P51 Plaque psoriasis patients with psoriatic arthritis demonstrate a reduced regulatory capacity for neutrophil elastase compared with plaque psoriasis patients without arthritis

Abstract Identifying which patients with psoriasis (PsO) may develop psoriatic arthritis (PsA) is a research priority. We have previously shown that Elafin along with IL-36g are excellent cutaneous biomarkers for PsO. The protease inhibitor Elafin and its target protease, neutrophil elastase (NE), can be detected in both serum and epidermal samples. Our aims were to assess if known PsO biomarkers are expressed differentially in patients affected by plaque PsO with and without PsA. Protein expression of NE and Elafin were analysed in matched epidermal samples and serum of PsO, PsA patients and healthy controls. Findings were validated in independent PsA and arthritis cohorts. The ratio between NE and Elafin differed significantly between PsO and PsA patients. Expression of elafin was reduced in PsA samples as compared with plaque PsO patients. The ratio of NE to secretory leukocyte protease inhibitor was also increased in PsA as compared with PsO patients with no PsA, healthy controls and other arthritis patients. PsA patients show a reduced NE inhibitor expression in both the skin and blood compartment compared with those with plaque PsO only. This may suggest differences in the ability to regulate neutrophil activity in PsA patients.