Ambient Air Pollution and Risk of Enterotomy, Gastrointestinal Cancer, and All-Cause Mortality among 4,708 Individuals with Inflammatory Bowel Disease: A Prospective Cohort Study

Chronic PM2.5 Exposure Disrupts Intestinal Barrier Integrity via Microbial Dysbiosis-Triggered TLR2/5-MyD88-NLRP3 Inflammasome Activation

BACKGROUND

PM2.5, a known public health risk, is increasingly linked to intestinal disorders, however, the mechanisms of its impact are not fully understood.

PURPOSE

This study aimed to explore the impact of chronic PM2.5 exposure on intestinal barrier integrity and to uncover the underlying molecular mechanisms.

METHODS

C57BL/6J mice were exposure to either concentrated ambient PM2.5 (CPM) or filtered air (FA) for six months to simulate urban pollution conditions. We evaluated intestinal barrier damage, microbial shifts, and metabolic changes using histopathology, metagenomics, and metabolomics. Analysis of the TLR signaling pathway was also conducted.

RESULTS

The mean concentration of PM2.5 in the CPM exposure chamber was consistently measured at 70.9 ± 26.8 μg/m³ throughout the study period. Our findings show that chronic CPM exposure significantly compromises intestinal barrier integrity, as indicated by reduced expression of the key tight junction proteins Occludin and Tjp1/Zo-1. Metagenomic sequencing revealed significant shifts in the microbial landscape, identifying 35 differentially abundant species. Notably, there was an increase in pro-inflammatory nongastric Helicobacter species and a decrease in beneficial bacteria, such as Lactobacillus intestinalis, Lactobacillus sp. ASF360, and Eubacterium rectale. Metabolomic analysis further identified 26 significantly altered metabolites commonly associated with intestinal diseases. A strong correlation between altered bacterial species and metabolites was also observed. For example, 4 Helicobacter species all showed positive correlations with 13 metabolites, including Lactate, Bile acids, Pyruvate and Glutamate. Additionally, increased expression levels of TLR2, TLR5, Myd88, and NLRP3 proteins were noted, and their expression patterns showed a strong correlation, suggesting a possible involvement of the TLR2/5-MyD88-NLRP3 signaling pathway.

CONCLUSIONS

Chronic CPM exposure induces intestinal barrier dysfunction, microbial dysbiosis, metabolic imbalance, and activation of the TLR2/5-MyD88-NLRP3 inflammasome. These findings highlight the urgent need for intervention strategies to mitigate the detrimental effects of air pollution on intestinal health and identify potential therapeutic targets.

Higher Dietary Quercetin Intake Is Associated with Lower Risk of Adverse Outcomes among Individuals with Inflammatory Bowel Disease in a Prospective Cohort Study

BACKGROUND

Cumulative preclinical evidence reported quercetin, a major flavonoid, can attenuate the disease activity of inflammatory bowel diseases (IBD). However, there is limited evidence that supports the benefits of quercetin for patients with IBD.

OBJECTIVES

To investigate whether dietary quercetin intake is associated with adverse outcomes among individuals with IBD in a prospective cohort study.

METHODS

We included 2293 participants with IBD (764 Crohn's disease [CD] and 1529 ulcerative colitis [UC]) from the UK Biobank. Dietary information was collected using validated 24-h dietary assessments, and quercetin intake was estimated based on national nutrient databases. Two outcomes, enterotomy and all-cause mortality, were obtained based on the national data. Cox proportional hazard models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

After a mean (standard deviation) follow-up of 9.6 (1.8) y, we documented 193 enterotomy events and 176 deaths. Compared with participants with the lowest quartile intake of quercetin, those in the highest quartiles were associated with lower risk of enterotomy (HR: 0.46; 95% CI: 0.28, 0.76) and all-cause mortality (HR: 0.53; 95% CI: 0.33, 0.83) in IBD. The inverse associations between quercetin and enterotomy were consistent in CD (HR: 0.30; 95% CI: 0.12, 0.78) but not UC (HR: 0.58; 95% CI: 0.32, 1.07), while the inverse associations between quercetin and mortality were consistent both in CD (HR: 0.37; 95% CI: 0.15, 0.92) and UC (HR: 0.55; 95% CI: 0.31, 0.95).

CONCLUSIONS

Higher dietary intake of quercetin was associated with lower risk of enterotomy and all-cause mortality in IBD. Our study provides novel evidence that further suggests the benefits of quercetin for patients with IBD, while also calling for further validation in other cohorts and clinical trials.

Causal association between air pollution and autoimmune diseases: a two-sample Mendelian randomization study

Background

In recent years, an increasing number of observational studies have reported the impact of air pollution on autoimmune diseases (ADs). However, no Mendelian randomization (MR) studies have been conducted to investigate the causal relationships. To enhance our understanding of causality, we examined the causal relationships between particulate matter (PM) and nitrogen oxides (NOx) and ADs.

Methods

We utilized genome-wide association study (GWAS) data on PM and NOx from the UK Biobank in European and East Asian populations. We also extracted integrated GWAS data from the Finnish consortium and the Japanese Biobank for two-sample MR analysis. We employed inverse variance weighted (IVW) analysis to assess the causal relationship between PM and NOx exposure and ADs. Additionally, we conducted supplementary analyses using four methods, including IVW (fixed effects), weighted median, weighted mode, and simple mode, to further investigate this relationship.

Results

In the European population, the results of MR analysis suggested a statistically significant association between PM2.5 and psoriasis only (OR = 3.86; 95% CI: 1.89-7.88; PIVW < 0.00625), while a potential association exists between PM2.5-10 and vitiligo (OR = 7.42; 95% CI: 1.02-53.94; PIVW < 0.05), as well as between PM2.5 and systemic lupus erythematosus (OR = 68.17; 95% CI: 2.17-2.1e+03; PIVW < 0.05). In East Asian populations, no causal relationship was found between air pollutants and the risk of systemic lupus erythematosus and rheumatoid arthritis (PIVW > 0.025). There was no pleiotropy in the results.

Conclusion

Our results suggest a causal association between PM2.5 and psoriasis in European populations. With the help of air pollution prevention and control, the harmful progression of psoriasis may be slowed.

Challenges of developing a green gastroenterology evidence base and how trainee research networks can fill the gaps

Trainee research networks are a collaborative effort to enable high-quality multicentre audits or research that is more widely accessible to trainees. Such networks lead, design and deliver research at a far higher scale than could be achieved locally and are carried out solely by trainees. There is an increasing focus on delivering research that is not only environmentally sustainable but also focuses on areas that can reduce the carbon footprint of service provision in gastroenterology and hepatology. In this manuscript, we performed a scoping review to understand the current evidence base of the impact of gastroenterology and hepatology services on the environment as well as exploring any association between pollution and climate change with gastrointestinal and liver disease. We further discuss the barriers that researchers face in delivering environmentally sustainable research, the limitation in clinical guidelines related to practicing environmentally sustainable gastroenterology and hepatology and how the trainee research networks are ideally placed to initiate change by developing, disseminating and implementing best practice in ‘green Gastroenterology’.

Editorial: Unravelling the fibres-low dietary fibre may lower risk of developing IBD. Authors' reply

This article is linked to Deng et al papers. To view these articles, visit https://doi.org/10.1111/apt.17649 and https://doi.org/10.1111/apt.17663