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

Levels of Lysozyme and SLPI in Bronchoalveolar Lavage: Exploring Their Role in Interstitial Lung Disease

Interstitial lung diseases (ILDs) are characterized by inflammation or fibrosis of the pulmonary parenchyma. Despite the involvement of immune cells and soluble mediators in pulmonary fibrosis, the influence of antimicrobial peptides (AMPs) remains underexplored. These effector molecules display a range of activities, which include immunomodulation and wound repair. Here, we investigate the role of AMPs in the development of fibrosis in ILD. We compare the concentration of different AMPs and different cytokines in 46 fibrotic (F-ILD) and 17 non-fibrotic (NF-ILD) patients by ELISA and using peripheral blood mononuclear cells from in vitro stimulation in the presence of lysozyme or secretory leukocyte protease inhibitor (SLPI) from 10 healthy donors. We observed that bronchoalveolar lavage (BAL) levels of AMPs were decreased in F-ILD patients (lysozyme: p < 0.001; SLPI: p < 0.001; LL-37: p < 0.001; lactoferrin: p = 0.47) and were negatively correlated with levels of TGF-β (lysozyme: p = 0.02; SLPI: p < 0.001) and IL-17 (lysozyme: p < 0.001; SLPI: p < 0.001). We observed that lysozyme increased the percentage of CD86+ macrophages (p < 0.001) and the production of TNF-α (p < 0.001). We showed that lysozyme and SLPI were associated with clinical parameters (lysozyme: p < 0.001; SLPI: p < 0.001) and disease progression (lysozyme: p < 0.001; SLPI: p = 0.01). These results suggest that AMPs may play an important role in the anti-fibrotic response, regulating the effect of pro-fibrotic cytokines. In addition, levels of lysozyme in BAL may be a potential biomarker to predict the progression in F-ILD patients.

Cathelicidin AS-12W Derived from the Alligator sinensis and Its Antimicrobial Activity Against Drug-Resistant Gram-Negative Bacteria In Vitro and In Vivo

Antimicrobial peptides (AMPs) have the potential to treat multidrug-resistant bacterial infections. Cathelicidins are a class of cationic antimicrobial peptides that are found in nearly all vertebrates. Herein, we determined the mature peptide region of Alligator sinensis cathelicidin by comparing its cathelicidin peptide sequence with those of other reptiles and designed nine peptide mutants based on the Alligator sinensis cathelicidin mature peptide. According to the antibacterial activity and cytotoxicity screening, the peptide AS-12W demonstrated broad-spectrum antibacterial activity and exhibited low erythrocyte hemolytic activity. In particular, AS-12W exhibited strong antibacterial activity and rapid bactericidal activity against carbapenem-resistant Pseudomonas aeruginosa in vitro. Additionally, AS-12W effectively removed carbapenem-resistant P. aeruginosa from blood and organs in vivo, leading to improved survival rates in septic mice. Furthermore, AS-12W exhibited good stability and tolerance to harsh conditions such as high heat, high salt, strong acid, and strong alkali, and it also displayed high stability toward trypsin and simulated gastric fluid (SGF). Moreover, AS-12W showed significant anti-inflammatory effects in vitro by inhibiting the production of proinflammatory factors induced by lipopolysaccharide (LPS). Due to its antibacterial mechanism against Escherichia coli, we found that this peptide could neutralize the negative charge on the surface of the bacteria and disrupt the integrity of the bacterial cell membrane. In addition, AS-12W has the ability to bind to the genomic DNA of bacteria and stimulate the production of reactive oxygen species (ROS) within bacteria, which is believed to be the reason for the good antibacterial activity of AS-12W. These results demonstrated that AS-12W exhibits remarkable antibacterial activity, particularly against carbapenem-resistant P. aeruginosa. Therefore, it is a potential candidate for antibacterial drug development.

Transient receptor potential melastatin 2 is involved in trinitrobenzene sulfonic acid-induced acute and chronic colitis-associated fibrosis progression in mice

Crohn's disease, a chronic and recurrent gastrointestinal disease, frequently causes intestinal fibrosis. Transient receptor potential melastatin 2 (TRPM2), a non-selective cation channel, is activated by reactive oxygen species. This study investigated the role of TRPM2 in acute colitis and chronic colitis-associated fibrosis progression. Acute colitis and chronic colitis-associated fibrosis were induced in TRPM2-deficient (TRPM2KO) and wild-type (WT) mice through single and repeated intrarectal injections of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Bone marrow-derived macrophages (BMDMs) from WT and TRPM2KO mice were stimulated using H2O2. In WT mice, a single TNBS injection induced acute colitis with upregulated inflammatory cytokines/chemokines and Th1/Th17-related cytokines, while repeated TNBS injections induced chronic colitis-associated fibrosis with upregulation of fibrogenic factors and Th2-related cytokines. Acute colitis and chronic colitis-associated fibrosis with cytokines/chemokine upregulation and fibrogenic factors were considerably suppressed in TRPM2KO mice. Treating BMDMs with H2O2 increased cytokine/chemokine expression and JNK, ERK, and p38 phosphorylation; however, these responses were significantly less in TRPM2KO than in WT mice. These findings suggest that TRPM2 contributes to acute colitis progression via Th1/Th17-mediated immune responses. Furthermore, TRPM2 may be directly involved in colitis-associated fibrosis induction, likely due to the regulation of Th2/TGF-β1-mediated fibrogenesis in addition to a consequence of acute colitis progression.

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.

