Telomere length is a determinant of emphysema susceptibility

Telomere length in COPD: Relationships with physical activity, exercise capacity, and acute exacerbations

RATIONALE

Shorter leukocyte telomere length (LTL) is associated with reduced health-related quality of life and increased risk for acute exacerbations (AEs) and mortality in chronic obstructive pulmonary disease (COPD). Increased physical activity and exercise capacity are associated with reduced risk for AEs and death. However, the relationships between LTL and physical activity, exercise capacity, and AEs in COPD are unknown.

METHODS

Data from 3 COPD cohorts were examined: Cohort 1 (n = 112, physical activity intervention trial), Cohorts 2 and 3 (n = 182 and 294, respectively, separate observational studies). Subjects completed a 6-minute walk test (6MWT) and provided blood for LTL assessment using real-time PCR. Physical activity was measured as average daily step count using an accelerometer or pedometer. Number of self-reported AEs was available for 1) the year prior to enrollment (Cohorts 1 and 3) and 2) prospectively after enrollment (all cohorts). Multivariate models examined associations between LTL and average daily step count, 6MWT distance, and AEs.

RESULTS

A significant association between longer LTL and increased 6MWT distance was observed in the three combined cohorts (β = 3x10-5, p = 0.045). No association between LTL and average daily step count was observed. Shorter LTL was associated with an increased number of AEs in the year prior to enrollment (Cohorts 1 and 3 combined, β = -1.93, p = 0.04) and with prospective AEs (Cohort 3, β = -1.3388, p = 0.0003).

CONCLUSIONS

Among COPD patients, increased LTL is associated with higher exercise capacity, but not physical activity. Shorter LTL was associated with AEs in a subgroup of cohorts.

Comorbidities in idiopathic pulmonary fibrosis: an underestimated issue

Idiopathic pulmonary fibrosis (IPF) is a progressive and fibrosing lung disease with a poor prognosis. Between 60% and 70% of IPF patients die of IPF; the remaining causes of death may be due to comorbidities occurring in this ageing population. Interest in the role played by comorbidities in IPF has increased in the past few years. The optimal clinical management of IPF is multifaceted and not only involves antifibrotic treatment, but also vaccinations, oxygen supplementation, evaluation of nutritional status as well as psychological support and patient education. Symptom management, pulmonary rehabilitation, palliative care and treatment of comorbidities represent further areas of clinical intervention. This review analyses the major comorbidities observed in IPF, focusing on those that have the greatest impact on mortality and quality of life (QoL). The identification and treatment of comorbidities may help to improve patients' health-related QoL (i.e. sleep apnoea and depression), while some comorbidities (i.e. lung cancer, cardiovascular diseases and pulmonary hypertension) influence survival. It has been outlined that gathering comorbidities data improves the prediction of survival beyond the clinical and physiological parameters of IPF.

GDF15 is an epithelial-derived biomarker of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most common and devastating of the interstitial lung diseases. Epithelial dysfunction is thought to play a prominent role in disease pathology, and we sought to characterize secreted signals that may contribute to disease pathology. Transcriptional profiling of senescent type II alveolar epithelial cells from mice with epithelial-specific telomere dysfunction identified the transforming growth factor-β family member, growth and differentiation factor 15 (Gdf15), as the most significantly upregulated secreted protein. Gdf15 expression is induced in response to telomere dysfunction and bleomycin challenge in mice. Gdf15 mRNA is expressed by lung epithelial cells, and protein can be detected in peripheral blood and bronchoalveolar lavage following bleomycin challenge in mice. In patients with IPF, GDF15 mRNA expression in lung tissue is significantly increased and correlates with pulmonary function. Single-cell RNA sequencing of human lungs identifies epithelial cells as the primary source of GDF15, and circulating concentrations of GDF15 are markedly elevated and correlate with disease severity and survival in multiple independent cohorts. Our findings suggest that GDF15 is an epithelial-derived secreted protein that may be a useful biomarker of epithelial stress and identifies IPF patients with poor outcomes.

Telomere Abnormalities in the Pathobiology of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) occurs primarily in older adults and the incidence is clearly associated with aging. This disease seems to be associated with several hallmarks of aging, including telomere attrition and cellular senescence. Increasing evidence suggests that abnormalities involving telomeres and their proteome play a significant role in the pathobiology of IPF. The aim of this study is to summarize present knowledge in the field, as well as to discuss its possible clinical implications. Numerous mutations in genes associated with telomere functioning were studied in the context of IPF, mainly for Telomerase Reverse Transcriptase (TERT) and Telomerase RNA Component (TERC). Such mutations may lead to telomere shortening, which seems to increase the risk of IPF, negatively influence disease progression, and contribute to worse prognosis after lung transplantation. Some evidence indicates the possibility for the use of telomerase activators as potential therapeutic agents in pulmonary fibrosis. To sum up, increasing evidence suggests the role of telomere abnormalities in the pathobiology of IPF, natural history and prognosis of the disease. There are also possibilities for telomerase targeting in the potential development of new treatment agents. However, all these aspects require further research.

TERT gene polymorphisms are associated with chronic obstructive pulmonary disease risk in the Chinese Li population

Background

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality worldwide and is characterized by a partially reversible airflow limitation. Currently, many studies put forward that COPD is associated with both genetic and environmental factors. It has been reported that germline mutations in telomerase are risk factors for COPD susceptibility. In this study, we validated the association between TERT polymorphisms and COPD risk with a case–control study in the Chinese Li population.

Methods

A total of 279 COPD patients and 290 control individuals were recruited. We identified five single nucleotide polymorphisms (SNPs) in TERT that were associated with COPD. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated in logistic regression models after adjusting for age and gender to assess the association.

Results

In the genetic model analysis, we found the “C/T‐T/T” genotype of rs10069690 in TERT was associated with an increased COPD risk in the dominant model (p = 0.046); the rs2853677 in TERT was significantly associated with increased COPD risk based on the codominant model (“A/G” genotype, p = 0.033), dominant model (A/G‐G/G genotype, p = 0.0091), and log‐additive model (p = 0.023). The rs2853676 in TERT could increase the risk of COPD in the dominant model (“C/T‐T/T” genotype, p = 0.026) and in the Log‐additive model (p = 0.022).

Conclusion

Our data shed new light on the association between TERT SNPs and COPD susceptibility in the Chinese Li population.

The Role of Telomerase and Telomeres in Interstitial Lung Diseases: From Molecules to Clinical Implications

Telomeres are distal chromosome regions associated with specific protein complexes that protect the chromosome against degradation and aberrations. Telomere maintenance capacity is an essential indication of healthy cell populations, and telomere damage is observed in processes such as malignant transformation, apoptosis, or cell senescence. At a cellular level, telomere damage may result from genotoxic stress, decreased activity of telomerase enzyme complex, dysfunction of shelterin proteins, or changes in expression of telomere-associated RNA such as TERRA. Clinical evidence suggests that mutation of telomerase genes (Tert/Terc) are associated with increased risk of congenital as well as age-related diseases (e.g., pneumonitis, idiopathic pulmonary fibrosis (IPF), dyskeratosis congenita, emphysema, nonspecific interstitial pneumonia, etc.). Thus, telomere length and maintenance can serve as an important prognostic factor as well as a potential target for new strategies of treatment for interstitial lung diseases (ILDs) and associated pulmonary pathologies.

