Naringin provides neuroprotection in CCL2-induced cognition impairment by attenuating neuronal apoptosis in the hippocampus

Basic approach on the protective effects of hesperidin and naringin in Alzheimer's disease

OBJECTIVES

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive impairment. This situation imposes a great burden on individuals, both economically and socially. Today, an effective method for treating the disease and protective approach to tau accumulation has not been developed yet. Studies have been conducted on the effects of hesperidin and naringin flavonoids found in citrus fruits on many diseases.

METHODS

In this review, the pathophysiology of AD is defined, and the effects of hesperidin and naringin on these factors are summarized.

RESULTS

Studies have shown that both components may potentially affect AD due to their antioxidative and anti-inflammatory properties. Based on these effects of the components, it has been shown that they may have ameliorative effects on Aβ, α-synuclein aggregation, tau pathology, and cognitive functions in the pathophysiology of AD.

DISCUSSION

There are studies suggesting that hesperidin and naringin may be effective in the prevention/treatment of AD. When these studies are examined, it is seen that more studies should be conducted on the subject.

Investigating the therapeutic potential of naringin in MK-801-induced schizophrenia model: focus on cognitive impairment and miR-25-3p-regulated pathways

AIM

The aim of this study was to assess the ameliorative effects of naringin (NR) on cognitive impairment in schizophrenia(SZ) from multiple perspectives using behavioral, histopathological and molecular biological approaches.

MATERIALS AND METHODS

SZ models were established in rats via acute intraperitoneal injection of MK-801 in all groups except the control group, which received saline. Cognitive function was assessed using the Morris water maze test 21 days after prophylactic NR administration. Subsequently, Serum interleukin-6 (IL-6) and homocysteine (HCY) levels were quantified using enzyme-linked immunosorbent assay (ELISA), and hippocampal neuronal and synaptic structures were observed via microscopy. Molecular detection was performed using real-time reverse transcription polymerase chain reaction (RT-qPCR) and western blotting (WB) to assess the expression levels of molecules related to the microRNA-25-3p/salt inducible kinase 1/CREB regulated transcription coactivator 2/cAMP responsive element binding protein 1 (miR-25-3p/SIK1/CRTC2/CREB1) pathway, thereby elucidating the mechanism by which NR ameliorates cognitive impairment in SZ.

RESULTS

NR was found to mitigate cognitive decline in learning and memory induced by MK-801. It lowered serum levels of IL-6 and HCY, reduced neuronal damage in the CA1 region of the hippocampus, increased the thickness of postsynaptic dense material, decreased the distance between synaptic gaps, decreased the expression of SIK1, and elevated the expression of miR-25-3p, CRTC2 and CREB1 in the hippocampus.

CONCLUSION

NR may protect neurons in the CA1 region of the hippocampus and enhance synaptic plasticity by regulating the miR-25-3p/SIK1/CRTC2/CREB1 signaling pathway, thereby promoting cognitive improvement.

Nicotinamide riboside alleviates sweeteners-induced brain and cognitive impairments in immature mice

The consumption of sweeteners is high around the world. Sweet beverages are one of the most important and popular sources of sweeteners. Previous studies have reported that excessive sweeteners might cause health hazards, including cognitive impairment. Nicotinamide riboside (NR), a precursor of NAD+, has been found to alleviate several cognitive impairments. However, the protective effects of NR against sweetener-induced cognitive impairment remain unclear. Hence, we evaluated the effects of sweeteners and NR (400 mg kg-1 d-1) on the brain and cognition of mice by simulating an extreme lifestyle of completely replacing water with sugar-sweetened beverage (simulated with 10% sucrose solution) or sugar-free sweet beverage (simulated with 0.05% aspartame solution) from weaning to adulthood. The results revealed that continuous exposure to sucrose or aspartame for eight weeks did not significantly cause differences in body weight but significantly induced cognitive impairments, including anxiety- and depressive-like behaviours, impairments in learning, memory and sociability. Moreover, sucrose or aspartame exposure induced neuronal injury, reduction of Nissl bodies, overactivation of the TLR4/NF-κB/NLRP3/ASC/Caspase-1 pathway and increased downstream inflammatory cytokines in mouse hippocampus, and also induced an imbalance of oxidative stress, apoptosis and autophagy, large consumptions of intracellular antioxidant factors, and overactivation of the PI3K/Akt/FOXO1 and PI3K/Akt/mTOR pathways in mouse brain. NR treatment increased NAD+ in the brain, and prevented and alleviated these impairments effectively. In summary, we found that NR supplementation protected against cognitive impairment caused by sucrose or aspartame in immature mice, which might be related to increased brain NAD+ level, relieved neuroinflammation and pyroptosis in the hippocampus, and maintained a balance of oxidative stress, apoptosis and autophagy in the brain.

