Current Knowledge of Asthma-COPD Overlap (ACO) Genetic Risk Factors, Characteristics, and Prognosis

Lysophospholipid Acyltransferase 9 Promotes Emphysema Formation via Platelet-activating Factor

Cigarette smoking is known to be the leading cause of chronic obstructive pulmonary disease (COPD). However, the detailed mechanisms have not been elucidated. PAF (platelet-activating factor), a potent inflammatory mediator, is involved in the pathogenesis of various respiratory diseases such as bronchial asthma and COPD. We focused on LPLAT9 (lysophospholipid acyltransferase 9), a biosynthetic enzyme of PAF, in the pathogenesis of COPD. LPLAT9 gene expression was observed in excised COPD lungs and single-cell RNA sequencing data of alveolar macrophages (AMs). LPLAT9 was predominant and upregulated in AMs, particularly monocyte-derived AMs, in patients with COPD. To identify the function of LPLAT9/PAF in AMs in the pathogenesis of COPD, we exposed systemic LPLAT9-knockout (LPALT9-/-) mice to cigarette smoke (CS). CS increased the number of AMs, especially the monocyte-derived fraction, which secreted MMP12 (matrix metalloprotease 12). Also, CS augmented LPLAT9 phosphorylation/activation on macrophages and, subsequently, PAF synthesis in the lung. The LPLAT9-/- mouse lung showed reduced PAF production after CS exposure. Intratracheal PAF administration accumulated AMs by increasing MCP1 (monocyte chemoattractant protein-1). After CS exposure, AM accumulation and subsequent pulmonary emphysema, a primary pathologic change of COPD, were reduced in LPALT9-/- mice compared with LPLAT9+/+ mice. Notably, these phenotypes were again worsened by LPLAT9+/+ bone marrow transplantation in LPALT9-/- mice. Thus, CS-induced LPLAT9 activation in monocyte-derived AMs aggravated pulmonary emphysema via PAF-induced further accumulation of AMs. These results suggest that PAF synthesized by LPLAT9 has an important role in the pathogenesis of COPD.

Sex-Specific Genetic Determinants of Asthma-COPD Phenotype and COPD in Middle-Aged and Older Canadian Adults: An Analysis of CLSA Data

The etiology of sex differences in the risk of asthma-COPD phenotype and COPD is still not completely understood. Genetic and environmental risk factors are commonly believed to play an important role. This study aims to identify sex-specific genetic markers associated with asthma-COPD phenotype and COPD using the Canadian Longitudinal Study on Aging (CLSA) Baseline Comprehensive and Genomic data. There were a total of 1,415 COPD cases. Out of them, 504 asthma-COPD phenotype cases were identified. 20,524 participants without a diagnosis of asthma and COPD served as controls. We performed genome-wide SNP-by-sex interaction analysis. SNPs with an interaction p-value < 10^-5 were included in a sex-stratified multivariable logistic regression for asthma-COPD phenotype and COPD outcomes. 18 and 28 SNPs had a significant interaction term p-value < 10^-5 with sex in the regression analyses of asthma-COPD phenotype and COPD outcomes, respectively. Sex-stratified multivariable analysis of asthma-COPD phenotype showed that 7 SNPs in/near SMYD3, FHIT, ZNF608, RIMBP2, ZNF133, BPIFB1, and S100B loci were significant in males. Sex-stratified multivariable analysis of COPD showed that 8 SNPs in/near MAGI1, COX18, OSTC, ELOVL5, C7orf72 FGF14, and NKAIN4 were significant in males, and 4 SNPs in/near genes CAMTA1, SATB2, PDE10A, and LINC00908 were significant in females. An SNP in the ZPBP gene was associated with COPD in both males and females. Identification of sex-specific loci associated with asthma-COPD phenotype and COPD may offer valuable evidence toward a better understanding of the sex-specific differences in the pathophysiology of the diseases.

[Developing Biomarkers in Precision Medicine for Asthma and COPD]

There is a growing demand for the implementation of precision medicine. There is an urgent need to move away from one-size-fits-all medicine, in which the treatment is based on the disease name alone, and to implement a precision-medicine approach. Chronic respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD) require a precision-medicine approach. Asthma and COPD are heterogeneous disorders with various phenotypes. In order to characterize the pathological features of a patient, it is important to analyze not only the phenotype, but also the molecular mechanisms underlying the clinical features, called endotypes. It is crucial to customize the treatment of the disease according to both the phenotype and endotype. Therefore, developing biomarkers enabling treatment stratification is essential to the practice of precision medicine. This approach of finding optimal treatment by identifying patient features using biomarkers is known as a treatable-traits approach. We conducted clinical and basic studies to identify patients with COPD who could be treated with asthma medications and to identify the pathological features of patients with COPD and asthma (asthma-COPD overlap: ACO). We identified several blood proteins and microRNAs that have potential for be clinically useful as biomarkers for customizing treatment in patients with ACO.

