Expression and methylation of mitochondrial transcription factor a in chronic obstructive pulmonary disease patients with lung cancer

Alterations in the molecular control of mitochondrial turnover in COPD lung and airway epithelial cells

Abnormal mitochondria have been observed in bronchial- and alveolar epithelial cells of patients with chronic obstructive pulmonary disease (COPD). However, it is unknown if alterations in the molecular pathways regulating mitochondrial turnover (mitochondrial biogenesis vs mitophagy) are involved. Therefore, in this study, the abundance of key molecules controlling mitochondrial turnover were assessed in peripheral lung tissue from non-COPD patients (n = 6) and COPD patients (n = 11; GOLDII n = 4/11; GOLDIV n = 7/11) and in both undifferentiated and differentiated human primary bronchial epithelial cells (PBEC) from non-COPD patients and COPD patients (n = 4-7 patients/group). We observed significantly decreased transcript levels of key molecules controlling mitochondrial biogenesis (PPARGC1B, PPRC1, PPARD) in peripheral lung tissue from severe COPD patients. Interestingly, mRNA levels of the transcription factor TFAM (mitochondrial biogenesis) and BNIP3L (mitophagy) were increased in these patients. In general, these alterations were not recapitulated in undifferentiated and differentiated PBECs with the exception of decreased PPARGC1B expression in both PBEC models. Although these findings provide valuable insight in these pathways in bronchial epithelial cells and peripheral lung tissue of COPD patients, whether or not these alterations contribute to COPD pathogenesis, underlie changes in mitochondrial function or may represent compensatory mechanisms remains to be established.

The Role of Mitochondrial Quality Control in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity, mortality, and health care use worldwide with heterogeneous pathogenesis. Mitochondria, the powerhouses of cells responsible for oxidative phosphorylation and energy production, play essential roles in intracellular material metabolism, natural immunity, and cell death regulation. Therefore, it is crucial to address the urgent need for fine-tuning the regulation of mitochondrial quality to combat COPD effectively. Mitochondrial quality control (MQC) mainly refers to the selective removal of damaged or aging mitochondria and the generation of new mitochondria, which involves mitochondrial biogenesis, mitochondrial dynamics, mitophagy, etc. Mounting evidence suggests that mitochondrial dysfunction is a crucial contributor to the development and progression of COPD. This article mainly reviews the effects of MQC on COPD as well as their specific regulatory mechanisms. Finally, the therapeutic approaches of COPD via MQC are also illustrated.

Mitochondrial damage-associated molecular patterns in chronic obstructive pulmonary disease: Pathogenetic mechanism and therapeutic target

Chronic obstructive pulmonary disease (COPD) is a common inflammatory airway disease characterized by enhanced inflammation. Recent studies suggest that mitochondrial damage-associated molecular patterns (DAMPs) may play an important role in the regulation of inflammation and are involved in a serial of inflammatory diseases, and they may also be involved in COPD. This review highlights the potential role of mitochondrial DAMPs during COPD pathogenesis and discusses the therapeutic potential of targeting mitochondrial DAMPs and their related signaling pathways and receptors for COPD. Research progress on mitochondrial DAMPs may enhance our understanding of COPD inflammation and provide novel therapeutic targets.

HDAC inhibition regulates oxidative stress in CD4+Thelper cells of chronic obstructive pulmonary disease and non-small cell lung cancer patients via mitochondrial transcription factor a (mtTFA) modulating NF-κB/HIF1α axis

Histone deacetylases (HDACs) play a crucial role in the epigenetic regulation of gene expression by remodelling chromatin. Isoenzymes of the HDAC family exhibit aberrant regulation in a wide variety of cancers as well as several inflammatory lung disorders like chronic obstructive pulmonary disease (COPD). Inhibition of HDACs is a potential therapeutic strategy that could be used to reverse epigenetic modification. Trichostatin A (TSA), a powerful histone deacetylase (HDAC) inhibitor, has anti-cancer effects in numerous cancer types. However, it is not yet apparent how HDAC inhibitors affect human non-small cell lung cancer cells (NSCLC) and COPD. This study aims to investigate TSA's role in restoring mitochondrial dysfunction and its effect on hypoxia and inflammation in CD4+T cells obtained from patients with COPD and lung cancer. As a result of treatment with TSA, there is a reduction in the expression of inflammatory cytokines and a decreased enrichment of transcriptional factors associated with inflammation at VEGFA gene loci. We have seen a substantial decrease in the expression of NF-κB and HIF1α, which are the critical mediators of inflammation and hypoxia, respectively. Following TSA treatment, mtTFA expression was increased, facilitating patients with COPD and NSCLC in the recovery of their dysfunctional mitochondria. Furthermore, we have discovered that TSA treatment in patients with COPD and NSCLC may lead to immunoprotective ness by inducing Th1ness. Our finding gives a new insight into the existing body of knowledge regarding TSA-based therapeutic methods and highlights the necessity of epigenetic therapy for these devastating lung disorders.

