Humans are exposed to agents and conditions that cause stress to dopaminergic neurons. Neurons can survive stress by modulating the biosynthesis and degradation of proteins within the endoplasmic reticulum (ER). The goals of this study are to determine if cells from patients with Parkinson’s disease have a defect in the ER stress response and to identify FDA approved drugs that can protect cells from ER stress produced by agents associated with Parkinson’s disease.
We have developed a highly sensitive assay to monitor ER stress in cultured cells using a secretable luciferase. This assay will be used to quantitate ER stress sensitivity in skin fibroblasts from patients with hereditary Parkinson’s disease and controls cells using drugs which produce parkinsonian symptoms in pre-clinical models. Using a high-throughput assay we have developed we will screen an National Institute of Health library of 1040 FDA-approved drugs, which are known to cross the blood brain and to be non-toxic to cells, to find drugs which can reduce ER stress sensitivity to parkinsonian-related stresses. Candidate drugs will be tested for protection of cells from death caused by agents known to cause Parkinson’s disease in humans, including rotenone, MPP+ and high levels of alpha-synuclein.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
When ER stress becomes too great it induces death of cells. Our strategy is to find drugs which can dampen the ER stress response and thereby to help sustain cells and survive toxic insults. By screening drugs which are already FDA approved and known to enter the brain, if we find a protective one it can be evaluated in clinical trials almost directly in an off-label capacity.
In the course of these studies we will be able to establish whether some forms of Parkinson’s disease and parkinsonian-stress agents are associated with an increased ER stress sensitivity leading to cell death. We will also be able to identify a few drugs which can reduce ER stress and help cells survive agents known to cause Parkinson’s disease. These drugs could then be evaluated clinically to promote survival of dopaminergic neurons in Parkinson’s patients.
Using fibroblasts from LRRK2, PINK1 and Parkin patients, Dr. Breakefield's screen suggested that LRRK2 fibroblasts were more sensitive to ER stress. Variability between cell lines, however, makes the results difficult to interpret at this time.