Limits...
Central administration of lipopolysaccharide induces depressive-like behavior in vivo and activates brain indoleamine 2,3 dioxygenase in murine organotypic hippocampal slice cultures.

Fu X, Zunich SM, O'Connor JC, Kavelaars A, Dantzer R, Kelley KW - J Neuroinflammation (2010)

Bottom Line: In accordance with the in vivo data, addition of LPS (10 ng/ml) to the medium of OHSCs induced steady-state expression of mRNA transcripts for IDO that peaked at 6 h and translated into increased IDO enzymatic activity within 8 h post-LPS.This activation of IDO by direct application of LPS was preceded by synthesis and secretion of TNFalpha and IL-6 protein and activation of iNOS while IFN gamma expression was undetectable.Targeting IDO itself may provide a novel therapy for inflammation-associated depression.

View Article: PubMed Central - HTML - PubMed

Affiliation: Integrative Immunology and Behavior Program, Department of Animal Sciences, College of ACES, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.

ABSTRACT

Background: Transient stimulation of the innate immune system by an intraperitoneal injection of lipopolysaccharide (LPS) activates peripheral and central expression of the tryptophan degrading enzyme indoleamine 2,3 dioxygenase (IDO) which mediates depressive-like behavior. It is unknown whether direct activation of the brain with LPS is sufficient to activate IDO and induce depressive-like behavior.

Methods: Sickness and depressive-like behavior in C57BL/6J mice were assessed by social exploration and the forced swim test, respectively. Expression of cytokines and IDO mRNA was measured by real-time RT-PCR and cytokine protein was measured by enzyme-linked immunosorbent assays (ELISAs). Enzymatic activity of IDO was estimated as the amount of kynurenine produced from tryptophan as determined by high pressure liquid chromatography (HPLC) with electrochemical detection.

Results: Intracerebroventricular (i.c.v.) administration of LPS (100 ng) increased steady-state transcripts of TNFalpha, IL-6 and the inducible isoform of nitric oxide synthase (iNOS) in the hippocampus in the absence of any change in IFN gamma mRNA. LPS also increased IDO expression and induced depressive-like behavior, as measured by increased duration of immobility in the forced swim test. The regulation of IDO expression was investigated using in situ organotypic hippocampal slice cultures (OHSCs) derived from brains of newborn C57BL/6J mice. In accordance with the in vivo data, addition of LPS (10 ng/ml) to the medium of OHSCs induced steady-state expression of mRNA transcripts for IDO that peaked at 6 h and translated into increased IDO enzymatic activity within 8 h post-LPS. This activation of IDO by direct application of LPS was preceded by synthesis and secretion of TNFalpha and IL-6 protein and activation of iNOS while IFN gamma expression was undetectable.

Conclusion: These data establish that activation of the innate immune system in the brain is sufficient to activate IDO and induce depressive-like behavior in the absence of detectable IFN gamma. Targeting IDO itself may provide a novel therapy for inflammation-associated depression.

Show MeSH

Related in: MedlinePlus

Time course of cell death in OHSCs. The OHSCs were treated with PI at different time points after the start of culture. Red fluorescence indicates the dead-cell population using PI staining. Bars represent the mean ± SEM (n = 3 in each group). Bars labeled with different letters (a, b or c) are significantly different from each other at p < 0.05. Scale bar = 500 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2921406&req=5

Figure 4: Time course of cell death in OHSCs. The OHSCs were treated with PI at different time points after the start of culture. Red fluorescence indicates the dead-cell population using PI staining. Bars represent the mean ± SEM (n = 3 in each group). Bars labeled with different letters (a, b or c) are significantly different from each other at p < 0.05. Scale bar = 500 μm.

Mentions: The viability of OHSCs was determined by PI staining [44]. As shown in Fig. 4, dead/dying cells could be detected in the dentate gyrus (DG), CA1 and CA3 regions (p < 0.01) during the first 3 days of OHSCs culture. This was followed by a gradual decline in the proportion of PI-positive cells. Quantitative analysis confirmed that PI uptake significantly increased on day 3 (p < 0.01) and then remained at rather low levels from days 7 through 14. The OHSCs responded very well to LPS at day 10 (Fig. 3), so the decline in proinflammatory cytokine expression that occurred with increasing time in culture was very unlikely to have been caused by cell death. Collectively, results of these experiments confirm that transversal slicing of the hippocampus causes an acute inflammatory response. These data also establish that OHSCs almost entirely recover from the explantation procedure within 7 days.


