Neuro-amelioration of cinnamaldehyde in aluminum-induced Alzheimer’s disease rat model

Cinnamaldehyde/lactulose combination therapy alleviates thioacetamide-induced hepatic encephalopathy via targeting P2X7R-mediated NLRP3 inflammasome signaling

AIMS

Cinnamaldehyde (CA), the main active constituent of cinnamon oil, is reported to have neuroprotective effects. However, the potential benefits of CA for brain protection in hepatic encephalopathy (HE) are still not understood. Thus, the present study investigates the possible ameliorative effect of CA (70 mg/kg/day, I.P.) either alone or in combination with lactulose (Lac) (5.3 g/kg/day, oral) against thioacetamide (TAA)-induced hepatic encephalopathy in rats.

MATERIALS AND METHODS

For induction of HE, TAA (200 mg/kg) was intraperitoneally administered for 1 week at alternative days. CA, Lac and Lac+CA were administered for 14 days prior to and for further 7 days together with TAA injection.

KEY FINDINGS

CA, Lac and Lac+CA combination effectively attenuated TAA-induced HE; as indicated by the improvement in behavioral tests, mitigation of pathological abnormalities in both liver and brain, the significant reduction in serum hyperammonemia and amelioration in liver function biomarkers; ALT and AST. This was accompanied with a substantial restoration of redox state in liver and brain; MDA and GSH levels. Moreover, CA, Lac and Lac+CA combination reduced neuroinflammation as demonstrated by the notable attenuation of P2X7R, NLRP3, caspase-1, IL-1β, GFAP and Iba1 brain levels, as well as the amelioration of brain edema as manifested by reduction in AQP4 levels in brain.

SIGNIFICANCE

Our study has demonstrated that CA in combination with Lac possesses a superior neuroprotective effect over Lac alone against TAA-induced HE by attenuation of P2X7R/NLRP3 mediated neuroinflammation and relieving brain edema.

Cinnamon and cognitive function: a systematic review of preclinical and clinical studies

Cinnamon is the inner bark of trees named Cinnamomum. Studies have shown that cinnamon and its bioactive compounds can influence brain function and affect behavioral characteristics. This study aimed to systematically review studies about the relationship between cinnamon and its key components in memory and learning. Two thousand six hundred five studies were collected from different databases (PubMed, Scopus, Google Scholar, and Web of Science) in September 2021 and went under investigation for eligibility. As a result, 40 studies met our criteria and were included in this systematic review. Among the included studies, 33 were In vivo studies, five were In vitro, and two clinical studies were also accomplished. The main outcome of most studies (n = 40) proved that cinnamon significantly improves cognitive function (memory and learning). In vivo studies showed that using cinnamon or its components, such as eugenol, cinnamaldehyde, and cinnamic acid, could positively alter cognitive function. In vitro studies also showed that adding cinnamon or cinnamaldehyde to a cell medium can reduce tau aggregation, Amyloid β and increase cell viability. For clinical studies, one study showed positive effects, and another reported no changes in cognitive function. Most studies reported that cinnamon might be useful for preventing and reducing cognitive function impairment. It can be used as an adjuvant in the treatment of related diseases. However, more studies need to be done on this subject.

Alzheimer's disease, a metabolic disorder: Clinical advances and basic model studies (Review)

Alzheimer's disease (AD) is a type of neurodegenerative disease characterized by cognitive impairment that is aggravated with age. The pathological manifestations include extracellular amyloid deposition, intracellular neurofibrillary tangles and loss of neurons. As the world population ages, the incidence of AD continues to increase, not only posing a significant threat to the well-being and health of individuals but also bringing a heavy burden to the social economy. There is epidemiological evidence suggesting a link between AD and metabolic diseases, which share pathological similarities. This potential link would deserve further consideration; however, the pathogenesis and therapeutic efficacy of AD remain to be further explored. The complex pathogenesis and pathological changes of AD pose a great challenge to the choice of experimental animal models. To understand the role of metabolic diseases in the development of AD and the potential use of drugs for metabolic diseases, the present article reviews the research progress of the comorbidity of AD with diabetes, obesity and hypercholesterolemia, and summarizes the different roles of animal models in the study of AD to provide references for researchers.