ROS Scavenging and inflammation-directed polydopamine nanoparticles regulate gut immunity and flora therapy in inflammatory bowel disease

Dysfunction of the intestinal mucosal immune system and dysbiosis of the intestinal microflora can induce inflammatory bowel disease. However, drug-mediated clinical treatment remains a challenge due to its poor therapeutic efficacy and severe side effects. Herein, a ROS scavenging and inflammation-directed nanomedicine is designed and fabricated by coupling polydopamine nanoparticles with mCRAMP, an antimicrobial peptide, while wrapping macrophage membrane in the outer layer. The designed nanomedicine reduced the secretion of pro-inflammatory cytokines and elevate the expression of anti-inflammatory cytokine in vivo and in vitro inflammation models, demonstrating its significant ability of improving inflammatory responses. Importantly, the macrophage membrane encapsulated nanoparticles exhibit the obviously enhanced targeting performance in local inflamed tissues. Furthermore, the 16S rRNA sequencing of fecal microorganisms showed that probiotics increased and pathogenic bacteria were inhibited after oral delivery the nanomedicine, indicating that the designed nano platform played a significant role in optimizing intestinal microbiome. Taken together, the designed nanomedicine are not only easy to prepare and exhibit high biocompatibility, but also show the inflammatory targeting property, anti-inflammatory function and positive regulation of intestinal flora, thus providing a new idea for the intervention and treatment of colitis. STATEMENT OF SIGNIFICANCE: Inflammatory bowel disease (IBD), a chronic and intractable disease, may lead to colon cancer in severe cases without effective treatment. However, clinical drugs are largely ineffective owing to insufficient therapeutic efficacies and side effects. Herein, we constructed a biomimetic polydopamine nanoparticle for oral administration to treat the IBD by modulating mucosal immune homeostasis and optimizing intestinal microorganisms. In vitro and in vivo experiments showed that the designed nanomedicine not only exhibits the anti-inflammatory function and inflammatory targeting property but also positively regulate the gut microflora. Taken together, the designed nanomedicine combined immunoregulation and intestinal microecology modulation to significantly enhance the therapeutic effect on colitis in mice, thus providing a new approach for the clinical treatment of colitis.

Mesenchymal stem cells in fibrotic diseases-the two sides of the same coin

Fibrosis is caused by extensive deposition of extracellular matrix (ECM) components, which play a crucial role in injury repair. Fibrosis attributes to ~45% of all deaths worldwide. The molecular pathology of different fibrotic diseases varies, and a number of bioactive factors are involved in the pathogenic process. Mesenchymal stem cells (MSCs) are a type of multipotent stem cells that have promising therapeutic effects in the treatment of different diseases. Current updates of fibrotic pathogenesis reveal that residential MSCs may differentiate into myofibroblasts which lead to the fibrosis development. However, preclinical and clinical trials with autologous or allogeneic MSCs infusion demonstrate that MSCs can relieve the fibrotic diseases by modulating inflammation, regenerating damaged tissues, remodeling the ECMs, and modulating the death of stressed cells after implantation. A variety of animal models were developed to study the mechanisms behind different fibrotic tissues and test the preclinical efficacy of MSC therapy in these diseases. Furthermore, MSCs have been used for treating liver cirrhosis and pulmonary fibrosis patients in several clinical trials, leading to satisfactory clinical efficacy without severe adverse events. This review discusses the two opposite roles of residential MSCs and external MSCs in fibrotic diseases, and summarizes the current perspective of therapeutic mechanism of MSCs in fibrosis, through both laboratory study and clinical trials.

Lactococcus lactis engineered to deliver hCAP18 cDNA alleviates DNBS-induced colitis in C57BL/6 mice by promoting IL17A and IL10 cytokine expression

With its antimicrobial and immunomodulating properties, the cathelicidin (LL37) plays an important role in innate immune system. Here, we attempted to alleviate chemically induced colitis using a lactococci strain that either directly expressed the precursor to LL37, hCAP18 (LL-pSEC:hCAP18), or delivered hCAP18 cDNA to host cells under the control of the cytomegalovirus promoter (LL-Probi-H1:hCAP18). We also investigated whether the alleviation of symptoms could be explained through modification of the gut microbiota by hCAP18. Mice were administered daily doses of LL-pSEC:hCAP18 or LL-Probi-H1:hCAP18. On day 7, colitis was induced by DNBS. During autopsy, we assessed macroscopic tissue damage in the colon and collected tissue samples for the characterization of inflammation markers and histological analysis. Feces were collected at day 7 for 16S DNA sequencing. We also performed a fecal transplant experiment in which mice underwent colon washing and received feces from Lactococcus lactis-treated mice before DNBS-colitis induction. Treatment with LL-Probi-H1:hCAP18 reduced the severity of colitis symptoms. The protective effects were accompanied by increased levels of IL17A and IL10 in mesenteric lymph node cells. L. lactis administration altered the abundance of Lachnospiraceae and Muribaculaceae. However, fecal transplant from L. lactis-treated mice did not improve DNBS-induced symptoms in recipient mice.

Elafin Reverses Intestinal Fibrosis by Inhibiting Cathepsin S-Mediated Protease-Activated Receptor 2

BACKGROUND & AIMS

More than half of Crohn's disease patients develop intestinal fibrosis-induced intestinal strictures. Elafin is a human protease inhibitor that is down-regulated in the stricturing intestine of Crohn's disease patients. We investigated the efficacy of elafin in reversing intestinal fibrosis and elucidated its mechanism of action.

