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LL-37 (trifluoroacetate salt)

Catalog No.: GC14377

LL-37 (trifluoroacetate salt) is a 37-residue, amphipathic, cathelicidin-derived antimicrobial peptide, which exhibits a broad spectrum of antimicrobial activity.

LL-37 (trifluoroacetate salt) Chemical Structure

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Cell experiment [1]:

Cell lines

HaCaT cells

Preparation Method

HaCaT cells were transfected with a 2 μg of empty vector and 0.1, 0.5, 1, or 2 μg of LL-37 plasmids for 6 h and then internalized with P. gingivalis (MOI 100, 6 h) using the antibiotic protection assay. Total RNA was extracted after 18 h.

Reaction Conditions

0.1, 0.5, 1, or 2 μg; 6 h


The qRT-PCR results showed that compared with the control cells, the number of live P. gingivalis was significantly reduced by 0.79, 0.62, and 0.69 times in cells transfected with 0.5, 1, or 2 μg of LL 37 plasmids, respectively. LL 37 mRNA expression gradually increased significantly as transfected with 0.1, 0.5, or 1 μg of LL 37 plasmids, which was followed by a decrease and reached a peak in cells treated with 1 μg of LL 37 plasmids.

Animal experiment [2]:

Animal models

BALB/c female mice

Preparation Method

Mice were intravenously injected with PBS (200 μl) or LL 37 (3 μg/200 μl in PBS) just prior to CLP or sham operation. Peritoneal exudates (3 ml) and blood were collected 14–16 h after the operation, and the number of bacteria and inflammatory cells was determined.

Dosage form

3 μg/200 μl in PBS; i.v.


LL 37 administration significantly reduced the bacterial load in the peritoneal exudates (PBS-CLP vs LL-37-CLP) as well as blood.


[1]. Yang X, et al. LL-37-Induced Autophagy Contributed to the Elimination of Live Porphyromonas gingivalis Internalized in Keratinocytes. Front Cell Infect Microbiol. 2020 Oct 15;10:561761.

[2]. Kumagai Y, et al. Antimicrobial peptide LL-37 ameliorates a murine sepsis model via the induction of microvesicle release from neutrophils. Innate Immun. 2020 Oct;26(7):565-579.


LL-37 contains 37 amino acid residues with the first two leucine residues (L1LGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES37) and mostly exists in epithelial cells and neutrophils.

In vitro experiment it shown that treatment with 4 and 10 μM LL-37 reduced both the number and viability of human osteoblast-like MG63 cell.[2] In vitro, the pretreatment of pMSCs with 1 and 10 μg/mL of LL-37 had not effect on the migratory cells ability. But the pretreatment with 1 μg/mL of LL-37 increased the migratory potential of pMSCs after 48 h.[4] In vitro study it indicated that at 1 µmol/L concentrations of LL-37 for 24 hours, LL-37 prevented LPS-induced stimulation of MCP-1 expression analyzed both on transcript and on protein levels, but had no effect on toll-like receptor (TLR)2 and TLR4 transcript expression. In the meanwhile, treatment with 0.1 and 1 µmol/L LL-37 for 60 minutes in PDL cell induced immunoreactivity for LL-37.[5]

In vivo study it suggested that treatment with 2 μg/mouse of LL-37 intravenously improves the survival of CLP septic mice in a dose-dependent effect. LL-37 ameliorates the level of ectosomes with higher antibacterial potential, result in reducing the bacterial load in CLP mice.[1] LL-37 dose-dependently (1, 3, or 10 μg/ml) induced ectosome release from neutrophil. Injection LL-37 supressed the infiltration of polymorphonuclear cells in CLP mice, where the bacterial burden and inflammatory response are decreased.[3]

[1].Nagaoka I, et al. Therapeutic Potential of Cathelicidin Peptide LL-37, an Antimicrobial Agent, in a Murine Sepsis Model. Int J Mol Sci. 2020 Aug 19;21(17):5973.
[2].Bankell E, et al. LL-37-induced caspase-independent apoptosis is associated with plasma membrane permeabilization in human osteoblast-like cells. Peptides. 2021 Jan;135:170432.
[3].Kumagai Y, et al. Antimicrobial peptide LL-37 ameliorates a murine sepsis model via the induction of microvesicle release from neutrophils. Innate Immun. 2020 Oct;26(7):565-579.
[4].Oliveira-Bravo M, et al. LL-37 boosts immunosuppressive function of placenta-derived mesenchymal stromal cells. Stem Cell Res Ther. 2016 Dec 30;7(1):189.
[5].Aidoukovitch A, et al. The host defense peptide LL-37 is internalized by human periodontal ligament cells and prevents LPS-induced MCP-1 production. J Periodontal Res. 2019 Dec;54(6):662-670.

