Inhibitory Effects of Auraptene and Naringin on Astroglial Activation, Tau Hyperphosphorylation, and Suppression of Neurogenesis in the Hippocampus of Streptozotocin-Induced Hyperglycemic Mice

Late pregnancy maternal naringin supplementation affects the mitochondria in the cerebellum of Wistar rat offspring via sirtuin 3 and AKT

Dietary polyphenol consumption is associated with a wide range of neuroprotective effects by improving mitochondrial function and signaling. Consequently, the use of polyphenol supplementation has been investigated as an approach to prevent neurodevelopmental diseases during gestation; however, the data obtained are still very inconclusive, mostly because of the difficulty of choosing the correct doses and period of administration to properly prevent neurodegenerative diseases without undermining normal brain development. Thus, we aimed to evaluate the effect of naringin supplementation during the third week of gestation on mitochondrial health and signaling in the cerebellum of 21-day-old offspring. The offspring born to naringin-supplemented dams displayed higher mitochondrial mass, membrane potential, and superoxide content in the cerebellum without protein oxidative damage. Such alterations were associated with dynamin-related protein 1 (DRP1) and phosphorylated AKT (p-AKT) downregulation, whereas the sirtuin 3 (SIRT3) levels were strongly upregulated. Our findings suggest that high dietary polyphenol supplementation during gestation may reduce mitochondrial fission and affect mitochondrial dynamics even 3 weeks after delivery via SIRT3 and p-AKT. Although the offspring born to naringin dams did not present neurobehavioral defects, the mitochondrial alterations elicited by naringin may potentially interfere during neurodevelopment and need to be further investigated.

Effect of 2-Week Naringin Supplementation on Neurogenesis and BDNF Levels in Ischemia-Reperfusion Model of Rats

BACKGROUND

Ischemic stroke is the leading cause of mortality and disability worldwide with more than half of survivors living with serious neurological sequelae; thus, it has recently attracted a lot of attention in the field of medical study.

PURPOSE

The aim of this study was to determine the effect of naringin supplementation on neurogenesis and brain-derived neurotrophic factor (BDNF) levels in the brain in experimental brain ischemia-reperfusion.

STUDY DESIGN

The research was carried out on 40 male Wistar-type rats (10-12 weeks old) obtained from the Experimental Animals Research and Application Center of Selçuk University. Experimental groups were as follows: (1) Control group, (2) Sham group, (3) Brain ischemia-reperfusion group, (4) Brain ischemia-reperfusion + vehicle group (administered for 14 days), and (5) Brain ischemia-reperfusion + Naringin group (100 mg/kg/day administered for 14 days).

METHODS

In the ischemia-reperfusion groups, global ischemia was performed in the brain by ligation of the right and left carotid arteries for 30 min. Naringin was administered to experimental animals by intragastric route for 14 days following reperfusion. The training phase of the rotarod test was started 4 days before ischemia-reperfusion, and the test phase together with neurological scoring was performed the day before and 1, 7, and 14 days after the operation. At the end of the experiment, animals were sacrificed, and then hippocampus and frontal cortex tissues were taken from the brain. Double cortin marker (DCX), neuronal nuclear antigen marker (NeuN), and BDNF were evaluated in hippocampus and frontal cortex tissues by Real-Time qPCR analysis and immunohistochemistry methods.

RESULTS

While ischemia-reperfusion increased the neurological score values, DCX, NeuN, and BDNF levels decreased significantly after ischemia in the hippocampus and frontal cortex tissues. However, naringin supplementation restored the deterioration to a certain extent.

CONCLUSION

The results of the study show that 2 weeks of naringin supplementation may have protective effects on impaired neurogenesis and BDNF levels after brain ischemia and reperfusion in rats.

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.

Effects of Citrus kawachiensis Peel in Frailty-like Model Mice Induced by Low Protein Nutrition Disorders

"Frailty" caused by a decline in physiological reserve capacity, chronic inflammation, and oxidative stress in the elderly has recently become a major social issue. The present study examined the effects of the peel of Citrus kawachiensis (CK), which exhibits anti-inflammatory, antioxidant, and pro-neurogenesis activities in frailty-like model mice. Male C57BL/6 mice (15 weeks old) were fed an 18% protein diet (CON), a 2.5% protein diet (PM), and PM mixed with 1% dried CK peel powder for approximately 1 month. Mice were euthanized 2 or 8 days after a single intraperitoneal administration of lipopolysaccharide (LPS) and tissues were dissected. Among peripheral tissues, muscle weight, liver weight, and blood glucose levels were significantly higher in the PM-LPS-CK group than in the PM-LPS group. In the behavioral analysis, locomotive activity was significantly lower in the PM-LPS group than in the PM group. The reduction in locomotive activity in the PM-LPS-CK group was significantly smaller than that in the PM-LPS group. The quantification of microglia in the hippocampal stratum lacunosum-moleculare revealed that increases in the PM-LPS group were significantly suppressed by the dried CK peel powder. Furthermore, the quantification of synaptic vesicle membrane proteins in the hippocampal CA3 region showed down-regulated expression in the PM-LPS group, which was significantly ameliorated by the administration of the dried CK peel powder. Collectively, these results suggest that CK inhibits inflammation and oxidative stress induced by PM and LPS in the central nervous system and peripheral tissue. Therefore, C. kawachiensis is highly effective against "frailty".

