Astrocytes in bipolar patients are not functioning normally
In the long human struggle to understand the mind's most disruptive storms, a team of neuroscientists has traced one thread of bipolar disorder's chaos to an unexpected source: not the neurons themselves, but the star-shaped support cells surrounding them. Published in Stem Cell Reports, the work from the Salk Institute, UC San Diego, and the Paris Institute of Psychiatry and Neuroscience reveals that astrocytes in bipolar patients overproduce an inflammatory protein called IL-6, quieting the very neural activity the brain depends on. It is a finding that reframes the disorder not merely as a crisis of mood, but as a condition with roots in cellular inflammation — and one that may open new doors for treatment.
- Bipolar disorder has long resisted clean biological explanation, but researchers now have a cellular suspect: astrocytes that flood the brain with an inflammatory protein called IL-6, suppressing neural activity.
- The urgency is sharpened by what was already known — bipolar patients carry higher IL-6 levels in their blood and suffer disproportionately from inflammation-linked conditions like hypertension and diabetes, suggesting the body has been signaling this problem for years.
- In a direct laboratory test, neurons exposed to bipolar patients' astrocytes showed measurably reduced activity — but when an IL-6-blocking antibody was introduced, those neurons recovered, pointing to a potentially targetable mechanism.
- Researchers are cautious: lab-grown cells are less mature than those in a living brain, and bipolar disorder is almost certainly shaped by many overlapping biological forces that no petri dish can fully replicate.
- The findings may reach beyond bipolar disorder — similar astrocyte dysfunction could be at work in schizophrenia and other inflammatory psychiatric conditions, widening the potential stakes of this line of research.
A team of neuroscientists has identified a cellular mechanism that may help explain a core feature of bipolar disorder: not a problem with neurons themselves, but with the star-shaped support cells called astrocytes that surround them. In people with bipolar disorder, these cells appear to trigger inflammation far more readily than they should, and that inflammation suppresses the electrical activity neurons need to function. The findings were published in Stem Cell Reports by researchers at the Salk Institute, UC San Diego, and the Institute of Psychiatry and Neuroscience of Paris.
The team focused on interleukin 6, or IL-6, a protein the body deploys during inflammatory responses. Prior research had already noted elevated IL-6 in the blood of bipolar patients, along with higher rates of inflammation-linked conditions like hypertension and diabetes. What was missing was a direct cellular source. To find it, the researchers grew astrocytes in the laboratory from stem cells donated by six bipolar patients and four healthy controls. The bipolar-derived astrocytes expressed the IL-6 gene at far higher levels and released substantially more of the protein. When neurons were exposed to these overactive cells, their activity dropped — but introducing an IL-6-blocking antibody reversed the effect.
The researchers are measured in their conclusions. Lab-grown astrocytes are less mature than those in a living brain, and bipolar disorder is shaped by biological complexity that no laboratory dish can fully capture. The road from a cellular finding to a clinical treatment remains long. Still, the implications may extend to other psychiatric conditions tied to inflammation, including schizophrenia, and the team hopes the work will encourage deeper investigation into how astrocyte dysfunction contributes to mental illness — and whether reversing that inflammation might one day offer relief.
A team of neuroscientists has identified a cellular mechanism that may help explain why bipolar disorder wreaks such havoc on the brain. The culprit is not a single rogue neuron, but rather a type of support cell called an astrocyte—star-shaped structures that normally help neurons function properly. In people with bipolar disorder, these cells appear to trigger inflammation more readily than they should, and that inflammation seems to dampen the electrical activity neurons need to work.
The research, published this week in Stem Cell Reports, comes from investigators at the Salk Institute for Biological Studies, UC San Diego, and the Institute of Psychiatry and Neuroscience of Paris. They focused on a specific protein called interleukin 6, or IL-6, which the body uses to mount an inflammatory response. Previous work had already hinted at a connection: people with bipolar disorder tend to have higher levels of IL-6 in their blood, and they're more prone to conditions linked to chronic inflammation, like hypertension and diabetes. Some studies had even shown that IL-6 spikes during manic episodes. But the new work traces the problem to its source—the astrocytes themselves.
To test their hypothesis, the researchers collected stem cells from six people with bipolar disorder and four without. They coaxed these cells to develop into astrocytes in the laboratory, then compared them side by side. The difference was striking. Astrocytes from bipolar patients had much higher expression of the IL-6 gene and released substantially more of the protein than control cells did. When the team exposed neurons to these overactive astrocytes, neural activity dropped noticeably. But when they introduced an antibody designed to block IL-6, the neurons recovered—a finding that pointed directly to IL-6 as the culprit.
Fred Gage, president of the Salk Institute and one of the study's authors, explained the reasoning in an email: the team wanted to understand whether the inflammation-driving signals in astrocytes might be altered in bipolar disorder. The answer appears to be yes. Co-author Renata Santos, who works at both the Salk Institute and the Paris research center, noted that the findings suggest astrocytes in bipolar patients are not functioning normally, and that this dysfunction contributes to brain inflammation.
Yet the researchers are careful not to overstate what they've found. Lab-grown astrocytes are not identical to those living inside an actual brain—they're less mature, for one thing, and the brain's biology is far more complex than any petri dish can capture. There may be many other biological factors, both in the brain and elsewhere in the body, that play a role in bipolar disorder. The path from a laboratory finding to a real treatment is long and uncertain.
Still, if the team is right, the implications could extend beyond bipolar disorder alone. Other psychiatric conditions linked to inflammation, such as schizophrenia, might also involve similar astrocyte dysfunction. The researchers hope their work will inspire further investigation into how these support cells contribute to mental illness—research that could eventually lead to treatments designed to reverse the inflammatory damage seen in bipolar patients and others with related conditions.
Citas Notables
Our study suggests that normal function of astrocytes is affected in bipolar disorder patients' brains, contributing to neuroinflammation— Renata Santos, Salk Institute and Institute of Psychiatry and Neuroscience of Paris
The findings elucidate aspects of the understudied role of astrocytes in neuroinflammation in psychiatric disorders, with relevance for altered IL-6 and inflammatory signalling in bipolar disorder patient astrocytes— Krishna Vadodaria, research associate at the Salk Institute
La Conversación del Hearth Otra perspectiva de la historia
So these astrocytes are supposed to help neurons. What goes wrong in bipolar disorder?
They start producing too much of a protein called IL-6, which triggers inflammation. That inflammation then suppresses the electrical activity neurons need to communicate properly.
And you found this by growing cells in a lab from bipolar patients. How confident are you that lab cells behave the same way as cells in an actual brain?
That's the honest answer—we're not entirely sure. Lab-grown astrocytes are less mature than the real thing. The brain is also vastly more complicated than a petri dish. This is a clue, not a proof.
If this holds up, what would a treatment look like?
Theoretically, something that blocks IL-6 or restores normal astrocyte function. But we're years away from knowing if that's even possible, let alone whether it would work in people.
You mentioned this might apply to other psychiatric disorders too?
Yes. Schizophrenia and other conditions also show signs of inflammation. If astrocytes are part of the problem there as well, the same approach might help.