An Animal Model to Test Reversal of Cognitive Decline Associated with Beta-Amyloid Pathologies

Amelioration of intracerebroventricular streptozotocin-induced cognitive dysfunction by Ocimum sanctum L. through the modulation of inflammation and GLP-1 levels

DPP-4 inhibitors have been shown to reverse amyloid deposition in Alzheimer's disease (AD) patients with cognitive impairment. Ocimum sanctum L. leaves reported the presence of important phytoconstituents which are reported to have DPP-4 inhibitory activity. To investigate the effects of petroleum ether extract of Ocimum sanctum L. (PEOS) in Intracerebroventricular streptozotocin (ICV-STZ) induced AD rats. ICV-STZ (3 mg/kg) was injected bilaterally into male Wistar rats, while sham animals received the artificial CSF. The ICV-STZ-induced rats were administered with three doses of PEOS (100, 200, and 400 mg/kg, p.o.) for thirty days. All experimental rats were subjected to behaviour parameters (radial arm maze task and novel object recognition test), neurochemical parameters such as GLP-1, Aβ42, and TNF-α levels, and histopathological examination (Congo red staining) of the left brain hemisphere. PEOS significantly reversed the spatial learning and memory deficit exhibited by ICV-STZ-induced rats. Furthermore, PEOS also shows promising results in retreating Aβ deposition, TNF α, and increasing GLP-1 levels. The histopathological study also showed a significant dose-dependent reduction in amyloid plaque formation and dense granule in PEOS -treated rats as compared to the ICV-STZ induced rats (Negative control). The results show that extract of Ocimum sanctum L. attenuated ICV-STZ-induced learning and memory deficits in rats and has the potential to be employed in the therapy of AD.

Sodium-calcium exchanger isoform-3 targeted Withania somnifera (L.) Dunal therapeutic intervention ameliorates cognition in the 5xFAD mouse model of Alzheimer's disease

The third isoform of the Na+-Ca2+ exchanger (NCX3) is crucial for a physiological fine-tuning of the Ca2+ fluxes in excitable tissues. In this view, the NCX3 accounts for the aberrant Ca2+ influx seen during neuronal excitotoxicity, such as in Alzheimer's disease (AD). However, little is known about NCX3 regulation and functional properties. Withania somnifera (L.) Dunal (W. somnifera), a traditional indigenous plant widely recognized for having numerous medicinal values, was undertaken to determine its potential therapeutic benefit against aggregated Aβ1-42-induced NCX3 dysregulation and the thereof cognition impairment in 5xFAD mice. The undertaken sourced dried roots of authenticated W. somnifera physicochemical compositional tests satisfied standards of pharmacognostic quality, and further phytochemical analysis of the roots methanol extract revealed the roots constitute several antioxidants. Following an intra-gastric gavage administration of synthesized W. somnifera roots methanolic extract from postnatal day 30 (P30) to P75, in vivo cognitional studies and then neurochemical examinations of the NCX3 expression level, Aβ plaque deposition, and antioxidant activities in the AD-associated brain regions of 4-month-old 5xFAD mice suggests that the oxidative stress normalizing effects of W. somnifera constituents, operating on the NCX3, may have a therapeutic role in the improvement of cognition in AD.

Cerebrospinal Fluid (CSF) Exchange Therapy with Artificial CSF Enriched with Mesenchymal Stem Cell Secretions Ameliorates Cognitive Deficits and Brain Pathology in Alzheimer's Disease Mice

BACKGROUND

The high complexity of neurodegenerative diseases, including Alzheimer's disease (AD), and the lack of effective treatments point to the need for a broader therapeutic approach to target multiple components involved in the disease pathogenesis.

OBJECTIVE

To test the efficacy of 'cerebrospinal fluid (CSF) exchange therapy' in AD-mice. This novel therapeutic approach we recently proposed is based on the exchange of the endogenous pathogenic CSF with a new and healthy one by drainage of the endogenous CSF and its continuous replacement with artificial CSF (aCSF) enriched with secretions from human mesenchymal stem cells (MSCs).

METHODS

We treated AD-mice (amyloid-beta injected) with MSC secretions-enriched-aCSF using an intracerebroventricular CSF exchange procedure. Cognitive and histological analysis were performed.

RESULTS

We show that the MSC secretions enriched CSF exchange therapy improved cognitive performance, paralleled with increased neuronal counts (NeuN positive cells), reduced astrocytic burden (GFAP positive cells), and increased cell proliferation and neurogenesis (Ki67 positive cells and DCX positive cells) in the hippocampus. This beneficial effect was noted on days 5-10 following 3-consecutive daily exchange treatments (3 hours a day). A stronger effect was noted using a more prolonged CSF exchange protocol (3-consecutive daily exchange treatments with 3 additional treatments twice weekly), with cognitive follow-up performed as early as 2-3 days after treatment. Some increase in hippocampal cell proliferation, but no change in the other histological parameters, was noticed when performing CSF exchange therapy using unenriched aCSF relative to untreated AD-mice, yet smaller than with the enriched aCSF treatment.

CONCLUSION

These findings point to the therapeutic potential of the CSF exchange therapy using MSC secretions-enriched aCSF in AD, and might be applied to other neurodegenerative and dementia diseases.

