Experimental study on the expression of ubiquitin-specific protease-25 in temporal cortex of epileptic rats

Abstract

Objective To study the expression of ubiquitin-specific protease 25 (USP25) in the temporal cortex of the kainic acid (KA) induced epilepsy rat model. Methods Fifty-two male SD rats were randomly divided into the epilepsy model group (n=39) and sham-operated control group (n=13) with the random number table. The epilepsy model group was established by injecting KA into the amygdala, then the epileptic rats were randomly divided into 3 groups according to the modeling success time: 1 day for acute period, 7 days for latent period and 30 days for chronic period (13 rats in each group). Those rats were sampled at the end of observation. Rats in the control group were injected with normal saline into the amygdala and sampled together with those in the experimental group. Immunohistochemistry and immunofluorescence double labeling was used to test USP25 expression and its co-expression with neurons (NeuN) and astrocytes (GFAP). Quantitative real-time PCR and Western blot were used to assess the change of USP25 in the temporal cortex of rats. Results In the ipsilateral temporal cortex, the positive cells of co-expression of USP25 and NeuN were increased in the later stage of epilepsy in the epilepsy model group, and the expression levels of USP25 mRNA and protein in different stages of epilepsy varied significantly (F= 25.48 and 7.68 respectively, both P<0.05). Compared with the control group (mRNA level: 1.00±0.36, protein level: 1.00±0.46), the expression of USP25 in the latent group (mRNA level: 10.80±4.82, protein level: 1.88±0.32) and the chronic group (mRNA level: 12.97±4.48, protein level: 1.92±0.26) were increased significantly (all P<0.05). In the contralateral temporal cortex, the expression levels of USP25 mRNA and protein in different stages of epilepsy also varied significantly (F=86.86 and 6.65 respectively, both P<0.05). Conclusions The increased expression of USP25 in the temporal cortex after the latent period has suggested that the deubiquitination pathway is involved in the chronic pathological process of temporal lobe epilepsy. Key words: Epilepsy, temporal lobe; Ubiquitin-specific protease 25; Rats