LL-37 secreted by epithelium promotes fibroblast collagen production: a potential mechanism of small airway remodeling in chronic obstructive pulmonary disease

Lung Fibroblasts from Chronic Obstructive Pulmonary Disease Subjects Have a Deficient Gene Expression Response to Cigarette Smoke Extract Compared to Healthy

Background and aim

Cigarette smoking is the most common cause of chronic obstructive pulmonary disease (COPD) but more mechanistic studies are needed. Cigarette smoke extract (CSE) can elicit a strong response in many COPD-related cell types, but no studies have been performed in lung fibroblasts. Therefore, we aimed to investigate the effect of CSE on gene expression in lung fibroblasts from healthy and COPD subjects.

Patients and methods

Primary lung fibroblasts, derived from six healthy and six COPD subjects (all current or ex-smokers), were either unstimulated (baseline) or stimulated with 30% CSE for 4 h prior to RNA isolation. The mRNA expression levels were measured using the NanoString nCounter Human Fibrosis V2 panel (760 genes). Pathway enrichment was assessed for unique gene ontology terms of healthy and COPD.

Results

At baseline, a difference in the expression of 17 genes was found in healthy and COPD subjects. Differential expression of genes after CSE stimulation resulted in significantly less changes in COPD lung fibroblasts (70 genes) than in healthy (207 genes), with 51 genes changed in both. COPD maintained low NOTCH signaling throughout and upregulated JUN >80%, indicating an increase in apoptosis. Healthy downregulated the Mitogen-activated protein kinase (MAPK) signaling cascade, including a ≥50% reduction in FGF2, CRK, TGFBR1 and MEF2A. Healthy also downregulated KAT6A and genes related to cell proliferation, all together indicating possible cell senescence signaling.

Conclusion

Overall, COPD lung fibroblasts responded to CSE stimulation with a very different and deficient expression profile compared to healthy. Highlighting that stimulated healthy cells are not an appropriate substitute for COPD cells which is important when investigating the mechanisms of COPD.

Epithelial-Mesenchymal Transition Mechanisms in Chronic Airway Diseases: A Common Process to Target?

Epithelial-to-mesenchymal transition (EMT) is a reversible process, in which epithelial cells lose their epithelial traits and acquire a mesenchymal phenotype. This transformation has been described in different lung diseases, such as lung cancer, interstitial lung diseases, asthma, chronic obstructive pulmonary disease and other muco-obstructive lung diseases, such as cystic fibrosis and non-cystic fibrosis bronchiectasis. The exaggerated chronic inflammation typical of these pulmonary diseases can induce molecular reprogramming with subsequent self-sustaining aberrant and excessive profibrotic tissue repair. Over time this process leads to structural changes with progressive organ dysfunction and lung function impairment. Although having common signalling pathways, specific triggers and regulation mechanisms might be present in each disease. This review aims to describe the various mechanisms associated with fibrotic changes and airway remodelling involved in chronic airway diseases. Having better knowledge of the mechanisms underlying the EMT process may help us to identify specific targets and thus lead to the development of novel therapeutic strategies to prevent or limit the onset of irreversible structural changes.

Antimicrobial Peptides: Challenging Journey to the Pharmaceutical, Biomedical, and Cosmeceutical Use

Antimicrobial peptides (AMPs), or host defence peptides, are short proteins in various life forms. Here we discuss AMPs, which may become a promising substitute or adjuvant in pharmaceutical, biomedical, and cosmeceutical uses. Their pharmacological potential has been investigated intensively, especially as antibacterial and antifungal drugs and as promising antiviral and anticancer agents. AMPs exhibit many properties, and some of these have attracted the attention of the cosmetic industry. AMPs are being developed as novel antibiotics to combat multidrug-resistant pathogens and as potential treatments for various diseases, including cancer, inflammatory disorders, and viral infections. In biomedicine, AMPs are being developed as wound-healing agents because they promote cell growth and tissue repair. The immunomodulatory effects of AMPs could be helpful in the treatment of autoimmune diseases. In the cosmeceutical industry, AMPs are being investigated as potential ingredients in skincare products due to their antioxidant properties (anti-ageing effects) and antibacterial activity, which allows the killing of bacteria that contribute to acne and other skin conditions. The promising benefits of AMPs make them a thrilling area of research, and studies are underway to overcome obstacles and fully harness their therapeutic potential. This review presents the structure, mechanisms of action, possible applications, production methods, and market for AMPs.

Effects of hypoxia on bronchial and alveolar epithelial cells linked to pathogenesis in chronic lung disorders

Introduction: Chronic lung disorders involve pathological alterations in the lung tissue with hypoxia as a consequence. Hypoxia may influence the release of inflammatory mediators and growth factors including vascular endothelial growth factor (VEGF) and prostaglandin (PG)E2. The aim of this work was to investigate how hypoxia affects human lung epithelial cells in combination with profibrotic stimuli and its correlation to pathogenesis.

Methods: Human bronchial (BEAS-2B) and alveolar (hAELVi) epithelial cells were exposed to either hypoxia (1% O2) or normoxia (21% O2) during 24 h, with or without transforming growth factor (TGF)-β1. mRNA expression of genes and proteins related to disease pathology were analysed with qPCR, ELISA or immunocytochemistry. Alterations in cell viability and metabolic activity were determined.

Results: In BEAS-2B and hAELVi, hypoxia significantly dowregulated genes related to fibrosis, mitochondrial stress, oxidative stress, apoptosis and inflammation whereas VEGF receptor 2 increased. Hypoxia increased the expression of Tenascin-C, whereas both hypoxia and TGF-β1 stimuli increased the release of VEGF, IL-6, IL-8 and MCP-1 in BEAS-2B. In hAELVi, hypoxia reduced the release of fibroblast growth factor, epidermal growth factor, PGE2, IL-6 and IL-8, whereas TGF-β1 stimulus significantly increased the release of PGE2 and IL-6. TGF-β1 stimulated BEAS-2B cells showed a decreased release of VEGF-A and IL-8, while TGF-β1 stimulated hAELVi cells showed a decreased release of PGE2 and IL-8 during hypoxia compared to normoxia. Metabolic activity was significantly increased by hypoxia in both epithelial cell types.

Discussion: In conclusion, our data indicate that bronchial and alveolar epithelial cells respond differently to hypoxia and profibrotic stimuli. The bronchial epithelium appears more responsive to changes in oxygen levels and remodelling processes compared to the alveoli, suggesting that hypoxia may be a driver of pathogenesis in chronic lung disorders.

Antibacterial peptides-loaded bioactive materials for the treatment of bone infection

Bacterial bone infection in open fractures is an urgent problem to solve in orthopedics. Antimicrobial peptides (AMPs), as a part of innate immune defense, have good biocompatibility. Their antibacterial mechanism and therapeutic application against bacteria have been widely studied. Compared with traditional antibiotics, AMPs do not easily cause bacterial resistance and can be a reliable substitute for antibiotics in the future. Therefore, various physical and chemical strategies have been developed for the combined application of AMPs and bioactive materials to infected sites, which are conducive to maintaining the local stability of AMPs, reducing many complications, and facilitating bone infection resolution. This review explored the molecular structure, function, and direct and indirect antibacterial mechanisms of AMPs, introduced two important AMPs (LL-37 and β-defensins) in bone tissues, and reviewed advanced AMP loading strategies and different bioactive materials. Finally, the latest progress and future development of AMPs-loaded bioactive materials for the promotion of bone infection repair were discussed. This study provided a theoretical basis and application strategy for the treatment of bone infection with AMP-loaded bioactive materials.

