Effect of indoleamine dioxygenase-1 deficiency and kynurenine pathway inhibition on murine cerebral malaria
Introduction
Malaria remains an important cause of mortality and morbidity, particularly for children living in sub-Saharan Africa. Cerebral malaria (CM) can be a serious neurological complication arising from Plasmodium falciparum infection, with patients presenting with convulsions, impaired consciousness, coma and death (WHO, 2000). Murine models of malaria are important tools in studying the pathogenesis of malaria, with numerous clinical and histopathological similarities described between human and murine malaria (Hunt and Grau, 2003).
While the pathogenesis of CM is incompletely understood, indoleamine 2,3-dioxygenase (INDO or IDO-1), the initial and rate-limiting enzyme of the kynurenine pathway, is thought to be involved. IDO-1 is a redox-regulated enzyme (Thomas et al., 2001) that converts tryptophan to N-formylkynurenine, which is metabolised to kynurenine and a cascade of biologically active molecules. Recently we have identified and characterised a new isoform of IDO-1, indoleamine 2,3-dioxygenase-like protein 1 (INDOL1 or IDO-2) (Ball et al., 2007). The role of the kynurenine pathway has been examined previously in human (Dobbie et al., 2000, Medana et al., 2002, Medana et al., 2003) and murine (Sanni et al., 1998, Hansen et al., 2004) CM. IDO-1 activity is increased in the brain during CM in CBA mice (Sanni et al., 1998) and clear correlations have been drawn between CM and enhanced levels of kynurenine pathway metabolites, including the neuroprotectant kynurenic acid (KA), the neuroexcitotoxin quinolinic acid (QA) and the proinflammatory molecule picolinic acid (PA) (Sanni et al., 1998, Dobbie et al., 2000, Medana et al., 2002, Medana et al., 2003). IDO-2 also might contribute to the pathogenesis of CM, as it shares similarities with IDO-1, including the ability to catalyse the conversion of tryptophan to kynurenine (Ball et al., 2007).
The endothelium is the predominant site of IDO-1 expression during malaria (Hansen et al., 2004) and this is may be part of the host protective response to Plasmodium infection (Hunt et al., 2006), since IDO-1 activity and immunoreactivity, as well as increased levels of kynurenine metabolites, are also found in the brain during the late-stages of a non-cerebral form of malaria (NCM) (Sanni et al., 1998, Hansen et al., 2004). Metabolites that might have tissue protective effects include the neuroprotectant KA, the NAD needed to counter the failure of aerobic glucose metabolism seen in CM (Rae et al., 2004), and the antioxidant 3-hydroxyanthranilic acid (Christen et al., 1990) given that reactive oxygen species have been proposed to be involved in the pathogenesis of malaria (Clark et al., 1986). The source of such reactive oxygen species is not, however, NADPH oxidase (Potter et al., 2005). An imbalance in the ratio of QA:KA, with heightened increases in QA levels compared with KA, has been described in CM in the CBA strain of mice (Sanni et al., 1998). Moreover, chemical inhibition of kynurenine-3-hydroxylase can confer protection against murine CM through its ability to increase KA and decrease PA levels in the brain (Clark et al., 2005). Overall, these studies suggest an important role for IDO-1 in the pathogenesis of CM, and are reinforced by the relationship between IDO-1 and IFN-γ, which is both an important mediator of CM and an inducer of IDO-1 (Grau et al., 1989, Sanni et al., 1998).
While a causal link between CM and these neuroactive metabolites of the kynurenine pathway has been hypothesised, the recent generation of IDO-1−/− mice (Mellor et al., 2003) allows direct experimental evaluation of the role of IDO-1 in murine CM. Moreover, Ro 61-8048, a compound that is able to inhibit kynurenine-3-hydroxylase, offers further insight into the influence of kynurenine pathway metabolites on the pathogenesis of murine CM. Here we describe partial protection against CM in PbA-infected C57BL/6 mice that were administered Ro 61-8048 but not in mice genetically deficient in IDO-1. Significantly, increased levels of PA correlated with the development of murine CM in both experimental groups, and this occurred independently of compensatory increases in either Ido-2 or tryptophan dioxygenase (Tdo) mRNAs. Brain levels of KA and QA did not correlate with the development of murine CM. These results provide evidence for the involvement of peripheral sources of kynurenine pathway metabolites, for example PA, in the pathogenesis of CM in C57BL/6 mice.