The Effects of Urolithin B and Auraptene on Quinolinic Acid-induced Toxicity in the SH-SY5Y Neuroblastoma Cell Line

The pathological accumulation of quinolinic acid (QA) is often associated with neuritis and neuronal cell death in several neurodegenerative diseases, through the overproduction of free radicals. Urolithin B and auraptene have been reported to exert potent antioxidant effects - however, little is known about the protective effects of these compounds against QA-induced neurotoxicity. Therefore, this study aimed to explore the in vitro protective effects of urolithin B and auraptene against QA-induced neurotoxicity in the SH-SY5Y neuroblastoma cell line. The MTT assay was used to evaluate cell viability, and flow cytometry was carried out to evaluate effects on the cell cycle and apoptosis. The intracellular levels of reactive oxygen species (ROS) were also determined. Our findings showed that auraptene at non-toxic concentrations had no protective effect on QA-induced toxicity. However, urolithin B at concentrations of 0.6 μM and 2.5 μM enhanced the viability of cells treated with QA. Moreover, while the percentage of apoptotic cells (i.e. in the sub-G1 phase) was shown to significantly increase after QA treatment, pre-treatment with urolithin B reduced the number of these apoptotic cells. Furthermore, urolithin B, as an antioxidant, also significantly reduced QA-induced ROS production. Our findings suggest that urolithin B may possess potent antioxidant and neuroprotective effects against QA-induced neurotoxicity that merit further investigation.

Cognitive and biological effects of citrus phytochemicals in subjective cognitive decline: a 36-week, randomized, placebo-controlled trial

Background

Auraptene (AUR) and naringenin (NAR) are citrus-derived phytochemicals that influence several biological mechanisms associated with cognitive decline, including neuronal damage, oxidative stress and inflammation. Clinical evidence of the efficacy of a nutraceutical with the potential to enhance cognitive function in cohorts at risk of cognitive decline would be of great value from a preventive perspective. The primary aim of this study is to determine the cognitive effects of a 36-week treatment with citrus peel extract standardized in levels of AUR and NAR in older adults experiencing subjective cognitive decline (SCD). The secondary aim is to determine the effects of these phytochemicals on blood-based biomarkers indicative of neuronal damage, oxidative stress, and inflammation.

Methods

Eighty older persons with SCD will be recruited and randomly assigned to receive the active treatment (400 mg of citrus peel extract containing 0.1 mg of AUR and 3 mg of NAR) or the placebo at a 1:1 ratio for 36 weeks. The primary endpoint is a change in the Repeatable Battery for the Assessment of Neuropsychological Status score from baseline to weeks 18 and 36. Other cognitive outcomes will include changes in verbal and nonverbal memory, attention, executive and visuospatial functions. Blood samples will be collected from a consecutive subsample of 60 participants. The secondary endpoint is a change in interleukin-8 levels over the 36-week period. Other biological outcomes include changes in markers of neuronal damage, oxidative stress, and pro- and anti-inflammatory cytokines.

Conclusion

This study will evaluate whether an intervention with citrus peel extract standardized in levels of AUR and NAR has cognitive and biological effects in older adults with SCD, facilitating the establishment of nutrition intervention in people at risk of cognitive decline.

Trial registration

The trial is registered with the United States National Library of Medicine at the National Institutes of Health Registry of Clinical Trials under the code NCT04744922 on February 9^th, 2021 (https://www.clinicaltrials.gov/ct2/show/NCT04744922).

Naringin Regulates Microglia BV-2 Activation and Inflammation via the JAK/STAT3 Pathway

Objective

Microglial BV-2 cells are activated in the brain following insomnia. Naringin (NAR) is a polymethoxylated flavonoid that is also commonly found in citrus fruits and is known for its antioxidant potential. However, the effect of NAR on microglial cells has rarely been studied in the brain of an organism after insomnia. This study aimed to investigate the effects and potential mechanisms of action of NAR on microglial cell activation and inflammation.

