Alterations of Plasma Galectin-3 and C3 Levels in Patients with Parkinson’s Disease

Parkinson’s disease (PD) is characterized by progressive neurodegeneration of dopaminergic neurons in the ventral midbrain. The complement-phagosome pathway is involved in the pathogenesis of PD. Here we measured levels of complement-phagocytosis molecules, including galectin-3, C3, C4, and cathepsin D, in the plasma of 56 patients with PD, and 46 normal controls (NCs). Plasma levels of galectin-3 (9.93 ± 3.94 ng/mL) were significantly higher in PD patients compared with NCs (8.39 ± 1.95 ng/mL, p = 0.012), and demonstrated a positive correlation with Hoehn and Yahr stages in PD patients (R(2) = 0.218, p < 0.001). On the other hand, plasma C3 levels were significantly lower in PD patients (305.27 ± 205.16 μg/mL) compared with NCs (444.34 ± 245.54 μg/mL, p = 0.002). However, the levels did not correlate with Hoehn and Yahr stages (R(2) = 0.010, p = 0.469). Plasma levels of C4 and cathepsin D in PD patients were similar to those in NCs. Our results show possible altered complement-phagocytosis signals in the peripheral blood of PD patients, highlighting the potential of galectin-3 as a biomarker of PD.