Benchmarking the proteomic profile of animal models of mesial temporal epilepsy

Abstract

Objectives: We compared the proteomic signatures of the hippocampal lesion induced in three different animal models of mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE+HS): the systemic pilocarpine model (PILO), the intracerebroventricular kainic acid model (KA), and the perforant pathway stimulation model (PPS).

Methods: We used shotgun proteomics to analyze the proteomes and find enriched biological pathways of the dorsal and ventral dentate gyrus (DG) isolated from the hippocampi of the three animal models. We also compared the proteomes obtained in the animal models to that from the DG of patients with pharmacoresistant MTLE+HS.

Results: We found that each animal model presents specific profiles of proteomic changes. The PILO model showed responses predominantly related to neuronal excitatory imbalance. The KA model revealed alterations mainly in synaptic activity. The PPS model displayed abnormalities in metabolism and oxidative stress. We also identified common biological pathways enriched in all three models, such as inflammation and immune response, which were also observed in tissue from patients. However, none of the models could recapitulate the profile of molecular changes observed in tissue from patients.

Significance: Our results indicate that each model has its own set of biological responses leading to epilepsy. Thus, it seems that only using a combination of the three models may one replicate more closely the mechanisms underlying MTLE+HS as seen in patients.

Figure 1

Image of the dorsal dentate gyrus (dDG) from the three animal models analyzed depicting the neuronal damage caused by the seizure induction. (A) The dorsal dentate gyrus of the perforant pathway stimulation (PPS‐dDG) model; (B) the dorsal dentate gyrus of the pilocarpine (PILO‐dDG) model; (C) the dorsal dentate gyrus of the kainic acid (KA‐dDG) model, and (D) the sham control dDG.

Figure 2

Upset plots with the total number of proteins identified in the three animal models of mesial temporal lobe epilepsy (MTLE). (A) The total number of proteins identified in the dorsal dentate gyrus from each model. dPILO, dorsal dentate gyrus of the pilocarpine model; dKA, dorsal dentate gyrus from the kainic acid model; dPPS, dorsal dentate gyrus of the perforant pathway stimulation model. (B) The total number of proteins identified in the ventral dentate gyrus from each model. vPILO, ventral dentate gyrus of the pilocarpine model; vKA, ventral dentate gyrus from the kainic acid model; vPPS, ventral dentate gyrus of the perforant pathway stimulation model. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 3

Gene Ontology (GO) biological processes identified from each model are divided into categories. The gray bars represent the processes observed in the pilocarpine dorsal dentate gyrus (PILO‐dDG), the yellow bars represent the data from the ventral dentate gyrus from the pilocarpine model (PILO‐vDG), the light blue bars represent the processes identified in the dorsal dentate gyrus of the kainic acid (KA‐dDG), the green bars mark the processes seen in the ventral dentate gyrus of the kainic acid (KA‐vDG), the dark blue bars represent the processes of the dorsal dentate gyrus perforant pathway stimulation (PPS‐dDG), the orange bars indicate the processes of the ventral dentate gyrus perforant pathway stimulation model (PPS‐vDG), and the dark blue bars show the processes of tissues from patients with mesial temporal lobe epilepsy (MTLE). The numbers above the bars show the number of processes identified in each category. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 4

Enriched pathways identified for each model are divided into categories. The gray bars represent the pathways of the dorsal dentate gyrus of the pilocarpine model (PILO‐dDG), the yellow bars represent the ventral dentate gyrus of the pilocarpine model (PILO‐vDG), the light blue bars represent the pathways identified in the dorsal dentate gyrus of the kainic acid model (KA‐dDG), the green bars show the pathways of the ventral dentate gyrus of the kainic acid model (KA‐vDG), the light blue bars represent the pathways of the dorsal dentate gyrus of the perforant pathway stimulation model (PPS‐dDG), the orange bars indicate the pathways of the ventral dentate gyrus of the perforant pathway stimulation model (PPS‐vDG), and the dark blue bars represent the pathways from tissues of patients with mesial temporal lobe epilepsy (MTLE). Numbers above the bars show the number of enriched pathways identified in each category. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 5

Gene homology analysis of the total number of proteins identified in the three animal models and patients with mesial temporal lobe epilepsy (MTLE). (A) Upset plot of the total number of proteins identified in the three animal models and patients. PILO, Pilocarpine model; KA, kainic acid model; PPS, perforant pathway stimulation model; MTLE, patients with mesial temporal lobe epilepsy. (B) List of the the top 20 genes in common among the four groups analyzed and their log2 fold‐change illustrating the abundancy variation in each group. dPILO, dorsal dentate gyrus from the pilocarpine model; vPILO, ventral dentate gyrus of the pilocarpine model; dKA, dorsal dentate gyrus of the kainic acid model; vKA, ventral dentate gyrus of the kainic acid model; dPPS, dorsal dentate gyrus of the perforant pathway stimulation model; vPPS, ventral dentate gyrus of the perforant pathway stimulation model. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 6

Principal component analysis (PCA) generated with the homologous human gene IDs converted from rats to humans (for the animal models) using the BioMart tool. The chart shows the distribution of the models and patients with mesial temporal lobe epilepsy (MTLE), according to their log2 fold‐change values and human gene IDs. PILO, Pilocarpine model; KA, kainic acid model; PPS, perforant pathway stimulation model; MTLE, patients with mesial temporal lobe epilepsy. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 7

Differentially abundant proteins were identified in each model and hippocampal region and the tissue from patients. The graph shows the percentage of upregulated and downregulated proteins. Blue bars represent the upregulated proteins, and red bars represent the downregulated proteins. PILO‐dDG, dorsal dentate gyrus of the pilocarpine model; PILO‐vDG, ventral dentate gyrus of the pilocarpine model; KA‐dDG, dorsal dentate gyrus of the kainic acid model; KA‐vDG, ventral dentate gyrus of the kainic acid model; PPS‐dDG, dorsal dentate gyrus of the perforant pathway stimulation model; PPS‐vDG, ventral dentate gyrus of the perforant pathway stimulation model. [Colour figure can be viewed at wileyonlinelibrary.com]