Central cholinergic function and metabolic changes in streptozotocin-induced rat brain injury

Auranofin-loaded PLGA nanoparticles alleviate cognitive deficit induced by streptozotocin in rats model: modulation of oxidative stress, neuroinflammatory markers, and neurotransmitters

Alzheimer's disease remains an unsolved neurological puzzle with no cure. Current therapies offer only symptomatic relief, hindered by limited uptake through the blood-brain barrier. Auranofin, an FDA-approved compound, exhibits potent antioxidative and anti-inflammatory properties targeting brain disorders. Yet, its oral bioavailability challenge prompts the exploration of nanoformulation-based solutions enhancing blood-brain barrier penetrability. The study aimed to investigate the neuroprotective potential of auranofin nanoparticles in streptozotocin-induced AD rats. Auranofin-containing polylactic-co-glycolic acid nanoparticles were formulated by the multiple emulsion solvent evaporation method. Characterization was done by determining entrapment efficiency, particle size distribution, surface charge, and morphology. An in vivo study was performed by administering streptozotocin (3 mg/kg/i.c.v., days 1 and 3), auranofin (5 and 10 mg/kg), auranofin nanoparticles (2.5 and 5 mg/kg), and donepezil (2 mg/kg) for 14 days orally. Behavioral deficits were evaluated using the open field test, Morris water maze, objective recognition test, change in oxidative stress levels, and AD markers in the brain. Following the decapitation of the rats, the brains were excised to isolate the hippocampus. Subsequent analyses included the quantification of biochemical and neuroinflammatory markers, as well as the assessment of neurotransmitter levels. The characterization of auranofin nanoparticles showed an entrapment efficiency of 98%, an average particle size of 101.5 ± 10.3 nm, a surface charge of 27.5 ± 5.10 mV, and a polydispersity index of 0.438 ± 0.12. In vivo, administration of auranofin and auranofin nanoparticles significantly reversed streptozotocin-induced cognitive deficits, biochemical alteration, neuroinflammatory markers, and neurotransmitter levels. The present finding suggests that auranofin nanoparticles have more significant neuroprotective potential than auranofin alone. The therapeutic efficacy may be attributed to its antioxidant and anti-inflammatory properties, as well as its positive neuromodulatory effects. Therefore, our findings suggest that it could be a promising candidate for Alzheimer's disease therapy.

Attenuation of PI3K/AKT signaling pathway by Ocimum gratissimum leaf flavonoid-rich extracts in streptozotocin-induced diabetic male rats

Diabetes is a group of medical conditions characterized by the body's inability to effectively control blood glucose levels, due to either insufficient insulin synthesis in type 1 diabetes or inadequate insulin sensitivity in type 2 diabetes. According to this research, the PI3K/AKT pathway of Ocimum gratissimum leaf flavonoid-rich extracts in streptozotocin-induced diabetic rats was studied. We purchased and used a total of forty (40) male Wistar rats for the study. We divided the animals into five (5) different groups: normal control (Group A), diabetic control (Group B), low dose (150 mg/kg body weight) of Ocimum gratissimum flavonoid-rich leaf extract (LDOGFL) (Group C), high dose (300 mg/kg body weight) of Ocimum gratissimum flavonoid-rich leaf extract (HDOGFL) (Group D), and 200 mg/kg of metformin (MET) (Group E). Streptozotocin induced all groups except Group A, which serves as the normal control group. The experiment lasted for 21 days, following which we sacrificed the animals and harvested their brains for biochemical analysis on the 22nd day. We carried out an analysis that included reduced glutathione (GSH), glutathione transferases (GST), catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD), along with GLUT4, MDA, pro-inflammatory cytokines, NO, neurotransmitters, cholinergic enzyme activities, cardiolipin, and the gene expression of PI3K/AKT. The obtained result indicates that the flavonoid-rich extracts of O. gratissimum significantly enhanced the levels of GSH, GST, CAT, GPx, and SOD, as well as GLUT4 and cardiolipin. The levels of GSH, GST, CAT, GPx, and SOD, as well as GLUT4 and cardiolipin, were significantly increased by gratissimum. Moreover, the extracts decrease the levels of MDA, pro-inflammatory cytokines, NO, neurotransmitters, and cholinergic enzyme activities. Additionally, the flavonoid-rich extracts of O. gratissimum significantly improved the AKT and PI3K gene expressions in diabetic rats. gratissimum had their AKT and PI3K gene expressions significantly (p < 0.05) improved. The findings indicate that O. gratissimum leaf flavonoids have the potential to treat diabetes mellitus. gratissimum leaf flavonoids possess therapeutic potential in themselves and can be applied in the management of diabetes mellitus. Although further analysis can be carried out in terms of isolating, profiling, or purifying the active compounds present in the plant's extract.

