Carriers of the so-called ‘Alzheimer’s gene’ (apoE4) comprise 65% of all Alzheimer's cases. A new study helps us understand why that’s true. Genetically engineered mice reveal that apoE4 is associated with the loss of GABAergic interneurons in the hippocampus. This is consistent with low levels of GABA (produced by these neurons) typically found in Alzheimer’s brains. This loss was associated with cognitive impairment in the absence of amyloid beta accumulation, demonstrating it is an independent factor in the development of this disease.
The relationship with the other major characteristic of the Alzheimer’s brain, tau tangles, was not independent. When the mice’s tau protein was genetically eliminated, the mice stopped losing GABAergic interneurons, and did not develop cognitive deficits. Previous research has shown that suppressing tau protein can also prevent amyloid beta from causing memory deficits.
Excitingly, daily injections of pentobarbital, a compound that enhances GABA action, restored cognitive function in the mice.
The findings suggest that increasing GABA signaling and reducing tau are potential strategies to treat or prevent apoE4-related Alzheimer's disease.
(2010). Apolipoprotein E4 Causes Age- and Tau-Dependent Impairment of GABAergic Interneurons, Leading to Learning and Memory Deficits in Mice.
J. Neurosci.. 30(41), 13707 - 13717.