A Scoping Analysis of Cathelicidin in Response to Organic Dust Exposure and Related Chronic Lung Illnesses

Over two billion people worldwide are exposed to organic dust, which can cause respiratory disorders. The discovery of the cathelicidin peptide provides novel insights into the lung’s response to organic dust; however, its role in the lung’s response to organic dust exposure and chronic lung diseases remains limited. We conducted a scoping review to map the current evidence on the role of cathelicidin LL-37/CRAMP in response to organic dust exposure and related chronic lung diseases: hypersensitivity pneumonitis (HP), chronic obstructive pulmonary disease (COPD) and asthma. We included a total of n = 53 peer-reviewed articles in this review, following the process of (i) a preliminary screening; (ii) a systematic MEDLINE/PubMed database search; (iii) title, abstract and full-text screening; (iv) data extraction and charting. Cathelicidin levels were shown to be altered in all clinical settings investigated; its pleiotropic function was confirmed. It was found that cathelicidin contributes to maintaining homeostasis and participates in lung injury response and repair, in addition to exerting a positive effect against microbial load and infections. In addition, LL-37 was found to sustain continuous inflammation, increase mucus formation and inhibit microorganisms and corticosteroids. In addition, studies investigated cathelicidin as a treatment modality, such as cathelicidin inhalation in experimental HP, which had positive effects. However, the primary focus of the included articles was on LL-37’s antibacterial effect, leading to the conclusion that the beneficial LL-37 activity has not been adequately examined and that further research is required.

LL-37, a Multi-Faceted Amphipathic Peptide Involved in NETosis

Innate immunity responds to infections and inflammatory stimuli through a carefully choreographed set of interactions between cells, stimuli and their specific receptors. Of particular importance are endogenous peptides, which assume roles as defensins or alarmins, growth factors or wound repair inducers. LL-37, a proteolytic fragment of cathelicidin, fulfills the roles of a defensin by inserting into the membranes of bacterial pathogens, functions as alarmin in stimulating chemotaxis of innate immune cells, and alters the structure and efficacy of various cytokines. Here, we draw attention to the direct effect of LL-37 on neutrophils and the release of extracellular traps (NETs), as NETs have been established as mediators of immune defense against pathogens but also as important contributors to chronic disease and tissue pathogenesis. We propose a specific structural basis for LL-37 function, in part by highlighting the structural flexibility of LL-37 and its ability to adapt to distinct microenvironments and interacting counterparts.

HB-EGF-induced IL-8 secretion from airway epithelium leads to lung fibroblast proliferation and migration

BACKGROUND

We have reported that heparin-binding epidermal growth factor (HB-EGF) is increased in patients with chronic obstructive pulmonary disease (COPD) and associated with collagen deposition, but the mechanisms remain unclear. In the present study, we aimed to investigated the inflammatory cytokines secreted by bronchial epithelial cells following exposure to HB-EGF that promoted proliferation and migration of human lung fibroblast.

METHODS

HB-EGF-induced inflammatory cytokines were assayed in two airway epithelial cells (primary human bronchial epithelial cells [HBECs] and BEAS-2B cells). Moreover, the culture supernatants derived from HB-EGF-treated HBECs and BEAS-2B cells were added to human primary lung fibroblasts. The effect of culture supernatants on proliferation and migration of fibroblasts was assessed.

RESULTS

IL-8 expression was significantly increased in bronchial epithelial cells treated with HB-EGF, which was at least partially dependent on NF-kB pathways activation. HB-EGF-induced IL-8 was found to further promote lung fibroblasts proliferation and migration, and the effects were attenuated after neutralizing IL-8.

CONCLUSIONS

These findings suggest that HB-EGF may be involved in the pathology of airway fibrosis by induction of IL-8 from airway epithelium, subsequently causing lung fibroblasts proliferation and migration. Thus, inhibition of HBEGF and/or IL-8 production could prevent the development of airway fibrosis by modulating fibroblast activation.

In vitro and ex vivo models in inhalation biopharmaceutical research - advances, challenges and future perspectives

Oral inhalation results in pulmonary drug targeting and thereby reduces systemic side effects, making it the preferred means of drug delivery for the treatment of respiratory disorders such as asthma, chronic obstructive pulmonary disease or cystic fibrosis. In addition, the high alveolar surface area, relatively low enzymatic activity and rich blood supply of the distal airspaces offer a promising pathway to the systemic circulation. This is particularly advantageous when a rapid onset of pharmacological action is desired or when the drug is suffering from stability issues or poor biopharmaceutical performance following oral administration. Several cell and tissue-based in vitro and ex vivo models have been developed over the years, with the intention to realistically mimic pulmonary biological barriers. It is the aim of this review to critically discuss the available models regarding their advantages and limitations and to elaborate further which biopharmaceutical questions can and cannot be answered using the existing models.

Family with sequence similarity 13 member A mediates TGF-β1-induced EMT in small airway epithelium of patients with chronic obstructive pulmonary disease

Background

To explore the role of family with sequence similarity 13 member A (FAM13A) in TGF-β1-induced EMT in the small airway epithelium of patients with chronic obstructive pulmonary disease (COPD).

Methods

Small airway wall thickness and protein levels of airway remodeling markers, EMT markers, TGF-β1, and FAM13A were measured in lung tissue samples from COPD and non-COPD patients. The correlations of FAM13A expression with COPD severity and EMT marker expression were evaluated. Gain- and loss-of-function assays were performed to explore the functions of FAM13A in cell proliferation, motility, and TGF-β1-induced EMT marker alterations in human bronchial epithelial cell line BEAS-2B.

Results

Independent of smoking status, lung tissue samples from COPD patients exhibited significantly increased small airway thickness and collagen fiber deposition, along with enhanced protein levels of remodeling markers (collagen I, fibronectin, and MMP-9), mesenchymal markers (α-SMA, vimentin, and N-cadherin), TGF-β1, and FAM13A, compared with those from non-COPD patients. FAM13A expression negatively correlated with FEV₁% and PO₂ in COPD patients. In small airway epithelium, FAM13A expression negatively correlated with E-cadherin protein levels and positively correlated with vimentin protein levels. In BEAS-2B cells, TGF-β1 dose-dependently upregulated FAM13A protein levels. FAM13A overexpression significantly promoted cell proliferation and motility in BEAS-2B cells, whereas FAM13A silencing showed contrasting results. Furthermore, FAM13A knockdown partially reversed TGF-β1-induced EMT marker protein alterations in BEAS-2B cells.

Conclusions

FAM13A upregulation is associated with TGF-β1-induced EMT in the small airway epithelium of COPD patients independent of smoking status, serving as a potential therapeutic target for anti-EMT therapy in COPD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01783-z.

Epithelial Barrier Dysfunction in Chronic Respiratory Diseases

Mucosal surfaces are lined by epithelial cells, which provide a complex and adaptive module that ensures first-line defense against external toxics, irritants, antigens, and pathogens. The underlying mechanisms of host protection encompass multiple physical, chemical, and immune pathways. In the lung, inhaled agents continually challenge the airway epithelial barrier, which is altered in chronic diseases such as chronic obstructive pulmonary disease, asthma, cystic fibrosis, or pulmonary fibrosis. In this review, we describe the epithelial barrier abnormalities that are observed in such disorders and summarize current knowledge on the mechanisms driving impaired barrier function, which could represent targets of future therapeutic approaches.

