Lysosomal Storage Disorders May Be Treatable With Existing Drugs

A potential new way to treat some of the most severe genetic diseases of childhood has been identified by researchers at the University of Rochester.

The diseases, called lysosomal storage disorders (LSDs), stem from disruptions in the functioning of the stomach of the cell, known as the lysosome.

Lysosomal storage disorders include Krabbe disease, Gaucher disease, metachromatic leukodystrophy, and about 40 related conditions. In their most aggressive forms, they cause death of affected children within a few years after birth.

Lysosomal Storage Disorders Acidity

Led by Mark Noble of the University of Rochester Medical Center, researchers discovered for the first time how specific toxic waste products that accumulate in LSDs cause multiple dysfunctions in affected cells. They also found that several drugs already approved for other uses have the unexpected ability of overcoming the cellular toxic build-up, providing new opportunities for treatment.

Two postdoctoral fellows in the department of biomedical genetics, Christopher Folts and Nicole Scott-Hewett, conducted the experiments to better understand the biology of lysosomal disorders. They showed that just like the stomach, lysosomes are usually more acidic than other parts of the cell and toxic substances that accumulate in several LSDs disrupt maintenance of the acidic environment.

They also demonstrated that restoring the normal acidity of the lysosome with drug treatment was sufficient to prevent multiple disruptions of normal lysosome function and to maintain critical cell functions, such as division and survival.

In a mouse model of Krabbe disease (one of the most severe LSDs), Noble’s team found that their lead study drug, colforsin, increased survival as effectively as seen in studies where disease-causing mutations were corrected by gene therapy. Colforsin is approved in Japan to treat cardiac disease, which provides information to investigators about its use in humans.

Treating Multiple Disorders

Increased survival in mice occurred even though treatment was started later than is necessary for gene therapy.

The treatment also decreased damage to the brain and improved quality of life in the diseased mice. All of these outcomes are critical goals in the treatment of children with Krabbe disease or related illnesses, says Noble.

“One of the great challenges in these diseases is that they are both rare and come in many different varieties, and advances have tended to focus on single diseases,” Noble says. “In contrast, our findings suggest our treatments will be relevant to multiple disorders. Also, we saw benefits of our treatment even without needing to correct the underlying genetic defects. That gives us great hope that we could combine our treatments with other candidate approaches to gain additional benefits.”

If the results translate to humans, Noble says, the repurposed drugs might improve the quality of life for afflicted children while more difficult experimental genetic treatments are pursued.

Lysosome dysfunction is recognized as important in other diseases, such as diabetes and macular degeneration. The latest discoveries, Noble adds, may extend beyond the treatment of lysosomal storage disorders.

Folts CJ, Scott-Hewitt N, Pröschel C, Mayer-Pröschel M, Noble M (2016)
Lysosomal Re-acidification Prevents Lysosphingolipid-Induced Lysosomal Impairment and Cellular Toxicity
PLoS Biol 14(12): e1002583. doi:10.1371/journal.pbio.1002583

Image: The green stain highlights myelin, a substance essential for a healthy nervous system that’s destroyed in children with Krabbe disease. University of Rochester Medical Center.

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