Elsevier

Brain Research

Volume 1217, 27 June 2008, Pages 78-85
Brain Research

Research Report
Localization and spatiotemporal expression of IDO following transient forebrain ischemia in gerbils

https://doi.org/10.1016/j.brainres.2008.02.067Get rights and content

Abstract

Indoleamine 2,3-dioxygenase (IDO) is the rate-limiting enzyme in the kynurenine pathway that converts l-tryptophan to l-kynurenine. Transient forebrain ischemia initiates a series of cellular events that lead to the delayed neuronal degeneration of several brain regions. The goal of this study was to determine the localization of IDO in gerbil brain, and analyze the spatiotemporal expression of IDO in a transient forebrain ischemic model. Expression of IDO in the normal gerbil brain was observed by using immunohistochemistry. Time-course of the expression of IDO following transient forebrain ischemic gerbils was examined by immunohistochemistry, combined with hematoxylin and eosin staining for morphological analysis, and in situ terminal dUTP-biotin nick end labeling of DNA fragments (TUNEL) method. In normal gerbils, IDO immunostaining was observed in thalamus, hypothalamus and amygdaloid nucleus. IDO expression was negative in the cingulate cortex, hippocampal CA1 region and parietal cortex. Following transient ischemia, we observed a time-dependent increase of IDO expression in CA1, cingulate cortex and hypothalamus. The peak of IDO expression in CA1 and cingulate cortex occurred at 48 h after ischemic insult and diminished by 2 weeks. TUNEL staining was observed only in the CA1 region at 72 and 96 h after transient ischemia. Thus, IDO protein is present in specific regions in gerbil brain, and dynamic changes of IDO expression was observed in some neurons following transient ischemia.

Introduction

Indoleamine 2,3-dioxygenase (IDO) is the rate-limiting enzyme for the tryptophan catabolism to kynurenine. IDO has long been of interest because it catabolizes l-tryptophan, leading to increases in the levels of metabolites, such as kynurenine and quinolinic acid (Saito et al., 1991). Growing evidence indicates that some of these metabolites are involved in the neurotoxicity associated with several brain disorders, such as Huntington's disease (Stoy et al., 2005), Parkinson's disease (Ogawa et al., 1992) and Alzheimer's disease (Guillemin and Brew, 2002), as well as in hepatic encephalopathy (Pearson and Reynolds, 1991) and glutaryl-CoA dehydrogenase deficiency (Heyes, 1987). However, the pathophysiology of the brain damage in these neurodegenerative disorders is not completely understood.

Transient cerebral ischemia initiates a process of cellular events that leads to delayed neuronal degeneration of several brain regions both in humans and in animal models (Pulsinelli et al., 1982, Petito and Pulsinelli, 1984, Horn and Schlote, 1992). Furthermore, a brief episode of ischemia causes “delayed neuronal death” in the CA1 sector of the hippocampus (Kirino, 1982). Accumulating evidence has indicated that the post-ischemic DNA fragmentation in the hippocampal CA1 area in experimental ischemic models is a key phenomenon for the delayed neuronal death, and is considered as apoptosis (Heron et al., 1993, Iwai et al., 1995, Hara et al., 1998a).

It has been reported that quinolinic acid and the kynurenine pathway enzyme, IDO were increased in several brain regions following transient forebrain ischemia (Saito et al., 1993a, Saito et al., 1993b). However, the specific brain localization of IDO has not yet been identified, in either normal brain or following transient forebrain ischemia. Of note, it has been reported that IDO is detectable only in microglia and astrocytes (Heyes et al., 1996), not in neurons (Schwarcz and Pellicciari, 2002), but more recently IDO has been reported as being present in human fetal neurons (Guillemin et al., 2005) and in murine neurons with upregulation in hippocampus by IFNγ (Roy et al., 2005). Thus, exact localization of IDO in central nervous system is still remains to be established. In the present study, we demonstrated the precise localization of IDO in normal gerbil brain by immunohistochemical detection, and secondly demonstrated the time-course changes of IDO following transient forebrain ischemia.

Section snippets

Localization of IDO by immunohistochemistry

IDO localization in normal gerbil brain was detected by immunohistochemistry. The expression areas of IDO were observed in normal thalamus (Figs. 1E and F), hypothalamus (Figs. 1I and J) and amygdaloid nucleus (Figs. 1K and L). However, IDO expressions were negative in the cingulate cortex (Figs. 1A and B), hippocampal CA1 sector (Figs. 1C and D) and parietal cortex (Figs. 1G and H).