Responsiveness of human bronchial fibroblasts and epithelial cells from asthmatic and non-asthmatic donors to the transforming growth factor-β1 in epithelial-mesenchymal trophic unit model

BACKGROUND

The asthma-related airway wall remodeling is associated i.a. with a damage of bronchial epithelium and subepithelial fibrosis. Functional interactions between human bronchial epithelial cells and human bronchial fibroblasts are known as the epithelial-mesenchymal trophic unit (EMTU) and are necessary for a proper functioning of lung tissue. However, a high concentration of the transforming growth factor-β₁ (TGF-β₁) in the asthmatic bronchi drives the structural disintegrity of epithelium with the epithelial-to-mesenchymal transition (EMT) of the bronchial epithelial cells, and of subepithelial fibrosis with the fibroblast-to-myofibroblast transition (FMT) of the bronchial fibroblasts. Since previous reports indicate different intrinsic properties of the human bronchial epithelial cells and human bronchial fibroblasts which affect their EMT/FMT potential beetween cells derived from asthmatic and non-asthmatic patients, cultured separatelly in vitro, we were interested to see whether corresponding effects could be obtained in a co-culture of the bronchial epithelial cells and bronchial fibroblasts. In this study, we investigate the effects of the TGF-β₁ on the EMT markers of the bronchial epithelial cells cultured in the air-liquid-interface and effectiveness of FMT in the bronchial fibroblast populations in the EMTU models.

RESULTS

Our results show that the asthmatic co-cultures are more sensitive to the TGF-β₁ than the non-asthmatic ones, which is associated with a higher potential of the asthmatic bronchial cells for a profibrotic response, analogously to be observed in '2D' cultures. They also indicate a noticeable impact of human bronchial epithelial cells on the TGF-β₁-induced FMT, stronger in the asthmatic bronchial fibroblast populations in comparison to the non-asthmatic ones. Moreover, our results suggest the protective effects of fibroblasts on the structure of the TGF-β₁-exposed mucociliary differentiated bronchial epithelial cells and their EMT potential.

CONCLUSIONS

Our data are the first to demonstrate a protective effect of the human bronchial fibroblasts on the properties of the human bronchial epithelial cells, which suggests that intrinsic properties of not only epithelium but also subepithelial fibroblasts affect a proper condition and function of the EMTU in both normal and asthmatic individuals.

A proposed role of neutrophil extracellular traps and their interplay with fibroblasts in ANCA-associated vasculitis lung fibrosis

ANCA-associated vasculitides (AAV) comprise three diseases: granulomatosis with polyangiitis, microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis. They are characterised by small vessel inflammation and have a broad range of clinical manifestations and multiorgan involvement which endanger the patient's life. An increasingly recognised complication of AAV, especially in MPA is lung fibrosis, for which no clearcut therapy in this context is available. The release of neutrophil extracellular traps (NETs) in these diseases has been related to the development of fibrosis, but the precise mechanisms are not fully unravelled. This review provides an overview of some of the important proteins known to compose NETs, and proposes some mechanisms by which these remarkable components may exert an impact on the different fibroblastic phenotypes leading to lung fibrosis.

Cathelicidin induces epithelial-mesenchymal transition to promote airway remodeling in smoking-related chronic obstructive pulmonary disease

Background

Epithelial-mesenchymal transition (EMT) is an important characteristic in the remodeling of airways that occurs in chronic obstructive pulmonary disease (COPD). Cigarette smoke is a potential driving factor of this EMT in COPD. However, the mechanisms by which cigarette smoke induce EMT remain uncertain. Cathelicidin has been implicated as a causal factor of airway inflammation and mucus hypersecretion in smoking-related COPD. This study aimed to investigate whether cathelicidin induces EMT to promote airway remodeling in this disease.

Methods

Human lung tissue was collected from smokers with COPD and smokers without COPD. The EMT markers E-cadherin and vimentin were examined by immunohistochemistry. Mouse models of COPD were established by taking mice with airway cathelin-related antimicrobial peptide (CRAMP), the murine homologue of cathelicidin, either upregulated or downregulated by intranasal introduction of lentiviral vectors and then exposing them to cigarette smoke. E-cadherin and vimentin expression in the airways of the model mice was examined using immunofluorescence. Tumor necrosis factor alpha (TNF-α) converting enzyme (TACE), transforming growth factor alpha (TGF-α), and epidermal growth factor receptor (EGFR) expression was analyzed by Western blot. Additionally, NCI-H292 human airway epithelial cells, both with and without cathelicidin downregulation, were stimulated with cigarette smoke extract (CSE) and LL-37 synthetic peptide, a bioactive fragment of cathelicidin. This was done to confirm that the TACE/TGF-α/EGFR signaling pathway is activated in humans exposed to cigarette smoke.

Results

Significant EMT was found in the small airways of smokers both with and without COPD, as well as in the airways of COPD model mice. Downregulation of CRAMP in COPD mice, however, ameliorated airway EMT induced by cigarette smoke. Conversely, upregulation of CRAMP enhanced airway EMT in vivo; TACE, TGF-α, and EGFR were found to be involved in this process. In vitro, EMT induced by CSE and LL-37 was inhibited by blocking TACE, TGF-α, and EGFR expression.

Conclusions

Cathelicidin promotes airway EMT by activating the TACE/TGF-α/EGFR signaling pathway. This mediates smoking-induced airway remodeling in the pathogenesis of COPD.

Distinct contributions of cathelin-related antimicrobial peptide (CRAMP) derived from epithelial cells and macrophages to colon mucosal homeostasis

The cathelin‐related antimicrobial peptide CRAMP protects the mouse colon from inflammation, inflammation‐associated carcinogenesis, and disrupted microbiome balance, as shown in systemic Cnlp^−/− mice (also known as Camp^−/− mice). However, the mechanistic basis for the role and the cellular source of CRAMP in colon pathophysiology are ill defined. This study, using either epithelial or myeloid conditional Cnlp^−/−mice, demonstrated that epithelial cell‐derived CRAMP played a major role in supporting normal development of colon crypts, mucus production, and repair of injured mucosa. On the other hand, myeloid cell‐derived CRAMP potently supported colon epithelial resistance to bacterial invasion during acute inflammation with exacerbated mucosal damage and higher rate of mouse mortality. Therefore, a well concerted cooperation of epithelial‐ and myeloid‐derived CRAMP is essential for colon mucosal homeostasis. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Expression of Matrix Metalloproteinase-2, Matrix Metalloproteinase-9, Tissue Inhibitor of Metalloproteinase-1, and Changes in Alveolar Septa in Patients with Chronic Obstructive Pulmonary Disease

Background

This study investigated the relationship between the pathological alteration of alveolar septa and (1) pulmonary function and (2) matrix metalloproteinase (MMP)-2, MMP-9, and tissue inhibitor matrix metalloproteinase 1 (TIMP-1) expression in chronic obstructive pulmonary disease (COPD).

Material/Methods

Sixty patients with pulmonary disease were divided into control (n=20) and COPD (n=40) groups. Postoperative lung tissue specimens were examined. Hematoxylin and eosin and elastin van Gieson staining detected pathological alterations of pulmonary alveolar septa. Septa thickness was measured. MMP-2, MMP-9, and TIMP-1 expression levels were detected by immunohistochemical staining. Correlations were determined by Pearson analysis.

