Disease-modifying effects of sodium selenate in a model of drug-resistant, temporal lobe epilepsy
- Department of Medicine, The Royal Melbourne Hospital, The University of Melbourne, Australia
- Department of Neuroscience, Central Clinical School, Monash University, Australia
- Monash Proteomics & Metabolomics Facility and Monash Biomedicine Discovery Institute, Monash University, Australia
- Department of Neurology, The Alfred Hospital, Commercial Road,, Australia
Figures
Figure 1 with 1 supplement
Sodium selenate has a sustained effect to reduce spontaneous seizures in the post-KA SE rat model of chronic drug-resistant temporal lobe epilepsy (TLE).
(A) Sodium selenate stopped the progression of seizures from treatment week four and significantly reduced seizure frequency eight weeks after the last day of treatment compared to vehicle-treated animals (B) average seizure duration and (C) seizure severity was not significantly different between the three treatment groups; (* significantly different from vehicle p<0.05). LEV levetiracetam. Two-way ANOVA with Dunn’s post hoc. Tx- treatment, wk week, WO, washout. Data shown as mean ± SEM. Post-SE +Vehicle (n=10), Post-SE +selenate (n=12), and Post-SE +levetiracetam (n=12). (D) Representative EEG example of an animal presenting a spontaneous seizure, 120 s window, low pass 70 Hz, high pass 1 Hz; arrows represent seizure start and seizure ends.
Figure 1—figure supplement 1
Seizure analysis - Single data points.
(A) Sodium selenate stopped the progression of seizures from treatment week four and significantly reduced seizure frequency eight weeks after the last day of treatment compared to vehicle-treated animals (B) average seizure duration and (C) seizure severity was not significantly different between the three treatment groups; (* significantly different from vehicle p<0.05). LEV levetiracetam. Two-way ANOVA with Dunn’s post hoc. Tx- treatment, wk week, WO, washout. Data shown as mean ± SEM.
Figure 2 with 2 supplements
Sodium selenate improves cognitive and sensorimotor impairments in the post-KA SE rat model of chronic drug-resistant temporal lobe epilepsy (TLE).
(A) Novel object placement (NOP). Vehicle and levetiracetam-treated animals showed a significantly reduced time examining the novel location of the object compared to shams. In contrast, sodium selenate treatment improved spatial memory in comparison to the vehicle in post-SE rats. (B) Novel object recognition (NOR). Post-SE animals treated with vehicle or levetiracetam showed significantly impaired recognition memory to shams. Sodium selenate rats spent more time evaluating the novel object introduced into the arena in contrast to the vehicle, which is a measure of improved recognition memory. (C) Post-SE rats treated with vehicle and levetiracetam had significantly longer search time in the water maze acquisition session in contrast to shams. (D) Water maze reversal, all of the post-SE rats showed significantly longer search times in comparison to the sham. For presentation purposes, data for water maze search time is graphed in blocks of two trials. (E) Post-SE rats treated with vehicle and levetiracetam exhibited more slips and falls on the beast compared to shams. In contrast, treatment with sodium selenate significantly reduced these impairments compared to the vehicle. (*p<0.05, **p<0.01, ***p<0.001; ##p<0.05, and ###p<0.001 significantly different to shams). Kruskal-Wallis with Dunn’s post hoc for the NOP and NOR. MWM two-way repeated measures ANOVA, with Dunnett’s post hoc. One-way ANOVA with Tukey’s post hoc for the beam task. Data are shown as mean ± SEM.
Figure 2—figure supplement 1
Morris Water Maze - Single data points.
(A) Post-SE rats treated with vehicle and levetiracetam had significantly longer search time in the water maze acquisition session in contrast to shams. (B) Water maze reversal, all the post-SE rats showed significantly longer search times in comparison to sham. For presentation purposes, data for water maze search time is graphed in blocks of two trials. (* p<0.05, **p<0.01, ***p<0.001; ##p<0.05, and ###p<0.001 significantly different to shams). Two-way repeated measures ANOVA, with Dunnett’s post hoc. Data shown as mean ± SEM. Post-SE rats develop depressive-like behavior in the sucrose preference test. Reduced sucrose preference can be interpreted as anhedonia, one of the major diagnostic criteria of depressive-like disorders in humans (Casillas-Espinosa et al., 2019b; Jones et al., 2008). Analysis of the 24 hr sucrose preference test (SPT) showed that post-SE animals treated with vehicle had a reduced preference for the 2% sucrose solution when compared to shams (p<0.05, Figure 2—figure supplement 1). Sucrose preference was not significantly different between selenate, levetiracetam, and shams.