Methods

BV-2 cells were obtained from the China Center for Type Culture Collection and randomly divided into five treatment groups: control, model, NAR (10 μM), WP1066 (5 μM), and NAR + WP1066. With the exception of the control group, all groups were stimulated with LPS (1 μg/mL) for 6 h. CCK8 was used to quantify cell viability and a scratch test was performed to detect cell migration. The expression levels of interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), interleukin 1 beta (IL-1β), nterleukin 10 (IL-10), and insulin like growth factor (1IGF-1) were measured by ELISA. Western blotting was performed to determine the levels of p-STAT3 and p-JAK. The Focalcheck™ Thin-Ring Fluorescent Microspheres kit was used to detect cell phagocytosis. Immunofluorescence was used to observe the expression of iNOS and arginase1 in BV-2 cells.

Results

Compared with the control group, cell migration, cell viability, and the expression of IL-1β, IL-6, TNF-α, and iNOS were significantly increased in the model group, whereas the expression levels of IL-10, IGF-1, and arginase 1, as well as cell phagocytosis were reduced. With the increase in NAR concentration, cell migration, cell viability, the expression levels of IL-1β, IL-6, TNF-α, and iNOS decreased, while the expression of IL-10, IGF-1, and arginase 1 increased. Compared with the control group, p-STAT3, and p-JAK expression in the model group were significantly increased (P<0.05). Compared with the model group, the expression of p-STAT3 and p-JAK in the NAR, NAR + WP1066, and WP1066 groups was significantly decreased (P < 0.05).

Conclusion

NAR treatment inhibited the proliferation, migration, and inflammation of BV-2 cells as well as the activation of microglia to the M1 phenotype. Conversely, NAR treatment promoted the activation of microglia to the M2 phenotype and enhanced the phagocytic function of BV-2 cells by regulating the activity of the JAK/STAT3 pathway.

Naringin Mediates Adult Hippocampal Neurogenesis for Antidepression via Activating CREB Signaling

The brain-derived neurotrophic factor/tropomyosin receptor kinase B/cAMP response element-binding protein (BDNF/TrkB/CREB) signaling pathway is a critical therapeutic target for inducing adult hippocampal neurogenesis and antidepressant therapy. In this study, we tested the hypothesis that naringin, a natural medicinal compound, could promote adult hippocampal neurogenesis and improve depression-like behaviors via regulating the BDNF/TrkB/CREB signaling pathway. We first investigated the effects of naringin on promoting adult hippocampal neurogenesis in both normal and chronic corticosterone (CORT)-induced depressive mice. Under physiological condition, naringin treatment enhanced the proliferation of neural stem/progenitor cells (NSPCs) and accelerated neuronal differentiation. In CORT-induced depression mouse model, naringin treatment promoted neuronal differentiation and maturation of NSPCs for hippocampal neurogenesis. Forced swim test, tail suspension test, and open field test confirmed the antidepressant and anxiolytic effects of naringin. Co-treatment of temozolomide (TMZ), a neurogenic inhibitor, abolished these antidepressant and anxiolytic effects. Meanwhile, naringin treatment increased phosphorylation of cAMP response element binding protein (CREB) but had no effect on the expression of brain-derived neurotrophic factor and phosphorylation of TrkB in the hippocampus of CORT-induced depressive mice. Co-treatment of CREB inhibitor 666-15, rather than TrkB inhibitor Cyc-B, abolished the neurogenesis-promoting and antidepressant effects of naringin. Taken together, naringin has antidepressant and anxiolytic effects, and the underlying mechanisms could be attributed to enhance hippocampal neurogenesis via activating CREB signaling.

Bioactive Compounds of Citrus Fruits: A Review of Composition and Health Benefits of Carotenoids, Flavonoids, Limonoids, and Terpenes

The increased consumption of fruits, vegetables, and whole grains contributes to the reduced risk of many diseases related to metabolic syndrome, including neurodegenerative diseases, cardiovascular disease (CVD), diabetes, and cancer. Citrus, the genus Citrus L., is one of the most important fruit crops, rich in carotenoids, flavonoids, terpenes, limonoids, and many other bioactive compounds of nutritional and nutraceutical value. Moreover, polymethoxylated flavones (PMFs), a unique class of bioactive flavonoids, abundantly occur in citrus fruits. In addition, citrus essential oil, rich in limonoids and terpenes, is an economically important product due to its potent antioxidant, antimicrobial, and flavoring properties. Mechanistic, observational, and intervention studies have demonstrated the health benefits of citrus bioactives in minimizing the risk of metabolic syndrome. This review provides a comprehensive view of the composition of carotenoids, flavonoids, terpenes, and limonoids of citrus fruits and their associated health benefits.