Results

Forced expiratory volume in 1 s (FEV₁), forced vital capacity, FEV₁ percent predicted (FEV₁%pre), and diffusion capacity of carbon monoxide percent predicted (DLCO%pre) in COPD patients were significantly lower than in those of the control group (P<0.05). MMP-2, MMP-9, and TIMP-1 expression levels were significantly higher in the COPD group than in control, especially the severe group (P<0.05). Septa thickness was negatively correlated with FEV₁%pre (r=−0.335; P<0.05) and positively correlated with MMP-2 and TIMP-1 expression (P<0.05). Proportion of collagenous fiber was negatively correlated with FEV₁%pre and DLCO%pre (P<0.01), and positively correlated with MMP-2, MMP-9, and TIMP-1 expression (P<0.01). Proportion of elastic fibers was negatively correlated with collagenous fiber.

Conclusions

The pathological alteration of alveolar septa was correlated with pulmonary function and expression levels of MMP-2, MMP-9, and TIMP-1, which can play vital roles in COPD progression.

Formyl peptide receptors in the mucosal immune system

Formyl peptide receptors (FPRs) belong to the G protein-coupled receptor (GPCR) family and are well known as chemotactic receptors and pattern recognition receptors (PRRs) that recognize bacterial and mitochondria-derived formylated peptides. FPRs are also known to detect a wide range of ligands, including host-derived peptides and lipids. FPRs are highly expressed not only in phagocytes such as neutrophils, monocytes, and macrophages but also in nonhematopoietic cells such as epithelial cells and endothelial cells. Mucosal surfaces, including the gastrointestinal tract, the respiratory tract, the oral cavity, the eye, and the reproductive tract, separate the external environment from the host system. In mucosal surfaces, the interaction between the microbiota and host cells needs to be strictly regulated to maintain homeostasis. By sharing the same FPRs, immune cells and epithelial cells may coordinate pathophysiological responses to various stimuli, including microbial molecules derived from the normal flora. Accumulating evidence shows that FPRs play important roles in maintaining mucosal homeostasis. In this review, we summarize the roles of FPRs at mucosal surfaces.

Epithelial-mesenchymal crosstalk in COPD: An update from in vitro model studies

Chronic Obstructive Pulmonary disease (COPD) involves airway inflammation and remodeling leading to small airways disease and emphysema, which results in irreversible airflow obstruction. During lung development, reciprocal interactions between the endoderm and mesoderm (epithelial-mesenchymal trophic unit (EMTU)) are essential for morphogenetic cues that direct cell proliferation, differentiation, and extracellular (ECM) production. In COPD, a significant number of the inflammation and remodeling mediators resemble those released during lung development, which has led to the hypothesis that aberrant activation of the EMTU may occur in the disease. Studies assessing lung epithelial and fibroblast function in COPD, have been primarily focused on monoculture studies. To capture the in vivo environment of the human lung and aid in the understanding of mechanisms and mediators involved in abnormal epithelial-fibroblast communication in COPD, complex co-culture models are required. In this review, we describe the studies that have used co-culture models to assess epithelial-fibroblast interactions and their role in the pathogenesis of COPD.

Vascular endothelial growth factor enhances profibrotic activities through modulation of calcium homeostasis in human atrial fibroblasts

Vascular endothelial growth factor (VEGF), a pivotal activator of angiogenesis and calcium (Ca²⁺) signaling in endothelial cells, was shown to increase collagen production in atrial fibroblasts. In this study, we evaluated whether VEGF may regulate Ca²⁺ homeostasis in atrial fibroblasts and contribute to its profibrogenesis. Migration, and proliferation analyses, patch-clamp assay, Ca²⁺ fluorescence imaging, and western blotting were performed using VEGF-treated (300 pg/mL or 1000 pg/mL) human atrial fibroblasts with or without coadministration of Ethylene glycol tetra-acetic acid (EGTA, 1 mmol/L), or KN93 (a Ca²⁺/calmodulin-dependent protein kinase II [CaMKII] inhibitor, 10 μmol/L). VEGF (1000 pg/mL) increased migration, myofibroblast differentiation, pro-collagen type I, pro-collagen type III production, and phosphorylated VEGF receptor 1 expression of fibroblasts. VEGF (1000 pg/mL) increased the nonselective cation current (I_NSC) of transient receptor potential (TRP) channels and potassium current of intermediate-conductance Ca²⁺-activated K⁺ (K_Ca3.1) channels thereby upregulating Ca²⁺ entry. VEGF upregulated phosphorylated ERK expression. An ERK inhibitor (PD98059, 50 μmol/L) attenuated VEGF-activated I_NSC of TRP channels. The presence of EGTA attenuated the profibrotic effects of VEGF on pro-collagen type I, pro-collagen type III production, myofibroblast differentiation, and migratory capabilities of fibroblasts. VEGF upregulated the expression of phosphorylated CaMKII in fibroblasts, which was attenuated by EGTA. In addition, KN93 reduced VEGF-increased pro-collagen type I, pro-collagen type III production, myofibroblast differentiation, and the migratory capabilities of fibroblasts. In conclusion, we found that VEGF increases atrial fibroblast activity through CaMKII signaling by enhancing Ca²⁺ entry. Our findings provide benchside evidence leading to a potential novel strategy targeting atrial myopathy and arrhythmofibrosis.

Pharmacological Modulation of Endotoxin-Induced Release of IL-26 in Human Primary Lung Fibroblasts

Background: Interleukin (IL)-26 is a neutrophil-mobilizing and bactericidal cytokine that is enhanced in human airways in vivo in response to endotoxin from Gram-negative bacteria. This cytokine is also enhanced in the airways during exacerbations of chronic obstructive pulmonary disease (COPD). Here, we investigated whether human primary lung fibroblasts (HLF) release IL-26 constitutively and in response to TLR4 stimulation by endotoxin and characterized the effects of bronchodilatory and anti-inflammatory drugs utilized in COPD.

Methods: The HLF were stimulated with different concentrations of endotoxin. Cells were also treated with different concentrations of bronchodilatory and anti-inflammatory drugs, with and without endotoxin stimulation. Cytokine protein concentrations were quantified in the cell-free conditioned media [enzyme-linked immunosorbent assay (ELISA)], and the phosphorylation levels of intracellular signaling molecules were determined (phosphoELISA).

Results: Whereas HLF displayed constitutive release of IL-26 into the conditioned medium, endotoxin markedly enhanced this release, as well as that of IL-6 and IL-8. This cytokine release was paralleled by increased phosphorylation of the intracellular signaling molecules NF-κB, c-Jun N-terminal kinase (JNK) 1-3, p38, and extracellular signal-regulated kinase (ERK) 1/2. The glucocorticoid hydrocortisone caused substantial inhibition of the endotoxin-induced release of IL-26, IL-6, and IL-8, an effect paralleled by a decrease of the phosphorylation of NF-κB, p38, and ERK1/2. The muscarinic receptor antagonist (MRA) tiotropium, but not aclidinium, caused minor inhibition of the endotoxin-induced release of IL-26 and IL-8, paralleled by a decreased phosphorylation of NF-κB. The β2-adrenoceptor agonist salbutamol caused modest inhibition of the endotoxin-induced release of IL-26 and IL-8, paralleled by a decreased phosphorylation of NF-κB, JNK1-3, and p38. Similar pharmacological effects were observed for the constitutive release of IL-26.