Insight into the emerging and common experimental in-vivo models of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial, rapidly progressing neurodegenerative disorder. As the exact cause of the disease is still unclear, the drug development is very challenging. This review encompasses the commonly used AD models involving various chemicals, heavy metals and endogenous substances induced models and the transgenic models. It also provides insight into the reliable emerging models of AD that may overcome the shortcomings associated with available models. Chemicals like streptozotocin, scopolamine, colchicine and okadaic acid render the animal susceptible to neuroinflammation and oxidative stress induced neurodegeneration along with amyloid-β deposition and tau hyperphosphorylation. Similarly, endogenous substances like acrolein and amyloid-β 1-42 are efficient in inducing the major pathologies of AD. Heavy metals like aluminum and fluoride and mixture of these have been reported to induce neurotoxicity therefore are used as animal models for AD. Transgenic models developed as a result of knock-in or knock-out of certain genes associated with AD including PDAPP, APP23, Tg2576, APP/PS1, 3 × Tg and 5 × FAD have also been incorporated in this study. Further, emerging and advanced pathomimetic models of AD are provided particular interest here which will add on to the current knowledge of animal models and may aid in the drug development process and deepen our understanding related to AD pathogenesis. These newly discovered models include oAβ25-35 model, transgenic model expressing 82-kDa ChAT, oDGal mouse and APP knock-in rat. This study may aid in the selection of suitable model for development of novel potent therapeutics and for exploring detailed pathogenic mechanism of AD.

Essential Oil Molecules Can Break the Loop of Oxidative Stress in Neurodegenerative Diseases

Essential oils (EOs) are mixtures of volatile compounds, extracted from aromatic plants, with multiple activities including antioxidant and anti-inflammatory ones. EOs are complex mixtures easy to find on the market and with low costs. In this mini narrative review, we have collected the results of in vitro and in vivo studies, which tested these EOs on validated models of neurodegeneration and in particular of the two main neurodegenerative diseases (NDs) that afflict humans: Alzheimer's and Parkinson's. Since EO compositions can vary greatly, depending on the environmental conditions, plant cultivar, and extraction methods, we focused our attention to studies involving single EO molecules, and in particular those that have demonstrated the ability to cross the blood-brain barrier. These single EO molecules, alone or in defined mixtures, could be interesting new therapies to prevent or slow down oxidative and inflammatory processes which are common mechanisms that contribute to neuronal death in all NDs.

Alzheimer's disease: Molecular aspects and treatment opportunities using herbal drugs

Alzheimer's disease (AD), also called senile dementia, is the most common neurological disorder. Around 50 million people, mostly of advanced age, are suffering from dementia worldwide and this is expected to reach 100-130 million between 2040 and 2050. AD is characterized by impaired glutamatergic and cholinergic neurotransmission, which is associated with clinical and pathological symptoms. AD is characterized clinically by loss of cognition and memory impairment and pathologically by senile plaques formed by Amyloid β deposits or neurofibrillary tangles (NFT) consisting of aggregated tau proteins. Amyloid β deposits are responsible for glutamatergic dysfunction that develops NMDA dependent Ca2+ influx into postsynaptic neurons generating slow excitotoxicity process leading to oxidative stress and finally impaired cognition and neuronal loss. Amyloid decreases acetylcholine release, synthesis and neuronal transport. The decreased levels of neurotransmitter acetylcholine, neuronal loss, tau aggregation, amyloid β plaques, increased oxidative stress, neuroinflammation, bio-metal dyshomeostasis, autophagy, cell cycle dysregulation, mitochondrial dysfunction, and endoplasmic reticulum dysfunction are the factors responsible for the pathogenesis of AD. Acetylcholinesterase, NMDA, Glutamate, BACE1, 5HT6, and RAGE (Receptors for Advanced Glycation End products) are receptors targeted in treatment of AD. The FDA approved acetylcholinesterase inhibitors Donepezil, Galantamine and Rivastigmine and N-methyl-D-aspartate antagonist Memantine provide symptomatic relief. Different therapies such as amyloid β therapies, tau-based therapies, neurotransmitter-based therapies, autophagy-based therapies, multi-target therapeutic strategies, and gene therapy modify the natural course of the disease. Herbal and food intake is also important as preventive strategy and recently focus has also been placed on herbal drugs for treatment. This review focuses on the molecular aspects, pathogenesis and recent studies that signifies the potential of medicinal plants and their extracts or chemical constituents for the treatment of degenerative symptoms related to AD.