Disease-Specific Comorbidity Clusters in COPD and Accelerated Aging

Background: Patients with chronic obstructive pulmonary disease (COPD) often suffer from multiple morbidities, which occur in clusters and are sometimes related to accelerated aging. This study aimed to assess the disease specificity of comorbidity clusters in COPD and their association with a biomarker of accelerated aging as a potential mechanistic factor. Methods: Body composition, metabolic, cardiovascular, musculoskeletal, and psychological morbidities were objectively evaluated in 208 COPD patients (age 62 ± 7 years, 58% males, FEV₁ 50 ± 16% predicted) and 200 non-COPD controls (age 61 ± 7 years, 45% males). Based on their presence and severity, the morbidities were clustered to generate distinct clusters in COPD and controls. Telomere length in circulating leukocytes was compared across the clusters. Results: (co)morbidities were more prevalent in COPD patients compared to controls (3.9 ± 1.7 vs. 2.4 ± 1.5, p < 0.05). A “Psychologic” and “Cachectic” cluster were only present in the COPD population. “Less (co)morbidity”, “Cardiovascular”, and “Metabolic” clusters were also observed in controls, although with less complexity. Telomere length was reduced in COPD patients, but did not differ between the (co)morbidity clusters in both populations. Conclusions: Two COPD-specific comorbidity clusters, a “Cachectic” and “Psychologic” cluster, were identified and warrant further studies regarding their development. Accelerated aging was present across various multimorbidity clusters in COPD.

Trade-offs in aging lung diseases: a review on shared but opposite genetic risk variants in idiopathic pulmonary fibrosis, lung cancer and chronic obstructive pulmonary disease

PURPOSE OF REVIEW

The process of aging involves biological changes that increases susceptibility for disease. In the aging lung disease IPF, GWAS studies identified genes associated with risk for disease. Recently, several of these genes were also found to be involved in risk for COPD or lung cancer. This review describes GWAS-derived risk genes for IPF that overlap with risk genes for lung cancer or COPD.

RECENT FINDINGS

Risk genes that overlap between aging lung diseases, include FAM13A, DSP and TERT. Most interestingly, disease predisposing alleles for IPF are opposite to those for COPD or lung cancer. Studies show that the alleles are associated with differential gene expression and with physiological traits in the general population. The opposite allelic effect sizes suggest the presence of trade-offs in the aging lung. For TERT, the trade-off involves cellular senescence versus proliferation and repair. For FAM13A and DSP, trade-offs may involve protection from noxious gases or tissue integrity.

SUMMARY

The overlap in risk genes in aging lung diseases provides evidence that processes associated with FAM13A, DSP and TERT are important for healthy aging. The opposite effect size of the disease risk alleles may represent trade-offs, for which a model involving an apicobasal gene expression gradient is presented.

Pulmonary phenotypes associated with genetic variation in telomere-related genes

PURPOSE OF REVIEW

Genomic mutations in telomere-related genes have been recognized as a cause of familial forms of idiopathic pulmonary fibrosis (IPF). However, it has become increasingly clear that telomere syndromes and telomere shortening are associated with various types of pulmonary disease. Additionally, it was found that also single nucleotide polymorphisms (SNPs) in telomere-related genes are risk factors for the development of pulmonary disease. This review focuses on recent updates on pulmonary phenotypes associated with genetic variation in telomere-related genes.

RECENT FINDINGS

Genomic mutations in seven telomere-related genes cause pulmonary disease. Pulmonary phenotypes associated with these mutations range from many forms of pulmonary fibrosis to emphysema and pulmonary vascular disease. Telomere-related mutations account for up to 10% of sporadic IPF, 25% of familial IPF, 10% of connective-tissue disease-associated interstitial lung disease, and 1% of COPD. Mixed disease forms have also been found. Furthermore, SNPs in TERT, TERC, OBFC1, and RTEL1, as well as short telomere length, have been associated with several pulmonary diseases. Treatment of pulmonary disease caused by telomere-related gene variation is currently based on disease diagnosis and not on the underlying cause.

SUMMARY

Pulmonary phenotypes found in carriers of telomere-related gene mutations and SNPs are primarily pulmonary fibrosis, sometimes emphysema and rarely pulmonary vascular disease. Genotype-phenotype relations are weak, suggesting that environmental factors and genetic background of patients determine disease phenotypes to a large degree. A disease model is presented wherever genomic variation in telomere-related genes cause specific pulmonary disease phenotypes whenever triggered by environmental exposure, comorbidity, or unknown factors.

Telomeres in Interstitial Lung Disease: The Short and the Long of It

Telomeres are repetitive nucleotide sequences that cap linear chromosomes, thereby limiting progressive chromosomal shortening during cell replication. In conjunction with environmental factors, common single-nucleotide polymorphisms and rare and ultra-rare telomere-related mutations are associated with accelerated telomere shortening resulting in organ dysfunction, including interstitial lung disease (ILD). The most common telomere-related mutation-associated ILD is idiopathic pulmonary fibrosis (IPF). Up to one-third of individuals with familial IPF have shortened telomeres and/or carry a telomere-related mutation, and 1 in 10 individuals with sporadic IPF have telomere-related mutations. Regardless of ILD phenotype, individuals with short telomeres and/or known telomere-related mutations have more rapid disease progression and shorter lung transplant-free survival. Management should include initiation of antifibrotic agents for those with an IPF phenotype and early referral to a transplant center. Patients with ILD being considered for transplant should be screened for short telomeres if there is a significant family history of pulmonary fibrosis or evidence of extrapulmonary organ dysfunction associated with a short telomere syndrome. Post-transplant management of recipients with telomere-related mutations should include careful adjustment of immunosuppression regimens on the basis of bone marrow reserve. Data on the impact of shortened telomeres on post-transplant outcomes, however, remain mixed.

Epithelial Injury and Dysfunction in the Pathogenesis of Idiopathic PulmonaryFibrosis

Idiopathic pulmonary fibrosis is a disease of older adults leading to progressive dyspnea and reduced exercise capacity, typically resulting in death within 3-5years of diagnosis. Underlying genetic susceptibility combined with environmental insults is proposed to trigger a chronic wound repair response, leading to activation of the fibrotic cascade. Perturbations in several molecular pathways mediate vulnerability of the alveolar epithelium to injurious agents, including the unfolded protein response, autophagy, mitophagy, and cellular senescence. These cellular responses are intricately intertwined and link genetic susceptibility to the progressive fibrotic phenotype. Ongoing studies investigating these pathways in type II alveolar epithelial cells show promise for identifying new targeted interventions that could prevent or halt the progression of IPF.

Pulmonary Diseases and Ageing

Chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis are regarded as a diseases of accelerated lung ageing and show all of the hallmarks of ageing, including telomere shortening, cellular senescence, activation of PI3 kinase-mTOR signaling, impaired autophagy, mitochondrial dysfunction, stem cell exhaustion, epigenetic changes, abnormal microRNA profiles, immunosenescence and a low grade chronic inflammation due to senescence-associated secretory phenotype (SASP). Many of these ageing mechanisms are driven by exogenous and endogenous oxidative stress. There is also a reduction in anti-ageing molecules, such as sirtuins and Klotho, which further accelerate the ageing process. Understanding these molecular mechanisms has identified several novel therapeutic targets and several drugs and dietary interventions are now in development to treat chronic lung disease.

