LL-37

This cleavage is primarily carried out by proteinase 3 in neutrophils. LL-37 is also produced by various epithelial cells, macrophages, mast cells, and keratinocytes.

Distribution and Function

LL-37 is found at barrier sites such as the skin, respiratory tract, and gastrointestinal tract. The peptide has been observed to have broad-spectrum antimicrobial activity in vitro against various Gram-positive and Gram-negative bacteria, fungi, and some viruses.

Immune Modulation

In addition to its antimicrobial properties, LL-37 is studied for its role as an immune modulator. Research models show it can recruit and activate immune cells, modulate inflammatory responses, and neutralize bacterial toxins such as lipopolysaccharide (LPS). It has also been shown to be involved in processes such as angiogenesis and apoptosis.

The expression of the gene for the LL-37 precursor protein is known to be regulated by factors including vitamin D. For example, some studies show that an increase in vitamin D can increase LL-37 production.

LL-37 is a pleiotropic peptide that functions through multiple mechanisms.

Direct Antimicrobial Action

Its antimicrobial activity is primarily attributed to its amphipathic structure, which allows it to disrupt microbial membranes. The peptide's cationic regions interact with negatively charged components of microbial membranes, while its hydrophobic regions insert into the lipid bilayer. This process can lead to pore formation, membrane destabilization, and leakage of cellular contents.

This membrane-disruption mechanism acts on fundamental structures of the microbial cell, a characteristic that is a focus of research into antimicrobial resistance.

Antiviral Activity

In vitro studies have shown LL-37 exhibits activity against enveloped viruses, including influenza, herpes simplex virus, and HIV, through similar membrane-disrupting mechanisms.

Immunomodulation

As an immunomodulator, LL-37 can act as a chemoattractant for neutrophils, monocytes, mast cells, and T cells by interacting with receptors such as formyl peptide receptor-like 1 (FPRL1). It can activate mast cells and neutrophils, leading to degranulation and the release of other immune factors.

The peptide's effect on cytokine production is context-dependent. It has been observed to both suppress pro-inflammatory cytokines like TNF-α and IL-6 in certain settings and to promote the production of chemokines and growth factors associated with tissue repair processes.

Wound Healing Models

In cellular models, LL-37 has been shown to affect keratinocyte and fibroblast migration and proliferation. It is also associated with angiogenesis through its influence on factors such as vascular endothelial growth factor (VEGF).

Anti-Biofilm Properties

LL-37 has demonstrated an ability to disrupt established bacterial biofilms in laboratory models. This is an area of interest for studying infections associated with biofilms.

LPS Neutralization

LL-37 can bind to and sequester bacterial lipopolysaccharide (LPS), which can attenuate the inflammatory cascade induced by endotoxin. This property is being explored in research models of sepsis.

Published nonclinical literature relevant to this material's molecular targets and experimental models is listed below for independent review. Findings involving other preparations or experimental systems should not be attributed to this research material.

This material is supplied solely for in vitro and other nonclinical laboratory research. It is not for human or veterinary use, consumption, administration, therapeutic use, or diagnostic use.

Laboratory Handling

Handle only in an appropriately equipped laboratory using applicable institutional procedures, personal protective equipment, and the storage conditions shown for the material. The purchaser is responsible for study design, handling controls, disposal, and regulatory compliance.

Research Limitations

Published observations involving other preparations, experimental systems, or study populations do not establish the identity, performance, or suitability of this research material for any particular experiment.