Peroxynitrite stimulates L-arginine transport system y(+) in glial cells. A potential mechanism for replenishing neuronal L-arginine.
We have reported previously that peroxynitrite stimulates L-arginine release from astrocytes, but the mechanism responsible for such an effect remains elusive. To explore this issue, we studied the regulation of L-[(3)H]arginine transport by either exogenous or endogenous peroxynitrite in glial cells. A 2-fold peroxynitrite-mediated stimulation of l-arginine release in C6 cells was found to be Na(+)-independent, was prevented by 5 mm L-arginine and, although only in the presence of Na(+), was blocked by 5 mm L-alanine or L-leucine. Peroxynitrite-mediated stimulation of L-arginine uptake was trans-stimulated by 10 mm L-arginine and was inhibited in a dose-dependent fashion (k(i) of approximately 40 microm) by the system y(+) inhibitor N-ethylmaleimide in C6 cells. Endogenous production of peroxynitrite in lipopolysaccharide-treated astrocytes triggered an increased L-arginine transport activity without affecting Cat1 l-arginine transporter mRNA levels. However, Western blot analyses of peroxynitrite-treated astrocytes and C6 glial cells revealed a 3-nitrotyrosinated anti-Cat1-immunopositive band, strongly suggesting peroxynitrite-mediated Cat1 nitration. Furthermore, peroxynitrite stimulation of L-arginine release was abolished in fibroblast cells homozygous for a targeted inactivation of the Cat1 gene. Finally, peroxynitrite-triggered L-arginine released from astrocytes was efficiently taken up by neurons in an insert-based co-culture system. These results strongly suggest that peroxynitrite-mediated activation of the Cat1 transporter in glial cells may serve as a mechanism focused to replenish L-arginine in the neighboring neurons.
Vega-Agapito
Victoria
V
Departamento de Bioquimica y Biologia Molecular, Universidad de Salamanca, 37007 Salamanca, Spain.
Almeida
Angeles
A
Hatzoglou
Maria
M
Bolaños
Juan P
JP
D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D018920:Coculture Techniques; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism
D002352:Carrier Proteins; D030421:Peroxynitrous Acid; D001120:Arginine; D012964:Sodium