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

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

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.

Unveiling the potential of perampanel and pregabalin in addressing pentylenetetrazole-induced electrographic alterations and neurobehavioral anomalies

Chemical kindling is broadly used experimental model to investigate novel treatments on the process of epileptogenesis and coexisting behavioral comorbidities. The current study aimed to investigate the low dose perampanel (PER) (0.125 and 0.5 mg/kg) and pregabalin (PG) (15 mg/kg) as standalone treatments and in combination on kindling-induced seizure progression with concurrent electroencephalographic alterations. Mice were subjected to pentylenetetrazole (PTZ)-induced kindling followed by neurobehavioral assessment for anxiety-like activity and cognitive deficit through behavioral experiments. The monotherapy with PER at 0.5 mg/kg and PG at 15 mg/kg delayed the kindling process but PRP+PG yielded pronounced benefits and hindered the development of seizures of higher severity. PER+PG combination relieved the animals from anxiety-like behavior in various employed anxiogenic tests. Furthermore, the kindling-associated cognitive deficit was protected by PER+PG combination as increased alteration behavior, discrimination index and latencies to enter the dark zone were noted in y-maze, object recognition and passive avoidance tests, respectively while shorter escape latencies were noted in water maze. The brain samples of kindled mice had elevated malondialdehyde and reduced catalase, superoxide dismutase and glutathione peroxidase enzymes while treatment with PER and PG combination shielded the mice from heightened kindling-associated oxidative stress. Overall, the findings of the present study illustrate that concurrent administration of PER and PG effectively hindered the process of epileptogenesis by protecting neuronal excitability and brain oxidative stress. The results predict the dominance of PER and PG combination over monotherapy which might serve as an effective novel combination to combat drug resistance and behavioral disorders in epileptic patients.

Ameliorative effects of Albizia adianthifolia aqueous extract against pentylenetetrazole-induced epilepsy and associated memory loss in mice: Role of GABAergic, antioxidant defense and anti-inflammatory systems

Albizia adianthifolia (Schumach.) (Fabaceae) is a medicinal herb used for the treatment of epilepsy and memory impairment. This study aims to investigate the anticonvulsant effects of Albizia adianthifolia aqueous extract against pentylenetetrazole (PTZ)-induced spontaneous convulsions in mice; and determine whether the extract could mitigate memory impairment, oxidative/nitrergic stress, GABA depletion and neuroinflammation. Ultra-high performance liquid chromatography/mass spectrometry analysis was done to identify active compounds from the extract. Mice were injected with PTZ once every 48 h until kindling was developed. Animals received distilled water for the normal group and negative control groups, doses of extract (40, 80, or 160 mg/kg) for the test groups and sodium valproate (300 mg/kg) for the positive control group. Memory was measured using Y maze, novel object recognition (NOR) and open field paradigms, while the oxidative/nitrosative stresses (MDA, GSH, CAT, SOD and NO), GABAergic transmission (GABA, GABA-T and GAD) and neuro-inflammation (TNF-α, IFN-γ, IL- 1β, and IL-6) were determined. Brain photomicrograph was also studied. Apigenin, murrayanine and safranal were identified in the extract. The extract (80-160 mg/kg) significantly protected mice against seizures and mortality induced by PTZ. The extract significantly increased the spontaneous alternation and the discrimination index in the Y maze and NOR tests, respectively. PTZ kindling induced oxidative/nitrosative stress, GABA depletion, neuroinflammation and neuronal cells death was strongly reversed by the extract. The results suggest that the anticonvulsant activity of Albizia adianthifolia extract is accompanied by its anti-amnesic property, and may be supported by the amelioration of oxidative stress, GABAergic transmission and neuroinflammation.

A Compared Study of Eicosapentaenoic Acid and Docosahexaenoic Acid in Improving Seizure-Induced Cognitive Deficiency in a Pentylenetetrazol-Kindling Young Mice Model

Epilepsy is a chronic neurological disorder that is more prevalent in children, and recurrent unprovoked seizures can lead to cognitive impairment. Numerous studies have reported the benefits of docosahexaenoic acid (DHA) on neurodevelopment and cognitive ability, while comparatively less attention has been given to eicosapentaenoic acid (EPA). Additionally, little is known about the effects and mechanisms of DHA and EPA in relation to seizure-induced cognitive impairment in the young rodent model. Current research indicates that ferroptosis is involved in epilepsy and cognitive deficiency in children. Further investigation is warranted to determine whether EPA or DHA can mitigate seizure-induced cognitive deficits by inhibiting ferroptosis. Therefore, this study was conducted to compare the effects of DHA and EPA on seizure-induced cognitive deficiency and reveal the underlying mechanisms focused on ferroptosis in a pentylenetetrazol (PTZ)-kindling young mice model. Mice were fed a diet containing DHA-enriched ethyl esters or EPA-enriched ethyl esters for 21 days at the age of 3 weeks and treated with PTZ (35 mg/kg, i.p.) every other day 10 times. The findings indicated that both EPA and DHA exhibited ameliorative effects on seizure-induced cognitive impairment, with EPA demonstrating a superior efficacy. Further mechanism study revealed that supplementation of DHA and EPA significantly increased cerebral DHA and EPA levels, balanced neurotransmitters, and inhibited ferroptosis by modulating iron homeostasis and reducing lipid peroxide accumulation in the hippocampus through activating the Nrf2/Sirt3 signal pathway. Notably, EPA exhibited better an advantage in ameliorating iron dyshomeostasis compared to DHA, owing to its stronger upregulation of Sirt3. These results indicate that DHA and EPA can efficaciously alleviate seizure-induced cognitive deficiency by inhibiting ferroptosis in PTZ-kindled young mice.

Molecular mechanisms underlying cyclophosphamide-induced cognitive impairment and strategies for neuroprotection in preclinical models

Cyclophosphamide has drastically enhanced the expectancy and quality of life of cancer patients. However, it is accompanied by diverse neurological complications which are considered a dose-limiting adverse effect. Neurotoxicity caused by cyclophosphamide can manifest in numerous manners including anxiety, depression, motor dysfunction and cognitive deficits. This review article offers an overview on cyclophosphamide-induced neurotoxicity, providing a unified point of view on the possible underlying molecular mechanisms including oxidative brain damage, neuroinflammation, apoptotic neuronal cell death as well as disruption of the balance of brain neurotransmitters and neurotrophic factors. Besides, this review sheds light on the promising protective agents that have been investigated using preclinical animal models as well as their biological targets and protection mechanisms. Despite promising results in experimental models, none of these agents has been studied in clinical trials. Thus, there is lack of evidence to advocate the use of any neuroprotective agent in the clinical setting. Furthermore, none of the protective agents has been evaluated for its effect on the anticancer activity of cyclophosphamide in tumor-bearing animals. Therefore, there is a great necessity for adequate well-designed clinical studies for evaluation of the therapeutic values of these candidates. Conclusively, this review summarizes the molecular mechanisms accounting for cyclophosphamide-induced neurotoxicity together with the potential protective strategies seeking for downgrading this neurological complication, thus enhancing the quality of life and well-being of cancer patients treated with cyclophosphamide.

