INGEBI   02650
INSTITUTO DE INVESTIGACIONES EN INGENIERIA GENETICA Y BIOLOGIA MOLECULAR "DR. HECTOR N TORRES"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Ascorbic acid is a positive modulator of recombinant alpha9alpha10 nicotinic cholinergic receptors
Autor/es:
JUAN CARLOS BOFFI; CAROLINA WEDEMEYER; ELEONORA KATZ,; DANIEL CALVO; ANA BELÉN ELGOYHEN
Lugar:
New Orleans
Reunión:
Congreso; Meeting of the Society for Neuroscience; 2012
Institución organizadora:
Society for Neuroscience Organization
Resumen:
The activation of α9α10 nicotinic
receptors in cochlear hair cells can ameliorate acoustic trauma. Therefore,
enhancing α9α10-mediated currents by means of a pharmacological potentiator may
be useful in the prevention or treatment of noise-induced hearing loss. In the
present work we aimed to characterized ascorbic acid (ASC) as a positive
modulator in α9α10 injected X. laevis
oocytes by two-electrode voltage-clamp recordings. Responses to 10μM acetylcholine
(ACh) were potentiated by ASC in a concentration-dependent manner (0.1-30mM
ASC). At 3mM ASC, a 64±6% (n=77) potentiation was
observed. Potentiation was more pronounced at lower (250±50%, 3μM ACh, n=9)
than at higher (140±40%, 1mM ACh, n=6) ACh concentrations. No significant
changes in the half maximal concentration of ACh and Hill coefficients were
observed in the pressence of 3mM ASC (EC50 = 18±1, nHill = 0.8±0.1,
n=5-9). Oxidized ASC blocked acetylcholine (ACh)-evoked responses at a 3mM
concentration (72±5% block at 1µM ACh, n=3), suggesting that reducing ASC is
the active compound. Alternatively, the equally reducing stereoisomer D-iso-ASC
also had a blocking effect (55±10% block at 1µM ACh, n=3), indicating that a
stereospecific interaction is also necessary. To test if a redox mechanism is
involved in ASC potentiation we mutated the extracellular residues CC192/193SS
(Torpedo α1 numbering). This substitutions
did not abolish ASC potentiation (90±10% potentiation at 1mM ACh, n=6), ruling
out the participation of these residues in the mechanism. Altogether, our
results indicate that ASC potentiates α9α10-mediated responses through an allosteric
and/or redox mechanism which does not involve C192-C193 disulfide bond.
Consequently, our results suggest that ASC has a potential therapeutic use in
noise-induced hearing loss.