Abstract
An important approach to an early diagnosis of Parkinson’s disease (PD) is screening for peripheral biomarkers in patients at the early clinical stage. In this study, we evaluated catecholamine concentration changes in the tear fluid of untreated PD patients as biomarkers. Norepinephrine and dopamine concentrations in the tear fluid of patients were found to increase compared to those in age controls, which was especially pronounced on the side where motor symptoms appeared. On the contrary, the epinephrine concentration in the tear fluid of patients was reduced bilaterally. Since there was no reason to consider the markers found in the clinical stage of PD as markers of the preclinical stage, we additionally studied the tear fluid composition in mouse neurotoxic models of PD preclinical and clinical stages. The norepinephrine concentration in the tear fluid of mice from the clinical stage model was found to be higher than that in controls; in the preclinical stage model, the norepinephrine concentration had a tendency to increase. Therefore, both PD patients and mice from PD preclinical and clinical stage models manifest unidirectional changes in their tear fluid compositions, which may be considered as promising biomarkers for the development of early diagnosis.
Highlights
Parkinson’s disease (PD) is a common neurodegenerative disorder that is characterized, in particular, by the death of the dopaminergic neurons of the brain nigrostriatal system
It should be emphasized that there is no data indicating that the biomarkers found in patients with a diagnosed clinical stage of PD could be related to the preclinical stage of this disease [1]
According to our general methodology, matching of the biomarkers found both in patients and in animal models of PD clinical stage indicates a correct reproduction of these aspects of the disease pathogenesis (Fig. 2)
Summary
Parkinson’s disease (PD) is a common neurodegenerative disorder that is characterized, in particular, by the death of the dopaminergic neurons of the brain nigrostriatal system. It should be emphasized that there is no data indicating that the biomarkers found in patients with a diagnosed clinical stage of PD could be related to the preclinical stage of this disease [1]. We performed a comparative analysis of catecholamine content changes in the tear fluid of untreated PD patients at the early clinical stage and animal models of the preclinical and clinical stages of PD.
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