METHODS

We developed a new method to mimic a stricturing Crohn's disease environment and induce fibrogenesis using stricturing Crohn's disease patient-derived serum exosomes to condition fresh human intestinal tissues and primary stricturing Crohn's disease patient-derived intestinal fibroblasts. Three mouse models of intestinal fibrosis, including SAMP1/YitFc mice, Salmonella-infected mice, and trinitrobenzene sulfonic acid-treated mice, were also studied. Elafin-Eudragit FS30D formulation and elafin-overexpressing construct and lentivirus were used.

RESULTS

Elafin reversed collagen synthesis in human intestinal tissues and fibroblasts pretreated with Crohn's disease patient-derived serum exosomes. Proteome arrays identified cathepsin S as a novel fibroblast-derived pro-fibrogenic protease. Elafin directly suppressed cathepsin S activity to inhibit protease-activated receptor 2 activity and Zinc finger E-box-binding homeobox 1 expression, leading to reduced collagen expression in intestinal fibroblasts. Elafin overexpression reversed ileal fibrosis in SAMP1/YitFc mice, cecal fibrosis in Salmonella-infected mice, and colonic fibrosis in trinitrobenzene sulfonic acid-treated mice. Cathepsin S, protease-activated receptor 2 agonist, and zinc finger E-box-binding homeobox 1 overexpression abolished the anti-fibrogenic effect of elafin in fibroblasts and all 3 mouse models of intestinal fibrosis. Oral elafin-Eudragit FS30D treatment abolished colonic fibrosis in trinitrobenzene sulfonic acid-treated mice.

CONCLUSIONS

Elafin suppresses collagen synthesis in intestinal fibroblasts via cathepsin S-dependent protease-activated receptor 2 inhibition and decreases zinc finger E-box-binding homeobox 1 expression. The reduced collagen synthesis leads to the reversal of intestinal fibrosis. Thus, modified elafin may be a therapeutic approach for intestinal fibrosis.

Revisiting fibrosis in inflammatory bowel disease: the gut thickens

Intestinal fibrosis, which is usually the consequence of chronic inflammation, is a common complication of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis. In the past few years, substantial advances have been made in the areas of pathogenesis, diagnosis and management of intestinal fibrosis. Of particular interest have been inflammation-independent mechanisms behind the gut fibrotic process, genetic and environmental risk factors (such as the role of the microbiota), and the generation of new in vitro and in vivo systems to study fibrogenesis in the gut. A huge amount of work has also been done in the area of biomarkers to predict or detect intestinal fibrosis, including novel cross-sectional imaging techniques. In parallel, researchers are embarking on developing and validating clinical trial end points and protocols to test novel antifibrotic agents, although no antifibrotic therapies are currently available. This Review presents the state of the art on the most recently identified pathogenic mechanisms of this serious IBD-related complication, focusing on possible targets of antifibrotic therapies, management strategies, and factors that might predict fibrosis progression or response to treatment.

Antimicrobial peptides and the gut microbiome in inflammatory bowel disease

Antimicrobial peptides (AMP) are highly diverse and dynamic molecules that are expressed by specific intestinal epithelial cells, Paneth cells, as well as immune cells in the gastrointestinal (GI) tract. They play critical roles in maintaining tolerance to gut microbiota and protecting against enteric infections. Given that disruptions in tolerance to commensal microbiota and loss of barrier function play major roles in the pathogenesis of inflammatory bowel disease (IBD) and converge on the function of AMP, the significance of AMP as potential biomarkers and novel therapeutic targets in IBD have been increasingly recognized in recent years. In this frontier article, we discuss the function and mechanisms of AMP in the GI tract, examine the interaction of AMP with the gut microbiome, explore the role of AMP in the pathogenesis of IBD, and review translational applications of AMP in patients with IBD.

Antimicrobial peptides: mechanism of action, activity and clinical potential

The management of bacterial infections is becoming a major clinical challenge due to the rapid evolution of antibiotic resistant bacteria. As an excellent candidate to overcome antibiotic resistance, antimicrobial peptides (AMPs) that are produced from the synthetic and natural sources demonstrate a broad-spectrum antimicrobial activity with the high specificity and low toxicity. These peptides possess distinctive structures and functions by employing sophisticated mechanisms of action. This comprehensive review provides a broad overview of AMPs from the origin, structural characteristics, mechanisms of action, biological activities to clinical applications. We finally discuss the strategies to optimize and develop AMP-based treatment as the potential antimicrobial and anticancer therapeutics.

Beneficial impact of cathelicidin on hypersensitivity pneumonitis treatment-In vivo studies

Cathelicidin (CRAMP) is a defence peptide with a wide range of biological responses including antimicrobial, immunomodulatory and wound healing. Due to its original properties the usefulness of CRAMP in the treatment of pulmonary fibrosis was assessed in a murine model of hypersensitivity pneumonitis (HP). The studies were conducted on mouse strain C57BL/6J exposed to a saline extract of Pantoea agglomerans cells (HP inducer). Cathelicidin was administered in the form of an aerosol during and after HP development. Changes in the composition of immune cell populations (NK cells, macrophages, lymphocytes: Tc, Th, Treg, B), were monitored in lung tissue by flow cytometry. Extracellular matrix deposition (collagens, hydroxyproline), the concentration of cytokines involved in inflammatory and the fibrosis process (IFNγ, TNFα, TGFβ1, IL1β, IL4, IL5, IL10, IL12α, IL13) were examined in lung homogenates by the ELISA method. Alterations in lung tissue morphology were examined in mouse lung sections stained with haematoxylin and eosin as well as Masson trichrome dyes. The performed studies revealed that cathelicidin did not cause any negative changes in lung morphology/structure, immune cell composition or cytokines production. At the same time, CRAMP attenuated the immune reaction induced by mice chronic exposure to P. agglomerans and inhibited hydroxyproline and collagen deposition in the lung tissue of mice treated with bacteria extract. The beneficial effect of CRAMP on HP treatment was associated with restoring the balance in quantity of immune cells, cytokines production and synthesis of extracellular matrix components. The presented study suggests the usefulness of cathelicidin in preventing lung fibrosis; however, cathelicidin was not able to reverse pathological changes completely.