The effect of intra-nasal co-treatment with insulin and growth factor-rich serum on behavioral defects, hippocampal oxidative-nitrosative stress, and histological changes induced by icv-STZ in a rat model

Impaired insulin and growth factor functions are thought to drive many alterations in neurodegenerative diseases like dementia and seem to contribute to oxidative stress and inflammatory responses. Recent studies revealed that nasal growth factor therapy could induce neuronal and oligodendroglia protection in rodent brain damage induction models. Impairment of several growth factors signaling was reported in neurodegenerative diseases. So, in the present study, we examined the effects of intranasal co-treatment of insulin and a pool of growth factor-rich serum (GFRS) which separated from activated platelets on memory, and behavioral defects induced by intracerebroventricular streptozotocin (icv-STZ) rat model also investigated changes in the hippocampal oxidative-nitrosative state and histology. We found that icv-STZ injection (3 mg/kg bilaterally) impairs spatial learning and memory in Morris Water Maze, leads to anxiogenic-like behavior in the open field arena, and induces oxidative-nitrosative stress, neuroinflammation, and neuronal/oligodendroglia death in the hippocampus. GFRS (1µl/kg, each other day, 9 doses) and regular insulin (4 U/40 µl, daily, 18 doses) treatments improved learning, memory, and anxiogenic behaviors. The present study showed that co-treatment (GFRS + insulin with respective dose) has more robust protection against hippocampal oxidative-nitrosative stress, neuroinflammation, and neuronal/oligodendroglia survival in comparison with the single therapy. Memory and behavioral improvements in the co-treatment of insulin and GFRS could be attributed to their effects on neuronal/oligodendroglia survival and reduction of neuroinflammation in the hippocampus.

Exploring the potential of a novel phenoxyethyl piperidine derivative with cholinesterase inhibitory properties as a treatment for dementia: Insights from STZ animal model of dementia

Alzheimer's disease (AD) is a neurodegenerative disease, often characterized by progressive deficits in memory and cognitive functions. Cholinesterase inhibitors have been introduced as promising agents to enhance cognition and memory in both human patients and animal models of AD. In the current study, we assessed the effects of a synthetic phenoxyethyl piperidine derivative, compound 7c, as a novel dual inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), on learning and memory, as well as serum and hippocampal AChE levels in an animal model of AD. The model of dementia was induced by intracerebroventricular injection of streptozotocin (STZ, 2 mg/kg) to male Wistar rats. STZ-treated rats received compound 7c (3, 30, and 300 µg/kg) for five consecutive days. ​Passive avoidance (PA) learning and memory, as well as spatial learning and memory using Morris water maze, were evaluated. The level of AChE was measured in the serum and the left and right hippocampus. Findings demonstrated that compound 7c (300 µg/kg) was able to reverse STZ-induced impairments in PA memory, while also reduced the increased AChE level in the left hippocampus. Taken together, compound 7c appeared to act as a central AChE inhibitor, and its role in alleviating cognitive deficits in the AD animal model suggests that it may have therapeutic potential in AD dementia. Further research is required to assess the effectiveness of compound 7c in more reliable models of AD in light of these preliminary findings.

