LL-37

Mechanism (as reported)

Sources describe LL-37 as a peptide with antimicrobial activity that can prevent immunostimulatory effects of bacterial lipopolysaccharide, and as interacting with host and microbial components in ways linked to inflammatory processes. In lung-related and other contexts, LL-37 is described as a multifunctional peptide that can include cytotoxicity to host cells, chemotaxis, epithelial activation, angiogenesis, and epithelial wound repair. In Legionella micdadei research, LL-37 is described as interacting with bacterial membrane phospholipids (with effects depending on phospholipid composition, including phosphatidylcholine fraction), and associated with perturbation of bacterial-derived phospholipid monolayers; growth inhibition was reported and was modulated by exogenous choline affecting membrane PC synthesis.

Key findings (each cites a source)

• A study/review reported that antimicrobial peptide LL-37 is the only known member of the cathelicidin family expressed in humans and is described as a multifunctional host defense molecule. [PMID 20049649, 15939310, 20600427]
• Research described LL-37 as having antimicrobial activity against different microorganisms and as being able to prevent immunostimulatory effects of bacterial wall molecules such as lipopolysaccharide. [PMID 20049649]
• A review reported additional activities for LL-37 including chemoattractant function, inhibition of neutrophil apoptosis, and stimulation of angiogenesis, tissue regeneration, and cytokine release (e.g., IL-8). [PMID 20049649]
• A review reported that LL-37 production in cells is affected by multiple factors, including bacterial products, host cytokines, oxygen availability, and sun exposure through activation of CAP-18 gene expression by vitamin D3. [PMID 20049649]
• Research/review described that at infection sites the function of LL-37 can be inhibited by charge-driven interactions with DNA and F-actin released from dead neutrophils and other lysed cells. [PMID 20049649]
• A lung-focused review reported that LL-37 (the C-terminal part of the human cathelicidin hCAP-18/hCAP-18 precursor) is mainly expressed by neutrophils and epithelial cells and is characterized as a broad-spectrum antimicrobial peptide with additional cellular activities related to inflammation. [PMID 15939310, 20600427]
• Reviews reported LL-37 activities in infection/inflammation contexts including chemotaxis, epithelial cell activation, angiogenesis, and epithelial wound repair (among other host-response effects). [PMID 15939310, 20600427]
• In sepsis research and review, antimicrobial peptides were described as first-line host defense and immunomodulators of inflammation; the LL-37 peptide originating from human cathelicidin (hCAP18) was described as a focus for understanding mechanisms relevant to sepsis. [PMID 40960088]
• A sepsis-focused source reported that LL-37 concentration changes dynamically in blood during sepsis and stated that in animal models, exogenous LL-37 peptide increased survival in mice with experimentally induced sepsis. [PMID 40960088]
• A review on rosacea reported that pro-inflammatory pathways involving cathelicidins and inflammasome complexes are central to rosacea pathogenesis. [PMID 38450615]
• In mycobacterial infection-focused discussion, research described hCAP18/LL-37 as a multifunctional molecule that may mediate host responses including bactericidal action, chemotaxis, epithelial cell activation, angiogenesis, epithelial wound repair, and activation of chemokine secretion, with LL-37 produced from human cells during mycobacterial infection. [PMID 20600427]
• In a plant expression study, researchers reported that signal peptide LL-37 (SP-LL-37) enhanced disease resistance in transgenic rice against bacterial leaf blight and blast, with stable expression confirmed by RT-PCR and ELISA and localization shown via GFP fusion. [PMID 28282452]