Exploring the effects of naringenin on cell functioning and energy synthesis in the hippocampus of male Wistar rats with chronic tinnitus, by examining genetic indicators such as Bax, Bcl-2, Tfam, and Pgc-1α

BACKGROUND

The pivotal factors, including neural plasticity, oxidative stress, neuronal inflammation, and apoptosis, play a significant role in the pathogenesis of tinnitus. The balance between Bax/Bcl-2 genes is an important factor in determining the rate of apoptosis. Pgc-1α and Tfam genes are fundamental regulators of mitochondrial biogenesis. Naringenin possesses significant antioxidant, neuroprotective, anti-inflammatory, anti-apoptotic, and antiviral properties, and its compounds are effective on cell signaling pathways.

AIMS

In light of the aforementioned information, we endeavored to evaluate the impact of naringenin on the expression levels of Bax, Bcl-2, Pgc-1α, and Tfam genes in the hippocampus of male Wistar rats with chronic tinnitus.

MATERIAL AND METHODS

To demonstrate the existence of tinnitus, all rats were instructed to complete an "active avoidance test" utilizing a conditioning box. The expression levels of genes mentioned above were assessed using real-time PCR.

RESULTS

The sodium salicylate at a dosage of 350 mg/kg showed an upregulation in the expression level of Bax and a downregulation in the expression level of the Bcl-2 gene (p < 0.001). Furthermore, the sodium salicylate displayed significantly higher expression levels of Tfam and Pgc-1α (p < 0.001) genes. The naringenin, at a dose of 100 mg/kg, led to a decrease in Bax gene expression (p < 0.05) and an increase in Bcl-2 gene expression (p < 0.05). On the other hand, naringenin restored the expression level of both Tfam (p < 0.001) and Pgc-1α (p < 0.01) genes.

CONCLUSIONS

Our research findings demonstrate that sodium salicylate-induced tinnitus leads to enhanced apoptosis and mitochondrial biogenesis within the hippocampus. Additionally, our evidence recommends that naringenin can reduce apoptosis effectively and maintain a balanced mitochondrial state.

Molecular Docking, Bioinformatic Analysis, and Experimental Verification for the Effect of Naringin on ADHD: Possible Inhibition of GSK-3β and HSP90

Background/Objectives: One of the most abundant and growing neurodevelopmental disorders in recent decades is attention deficit hyperactivity disorder (ADHD). Many trials have been performed on using drugs for the improvement of ADHD signs. This study aimed to detect the possible interaction of naringin with Wnt/β-catenin signaling and its putative anti-inflammatory and protective effects in the mouse ADHD model based on bioinformatic, behavioral, and molecular investigations. Furthermore, molecular docking was applied to investigate possible interactions with the GSK-3β and HSP90 proteins. Methods: Male Swiss albino mice were divided into four groups, a normal control group, monosodium glutamate (SGL) control, SGL + naringin 50 mg/kg, and SGL + naringin 100 mg/kg. The psychomotor activity of the mice was assessed using the self-grooming test, rope crawling test, and attentional set-shifting task (ASST). In addition, biochemical analyses were performed using brain samples. Results: The results of the SGL group showed prolonged grooming time (2.47-folds), a lower percentage of mice with successful crawling on the rope (only 16.6%), and a higher number of trials for compound discrimination testing in the ASST (12.83 ± 2.04 trials versus 5.5 ± 1.88 trials in the normal group). Treatment with naringin (50 or 100 mg per kg) produced significant shortening in the grooming time (31% and 27% reductions), as well as a higher percentage of mice succeeding in crawling with the rope (50% and 83%, respectively). Moreover, the ELISA assays indicated decreased dopamine levels (0.36-fold) and increased TNF-α (2.85-fold) in the SGL control group compared to the normal mice, but an improvement in dopamine level was observed in the naringin (50 or 100 mg per kg)-treated groups (1.58-fold and 1.97-fold). Similarly, the PCR test showed significant declines in the expression of the Wnt (0.36), and β-catenin (0.33) genes, but increased caspase-3 (3.54-fold) and BAX (5.36-fold) genes in the SGL group; all these parameters were improved in the naringin 50 or 100 mg/kg groups. Furthermore, molecular docking indicated possible inhibition for HSP90 and GSK-3β. Conclusions: Overall, we can conclude that naringin is a promising agent for alleviating ADHD symptoms, and further investigations are required to elucidate its mechanism of action.

Metabolomics integrated with network pharmacology of blood-entry constituents reveals the bioactive component of Xuefu Zhuyu decoction and its angiogenic effects in treating traumatic brain injury

BACKGROUND

Xuefu Zhuyu decoction (XFZYD) has been extensively utilized to treat traumatic brain injury (TBI). However, the bioactive compounds and the underlying mechanisms have not yet been elucidated.

OBJECTIVES

This study aimed to investigate the bioactive constituents of XFYZD that are absorbed in the blood and the mechanisms in treating TBI.

METHODS

The study presents an integrated strategy in three steps to investigate the material basis and pharmacological mechanisms of XFZYD. The first step involves: (1) performing metabolomics analysis of XFZYD to obtain the main functions and targets; (2) screening the blood-entry ingredients and targets of XFZYD from databases; (3) obtaining the potential components targeting the key functions by integrated analysis of metabolomics and network pharmacology. The second step involves screening pharmacological effects with active ingredients in vitro. In the third step, the effects of the top active compound were validated in vivo, and the mechanisms were explored by protein antagonist experiments.