Comparative Study of Time-Dependent Aluminum Exposure and Post-Exposure Recovery Shows Better Improvement in Synaptic Changes and Neuronal Pathology in Rat Brain After Short-Term Exposure

Aluminum is a ubiquitous metal that causes multiple brain pathologies such as, cognitive dysfunction and Alzheimer's disease like symptoms. Exposure to aluminum through drinking water is responsible for hampering learning and memory. This study aimed to compare (1) the time-dependent effect of aluminum exposure (keeping total exposure of 5850 mg/kg same) in two durations, 30 and 45 days, and (2) to compare post-exposure self-recovery effect after 20 days in both (30 and 45 days exposure) groups. Rats were given 130 and 195 mg/kg of AlCl₃·6H₂O for 45 and 30 days respectively, to see the time-dependent exposure effect. At the end of exposure, rats were given distilled water and allowed to self-recover for 20 days to study the recovery. Expression levels of synaptic genes (Syp, SNAP25, Nrxn1/2, PSD95, Shank1/2, Homer1, CamkIV, Nrg1/2 and Kalrn) were measured using qPCR and compared in the exposure and recovery groups. Cellular morphology of the rat brain cortex and hippocampus was also investigated. Damage in lipid and protein profile was measured by employing FTIR. Results showed downregulation of mRNA expression of synaptic genes, plaques deposition, disorganization in lipid and protein profile by increasing membrane fluidity, and disorder and alteration of protein secondary structure after both exposure periods. However, better improvement/recovery in these parameters were observed in recovery group of 30 days aluminum exposure compared to 45 days aluminum exposure group. Taken together, these results suggested that short-term exposure resulted in better restoration of lipid and protein profile after time-dependent exposure of aluminum than prolonged exposure.

Effect of the Reelin-Dab1 signaling pathway on the abnormal metabolism of Aβ protein induced by aluminum

Aluminum (Al) is a common neurotoxic element that can exacerbate intracellular β-amyloid (Aβ) deposition. Reelin is a highly conserved extracellular glycoprotein that is involved in intracellular Aβ deposition. However, the action of Reelin on aluminum-induced Aβ deposition is not fully understood. Here, we investigated the effects of the Reelin-Dab1 signaling pathway on Aβ deposition in aluminum maltol (Al(mal)₃) exposure in rat pheochromocytoma-derived cells (PC12). Our results showed that Al(mal)₃ exposure decreased activity of PC12, increased expression of Aβ₄₂, and decreased expression of Aβ₄₀. Moreover, Al(mal)₃ exposure in PC12 induced Reelin-Dab1 signaling pathway-associated proteins changed, decreased expression of Reelin and Dab1, and increased expression of pdab1. Moreover, the expression of Reelin, Dab1, and Aβ₄₀ was found to be elevated in PC12 exposed to Al(mal)₃ and corticosterone compared to those exposed to Al(mal)₃. Also, the expression of Reelin, Dab1, and Aβ₄₀ was found to be depressed in PC12 exposed to Al(mal)₃ and streptozotocin compared with cells exposed to Al(mal)₃ alone. These results suggested that Al(mal)₃ inhibits the expression of the Reelin-Dab1 signaling pathway, promoting Aβ deposition. Thus, our findings provided important evidence to better understand how the Reelin-Dab1 signaling pathway may be a potential mechanism of Aβ deposition induced by aluminum.

