Maternal exposure to particulate matter alters early post-natal lung function and immune cell development

The developmental toxicity of PM2.5 on the early stages of fetal lung with human lung bud tip progenitor organoids

Exposure to air pollution has been proven to be associated with impaired fetal lung development. However, due to the lack of reliable human source models, it is still challenging to deeply understand the human fetal lung development under PM2.5 exposure. Here, we utilized human embryonic stem cell (hESC) line H9 to generate lung bud tip progenitor organoids (LPOs), a process that mimics early stages of fetal lung development including definitive endoderm (DE) formation, anterior foregut endoderm (AFE) differentiation and lung progenitor cell specification, to evaluate potential pulmonary developmental toxicity of PM2.5. We demonstrated that PM2.5 exposure the entire LPOs induction from hESCs significantly affected cellular proliferation of LPOs, and altered the expression of lung progenitor cell markers NKX2.1, SOX2 and SOX9, which are canonically defined subsequently proximal-distal airways specification. To explore the dynamic influences of PM2.5 exposure at different stages of LPOs specification, we also found that PM2.5 exposure significantly affected the expression of several transcriptional factors that are important for the differentiation of DE and AFE. Mechanistically, we suggested PM2.5-induced developmental toxicity to LPOs was partially linked with the Wnt/β-catenin signaling pathway. Therefore, our findings further emphasize the substantial health risks in the development of respiratory system associated with prenatal exposure to PM2.5.

Particulate Matter and Its Components Induce Alteration on the T-Cell Response: A Population Biomarker Study

Compared with the T-cell potential of particulate matter (PM) in animal studies, comprehensive evaluation on the impairments of T-cell response and exposure-response from PM and its components in human population is limited. There were 768 participants in this study. We measured environmental PM and its polycyclic aromatic hydrocarbons (PAHs) and metals and urinary metabolite levels of PAHs and metals among population. T lymphocyte and its subpopulation (CD4⁺ T cells and CD8⁺ T cells) and the expressions of T-bet, GATA3, RORγt, and FoxP3 were measured. We explored the exposure-response of PM compositions by principal component analysis and mode of action by mediation analysis. There was a significant decreasing trend for T lymphocytes and the levels of T-bet and GATA3 with increased PM levels. Generally, there was a negative correlation between PM, urinary 1-hydroxypyrene, urinary metals, and the levels of T-bet and GATA3 expression. Additionally, CD4⁺ T lymphocytes were found to mediate the associations of PM_2.5 with T-bet expression. PM and its bound PAHs and metals could induce immune impairments by altering the T lymphocytes and genes of T-bet and GATA3.

Can Maternal Exposure to Air Pollution Affect Post-Natal Liver Development?

Emerging evidence suggests that inhalation of particulate matter (PM) can have direct adverse effects on liver function. Early life is a time of particular vulnerability to the effects of air pollution. On that basis, we tested whether in utero exposure to residential PM has an impact on the developing liver. Pregnant mice (C57BL/6J) were intranasally administered 100 µg of PM sampled from residential roof spaces (~5 mg/kg) on gestational days 13.5, 15.5, and 17.5. The pups were euthanized at two weeks of age, and liver tissue was collected to analyse hepatic metabolism (glycogen storage and lipid level), cellular responses (oxidative stress, inflammation, and fibrosis), and genotoxicity using a range of biochemical assays, histological staining, ELISA, and qPCR. We did not observe pronounced effects of environmentally sampled PM on the developing liver when examining hepatic metabolism and cellular response. However, we did find evidence of liver genomic DNA damage in response to in utero exposure to PM. This effect varied depending on the PM sample. These data suggest that in utero exposure to real-world PM during mid-late pregnancy has limited impacts on post-natal liver development.

Early life exposure to air pollution and cell-mediated immune responses in preschoolers

BACKGROUND

Exposure to air pollution has been linked with altered immune function in adults, but little is known about its effects on early life. This study aimed to investigate the effects of exposure to air pollution during prenatal and postnatal windows on cell-mediated immune function in preschoolers.