Mitochondria-Related TFAM and POLG Gene Variants and Associations with Tumor Characteristics and Patient Survival in Head and Neck Cancer

In 2020, 878,348 newly reported cases and 444,347 deaths related to head and neck cancer were reported. These numbers suggest that there is still a need for molecular biomarkers for the diagnosis and prognosis of the disease. In this study, we aimed to analyze mitochondria-related mitochondrial transcription factor A (TFAM) and DNA polymerase γ (POLG) single-nucleotide polymorphisms (SNPs) in the head and neck cancer patient group and evaluate associations between SNPs, disease characteristics, and patient outcomes. Genotyping was performed using TaqMan probes with Real-Time polymerase chain reaction. We found associations between TFAM gene SNPs rs11006129 and rs3900887 and patient survival status. We found that patients with the TFAM rs11006129 CC genotype and non-carriers of the T allele had longer survival times than those with the CT genotype or T-allele carriers. Additionally, patients with the TFAM rs3900887 A allele tended to have shorter survival times than non-carriers of the A allele. Our findings suggest that variants in the TFAM gene may play an important role in head and neck cancer patient survival and could be considered and further evaluated as prognostic biomarkers. However, due to the limited sample size (n = 115), further studies in larger and more diverse cohorts are needed to confirm these findings.

Effects of the anti-inflammatory drug celecoxib on cell death signaling in human colon cancer

The anti-inflammatory drug celecoxib, the only inhibitor of cyclooxygenase-2 (COX-2) with anticancer activity, is used to treat rheumatoid arthritis and can cause endoplasmic reticulum (ER) stress by inhibiting sarco/ER Ca^{2 +}-ATPase activity in cancer cells. This study aimed to investigate the correlation between celecoxib-induced ER stress and the effects of celecoxib against cell death signaling. Treatment of human colon cancer HCT116 cells with celecoxib reduced their viability and resulted in a loss of mitochondrial membrane potential ([Formula: see text]). Additionally, celecoxib treatment reduced the expression of genes involved in mitochondrial biogenesis and metabolism such as mitochondrial transcription factor A (TFAM) and uncoupling protein 2 (UCP2). Furthermore, celecoxib reduced transmembrane protein 117 (TMEM117), and RNAi-mediated knockdown of TMEM117 reduced TFAM and UCP2 expressions. These results suggest that celecoxib treatment results in the loss of [Formula: see text] by reducing TMEM117 expression and provide insights for the development of novel drugs through TMEM117 expression.

Disruption of the Molecular Regulation of Mitochondrial Metabolism in Airway and Lung Epithelial Cells by Cigarette Smoke: Are Aldehydes the Culprit?

Chronic obstructive pulmonary disease (COPD) is a devastating lung disease for which cigarette smoking is the main risk factor. Acetaldehyde, acrolein, and formaldehyde are short-chain aldehydes known to be formed during pyrolysis and combustion of tobacco and have been linked to respiratory toxicity. Mitochondrial dysfunction is suggested to be mechanistically and causally involved in the pathogenesis of smoking-associated lung diseases such as COPD. Cigarette smoke (CS) has been shown to impair the molecular regulation of mitochondrial metabolism and content in epithelial cells of the airways and lungs. Although it is unknown which specific chemicals present in CS are responsible for this, it has been suggested that aldehydes may be involved. Therefore, it has been proposed by the World Health Organization to regulate aldehydes in commercially-available cigarettes. In this review, we comprehensively describe and discuss the impact of acetaldehyde, acrolein, and formaldehyde on mitochondrial function and content and the molecular pathways controlling this (biogenesis versus mitophagy) in epithelial cells of the airways and lungs. In addition, potential therapeutic applications targeting (aldehyde-induced) mitochondrial dysfunction, as well as regulatory implications, and the necessary required future studies to provide scientific support for this regulation, have been covered in this review.

