Chemokine levels in skin and blood linked to dog atopic dermatitis

Abstract

BACKGROUND: 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. OBJECTIVE: 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. MATERIALS AND METHODS: 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, 4iteration (CADESI-04) and a validated pruritus Visual Analog Scale (pVAS). RESULTS: 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. CONCLUSIONS AND CLINICAL IMPORTANCE: 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.