SERPINA1 and Parkinson disease: Among these 33 differentially expressed proteins, three upregulated, cystatin-C, cathepsin L1, Annexin A2, and two downregulated, Aldehyde dehydrogenase 1 and alpha-1-antitrypsin, proteins in PD samples deserve a particular attention as they also appeared dysregulated in previous publications involving PD or other neurological disorders.