Gene susceptibility identification in a longitudinal study confirms new loci in the development of chronic obstructive pulmonary disease and influences lung function decline

Impact of HHIP gene polymorphisms on phenotypes, serum IL-17 and IL-18 in COPD patients of the Chinese Han population

BACKGROUND

Genetic factors, including the Hedgehog Interacting Protein (HHIP) gene, play a crucial role in Chronic Obstructive Pulmonary Disease (COPD) susceptibility. This study examines the association between HHIP gene polymorphisms and COPD susceptibility, phenotypes, and serum IL-17 and IL-18 levels in a Han Chinese population.

METHODS

A case-control study was conducted with 300 COPD patients and 300 healthy controls in Chinese Han population. Participants underwent genotyping for HHIP gene polymorphisms, pulmonary function tests, and quantitative CT scans. DNA samples were sequenced using a custom chip targeting the HHIP gene. Serum IL-17 and IL-18 levels were measured by enzyme-linked immunosorbent assay. Associations between SNPs, COPD susceptibility, and phenotypes were analyzed using logistic and multiple linear regression models, adjusting for confounders.

RESULTS

Our study identified the rs11100865 polymorphism in the HHIP gene as significantly associated with COPD susceptibility (OR 2.479, 95% CI 1.527-4.024, P = 2.39E-04) after screening 114 SNPs through rigorous quality control. Stratified analyses further indicated this association was particularly in individuals aged 60 or older. Serum levels of IL-17 and IL-18 were significantly elevated in COPD patients compared to controls, with rs11100865 showing a notable association with IL-18 levels (B = 49.654, SE = 19.627, P = 0.012). However, no significant associations were observed between rs11100865 and serum IL-17 levels, COPD-related imaging parameters, or clinical phenotypes.

CONCLUSION

This study identified a significant association between HHIP gene polymorphisms and COPD susceptibility in a Han Chinese population, with connections to inflammation, but found no significant associations between this SNP and COPD-related imaging or clinical phenotypes.

TRIAL REGISTRATION

www.chictr.org.cn ID: ChiCTR2300071579 2023-05-18.

Association of Human Hedgehog Interacting Protein Gene Polymorphisms with the Risk of Chronic Obstructive Pulmonary Disease: a Meta-Analysis

OBJECTIVE

To date, some studies revealed that HHIP gene polymorphisms may be associated with the risk of chronic obstructive pulmonary disease (COPD). Therefore, this meta-analysis explored the association between single-nucleotide polymorphisms (SNPs) of the human hedgehog interacting protein (HHIP) gene and susceptibility to COPD.

METHODS

Seven Chinese and English electronic databases were searched for eligible studies up to May 30, 2020. After the inclusion criteria were strictly followed, the Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of the included studies. The pooled odds ratio (OR) of the 95% confidence interval (CI) under four different genetic models was calculated to evaluate the association strength between the SNPs and COPD. Egger's test was used to evaluate publication bias.

RESULTS

This meta-analysis was registered at PROSPERO (CRD42021235708). In total, 12 studies involving 6623 COPD patients and 11373 healthy controls were included. Regarding rs13118928 and rs1828591, an A>G mutation increased the risk of COPD in Asian and Caucasian individuals, and the rs13147758 A>G mutation and rs10519717 C>T mutation increased the risk of COPD only in Asian people. No significant publication bias was observed.

CONCLUSION

This meta-analysis provides a theoretical basis suggesting that HHIP gene polymorphisms may be associated with the risk of COPD.

Genetics of COPD

Although chronic obstructive pulmonary disease (COPD) risk is strongly influenced by cigarette smoking, genetic factors are also important determinants of COPD. In addition to Mendelian syndromes such as alpha-1 antitrypsin deficiency, many genomic regions that influence COPD susceptibility have been identified in genome-wide association studies. Similarly, multiple genomic regions associated with COPD-related phenotypes, such as quantitative emphysema measures, have been found. Identifying the functional variants and key genes within these association regions remains a major challenge. However, newly identified COPD susceptibility genes are already providing novel insights into COPD pathogenesis. Network-based approaches that leverage these genetic discoveries have the potential to assist in decoding the complex genetic architecture of COPD.