Conclusions: The HLF constitute an abundant source of IL-26 that may contribute to local host defense against Gram-negative bacteria. Among the tested drugs, the glucocorticoid displayed the most powerful inhibitory effect, affecting the NF-κB, p38, and ERK1/2 signaling pathways. Whether or not this inhibition of IL-26 contributes to an increased risk for local infections in COPD requires further evaluation.

Cathelicidin LL-37 restoring glucocorticoid function in smoking and lipopolysaccharide-induced airway inflammation in rats

Background

Glucocorticoids have been widely used to treat patients with chronic obstructive pulmonary disease (COPD). Nevertheless, corticosteroid insensitivity is a major barrier to the effective treatment of COPD and its mechanism remains unclear. This study aimed to evaluate the effect of cathelicidin LL-37 on corticosteroid insensitivity in COPD rat model, and to explore the involved mechanisms.

Methods

COPD model was established by exposing male Wistar rats to cigarette smoke combined with intratracheal instillation of lipopolysaccharide (LPS). Inhaled budesonide and LL-37 were consequently applied to COPD models separately or collectively to confirm the effects on inflammatory cytokines (tumor necrosis factor [TNF]-α and transforming growth factor [TGF]-β) by enzyme-linked immunosorbent assay (ELISA) and lung tissue histopathological morphology. Expression of histone deacetylase-2 (HDAC2) and phosphorylation of Akt (p-AKT) in lung were also measured.

Results

Briefly, COPD model rats showed an increased basal release of inflammatory cytokines (lung TNF-α: 45.7 ± 6.1 vs. 20.1 ± 3.8 pg/mL, P < 0.01; serum TNF-α: 8.9 ± 1.2 vs. 6.7 ± 0.5 pg/mL, P = 0.01; lung TGF-β: 122.4 ± 20.8 vs. 81.9 ± 10.8 pg/mL, P < 0.01; serum TGF-β: 38.9 ± 8.5 vs. 20.6 ± 2.3 pg/mL, P < 0.01) and COPD related lung tissue histopathological changes, as well as corticosteroid resistance molecular profile characterized by an increase in phosphoinositide 3-kinase (PI3K)/Akt (0.5 ± 0.1 fold of control vs. 0.2 ± 0.1 fold of control, P = 0.04) and a decrease in HDAC2 expression and activity (expression: 13.1 ± 0.4 μmol/μg vs. 17.4 ± 1.1 μmol/μg, P < 0.01; activity: 1.1 ± 0.1 unit vs. 1.4 ± 0.1 unit, P < 0.01), compared with control group. In addition, LL-37 enhanced the anti-inflammatory effect of budesonide in an additive manner. Treatment with combination of inhaled corticosteroids (ICS) and LL-37 led to a significant increase of HDAC2 expression and activity (expression: 15.7 ± 0.4 μmol/μg vs. 14.1 ± 0.9 μmol/μg, P < 0.01; activity: 1.3 ± 0.1 unit vs. 1.0 ± 0.1 unit, P < 0.01), along with decrease of p-AKT compared to budesonide monotherapy (0.1 ± 0.0 fold of control vs. 0.3 ± 0.1 fold of control, P < 0.01).

Conclusions

This study suggested that LL-37 could improve the anti-inflammatory activity of budesonide in cigarette smoke and LPS-induced COPD rat model by enhancing the expression and activity of HDAC2. The mechanism of this function of LL-37 might involve the inhibition of PI3K/Akt pathway.

Extracellular Matrix Component Remodeling in Respiratory Diseases: What Has Been Found in Clinical and Experimental Studies?

Changes in extracellular matrix (ECM) components in the lungs are associated with the progression of respiratory diseases, such as asthma, chronic obstructive pulmonary disease (COPD), and acute respiratory distress syndrome (ARDS). Experimental and clinical studies have revealed that structural changes in ECM components occur under chronic inflammatory conditions, and these changes are associated with impaired lung function. In bronchial asthma, elastic and collagen fiber remodeling, mostly in the airway walls, is associated with an increase in mucus secretion, leading to airway hyperreactivity. In COPD, changes in collagen subtypes I and III and elastin, interfere with the mechanical properties of the lungs, and are believed to play a pivotal role in decreased lung elasticity, during emphysema progression. In ARDS, interstitial edema is often accompanied by excessive deposition of fibronectin and collagen subtypes I and III, which can lead to respiratory failure in the intensive care unit. This review uses experimental models and human studies to describe how inflammatory conditions and ECM remodeling contribute to the loss of lung function in these respiratory diseases.

Differential Expression of Antimicrobial Peptides in Streptococcus pneumoniae Keratitis and STAT3-Dependent Expression of LL-37 by Streptococcus pneumoniae in Human Corneal Epithelial Cells

Streptococcus pneumoniae is the leading cause of bacterial keratitis in the developing world with a growing trend of acquiring resistance against various antibiotics. In the current study, we determined the expression of different antimicrobial peptides (AMPs) in response to S. pneumoniae in patients, as well as in primary and immortalized human corneal epithelial cells. We further focused on LL-37 and determined its expression in human cornea infected with S. pneumoniae and studied the killing ability of LL-37 against S. pneumoniae. The expression of AMPs was determined by quantitative PCR and the phosphorylation of signaling proteins was evaluated by immunoblot analysis. LL-37 expression was also determined by immunofluorescence and Western blot method and the killing ability of LL-37 against S. pneumoniae was determined by colony-forming units. Differential expression of antimicrobial peptides was observed in patients with S. pneumoniae keratitis. Although S. pneumoniae induced expression of the AMPs in human corneal epithelial cells (HCEC), it did not induce AMP expression in U937, a human monocyte cell line. S. pneumoniae also caused activation of nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB)and mitogen activated protein kinase (MAPK) pathways in corneal epithelial cells. LL-37 was found to be effective against both laboratory and clinical strains of S. pneumoniae. LL-37 induction by S. pneumoniae in human corneal epithelial cells was mediated by signal transducer and activator of transcription 3 (STAT3) activation, and inhibition of STAT3 activation significantly reduced LL-37 expression. Our study determines an extensive profile of AMPs expressed in the human cornea during S. pneumoniae infection, and suggests the potential of LL-37 to be developed as an alternative therapeutic intervention to fight increasing antibiotic resistance among bacteria.

Plasma cathelicidin and longitudinal lung function in current and former smokers

INTRODUCTION

Cathelicidin (also known as LL-37 in humans) is an antimicrobial peptide secreted by epithelial and immune cells and regulated by vitamin D. The immunological roles of cathelicidin make it a putative biomarker to identify individuals at risk for reduced lung function. The objective of this study is to determine potential independent associations between low plasma cathelicidin and longitudinal lung function in current or former smokers without COPD.

METHODS

In a nested analysis of 308 participants from an observational cohort study, plasma cathelicidin and serum 25-hydroxy-vitamin D measurements were obtained at baseline, years three and five. The independent association between lowest quartile cathelicidin (<35 ng/ml) and forced-expiratory-volume-in-1-second (FEV1) at baseline, six and 18 months from each cathelicidin measurement was assessed with generalized estimating equations after adjusting for age, sex, race, smoking status and intensity. The long-term stability of cathelicidin and relationship with vitamin D was evaluated.

