Characterization of the kynurenine pathway in NSC‐34 cell line: implications for amyotrophic lateral sclerosis

Abstract

J. Neurochem. (2011) 118, 816–825. Abstract Amyotrophic lateral sclerosis (ALS) is the most common type of motor neuron degenerative disease for which the aetiology is still unknown. The kynurenine pathway (KP) is a major degradative pathway of tryptophan ultimately leading to the production of NAD+ and is also one of the major regulatory mechanisms of the immune response. The KP is known to be involved in several neuroinflammatory disorders. Among the KP intermediates, quinolinic acid (QUIN) is a potent excitotoxin, while kynurenic acid and picolinic acid are both neuroprotectant. This study aimed to (i) characterize the components of the KP in NSC‐34 cells (a rodent motor neuron cell line) and (ii) assess the effects of QUIN on the same cells. RT‐PCR and immunocytochemistry were used to characterize the KP enzymes, and lactate dehydrogenase (LDH) test was used to assess the effect of QUIN in the absence and presence of NMDA receptor antagonists, kynurenines and 1‐methyl tryptophan. Our data demonstrate that a functional KP is present in NSC‐34 cells. LDH tests showed that (i) QUIN toxicity on NSC‐34 cells increases with time and concentration; (ii) NMDA antagonists, 2‐amino‐5‐phosphonopentanoic acid, MK‐801 and memantine, can partially decrease QUIN toxicity; (iii) kynurenic acid can decrease LDH release in a linear manner, whereas picolinic acid does the same but non‐linearly; and (iv) 1‐methyl tryptophan is effective in decreasing QUIN release by the rodent microglial cell line BV‐2 and thus protects NSC‐34 from cell death. There is currently a lack of effective treatment for ALS and our in vitro results provide a novel therapeutic strategy for ALS patients.

The kynurenine pathway and the brain: Challenges, controversies and promises

“…Thus, though observations of intracellular biochemical events or effector targets (receptors, ion channels) of kynurenines in neuronal and glial cultures continue to be useful, great caution must be exercised when extrapolating such data with regard to functional interactions between various cell types. The continuous biochemical dialogue between neurons and glia, and between intra- and extracellular compartments of these cells, as well as the presence in the CNS of a considerable number of small molecule regulators of kynurenine pathway metabolism (Chen et al, 2011; Guillemin et al, 2007; Guillemin et al, 2005), present far greater challenges to experimental reproducibility and interpretation than studies using dissociated cells of peripheral origin, such as hepatocytes or myocytes.…”

“…The generally accepted view holds that the main branch of the cascade, leading to 3-hydroxykynurenine, 3-hydroxyanthranilic acid, quinolinic acid and beyond, is normally contained in microglial cells whereas kynurenic acid is formed in astrocytes in a second, competing branch of the pathway (Figure 1). This conclusion is largely based on in vitro studies using individual cell types in culture (Chen et al, 2011; Chiarugi et al, 2001; Heyes et al, 1997; Kiss et al, 2003; Kocki et al, 2002) and, unfortunately to a far lesser extent, immunocytochemical analyses with antibodies directed against purified enzymes or against metabolites themselves (Guidetti et al, 2007; Lehrmann et al, 2001). Specifically, in the absence of anti-KMO antibodies that can be used for unambiguous microscopic localization of the enzyme, evidence for a microglial localization of this pivotal pathway enzyme rests mostly on ex vivo studies (Guillemin et al, 2005; Parrott and O’Connor, 2015).…”

Kynurenine pathway metabolites and suicidality

“…The most firmly established physiological characteristic of PIC is its ability to efficiently chelate iron, copper and other metals (Grant et al, 2009). In addition, PIC is able to antagonize QUIN neurotoxicity in both cell culture and animal models by a currently unknown mechanism, which may involve chelation of endogenous zinc (Beninger et al, 1994; Chen et al, 2011; Cockhill et al, 1992; Jhamandas et al, 1998). …”

A single nucleotide polymorphism in the coding region of PGC-1α is a male-specific modifier of Huntington disease age-at-onset in a large European cohort

“…Further SNPs, for which an effect on AO was reported, include rs2970870, rs2970848 and rs6821591 [15,19,20]. These SNPs all map to non-coding portions of the gene.…”