eIF4E phosphorylation mediated LPS induced depressive-like behaviors via ameliorated neuroinflammation and dendritic loss.

The translational defect has emerged as a common feature of neurological disorders. Studies have suggested that alterations between opposing and balanced synaptic protein synthesis and turnover processes could lead to synaptic abnormalities, followed by depressive symptoms. Further studies link this phenomenon with eIF4E and TrkB/BDNF signaling. However, the interplay between the eIF4E and TrkB/BDNF signaling in the presence of neuroinflammation is yet to be explored. To illuminate the role of eIF4E activities within LPS-induced neuroinflammation and depression symptomology, we applied animal behavioral, biochemical, and pharmacological approaches. In addition, we sought to determine whether eIF4E dysregulated activities correlate with synaptic protein loss via the TrkB/BDNF pathway. Our results showed that LPS administration induced depressive-like behaviors, accompanied by neuroinflammation, reduced spine numbers, and synaptic protein dysregulation. Concurrently, LPS treatment enhanced eIF4E phosphorylation and TrkB/BDNF signaling defects. However, eFT508 treatment rescued the LPS-elicited neuroinflammation and depressive behaviors, as well as altered eIF4E phosphorylation, synaptic protein expression, and TrkB/BDNF signaling. The causal relation of eIF4E with BDNF signaling was further explored with TrkB antagonist K252a, which could reverse the effects of eFT508, validating the interplay between the eIF4E and TrkB/BDNF signaling in regulating depressive behaviors associated with neuroinflammation via synaptic protein translational regulation. In conclusion, our results support the involvement of eIF4E-associated translational dysregulation in synaptic protein loss via TrkB/BDNF signaling, eventually leading to depressiven-like behaviors upon inflammation-linked stress.