NIHR Leicester Respiratory Biomedical Research Unit

"Reply to: PCSK6: The endogenous PAR-1 agonist driving pulmonary fibrosis?." American Journal of Respiratory and Critical Care Medicine, 0(ja), pp.

The risk of airflow limitation and chronic obstructive pulmonary disease (COPD) is influenced by combinations of cigarette smoking and genetic susceptibility, yet it remains unclear whether gene-by-smoking interactions are associated with quantitative measures of lung function. To assess the interaction of cigarette smoking and polygenic risk score in association with reduced lung function. This UK Biobank cohort study included UK citizens of European ancestry aged 40 to 69 years with genetic and spirometry data passing quality control metrics. Data was analyzed from July 2020 to March 2021. PRS of combined forced expiratory volume in 1 second (FEV1) and percent of forced vital capacity exhaled in the first second (FEV1/FVC), self-reported pack-years of smoking, ever- vs never-smoking status, and current- vs former- or never-smoking status. FEV1/FVC was the primary outcome. Models were used to test for interactions with models, including the main effects of PRS, different smoking variables, and their cross-product terms. The association between pack-years of smoking and FEV1/FVC were compared for those in the highest vs lowest decile of estimated genetic risk for low lung function. We included 319 730 individuals, of whom 24 915 (8%) had moderate-to-severe COPD cases, and 44.4% were men. Participants had a mean (SD) age 56.5 of (8.02) years. The PRS and pack-years were significantly associated with lower FEV1/FVC (PRS: β, -0.03; 95% CI, -0.031 to -0.03; pack-years: β, -0.0064; 95% CI, -0.0064 to -0.0063) and the interaction term (β, -0.0028; 95% CI, -0.0029 to -0.0026). A stepwise increment in estimated effect sizes for these interaction terms was observed per 10 pack-years of smoking exposure. The interaction of PRS with 11 to 20, 31 to 40, and more than 50 pack-years categories were β (interaction) -0.0038 (95% CI, -0.0046 to -0.0031); -0.013 (95% CI, -0.014 to -0.012); and -0.017 (95% CI, -0.019 to -0.016), respectively. There was evidence of significant interaction between PRS with ever- or never- smoking status (β, interaction; -0.0064; 95% CI, -0.0068 to -0.0060) and current or not-current smoking (β, interaction; -0.0091; 95% CI, -0.0097 to -0.0084). For any given level of pack-years of smoking exposure, FEV1/FVC was significantly lower for individuals in the tenth decile (ie, highest risk) than the first decile (ie, lowest risk) of genetic risk. For every 20 pack-years of smoking, those in the tenth decile compared with the first decile of genetic risk showed nearly a 2-fold reduction in FEV1/FVC. COPD is characterized by diminished lung function, and our analyses suggest there is substantial interaction between genome-wide PRS and smoking exposures. While smoking was associated with decreased lung function across all genetic risk categories, the associations were strongest in individuals with higher estimated genetic risk.

Background: Lung function is highly heritable and differs between the sexes throughout life. However, little is known about sex-differential genetic effects on lung function. We aimed to conduct the first genome-wide genotype-by-sex interaction study on lung function to identify genetic effects that differ between males and females. Methods: We tested for interactions between 7,745,864 variants and sex on spirometry-based measures of lung function in UK Biobank (N=303,612), and sought replication in 75,696 independent individuals from the SpiroMeta consortium. Results: Five independent single-nucleotide polymorphisms (SNPs) showed genome-wide significant (P<5x10 -8) interactions with sex on lung function, and 21 showed suggestive interactions (P<1x10 -6). The strongest signal, from rs7697189 (chr4:145436894) on forced expiratory volume in 1 second (FEV 1) (P=3.15x10 -15), was replicated (P=0.016) in SpiroMeta. The C allele increased FEV 1 more in males (untransformed FEV 1 β=0.028 [SE 0.0022] litres) than females (β=0.009 [SE 0.0014] litres), and this effect was not accounted for by differential effects on height, smoking or pubertal age. rs7697189 resides upstream of the hedgehog-interacting protein ( HHIP) gene and was previously associated with lung function and HHIP lung expression. We found HHIP expression was significantly different between the sexes (P=6.90x10 -6), but we could not detect sex differential effects of rs7697189 on expression. Conclusions: We identified a novel genotype-by-sex interaction at a putative enhancer region upstream of the HHIP gene. Establishing the mechanism by which HHIP SNPs have different effects on lung function in males and females will be important for our understanding of lung health and diseases in both sexes.