Involvement of inflammatory cytokines and epigenetic modification of the mtTFA complex in T-helper cells of patients' suffering from non-small cell lung cancer and chronic obstructive pulmonary disease

Dysregulated inflammatory response plays a crucial role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and Non-Small cell lung cancer (NSCLC). Hence, the purpose of this research is to uncover the link between alterations in inflammatory cytokine levels and disease progression in CD4⁺T cells of patients suffering from COPD and lung cancer. We also investigated the epigenetic regulation of mtTFA to delineate the role of oxidative stress-mediated inflammation in Lung cancer and COPD. The RT² Profiler PCR array was used to examine the differential expression pattern of inflammatory genes in CD4⁺ T helper (Th) cells from COPD, NSCLC, and control subjects. Candidate inflammatory gene loci were selected and the enrichment of transcriptional factor and histone modifiers was analysed using ChIP-qPCR. In comparison to control subjects, a set of genes (e.g., BMP2, CCL2, IL5, VEGFA, etc.) are over-expressed whereas another set of genes (e.g., AIMP1, IFNG, LTA, LTB, TNF, etc.) are under-expressed in both COPD and NSCLC patients. The increased percent enrichment of inflammation-associated transcription factors including NF-kB, CREB, HIF1, and MYC at the loci of inflammatory genes was revealed by our chromatin immunoprecipitation (ChIP) data. H3K4me3, H3K9me3, H3K14Ac, HDAC1, 2, 3, 6 all showed dysregulated enrichment at the VEGFA gene locus. One of the epigenetic modifications, histone methylation, was found to be abnormal in the mtTFA complex in COPD and NSCLC patients in comparison to controls. Although there is mounting evidence of several links between these disorders, therapeutic options remain inadequate. Our findings contribute to the body of knowledge about therapeutic techniques that use inflammatory cytokines as a prognostic marker and highlight the need for epigenetic therapy for these debilitating lung diseases.

Oxidative stress links the tumour suppressor p53 with cell apoptosis induced by cigarette smoke

This study was to investigate the effects of oxidative stress in cigarette smoke (CS)-induced cell apoptosis in mice with emphysema. Thirty-two mice were divided into four groups: the control group, the CS group, the CS + Pifithrin-α group, and the CS + NAC group. Pathological changes and apoptosis in lung tissue of mice were detected. The activity of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC) were measured using spectrophotometer. The proteins expression of p53, Bcl-2, Bax, and caspase-3 were determined by western blot. The results showed that cell apoptosis, lung structural damage, and the activity of MDA, as well as the expression of apoptosis-related proteins Bax, total caspase-3, and cleaved caspase-3 were increased in CS-treated mice. The activity of SOD, CAT, and T-AOC, as well as the expression of anti-apoptosis protein Bcl-2 were decreased in CS-treated mice when compared with the control group. However, Pifithrin-α (p53 inhibitor) and N-Acetylcysteine (NAC) could reduce cell apoptosis, lung structural damage and oxidative stress, accelerate the expression of Bcl-2, while suppressing the expression of Bax, total caspase-3 and cleaved caspase-3. More importantly, the treatment with NAC even inhibited the expression of p53. In conclusions, oxidative stress linking the p53 is involved in cell apoptosis in CS-treated emphysema mice.

Mitochondria-related TFAM gene variants and their effects on patients with cervical cancer

Cervical cancer is the fourth most common type of cancer in women worldwide, with high incidence and mortality rates, particularly in developing countries. There are human papillomavirus vaccines and cytological screening programs available; however, there are no molecular markers that would aid the prognosis of the course of the disease or prediction of the outcomes of the patients. The aim of the present study was to investigate the associations between single nucleotide polymorphisms (SNPs) of the mitochondrial transcription factor A (TFAM) gene (rs11006132, rs11006129, rs1937, rs16912174, rs16912202 and rs3900887), and the clinical parameters and tumor phenotype of patients with cervical cancer. DNA isolated from patients with cervical cancer (n=172) was used for genotyping using Real-Time PCR using TaqMan probes. It was revealed that the TFAM rs3900887 TT and AT genotypes were associated with a lower risk of developing larger tumors. The results showed an association between the rs3900887 SNP and tumor phenotype, indicating TFAM rs3900887 as a potential biomarker for tumor size in cervical cancer.

