Retinoprotective effect of donepezil in diabetic mice involves mitigation of excitotoxicity and activation of PI3K/mTOR/BCl2 pathway

Donepezil protects against cyclophosphamide-induced premature ovarian failure in mice: A focus on proinflammatory cytokines and NLRP3/TLR-4/NF-κB interplay

BACKGROUND AND AIM

Cyclophosphamide (CP) chemotherapy is a significant iatrogenic component of premature ovarian failure (POF). The aim of this work was to evaluate the potential protective effects of donepezil, a centrally acting acetylcholinesterase (AChE) inhibitor, on CP-induced POF in mice.

METHODS

40 female Swiss albino mice were split into 5 equal groups: group 1 (control), group 2 (CP-POF); induced by intraperitoneal injection of CP on 8th day of the experiment, and group (3-5); mice received oral donepezil daily (1, 2, or 4 mg/kg, respectively) 8 days before CP injection. Mice were euthanized after 24 h of CP injection, and blood samples were collected to assay serum anti-Mullerian hormone (AMH) levels. Ovarian tissues were dissected, and the right ovary was processed for further assays of nitric oxide (NO), tumor necrosis factor-α (TNF-α), interlukin-6 (IL-6), nucleotide-binding domain-like receptor family, the Pyrin domain-containing 3 (NLRP3) inflammasome, and Toll-like receptor 4 (TLR-4), while the left one was processed for histopathological and immunohistochemical examination of nuclear factor-Kappa beta (NF-κB) and caspase-3.

RESULTS

Donepezil, in a dose-dependent manner particularly (4 mg/kg), has an inhibitory action on NO (40 ± 2.85 vs. 28.20 ± 2.23, P < 0.001), proinflammatory cytokines (P < 0.001), the TLR-4/ NF-κB / NLRP3 inflammasome pathway (P < 0.001), and apoptosis (P < 0.001), with a significant elevation in the AMH levels (4.57 ± 1.08 vs. 8.57 ± 0.97, P < 0.001) versus CP-POF group.

CONCLUSION

Donepezil may be a potential protective agent against CP-induced POF in mice, but further research is needed to fully understand its therapeutic function experimentally and clinically.

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.

Topiramate affords neuroprotection in diabetic neuropathy model via downregulating spinal GFAP/inflammatory burden and improving neurofilament production

The current study aimed to test the neuroprotective action of topiramate in mouse peripheral diabetic neuropathy (DN) and explored some mechanisms underlying this action. Mice were assigned as vehicle group, DN group, DN + topiramate 10-mg/kg and DN + topiramate 30-mg/kg. Mice were tested for allodynia and hyperalgesia and then spinal cord and sciatic nerves specimens were examined microscopically and neurofilament heavy chain (NEFH) immunostaining was performed. Results indicated that DN mice had lower the hotplate latency time (0.46-fold of latency to licking) and lower von-Frey test pain threshold (0.6-fold of filament size) while treatment with topiramate increased these values significantly. Sciatic nerves from DN control mice showed axonal degeneration while spinal cords showed elevated GFAP (5.6-fold) and inflammatory cytokines (∼3- to 4-fold) but lower plasticity as indicated by GAP-43 (0.25-fold). Topiramate produced neuroprotection and suppressed spinal cord GFAP/inflammation but enhanced GAP-43. This study reinforces topiramate as neuroprotection and explained some mechanisms included in alleviating neuropathy.

Serum cholinesterase is associated with incident diabetic retinopathy: the Shanghai Nicheng cohort study

BACKGROUND

Serum cholinesterase (ChE) is positively associated with incident diabetes and dyslipidemia. We aimed to investigate the relationship between ChE and the incidence of diabetic retinopathy (DR).

