Query: ll-37

title: A comprehensive summary of LL 37, the factotum human cathelicidin peptide.
abstract: Cathelicidins are a group of antimicrobial peptides. Since their discovery, it has become clear that they are an exceptional class of peptides, with some members having pleiotropic effects. Not only do they possess an antibacterial, antifungal and antiviral function, they also show a chemotactic and immunostimulatory/ modulatory effect. Moreover, they are capable of inducing wound healing, angiogenesis and modulating apoptosis. Recent insights even indicate for a role of these peptides in cancer. This review provides a comprehensive summary of the most recent and relevant insights concerning the human cathelicidin LL 37.

title: Little Peptide, Big Effects: The Role of LL 37 in Inflammation and Autoimmune Disease
abstract: The innate immune system utilizes many approaches for defense against invading microorganisms, including complement mediated lysis, engulfment, formation of neutrophil extracellular traps, and release of antimicrobial peptides. Although classically thought to be driven by adaptive immunity, the development of autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus is increasingly associated with dysregulated innate immune pathways. An emerging theme within this literature is the contribution of antimicrobial peptides to the development of autoimmune disorders. This is best exemplified in atopic dermatitis and psoriasis where the defensins and the single human cathelicidin, LL 37, may contribute to disease. Furthermore, in the past few years, a role for LL 37 has emerged in the pathogenesis of systemic lupus erythematosus, rheumatoid arthritis, atherosclerosis, and possibly other diseases. In this review, we discuss the role of LL 37 and its murine ortholog, mCRAMP, in the modulation of immune and inflammatory pathways and their effects on autoimmune and inflammatory diseases.

title: The human cathelicidin LL 37 A pore forming antibacterial peptide and host cell modulator.
abstract: The human cathelicidin hCAP18/LL 37 has become a paradigm for the pleiotropic roles of peptides in host defence. It has a remarkably wide functional repertoire that includes direct antimicrobial activities against various types of microorganisms, the role of 'alarmin' that helps to orchestrate the immune response to infection, the capacity to locally modulate inflammation both enhancing it to aid in combating infection and limiting it to prevent damage to infected tissues, the promotion of angiogenesis and wound healing, and possibly also the elimination of abnormal cells. LL 37 manages to carry out all its reported activities with a small and simple, amphipathic, helical structure. In this review we consider how different aspects of its primary and secondary structures, as well as its marked tendency to form oligomers under physiological solution conditions and then bind to molecular surfaces as such, explain some of its cytotoxic and immunomodulatory effects. We consider its modes of interaction with bacterial membranes and capacity to act as a pore forming toxin directed by our organism against bacterial cells, contrasting this with the mode of action of related peptides from other species. We also consider its different membrane dependent effects on our own cells, which underlie many of its other activities in host defence. This article is part of a Special Issue entitled: Pore Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.

title: Activation of HIF 1a and LL 37 by commensal bacteria inhibits Candida albicans colonization
abstract: Candida albicans colonization is required for invasive disease. Unlike humans, adult mice with mature intact gut microbiota are resistant to C. albicans gastrointestinal (GI) colonization, but the factors that promote C. albicans colonization resistance are unknown. Here we demonstrate that commensal anaerobic bacteria specifically clostridial Firmicutes (clusters IV and XIVa) and Bacteroidetes are critical for maintaining C. albicans colonization resistance in mice. Using Bacteroides thetaiotamicron as a model organism, we find that hypoxia inducible factor 1a (HIF 1a) a transcription factor important for activating innate immune effectors, and the antimicrobial peptide LL 37 (CRAMP in mice) are key determinants of C. albicans colonization resistance. Although antibiotic treatment enables C. albicans colonization, pharmacologic activation of colonic Hif1a induces CRAMP expression and results in a significant reduction of C. albicans GI colonization and a 50% decrease in mortality from invasive disease. In the setting of antibiotics, Hif1a and Camp (which encodes CRAMP) are required for B. thetaiotamicron induced protection against C. albicans colonization of the gut. Thus, modulating C. albicans GI colonization by activation of gut mucosal immune effectors may represent a novel therapeutic approach for preventing invasive fungal disease in humans.

