Ursolic acid alleviates airway-vessel remodeling and muscle consumption in cigarette smoke-induced emphysema rats

Inhalation of patchouli essential oil alleviates airway inflammation in cigarette smoke-induced COPD mice

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide, characterized by persistent respiratory symptoms and airflow limitations resulting from small airway injury, bronchial wall thickening, and hypersecretion of mucus. Current pharmacological interventions are ineffective in reversing these airflow limitations; In our study, we investigated the potential role of patchouli essential oil (PEO) in the treatment of COPD and its underlying molecular mechanisms, both in vitro and in vivo. To establish a cigarette smoke-induced COPD mice model, we exposed the mice to cigarette smoke (CS) and administered nasal drip of lipopolysaccharides (LPS). During the modeling process, the mice were nebulized daily with PEO; Treatment with PEO significantly ameliorated the inflammatory response in CS-induced COPD mice, leading to improved lung function. Histopathological examination revealed that PEO treatment improved lung tissue changes, as observed through staining. Furthermore, PEO treatment reduced the levels of inflammatory factors IL-6, IL-1β, and TNF-α, and reversed the CS-induced elevation of mRNA levels of these factors. Additionally, PEO treatment significantly countered cigarette smoke-induced COPD via the NF-κB signaling pathway in mice; Our result has shown that inhalation of PEO can substantially alleviate the increase in inflammatory factors, mitigate lung function impairment, and reduce airway remodeling in cigarette smoke-induced COPD mice.

Cigarette smoke-induced galectin-3 as a diagnostic biomarker and therapeutic target in lung tissue remodeling

Galectin-3 (Gal-3), a multifunctional carbohydrate-binding lectin, has emerged as a key player in various biological processes including inflammation, cancer, cardiovascular diseases and fibrotic disorders, however it remains unclear if Gal-3 is a bystander or drives lung tissue remodeling (LTR). Persistent exposure to cigarette smoke (CS) is the leading cause of oxidative and inflammatory damage to the lung tissues. CS-induced pathological increase in Gal-3 expression has been implicated in the pathogenesis of various respiratory conditions, such as chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and lung cancer. We and others have reported that CS induces Gal-3 synthesis and secretion, which modulates the pathological signaling pathways in lung epithelial cells implicating Gal-3 as a novel diagnostic marker and a factor driving LTR in CS-exposed lungs. Therefore, pharmacological interventions targeting Gal-3 and its upstream and downstream signaling pathways can help combat CS-induced LTR. Excitingly, preclinical models have demonstrated the efficacy of interventions such as Gal-3 expression inhibition, Gal-3 receptor blockade, and signaling pathways modulation open up promising avenues for future therapeutic interventions. Furthermore, targeting extracellular vesicles-mediated Gal-3 release and the potential of microRNA-based therapy are emerging as novel therapeutic approaches in CS-induced LTR and have been discussed in this article.

The Nexus of Inflammation-Induced Epithelial-Mesenchymal Transition and Lung Cancer Progression: A Roadmap to Pentacyclic Triterpenoid-Based Therapies

Lung cancer is the leading cause of cancer-related death worldwide. Its high mortality is partly due to chronic inflammation that accompanies the disease and stimulates cancer progression. In this review, we analyzed recent studies and highlighted the role of the epithelial-mesenchymal transition (EMT) as a link between inflammation and lung cancer. In the inflammatory tumor microenvironment (iTME), fibroblasts, macrophages, granulocytes, and lymphocytes produce inflammatory mediators, some of which can induce EMT. This leads to increased invasiveness of tumor cells and self-renewal of cancer stem cells (CSCs), which are associated with metastasis and tumor recurrence, respectively. Based on published data, we propose that inflammation-induced EMT may be a potential therapeutic target for the treatment of lung cancer. This prospect is partially realized in the development of EMT inhibitors based on pentacyclic triterpenoids (PTs), described in the second part of our study. PTs reduce the metastatic potential and stemness of tumor cells, making PTs promising candidates for lung cancer therapy. We emphasize that the high diversity of molecular mechanisms underlying inflammation-induced EMT far exceeds those that have been implicated in drug development. Therefore, analysis of information on the relationship between the iTME and EMT is of great interest and may provide ideas for novel treatment approaches for lung cancer.