RESULTS

The cohort was 91% African-American, mean age 48.6 years, 32% female, and 81% current smokers. Participants with low cathelicidin were more likely to be female and have lower FEV1. Low cathelicidin was not independently associated with baseline FEV1. There was an independent association between low cathelicidin and reduced FEV1 at six months [-72 ml (95% CI, -140 to -8ml); p = 0.027] and 18 months [-103 ml (95% CI, -180 to -27 ml); p = 0.007]. Cathelicidin was stable over time and not correlated with vitamin D level.

CONCLUSION

In current and former smokers with preserved lung function, low cathelicidin is associated with sustained lung function reductions at six and 18 months, suggesting that cathelicidin may be an informative biomarker to predict persistent lung function disparities among at-risk individuals.

Evaluation of plasma antimicrobial peptide LL-37 and nuclear factor-kappaB levels in stable chronic obstructive pulmonary disease

Background

Antimicrobial peptides are effectors of host defence against infection and inflammation and can encourage wound repair.

Objectives

The objectives of this study were to investigate the plasma antimicrobial peptide LL-37 and nuclear factor-kappaB (NF-κB) levels in patients with stable COPD compared with a control group and to highlight their importance in immune inflammation.

Methods

One hundred and thirty-eight stable COPD patients and 33 control subjects were enrolled in the study. The COPD patients were classified into four groups based on FEV₁ (groups I-IV) and also divided into "low-risk and high-risk" groups (groups A-B [low risk], C-D [high risk]).

Results

Plasma LL-37 levels were significantly lower while plasma NF-κB levels of the COPD patients were significantly higher than those of the control subjects (P<0.001, both). LL-37 levels were significantly lower in group IV than in groups I, II, and III (P<0.01, all). NF-κB levels were significantly higher in groups III and IV than in groups I and II (P<0.05, both). There was a positive correlation between FEV₁ and FEV₁/FVC in all COPD patients (r=0.742, P<0.001) and in group D (r=0.741, P<0.001). Furthermore, there was an inverse correlation between LL-37 and NF-κB in both the groups C (r=-0.566, P<0.001) and D (r=-0.694, P<0.001) and group C+D combined (r=-0.593, P<0.001). Furthermore, in group C, LL-37 and FEV₁ were positively correlated (r=0.633, P<0.001).

Conclusion

Our study indicated that plasma LL-37 and NF-κB may play an important role in chronic immune inflammation. Decreased LL-37 levels may be particularly high risk for patients in stage IV disease. The role of LL-37 as a target for treatment of the immune system and COPD must be widely evaluated.

The role of FGF-2 in smoke-induced emphysema and the therapeutic potential of recombinant FGF-2 in patients with COPD

Although the positive effects of recombinant fibroblast growth factor-2 (rFGF-2) in chronic obstructive pulmonary disease (COPD) have been implicated in previous studies, knowledge of its role in COPD remains limited. The mechanism of FGF2 in a COPD mouse model and the therapeutic potential of rFGF-2 were investigated in COPD. The mechanism and protective effects of rFGF-2 were evaluated in cigarette smoke-exposed or elastase-induced COPD animal models. Inflammation was assessed in alveolar cells and lung tissues from mice. FGF-2 was decreased in the lungs of cigarette smoke-exposed mice. Intranasal use of rFGF-2 significantly reduced macrophage-dominant inflammation and alveolar destruction in the lungs. In the elastase-induced emphysema model, rFGF-2 improved regeneration of the lungs. In humans, plasma FGF-2 was decreased significantly in COPD compared with normal subjects (10 subjects, P = 0.037). The safety and efficacy of inhaled rFGF-2 use was examined in COPD patients, along with changes in respiratory symptoms and pulmonary function. A 2-week treatment with inhaled rFGF-2 in COPD (n = 6) resulted in significantly improved respiratory symptoms compared with baseline levels (P < 0.05); however, the results were not significant compared with the placebo. The pulmonary function test results of COPD improved numerically compared with those in the placebo, but the difference was not statistically significant. No serious adverse events occurred during treatment with inhaled rFGF-2. The loss of FGF-2 production is an important mechanism in the development of COPD. Inhaling rFGF-2 may be a new therapeutic option for patients with COPD because rFGF-2 decreases inflammation in lungs exposed to cigarette smoke.

Heparin-binding epidermal growth factor contributes to COPD disease severity by modulating airway fibrosis and pulmonary epithelial-mesenchymal transition

Although airway fibrosis and epithelial-mesenchymal transition (EMT) contribute to airway remodeling in chronic obstructive pulmonary disease (COPD), the mechanisms underlying their development have not been fully elucidated. In the present study, we aimed to assess heparin-binding epidermal growth factor (HB-EGF) expression in the airways of patients with COPD and to elucidate the possible role of HB-EGF in the pathology of COPD. Sputum and lung tissue HB-EGF expression was evaluated in control subjects and patients with COPD. The relationships between HB-EGF expression, disease severity, collagen deposition (fibrosis), and EMT were investigated. In vitro, human bronchial epithelial (HBE) cells and lung fibroblast cells exposed to the recombinant HB-EGF, collagen deposition and EMT were assessed. We found that sputum HB-EGF expression was significantly increased in patients with COPD compared with non-smokers and smokers without COPD. There was a significant positive correlation between sputum HB-EGF and COPD assessment test (CAT) score. HB-EGF expression was significantly increased in the lung tissue samples of patients with COPD and associated with collagen deposition and N- and E-cadherin, and vimentin expression. In vitro, HB-EGF promoted collagen production in lung fibroblasts. Moreover, HB-EGF induced the EMT process through induction of N-and E-cadherin, and vimentin expression in HBE cells. Collectively, HB-EGF induces airway remodeling by modulating airway fibrosis and pulmonary EMT, and contributes to the COPD severity. The current data may provide insight into the underlying pathogenesis of COPD, in which HB-EGF has an important pathogenic role.

Breaking the frontiers of cosmetology with antimicrobial peptides

Antimicrobial peptides (AMPs) are mostly endogenous, cationic, amphipathic polypeptides, produced by many natural sources. Recently, many biological functions beyond antimicrobial activity have been attributed to AMPs, and some of these have attracted the attention of the cosmetics industry. AMPs have revealed antioxidant, self-renewal and pro-collagen effects, which are desirable in anti-aging cosmetics. Additionally, AMPs may also be customized to act on specific cellular targets. Here, we review the recent literature that highlights the many possibilities presented by AMPs, focusing on the relevance and impact that this potentially novel class of active cosmetic ingredients might have in the near future, creating new market outlooks for the cosmetic industry with these molecules as a viable alternative to conventional cosmetics.

Defective formyl peptide receptor 2/3 and annexin A1 expressions associated with M2a polarization of blood immune cells in patients with chronic obstructive pulmonary disease

Background

Controversy exists in previous studies on macrophage M1/M2 polarization in chronic obstructive pulmonary disease (COPD). We hypothesized that formyl peptide receptor (FPR), a marker of efferocytosis and mediator of M1/M2 polarization, may be involved in the development of COPD.

Methods

We examined FPR 1/2/3 expressions of blood M1/M2a monocyte, neutrophil, natural killer (NK) cell, NK T cell, T helper (Th) cell, and T cytotoxic (Tc) cell by flowcytometry method in 40 patients with cigarette smoking-related COPD and 16 healthy non-smokers. Serum levels of five FPR ligands were measured by ELISA method.

