Affiliations: [a] Department of Molecular Neurobiology, University of Groningen, Groningen, The Netherlands | [b] Department of Psychiatry, University Medical Center Groningen, Groningen, The Netherlands | [c] Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, Groningen, The Netherlands | [d] Department of Laboratory Medicine, University Medical Center Groningen, Groningen, The Netherlands
Correspondence:
[*]
Correspondence to: U.L.M. Eisel, Department of Molecular Neurobiology, Center for Life Sciences, Nijenborgh 7, 9747 AG Groningen, The Netherlands. Tel.: +31 50 363 2366; Fax: +31 50 363 2331; E-mail: [email protected].
Abstract: Indoleamine 2,3-dioxygenase (IDO), an enzyme which is activated by pro-inflammatory cytokines, has been suggested as a potential link between neuroinflammatory processes in neurodegenerative diseases (like Alzheimer's disease) and depression. The present study aimed to determine whether neuroinflammation-induced increased IDO levels in the mammalian brain will lead to depressive-like behavior. Neuroinflammation was initiated in mice by a single intracerebroventricular injection of lipopolysaccharide (LPS). Cerebral inflammation was monitored 1, 2, 3 and 4 days after the injection with small-animal positron emission tomography (PET) using the inflammatory marker [11C]-PK11195. In the presence or absence of systemically applied 1-methyl-tryptophan (1-MT), a competitive IDO-inhibitor, we assessed the development of depressive-like behavioral symptoms in parallel with IDO expression and activity. The PK11195 PET signal reached a highly significant peak 3 days after LPS injection, while these animals displayed a significant increase of depressive-like behavior in the forced swim test compared to vehicle-injected animals. These findings were paralleled by a significant increase of IDO in the brainstem, and an increased kynurenine/tryptophan ratio in the serum. Moreover, we report here for the first time, that inhibition of IDO by 1-MT in centrally induced neuroinflammation under experimental conditions can prevent the development of depressive-like behavior.