METHODS

Pre-school aged children (2.9 ± 0.5 y old, n = 391) were recruited from a mother-child cohort study in Wuhan, China. We used a spatial-temporal land use regression (LUR) model to estimate exposures of particulate matter with aerodynamic diameters ≤2.5 μm (PM_2.5) and ≤10 μm (PM₁₀), and nitrogen dioxide (NO₂) during the specific trimesters of pregnancy and the first two postnatal years. We measured peripheral blood T lymphocyte subsets and plasma cytokines as indicators of cellular immune function. We used multiple informant models to examine the associations of prenatal and postnatal exposures to air pollution with cell-mediated immune function.

RESULTS

Prenatal exposures to PM_2.5, PM₁₀, and NO₂ during early pregnancy were negatively associated with %CD3⁺ and %CD3⁺CD8⁺ cells, and during late pregnancy were positively associated with %CD3⁺ cells. Postnatal exposures to these air pollutants during 1-y or 2-y childhood were positively associated with IL-4, IL-5, IL-6, and TNF-α. We also observed that the associations of prenatal or postnatal air pollution exposures with cellular immune responses varied by child's sex.

CONCLUSIONS

Our results suggest that exposure to air pollution during different critical windows of early life may differentially alter cellular immune responses, and these effects appear to be sex-specific.

Prenatal Exposure to Air Pollution and Immune Thrombocytopenia: A Nationwide Population-Based Cohort Study

INTRODUCTION

Immune thrombocytopenia (ITP) is one of the most common hematologic disorders in children. However, its etiology is still unclear. Epidemiological studies have shown that air pollution is a plausible risk factor in stimulation of oxidative stress, induction of inflammation, and onset of autoimmune diseases. The objective of this article is to examine the effects of prenatal exposure to air pollution on the occurrence of immune thrombocytopenia (ITP) in children.

MATERIALS AND METHODS

This is a nationwide, population-based, matched case-control study. Using data from Taiwan's Maternal and Child Health Database (MCHD), we identified 427 children with ITP less than 6 years of age and age-matched controls without ITP between 2004 and 2016. Levels of prenatal exposure to air pollutants were obtained from 71 Environmental Protection Administration monitoring stations across Taiwan according to the maternal residence during pregnancy. Patients who had outpatient visits or admission with diagnosis of ITP and subsequently received first-line treatment of intravenous immunoglobulin or oral glucocorticoids were defined as incidence cases.

RESULTS

Prenatal exposure to particulate matter <10 μm (PM10) in diameter and the pollutant standard index (PSI) increased the risk of childhood ITP. Conversely, carbon monoxide (CO) exposure during pregnancy was negatively associated with the development of ITP.

CONCLUSION

Certain prenatal air pollutant exposure may increase the incidence of ITP in children.

Adverse effects of prenatal exposure to residential dust on post-natal brain development

BACKGROUND

Previous studies have shown an association between prenatal exposure to particulate matter (PM) and adverse brain development. However, it is unclear whether gestational exposure to community-sampled residential PM has an impact on the developing brain.

OBJECTIVES

We aimed to test whether in utero exposure to PM from residential roof spaces (ceiling voids) alters critical foetal neurodevelopmental processes.

METHODS

Pregnant C57BL/6 mice were intranasally exposed to 100 μg of roof space particles (~5 mg kg^-1) in 50 μl of saline, or saline alone under light methoxyflurane anaesthesia, throughout mid-to-late gestation. At 2 weeks post-natal age, pups were sacrificed and assessed for body and brain growth. The brain tissue was collected and examined for a range of neurodevelopmental markers for synaptogenesis, synaptic plasticity, gliogenic events and myelination by immunohistochemistry.

RESULTS

Gestational exposure to roof space PM reduced post-natal body and brain weights. There was no significant effect of roof space PM exposure on synaptogenesis, synaptic plasticity or astrocyte density. However, PM exposure caused increased myelin load in the white matter and elevated microglial density which was dependent on the PM sample. These effects were found to be consistent between male and female mice.

CONCLUSIONS

Our data suggest that exposure to residential roof space PM during pregnancy impairs somatic growth and causes neuropathological changes in the developing brain.

