title: A comparison of in vitro properties of resting SOD1 transgenic microglia reveals evidence of reduced neuroprotective function.
abstract: BACKGROUND
  Overexpression of mutant copper/zinc superoxide dismutase (SOD1) in rodents has provided useful models for studying the pathogenesis of amyotrophic lateral sclerosis (ALS). Microglia have been shown to contribute to ALS disease progression in these models, although the mechanism of this contribution remains to be elucidated. Here, we present the first evidence of the effects of overexpression of mutant (TG G93A) and wild type (TG WT) human SOD1 transgenes on a set of functional properties of microglia relevant to ALS progression, including expression of integrin β-1, spreading and migration, phagocytosis of apoptotic neuronal cell debris, and intracellular calcium changes in response to an inflammatory stimulus.
  
  
  RESULTS
  TG SOD1 G93A but not TG SOD1 WT microglia had lower expression levels of the cell adhesion molecule subunit integrin β-1 than their NTG control cells [NTG (G93A) and NTG (WT), respectively, 92.8 ± 2.8% on TG G93A, 92.0 ± 6.6% on TG WT, 100.0 ± 1.6% on NTG (G93A), and 100.0 ± 2.7% on NTG (WT) cells], resulting in decreased spreading ability, with no effect on ability to migrate. Both TG G93A and TG WT microglia had reduced capacity to phagocytose apoptotic neuronal cell debris (13.0 ± 1.3% for TG G93A, 16.5 ± 1.9% for TG WT, 28.6 ± 1.8% for NTG (G93A), and 26.9 ± 2.8% for NTG (WT) cells). Extracellular stimulation of microglia with ATP resulted in smaller increase in intracellular free calcium in TG G93A and TG WT microglia relative to NTG controls (0.28 ± 0.02 μM for TG G93A, 0.24 ± 0.03 μM for TG WT, 0.39 ± 0.03 μM for NTG (G93A), and 0.37 ± 0.05 μM for NTG (WT) microglia).
  
  
  CONCLUSIONS
  These findings indicate that, under resting conditions, microglia from mutant SOD1 transgenic mice have a reduced capacity to elicit physiological responses following tissue disturbances and that higher levels of stimulatory signals, and/or prolonged stimulation may be necessary to initiate these responses. Overall, resting mutant SOD1-overexpressing microglia may have reduced capacity to function as sensors of disturbed tissue/cellular homeostasis in the CNS and thus have reduced neuroprotective function.
authors.affiliation: Department of Medicine, University of Colorado Denver School of Medicine, CO, USA. anna_sargsyan@hotmail.com
authors.forename: Siranush A
authors.initials: SA
authors.lastname: Sargsyan
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Blackburn
authors.forename: Siân C
authors.initials: SC
authors.lastname: Barber
authors.forename: Julian
authors.initials: J
authors.lastname: Grosskreutz
authors.forename: Kurt J
authors.initials: KJ
authors.lastname: De Vos
authors.forename: Peter N
authors.initials: PN
authors.lastname: Monk
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Shaw
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002465:Cell Movement / Q000235:genetics; D006706:Homeostasis / Q000235:genetics; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D017628:Microglia / Q000201:enzymology* / Q000473:pathology* / Q000502:physiology; D009154:Mutation; D009433:Neural Inhibition / Q000235:genetics; D018696:Neuroprotective Agents / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology; D010587:Phagocytosis / Q000235:genetics; D061251:Primary Cell Culture; D016192:Resting Phase, Cell Cycle / Q000235:genetics; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D000072105:Superoxide Dismutase-1
chemical_list: D018696:Neuroprotective Agents; C000606290:SOD1 protein, human; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1