Interestingly, time-dependent increase of IDO expression following transient ischemia was observed in CA1,

Discussion

The present immunohistochemical study showed that IDO staining was observed in thalamus, hypothalamus and amygdaloid nucleus of normal gerbil brain. The gerbil, which lacks posterior communication arteries necessary to complete the circle of Willis, commonly shows delayed neuronal death mainly in the CA2 pyramidal area of the hippocampus after 5 min of bilateral carotid occlusion (Kirino, 1982, Iwai et al., 1995).

Increased expression of IDO following transient forebrain ischemia was observed in

Animals

Male Mongolian gerbils, weighing 65–75 g, were subjected to severe forebrain ischemia as described previously (Hara et al., 1998b, Hara et al., 1999, Niwa et al., 1998). Briefly, the bilateral common carotid arteries were isolated through an anterior midcervical incision and occluded with microclips. After 5 min of forebrain ischemia, the clips were removed. Rectal temperatures were maintained at 37 ± 0.3 °C using a heating pad from the induction of anesthesia until 3 h following ischemia.

Acknowledgments

We would like to thank Kyoko Takahashi and Ayako Suga for their excellent technical assistance.

References (34)

  • T. Ohnishi et al.

    Indoleamine 2,3-dioxygenase. Potassium superoxide as substrate

    J. Biol. Chem.

    (1977)
  • S.J. Pearson et al.

    Determination of 3-hydroxykynurenine in human brain and plasma by high-performance liquid chromatography with electrochemical detection. Increased concentrations in hepatic encephalopathy

    J. Chromatogr.

    (1991)
  • Z.H. Qin et al.

    Stimulation of N-methyl-d-aspartate receptors induces apoptosis in rat brain

    Brain Res.

    (1996)
  • RoyE.J. et al.

    Neuronal localization of indoleamine 2,3-dioxygenase in mice

    Neurosci. Lett.

    (2005)
  • K. Saito et al.

    Chronic effects of gamma-interferon on quinolinic acid and indoleamine-2,3-dioxygenase in brain of C57BL6 mice

    Brain Res.

    (1991)
  • Y. Gavrieli et al.

    Identification of programmed cell death in situ via specific labeling of nuclear DNA fragmentation

    J. Cell Biol.

    (1992)
  • G.J. Guillemin et al.

    Implications of the kynurenine pathway and quinolinic acid in Alzheimer's disease

    Redox Rep.

    (2002)
  • Cited by (12)

    • Indoleamine 2,3-dioxygenase 1 is upregulated in activated microglia in mice cerebellum during acute viral encephalitis

      2014, Neuroscience Letters
      Citation Excerpt :

      However, more recently IDO has been reported as being present in human fetal neurons [15] and in murine hippocampal neurons, where levels are upregulated by interferon (IFN) [16]. We have reported that transient forebrain ischemia in gerbils produces tissue/cell-specific and time-dependent expressions of IDO in hippocampal CA1, cingulate cortex and hypothalamus, which was not related to glial cell activation [17]. Thus, exact localization of IDO in central nervous system still remains to be established.

    • PBN fails to suppress in delayed neuronal death of hippocampal CA1 injury following transient forebrain ischemia in gerbils

      2012, Neuroscience Letters
      Citation Excerpt :

      Thus, the effects of PBN against delayed neuronal death are contradictory or species-dependent. Furthermore, we have shown that radical scavengers failed to reduce the neuronal injury following transient forebrain ischemia in gerbils [35]. Interestingly, it has been reported that oxidative damage contributes to neuronal injury in transient forebrain ischemia in gerbils [1].

    • Inflammatory stimuli reduce survival of serotonergic neurons and induce neuronal expression of indoleamine 2,3-dioxygenase in rat dorsal raphe nucleus organotypic brain slices

      2011, Neuroscience
      Citation Excerpt :

      Activation of IDO by for example, pro-inflammatory stimuli leads to depletion of tryptophan and to a reduced synthesis of serotonin in the brain, which may play a role in depression (Saito et al., 1991; Wichers and Maes, 2002). IDO is ubiquitously expressed in the brain and periphery (Potula et al., 2005; Roy et al., 2005; Guillemin et al., 2005a; Taguchi et al., 2008; Dai and Zhu, 2010), although the reports on cellular IDO expression are very divergent (Roy et al., 2005; Guillemin et al., 2005b). Here, we found a granular, cytoplasmic IDO staining in neurons, including expression in serotonergic neurons, but not in astrocytes or microglia.

    View all citing articles on Scopus
    View full text