Allergic and non-allergic asthma phenotypes and exposure to air pollution

Causal relationships between allergic diseases and significant declines in lung function: a multivariable Mendelian randomization study

BACKGROUND

Asthma and other allergic diseases are increasing globally each year, with some patients experiencing the co-occurrence of two or more conditions, significantly impacting their quality of life. While these diseases may share certain immune mechanisms, the independent causal relationships between them and lung function remain unclear.

OBJECTIVE

This study aims to investigate the independent and interactive effects of allergic asthma, atopic dermatitis, allergic rhinitis, and allergic conjunctivitis on significant declines in lung function. By elucidating the potential causal relationships between these allergic diseases and reduced lung function, we hope to provide valuable scientific evidence for managing asthma patients who are co-morbid with multiple allergic conditions.

METHODS

In this study, we conducted Mendelian randomization (MR) analysis using data from the FinnGen database and the UK Biobank. We rigorously selected instrumental variables (IVs) based on established criteria and employed both univariable and multivariable MR approaches to investigate the relationship between various allergic diseases and significant declines in lung function.

RESULTS

In univariable MR analysis, the inverse variance-weighted (IVW) method or the weighted median approach indicated a causal relationship between allergic conjunctivitis, atopic dermatitis, and allergic asthma with significant declines in lung function. However, in multivariable MR analysis, the independent effects of atopic dermatitis and allergic conjunctivitis on lung function were no longer significant. Only allergic asthma continued to show a significant causal relationship with decreased lung function (OR [95%CI]: 1.019 [1.008-1.030], p < .001).

CONCLUSIONS

This study suggests that while atopic dermatitis and allergic conjunctivitis may indirectly affect lung function and lead to significant declines, their independent effects are not notable when asthma is well-controlled. Therefore, clinicians should recognize that acute exacerbations of allergic diseases are unlikely to be the primary reason for significant declines in lung function among asthma patients with multiple allergic conditions, provided that their asthma is well-managed.

Filter blot method: A simple method for measuring 3-nitrotyrosine in proteins of atmospheric particulate matter

Air pollutants, such as nitrogen dioxide (NO₂), ozone (O₃), and particulate matter (PM), have been epidemiologically reported to contribute to the onset and exacerbation of asthma. We have previously shown that several proteins in atmospheric PM are allergenic in mouse asthma models and that these proteins are nitrated by atmospheric NO₂ and O₃ in chemical reactions. Based on these results, the amount of 3-nitrotyrosine (3-NT) in atmospheric PM could be an air pollution marker integrating NO₂, O₃, and PM. We established a method to measure 3-NT by high-performance liquid chromatography electrochemical detection (HPLC-ECD). Although this method is accurate, it requires a filter treatment process, which is time-consuming and costly for an environmental monitoring tool, in which many samples are measured simultaneously. Therefore, in this study, we investigated a simple immunoblotting method in which atmospheric PM proteins were directly transferred to a polyvinylidene fluoride (PVDF) membrane and measured using an anti-3-NT antibody (the filter blot method). The 3-NT value obtained from this method was significantly correlated (r = 0.809, p < 0.001) with that of the HPLC-ECD method, with a detection power of 0.1 μg/mL for tyrosine nitrated bovine serum albumin equivalents. Multiple regression analysis using the filter blot method showed that the amount of 3-NT in atmospheric PM was significantly associated with the published environmental measurements of O₃ and PM in the region. Therefore, the filter blot method may be useful for the environmental monitoring of 3-NT in atmospheric PM.