Central administration of lipopolysaccharide induces depressive-like behavior in vivo and activates brain indoleamine 2,3 dioxygenase in murine organotypic hippocampal slice cultures.

Fu X, Zunich SM, O'Connor JC, Kavelaars A, Dantzer R, Kelley KW - J Neuroinflammation (2010)

Time course of cell death in OHSCs. The OHSCs were treated with PI at different time points after the start of culture. Red fluorescence indicates the dead-cell population using PI staining. Bars represent the mean ± SEM (n = 3 in each group). Bars labeled with different letters (a, b or c) are significantly different from each other at p < 0.05. Scale bar = 500 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2921406&req=5

Figure 4: Time course of cell death in OHSCs. The OHSCs were treated with PI at different time points after the start of culture. Red fluorescence indicates the dead-cell population using PI staining. Bars represent the mean ± SEM (n = 3 in each group). Bars labeled with different letters (a, b or c) are significantly different from each other at p < 0.05. Scale bar = 500 μm.
Mentions: The viability of OHSCs was determined by PI staining [44]. As shown in Fig. 4, dead/dying cells could be detected in the dentate gyrus (DG), CA1 and CA3 regions (p < 0.01) during the first 3 days of OHSCs culture. This was followed by a gradual decline in the proportion of PI-positive cells. Quantitative analysis confirmed that PI uptake significantly increased on day 3 (p < 0.01) and then remained at rather low levels from days 7 through 14. The OHSCs responded very well to LPS at day 10 (Fig. 3), so the decline in proinflammatory cytokine expression that occurred with increasing time in culture was very unlikely to have been caused by cell death. Collectively, results of these experiments confirm that transversal slicing of the hippocampus causes an acute inflammatory response. These data also establish that OHSCs almost entirely recover from the explantation procedure within 7 days.

Bottom Line: In accordance with the in vivo data, addition of LPS (10 ng/ml) to the medium of OHSCs induced steady-state expression of mRNA transcripts for IDO that peaked at 6 h and translated into increased IDO enzymatic activity within 8 h post-LPS.This activation of IDO by direct application of LPS was preceded by synthesis and secretion of TNFalpha and IL-6 protein and activation of iNOS while IFN gamma expression was undetectable.Targeting IDO itself may provide a novel therapy for inflammation-associated depression.

View Article: PubMed Central - HTML - PubMed

Affiliation: Integrative Immunology and Behavior Program, Department of Animal Sciences, College of ACES, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.

ABSTRACT

Background: Transient stimulation of the innate immune system by an intraperitoneal injection of lipopolysaccharide (LPS) activates peripheral and central expression of the tryptophan degrading enzyme indoleamine 2,3 dioxygenase (IDO) which mediates depressive-like behavior. It is unknown whether direct activation of the brain with LPS is sufficient to activate IDO and induce depressive-like behavior.

Methods: Sickness and depressive-like behavior in C57BL/6J mice were assessed by social exploration and the forced swim test, respectively. Expression of cytokines and IDO mRNA was measured by real-time RT-PCR and cytokine protein was measured by enzyme-linked immunosorbent assays (ELISAs). Enzymatic activity of IDO was estimated as the amount of kynurenine produced from tryptophan as determined by high pressure liquid chromatography (HPLC) with electrochemical detection.

Results: Intracerebroventricular (i.c.v.) administration of LPS (100 ng) increased steady-state transcripts of TNFalpha, IL-6 and the inducible isoform of nitric oxide synthase (iNOS) in the hippocampus in the absence of any change in IFN gamma mRNA. LPS also increased IDO expression and induced depressive-like behavior, as measured by increased duration of immobility in the forced swim test. The regulation of IDO expression was investigated using in situ organotypic hippocampal slice cultures (OHSCs) derived from brains of newborn C57BL/6J mice. In accordance with the in vivo data, addition of LPS (10 ng/ml) to the medium of OHSCs induced steady-state expression of mRNA transcripts for IDO that peaked at 6 h and translated into increased IDO enzymatic activity within 8 h post-LPS. This activation of IDO by direct application of LPS was preceded by synthesis and secretion of TNFalpha and IL-6 protein and activation of iNOS while IFN gamma expression was undetectable.

Conclusion: These data establish that activation of the innate immune system in the brain is sufficient to activate IDO and induce depressive-like behavior in the absence of detectable IFN gamma. Targeting IDO itself may provide a novel therapy for inflammation-associated depression.

Show MeSH
Related in: MedlinePlus