Evaluation of cutaneous and circulating (serum and exosomes) levels of chemokines (CCL17, CCL22, CCL27 and CCL28) in atopic dogs and their correlation with severity of the disease.

Abstract

Canine atopic dermatitis (AD) is a complex multifactorial disease characterised by an exaggerated immunological response. Little is known about the role that cutaneous and circulating chemokines play in disease severity. To evaluate the messenger (m)RNA and protein levels of selected chemokines in skin and serum of healthy and atopic dogs, and in the atopic group to determine whether there is a correlation with disease severity. Skin biopsies and blood samples were taken from 12 privately owned atopic [lesional (AD-L) and nonlesional (AD-NL) skin] and 12 privately owned healthy dogs. Circulating exosomes were extracted from the serum. Cutaneous and exosomal mRNA levels of CCL17, CCL22, CCL27 and CCL28 were quantified using quantitative real-time PCR. Protein levels were evaluated using canine-specific ELISA kits. The severity and extent of the clinical signs also were assessed in the atopic dogs using Canine Atopic Dermatitis Extent and Severity Index, 4th iteration (CADESI-04) and a validated pruritus Visual Analog Scale (pVAS). The expression of CCL28 exosomes in skin was greater in AD-L when compared to healthy (P = 0.019) and AD-NL (P = 0.002) samples. However, serum expression was lower in dogs with AD compared to healthy dogs (P = 0.03). A higher expression of CCL17 and CCL22 was seen in AD-L when compared to healthy skin (P = 0.018 and P = 0.019, respectively). There also was a positive correlation between clinical scores and CCL22 (AD-NL; r = 0.6, P = 0.05) and between the pruritus score and CCL22 (AD-L; r = 0.6, P = 0.05). Differences in CCL27 concentrations were not observed. This study suggests that CCL17, CCL22 and CCL28 may play a role in the cutaneous inflammatory response in atopic dogs. They may be considered as markers of disease severity, although further studies are needed to validate these findings.