By Rich Van Konynenburg, Ph.D.
A workshop on Neuro-Immune Mechanisms and Chronic Fatigue Syndrome was held at Bethesda, Maryland on June 12 and 13, 2003 by the NIH Office of Research on Women's Health and the Trans-NIH Working Group for Research on Chronic Fatigue Syndrome.
In my opinion, one of the most significant talks presented at the workshop was given by Suzanne Vernon from the Centers for Disease Control and Prevention (CDC). She gave a summary of the ongoing work on CFS at the CDC, and focused particularly on their gene expression work.
As readers may know, the CDC group has been working on gene expression in CFS for about five years. In this type of analysis, they are able to query a large number of genes from cells of PWCs at the same time, to see which ones are being expressed to a greater or lesser degree than in normal, healthy people. (Gene expression means that the cell is transcribing the DNA of the gene into messenger RNA, and what is measured in this analysis technique is the amount of this RNA for each of the genes.
In the cells, the RNA is normally used as the coded instruction for assembling an enzyme or other protein, one corresponding to each gene, so that in a normally operating cell, the amount of gene expression into messenger RNA would correspond more or less to the amount of each protein being produced. Since the proteins carry on the "business" of the cell, gene expression measurements can give clues about how the cell's operation is perturbed from normal.)
The reason for studying gene expression in CFS is to get clues about what is different in the cells of a PWC from those of a healthy, normal person. It is considered to be a "hypothesis-generating" activity. I think this technique holds powerful potential for helping us to understand CFS, as it is also doing with many other disorders.
There are at least three other groups working in this area now, also. Dr. Patrick Gaffney at the University of Minnesota Medical School leads one of them. The Glasgow University group, represented at the most recent AACFS meeting by Dr. Wilhelmina Behan, is looking at gene expression in muscle cells. Dr. Ben Natelson from the New Jersey Medical School commented at the NIH workshop that his group is looking at cerebrospinal fluid.
The CDC group has chosen to study genes from peripheral blood mononuclear cells (PBMCs), which are certain white cells taken from blood samples, including lymphocytes and monocytes, because of the relative convenience and low cost of taking blood samples as compared with other types of tissue. They, like probably most of the funded CFS researchers at this time, believe that many of the answers to puzzle of CFS lie in the brain, so they are hoping that since the white cells are known to circulate in and out of the brain, they will be good guides as to what is going on in the brain.
As readers may know, in the past Suzanne and the group at the CDC have published results showing that gene expression is consistent and reproducible over time in a given individual, showing it to be a stable, reliable indicator of what's going on in the cells of an individual. They have also published results showing that they are able to distinguish between PWCs and normal, healthy people on the basis of their gene expression. Up to now, they hadn't commented in detail on which genes are expressed differently in PWCs, and what enzymes those genes code for.
The new work that Suzanne reported at the NIH workshop involved a larger study of PWCs (from the ongoing CDC Wichita study) and controls, looking at 4,000 genes. (Note that there are a total of about 30,000 to 40,000 genes in the human genome, and the earlier CDC work looked at "only" about 1,000.)
In this recent work, they found that 112 out of the 4,000 genes were either up- or down-regulated in terms of gene expression in the PWCs relative to the normal, healthy people. They also found that most of these genes code for enzymes involved in intermediary metabolism, not those associated with cytokines or receptors.
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They tried to see if they could separate the PWCs into different gene expression behavior based on their symptoms, and they found that this did not work. That is, the symptoms in CFS do not appear to correlate with gene expression differences.
What they did find was that they could separate the PWCs into a rapid onset group (onset over a period of less than one month) and a gradual onset group (onset occurring over a period of more than one month) based on gene expression differences. Furthermore, they found that the majority of the genes that were upregulated in the rapid onset group were also genes associated with metabolism.
In addition, they tried to see if they could use blood samples from PWCs who were ill to predict which ones would later recover, based on their gene expression, and they found that they could, using primarily metabolic genes, including mitochondrial transport genes and lipid metabolism genes. For this work they used information taken on the same set of people over time in the Wichita study, showing that some people from whom they had initially taken blood samples while ill, later recovered.
They did not see any genes for novel proteins being expressed in the PWC cells, only either higher or lower expression of those normally expressed.
I think this is essentially all the detailed information about the results that she presented, but she mentioned that a paper describing this work has been submitted to a journal, so more information should be forthcoming soon.
The following are my personal opinions, and may or may not agree with those of the CDC researchers:
I think this is a major development. What I think it suggests is that the reason the immune cells are not able to function correctly in CFS is that there is something wrong with their intermediary metabolism, i.e. their ability to burn fuel and generate ATP to power the activities of the cells. I think this supports focusing more research on the metabolism of the cells of the immune system, rather than only on the cytokines and receptors. Not that these latter topics aren't important, but in the light of this new research, it appears that problems in the metabolism of these cells may explain the dysfunction of the immune system in CFS.
I have thought in the past, based on reports from PWCs, that the metabolism in the immune cells and the skeletal muscle cells shows up as having problems right at the time of onset of CFS, in those with sudden onset, at least. (Note that Dr. Gustavo Bounous and Mr. John Molson have published a CFS onset hypothesis involving competition between skeletal muscles and the immune system for the synthesis of glutathione. I think they are on the right track with this hypothesis.)
I also think it is possible that there are partial blockades in the metabolism of the mononuclear cells, just as I believe there are in the Type 1 skeletal muscle cells and probably also the neurons. I think that glutathione depletion (as was first reported in CFS by Dr. Paul Cheney in early 1999) could be the cause of the partial blockades, giving rise to elevated peroxynitrite. (Increased peroxynitrite has been theorized to be important in CFS by Prof. Martin Pall in several publications. Although we differ on which comes first, I agree with him that elevated peroxynitrite is likely to be a significant part of the pathogenesis of at least a major subset of CFS.)
The cells may also be short of cysteine because of the glutathione depletion, and may be unable to make the proteins that contain cysteine. (Note that cysteine is usually the rate-limiting amino acid for the synthesis of glutathione, so that when glutathione is depleted, cysteine is also likely to be depleted.)
In this situation, the cells may be expressing the genes for these proteins at an elevated level, because of feedback indicating that there still aren't enough of them. Just because the gene that codes for a protein is overexpressed, that doesn't necessarily mean that the corresponding protein is being produced in higher than normal quantity, because there may be a shortage of raw material that is blocking the translation into proteins.
I look forward to hearing and reading more about the results of gene expression research in CFS from the CDC and the other groups working in this field, because I think this technique holds powerful potential for helping us to understand CFS, as it is also currently doing with many other disorders.