Cinnamaldehyde Regulates Insulin and Caspase-3 Signaling Pathways in the Sporadic Alzheimer's Disease Model: Involvement of Hippocampal Function via IRS-1, Akt, and GSK-3β Phosphorylation

Insulin signaling disruption and caspase-3 cleavage play a pathologic role in Alzheimer's disease (AD). Evidence suggested that cinnamaldehyde (Cin), the major component of cinnamon, has the ability to act as a neuroprotective agent. However, little evidence is available to demonstrate its effectiveness in regulating the insulin and caspase-3 signaling pathways and underlying molecular mechanisms. Therefore, the present study was conducted to correlate the molecular mechanisms of these signaling pathways and Cin treatment on animal behavioral performance in an intracerebroventricular (ICV)-streptozotocin (STZ, 3 mg/kg) model. The sporadic AD rat model was treated with Cin (10 and 100 mg/kg; intraperitoneal, i.p) daily for 2 weeks. Novel object recognition (NOR), Morris water maze (MWM), and elevated plus maze (EPM) tests were performed to assess recognition/spatial memory and anxiety-like behavior, respectively. Hippocampal Aβ aggregation was assessed using Congo red staining. The activity of hippocampal caspase-3 and IRS-1/Akt/GSK-3β signaling pathways were analyzed using the Western blot technique. The results revealed that Cin (100 mg/kg, effective dose) improved recognition/spatial memory deficits and anxiety-like behavior. In addition, Cin negated the effects of STZ on Aβ aggregation and caspase-3 cleavage in the hippocampus. Furthermore, the Western blot method showed that hippocampal IRS-1/AKT/GSK-3β phosphorylation was altered in ICV-STZ animal model, while Cin modulated this signaling pathway through decreasing Phospho.IRS-1_Ser307/Total.IRS-1 ratio and also increasing Phospho.Akt_Ser473/Total.Akt and Phospho.GSK-3β_Ser9/Total.GSK-3β ratios. These findings suggest that Cin is involved in the regulation of hippocampal IRS-1/AKT/GSK-3β and caspase-3 pathways in a sporadic AD model, and modulation of these signaling pathways also influences the animal behavioral performance.

Tau-aggregation inhibition: promising role of nanoencapsulated dietary molecules in the management of Alzheimer's disease

Alzheimer's disease (AD) is a cumulative form of dementia associated with memory loss, cognition impairment, and finally leading to death. AD is characterized by abnormal deposits of extracellular beta-amyloid and intracellular Tau-protein tangles throughout the brain. During pathological conditions of AD, Tau protein undergoes various modifications and aggregates over time. A number of clinical trials on patients with AD symptoms have indicated the effectiveness of Tau-based therapies over anti-Aβ treatments. Thus, there is a huge paradigm shift toward Tau aggregation inhibitors. Several bioactives of plants and microbes have been suggested to cross the neuronal cell membrane and play a crucial role in managing neurodegenerative disorders. Bioactives mainly act as active modulators of AD pathology besides having antioxidant and anti-inflammatory potential. Studies also demonstrated the potential role of dietary molecules in inhibiting the formation of Tau aggregates and removing toxic Tau. Further, these molecules in nonencapsulated form exert enhanced Tau aggregation inhibition activity both in in vitro and in vivo studies suggesting a remarkable role of nanoencapsulation in AD management. The present article aims to review and discuss the structure-function relationship of Tau protein, the post-translational modifications that aid Tau aggregation and potential bioactives that inhibit Tau aggregation.

