Effects of urban particulate matter on the quality of erythrocytes

Staphylococcus aureus β-hemolysin impairs oxygen transport without causing hemolysis

Staphylococcus aureus (S. aureus) infection can lead to the occurrence of hypoxia, however, the underlying mechanisms have not been fully elucidated. β-hemolysin (Hlb) induced hemolysis of red blood cells (RBCs) requires a temperature transition from "hot" to "cold," a phenomenon not observed under physiological conditions. In this study, we discovered that RBCs treated with Hlb exhibited a high level of intracellular Ca2+ and underwent a shape transformation from biconcave discoid to spherical, which was contingent upon the degradation of sphingomyelin of the cell membrane and led to impaired oxygen transport. The increase in intracellular Ca2+ levels induced by Hlb was dependent on the activation of the ion channel N-methyl-D-aspartate receptor. Furthermore, we found that Hlb-induced Ca2+ influx increased the cytoplasmic pH and subsequently attenuated the oxygen release from RBCs, which were also observed in both hlb transgenic mice and a murine model with S. aureus challenge. Our findings reveal a novel role for Hlb as sphingomyelinase in impairing RBC function under non-lytic conditions, shedding light on the mechanism behind hypoxia associated with S. aureus infection.

Unraveling Potential Causative Components for the Deleterious Effect of Atmospheric Fine Particulate Matter on Red Blood Cells

Atmospheric fine particulate matter (PM2.5) poses threats to the cardiovascular system. Red blood cells (RBCs) are the most abundant cells in blood, which are actively involved in multiple hematological diseases, such as blood clot formation and thrombosis. Exploring how PM2.5 with spatiotemporal heterogeneity influences the hematological system by targeting RBCs would help gain insights into the deleterious effects of PM2.5 and provide clues for finding the causative components therein. Herein, the PM2.5 samples collected from 3 urban sites in Beijing (i.e., Chaoyang, Shunyi, and Yanqing districts) during 4 seasons of 2022 were studied for their toxicities to mouse RBCs, and the main contributing components were further explored through chemical analysis and correlation measure. The results showed that exposure to PM2.5 samples decreased adenosine triphosphate (ATP) levels and increased phosphatidylserine (PS) externalization of RBCs, causing cell morphological deformity. The Pearson correlation analysis showed that the aromaticity of the dissolved organic matter (DOM) in PM2.5 samples was positively correlated with PS exposure of RBCs, showing that the lignin-like compounds were the potential contributors. The negative correlation of zeta potentials of PM2.5 samples with PS exposure of RBCs showed the particle-derived bioactivities of this airborne pollutant. The simulative test based on artificial nanomaterials of carbon black (CB) and oxidized CB (OCB) confirmed the crucial role of particulate carbon in PM2.5-induced effects on RBCs, and soot with a certain oxidation degree was, thus, recognized as another contributor, given its ubiquitous existence in PM2.5 samples. This study, for the first time, revealed PM2.5-induced PS exposure of RBCs, and the causative components of DOM and soot were unraveled. Considering the inevitable contact of airborne PM2.5 with RBCs in the blood circulatory system, the findings obtained herein would help bridge the gap between PM2.5 exposure and the risk of cardiovascular diseases, like thrombogenesis.

Associations of air pollutants and related metabolites with preterm birth during pregnancy

OBJECTIVE

This study aimed to investigate the influence of exposure to ambient fine particulate matter (PM2.5) and its components during pregnancy on the prevalence of preterm birth (PTB). Additionally, we sought to identify the susceptible exposure window. Furthermore, we explored the potential mediating role of blood analysis and a comprehensive metabolic panel in the association between pollutant exposure and PTB incidence.

METHODS

This birth cohort study recruited 139 participants with PTB outcomes and 1713 controls from Fujian Maternal and Child Health Hospital between January 2021 and June 2023. Sociodemographic characteristics and clinical treatment data during participants' first pregnancies were collected. The exposure levels to pollutants during pregnancy were estimated via a combined geographic-statistical model utilising satellite remote sensing data. The distributional lag nonlinear modelling was employed to assess associations between pollutant exposure during pregnancy and the prevalence of PTB. Weighted quantile regression was used to identify key components associated with PM2.5 and PTB during pregnancy. Additionally, a mediating effect analysis was conducted to evaluate the role of blood analysis. The metabolic profile was used to screen for differentially abundant metabolites associated with PTB and explore their relative expression in relation to air pollutants and PTB incidence.

RESULTS

Following the adjustment for potential confounding variables, the mean weekly susceptibility windows for PM2.5 were identified as 7-10, 16-19, and 22-28 weeks; 8-10, and 15-19 weeks for inorganic sulfate; 6-10, and 15-28 weeks for nitrate; 6-12, and 15-28 weeks for ammonium (NH4+); and 7-9, 18-20, and 22-36 weeks for organic matter. During mixed exposure to PM2.5 components, the key component is NH4+. In the mixed exposure to PM2.5 components, NH4+ emerged as a key contributor. The results of the mediation analysis revealed that haemoglobin played a mediating role, accounting for 21.53 % of the association between exposure to environmental pollutants and the prevalence of PTB. It is noteworthy that, no mediating effects were observed for the other variables. Furthermore, non-targeted metabolomics identified 17 metabolites associated with PTB. Among these factors, hydrogen phosphate may impact metabolic pathways such as oxidative phosphorylation, influencing the risk of PTB. The interplay between environmental pollutants and metabolites, particularly through oxidative phosphorylation pathways, may contribute to PTB incidence.

