Association of long-term exposure to ambient PM2.5 and its constituents with gut microbiota: Evidence from a China cohort

Mediation role of gut microbiota in the association between ambient fine particulate matter components and cardiovascular disease: Evidence from a China cohort

BACKGROUND

Pairwise associations among fine particulate matter (PM2.5), gut microbiota, and cardiovascular disease (CVD) have been established. However, the mediating role of gut microbiota in the relationship between PM2.5 and its components and CVD remains unclear.

METHODS

We included 1459 participants from the China Multi-Ethnic Cohort between May 2018 and September 2019. CVD was identified using ICD-10 codes based on hospital surveillance system. PM2.5 and its components were sourced from the ChinaHighAirPollutants dataset. Gut microbiota was obtained from 16S rRNA sequencing of stool samples, and five α-indexes along with 1088 gut compositions were used as mediators. Cox proportional hazards and multiple linear regression were used to explore the associations among PM2.5 and its components, gut microbiota, and CVD. Causal mediation analysis was conducted to evaluate the potential mediating role of gut microbiota between PM2.5 and its components and CVD.

RESULTS

Among all the participants, 204 (14.0 %) had developed CVD during a 5501 person-year follow-up (median, 3.8 years). The ACE, Chao1, and Obs indexes positively mediated the associations of PM2.5 and its components with both CVD and stroke, with mediation proportions ranging from 7.9 % to 8.9 % for CVD and 10.0 %-12.1 % for stroke. The ACE index had the highest mediation proportion (12.1 %) in the relationship between sulfate and stroke. The genus Pasteurella also demonstrated a mediating role, accounting for 2.6 %-3.2 % for CVD, and 2.5 %-3.6 % for stroke, exhibiting the highest mediation proportion (3.6 %) on the association between black carbon or nitrate and stroke.

CONCLUSION

Three α-indexes (ACE, Chao1, and Obs) and the Pasteurella positively mediated the association between PM2.5 and its components and CVD risk. Enhancing the richness of gut microbiota could potentially reduce the risk of CVD induced by PM2.5 and its components.

Combined health effects of air pollutant mixtures on respiratory mortality using BKMR in Hangzhou, China

Previous research on respiratory system mortality primarily focused on understanding their combined effects and have neglected the fact that air pollution mixtures are interrelated. This study used Bayesian kernel machine regression (BKMR) to analyze the relationship between air pollutant mixtures and respiratory mortality in Hangzhou, China from 2014 to 2018. The results showed a significant association between pollutant mixtures and respiratory system mortality primarily driven by PM2.5 and SO2. The joint exposure of air pollutants was positively correlated with respiratory system mortality at lag 01 and lag 02 days. The estimated joint effects of log-transformed mixture air pollution exposure on log-transformed respiratory system mortality increased from -0.02 (95% CI: -0.08-0.02) and -0.01 (95% CI: -0.05-0.04) at the 25th percentile to 0.06 (95% CI: 0.01-0.12) and 0.04 (95% CI: -0.001, 0.09) at the 75th percentile. Additionally, there was evidence of an interaction between O3 and PM10. This study confirms that exposure to multiple pollutants is a significant public health problem facing the Hangzhou population given the compounded effect proven with regression analysis, while furthermore, the control of PM2.5 and SO2 also represents a serious concern.Implications: Evidence indicates interactions between O3 and PM10. This study demonstrates that exposure to multiple pollutants exerts combined effects on the public health of the Hangzhou population, highlighting the importance of controlling PM2.5 and SO2.

The influence of pre- and postnatal exposure to air pollution and green spaces on infant's gut microbiota: Results from the MAMI birth cohort study

BACKGROUND

Animal and human studies indicate that exposure to air pollution and natural environments might modulate the gut microbiota, but epidemiological evidence is very scarce.

OBJECTIVES

To assess the potential impact of pre- and postnatal exposure to air pollution and green spaces on infant gut microbiota assembly and trajectories during the first year of life.