Results

The COPD patients had lower M2a percentage and higher percentages of NK, NK T, Th, and Tc cells than the healthy non-smokers. FPR2 expressions on Th/Tc cells, FPR3 expressions of M1, M2a, NK, NK T, Th, and Tc cells, and serum annexin A1 (an endogenous FPR2 ligand) levels were all decreased in the COPD patients as compared with that in the healthy non-smokers. FPR1 expression on neutrophil was increased in the COPD patient with a high MMRC dyspnea scale, while FPR2 expression on neutrophil and annexin A1 were both decreased in the COPD patients with a history of frequent moderate exacerbation (≥ 2 events in the past 1 year). In 10 COPD patients whose blood samples were collected again after 1-year treatment, M2a percentage, FPR3 expressions of M1/NK/Th cells, FPR2 expression on Th cell, and FPR1 expression on neutrophil were all reversed to normal, in parallel with partial improvement in small airway dysfunction.

Conclusions

Our findings provide evidence for defective FPR2/3 and annexin A1 expressions that, associated with decreased M2a polarization, might be involved in the development of cigarette smoking induced persistent airflow limitation in COPD.

Positive Rates and Factors Associated with Abnormal Lung Function of Greenhouse Workers in China: A Cross-Sectional Study

Since the number of greenhouse workers are increasing in China, this observational cross-sectional study was designed to evaluate lung function and discuss the potential risk factors, to provide evidence in the surveillance of greenhouse workers' health. 678 greenhouse workers in Gansu Province, China were enrolled. A questionnaire which included demographic and occupational information was used. Vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), and FEV₁:FVC ratios (FEV₁/FVC), maximal expiratory flow after 50% of the FVC has not been exhaled (MEF₅₀), maximal expiratory flow after 25% of the FVC has not been exhaled (MEF₂₅) and maximal mid-expiratory flow curve (MMEF) were measured as lung function indicators. The mean values and standard deviations (SDs) of VC% predicted, FVC% predicted, FEV₁% predicted and FEV₁/FVC ratio were 106.07 ± 13.36, 107.60 ± 13.95, 97.19 ± 14.80 and 89.76 ± 10.78 respectively. The positive rates of above four and abnormal lung ventilation function were 2.9%, 2.8%, 11.2%, 4.6% and 6.5% respectively. Gender, age, BMI and number of greenhouses owned were influence factors of lung ventilation function (p < 0.05). The mean values and SDs of MEF₅₀% predicted, MEF₂₅% predicted and MMEF% predicted were 69.63 ± 24.95, 54.04 ± 24.94 and 66.81 ± 24.53. The positive rates of above three and abnormal small airway function were 45.0%, 72.1%, 47.2% and 49.4% respectively. Age, education and number of greenhouses owned were influence factors for small airway function (p < 0.05). Working in a greenhouse might influence lung function of the workers. Small airway function indicators could be used as priority indicators for the surveillance of greenhouse workers' health.

Use of airway epithelial cell culture to unravel the pathogenesis and study treatment in obstructive airway diseases

Asthma and chronic obstructive pulmonary disease (COPD) are considered as two distinct obstructive diseases. Both chronic diseases share a component of airway epithelial dysfunction. The airway epithelium is localized to deal with inhaled substances, and functions as a barrier preventing penetration of such substances into the body. In addition, the epithelium is involved in the regulation of both innate and adaptive immune responses following inhalation of particles, allergens and pathogens. Through triggering and inducing immune responses, airway epithelial cells contribute to the pathogenesis of both asthma and COPD. Various in vitro research models have been described to study airway epithelial cell dysfunction in asthma and COPD. However, various considerations and cautions have to be taken into account when designing such in vitro experiments. Epithelial features of asthma and COPD can be modelled by using a variety of disease-related invoking substances either alone or in combination, and by the use of primary cells isolated from patients. Differentiation is a hallmark of airway epithelial cells, and therefore models should include the ability of cells to differentiate, as can be achieved in air-liquid interface models. More recently developed in vitro models, including precision cut lung slices, lung-on-a-chip, organoids and human induced pluripotent stem cells derived cultures, provide novel state-of-the-art alternatives to the conventional in vitro models. Furthermore, advanced models in which cells are exposed to respiratory pathogens, aerosolized medications and inhaled toxic substances such as cigarette smoke and air pollution are increasingly used to model e.g. acute exacerbations. These exposure models are relevant to study how epithelial features of asthma and COPD are affected and provide a useful tool to study the effect of drugs used in treatment of asthma and COPD. These new developments are expected to contribute to a better understanding of the complex gene-environment interactions that contribute to development and progression of asthma and COPD.

Susceptibility for cigarette smoke-induced DAMP release and DAMP-induced inflammation in COPD

Cigarette smoke (CS) exposure is a major risk factor for chronic obstructive pulmonary disease (COPD). We investigated whether CS-induced damage-associated molecular pattern (DAMP) release or DAMP-mediated inflammation contributes to susceptibility for COPD. Samples, including bronchial brushings, were collected from young and old individuals, susceptible and nonsusceptible for the development of COPD, before and after smoking, and used for gene profiling and airway epithelial cell (AEC) culture. AECs were exposed to CS extract (CSE) or specific DAMPs. BALB/cByJ and DBA/2J mice were intranasally exposed to LL-37 and mitochondrial (mt)DAMPs. Functional gene-set enrichment analysis showed that CS significantly increases the airway epithelial gene expression of DAMPs and DAMP receptors in COPD patients. In cultured AECs, we observed that CSE induces necrosis and DAMP release, with specifically higher galectin-3 release from COPD-derived compared with control-derived cells. Galectin-3, LL-37, and mtDAMPs increased CXCL8 secretion in AECs. LL-37 and mtDAMPs induced neutrophilic airway inflammation, exclusively in mice susceptible for CS-induced airway inflammation. Collectively, we show that in airway epithelium from COPD patients, the CS-induced expression of DAMPs and DAMP receptors in vivo and the release of galectin-3 in vitro is exaggerated. Furthermore, our studies indicate that a predisposition to release DAMPs and subsequent induction of inflammation may contribute to the development of COPD.

LL-37: Cathelicidin-related antimicrobial peptide with pleiotropic activity

Antimicrobial peptides (AMPs) is a large family of compounds serving as natural antibiotics, widely distributed across the organism, mainly in mucus layers. They are designed to prevent pathogens from colonization. Among them, defensins and cathelicidins could be found. LL-37, the sole human cathelicidin draws particular attention because of its outstanding abilities. In addition to being a broad spectrum antibiotic, LL-37 has potent chemotactic and immunomodulatory properties. In this review, we discussed the potency of LL-37 as a therapeutic agent in four systems: immunological, respiratory, gastrointestinal and in the skin. We analyzed the main molecular pathways dependent on human cathelicidin and related them to specific diseases. We conclude that LL-37 shows a great potential to be further investigated and developed as a drug with clinical use.

YKL-40 expression in chronic obstructive pulmonary disease: relation to acute exacerbations and airway remodeling

BACKGROUND

Recent studies suggest that YKL-40, also called chitinase-3-like-1 protein, has been implicated in the pathogenesis of various inflammatory diseases. It is currently unknown, however, whether YKL-40 plays a role in acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and airway remodeling.