The role of cigarette smoke-induced pulmonary vascular endothelial cell apoptosis in COPD

Chronic obstructive pulmonary disease (COPD) is one of the most common chronic respiratory diseases with high morbidity and mortality. It has become the fifth most burdened and the third most deadly disease in the global economy and increases year by year. The prevention and treatment of COPD are urgent. Smoking is the main and most common risk factor for COPD. Cigarette smoke (CS) contains a large number of toxic substances, can cause a series of changes in the trachea, lung tissue, pulmonary blood vessels, and promotes the occurrence and development of COPD. In recent years, the development of epigenetics and molecular biology have provided new guidance for revealing the pathogenesis, diagnosis, and treatment of diseases. The latest research indicates that pulmonary vascular endothelial cell apoptosis initiates and participates in the pathogenesis of COPD. In this review, we summarize the current research on the epigenetic mechanisms and molecular biology of CS-induced pulmonary vascular endothelial cell apoptosis in COPD, providing a new research direction for pathogenesis of COPD and a new target for the diagnosis, treatment, and prevention of COPD.

Resveratrol attenuates cigarette smoke induced endothelial apoptosis by activating Notch1 signaling mediated autophagy

Background

Increasing evidence shows that endothelial apoptosis contributes to cigarette smoke (CS)-induced disease progression, such as chronic obstructive pulmonary disease (COPD). Our previous studies have validated Notch1 as an anti-apoptotic signaling in CS-induced endothelial apoptosis. Resveratrol (RESV) is a naturally occurring polyphenol that exhibits an anti-apoptotic activity in endothelial cells that exposed to many kinds of destructive stimulus. However, the effects of resveratrol on Notch1 signaling in CS-induced endothelial apoptosis have not yet been fully elucidated. Therefore, the aim of this study was to examine whether RESV can protect endothelial cells from CS-induced apoptosis via regulating Notch1 signaling.

Methods

Human umbilical vein endothelial cells (HUVECs) were pretreated with RESV for 2 h, followed by cotreatment with 2.5%CSE for 24 h to explore the role of RESV in CSE induced endothelial apoptosis. 3-methyladenine (3-MA) or rapamycin was used to alter autophagic levels. Lentivirus Notch1 intracellular domain (LV-N1ICD), γ-secretase inhibitor (DAPT) and Notch1 siRNA were used to change Notch1 expression. The expression of Notch1, autophagic and apoptotic markers were examined by Western blot and the apoptosis rate was detected by Flow cytometry analysis.

Results

Our results showed that activating autophagy reduced CSE-induced endothelial apoptosis, while blocking autophagy promoted cell apoptosis in HUVECs. RESV pretreatment attenuated the CSE-induced endothelial apoptosis and activated Notch1 signaling. RESV pretreatment also increased LC3b-II and Beclin1 production, decreased p62 and mTOR expression. 3-MA treatment inhibited autophagy and aggravated CSE induced apoptosis, while rapamycin promoted autophagy, led to a decrease in cell apoptosis. LV-N1ICD transfection upregulated autophagy and reduced apoptosis. However, this protective effect was abolished by 3-MA treatment. In cells treated with DAPT or Notch1 siRNA, autophagy was decreased, while apoptosis was increased. RESV partly rescued the DAPT or Notch1 siRNA induced apoptosis by activating Notch1 signaling.

Conclusion

In HUVECs, RESV attenuates CSE induced endothelial apoptosis by inducing autophagy in a Notch1-dependent manner.

Mitochondrial HMG-Box Containing Proteins: From Biochemical Properties to the Roles in Human Diseases

Mitochondrial DNA (mtDNA) molecules are packaged into compact nucleo-protein structures called mitochondrial nucleoids (mt-nucleoids). Their compaction is mediated in part by high-mobility group (HMG)-box containing proteins (mtHMG proteins), whose additional roles include the protection of mtDNA against damage, the regulation of gene expression and the segregation of mtDNA into daughter organelles. The molecular mechanisms underlying these functions have been identified through extensive biochemical, genetic, and structural studies, particularly on yeast (Abf2) and mammalian mitochondrial transcription factor A (TFAM) mtHMG proteins. The aim of this paper is to provide a comprehensive overview of the biochemical properties of mtHMG proteins, the structural basis of their interaction with DNA, their roles in various mtDNA transactions, and the evolutionary trajectories leading to their rapid diversification. We also describe how defects in the maintenance of mtDNA in cells with dysfunctional mtHMG proteins lead to different pathologies at the cellular and organismal level.

