Thirty years ago, George H.W. Bush was the U.S. President, and the United States was in a two-month war: Operation Desert Storm. A total of 154 U.S. service members died and approximately 250,000 returned home suffering from a host of chronic symptoms, ranging from memory deficits, mood disorders, gastrointestinal problems, to headaches and sleep disorders. These health problems, caused by exposure during battle to chemicals such as pesticides, nerve agents and certain prophylactic drugs, continue to plague these veterans — a diagnosis known as Gulf War Illness.
Professor Peter Baas, PhD and Assistant Professor Liang Oscar Qiang, MD, PhD have been leading research into this strange and complex illness for the past several years. Their 2017 paper in Neurology detailed their development of human-induced pluripotent stem cell lines derived from blood of Gulf War veterans. These cells have the potency to differentiate into all kinds of cells in the human body and thereby help the research team dig into the causes of the symptoms of this illness and test new drugs for treating it. (We also covered this research in the Drexel News blog.)
In our first reporting on this, back in 2017, the project had just started. Fast forward five years later, the researchers are now unpacking the insights they’ve gleaned, leading to new treatments for this disease — reported in a paper recently published in Cellular and Molecular Life Sciences.
As part of the research, the team attempted to simulate the conditions the cells of servicemembers would experience on the battlefield. The researchers took the newly created pluripotent stem cells, originated from veterans – some suffering with Gulf War Illness and some from those who fought alongside them, but did not develop the illness – and exposed them to a sarin gas analog and the stress hormone cortisol. The stress hormone mimics the physical stress soldiers experienced on the battlefield while they were exposed to the toxicants.
Leading a team of scientists at Drexel, Baas and Qiang explored vulnerability — pre-disposition to getting the disease — by measuring cellular defects associated with exposure to the toxicants. They looked to see if brain cells differentiated from the pluripotent cell lines from soldiers diagnosed with Gulf War Illness were more vulnerable to toxicants than the cells of those without the disease.
What they found was the brain cells exposed to the toxic chemicals displayed higher amounts of total and phosphorylated tau (which is implicated in Alzheimer’s, Parkinson’s and other forms of dementia), a drop in microtubule acetylation (a marker of the cells being more vulnerable to breakdown and stress), a change in the function of mitochondria (which is critical for the body to generate the energy to function properly) and reduced nervous system activity.
The authors say that using brain cells derived from pluripotent stem cell models for testing possible drugs can do what rat or mouse studies cannot, which is to explain why some soldiers got the disease, while other, similarly exposed, soldiers did not.
“When it comes to a deep dive into the cellular mechanisms underlying the disease and potential therapies, the rodents are not close enough to humans to be the most useful tool, mechanistically or therapeutically,” said Baas. “We can now study genetic predisposition, or in other words, what makes some soldiers less able than others to tolerate certain types of chemical exposures in the battlefield? We can also find biomarkers that help diagnose the disease so that appropriate treatments can be prescribed.”
The researchers note that human-derived pluripotent stem cells open a world of new possibilities in finding answers for a population of sufferers that has waited too long for effective treatments.
“The power of these cell lines is that they proliferate in culture, providing an infinite supply of the cells, which we can then differentiate into almost any kind of cell: different types of nerve cells, astrocytes, even gut cells, for whatever aspect you’re studying,” said Baas. “All of these cells are relevant to different symptoms of Gulf War Illness — memory deficits, mood disorders, fatigue, headache, sleep disorders and the list goes on.”
The researchers are also differentiating the cells into multi-cellular structures named organoids — also known as “mini brains” — 3D structures the researchers create in culture that mimic brain tissue. The Drexel team is finding pathologies in those structures that are likely happening in the brains of the veterans suffering from Gulf War Illness.
Different individuals were exposed differently, some to sarin gas, pesticides, black smoke from burned oil, and this variation in exposure means there may be different biomarkers to measure characteristics of the disease and different therapeutics to treat individuals.
“This is the realization of personalized medicine to treat this disease,” said Qiang. “In our study we found heightened susceptibility or predisposition in cells from veterans who are afflicted with the disease to the ill effects of the toxicants. In the case of cells from the veterans suffering from Gulf War Illness, those differentiated into neurons and then exposed to the toxicants display greater reductions in chemoelectrical activity, more tau pathology, and greater defects in mitochondria, which are the energy supplying organelles in our cells.”
“Generally, up to this point, Gulf War Illness had been thought of as a self-perpetuating neuroinflammatory illness that doesn’t resolve on its own,” Baas says, “but our studies are showing that the story is more complicated.”
Could a pre-disposition to tau pathology make some soldiers more vulnerable to Gulf War Illness than others? That is still uncertain, but the tau-related responses open the door to genome-wide association studies and also help explain the memory loss and other poor central nervous system functioning in these patients.
“The question is, what causes the cellular effects and what do they, in turn, cause?” said Baas. “We think both upstream and downstream, the disease mechanisms are not things that are unfamiliar to the medical world. Looking at tau, for example, we found that when we exposed these cell lines to the toxicants, there is a strong reaction with tau — the levels of tau go up and become more phosphorylated.”
Thanks to Baas, Qiang and their colleagues, the research community now has a cell-based model to test therapies based on mechanisms and various biomarkers, and study predisposition to disease. There are still many more questions than answers, but the researchers feel a strong foundation has been laid to find the answers. “When toxicant exposures synergize with stress, this is what happens,” said Baas. “The U.S. military is protecting our soldiers more effectively with better gear so this doesn’t repeat itself, but there’s still bioterrorism and irresponsible countries putting a lot of toxicants into the environment. We may be looking at vast human populations suffering from fatigue, memory deficits, headaches because of this synergy between toxicants and stress. Solving this has global implications beyond just these veterans.”