Objective: To assess the utility of the myeloperoxidase enzyme level as a diagnostic biomarker in Parkinson’s disease.

Background: Myeloperoxidase (MPO) contributes to Parkinson’s disease (PD) pathogenesis by promoting oxidative modification and aggregation of α-synuclein, amplifying neuroinflammation, and mediating dopaminergic neurodegeneration. The serum MPO reflects systemic inflammation and oxidative stress; CSF MPO may be more closely related to disease duration and central nervous system pathology, particularly in men with advanced PD. We carried out a comprehensive meta-analysis to explore differences in MPO levels between PD and control.

Method: We screened PubMed, Embase, Scopus, and Web of Science for articles until February 2026 about comparing MPO levels and activity. Data were extracted and checked by two authors for accuracy. Between-studies heterogeneity was assessed using the I² statistic. The summary standardized mean difference (SMD) and 95% confidence interval (CI) in the MPO level were calculated using a random or fixed effect model, as per the heterogeneity, using RevMan version 5.4.

Results: The meta-analysis of four studies revealed that serum MPO levels were significantly higher in PD patients compared to healthy controls. This finding was supported by an SMD of 0.82 (95% CI: 0.51 to 1.13; p < 0.00001, I² = 53%), Figure 1. Similarly, analysis of three studies showed that CSF MPO levels were significantly elevated in the PD group. The CSF comparison yielded an SMD of 0.40 (95% CI: 0.02 to 0.78; p = 0.04, I² = 52%), Figure 2. Furthermore, the study assessed serum MPO activity, finding a substantial and highly consistent increase in PD patients compared to controls. This activity level showed the strongest statistical effect with an SMD of 1.11 (95% CI: 0.91 to 1.30; p < 0.00001, I² = 0%), Figure 3. Collectively, these findings suggest that both the concentration and enzymatic activity of MPO are significantly elevated in PD, highlighting its potential as a diagnostic biomarker.

Conclusion: Our findings demonstrate that both MPO concentration and its enzymatic activity are significantly elevated in PD across peripheral and central compartments. The high consistency in MPO activity results suggests that it may serve as a reliable biomarker for neuroinflammation and a potential therapeutic target for mitigating oxidative damage in PD.

Figure 1

Figure 2

Figure 3

References: 1. Fernández-Espejo E, Rodríguez De Fonseca F, Gavito AL, Córdoba-Fernández A, Chacón J, Martín De Pablos Á. Myeloperoxidase and Advanced Oxidation Protein Products in the Cerebrospinal Fluid in Women and Men with Parkinson’s Disease. Antioxidants. 2022 May 30;11(6):1088. doi:10.3390/antiox11061088
2. Fernández‐Espejo E, Guerra M, Castellano S, Rodríguez De Fonseca F, De Pablos ÁM. Serum Myeloperoxidase Activity Is Associated with Hoehn‐Yahr Staging and Striatal Dopamine‐Transporter Binding in Parkinson’s Disease. Mov Disord Clin Pract. 2025 Sep;12(9):1326–36. doi:10.1002/mdc3.70112
3. Gellhaar S, Sunnemark D, Eriksson H, Olson L, Galter D. Myeloperoxidase-immunoreactive cells are significantly increased in brain areas affected by neurodegeneration in Parkinson’s and Alzheimer’s disease. Cell Tissue Res. 2017 Sep;369(3):445–54. doi:10.1007/s00441-017-2626-8
4. Espejo EF, Guerra M del M, Castellano S. Association between serum myeloperoxidase enzyme activity and Parkinson’s disease status. Npj Park Dis. 2025 Apr 26;11(1):94. doi:10.1038/s41531-025-00941-0

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MDS Abstracts - https://www.mdsabstracts.org/abstract/elevated-myeloperoxidase-levels-and-activity-as-potential-biomarkers-for-parkinsons-disease-a-systematic-review-and-meta-analysis/