Investigator/Author:  Brian Daniels, PhD

Objective:  Our study will investigate the role of the protein RIPK3 in the inflammatory response in the brains of people with Parkinson’s disease. 

Background:  Inflammation in the brain plays an important role in the pathologic changes of PD. Astrocytes, a cell type in the brain with a variety of functions, can become activated during the neurodegeneration of PD and promote inflammation. Recent work has also shown that a group of proteins called Receptor Interacting Protein Kinases (RIPKs) are key players in promoting inflammation in a variety of neurodegenerative conditions, and inhibitors of RIPKs are currently in clinical trials for both Alzheimer’s disease and Amyotrophic lateral sclerosis. Increased RIPK activity has been observed in PD as well, but its role is not fully understood.  This study will investigate the specific role of RIPK3 signaling in the development of neuroinflammation in PD.

Methods/Design:  Dr. Daniels will utilize several genetic systems to change RIPK3 signaling in astrocytes, both in a cell culture model and a mouse model of PD. For the mouse studies, he will use a well-established model in which mice are administered a neurotoxin that selectively kills dopamine neurons in the midbrain. He will then assess how astrocytes respond to inflammation as RIPK3 is being artificially suppressed or increased.

Relevance to Diagnosis/Treatment of Parkinson’s Disease: If we understand the processes by which RIPKs contribute to inflammation in PD, inhibitors of RIPK, which are already in clinical development, can be tried as new PD therapies.

November 2020 Project Update:

Over the past year, we have collected data strongly supporting our hypothesis that RIPK3 signaling in astrocytes contributes to the pathogenesis of Parkinson’s disease (PD). Using a mouse model of PD, we have shown that genetic deletion of RIPK3 in astrocytes protects dopamine neurons from cell death in the midbrain and decreases harmful inflammation. In contrast, experimental activation of RIPK3 in midbrain astrocytes promotes neuroinflammation and death of dopamine neurons. We have confirmed these findings in cell culture models of PD using human astrocytes and neurons, suggesting that our findings in mouse models are relevant in human cells. In addition to these studies, using a toxin-based model of PD, we have performed additional studies demonstrating that aggregates of alpha synuclein can induce RIPK3 activation in midbrain astrocytes, causing them to undergo inflammatory activation and exert neurotoxic activity. Together, our findings identify an exciting new molecular target for treating harmful neuroinflammation during PD. Future work in our lab will be aimed at developing therapeutic strategies for PD which focus on modulating RIPK3 activity in astrocytes.

October 2021 Project Update:

We continued to collect data supporting our hypothesis that RIPK3 signaling in astrocytes contributes to the pathogenesis of Parkinson’s disease (PD).

Over the course of the year, we further assessed the impact of astrocytic RIPK3 on PD brain circuitry. In a new set of experiments, we performed staining for dopamine neurons in the part of the brain where dopamine axons end. We also stained with SMI32, a marker for axonal injury. As expected, our mouse model of PD showed decreased dopamine neurons and increased damaged axons. Strikingly, however, genetically blocking RIPK3 improved both of these elements, preserving dopamine neurons and decreasing the number of damaged axons. These findings suggest that genetic blockade of RIPK3 signaling is sufficient to preserve dopaminergic signaling. We will continue to follow up on these results in future studies by examining functional and behavioral correlates of these molecular findings.

Investigators/Authors:  Vikram Khurana, MD, PhD

Objectives: Our study will investigate the dysregulation of messenger RNA (mRNA) in Parkinson’s disease (PD)

Background: In past work, Dr. Khurana studied the interactions of α -synuclein, the protein that accumulates in the brains of people with Parkinson’s disease, in living cells. He surprisingly discovered that α -synuclein interacts with messenger ribonucleic acids (mRNAs), which are the intermediary molecules between DNA and the proteins that they encode. In this project, he delves into this interaction, studying the exact role of mRNA dysfunction in PD neurons.

Methods/Design: Dr. Khurana has created a series of induced pluripotent stem cell (IPSCs) lines, which are stem cells created from adult tissue. The cell lines are generated from people with specific mutations in α -synuclein or over-expression of α -synuclein. Dr. Khurana then differentiates these stem cells into dopamine neurons and studies the effects that the α -synuclein mutations have on the biology of the cells. Dr. Khurana will use these cells to investigate the changes in mRNA biology that can be attributed to α -synuclein mutations.

Relevance to Diagnosis/Treatment of PD: By understanding how PD changes mRNA functioning, gene therapy treatments can be developed that manipulate the RNA biology to function properly.

November 2020 Project Update:

Over the course of this year, we investigated the relationship between alpha-synuclein and mRNA biology in neurons in multiple ways. Our focus is on P-bodies, structures in the cell that play a fundamental role in mRNA storage and decay. By using induced pluripotent stem cell (IPSC) lines created from people with specific alpha-synuclein mutations, we were able to show that alpha-synuclein not only interacts with, but also changes the internal composition of P-bodies in human neurons. We are currently investigating these interactions in post-mortem brains of people with PD.
 
Our findings help to explain the relationship between alpha-synuclein and impaired mRNA biology, with the ultimate aim of creating gene therapies that manipulate mRNAs to function properly in the context of PD.

October 2021 Project Update:

Over the course of the last two years, we investigated the relationship between alpha-synuclein and mRNA biology in neurons in multiple ways. Our focus is on P-bodies, structures in the cell that play a fundamental role in mRNA storage and decay. By using induced pluripotent stem cell (IPSC) lines created from people with specific alpha-synuclein mutations, we were able to show that alpha-synuclein not only interacts with, but also changes the internal composition of P-bodies in human neurons.

In this last year, we have made some exciting progress. We have shown that what we identified in stem-cell derived brain cell from patients also occurs within the postmortem brains of patients. Moreover, we see strongly suggestive indications in human genetic analysis that this pathway is important in contributing to PD risk.

Our findings help to explain the relationship between alpha-synuclein and impaired mRNA biology, with the ultimate aim of creating gene therapies that manipulate mRNAs to function properly in the context of PD.