Naproxen as a potential candidate for promoting rivastigmine anti-Alzheimer activity against aluminum chloride-prompted Alzheimer's-like disease in rats; neurogenesis and apoptosis modulation as a possible underlying mechanism

BACKGROUND AND AIM

Alzheimer's disease (AD) is one of the leading causes of dependence and disability among the elderly worldwide. The traditional anti-Alzheimer medication, rivastigmine, one of the cholinesterase inhibitors (ChEIs), fails to achieve a definitive cure. We tested the hypothesis that naproxen administration to the rivastigmine-treated aluminum chloride (AlCl3) Alzheimer's rat model could provide an additive neuroprotective effect compared to rivastigmine alone.

MATERIALS AND METHODS

The studied groups were control (Cont), AlCl₃ treated (Al), rivastigmine treated (RIVA), naproxen treated (Napro), and combined rivastigmine and naproxen treated (RIVA + Napro). Rats' memory, spatial learning, and cognitive behavior were assessed followed by evaluation of hippocampal acetylcholinesterase (AChE) activity. Hippocampal and cerebellar histopathology were thoroughly examined. Activated caspase-3 and the neuroepithelial stem cells marker; nestin expressions were immunohistochemically assayed.

RESULTS

AD rats displayed significantly impaired memory and cognitive function, augmented hippocampal AChE activity; massive neurodegeneration associated with enhanced astrogliosis, apoptosis, and impaired neurogenesis. Except for the enhancement of neurogenesis and suppression of apoptosis, the combination therapy had no additional neuroprotective benefit over rivastigmine-only therapy.

CONCLUSION

Naproxen's efficacy was established by its ability to function at the cellular level, improved neurogenesis, and decreased, apoptosis without having an additional mitigating impact on cognitive impairment in rivastigmine-treated AD rats.

Protective Effect of Ginkgolide B against Cognitive Impairment in Mice via Regulation of Gut Microbiota

Ginkgolide B (GB) is one of the main bioactive components of Ginkgo biloba leaf extracts with neuroprotective activity. However, the neuroprotective mechanism link between the anti-Alzheimer's disease (AD) efficiency of GB and gut microbiota have remained elusive. Here, we elucidated the effect and possible mechanism of GB against cognitive impairment in mice. Male mice were induced with d-galactose and aluminum chloride to establish an AD animal model, and then intragastrically treated with GB. Cognitive function was assessed by an object recognition test and an open-field test. Amyloid deposition and neuropathological change were detected. The levels of receptor for advanced glycation end products (RAGE), Bcl-2, and Bax were detected. Moreover, microbial compositions were measured by 16s rRNA sequencing. Our results showed that GB significantly alleviated cognitive dysfunction, neurodegeneration, and neuropathological changes in AD model mice. Moreover, GB treatment remarkably reduced the levels of RAGE and Bax and increased the level of Bcl-2 in AD model mice. GB treatment reversed the decreased abundance of Lactobacillus and the increased abundance of Bacteroidales, Muribaculaceae, and Alloprevotella, which led to reconstruction of gut microbiota. These findings demonstrated the neuroprotective effects of GB in AD mice, which were partly mediated by modulating gut dysbiosis, indicating that GB might be a potentially active supplement to alleviate AD.

Long-term exposure to environmentally relevant concentrations of ibuprofen and aluminum alters oxidative stress status on Danio rerio

Despite the ubiquitous presence of multiple pollutants in aqueous environments have been extensively demonstrated, the ecological impact of chemical cocktails has not been studied in depth. In recent years, environmental studies have mainly focused on the risk assessment of individual chemical substances neglecting the effects of complex mixtures even though it has been demonstrated that combined effects exerted by pollutants might represent a greater hazard to the biocenosis. The current study evaluates the effects on the oxidative stress status induced by individual forms and binary mixtures of ibuprofen (IBU) and aluminum (Al) on brain, gills, liver and gut tissues of Danio rerio after long-term exposure to environmentally relevant concentrations (0.1-11 μg L^-1 and 0.05 mg L^-1- 6 mg L^-1, respectively). Lipid peroxidation (LPO), Protein carbonyl content (PCC) and activity of Superoxide Dismutase (SOD), Catalase (CAT), and Glutathione Peroxidase (GPX) were evaluated. Moreover, concentrations of both toxicants and the metabolite 2-OH-IBU were quantified on test water and tissues. Results show that ibuprofen (IBU) and aluminum (Al) singly promote the production of radical species and alters the oxidative stress status in all evaluated tissues of zebrafish, nevertheless, higher effects were elicited by mixtures as different interactions take place.