Chemical Properties

Cas No. 154947-66-7 SDF
Canonical SMILES CC[C@]([C@@](/N=C(O)/[C@](/N=C(O)/[C@](/N=C(O)/[C@](/N=C(O)/[C@](/N=C(O)/[C@](/N=C(O)/[C@](/N=C(O)/[C@](/N=C(O)/[C@](/N=C(O)/[C@](/N=C(O)/C/N=C(O)/[C@](/N=C(O)/[C@](N)([H])CC(C)C)([H])CC(C)C)([H])CC(O)=O)([H])CC1=CC=CC=C1)([H])CC2=CC=CC=C2)([H])CCCNC(N)=N
Formula C205H340N60O53 M.Wt 4493.32
Solubility Water: 1 mg/ml Storage Store at -20°C
General tips For obtaining a higher solubility , please warm the tube at 37 ℃ and shake it in the ultrasonic bath for a while.Stock solution can be stored below -20℃ for several months.
Shipping Condition Evaluation sample solution : ship with blue ice
All other available size: ship with RT , or blue ice upon request

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Research Update

Therapeutic Potential of Cathelicidin Peptide LL-37, an Antimicrobial Agent, in a Murine Sepsis Model

Int J Mol Sci2020 Aug 19;21(17):5973.PMID: 32825174DOI: 10.3390/ijms21175973

Among the mechanisms put-up by the host to defend against invading microorganisms, antimicrobial peptides represent the first line. In different species of mammals, the cathelicidin family of antimicrobial peptides AMPs has been identified, and in humans, LL-37 is the only type of cathelicidin identified. LL-37 has many different biological activities, such as regulation of responses to inflammation, besides its lipopolysaccharide (LPS)-neutralizing and antimicrobial and activities. Recently, employing a murine septic model that involves cecal ligation and puncture (CLP), we examined the effect of LL-37. The results indicated that LL-37 exhibits multiple protective actions on septic mice; firstly, the survival of CLP mice was found to be improved by LL-37 by the suppression of the macrophage pyroptosis that induces the release of pro-inflammatory cytokines (such as IL-1β) and augments inflammatory reactions in sepsis; secondly, the release of neutrophil extracellular traps (NETs), which have potent bactericidal activity, is enhanced by LL-37, and protects mice from CLP-induced sepsis; thirdly, LL-37 stimulates neutrophils to release antimicrobial microvesicles (ectosomes), which improve the pathological condition of sepsis. These findings indicate that LL-37 protects CLP septic mice through at least three mechanisms, i.e., the suppression of pro-inflammatory macrophage pyroptosis and the release of antimicrobial NETs (induction of NETosis) and ectosomes from neutrophils. Thus, LL-37 can be a potential therapeutic candidate for sepsis due to its multiple properties, including the modulation of cell death (pyroptosis and NETosis) and the release of antimicrobial NETs and ectosomes as well as its own bactericidal and LPS-neutralizing activities.

Roles and Mechanisms of Human Cathelicidin LL-37 in Cancer

Cell Physiol Biochem2018;47(3):1060-1073.PMID: 29843147DOI: 10.1159/000490183

LL-37, the C-terminal peptide of human cathelicidin antimicrobial peptide (CAMP, hCAP18), reportedly increases resistance to microbial invasion and exerts important physiological functions in chemotaxis, promotion of wound closure, and angiogenesis. Accumulating evidence indicates that LL-37 also plays a significant role in human cancer. LL-37 induces tumorigenic effects in cancers of the ovary, lung, breast, prostate, pancreas, as well as in malignant melanoma and skin squamous cell carcinoma. In contrast, LL-37 displays an anti-cancer effect in colon cancer, gastric cancer, hematologic malignancy and oral squamous cell carcinoma. Mechanistically, LL-37-induced activation of membrane receptors and subsequent signaling pathways lead to alteration of cellular functions. Different membrane receptors on various cancer cells appear to be responsible for the tissue-specific effects of LL-37. Meanwhile, the findings that vitamin D-dependent induction of cathelicidin in human macrophages activates the anti-cancer activity of tumor-associated macrophages (TAMs) and enhances antibody-dependent cellular cytotoxicity (ADCC) support critical roles of vitamin D-dependent induction of cathelicidin in cancer progression. This review describes novel advances involving the roles and mechanisms of human cathelicidin LL-37 in cancer.

