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A New Role for Estrogen: Protecting the Brain Professor Colin Saldanha’s research on songbirds shows how the hormone can prevent brain inflammation.

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A zebra finch perched.

Professor of Biology and Neuroscience Colin Saldanha has long been fascinated by the ability of certain songbirds to recover rapidly from brain injury. He has published research that shows that the main female sex hormone, estrogen, can protect the brain of zebra finches from dangerous inflammation after traumatic injury. These findings could have future implications for recovery in humans after strokes, or the onset of Parkinson's disease, Alzheimer's disease, and other neurological injuries. 

Now Saldanha's most recent research goes even further, providing tantalizing indications that estrogen, which is also present in males, might also prevent neuroinflammation after viral and bacterial diseases present themselves in other parts of the body.

The Response

So why would the zebra finch brain start making a sex hormone in response to sickness? 

Saldanha explains that although estrogen was first discovered as a sex hormone, it is actually part of a group of hormones that are potent regulators of gene expression in general. It is therefore quite likely, he says, that estrogen may regulate many processes other than sex and affect gene expression in non-reproductive tissues as well. 

"Estrogen controls several processes other than sex, and we are now learning that one of these processes is neuroinflammation," he said. "It appears that estrogen synthesis in the songbird may protect neural circuits from the damage of infection if it travels to the brain."

The Process

In the experiment, researchers injected songbirds with a chemical to activate the immune system and simulate a bacterial infection. Birds in the control group received an injection of saline. Within two hours, the pathogen-injected birds showed classic signs of immune response and sickness behaviors like listlessness, fever, and loss of appetite. After 24 hours, the sick birds were on the rebound-and showing elevated levels of estrogen in their brains and a decrease in cytokines, proteins secreted as part of the immune response. 

More research is needed, but the findings, published earlier this year in Scientific Reports, are strong evidence for a correlation between estrogen synthesis and inflammation control following an infection in the body. Understanding the natural processes in songbirds paves the way for study in mammals, which could lead to potential groundbreaking human therapies to slow brain degeneration and inflammation.