Maternal Particulate Matter Exposure Impairs Lung Health and Is Associated with Mitochondrial Damage

Relatively little is known about the transgenerational effects of chronic maternal exposure to low-level traffic-related air pollution (TRAP) on the offspring lung health, nor are the effects of removing such exposure before pregnancy. Female BALB/c mice were exposed to PM_2.5 (PM_2.5, 5 µg/day) for 6 weeks before mating and during gestation and lactation; in a subgroup, PM was removed when mating started to model mothers moving to cleaner areas during pregnancy to protect their unborn child (Pre-exposure). Lung pathology was characterised in both dams and offspring. A subcohort of female offspring was also exposed to ovalbumin to model allergic airways disease. PM_2.5 and Pre-exposure dams exhibited airways hyper-responsiveness (AHR) with mucus hypersecretion, increased mitochondrial reactive oxygen species (ROS) and mitochondrial dysfunction in the lungs. Female offspring from PM_2.5 and Pre-exposure dams displayed AHR with increased lung inflammation and mitochondrial ROS production, while males only displayed increased lung inflammation. After the ovalbumin challenge, AHR was increased in female offspring from PM_2.5 dams compared with those from control dams. Using an in vitro model, the mitochondria-targeted antioxidant MitoQ reversed mitochondrial dysfunction by PM stimulation, suggesting that the lung pathology in offspring is driven by dysfunctional mitochondria. In conclusion, chronic exposure to low doses of PM_2.5 exerted transgenerational impairment on lung health.

Particulate Matter, an Intrauterine Toxin Affecting Foetal Development and Beyond

Air pollution is the 9th cause of the overall disease burden globally. The solid component in the polluted air, particulate matters (PMs) with a diameter of 2.5 μm or smaller (PM_2.5) possess a significant health risk to several organ systems. PM_2.5 has also been shown to cross the blood–placental barrier and circulate in foetal blood. Therefore, it is considered an intrauterine environmental toxin. Exposure to PM_2.5 during the perinatal period, when the foetus is particularly susceptible to developmental defects, has been shown to reduce birth weight and cause preterm birth, with an increase in adult disease susceptibility in the offspring. However, few studies have thoroughly studied the health outcome of foetuses due to intrauterine exposure and the underlying mechanisms. This perspective summarises currently available evidence, which suggests that intrauterine exposure to PM_2.5 promotes oxidative stress and inflammation in a similar manner as occurs in response to direct PM exposure. Oxidative stress and inflammation are likely to be the common mechanisms underlying the dysfunction of multiple systems, offering potential targets for preventative strategies in pregnant mothers for an optimal foetal outcome.

In utero exposure to diesel exhaust particles, but not silica, alters post-natal immune development and function

Our understanding of the impact of in utero exposure to PM on post-natal immune function and the subsequent response to PM exposure is limited. Similarly, very few studies have considered the effect of exposure to PM from different sources. Thus, the aim of this study was to examine how in utero exposure to PM from different sources effects the post-natal response to pro-inflammatory and immune stimuli. C56BL/6J pregnant mice were exposed intranasally on gestational day (E)7.5, E12.5 and E17.5-50 μg of diesel exhaust particles (DEP), silica or saline. At 4-weeks post-natal age, sub-groups of male and female mice were exposed intranasally to 50 μg of DEP or saline. Lung inflammatory responses were assessed 6 h later by quantifying inflammatory cells and cytokine production (MCP-1, MIP-2, IL-6). In separate groups of mice, the spleen was harvested to quantify B and T cell populations. Splenocytes were isolated and exposed to lipopolysaccharide or poly I:C for assessment of cytokine production. Exposure to DEP in utero decreased %CD1d^highCD5+ B cells in female mice and IFN-γ production by splenocytes in both sexes. Male mice had elevations in macrophage and lymphocyte numbers in response to DEP whereas female mice only had elevated IL-6, MCP-1 and MIP-2 levels. In utero exposure to silica had no effect on these measures. These data suggest that in utero exposure to PM alters immune development and post-natal immune function. This response is dependent on the source of PM, which has implications for understanding the community health effects of exposure to air pollution.

Fetotoxicity of Nanoparticles: Causes and Mechanisms

The application of nanoparticles in consumer products and nanomedicines has increased dramatically in the last decade. Concerns for the nano-safety of susceptible populations are growing. Due to the small size, nanoparticles have the potential to cross the placental barrier and cause toxicity in the fetus. This review aims to identify factors associated with nanoparticle-induced fetotoxicity and the mechanisms involved, providing a better understanding of nanotoxicity at the maternal–fetal interface. The contribution of the physicochemical properties of nanoparticles (NPs), maternal physiological, and pathological conditions to the fetotoxicity is highlighted. The underlying molecular mechanisms, including oxidative stress, DNA damage, apoptosis, and autophagy are summarized. Finally, perspectives and challenges related to nanoparticle-induced fetotoxicity are also discussed.

