Alteration of immunoproteasome mRNA in PBMCs of patients with Parkinson’s disease

Abstract Background Immunoproteasome, a part of ubiquitin–proteasome system, is involved in protein degradation and immune response. However, the relationship between immunoproteasome and Parkinson’s disease (PD) was not evaluated clearly. We hypothesized that the shift of immunoproteasome attributes to PD due to its role in immune system and protein homeostasis. Objective To determine whether immunoproteasome mRNA in peripheral blood mononuclear cells is expressed differently between patients with PD and healthy controls and to test its value as a biomarker of PD Methods Blood samples were collected from 19 healthy controls and 40 patients with PD of comparable ages. Peripheral blood mononuclear cells were isolated and used to measure by RT-qPCR the mRNA levels of three catalytic subunits of immunoproteasome, namely, PSMB8, PSMB9, and PSMB10. Results The levels PSMB9 and PSMB10 mRNA were not different between the PD group and healthy control group, whereas the PSMB8 mRNA in PD group significantly increased. The ratio of PSMB10 and PSMB8 (PSMB10/8) best reflected significant difference between the PD group and healthy control group (p = 0.002). This ratio can discriminate all PD, mild PD (Hoehn and Yahr ≤ 2.5), and drug-naive PD from healthy controls. We found correlation between the PSMB10/8 ratio with the UPDRS total and Part III score in the mild PD subgroup and drug-naive PD subgroups Conclusion The expression of PSMB8 mRNA increased in PD, and the PSMB10/8 ratio can differentiate Parkinson’s disease from healthy controls.