Redox-active phytoconstituents ameliorate cell damage and inflammation in rat hippocampal neurons exposed to hyperglycemia+Aβ1-42 peptide

Alzheimer's disease (AD) is the most common dementia causing progressive loss of memory and compromised cognitive functions. Although the neurotoxic mechanisms underlying AD have yet to be fully elucidated, hyperglycemia seems to trigger oxidative and inflammatory responses in the brain of afflicted patients. Removal of free radicals reduces the neurotoxic effects of hyperglycemia in AD models. In this study we investigated the neuroprotective effects of the antioxidant phytoconstituents oleuropein (OLE), rutin (RUT), luteolin (LUT) and S-allylcysteine (SAC) in an experimental model combining the exposure to high glucose (HG, mimicking chronic hyperglycemia) plus amyloid-β peptide 1-42 (Aβ_1-42, mimicking AD) in primary hippocampal neurons. Cells were pre-treated with OLE, RUT, LUT or SAC (10-1000 nM), and then co-treated with high glucose (GLU, 150 mM) for 24 h plus 500 nM oligomeric Aβ_1-42 for 24 h more. Cell viability and reactive oxygen species (ROS) formation were assessed as indices of survival/toxicity and oxidative stress, respectively. Activity/expression of antioxidant enzymes, toxic adducts, inflammatory molecules, mitochondrial membrane potential (ΔΨm) and the pattern of amyloid aggregation were also assessed. The GLU + Aβ_1-42 treatment significantly decreased cell viability, increased ROS formation, reduced superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities, augmented Advanced Glycation End Products- and 4-hydroxynonenal-adducts generation, increased 3-nitrotyrosine and inflammatory outcomes such as inducible nitric oxide synthase, interleukin 1β and Tumor Necrosis Factor α, decreased MMP and augmented amyloid aggregation. All phytoconstituents reduced in a differential manner all toxic endpoints, with SAC showing the highest efficacy in preventing loss of cell viability and oxidative damage, whereas RUT was most efficacious in mitigating inflammatory endpoints. Combined, the results of this study suggest that protection afforded by these compounds against GLU + Aβ_1-42-induced cell damage in hippocampal neurons is attributable to their properties as redox modulators, which might act through a concerted mechanism oriented to reduce oxidative stress and neuroinflammation.

Mitochondrial Transfer Ameliorates Cognitive Deficits, Neuronal Loss, and Gliosis in Alzheimer's Disease Mice

Pathogenesis of neurodegenerative diseases involves dysfunction of mitochondria, one of the most important cell organelles in the brain, with its most prominent roles in producing energy and regulating cellular metabolism. Here we investigated the effect of transferring active intact mitochondria as a potential therapy for Alzheimer's disease (AD), in order to correct as many mitochondrial functions as possible, rather than a mono-drug related therapy. For this purpose, AD-mice (amyloid-β intracerebroventricularly injected) were treated intravenously (IV) with fresh human isolated mitochondria. One to two weeks later, a significantly better cognitive performance was noticed in the mitochondria treated AD-mice relative to vehicle treated AD-mice, approaching the performance of non-AD mice. We also detected a significant decrease in neuronal loss and reduced gliosis in the hippocampus of treated mice relative to untreated AD-mice. An amelioration of the mitochondrial dysfunction in brain was noticed by the increase of citrate-synthase and cytochrome c oxidase activities relative to untreated AD-mice, reaching activity levels of non-AD-mice. Increased mitochondrial activity was also detected in the liver of mitochondria treated mice. No treatment-related toxicity was noted. Thus, IV mitochondrial transfer may possibly offer a novel therapeutic approach for AD.

Cannabinoid-profiled agents improve cell survival via reduction of oxidative stress and inflammation, and Nrf2 activation in a toxic model combining hyperglycemia+Aβ1-42 peptide in rat hippocampal neurons

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder linked to various converging toxic mechanisms. Evidence suggests that hyperglycemia induces oxidative stress, mitochondrial dysfunction, inflammation and excitotoxicity, all of which play important roles in the onset and progression of AD pathogenesis. The endocannabinoid system (ECS) orchestrates major physiological responses, including neuronal plasticity, neuroprotection, and redox homeostasis, to name a few. The multi-targeted effectiveness of the ECS emerges as a potential approach to treat AD. Here we characterized the protective properties of the endocannabinoids arachidonylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG), the synthetic cannabinoids CP 55-940 and WIN 55,212-2, and the fatty acid amide hydrolase (FAAH) inhibitor URB597, on a combined hyperglycemia + oligomeric amyloid β peptide (Aβ1-42) neurotoxic model in primary hippocampal neurons which exhibit several AD features. Cells were treated with cannabinoid agents at increased concentrations (1 nM-1 μM) for 6 h, and then co-treated with 150 mM glucose (GLU, 24 h), followed by incubation with 500 nM Aβ1-42 (24 h). Cell viability/survival, reactive oxygen species (ROS) levels, antioxidant enzyme (SOD, CAT, GPx and GRx) activities, biological products of oxidative damage (AGE and HNE adducts) and nitrosative stress (3-NT), several endpoints of inflammation (iNOS, IL-1β and TNF-α), amyloid quantification, mitochondrial membrane potential, and the involvement of the Nrf2 pathway, were all evaluated. The combined high glucose + amyloid beta 1-42 (GLU + Aβ1-42) condition decreased cell viability and mitochondrial membrane potential, while augmenting oxidative damage and inflammation. All agents tested preserved cell viability and stimulated mitochondrial membrane potential, while reducing all the evaluated toxic endpoints in a differential manner, with URB597 showing the highest efficacy. The neuroprotective efficacy of all cannabinoid agents, except for URB597, led to partial recruitment of specific antioxidant activity and Nrf2 pathway regulation. Our results support the neuroprotective potential of these agents at low concentrations against the damaging effects of GLU + Aβ1-42, affording new potential modalities for the design of AD therapies.