The LL-37 peptide, a member of the cathelicidin family, is a multifunctional component of the innate immune system with several key roles:
1.Antimicrobial Activity:
○Broad-Spectrum Defense: Exhibits potent activity against bacteria (both Gram-positive and Gram-negative), viruses (e.g., influenza, herpes simplex), fungi, and parasites. It disrupts microbial membranes via its cationic, amphipathic structure, leading to cell lysis.
○Neutralization of Toxins: Binds and neutralizes pathogen-associated molecules like lipopolysaccharides (LPS), reducing inflammatory responses.
2.Immune Modulation:
○Chemotaxis: Attracts immune cells (neutrophils, monocytes, T-cells) to infection sites, enhancing pathogen clearance.
○Cytokine Regulation: Influences production of pro-inflammatory (e.g., IL-6, IL-8) and anti-inflammatory cytokines, balancing immune responses.
○Autoimmunity and Inflammation: Dysregulation (e.g., overexpression in psoriasis) can drive inflammatory diseases, while deficiencies may impair infection control.
3.Wound Healing and Tissue Repair:
○Promotes angiogenesis, epithelial cell migration, and tissue regeneration by interacting with receptors like FPR2 and EGFR.
○Enhances re-epithelialization in chronic wounds (e.g., diabetic ulcers).
4.Additional Roles:
○Antiviral Action: Disrupts viral envelopes and inhibits replication.
○Cancer Context: Exhibits dual roles (pro- or anti-tumor effects depending on microenvironment).
○DNA Interaction: Binds extracellular DNA, modulating immune responses in conditions like psoriasis.
Clinical Relevance: Altered LL-37 levels are linked to infections, chronic inflammation, and autoimmune disorders. Therapeutic strategies aim to harness its antimicrobial properties or modulate its activity in inflammatory diseases.
In summary, LL-37 is a versatile peptide critical for innate immunity, infection control, tissue homeostasis, and immune regulation, with implications in both health and disease.
