LL-37 is an antimicrobial peptide with various biological activities, belonging to the human defensin family. It plays an important role in the immune system and has a wide range of antibacterial, antiviral, antifungal and anti-tumor properties.

Basic information about LL-37:

Chemical structure:

LL-37 is a 37-amino acid polypeptide with the sequence LALWMLSLTALVCLLTGFGG. It is the active form of human cathelicidin (a type of antimicrobial peptide).

Mechanism of action:

LL-37 interferes with the integrity of the bacterial membrane by binding to the cell membrane, leading to cell death. In addition, it can also promote wound healing and anti-inflammatory responses by regulating the function of immune cells.

Potential uses:

Antibacterial action: effective against a variety of bacteria, viruses and fungi.

Immunomodulation: By regulating the activity of immune cells, it is possible to positively affect infection and inflammatory responses.

Promotes wound healing: plays an important role in the healing process, promoting cell proliferation and migration.

Side effects:

It is generally considered safe, but allergic reactions or local irritation may occur in individual patients.

What is the main role of LL-37?

LL-37 is a natural antimicrobial peptide (AMP) that plays an important role in the body's immune defense system. It belongs to the cathelicidin antimicrobial peptide (CAMP) family and is the only known cathelicidin peptide in the human body, which has a wide range of biological functions. In addition to its antibacterial properties, LL-37 is involved in a variety of biological processes such as immune regulation, tissue repair, anti-inflammatory, and anti-tumor. The main roles of LL-37 and its potential in medicine and health management will be discussed below.

Antibacterial properties

LL-37 is best known for its powerful antibacterial ability against a variety of pathogens, including bacteria, fungi, and viruses. It causes structural damage to microorganisms by directly destroying their cell membranes, which leads to their death. Its mechanism of action includes:

Cell membrane destruction: LL-37 is a cationic peptide that binds to negatively charged pathogen cell membranes, causing instability in the membrane structure and resulting in cell lysis.

Intrinsic bactericidal action: LL-37 can also promote phagocytosis of macrophages and neutrophils by activating the host immune system to further clear the source of infection.

This broad-spectrum antimicrobial ability makes it a potential alternative or complementary therapy against bacterial infections, including antibiotic-resistant bacteria.

Immune regulation

As part of the natural immune system, LL-37 plays an important role in immune regulation. It can regulate innate immunity and adaptive immune response, and participate in the coordinated operation of the immune system through interaction with a variety of immune cells.

Promotes inflammation: In the initial stages of infection or injury, LL-37 promotes cytokine release by activating neutrophils, monocytes, and macrophages to enhance the inflammatory response against pathogens.

Inhibits excessive inflammation: Although it can promote the inflammatory response, LL-37 also has a role in regulating inflammation and preventing tissue damage caused by excessive inflammation. For example, it is able to inhibit the excessive release of certain pro-inflammatory cytokines, such as TNF-α, balancing the inflammatory response.

This bidirectional regulatory ability makes LL-37 an important regulator in the immune system, helping to maintain the balance of the immune system.

Tissue repair and regeneration

LL-37 is also believed to play a key role in wound healing and tissue repair. Studies have shown that it can promote tissue regeneration and repair through the following mechanisms:

Epithelial cell migration and proliferation: LL-37 promotes the migration and proliferation of epithelial cells in skin and other tissues, thereby accelerating wound healing.

Angiogenesis: It stimulates the formation of new blood vessels (angiogenesis), a process essential for wound healing and tissue regeneration, as the blood supply plays an important role in providing oxygen and nutrients.

Reduces scarring: While promoting healing, LL-37 also helps reduce excessive scar tissue formation, which has potential benefits for aesthetic and functional wound recovery.

Therefore, LL-37 is considered to have important application prospects in wound repair, postoperative recovery and skin injury treatment.

Anti-inflammatory and anti-tumor effects

The anti-inflammatory effects of LL-37 are not limited to local immune regulation at the site of infection, it is also able to play a role in chronic inflammation and reduce the risk of inflammation-related diseases. In some chronic inflammatory diseases (e.g., psoriasis, inflammatory bowel disease), LL-37 is able to regulate the immune response and reduce the burden of inflammation.

In addition, LL-37 also showed some anti-tumor potential. Studies have shown that LL-37 can inhibit the proliferation and metastasis of tumor cells in certain cancer models. Possible mechanisms include:

Induces tumor cell apoptosis: LL-37 directly kills tumor cells by destroying tumor cell membranes or activating apoptosis pathways.

Immune activation: It also enhances the ability of immune cells to recognize and clear tumor cells by modulating the host immune system.

Although the antitumor effects of LL-37 are still being studied, its application as a potential anticancer drug, especially in enhanced immunotherapy, holds wide promise.

Potential therapeutic applications

Due to its multiple biological roles, LL-37 has potential applications in several clinical areas:

Infection treatment: In the context of increasing antibiotic resistance, LL-37, as a natural antimicrobial peptide, is expected to become an alternative choice for antibiotic therapy, especially in the treatment of complex infections (such as chronic wound infections, lung infections, etc.).

Skin treatment: LL-37 may be helpful in treating chronic skin diseases (such as eczema, psoriasis, etc.) by regulating inflammation and promoting skin repair to improve symptoms.

Wound healing: In poor wound healing or post-operative recovery, LL-37 can be used to accelerate wound healing and reduce scarring, especially in people with diabetes, where this peptide may appear especially important.

Immunomodulation: Due to its bidirectional ability to regulate the immune system, LL-37 is also promising for the treatment of autoimmune diseases such as rheumatoid arthritis and inflammatory bowel disease.

Side effects and challenges

Although LL-37 has shown potential therapeutic benefits in many ways, its use comes with some challenges. First, it is less stable in the human body and needs to be enhanced by synthetic modifications or delivery systems to enhance its biological activity. In addition, excessive use may trigger an overactivation of the immune system, increasing the risk of an inflammatory response. Therefore, future studies need to further clarify the most effective and safe dose range.

Conclusion

As a powerful natural antimicrobial peptide, LL-37 not only plays a role in antimicrobial defense, but also shows extensive potential in immune regulation, tissue repair and anti-tumor. Its multiple biological functions make it a candidate for the future treatment of a variety of infectious diseases, inflammatory diseases, and skin lesions. However, more clinical studies are still needed to ensure its safety and efficacy in humans. With a better understanding of the mechanism of LL-37, it is expected to become a key component in the next generation of antibiotics and immunotherapies.