DPP-4 inhibitors and type 2 diabetes mellitus in Parkinson's disease: a mutual relationship

Parkinson's disease (PD) usually occurs due to the degeneration of dopaminergic neurons in the substantia nigra (SN). Management of PD is restricted to symptomatic improvement. Consequently, a novel treatment for managing motor and non-motor symptoms in PD is necessary. Abundant findings support the protection of dipeptidyl peptidase 4 (DPP-4) inhibitors in PD. Consequently, this study aims to reveal the mechanism of DPP-4 inhibitors in managing PD. DPP-4 inhibitors are oral anti-diabetic agents approved for managing type 2 diabetes mellitus (T2DM). T2DM is linked with an increased chance of the occurrence of PD. Extended usage of DPP-4 inhibitors in T2DM patients may attenuate the development of PD by inhibiting inflammatory and apoptotic pathways. Thus, DPP-4 inhibitors like sitagliptin could be a promising treatment against PD neuropathology via anti-inflammatory, antioxidant, and anti-apoptotic impacts. DPP-4 inhibitors, by increasing endogenous GLP-1, can also reduce memory impairment in PD. In conclusion, the direct effects of DPP-4 inhibitors or indirect effects through increasing circulating GLP-1 levels could be an effective therapeutic strategy in treating PD patients through modulation of neuroinflammation, oxidative stress, mitochondrial dysfunction, and neurogenesis.

Oxidative Stress and Neurodegeneration in Animal Models of Seizures and Epilepsy

Free radicals are generated in the brain, as well as in other organs, and their production is proportional to the brain activity. Due to its low antioxidant capacity, the brain is particularly sensitive to free radical damage, which may affect lipids, nucleic acids, and proteins. The available evidence clearly points to a role for oxidative stress in neuronal death and pathophysiology of epileptogenesis and epilepsy. The present review is devoted to the generation of free radicals in some animal models of seizures and epilepsy and the consequences of oxidative stress, such as DNA or mitochondrial damage leading to neurodegeneration. Additionally, antioxidant properties of antiepileptic (antiseizure) drugs and a possible use of antioxidant drugs or compounds in patients with epilepsy are reviewed. In numerous seizure models, the brain concentration of free radicals was significantly elevated. Some antiepileptic drugs may inhibit these effects; for example, valproate reduced the increase in brain malondialdehyde (a marker of lipid peroxidation) concentration induced by electroconvulsions. In the pentylenetetrazol model, valproate prevented the reduced glutathione concentration and an increase in brain lipid peroxidation products. The scarce clinical data indicate that some antioxidants (melatonin, selenium, vitamin E) may be recommended as adjuvants for patients with drug-resistant epilepsy.

Oleanolic acid suppresses pentylenetetrazole-induced seizure in vivo

The aim of this study was to investigate the protective effects of triterpene oleanolic acid on the brain tissue of mice with pentylenetetrazole (PTZ)-induced epileptic seizures. Male Swiss albino mice were randomly separated into five groups as the PTZ, control, and oleanolic acid (10, 30, and 100 mg/kg) groups. PTZ injection was seen to cause significant seizures compared with the control group. Oleanolic acid significantly prolonged the latency to onset of myoclonic jerks and the duration of clonic convulsions, and decreased mean seizure scores following PTZ administration. Pretreatment with oleanolic acid also led to an increase in antioxidant enzyme activity (CAT and AChE) and levels (GSH and SOD) in the brain. The data obtained from this study support oleanolic acid may have anticonvulsant potential in PTZ-induced seizures, prevent oxidative stress and protect against cognitive disturbances. These results may provide useful information for the inclusion of oleanolic acid in epilepsy treatment.

Pharmacological modulation of autophagy for epilepsy therapy: opportunities and obstacles

Epilepsy (EP) is a long-term neurological disorder characterized by neuroinflammatory responses, neuronal apoptosis, imbalance between excitatory and inhibitory neurotransmitters, and oxidative stress in the brain. Autophagy is a process of cellular self-regulation to maintain normal physiological functions. Emerging evidence suggests that dysfunctional autophagy pathways in neurons are a potential mechanism underlying EP pathogenesis. In this review, we discuss current evidence and molecular mechanisms of autophagy dysregulation in EP and the probable function of autophagy in epileptogenesis. Moreover, we review the autophagy modulators reported for the treatment of EP models, and discuss the obstacles to, and opportunities for, the potential therapeutic applications of novel autophagy modulators as EP therapies. Teaser: Defective autophagy affects the onset and progression of epilepsy, and many anti-epileptic drugs have autophagy-modulating effects.

Antidiabetic drug sitagliptin blocks cyclophosphamide cerebral neurotoxicity by activating Nrf2 and suppressing redox cycle imbalance, inflammatory iNOS/NO/NF-κB response and caspase-3/Bax activation in rats

Cyclophosphamide (CYP) is a classic DNA-interacting anticancer agent with broad application in chemotherapy. However, CYP cerebral neurotoxicity is a worrisome side effect for clinicians and patients. Strategies to mitigate the underlying oxidative inflammatory cascades and neuroapoptosis induced by CYP are urgently needed. Herein, we have repurposed an antidiabetic drug, sitagliptin (STG), for a possible abrogation of CYP-induced cerebral neurotoxicity in rats. Healthy rats were administered STG (20 mg/kg body weight) for 5 days prior to neurotoxicity induced by CYP (200 mg/kg body weight, ip) on day 5 only, and rats were sacrificed after 24 h post-CYP injection. CYP caused profound increases in the cerebral levels of nitric oxide (NO), acetylcholinesterase (AChE), malondialdehyde (MDA), interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), nuclear factor-kappaB (NF-κB), inducible nitric oxide synthase (iNOS), caspase-3 and Bax protein compared to the control. Furthermore, CYP markedly depressed the activities of glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD), along with levels of reduced glutathione (GSH) and nuclear factor erythroid 2-related factor2 (Nrf2) compared to the control (p < 0.05). Interestingly, STG pretreatment inhibited the CYP-induced alterations in caspase-3, Bax, pro-inflammatory cytokines, NO, iNOS, AChE, NF-κB, and restored the cerebral antioxidant apparatus, including the Nrf2 and histopathological abrasions. Therefore, these findings show that STG could be repurposed to prevent CYP-induced cerebral toxicity in the brain.

Monosodium glutamate induces cortical oxidative, apoptotic, and inflammatory challenges in rats: the potential neuroprotective role of apigenin

Monosodium glutamate (MSG) is used as a flavor, and a taste enhancer was reported to evoke marked neuronal impairments. This study investigated the neuroprotective ability of flavonoid apigenin against neural damage in MSG-administered rats. Adult male rats were allocated into four groups: control, apigenin (20 mg/kg b.wt, orally), MSG (4 g/kg b.wt, orally), and apigenin + MSG at the aforementioned doses for 30 days. Regarding the levels of neurotransmitters, our results revealed that apigenin augmented the activity of acetylcholinesterase (AChE) markedly, and levels of brain monoamines (dopamine, norepinephrine, and serotonin) accompanied by lessening the activity of monoamine oxidase (MAO) as compared to MSG treatment. Moreover, apigenin counteracted the MSG-mediated oxidative stress by decreasing the malondialdehyde (MDA) levels together with elevating the glutathione (GSH) levels. In addition, pretreatment with apigenin induced notable increases in the activities of cortical superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR). Furthermore, apigenin attenuated the cortical inflammatory stress as indicated by lower levels of pro-inflammatory mediators such as interleukin-1 b (IL-1b), tumor necrosis factor-α (TNF-α), and nitric oxide (NO) as well as downregulated inducible nitric oxide synthase (iNOS) expression levels. Histopathological screening validated the abovementioned results and revealed that apigenin restored the distorted cytoarchitecture of the brain cortex. Thus, the present findings collectively suggest that apigenin exerted significant protection against MSG-induced neurotoxicity by enhancing the cellular antioxidant response and attenuating inflammatory machineries in the rat brain cortex.

