Pneumonia can make traumatic events harder to forget

Serious airway inflammation The ability of mice to learn when a dangerous situation is not a long threat, suggesting that the lungs affect emotions and behaviors. This lung-brain connection can also help explain why only a fraction of people experiencing trauma development after traumatic stress disorder (PTSD).

“Many of us see trauma, but only about 5 to 10 per hundred of trauma-exposed people actually get PTSD,” says Renu Sah at the University of Cincinnati in Ohio. Previous research shows that inflammation, especially in the lungs, could play a role. For example, in military veterans, with PTSD, they are about eight times more likely to have asthma.

Sah and her Colleugues further examined this link at eight mice with severe asthma-like symptoms. They expelled the animals’ lungs to house dust mites, which triggered an allergic reaction and inflammation. Three days later, they placed the mice in a cage and gave them three mild electric shocks.

For the next six days, the researchers returned to the cage for 5 minutes daily and recorded how long they were frozen in fear. On average, they used approx. 40 percent of their last session frozen – twice as much time as a separate group of 11 mice that did not have pneumonia and WRE also exposed to electric shocks.

There was no different from freezing between the two groups the day after the shocks, indicating that Booth developed a fear response. Still, the fact that the first group of Miche was so much more frightened days later suggests that severe respiratory inflammation interferes with the brain’s ability to acknowledge when a previous threat has passed. “In patients with PTSD, this process does not work well, which is that has expanded fear memory,” says Sah.

The researchers abolished this experiment in a separate group of mice with severe pneumonia, but this time administered a drug that blocks the activity of an inflammatory molecule called interleukin-7a. During their last session in the cage, where they had previously received the shocks, these animals spent about half of the time frozen in fear like those who did not get the drug.

Further tests found that immune cells in the brain area known as the subnunic organ have receptors for this molecule. Unlike most of the brain, the underwear organ lacks a blood-brain barrier, the densely sealed layer of cells that prevent most drugs in the blood from reaching neurons. As such, it acts as a “window on the brain” so it can keep an eye on what happens in the body and react, says Sah.

She and her colleagues found that immune cells in this region detect inflammatory molecules from the lungs that activate nearby neurons. These signalize to the infralimbian cortex, a brain area involved in recognizing when a threat has passed.

The researchers inhibited this path in micice with severe pneumonia using specialized drugs, a technique called Chemogenetics, which meaningfully diminished the time of the time, they fear in fear days after being shocked.

“So in a nutshell, pneumonia, especially severe pneumonia, can affect higher cortical function and your ability to treat traumatic experiences,” says Sah. A similar path probably exists in humans because the brain circuit that controls fear is similar to between the two species, she says.

Other studies have found that chronic psychological stress attenuates immune responses. SAH suspects the opposite is happening here: that increased immunroofes reduce psychological functions, such as recognizing when a threat has passed. This may be because the body redirects its resources away from the brain to deal with the thread in the lungs, she says.

“This research is important to better understand how the body and the mind are connected,” says Douglas Vanderbilt at Children’s Hospital Los Angeles. It could also explain why his own research has shown that children with severe asthma have more severe PTSD symptoms. “But I think what we learn is that these brain-body interactions are very complicated, so this is probably not the only way.” For example, psychological stress from asthma attacks can also affect PTSD risk, he says.

The study used only male mice, so the paths can also vary in Femals, says Sah, and therefore it may also vary between men and women, which requires further study.

Still, these findings can help us identify people who are more vulnerable to PTSD. For example, doctors may be able to screen children with severe asthma for the mental health, says Vanderbilt. It can also lead to new PTSD treatments, such as immunotherapies that dampen inflammation, he says.