Proinflammatory profile in the skin of Parkinson’s disease patients with and without pain

Abstract

Background Pain is a common non-motor symptom of Parkinson‘s disease (PD), however, its pathomechanism remains elusive. Objective We aimed to investigate the local gene expression of selected proinflammatory mediators in patients with PD and correlated our data with patients‘pain phenotype. Methods We recruited 30 patients with PD and 30 healthy controls. Pain intensity of patients was assessed using the Numeric Rating Scale (NRS) and patients were stratified into PD pain (NRS≥4) and PD No Pain (NRS<4) subgroups. Skin punch biopsies were immunoassayed for protein-gene product 9.5 as a pan-neuronal marker and intraepidermal nerve fiber density (IEFND). Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was performed to assess the gene expression of inflammatory mediators in the skin compared to controls. Results Patients with PD had lower distal IENFD compared to healthy controls. In skin samples, IL-2 (p<0.001) and TNF-α (p<0.01) were expressed higher in PD patients compared to controls. IL-1β (p<0.05) was expressed higher in the PD pain group compared to healthy controls. PD patients with pain receiving analgesics had a lower expression of TNF-α (p<0.05) in the skin compared to those not receiving treatment. Conclusions Our data suggest the occurrence of a local, peripheral inflammatory response in the skin in PD, but do not support this being a relevant factor contributing to pain in PD.