Effects of Piper nigrum fruit and Cinnamum zeylanicum bark alcoholic extracts, alone and in combination, on scopolamine-induced memory impairment in mice

Background and purpose:

Alzheimer’s disease is a progressive brain disorder that is thought to be triggered via disruption of cholinergic neurons and enhanced oxidative stress. Therefore, antioxidant phytochemicals with the ability to fortify cholinergic function should help in preventing the progress of the disease. This study aimed at evaluating the combinational effects of two popular herbs one with anticholinesterase activity namely Piper nigrum and the other with antioxidant capacity, Cinnamomum zeylanicum.

Experimental approach:

In this study, P. nigrum extract (PN) (50, 100 mg/kg, ip) and C. zeylanicum extract (CZ) (100, 200, 400 mg/kg, ip) and their combinations were administered for 8 days before the injection of scopolamine (1 mg/kg, ip). Mice were then tested for their memory using two behavioral models, namely the object recognition test and the passive avoidance task.

Findings/Results:

Administration of scopolamine significantly impaired memory performance in both memory paradigms. In the passive avoidance test (PAT) model, PN at doses up to 100 mg/kg and CZ at doses up to 400 mg/kg did not significantly alter the memory impairment induced by scopolamine. The combination of these two plant extracts did not change the PAT parameters. In the object recognition test (ORT) model, however, administration of 100 mg/kg CZ alone and a combination of PN (50 mg/kg) with CZ (400 mg/kg), significantly increased the recognition index (P < 0.05).

Conclusion and implications:

Two plant extracts when administered alone or in combinations affected the memory performance differently in two memory paradigms. In the PAT model, the extracts did not show any memory improvement, in ORT, however, some improvements were observed after plant extracts.

Sanweidoukou decoction, a Chinese herbal formula, ameliorates β-amyloid protein-induced neuronal insult via modulating MAPK/NF-κB signaling pathways: Studies in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional Chinese medicine Sanweidoukou decoction (DK-3) was a classical formula for the treatment of nervous system diseases, recorded in the Chinese medical classic Sibu Yidian.

AIM OF THE STUDY

The present study is aim to investigate the neuroprotective effects of DK-3 on β-amyloid (Aβ) protein -induced AD-like pathologies and underlying molecular mechanisms both in vitro and in vivo studies.

MATERIALS AND METHODS

Hydrolysates of DK-3 were analyzed by LC-ESI-MS/MS. In vitro, MTT was utilized to examine effects of DK-3 on Aβ_25-35-induced cytotoxicity in PC12 cells. In vivo, male Sprague-Dawley rats were administered with Aβ_25-35 to induce AD-like pathologies and behavioral evaluations were conducted via Morris water maze (MWM) test. Histopathological changes were observed by Hematoxylin-eosin (HE) straining. Immunohistochemistry (IHC) was used to detect the tau hyperphosphorylation at Thr181 site. The expression levels of tau hyperphosphorylation, inflammation-related cytokines such as COX-2, iNOS, TNF-α, IL-1β, IL-6, the phosphorylated state of various mitogen-activated protein kinase (MAPK) signaling molecules (p38 MAPK, ERK, and JNK) and activation of nuclear factor κB (NF-κB) in vitro and in vivo were assessed via Western blot.

RESULTS

In vitro, DK-3 dose-dependently increased cell viability of PC12 cells induced by Aβ_25-35. In vivo, DK-3 improved learning and memory abilities of Aβ_25-35-induced AD-like rats. Moreover, DK-3 reversed hyperphosphorylation of tau and reduced the production of inflammation-related cytokines through significantly inhibited MAPK and NF-κB signaling pathways both in vitro and in vivo studies.