title: pH modulates the activity and synergism of the airway surface liquid antimicrobials b defensin 3 and LL 37
abstract: Although lungs are continuously bombarded by bacteria, pulmonary defense mechanisms normally keep them sterile. Those defenses include a complex mixture of antimicrobial peptides in the thin layer of liquid coating the airway surface. In cystic fibrosis, impaired bicarbonate secretion causes the airway surface liquid to become abnormally acidic. Here we found that an acidic pH impairs the ability of two key airway antimicrobial peptides, b defensin 3 and LL 37, to kill bacteria. When these peptides were combined, they exhibited synergistic killing of Staphylococcus aureus, an organism that infects cystic fibrosis lungs. However, an acidic pH reduced their synergistic effect. Thus, an acidic pH impairs an important respiratory defense mechanism and may predispose the lungs of people with cystic fibrosis to bacterial infection. The pulmonary airways are continuously exposed to bacteria. As a first line of defense against infection, the airway surface liquid (ASL) contains a complex mixture of antimicrobial factors that kill inhaled and aspirated bacteria. The composition of ASL is critical for antimicrobial effectiveness. For example, in cystic fibrosis an abnormally acidic ASL inhibits antimicrobial activity. Here, we tested the effect of pH on the activity of an ASL defensin, human b defensin 3 (hBD 3) and the cathelicidin related peptide, LL 37. We found that reducing pH from 8.0 to 6.8 reduced the ability of both peptides to kill Staphylococcus aureus. An acidic pH also attenuated LL 37 killing of Pseudomonas aeruginosa. In addition, we discovered synergism between hBD 3 and LL 37 in killing S. aureus. LL 37 and lysozyme were also synergistic. Importantly, an acidic pH reduced the synergistic effects of combinations of ASL antibacterials. These results indicate that an acidic pH reduces the activity of individual ASL antimicrobials, impairs synergism between them, and thus may disrupt an important airway host defense mechanism.

title: High quality 3D structures shine light on antibacterial, anti biofilm and antiviral activities of human cathelicidin LL 37 and its fragments.
abstract: Host defense antimicrobial peptides are key components of human innate immunity that plays an indispensible role in human health. While there are multiple copies of cathelicidin genes in horses, cattle, pigs, and sheep, only one cathelicidin gene is found in humans. Interestingly, this single cathelicidin gene can be processed into different forms of antimicrobial peptides. LL 37, the most commonly studied form, is not only antimicrobial but also possesses other functional roles such as chemotaxis, apoptosis, wound healing, immune modulation, and cancer metastasis. This article reviews recent advances made in structural and biophysical studies of human LL 37 and its fragments, which serve as a basis to understand their antibacterial, anti biofilm and antiviral activities. High quality structures were made possible by using improved 2D NMR methods for peptide fragments and 3D NMR spectroscopy for intact LL 37. The two hydrophobic domains in the long amphipathic helix (residues 2 31) of LL 37 separated by a hydrophilic residue serine 9 explain its cooperative binding to bacterial lipopolysaccharides (LPS) Both aromatic rings (F5, F6, F17, and F27) and interfacial basic amino acids of LL 37 directly interact with anionic phosphatidylglycerols (PG) Although the peptide sequences reported in the literature vary slightly, there is a consensus that the central helix of LL 37 is essential for disrupting superbugs (e.g. MRSA) bacterial biofilms, and viruses such as human immunodeficiency virus 1 (HIV 1) and respiratory syncytial virus (RSV) In the central helix, the central arginine R23 is of particular importance in binding to bacterial membranes or DNA. Mapping the functional roles of the cationic amino acids of the major antimicrobial region of LL 37 provides a basis for designing antimicrobial peptides with desired properties. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.

title: LL 37 stimulates the functions of adipose derived stromal/stem cells via early growth response 1 and the MAPK pathway
abstract: BackgroundLL 37 is a naturally occurring antimicrobial peptide found in the wound bed and assists wound repair. No published study has characterized the role of LL 37 in the function(s) of human mesenchymal stem cells (MSCs) This study investigated the functions of adipose derived stromal/stem cells (ASCs) activated by LL 37 by performing both in vitro assays with cultured cells and in vivo assays with C57BL/6 mice with hair loss.MethodsHuman ASCs were isolated from healthy donors with written informed consent. To examine the effects of LL 37 on ASC function, cell proliferation and migration were measured by a cell counting kit (CCK 8) and a Transwell migration assay. Early growth response 1 (EGR1) mRNA expression was determined by microarray and real time PCR analyses. The protein levels of EGR1 and regenerative factors were analyzed by specific enzyme linked immunosorbent assays and western blotting.ResultsLL 37 treatment enhanced the proliferation and migration of human ASCs expressing formyl peptide receptor like 1. Microarray and real time PCR data showed that EGR1 expression was rapidly and significantly increased by LL 37 treatment. LL 37 treatment also enhanced the production of EGR1. Moreover, small interfering RNA mediated knockdown of EGR1 inhibited LL 37 enhanced ASC proliferation and migration. Activation of mitogen activated protein kinases (MAPKs) was essential not only for LL 37 enhanced ASC proliferation and migration but also EGR1 expression; treatment with a specific inhibitor of extracellular signal regulated kinase, p38, or c Jun N terminal kinase blocked the stimulatory effect of LL 37. EGR1 has a strong paracrine capability and can influence angiogenic factors in ASCs; therefore, we evaluated the secretion levels of vascular endothelial growth factor, thymosin beta 4, monocyte chemoattractant protein 1, and stromal cell derived factor 1. LL 37 treatment increased the secretion of these regenerative factors. Moreover, treatment with the conditioned medium of ASCs pre activated with LL 37 strongly promoted hair growth in vivo.ConclusionsThese findings show that LL 37 increases EGR1 expression and MAPK activation, and that preconditioning of ASCs with LL 37 has a strong potential to promote hair growth in vivo. This study correlates LL 37 with MSC functions (specifically those of ASCs) including cell expansion, cell migration, and paracrine actions, which may be useful in terms of implantation for tissue regeneration.

