Microglia in ALS: The Good, The Bad, and The Resting
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Inflammation, including microglial activation and T cell infiltration, is a neuropathological hallmark of amyotrophic lateral sclerosis (ALS), a rapidly progressing neurodegenerative disease. The identification of mutations in the gene for Cu2+/Zn2+ superoxide dismutase (SOD1) from patients with an inherited form of ALS enabled the creation of transgenic mice overexpressing mutant forms of SOD1 (mSOD1) which develop a motoneuron disease that resembles the disease seen in ALS patients. These transgenic mice display similar inflammatory reactions at sites of motoneuron injury as detected in ALS patients, enabling the observation that this inflammation is not simply a late consequence of motoneuron degeneration, but actively contributes to the balance between neuroprotection and neurotoxicity. The microglial and T cell activation states influence the rate of disease progression. Initially, microglia and T cells can slow disease progression, while they may later contribute to the acceleration of disease. Accumulation of intracellular and extracellular misfolded mSOD1 may be key events regulating the transformation from neuroprotective alternatively activated M2 microglia to cytotoxic classically activated M1 microglia. Intracellular and extracellular mSOD1 utilizing different pathways may enhance the production and release of reactive oxygen species (ROS) and augment the inflammatory cytokine cascade from microglia. These ROS and cytokines may increase the susceptibility of motoneurons to glutamate toxicity and inhibit the function and expression of astrocytic glutamate transporters resulting in further neurotoxicity. Thus, the cumulative evidence suggests that inflammation plays a central role in ALS and manipulating these microglial effector functions may potentially modify the outcome of this devastating disease.
KeywordsM2 alternatively activated M1 classically activated regulatory Treg
This study was supported by grants from the Muscular Dystrophy Association and the NIH.
- Bruijn LI, Becher MW, Lee MK, Anderson KL, Jenkins NA, Copeland NG, Sisodia SS, Rothstein JD, Borchelt DR, Price DL, Cleveland DW (1997) ALS-linked SOD1 mutant G85R mediates damage to astrocytes and promotes rapidly progressive disease with SOD1-containing inclusions. Neuron 18:327–338CrossRefPubMedGoogle Scholar
- Clement AM, Nguyen MD, Roberts EA, Garcia ML, Boillée S, Rule M, McMahon AP, Doucette W, Siwek D, Ferrante RJ, Brown RH Jr, Julien JP, Goldstein LS, Cleveland DW (2003) Wild-type nonneuronal cells extend survival of SOD1 mutant motor neurons in ALS mice. Science 302:113–117CrossRefPubMedGoogle Scholar
- Gowing G, Philips T, Van Wijmeersch B, Audet JN, Dewil M, Van Den Bosch L, Billiau AD, Robberecht W, Julien JP (2008) Ablation of proliferating microglia does not affect motor neuron degeneration in amyotrophic lateral sclerosis caused by mutant superoxide dismutase. J Neurosci 28:10234–10244CrossRefPubMedGoogle Scholar
- Gruzman A, Wood WL, Alpert E, Prasad MD, Miller RG, Rothstein JD, Bowser R, Hamilton R, Wood TD, Cleveland DW, Lingappa VR, Liu J (2007) Common molecular signature in SOD1 for both sporadic and familial amyotrophic lateral sclerosis. Proc Natl Acad Sci U S A 104:12524–12529CrossRefPubMedGoogle Scholar
- Hensley K, Floyd RA, Gordon B, Mou S, Pye QN, Stewart C, West M, Williamson K (2002) Temporal patterns of cytokine and apoptosis-related gene expression in spinal cords of the G93A-SOD1 mouse model of amyotrophic lateral sclerosis. J Neurochem 82:365–374 Erratum in: J Neurochem 2002 82:1570CrossRefPubMedGoogle Scholar
- Hensley K, Fedynyshyn J, Ferrell S, Floyd RA, Gordon B, Grammas P, Hamdheydari L, Mhatre M, Mou S, Pye QN, Stewart C, West M, West S, Williamson KS (2003) Message and protein-level elevation of tumor necrosis factor alpha (TNF alpha) and TNF alpha-modulating cytokines in spinal cords of the G93A-SOD1 mouse model for amyotrophic lateral sclerosis. Neurobiol Dis 14:74–80CrossRefPubMedGoogle Scholar
- Howland DS, Liu J, She Y, Goad B, Maragakis NJ, Kim B, Erickson J, Kulik J, DeVito L, Psaltis G, DeGennaro LJ, Cleveland DW, Rothstein JD (2002) Focal loss of the glutamate transporter EAAT2 in a transgenic rat model of SOD1 mutant-mediated amyotrophic lateral sclerosis (ALS). Proc Natl Acad Sci U S A 99:1604–1609CrossRefPubMedGoogle Scholar
- Rosen DR, Siddique T, Patterson D, Figlewicz DA, Sapp P, Hentati A, Donaldson D, Goto J, O’Regan JP, Deng HX, Rahmani Z, Krizus A, McKenna-Yasek D, Cayabyab A, Gaston SM, Berger R, Tanzi RE, Halperin JJ, Herzfeldt B, Van den Bergh R, Hung W-Y, Bird T, Deng G, Mulder DW, Smyth C, Laing NG, Soriano E, Pericak-Vance MA, Haines J, Rouleau GA, Gusella JS, Horvitz HR, Brown RH (1993) Mutations in Cu/Zn superoxide dismutase gene are associated with familial amyotrophic lateral sclerosis. Nature 362:59–62CrossRefPubMedGoogle Scholar
- Tanaka M, Kikuchi H, Ishizu T, Minohara M, Osoegawa M, Motomura K, Tateishi T, Ohyagi Y, Kira J (2006) Intrathecal upregulation of granulocyte colony stimulating factor and its neuroprotective actions on motor neurons in amyotrophic lateral sclerosis. J Neuropathol Exp Neurol 65:816–825CrossRefPubMedGoogle Scholar
- Yoshihara T, Ishigaki S, Yamamoto M, Liang Y, Niwa J, Takeuchi H, Doyu M, Sobue G (2002) Differential expression of inflammation- and apoptosis-related genes in spinal cords of a mutant SOD1 transgenic mouse model of familial amyotrophic lateral sclerosis. J Neurochem 80:158–167CrossRefPubMedGoogle Scholar
- Zhao W, Beers DR, Henkel JS, Zhang W, Urushitani M, Julien J-P, Appel SH (2009) Extracellular mutant SOD1 induces microglial-mediated motoneuron injury. Glia (in press)Google Scholar