Background: Forkhead box, class O (FoxO) transcription factors play important roles in cell fate, differentiation, survival, and stress regulation. A subtype of mammalian FoxO transcription factors, FoxO3a, is widely distributed in the brain, and its activity is regulated by neurotrophins, such as brain-derived neurotrophic factor (BDNF), resulting in transcriptional inactivation of FoxO3a. Searching for therapeutic targets downstream of BDNF signaling will facilitate the development of new treatment approaches for mood disorders.
Methods: Transcriptional activity, target gene expression, and protein levels of FoxO3a were measured in cultured cells and mouse brain after lithium treatment.
Results: Lithium significantly reduced FoxO3a transcriptional activity and gene expression. The effect of lithium may be the result of a significant reduction of the FoxO3a protein levels in both the cytosol and nucleus that was mediated by an Akt-independent action. More importantly, this effect of lithium was observed in cells and mouse brain after therapeutically relevant lithium treatments.
Conclusions: Lithium, an established treatment for mood disorders, has a prominent effect on FoxO3a transcriptional activity and the effect is likely therapeutically relevant. These results warrant further study to identify if FoxO3a is a transcriptional target in the neuropathology and treatment of mood disorders.