The effect of glucagon like peptide-1 receptor agonist on behavioral despair and anxiety-like behavior in ovariectomized rats: Modulation of BDNF/CREB, Nrf2 and lipocalin 2

Ovariectomized (OVX) rodents show behavioral despair and anxiety-like behaviors. Glucagon-like peptide-1 receptor agonists (GLP-1RA) possess neuroprotective effects by reducing oxidative stress and neuroinflammation, thereby preventing synaptic loss. The objective of the present study is to evaluate the effect of GLP-1RA, namely liraglutide, on emotional behaviors, and to identify the level of oxidative stress, neuroinflammation, and BDNF signaling in the hippocampus of OVX rats. Forty female young Wistar rats were divided into 5 groups: Control, Control+liraglutide treated, OVX, OVX+fluoxetine, and OVX+liraglutide (150 µg/kg for 15 days, sc). Open field test and elevated plus-maze test were used to evaluate behaviors that are suggestive of anxiety. A forced swimming test was used to evaluate behavioral despair. At the end of the experiments, blood glucose level and body weight gain were measured. The levels of BDNF, CREB, Nrf2, and lipocalin 2 in the hippocampal tissue were measured by ELISA. Malondialdehyde (MDA) and glutathione levels were also evaluated. Statistical analysis was conducted through ANOVA and Bonferroni tests. Seven weeks post-OVX rats exhibited high anxiety related behavior and behavioral despair in comparison with the control groups. These behavioral changes were associated with increased lipocalin 2 and MDA levels in rats. Moreover, BDNF, CREB, and Nrf2 levels decreased significantly in the hippocampus of OVX rats. Liraglutide treatment limited the reduction of BDNF and Nrf2 levels in the hippocampus, maintaining them at the control levels. Liraglutide treatment also prevented the symptoms of behavioral despair and anxiety related behavior. As the main finding of the study GLP-1RA reduced behavioral despair and anxiety level and this may be related to the preservation of BDNF/Nrf2 levels and the decrease in oxidative stress and lipocalin 2 levels in the hippocampus.

Dipeptidyl Peptidase-4 Inhibitor Sitagliptin Exhibits Antioxidant Mechanism for Abrogation of Cyclophosphamide-Induced Cardiac Damage and Oxidative Hepatorenal Toxicity in Rats

Cyclophosphamide (CYP) is a potent DNA-interactive anticancer drug; however, its clinical drawbacks are chiefly associated with induction of oxidative multi-organ toxicity. Sitagliptin (STG) is an antidiabetic dipeptidyl peptidase-4 inhibitor drug with antioxidant efficacy. Herein, we have explored whether STG could abrogate the CYP-induced oxidative stress-mediated cardiac and hepatorenal toxicities in male rats. Sitagliptin (20 mg/kg, o.p) was administered to rats for 5 consecutive days against organ toxicities induced by CYP (200 mg/kg, i.p) on day 5 only. CYP induced marked injuries in the liver, kidney and heart underscored by prominent increases in serum activities of ALT, AST, LDH, creatine kinase and levels of urea, uric acid and creatinine, while albumin level significantly decreased compared to normal control rats. Further, CYP considerably reduced the activities of SOD, CAT, GPx, and levels of GSH, whereas MDA level increased significantly in comparison to control rats. These biochemical alterations were confirmed by multiple histopathological lesions in the tissues. Interestingly, the STG pretreatment abrogated the biochemical and histopathological changes induced by CYP. These results provide first evidence that repurposing STG may protect the liver, kidney and heart from the oxidative deterioration associated with CYP chemotherapy.

4-Phenylbutyric Acid Plus Valproic Acid Exhibits the Therapeutic and Neuroprotective Effects in Acute Seizures Induced by Pentylenetetrazole

Endoplasmic reticulum (ER) stress and apoptosis are implicated in the pathogenesis of epilepsy. Here we examine the effects of valproic acid (VA) plus 4-phenylbutyric acid (4-PBA) on abnormal electrical brain activity, ER stress and apoptosis in acute seizures induced by pentylenetetrazole (PTZ). Forty male rats were randomly divided into five groups, each consisting of 8 rats as follows: Sham, PTZ, VA+PTZ, 4-PBA+PTZ, and VA plus 4-PBA+PTZ. The treated groups received VA, 4-PBA and VA plus 4-PBA by intraperitoneal application for 7 days prior to PTZ-induced seizure. On the 8th day, acute epileptic seizures were induced by PTZ (50 mg/kg, i.p.) injection, except for the sham group. Then, the seizure stage was observed and ECoG activities were recorded during the 30 min. At 24th post seizures, the hippocampus and blood samples were collected for biochemical and histopathological examinations. Administration of VA plus 4-PBA prior to PTZ-induced seizures significantly decreased seizure stage, the duration of generalized tonic-clonic seizure and the total number of spikes as increased the latency to the first myoclonic jerk when compared to the PTZ group. 4-PBA suppressed the increased levels of ER stress markers GRP78 and CHOP in the hippocampus. VA plus 4-PBA treatment before seizures significantly inhibited PTZ-induced elevations of apoptosis-related indicators caspase-3 and caspase-12, and significantly reduced the number of histopathological lesions of the hippocampus region at 24th post seizures. These findings suggest that administration of VA plus 4-PBA prior to PTZ-induced seizures may be involved in the neuroprotective potential of these agents for seizures.

The Function of NF-Kappa B During Epilepsy, a Potential Therapeutic Target

The transcriptional regulator nuclear factor kappa B (NF-κB) modulates cellular biological activity by binding to promoter regions in the nucleus and transcribing various protein-coding genes. The NF-κB pathway plays a major role in the expressing genes related to inflammation, including chemokines, interleukins, and tumor necrosis factor. It also transcribes genes that can promote neuronal survival or apoptosis. Epilepsy is one of the most common brain disorders and it not only causes death worldwide but also affects the day-to-day life of affected individuals. While epilepsy has diverse treatment options, there remain patients who are not sensitive to the existing treatment methods. Recent studies have implicated the critical role of NF-κB in epilepsy. It is upregulated in neurons, glial cells, and endothelial cells, due to neuronal loss, glial cell proliferation, blood-brain barrier dysfunction, and hippocampal sclerosis through the glutamate and γ-aminobutyric acid imbalance, ion concentration changes, and other mechanisms. In this review, we summarize the functional changes caused by the upregulation of NF-κB in the central nervous system during different periods after seizures. This review is the first to deconvolute the complicated functions of NF-κB, and speculate that the regulation of NF-κB can be a safe and effective treatment strategy for epilepsy.

