Cytotoxicity and chemical composition of women's personal PM2.5 exposures from rural China

In vitro genotoxic and mutagenic potentials of combustion particles from marine fuels with different sulfur contents

Ship emissions significantly impact both the environment and human health. To address these concerns, the International Maritime Organization has imposed restrictions on the sulfur content in marine fuels. Specifically, the fuel sulfur content (FSC) must be below 0.5% m/m globally and below 0.1% m/m in designated sulfur emission control areas. These regulations apply to a range of fuels including distillate diesel-like fuels and low-sulfur heavy fuel oils (HFOs). As a result, there has been a reduction in emissions, particularly sulfur oxides and particulate matter (PM). However, the relationship between FSC and the toxicity of ship emissions remains unclear. This study aimed to investigate how the physical and chemical properties of PM from a marine engine operating on five marine fuels with varying FSCs, influence toxicological outcomes. For this scope, the study assessed cytotoxic, genotoxic, mutagenic, and pro-inflammatory effects of the emitted particles using lung cell models. The involvement of intracellular reactive oxygen species and xenobiotic metabolism was also exanimated. The results showed that PM from the combustion of different fuels reduced cell viability and clonogenicity at the highest concentration. However, other toxicological outcomes, such as genotoxic potential, were more strongly associated with the polycyclic aromatic hydrocarbon content of the PM than with FSC. Notably, an aromatic-rich HFO with intermediate FSC induced a significant increase in gene mutation frequency and alterations of cellular processes. In conclusion, while reducing FSC is an important step in mitigating ship emissions, this study underscores the need for a comprehensive evaluation of fuel properties.

Review of in vitro studies evaluating respiratory toxicity of aerosols: impact of cell types, chemical composition, and atmospheric processing

In recent decades, several cell-based and acellular methods have been developed to evaluate ambient particulate matter (PM) toxicity. Although cell-based methods provide a more comprehensive assessment of PM toxicity, their results are difficult to comprehend due to the diversity in cellular endpoints, cell types, and assays and the interference of PM chemical components with some of the assays' techniques. In this review, we attempt to clarify some of these issues. We first discuss the morphological and immunological differences among various macrophage and epithelial cells, belonging to the respiratory systems of human and murine species, used in the in vitro studies evaluating PM toxicity. Then, we review the current state of knowledge on the role of different PM chemical components and the relevance of atmospheric processing and aging of aerosols in the respiratory toxicity of PM. Our review demonstrates the need to adopt more physiologically relevant cellular models such as epithelial (or endothelial) cells instead of macrophages for oxidative stress measurement. We suggest limiting macrophages for investigating other cellular responses (e.g., phagocytosis, inflammation, and DNA damage). Unlike monocultures (of macrophages and epithelial cells), which are generally used to study the direct effects of PM on a given cell type, the use of co-culture systems should be encouraged to investigate a more comprehensive effect of PM in the presence of other cells. Our review has identified two major groups of toxic PM chemical species from the existing literature, i.e., metals (Fe, Cu, Mn, Cr, Ni, and Zn) and organic compounds (PAHs, ketones, aliphatic and chlorinated hydrocarbons, and quinones). However, the relative toxicities of these species are still a matter of debate. Finally, the results of the existing studies investigating the effect of aging on PM toxicity are ambiguous, with varying results due to different cell types, different aging conditions, and the presence/absence of specific oxidants. More systematic studies are necessary to understand the role of different SOA precursors, interactions between different PM components, and aging conditions in the overall toxicity of PM. We anticipate that our review will guide future investigations by helping researchers choose appropriate cell models, resulting in a more meaningful interpretation of cell-based assays and thus ultimately leading to a better understanding of the health effects of PM exposure.

Particulate matter composition drives differential molecular and morphological responses in lung epithelial cells

Particulate matter (PM) is a ubiquitous component of indoor and outdoor air pollution that is epidemiologically linked to many human pulmonary diseases. PM has many emission sources, making it challenging to understand the biological effects of exposure due to the high variance in chemical composition. However, the effects of compositionally unique particulate matter mixtures on cells have not been analyzed using both biophysical and biomolecular approaches. Here, we show that in a human bronchial epithelial cell model (BEAS-2B), exposure to three chemically distinct PM mixtures drives unique cell viability patterns, transcriptional remodeling, and the emergence of distinct morphological subtypes. Specifically, PM mixtures modulate cell viability and DNA damage responses and induce the remodeling of gene expression associated with cell morphology, extracellular matrix organization and structure, and cellular motility. Profiling cellular responses showed that cell morphologies change in a PM composition-dependent manner. Lastly, we observed that particulate matter mixtures with high contents of heavy metals, such as cadmium and lead, induced larger drops in viability, increased DNA damage, and drove a redistribution among morphological subtypes. Our results demonstrate that quantitative measurement of cellular morphology provides a robust approach to gauge the effects of environmental stressors on biological systems and determine cellular susceptibilities to pollution.

The Aryl Hydrocarbon Receptor (AHR): A Novel Therapeutic Target for Pulmonary Diseases?

The aryl hydrocarbon receptor (AHR) is a cytoplasmic transcription factor that is well-known for regulating xenobiotic metabolism. Studies in knockout and transgenic mice indicate that the AHR plays a vital role in the development of liver and regulation of reproductive, cardiovascular, hematopoietic, and immune homeostasis. In this focused review on lung diseases associated with acute injury and alveolar development, we reviewed and summarized the current literature on the mechanistic role(s) and therapeutic potential of the AHR in acute lung injury, chronic obstructive pulmonary disease, and bronchopulmonary dysplasia (BPD). Pre-clinical studies indicate that endogenous AHR activation is necessary to protect neonatal and adult lungs against hyperoxia- and cigarette smoke-induced injury. Our goal is to provide insight into the high translational potential of the AHR in the meaningful management of infants and adults with these lung disorders that lack curative therapies.