METHODS

MAMI ("MAternal MIcrobes") birth cohort (Valencia, Spain, N = 162) was used to study the impact of environmental exposure (acute and chronic) on infant gut microbiota during the first year of life (amplicon-based 16S rRNA sequencing). At 7 days and at 1, 6 and 12 months, residential pre- and postnatal exposure to air pollutants (NO2, black carbon -BC-, PM2.5 and O3) and green spaces indicators (NDVI and area of green spaces at 300, 500 and 1000 m buffers) were obtained. For the association between exposures and alpha diversity indicators linear regression models (cross-sectional analyses) and mixed models, including individual as a random effect (longitudinal analyses), were applied. For the differential taxon analysis, the ANCOM-BC package with a log count transformation and multiple-testing corrections were used.

RESULTS

Acute exposure in the first week of life and chronic postnatal exposure to NO2 were associated with a reduction in microbial alpha diversity, while the effects of green space exposure were not evident. Acute and chronic (prenatal or postnatal) exposure to NO2 resulted in increased abundance of Haemophilus, Akkermansia, Alistipes, Eggerthella, and Tyzerella populations, while increasing green space exposure associated with increased Negativicoccus, Senegalimassilia and Anaerococcus and decreased Tyzzerella and Lachnoclostridium populations.

DISCUSSION

We observed a decrease in the diversity of the gut microbiota and signs of alteration in its composition among infants exposed to higher levels of NO2. Increasing green space exposure was also associated with changes in gut microbial composition. Further research is needed to confirm these findings.

Interactive and lag effects of environmental factors on the density of schistosome-transmitting Oncomelania hupensis: A twelve-year monthly repeated survey

Schistosomiasis is a significant public health threat, and Oncomelania hupensis is the only intermediate host for schistosoma japonicum. We conducted 12-year monthly repeated surveys to explore the interactive and lag effects of environmental factors on snail density and to monitor their long-term and seasonal trends in a bottomland around the Dongting Lake region in China. Relevant environmental data were obtained from multiple sources. A Bayesian kernel machine regression model and a Bayesian temporal model combined with a distributed lag model were constructed to analyze interactive and lag effects of environmental factors on snail density. The results indicated the average annual snail density in the study site exhibited an increasing and then decreasing trend, peaking in 2013. Snail densities were the highest in October and the lowest in January in a year. Normalized Difference Vegetation Index (NDVI) and water level were the most effective predictors of snail density, with potential interactions among temperature, precipitation, and NDVI. The mean minimum temperature in January, water level, precipitation and NDVI were positively correlated with snail density at lags ranging from 1 to 4 months. These findings could serve as references for relevant authorities to monitor the changing trend of snail density and implement control measures, thereby reducing the occurrence of schistosomiasis.

A multi-omics investigation of the lung injury induced by PM2.5 at environmental levels via the lung-gut axis

Long-term exposure to fine particulate matter (PM2.5) posed injury for gastrointestinal and respiratory systems, ascribing with the lung-gut axis. However, the cross-talk mechanisms remain unclear. Here, we attempted to establish the response networks of lung-gut axis in mice exposed to PM2.5 at environmental levels. Male Balb/c mice were exposed to PM2.5 (dose of 0.1, 0.5, and 1.0 mg/kg) collected from Chengdu, China for 10 weeks, through intratracheally instillation, and examined the effect of PM2.5 on lung functions of mice. The changes of lung and gut microbiota and metabolic profiles of mice in different groups were determined. Furthermore, the results of multi-omics were conjointly analyzed to elucidate the primary microbes and the associated metabolites in lung and gut responsible for PM2.5 exposure. Accordingly, the cross-talk network and key pathways between lung-gut axis were established. The results indicated that exposed to PM2.5 0.1 mg/kg induced obvious inflammations in mice lung, while emphysema was observed at 1.0 mg/kg. The levels of metabolites guanosine, hypoxanthine, and hepoxilin B3 increased in the lung might contribute to lung inflammations in exposure groups. For microbiotas in lung, PM2.5 exposure significantly declined the proportions of Halomonas and Lactobacillus. Meanwhile, the metabolites in gut including L-tryptophan, serotonin, and spermidine were up-regulated in exposure groups, which were linked to the decreasing of Oscillospira and Helicobacter in gut. Via lung-gut axis, the activations of pathways including Tryptophan metabolism, ABC transporters, Serotonergic synapse, and Linoleic acid metabolism contributed to the cross-talk between lung and gut tissues of mice mediated by PM2.5. In summary, the microbes including Lactobacillus, Oscillospira, and Parabacteroides, and metabolites including hepoxilin B3, guanosine, hypoxanthine, L-tryptophan, and spermidine were the main drivers. In this lung-gut axis study, we elucidated some pro- and pre-biotics in lung and gut microenvironments contributed to the adverse effects on lung functions induced by PM2.5 exposure.