CONCLUSION

The present study suggested that the traditional Chinese medicine DK-3 may play a role in preventing and treating AD by reducing the hyperphosphorylation of tau protein and the expressions of inflammation-related cytokines via modulating the MAPK/NF-κB signaling pathways.

Critical Review of the Alzheimer's Disease Non-Transgenic Models: Can They Contribute to Disease Treatment?

Alzheimer's disease (AD) is a growing neurodegenerative disease without effective treatments or therapies. Despite the use of different approaches and an extensive variety of genetic amyloid based models, therapeutic strategies remain elusive. AD is characterized by three main pathological hallmarks that include amyloid-β plaques, neurofibrillary tangles, and neuroinflammatory processes; however, many other pathological mechanisms have been described in the literature. Nonetheless, the study of the disease and the screening of potential therapies is heavily weighted toward the study of amyloid-β transgenic models. Non-transgenic models may aid in the study of complex pathological states and provide a suitable complementary alternative to evaluating therapeutic biomedical and intervention strategies. In this review, we evaluate the literature on non-transgenic alternatives, focusing on the use of these models for testing therapeutic strategies, and assess their contribution to understanding AD. This review aims to underscore the need for a shift in preclinical research on intervention strategies for AD from amyloid-based to alternative, complementary non-amyloid approaches.

Natural Cinnamaldehyde and Its Derivatives Ameliorate Neuroinflammatory Pathways in Neurodegenerative Diseases

Neurodegenerative diseases are devastating and incurable disorders characterized by neuronal dysfunction. The major focus of experimental and clinical studies are conducted on the effects of natural products and their active components on neurodegenerative diseases. This review will discuss an herbal constituent known as cinnamaldehyde (CA) with the neuroprotective potential to treat neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD). Accumulating evidence supports the notion that CA displays neuroprotective effects in AD and PD animal models by modulating neuroinflammation, suppressing oxidative stress, and improving the synaptic connection. CA exerts these effects through its action on multiple signaling pathways, including TLR4/NF-κB, NLRP3, ERK1/2-MEK, NO, and Nrf2 pathways. To summarize, CA and its derivatives have been shown to improve pathological changes in AD and PD animal models, which may provide a new therapeutic option for neurodegenerative interventions. To this end, further experimental and clinical studies are required to prove the neuroprotective effects of CA and its derivatives.

Effect of Treadmill Exercise and Trans-Cinnamaldehyde against d-Galactose- and Aluminum Chloride-Induced Cognitive Dysfunction in Mice

Mild cognitive impairment (MCI) generally refers to impairment in cognition above that which accompanies the normal age-related cognitive decline and has attracted attention in recent years. Trans-cinnamaldehyde (TCA), which is isolated from cinnamon, has anti-inflammatory and antioxidant properties. Treadmill exercise also has diverse positive effects. The purpose of this study was to investigate the combination effects of TCA and treadmill exercise on learning and memory in a cognitive impairment mouse induced by a combination of d-galactose (d-gal) and aluminum chloride (AlCl₃). We found that exercise and TCA attenuated cognitive impairment in mice with induced MCI. This effect was further increased by costimulation of exercise and TCA. To clarify the mechanisms of the positive effects of TCA and exercise, we analyzed the nuclear factor erythroid 2-related factor (Nrf2) and related signaling pathways. We found that TCA and exercise upregulated Nrf2, NAD(P)H dehydrogenase quinone 1 (NQO-1), heme oxygenase 1 (HO-1), and superoxide dismutase 1 (SOD-1); this suggests that TCA and exercise attenuate cognitive dysfunction by reducing oxidative stress. We also found that Nrf2-related signaling pathways, i.e., the AMP-activated protein kinase (AMPK)/Nrf2 and SIRT1/PGC-1a/Nrf2-ARE pathways, exerted antioxidant effects. Together, these results suggest that costimulation with TCA and exercise may be a therapeutic candidate for mild cognitive impairment.