Mitochondrial dysfunction: roles in skeletal muscle atrophy

Mitochondria play important roles in maintaining cellular homeostasis and skeletal muscle health, and damage to mitochondria can lead to a series of pathophysiological changes. Mitochondrial dysfunction can lead to skeletal muscle atrophy, and its molecular mechanism leading to skeletal muscle atrophy is complex. Understanding the pathogenesis of mitochondrial dysfunction is useful for the prevention and treatment of skeletal muscle atrophy, and finding drugs and methods to target and modulate mitochondrial function are urgent tasks in the prevention and treatment of skeletal muscle atrophy. In this review, we first discussed the roles of normal mitochondria in skeletal muscle. Importantly, we described the effect of mitochondrial dysfunction on skeletal muscle atrophy and the molecular mechanisms involved. Furthermore, the regulatory roles of different signaling pathways (AMPK-SIRT1-PGC-1α, IGF-1-PI3K-Akt-mTOR, FoxOs, JAK-STAT3, TGF-β-Smad2/3 and NF-κB pathways, etc.) and the roles of mitochondrial factors were investigated in mitochondrial dysfunction. Next, we analyzed the manifestations of mitochondrial dysfunction in muscle atrophy caused by different diseases. Finally, we summarized the preventive and therapeutic effects of targeted regulation of mitochondrial function on skeletal muscle atrophy, including drug therapy, exercise and diet, gene therapy, stem cell therapy and physical therapy. This review is of great significance for the holistic understanding of the important role of mitochondria in skeletal muscle, which is helpful for researchers to further understanding the molecular regulatory mechanism of skeletal muscle atrophy, and has an important inspiring role for the development of therapeutic strategies for muscle atrophy targeting mitochondria in the future.

PDK1 inhibition reduces autophagy and cell senescence through the PI3K/AKT signalling pathway in a cigarette smoke mouse emphysema model

A number of previous studies have demonstrated the pivotal role of PI3K/AKT signalling in cigarette smoke (CS)-induced emphysema, where phosphoinositide dependent protein kinase 1 (PDK1) is a critical component of this pathway. Therefore, the present study aimed to investigate the effects of a PDK1 inhibitor (GSK-2334470) on the expression levels of PI3K, AKT, cyclin-dependent kinase inhibitor 2A (p16) and LC3B in a CS + CS extract (CSE)-induced mouse emphysema model. CS exposure and intraperitoneal injections of CSE were combined for 4 weeks to establish an emphysema model. Mice (n=35) were randomly divided into the normal control, emphysema (CS), PI3K inhibitor (CS3) and PDK1 inhibitor (CS1) groups. Immunohistochemistry staining of lung tissues was used to measure the expression of the PI3K, PDK1 and AKT proteins in airway epithelial tissues. Immunofluorescence staining was also used to measure the levels of p16 and LC3BII protein expression in the airway epithelial tissues. In addition, PI3K, PDK1, AKT, p16 and LC3B protein expression was semi-quantified using western blotting. The expression of PDK1, PI3K and AKT proteins in the airway epithelial tissues was significantly increased in the CS + CSE group compared with that in the control group. The expression levels of p16 and LC3B were also increased as well in the CS + CSE group compared with those in the control group. The expression levels of PI3K, PDK1, AKT, LC3B and p16 in the airway epithelial tissues of the CS3 group were lower compared with those in the CS + CSE group. A decrease in the expression levels of PDK1, AKT, p16 and LC3B in the airway epithelial tissues of the CS1 group compared with those in the CS + CSE group was also observed. However, there were no significant differences in the expression levels of PI3K between the CS1 and the CS groups. The present study concluded that the inhibition of PDK1 can potentially reduce autophagy and cell senescence by downregulating the expression of PI3K/AKT pathway related proteins in airway epithelial cells, thereby protecting against CS + CSE-induced emphysema in mice.