Bringing Light to Chronic Obstructive Pulmonary Disease Pathogenesis and Resilience

The pathogenesis of chronic obstructive pulmonary disease remains elusive; investigators in the field have struggled to decipher the cellular and molecular processes underlying chronic bronchitis and emphysema. Studies in the past 20 years have underscored that the tissue destruction, notably in emphysema, involves a multitude of injurious stresses, with progressive engagement of endogenous destructive processes triggered by decades of exposure to cigarette smoke and/or pollutants. These lead to an aged lung, with evidence of macromolecular damage that is unlikely to repair. Here we discuss these key pathogenetic elements in the context of organismal evolution as this concept may best capture the challenges facing chronic obstructive pulmonary disease.

Cell Death in the Lung: The Apoptosis-Necroptosis Axis

Regulated cell death is a major mechanism to eliminate damaged, infected, or superfluous cells. Previously, apoptosis was thought to be the only regulated cell death mechanism; however, new modalities of caspase-independent regulated cell death have been identified, including necroptosis, pyroptosis, and autophagic cell death. As an understanding of the cellular mechanisms that mediate regulated cell death continues to grow, there is increasing evidence that these pathways are implicated in the pathogenesis of many pulmonary disorders. This review summarizes our understanding of regulated cell death as it pertains to the pathogenesis of chronic obstructive pulmonary disease, asthma, idiopathic pulmonary fibrosis, acute respiratory distress syndrome, and pulmonary arterial hypertension.

Telomere length, ZNF208 genetic variants and risk of chronic obstructive pulmonary disease in the Hainan Li population

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a disease characterized by airflow limitation. It is not completely reversible and shows progressive development. ZNF208 rs8105767 affects telomere length, although the impact of telomere on COPD is still controversial. In the present study, we aimed to explore the impact of the ZNF208 gene polymorphism on telomere length and also that of telomere length on COPD in the Hainan Li population.

METHODS

In total, 270 COPD patients and 288 controls were recruited. Telomere length was measured by a quantitative real-time polymerase chain reaction. Five single nucleotide polymorphisms in ZNF208 were selected and genotyping was performed using MassARRAY software (Agena Bioscience Co. Ltd, San Diego, CA, USA). Differences in telomere length among the subjects with three genotypes of related genes were assessed using analysis of variance. Unconditional logistic regression was used to calculate odds ratios (OR) as the indicator of association between telomere length and COPD risk.

RESULTS

Relative telomere length in the COPD group and control group was 0.66 ± 0.47 and 1.44 ± 0.89, respectively. We grouped according to a median of 0.8284 for telomere length and observed that the risk of COPD for individuals with a telomere length less than 0.8284 is 2.92 times that for individuals with a telomere length longer than 0.8284 (OR = 2.92, 95% confidence interval = 2.01-4.25, p = 1.91 × 10^-8 ). Subjects carrying the G allele of rs2188972 had a longer telomere length. Subjects carrying the carrying the CA genotype of rs8103163 and AC genotype of rs7248488 had a longer telomere length compared to wild-type individuals.

CONCLUSIONS

Shorter telomeres increase COPD risk and the ZNF208 polymorphism affects telomere length in COPD patients.

Short telomere syndromes cause a primary T cell immunodeficiency

The mechanisms that drive T cell aging are not understood. We report that children and adult telomerase mutation carriers with short telomere length (TL) develop a T cell immunodeficiency that can manifest in the absence of bone marrow failure and causes life-threatening opportunistic infections. Mutation carriers shared T cell-aging phenotypes seen in adults 5 decades older, including depleted naive T cells, increased apoptosis, and restricted T cell repertoire. T cell receptor excision circles (TRECs) were also undetectable or low, suggesting that newborn screening may identify individuals with germline telomere maintenance defects. Telomerase-null mice with short TL showed defects throughout T cell development, including increased apoptosis of stimulated thymocytes, their intrathymic precursors, in addition to depleted hematopoietic reserves. When we examined the transcriptional programs of T cells from telomerase mutation carriers, we found they diverged from older adults with normal TL. Short telomere T cells upregulated DNA damage and intrinsic apoptosis pathways, while older adult T cells upregulated extrinsic apoptosis pathways and programmed cell death 1 (PD-1) expression. T cells from mice with short TL also showed an active DNA-damage response, in contrast with old WT mice, despite their shared propensity to apoptosis. Our data suggest there are TL-dependent and TL-independent mechanisms that differentially contribute to distinct molecular programs of T cell apoptosis with aging.

Relationship of Absolute Telomere Length With Quality of Life, Exacerbations, and Mortality in COPD

BACKGROUND

COPD is an age-related disease. The role of cellular senescence in COPD has not been fully elucidated. This study examined the relationship between telomere length of peripheral blood leukocytes and clinical outcomes, including health status, rate of exacerbations, and risk of mortality in individuals with COPD.

METHODS

Using quantitative polymerase chain reaction, we measured the absolute telomere length (aTL) of DNA extracted from blood samples of 576 participants with moderate-to-severe COPD treated with either azithromycin or placebo for 12 months in the Macrolide Azithromycin for Prevention of Exacerbations of COPD (MACRO) study. All participants were followed for approximately 13 months, during which time health status and exacerbations were carefully ascertained, and an additional 29 months for mortality. The rates of exacerbation and mortality were determined by dividing the aTL into two groups using the median value as the cutoff.

RESULTS

Participants with shorter telomere length had worse health status defined by higher St. George's Respiratory Questionnaire scores (β = -0.09, P = .034). In the placebo arm of the study, the rate of exacerbation (rate ratio, 1.50; 95% CI, 1.16-1.95; P = .002) and the risk of mortality (hazard ratio, 9.45; 95% CI, 2.85-31.36; P = .015) were significantly higher in the shorter telomere group than in the longer telomere group; these differences were not observed in the azithromycin arm (interaction P = .008 for exacerbation and interaction P = .017 for mortality) CONCLUSIONS: These data suggest that replicative senescence may help to predict poor outcomes in COPD. Shorter leukocyte telomere lengths may represent a clinically translatable biomarker for identifying individuals at increased risk of poor clinical outcomes in COPD.

Short Telomere Syndromes in Clinical Practice: Bridging Bench and Bedside

Short telomere syndromes (STSs) are accelerated aging syndromes often caused by inheritable gene mutations resulting in decreased telomere lengths. Consequently, organ systems with increased cell turnover, such as the skin, bone marrow, lungs, and gastrointestinal tract, are commonly affected. Owing to diverse clinical presentations, STSs pose a diagnostic challenge, with bone marrow failure and idiopathic pulmonary fibrosis being frequent manifestations, occurring in association with gene mutations involving DKC1 (for expansion of gene symbols, use search tool at www.genenames.org), TERT, TERC, and others. Inherited STSs demonstrate genetic anticipation, occurring at an earlier age with more severe manifestations in the affected progeny. Telomere lengths can be assessed in peripheral blood granulocytes and lymphocytes using a sensitive technique called flow cytometry-fluorescence in situ hybridization, and mutational analysis can be performed using next-generation sequencing assays. In approximately 40% of patients with shortened telomere lengths, gene mutations cannot be identified due to the fact that all STS-associated genes have not yet been defined or due to alternative mechanisms of telomere shortening. Danazol, an anabolic steroid, has been associated with hematologic responses in patients with STSs and associated bone marrow failure; however, its reported ability to increase telomerase activity and reduce telomere attrition needs further elucidation. Organ transplant is reserved for patients with end-organ failure and is associated with substantial morbidity and mortality. Herein, we summarize the clinical and laboratory characteristics of STSs and offer a stepwise approach to diagnose and manage complications in affected patients.

