Li-Huei Tsai of the Massachusetts Institute of Technology and colleagues have discovered that histone deacetylase inhibitors (HDACis) may be a permanent fix for post-traumatic stress disorder (PTSD) and other anxiety disorders in research that was published in the Jan. 16, 2014, edition of the journal Cell.
The researchers note that present therapies like exposure-based therapy, which involves exposing patients to fear-evoking thoughts or events in a safe environment, work for traumatic events that occurred in a recent time frame but have shown little success in traumatic events that occurred in the relatively distant past that produce PTSD.
The researchers demonstrated their discovery in a mouse model. Mice were conditioned to produce a fear response that was the result of electric shock. The mice were trained to associate the fear with the sound of a bell. The mice demonstrated the fear response without electric shock when the bell sounded.
The researchers found that conditioning similar to exposure-based therapy stopped the mice from exhibiting a fear response but the therapy only worked in mice 24 hours after the fear conditioning had been learned. The researchers consider the fear behavior to have produced a genetic change.
Addition of HDACis to the therapy produced the capacity for mice to unlearn a fear response that had been conditioned in the mice for a month or longer. The HDACis are thought to activate genes that produce the learning of new memories to replace fear memories.
Human trials are planned. Histone deacetylase inhibitors have been used successfully in cancer treatment with minimal side effects.