Expression levels and mechanism of microRNA-34a and Notch1 signaling pathway in hippocampi of temporal lobe epilepsy rats

Abstract

Objective To explore the expression levels of microRNA(miR)-34a in hippocampus of temporal lobe epilepsy rats and the effect of miR-34a on its target signaling pathway Notch1. Methods Rats were divided randomly into experiment group (n=40) and control group (n=40) by adopting random number table method.The status epilepticus model and the temporal lobe epilepsy model were induced by using lithium-pilocarpine for experiment group.The control group rats received an injection of an equal amount of 9 g/L saline as instead of pilocarpine.Racine grading was performed at 24 hours, day 3, day 7, day 15, and 1 month after modeling to evaluate the behavior.Real-time fluorescent quantitative polymerase chain reaction was used to test the mRNA expressions of miR-34a and Notch1.Western blot was performed to explore the protein expression of Notch1. Results The expression levels of miR-34a at post-status epilepticus in 24 hours, day 3, day 7, day 15 were 2.55±0.29, 2.11±0.17, 1.68±0.49 and 1.84±0.42, respectively, which showed statistically significant difference compared with the control group (1.00±0.00) (t=-1.55, -1.11, -0.68, -0.84, all P<0.05). The expression levels of Notch1 mRNA at post-status epilepticus in 24 hours, day 3, day 7, day 15, 1 month were 1.44±0.31, 1.27±0.13, 1.52±0.28, 0.91±0.33, and 0.80±0.09 respectively.There were significant differences at 24 hours, day 7 in Notch1 mRNA expression (t=-0.44, -0.52, all P<0.05) compared with the control group(1.00±0.00). The expression level of Notch1 mRNA on day 15 was significantly lower than 24 hours and day 7 (t=-0.54, -0.62, all P<0.05), and the expression in 1 month was significantly lower than in 24 hours, or day 3 and day 7 (t=-0.64, -0.46, -0.72, all P<0.05). The expression levels of Notch1 protein at post-status epilepticus 24 hours, day 3, day 7, day 15, 1 month were 0.78±0.09, 0.57±0.13, 0.55±0.16, 0.42±0.13, and 0.33±0.09, respectively.There was significantly up-regulated at 24 hours of Notch1 protein expression compared with control group (0.51±0.15)(t=-0.20, P<0.05); and the expression level at day 15 were significantly lower than 24 hours (t=-0.26, P<0.05), while the expression in 1 month was significantly lower than in 24 hours and on day 3 (t=-0.36, -0.24, all P<0.05). Conclusion miR-34a is significantly up-regulated in the post-status epilepticus rat hippocampus, and it may contribute to temporal lobe epilepsy by activating Notch1 signaling pathway. Key words: microRNA-34a; Temporal lobe epilepsy; Notch1