Evaluation of canine antimicrobial peptides in infected and noninfected chronic atopic skin

Background Antimicrobial peptides (AMPs) are small immunomodulatory peptides produced by epithelial and immune cells. beta-Defensins (BDs) and cathelicidins (Caths) are the most studied AMPs. Recently, increased cutaneous expression of AMPs was reported in atopic humans and in beagles with experimentally induced atopy. Hypothesis/Objectives Our goal was to analyse mRNA expression and protein levels of canine (c)BD1-like, cBD2-like/122, cBD3-like, cBD103 and cCath in healthy and naturally affected atopic dogs, with and without active skin infection, along with their distribution in the epidermis using indirect immunofluorescence. Animals Skin biopsies were taken from 14 healthy and 11 atopic privately owned dogs. Methods The mRNA levels of cBD1-like, cBD2-like/122, cBD3-like, cBD103 and cCath were quantified using quantitative real-time PCR. The protein levels of cBD3-like and cCath were analysed by relative competitive inhibition enzyme-linked immunosorbent assay, while the distributions of cBD2-like/122, cBD3-like and cCath were detected by indirect immunofluorescence. Results Dogs with atopic dermatitis had significantly greater mRNA expression of cBD103 (P = 0.04) than control dogs. Furthermore, atopic skin with active infection had a higher cBD103 mRNA expression (P = 0.01) and a lower cBD1-like mRNA expression (P = 0.04) than atopic skin without infection. No significant differences in protein levels (cBD3-like and cCath) or epidermal distribution of AMPs (cBD2-like/122, cBD3-like and cCath) were seen between healthy and atopic dogs. Conclusions and clinical importance Expression of cBD103 mRNA was greater, while expression of cBD1-like mRNA was lower in dogs with atopic dermatitis that had active infections. Work is needed to clarify the biological mechanisms and possible therapeutic options to maintain a healthy canine skin.