Regulation of system x(c)(-)activity and expression in astrocytes by interleukin-1β: implications for hypoxic neuronal injury.
We recently demonstrated that interleukin-1β (IL-1β) increases system x(c)(-) (cystine/glutamate antiporter) activity in mixed cortical cell cultures, resulting in an increase in hypoxic neuronal injury when glutamate clearance is impaired. Herein, we demonstrate that neurons, astrocytes, and microglia all express system x(c)(-) subunits (xCT, 4F2hc, RBAT) and are capable of cystine import. However, IL-1β stimulation increases mRNA for xCT--the light chain that confers substrate specificity--in astrocytes only; an effect blocked by the transcriptional inhibitor actinomycin D. Additionally, only astrocytes show an increase in cystine uptake following IL-1β exposure; an effect associated with a change in xCT protein. The increase in cystine uptake that follows IL-1β is lacking in astrocytes derived from mice harboring a mutation in Slc7a11 (sut gene), which encodes for xCT, and in wild-type astrocytes treated with the protein synthesis inhibitor cycloheximide. IL-1β does not regulate the light chain of the amino acid transporter, LAT2, or the expression and function of astrocytic excitatory amino acid transporters (EAATs), demonstrating some target selectivity. Finally, the enhanced neuronal vulnerability to hypoxia that followed IL-1β treatment in our mixed culture system was not observed in chimeric cultures consisting of wild-type neurons plated on top of sut astrocytes. Nor was it observed in wild-type cultures treated with a system x(c)(-) inhibitor or an NMDA receptor antagonist. Overall, our data demonstrate that IL-1β selectively regulates system x(c)(-) activity in astrocytes and that this change is specifically responsible for the deleterious, excitotoxic effects of IL-1β found under hypoxic conditions.
Jackman
Nicole A
NA
Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030-3401, USA.
Uliasz
Tracy F
TF
Hewett
James A
JA
Hewett
Sandra J
SJ
D027182:Amino Acid Transport System y+ / Q000235:genetics / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001224:Aspartic Acid / Q000378:metabolism; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism*; D001565:Benzoates / Q000494:pharmacology; D002247:Carbon Isotopes / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D003553:Cystine / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D027341:Excitatory Amino Acid Transporter 1 / Q000235:genetics / Q000378:metabolism; D027342:Excitatory Amino Acid Transporter 2 / Q000235:genetics / Q000378:metabolism; D027301:Fusion Regulatory Protein 1, Light Chains / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D053583:Interleukin-1beta / Q000494:pharmacology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors
D027182:Amino Acid Transport System y+; D001565:Benzoates; D002247:Carbon Isotopes; D018691:Excitatory Amino Acid Antagonists; D027341:Excitatory Amino Acid Transporter 1; D027342:Excitatory Amino Acid Transporter 2; D027301:Fusion Regulatory Protein 1, Light Chains; D053583:Interleukin-1beta; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; C518286:SLC7A8 protein, mouse; C079694:alpha-methyl-4-carboxyphenylglycine; D003609:Dactinomycin; D001224:Aspartic Acid; D003553:Cystine; D007770:L-Lactate Dehydrogenase; D005998:Glycine