Researchers tested small pieces of the natural skin peptide LL‑37 and related molecules on human skin cells in a dish and found they can reduce UV‑induced damage, lower inflammation, boost antioxidant defenses, help cells move and make more collagen, and even cut down on sugar‑linked aging and melanin production.

Cathelicidin LL-37, an antimicrobial peptide (AMP) of the innate immune system, wards off bacterial infections. Recent research has identified plenty of biological functions of AMPs beyond their antimicrobial activity, including antioxidant, self-renewal, and procollagen properties, making them valuable for antiaging products. In this study, we assessed the antiphotoaging potential of cathelicidin LL-37 fragments and KR-12 analogs using human immortalized keratinocytes (HaCaT) and human dermal fibroblasts (HDF). Our results reveal that these peptides can modulate ultraviolet-radiation-induced photodamage, exhibiting anti-inflammatory and antioxidant properties. Notably, we proved the immune modulation effects of LL-23. Additionally, these peptides promote cell migration and collagen synthesis, inhibit glycation, and suppress melanin production. We propose that the antiphotoaging effects exhibited by LL-37 fragments and KR-12 analogs are related to the alleviation of inflammation, and we attempt to elucidate the possible underlying mechanisms. These findings support their efficacy as antiaging agents in dermatological applications.