Role of PM2.5 in the development and progression of COPD and its mechanisms

BACKGROUND

A multitude of epidemiological studies have shown that ambient fine particulate matter 2.5 (diameter < 2.5um; PM_2.5) was associated with increased morbidity and mortality of chronic obstructive pulmonary disease (COPD). However, the underlying associated mechanisms have not yet been elucidated. We conducted this study to investigate the role of PM_2.5 in the development of COPD and associated mechanisms.

METHODS

We firstly conducted a cross-sectional study in Chinese han population to observe PM_2.5 effects on COPD morbidity. Then, in vitro, we incubated human bronchial epithelial cells to different concentrations of PM_2.5 for 24 h. The expression levels of IL-6 and IL-8 were detected by ELISA and the levels of MMPs, TGF-β1, fibronectin and collagen was determined by immunoblotting. In vivo, we subjected C57BL/6 mice to chronic prolonged exposure to PM_2.5 for 48 weeks to study the influence of PM_2.5 exposure on lung function, pulmonary structure and inflammation.

RESULTS

We found that the effect of PM_2.5 on COPD morbidity was associated with its levels and that PM_2.5 and cigarette smoke could have a synergistic impact on COPD development and progression. Both vitro and vivo studies demonstrated that PM_2.5 exposure could induce pulmonary inflammation, decrease lung function, and cause emphysematous changes. Furthermore, PM_2.5 could markedly aggravated cigarette smoke-induced changes.

CONCLUSIONS

In short, we found that prolonged chronic exposure to PM_2.5 resulted in decreased lung function, emphysematous lesions and airway inflammation. Most importantly, long-term PM_2.5 exposure exacerbateed cigarette smoke-induced changes in COPD.

Genetic variants in FAM13A and IREB2 are associated with the susceptibility to COPD in a Chinese rural population: a case-control study

Background

Genome-wide association studies identified several genomic regions associated with the risk of chronic obstructive pulmonary disease (COPD), including the 4q22 and 15q25 regions. These regions contain the FAM13A and IREB2 genes, which have been associated with COPD but data are lacking for Chinese patients. The objective of the study was to identify new genetic variants in the FAM13A and IREB2 associated with COPD in Northwestern China.

Methods

This was a case-control study performed in the Ningxia Hui Autonomous Region between January 2014 and December 2016. Patients were grouped as COPD and controls based on FEV₁/FVC<70%. Seven tag single-nucleotide polymorphisms (SNPs) in the FAM13A and IREB2 genes were genotyped using the Agena MassARRAY platform. Logistic regression was used to determine the association between SNPs and COPD risk.

Results

rs17014601 in FAM13A was significantly associated with COPD in the additive (odds ratio [OR]=1.36, 95% confidence interval [CI]: 1.11-1.67, P=0.003), heterozygote (OR=1.76, 95% CI: 1.33-2.32, P=0.0001), and dominant (OR=1.67, 95% CI: 1.28-2.18, P=0.0001) models. Stratified analyses indicated that the risk was higher in never smokers. rs16969858 in IREB2 was significantly associated with COPD but in the univariate analysis only, and the multivariate analysis did not show any association.

Conclusion

The results suggest that the new variant rs17014601 in the FAM13A gene was significantly associated with COPD risk in a Chinese rural population. Additional studies are required to confirm the role of this variant in COPD development and progression.

Smoking status and gene susceptibility play important roles in the development of chronic obstructive pulmonary disease and lung function decline: A population-based prospective study

BACKGROUND

We conducted this study to identify the influences and synergistic effects of smoking status and polymorphisms in hedgehog interacting protein (HHIP) on chronic obstructive pulmonary disease (COPD) and lung function decline.

