Protein phosphatase 2A inhibitors: a possible pharmacotherapy for benzodiazepine dependence.

Objectives: Benzodiazepines (BZDs) activate the γ-aminobutyric acid (GABA) subtype A (GABAA) receptors, and thus are widely used medicines for the treatment of anxiety and insomnia. For chronic use, tolerance to BZDs is a major problem. Patients with chronic insomnia that develop tolerance to BZDs lose therapeutic effects but also potentially suffer from BZD dependence resulting in BZD withdrawal. The development of such treatments is important for the appropriate use of BZDs.

Methods: Research articles regarding investigation of BZD dependence were searched on PubMed, Embase, and Scopus databases using keywords "benzodiazepine", "dependence", "treatment".

Key findings: When BZDs are taken chronically, continuous GABAA binding results in up-regulation of α-amino-3-hydroxy-5-methyl-4-lisoxazolepropionic acid (AMPA) glutamate receptor function and release of brain-derived neurotrophic factor (BDNF). Released BDNF binds to its specific receptor tropomyosin-related kinase receptor B (TrkB). Enhanced BDNF-TrkB signaling activates protein phosphatase 2A (PP2A). Activated PP2A dephosphorylates GABAA receptors, resulting in the downregulation of the GABAA receptor function. Reduced GABAA receptor function augments long-term potentiation (LTP), AMPA-mediated glutamatergic neuroplasticity, by reducing LTP inhibition by GABAA receptor function. Augmented LTP enhances extreme anxiety, which leads to BZD dependence.

Conclusion: Therefore, iInhibiting dephosphorylation of the GABAA receptor by PP2A, PP2A inhibitors could reduce LTP and anxiety, restoring BZD effectiveness and resulting in possible therapeutic effects for BZD dependence.