Cathelicidin - A Novel Potential Marker of Pediatric Inflammatory Bowel Disease

Introduction

Cathelicidin is a multifunctional host defense peptide which may also exert pro-inflammatory signals and contribute to the development of autoimmune disorders. We aimed to assess serum concentration of cathelicidin in children with inflammatory bowel disease (IBD) compared to healthy controls and to evaluate its relationship with disease activity and phenotype.

Patients and Methods

The study group included 68 children with IBD. The control group comprised 20 children with functional abdominal pain. All patients and controls were tested for complete blood count, C-reactive protein, erythrocyte sedimentation rate and cathelicidin. Stool samples were collected to assess calprotectin.

Results

Cathelicidin was significantly increased in patients with ulcerative colitis (1073.39±214.52 ng/mL) and Crohn’s disease (1057.63±176.03 ng/mL) patients compared to controls (890.56±129.37 ng/mL) (H=16.28; p=0.0003). Cathelicidin was significantly elevated in children with active IBD (1044.90±176.17 ng/mL) and IBD remission (1098.10±227.87 ng/mL) compared to controls (Z=3.21; p=0.001; Z=−4.12; p<0.0001, respectively). Negative correlation between cathelicidin and calprotectin in children with ulcerative colitis was found (R=−0.39; p=0.02). Cathelicidin exhibited AUC of 0.815 for differentiation children with ulcerative colitis from the control group.

Conclusion

Serum cathelicidin is increased in children with Crohn’s disease and ulcerative colitis regardless of clinical activity of the disease suggesting that it may be a potential biomarker of IBD. Inverse correlation between cathelicidin and fecal calprotectin may imply a disparate role of these molecules in the pathophysiology of pediatric ulcerative colitis.

Antimicrobial peptides - Advances in development of therapeutic applications

The severe infection is becoming a significant health problem which threaten the lives of patients and the safety and economy of society. In the way of finding new strategy, antimicrobial peptides (AMPs) - an important part of host defense family, emerged with tremendous potential. Up to date, huge numbers of AMPs has been investigated from both natural and synthetic sources showing not only the ability to kill microbial pathogens but also propose other benefits such as wound healing, anti-tumor, immune modulation. In this review, we describe the involvements of AMPs in biological systems and discuss the opportunity in developing AMPs for clinical applications. In the detail, their properties in antibacterial activity is followed by their application in some infection diseases and cancer. The key discussions are the approaches to improve biological activities of AMPs either by modifying chemical structure or incorporating into delivery systems. The new applications and perspectives for the future of AMPs would open the new era of their development.

Antimicrobial Peptide JH-3 Effectively Kills Salmonella enterica Serovar Typhimurium Strain CVCC541 and Reduces Its Pathogenicity in Mice

Salmonella is an important zoonotic pathogen and is a major cause of gastrointestinal diseases worldwide. The current serious problem of antibiotic abuse has prompted the search for new substitutes for antibiotics. JH-3 is a small antimicrobial peptide with broad-spectrum bactericidal activity. In this study, we showed that JH-3 has good bactericidal activity towards the clinical isolate Salmonella enterica serovar Typhimurium strain CVCC541. The minimum inhibitory concentration (MIC) of JH-3 against this bacterium was determined to be 100 μg/mL, which could decrease the number of CVCC541 cells by 1000-fold in vitro within 5 h. The transmission electron microscopy (TEM) results showed that JH-3 can damage the cell wall and membrane of CVCC541, leading to the leakage of cell contents and subsequent cell death. To measure the bactericidal activity of CVCC541-infected mice were treated intraperitoneally 40 or 10 mg/kg JH-3 at 2 h or 3 days postinfection. Our results showed that treatment with 40 mg/kg JH-3 at 2 h postinfection had the best therapeutic effect and could significantly protect mice from a lethal dose of CVCC541. Furthermore, the clinical symptoms, bacterial burden in blood and organs, and intestinal pathological changes were all decreased and were close to normal. This study examined the therapeutic effect of the antimicrobial peptide JH-3 against S. enterica CVCC541 infection for the first time and determined the therapeutic effect of different JH-3 doses and treatment times, laying the foundation for studies of new antimicrobial agents.

Cathelicidin Mediates a Protective Role of Vitamin D in Ulcerative Colitis and Human Colonic Epithelial Cells

BACKGROUND

Vitamin D plays a protective role in ulcerative colitis (UC) patients through unclear mechanisms. Cathelicidin is an antimicrobial peptide induced by 1,25(OH)D2. Our goal was to evaluate the link between cathelicidin and vitamin D-associated clinical outcomes in UC patients, explore vitamin D induction of cathelicidin in human colon cells, and evaluate the effects of intrarectal human cathelicidin on a murine model of colitis.

METHODS

Serum and colonic cathelicidin levels were measured in UC patients and correlated with clinical and histologic outcomes. Human colon cells were treated with 1,25(OH)2D and production of cathelicidin and cytokines were quantified. Antimicrobial activity against Escherichia coli from cell culture supernatants was measured. Mice were treated with intrarectal cathelicidin, and its effects on DSS colitis and intestinal microbiota were evaluated.

