By Yosef Scher, Senior Science and Technology Editor
Lately, the scientific community has had a particular interest in trying to discover treatments for neurodegenerative diseases – and for good reason. Approximately fifty million Americans are affected annually by a neurodegenerative disease, a number that will surely increase in the near future. Therefore it is no wonder why scientists want to find treatments that can lead to cures. Researchers from the University of Cologne are optimistic that patients diagnosed with neurodegenerative diseases, especially Huntington’s disease, can benefit from their latest discovery: a chloroplast enzyme called stromal processing peptidase (SPP).
Huntington’s disease is an autosomal dominant inherited disease that causes the progressive degeneration of nerve cells in the brain. People with this disease tend to have trouble with basic movements, have rapid cognitive decline, and develop certain psychiatric disorders, such as insomnia, depression, and bipolar disorder. Currently, there are medications, like haloperidol, tetrabenazine, and amantadine, available that can help people manage their symptoms, but they do not prevent the physical, mental, and behavioral decline associated with the condition. Dr. Ernesto Llamas, the lead author of the paper published in Nature Aging, hopes to change that.
By using plants as a novel approach to tackle the lack of success with current medications for Huntington’s disease, Dr. Llamas provided the scientific community with a potentially more effective treatment for patients with Huntington’s disease. Unlike humans, plants are not able to escape when faced with a threat like disease. That being said, plants have evolved to be resilient to many diseases through various biological mechanisms that allow them to live long. One of the critical biological mechanisms that Dr. Llamas and his team investigated was a plant’s ability to resist the aggregation of proteins that usually lead to the development of neurodegenerative diseases in people. To expand on this, Dr. Llamas introduced huntingtin, the toxic mutant protein that results in Huntington’s disease, into plants and found that the plants resisted protein aggregation significantly better compared to humans and animals. Next, the scientists transferred the plants’ aggregation resistance into human-cultivated cells and animal models with Huntington’s disease. They found that the human-cultivated cells and animal models with the disease reduced protein clumps and symptoms of the disease.
While the researchers were glad that they made this discovery, they wanted to understand why plants could resist protein aggregation of huntingtin. After running some tests, Dr. Llamas found that chloroplasts, the organelle in plants that convert light energy into chemical energy for the plant to use, were the source of the plant’s protection that “provide[d] … expanded molecular machinery to get rid of toxic protein aggregates.” More specifically, his team identified SPP as the main reason huntingtin did not aggregate in plants as it did in humans and animals. Dr. Hyun Ju Lee, a postdoc student working in Dr. Llamas’s laboratory, told Science Daily that “[the team was] pleased to observe that expression of the plant SPP protein improved motility of C. elegans worms affected by huntingtin even at later aging stages where the symptoms are even worse.”
Llamas believes that additional research still needs to be conducted regarding plants and how they can avoid pathological symptoms of neurodegenerative disease. Although it is not definitive that this treatment will benefit people with Huntington’s disease, it is clear that this is a major breakthrough that will advance the field of science in the area of neurodegenerative diseases.