Research on a gene linked with a rare type of Parkinson’s disease could lead to a new drug target, scientists at the University of Colorado believe.

    Although most people who develop Parkinson’s have environmental, not genetic, versions of the disease, several genes have been associated with its incidence, explained Curt Freed, professor of clinical pharmacology and toxicology at the University of Colorado Health Sciences Center.

    Freed co-authored a paper about one such gene, DJ-1. His research showed that cells engineered to produce more than the normal amount of DJ-1 showed improved hardiness in the face of two types of stress that scientists believe are associated with Parkinson’s.

    Parkinson’s occurs with the death of brain cells that produce dopamine, a brain chemical that interacts with nerve cells that determine muscle movement, Freed said. This leaves patients with very low levels of this important neurotransmitter.

    Usually the cause of Parkinson’s is unknown, Freed explained, but one suspected cause is stress from exposure to harsh chemicals that oxidize the cellular environment. Dopamine-producing neurons are particularly sensitive to chemical stress, he said.

    When Freed and his colleague, Wenbo Zhou, exposed neurons that over-expressed DJ-1 to hydrogen peroxide, an oxidizer that kills dopamine cells in culture, their survival rate improved. When they exposed similar cells with no DJ-1 to hydrogen peroxide, a lower-than-normal number of cells survived. According to Freed, DJ-1 responded to the stress by turning on a gene that produced an anti-oxidant, glutathione.

    One sign of Parkinson’s disease is the presence of built-up protein deposits called Lewy bodies in the neurons, Freed said. These disruptive structures contain the protein alpha-synuclein. Mutations in the gene for alpha-synuclein are associated with genetic Parkinson’s disease.

    Freed and Zhou created cells with a mutation in the alpha-synuclein gene that cause the protein to aggregate and have toxic effects. Engineering these cells to over-express DJ-1 improved survival. When the mutant alpha-synuclein cells had no DJ-1, they were less viable than usual.

    When exposed to deposits of alpha-synuclein, DJ-1 activated an enzyme known to inhibit clumping, heat shock protein 70 (Hsp70).

    According to Freed, these findings make DJ-1 a good candidate for drug development. He and his colleagues are investigating two avenues for using DJ-1 to treat Parkinson’s.

    The first involves using gene therapy to insert the over-expressing DJ-1 gene into dopamine neurons. In theory, this could increase the presence of DJ-1 enough to protect the cells from oxidation and protein aggregation.         

    But Freed admits that gene therapy is challenging.

   He also imagines discovering a compound that turns on DJ-1 and triggers protective effects without damaging the cells.

    Even so, Freed acknowledged that even if either of these methods were successful in increasing the amount of DJ-1 present in a dopamine neuron, this would not necessarily prevent Parkinson’s symptoms.

    Demetrius Maraganore, a professor of neurology at the Mayo Clinic in Rochester, doubts that DJ-1 is the answer.

    A mutation in the DJ-1 gene is such a rare cause of Parkinson’s disease that Maraganore finds it unlikely that the protein could lead to a new treatment. He even thinks it is possible that the mutation causes a similar disease that is not actually Parkinson’s.

    “I have some cynicism as to whether that particular gene, or its encoded protein, are the best target for research, let alone new therapies,” he said.

    His statements are based on research that he and other Mayo scientists conducted on all of the genes associated with Parkinson’s. Certain mutations in these genes can cause rare forms of the disease, he said. If the mutation happens, an individual will get Parkinson’s. The Parkinson’s associated with DJ-1 falls into this category.

    But common variations throughout the population of some genes that Maraganore studied could influence an individual’s risk of developing Parkinson’s, he said. For example, certain variations of the alpha-synuclein gene could increase the likelihood of Parkinson’s symptoms, depending on environmental factors.

    In Maraganore’s research, the common variants of the DJ-1 gene were not associated with increased risks.

    He added, however, that even if he is right and DJ-1 is not central to the disease, studying the gene has some merits for general knowledge about Parkinson’s.

Articles

Two experts are split over the importance of research on a gene linked with a rare genetic type of Parkinson’s disease. One thinks it could hold the key to new treatment. The other thinks it is too rare to be relevant.

Genetic Research Yields Controversial Parkinsons Drug Target

Allan Brett is a professor at the University of South Carolina and director of the General Internal Medicine division. He co-wrote a Perspective article in the Dec. 22, 2005 issue of the New England Journal of Medicine addressing the issue of how physicians should handle patient requests for personal stockpiles of Tamiflu.

You express concern in your piece that patients who received Tamiflu on demand could use it for other illnesses. Do you believe this is because they would be incorrectly diagnosing themselves as having avian flu, or would they use it for other purposes?

I wasn’t trying to say that most people would. That was listed as one of the factors that, taken together, converge in that direction. It would be all kinds of things. 

Understandably, according to human nature, perhaps some people would use it for any sort of viral respiratory infection they had. Many others would keep it under lock, but as reports about avian flu increased fear, there is a fairly high probability that at the hint of an epidemic they might take it at the wrong time. 

But I want to keep making the point that my whole article is a collection of things.

Should we be concerned about stockpiling leading to Tamiflu resistance?

It’s really unclear. It’s another thing that has to be weighed. I think that inappropriate use of the drug might enhance the chance of resistance. I think it’s a factor, but it’s not clear how big of a factor. 

It’s another issue to be weighed in trying to analyze when it’s appropriate for individuals to stockpile, but it’s not the overriding one.

