Biohacking
Brain immune cells, not neurons, drive alcohol damage in mice and human tissue
By Life and Health Today Staff, . Life and Health Today.
The assumption has held for decades: alcohol damages the brain by acting directly on neurons, the cells that carry signals. A study from the Cleveland Clinic, published in the journal Immunity, says that picture is incomplete, and that the real driver may be the immune system inside the skull.
Microglia are the brain's resident immune cells. Under normal conditions they extend fine, branch-like projections to survey surrounding tissue, clear waste, and trim excess connections between neurons. The Cleveland Clinic team, led by Dimitrios Davalos, tracked individual microglial cells in living mice before and after repeated alcohol exposure using real-time imaging. What they saw was not passive response to neuronal injury. The microglia retracted their branches and began dismantling the extracellular matrix, the dense protein scaffold that holds brain cells in place and keeps synaptic connections stable. Synapse loss and reduced neuronal activity followed. So did sedation and impaired movement in the animals.
The key to the whole sequence, the researchers found, was a signaling protein called MyD88. It functions as an activation switch inside microglia, turning them aggressive when they detect danger signals or ethanol metabolites. When the team deleted the MyD88 gene specifically from microglia before alcohol exposure, the immune cells stayed calm, the scaffolding stayed intact, and the mice showed far less sedation and motor impairment, even though their blood alcohol levels were the same as untreated animals.
To check whether the same destruction shows up in people, the team examined frontal cortex tissue collected after death from individuals diagnosed with severe alcohol use disorder. The tissue came from a collaboration with the Northern Ohio Alcohol Center and the Cleveland Clinic's Pathology and Laboratory Medicine Institute. The same pattern of scaffolding breakdown was present. The report describes this as the first direct confirmation that microglial dismantling of neural scaffolding occurs in the human brain during chronic alcohol abuse.
"For years, alcohol's effects on the brain were largely viewed through the lens of neurons, and for good reason: alcohol acts directly on neuronal receptors," Davalos said, as quoted by Neuroscience News. "By following microglia in real time, we were able to see that they aren't simply responding to damage. They drive the detrimental changes alcohol causes in the brain. And if they drive the damage, they can be targeted with treatment."
What this does not show is whether blocking MyD88 in people would be safe or effective. The gene-deletion approach used in mice is not a therapy available to humans, and no clinical trial has tested a MyD88 inhibitor for alcohol use disorder. The human tissue finding confirms the pattern exists in people but cannot establish that targeting microglia would slow or prevent it.
Davalos noted a broader possibility: "We discovered a specific neuroimmune route that alcohol activates, but it's possible that other drugs can turn that pathway on as well," adding that his lab is investigating whether the same mechanism operates in other neurological diseases.
The open question is whether a drug that protects the extracellular matrix, or specifically quiets microglial MyD88 signaling, could be developed and shown to reduce brain injury in people with alcohol use disorder without disrupting the immune surveillance microglia normally provide. That work has not been done. What this study establishes is the target and the mechanism, in mice, with a human tissue signal pointing in the same direction. Whether it translates into a treatment is the next test.
Source: https://neurosciencenews.com/alcohol-microglia-neuroscience-31311/
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