Single-cell sequencing reveals that endothelial cells, EndMT cells and mural cells contribute to the pathogenesis of cavernous malformations

Cavernous malformations (CMs) invading the central nervous system occur in ~0.16-0.4% of the general population, often resulting in hemorrhages and focal neurological deficits. Further understanding of disease mechanisms and therapeutic strategies requires a deeper knowledge of CMs in humans. Herein, we performed single-cell RNA sequencing (scRNA-seq) analysis on unselected viable cells from twelve human CM samples and three control samples. A total of 112,670 high-quality cells were clustered into 11 major cell types, which shared a number of common features in CMs harboring different genetic mutations. A new EC subpopulation marked with PLVAP was uniquely identified in lesions. The cellular ligand‒receptor network revealed that the PLVAP-positive EC subcluster was the strongest contributor to the ANGPT and VEGF signaling pathways in all cell types. The PI3K/AKT/mTOR pathway was strongly activated in the PLVAP-positive subcluster even in non-PIK3CA mutation carriers. Moreover, endothelial-to-mesenchymal transition (EndMT) cells were identified for the first time in CMs at the single-cell level, which was accompanied by strong immune activation. The transcription factor SPI1 was predicted to be a novel key driver of EndMT, which was confirmed by in vitro and in vivo studies. A specific fibroblast-like phenotype was more prevalent in lesion smooth muscle cells, hinting at the role of vessel reconstructions and repairs in CMs, and we also confirmed that TWIST1 could induce SMC phenotypic switching in vitro and in vivo. Our results provide novel insights into the pathomechanism decryption and further precise therapy of CMs.

Pseudognaphalium affine Extract Alleviates COPD by Inhibiting the Inflammatory Response via Downregulation of NF-κB

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disease with limited therapeutic options. Pseudognaphalium affine (D. Don) Anderb. is a medicinal and edible plant used to treat cough, asthma, and COPD for a long time in folk medicine. The objective of this study is to evaluate the effect of Pseudognaphalium affine (D. Don) Anderb. extract (GAE) and investigate the possible underlying mechanism in vivo and in vitro. In vivo, the administration of GAE in a rat COPD model could significantly ameliorate lung damage and pulmonary function by inhibiting the production of pro-inflammatory cytokines. Western blot and real-time PCR results showed that GAE could suppress nuclear translocation of nuclear factor-kappa B (NF-κB), which indicated that GAE down-regulated the NF-κB pathway. Moreover, GAE protected against tumor necrosis factor (TNF)-α induced inflammatory response in BEAS-2B and inhibited the NF-κB pathway. All data suggested that GAE exhibited its anti-COPD effect by inhibiting pro-inflammatory cytokines, which may be associated with the inhibition of the NF-κB pathway.

Therapeutic effect of sodium‑glucose cotransporter 2 inhibitor and benazepril on diabetic nephropathic rats

The present study aimed to compare the therapeutic effect of sodium/glucose cotransporter 2 (SGLT2) inhibitor and benazepril on diabetic nephropathy (DN) rats and provide a potential novel agent for the clinical treatment of DN. The DN model was established on rats. Animals were dosed orally with SGLT2 and benazepril daily for 4 weeks. The pathological state of renal tissues were evaluated using hematoxylin and eosin, Masson and periodic acid-Schiff staining. The change in the morphology of renal tissues was observed through transmission electron microscopy. Western blotting was utilized to determine the expression level of TGF-β, N-terminal fragment of the B-type natriuretic peptide precursor (NT-proBNP) and matrix metalloproteinase-9 (MMP-9). The expression level of endothelin 1 (ET-1), von Willebrand factor (vWF), collagen (col)-I and α smooth muscle actin (α-SMA) in renal tissues was visualized using immunohistochemical assay. Significant pathological changes in the glomerular basement membrane, mesangial membrane, renal tubules, lumen, renal interstitial region and renal tubular epithelial cells were observed in DN rats, accompanied by increased collagen fibers. SGLT2 inhibitor treatment demonstrated more alleviatory effects on the pathological changes of renal tissues compared with benazepril. Compared with control, TGF-β and NT-proBNP were upregulated in DN rats, accompanied by the downregulation of MMP-9, ET-1, vWF, col-I and α-SMA, which were markedly reversed by treatment with SGLT2 inhibitor and benazepril. Compared with benazepril, the effects of SGLT2 inhibitor on the expression level of TGF-β, NT-proBNP, MMP-9, ET-1, vWF, col-I and α-SMA were more significant. Overall, SGLT2 inhibitor demonstrated an increased therapeutic effect against DN rats compared with benazepril by regulating cytokines, renal fibrosis and extracellular matrix degradation.

