Unlocking the Therapeutic Potential: Sitagliptin's Multifaceted Approach in Drug-Resistant Epilepsy through a Novel Mechanism Inhibiting Protein Kinase C-γ and a Long-Term Potentiation Pathway

Abstract

Drug-resistant epilepsy is a prominent challenge in chronic neurological disorders. Valproate, commonly used to treat epilepsy, can fail due to various side effects and interactions, necessitating the exploration of alternative treatments. Our study primarily investigated sitagliptin's potential as a therapeutic agent for drug-resistant epilepsy. Employing computational modeling and enzyme assay testing, three lead compounds, emixustat, sitagliptin, and distigmine bromide, were evaluated against the target enzyme protein kinase C-γ. In vivo, experiments on a pentylenetetrazolium-induced lamotrigine-resistant epilepsy model were conducted to test sitagliptin's antiseizure effects, compared with the standard phenobarbital treatment. Emixustat and sitagliptin showcased strong inhibitory properties, while distigmine bromide was less effective in the enzyme assay. Mechanistic insights revealed sitagliptin's ability to modulate the seizure grade and first myoclonic jerk latency via oxidative stress markers, like reduced glutathione and glutathione peroxidase emphasizing its antioxidative role in epilepsy. Additionally, it demonstrated anti-inflammatory effects by significantly reducing proinflammatory markers interleukin-1β and interleukin-6. The modulation of key genes of the long-term potentiation pathway, particularly protein kinase C-γ and metabotropic glutamate receptor 5, was evident through mRNA expression levels. Finally, sitagliptin showed potential neuroprotective properties, limiting pentylenetetrazolium-induced neuronal loss in the hippocampal region. Collectively, our findings suggest sitagliptin's multidimensional therapeutic potential for drug-resistant epilepsy specifically via a long-term potentiation pathway by inhibiting protein kinase C-γ.

Figure 1

PKCG enzyme activity dose–response curve and determination of the IC₅₀ for the top leads. (A) Emixustat (0.48 nM), (B) sitagliptin (0.73 nM), and (C) distigmine bromide (32.4 μM).

Figure 2

Effect of sitagliptin in drug-resistant animal groups against the pentylenetetrazole-induced kindling seizure score. Comparison of 10-day mean seizure score. ANOVA followed by pairwise t-tests. n = 9, *p-value < 0.05, **p-value < 0.01, ***p-value < 0.001, and ****p-value < 0.0001.

Figure 3

Effect of sitagliptin on drug-resistant animal groups against pentylenetetrazole-induced kindling on latency of FMJ. Comparison of 10-day mean FMJ latency (ANOVA followed by pairwise t-tests). n = 9, *p-value < 0.05, **p-value < 0.01, ***p-value < 0.001, and ****p-value < 0.0001.

Figure 4

Effect of sitagliptin on drug-resistant animal groups against pentylenetetrazole-induced kindling relative mRNA expression of the LTP pathway key-role playing genes. (a) PKCG, (b) GRM5, (c) GRM7, and (d) GABA_A (ANOVA followed by pairwise t-tests). n = 3, *p-value < 0.05, **p-value < 0.01, ***p-value < 0.001, and ****p-value < 0.0001.

Figure 5

Effect of sitagliptin in drug-resistant animal groups against pentylenetetrazol-induced kindling on histological changes. (a) Dentate gyrus at 10× magnification and (b) 40× magnification and (c) quantification and comparison of neuronal loss in the hippocampus. ANOVA followed by pairwise t-tests. n = 3, *p-value < 0.05, **p-value < 0.01, ***p-value < 0.001, and ****p-value < 0.0001.