Hippocampal GPR35 is involved in the depression-like behaviors induced by inflammation and mediates the antidepressant effects of fluoxetine in mice

Abstract

Background

Neuroinflammation plays a pivotal role in the pathogenesis of depression. G protein-coupled receptor 35 (GPR35) is expressed in the brain and plays a role in regulating inflammatory processes. However, its specific role in depression remains unclear. Herein, we investigate the role of GPR35 in depressive behaviors induced by lipopolysaccharide (LPS) in mice.

Methods

We employed an LPS-induced depression mouse model and conducted behavioral tests, molecular analyses, and morphological assessments, along with chemogenetic techniques, to investigate the role of GPR35 in depression.

Results

Our results showed a significant increase in GPR35 expression in the brain of LPS-treated mice. Both pharmacological inhibition and genetic knockdown of GPR35 alleviated LPS-induced depressive-like behaviors by mitigating neuroinflammation, oxidative stress, synaptic plasticity deficits, and TLR4/NF-κB signaling in mice. Conversely, pharmacological activation of GPR35 notably exacerbated LPS-induced depressive-like behaviors in mice. Additionally, the GPR35 antagonist ML-145 effectively prevented LPS-induced inflammation responses in BV-2 microglia cells. Moreover, fluoxetine treatment effectively mitigated the upregulation of hippocampal GPR35 expression induced by LPS in mice. However, administration of the GPR35 agonist zaprinast reversed the antidepressant effects of fluoxetine. Chemogenetic activation of hippocampal glutamatergic neurons attenuated LPS-induced depression-like behaviors, accompanied by decreased GPR35 expression.

Conclusion

Hippocampal GPR35 is closely associated with depressive behaviors in the inflammatory model, highlighting its potential as a therapeutic target for antidepressant drug development.