Anticonvulsant activity of β-caryophyllene in association with pregabalin in a seizure model in rats

Epilepsy is a common chronic neurological disease. The hallmark of epilepsy is recurrent, unprovoked seizures. Unfortunately, drug resistance is frequent in patients with epilepsy, and therefore improved therapeutic strategies are needed. In the present study, we tested the effect of pregabalin in association with beta-caryophyllene, an FDA-approved food additive and naturally occurring agonist of cannabinoid receptor subtype 2 against pentylenetetrazol (PTZ)-induced seizures in rats. In addition, selected neurochemical parameters were evaluated in the cerebral cortex. Adult male Wistar rats received beta-caryophyllene (100 mg/kg), pregabalin (40 mg/kg) or their combination before PTZ (60 mg/kg). Appropriated vehicle-treated control groups were included for each treatment. Animals were monitored by video-EEG and the latency to myoclonic seizures, latency to tonic-clonic seizures, tonic-clonic seizure duration and overall seizure score were measured. Glial fibrillary acidic protein (GFAP) release, erythroid-related factor 2 (Nrf2), c-fos and 3-nitrotyrosine (3-NT) levels were evaluated in the frontal cortex. We found that beta-caryophyllene plus pregabalin increased the latency to PTZ-induced myoclonic and tonic-clonic seizures and decreased the tonic-clonic seizure duration and overall seizure score. Interestingly, lower levels of GFAP, c-Fos and 3-NT were observed in animals receiving beta-caryophyllene and pregabalin treatments. Our results suggest a possible synergic effect of beta-caryophyllene plus pregabalin against PTZ induced-seizures.

Pregabalin Protects Brain Tissue from Subarachnoid Hemorrhage by Enhancing HIF-1α/eNOS Signaling and VEGF Production

OBJECTIVE

We investigated the effects of different doses of pregabalin on the pathophysiologic changes in early brain injury after subarachnoid hemorrhage (SAH) in rats.

METHODS

Thirty-eight Wistar albino rats were divided into 4 groups: control (n = 8), SAH (n = 10), SAH plus 30 mg/kg/day of pregabalin (n = 10), and SAH plus 60 mg/kg/day of pregabalin (n = 10). SAH was induced with 0.3 mL of autologous blood injected to the cisterna magna of rats. Pregabalin was administered intraperitoneally. Oxidative stress markers, mRNA expression of endothelial nitric oxide synthase, hypoxia-inducible factor-1α, and vascular endothelial growth factor, and histopathological changes were evaluated.

RESULTS

Pregabalin increased mRNA expression of endothelial nitric oxide synthase, hypoxia-inducible factor-1α, and vascular endothelial growth factor in a dose-dependent manner. Significant improvement in the histopathological parameters was observed at 60 mg/kg, including a decrease in diffuse hemorrhagic areas, edema and apoptotic bodies in the associated cortical area, evident vacuolization in the hippocampal area, and apoptotic bodies. However, these improvements were not observed with the lower dose (30 mg/kg). In contrast, the antioxidant effect was greater with 30 mg/kg of pregabalin than with 60 mg/kg.

CONCLUSIONS

Although the antioxidant effect was significant with the lower dose of pregabalin, the anti-inflammatory effects via vasodilatation were more marked with the higher dose. Significant improvements in the histopathological changes were observed with the higher dose of pregabalin. The dose-dependent effects of pregabalin on SAH should be evaluated in animal studies as a function of time and in the acute and chronic phases.

Gamma-Decanolactone Alters the Expression of GluN2B, A1 Receptors, and COX-2 and Reduces DNA Damage in the PTZ-Induced Seizure Model After Subchronic Treatment in Mice

Gamma-decanolactone (GD) has been shown to reduce epileptic behavior in different models, inflammatory decreasing, oxidative stress, and genotoxic parameters. This study assessed the GD effect on the pentylenetetrazole (PTZ) model after acute and subchronic treatment. We evaluated the expression of the inflammatory marker cyclooxygenase-2 (COX-2), GluN2B, a subunit of the NMDA glutamate receptor, adenosine A1 receptor, and GD genotoxicity and mutagenicity. Male and female mice were treated with GD (300 mg/kg) for 12 days. On the tenth day, they were tested in the Hot Plate test. On the thirteenth day, all animals received PTZ (90 mg/kg), and epileptic behavior PTZ-induced was observed for 30 min. Pregabalin (PGB) (30 mg/kg) was used as a positive control. Samples of the hippocampus and blood were collected for Western Blotting analyses and Comet Assay and bone marrow to the Micronucleus test. Only the acute treatment of GD reduced the seizure occurrence and increased the latency to the first stage 3 seizures. Males treated with GD for 12 days demonstrated a significant increase in the expression of the GluN2B receptor and a decrease in the COX-2 expression. Acute and subchronic treatment with GD and PGB reduced the DNA damage produced by PTZ in males and females. There is no increase in the micronucleus frequency in bone marrow after subchronic treatment. This study suggests that GD, after 12 days, could not reduce PTZ-induced seizures, but it has been shown to protect against DNA damage, reduce COX-2 and increase GluN2B expression.

Repurposing of Omarigliptin as a Neuroprotective Agent Based on Docking with A2A Adenosine and AChE Receptors, Brain GLP-1 Response and Its Brain/Plasma Concentration Ratio after 28 Days Multiple Doses in Rats Using LC-MS/MS

The authors in the current work suggested the potential repurposing of omarigliptin (OMR) for neurodegenerative diseases based on three new findings that support the preliminary finding of crossing BBB after a single dose study in the literature. The first finding is the positive results of the docking study with the crystal structures of A_2A adenosine (A2AAR) and acetylcholine esterase (AChE) receptors. A2AAR is a member of non-dopaminergic GPCR superfamily receptor proteins and has essential role in regulation of glutamate and dopamine release in Parkinson’s disease while AChE plays a major role in Alzheimer’s disease as the primary enzyme responsible for the hydrolytic metabolism of the neurotransmitter acetylcholine into choline and acetate. Docking showed that OMR perfectly fits into A2AAR binding pocket forming a distinctive hydrogen bond with Threonine 256. Besides other non-polar interactions inside the pocket suggesting the future of the marketed anti-diabetic drug (that cross BBB) as a potential antiparkinsonian agent while OMR showed perfect fit inside AChE receptor binding site smoothly because of its optimum length and the two fluorine atoms that enables quite lean fitting. Moreover, a computational comparative study of OMR docking, other 12 DPP-4 inhibitors and 11 SGLT-2 inhibitors was carried out. Secondly, glucagon-like peptide-1 (GLP-1) concentration in rats’ brain tissue was determined by the authors using sandwich GLP-1 ELISA kit bio-analysis to ensure the effect of OMR after the multiple doses’ study. Brain GLP-1 concentration was elevated by 1.9-fold following oral multiple doses of OMR (5 mg/kg/day, p.o. for 28 days) as compared to the control group. The third finding is the enhanced BBB crossing of OMR after 28 days of multiple doses that had been studied using LC-MS/MS method with enhanced liquid–liquid extraction. A modified LC-MS/MS method was established for bioassay of OMR in rats’ plasma (10–3100 ng/mL) and rats’ brain tissue (15–2900 ng/mL) using liquid–liquid extraction. Alogliptin (ALP) was chosen as an internal standard (IS) due to its LogP value of 1.1, which is very close to the LogP of OMR. Extraction of OMR from samples of both rats’ plasma and rats’ brain tissue was effectively achieved with ethyl acetate as the extracting solvent after adding 1N sodium carbonate to enhance the drug migration, while choosing acetonitrile to be the diluent solvent for the IS to effectively decrease any emulsion between the layers in the stated method of extraction. Validation results were all pleasing including good stability studies with bias of value below 20%. Concentration of OMR in rats’ plasma were determined after 2 h of the latest dose from 28 days multiple doses, p.o, 5 mg/kg/day. It was found to be 1295.66 ± 684.63 ng/mL estimated from the bio-analysis regression equation. OMR passed through the BBB following oral administration and exhibited concentration of 543.56 ± 344.15 ng/g in brain tissue, taking in consideration the dilution factor of 10. The brain/plasma concentration ratio of 0.42 (543.56/1295.66) was used to illustrate the penetration power through the BBB after the multiple doses for 28 days. Results showed that OMR passed through the BBB more effectively in the multiple dose study as compared to the previously published single dose study by the authors. Thus, the present study suggests potential repositioning of OMR as antiparkinsonian agent that will be of interest for researchers interested in neurodegenerative diseases.