The effects of epithelial-mesenchymal transitions in COPD induced by cigarette smoke: an update

Cigarette smoke is a complex aerosol containing a large number of compounds with a variety of toxicity and carcinogenicity. Long-term exposure to cigarette smoke significantly increases the risk of a variety of diseases, including chronic obstructive pulmonary disease (COPD) and lung cancer. Epithelial–mesenchymal transition (EMT) is a unique biological process, that refers to epithelial cells losing their polarity and transforming into mobile mesenchymal cells, playing a crucial role in organ development, fibrosis, and cancer progression. Numerous recent studies have shown that EMT is an important pathophysiological process involved in airway fibrosis, airway remodeling, and malignant transformation of COPD. In this review, we summarized the effects of cigarette smoke on the development and progression of COPD and focus on the specific changes and underlying mechanisms of EMT in COPD induced by cigarette smoke. We spotlighted the signaling pathways involved in EMT induced by cigarette smoke and summarize the current research and treatment approaches for EMT in COPD, aiming to provide ideas for potential new treatment and research directions.

Recent Advances Regarding the Molecular Mechanisms of Triterpenic Acids: A Review (Part I)

Triterpenic acids are phytocompounds with a widespread range of biological activities that have been the subject of numerous in vitro and in vivo studies. However, their underlying mechanisms of action in various pathologies are not completely elucidated. The current review aims to summarize the most recent literature, published in the last five years, regarding the mechanism of action of three triterpenic acids (asiatic acid, oleanolic acid, and ursolic acid), corelated with different biological activities such as anticancer, anti-inflammatory, antidiabetic, cardioprotective, neuroprotective, hepatoprotective, and antimicrobial. All three discussed compounds share several mechanisms of action, such as the targeted modulation of the PI3K/AKT, Nrf2, NF-kB, EMT, and JAK/STAT3 signaling pathways, while other mechanisms that proved to only be specific for a part of the triterpenic acids discussed, such as the modulation of Notch, Hippo, and MALAT1/miR-206/PTGS1 signaling pathway, were highlighted as well. This paper stands as the first part in our literature study on the topic, which will be followed by a second part focusing on other triterpenic acids of therapeutic value.

Natural products in the treatment of pulmonary emphysema: Therapeutic effects and mechanisms of action

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a class of lung diseases including chronic bronchitis, asthma, and emphysema. Long-time smoking is considered the main reason for developing emphysema. Emphysema can be defined as damage to the walls of the air sacs (alveoli) of the lung. It has been demonstrated that natural compounds with antioxidant and anti-inflammatory effects can effectively improve or protect the lung against this disease. This paper is dedicated to systematically review the effective natural compounds in the treatment of pulmonary emphysema.

PURPOSE

This is the first systematic and comprehensive review on the role of plant-derived secondary metabolites in managing and/or treating pulmonary emphysema STUDY DESIGN AND METHODS: A systematic and comprehensive review was done based on Scopus, PubMed, and Cochrane Library databases were searched using the "emphysema", "plant", "herb", and "phytochemical" keywords. Non-English, review, and repetitive articles were excluded from the study. Search results were included in the Prisma diagram.

RESULTS

From a total of 1285 results, finally, 22 articles were included in the present study. The results show that some herbs such as Scutellaria baicalensis Georgi and Monascus adlay and some phytochemicals such as gallic acid and quercetin and blackboard tree indole alkaloids affect more factors in improving the lung emphysema. Also, some natural compounds such as marijuana smoke and humic acid also play an aggravating role in this disease. It also seems that some of the medicinal plants such as PM014 herbal formula, pomegranate juice and açaí berry sometimes have side effects that are inconsistent with their therapeutic effects.

CONCLUSION

We concluded that natural compounds can effectively improve pulmonary emphysema due to their antioxidant, anti-inflammatory, and anti-apoptotic properties. However, additional studies are suggested to prove efficacy and side effects.