METHODS

Based on a community-based cohort study followed for 4.6 years, 1133 participants aged 55-70 years with diabetes were analyzed. Fundus photographs were taken for each eye at both baseline and follow-up investigations. The presence and severity of DR were categorized into no DR, mild non-proliferative DR (NPDR), and referable DR (moderate NPDR or worse). Binary and multinomial logistic regression models were used to estimate the risk ratio (RR) and 95% confidence interval (CI) between ChE and DR.

RESULTS

Among the 1133 participants, 72 (6.4%) cases of DR occurred. The multivariable binary logistic regression showed that the highest tertile of ChE (≥ 422 U/L) was associated with a 2.01-fold higher risk of incident DR (RR 2.01, 95%CI 1.01-4.00; P for trend < 0.05) than the lowest tertile (< 354 U/L). The multivariable binary and multinomial logistic regression showed that the risk of DR increased by 41% (RR 1.41, 95%CI 1.05-1.90), and the risk of incident referable DR was almost 2-fold higher than no DR (RR 1.99, 95%CI 1.24-3.18) with per 1-SD increase of log_e-transformed ChE. Furthermore, multiplicative interactions were found between ChE and elderly participants (aged 60 and older; P for interaction = 0.003) and men (P for interaction = 0.044) on the risk of DR.

CONCLUSIONS

In this study, ChE was associated with the incidence of DR, especially referable DR. ChE was a potential biomarker for predicting the incident DR.

Memantine mitigates ROS/TXNIP/NLRP3 signaling and protects against mouse diabetic retinopathy: Histopathologic, ultrastructural and bioinformatic studies

Diabetic retinopathy (DRET) triggers vision loss in adults, however, little therapeutic options are existing. Memantine is an anti-Alzheimer drug that antagonizes the activity of glutamate at N-methyl-D-aspartate (NMDA) receptors. Glutamate and thioredoxin-interacting protein (TXNIP) are known to be overexpressed in diabetic retinas and can produce activation of NOD-like receptor protein 3 (NLRP3) with subsequent secretion of interlukin-1β. This study repurposed memantine for its neuroprotective effect in experimental DRET and tested its impact on ROS/TXNIP/NLRP3. In addition, KEGG pathway database and STRING database identified the protein-protein interaction between glutamate receptors and TXNIP/NLRP3. Male Swiss albino mice received alloxan (180 mg/kg) to induce DRET. After 9 weeks, we divided the mice into groups: (a) saline, (ii) DRET, (iii and iv) DRET + oral memantine (5 or 10 mg per kg) for 28 days. Then, mice were euthanized, and eyeballs were removed. Retinal samples were utilized for biochemical, histopathological, and electron microscopy studies. Retinal levels of glutamate, TXNIP, NLRP3 and interlukin-1β were estimated using ELISA technique as well as retinal malondialdehyde. Histopathological and ultrastructural examination demonstrated that oral memantine attenuated vacuolization and restored normal retinal cell layers. Moreover, memantine reduced TXNIP, NLRP3, interleukin-1β and MDA concentrations. These results provide evidence demonstrating memantine' efficacy in alleviating DRET via suppressing reactive oxygen species/TXNIP/NLRP3 signaling cascade. Therefore, memantine might serve as a potential therapy for retinopathy after adequate clinical research.

Metabolism Dysregulation in Retinal Diseases and Related Therapies

The human retina, which is part of the central nervous system, has exceptionally high energy demands that requires an efficient metabolism of glucose, lipids, and amino acids. Dysregulation of retinal metabolism disrupts local energy supply and redox balance, contributing to the pathogenesis of diverse retinal diseases, including age-related macular degeneration, diabetic retinopathy, inherited retinal degenerations, and Macular Telangiectasia. A better understanding of the contribution of dysregulated metabolism to retinal diseases may provide better therapeutic targets than we currently have.

Pantao Pill Improves the Learning and Memory Abilities of APP/PS1 Mice by Multiple Mechanisms

Background: To explore the effect and mechanisms of Pantao Pill (PTP) on cognitive impairment.

