1210 Immunosuppressant FK506 prevents kainic acid-induced neuronal disorder and neuronal death in the rat hippocampus

Abstract

This study tested the hypothesis that the expression of uncoupling proteins (UCPs) and dopamine (DA) system genes is responsive to 3-nitropropionic acid (3-NPA) neurotoxic effects and to the neuroprotective effects of the mitochondrial enhancer, l-carnitine (LC), in the rat striatum. Inactivation of mitochondrial succinate dehydrogenase (SDH) by 3-NPA results in hypoxic brain damage. Hypoxic conditions induce uncoupling protein-2 (UCP-2). An increase in UCP-2 expression may lead to a decrease in production of reactive oxygen species (ROS) associated with energy depletion. However, this adaptive response can also lead to a reduction of ATP that may further contribute to energy deficit and mitochondrial dysfunction. Here, male adult Sprague–Dawley rats (n = 5/group) were injected either with saline or 3-NPA at 30 mg/kg, s.c. alone or 30 min after pre-treatment with LC (100 mg/kg, i.p.). Rectal temperature was monitored before treatment and 4 h following 3-NPA administration. Animals were sacrificed 4 h post-treatment. Total RNA was isolated from the striatum and transcripts of UCP-2, UCP-4 and UCP-5 genes, as well as genes related to dopamine metabolism, such as DA D1 and D2 receptors, tyrosine hydroxylase (TH), monoamine oxidase-B (MAO-B), and vesicular monoamine transporter-2 (VMAT-2), were measured using real-time reverse transcription polymerase chain reaction (RT-PCR). While core temperature decreased significantly in 3-NPA-treated rats, LC significantly inhibited the hypothermic effect of 3-NPA (p < 0.05). 3-NPA caused a significant increase in UCP-2 and DA D1 receptor gene expression in the striatum and both effects were attenuated by pre-treatment with LC. Since LC maintains the ATP/ADP ratio and was previously shown to be neuroprotective against 3-NPA toxicity, the modulation of UCP-2 expression by LC suggests that LC counteracts energy dissipation and thus prevents the negative effects of ATP decline on DA neurotransmission.