Creation of New Brain Cells Plays an Underappreciated Role in Alzheimer's Disease

A study published in the Journal of Neuroscience demonstrates that in hereditary forms of Alzheimer's disease, the creation of new brain cells can be disrupted by the brain's own immune cells, reports ScienceDaily . Some varieties of early-onset genetic Alzheimer's are triggered by mutations in the presenilin 1 (PS1) and presenilin 2 (PS2) genes. Previous research showed that when healthy mice are placed into an "enriched" environment where they can exercise, play, and interact, many more new neurons are created in the hippocampus — while mice carrying mutations to PS1 and PS2 do not exhibit the same uptake, and show signs of anxiety. When the mice were administered a drug that causes microglia to die, neurogenesis reverted to normal, and specimens with presenilin mutations placed into an enriched environment exhibited no memory deficits or anxiety, and generated a nominal number of new neurons. The implication is that microglia could be overplaying their immune system role in this instance. Alzheimer's typically causes inflammation in the microglia, so when they encounter newly-formed neurons with presenilin mutations, they may overreact and prematurely kill them off.