Therapeutic effects of telomerase in mice with pulmonary fibrosis induced by damage to the lungs and short telomeres

Pulmonary fibrosis is a fatal lung disease characterized by fibrotic foci and inflammatory infiltrates. Short telomeres can impair tissue regeneration and are found both in hereditary and sporadic cases. We show here that telomerase expression using AAV9 vectors shows therapeutic effects in a mouse model of pulmonary fibrosis owing to a low-dose bleomycin insult and short telomeres. AAV9 preferentially targets regenerative alveolar type II cells (ATII). AAV9-Tert-treated mice show improved lung function and lower inflammation and fibrosis at 1–3 weeks after viral treatment, and improvement or disappearance of the fibrosis at 8 weeks after treatment. AAV9-Tert treatment leads to longer telomeres and increased proliferation of ATII cells, as well as lower DNA damage, apoptosis, and senescence. Transcriptome analysis of ATII cells confirms downregulation of fibrosis and inflammation pathways. We provide a proof-of-principle that telomerase activation may represent an effective treatment for pulmonary fibrosis provoked or associated with short telomeres.

Idiopathic pulmonary fibrosis (or IPF for short) is a rare disease that scars the lungs. The condition gets worse over time, making it harder and harder to breathe, and eventually leading to death. Patients typically only survive for a few years after being diagnosed with IPF. This is because, as yet, there is no cure; the available treatments only act to lessen the symptoms.

Several risk factors have linked to the development of IPF, among them, the presence of short telomeres. Like the plastic tips on shoelaces, telomeres are protective structures at the ends of chromosomes. Telomeres shorten with age, and when they become too short the cell stops dividing and often dies in a process known as apoptosis. IPF can develop when the telomeres in the cells that repair everyday wear and tear in the lungs (known as ATII cells) become too short. This means that the damage goes unrepaired, triggering an immune reaction and uncontrolled scarring.

Telomerase is an enzyme that can lengthen short telomeres, and Povedano, Martínez et al. set out to develop a new treatment approach that would use this enzyme to correct the short telomeres, and cure the scarring seen in IPF. Gene therapy was used to introduce the gene for telomerase into mice that had scarring in their lungs due to short telomeres.

Povedano, Martínez et al. found that, when injected into the mice, the telomerase gene therapy was able to reach ATII cells and could help to heal the lungs. At the level of individual cells, mice treated with telomerase had longer telomeres, meaning that more of their ATII cells stayed alive and kept dividing to regenerate the lung tissue. Consistent with previous studies, the telomerase gene therapy caused no negative side effects in the mice; for example, there was no increased risk of cancer.

These findings may possibly lead to new treatments for those patients suffering from IPF associated with short telomeres. Developing this approach into a clinical trial could in the future benefit many IPF patients who currently have very limited treatment options.

Telomerase and the Genetics of Emphysema Susceptibility. Implications for Pathogenesis Paradigms and Patient Care

In the past five decades, alpha-1 antitrypsin deficiency has been the only known genetic cause of emphysema, yet it explains the genetics in only 1-2% of severe cases. Recently, mutations in telomerase genes were found to induce susceptibility to young-onset, severe, and familial emphysema at a frequency comparable to that of alpha-1 antitrypsin deficiency. Telomerase mutation carriers with emphysema report a family history of idiopathic pulmonary fibrosis, and both lung phenotypes show autosomal dominant inheritance within families. The data so far point to a strong gene-environment interaction that determines the lung disease type. In never-smokers, pulmonary fibrosis predominates, while smokers, especially females, are at risk for developing emphysema alone or in combination with pulmonary fibrosis. The telomere-mediated emphysema phenotype appears to have clinically recognizable features that are distinct from alpha-1 antitrypsin deficiency, and patients are prone to developing short telomere syndrome comorbidities that influence clinical outcomes. In animal models, telomere dysfunction causes alveolar epithelial stem cell senescence, which is sufficient to drive lung remodeling and recruit inflammation. Here, we review the implications of these discoveries for understanding emphysema biology as well as for patient care.

Alpha-1 Antitrypsin Investigations Using Animal Models of Emphysema

Animal models of disease help accelerate the translation of basic science discoveries to the bedside, because they permit experimental interrogation of mechanisms at relatively high throughput, while accounting for the complexity of an intact organism. From the groundbreaking observation of emphysema-like alveolar destruction after direct instillation of elastase in the lungs to the more clinically relevant model of airspace enlargement induced by chronic exposure to cigarette smoke, animal models have advanced our understanding of alpha-1 antitrypsin (AAT) function. Experimental in vivo models that, at least in part, replicate clinical human phenotypes facilitate the translation of mechanistic findings into individuals with chronic obstructive pulmonary disease and with AAT deficiency. In addition, unexpected findings of alveolar enlargement in various transgenic mice have led to novel hypotheses of emphysema development. Previous challenges in manipulating the AAT genes in mice can now be overcome with new transgenic approaches that will likely advance our understanding of functions of this essential, lung-protective serine protease inhibitor (serpin).

Dysfunctional telomeres and hematological disorders

Telomere biology disorders, which are characterized by telomerase activity haploinsufficiency and accelerated telomere shortening, most commonly manifest as degenerative diseases. Tissues with high rates of cell turnover, such as those in the hematopoietic system, are particularly vulnerable to defects in telomere maintenance genes that eventually culminate in bone marrow (BM) failure syndromes, in which the BM cannot produce sufficient new blood cells. Here, we review how telomere defects induce degenerative phenotypes across multiple organs, with particular focus on how they impact the hematopoietic stem and progenitor compartment and affect hematopoietic stem cell (HSC) self-renewal and differentiation. We also discuss how both the increased risk of myelodysplastic syndromes and other hematological malignancies that is associated with telomere disorders and the discovery of cancer-associated somatic mutations in the shelterin components challenge the conventional interpretation that telomere defects are cancer-protective rather than cancer-promoting.

Loss-of-function mutations in the RNA biogenesis factor NAF1 predispose to pulmonary fibrosis-emphysema

Chronic obstructive pulmonary disease and pulmonary fibrosis have been hypothesized to represent premature aging phenotypes. At times, they cluster in families, but the genetic basis is not understood. We identified rare, frameshift mutations in the gene for nuclear assembly factor 1, NAF1, a box H/ACA RNA biogenesis factor, in pulmonary fibrosis-emphysema patients. The mutations segregated with short telomere length, low telomerase RNA levels, and extrapulmonary manifestations including myelodysplastic syndrome and liver disease. A truncated NAF1 was detected in cells derived from patients, and, in cells in which the frameshift mutation was introduced by genome editing, telomerase RNA levels were reduced. The mutant NAF1 lacked a conserved carboxyl-terminal motif, which we show is required for nuclear localization. To understand the disease mechanism, we used CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR-associated protein-9 nuclease) to generate Naf1(+/-) mice and found that they had half the levels of telomerase RNA. Other box H/ACA RNA levels were also decreased, but rRNA pseudouridylation, which is guided by snoRNAs, was intact. Moreover, first-generation Naf1(+/-) mice showed no evidence of ribosomal pathology. Our data indicate that disease in NAF1 mutation carriers is telomere-mediated; they show that NAF1 haploinsufficiency selectively disturbs telomere length homeostasis by decreasing the levels of telomerase RNA while sparing rRNA pseudouridylation.

