Objective/Rationale:
Mitochondria dysfunction has long been proposed to contribute to the pathogenesis of Parkinson’s Disease. In addition to their role in ATP production, mitochondria play an essential role in the regulation of cellular calcium homeostasis. Pathological conditions may result in mitochondria calcium overload inducing mitochondrial permeability transition induction which is a key event in several forms of neuronal death. This application proposes to inhibit the mitochondrial permeability transition induction as a potential means of attenuating Parkinson’s disease-related neurodegeneration.
Project Description:
Recent studies have convincingly demonstrated that the mitochondrial protein cyclophilin D is a key regulator of mitochondrial permeability transition induction. Thus, overall our route to target validation hinges on inactivating cyclophilin D as a method of predicting outcomes of pharmacological approaches that target this mitochondrial protein or mechanism associated with this protein in Parkinson’s disease. The use of mammalian neuronal cultures for understanding cellular mechanisms relevant to PD has become well established, and our first approach to determine whether inactivation of cyclophilin D is protective in mammalian cellular model systems of Parkinson’s disease. An important test for a potential therapeutic approach is the assessment in an animal model, and our second approach, in collaboration with Dr. Standaert laboratory, we will use two Parkinson’s disease relevant pre-clinical models to determine whether cyclophilin D is a valid therapeutic target in Parkinson’s disease. First, we will examine whether inactivation of cyclophilin D affects the vulnerability of dopamine neurons and the behavioral of mice in the 6-hydroxydopamine Parkinson’s disease model. Our second approach will determine whether inactivation of cyclophilin D prevents the vulnerability of dopamine neurons to a viral-mediated alpha-synuclein overexpression in mice.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
While mitochondrial dysfunction has been implicated in Parkinson’s disease, no definitive evidence has been provided whether or not mitochondria are critically involved in the initiation of the pathogenesis. Understanding the nature of the mitochondrial dysfunction will certainly impact our comprehension of the disease and unveil rational therapeutic target.
Anticipated Outcome:
The outcomes of this project will determine whether inactivation of cyclophilin D is protective in cellular and whole-animal models of Parkinson’s disease and therefore constitutes a valid target for Parkinson’s disease therapy. Beneficial effect of cyclophilin D inactivation would promote efforts to develop pharmacological strategies to inhibit cyclophilin D or more broadly to prevent induction of the mitochondrial permeability transition for Parkinson’s disease therapy.
Progress Report
The overall goal of our project is to determine if inhibiting the induction of the mitochondrial permeability transition (MPT) provides beneficial outcomes in cellular and pre-clinical models of Parkinson’s disease (PD). Mitochondria dysfunction has long been linked to PD and conditions associated with an increased of cytosolic free Ca2+, ROS production and decreased mitochondrial membrane potential which are prominent features in the tissues from patients with PD and promote PTP opening. To accomplish our goals we are using an approach that targets cyclophilin D (Cyp-D), a mitochondrial matrix protein and a key regulator of the MPT. Using cultures of TH+ dopaminergic neurons from wild type (WT) and Cyp-D knockout mice, our initial results reveal that CypD inactivation did not provide beneficial effect against the rotenone mediated death of TH+ neurons. Using a PD relevant pre-clinical models we have examined whether inactivation of Cyp-D affects the vulnerability of dopamine neurons in the 6-hydroxydopamine (6-OHDA) PD model. Injection of 6-OHDA into the striatum of wild type mice produced a protracted retrograde degeneration of nigro-striatal and ventral tegmental neurons and leads to depletion of TH+ nigral neurons. Our initial results suggest that of inactivation of CypD mediates partial protection against the 6-OHDA-mediated death of TH+ neurons.