Oxidative and excitotoxic insults exert differential effects on spinal motoneurons and astrocytic glutamate transporters: Implications for the role of astrogliosis in amyotrophic lateral sclerosis.
In amyotrophic lateral sclerosis (ALS) non-neuronal cells play key roles in disease etiology and loss of motoneurons via noncell-autonomous mechanisms. Reactive astrogliosis and dysfunctional transporters for L-glutamate [excitatory amino acid transporters, (EAATs)] are hallmarks of ALS pathology. Here, we describe mechanistic insights into ALS pathology involving EAAT-associated homeostasis in response to a destructive milieu, in which oxidative stress and excitotoxicity induce respectively astrogliosis and motoneuron injury. Using an in vitro neuronal-glial culture of embryonic mouse spinal cord, we demonstrate that EAAT activity was maintained initially, despite a loss of cellular viability induced by exposure to oxidative [3-morpholinosydnonimine chloride (SIN-1)] and excitotoxic [(S)-5-fluorowillardiine (FW)] conditions. This homeostatic response of EAAT function involved no change in the cell surface expression of EAAT1/2 at 0.5-4 h, but rather alterations in kinetic properties. Over this time-frame, EAAT1/2 both became more widespread across astrocytic arbors in concert with increased expression of glial fibrillary acidic protein (GFAP), although at 8-24 h there was gliotoxicity, especially with SIN-1 rather than FW. An opposite picture was found for motoneurons where FW, not SIN-1, produced early and extensive neuritic shrinkage and blebbing (> or =0.5 h) with somata loss from 2 h. We postulate that EAATs play an early homeostatic and protective role in the pathologic milieu. Moreover, the differential profiles of injury produced by oxidative and excitotoxic insults identify two distinct phases of injury which parallel important aspects of the pathology of ALS.
Zagami
Chrissandra J
CJ
Brain Injury and Repair Group, Howard Florey Institute, VIC 3010, Australia.
Beart
Philip M
PM
Wallis
Nicole
N
Nagley
Phillip
P
O'Shea
Ross D
RD
D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism* / Q000503:physiopathology; D000818:Animals; D000870:Anterior Horn Cells / Q000378:metabolism* / Q000473:pathology; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D019610:Cytoprotection / Q000187:drug effects / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D027341:Excitatory Amino Acid Transporter 1 / Q000378:metabolism*; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005911:Gliosis / Q000378:metabolism* / Q000503:physiopathology; D018698:Glutamic Acid / Q000378:metabolism / Q000633:toxicity; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008981:Molsidomine / Q000031:analogs & derivatives / Q000633:toxicity; D009498:Neurotoxins / Q000378:metabolism / Q000633:toxicity; D020030:Nitric Oxide Donors / Q000633:toxicity; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D018690:Excitatory Amino Acid Agonists; D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D005904:Glial Fibrillary Acidic Protein; D009498:Neurotoxins; D020030:Nitric Oxide Donors; C493396:Slc1a2 protein, mouse; C493393:Slc1a3 protein, mouse; D018698:Glutamic Acid; C002385:linsidomine; D008981:Molsidomine