Examining the role of dipeptidyl peptidase IV (DPPIV) in psoriatic disease.

Abstract

Chemokine CXCL10 plays an important role in Psoriatic Arthritis (PsA), an inflammatory arthritis associated with psoriasis. CXCL10 is post-translationally regulated by dipeptidyl peptidase-4 (DPPIV). The objectives of this study were to measure levels of DPPIV, CXCL10 and DPPIV enzyme activity (EA) in patients with PsA, psoriasis without arthritis (PsC), osteoarthritis (OA) and healthy controls (HC), and in PsA patients before and after methotrexate (MTX) treatment initiation. Serum samples from 80 PsA, 80 PsC, 40 HC, and 40 patients before and after 24 weeks of MTX treatment. Synovial fluid (SF) and matched serum were collected from 14 PsA and 14 sex- matched OA patients. Levels of DPPIV, CXCL10, were quantified using ELISA, DPPIV EA was measured using a luminescent protease assay. Patients with PsA had higher DPPIV levels than PsC, whereas HC had the highest level compared with both. Significant increase in DPPIV levels was observed in PsA patients after MTX treatment, whereas CXCL10 levels decreased significantly. DPPIV levels were negatively correlated with CXCL10 levels after MTX treatment (r=-0.27, p= 0.02). DPPIV levels were significantly higher in SF of PsA compared with OA patients. Higher DPPIV levels were detected in SF compared with serum samples of PsA patients. CXCL10 concentration in synovial fluid displayed similar patterns to DPPIV. Our exploratory findings suggest that DPPIV synovial fluid levels may be an important indicator of joint inflammation in PsA patients. In PsA patients, DPPIV may be associated with MTX response. CXCL10 may be regulated post translationally by DPPIV.