Neurotoxic effects of pregabalin dependence on the brain frontal cortex in adult male albino rats

Pregabalin (PGB) is an analog of the inhibitory neurotransmitter gamma-aminobutyric acid. The currently available evidence favors the misuse and abuse potential of PGB. However, its neurotoxicity remains unclear. Therefore, this study assessed the toxic effects of chronic pregabalin dependence as well as withdrawal on the cortical neurons of the frontal lobe. This study included eighty adult male albino rats which were divided into three groups. Group I (Control) included 40 rats and was further subdivided into two equal subgroups (IA and IB) as negative and positive controls. Group II (PGB-dependent) included 20 rats which received PGB starting with the therapeutic dose (300 mg/day), then the doses were gradually increased until they reached the dependent dose (3400 mg/day) by the end of the first month. Further, the dependent dose was given daily for another 2 months. Group III (PGB withdrawal) included 20 rats which received PGB as described in group II. After that, administration of PGB was stopped and the rats were kept for another one month. By the end of the experiment, all animals were sacrificed by cervical decapitation. The specimens were taken from the frontal cortex for histologic and immunohistochemical staining as well as morphometric analysis. Sections of the frontal cortex of group II showed changes in the form of disturbed architectural pattern of cortical layers, apoptotic cells, weak immunoexpression of Bcl-2 and VEGF as well as moderate-strong immunoexpression of iNOS and nestin. These expressions were significantly different from the control groups, but they were non-significant in comparison with group III. These findings indicate that chronic PGB dependence induces neurotoxic effects mainly in the form of neuronal apoptosis, gliosis, and oxidative stress injury of the frontal cortex. The PGB- induced neurotoxic effects persisted after withdrawal. The influence of these neurotoxic effects and their relevance to the cognitive or neurologic disorders in PGB-dependent individuals warrants further research. Furthermore, it is recommended to quantify the behavioral changes related to PGB dependence as well as withdrawal in future studies.

Activation of autophagy by sitagliptin attenuates cadmium-induced testicular impairment in rats: Targeting AMPK/mTOR and Nrf2/HO-1 pathways

AIMS

Cadmium (Cd) is a prevalent environmental contaminant that incurs deleterious health effects, including testicular impairment. Sitagliptin, a selective dipeptidyl peptidase-4 (DPP-4) inhibitor, has demonstrated marked cardio-, hepato-, and reno-protective actions, however, its impact on Cd-triggered testicular dysfunction has not been formerly investigated. Hence, the present study aimed to explore the probable beneficial impact of sitagliptin against Cd-evoked testicular impairment which may add to its potential clinical utility. The underlying mechanisms pertaining to the balance between testicular autophagy and apoptosis were explored, including the AMPK/mTOR and Nrf2/HO-1 pathways.

MATERIALS AND METHODS

The testicular tissues were examined using histopathology, immunohistochemistry, Western blotting, and ELISA. Sitagliptin (10 mg/kg/day, by gavage) was administered for 4 consecutive weeks.

KEY FINDINGS

Sitagliptin attenuated the testicular impairment via improvement of the relative testicular weight, sperm count/motility, sperm abnormalities, and serum testosterone. Additionally, sitagliptin counteracted Cd-induced histologic aberrations/disrupted spermatogenesis. Interestingly, sitagliptin augmented the defective autophagy as demonstrated by upregulating Beclin 1 protein expression and lowering p62 SQSTM1 protein accumulation. These effects were mediated via the activation of testicular AMPK/mTOR pathway as proven by increasing p-AMPK (Ser485, Ser491)/total AMPK and diminishing p-mTOR (Ser2448)/total mTOR protein expression. Additionally, sitagliptin suppressed the testicular apoptotic events via downregulating Bax and upregulating Bcl-2 protein expression. In tandem, sitagliptin suppressed the oxidative stress through lowering lipid peroxides and activating Nrf2/HO-1 pathway via upregulating the protein expression of Nrf2, and the downstream effectors HO-1 and GPx.

SIGNIFICANCE

Sitagliptin attenuated Cd-induced testicular injury via boosting the autophagy/apoptosis ratio through activation of AMPK/mTOR and Nrf2/HO-1 pathways.

Tiron alleviates MPTP-induced Parkinsonism in mice via activation of Keap-1/Nrf2 pathway

Parkinsonism is a neurodegenerative disease that is common all over the world. This study aimed at exploring the neuroprotective effect of tiron against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinsonism. MPTP (30 mg/kg, intraperitoneally [ip]) was injected in mice daily for 5 consecutive days. Mice were treated with tiron (140 and 280 mg/kg, ip) or levodopa (8.4 mg/kg, orally) for 10 consecutive days starting 5 days before MPTP injection. At the end of the experiment, behavioral tests were conducted to assess the neuroprotective effect of tiron. Moreover, oxidative stress was assessed via measuring antioxidant enzyme, such as catalase, and lipid peroxidation was evaluated as malondialdehyde. Neuronal damage was also detected by histopathological examination and via estimating hippocampal levels of dopamine, γ-aminobutyric acid, and nuclear factor erythroid-derived 2-like 2. In addition, the expression of Kelch-like ECH-associated protein 1 and heme oxygenase-1 was assessed by immunohistochemistry. Compared with the blank control group and the positive control group, the inhibitory effect of tiron on MPTP-induced neurodegenerative injury was statistically significant.

Protective effect of pregabalin on the brain tissue of diabetic rats

Purpose

Diabetes mellitus (DM) is a metabolic disorder characterized by insulin deficiency or insulin resistance. Pregabalin (PGB) is an antiepileptic drug with proven efficacy in the treatment of epilepsy, generalized anxiety disorder, and neuropathic pain. In this study, we aimed to investigate the protective effects of PGB in brain tissue of rats with streptozotocin (STZ)-induced experimental diabetes.