METHODS

A cohort containing 306 COPD patients and 743 healthy subjects was recruited from 25,000 subjects. All selected subjects had chronic cough for over 2 years or a smoking history above 20 pack-years. After 8 years, all subjects were divided into 2 cohorts according to whether they had quit smoking or not. A follow-up of all patients was completed after another period of 10 years. Three variants in HHIP were genotyped to investigate the impacts of gene susceptibility on the development of COPD and lung function decline.

RESULTS

During the follow-up tests, forced expiratory volume in 1 s (FEV1) ratios decreased more significantly in COPD patients than in healthy subjects. For variant rs7654947, FEV1 decreased more significantly in CC and CT subjects than in TT subjects. FEV1 in COPD patients with a CC genotype from smoking cohorts reduced markedly when compared to ex-smoking cohorts (case, 30.75% vs. 35.5%; total, 28% vs. 32%).

CONCLUSIONS

Our results showed that smoking and HHIP variant rs7654947 were associated with COPD development and lung function decline. Moreover, we found that cigarette smoking and gene susceptibility have cooperative effects on COPD risk and lung function decline.

Increased Transcript Complexity in Genes Associated with Chronic Obstructive Pulmonary Disease

Genome-wide association studies aim to correlate genotype with phenotype. Many common diseases including Type II diabetes, Alzheimer’s, Parkinson’s and Chronic Obstructive Pulmonary Disease (COPD) are complex genetic traits with hundreds of different loci that are associated with varied disease risk. Identifying common features in the genes associated with each disease remains a challenge. Furthermore, the role of post-transcriptional regulation, and in particular alternative splicing, is still poorly understood in most multigenic diseases. We therefore compiled comprehensive lists of genes associated with Type II diabetes, Alzheimer’s, Parkinson’s and COPD in an attempt to identify common features of their corresponding mRNA transcripts within each gene set. The SERPINA1 gene is a well-recognized genetic risk factor of COPD and it produces 11 transcript variants, which is exceptional for a human gene. This led us to hypothesize that other genes associated with COPD, and complex disorders in general, are highly transcriptionally diverse. We found that COPD-associated genes have a statistically significant enrichment in transcript complexity stemming from a disproportionately high level of alternative splicing, however, Type II Diabetes, Alzheimer’s and Parkinson’s disease genes were not significantly enriched. We also identified a subset of transcriptionally complex COPD-associated genes (~40%) that are differentially expressed between mild, moderate and severe COPD. Although the genes associated with other lung diseases are not extensively documented, we found preliminary data that idiopathic pulmonary disease genes, but not cystic fibrosis modulators, are also more transcriptionally complex. Interestingly, complex COPD transcripts are more often the product of alternative acceptor site usage. To verify the biological importance of these alternative transcripts, we used RNA-sequencing analyses to determine that COPD-associated genes are frequently expressed in lung and liver tissues and are regulated in a tissue-specific manner. Additionally, many complex COPD-associated genes are spliced differently between COPD and non-COPD patients. Our analysis therefore suggests that post-transcriptional regulation, particularly alternative splicing, is an important feature specific to COPD disease etiology that warrants further investigation.

Candidate genes for COPD: current evidence and research

COPD is a common complex disease characterized by progressive airflow limitation. Several genome-wide association studies (GWASs) have discovered genes that are associated with COPD. Recently, candidate genes for COPD identified by GWASs include CHRNA3/5 (cholinergic nicotine receptor alpha 3/5), IREB2 (iron regulatory binding protein 2), HHIP (hedgehog-interacting protein), FAM13A (family with sequence similarity 13, member A), and AGER (advanced glycosylation end product–specific receptor). Their association with COPD susceptibility has been replicated in multiple populations. Since these candidate genes have not been considered in COPD, their pathological roles are still largely unknown. Herein, we review some evidences that they can be effective drug targets or serve as biomarkers for diagnosis or subtyping. However, more study is required to understand the functional roles of these candidate genes. Future research is needed to characterize the effect of genetic variants, validate gene function in humans and model systems, and elucidate the genes’ transcriptional and posttranscriptional regulatory mechanisms.