ALS Association Co-Funds Study Showing Boosting the Body’s Detoxifying System Counteracts Nerve Cell Loss in ALS Mice; New Therapies Suggested

In a study that demonstrates a much-anticipated proof of principle, scientists report today that raising activity of a natural detoxification system in the body can counteract the progressive loss of nerve cells that characterizes amyotrophic lateral sclerosis (ALS), significantly delaying the onset of disease and extending life.

The research, led by ALS Association-funded scientist Jeffrey Johnson at the University of Wisconsin, was carried out on two different mouse models carrying the human gene for a familial (inherited) type of ALS (Lou Gehrig’s Disease) and on cultures of motor neurons at risk of death from the gene.

Studies elsewhere have shown that action of the detox system benefits models of acute injury, such as stroke. This new work, however, reveals that ramping up this system in live animals is effective against a chronic neuron-killing disease such as ALS and that the benefits can occur before its onset.

Johnson’s ongoing encouraging studies of the principle in Parkinson’s, Huntington’s and Alzheimer’s disease models suggest its broad application.

The published research also verifies key parts of the protective pathway, suggesting new targets for therapies to come. “Even though we did this study in a mutant mouse model,” Johnson says, “this pathway — and the reason it’s needed — is the same in humans. That’s true, studies show, both in patients with the familial form of ALS or with the more common sporadic form. “We believe that bodes well that our results will apply to ALS in general,” Johnson says.

“We are excited about the potential new pathways for ALS therapy suggested in this research,” said Dr. Lucie Bruijn, Ph.D., senior vice president for research and development at The ALS Association.

An account of the research appears this week in the Journal of Neuroscience.

Amyotrophic lateral sclerosis is the most common adult-onset disease of motor neurons — those that spark movement. It destroys motor neurons in the spinal cord, brain stem and in higher brain centers specific for movement.

The current study centers in part on a detox system that has received increasing attention in the last decade. Cells rely on the so-called phase II detoxification enzymes — the same system that broccoli chemicals stimulate — to blunt the flood of damaging free radicals that occurs in many illnesses, including ALS.

Johnson has focused on what activates that system, what turns on the battery of genes coding for its protective proteins.

A body of work, including his, shows that the main “on” switch for the response is a complex dubbed Nrf2-ARE. And, what caught Johnson’s eye were places in which Nrf2-ARE is most active. These are the astrocytes — star-shaped cells found widely in the central nervous system. It’s no surprise that they’d carry a detox package, Johnson says; the nervous system’s complexity and high energy requirement make it especially vulnerable to damage.

Astrocytes are companion cells to motor neurons, exchanging many molecules with them and, in general, shaping their survival. Because part of this conversation involves the Nrf2-ARE pathway, astrocytes became a focal point of the study. “We reasoned that upping Nrf2-ARE in neighboring astrocytes might protect neurons in chronic distress,” Johnson explains.

The team explored this possibility in rodents. They created transgenic mice whose astrocytes overproduced Nrf2. As a test of the protective power of the Nrf2-ARE pathway, they then crossed those mice with ALS models. (ALS model mice carry the human SOD1 gene that causes that disease in some families.)

Normally, such mice die in 128 days. But those with Nrf2 over-expressing astrocytes lived some 21 days longer — that’s highly significant in this field. Also, onset of disease was delayed by 17 days. In follow up tissue studies, the team showed that normal nerve-muscle connections held much longer — they deteriorate in ALS mice — keeping muscles active longer and slowing atrophy. The same studies with a second type of ALS model mouse showed similar benefits.

Also revealing was the team’s research that focused on cell cultures. It built on earlier work by the study’s first author Marcelo Vargas, recipient of the Milton Safenowitz Postdoctoral Fellowship Award for ALS Research. When Vargas layered healthy young motor neurons atop a layer of astrocytes from ALS mice, 40 percent of the motor neurons died. In this new work, the team placed the healthy motor neurons atop a layer of astrocytes from the ALS-Nrf2 combo mice. That completely reversed the toxic effect.

“What’s so interesting,” Johnson says, “is that the mutant gene is still in the astrocytes; but adding Nrf2 to them neutralizes its effects. That saves the neurons.”

Finally, to help explain what actually was protecting the motor neurons, the team checked neighboring astrocytes for the molecule glutathione. Glutathione is the major antioxidant source in cells, Johnson says. It’s a key part of nerve cells’ Phase II protective pathway, which branches out in a host of specific directions after glutathione is formed.

Astrocytes cultured from the Nrf2-bountiful mice had twice the usual concentration of glutathione. Further tests showed that protection of the nearby motor neurons depended on glutathione secretion into their environment. “It’s extremely difficult to increase glutathione experimentally in the central nervous system,” Johnson explains. “You can’t just shoot it into people or animals. But we found a 25 percent increase in the molecule in the spinal cords of the Nrf2-ALS mice.

“What we’re doing,” he adds, “is highjacking the cell’s normal pathway and upregulating it to make the motor neurons stronger, more able to withstand assault.

“It shows that by targeting astrocytes, it’s possible to improve their benefits to motor neurons and thus alter the course of ALS. Our work also validates Nrf2 as a viable target for therapy in chronic neurodegenerative disease.”

Delinda Johnson, Daniel Sirkis and Albee Messing were also members of the University of Wisconsin research team. The study was funded by The ALS Association, the Robert Packard Center for ALS Research at Johns Hopkins, and National Institutes of Health grants.

The mission of The ALS Association is to lead the fight to cure and treat ALS through global, cutting-edge research, and to empower people with Lou Gehrig’s Disease and their families to live fuller lives by providing them with compassionate care and support. For more information on The ALS Association’s global research program, visit http://www.alsa.org/.