Citrus Polyphenols in Brain Health and Disease: Current Perspectives

In addition to essential micronutrients such as vitamin C, citrus fruits represent a considerably rich source of non-essential bioactive compounds, in particular flavanones which form a sub-set of the flavonoid group. Preclinical studies have demonstrated the neuroprotective potential of citrus flavonoids and have highlighted both the well-established (anti-inflammatory and anti-oxidative properties), and newly emerging (influence upon blood-brain barrier function/integrity) mechanistic actions by which these neurological effects are mediated. Encouragingly, results from human studies, although limited in number, appear to support this preclinical basis, with improvements in cognitive performance and disease risk observed across healthy and disease states. Therefore, citrus fruits - both as whole fruit and 100% juices - should be encouraged within the diet for their potential neurological benefit. In addition, there should be further exploration of citrus polyphenols to establish therapeutic efficacy, particularly in the context of well-designed human interventions.

[The Search for Citrus Components with Neuroprotective and Anti-dementia Effects in the Mouse Brain]

Citrus kawachiensis (Kawachi Bankan), is a citrus species grown in Ehime, Japan, and its peel is abundant in 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF). We have recently revealed that HMF, one of the citrus flavonoids, has anti-inflammatory activity and neuroprotective abilities in the brain against global cerebral ischemia. HMF rescued neuronal cell death in the hippocampus and suppressed the activation of microglia, whose activation have been shown to significantly aggravate neurological deficit scores for ischemic mice. In the Y-maze test, HMF showed protection against ischemia-induced short-term memory dysfunction; in addition, HMF enhanced the expression of brain-derived neurotrophic factor and accelerated neurogenesis in the hippocampus. Similarly, the powder of the peel of C. kawachiensis showed anti-inflammatory activity and neuroprotective abilities in the ischemic brain. To further examine the effect of the peel of C. kawachiensis, we administered it to senescence-accelerated-mouse prone 8 (SAMP8) mice, which show memory impairment and brain inflammation, tau hyperphosphorylation, and neuronal dysfunction. The C. kawachiensis treatment inhibited microglial activation and the hyperphosphorylation of tau protein in hippocampal neurons, and also relieved the suppression of neurogenesis in the dentate gyrus of the hippocampus in SAMP8. These results suggest that HMF and the peel of C. kawachiensis have potential effects as neuroprotective and anti-dementia agents.

Soy isoflavones ameliorate the cognitive dysfunction of Goto-Kakizaki rats by activating the Nrf2-HO-1 signalling pathway

Soy isoflavones (SIF) are soybean phytochemicals that are considered to be biologically active components that protect from neurodegenerative diseases. In this study, the therapeutic effect of SIF was evaluated in a diabetic Goto-Kakizaki (GK) rat model. Twenty male GK rats were randomly divided into diabetes mellitus (DM) model group and SIF+DM group (n=10 in each group). Twenty age-matched male Wistar rats were randomly divided into control group (CON group) and CON+SIF group, with 10 rats in each group. The learning and memory functions of the animals were determined by the Morris water maze (MWM) test. Hematoxylin-eosin staining (HE) was performed to examine pyramidal neuron loss in the CA1 area of the hippocampus. Markers of oxidative stress (OS) were measured to evaluate oxidative stress-mediated injury. RT-PCR and western blotting were used to analyze the expression of nuclear factorerythroid2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H dehydrogenase quinone1 (NQO1). Treatment with SIF for 4 weeks alleviated the cognitive dysfunction of the GK rats as determined by the MWM test. Moreover, SIF treatment also reduced diabetes-related oxidative reactions. In addition, SIF enhanced the expression of Nrf2, HO-1 and NQO1, suggesting a potential antioxidation mechanism for the effect of SIF. These findings suggest that SIF can be considered candidates for inhibiting the progression of diabetes-induced cognitive dysfunction, provide novel insights into the antioxidant effect of SIF and further strengthen the link between oxidative stress and diabetes.

