Expression and distribution of canine antimicrobial peptides in the skin of healthy and atopic beagles

Antimicrobial peptides (AMPs) are small immuno-modulatory proteins important in defense against pathogenic organisms. Defensins and cathelicidin are the most frequently studied human AMPs. An increase in AMPs in atopic humans has been reported recently. Our goals were to determine the distribution of AMPs and evaluate their mRNA and protein expression in non-lesional (Day 0), acute lesional skin (Day 3) and post-challenged skin after resolution of skin lesions (Day 10) using a canine model of atopic dermatitis (AD). All dogs were environmentally challenged for three consecutive days with house dust mite. Clinical evaluation of atopic beagles was performed using a CADESI score at each time point before and after environmental challenge. Skin biopsies were taken from six healthy and seven atopic beagles before and after allergen challenge (Day 0, Day 3 and Day 10). The transcription of canine cathelicidin (cCath) and beta-defensins (cBD)-1, -2 and -3 mRNA was quantified using quantitative-RT-PCR while the protein distribution of cBD2, cBD3 and cCath was detected by indirect immunofluorescence. A significant effect, over-time, was seen in CADESI score in AD beagles with an increase score after challenge (Day 3). Quantitative analysis showed a significant difference in mRNA transcript levels between groups (with atopic dogs having more than controls) for all AMPs but cBD2. No effect over time was evident for either group. No significant differences were seen for the AMP protein patterns of distribution (homogenous distribution). Although, these results showed no differences in AMP's localization after allergen exposure in each group; atopic dogs had a higher mRNA expression of AMPs when compared with healthy dogs, a similar finding to humans.