Cellular iron concentrations directly affect the expression levels of norepinephrine transporter in PC12 cells and rat brain tissue.
Neurological development and functioning are adversely affected by iron deficiency in early life. Iron-deficient rats are known to have elevations in extracellular DA and NE, suggesting alterations in reuptake of these monoamines. To explore possible mechanisms by which cellular iron concentrations may alter NE transporter functioning, we utilized NET expressing PC12 cells and iron-deficient rats to explore the relationship between NET protein and mRNA expression patterns and iron concentrations. Treatment of PC12 with the iron chelator, desferrioxamine mesylate (DFO, 50 microM for 24 h), significantly decreased [3H] NE uptake by more than 35% with no apparent change in Km. PC12 cells exposed to increasing concentrations of DFO (25-100 microM) exhibited a dose response decrease in [3H] NE uptake within 24 h (38-73% of control) that paralleled a decrease in cellular NET protein content. Inhibition of protein synthesis with cycloheximide resulted in NET disappearance rates from DFO-treated cells greatly exceeding the rate of loss from control cells. RT-PCR analysis revealed only a modest decrease in NET mRNA levels. Rat brain locus ceruleus and thalamus NET mRNA levels were also only modestly decreased (10-15%) despite a 40% reduction in regional brain iron. In contrast, NET proteins levels in thalamus and locus ceruleus were strongly affected by regional iron deficiency with high correlations with iron concentrations (r > 0.94 and r > 0.80 respectively). The present findings demonstrate that NET protein concentrations and functioning are dramatically reduced with iron deficiency; the modest effect on mRNA levels suggests a stronger influence on NET trafficking and degradation than on protein synthesis.
Beard
John L
JL
Department of Nutritional Science, S-128 Henderson South Building, The Pennsylvania State University, University Park, PA 16802, USA. jbeard@psu.edu
Wiesinger
Jason A
JA
Jones
Byron C
BC
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D003676:Deferoxamine / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005526:Food, Formulated / Q000009:adverse effects; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D007502:Iron Chelating Agents / Q000494:pharmacology; D000090463:Iron Deficiencies; D019189:Iron Metabolism Disorders / Q000378:metabolism* / Q000503:physiopathology; D008125:Locus Coeruleus / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D016716:PC12 Cells; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013788:Thalamus / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology
D007502:Iron Chelating Agents; D050484:Norepinephrine Plasma Membrane Transport Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; C493226:Slc6a2 protein, rat; D003676:Deferoxamine; D009638:Norepinephrine