Superoxide dismutase (SOD) protects living cells from reactive free-radicals, and is the site of the genetic defect of familial ALS. An effective treatment for ALS might be found in drugs that can supply or compensate for a missing function represented by SOD. The obvious problem is that familial ALS is very rare, and may not be a good representation of the other 90-95 percent of patients with no obvious genetic basis, and no deficiency in SOD. In this application, evidence is presented that the common pathway of protection from oxidative stress is reflected by glutathione levels in cells. If reduced glutathione (GSH) is found to be depleted in ALS, then both a cause and a possible cure are immediately available. Clinical trials of new drugs cost many millions of dollars, and years of patient's lives. A way to screen drugs and vitamins based on a blood test is obviously desirable, prior to entering into an expensive time- consuming clinical efficacy trial. Valentine and Gralla, consultants and collaborators in this project, showed that yeast cells deficient in SOD1 grow poorly in oxygen, and are sensitive to damage by free- radicals. Furthermore, the same group recently showed that metallothionein genes can partially correct the defect of SOD1-deficient yeast cells, prompting the interpretation of the elevation of metallothionein reported in ALS tissues as a homeostatic reaction to oxidative stress. More work from the same collaborators' laboratory showed that levels of GSH increase as compensation for the SOD1- deficiency. This is important because glutathione is present in reduced (GSH) and oxidized (GSSG) forms, and the ratio is an indicator of the oxidation - reduction potential inside the cell. Any defect in regulation of the redox potential in the cell will ultimately function by changing the intracellular GSH level. GSH has never been studied in cells of patients with ALS, but is depressed in Parkinson's disease. The GSH tripeptide is present in relatively large amounts (1-10 mM) in cells, and among other roles, it protects cells against oxidizing agents and free radicals. Data for yeast and red blood cells tell us that: 1) When GSH is decreased SOD is up-regulated. 2) When SOD is decreased levels of GSH are up- regulated as a compensation. 3) If GSH level subsequently decline, the result is cell death or dysfunction. Thus, intracellular GSH signals the oxidative stress of the cell. A deficiency of SOD or any similar cellular mechanism might be reflected in a compensatory increase in GSH. Later, if GSH levels fell, disease might ensue. Studies of GSH in ALS patients are urgently needed, and will immediately suggest a treatment for patients, as there are drugs which can raise the intracellular levels of GSH. The project will identify and characterize 20 patients with non-inherited ALS, up to 20 with familial ALS and test about levels of glutathione in white and red blood cells, for comparison to normal controls. The relationship of GSH findings to duration and to severity of disease will be determined. If a change in GSH is detected in ALS, there will be a strong indication to begin treatment trials with drugs capable of restoring cellular GSH levels.