Animal model of Alzheimer's disease induced by streptozotocin: New insights about cholinergic pathway

Alzheimer's disease (AD) is of multifactorial origin, and still presents several gaps regarding its development and progression. Disorders of the cholinergic system are well known to be involved in the pathogenesis of AD, characterized by increased acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and decreased acetyltransferase (ChAT) enzymatic activities. Late onset AD (LOAD) animal model induced by intracerebroventricular injection of streptozotocin (icv-STZ) showed promising results in this context, due to the similarity with the pathophysiology of human LOAD. Thus, this study aimed to assess the long-term effects of icv-STZ on the cholinergic system, through the measuring of AChE and BChE enzymatic activities in hippocampus, prefrontal cortex and liver of animals euthanized 30 and 120-days after the icv-STZ. Regarding the cholinergic response to icv-STZ, the 30-days and 120-days STZ-induced rats exhibit decreased AChE and BChE activities only in the hippocampus. The cognitive deficit was more consistent in the 30-days post icv-STZ animals, as was the weight loss. This is the first study to investigate the long-term effects (more than 60 days) of the icv-STZ on AChE and BChE activities, and our results, as well as those of a recent study, suggest that the cholinergic system may not be compromised by icv-STZ, at least in the long term, which means that this model may not be the best model for studying the cholinergic system in AD or that it is informative only for a short period.

Cognitive Dysfunction and Anxiety Resulting from Synaptic Downscaling, Hippocampal Atrophy, and Ventricular Enlargement with Intracerebroventricular Streptozotocin Injection in Male Wistar Rats

Insulin-resistant brain state is proposed to be the early sign of Alzheimer's disease (AD), which can be studied in the intracerebroventricular streptozotocin (ICV-STZ) rodent model. ICV-STZ is reported to induce sporadic AD with the majority of the disease hallmarks as phenotype. On the other hand, available experimental evidence has used varying doses of STZ (< 1 to 3 mg/kg) and studied its effect for different study durations, ranging from 14 to 270 days. Though these studies suggest 3 mg/kg of ICV-STZ to be the optimum dose for progressive pathogenesis, the reason for such is elusive. Here, we sought to investigate the mechanism of action of 3 mg/kg ICV-STZ on cognitive and non-cognitive aspects at a follow-up interval of 2 weeks for 2 months. On the 60th day, we examined the layer thickness, cell density, ventricular volume, spine density, protein expression related to brain metabolism, and mitochondrial function by histological examination. The findings suggest a progressive loss of a spatial, episodic, and avoidance memory with an increase in anxiety in a span of 2 months. Furthermore, hippocampal neurodegeneration, ventricular enlargement, diffused amyloid plaque deposition, loss of spine in the dentate gyrus, and imbalance in energy homeostasis were found on the 60th day post-injection. Interestingly, AD rats showed a uniform fraction of time spent in four quadrants of the water maze with a change in strategy when they were exposed to height. Our findings reveal that ICV-STZ injection at a dose of 3 mg/kg can cause cognitive and neuropsychiatric abnormalities due to structural loss both at the neuronal as well as the synaptic level, which is tightly associated with the change in neuronal metabolism.

Effects of Magnesium Orotate, Benfotiamine and a Combination of Vitamins on Mitochondrial and Cholinergic Function in the TgF344-AD Rat Model of Alzheimer's Disease

Glucose hypometabolism, mitochondrial dysfunction, and cholinergic deficits have been reported in early stages of Alzheimer’s disease (AD). Here, we examine these parameters in TgF344-AD rats, an Alzheimer model that carries amyloid precursor protein and presenilin-1 mutations, and of wild type F344 rats. In mitochondria isolated from rat hippocampi, we found reductions of complex I and oxidative phosphorylation in transgenic rats. Further impairments, also of complex II, were observed in aged (wild-type and transgenic) rats. Treatment with a “cocktail” containing magnesium orotate, benfotiamine, folic acid, cyanocobalamin, and cholecalciferol did not affect mitochondrial activities in wild-type rats but restored diminished activities in transgenic rats to wild-type levels. Glucose, lactate, and pyruvate levels were unchanged by age, genetic background, or treatment. Using microdialysis, we also investigated extracellular concentrations of acetylcholine that were strongly reduced in transgenic animals. Again, ACh levels in wild-type rats did not change upon treatment with nutrients, whereas the cocktail increased hippocampal acetylcholine levels under physiological stimulation. We conclude that TgF344-AD rats display a distinct mitochondrial and cholinergic dysfunction not unlike the findings in patients suffering from AD. This dysfunction can be partially corrected by the application of the “cocktail” which is particularly active in aged rats. We suggest that the TgF344-AD rat is a promising model to further investigate mitochondrial and cholinergic dysfunction and potential treatment approaches for AD.