Figure 2—figure supplement 2
Post-SE rats show depressive-like behavior as assessed by the sucrose preference test.
Post-SE animals treated with vehicle had a reduced sucrose preference compared to shams (*p<0.05). One-way ANOVA with Tukey’s post hoc. Data are shown as mean ± SEM.
Figure 3 with 3 supplements
Differential expression analysis of all detected proteins in (A) somatosensory cortex and (B) hippocampus of all post-SE treatment groups and shams.
One-way ANOVA was used to identify the difference in protein abundance among selenate, levetiracetam, and vehicle-treated groups and shams. Difference between specific groups was determined via Tukey’s honestly significant difference (HSD) test. Significance threshold was set to FDR <0.05, and significantly different proteins are labeled red.
Figure 3—figure supplement 1
The top 25 differentially regulated pathways in the (A) somatosensory cortex and (B) hippocampus of selenate treated rats compared to vehicle group.
The quantitative enrichment analysis (PADOG) was carried out using the Reactome database resource. The Log2_FC (X axis) indicates the direction of pathway regulation. Pathways with adjusted p-value of <0.05 were considered differentially regulated between selenate and vehicle groups. All Reactome pathways were manually curated and organized hierarchically.
Figure 3—figure supplement 2
Partial least squares-discriminant analysis (PLS-DA) of the (A) proteomics from the somatosensory cortex, (B) proteomics from the hippocampus, (C) metabolomics from the somatosensory cortex, (D) metabolomics from the hippocampus.
Principal Component Analysis (PCA) plots of the (E) proteomics from the somatosensory cortex, (F) proteomics from the hippocampus, (G) metabolomics from the somatosensory cortex, (H) metabolomics from the hippocampus. LEV, levetiracetam, SEL, sodium selenate, and VEH, vehicle.
Figure 3—figure supplement 3
Sodium selenate modifies hyperphosphorylated-tau and protein phosphatase 2A (PP2A) expression.
Post-mortem analysis of brain tissue showed that sodium selenate had persistent effects in reducing hyperphosphorylated-tau in (A) the somatosensory cortex of drug-resistant temporal lobe epilepsy (TLE) rats. Similarly, (B) PP2A expression was significantly increased in the sodium selenate somatosensory cortex in comparison to the other treatment groups (*p<0.05, **p<0.01, ****p<0.0001). One-way ANOVA with Tukey’s post hoc. Data are shown as mean ± SEM.
Figure 4
Sodium selenate prevents telomere shortening in drug-resistant temporal lobe epilepsy (TLE) rats.
Chronic post-SE rats treated with levetiracetam and vehicle showed significantly reduced telomere length in comparison to sham. In contrast, sodium selenate-treated animals had significantly longer telomeres in comparison to the vehicle. kbp, kilobase pairs (*p<0.05, **p<0.01). One-way ANOVA with Tukey’s post hoc. Data are shown as mean ± SEM.
Figure 5
Hippocampal and somatosensory cortex module-trait correlation heatmaps .
The relationship of protein-metabolite modules (in the Y-axis) with measured clinical traits (X-axis) in (A) the hippocampus and (B) somatosensory cortex. Modules are labeled by color and representative enriched pathway. Each block of the heatmap shows the Spearman correlation coefficient (SCC) of every module with clinical traits as well as the associated P value in brackets. The SCC values range from –1 to +1, depending on the strength and direction of the correlation.
Figure 6
Experimental protocol in the post-status epilepticus model of temporal lobe epilepsy (TLE).
SE = KA-induced status epilepticus, vEEG = video-electroencephalogram; weeks = weeks post-SE.
Additional files
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Supplementary file 1
Untargeted proteomic analysis from the somatosensory cortex.
- https://cdn.elifesciences.org/articles/78877/elife-78877-supp1-v2.xlsx
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Supplementary file 2
Untargeted proteomic analysis from the hippocampus.
- https://cdn.elifesciences.org/articles/78877/elife-78877-supp2-v2.xlsx
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Supplementary file 3
Untargeted metabolomic analysis from the somatosensory cortex.
- https://cdn.elifesciences.org/articles/78877/elife-78877-supp3-v2.xlsx
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Supplementary file 4
Untargeted metabolomic analysis from the hippocampus.
- https://cdn.elifesciences.org/articles/78877/elife-78877-supp4-v2.xlsx
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Transparent reporting form
- https://cdn.elifesciences.org/articles/78877/elife-78877-transrepform1-v2.pdf
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Disease-modifying effects of sodium selenate in a model of drug-resistant, temporal lobe epilepsy
eLife 12:e78877.
https://doi.org/10.7554/eLife.78877
