Chronic stress can inflame our brain, destroy the connections between our neurons and result in depression. (2019) Digest
From the article:
The complement system, named because it was first found to help the immune system fight invaders, is part of this innate immune response, and Pillai has found elevated levels of C3 – which he calls the hub of all complement activation pathways – in both the brains of people with depression and animal models.
The complement system also has the important job during development of removing bad connections between neurons, and there is good evidence the same thing happens in a developed brain in problems like major depressive disorder and Alzheimer’s, when losing these important connections, called synapses, is problematic rather than helpful.
“You have to have a functioning complement system during development,” says Pillai. But he and his research colleagues have put together some of the first evidence that in depression, the complement also is active, causing inflammation and synaptic loss in the prefrontal cortex, an area of the brain important to working memory, personality and executive function. “Under chronic stress you are losing your synapses,” he says.
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C3 is known to play a key role in inflammation in the brain, and microglia, the resident immune cells in the brain, are known to use C3 during brain development to eliminate synapses.
“We expect that chronic stress increases C3,” Pillai says as he continues to put the complex puzzle together.
[…]
Their early findings indicate that when NF-kappa B, a transcription factor that regulates both innate and adaptive immunity and is implicated as a key regulator of inflammation in depression, is inhibited, stress-induced increases of C3 in a mouse’s prefrontal cortex are reduced. Depleting microglia appears to do essentially the same thing.