System x(c)- activity and astrocytes are necessary for interleukin-1 beta-mediated hypoxic neuronal injury.
The purpose of this study was to elucidate the cellular/biochemical pathway(s) by which interleukin-1beta (IL-1beta) contributes to the pathogenesis of hypoxic-ischemic brain damage. In vivo, IL-1 receptor type I (IL-1RI)-deficient mice showed smaller infarcts and less neurological deficits than wild-type animals after a 90 min reversible middle cerebral artery occlusion. In vitro, IL-1beta mediated an enhancement of hypoxic neuronal injury in murine cortical cultures that was lacking in cultures derived from IL-1RI null mutant animals and was blocked by the IL-1 receptor antagonist or an IL-1RI blocking antibody. This IL-1beta-mediated potentiation of hypoxic neuronal injury was associated with an increase in both cellular cystine uptake ([cystine]i) and extracellular glutamate levels ([glutamate]e) and was prevented by either ionotropic glutamate receptor antagonism or removal of L-cystine, suggesting a role for the cystine/glutamate antiporter (System x(c)-). Indeed, dual System x(c)-/metabotropic glutamate receptor subunit 1 (mGluR1) antagonism but not selective mGluR1 antagonism prevented neuronal injury. Additionally, cultures derived from mGluR1-deficient mice exhibited the same potentiation in injury after treatment with IL-1beta as wild-type cultures, an effect prevented by System x(c)-/mGluR1 antagonism. Finally, assessment of System x(c)- function and kinetics in IL-1beta-treated cultures revealed an increase in velocity of cystine transport (Vmax), in the absence of a change in affinity (Km). Neither the enhancement in [cystine]i, [glutamate]e, or neuronal injury were observed in chimeric cultures consisting of IL-1RI(+/+) neurons plated on top of IL-1RI(-/-) astrocytes, highlighting the importance of astrocyte-mediated alterations in System x(c)- as a novel contributor to the development and progression of hypoxic neuronal injury.
Fogal
Birgit
B
Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
Li
Jun
J
Lobner
Doug
D
McCullough
Louise D
LD
Hewett
Sandra J
SJ
D027182:Amino Acid Transport System y+ / Q000819:agonists / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques / Q000379:methods; D020925:Hypoxia-Ischemia, Brain / Q000139:chemically induced / Q000378:metabolism*; D053583:Interleukin-1beta / Q000502:physiology / Q000633:toxicity*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*
D027182:Amino Acid Transport System y+; D053583:Interleukin-1beta; C492255:Slc7a11 protein, mouse