Sitagliptin enhances the neuroprotective effect of pregabalin against pentylenetetrazole-induced acute epileptogenesis in mice: Implication of oxidative, inflammatory, apoptotic and autophagy pathways

The current investigation aimed at studying the anti-epileptogenic effect of sitagliptin. The possible effect of the drug in combination with pregabalin in pentylenetetrazole (PTZ)- induced seizures was studied. In addition, the postulated mechanisms that could mediate such effect were explored namely, suppression of oxidative stress and neuro-inflammatory markers, autophagy and apoptosis. Seven days prior to PTZ (60 mg/kg, sc) injection, mice were treated with sitagliptin (5, 15, and 60 mg/kg, twice daily, orally) or pregabalin (30 mg/kg, once daily, orally) or their combination. At the end of the experiment, several parameters were assessed including: oxidative/nitro-oxidative stress such as superoxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidase (GP-x) catalase (CAT), and lipid peroxidation assessed as malondialdehyde (MDA), nitrate/nitrite (NOx), 3-nitrotyrosine (3-NT). Seizure latency was evaluated. Neuronal damage was also assessed by performing tissue staining by hematoxylin and eosin, estimating hippocampus level of glutamate, gamma-aminobutyric acid (GABA), glial fibrillary acidic protein (GFAP) and brain-derived neurotrophic factor (BDNF). Also, markers for inflammation, autophagy and apoptosis were measured, nuclear factor erythroid-derived 2- like 2 (Nrf2), nuclear factor kappa-B (NF-κB), phosphatidylethanolamine-conjugated form of microtubule-associated protein light chain-3 (LC3-II), casapase-3, Bcl-2-like protein 4 (BAX) and glucagon like peptide-1 (GLP-1) activity. Sitagliptin significantly suppressed epileptogenesis in PTZ-induced seizures. Sitagliptin counteracted neuronal damage and all biochemical, and histo-chemical alteration induced by PTZ. Also, a more significant protective effect was observed after combination with pregabalin. This study is indicative for the antiepileptogenic potential of sitagliptin with or without pregabalin in the PTZ model of epilepsy which is likely to be through its effect on antioxidant, anti-apoptotic and autophagic pathways.