Current monoaminergic antidepressants demonstrate limited efficacy and delayed onset, necessitating novel treatment strategies. Previous studies have identified salt-inducible kinase 1 (SIK1) in the paraventricular nucleus (PVN) as an important regulator of depression pathogenesis by controlling nuclear translocation of cAMP response element-binding protein (CREB)-regulated transcription coactivator 1 (CRTC1) and activity of the hypothalamus-pituitary-adrenal (HPA) axis. The current study investigated the antidepressant-like efficacy of phanginin A, a newly discovered potent SIK1 activator, in male C57BL/6 J mice.

Two well-validated depression models (chronic social defeat stress and chronic unpredictable mild stress) were established to examine the efficacy of phanginin A treatment against chronic stress-induced HPA hyperactivity and depression-like behaviors including desperate mood, anhedonia, and social avoidance. Western blotting, immunofluorescence, and co-immunoprecipitation were then conducted to evaluate the biological changes in not only the SIK1-CRTC1 signaling in PVN neurons but also the hippocampal brain derived neurotrophic factor (BDNF) signaling and adult neurogenesis among all groups. To further determine the antidepressant mechanism of phanginin A, model mice were re-examined following genetic knockdown of SIK1 in the PVN.

Phanginin A administration suppressed depression-like behaviors in both models, normalized chronic stress-induced alteration in the SIK1-CRTC1 signaling in PVN neurons, and rescued chronic stress-induced impairments in hippocampal BDNF signaling and adult neurogenesis. Knockdown of SIK1 in the PVN abrogated the antidepressant-like actions of Phanginin A in male mice.

Our findings further establish SIK1 in the PVN as an antidepressant target and support phanginin A as a potential antidepressant candidate.