Current Concepts in Pathogenesis, Diagnosis, and Management of Smoking-Related Interstitial Lung Diseases

Tobacco exposure results in various changes to the airways and lung parenchyma. Although emphysema represents the more common injury pattern, in some individuals, cigarette smoke injures alveolar epithelial cells and other lung cells, resulting in diffuse infiltrates and parenchymal fibrosis. Smoking can trigger interstitial injury patterns mediated via recruitment and inappropriate persistence of myeloid and other immune cells, including eosinophils. As our understanding of the role of cigarette smoke constituents in triggering lung injury continues to evolve, so does our recognition of the spectrum of smoking-related interstitial lung changes. Although respiratory bronchiolitis-interstitial lung disease, desquamative interstitial pneumonia, pulmonary Langerhans cell histiocytosis, and acute eosinophilic pneumonia have a well-established association with tobacco use, its role and impact on idiopathic pulmonary fibrosis, combined pulmonary fibrosis and emphysema, and connective tissue disease-related interstitial lung diseases is still ambiguous. Smoking-related interstitial fibrosis is a relatively newly appreciated entity with distinct histopathologic features but with unclear clinical ramifications. Increased implementation of lung cancer screening programs and utilization of CT scans in thoracic imaging have also resulted in increased identification of "incidental" or "subclinical" interstitial lung changes in smokers, the ensuing impact of which remains to be studied.

Deregulated angiogenesis in chronic lung diseases: a possible role for lung mesenchymal progenitor cells (2017 Grover Conference Series)

Chronic lung disease (CLD), including pulmonary fibrosis (PF) and chronic obstructive pulmonary disease (COPD), is the fourth leading cause of mortality worldwide. Both are debilitating pathologies that impede overall tissue function. A common co-morbidity in CLD is vasculopathy, characterized by deregulated angiogenesis, remodeling, and loss of microvessels. This substantially worsens prognosis and limits survival, with most current therapeutic strategies being largely palliative. The relevance of angiogenesis, both capillary and lymph, to the pathophysiology of CLD has not been resolved as conflicting evidence depicts angiogenesis as both reparative or pathologic. Therefore, we must begin to understand and model the underlying pathobiology of pulmonary vascular deregulation, alone and in response to injury induced disease, to define cell interactions necessary to maintain normal function and promote repair. Capillary and lymphangiogenesis are deregulated in both PF and COPD, although the mechanisms by which they co-regulate and underlie early pathogenesis of disease are unknown. The cell-specific mechanisms that regulate lung vascular homeostasis, repair, and remodeling represent a significant gap in knowledge, which presents an opportunity to develop targeted therapies. We have shown that that ABCG2^pos multipotent adult mesenchymal stem or progenitor cells (MPC) influence the function of the capillary microvasculature as well as lymphangiogenesis. A balance of both is required for normal tissue homeostasis and repair. Our current models suggest that when lymph and capillary angiogenesis are out of balance, the non-equivalence appears to support the progression of disease and tissue remodeling. The angiogenic regulatory mechanisms underlying CLD likely impact other interstitial lung diseases, tuberous sclerosis, and lymphangioleiomyomatosis.

The Intersection of Aging Biology and the Pathobiology of Lung Diseases: A Joint NHLBI/NIA Workshop

Death from chronic lung disease is increasing and chronic obstructive pulmonary disease has become the third leading cause of death in the United States in the past decade. Both chronic and acute lung diseases disproportionately affect elderly individuals, making it likely that these diseases will become more frequent and severe as the worldwide population ages. Chronic lung diseases are associated with substantial morbidity, frequently resulting in exercise limiting dyspnea, immobilization, and isolation. Therefore, effective strategies to prevent or treat lung disease are likely to increase healthspan as well as life span. This review summarizes the findings of a joint workshop sponsored by the NIA and NHLBI that brought together investigators focused on aging and lung biology. These investigators encouraged the use of genetic systems and aged animals in the study of lung disease and the development of integrative systems-based platforms that can dynamically incorporate data sets that describe the genomics, transcriptomics, epigenomics, metabolomics, and proteomics of the aging lung in health and disease. Further research was recommended to integrate benchmark biological hallmarks of aging in the lung with the pathobiology of acute and chronic lung diseases with divergent pathologies for which advanced age is the most important risk factor.

Genetics in Idiopathic Pulmonary Fibrosis Pathogenesis, Prognosis, and Treatment

Idiopathic pulmonary fibrosis (IPF), the most common form of idiopathic interstitial pneumonia (IIP), is characterized by irreversible scarring of the lung parenchyma and progressive decline in lung function leading to eventual respiratory failure. The prognosis of IPF is poor with a median survival of 3–5 years after diagnosis and no curative medical therapies. Although the pathogenesis of IPF is not well understood, there is a growing body of evidence that genetic factors contribute to disease risk. Recent studies have identified common and rare genetic variants associated with both sporadic and familial forms of pulmonary fibrosis, with at least one-third of the risk for developing fibrotic IIP explained by common genetic variants. The IPF-associated genetic loci discovered to date are implicated in diverse biological processes, including alveolar stability, host defense, cell–cell barrier function, and cell senescence. In addition, some common variants have also been associated with distinct clinical phenotypes. Better understanding of how genetic variation plays a role in disease risk and phenotype could identify potential therapeutic targets and inform clinical decision-making. In addition, clinical studies should be designed controlling for the genetic backgrounds of subjects, since clinical outcomes and therapeutic responses may differ by genotype. Further understanding of these differences will allow the development of personalized approaches to the IPF management.

Early pregnancy intrauterine fetal exposure to maternal smoking and impact on fetal telomere length

BACKGROUND

Reduced telomere length, or its accelerated attrition, has been implicated in aging, mortality, and several human diseases, including respiratory diseases. Age dependent manifestation of telomere-mediated disease during life span indicates the role of developmental stage in these diseases and highlights the importance of fetal developmental process in utero and at earlier life stages. Environmental determinants during developmental and later stages of life could affect telomere length. Smoke exposure as one of these significant determinants have been investigated in association with telomere length in neonates at time of delivery, children and adults.

OBJECTIVE

We sought to investigate whether intrauterine fetal exposure to tobacco smoking characterized by placenta cotinine levels during early weeks of pregnancy might be associated with shorter relative telomere length (T/S ratio) as compared to fetuses without exposure to tobacco smoking.

STUDY DESIGN

207 Human placenta and epithelial lung samples were used for both fetal lung telomere length assessment and measurement of placental cotinine levels. Tissues were obtained from two NICHD-supported tissue retrieval programs with registries for elective abortions, the University of Washington Center for Birth Defects Research (Seattle, WA) and the University of Maryland Brain and Tissue Bank for Developmental Disorders (Baltimore, MD). Cotinine levels (ng/g total placental tissue) were determined in whole cell extracts prepared from human placenta samples to characterize and confirm the cotinine exposure status associated with maternal smoking. Relative telomere length (T/S ratio) in genomic DNA extracted from fetal lung tissue was measured by use of quantitative real-time polymerase chain reaction. Multivariable linear regression was used to investigate the relationship between fetal Telomere-to-Single Copy (T/S) ratio and tobacco exposure.

