Essential role of microglial transforming growth factor-β1 in antidepressant actions of ( R )-ketamine and the novel antidepressant TGF-β1

In rodent models of depression, ( R )-ketamine has greater potency and longer-lasting antidepressant effects than ( S )-ketamine; however, the precise molecular mechanisms underlying the antidepressant actions of ( R )-ketamine remain unknown. Using RNA-sequencing analysis, we identified novel molecular targets that contribute to the different antidepressant effects of the two enantiomers. Either ( R )-ketamine (10 mg/kg) or ( S )-ketamine (10 mg/kg) was administered to susceptible mice after chronic social defeat stress (CSDS). RNA-sequencing analysis of prefrontal cortex (PFC) and subsequent GSEA (gene set enrichment analysis) revealed that transforming growth factor (TGF)-β signaling might contribute to the different antidepressant effects of the two enantiomers. ( R )-ketamine, but not ( S )-ketamine, ameliorated the reduced expressions of Tgfb1 and its receptors ( Tgfbr1 and Tgfbr2 ) in the PFC and hippocampus of CSDS susceptible mice. Either pharmacological inhibitors (i.e., RepSox and SB431542) or neutralizing antibody of TGF-β1 blocked the antidepressant effects of ( R )-ketamine in CSDS susceptible mice. Moreover, depletion of microglia by the colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX3397 blocked the antidepressant effects of ( R )-ketamine in CSDS susceptible mice. Similar to ( R )-ketamine, the recombinant TGF-β1 elicited rapid and long-lasting antidepressant effects in animal models of depression. Our data implicate a novel microglial TGF-β1-dependent mechanism underlying the antidepressant effects of ( R )-ketamine in rodents with depression-like phenotype. Moreover, TGF-β1 and its receptor agonists would likely constitute a novel rapid-acting and sustained antidepressant in humans.