Potential Natural Small Molecular Compounds for the Treatment of Chronic Obstructive Pulmonary Disease: An Overview

Chronic obstructive pulmonary disease (COPD) is one of the major diseases threatening human life and health. According to the report released by the World Health Organization (WHO) in 2020, COPD has become the third leading cause of death in the world, featuring a sustainable growth of incidence rate as well as population age. The purpose of this review focuses on the advancement of bioactive natural compounds, such as baicalin, quercetin, resveratrol, and curcumin, which demonstrate promising therapeutic/interventional effects on CODP in vitro and in vivo. Information emphasizing on COPD was systematically collected from several authoritative internet databases including Web of Science, PubMed, Elsevier, Wiley Online Library, and Europe PMC, with a combination of keywords containing “COPD” and “natural small molecular compounds”. The new evidence indicated that these valuable molecules featured unique functions in the treatment of COPD through various biological processes such as anti-inflammatory, anti-oxidant, anti-apoptosis, and anti-airway fibrosis. Moreover, we found that the promising effects of these natural compounds on COPD were mainly achieved through JAK3/STAT3/NF-κB and MAPK inflammatory signaling pathways, Nrf2 oxidative stress signaling pathway, and TGF-β1/Smad 2/3 fibrosis signaling pathway, which referenced to multiple targets like TNF-α, IL-6, IL-8, TIMP-1, MMP, AKT, JAK3, IKK, PI3K, HO-1, MAPK, P38, ERK, etc. Current challenges and future directions in this promising field are also discussed at the end of this review. For the convenience of the readers, this review is divided into ten parts according to the structures of potential natural small molecular compounds. We hope that this review brings a quick look and provides some inspiration for the research of COPD.

Clerodendrum serratum extract attenuates production of inflammatory mediators in ovalbumin-induced asthma in rats

In the present study, ethanolic extract of Clerodendrum serratum roots was investigated for its potential to reverse some features of bronchial asthma in ovalbumin-induced murine model of asthma. Clerodendrum serratum commonly called bharangi, (family Solanaceae) is a well-known anti-allergic drug in Asian folk system of medicines. In the present work, pharmacological studies are done to provide scientific evidence for therapeutic potential of plant in allergic asthma. Asthma was induced in experimental rats with allergen suspension of ovalbumin and aluminum hydroxide followed by treatment with dexamethasone (2.5 mg/kg, po) or C. serratum root extract (0.53 and 5.3 mg/kg, b. w., po). Biomarkers of inflammatory response including cell counts, immunoglobulin E, cytokines such as interleukin (IL) -4, -5, -1β, tumor necrosis factor-α (TNF-α), leukotriene (LTD-4), and nitrite concentration in blood as well as bronchial (BAL) fluid were tested. Lung functions in asthmatic and treated animals were evaluated as breathing rate and tidal volume. Treatment with C. serratum extract markedly (p < 0.001, p < 0.01, and p < 0.05) diminished infiltration of inflammatory cells, IgE, cytokines, and nitrites in blood serum and bronchial fluid. Improvement in lung functions (p < 0.05) of asthmatic animals after CSE treatment also supports our findings. Results of the study suggest therapeutic potential of C. serratum in allergic asthma that can be related to ability of plant to attenuate response of inflammatory cells and thereby, production of inflammatory and proinflammatory cytokines in airways.

Ursolic Acid Alleviates Mucus Secretion and Tissue Remodeling in Rat Model of Allergic Rhinitis After PM2.5 Exposure

BACKGROUND

According to recent epidemiologic studies, exposure to fine particulate matter (particulate matter 2.5 ≤ µm [PM2.5]) in the air increases the incidence and severity of allergic rhinitis (AR). Ursolic acid (UA) has activities in immune regulation and anti-inflammatory. However, the role of UA intervention on PM2.5-exposed AR remains unknown. In this study, we investigated the effects of UA on tissue remodeling and mucus hypersecretion in a rat model of AR after PM2.5 exposure.

METHODS

AR was induced in rats with ovalbumin (OVA) and they were exposed to ambient PM2.5(200 µg/m3) via a PM2.5 inhalation exposure system for 30 days(ARE group). Ursolic acid intervention was administrated in the AR model after PM2.5 exposure (UA group). Hyperplasia of goblet cells was detected by periodic acid-Schiff (PAS) staining and collagen deposition in the nasal mucosa was detected by Masson trichrome (MT) staining.MUC5AC expression was measured by immunohistochemistry.

RESULTS

UA group showed reduced goblet cell hyperplasia and collagen deposition in the nasal mucosa which exacerbated after PM2.5 exposure, as reflected by PAS and MT staining when compared with the ARE group. Immunohistochemical results showed that the expression of MUC5AC in the UA group was lower than that in the ARE group.

