Salivary exosomal PSMA7: a promising biomarker of inflammatory bowel disease

Inflammatory bowel disease (IBD) is an intestinal immune-dysfunctional disease worldwide whose prevalence increasing in Asia including China. It is a chronic disease of the gastrointestinal tract with unknown cause. Exosomes are small vesicles in various body fluids. They have diameters of 40-120 nm, and one of their functions is long-distance transfer of various substances. In this study, we investigated the contents of salivary exosomes in patients with IBD and in healthy controls to explore a new biomarker in patients with IBD. In this study, whole saliva was obtained from patients with IBD (ulcerative colitis (UC), n = 37; Crohn's disease (CD), n = 11) and apparently healthy individuals (HC, n = 10). Salivary exosomes were extracted from samples, and the proteins within the exosomes were identified by liquid chromatograph-mass spectrometer (LC-MS/MS). The results showed that more than 2000 proteins were detected in salivary exosomes from patients with IBD. Through gene ontology analysis, we found that proteasome subunit alpha type 7 (PSMA7) showed especially marked differences between patients with IBD and the healthy controls, in that its expression level was much higher in the CD and UC groups. This exosomal protein is related to proteasome activity and inflammatory responses. So we conclude that in this research, salivary exosomal PSMA7 was present at high levels in salivary exosomes from subjects with IBD. It can be a very promising biomarker to release the patients from the pain of colonoscopy.