In-silico and biophysical investigation of biomolecular interaction between naringin and nsP2 of the chikungunya virus

Chikungunya virus; the pathogen for chikungunya febrile and arthritic disease, having 11.8 kb positive-sense RNA genome encodes polyproteins for structural and non-structural regions. The polyprotein (P1234) corresponding to the non-structural part from 5' end gets auto-cleaved by the action of nsP2 protease, which leads to the generation of individual functional enzymatic proteins like nsP4, nsP1, nsP2 and nsP3. Thus, nsP2 protein initiates viral replication. Targeting nsP2 to block virus replication has always been the foremost strategy to develop antivirals. Plant-based molecules are one of the top choices to develop as inhibitor due to their less toxicity and wide availability. Using a combination of receptor-based docking and MD simulations, we identified a flavanone glycoside- naringin, which binds to nsP2 protease at nM affinity. The biomolecular interaction between naringin and nsP2 was established through SPR. As discerned through FTIR and intrinsic fluorescence studies, upon binding with naringin, a global structural change in nsP2 occurs. This structural modulation in nsP2 due to binding of naringin is likely to interfere with the normal functioning of this enzyme during the viral life cycle. In conclusion, this report highlights the potential of naringin as an anti-viral agent against Chikungunya.

A review of the pharmacological and therapeutic effects of auraptene

There is a growing awareness in herbal medications as they are usually safe and devoid of significant adverse effects. Auraptene is a natural bioactive monoterpene coumarin ether and is consumed all over the world. There is growing evidence of the therapeutic benefits of auraptene. Auraptene, also known as auraptene and 7-geranyloxycoumarin, is a bioactive monoterpene coumarin from Rutaceae family, which is isolated from Citrus aurantium (Seville orange) and Aegle marmelos (bael fruit). Auraptene is a highly pleiotropic molecule, which can modulate intracellular signaling pathways that control inflammation, cell growth, and apoptosis. It has a potential therapeutic role in the prevention and treatment of various diseases due to its anti-inflammatory and antioxidant activities as well as its excellent safety profile. In the present article, various pharmacological and therapeutic effects of auraptene were reviewed. Different online databases using keywords such as auraptene, therapeutic effects and pharmacological effects were searched until the end of September 2018, for this purpose. Auraptene has been suggested to be effective in the treatment of a broad range of disorders including inflammatory disorders, dysentery, wounds, scars, keloids, and pain. In addition, different studies have demonstrated that auraptene possesses numerous pharmacological properties including anti-inflammatory, anti-oxidative, anti-diabetic, anti-hypertensive and anti-cancer as well as neuroprotective effects. The present review provides a detailed survey of scientific researches regarding pharmacological properties and therapeutic effects of auraptene.

Therapeutic potential of naringin in neurological disorders

Neurological illnesses are multifactorial incurable debilitating disorders that may cause neurodegeneration. These diseases influence approximately 30 million people around the world. Despite several therapies, effective management of such disorders remains a global challenge. Thus, natural products might offer an alternative therapy for the treatment of various neurological disorders. Polyphenols, such as curcumin, resveratrol, myricetin, mangiferin and naringin (NRG) have been shown to possess promising potential in the treatment of neurogenerative illness. In this review, we have targeted the therapeutic potential of naringin as a neuroprotective agent. The overall neuroprotective effects and different possible underlying mechanisms related to NRG are discussed. In light of the strong evidence for the neuropharmacological efficacy of NRG in various experimental paradigms, it is concluded that this molecule should be further considered and studied as a potential candidate for neurotherapeutics, focusing on mechanistic and clinical trials to ascertain its efficacy.

Maternal Flavonoids Intake Reverts Depression-Like Behaviour in Rat Female Offspring

Maternal hypercaloric exposure during pregnancy and lactation is a risk factor for developing diseases associated with inflammation such as obesity, diabetes and, neurological diseases in the offspring. Neuroinflammation might modulate neuronal activation and flavonoids are dietary compounds that have been proven to exert anti-inflammatory properties. Thus, the aim of the present study is to evaluate the effect of maternal supplementation with flavonoids (kaempferol-3-O-glucoside and narirutin) on the prevention of depression-like behaviour in the female offspring of dams fed with an obesogenic diet during the perinatal period. Maternal programming was induced by high fat (HFD), high sugar (HSD), or cafeteria diets exposure and depressive like-behaviour, referred to as swimming, climbing, and immobility events, was evaluated around postnatal day 56–60 before and after 30 mg/kg i.p. imipramine administration in the female offspring groups. Central inflammation was analyzed by measuring the TANK binding kinase 1 (TBK1) expression. We found that the offspring of mothers exposed to HSD programming failed to show the expected antidepressant effect of imipramine. Also, imipramine injection, to the offspring of mothers exposed to cafeteria diet, displayed a pro-depressive like-behaviour phenotype. However, dietary supplementation with flavonoids reverted the depression-like behaviour in the female offspring. Finally, we found that HSD programming increases the TBK1 inflammatory protein marker in the hippocampus. Our data suggest that maternal HSD programming disrupts the antidepressant effect of imipramine whereas cafeteria diet exposure leads to depressive-like behaviour in female offspring, which is reverted by maternal flavonoid supplementation.