California Pacific Currents 2001
Are Oxygen-Free Radicals Responsible for Lou Gehrig's Disease?
A Conversation with Nancy M. Lee, PhD
Senior scientist Nancy M. Lee, PhD, of the Research Institute, has conducted ground-breaking research into opioid tolerance and addiction as well as the role of the human body's own natural opioids: the endorphins (see “The Yin/Yang Regulator,” California Pacific Currents, Fall 1996). As her work in this field rapidly unfolds, she has also begun investigations into the molecular biology of amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease), a severely debilitating neurodegenerative disease that is nearly always fatal within a few years of diagnosis. We asked Dr. Lee to tell us about her work, especially in ALS.
Q: You've done extensive research on endorphins, in particular the neuropeptide dynorphin, and now you're beginning to investigate ALS. How would you characterize the overall focus of your research?
A: Broadly speaking, the central theme of my research is to understand what keeps cells healthy and, by contrast, identify how they become diseased. The best way to do this is to study healthy cells and compare them with unhealthy cells as early as possible in their life cycle. For example, if you see a car that looks as though it has been sitting in the junkyard for a number of years, you can't begin to imagine the trail of events that led it there. The same is true of unhealthy cells.
Cell disease can result in one of two outcomes: cell death or cell mutation. In cell death, the cells can no longer compensate or adapt to their environment. In cell mutation, the cell escapes the body's normal control mechanisms and grows uncontrollably, possibly becoming cancerous. Cell death and uncontrolled cell proliferation are—in a sense—two sides of the same coin: both are extreme reactions to change.
Q You've begun to study ALS. What specifically will you be investigating?
A: We don't know what causes ALS. All we know is the end result, that motor neurons—the nerve cells that control our muscles—die. The theory I'm pursuing is that oxidative stress may be the cause. Oxidative stress is caused by oxygen-free radicals, which are highly reactive compounds that can cause DNA mutations and cell damage.
Q: What is the source of oxygen-free radicals? How do they get into our bodies?
A: Our intestines absorb the food we eat, breaking it down into its components, or nutrients, such as sugars and amino acids. These nutrients go through the bloodstream and are absorbed by the cells of the body to produce proteins, the body's building blocks, and supply the body with energy. This normal cell metabolism is key to our body's proper functioning, but it also produces potentially harmful byproducts such as oxygen-free radicals.
Our bodies have a natural mechanism for neutralizing free radicals, but not all of these mechanisms are created equal. One person's neutralizing system may be adequate to rid his body of the free radicals produced from a normal life. But if that person experiences changes, such as a prolonged period of poor diet, excessive physical exercise, or undue emotional stress, his neutralizing system may become overwhelmed. When that happens, oxygen-free radicals accumulate, and the cells of the body move from a healthy state to an unhealthy state. During the initial stages of oxygen-free radical accumulation, a person can seem perfectly healthy, but changes at the cellular level are already taking place. He or she just hasn't manifested any clinical symptoms yet.
Remember the comedian George Burns? He lived to be 100 years old and smoked cigars just about all his life. If you consider only George Burns, you might draw the conclusion that a lifetime of smoking cigars is okay. But we know that it's not. He must have had enhanced systems that could repair the damage done to his body by smoking.
Q: How will you explore your theory about ALS?
A: I'm going to examine the genes involved in handling oxidative stress and ask specific questions such as: Which genes and which cell mechanisms are involved in managing oxidative stress? What gene products are different in ALS-diseased cells compared with healthy cells? Can we study gene expression from birth through disease progression? Can we push time back to early cellular changes that occur long before the manifestation of any clinical signs?
If we can identify genes that compensate early in the disease cycle (either by increasing or decreasing protein production), maybe we can interfere in some way to regulate their function and stop, or at least slow, the progression of the disease.
Q: What studies do you conduct in tissue culture?
A: We take cells from animals and “immortalize” them to make tissue cultures. We produce one healthy set of cells; the other is “ALS-altered.” The cells produce identical cells for thousands of generations—billions of cells. Then we study these two cell lines as they grow in normal conditions with plenty of nutrients. Next we look at the expression levels of certain gene products that we are interested in and measure the exact amounts of these proteins as they are produced by their genes.
Because our hypothesis is that oxidative stress may be causing ALS, we give the cells excess amounts of free radicals. Then we determine what gene products are expressed and how they differ between the healthy cells and the ALS cells. We can also limit the oxygen supply and see how the cells change to compensate.
We go back and forth, testing and analyzing. We see patterns. Some genes never change; some genes change a great deal in response to the stimuli. From patterns, we can see connections, pathways, and trends. We devise more experiments. That's how it goes.
Q: How are the results from your laboratory studies applicable to ALS patients?
A: Once we have confirmed that the same gene expression in laboratory animals is found in humans, we are in a position to point the way towards development of treatments. We can suggest to ALS clinicians, “Here is the hypothesis: We have data from animal studies supporting the use of this medication to cure, or at least delay, the onset of severe disease.” Then we can do a small clinical trial in humans, and from that, look again at the animal model to ask more questions. We keep doing this until we can design a highly targeted and effective medication.