RESULTS

In UC patients, serum 25(OH)D positively correlated with serum and colonic cathelicidin. Higher serum cathelicidin is associated with decreased risk of histologic inflammation and clinical relapse but not independent of 25(OH)D or baseline inflammation. The 1,25(OH)2D treatment of colon cells induced cathelicidin and IL-10, repressed TNF-α, and suppressed Escherichia coli growth. This antimicrobial effect was attenuated with siRNA-cathelicidin transfection. Intrarectal cathelicidin reduced the severity of DSS colitis but did not mitigate the impact of colitis on microbial composition.

CONCLUSIONS

Cathelicidin plays a protective role in 25(OH)D-associated UC histologic outcomes and murine colitis. Cathelicidin is induced by vitamin D in human colonic epithelial cells and promotes antimicrobial activity against E. coli. Our study provides insights into the vitamin D-cathelicidin pathway as a potential therapeutic target.

Significance of LL-37 on Immunomodulation and Disease Outcome

LL-37, also called cathelicidin, is an important part of the human immune system, which can resist various pathogens. A plethora of experiments have demonstrated that it has the multifunctional effects of immune regulation, in addition to antimicrobial activity. Recently, there have been increasing interest in its immune function. It was found that LL-37 can have two distinct functions in different tissues and different microenvironments. Thus, it is necessary to investigate LL-37 immune functions from the two sides of the same coin. On the one side, LL-37 promotes inflammation and immune response and exerts its anti-infective and antitumor effects; on the other side, it has the ability to inhibit inflammation and promote carcinogenesis. This review presents a brief summary of its expression, structure, and immunomodulatory effects as well as brief discussions on the role of this small peptide as a key factor in the development and treatment of various inflammation-related diseases and cancers.

Pantoea agglomerans chronic exposure induces epithelial-mesenchymal transition in human lung epithelial cells and mice lungs

Pantoea agglomerans is gram-negative bacteria widely distributed in nature. It predominates in inhalable dust from grain, herbs, and flax, and was identified as the most important cause of hypersensitivity pneumonitis (HP) in eastern Poland. To better understand the molecular mechanism of HP development studies focused on the interactions between P. agglomerans and alveolar epithelial cells as well as lung tissue with particular emphasis on the epithelial-mesenchymal transition (EMT). The studies were conducted on human normal lung epithelial NL20 cells and mice strain C57BL/6J. Cells and mice underwent chronic exposure to saline extract of P. agglomerans (SE-PA). Morphological changes were evaluated under light microscopy, the concentration of fibrosis markers was examined by the ELISA method, while the expression of genes involved in EMT was evaluated by RealTime PCR. During incubation with SE-PA epithelial cells underwent conversion and assumed fibroblast phenotype characterized by a decrease in epithelial cells markers (CDH1, CLDN1, JUP) and increase in mesenchymal cells markers (FN1, VIM, CDH2). Mice lungs collected after 14 days of SE-PA treatment revealed inflammation with marked lymphocytes infiltration. The intensified inflammatory process accompanied by increased proliferation of fibrous connective tissue was noted in mice lungs after 28 days of SE-PA exposure. Histological changes correlated with an increase of fibrosis markers (hydroxyproline, collagens), downregulation of epithelial markers (Cdh1, Cldn1, Jup, Ocln) and upregulation of myofibroblasts markers (Acta2, Cdh2, Fn1, Vim). Obtained results revealed SE-PA ability to induce EMT in human lung epithelial cells and mice lung tissue, with the scale of changes proportional to the time of treatment.

High circulating elafin levels are associated with Crohn's disease-associated intestinal strictures

Background

Antimicrobial peptide expression is associated with disease activity in inflammatory bowel disease (IBD) patients. IBD patients have abnormal expression of elafin, a human elastase-specific protease inhibitor and antimicrobial peptide. We determined elafin expression in blood, intestine, and mesenteric fat of IBD and non-IBD patients.

Methods

Serum samples from normal and IBD patients were collected from two UCLA cohorts. Surgical resection samples of human colonic and mesenteric fat tissues from IBD and non-IBD (colon cancer) patients were collected from Cedars-Sinai Medical Center.

Results

High serum elafin levels were associated with a significantly elevated risk of intestinal stricture in Crohn’s disease (CD) patients. Microsoft Azure Machine learning algorithm using serum elafin levels and clinical data identified stricturing CD patients with high accuracy. Serum elafin levels had weak positive correlations with clinical disease activity (Partial Mayo Score and Harvey Bradshaw Index), but not endoscopic disease activity (Mayo Endoscopic Subscore and Simple Endoscopic Index for CD) in IBD patients. Ulcerative colitis (UC) patients had high serum elafin levels. Colonic elafin mRNA and protein expression were not associated with clinical disease activity and histological injury in IBD patients, but stricturing CD patients had lower colonic elafin expression than non-stricturing CD patients. Mesenteric fat in stricturing CD patients had significantly increased elafin mRNA and protein expression, which may contribute to high circulating elafin levels. Human mesenteric fat adipocytes secrete elafin protein.

Conclusions

High circulating elafin levels are associated with the presence of stricture in CD patients. Serum elafin levels may help identify intestinal strictures in CD patients.