RESULTS

Metabolomics analysis revealed that XFZYD treated TBI mice mainly through affecting the functions of blood vessels. We screened 62 blood-entry ingredients of XFZYD by network pharmacology. Then, we focused on 39 blood-entry ingredients related to vascular genes enriched by XFZYD-responsive metabolites. Performing the natural products library, we verified that hydroxysafflor yellow A (HSYA), vanillin, ligustilide, paeoniflorin, and other substances promoted endothelial cell proliferation significantly compared to the control group. Among them, the efficacy of HSYA was superior. Further animal studies demonstrated that HSYA treatment alleviated neurological dysfunction in TBI mice by mNSS and foot fault test, and decreased neuronal damage by HE, nissl, and TUNEL staining. HSYA increased the density of cerebral microvessels, raised the expression of angiogenesis marker proteins VEGFA and CD34, and activated the PI3K/Akt/mTOR signaling pathway significantly. The angiogenic effects disappeared after the intervention of PI3K antagonist LY294002.

CONCLUSION

By applying a novel strategy of integrating network pharmacology of constituents absorbed in blood with metabolomics, the research screened HSYA as one of the top bioactive constituents of XFZYD, which stimulates angiogenesis by activating the PI3K/Akt/mTOR signaling pathway after TBI.

The neuroprotective potential of phytochemicals in traumatic brain injury: mechanistic insights and pharmacological implications

Traumatic brain injury (TBI) leads to brain damage, comprising both immediate primary damage and a subsequent cascade of secondary injury mechanisms. The primary injury results in localized brain damage, while the secondary damage initiates inflammatory responses, followed by the disruption of the blood-brain barrier, infiltration of peripheral blood cells, brain edema, and the release of various immune mediators, including chemotactic factors and interleukins. TBI disrupts molecular signaling, cell structures, and functions. In addition to physical tissue damage, such as axonal injuries, contusions, and haemorrhages, TBI interferes with brain functioning, impacting cognition, decision-making, memory, attention, and speech capabilities. Despite a deep understanding of the pathophysiology of TBI, an intensive effort to evaluate the underlying mechanisms with effective therapeutic interventions is imperative to manage the repercussions of TBI. Studies have commenced to explore the potential of employing natural compounds as therapeutic interventions for TBI. These compounds are characterized by their low toxicity and limited interactions with conventional drugs. Moreover, many natural compounds demonstrate the capacity to target various aspects of the secondary injury process. While our understanding of the pathophysiology of TBI, there is an urgent need for effective therapeutic interventions to mitigate its consequences. Here, we aimed to summarize the mechanism of action and the role of phytochemicals against TBI progression. This review discusses the therapeutic implications of various phytonutrients and addresses primary and secondary consequences of TBI. In addition, we highlighted the roles of emerging phytochemicals as promising candidates for therapeutic intervention of TBI. The review highlights the neuroprotective roles of phytochemicals against TBI and the mechanistic approach. Furthermore, our efforts focused on the underlying mechanisms, providing a better understanding of the therapeutic potential of phytochemicals in TBI therapeutics.

Pre-clinical Evidence-based Neuroprotective Potential of Naringin against Alzheimer's Disease-like Pathology: A Comprehensive Review

Neurodegenerative disorders (NDs) are a group of progressive, chronic, and disabling disorders that are highly prevalent and the incidence is on a constant rise globally. Alzheimer's disease (AD), one of the most common neurodegenerative disorders is hallmarked by cognitive impairment, amyloid-β (Aβ) deposition, hyperphosphorylation of tau protein, cholinergic dysfunction, mitochondrial toxicity, and neurodegeneration. Available therapeutic agents only provide symptomatic relief and their use are limited due to serious side effects. Recent research has recognized flavonoids as potential multi-target biomolecules that can reduce the pathogenesis of AD. Naringin, a natural citrus flavonoid has been traditionally used to treat various NDs including AD, and has gained special attention because exhibits a neuroprotective effect by affecting numerous signaling pathways with minimum adverse effects. Naringin reduces deposition of Aβ, hyperphosphorylation of tau protein, cholinergic dysfunction, oxidative stress burden, mitochondrial toxicity, the activity of glutamate receptors, and apoptosis of the neuronal cells. Additionally, it reduces the expression of phosphorylated-P38/P38 and the NF-κB signaling pathway, showing that a wide range of molecular targets is involved in naringin's neuroprotective action. The present study describes the possible pharmacological targets, signaling pathways, and molecular mechanisms of naringin involved in neuroprotection against AD-like pathology. Based on the above pre-clinical reports it can be concluded that naringin could be an alternative therapeutic agent for the management of AD-like manifestation. Thus, there is a strong recommendation to perform more preclinical and clinical studies to develop naringin as a novel molecule that could be a multi-target drug to counteract AD.