METHODS

We evaluated serum YKL-40 levels in patients with AECOPD (n = 37) and stable COPD (n = 44), as well as in controls (n = 47). The association between YKL-40 expression and airway remodeling was analyzed. The effects of YKL-40 on collagen synthesis of primary human lung fibroblasts were also evaluated.

RESULTS

Serum YKL-40 levels were elevated at AECOPD onset as compared to stable disease (median [interquartile range], 78.6 [52.3-122.2] ng/ml versus 46.7 [31.2-75.5] ng/ml; p = 0.0005). The ideal cutoff point for distinguishing patients with AECOPD from those with stable COPD was 64.7 ng/ml (AUC: 0.71; 95%CI: 0.596 to 0.823). YKL-40 expression correlated with airflow obstruction, C-reactive protein, and collagen deposition. Stimulation with YKL-40 promoted collagen production in lung fibroblasts through ERK- and p38-dependent mechanisms.

CONCLUSIONS

YKL-40 expression is up-regulated in patients with COPD and correlates with exacerbation attacks and may contribute to airway remodeling by acting on lung fibroblasts. The current data may provide insight into the underlying pathogenesis of COPD, in which YKL-40 has an important pathogenic role.

TRIAL REGISTRATION

ChiCTR-OCC-13003567.

Inflammatory Diseases of the Lung Induced by Conventional Cigarette Smoke: A Review

Smoking-induced lung diseases were extremely rare prior to the 20th century. With commercialization and introduction of machine-made cigarettes, worldwide use skyrocketed and several new pulmonary diseases have been recognized. The majority of pulmonary diseases caused by cigarette smoke (CS) are inflammatory in origin. Airway epithelial cells and alveolar macrophages have altered inflammatory signaling in response to CS, which leads to recruitment of lymphocytes, eosinophils, neutrophils, and mast cells to the lungs-depending on the signaling pathway (nuclear factor-κB, adenosine monophosphate-activated protein kinase, c-Jun N-terminal kinase, p38, and signal transducer and activator of transcription 3) activated. Multiple proteins are upregulated and secreted in response to CS exposure, and many of these have immunomodulatory activities that contribute to disease pathogenesis. In particular, metalloproteases 9 and 12, surfactant protein D, antimicrobial peptides (LL-37 and human β defensin 2), and IL-1, IL-6, IL-8, and IL-17 have been found in higher quantities in the lungs of smokers with ongoing inflammation. However, many underlying mechanisms of smoking-induced inflammatory diseases are not yet known. We review here the known cellular and molecular mechanisms of CS-induced diseases, including COPD, respiratory bronchiolitis-interstitial lung disease, desquamative interstitial pneumonia, acute eosinophilic pneumonia, chronic rhinosinusitis, pulmonary Langerhans cell histiocytosis, and chronic bacterial infections. We also discuss inflammation induced by secondhand and thirdhand smoke exposure and the pulmonary diseases that result. New targeted antiinflammatory therapeutic options are currently under investigation and hopefully will yield promising results for the treatment of these highly prevalent smoking-induced diseases.

Antimicrobial Peptides and Innate Lung Defenses: Role in Infectious and Noninfectious Lung Diseases and Therapeutic Applications

Respiratory infections are a major clinical problem, and treatment is increasingly complicated by the emergence of microbial antibiotic resistance. Development of new antibiotics is notoriously costly and slow; therefore, alternative strategies are needed. Antimicrobial peptides, central effector molecules of the immune system, are being considered as alternatives to conventional antibiotics. These peptides display a range of activities, including not only direct antimicrobial activity, but also immunomodulation and wound repair. In the lung, airway epithelial cells and neutrophils in particular contribute to their synthesis. The relevance of antimicrobial peptides for host defense against infection has been demonstrated in animal models and is supported by observations in patient studies, showing altered expression and/or unfavorable circumstances for their action in a variety of lung diseases. Importantly, antimicrobial peptides are active against microorganisms that are resistant against conventional antibiotics, including multidrug-resistant bacteria. Several strategies have been proposed to use these peptides in the treatment of infections, including direct administration of antimicrobial peptides, enhancement of their local production, and creation of more favorable circumstances for their action. In this review, recent developments in antimicrobial peptides research in the lung and clinical applications for novel therapies of lung diseases are discussed.

Group A Streptococcal M1 Protein Sequesters Cathelicidin to Evade Innate Immune Killing

The antimicrobial peptide LL-37 is generated upon proteolytic cleavage of cathelicidin and limits invading pathogens by directly targeting microbial membranes as well as stimulating innate immune cell function. However, some microbes evade LL-37-mediated defense. Notably, group A Streptococcus (GAS) strains belonging to the hypervirulent M1T1 serogroup are more resistant to human LL-37 than other GAS serogroups. We show that the GAS surface-associated M1 protein sequesters and neutralizes LL-37 antimicrobial activity through its N-terminal domain. M1 protein also binds the cathelicidin precursor hCAP-18, preventing its proteolytic maturation into antimicrobial forms. Exogenous M1 protein rescues M1-deficient GAS from killing by neutrophils and within neutrophil extracellular traps and neutralizes LL-37 chemotactic properties. M1 also binds murine cathelicidin, and its virulence contribution in a murine model of necrotizing skin infection is largely driven by its ability to neutralize this host defense peptide. Thus, cathelicidin resistance is essential for the pathogenesis of hyperinvasive M1T1 GAS.

Anti-fibrogenic effects of the anti-microbial peptide cathelicidin in murine colitis-associated fibrosis

BACKGROUND AND AIMS

Cathelicidin (LL-37 in human and mCRAMP in mice) represents a family of endogenous antimicrobial peptides with anti-inflammatory effects. LL-37 also suppresses collagen synthesis, an important fibrotic response, in dermal fibroblasts. Here we determined whether exogenous cathelicidin administration modulates intestinal fibrosis in two animal models of intestinal inflammation and in human colonic fibroblasts.

METHODS

C57BL/6J mice (n=6 per group) were administered intracolonically with a trinitrobenzene sulphonic acid (TNBS) enema to induce chronic (6-7 weeks) colitis with fibrosis. mCRAMP peptide (5 mg/kg every 3 day, week 5-7) or cathelicidin gene (Camp)-expressing lentivirus (10⁷ infectious units week 4) were administered intracolonically or intravenously, respectively. 129Sv/J mice were infected with Salmonella typhimurium orally to induce cecal inflammation with fibrosis. Camp expressing lentivirus (10⁷ infectious units day 11) was administered intravenously.

RESULTS

TNBS-induced chronic colitis was associated with increased colonic collagen (col1a2) mRNA expression. Intracolonic cathelicidin (mCRAMP peptide) administration or intravenous delivery of lentivirus-overexpressing cathelicidin gene significantly reduced colonic col1a2 mRNA expression in TNBS-exposed mice, compared to vehicle administration. Salmonella infection also caused increased cecal inflammation associated with collagen (col1a2) mRNA expression that was prevented by intravenous delivery of Camp-expressing lentivirus. Exposure of human primary intestinal fibroblasts and human colonic CCD-18Co fibroblasts to transforming growth factor-beta1 (TGF-beta1) and/or insulin-like growth factor 1 induced collagen protein and mRNA expression, that was reduced by LL-37 (3-5 µM) through a MAP kinase-dependent mechanism.

CONCLUSION

Cathelicidin can reverse intestinal fibrosis by directly inhibiting collagen synthesis in colonic fibroblasts.