Mitochondrial biology in airway pathogenesis and the role of NRF2

A constant improvement in understanding of mitochondrial biology has provided new insights into mitochondrial dysfunction in human disease pathogenesis. Impaired mitochondrial dynamics caused by various stressors are characterized by structural abnormalities and leakage, compromised turnover, and reactive oxygen species overproduction in mitochondria as well as increased mitochondrial DNA mutation frequency, which leads to modified energy production and mitochondria-derived cell signaling. The mitochondrial dysfunction in airway epithelial, smooth muscle, and endothelial cells has been implicated in diseases including chronic obstructive lung diseases and acute lung injury. Increasing evidence indicates that the NRF2-antioxidant response element (ARE) pathway not only enhances redox defense but also facilitates mitochondrial homeostasis and bioenergetics. Identification of functional or potential AREs further supports the role for Nrf2 in mitochondrial dysfunction-associated airway disorders. While clinical reports indicate mixed efficacy, NRF2 agonists acting on respiratory mitochondrial dynamics are potentially beneficial. In lung cancer, growth advantage provided by sustained NRF2 activation is suggested to be through increased cellular antioxidant defense as well as mitochondria reinforcement and metabolic reprogramming to the preferred pathways to meet the increased energy demands of uncontrolled cell proliferation. Further studies are warranted to better understand NRF2 regulation of mitochondrial functions as therapeutic targets in airway disorders.

Hypermethylation of mitochondrial transcription factor A induced by cigarette smoke is associated with chronic obstructive pulmonary disease

Purpose of the study: Cigarette smoking is a leading environmental contributor to chronic obstructive pulmonary disease (COPD), but its epigenetic regulation of mtTFA gene remains elusive. This study aims to explore the relationship of DNA methylation of mtTFA and cigarette smoking in COPD. Materials and Methods: We analyzed DNA methylation on mtTFA promoters in clinical samples from COPD patients and subjects with normal pulmonary function. Expression of mtTFA mRNA in the clinical samples and mtTFA mRNA and protein in human umbilical vein endothelial cells(HUVECs) treated with cigarette smoke extract (CSE) was evaluated. mtTFA mRNA and protein levels were measured to determine effects of demethylation agents on CSE-treated HUVECs. Results: The DNA methylation level of the mtTFA promoter was significantly increased in COPD group. Expression of mtTFA mRNA was downregulated in the lungs as a consequence of hypermethylation of mtTFA promoter. Expression of mtTFA mRNA and protein was downregulated in CSE-treated HUVECs as a consequence of hypermethylation of the mtTFA promoter. mtTFA expression in CSE-treated HUVECs was restored by the methylation inhibitor, 5-aza-2'-deoxycytidine(AZA). Conclusions: Cigarette smoke-induced hypermethylation of the mtTFA promoter is related to the initiation and progression of COPD. Our finding may provide a new strategy for the intervention of COPD by developing demethylation agents targeting mtTFA hypermethylation.

Notch promotes DNMT-mediated hypermethylation of Klotho leads to COPD-related inflammation

AIM

Klotho expression significantly declines in alveolar macrophages and airway epithelial cells in chronic obstructive pulmonary disease (COPD) patients, and cigarette smoke extract dramatically inhibits the expression and secretion of α-Klotho. This suggests that the silencing of Klotho is the major factor promoting COPD related inflammatory responses. This study aims to investigate the mechanism of Klotho downregulation and its effect on the inflammatory cytokines secretion and cell apoptosis.

METHODS

Expression of DNA methyltransferases (DNMTs) and Notch signaling activation were quantified in MH-S and 16HBE cells stimulated with cigarette smoke extract (CSE) solution. Specific inhibitors of DNMTs or Notch pathway were added together with CSE into treated and control cells. Inflammatory cytokines, cell viability and cell death were determined to explore the effect of Klotho on COPD related inflammation.