Protective effect of naringin against radiation-induced heart disease in rats via Sirt1/NF-κB signaling pathway and endoplasmic reticulum stress

This study was designed to explore the protective effect and mechanism of naringin (NG) on radiation-induced heart disease (RIHD) in rats. Rats were divided into four x-ray (XR) irradiation groups with different absorbed doses (0/10/15/20 Gy), or into three groups (control, XR, and XR + NG groups). Subsequently, the ultrasonic diagnostic apparatus was adopted to assess and compare the left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), left ventricular internal diameter at end diastole (LVIDd), and left ventricular internal diameter at end systole (LVIDs) in rats. Hematoxylin-eosin (H&E) staining and Masson staining were applied to detect the pathological damage and fibrosis of heart tissue. Western blot was used to measure the expression levels of myocardial fibrosis-related proteins, endoplasmic reticulum stress-related proteins, and Sirt1 (silent information regulator 1)/NF-κB (nuclear factor kappa-B) signaling pathway-related proteins in cardiac tissues. Additionally, enzyme-linked immunosorbent assay was utilized to detect the activities of pro-inflammatory cytokines, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) in cardiac tissue. The results showed that NG treatment significantly attenuated the 20 Gy XR-induced decline of LVEF and LVFS and the elevation of LVIDs. Cardiac tissue damage and fibrosis caused by 20 Gy XR were significant improved after NG treatment. Meanwhile, in rats irradiated by XR, marked downregulation was identified in the expressions of fibrosis-related proteins (Col I, collagen type I; α-SMA, α-smooth muscle actin; and TGF-β1, transforming growth factor-beta 1) and endoplasmic reticulum stress-related proteins (GRP78, glucose regulatory protein 78; CHOP, C/EBP homologous protein; ATF6, activating transcription factor 6; and caspase 12) after NG treatment. Moreover, NG treatment also inhibited the production of pro-inflammatory cytokines [interleukin-6, interleukin-1β, and monocyte chemoattractant protein-1 (MCP-1)], reduced the expression of MDA, and promoted the activities of SOD and CAT. Also, NG treatment promoted Sirt1 expression and inhibited p65 phosphorylation. Collectively, XR irradiation induced cardiac injury in rats in a dose-dependent manner. NG could improve the cardiac injury induced by XR irradiation by inhibiting endoplasmic reticulum stress and activating Sirt1/NF-κB signaling pathway.

Protective potential of naringenin and its nanoformulations in redox mechanisms of injury and disease

Increasing evidence suggests that elevated intracellular levels of reactive oxygen species (ROS) play a significant role in the pathogenesis of many diseases. Increased intracellular levels of ROS can lead to the oxidation of lipids, DNA, and proteins, contributing to cellular damage. Hence, the maintenance of redox hemostasis is essential. Naringenin (NAR) is a flavonoid included in the flavanones subcategory. Various pharmacological actions have been ascribable to this phytochemical composition, including antioxidant, anti-inflammatory, antibacterial, antiviral, antitumor, antiadipogenic, neuro-, and cardio-protective activities. This review focused on the underlying mechanism responsible for the antioxidative stress properties of NAR and its' nanoformulations. Several lines of in vitro and in vivo investigations suggest the effects of NAR and its nanoformulation on their target cells via modulating signaling pathways. These nanoformulations include nanoemulsion, nanocarriers, solid lipid nanoparticles (SLN), and nanomicelle. This review also highlights several beneficial health effects of NAR nanoformulations on human diseases including brain disorders, cancer, rheumatoid arthritis, and small intestine injuries. Employing nanoformulation can improve the pharmacokinetic properties of NAR and consequently efficiency by reducing its limitations, such as low bioavailability. The protective effects of NAR and its' nanoformulations against oxidative stress may be linked to the modulation of Nrf2-heme oxygenase-1, NO/cGMP/potassium channel, COX-2, NF-κB, AMPK/SIRT3, PI3K/Akt/mTOR, BDNF, NOX, and LOX-1 pathways. Understanding the mechanism behind the protective effects of NAR can facilitate drug development for the treatment of oxidative stress-related disorders.

Effects of aerobic exercise and dietary flavonoids on cognition: a systematic review and meta-analysis

Introduction: Studies have shown that exercise increases angiogenesis and perfusion in the hippocampus, activates neurogenesis in the dentate gyrus and increases synaptic plasticity, as well as increases the complexity and number of dendritic spines, all of which promote memory function and protect against cognitive decline. Flavonoids are gaining attention as antioxidants in health promotion due to their rich phenolic content, particularly for their modulating role in the treatment of neurodegenerative diseases. Despite this, there has been no comprehensive review of cognitive improvement supplemented with flavonoid and prescribed with exercise or a combination of the two interventions has been conducted. The purpose of this review is to determine whether a combined intervention produces better results when given together than when given separately. Methods: Relevant articles assessing the effect of physical exercise, flavonoid or in combination on cognitive related biomarkers and neurobehavioral assessments within the timeline of January 2011 until June 2023 were searched using three databases; PubMed, PROQUEST and SCOPUS. Results: A total of 705 articles were retrieved and screened, resulting in 108 studies which are in line with the objective of the current study were included in the analysis. Discussion: The selected studies have shown significant desired effect on the chosen biomarkers and neurobehavioral assessments. Systematic Review Registration: identifier: [CRD42021271001].

