Somatic DNA alterations in lung epithelial barrier cells in COPD patients

Genomic instability and the link to infertility: A focus on microsatellites and genomic instability syndromes

Infertility is associated to multiple types of different genomic instabilities and is a genetic feature of genomic instability syndromes. While the mismatch repair machinery contributes to the maintenance of genome integrity, surprisingly its potential role in infertility is overlooked. Defects in mismatch repair mechanisms contribute to microsatellite instability and genomic instability syndromes, due to the inability to repair newly replicated DNA. This article reviews the literature to date to elucidate the contribution of microsatellite instability to genomic instability syndromes and infertility. The key findings presented reveal microsatellite instability is poorly researched in genomic instability syndromes and infertility.

The ageing lung under stress

Healthy ageing of the lung involves structural changes but also numerous cell-intrinsic and cell-extrinsic alterations. Among them are the age-related decline in central cellular quality control mechanisms such as redox and protein homeostasis. In this review, we would like to provide a conceptual framework of how impaired stress responses in the ageing lung, as exemplified by dysfunctional redox and protein homeostasis, may contribute to onset and progression of COPD and idiopathic pulmonary fibrosis (IPF). We propose that age-related imbalanced redox and protein homeostasis acts, amongst others (e.g.cellular senescence), as a “first hit” that challenges the adaptive stress-response pathways of the cell, increases the level of oxidative stress and renders the lung susceptible to subsequent injury and disease. In both COPD and IPF, additional environmental insults such as smoking, air pollution and/or infections then serve as “second hits” which contribute to persistently elevated oxidative stress that overwhelms the already weakened adaptive defence and repair pathways in the elderly towards non-adaptive, irremediable stress thereby promoting development and progression of respiratory diseases. COPD and IPF are thus distinct horns of the same devil, “lung ageing”.

Shared mechanisms of multimorbidity in COPD, atherosclerosis and type-2 diabetes: the neutrophil as a potential inflammatory target

Multimorbidity is increasingly common and current healthcare strategies are not always aligned to treat this complex burden of disease. COPD, type-2 diabetes mellitus (T2D) and cardiovascular disease, especially atherosclerosis, occur more frequently together than expected, even when risk factors such as smoking, obesity, inactivity and poverty are considered. This supports the possibility of unifying mechanisms that contribute to the pathogenesis or progression of each condition.Neutrophilic inflammation is causally associated with COPD, and increasingly recognised in the pathogenesis of atherosclerosis and T2D, potentially forming an aetiological link between conditions. This link might reflect an overspill of inflammation from one affected organ into the systemic circulation, exposing all organs to an increased milieu of proinflammatory cytokines. Additionally, increasing evidence supports the involvement of other processes in chronic disease pathogenesis, such as cellular senescence or changes in cellular phenotypes.This review explores the current scientific evidence for inflammation, cellular ageing and cellular processes, such as reactive oxygen species production and phenotypic changes in the pathogenesis of COPD, T2D and atherosclerosis; highlighting common mechanisms shared across these diseases. We identify emerging therapeutic approaches that target these areas, but also where more work is still required to improve our understanding of the underlying cellular biology in a multimorbid disease setting.

Neutralization of both IL-1α/IL-1β plays a major role in suppressing combined cigarette smoke/virus-induced pulmonary inflammation in mice

Smoking is an important risk factor for the development of chronic obstructive pulmonary disease (COPD) and viral infections are believed to be major triggers of exacerbations, which periodically lead to a worsening of symptoms. The pro-inflammatory IL-1 family members IL-1α and IL-1β are increased in COPD patients and might contribute to disease pathology. We investigated whether individual or combined inhibition of these cytokines reduced lung inflammation in cigarette smoke (CS)-exposed and H1N1-infected BALB/c mice. Animals were treated with individual or combined antibodies (Abs) directed against IL-1α, IL-1β or IL-1R1. Cells in BAL fluid and cytokines/chemokines in lung homogenate were determined. The viral load was investigated. Blocking IL-1α had significant suppressive effects on total cells, neutrophils, and macrophages. Furthermore, it reduced KC levels significantly. Blocking of IL-1β did not provide significant activity. In primary human bronchial epithelial air-liquid-interface cell cultures infected with H1N1, IL-1α Abs but not IL-1β Abs reduced levels of TNF-α and IL-6. Concomitant usage of Abs against IL-1α/IL-1β revealed strong effects in vivo and reduced total cells, neutrophils and macrophages. Additionally, levels of KC, IL-6, TNF-α, MCP-1, MIP-1α and MIP-1β were significantly reduced and ICAM-1 and MUC5 A/C mRNA expression was attenuated. The viral load decreased significantly upon combined IL-1α/IL-1β Ab treatment. Blocking the IL-1R1 provided significant effects on total cells, neutrophils and macrophages but was inferior compared to inhibiting both its soluble ligands IL-1α/IL-1β. Our results suggest that combined inhibition of IL-1α/IL-1β might be beneficial to reduce CS/H1N1-induced airway inflammation. Moreover, combined targeting of both IL-1α/IL-1β might be more efficient compared to individual neutralization IL-1α or IL-1β or inhibition of the IL-1R1.