RESULTS

CSE treatment statistically increased the level of DNMTs expression, Klotho promoter methylation, and activated the Notch signaling pathway. Notch signal activation played a critical role in the process of modification of Klotho promoter methylation. The inhibition of DNMTs and Notch pathway rescued Klotho levels and inhibited inflammation and cell apoptosis after CSE treatment.

CONCLUSION

Notch-mediated Klotho hypermethylation inhibited Klotho expression, which promoted inflammatory response and cell apoptosis that were associated with the development of COPD.

Notch1 regulates endothelial apoptosis via the ERK pathway in chronic obstructive pulmonary disease

The Notch signaling pathway plays critical role for determining cell fate by controlling proliferation, differentiation, and apoptosis. In the current study, we investigated the roles of the Notch signaling pathway in cigarette smoke (CS)-induced endothelial apoptosis in chronic obstructive pulmonary disease (COPD). We obtained surgical specimens from 10 patients with COPD and 10 control participants. Notch1, 2, and 4 express in endothelial cells, whereas Notch3 mainly localizes in smooth muscle cells. Compared with control groups, we found that the expression of Notch1, 3, and 4 decreased, as well as their target genes Hes1 and Hes2, while the expression of Notch2 and extracellular signal-regulated kinase (ERK)1/2 increased in COPD patients compared with controls, as well as in human pulmonary microvascular endothelial cells (HPMECs) when exposed to CS extract (CSE). Overexpression of Notch1 with N1ICD in HPMECs markedly alleviated the cell apoptosis induced by CSE. The ERK signaling pathway was significantly activated by CSE, which correlated with CSE-induced apoptosis. However, this activation can be abolished by N1ICD overexpression. Furthermore, treatment of PD98059 (ERK inhibitor) significantly alleviated CSE-induced apoptosis, as well as reduced the methylation of mitochondrial transcription factor A (mtTFA) promoter, which was correlated with CS-induced endothelial apoptosis. These results suggest that CS alters Notch signaling in pulmonary endothelial cells. Notch1 protects against CS-induced endothelial apoptosis in COPD through inhibiting the ERK pathway, while the ERK pathway further regulates the methylation of mtTFA promotor.

Is mitochondrial dysfunction a driving mechanism linking COPD to nonsmall cell lung carcinoma?

Chronic obstructive pulmonary disease (COPD) patients are at increased risk of developing nonsmall cell lung carcinoma, irrespective of their smoking history. Although the mechanisms behind this observation are not clear, established drivers of carcinogenesis in COPD include oxidative stress and sustained chronic inflammation. Mitochondria are critical in these two processes and recent evidence links increased oxidative stress in COPD patients to mitochondrial damage. We therefore postulate that mitochondrial damage in COPD patients leads to increased oxidative stress and chronic inflammation, thereby increasing the risk of carcinogenesis.

The functional state of the mitochondrion is dependent on the balance between its biogenesis and degradation (mitophagy). Dysfunctional mitochondria are a source of oxidative stress and inflammasome activation. In COPD, there is impaired translocation of the ubiquitin-related degradation molecule Parkin following activation of the Pink1 mitophagy pathway, resulting in excessive dysfunctional mitochondria. We hypothesise that deranged pathways in mitochondrial biogenesis and mitophagy in COPD can account for the increased risk in carcinogenesis. To test this hypothesis, animal models exposed to cigarette smoke and developing emphysema and lung cancer should be developed. In the future, the use of mitochondria-based antioxidants should be studied as an adjunct with the aim of reducing the risk of COPD-associated cancer.

Mitochondria in chronic obstructive pulmonary disease and lung cancer: where are we now?

Recent advances in mitochondrial biogenesis have provided the emerging recognition that mitochondria do much more than 'simply providing energy for cellular function'. Currently, a constantly improving understanding of the mitochondrial structure and function has been providing valuable insights into the contribution of defects in mitochondrial metabolism to various human diseases, including chronic obstructive pulmonary disease and lung cancer. The growing interest in mitochondria research led to development of new biomedical fields in the two main smoking-related lung diseases. However, there is considerable paucity in our understanding of mechanisms by which mitochondrial dynamics regulate lung diseases. In this review, we will discuss our current knowledge on the role of mitochondrial dysfunction in the pathogenesis of chronic obstructive pulmonary disease and non-small-cell lung cancer.