Cathelicidin Suppresses Colon Cancer Metastasis via a P2RX7-Dependent Mechanism

The antimicrobial peptide cathelicidin inhibits development of colitis-associated colon cancer. However, the role of cathelicidin in colon cancer metastasis remains unknown. We hypothesized that cathelicidin is effective in inhibiting colon cancer metastasis. Human colon cancer HT-29 cells were injected intravenously into nude mice. Control HA-tagged adeno-associated virus (HA-AAV) or cathelicidin-overexpressing AAV (CAMP-HA-AAV) were injected intravenously into nude mice on the same day. Four weeks later, the nude mice were assessed for lung and liver metastases. Human colon cancer SW620 cells were used to study the effect of cathelicidin on cell migration and cytoskeleton. Incubation of SW620 cells with cathelicidin dose-dependently reduced cell migration, disrupted cytoskeletal structure, and reduced βIII-tubulin (TUBB3) mRNA expression. The addition of the P2RX7 antagonist KN62, but not the FPRL1 antagonist WRW4, prevented the LL-37-mediated inhibition of cell migration and TUBB3 mRNA expression. The CAMP-HA-AAV-overexpressing group showed significantly reduced human CK20 protein (by 60%) and TUBB3 mRNA expression (by 40%) in the lungs and liver of the HT-29-loaded nude mice, compared to the HA-AAV control group. Intraperitoneal injection of KN62 reversed the CAMP-HA-AAV-mediated inhibition of human CK20 and TUBB3 expression in the lungs and liver of HT-29-loaded nude mice. In conclusion, cathelicidin inhibits colon cancer metastasis via a P2RX7-dependent pathway.

The Critical Role of the Antimicrobial Peptide LL-37/ CRAMP in Protection of Colon Microbiota Balance, Mucosal Homeostasis, Anti-Inflammatory Responses, and Resistance to Carcinogenesis

Mouse cathelin-related antimicrobial peptide (CRAMP) and its homologue human cathelicidin (LL-37) play active roles in innate immune responses, angiogenesis, and wound healing. In addition, LL-37/CRAMP fends off microbes and protects against infections in the colon, where the epithelium is exposed to myriad of enteric pathogens. It is increasingly recognized that LL-37/CRAMP maintains colon mucosal barrier integrity, shapes the composition of microbiota, and protects the host from tumorigenesis. In this review, we discuss the importance of LL-37/CRAMP in the homeostasis of the host, with novel findings derived from mice deficient in CRAMP that support the proposition for this natural antimicrobial peptide and an immune modulator as a drug lead for therapeutic development.

Ceragenin CSA13 Reduces Clostridium difficile Infection in Mice by Modulating the Intestinal Microbiome and Metabolites

BACKGROUND & AIMS

Clostridium difficile induces intestinal inflammation by releasing toxins A and B. The antimicrobial compound cationic steroid antimicrobial 13 (CSA13) has been developed for treating gastrointestinal infections. The CSA13-Eudragit formulation can be given orally and releases CSA13 in the terminal ileum and colon. We investigated whether this form of CSA13 reduces C difficile infection (CDI) in mice.

METHODS

C57BL/6J mice were infected with C difficile on day 0, followed by subcutaneous administration of pure CSA13 or oral administration of CSA13-Eudragit (10 mg/kg/d for 10 days). Some mice were given intraperitoneal vancomycin (50 mg/kg daily) on days 0-4 and relapse was measured after antibiotic withdrawal. The mice were monitored until day 20; colon and fecal samples were collected on day 3 for analysis. Blood samples were collected for flow cytometry analyses. Fecal pellets were collected each day from mice injected with CSA13 and analyzed by high-performance liquid chromatography or 16S sequencing; feces were also homogenized in phosphate-buffered saline and fed to mice with CDI via gavage.

RESULTS

CDI of mice caused 60% mortality, significant bodyweight loss, and colonic damage 3 days after infection; these events were prevented by subcutaneous injection of CSA13 or oral administration CSA13-Eudragit. There was reduced relapse of CDI after administration of CSA13 was stopped. Levels of CSA13 in feces from mice given CSA13-Eudragit were significantly higher than those of mice given subcutaneous CSA13. Subcutaneous and oral CSA13 each significantly increased the abundance of Peptostreptococcaceae bacteria and reduced the abundance of C difficile in fecal samples of mice. When feces from mice with CDI and given CSA13 were fed to mice with CDI that had not received CSA13, the recipient mice had significantly increased rates of survival. CSA13 reduced fecal levels of inflammatory metabolites (endocannabinoids) and increased fecal levels of 4 protective metabolites (ie, citrulline, 3-aminoisobutyric acid, retinol, and ursodeoxycholic acid) in mice with CDI. Oral administration of these CSA13-dependent protective metabolites reduced the severity of CDI.

CONCLUSIONS

In studies of mice, we found the CSA13-Eudragit formulation to be effective in eradicating CDI by modulating the intestinal microbiota and metabolites.

Exogenous murine antimicrobial peptide CRAMP significantly exacerbates Ovalbumin-induced airway inflammation but ameliorates oxazolone-induced intestinal colitis in BALB/c mice

Cathelicidin has been reported to be multifunctional. The current study aimed to investigate the influences of exogenous cathelicidin-related antimicrobial peptide (CRAMP) on inflammatory responses in different disease models. In OVA-induced allergic airway inflammation, CRAMP significantly enhanced the infiltration of inflammatory cells and accumulation of proinflammatory Th2 cytokine IL-13 and IL-33 in bronchial alveolar lavage fluid (BALF), exacerbated lung tissue inflammation and airway goblet cell hyperplasia, and elevated OVA-specific IgE level in serum. In oxazolone-induced intestinal colitis, the expression levels of CRAMP and its receptor FPR2 significantly increased in comparison with those of TNBS-induced mice, vesicle and normal controls. Exogenous CRAMP significantly prevented the development of ulcerative colitis, evidenced by improved body weight regain, decreased colons weight/length ratio, elevated epithelial integrity, and ameliorated colon tissue inflammation. In addition, pro-inflammatory cytokines TNF-α, IL-1β, IL-4 and IL-13, as well as chemokines CXCL2 and CXCL5 for neutrophils recruitment were significantly decreased in CRAMP-treated mice, and epithelial repair-related factors MUC2 and Claudin1 were increased, determined by real time-PCR and ELISAs. The results indicated that although CRAMP has pro-inflammatory effects in airway, local application of exogenous CRAMP might be a potential approach for the treatment of ulcerative colitis.