RESULTS

The estimated post-conception ages for included samples in the study ranged from 54 to 137days (7-19 weeks of gestation); 47.37% of fetal samples had female sex. Of the samples included in the analysis 96 and 111 fetal samples with and without intrauterine tobacco smoking exposure were distinguished. While T/S ratio was not different between those with and without smoking exposure (1.24±0.41 and 1.27±0.48, respectively; P=0.70), a significant effect modification of post-conception age on the relationship of intrauterine smoke exposure on fetal T/S ratio was observed (adjusted coefficient=-0.008, 95% CI: -0.016, -0.0004). The smoke exposure status was associated with T/S ratio after 93-day post conception (adjusted coefficient=-0.29, 95% CI: -0.53, -0.052).

CONCLUSIONS

Our results demonstrate a significant association of smoke exposure in utero at early pregnancy with shortened fetal relative telomere length in the developing lung and suggest that the detrimental effect of smoking exposure on future disease sequelae may start at the early stages of pregnancy.

Chronic obstructive pulmonary disease with mild airflow limitation: current knowledge and proposal for future research - a consensus document from six scientific societies

Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality and morbidity worldwide, with high and growing prevalence. Its underdiagnosis and hence under-treatment is a general feature across all countries. This is particularly true for the mild or early stages of the disease, when symptoms do not yet interfere with daily living activities and both patients and doctors are likely to underestimate the presence of the disease. A diagnosis of COPD requires spirometry in subjects with a history of exposure to known risk factors and symptoms. Postbronchodilator forced expiratory volume in 1 second (FEV₁)/forced vital capacity <0.7 or less than the lower limit of normal confirms the presence of airflow limitation, the severity of which can be measured by FEV₁% predicted: stage 1 defines COPD with mild airflow limitation, which means postbronchodilator FEV₁ ≥80% predicted. In recent years, an elegant series of studies has shown that "exclusive reliance on spirometry, in patients with mild airflow limitation, may result in underestimation of clinically important physiologic impairment". In fact, exercise tolerance, diffusing capacity, and gas exchange can be impaired in subjects at a mild stage of airflow limitation. Furthermore, growing evidence indicates that smokers without overt abnormal spirometry have respiratory symptoms and undergo therapy. This is an essential issue in COPD. In fact, on one hand, airflow limitation, even mild, can unduly limit the patient's physical activity, with deleterious consequences on quality of life and even survival; on the other hand, particularly in younger subjects, mild airflow limitation might coincide with the early stage of the disease. Therefore, we thought that it was worthwhile to analyze further and discuss this stage of "mild COPD". To this end, representatives of scientific societies from five European countries have met and developed this document to stimulate the attention of the scientific community on COPD with "mild" airflow limitation. The aim of this document is to highlight some key features of this important concept and help the practicing physician to understand better what is behind "mild" COPD. Future research should address two major issues: first, whether mild airflow limitation represents an early stage of COPD and what the mechanisms underlying the evolution to more severe stages of the disease are; and second, not far removed from the first, whether regular treatment should be considered for COPD patients with mild airflow limitation, either to prevent progression of the disease or to encourage and improve physical activity or both.

Germline Mutations in DNA Repair Genes in Lung Adenocarcinoma

INTRODUCTION

Although lung cancer is generally thought to be environmentally provoked, anecdotal familial clustering has been reported, suggesting that there may be genetic susceptibility factors. We systematically tested whether germline mutations in eight candidate genes may be risk factors for lung adenocarcinoma.

METHODS

We studied lung adenocarcinoma cases for which germline sequence data had been generated as part of The Cancer Genome Atlas project but had not been previously analyzed. We selected eight genes, ATM serine/threonine kinase gene (ATM), BRCA2, DNA repair associated gene (BRCA2), checkpoint kinase 2 gene (CHEK2), EGFR, parkin RBR E3 ubiquitin protein ligase gene (PARK2), telomerase reverse transcriptase gene (TERT), tumor protein p53 gene (TP53), and Yes associated protein 1 gene (YAP1), on the basis of prior anecdotal association with lung cancer or genome-wide association studies.

RESULTS

Among 555 lung adenocarcinoma cases, we detected 14 pathogenic mutations in five genes; they occurred at a frequency of 2.5% and represented an OR of 66 (95% confidence interval: 33-125, p < 0.0001 [chi-square test]). The mutations fell most commonly in ATM (50%), followed by TP53, BRCA2, EGFR, and PARK2. Most (86%) of these variants had been reported in other familial cancer syndromes. Another 12 cases (2%) carried ultrarare variants that were predicted to be deleterious by three protein prediction programs; these most frequently involved ATM and BRCA2.

CONCLUSIONS

A subset of patients with lung adenocarcinoma, at least 2.5% to 4.5%, carry germline variants that have been linked to cancer risk in Mendelian syndromes. The genes fall most frequently in DNA repair pathways. Our data indicate that patients with lung adenocarcinoma, similar to other solid tumors, include a subset of patients with inherited susceptibility.

Lung Diseases of the Elderly: Cellular Mechanisms

Natural lung aging is characterized by molecular and cellular changes in multiple lung cell populations. These changes include shorter telomeres, increased expression of cellular senescence markers, increased DNA damage, oxidative stress, apoptosis, and stem cell exhaustion. Aging, combined with the loss of protective repair processes, correlates with the development and incidence of chronic respiratory diseases, including idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease. Ultimately, it is the interplay of age-related changes in biology and the subsequent responses to environmental exposures that largely define the physiology and clinical course of the aging lung.

Impaired calcium signaling in muscle fibers from intercostal and foot skeletal muscle in a cigarette smoke-induced mouse model of COPD

INTRODUCTION

Respiratory and locomotor skeletal muscle dysfunction are common findings in chronic obstructive pulmonary disease (COPD); however, the mechanisms that cause muscle impairment in COPD are unclear. Because Ca2+ signaling in excitation-contraction (E-C) coupling is important for muscle activity, we hypothesized that Ca2+ dysregulation could contribute to muscle dysfunction in COPD.

METHODS

Intercostal and flexor digitorum brevis muscles from control and cigarette smoke-exposed mice were investigated. We used single cell Ca2+ imaging and Western blot assays to assess Ca2+ signals and E-C coupling proteins.

RESULTS

We found impaired Ca2+ signals in muscle fibers from both muscle types, without significant changes in releasable Ca2+ or in the expression levels of E-C coupling proteins.

CONCLUSIONS

Ca2+ dysregulation may contribute or accompany respiratory and locomotor muscle dysfunction in COPD. These findings are of significance to the understanding of the pathophysiological course of COPD in respiratory and locomotor muscles. Muscle Nerve 56: 282-291, 2017.

Smoking, telomere length and lung function decline: a longitudinal population-based study

Telomere shortening is associated with COPD and impaired lung function in cross-sectional studies, but there is no longitudinal study. We used data from 448 participants recruited as part of the French follow-up of the European Community Respiratory Health Survey. We found no relationship between telomere length at baseline and FEV₁ decline after 11 years of follow-up. However, heavy smoking was associated with an accelerated FEV₁ decline in individuals with short telomeres, but not in subjects with longer telomeres (p for interaction p=0.08). Our findings suggest that short telomere length in peripheral leucocytes might be a marker for increased susceptibility to the effect of smoking.

