Bipolar disorder (BPD) is a mental disorder that causes unusual shifts in mood, energy, activity levels, concentration, and the ability to carry out day-to-day tasks. In the United States, recent research has shown that 1.6% of the population has BPD, which is roughly over 4 million people. Those with BPD are more likely to have conditions associated with chronic inflammation such as hypertension and diabetes. It is because of this that scientists have been studying the connection between inflammation and BPD for quite some time.

In a new study, researchers at the Salk Institute for Biological Studies, UC San Diego, and the Institute of Psychiatry and Neuroscience of Paris have found evidence that astrocytes, a certain type of brain cell, can trigger inflammation more easily in those that have BPD. What’s more, these astrocytes can be linked to decreased brain activity that could be harmful to mental health.

Astrocytes are star shaped (as the word “astro” might suggest) and help support neurons, the cells that relay information around the brain. One of these supporting roles includes helping trigger inflammation in the brain and the surrounding nervous system to help with injury or infection. The researchers believe that this process can go wrong in people with BPD and that astrocytes can play a role in this dysfunctional inflammation.

For this study, the team used induced pluripotent stem cells (iPSCs), a kind of stem cell that can turn into virtually any type of cell, that they created from patients with BPD and patients without BPD. They converted these iPSCs into astrocytes and compared those that came from BPD patients to those that did not. What they found is that the astrocytes from patients with BPD were noticeably different. The BPD astrocytes had a higher expression of a protein that triggers an inflammatory response when compared to the non-BPD astrocytes. When they exposed neurons to the BPD astrocytes, the team saw decreased levels of neural activity compared to the non-BPD astrocytes. Lastly, when the researchers blocked the inflammatory protein, the neurons were less affected by the BPD astrocytes.

“Our study suggests that normal function of astrocytes is affected in bipolar disorder patients’ brains, contributing to neuroinflammation,” said Dr. Renata Santos, a researcher at the Salk Institute as well as the Institute of Psychiatry and Neuroscience of Paris, in a news release.

The team hopes that their findings can not only provide insight into BPD, but to other mental illnesses linked to inflammation such as schizophrenia. The ultimate goal is to help advance research into astrocytes and inflammation in order to develop treatments that might reverse the harmful bodily changes seen in those with BPD and other mental disorders.

The full study was published in Stem Cell Reports.