Materials and methods

Twenty-eight Wistar albino male rats were randomly divided into four groups with seven rats each: (I) Control group, (II) PGB (50 mg/kg PBG), (III) DM, and (IV) DM + PGB (50 mg/kg/day PGB per orally for 8 weeks). Diabetes was induced with an intraperitoneal (i.p.) STZ injection (Sigma Chemical Co Louis Missour, USA) at a dose of 180 mg/kg. STZ was dissolved in 0.1 M phosphate-citrate tampon (pH 4.5). Paraffin sections were examined using histological and immunohistochemical analyses. To detect oxidative damage biochemically, malondialdehyde (MDA), the end product of lipid peroxidation; superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and glutathione peroxidase (GPx) which are antioxidant enzymes, levels were studied. In addition, bax, caspase-3 enzyme activities and TUNEL assay were studied to evaluate the apoptosis status.

Results

In the DM group, MDA concentrations were significantly higher and GPx and SOD activities were significantly lower compared to the control group. MDA concentrations were significantly lower and SOD activity was significantly higher in the DM + PGB group than in the DM group. The GPx activity in the DM group decreased significantly compared to the control group. In immunohistochemical examinations (Bax, Caspase-3 and TUNEL), the apoptosis rate was significantly lower in the in DM + PGB group than in the DM group.

Conclusion

Pregabalin may prevent harmful effects of oxidative damage by decreasing the MDA levels and increasing the SOD levels. In addition, it was thought that PGB may have antiapoptotic properties due to decreased bax and caspase-3 immunoreactivity and TUNEL positivity in PGB groups. Based on these findings, we think that PGB may be effective in reducing the risk of brain damage associated with DM.

Autophagy associated with the efficacy of valproic acid in PTZ-induced epileptic rats

Valproic acid (VPA) is a widely used antiepileptic drugs. Patients who are non-responsive to VPA often present to the clinic; however, the mechanism of resistance is unclear. In this study, we found that responder and non-responder pentylenetetrazole-induced chronic epileptic rats had no significant differences in VPA concentrations in their plasma and brain tissues. Furthermore, through an RNA-sequence method, we identified 334 differentially expressed genes between VPA-responsive and non-responsive rats, while 21 pathways were enriched. Interestingly, 16 pathways, including the phagosome pathway, were commonly enriched compared to those in patients. We used transmission electron microscopy and immunofluorescence microscopy to further assess the level of autophagy in responder and non-responder rats. Non-responders had more autophagic vacuoles and an increased level of LC3B expression. Furthermore, epileptic rats that were previously administered 3-methyadenine (an inhibitor of autophagy) exhibited a slight increase in VPA efficacy. In conclusion, autophagy was associated with the efficacy of VPA.

Ameliorative effects of pregabalin on LPS induced endothelial and cardiac toxicity

We investigated the antioxidant, anti-inflammatory and anti-apoptotic effects of pregabalin (PREG) on lipopolysaccharide (LPS) induced sepsis related cardiotoxicity via NF-kβ pathways. We used 24 female Wistar albino rats divided into three groups: control, LPS treated and LPS + PREG treated. Total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), tumor necrosis factor alpha (TNF-α), nuclear factor kappa beta (NF-kβ)/p65, p-NF-kβ/p65, caspase-3 (Cas-3) and cleaved Cas-3 were measured in cardiac tissues and creatine kinase MB (CKMB), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) levels were measured in blood samples. Also, Cas-3, granulocyte-colony stimulating factors (G-CSF), interleukin-6 (IL-6), serum amyloid A (SAA) and inducible nitric oxide synthase (iNOS) were measured immunohistochemically in heart and aorta tissue. In the LPS group; the levels of CKMB, AST, LDH, TOS, OSI increased and TAS decreased. TNF-α, p-NF-kβ/p65 and Cas-3 protein levels also increased in the LPS group. Immunohistochemical evaluation of the heart and aorta revealed a significant increase in the levels of Cas-3, G-CSF, SAA, IL-6 and iNOS in the LPS group. PREG treatment restored all measurements to near normal. LPS induced cardiovascular toxicity was due to inflammation, oxidative stress and apoptosis. PREG ameliorated the damage by inhibition of NF-kβ phosphorylation.

Pregabalin administration and withdrawal affect testicular structure and functions in rats

The aim of this prospective experimental study was to investigate the effects of pregabalin (PG) administration and withdrawal on testicular structures and functions in rats. A total of 24 male Wistar rats were divided into two groups (n = 12 each): a control group received normal saline, and PG-treated group received 62 mg kg^-1  day^-1 PG for 2 months. Half the animals of each group were sacrificed for the collection of blood and testicular samples. The remaining animals were bred for another 2 months without treatment before collection of blood and testicular samples. PG administration decreased testosterone and increased luteinising hormone (LH) and follicle-stimulating hormone (FSH) levels versus controls. PG withdrawal led to a decrease in both FSH and LH and an increase in testosterone levels versus saline withdrawal. Compared to controls, PG administration caused degeneration of seminiferous tubules and decreased the number of spermatogenic but increased the number of Leydig cells. After PG withdrawal, these cells showed a rebound reverse. Reduced glutathione levels increased with PG administration while PG withdrawal increased malondialdehyde levels. Conclusion: PG administration affected testicular morphometry, gonadotrophic and sex hormones; however, there was a rebound reversal in all these parameters and a significant oxidative stress in PG withdrawal.

Role of oxidative stress in epileptogenesis and potential implications for therapy

In a state of balance between oxidants and antioxidants, free radicals play an advantageous role of “redox messengers”. In a state of oxidative stress, they trigger a cascade of events leading to epileptogenesis. During this latent, free of seizures period, a cascade of neurological changes takes place and finally leads to spontaneous recurrent seizures. The main processes involved in seizure generation are: neuroinflammation, neurodegeneration with anomalous neuroregeneration and lowering seizure threshold. Time of epileptogenesis offers a unique therapeutic window to prevent or at least attenuate seizure development. Animal data indicate that some antioxidants (for instance, resveratrol) may bear an anti-epileptogenic potential.

mTOR-Related Cell-Clearing Systems in Epileptic Seizures, an Update

Recent evidence suggests that autophagy impairment is implicated in the epileptogenic mechanisms downstream of mTOR hyperactivation. This holds true for a variety of genetic and acquired epileptic syndromes besides malformations of cortical development which are classically known as mTORopathies. Autophagy suppression is sufficient to induce epilepsy in experimental models, while rescuing autophagy prevents epileptogenesis, improves behavioral alterations, and provides neuroprotection in seizure-induced neuronal damage. The implication of autophagy in epileptogenesis and maturation phenomena related to seizure activity is supported by evidence indicating that autophagy is involved in the molecular mechanisms which are implicated in epilepsy. In general, mTOR-dependent autophagy regulates the proliferation and migration of inter-/neuronal cortical progenitors, synapse development, vesicular release, synaptic plasticity, and importantly, synaptic clustering of GABA_A receptors and subsequent excitatory/inhibitory balance in the brain. Similar to autophagy, the ubiquitin–proteasome system is regulated downstream of mTOR, and it is implicated in epileptogenesis. Thus, mTOR-dependent cell-clearing systems are now taking center stage in the field of epilepsy. In the present review, we discuss such evidence in a variety of seizure-related disorders and models. This is expected to provide a deeper insight into the molecular mechanisms underlying seizure activity.