Emerging role of mitochondria in airborne particulate matter-induced immunotoxicity

The immune system is one of the primary targets of airborne particulate matter. Recent evidence suggests that mitochondria lie at the center of particulate matter-induced immunotoxicity. Particulate matter can directly interact with mitochondrial components (proteins, lipids, and nucleic acids) and impairs the vital mitochondrial processes including redox mechanisms, fusion-fission, autophagy, and metabolic pathways. These disturbances impede different mitochondrial functions including ATP production, which acts as an important platform to regulate immunity and inflammatory responses. Moreover, the mitochondrial DNA released into the cytosol or in the extracellular milieu acts as a danger-associated molecular pattern and triggers the signaling pathways, involving cGAS-STING, TLR9, and NLRP3. In the present review, we discuss the emerging role of mitochondria in airborne particulate matter-induced immunotoxicity and its myriad biological consequences in health and disease.

Sex difference in bronchopulmonary dysplasia of offspring in response to maternal PM2.5 exposure

The adverse effects of fine particulate matters (PM_2.5) on respiratory diseases start in utero. In order to investigate whether maternal PM_2.5 exposure could lead to bronchopulmonary dysplasia (BPD) in offspring, PM_2.5 was collected in Taiyuan, Shanxi, China during the annual heating period. Mice were mated and gestation day 0 (GD0) was considered the day on which a vaginal plug was observed. The plug-positive mice received 3 mg/kg b.w. PM_2.5 by oropharyngeal aspiration every other day starting on GD0 and throughout the gestation period. Offspring were sacrificed at postnatal days (PNDs) 1, 7, 14 and 21. We assessed some typical BPD-like symptoms in offspring. The results showed that maternal PM_2.5 exposure caused low birth weight, hypoalveolarization, decreased angiogenesis, suppressed production of secretory and surfactant proteins, and increased inflammation in the lungs of male offspring. However, maternal PM_2.5 exposure induced only hypoalveolarization and inflammation in the lungs of female offspring. Furthermore, these alterations were reversed during postnatal development. Our results demonstrated that maternal exposure to PM_2.5 caused reversible BPD-related consequences in offspring, and male offspring were more sensitive than females. However, these alterations were reversed during postnatal development.

Pregnancy protects against the pro-inflammatory respiratory responses induced by particulate matter exposure

BACKGROUND

Little is known about the effect of pregnancy on the response to particulate matter. The aim of this study was to determine if pregnancy increases the susceptibility to PM from different sources using a mouse model.

METHODS

Pregnant, eight-week-old C57BL/6J mice were exposed intranasally to 50 μg of diesel exhaust particles (DEP), iron oxide (Fe₂O₃) or silica (SiO₂) in 50 μL of saline, or saline alone, on gestational day (E)7.5, E12.5 and E17.5. Groups of non-pregnant mice were exposed on day (D)0, D5 and D10. Biological samples were collected 24 h after the last exposure. Serum IL-4 and IL-6 levels were quantified by ELISA. Bronchoalveolar lavage (BAL) fluid was collected for inflammatory cells counts and assessment of IFN-ɣ, IL-4, IL-5, IL-6, IL-8 and IL-10 levels by ELISA. The spleen and thymus were also collected and the percentage of B cells and CD4⁺, CD8⁺ and CD4⁺CD25 ⁺ T cells were determined by flow cytometry.

RESULTS

Exposure to silica caused an influx of lymphocytes, eosinophils and neutrophils into the lung. The magnitude of this response was suppressed by pregnancy. Pregnancy also enhanced the production of CD4⁺CD25 ⁺ T cells in response to DEP and silica exposure.

CONCLUSIONS

Collectively, our data suggest that pregnancy reduces the inflammatory response to silica and alters the immune response to DEP. These responses were accompanied by pregnancy related changes including increased IL-4 production, reduced IL-8 production and an increase in the proportion of CD4⁺CD25 ⁺ T cells in response to PM exposure.