Lack of association between increased mitochondrial DNA4977 deletion and ATP levels of sputum cells from chronic obstructive pulmonary disease patients versus healthy smokers

In this study we looked at smokers with and without chronic obstructive pulmonary disease (COPD) patients in order to evaluate the incidence of 4977 base pair (bp) mtDNA (mtDNA⁴⁹⁷⁷) deletion and mtDNA copy number in sputum cells and in peripheral blood leukocytes (PBLs) in relation to mitochondrial function and oxidative stress status. Twenty-five COPD patients who were current smokers, 22 smokers and 23 healthy nonsmokers (for only PBLs studies) participated in this study. The 4977-bp deletion was detected in all examined samples within 40 cyles of PCR amplification, using a quantitative real time PCR. The frequency of the mtDNA⁴⁹⁷⁷ was significantly higher in the sputum cells of patients with COPD compared to smokers without COPD (p < 0.0001). This difference was not observed in PBLs. Levels of cellular oxidative stress were significantly higher in the sputum cells of subjects with COPD than in the smoker group. However, mtDNA copy number, mitochondrial membrane potential (ΔΨm) and cellular ATP levels in PBLs and sputum cells were not significantly different between the studied groups. The Pearson analysis revealed no correlations between the accumulation of mtDNA⁴⁹⁷⁷, and intracellular ATP content and ΔΨm values of the sputum cells, although there was a positive correlation between the increase in the percentage of deleted mtDNA⁴⁹⁷⁷ and the levels of cellular oxidative stress in COPD patients (r = 0.80, p < 0.0001). Our studies may suggest that the accumulation of mtDNA⁴⁹⁷⁷ in the sputum cells of smokers with COPD does not seem to have an important impact on mitochondrial dysfunction in relation to ATP production and ΔΨm when compared to those of healthy smokers.

Transposable elements and their potential role in complex lung disorder

Transposable elements (TEs) are a class of mobile genetic elements (MGEs) that were long regarded as junk DNA, which make up approximately 45% of the genome. Although most of these elements are rendered inactive by mutations and other gene silencing mechanisms, TEs such as long interspersed nuclear elements (LINEs) are still active and translocate within the genome. During transposition, they may create lesions in the genome, thereby acting as epigenetic modifiers. Approximately 65 disease-causing LINE insertion events have been reported thus far; however, any possible role of TEs in complex disorders is not well established. Chronic obstructive pulmonary disease (COPD) is one such complex disease that is primarily caused by cigarette smoking. Although the exact molecular mechanism underlying COPD remains unclear, oxidative stress is thought to be the main factor in the pathogenesis of COPD. In this review, we explore the potential role of oxidative stress in epigenetic activation of TEs such as LINEs and the subsequent cascade of molecular damage. Recent advancements in sequencing and computation have eased the identification of mobile elements. Therefore, a comparative study on the activity of these elements and markers for genome instability would give more insight on the relationship between MGEs and complex disorder such as COPD.

