Paroxetine modulates immune responses by activating a JAK2/STAT3 signaling pathway

Paroxetine, a representative of serotonin reuptake inhibitors, has recently gained attention due to its anti-inflammatory properties. However, underlying mechanisms responsible for its immunosuppressive effects remain to be unveiled. To understand the responsible signaling mechanisms, we examined paroxetine's effect on the Janus kinase 2-signal transducer and activator of transcription 3 (JAK2-STAT3) signaling pathway on lipopolysaccharide + phytohemagglutinin-induced human peripheral blood mononuclear cells culture. We also evaluate the possible dependency of paroxetine immunomodulation effects on the 5-HT system of immune cells. Our results indicated that paroxetine attenuates proinflammatory cytokine production (interleukin-1β [IL-1β], IL-17, and tumor necrosis factor-α) and increases expression of IL-10 and JAK2/STAT3 evidence for macrophages polarization to M2 subset and functional dendritic cells depletion. In conclusion, paroxetine can exert its anti-inflammatory effects via both the 5-HT systems present in immune cells and the JAK2-STAT3 pathway. Our results also suggest that paroxetine exerted its immunosuppressive effects partially via serotonin. Nonetheless, JAK2/STAT3-modulated paroxetine effects were independent of serotonin, hence sufficiently applicable for inflammation repression.