Notch signaling in lung diseases: focus on Notch1 and Notch3

Notch signaling is an evolutionarily conserved cell–cell communication mechanism that plays a key role in lung homeostasis, injury and repair. The loss of regulation of Notch signaling, especially Notch1 and Notch3, has recently been linked to the pathogenesis of important lung diseases, in particular, chronic obstructive pulmonary disease (COPD), asthma, pulmonary fibrosis, pulmonary arterial hypertension (PAH), lung cancer and lung lesions in some congenital diseases. This review focuses on recent advances related to the mechanisms and the consequences of aberrant or absent Notch1/3 activity in the initiation and progression of lung diseases. Our increasing understanding of this signaling pathway offers great hope that manipulating Notch signaling may represent a promising alternative complementary therapeutic strategy in the future.

Leukocyte Mitochondrial DNA Copy Number Is Associated with Chronic Obstructive Pulmonary Disease

BACKGROUND

Oxidative stress is known to be involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). Evidence suggests that leukocytes mitochondria DNA (mtDNA) is susceptible to undergo mutations, insertions, or depletion in response to reactive oxidative stress (ROS). We hypothesize that mtDNA copy number is associated with the development of COPD.

METHODOLOGY/PRINCIPAL FINDINGS

Relative mtDNA copy number was measured by a quantitative real-time PCR assay using DNA extracted from peripheral leukocytes. MtDNA copy number of peripheral leukocytes in the COPD group (n = 86) is significantly decreased compared with non-smoker group (n = 77) (250.3± 21.5 VS. 464.2± 49.9, P<0.001). MtDNA copy number in the COPD group was less than that in the healthy smoking group, but P value nearly achieved significance (250.3± 21.5 VS. 404.0± 76.7, P = 0.08) MtDNA copy number has no significance with age, gender, body mass index, current smoking, and pack-years in COPD group, healthy smoker group and no smoker group, respectively. Serum glutathione level in the COPD group is significantly decreased compared with healthy smoker and non-smoker groups (4.5± 1.3 VS. 6.2± 1.9 and 4.5± 1.3 VS. 7.1±1.1 mU/mL; P<0.001 respectively). Pearson correlation test shows a significant liner correlation between mtDNA copy number and serum glutathione level (R = 0.2, P = 0.009).

CONCLUSIONS/SIGNIFICANCE

COPD is associated with decreased leukocyte mtDNA copy number and serum glutathione. COPD is a regulatory disorder of leukocytes mitochondria. However, further studies are needed to determine the real mechanisms about the gene and the function of mitochondria.

The relationship between COPD and lung cancer

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COPD is a risk factor for lung cancer beyond their shared aetiology.

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Both are driven by oxidative stress.

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Both are linked to cellular aging, senescence and telomere shortening.

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Both have been linked to genetic predisposition.

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Both show altered epigenetic regulation of gene expression.

Both COPD and lung cancer are major worldwide health concerns owing to cigarette smoking, and represent a huge, worldwide, preventable disease burden. Whilst the majority of smokers will not develop either COPD or lung cancer, they are closely related diseases, occurring as co-morbidities at a higher rate than if they were independently triggered by smoking.

Lung cancer and COPD may be different aspects of the same disease, with the same underlying predispositions, whether this is an underlying genetic predisposition, telomere shortening, mitochondrial dysfunction or premature aging. In the majority of smokers, the burden of smoking may be dealt with by the body’s defense mechanisms: anti-oxidants such as superoxide dismutases, anti-proteases and DNA repair mechanisms. However, in the case of both diseases these fail, leading to cancer if mutations occur or COPD if damage to the cell and proteins becomes too great.

Alternatively COPD could be a driving factor in lung cancer, by increasing oxidative stress and the resulting DNA damage, chronic exposure to pro-inflammatory cytokines, repression of the DNA repair mechanisms and increased cellular proliferation. Understanding the mechanisms that drive these processes in primary cells from patients with these diseases along with better disease models is essential for the development of new treatments.

NSFC spurs significant basic research progress of respiratory medicine in China

Over the years, research in respiratory medicine has progressed rapidly in China. This commentary narrates the role of the National Natural Science Foundation of China (NSFC) in supporting the basic research of respiratory medicine, summarizes the major progress of respiratory medicine in China, and addresses the main future research directions sponsored by the NSFC.