Differential telomerase expression in idiopathic pulmonary fibrosis and non-small cell lung cancer

Telomerase is a reverse transcriptase ribonucleo-protein (h-TERT) that synthesizes telomeric repeats using its RNA component (h-TERC) as a template. Telomerase dysfunction has been associated with both fibrogenesis and carcinogenesis. In this study, we aimed to evaluate the telomerase mRNA expression levels of both subunits (h-TERT and h-TERC) in lung tissue and bronchoalveolar lavage fluid (BALF) from patients with idiopathic pulmonary fibrosis (IPF) and non-small cell lung cancer (NSCLC), since there are indications of common pathogenetic pathways in these diseases. We prospectively examined lung tissue samples from 29 patients with IPF, 10 patients with NSCLC and 21 controls. Furthermore, we examined BALF samples from 31 patients with NSCLC, 23 patients with IPF and 12 control subjects. The mRNA expression for both h-TERT and h-TERC was measured by real-time RT-PCR. In the lung tissue samples, both h-TERT and h-TERC mRNA expression levels varied among the 3 groups (p=0.036 and p=0.002, respectively). h-TERT mRNA levels in the patients with IPF were lower compared with those in the controls (p=0.009) and patients with NSCLC (p=0.004). h-TERC mRNA levels in the patients with IPF were lower compared with those in the controls (p=0.0005) and patients with NSCLC (p=0.0004). In the BALF samples, h-TERT mRNA expression levels varied among the groups (p=0.012). More specifically, h-TERT mRNA levels in the patients with IPF were higher compared with those in the controls (p=0.03) and patients with NSCLC (p=0.007). The attenuation of telomerase gene expression in IPF in comparison to lung cancer suggests a differential role of this regulatory gene in fibrogenesis and carcinogenesis. Further functional studies are required in order to further elucidate the role of telomerase in these devastating diseases.

DNA damage due to oxidative stress in Chronic Obstructive Pulmonary Disease (COPD)

According to the American Thorasic Society (ATS)/European Respiratory Society (ERS) Statement, chronic obstructive pulmonary disease (COPD) is defined as a preventable and treatable disease with a strong genetic component, characterized by airflow limitation that is not fully reversible, but is usually progressive and associated with an enhanced inflammatory response of the lung to noxious particles or gases. The main features of COPD are chronic inflammation of the airways and progressive destruction of lung parenchyma and alveolar structure. The pathogenesis of COPD is complex due to the interactions of several mechanisms, such as inflammation, proteolytic/antiproteolytic imbalance, oxidative stress, DNA damage, apoptosis, enhanced senescence of the structural cells and defective repair processes. This review focuses on the effects of oxidative DNA damage and the consequent immune responses in COPD. In susceptible individuals, cigarette smoke injures the airway epithelium generating the release of endogenous intracellular molecules or danger-associated molecular patterns from stressed or dying cells. These signals are captured by antigen presenting cells and are transferred to the lymphoid tissue, generating an adaptive immune response and enhancing chronic inflammation.

Oxidative DNA damage and somatic mutations: a link to the molecular pathogenesis of chronic inflammatory airway diseases

BACKGROUND

Acquired somatic mutations induced by oxidative stress may contribute to the molecular pathogenesis of chronic inflammatory airway diseases. The objective of this study was to assess the intensity of oxidative DNA damage and the presence of microsatellite DNA instability (MSI), a marker of acquired somatic mutations, in patients with COPD, patients with noncystic fibrosis bronchiectasis, and control subjects.

METHODS

Induced sputum and peripheral blood from 97 subjects were analyzed; 36 patients with COPD, 36 patients with bronchiectasis, 15 smokers without COPD, and 10 healthy control subjects. DNA was extracted and analyzed for MSI. 8-hydroxy-2'-deoxyguanosine (8-OHdG), a specific marker of oxidant-induced DNA damage, was measured in serum and sputum supernatants.

RESULTS

None of the patients with bronchiectasis or control subjects (non-COPD smokers, healthy subjects) exhibited any genetic alteration. In contrast, MSI was found in 38% of COPD specimens. Sputum 8-OHdG was statistically significantly increased in COPD when compared with subjects with bronchiectasis (P = .0002), smokers without COPD (P = .0056), and healthy subjects (P = .0003). Sputum 8-OHdG in MSI-positive patients with COPD differed significantly from that of MSI-negative patients with COPD (P = .04) and smokers without COPD (P = .008), but was not statistically different (P = .07) among MSI-negative patients with COPD and smokers without COPD. Serum 8-OHdG was significantly increased in MSI-positive compared with MSI-negative patients with COPD (P = .001), but was not statistically significant in smokers without COPD (P = .09). Serum 8-OHdG was increased in smokers without COPD compared with MSI-negative patients with COPD (P = .009).

CONCLUSIONS

There is a clear disparity in COPD regarding oxidant-induced DNA damage and somatic mutations. This may reflect a difference in the oxidative stress per se or a deficient antioxidant and/or repair capacity in the lungs of patients with COPD.