title: Doxycycline indirectly inhibits proteolytic activation of tryptic kallikrein-related peptidases and activation of cathelicidin.
abstract: The increased abundance and activity of cathelicidin and kallikrein 5 (KLK5), a predominant trypsin-like serine protease (TLSP) in the stratum corneum, have been implicated in the pathogenesis of rosacea, a disorder treated by the use of low-dose doxycycline. Here we hypothesized that doxycycline can inhibit activation of tryptic KLKs through an indirect mechanism by inhibition of matrix metalloproteinases (MMPs) in keratinocytes. The capacity of doxycycline to directly inhibit enzyme activity was measured in surface collections of human facial skin and extracts of cultured keratinocytes by fluorescence polarization assay against fluorogenic substrates specific for MMPs or TLSPs. Doxycycline did inhibit MMP activity but did not directly inhibit serine protease activity against a fluorogenic substrate specific for TLSPs. However, when doxycycline or other MMP inhibitors were added to live keratinocytes during the production of tryptic KLKs, this treatment indirectly resulted in decreased TLSP activity. Furthermore, doxycycline under these conditions inhibited the generation of the cathelicidin peptide LL-37 from its precursor protein hCAP18, a process dependent on KLK activity. These results demonstrate that doxycycline can prevent cathelicidin activation, and suggest a previously unknown mechanism of action for doxycycline through inhibiting generation of active cathelicidin peptides.
authors.affiliation: Division of Dermatology, Department of Medicine, University of California, San Diego, San Diego, California 92093, USA.
authors.forename: Kimberly N
authors.initials: KN
authors.lastname: Kanada
authors.forename: Teruaki
authors.initials: T
authors.lastname: Nakatsuji
authors.forename: Richard L
authors.initials: RL
authors.lastname: Gallo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000187:drug effects / Q000378:metabolism*; D007611:Aprotinin / Q000494:pharmacology; D002478:Cells, Cultured; D004318:Doxycycline / Q000494:pharmacology*; D006801:Humans; D007610:Kallikreins / Q000187:drug effects / Q000378:metabolism*; D015603:Keratinocytes / Q000187:drug effects / Q000201:enzymology*; D020782:Matrix Metalloproteinases / Q000187:drug effects / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D012867:Skin / Q000187:drug effects / Q000201:enzymology*; D013450:Sulfones / Q000494:pharmacology; D054804:Cathelicidins
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D015842:Serine Proteinase Inhibitors; D013450:Sulfones; C002010:4-(2-aminoethyl)benzenesulfonylfluoride; D007611:Aprotinin; C400147:KLK5 protein, human; D007610:Kallikreins; D020782:Matrix Metalloproteinases; D004318:Doxycycline; D054804:Cathelicidins