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. β-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- ThemRNA levels of cBD1-like, cBD2-like/122, cBD3-like, cBD103 and cCath werequantified 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.