microglia co-cultures via increasing IL-1β production. Further, PM2.5-induced IL-1β production in oAβ-stimulated microglia was possibly dependent on NLRP3 inflammasome activation. Meanwhile, PM2.5 exposure increased ROS level in oAβ-stimulated microglia. ROS was required for PM2.5-induced IL-1β production and NLRP3 inflammasome activation in oAβ-stimulated microglia. More importantly, ROS and NLRP3 inflammasome activation was required for PM2.5-induced neuronal injury in neurons-microglia co-cultures.

Conclusions

For the first time, these results suggested that the effects of PM2.5 under AD context were possibly mediated by NLRP3 inflammasome activation, which was triggered by ROS. Taken together, these findings have deepened our understanding on the role of PM2.5 in AD pathogenesis.

Current developments and applications of microfluidic technology toward clinical translation of nanomedicines

Nanoparticulate drug delivery systems hold great potential for the therapy of many diseases, especially cancer. However, the translation of nanoparticulate drug delivery systems from academic research to industrial and clinical practice has been slow. This slow translation can be ascribed to the high batch-to-batch variations and insufficient production rate of the conventional preparation methods, and the lack of technologies for rapid screening of nanoparticulate drug delivery systems with high correlation to the in vivo tests. These issues can be addressed by the microfluidic technologies. For example, microfluidics can not only produce nanoparticles in a well-controlled, reproducible, and high-throughput manner, but also create 3D environments with continuous flow to mimic the physiological and/or pathological processes. This review provides an overview of the microfluidic devices developed to prepare nanoparticulate drug delivery systems, including drug nanosuspensions, polymer nanoparticles, polyplexes, structured nanoparticles and theranostic nanoparticles. We also highlight the recent advances of microfluidic systems in fabricating the increasingly realistic models of the in vivo milieu for rapid screening of nanoparticles. Overall, the microfluidic technologies offer a promise approach to accelerate the clinical translation of nanoparticulate drug delivery systems.

An in vitro cytotoxicities comparison of 16 priority polycyclic aromatic hydrocarbons in human pulmonary alveolar epithelial cells HPAEpiC

In present study, we compared for the first time the cytotoxicities of the 16 priority polycyclic aromatic hydrocarbons (PAHs) in human pulmonary alveolar epithelial cells HPAEpiC. Moreover, we examined the effects of each PAH on oxidative stress (SOD, GSH, and ROS), cell viability, extracellular LDH, and apoptosis. The 16 priority PAHs were classified into four levels of cytotoxicity: (1) high cytotoxicity, BkF, BaP, and DBA; (2) moderate cytotoxicity, BbF, IND, BghiP, BaA, and CHR; (3) low cytotoxicity, PA, FL, and Pyr; and (4) mild cytotoxicity, Nap, AcPy, Acp, Flu, and Ant. Most of the PAHs showed benzene-ring-related cytotoxicity, except PA with 3-ring structure, cytotoxicity of which is similar to those of FL and Pyr with 4-ring structure. Results indicated the need for more studies on DBA, IND, and BghiP, among others, which are rarely investigated. PA, FL, and Pyr with little carcinogenicity should also be evaluated. This study will provide useful references for studies on the effects of PAHs on different cells or animal models.

Concentrated Ambient PM2.5-Induced Inflammation and Endothelial Dysfunction in a Murine Model of Neural IKK2 Deficiency

BACKGROUND

Exposure to ambient fine particulate matter (PM_2.5) is associated with cardiovascular mortality, but underlying pathophysiologic mechanisms are not fully understood. Hypothalamic inflammation, characterized by the activation of Inhibitor kappaB kinase 2/Nuclear factor kappaB (IKK2/NF-κB) signaling pathway, may play an important role in the pathogenesis of cardiovascular diseases. We recently demonstrated that hypothalamic inflammation is increased in mice exposed to concentrated ambient PM_2.5 (CAP).

OBJECTIVES

In the present study, we used a neuron-specific IKK2 knockout mouse model to examine the role of neural IKK2 expression and hypothalamic inflammation in the pathophysiologic effects of PM_2.5.

METHODS

We assessed inflammatory and vascular responses in Nestin-creIKK2^flox/flox (IKK2^Neu-KO) and littermate Nestin-creIKK2^flox/+ (control) mice after 4 mo of exposure to filtered air (FA) or CAP.

RESULTS

CAP exposure was associated with significantly higher tumor necrosis factor-α (TNFα) and interleukin (IL)-6 mRNA in the hypothalamus of control mice, but not IKK2^Neu-KO mice. In addition, CAP exposure-induced increases in bronchoalveolar lavage fluid (BALF) leukocytes, pulmonary macrophage infiltration and IL-6 expression, plasma TNFα and IL-1β levels, adipose macrophage infiltration and IL-1β expression, and endothelial dysfunction were reduced or absent in IKK2^Neu-KO mice compared with controls.

CONCLUSIONS

Our findings support a role of neural IKK2 in CAP exposure-induced local and systemic pro-inflammatory cytokine expression, pulmonary and adipose inflammation, and endothelial dysfunction, thus providing insight into pathophysiologic mechanisms that may mediate effects of PM_2.5 exposure. https://doi.org/10.1289/EHP2311.