title: Astrocyte plasticity revealed by adaptations to severe proteotoxic stress.
abstract: Neurodegeneration is characterized by an accumulation of misfolded proteins in neurons. It is less well appreciated that glia often also accumulate misfolded proteins. However, glia are highly plastic and may adapt to stress readily. Endogenous adaptations to stress can be measured by challenging stressed cells with a second hit and then measuring viability. For example, subtoxic stress can elicit preconditioning or tolerance against second hits. However, it is not known if severe stress that kills half the population can elicit endogenous adaptations in the remaining survivors. Glia, with their resilient nature, offer an ideal model in which to test this new hypothesis. The present study is the first demonstration that astrocytes surviving one LC50 hit of the proteasome inhibitor MG132 were protected against a second MG132 hit. ATP loss in response to the second hit was also prevented. MG132 caused compensatory rises in stress-sensitive heat shock proteins. However, stressed astrocytes exhibited an even greater rise in ubiquitin-conjugated proteins upon the second hit, illustrating the severity of the proteotoxicity and verifying the continued impact of MG132. Despite this stress, MG132-pretreated astrocytes were completely prevented from losing glutathione with the second hit. Furthermore, inhibiting glutathione synthesis rendered astrocytes sensitive to the second hit, unmasking the cumulative impact of two hits by removal of an endogenous adaptation. These findings suggest that stressed astrocytes become progressively harder to kill by virtue of antioxidant defenses. Such plasticity may permit astrocytes under severe stress to better support neurons and help explain the protracted nature of neurodegeneration.
authors: Division of Pharmaceutical Sciences, Mylan School of Pharmacy, Duquesne University, 600 Forbes Ave, Pittsburgh, PA 15282, USA.
authors: Amanda M
authors: AM
authors: Titler
authors: Jessica M
authors: JM
authors: Posimo
authors: Rehana K
authors: RK
authors: Leak
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D001343:Autophagy / Q000187:drug effects; D015153:Blotting, Western; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D007150:Immunohistochemistry; D007976:Leupeptins / Q000494:pharmacology; D052119:Lysosomal-Associated Membrane Protein 2 / Q000378:metabolism; D009473:Neuronal Plasticity / Q000187:drug effects*; D011506:Proteins / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064568:S100 Calcium Binding Protein beta Subunit / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects*
chemical_list: D005904:Glial Fibrillary Acidic Protein; D007976:Leupeptins; D052119:Lysosomal-Associated Membrane Protein 2; D011506:Proteins; D064568:S100 Calcium Binding Protein beta Subunit; D019328:Buthionine Sulfoximine; D005978:Glutathione; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde