Cathelicidin LL-37: a multitask antimicrobial peptide. — VialBase Research

Summary

This narrative review establishes the basic biology of LL-37, the only known member of the cathelicidin family of peptides expressed in humans and a multifunctional host defense molecule described as essential for normal immune responses to infection and tissue injury. The review characterizes LL-37 as a potent killer of different microorganisms with the additional ability to prevent the immunostimulatory effects of bacterial wall molecules such as lipopolysaccharide, which the authors note can therefore protect against lethal endotoxemia. Beyond direct microbial killing, the reported activity list is broad: chemoattractant function, inhibition of neutrophil apoptosis, and stimulation of angiogenesis, tissue regeneration, and cytokine release such as IL-8. The review also covers regulation of the peptide’s own production, which is affected by multiple factors including bacterial products, host cytokines, availability of oxygen, and sun exposure acting through vitamin D3 activation of CAP-18 gene expression — the mechanistic basis of the vitamin D to cathelicidin link. Critically for anyone reasoning about real-world efficacy, the review flags that at infection sites LL-37’s function can be inhibited by charge-driven interactions with DNA and F-actin released from dead neutrophils and other cells lysed as a result of inflammation, meaning the peptide’s in vitro potency is not automatically preserved in an inflamed wound environment. The authors conclude that better understanding of LL-37’s biological properties is necessary before therapeutic application for immunomodulatory purposes or bacterial infection.

Key Findings

• LL-37 is the only known human cathelicidin, functioning as a multifunctional host defense molecule in immune responses to infection and tissue injury
• It kills a range of microorganisms and neutralizes the immunostimulatory effect of bacterial wall molecules such as lipopolysaccharide, with reported protection against lethal endotoxemia
• Additional reported activities: chemoattraction, inhibition of neutrophil apoptosis, stimulation of angiogenesis, tissue regeneration, and cytokine release including IL-8
• Endogenous LL-37 production is modulated by bacterial products, host cytokines, oxygen availability, and sun exposure through vitamin D3 activation of CAP-18 gene expression
• At infection sites, LL-37 activity can be inhibited by charge-driven binding to DNA and F-actin released from lysed neutrophils and other inflamed tissue — a real-world limit on its antimicrobial function

Relevance to LL-37

This review is the reference point for what LL-37 actually is — the human cathelicidin, an endogenous innate-immunity peptide rather than a designed drug — and it is the cleanest source for the breadth of its reported biological roles, spanning direct antimicrobial killing, endotoxin neutralization, immune cell recruitment, angiogenesis and tissue regeneration. Two details deserve to survive any summary. The vitamin D3 to CAP-18 pathway explains why cathelicidin expression is tied to vitamin D status and sun exposure, which is frequently cited but rarely sourced. And the observation that DNA and F-actin released by dying cells bind and inhibit LL-37 at infection sites is a direct caution against extrapolating clean in vitro antimicrobial results to inflamed human tissue. Because this is a narrative review rather than a trial, nothing in it constitutes clinical evidence for supplementing or administering LL-37; the authors explicitly frame therapeutic application as a possibility requiring better understanding, not an established use.

Citation

Bucki R, Leszczyńska K, Namiot A, et al. Cathelicidin LL-37: a multitask antimicrobial peptide. Archivum immunologiae et therapiae experimentalis. 2010;58(1):15-25. doi:10.1007/s00005-009-0057-2.

See Also

• Parent compound: LL-37