The protective roles of citrus flavonoids, naringenin, and naringin on endothelial cell dysfunction in diseases

The endothelial cells (ECs) make up the inner lining of blood vessels, acting as a barrier separating the blood and the tissues in several organs. ECs maintain endothelium integrity by controlling the constriction and relaxation of the vasculature, blood fluidity, adhesion, and migration. These actions of ECs are efficiently coordinated via an intricate signaling network connecting receptors, and a wide range of cellular macromolecules. ECs are naturally quiescent i.e.; they are not stimulated and do not proliferate. Upon infection or disease, ECs become activated, and this alteration is pivotal in the pathogenesis of a spectrum of human neurological, cardiovascular, diabetic, cancerous, and viral diseases. Considering the central position that ECs play in disease pathogenesis, therapeutic options have been targeted at improving ECs integrity, assembly, functioning, and health. The dietary intake of flavonoids present in citrus fruits has been associated with a reduced risk of endothelium dysfunction. Naringenin (NGN) and Naringin (NAR), major flavonoids in grapefruit, tomatoes, and oranges possess anti-inflammatory, antioxidant properties, and cell survival potentials, which improve the health of the vascular endothelium. In this review, we provide a comprehensive summary and present the advances in understanding of the mechanisms through which NGN and NAR modulate the biomarkers of vascular dysfunction and protect the endothelium against unresolved inflammation, oxidative stress, atherosclerosis, and angiogenesis. We also provide perspectives and suggest further studies that will help assess the efficacy of citrus flavonoids in the therapeutics of human vascular diseases.

Antidepressant-like effect of acute dose of Naringin involves suppression of NR1 and activation of protein kinase A/cyclic adenosine monophosphate response element-binding protein/brain-derived neurotrophic factor signaling in hippocampus

Naringin (Nr) has been identified to have antidepressant-like effects through repeated treatment. However, the underlying mechanism of the rapid antidepressant-like effects of Nr was still unclear. The present study used behavioral tests, classic depressive model and pharmacological methods to reveal the rapid antidepressant-like potential of Nr. We found that a single dose of Nr (20 mg/kg) produced antidepressant-like action after 2 h in the tail suspension test (TST) and forced swimming test (FST). Moreover, ketamine-like effects were also demonstrated by using the chronic mild stress model (CMS) and learned helplessness (LH), and the results showed that Nr reversed all behavioral defects, TST, FST, source preference test (SPT) in CMS, and LH testing, TST, FST in LH model, at 2 h after a single administration. In addition, Nr (20 mg/kg) could improve the abnormal expressions of NMDA receptor NR1 and PKA/CREB/BDNF pathway in hippocampus 2 h after a single administration in CMS mice. Further investigation revealed that activation of NMDA receptors by NMDA (750 mg/kg) could block the antidepressant effects of acute administration of Nr (20 mg/kg). However, the inhibition of NMDA receptors by MK-801 (0.05 mg/kg) promoted the subdose of Nr (10 mg/kg) to have antidepressant effect, which was similar to the effective dose Nr (20 mg/kg). Taken together, acute dose of Nr produces rapid antidepressant-like action, and the underlying mechanism could be through inhibiting NMDA receptors in the hippocampus.

Naringin enhances long-term potentiation and recovers learning and memory deficits of amyloid-beta induced Alzheimer's disease-like behavioral rat model

Alzheimer's disease (AD), as the most typical type of dementia, is a chronic neurodegenerative disorder characterized by progressive learning and memory impairment. It is known that the main causes of AD are the accumulation of β-amyloid (Aβ) plaques and neurofibrillary tangles (NFT) containing hyperphosphorylated tau protein. Naringin is a flavonoid from citrus fruits, especially in grapefruit, which has anti-inflammatory, antioxidant, anti-apoptotic, and neuroprotective activities. However, the effect of naringin in AD caused by Aβ has not been clearly studied, and there are few studies on the electrophysiological aspect. Thus, we investigated the ex vivo neuroprotective effect of naringin through the long-term potentiation (LTP) on organotypic hippocampal slice cultures. We evaluated the in vivo effects of naringin (100 mg/kg/day) orally treated for 20 days on learning, memory, and cognition which was impaired by bilateral CA1 subregion injection of Aβ. Cognitive behaviors were measured 2 weeks after Aβ injection using behavioral tests and the hippocampal expression of apoptotic and neurotrophic regulators were measured by immunoblotting. In hippocampal tissue slices, naringin dose-dependently increased the field excitatory postsynaptic potential (fEPSP) after theta burst stimulation and attenuated Aβ-induced blockade of fEPSP in the hippocampal CA1 area. In Aβ injected rats, naringin improved object recognition memory in the novel object test, avoidance memory in the passive avoidance test and spatial recognition memory in the Morris water maze test. In the hippocampus, naringin attenuated the Aβ-induced cyclooxygenase-2, Bax activation and Bcl-2, CREB, BDNF and TrkB inhibition. These results suggest that naringin has therapeutic potential to reduce neuronal inflammation and apoptosis induced by Aβ related with the BDNF/TrkB/CREB signaling.