There is increasing evidence that ventilation heterogeneity and small airway disease are significant factors in asthma, with evidence suggesting that the small airways are involved from an early stage in childhood asthma. Spirometry is commonly used to monitor lung function in asthmatics; however, it is not sensitive to small airway disease. There has been renewed interest in multibreath washout (MBW) tests, with recognition of the lung clearance index (LCI) as a global index of abnormality in gas mixing of the lungs that therefore also reflects small airway disease. This review summarises the technical and practical aspects of the MBW/LCI in children, and the differences between commercially available equipment. Children with severe asthma are more likely to have an abnormal LCI, whereas most children with mild-to-moderate asthma have an LCI within the normal range, but slightly higher than age-matched healthy controls. Monitoring children with asthma with MBW alongside standard spirometry may provide useful additional information.

Group 2 innate lymphoid cells (ILC2) are effectors of barrier immunity, with roles in infection, wound healing, and allergy. A proportion of ILC2 express MHCII (major histocompatibility complex II) and are capable of presenting peptide antigens to T cells and amplifying the subsequent adaptive immune response. Recent studies have highlighted the importance of CD1a-reactive T cells in allergy and infection, activated by the presentation of endogenous neolipid antigens and bacterial components. Using a human skin challenge model, we unexpectedly show that human skin-derived ILC2 can express CD1a and are capable of presenting endogenous antigens to T cells. CD1a expression is up-regulated by TSLP (thymic stromal lymphopoietin) at levels observed in the skin of patients with atopic dermatitis, and the response is dependent on PLA2G4A. Furthermore, this pathway is used to sense Staphylococcus aureus by promoting Toll-like receptor-dependent CD1a-reactive T cell responses to endogenous ligands. These findings define a previously unrecognized role for ILC2 in lipid surveillance and identify shared pathways of CD1a- and PLA2G4A-dependent ILC2 inflammation amenable to therapeutic intervention.

Chronic obstructive pulmonary disease (COPD) is characterized in the later stages by acute exacerbations that often require hospitalization. Pulmonary rehabilitation is recommended for patients with COPD to aid symptom control, improve quality of life and increase physical activity. We have previously reported a large intervention trial commenced during a hospital admission. The aim of this sub-study was to evaluate the patients’ experiences of discharge following the hospitalization for an acute exacerbation of COPD. During a programme of early rehabilitation (ER) patient perceptions, experiences and healthcare use were collated during the month that followed their discharge. ER (started during their admission) was comprised of exercise training techniques that were modified to suit the environment of acute illness, together with an education and self-management programme. Each patient was then supported on the programme by telephone contact, following their discharge home, at 48 hours, 2 weeks and 4 weeks. We collected information in relation to the walking and exercise progression; we monitored patient recall of healthcare use, compliance/understanding of medical therapy, as well as their wider perceptions that may have influenced the recovery process. Healthcare use was captured using GP records and data analysis. Of the 100 patients, 47 males, (mean (standard deviation)) 71 (9.3) years, FEV1 1.14 L (0.6), BMI 26.6 (6.9), pack smoked years 45.8 (29.6), ethnicity White British 97%, were discharged home following an acute exacerbation of their respiratory symptoms, to an ER programme. At 48 hours following discharge, a minority (20%) of patients stated their symptoms were ‘feeling better’; 15% highlighted that they found the prescribed ‘exercise difficult’; 44% of patients felt at the end of the month that prescribed exercise programme had a ‘positive effect’ on their recovery from their exacerbation; 38% of patients felt their family had a positive effect on their recovery; 11% felt their family hindered. Patients reported a mean confidence score of 8.21 (2.1) for exercise that did not vary over the three contacts (p = 0.166). A similar mean confidence score of 7.76 (2.6) was reported for walking with a non-statistical change also noted (p = 0.223). When patient recall of primary health care contact was compared with actual use, there was statistical significance shown (p = 0.002); patients underestimated the amount of care they received. The data indicate that patients do recover at home within the support of an early intervention. Patients are positive about the benefit of ER in the process of recovery; however, this is uncontrolled data.