CONCLUSION

Analysis of our data indicated that UA could attenuate nasal remodeling and mucus hypersecretion in aggravation of AR after PM2.5 exposure, which may be the pathophysiologic mechanisms for the prevention of AR exacerbated by exposure to PM2.5.

Circ0061052 regulation of FoxC1/Snail pathway via miR-515-5p is involved in the epithelial-mesenchymal transition of epithelial cells during cigarette smoke-induced airway remodeling

Circular RNA (circRNA) has been shown to be widely involved in a variety of lung diseases. Cigarette smoke (CS) may induce epithelial-mesenchymal transition (EMT) of airway remodeling in chronic obstructive pulmonary disease (COPD), however, in which the roles and mechanisms of circRNA have not been elucidated. In this study, we aimed to determine whether circ0061052 is involved in the EMT of human bronchial epithelial (HBE) cells and its potential mechanism for playing a biological role. Cigarette smoke extract (CSE) caused elevated EMT indicators and the increases of circ0061052 in HBE cells. Circ0061052 has a ring structure and is mainly present in the cytoplasm of HBE cells. We analyzed the regulatory relationship between circ0061052 and miR-515-5p using bioinformatics, a luciferase reporter gene, and qRT-PCR. We found that circ0061052 is mainly distributed in the cytoplasm and competitively binds to miR-515-5p, acting as a sponge for miR-515-5p. The luciferase reporter gene showed that miR-515-5p binds to the 3'UTR region of FoxC1 mRNA to inhibit its transcription. For HBE cells, overexpression of miR-515-5p antagonized the CSE-induced EMT. In addition, circ0061052 acts by binding miR-515-5p competitively to regulate the expression of FoxC1/Snail. When circ0061052 siRNA and miR-515-5p inhibitor were co-transfected into HBE cells, the inhibitor reversed the effect of circ0061052 siRNA on reducing EMT. Chronic exposure of mice to CS induced increases of circ0061052 levels, decreases of miR-515-5p levels, and the EMT in lung tissue, which caused dysfunction and airway obstruction. Overall, the results show that, by regulating miR-515-5p through a FoxC1/Snail regulatory axis, circ0061052 is involved in the CS-induced EMT and airway remodeling in COPD.

Plants derived therapeutic strategies targeting chronic respiratory diseases: Chemical and immunological perspective

The apparent predicament of the representative chemotherapy for managing respiratory distress calls for an obligatory deliberation for identifying the pharmaceuticals that effectively counter the contemporary intricacies associated with target disease. Multiple, complex regulatory pathways manifest chronic pulmonary disorders, which require chemotherapeutics that produce composite inhibitory effect. The cost effective natural product based molecules hold a high fervor to meet the prospects posed by current respiratory-distress therapy by sparing the tedious drug design and development archetypes, present a robust standing for the possible replacement of the fading practice of poly-pharmacology, and ensure the subversion of a potential disease relapse. This study summarizes the experimental evidences on natural products moieties and their components that illustrates therapeutic efficacy on respiratory disorders.

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Plant derived therapeutics for managing chronic respiratory disorders.

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Activity of natural product based molecules on key regulatory pathways of COPD.

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Preclinical evidence for the efficacy of natural product moieties.

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Clinical significance of plant derived molecules in pulmonary distress.

Lung epithelium damage in COPD - An unstoppable pathological event?

Chronic obstructive pulmonary disease (COPD) is a common term for alveolar septal wall destruction resulting in emphysema, and chronic bronchitis accompanied by conductive airway remodelling. In general, this disease is characterized by a disbalance of proteolytic/anti-proteolytic activity, augmented inflammatory response, increased oxidative/nitrosative stress, rise in number of apoptotic cells and decreased proliferation. As the first responder to the various environmental stimuli, epithelium occupies an important position in different lung pathologies, including COPD. Epithelium sequentially transitions from the upper airways in the direction of the gas exchange surface in the alveoli, and every cell type possesses a distinct role in the maintenance of the homeostasis. Basically, a thick ciliated structure of the airway epithelium has a major function in mucus secretion, whereas, alveolar epithelium which forms a thin barrier covered by surfactant has a function in gas exchange. Following this line, we will try to reveal whether or not the chronic bronchitis and emphysema, being two pathological phenotypes in COPD, could originate in two different types of epithelium. In addition, this review focuses on the role of lung epithelium in COPD pathology, and summarises underlying mechanisms and potential therapeutics.