Researchers: PTSD biomarkers also govern the immune system

Chuck Bednar for redOrbit.com – @BednarChuck

By analyzing blood samples from US Marines, researchers have discovered genetic indicators associated with the risk of post-traumatic stress disorder (PTSD) – biomarkers which also play a role in regulating innate immune function and interferon signaling.

According to UPI reports published Tuesday, experts from the University of California, San Diego School of Medicine, and the Veterans Affairs San Diego Healthcare System took blood samples from 188 soldiers both prior to and after deployment to combat zones.

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By analyzing those samples, the study authors identified modules of co-regulated genes involved in innate immune response, which act as the body’s first line of defense against disease-causing pathogens, and interferon signaling that were also associated with PTSD. Interferons are proteins released by host cells in response to pathogens, the researchers explained.

Systems-level approach study

In their study, they demonstrated that those proteins also take part in the pathology of PTSD, and the results were replicated in a study involving a second, independent group of 96 Marines. The findings, published online this week in the journal Molecular Psychiatry, could lead to new ways to help diagnose and treat the condition, as well as help predict who is most at-risk for PTSD.

Unlike previous genomic studies of the disorder, which focused upon identifying differences in gene expression between people with PTSD and those without it, the new study uses what first author Michael S. Breen of the University of Southampton calls a “systems-level approach.”

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“By comparing US Marines who develop PTSD symptoms to those who do not, we can measure differences in genes, but also take into consideration the dynamic relationships between and among them, their connectivity,” Breen said in a statement. “Because PTSD is thought to be such a complex disorder, measuring these dynamic relationships is crucial to better understanding the PTSD pathology.”

“What’s interesting is that molecular signatures of innate immunity and interferon signaling were identified both after developing PTSD as well as before developing PTSD,” added Dewleen G. Baker, a psychiatry professor at UC San Diego and a research director at the VA Center of Excellence for Stress and Mental Health. “The question to ask is what’s stimulating an interferon response prior to PTSD development. The answer could be any number of factors.”

A challenging disorder – both to have and to study

Those factors could include a simple explanation such as increased levels of anticipatory stress prior to deployment, or more complex scenarios where a soldier may experience an increased viral load, Baker added. That will have to be resolved by future studies. What makes PTSD more challenging to study than other psychiatric disorders is the presence of a traumatic event.

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“The odds of obtaining a sample both before and after a traumatic event are incredibly small,” said Christopher H. Woelk, co-senior author, assistant adjunct professor at UC San Diego School of Medicine and a reader in bioinformatics and genomics at the University of Southampton.

“Under this experimental design, not only can we identify differences between U.S. Marines with PTSD and without, but we can go back in time, so to speak, to see if any of the Marines who eventually developed PTSD contain prognostic signatures that might be indicative of eventual PTSD emergence,” he added. “In this vein, we are able to start labeling findings as being putatively ‘causal’ in nature.”

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