Naringin Prevents Cognitive Dysfunction in Aging Rats by Inhibiting Toll-Like Receptor 4 (TLR4)/NF-κB Pathway and Endoplasmic Reticulum Stress

Objective

Naringin is a flavonoid derived from Chinese herbs. According to earlier studies, naringin may have the potential to alleviate aging-induced cognitive dysfunction. Therefore, this study attempted to explore the protective effect and underlying mechanism of naringin on aging rats with cognitive dysfunction.

Methods

After the construction of a model of aging rats with cognitive dysfunction through subcutaneous injection of D-galactose (D-gal; 150 mg/kg), intragastric administration of naringin (100 mg/kg) was performed for treatment. Behavioral tests, including Morris water maze test (MWM), novel object recognition test (NORT), and fear conditioning test, were used to measure the cognitive function; ELISA and biochemical tests were used to determine the levels of interleukin (IL)-1β, IL-6, monocyte chemoattractant protein-1 (MCP-1), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) in the hippocampus of rats in each group, respectively; H&E staining was used to observe the pathological changes in the hippocampus; Western blot was used to examine the expression of toll-like receptor 4 (TLR4)/NF-κB pathway-related proteins and endoplasmic reticulum (ER) stress-related proteins in the hippocampus.

Results

The model was successfully constructed by subcutaneous injection of D-gal (150 mg/kg). The behavioral test results showed that naringin could ameliorate the cognitive dysfunction and alleviate the histopathological damage of hippocampus. Moreover, naringin significantly improve the inflammatory response (the levels of IL-1β, IL-6, and MCP-1 were decreased), oxidative stress response (MDA level was increased while GSH-Px activity was decreased), and ER stress (the expression of glucose-regulated protein 78 (GRP78), C/-EBP homologous protein (CHOP), and transcription factor 6 (ATF6) expression was downregulated), and increased the levels of neurotrophic factors BDNF and NGF in D-gal rats. Besides, further mechanistic studies revealed the downregulation of naringin on TLR4/NF-κB pathway activity.

Conclusion

Naringin may inhibit inflammatory response, oxidative stress, and ER stress by downregulating TLR4/NF-κB pathway activity, thereby improving cognitive dysfunction and alleviating histopathological damage of hippocampus in aging rats. Briefly, naringin is an effective drug for the treatment of cognitive dysfunction.

Beneficial effects of natural flavonoids on neuroinflammation

Neuroinflammation is the fundamental immune response against multiple factors in the central nervous system and is characterized by the production of inflammatory mediators, activated microglia and astrocytes, and the recruitment of innate and adaptive immune cells to inflammatory sites, that contributes to the pathological process of related brain diseases, such as Alzheimer’s disease, Parkinson’s disease, depression, and stroke. Flavonoids, as a species of important natural compounds, have been widely revealed to alleviate neuroinflammation by inhibiting the production of pro-inflammatory mediators, elevating the secretion of anti-inflammatory factors, and modulating the polarization of microglia and astrocyte, mainly via suppressing the activation of NLRP3 inflammasome, as well as NF-κB, MAPK, and JAK/STAT pathways, promoting Nrf2, AMPK, BDNF/CREB, Wnt/β-Catenin, PI3k/Akt signals and SIRT1-mediated HMGB1 deacetylation. This review will provide the latest and comprehensive knowledge on the therapeutic benefits and mechanisms of natural flavonoids in neuroinflammation, and the natural flavonoids might be developed into food supplements or lead compounds for neuroinflammation-associated brain disorders.

Targeting Oxidative Stress and Inflammation in Intervertebral Disc Degeneration: Therapeutic Perspectives of Phytochemicals

Low back pain is a major cause of disability worldwide that declines the quality of life; it poses a substantial economic burden for the patient and society. Intervertebral disc (IVD) degeneration (IDD) is the main cause of low back pain, and it is also the pathological basis of several spinal degenerative diseases, such as intervertebral disc herniation and spinal stenosis. The current clinical drug treatment of IDD focuses on the symptoms and not their pathogenesis, which results in frequent recurrence and gradual aggravation. Moreover, the side effects associated with the long-term use of these drugs further limit their use. The pathological mechanism of IDD is complex, and oxidative stress and inflammation play an important role in promoting IDD. They induce the destruction of the extracellular matrix in IVD and reduce the number of living cells and functional cells, thereby destroying the function of IVD and promoting the occurrence and development of IDD. Phytochemicals from fruits, vegetables, grains, and other herbs play a protective role in the treatment of IDD as they have anti-inflammatory and antioxidant properties. This article reviews the protective effects of phytochemicals on IDD and their regulatory effects on different molecular pathways related to the pathogenesis of IDD. Moreover, the therapeutic limitations and future prospects of IDD treatment have also been reviewed. Phytochemicals are promising candidates for further development and research on IDD treatment.