Metabolomics of asthma, COPD, and asthma-COPD overlap: an overview

The two common progressive lung diseases, asthma and chronic obstructive pulmonary disease (COPD), are the leading causes of morbidity and mortality worldwide. Asthma-COPD overlap, referred to as ACO, is another complex pulmonary disease that manifests itself with features of both asthma and COPD. The disease has no clear diagnostic or therapeutic guidelines, thereby making both diagnosis and treatment challenging. Though a number of studies on ACO have been documented, gaps in knowledge regarding the pathophysiologic mechanism of this disorder exist. Addressing this issue is an urgent need for improved diagnostic and therapeutic management of the disease. Metabolomics, an increasingly popular technique, reveals the pathogenesis of complex diseases and holds promise in biomarker discovery. This comprehensive narrative review, comprising 99 original research articles in the last five years (2017-2022), summarizes the scientific advances in terms of metabolic alterations in patients with asthma, COPD, and ACO. The analytical tools, nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS), commonly used to study the expression of the metabolome, are discussed. Challenges frequently encountered during metabolite identification and quality assessment are highlighted. Bridging the gap between phenotype and metabotype is envisioned in the future.

Identification of Sex-Specific Genetic Polymorphisms Associated with Asthma in Middle-Aged and Older Canadian Adults: An Analysis of CLSA Data

Purpose

Asthma is a chronic heterogeneous respiratory disease resulting from a complex interplay between genetic variations and environmental exposures. There are sex disparities in the prevalence and severity of asthma in males and females. Asthma prevalence is higher in males during childhood but increases in females in adulthood. The mechanisms underlying these sex differences are not well understood; nevertheless, genetic variations, hormonal changes, and environmental influences are thought to play important roles. This study aimed to identify sex-specific genetic variants associated with asthma using CLSA genomic and questionnaire data.

Methods

First, we conducted a genome-wide SNP-by-sex interaction analysis on 23,323 individuals, examining 416,562 single nucleotide polymorphisms (SNPs) after quality control, followed by sex-stratified survey logistic regression of SNPs with interaction p-value less than 10^¯5.

Results

Out of the 49 SNPs with interaction p-value less than 10^-5, a sex-stratified survey logistic regression showed that five male-specific SNPs (rs6701638, rs17071077, rs254804, rs6013213, and rs2968822) in/near KIF26B, NMBR, PEPD, RTN4, and NFATC2 loci, and three female-specific SNPs (rs2968801, rs2864052, and rs9525931) in/near RTN4, and SERP2 loci were significantly associated with asthma after Bonferroni correction. An SNP (rs36213) in the EPHB1 gene was significantly associated with an increased risk of asthma in males [OR=1.35, 95% CI (1.14, 1.60)] but with a reduced risk of asthma in females [OR=0.84, 95% CI (0.76, 0.92)] after Bonferroni correction.

Conclusion

We discovered novel sex-specific genetic markers in/near the KIF26B, RTN4, EPHB1, NMBR, SERP2, PEPD, and NFATC2 genes that could potentially shed light on the sex differences in asthma susceptibility in males and females. Future mechanistic studies are required to understand better the underlying sex-related pathways of the identified loci in asthma development.

Using inflammatory index to distinguish asthma, asthma-COPD overlap and COPD: A retrospective observational study

BACKGROUND

Although asthma and chronic obstructive pulmonary disease (COPD) are two well-defined and distinct diseases, some patients present combined clinical features of both asthma and COPD, particularly in smokers and the elderly, a condition termed as asthma-COPD overlap (ACO). However, the definition of ACO is yet to be established and clinical guidelines to identify and manage ACO remain controversial. Therefore, in this study, inflammatory biomarkers were established to distinguish asthma, ACO, and COPD, and their relationship with the severity of patients' symptoms and pulmonary function were explored.

MATERIALS AND METHODS

A total of 178 patients, diagnosed with asthma (n = 38), ACO (n = 44), and COPD (n = 96) between January 2021 to June 2022, were enrolled in this study. The patients' pulmonary function was examined and routine blood samples were taken for the analysis of inflammatory indexes. Logistic regression analysis was used to establish inflammatory biomarkers for distinguishing asthma, ACO, and COPD; linear regression analysis was used to analyze the relationship between inflammatory indexes and symptom severity and pulmonary function.

RESULT

The results showed that, compared with ACO, the higher the indexes of platelet, neutrophil-lymphocyte ratio (NLR) and eosinophil-basophil ratio (EBR), the more likely the possibility of asthma and COPD in patients, while the higher the eosinophils, the less likely the possibility of asthma and COPD. Hemoglobin and lymphocyte-monocyte ratio (LMR) were negatively correlated with the severity of patients' symptoms, while platelet-lymphocyte ratio (PLR) was negatively correlated with forced expiratory volume in the 1 s/forced vital capacity (FEV1/FVC) and FEV1 percent predicted (% pred), and EBR was positively correlated with FEV1% pred.

CONCLUSION

Inflammatory indexes are biomarkers for distinguishing asthma, ACO, and COPD, which are of clinical significance in therapeutic strategies and prognosis evaluation.