Identification and Verification of S-Nitrosylated Proteins in Bodily Fluids as Biomarkers for Parkinson's Disease and Lewy Body Dementia - Parkinson’s disease (PD) and Lewy body dementia (LBD) manifest pathological deposition of misfolded α- synuclein (αSyn). Concerning LBD diagnoses, dementia with Lewy bodies (DLB) patients may show cognitive decline and dementia from the onset of the disease, while other patients, initially diagnosed as PD with motor symptoms, later progress to PD with dementia (PDD). However, there are no specific biomarkers to identify patients at risk for PD or LBD prior to the appearance of clinical symptoms, or to objectively monitor motor- or non-motor (e.g., dementia and depression) burdens to assess disease severity and progression. Moreover, significant overlaps in clinical and neuropathological characteristics between Alzheimer’s disease (AD) and LBD can make differential diagnosis of these conditions in some cases particularly challenging during life. In PD, LBD and AD, synaptic injury and neuronal damage result at least in part from excessive generation of reactive oxygen and nitrogen species (ROS/RNS) engendered by toxic forms of oligomeric αSyn or Aβ. We previously demonstrated that RNS can trigger aberrant protein S-nitrosylation (SNO-protein formation), resulting in synaptic/neuronal damage. Our data provide evidence that S-nitrosylation of Parkin, PINK1, DJ-1, and Uch-L1 each plays a causative role in disease-related neuronal damage in sporadic human PD and LBD. Specifically, we demonstrate that prevention of aberrant protein S-nitrosylation ameliorates mitochondrial dysfunction, protein misfolding, synaptic damage, and neuronal loss in both cell-based and animal models manifesting misfolded αSyn or Aβ. Moreover, we recently found significantly elevated levels of SNO-proteins, including SNO-DJ-1 and SNO-UchL1, in CSF and serum of patients with PD and LBD synucleinopathies. Hence, here we propose to establish SNO-Proteins as potential biomarkers in biofluids (i.e., CSF and serum), serving as indicators of disease diagnosis, progression, and severity to PD/LBD. We will employ unbiased screening approaches as well as previously identified SNO-proteins to develop biochemical biomarkers for PD/LBD, distinguishable from AD. Upon successful completion of the proposed studies, we will establish a clear Context-of-Use (COU) for a diagnostic/prognostic biomarker with SNO-proteins to support enrichment of PD and LBD clinical study/trial populations; thus, these SNO biomarkers and their detailed methods of detection will be ready to enter the next phase (i.e., analytical validation) of the biomarker development process. Accordingly, we will identify novel SNO-proteins in patient serum and CSF using proteomics approaches (R61/Aim #1), develop ELISA-based assays for these SNO-proteins (R61/Aim #2), and examine if SNO-proteins can serve as potential diagnostic or prognostic biomarkers for PD/LBD using serum and CSF obtained from human patients (R61/Aim #3 and R33/Aim#4).