Anti-inflammatory potentials of incretin-based therapies used in the management of diabetes

GLP-1 receptor agonists (GLP-1RA) and dipeptidyl peptidase 4 inhibitors (DPP-4i) are two classes of antidiabetic agents used in the management of diabetes based on incretin hormones. There is emerging evidence that they have anti-inflammatory effects. Since most long-term complications of diabetes have a background of chronic inflammation, these agents may be beneficial against diabetic complications not only due to their hypoglycemic potential but also via their anti-inflammatory effects. However, the exact molecular mechanisms by which GLP-1RAs and DPP-4i exert their anti-inflammatory effects are not clearly understood. In this review, we discuss the potential molecular pathways by which these incretin-based therapies exert their anti-inflammatory effects.

Neuroprotective Effects of Brain-Gut Peptides: A Potential Therapy for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease and is typically associated with progressive motor and non-motor dysfunctions. Currently, dopamine replacement therapy is mainly used to relieve the motor symptoms, while its long-term application can lead to various complications and does not cure the disease. Numerous studies have demonstrated that many brain-gut peptides have neuroprotective effects in vivo and in vitro, and may be a promising treatment for PD. In recent years, some progress has been made in studies on the neuroprotective effects of some newly-discovered brain-gut peptides, such as glucagon-like peptide 1, pituitary adenylate cyclase activating polypeptide, nesfatin-1, and ghrelin. However, there is still no systematic review on the neuroprotective effects common to these peptides. Thus, here we review the neuroprotective effects and the associated mechanisms of these four peptides, as well as other brain-gut peptides related to PD, in the hope of providing new ideas for the treatment of PD and related clinical research.

Investigating the possible pain attenuating mechanisms of pregabalin in chronic constriction injury-induced neuropathic pain in rats

Aim of the study: The current study was aimed to investigate the neuropathic pain attenuating mechanism of pregabalin using chronic constriction injury (CCI) model in rats. Material and Methods: The sciatic nerve was ligated by placing four loose ligatures around it to induce neuropathic pain. The pain development in terms of cold allodynia, mechanical hyperalgesia, and heat hyperalgesia was assessed on the 7th and 14th day after surgery, using acetone drop, pinprick, and hot plate tests. On the 14th day after the injury, pain parameters were assessed 30 minutes after administration of pregabalin (30 mg/kg) and sodium nitroprusside (5 mg/kg) in CCI-subjected rats. Results: CCI led to induction of neuropathic pain, which was more prominent on 14th day in comparison to 7th day. A single administration of pregabalin and sodium nitroprusside on 14th day, markedly reduced pain parameters and increased serum nitrite levels. Pretreatment with L-NAME abolished neuropathic pain attenuating effects of pregabalin suggesting that pregabalin may increase the levels of nitric oxide to mitigate neuropathic pain. Pretreatment with naloxone significantly abrogated pain attenuating effects of pregabalin and sodium nitroprusside in CCI-subjected rats suggesting that pregabalin and nitric oxide-mediated analgesic action are mediated through release of endogenous opioids. Moreover, naloxone failed to modulate pregabalin-induced increase in nitric oxide levels suggesting that the opioid system does not control the nitric oxide levels, and opioids may be downstream modulators of nitric oxide. Conclusion: Pregabalin may increase the release of nitric oxide, which may increase the release of endogenous opioids to attenuate neuropathic pain in CCI subjected rats.

GLP-1's role in neuroprotection: a systematic review

Glucagon-like peptide 1 (GLP-1) is a target for treatment of diabetes; however, its function in the brain is not well studied. In this systematic review, we aimed to analyze the neuroprotective role of GLP-1 and its defined mechanisms. Methods: We searched 'Web of Science' and 'Pubmed' to identify relevant studies using GLP-1 as the keyword. Two hundred and eighty-nine clinical and preclinical studies have been included. Data have been presented by grouping neurodegenerative, neurovascular and specific cell culture models. Results: Recent literature shows that GLP-1 and its agonists, DPP-4 inhibitors and combined GLP-1/GIP molecules are effective in partially or fully reversing the effects of neurotoxic compounds, neurovascular complications of diabetes, neuropathological changes related with Alzheimer's disease, Parkinson's disease or vascular occlusion. Possible mechanisms that provide neuroprotection are enhancing the viability of the neurons and restoring neurite outgrowth by increased neurotrophic factors, increasing subventricular zone progenitor cells, decreasing apoptosis, decreasing the level of pro-inflammatory factors, and strengthening blood-brain barrier. Conclusion: Based on the preclinical studies, GLP-1 modifying agents are promising targets for neuroprotection. On the other hand, the number of clinical studies that investigate GLP-1 as a treatment is low and further clinical trials are needed for a benchside to bedside translation of recent findings.

Neuroprotective influence of sitagliptin against cisplatin-induced neurotoxicity, biochemical and behavioral alterations in Wistar rats

Cisplatin has been extensively used as a chemotherapeutic agent since around 40 years, though its usage is limited due to severe adverse effects like neurotoxicity that might be because of oxidative stress. Hence, the present study was planned to investigate the possible protective role of sitagliptin against cisplatin-associated neurotoxic, biochemical, and behavioral alterations in male Wistar rats. Sitagliptin is a dipeptidyl peptidase-4 inhibitor that shows dual effects by improving the control on metabolism as well as decreasing the debility in cognitive function that is associated with increased insulin sensitivity and antioxidant property. For the in vitro assay, cultured rat pheochromocytoma (PC12) cells were exposed to different concentrations (10, 20, and 50 mM) of sitagliptin for 24 h. Cisplatin at 5 mM concentrations was added and cell viability was assessed using MTT assay. For in vivo study, animals were divided into four groups. Group I (Vehicle control): animals were administered 0.9% (w/v) of normal saline (1 mL/100 g; p.o.). Group II (Cisplatin): animals were treated with cisplatin (2 mg/kg; i.p.). Group III (Cisplatin + sitagliptin): animals were administered cisplatin along with sitagliptin. Group IV (Sitagliptin): animals were given sitagliptin (10 mg/kg; p.o.). All the treatments were administered for 8 weeks. On last day of treatment, behavioral evaluations including locomotor and rotarod studies were performed. In addition, several antioxidant enzymes were also estimated from cerebellum tissues; such as levels of thiobarbituric acid reactive substance (TBARS) were determined as a marker of lipid peroxidation, reduced glutathione (GSH) and catalase (CAT) were also estimated. Histological study of cerebellum tissue was also performed after performing the behavioral study. Exposure to cisplatin decreased cell viability in PC12 cells which were significantly increased by co-treatment with sitagliptin. In in vivo study, cisplatin significantly elevated the level of TBARS and reduced the level of antioxidant enzymes such as GSH and CAT which were significantly restored in sitagliptin + cisplatin group of rats. In addition, cisplatin impaired performance on the locomotor and rotarod activities, whereas sitagliptin significantly improved the performance of both activities. These results suggested the neuroprotective influence of sitagliptin by protecting cerebellum part of brain against cisplatin-induced toxicity.

