PT  - JOURNAL ARTICLE
AU  - Ria Göttert
AU  - Pawel Fidzinski
AU  - Larissa Kraus
AU  - Ulf Christoph Schneider
AU  - Martin Holtkamp
AU  - Matthias Endres
AU  - Karen Gertz
AU  - Golo Kronenberg
TI  - Lithium inhibits tryptophan catabolism via the inflammation-induced kynurenine pathway in human microglia
AID  - 10.1101/2020.11.24.388470
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.11.24.388470
4099  - http://biorxiv.org/content/early/2020/11/24/2020.11.24.388470.short
4100  - http://biorxiv.org/content/early/2020/11/24/2020.11.24.388470.full
AB  - Activation of the kynurenine pathway may lead to depletion of the serotonin precursor tryptophan, which has been implicated in the neurobiology of depression. This study describes a mechanism whereby lithium inhibits inflammatory tryptophan breakdown. Upon activation, immortalized human microglia showed a robust increase in indoleamine-2,3-dioxygenase (IDO1) mRNA transcription, IDO1 protein expression, and activity. Further, chromatin immunoprecipitation verified enriched binding of both STAT1 and STAT3 to the IDO1 promoter. Lithium counteracted these effects, increasing inhibitory GSK3βS9 phosphorylation and reducing STAT1S727 and STAT3Y705 phosphorylation levels in activated cells. Experiments in primary human microglia and human induced pluripotent stem cell (hiPSC)-derived microglia corroborated lithium’s effects. Moreover, IDO activity was reduced by GSK3 inhibitor SB-216763 and STAT inhibitor nifuroxazide via downregulation of P-STAT1S727 and P-STAT3Y705. Our study demonstrates that lithium inhibits the inflammatory kynurenine pathway in the microglia compartment of the human brain.Competing Interest StatementThe authors have declared no competing interest.