NMDA receptor antagonists engender neuroprotection against gp120-induced cognitive dysfunction in Rats through Modulation of PKR activation, oxidative stress, ER stress and IRE1α Signal Pathway

It is widely accepted that the surface glycoprotein (gp120) of human immunodeficiency virus-1 (HIV-1) plays an important role in HIV-1-induced nerve damage and pathogenesis of HIV-associated neurocognitive disorders (HAND). Our previous work has demonstrated that gp120 enhanced excitatory postsynaptic currents (EPSCs) mediated by N-methyl-D-aspartate receptors (NMDARs) and caused neural injury. However, the relationship between gp120, NMDARs and HAND is still unclear. Several lines of evidence indicate that double-stranded RNA-activated protein kinase (PKR) is involved in NMDA-induced cerebral ischemia and retinal damage, but because its role in neuropathology is still debated, we examined whether PKR links oxidative stress and endoplasmic reticulum (ER) stress to exert a deleterious role in the rat model with gp120 induced dementia. In this study, we found that NMDAR antagonist memantine or PKR inhibitor C16 improved gp120-induced learning and memory impairment, and inhibited gp120-induced PKR activity. Furthermore, memantine or C16 was found to attenuate gp120-inducd neuroinflammation, oxidative stress, ER stress and its downstream IRE1α/JNK pathway. Additionally, memantine or C16 evidently inhibited apoptotic pathways by reducing the Bax and caspase-3, 8, 9 expressions and increasing Bcl-2 expression. So the NMDA receptor antagonists could alleviate HIV/gp120 induced dementia in the rat model by altering PKR level. In conclusion, this study demonstrates that NMDARs plays a key role in HIV/gp120 induced hippocampal damage and cognitive dysfunction through PKR mediated oxidative stress, ER stress, and IRE1α/JNK signaling pathway in rats, implicating PKR inhibitors could provide a novel neuroprotective strategy for HAND via inhibiting ER stress and its downstream IRE1α signaling pathway.

Naringin treatment improved main clozapine-induced adverse effects in rats; emphasis on weight gain, metabolic abnormalities, and agranulocytosis

Schizophrenia is one of the major neuropsychiatric disorders affecting people worldwide. Unfortunately, currently available antipsychotic medications possess several side effects. Among them, clozapine is one of the atypical antipsychotics prescribed in schizophrenia wing to its blocking effect on dopamine (D2) and serotonin (5-HT1c ) receptors. However, it has been recently reserved for resistant schizophrenia due to its several side effects. The current research aimed at investigating potential naringin add-on benefit to cease the main side effects of clozapine in ketamine-induced psychosis in rats. In this study, schizophrenia was induced in rats via ketamine administration that could promote neuropathological patterns of schizophrenia. Afterwards, clozapine and naringin were administered to rats in order to improve such effects induced by ketamine. Clozapine administration promoted weight gain, hyperglycemia, dyslipidemia, and agranulocytosis. However, naringin was able to reduce such adverse effects when added to clozapine treatment. Naringin increased total leukocyte count preventing agranulocytosis either when administered alone or in combination with clozapine. In addition, via its metabolic activities, naringin treatment lowered serum total cholesterol and triglycerides levels. Moreover, naringin prevented weight gain when administered. Finally, naringin reduced serum glucose level preventing hyperglycemia associated with clozapine treatment. Collectively, these findings may suggest that naringin possesses a potential add-on benefit to clozapine in treatment of schizophrenia.

Apoptotic Pathways and Alzheimer's Disease: Probing Therapeutic Potential

Apoptosis is an intrinsic biochemical, cellular process that regulates cell death and is crucial for cell survival, cellular homeostasis, and maintaining the optimum functional status. Apoptosis in a predetermined and programmed manner regulates several molecular events, including cell turnover, embryonic development, and immune system functions but may be the exclusive contributor to several disorders, including neurodegenerative manifestations, when it functions in an aberrant and disorganized manner. Alzheimer's disease (AD) is a fatal, chronic neurodegenerative disorder where apoptosis has a compelling and divergent role. The well-characterized pathological features of AD, including extracellular plaques of amyloid-beta, intracellular hyperphosphorylated tangles of tau protein (NFTs), inflammation, mitochondrial dysfunction, oxidative stress, and excitotoxic cell death, also instigate an abnormal apoptotic cascade in susceptible brain regions (cerebral cortex, hippocampus). The apoptotic players in these regions affect cellular organelles (mitochondria and endoplasmic reticulum), interact with trophic factors, and several pathways, including PI3K/AKT, JNK, MAPK, mTOR signalling. This dysregulated apoptotic cascade end with an abnormal neuronal loss which is a primary event that may precede the other events of AD progression and correlates well with the degree of dementia. The present review provides insight into the diverse and versatile apoptotic mechanisms that are indispensable for neuronal survival and constitute an integral part of the pathological progression of AD. Identification of potential targets (restoring apoptotic and antiapoptotic balance, caspases, TRADD, RIPK1, FADD, TNFα, etc.) may be valuable and advantageous to decide the fate of neurons and to develop potential therapeutics for treatment of AD.