Neuroprotective Activity of Sitagliptin via Reduction of Neuroinflammation beyond the Incretin Effect: Focus on Alzheimer's Disease

Sitagliptin is a member of a class of drugs that inhibit dipeptidyl peptidase (DPP-4). It increases the levels of the active form of incretins such as GLP-1 (glucagon-like peptide-1) or GIP (gastric inhibitory polypeptide) and by their means positively affects glucose metabolism. It is successfully applied in the treatment of diabetes mellitus type 2. The most recent scientific reports suggest beneficial effect of sitagliptin on diseases in which neuron damage occurs. Result of experimental studies may indicate a reducing influence of sitagliptin on inflammatory response within encephalon area. Sitagliptin decreased the levels of proinflammatory factors: TNF-α (tumor necrosis factor-α), IL-6 (interleukin-6), IL-17 (interleukin-17), and CD-163 (cluster of differentiation 163), and contributed to an increase in levels of anti-inflammatory factors: IL-10 (interleukin-10) and TGF-β (transforming growth factor β). Moreover, sitagliptin demonstrated antioxidative and antiapoptotic properties by modifying glutamate and glutathione levels within the region of hippocampus in mice. It has been observed that sitagliptin decreases accumulation of β-amyloid within encephalon structures in experimental models of Alzheimer's dementia. This effect may be connected with SDF-1α (stromal cell-derived factor 1α) concentration. Administration of sitagliptin caused a significant improvement in MMSE (Mini-Mental State Examination) tests used for assessment of dementias. The paper presents potential mechanisms of sitagliptin activity in conditions connected with neuroinflammation with special emphasis on Alzheimer's disease.

Repositioning of Omarigliptin as a once-weekly intranasal Anti-parkinsonian Agent

Drug repositioning is a revolution breakthrough of drug discovery that presents outstanding privilege with already safer agents by scanning the existing candidates as therapeutic switching or repurposing for marketed drugs. Sitagliptin, vildagliptin, saxagliptin & linagliptin showed antioxidant and neurorestorative effects in previous studies linked to DPP-4 inhibition. Literature showed that gliptins did not cross the blood brain barrier (BBB) while omarigliptin was the first gliptin that crossed it successfully in the present work. LC-MS/MS determination of once-weekly anti-diabetic DPP-4 inhibitors; omarigliptin & trelagliptin in plasma and brain tissue was employed after 2 h of oral administration to rats. The brain/plasma concentration ratio was used to deduce the penetration power through the BBB. Results showed that only omarigliptin crossed the BBB due to its low molecular weight & lipophilic properties suggesting its repositioning as antiparkinsonian agent. The results of BBB crossing will be of interest for researchers interested in Parkinson's disease. A novel intranasal formulation was developed using sodium lauryl sulphate surfactant to solubilize the lipophilic omarigliptin with penetration enhancing & antimicrobial properties. Intranasal administration showed enhanced brain/plasma ratio by 3.3 folds compared to the oral group accompanied with 2.6 folds increase in brain glucagon-like peptide-1 concentration compared to the control group.

Sitagliptin rescues memory deficits in Parkinsonian rats via upregulating BDNF to prevent neuron and dendritic spine loss

OBJECTIVES

Parkinson's disease (PD) is a neurodegenerative disease with high morbidity among adults worldwide that causes tremendous trouble to people's lives. The purpose of this study was to investigate the impact of sitagliptin on PD and its potential mechanism.

METHODS

First, the memory of rats in each group was evaluated with the Morris water maze (MWM) test and the passive avoidance test. Then, both brain-derived neurotrophic factor (BDNF) protein and mRNA levels were detected by ELISA and qPCR assays, respectively. Then, rapid Golgi impregnation was used to observe the density of dendritic spines in the hippocampal CA1 area. Finally, k252a, an antagonist of Trk receptors, was used to block the binding of BDNF with its receptors, and the effects of sitagliptin on PD improvement were detected.

RESULTS

Our study showed that sitagliptin improved memory deficits in PD rats. Meanwhile, the expression level of BDNF and tyrosine hydroxylase (TH) was upregulated, and the density of dendritic spine was increased by sitagliptin administration. Moreover, K252a administration blocked the positive effects of sitagliptin on memory in PD rats.

DISCUSSION

Sitagliptin rescued the memory deficits, which was achieved by upregulating BDNF to prevent neuronal death and dendritic spine loss. Our findings indicate that sitagliptin might be a promising potential drug for PD treatment in the future.

A predictive index of biomarkers for ictogenesis from tier I safety pharmacology testing that may warrant tier II EEG studies

Three significant contributions to the field of safety pharmacology were recently published detailing the use of electroencephalography (EEG) by telemetry in a critical role in the successful evaluation of a compound during drug development (1] Authier, Delatte, Kallman, Stevens & Markgraf; JPTM 2016; 81:274-285; 2] Accardi, Pugsley, Forster, Troncy, Huang & Authier; JPTM; 81: 47-59; 3] Bassett, Troncy, Pouliot, Paquette, Ascaha, & Authier; JPTM 2016; 70: 230-240). These authors present a convincing case for monitoring neocortical biopotential waveforms (EEG, ECoG, etc) during preclinical toxicology studies as an opportunity for early identification of a central nervous system (CNS) risk during Investigational New Drug (IND) Enabling Studies. This review is about "ictogenesis" not "epileptogenesis". It is intended to characterize overt behavioral and physiological changes suggestive of drug-induced neurotoxicity/ictogenesis in experimental animals during Tier 1 safety pharmacology testing, prior to first dose administration in man. It is the presence of these predictive or comorbid biomarkers expressed during the requisite conduct of daily clinical or cage side observations, and in early ICH S7A Tier I CNS, pulmonary and cardiovascular safety study designs that should initiate an early conversation regarding Tier II inclusion of EEG monitoring. We conclude that there is no single definitive clinical marker for seizure liability but plasma exposures might add to set proper safety margins when clinical convulsions are observed. Even the observation of a study-related full tonic-clonic convulsion does not establish solid ground to require the financial and temporal investment of a full EEG study under the current regulatory standards.

PREFATORY NOTE

For purposes of this review, we have adopted the FDA term "sponsor" as it refers to any person who takes the responsibility for and initiates a nonclinical investigations of new molecular entities; FDA uses the term "sponsor" primarily in relation to investigational new drug application submissions.

Journey to the Center of the Fetal Brain: Environmental Exposures and Autophagy

Fetal brain development is known to be affected by adverse environmental exposures during pregnancy, including infection, inflammation, hypoxia, alcohol, starvation, and toxins. These exposures are thought to alter autophagy activity in the fetal brain, leading to adverse perinatal outcomes, such as cognitive and sensorimotor deficits. This review introduces the physiologic autophagy pathways in the fetal brain. Next, methods to detect and monitor fetal brain autophagy activity are outlined. An additional discussion explores possible mechanisms by which environmental exposures during pregnancy alter fetal brain autophagy activity. In the final section, a correlation of fetal autophagy activity with the observed postnatal phenotype is attempted. Our main purpose is to provide the current understanding or a lack thereof mechanisms on autophagy, underlying the fetal brain injury exposed to environmental insults.