The PARK2 Mutation Associated with Parkinson's Disease Enhances the Vulnerability of Peripheral Blood Lymphocytes to Paraquat.

Fengyu Ming,Lixia Qin,Hainan Zhang,Chunyu Wang,Jieqiong Tan,Jianguang Tang,Xuling Tan

doi:10.1155/2020/4658109

Abstract

Parkinson's disease (PD) is the second most common neurodegenerative disease in middle-aged and elderly people. However, the etiology and pathogenesis of PD are still unclear and there is a lack of reliable biomarkers for early molecular diagnosis. Parkin (encoded by PARK2) is a ubiquitin E3 ligase that participates in mitochondrial homeostasis, the ubiquitin-proteasome pathway, oxidative stress response, and cell death pathways, which are involved in the pathogenesis of PD. However, Parkin is also expressed in peripheral blood lymphocytes (PBLs). In this study, permanent lymphocyte lines were established from the peripheral blood of sporadic PD (sPD) patients, PARK2 mutation carriers, and healthy controls. Reactive oxygen species (ROS), function of the mitochondrial respiratory chain complex I, and apoptosis were analyzed in the PBLs. There was no significant difference in ROS, mitochondrial respiratory chain complex I, and apoptosis between the experimental groups and the control group without paraquat treatment. Compared with the control group of healthy subjects, we found an increase of ROS (control 100 ± 0, sPD 275.53 ± 79.11, and C441R 340 ± 99.67) and apoptosis, as well as a decline in the function of mitochondrial respiratory chain complex I in PBLs of PARK2 mutation carriers and sPD after the treatment of paraquat (control 0.65 ± 0.08, sPD 0.44 ± 0.08, and C441R 0.32 ± 0.08). Moreover, overexpression of the wild-type (WT) PARK2 in HeLa cells and immortalized PBLs could rescue mitochondrial function and partially inhibit apoptosis following paraquat treatment, while the C441R mutation could not. Thus, ROS levels, activity of mitochondrial respiratory chain complex I, and apoptosis of PBLs are potential diagnostic biomarkers of PD.

Highlights

Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease (AD), with more than six million estimated cases in 2016 worldwide [1,2,3]
We found that the reactive oxygen species (ROS) levels were significantly increased in peripheral blood lymphocytes (PBLs) from both sporadic PD (sPD) patients and those with the PARK2 C441R mutation compared to healthy controls (control 100 ± 0, sPD 275:53 ± 79:11, and C441R 340 ± 99:67; Figures 1(a) and 1(b))
The results showed an increase of apoptosis in PBLs from sPD and Parkin mutation patients compared with healthy controls (Figure 1(d))

Summary

Introduction

Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease (AD), with more than six million estimated cases in 2016 worldwide [1,2,3]. The PARK2 ( known as PRKN/PARKIN) mutation causes the second most common form of familial PD and accounts for the majority of autosomal recessive PD (ARPD) cases, including both autosomal recessive juvenile PD (ARJPD) and late-onset PD (LOPD) [14,15,16,17]. Previous findings suggested that the absence of Parkin and PINK1 could increase the vulnerability of dopaminergic neurons to the effects of exogenous environmental stressors [26]. Mutations of PARK2 impair its targeting to depolarized mitochondria and further inhibit mitophagy [20]. In spite of these earlier findings, there are no studies investigating whether PARK2 mutations, and especially C441R, can increase the vulnerability of humans PBLs to environmental toxins. We collected PBLs from 5 PD patients with PARK2 C441R mutation, 5 cases of sporadic PD (sPD) without any known mutations and agematched controls, to determine the vulnerability of PBLs carrying the PARK2 C441R mutation to environmental toxins [27, 28]

Materials and Methods

Results

Discussion

Conflicts of Interest