Severe pulmonary hypertension due to combined pulmonary fibrosis and emphysema: another cause of death among smokers

In 2005, the combined pulmonary fibrosis and emphysema (CPFE) was first defined as a distinct entity, which comprised centrilobular or paraseptal emphysema in the upper pulmonary lobes, and fibrosis in the lower lobes accompanied by reduced diffused capacity of the lungs for carbon monoxide (DLCO). Recently, the fibrosis associated with the connective tissue disease was also included in the diagnosis of CPFE, although the exposure to tobacco, coal, welding, agrochemical compounds, and tire manufacturing are the most frequent causative agents. This entity characteristically presents reduced DLCO with preserved lung volumes and severe pulmonary hypertension, which is not observed in emphysema and fibrosis alone. We present the case of a 63-year-old woman with a history of heavy tobacco smoking abuse, who developed progressive dyspnea, severe pulmonary hypertension, and cor pulmonale over a 2-year period. She attended the emergency facility several times complaining of worsening dyspnea that was treated as decompensate chronic obstructive pulmonary disease (COPD). The imaging examination showed paraseptal emphysema in the upper pulmonary lobes and fibrosis in the middle and lower lobes. The echo Doppler cardiogram revealed the dilation of the right cardiac chambers and pulmonary hypertension, which was confirmed by pulmonary trunk artery pressure measurement by catheterization. During this period, she was progressively restricted to the minimal activities of daily life and dependent on caregivers. She was brought to the hospital neurologically obtunded, presenting anasarca, and respiratory failure, which led her to death. The autopsy showed signs of pulmonary hypertension and findings of fibrosis and emphysema in the histological examination of the lungs. The authors highlight the importance of the recognition of this entity in case of COPD associated with severe pulmonary hypertension of unknown cause.

Shelterin Telomere Protection Protein 1 Reduction Causes Telomere Attrition and Cellular Senescence via Sirtuin 1 Deacetylase in Chronic Obstructive Pulmonary Disease

Lung cellular senescence and inflammatory response are the key events in the pathogenesis of chronic obstructive pulmonary disease (COPD) when cigarette smoke (CS) is the main etiological factor. Telomere dysfunction is induced by either critical shortening or disruption of the shelterin complex, leading to cellular senescence. However, it remains unknown whether disruption of the shelterin complex is responsible for CS-induced lung cellular senescence. Here we show that telomere protection protein 1 (TPP1) levels are reduced on telomeres in lungs from mice with emphysema, as well as in lungs from smokers and from patients with COPD. This is associated with persistent telomeric DNA damage, leading to cellular senescence. CS disrupts the interaction of TPP1 with the Sirtuin 1 (Sirt1) complex, leading to increased TPP1 acetylation and degradation. Lung fibroblasts deficient in Sirt1 or treated with a selective Sirt1 inhibitor exhibit increased cellular senescence and decreased TPP1 levels, whereas Sirt1 overexpression and pharmacological activation protect against CS-induced TPP1 reduction and telomeric DNA damage. Our findings support an essential role of TPP1 in protecting CS-induced telomeric DNA damage and cellular senescence, and therefore provide a rationale for a potential therapy for COPD, on the basis of the shelterin complex, in attenuating cellular senescence.

RTP801 Amplifies Nicotinamide Adenine Dinucleotide Phosphate Oxidase-4-Dependent Oxidative Stress Induced by Cigarette Smoke

Tobacco smoke (TS) causes chronic obstructive pulmonary disease, including chronic bronchitis, emphysema, and asthma. Rtp801, an inhibitor of mechanistic target of rapamycin, is induced by oxidative stress triggered by TS. Its up-regulation drives lung susceptibility to TS injury by enhancing inflammation and alveolar destruction. We postulated that Rtp801 is not only increased by reactive oxygen species (ROS) in TS but also instrumental in creating a feedforward process leading to amplification of endogenous ROS generation. We used cigarette smoke extract (CSE) to model the effect of TS in wild-type (Wt) and knockout (KO-Rtp801) mouse lung fibroblasts (MLF). The production of superoxide anion in KO-Rtp801 MLF was lower than that in Rtp801 Wt cells after CSE treatment, and it was inhibited in Wt MLF by silencing nicotinamide adenine dinucleotide phosphate oxidase-4 (Nox4) expression with small interfering Nox4 RNA. We observed a cytoplasmic location of ROS formation by real-time redox changes using reduction-oxidation-sensitive green fluorescent protein profluorescent probes. Both the superoxide production and the increase in the cytoplasmic redox were inhibited by apocynin. Reduction in the activity of Sod and decreases in the expression of Sod2 and Gpx1 genes were associated with Rtp801 CSE induction. The ROS produced by Nox4 in conjunction with the decrease in cellular antioxidant enzymatic defenses may account for the observed cytoplasmic redox changes and cellular damage caused by TS.

Management of suspected monogenic lung fibrosis in a specialised centre

At least 10% of patients with interstitial lung disease present monogenic lung fibrosis suspected on familial aggregation of pulmonary fibrosis, specific syndromes or early age of diagnosis. Approximately 25% of families have an identified mutation in genes mostly involved in telomere homeostasis, and more rarely in surfactant homeostasis.

Beyond pathophysiological knowledge, detection of these mutations has practical consequence for patients. For instance, mutations involved in telomere homeostasis are associated with haematological complications after lung transplantation and may require adapted immunosuppression. Moreover, relatives may benefit from a clinical and genetic evaluation that should be specifically managed.

The field of genetics of pulmonary fibrosis has made great progress in the last 10 years, raising specific problems that should be addressed by a specialised team.

Understanding COPD-overlap syndromes

INTRODUCTION

Chronic obstructive pulmonary disease accounts for a large burden of lung disease. It can 'overlap' with other respiratory diseases including bronchiectasis, fibrosis and obstructive sleep apnea (OSA). While COPD alone confers morbidity and mortality, common features with contrasting clinical outcomes can occur in COPD 'overlap syndromes'. Areas covered: Given the large degree of heterogeneity in COPD, individual variation to treatment is adopted based on its observed phenotype, which in turn overlaps with features of other respiratory disease states such as asthma. This is coined asthma-COPD overlap syndrome ('ACOS'). Other examples of such overlapping clinical states include bronchiectasis-COPD ('BCOS'), fibrosis-COPD ('FCOS') and OSA-COPD ('OCOS'). The objective of this review is to highlight similarities and differences between the COPD-overlap syndromes in terms of risk factors, pathophysiology, diagnosis and potential treatment differences. Expert commentary: As a consequence of COPD overlap syndromes, a transition from the traditional 'one size fits all' treatment approach is necessary. Greater treatment stratification according to clinical phenotype using a precision medicine approach is now required. In this light, it is important to recognize and differentiate COPD overlap syndromes as distinct disease states compared to individual diseases such as asthma, COPD, fibrosis or bronchiectasis.

Telomere-driven diseases and telomere-targeting therapies

Martínez and Blasco review the molecular mechanisms underlying diseases associated with telomere dysfunction, including telomeropathies, age-related disorders, and cancer. Current and future therapeutic strategies to treat and prevent these diseases, including preclinical development of telomere-targeted therapies using mouse models, are discussed.