BackgroundGenome-wide association studies have identified numerous genetic regions that influence cross-sectional lung function. Longitudinal decline in lung function also includes a heritable component but the genetic determinants have yet to be defined.ObjectivesWe aimed to determine whether regions associated with cross-sectional lung function were also associated with longitudinal decline and to seek novel variants which influence decline.MethodsWe analysed genome-wide data from 4167 individuals from the Busselton Health Study cohort, who had undergone spirometry (12 695 observations across eight time points). A mixed model was fitted and weighted risk scores were calculated for the joint effect of 26 known regions on baseline and longitudinal changes in FEV1 and FEV1/FVC. Potential additional regions of interest were identified and followed up in two independent cohorts.ResultsThe 26 regions previously associated with cross-sectional lung function jointly showed a strong effect on baseline lung function (p=4.44×10−16 for FEV1/FVC) but no effect on longitudinal decline (p=0.160 for FEV1/FVC). This was replicated in an independent cohort. 39 additional regions of interest (48 variants) were identified; these associations were not replicated in two further cohorts.ConclusionsPreviously identified genetic variants jointly have a strong effect on cross-sectional lung function in adults but little or no effect on the rate of decline of lung function. It is possible that they influence COPD risk through lung development. Although no genetic variants have yet been associated with lung function decline at stringent genome-wide significance, longitudinal change in lung function is heritable suggesting that there is scope for future discoveries.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide; smoking is the main risk factor for COPD, but genetic factors are also relevant contributors. Genome-wide association studies (GWAS) of the lung function measures used in the diagnosis of COPD have identified a number of loci, however association signals are often broad and collectively these loci only explain a small proportion of the heritability. In order to examine the association with COPD risk of genetic variants down to low allele frequencies, to aid fine-mapping of association signals and to explain more of the missing heritability, we undertook a targeted sequencing study in 300 COPD cases and 300 smoking controls for 26 loci previously reported to be associated with lung function. We used a pooled sequencing approach, with 12 pools of 25 individuals each, enabling high depth (30x) coverage per sample to be achieved. This pooled design maximised sample size and therefore power, but led to challenges during variant-calling since sequencing error rates and minor allele frequencies for rare variants can be very similar. For this reason we employed a rigorous quality control pipeline for variant detection which included the use of 3 independent calling algorithms. In order to avoid false positive associations we also developed tests to detect variants with potential batch effects and removed them before undertaking association testing. We tested for the effects of single variants and the combined effect of rare variants within a locus. We followed up the top signals with data available (only 67% of collapsing methods signals) in 4,249 COPD cases and 11,916 smoking controls from UK Biobank. We provide suggestive evidence for the combined effect of rare variants on COPD risk in TNXB and in sliding windows within MECOM and upstream of HHIP. These findings can lead to an improved understanding of the molecular pathways involved in the development of COPD.

Introduction: Investigating airway inflammation and pathology in wheezy preschool children is challenging from both a technical and ethical standpoint. Novel non-invasive tests need to be identified and validated. Real-time analysis of eVOC may be useful in the diagnosis and monitoring of these children. Aims: To evaluate eVOC patterns in wheezy preschool children, to assess reproducibility and compare eVOC patterns with those obtained from healthy adults. Methods: Children breathed room air tidally via a facemask for 80 secs and eVOC were analysed instantly by Proton-Transfer-Reaction time-of-flight mass spectrometry coupled to Loccioni breath collection apparatus. Repeat samples were obtained 15 min after the initial sample. Using a MATLAB programme we identified mass channels within each breath sample that changed with breathing. Results: 9 children (14 – 74 months) participated, of which 6 were able to produce analysable results. A total of 55 of 249 channels varied with the breathing cycle. 5 mass channels were common to all analysable preschool wheeze samples with 11 mass channels found in 4 of the breath samples. The adult samples showed similar patterns, with 6 out of 9 adult samples containing the same 5 channels. There were 11 unique channels within the children9s samples in comparison to the adult channels.Currently one sample has been repeated, with 91% commonality of channels. Conclusion: eVOC measurements in preschool children are feasible, well tolerated and appear reproducible, with channels not significantly different in adults and children. Further work is required to confirm repeatability and to compare patterns in children with preschool wheeze with that of healthy controls.