CSA13 inhibits colitis-associated intestinal fibrosis via a formyl peptide receptor like-1 mediated HMG-CoA reductase pathway

Many Crohn’s disease (CD) patients develop intestinal strictures, which are difficult to prevent and treat. Cationic steroid antimicrobial 13 (CSA13) shares cationic nature and antimicrobial function with antimicrobial peptide cathelicidin. As many functions of cathelicidin are mediated through formyl peptide receptor-like 1 (FPRL1), we hypothesize that CSA13 mediates anti-fibrogenic effects via FPRL1. Human intestinal biopsies were used in clinical data analysis. Chronic trinitrobenzene sulfonic acid (TNBS) colitis-associated intestinal fibrosis mouse model with the administration of CSA13 was used. Colonic FPRL1 mRNA expression was positively correlated with the histology scores of inflammatory bowel disease patients. In CD patients, colonic FPRL1 mRNA was positively correlated with intestinal stricture. CSA13 administration ameliorated intestinal fibrosis without influencing intestinal microbiota. Inhibition of FPRL1, but not suppression of intestinal microbiota, reversed these protective effects of CSA13. Metabolomic analysis indicated increased fecal mevalonate levels in the TNBS-treated mice, which were reduced by the CSA13 administration. CSA13 inhibited colonic HMG-CoA reductase activity in an FPRL1-dependent manner. Mevalonate reversed the anti-fibrogenic effect of CSA13. The increased colonic FPRL1 expression is associated with severe mucosal disease activity and intestinal stricture. CSA13 inhibits intestinal fibrosis via FPRL1-dependent modulation of HMG-CoA reductase pathway.

Intestinal fibrosis: ready to be reversed

PURPOSE OF REVIEW

Intestinal fibrosis is a common complication of several enteropathies, with inflammatory bowel disease (IBD) being the major cause. Intestinal fibrosis affects both ulcerative colitis and Crohn's disease, and no specific antifibrotic therapy exists. This review highlights recent developments in this area.

RECENT FINDINGS

The pathophysiology of intestinal stricture formation includes inflammation-dependent and inflammation-independent mechanisms. A better understanding of the mechanisms of intestinal fibrogenesis and the availability of compounds for other nonintestinal fibrotic diseases bring clincial trials in stricturing Crohn's disease within reach.

SUMMARY

Improved understanding of its mechanisms and ongoing development of clinical trial endpoints for intestinal fibrosis will allow the testing of novel antifibrotic compounds in IBD.

Organoid-based epithelial to mesenchymal transition (OEMT) model: from an intestinal fibrosis perspective

The current in vitro or in vivo intestinal fibrosis models have many limitations. Recent advancements in the isolation and culturing of organoids has led to development of various three-dimensional (3D) intestinal disease models with in vivo physiology. In this study, we generated an organoid-based epithelial to mesenchymal transition (OEMT) model, which could be used as a novel intestinal fibrosis model. Intestinal epithelial organoids (IEOs) were isolated and cultured from the small intestines of normal mice. IEOs were treated with transforming growth factor- β1 (TGF-β1) or Tumor necrosis factor-α (TNF-α) to evaluate their phenotypic change. Raw 264.7 cells (macrophage) stimulated with lipopolysaccharide were co-cultured with IEOs in growth media with or without TGF-β1. TGF-β1 alone slightly induced epithelial to mesenchymal transition (EMT) in the IEOs but mainly disrupted them. Macrophage released cytokines synergistically induced mesenchymal phenotypic changes in TGF-β1 stimulated intestinal organoids. TNF-α and TGF-β1 synergistically induced proliferation of mesenchymal cells as well as EMT in the IEOs. We generated a novel OEMT model based on our finding that TNF-α and TGF-β synergistically induce type 2 EMT in IEOs. This 3D EMT model with in vivo physiology could be used to study EMT associated intestinal fibrosis.

Circulating cathelicidin levels correlate with mucosal disease activity in ulcerative colitis, risk of intestinal stricture in Crohn's disease, and clinical prognosis in inflammatory bowel disease

Background

Cathelicidin (LL-37) is an antimicrobial peptide known to be associated with various autoimmune diseases. We attempt to determine if cathelicidin can accurately reflect IBD disease activity. We hypothesize that serum cathelicidin correlates with mucosal disease activity, stricture, and clinical prognosis of IBD patients.

Methods

Serum samples were collected from two separate cohorts of patients at the University of California, Los Angeles. Cohort 1 consisted of 50 control, 23 UC, and 28 CD patients. Cohort 2 consisted of 20 control, 57 UC, and 67 CD patients. LL-37 levels were determined by ELISA. Data from both cohorts were combined for calculation of accuracies in indicating mucosal disease activity, relative risks of stricture, and odds ratios of predicting disease development.

Results

Serum cathelicidin levels were inversely correlated with Partial Mayo Scores of UC patients and Harvey-Bradshaw Indices of CD patients. Among IBD patients with moderate or severe initial disease activity, the patients with high initial LL-37 levels had significantly better recovery than the patients with low initial LL-37 levels after 6–18 months, suggesting that high LL-37 levels correlate with good prognosis. Co-evaluation of LL-37 and CRP levels was more accurate than CRP alone or LL-37 alone in the correlation with Mayo Endoscopic Score of UC patients. Low LL-37 levels indicated a significantly elevated risk of intestinal stricture in CD patients.

