The Identification, Comparison and Validation of Proteins in Atopic Dermatitis and Psoriasis Using Microdialysis and Proteomics

Cutaneous microdialysis is a minimally invasive technique that allows for the in vivo sampling of substances in the skin’s extracellular fluid. The microdialysis system consists of a catheter with a semipermeable membrane, for passive diffusion, and a microdialysis pump. Microdialysis provides dynamic real- time information on changes in the tissue.. Coupling skin microdialysis with proteomic technology can provide an accurate snapshot of the inflammatory status of the tissue. The aim of this study is to extend the knowledge of microdialysis analysis using liquid chromatography- mass spectrometry technique in ‘shot gun’ mode. The study included 60 participants. 20 healthy volunteers , 24 psoriasis and 16 atopic dermatitis respectively. The mean PASI and EASI of each group is 11.32 and 14.48 respectively and all groups are naïve to systemic treatment. 54 proteins have been identified in healthy skin using Maxquant software, 60% threshold majority vote analysis and matched to the Uniprot database. These proteins are mostly involved in cellular component organization and structural support. There are 32 and 205 proteins unique to the psoriatic and AD cohorts respectively, which are predominantly involved in the same function but also have anti-microbial and anti- inflammatory activity. Additionally, AD proteins have vitamin D and E binding and iron storage properties. Annexin A1 is an anti-inflammatory protein and has been validated and compared in skin biopsies of both psoriatic and AD groups. RNA expression of annexinA1 is increased by 2.5 and 3 fold in psoriatic and AD lesional skin compared to the skin of healthy volunteers.