Section snippets
Murine models of malaria
six- to eight- week-old female C57BL/6 (WT) and IDO-1−/− mice were housed in the Blackburn Animal House, University of Sydney and given food and water ad libitum. Inoculation of C57BL/6 mice (i.p.) with 1 × 106 Plasmodium berghei ANKA (PbA) parasitised red blood cells (courtesy of Prof. G. Grau, University of Sydney, Australia) is a well described model of murine CM, in which mice display neurological symptoms by days 6–7 p.i. (Ma et al., 1996). The parasite used has not been cloned and is
IDO-1−/− mice are not protected from murine CM
Susceptibility to murine CM was followed in C57BL/6 (WT) and IDO-1−/− mice after inoculation with PbA. All WT (n = 17) and IDO-1−/− (n = 15) mice developed murine CM by day 6 p.i., with similar levels of parasite burden and showing typical clinical signs of murine CM, including brain histopathological features (e.g. petechial haemorrhages, oedema and leukocyte adherence; data not shown). Uninfected mice did not show these features. Although Ido-1 mRNA is up-regulated in WT kidney and liver tissue
Discussion
The results from this study show that IDO-1 is not directly involved in the pathogenesis of CM in C57BL/6 mice, since genetic deficiency in IDO-1 did not confer any protection against CM, with mice developing similar clinical and histopathological features to their WT counterparts. Levels of KA were not found to increase during CM in these mice, in contrast to the CBA/T6 strain (Sanni et al., 1998), and were considerably reduced in IDO-1−/− mice. On the other hand, QA was found to increase
Acknowledgements
We thank Cacang Suarna for help with the KA assays. This work was supported by Grants from the National Health and Medical Research Council of Australia and Australian Research Council to NH. JM was supported by an Australian Postgraduate Award. HB was a Rolf Edgar Lake Research Fellow of the Faculty of Medicine, University of Sydney.
References (45)
- et al.
Characterization of an indoleamine 2, 3-dioxygenase-like protein found in humans and mice
Gene
(2007) - et al.
Picolinic acid blocks the neurotoxic but not the neuroexcitant properties of quinolinic acid in the rat brain: Evidence from turning behaviour and tyrosine hydroxylase immunohistochemistry
Neuroscience
(1994) - et al.
Pattern of cytokine gene expression in brains of mice protected by picolinic acid against lethal intracerebral infection with Candida albicans
J. Neuroimmunol.
(1994) - et al.
Kynurenine 3-mono-oxygenase activity and neurotoxic kynurenine metabolites increase in the spinal cord of rats with experimental allergic encephalomyelitis
Neuroscience
(2001) - et al.
Quinolinic acid formation in immune-activated mice. studies with (m-nitrobenzoyl)-alanine (mNBA) and 3, 4-dimethoxy-[-N-4-(-3-nitrophenyl) thiazol-2yl]-benzenesulfonamide (Ro 61–8048), two potent and selective inhibitors of kynurenine hydroxylase
Neuropharmacology
(1999) - et al.
Oxygen-derived free radicals in the pathogenesis of parasitic disease
Adv. Parasitol.
(1986) - et al.
Action of picolinic acid and structurally related pyridine carboxylic acids on quinolinic acid-induced cortical cholinergic damage
Brain Res.
(1992) - et al.
Increased expression of indoleamine 2, 3-dioxygenase in murine malaria infection is predominantly localised to the vascular endothelium
Int. J. Parasitol.
(2004) - et al.
Immunopathogenesis of cerebral malaria
Int. J. Parasitol.
(2006) - et al.
Cytokines: accelerators and brakes in the pathogenesis of cerebral malaria
Trends Immunol.
(2003)
Regulation of nitric-oxide synthase mRNA expression by interferon-γ and picolinic acid
J. Biol. Chem.
A role for Fas-Fas ligand interactions during the late-stage neuropathological processes of experimental cerebral malaria
J. Neuroimmunol.
A mechanism for increased quinolinic acid formation following acute systemic immune stimulation
J. Biol. Chem.
Concurrent quantification of quinolinic, picolinic, and nicotinic acids using electron-capture negative-ion gas chromatography-mass spectrometry
Anal. Biochem.
Role of human brain microvascular endothelial cells during central nervous system infection. Significance of indoleamine 2, 3-dioxygenase in antimicrobial defence and immunoregulation
Thromb. Haemost.
Cyclooxygenase-2 in the pathogenesis of murine cerebral malaria
J. Infect. Dis.
The tryptophan catabolite picolinic acid selectively induces the chemokines macrophage inflammatory protein-1α and -1β in macrophages
J. Immunol.
Antioxidant activities of some tryptophan metabolites: possible implication for inflammatory diseases
Proc. Natl. Acad. Sci. USA
Prolonged survival of a murine model of cerebral malaria by kynurenine pathway inhibition
Infect. Immun.
Kynurenine hydroxylase inhibitors reduce ischemic brain damage: studies with (m-nitrobenzoyl)-alanine (mNBA) and 3, 4-dimethoxy-[-N-4-(nitrophenyl)thiazol-2yl]-benzenesulfonamide (Ro 61–8048) in models of focal or global brain ischemia
J. Cereb. Blood Flow Metab.
Immunological aspects of cerebral lesions in murine malaria
Clin. Exp. Immunol.
Cerebrospinal fluid studies in children with cerebral malaria: an excitotoxic mechanism?
Am. J. Trop. Med. Hyg.
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Present address: Department of Medicine, McGill University, Montreal, Que., Canada.