Conclusion

Co-evaluation of LL-37 and CRP can indicate mucosal disease activity in UC patients. LL-37 can predict future clinical activity in IBD patients and indicate risk of intestinal stricture in CD patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-017-0619-4) contains supplementary material, which is available to authorized users.

Cathelicidin Antimicrobial Peptides with Reduced Activation of Toll-Like Receptor Signaling Have Potent Bactericidal Activity against Colistin-Resistant Bacteria

The world is at the precipice of a postantibiotic era in which medical procedures and minor injuries can result in bacterial infections that are no longer effectively treated by antibiotics. Cathelicidins are peptides produced by animals to combat bacterial infections and to regulate innate immune responses. However, cathelicidins are potent activators of the inflammatory response. Cathelicidins with reduced proinflammatory activity and potent bactericidal activity in the low micromolar range against Gram-negative bacteria have been identified. Motifs in cathelicidins that impact bactericidal activity and cytotoxicity to human cells have been elucidated and used to generate peptides that have reduced activation of proinflammatory cytokine production and reduced cytotoxicity to human cells. The resultant peptides have bactericidal activities comparable to that of colistin and can kill colistin-resistant bacteria.

Cathelicidins are antimicrobial peptides that can also increase inflammatory responses. This combination of activities can cause complications in the treatment of bacterial infections despite the pressing need for new antimicrobials. We have identified cathelicidins with decreased activation of inflammatory responses. The peptides kill Gram-negative bacteria at low micromolar concentrations by binding to and perturbing the integrity of the bacterial membrane. The peptides were also engineered to further decrease lysis of human red blood cells. The peptides have activities comparable to those of the polymyxins, a class of antibiotics to which plasmid-borne resistance is rapidly spreading and can kill colistin-resistant bacteria. These peptides are promising candidates for the development of novel antibacterial agents.

The Roles of Cathelicidin LL-37 in Inflammatory Bowel Disease

Human cathelicidin LL-37, the only member of the cathelicidin family of host defense peptides expressed in humans, plays a crucial role in host defense against pathogen invasion, as well as in regulating the functions of anti-inflammation, antitumorigenesis, and tissue repair. It is primarily produced by phagocytic leukocytes and epithelial cells, and mediates a wide range of biological responses. Emerging evidence from several studies indicates that LL-37 plays a prominent and complex role in inflammatory bowel disease (IBD). Although overexpression of LL-37 has been implicated in the inflamed and noninflamed colon mucosa in patients with ulcerative colitis, LL-37 expression was not changed in the inflamed or noninflamed colon or ileal mucosa in patients with Crohn's disease. Furthermore, studies in animal models and human patients further characterized the protective effect of cathelicidins both in ulcerative colitis and Crohn's disease. These data suggest the intricate functions of LL-37 in IBD. They will also create many strategies and opportunities for therapeutic intervention in IBD in the future. This review aims to elucidate the structure and bioactivity of LL-37 and also discuss the recent progress in understanding the relationship between LL-37 and IBD.

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.

AP-1-Targeted Anti-Inflammatory Activities of the Nanostructured, Self-Assembling S5 Peptide

Peptide-based therapeutics have received increasing attention in medical research. However, the local delivery of such therapeutics poses unique challenges. Self-assembling peptides that use decorated nanofibers are one approach by which these therapeutics may be delivered. We previously found that the self-assembling K5 peptide affects the anti-inflammatory response. The aim of the present study was to investigate another self-assembling peptide, S5. Unlike the K5 peptide which has a positive charge, the S5 peptide has a free hydroxyl (-OH) group. We first examined whether the S5 peptide regulates the inflammatory response in primary cells and found that the S5 peptide reduced the production of prostaglandin E₂ (PGE₂) and tumor necrosis factor (TNF)-α in lipopolysaccharide- (LPS-) treated bone marrow-derived macrophages. Moreover, the S5 peptide significantly downregulated cyclooxygenase- (COX-) 2, TNF-α, and interleukin- (IL-) 1β expression by blocking the nuclear translocation of c-Jun. Consistent with this finding, the S5 peptide diminished the activation of inflammatory signaling enzymes related to p38. The S5 peptide also inhibited the formation of the p38/c-Jun signaling complex in RAW264.7 cells. Similarly, p38 and MKK3/6 were inhibited by the S5 peptide in LPS-activated peritoneal macrophages. Taken together, these results strongly suggest that the S5 peptide could exert anti-inflammatory effects by inhibiting the c-Jun/p38 signaling pathway.

Experimental Models of Inflammatory Bowel Diseases

The understanding of the intestinal inflammation occurring in the inflammatory bowel diseases (IBD) has been immeasurably advanced by the development of the now numerous murine models of intestinal inflammation. The usefulness of this research tool in IBD studies has been enabled by our improved knowledge of mucosal immunity and thus our improved ability to interpret the complex responses of mice with various causes of colitis; in addition, it has been powered by the availability of models in which the mice have specific genetic and/or immunologic defects that can be related to the origin of the inflammation. Finally, and more recently, it has been enhanced by our newly acquired ability to define the intestinal microbiome under various conditions and thus to understand how intestinal microorganisms impact on inflammation. In this brief review of murine models of intestinal inflammation we focus mainly on the most often used models that are, not incidentally, also the models that have yielded major insights into IBD pathogenesis.