Bactericidal/Permeability-Increasing Protein Improves Cognitive Impairment in Diabetic Mice via Blockade of the LPS-LBP-TLR4 Signaling Pathway

Emerging evidence suggests that the bactericidal/permeability-increasing protein (BPI) is involved in the process of cognitive impairment in diabetes. However, its underlying mechanism remains elusive. In this study, we found that BPI affects cognitive impairment due to diabetes through the lipopolysaccharide (LPS)-lipopolysacharide-binding protein (LBP)-toll-like receptor 4 (TLR4) signaling pathway. We examined the expression of BPI, LPS, LBP, CD14, and TLR4 in established mouse models of diabetes induced by high-fat diet (HFD) in combination with streptozotocin (STZ). Diabetic mice were then injected with adeno-associated-virus carrying BPI overexpression vectors and LPS. Fasting blood glucose, plasma insulin, and serum levels of inflammatory factors were examined. Then, glucose tolerance and, insulin resistance tests were used to measure systemic insulin sensitivity. Next, hippocampal tissue injury and cell apoptosis were examined by hematoxylin-eosin (HE) and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. Diabetic mice displayed increased LPS expression and activation of the LPS-CD14-TLR4 signaling pathway. HFD mice following LPS treatment showed significantly increased serum levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6, and expressions of Bcl-2-associated X protein (Bax) and Aβ but decreased expression of Bcl-2 in hippocampal tissues, as well as enhanced fasting blood glucose, plasma insulin, glucose tolerance, insulin tolerance, cell apoptosis, aggravated hippocampal tissue injury and, ultimately, cognitive impairment. However, overexpression of BPI was able to rescue the aforementioned phenotypes driven by LPS treatment. Taken together, BPI could potentially provide relief from cognitive impairment in diabetic mice by disrupting the LPS-LBP-TLR4 signaling pathway, underscoring a possible alternative therapeutic strategy against the cognitive impairment associated with diabetes.

Effect of Naringin Treatment on Postmenopausal Osteoporosis in Ovariectomized Rats: A Meta-Analysis and Systematic Review

Background

Osteoporosis is a major disease that affects the quality of life of middle-aged and old people, so it is very important to find efficient and safe drugs to treat osteoporosis. The purpose of this study was to investigate the therapeutic effect of naringin on postmenopausal osteoporosis in ovariectomized (OVX) rats.

Methods

Chinese biomedical databases, CNKI, PubMed, EMBASE, and Wan Fang were searched for articles from inception to March 2020. Two independent researchers screened articles according to inclusion criteria. RevMan 5.3 was used for data analysis.

Results

Ten studies were included in the systematic review. The bone mineral density (BMD) significantly increased after naringin treatment (weighted mean difference, 0.06; 95% CI, 0.03–0.09; P < 0.01). There was no significant increase in BMD after estrogen treatment compared with naringin (weighted mean difference, 0.00; 95% CI, −0.00 to 0.01; P = 0.06). The trabecular bone volume (BV/TV) (weighted mean difference, 2.09; 95% CI, 1.85–2.34; P < 0.01) and trabecular thickness (Tb.Th) (weighted mean difference, 6.65; 95% CI, 6.55–6.74; P < 0.01) significantly increased after using naringin.

Conclusions

Naringin had been shown to promote bone formation in OVX rats. However, the mechanism of naringin needs more research to confirm.

Chemokine CCL2 impairs spatial memory and cognition in rats via influencing inflammation, glutamate metabolism and apoptosis-associated genes expression- a potential mechanism for HIV-associated neurocognitive disorder

AIMS

To explore the role of chemokine CC motif ligand 2 (CCL2) in spatial memory and cognition impairment, and the underlying mechanisms focused on inflammatory, glutamate metabolistic and apoptotic- associated mRNA expression.

MATERIALS AND METHODS

Stereotaxic surgery was performed here to establish a rat model by bilateral intra-hippocampal injection of CCL2. Morris water maze (MWM) and Novel object recognition test (NORT) were used to assess the learning, memory and cognitive ability respectively. RT-PCR was used to detect the relative mRNA expression of inflammatory, glutamate metabolistic and apoptotic- associated indexes. Nissl and TUNEL staining were performed to observe the morphological changes of hippocampal CA1 zone and quantified the apoptosis of hippocampal neurons of CA1 zones respectively.

KEY FINDINGS

We found CCL2 injured cognitive function in rats. Six days after CCL2 injection, we revealed the following obvious mRNA expression changes: (1) increasing of the neuroinflammatory cytokines IL-1β, CXCL-10, IL-6; (2) decreasing of the glutamate transporters GLT-1 and GLAST and increasing of PAG; (3) increasing of the apoptotic genes caspase-8, caspase-3 and Bax, while decreasing the anti-apoptotic gene Bcl-2. Further, Nissl staining and TUNEL confirmed the injury of the structure of hippocampal CA1 zones and the apoptosis of hippocampal neurons.

SIGNIFICANCE

Our results indicated that CCL2 impaired spatial memory and cognition, the involving mechanisms may link to the up-regulation of mRNA expression of the three major pathological events: inflammation, excitotoxicity and neuronal apoptosis, which were involved in HIV-associated neurocognitive disorder (HAND). Taken together, these findings suggest a potential therapeutic strategy against CCL2.