Long-term expression of metabolism-associated genes in the rat hippocampus following recurrent neonatal seizures and its regulation by melatonin.

Despite the effective use of antiepileptic drugs (AEDs) for epilepsy, therapeutic failure occurs in 30% of patients. Novel approaches are targeting the inhibition of epileptogenesis. N-acetyl-5-methoxytryptamine (melatonin) is an indoleamine produced mainly by the pineal gland, and has been observed to exhibit antiepileptic and neuroprotective effects in experimental and clinical investigations. In the present study, the underlying protective mechanism of melatonin on neonatal seizure-induced long-term excitotoxicity was examined in the hippocampus of rats, predominantly on the metabolism-associated genes. Sprague Dawley rats (6-day-old; P6) were randomly divided into four groups, the control (Cont), melatonin-treated control (Mel), recurrent neonatal seizure (RS) and treatment with melatonin and RS combined (Mel+RS). At P35, mossy fiber sprouting and changes in gene expression in hippocampus were assessed using Timm staining, reverse transcription-quantitative polymerase chain reaction and use of the 2(-ΔCT) methods, respectively. The aberrant mossy fiber sprouting in the supra granular region of the dentate gyrus and CA3 subfield of the hippocampus was suppressed by pretreatment with melatonin. In addition, among the nineteen genes identified, four energy metabolism-associated genes (Kcnj11, leptin receptor, dopamine receptor D2 and melanocortin 4 receptor), four lipid metabolism-associated genes (apolipoprotein A-I, opioid receptor κ 1, pyruvate dehydrogenase kinase, isozyme 4 and cytochrome P450, family 46, subfamily a, polypeptide 1) and zinc transporter 1 (ZnT1), sphingomyelinase (nSMase) and Cathepsin-E, were markedly downregulated by melatonin treatment in the Mel group or in the developmental seizure RS and Mel + RS groups, compared with that in the Cont group. Furthermore, the melatonin-pretreated seizure rats (Mel + RS) exhibited a significantly upregulated expression of calcium/calmodulin-dependent protein kinase II α (CaMKIIα), acetyl-Coenzyme A acetyltransferase 1 (ACAT1), ZnT-1, metallothionein 1 (MT-1), nSMase and Cathepsin-E, compared with the RS rats. Thus, the present study investigated changes in the expression of metabolic genes in the hippocampus following pretreatment with melatonin. Fluorthyl-induced decreases in the expression levels of ACAT1/nSMase/Cathepsin-E, ZnT-1/MT-1 and CaMKIIα in the hippocampus, and the reversal by melatonin may be associated with a decrease in neonatal seizure-induced aberrant mossy fiber sprouting, which requires further investigation.