CONCLUSIONS

The evidence indicates that exposure to PM2.5 and its components during pregnancy were a significant risk factor for PTB. Notably, specific weekly exposure windows were identified for pollutants during pregnancy. Among the PM2.5 components, NH4+ exhibited the most substantial weight in the association analysis between exposure to the mixture of components and PTB. Furthermore, our mediation analysis revealed that haemoglobin serves as a partial mediator in the relationship between exposure to pollutants during pregnancy and the prevalence of PTB. Additionally, maternal serum metabolic profiles differed between the preterm and control groups. Notably, a combined effect involving hydrogen phosphate and mixed exposure to PM2.5 fractions further contributed to the development of PTB. Oxidative phosphorylation pathways may play pivotal roles in this intricate association.

In-utero exposure to multiple air pollutants and childhood undernutrition in India

BACKGROUND

Several studies have been conducted to understand the impact of socioeconomic and maternal factors on child undernutrition. However, the past literature has not directly examined the joint impacts of fuel use and ambient pollution and have primarily focused on PM2.5.

OBJECTIVE

This study explored the individual and community-level associations of both indoor (cooking fuel type) and ambient air pollution (PM2.5, NO2 and SO2) during maternal gestation on child undernutrition.

METHODS

This study analysed stunting, being underweight, and anaemia of children aged 0-59 months (n = 259,627) using the National Family Health Survey. In-utero exposures to ambient PM2.5, NO2, and SO2 were measured using satellite data and self-reported fuel type was a marker of indoor pollution exposure. The study used univariate and bivariate Moran's I, spatial lag model and multivariable logistic regression models after adjusting for other covariates to understand the effect of pollution on in-utero exposure and child health status at the individual and community-levels.

RESULTS

Higher concentration of indoor and ambient air pollution was found in the Northern and parts of Central regions of India. Estimates of spatial modelling show that each 1 μg/m-3 increase in maternal exposure to ambient PM2.5 across the clusters of India was associated with a 0.11, 9 and 19 percentage points increase in the prevalence of stunting, underweight and anaemia, respectively. The results of multi-pollutant model show that a higher ambient PM2.5 exposure during pregnancy was linked to higher odds of stunting (AOR:1.38; 95% CI:1.32-1.44), underweight (AOR:1.59; 95% CI:1.51-1.67) and anaemia (AOR:1.61; 95% CI:1.52-1.69) in children. Weaker but similar associations were observed for NO2, but not with SO2. Indoor pollution exposure during in-utero periods was also significantly associated with childhood undernutrition and this association was modified by ambient PM2.5 levels, where exposure to both indoor and ambient air pollution had even greater odds of being undernourished.

IMPACT STATEMENT

Our research on multi-pollutant models has revealed the initial proof of the individual impacts of indoor and outdoor pollution (PM2.5, NO2, and SO2) exposure during fetal development on children's nutrition.

Hemolytic Properties of Fine Particulate Matter (PM2.5) in In Vitro Systems

Epidemiological studies have suggested that inhalation exposure to particulate matter (PM) air pollution, especially fine particles (i.e., PM2.5 (PM with an aerodynamic diameter of 2.5 microns or less)), is causally associated with cardiovascular health risks. To explore the toxicological mechanisms behind the observed adverse health effects, the hemolytic activity of PM2.5 samples collected during different pollution levels in Beijing was evaluated. The results demonstrated that the hemolysis of PM2.5 ranged from 1.98% to 7.75% and demonstrated a clear dose-response relationship. The exposure toxicity index (TI) is proposed to represent the toxicity potential of PM2.5, which is calculated by the hemolysis percentage of erythrocytes (red blood cells, RBC) multiplied by the mass concentration of PM2.5. In a pollution episode, as the mass concentration increases, TI first increases and then decreases, that is, TI (low pollution levels) < TI (heavy pollution levels) < TI (medium pollution levels). In order to verify the feasibility of the hemolysis method for PM toxicity detection, the hemolytic properties of PM2.5 were compared with the plasmid scission assay (PSA). The hemolysis results had a significant positive correlation with the DNA damage percentages, indicating that the hemolysis assay is feasible for the detection of PM2.5 toxicity, thus providing more corroborating information regarding the risk to human cardiovascular health.

Is there a downside to plant ecological services in the city? Influences of particulate matter on the two-spotted spider mite (Tetranychus urticae) foraging on the small-leaved lime in urban conditions

The aim of this research was to examine how particulate matter (PM) pollution affects the life history of the two-spotted spider mite (TSSM), Tetranychus urticae (Trombidiformes: Tetranychidae), in modelled urban conditions. For this purpose, experimental populations of TSSM were cultured on the foliage of small-leaved lime (Tilia cordata) contaminated with PM at intensities corresponding to differing city zones such as a park, a busy road and an industrial area. The control samples in the study were washed, unpolluted leaves. The spider mite was selected as a model organism due to its cosmopolitan distribution, broad host spectrum, resistance to a variety of pesticides and food-intake mode involving cell-content sucking, while T. cordata is widely planted in cities and has demonstrated a considerable capability for PM capture. Data on the longevity and mortality of particular instars and on female fecundity at different pollution levels were collected and statistically evaluated. Concentrations of PM typical for roads and industrial city zones significantly reduced total female fecundity (avg. 53.9 and 55.9 eggs/female, respectively, vs 79.2 in control), which entailed a slower population increase, while the survival rate of particular developmental instars (P = 0.52) and fertility curves (P = 0.19) remained unchanged. The presence of PM caused physiological effects in the mites, despite the lack of direct consumption of the pollutant by adult and juvenile instars. Considering the incomparable resilience of TSSM to unfavourable environmental factors, it is predicted that the detrimental influence of PM on other representatives of urban arthropods may be even more severe. The results suggest that there is a need for further investigations into the ecological ramifications of air purification provided by urban green spaces.