Protective Effect of Topiramate against Diabetic Retinopathy and Computational Approach Recognizing the Role of NLRP3/IL-1β/TNF-α Signaling

The possible impact of topiramate against diabetic retinopathy (DREN) and its molecular mechanisms in relation to the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome has not been studied before. Thus, in the present study, we aimed to utilize a computational approach to investigate the possible protective effect of topiramate on experimental DREN and explore its impact on NLRP3/interlukin-1β signaling and brain-derived neurotrophic factor (BDNF) expression. Male albino mice were distributed to four experimental groups and assigned the following categorizations: (i) saline, (ii) diabetic, (iii) diabetic + topiramate 10 mg/kg and (iv) diabetic + topiramate 30 mg/kg. We observed shrinkage of total retinal thickness and elevation in retinal glutamate, malondialdehyde, NLRP3 and interlukin-1β but decreased glutathione (GSH) levels in the diabetic mice. Additionally, retinal ultra-structures in the diabetic group showed abnormalities and vacuolations in the pigmented epithelium, the photoreceptor segment, the outer nuclear layer, the inner nuclear layer and the ganglion cell layer (GCL). Mice treated with topiramate 10 or 30 mg/kg showed downregulation in retinal malondialdehyde, NLRP3 and interlukin-1β levels; improvements in the retinal pathologies; enhanced immunostaining for BDNF and improved ultra-structures in different retinal layers. Overall, the current results suggest topiramate as a neuroprotective agent for DREN, and future studies are warranted to further elucidate the mechanism of its protective action.

Carbamazepine Alleviates Retinal and Optic Nerve Neural Degeneration in Diabetic Mice via Nerve Growth Factor-Induced PI3K/Akt/mTOR Activation

Aim: Diabetic retinopathy causes loss of vision in adults at working-age. Few therapeutic options are available for treatment of diabetic retinopathy. Carbamazepine (CARB), a widely used antiepileptic drug, was recently accounted for its neuroprotective effect. Nerve growth factor (NGF) activates various cascades among which, PI3K/Akt/mTOR pathway has a vital action in NGF-mediated neuronal differentiation and survival. This study evaluated the effect of CARB in the treatment of diabetic retina and unveiled some of the underlying molecular mechanisms. Main Methods: Alloxan diabetes model was induced in 36 albino well-acclimatized mice. After establishment of the diabetic model in 9 weeks, mice were assigned to treatment groups: (1) saline, (2) alloxan-diabetic, (3 and 4) alloxan+CARB (25 or 50 mg per kg p.o) for 4 weeks. After completion of the therapeutic period, mice were sacrificed and eyeballs were enucleated. Retinal levels of NGF and PI3K/Akt were assessed using real-time polymerase chain reaction. Further, total and phosphorylated TrKA, PI3K, Akt, mTOR as well as Caspase-3 were measured by Western blot analysis. Key Findings: Histopathological examination demonstrated that CARB attenuated vacuolization and restored normal thickness and organization of retinal cell layers. In addition, CARB increased pTrKA/TrKA ratio and ameliorated diabetes-induced reduction of NGF mRNA and immunostaining in retina. Additionally, it augmented the mRNA expression of PI3K and Akt, as well as the protein level of the phosphorylated PI3/Akt/mTOR. Significance: Results highlighted, for the first time, the neuronal protective effect for CARB in diabetic retina, which is mediated, at least in part, by activation of the NGF/PI3K/Akt/mTOR pathway.

Standarized Tribulus terrestris extract protects against rotenone-induced oxidative damage and nigral dopamine neuronal loss in mice

Strong evidence proposes that brain oxidative DNA damage and microglia activation contribute to Parkinson's disease (PD) pathogenesis. Traditional therapeutic regimens for PD can only relieve the symptoms. Tribulus terrestris (T. terrestris), a flowering plant from family Zygophyllaceae, is used in traditional medicine for treating different disorders and exerts neuroprotective and antioxidant effects in experimental models. The current study attempted to test whether treatment with T. terrestris standardized extract (TTE) can improve motor dysfunction and alleviate rotenone induced oxidative DNA damage and neurotoxicity in mice. Six groups of male Swiss albino mice were utilized. Group (1) was the vehicle (oil) group, group 2 was the rotenone control group (1 mg/kg/48 hours, subcutaneously) for 9 times, groups 3 and 4 were injected with rotenone and treated with TTE (5 or 10 mg per kg, by oral gavage) for 17 days, groups 5 and 6 served as TTE (5 or 10 mg per kg) per se groups. Motor function was measured by the pole and the open-field tests. Then, mouse brains were dissected, one hemisphere was employed for biochemical assays and the other one was used in histopathological studies. Results demonstrated that TTE ameliorated the motor dysfunctions induced by rotenone as well as markers of inflammation and DNA damage (8-OHdG and MTH1 expression). Indicators of oxidative stress and upregulation of the microglia marker (CD₁₁b) were suppressed by the higher dose of TTE (10 mg per kg). Finally, the higher dose of TTE improved the Cresyl violet staining and tyrosine hydroxylase immunostaining in the substantia nigra. In summary, TTE ameliorated the locomotor dysfunction and dampened the DNA damage and oxidoinflammatory stress in rotenone-parkinsonian mice. These results suggest TTE as a potential candidate for neurodegenerative diseases.