ABSTRACT
Background: ATP13A2 holds promise as biomarker for Parkinsons disease (PD). No study has examined how salivary ATP13A2 is related to motor features in idiopathic PD. Methods: Salivary ATP13A2 concentration was evaluated with ELISA, and statistical correlations of ATP13A2 level with PD parameters were examined. The dose intensity of the dopaminergic medication regimen was expressed as levodopa equivalent daily dose (LEDD). ATP13A2 expression on histological sections of submandibular glands was evaluated using immunohistochemistry. Results: Salivary ATP13A2 was undetectable in many subjects (28 % of patients, 43.7 % of controls). However, all the patients with motor complications (n = 28) showed quantifiable levels of ATP13A2, that positively correlated with MDS-UPDRS (total, parts III and IV), and LEDD (p < 0.05). Dyskinetic patients showed the highest LEDD values (p < 0.05). The histological study revealed: a) ATP13A2 staining was very intense in duct cells and vascular endothelium, and b) two patterns of ATP13A2-positive deposits are observed: rounded inclusions of 10-20 µm in diameter located in the interlobular tissue of the patients, and amorphous aggregates inside duct lumen in controls and patients. Conclusions: The sensitivity of the ELISA assay was a major limitation for quantifying ATP13A2. However, salivary ATP13A2 was detected in all patients with motor complications, where a direct relationship among ATP13A2 concentration, levodopa equivalent daily dose, and MDS-UPDRS was found. Therefore, salivary ATP13A2 might be a reliable index of therapy-induced motor complications. ATP13A2 was expressed by rounded inclusions in the submandibulary gland of patients. This is the first description of ATP13A2-positive inclusions outside the nervous system.
ABSTRACT
Background. Salivary α-synuclein (aSyn) and its nitrated form, or 3-nitrotyrosine-α-synuclein (3-NT-αSyn), hold promise as biomarkers for idiopathic Parkinson's disease (IPD). Nitrative stress that is characterized by an excess of 3-nitrotyrosine proteins (3-NT-proteins) has been proposed as a pathogenic mechanism in IPD. The objective is to study the pathological role of native αSyn, 3-NT-αSyn, and 3-NT-proteins in the saliva and submandibulary glands of patients with IPD. Methods. The salivary and serum αSyn and 3-NT-proteins concentration is evaluated with ELISA in patients and controls. Correlations of αSyn and 3-NT-proteins content with clinical features of the disease are examined. Immunohistochemical 3-NT-αSyn expression in submandibulary gland sections is analyzed. Results. (a) Salivary concentration and saliva/serum ratios of native αSyn and 3-NT-proteins are similar in patients and controls; (b) salivary αSyn and 3-NT-proteins do not correlate with any clinical feature; and (c) three patterns of 3-NT-αSyn-positive inclusions are observed on histological sections: rounded "Lewy-type" aggregates of 10-25 µm in diameter, coarse deposits with varied morphology, and spheroid inclusions or bodies of 3-5 µm in diameter. "Lewy-type" and coarse inclusions are observed in the interlobular connective tissue of the gland, and small-sized bodies are located within the cytoplasm of duct cells. "Lewy-type" inclusions are only observed in patients, and the remaining patterns of inclusions are observed in both the patients and controls. Conclusions. The patients' saliva presents a similar concentration of native αSyn and 3-nitrotyrosine-proteins than that of the controls, and no correlations with clinical features are found. These findings preclude the utility of native αSyn in the saliva as a biomarker, and they indicate the absence of nitrative stress in the saliva and serum of patients. As regards nitrated αSyn, "Lewy-type" inclusions expressing 3-NT-αSyn are observed in the patients, not the controls-a novel finding that suggests that a biopsy of the submandibulary gland, if proven safe, could be a useful technique for diagnosing IPD. Finally, to our knowledge, this is also the first description of 3-NT-αSyn-immunoreactive intracytoplasmic bodies in cells that are located outside the nervous system. These intracytoplasmic bodies are present in duct cells of submandibulary gland sections from all subjects regardless of their pathology, and they can represent an aging or involutional change. Further immunostaining studies with different antibodies and larger samples are needed to validate the data.
ABSTRACT
Protein and amine halogenation is a type of oxidative stress induced by phagocytic overstimulation, and its role in Parkinson's disease (PD) has not been discerned. We have detected that advanced oxidized protein products, markers of protein halogenation, are reliably enhanced in serum of patients with PD (n=60) relative to control subjects (n=45, p<0.012), and to a lesser extent in the cerebrospinal fluid. Amine halogenation, as evaluated through 3-chlorotyrosine, is not affected. Mieloperoxidase and hydrogen peroxide levels, halogenative factors of phagocytes, are devoid of changes. Levels of advanced oxidized protein products are progressively reduced over time, and the duration of PD is larger in the Hoehn-Yahr-stage-2/3 patients (n=34) with low serum levels (R(2)=0.0145, p<0.003). Levodopa treatment contributes to this reduction (R(2)=0.259, p<0.001). These protein products are not cytotoxic, unlike 3-chlorotyrosine, but they are known to form inflammatory mediators after conjugation with serum albumin. Our observations lead to the hypothesis that the serum level of advanced oxidized protein products is a prognostic marker of PD duration, and these oxidized proteins could participate in the development of parkinsonian neurodegeneration.