title: Phenylbutyrate induces LL 37 dependent autophagy and intracellular killing of Mycobacterium tuberculosis in human macrophages
abstract: LL 37 is a human antimicrobial peptide (AMP) of the cathelicidin family with multiple activities including a mediator of vitamin D induced autophagy in human macrophages, resulting in intracellular killing of Mycobacterium tuberculosis (Mtb) In a previous trial in healthy volunteers, we have shown that LL 37 expression and subsequent Mtb killing can be further enhanced by 4 phenylbutyrate (PBA) also an inducer of LL 37 expression. Here, we explore a potential mechanism(s) behind PBA and LL 37 induced autophagy and intracellular killing of Mtb. Mtb infection of macrophages downregulated the expression of both the CAMP transcript and LL 37 peptide as well as certain autophagy related genes (BECN1 and ATG5) at both the mRNA and protein levels. In addition, activation of LC3 II in primary macrophages and THP 1 cells was not detected. PBA and the active form of vitamin D3 (1,25[OH]2D3) separately or particularly in combination, were able to overcome Mtb induced suppression of LL 37 expression. Notably, reactivation of autophagy occurred by stimulation of macrophages with PBA and promoted colocalization of LL 37 and LC3 II in autophagosomes. Importantly, PBA treatment failed to induce autophagy in Mtb infected THP 1 cells, when the expression of LL 37 was silenced. However, PBA induced autophagy was restored when the LL 37 knockdown cells were supplemented with synthetic LL 37. Interestingly, we have found that LL 37 induced autophagy was mediated via P2RX7 receptor followed by enhanced cytosolic free Ca2+ and activation of AMPK and PtdIns3K pathways. Altogether, these results suggest a novel activity for PBA as an inducer of autophagy, which is LL 37 dependent and promotes intracellular killing of Mtb in human macrophages.

title: P2X7 Receptor Regulates Internalization of Antimicrobial Peptide LL 37 by Human Macrophages That Promotes Intracellular Pathogen Clearance
abstract: Bioactive peptide LL 37/hCAP18, the only human member of the cathelicidin family, plays important roles in killing various pathogens, as well as in immune modulation. We demonstrate that LL 37 is internalized by human macrophages in a time dose temperature and peptide sequence dependent endocytotic process. Both clathrin and caveolae/lipid raft mediated endocytosis pathways are involved in LL 37 internalization. We find that the P2X7 receptor (P2X7R) plays an important role in LL 37 internalization by human macrophages because significantly less internalized LL 37 was detected in macrophages pretreated with P2X7R antagonists or, more specifically, in differentiated THP 1 cells in which the P2X7R gene had been silenced. Furthermore, this P2X7R mediated LL 37 internalization is primarily connected to the clathrin mediated endocytosis pathway. In addition, our results demonstrate that internalized LL 37 traffics to endosomes and lysosomes and contributes to intracellular clearance of bacteria by human macrophages, coinciding with increased reactive oxygen species and lysosome formation. Finally, we show that human macrophages have the potential to import LL 37 released from activated human neutrophils. In conclusion, our study unveils a novel mechanism by which human macrophages internalize antimicrobial peptides to improve their intracellular pathogen clearance.

title: Antimicrobial peptide LL 37 promotes bacterial phagocytosis by human macrophages
abstract: LL 37/hCAP 18 is the only human member of the cathelicidin family and plays an important role in killing various pathogens, as well as in immune modulation. In this study, we investigated the effect of LL 37 on bacterial phagocytosis by macrophages and demonstrate that LL 37 enhances phagocytosis of IgG opsonized Gram negative and Gram positive bacteria in a dose and time dependent manner by dTHP 1 cells. In addition, LL 37 enhanced phagocytosis of nonopsonized Escherichia coli by human macrophages. Consistently, LL 37 elevated the expression of FcgRs on macrophages but not the complement receptors CD11b and c. Further studies revealed that the expression of TLR4 and CD14 is also increased on LL 37 treated macrophages. Several lines of evidence indicated that the FPR2/ALX receptor mediated LL 37 induced phagocytosis. However, TLR4 signaling was also coupled to the phagocytic response, as a specific TLR4 antibody significantly suppressed phagocytosis of IgG opsonized E. coli and nonopsonized E. coli by dTHP 1 cells. Finally, macrophages from Cnlp mice exhibited diminished bacterial phagocytosis compared with macrophages from their WT littermates. In conclusion, we demonstrate a novel, immune modulatory mechanism of LL 37, which may contribute to bacterial clearance.