Effect of aerobic exercise and particulate matter exposure duration on the diversity of gut microbiota

Inhalation of ambient particulate matter (PM) can disrupt the gut microbiome, while exercise independently influences the gut microbiome by promoting beneficial bacteria. In this study, we analyzed changes in gut microbial diversity and composition in response to combined interventions of PM exposure and aerobic exercise, extending up to 12 weeks. This investigation was conducted using mice, categorized into five groups: control group (Con), exercise group (EXE), exercise group followed by 3-day exposure to PM (EXE + 3-day PM), particulate matter exposure (PM), and PM exposure with concurrent treadmill exercise (PME). Notably, the PM group exhibited markedly lower alpha diversity and richness compared to the Con group and our analysis of beta diversity revealed significant variations among the intervention groups. Members of the Lachnospiraceae family showed significant enhancement in the exercise intervention groups (EXE and PME) compared to the Con and PM groups. The biomarker Lactobacillus, Coriobacteraceae, and Anaerofustis were enriched in the EXE group, while Desulfovibrionaceae, Mucispirillum schaedleri, Lactococcus and Anaeroplasma were highly enriched in the PM group. Differential abundance analysis revealed that Paraprevotella, Bacteroides, and Blautia were less abundant in the 12-week PM exposure group than in the 3-day PM exposure group. Moreover, both the 3-day and 12-week PM exposure groups exhibited a reduced relative abundance of Bacteroides uniformis, SMB53, and Staphylococcus compared to non-PM exposure groups. These findings will help delineate the possible roles and associations of altered microbiota resulting from the studied interventions, paving the way for future mechanistic research.

PM2.5 induced neurotoxicity through unbalancing vitamin B12 metabolism by gut microbiota disturbance

Fine particulate matter (PM2.5) in the atmosphere is easily accompanied by toxic and harmful substances, causing serious harm to human health, including cognitive impairment. Vitamin B12 (VitB12) is an essential micronutrient that is synthesized by bacteria and contributes to neurotransmitter synthesis as a nutrition and signaling molecule. However, the relationship between VitB12 attenuation of cognitive impairment and intestinal microbiota regulation in PM2.5 exposure has not been elucidated. In this study, we demonstrated that PM2.5 caused behavioral defects and neuronal damage in Caenorhabditis elegans (C. elegans), along with significant gene expression changes in neurotransmitter receptors and a decrease in VitB12 content, causing behavioral defects and neuronal damage in C. elegans. Methylcobalamin (MeCbl), a VitB12 analog, alleviated PM2.5-induced neurotoxicity in C. elegans. Moreover, using in vivo and in vitro models, we discovered that long-term exposure to PM2.5 led to changes in the structure of the gut microbiota, resulting in an imbalance of the VitB12-associated metabolic pathway followed by cognitive impairment. MeCbl supplementation could increase the diversity of the bacteria, reduce harmful substance contents, and restore the concentration of short-chain fatty acids (SCFAs) and neurotransmitters to the level of the control group to some degree. Here, a new target to mitigate the harm caused by PM2.5 was discovered, supplying MeCbl for relieving intestinal and intracellular neurotransmitter disorders. Our results also provide a reference for the use of VitB12 to target the adjustment of the human intestinal microbiota to improve metabolic disorders in people exposed to PM2.5.