Cathelicidins

Antimicrobial peptides detectable in many mammals (also known as alarmins ), which are found in lysosomes of neutrophil granulocytes (PMN) and macrophages. Cathelicidins are translated in these cells from a precursor peptide (hCAP 18) after activation by bacteria, viruses, fungi or hormones (e.g. vitamin D3: questionable influence of UV irradiation) and further processed by the serine proteases kallikrein 5 and kallikrein 7 to the active cathelicin peptide LL37 .

Cathelicidins have less than 100 amino acids and are found on the skin and in the large intestine. They have a broad spectrum of activity and can render Gram-positive and Gram-negative bacteria and fungi harmless. Together with defensins, they are among the most important representatives of the so-called antimicrobial peptides.

Cathelicidins are only slightly expressed in healthy skin. High concentrations are found in barrier disorders in the skin caused by wounds or infections. Certain skin diseases such as atopic eczema or psoriasis are characterized by dysregulation of cathelicidins.

Immunological activity is also attributed to the adipocytes of the subcutaneous fatty tissue. For example, after an infection of the skin with Staphylococcus aureus, there is a rapid proliferation of preadipocytes and an expansion of the SAT (subcutaneous adipose tissue). The defense functions of the SAT are mediated by the production of cathelicidin, which is secreted by adipocytes. In animal experiments, inhibited adipogenesis induces a reduced production of cathelicidin and an increased infection rate. Taken together, these results show that the production of the antimicrobial peptide cathelicidin by adipocytes is an important factor in protecting the skin from infection with S. aureus (Zhang LJ et al. (2015).

According to current knowledge, proinflammatory signaling pathways involving cathelicidins and inflammasome complexes play a central role in the pathogenesis of rosacea. Common triggers of rosacea modulate these signaling pathways in complex ways, which may contribute to the varying severity and clinical manifestations of rosacea. Elevated levels of cathelicidin have been shown in patients with rosacea (Geng RSQ et al. 2024).

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2. Elias PM et al (2005) Interactions among stratum corneum defensive functions. Experimental Dermatol 14: 719-726
3. Geng RSQ et al. (2024) Rosacea: Pathogenesis and Therapeutic Correlates. J Cutan Med Surg 28:178-189.

4. Zhang LJ et al. (2015) Innate immunity. Dermal adipocytes protect against invasive Staphylococcus aureus skin infection. Science 347:67-71.