Proteomic study of salivary peptides and proteins in patients with Sjögren's syndrome before and after pilocarpine treatment

Abstract

To investigate the effect of pilocarpine on the salivary peptide and protein profile in patients with primary Sjögren's syndrome (SS) and to study the differences between patients with primary SS, patients with SS associated with other rheumatic diseases, and healthy control subjects. Saliva specimens were obtained from 9 primary SS patients, 9 secondary SS patients, and 10 healthy controls. Samples were analyzed for levels of 62 different salivary proteins using high-performance liquid chromatography coupled with mass spectrometry using a spectrometer equipped with an electrospray ionization source. In 6 of the primary SS patients, saliva was collected at 30 minutes, 60 minutes, and 24 hours after taking 5 mg of pilocarpine. Before pilocarpine, approximately 60% of salivary proteins in samples from primary SS patients were not identifiable or showed lower levels than those in healthy controls. After 30-60 minutes following pilocarpine treatment, approximately one-third of the less represented proteins was found in a similar percentage of primary SS patients and controls. Almost all of the proteins that were detectable at lower levels in primary SS patients compared with controls reached levels similar to those in controls at 30-60 minutes after pilocarpine. The parotid gland proteins had the best response to pilocarpine. Primary SS patients were characterized by higher alpha-defensin 1 levels and by the presence of beta-defensin 2. Secondary SS patients showed an intermediate protein profile between that of the primary SS patients and the controls. Pilocarpine partially restored the levels and numbers of identifiable proteins in saliva from patients with primary SS. Higher levels of alpha-defensin 1 and the presence of beta-defensin 2 in the saliva of patients with primary SS could be markers of oral inflammation in this patient group.