Methods: Network pharmacology was performed to analyze the mechanism of PTP treating cognitive impairment. The targets of PTP and cognitive impairment were predicted and used to construct protein-protein interaction (PPI) networks. The intersection network was selected, and the core network was obtained through topological analysis. Enrichment analysis was conducted to obtain the GOBP terms and KEGG pathways. We then performed experiments to validate the results of the network pharmacology by using an APP/PS1 transgenic mouse model. The APP/PS1 mice were divided into four groups: the model group, the high-dose PTP (3.6 g/kg·d) group, the low-dose PTP (1.8 g/kg·d) group, and the positive control group (donepezil hydrochloride, 2 mg/kg·d). Wild-type (WT) C57 mice served as a normal control group. PTP and donepezil were administered by gavage for 8 weeks.

Results: Network pharmacology showed that PTP might improve cognitive impairment by regulating autophagy, apoptosis, and oxidative stress. For the Morris water maze test, a significant difference was shown in the total swimming distance among groups (p < 0.05) in the positioning navigation experiment, and with training time extension, the swimming speed increased (p < 0.01). In the space probe test, PTP administration significantly reduced the swimming path length and the escape latency of APP/PS1 mice (p < 0.05 or p < 0.01), whereas it had no effect on the swimming speed (p > 0.05). PTP (3.6 g/kg/d) rescued the reduction of norepinephrine and acetylcholine levels (p < 0.05), and increased the acetylcholinesterase concentration (p < 0.05) in the brain tissue. PTP (1.8 g/kg/d) increased the norepinephrine level (p < 0.01). PTP rescued the activity reduction of superoxide dismutase in the brain tissue (p < 0.01) and the neuron cell pyknosis in the hippocampal CA region (p < 0.05). PTP reduced ATG12 and PS1 expression (p < 0.05 or p < 0.01), and increased Bcl-2 expression in the brain tissue (p < 0.05).

Conclusion: PTP can significantly improve the learning and memory abilities of APP/PS1 mice, and the mechanism may be related to the increase of neurotransmitter acetylcholine and norepinephrine levels, the reduction of the excessive autophagic activation, and the suppression of oxidative stress and excessive apoptotic activity.

Protective effect of metformin on rat diabetic retinopathy involves suppression of toll-like receptor 4/nuclear factor-k B expression and glutamate excitotoxicity

Microvascular complications of diabetes mellitus are progressively significant reasons for mortality. Metformin (MET) is considered as the first-line therapy for type 2 diabetes patients, and may be especially beneficial in cases of diabetic retinopathy although the precise mechanisms of MET action are not fully elucidated. The current study was designed to inspect the antioxidant and modulatory actions of MET on DRET in streptozotocin-induced diabetic rats. The effect of MET on the toll-like receptor 4/nuclear factor kappa B (TLR4/NFkB), inflammatory burden and glutamate excitotoxicity was assessed. Twenty-four male rats were assigned to four experimental groups: (1) Vehicle group, (2) Diabetic control: developed diabetes by injection of streptozotocin (60 mg/kg, i.p.). (3&4) Diabetic + MET group: diabetic rats were left for 9 weeks without treatment and then received oral MET 100 and 200 mg/kg for 6 weeks. Retinal samples were utilized in biochemical, histological, immunohistochemical and electron microscopic studies. MET administration significantly decreased retinal level of insulin growth factor and significantly suppressed the diabetic induced increase of malondialdehyde, glutamate, tumor necrosis factor-α and vascular endothelial growth factor (VEGF). Further, MET decreased the retinal mRNA expression of NFkB, tumor necrosis factor-α and TLR4 in diabetic rats. The current findings shed the light on MET's efficacy as an adjuvant therapy to hinder the development of diabetic retinopathy, at least partly, via inhibition of oxidative stress-induced NFkB/TLR4 pathway and suppression of glutamate excitotoxicity.