Telomeres, the protective ends of linear chromosomes, shorten throughout an individual’s lifetime. Telomere shortening is proposed to be a primary molecular cause of aging. Short telomeres block the proliferative capacity of stem cells, affecting their potential to regenerate tissues, and trigger the development of age-associated diseases. Mutations in telomere maintenance genes are associated with pathologies referred to as telomere syndromes, including Hoyeraal-Hreidarsson syndrome, dyskeratosis congenita, pulmonary fibrosis, aplastic anemia, and liver fibrosis. Telomere shortening induces chromosomal instability that, in the absence of functional tumor suppressor genes, can contribute to tumorigenesis. In addition, mutations in telomere length maintenance genes and in shelterin components, the protein complex that protects telomeres, have been found to be associated with different types of cancer. These observations have encouraged the development of therapeutic strategies to treat and prevent telomere-associated diseases, namely aging-related diseases, including cancer. Here we review the molecular mechanisms underlying telomere-driven diseases and highlight recent advances in the preclinical development of telomere-targeted therapies using mouse models.

Senescence in COPD and Its Comorbidities

Chronic obstructive pulmonary disease (COPD) is regarded as a disease of accelerated lung aging. This affliction shows all of the hallmarks of aging, including telomere shortening, cellular senescence, activation of PI3 kinase-mTOR signaling, impaired autophagy, mitochondrial dysfunction, stem cell exhaustion, epigenetic changes, abnormal microRNA profiles, immunosenescence, and a low-grade chronic inflammation (inflammaging). Many of these pathways are driven by chronic exogenous and endogenous oxidative stress. There is also a reduction in antiaging molecules, such as sirtuins and Klotho, which further accelerate the aging process. COPD is associated with several comorbidities (multimorbidity), such as cardiovascular and metabolic diseases, that share the same pathways of accelerated aging. Understanding these mechanisms has helped identify several novel therapeutic targets, and several drugs and dietary interventions are now in development to treat multimorbidity.

Inhaled resveratrol treatments slow ageing-related degenerative changes in mouse lung

BACKGROUND

Lung ageing, a significant risk factor for chronic human lung diseases such as COPD and emphysema, is characterised by airspace enlargement and decreasing lung function. Likewise, in prematurely ageing telomerase null (terc-/-) mice, p53 stabilisation within diminishing numbers of alveolar epithelial type 2 cells (AEC2) accompanies reduced lung function. Resveratrol (RSL) is a plant phytoalexin that has previously showed efficacy in enhancing invertebrate longevity and supporting mammalian muscle metabolism when delivered orally. Here, we tested whether inhaled RSL could protect young, terc-/- mice from accelerated ageing of the lung.

METHODS

terc-/- mice aged 2 months inhaled 1 mg/kg RSL that was instilled intratracheally once per month for 3 months. One month after the last inhalation, whole lung function, structure and cellular DNA damage were evaluated and AEC2 survival was assessed by western blotting for survival pathway gene expression.

RESULTS

RSL treatments delayed the loss of lung compliance (p<0.05), maintained lung structure (p<0.001) and blocked parenchymal cell DNA damage as measured by TdT Nick-End Labeling (TUNEL). RSL, a known agonist of deacetylase SIRT1, supported AEC2 survival by stimulating SIRT1 expression, promoting p53 destabilisation and decreasing Bax expression and by maintaining expression levels of Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), activated p-Akt and p-Mdm2 and inactivated Phospho-Phosphatase and tensin homolog (p-PTEN).

CONCLUSIONS

RSL prophylaxis by inhalation is a potential approach for slowing ageing-related deterioration of lung function and structure by maintaining AEC2 integrity.

Telomere Damage Response and Low-Grade Inflammation

Telomeres at the ends of chromosomes safeguard genome integrity and stability in human nucleated cells. However, telomere repeats shed off during cell proliferation and other stress responses. Our recent studies show that telomere attrition induces not only epithelial stem cell senescence but also low-grade inflammation in the lungs. The senescence-associated low-grade inflammation (SALI) is characteristic of alveolar stem cell replicative senescence, increased proinflammatory and anti-inflammatory cytokines, infiltrated immune cells, and spillover effects. To date, the mechanisms underlying SALI remain unclear. Investigations demonstrate that senescent epithelial stem cells with telomere erosion are not the source of secreted cytokines, containing no significant increase in expression of the genes coding for increased cytokines, suggesting an alternative senescence-associated secretory phenotype (A-SASP). Given that telomere loss results in significant alterations in the genomes and accumulations of the cleaved telomeric DNA in the cells and milieu externe, we conclude that telomere position effects (TPEs) on gene expression and damage-associated molecular patterns (DAMPs) in antigen presentation are involved in A-SASP and SALI in response to telomere damage in mammals.

Connective Tissue Growth Factor Promotes Pulmonary Epithelial Cell Senescence and Is Associated with COPD Severity

The purpose of this study was to determine whether expression of connective tissue growth factor (CTGF) protein in chronic obstructive pulmonary disease (COPD) is consistent in humans and animal models of COPD and to investigate the role of this protein in lung epithelial cells. CTGF in lung epithelial cells of ex-smokers with COPD was compared with ex-smokers without COPD by immunofluorescence. A total of twenty C57Bl/6 mice and sixteen non-human primates (NHPs) were exposed to cigarette smoke (CS) for 4 weeks. Ten mice of these CS-exposed mice and eight of the CS-exposed NHPs were infected with H3N2 influenza A virus (IAV), while the remaining ten mice and eight NHPs were mock-infected with vehicle as control. Both mRNA and protein expression of CTGF in lung epithelial cells of mice and NHPs were determined. The effects of CTGF overexpression on cell proliferation, p16 protein, and senescence-associated β-galactosidase (SA-β-gal) activity were examined in cultured human bronchial epithelial cells (HBECs). In humans, CTGF expression increased with increasing COPD severity. We found that protein expression of CTGF was upregulated in lung epithelial cells in both mice and NHPs exposed to CS and infected with IAV compared to those exposed to CS only. When overexpressed in HBECs, CTGF accelerated cellular senescence accompanied by p16 accumulation. Both CTGF and p16 protein expression in lung epithelia are positively associated with the severity of COPD in ex-smokers. These findings show that CTGF is consistently expressed in epithelial cells of COPD lungs. By accelerating lung epithelial senescence, CTGF may block regeneration relative to epithelial cell loss and lead to emphysema.

Telomere attrition and restoration in the normal teleost Oryzias latipes are linked to growth rate and telomerase activity at each life stage

Telomere shortening occurs when cells divide, both in vitro and in vivo. On the other hand, telomerase is able to maintain telomere length in cells by adding TTAGGG repeats to the ends of telomeres. However, the interrelationships existing among telomere length, telomerase activity and growth in vertebrates remain to be clarified. In the present study we measured telomere length (terminal restriction fragment length), telomerase activity and body growth of Oryzias latipes from the embryo stage until senescence. During the rapid growth stage (age 0–7 months), telomeres shortened in parallel with decreasing telomerase activity. Then, during adolescence (age 7 months – 1 year), telomeres lengthened quickly as growth slowed and telomerase activity increased. In the adult stage (age 1–4 years) characterized by little growth, telomerase activity decreased gradually and telomeres shortened. Our data indicate that telomere attrition and restoration are linked to growth and telomerase activity, and suggest that critical loss of telomere homeostasis is associated with mortality in this animal.