Antimicrobial Peptide LL-37 Drives Rosacea-Like Skin Inflammation in an NLRP3-Dependent Manner

J Invest Dermatol2021 Dec;141(12):2885-2894.e5.PMID: 33745908DOI: 10.1016/j.jid.2021.02.745

Rosacea is a chronic inflammatory skin disease characterized by immune response-dependent erythema and pustules. Although the precise etiology of rosacea remains elusive, its pathogenesis is reportedly associated with an increased level of antimicrobial peptide LL-37. However, molecular mechanisms underlying the progression of rosacea via LL-37 remain poorly understood. Here, we examined the potential role of LL-37 in rosacea-like skin inflammatory phenotypes at a molecular level. Our in vitro data demonstrated that LL-37 promotes NLRP3-mediated inflammasome activation in lipopolysaccharide-primed macrophages, indicated by the processing of caspase-1 and IL-1β. LL-37 was internalized into the cytoplasm of macrophages through P2X7 receptor-mediated endocytosis. Intracellular LL-37 triggered the assembly and activation of NLRP3-ASC inflammasome complex by facilitating lysosomal destabilization. Consistent with these in vitro results, intradermal LL-37 administration induced in vivo caspase-1 activation and ASC speck formation in the skin of Nlrp3-expressing, but not in Nlrp3-deficient, mice. Intradermal injection of LL-37 elicited profound recruitment of inflammatory Gr1+ cells and subsequent skin inflammation. However, LL-37-induced rosacea-like skin inflammation was significantly abrogated in Nlrp3-deficient mice. Furthermore, an NLRP3-specific inhibitor, MCC950, markedly reduced LL-37-triggered rosacea-like phenotypes. Taken together, our findings clearly indicate that NLRP3 inflammasome activation plays a crucial role in LL-37-induced skin inflammation and rosacea pathogenesis.

The Potential of Human Peptide LL-37 as an Antimicrobial and Anti-Biofilm Agent

Antibiotics (Basel)2021 May 29;10(6):650.PMID: 34072318DOI: 10.3390/antibiotics10060650

The rise in antimicrobial resistant bacteria threatens the current methods utilized to treat bacterial infections. The development of novel therapeutic agents is crucial in avoiding a post-antibiotic era and the associated deaths from antibiotic resistant pathogens. The human antimicrobial peptide LL-37 has been considered as a potential alternative to conventional antibiotics as it displays broad spectrum antibacterial and anti-biofilm activities as well as immunomodulatory functions. While LL-37 has shown promising results, it has yet to receive regulatory approval as a peptide antibiotic. Despite the strong antimicrobial properties, LL-37 has several limitations including high cost, lower activity in physiological environments, susceptibility to proteolytic degradation, and high toxicity to human cells. This review will discuss the challenges associated with making LL-37 into a viable antibiotic treatment option, with a focus on antimicrobial resistance and cross-resistance as well as adaptive responses to sub-inhibitory concentrations of the peptide. The possible methods to overcome these challenges, including immobilization techniques, LL-37 delivery systems, the development of LL-37 derivatives, and synergistic combinations will also be considered. Herein, we describe how combination therapy and structural modifications to the sequence, helicity, hydrophobicity, charge, and configuration of LL-37 could optimize the antimicrobial and anti-biofilm activities of LL-37 for future clinical use.

Design of Antimicrobial Peptides: Progress Made with Human Cathelicidin LL-37

Adv Exp Med Biol2019;1117:215-240.PMID: 30980360DOI: 10.1007/978-981-13-3588-4_12

The incorporation of the innate immune system into humans is essential for survival and health due to the rapid replication of invading microbes and the delayed action of the adaptive immune system. Antimicrobial peptides are important components of human innate immunity. Over 100 such peptides have been identified in various human tissues. Human cathelicidin LL-37 is best studied, and there has been a growing interest in designing new peptides based on LL-37. This chapter describes the alternative processing of the human cathelicidin precursor, protease digestion, and lab cutting of LL-37. Both a synthetic peptide library and structure-based design are utilized to identify the active regions. Although challenging, the determination of the 3D structure of LL-37 enabled the identification of the core antimicrobial region. The minimal region of LL-37 can be function-dependent. We discuss the design and potential applications of LL-37 into antibacterial, antibiofilm, antiviral, antifungal, immune modulating, and anticancer peptides. LL-37 has been engineered into 17BIPHE2, a stable, selective, and potent antimicrobial, antibiofilm, and anticancer peptide. Both 17BIPHE2 and SAAP-148 can eliminate the ESKAPE pathogens and show topical in vivo antibiofilm efficacy. Also discussed are other application strategies, including peptide formulation, antimicrobial implants, and peptide-inducing factors such as vitamin D and sunlight. Finally, we summarize what we learned from peptide design based on human LL-37.


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