Are you concerned that stockpiling Tamiflu against an avian flu epidemic could decrease effective treatment of seasonal influenza?

It is yet one other factor that one can put on a list. Is it the single over-riding one? No.

Tamiflu is not a panacea for human influenza. It shortens the average duration by about a day, but it doesn’t obliterate it. 

From a public health perspective, couldn’t individual supplies of Tamiflu prevent a flu outbreak from spreading by keeping those infected out of medical facilities, as presented by Dr. Anne Moscona in a 

 perspective article concurrent with yours?

If experts in controlling an epidemic, which I’m not, end up believing the benefit of having a certain drug at home would outweigh the harm of it. 

But is has to come down to individual physicians. What I was writing about was willly-nilly, 

 requests. That would be okay, what you are describing, if it was well organized with public health officials and physicians working together.

What made me write this was that in September and October physicians started to get these phone calls, or maybe requests tacked on at the end of a visit, and there was no guidance on how to handle it. No directives physicians could use to make these judgments. 

What lessons from the 2001 anthrax attacks and subsequent paranoia can be used to deal with this situation?

The lessons from these things collectively -- I think they show reasonable and sensible judgments have to be made by people with public health authority. Where that authority lies is something for people to talk about. 

In an instance where individual physicians are caught between individual patients asking for something and a larger public health issue, it’s unfair to leave physicians floundering around on their own. Something above physicians needs to provide organized guidance. It didn’t happen for anthrax and it hasn’t happened with this until now.

In South Carolina public health officials sent an advisory saying no personal stockpiling. But when I was writing this paper in early November, I really couldn’t find anybody. There were many discussions about avian flu, but there hadn’t been any definite statements telling physicians how to deal with avian flu.

Q&A with Dr. Allan Brett, professor at the University of South Carolina and director of the General Internal Medicine division. He authored a recent perspective about on-demand Tamiflu prescriptions in the New England Journal of Medicine.

Physician Calls for Guidelines on Tamiflu Stockpiling

Researchers at the University of Central Florida are betting that transplanting anthrax genes into tobacco plants can cheaply produce enormous amounts of a vaccine against the deadly bacteria.

    Dr. Henry Daniell, a professor of molecular biology and microbiology at the University of Central Florida, identified three problems with how anthrax vaccine is currently produced: cost, capacity, and contamination. The new production solves all three, he says.

    Traditional vaccine production methods rely on fermenting machines to grow large quantities of anthrax bacteria. These are very expensive, Daniell said. The protein protective antigen (PA) is purified from fermented anthrax cell cultures.

    PA enables anthrax to inject its toxin into cells once the spores have entered the body. The purified PA is used, along with an adjuvant, to vaccinate people against anthrax. Exposing the immune system to the protein allows recipients to develop antibodies against PA, which is harmless.

    The size and number of fermenters limits the production of PA, Daniell said. Worse, the purification fails to remove trace amounts of anthrax toxin, Daniell said, which probably cause side effects and reactions such as pain, swelling, inflammation, and flu-like symptoms.

    He and his colleagues inserted a clone of the gene for PA into tobacco plants. They purified the protein from the leaves and injected it into mice, along with the alhydrogel adjuvant.

    “What we have done is improve the method of production,” Daniell said.

The mice were tested for the presence of active antibodies against PA and then sent to the National Institute of Health. The NIH challenged their immunity with an exposure to anthrax toxin, which all of the mice survived.      The mice vaccinated with plant-derived PA had the same ability to survive this exposure as mice injected with PA harvested from anthrax bacteria.

Daniell claims his method would yield an average of 150 milligrams of PA per plant.  So one acre of tobacco could vaccinate 360 million people, he said.

    Why this large capacity? Daniell inserts the PA gene into DNA in the plant’s chloroplasts, rather than the nucleus. Chloroplasts, the cellular organelles where photosynthesis takes place, have their own DNA.

    Because there are hundreds of chloroplasts in every cell, inserting a gene into this DNA can produce a great deal of protein, explained Kent Bradford, director of the Seed Biotechnology Center at University of California Davis. In addition, Bradford said, the chloroplast DNA does not leave the plant – as nuclear DNA does via pollen and seeds – so there is no worry about contaminating other plants in the wild.

    “Tobacco is probably a good target for this because there are not many relatives around,” he added. This offers an extra layer of protection against contamination.

    He said using chloroplast DNA is a good strategy for producing pharmaceuticals in plants. The technique has one major drawback: protein must be harvested immediately after the leaves are picked, since it cannot remain viable in dead leaves. When genes are inserted into nuclear DNA, dried seeds can store the protein for long periods.

    The next step, according to Daniell, is to demonstrate that PA derived from plants is not harmful to humans and is equivalent to the traditional vaccine. The end product should be no different, he said. Only the production method has changed.

    Daniell and his colleagues are also working on inserting PA into carrot cells, which he believes could be dried and administered orally in pill form, and on producing other drugs, including insulin, in plants.

    “I believe it’s going to significantly change the way medicine is delivered,” he said.

In order to increase production and lower the costs of making anthrax vaccines, a research team grew a protein from anthrax bacteria in tobacco leaves.

Pharmaceutical Executive-01-05-2006

Genetic Research Yields Controversial Parkinsons Drug Target

Physician Calls for Guidelines on Tamiflu Stockpiling

Researchers Use Transgenic Plants to Produce Anthrax Vaccine