The Jnk Inhibitor, Sp600125, Potentiates The Glial Response And Cell Death Induced By Methamphetamine In The Mouse Striatum

This study investigates the effect of the selective Jun NH2-terminal kinase 1/2 (JNK1/2) inhibitor, (SP600125) on the striatal dopamine nerve terminal loss and on the increased interleukin-15 (IL-15) expression and glial response induced by methamphetamine (METH). Mice were given repeated low doses of METH (4mg/kg, i.p., three times separated by 3h) and killed 24h or 7 d after the last dose. SP600125 (30mg/kg, i.p) was administered 30min before the last METH injection. Results indicate that METH produced dopaminergic axonal neurotoxicity reflected as a marked decrease in the striatal density of tyrosine hydroxylase-immunoreactive (TH-ir) fibres and dopamine transporter-immunoreactivity (DAT-ir) 24h after dosing. These effects were not modified by SP600125. This compound also failed to prevent the long-term loss of dopamine levels and DAT observed 7 d following METH injection. Nevertheless, SP600125 potentiated METH-induced striatal cell loss reflected by an increase in Fluoro-Jade immunostaining, cleaved capase-3 immunoreactivity and the number of terminal deoxyncleotidyl transferase-mediated dUTP nick end labelling (TUNEL) positive cells. In line with a deleterious effect of JNK1/2 inhibition, SP600125 increased the astroglial and microglial response induced by METH and interfered with drug-induced IL-15 expression. Together these data indicate that, not only does SP600125 fail to protect against the dopaminergic damage induced by METH but also, in fact, it potentiates the glial response and the non-dopaminergic striatal cell loss caused by the drug.