Modulation of Akt, JNK, and p38 activation is involved in citrus flavonoid-mediated cytoprotection of PC12 cells challenged by hydrogen peroxide

Effects of isosakuranetin on cerebral infarction and blood brain barrier damage from cerebral ischemia/reperfusion injury in a rat model

This study investigated the effects of isosakuranetin (5,7-dihydroxy-4'-methoxyflavanone) on cerebral infarction and blood brain barrier (BBB) damage in cerebral ischemia and reperfusion (I/R) in a rat model. The right middle cerebral artery was occluded for 2 h followed by reperfusion. The experimental rats were divided into five groups: a sham, or control group; vehicle group; and 5 mg/kg, 10 mg/kg, and 20 mg/kg bodyweight isosakuranetin-treated I/R groups. After 24 h of reperfusion, the rats were tested using a six-point neurological function score. The percentage of cerebral infarction was evaluated using 2,3,5-triphenyltetrazolium chloride (TTC) staining. BBB leakage was determined by Evan Blue injection assay and brain morphology changes were observed under light microscopy following staining with hematoxylin and eosin (H&E). The results of neurological function score revealed that isosakuranetin reduced the severity of neurological damage. A dose of 10 and 20 mg/kg bodyweight of isosakuranetin significantly decreased the infarct volume. All three doses of isosakuranetin significantly decreased Evan Blue leakage. The penumbra area of the I/R brains revealed the characteristics of apoptotic cell death. Therefore, isosakuranetin-treated I/R attenuated the brain damage from cerebral I/R injury and further investigation of the mechanisms warrant further investigation to assist in the development of protective strategies against cerebral I/R injury in clinical trials.Communicated by Ramaswamy H. Sarma.

Metal Nanoparticle-Flavonoid Connections: Synthesis, Physicochemical and Biological Properties, as Well as Potential Applications in Medicine

Flavonoids are polyphenolic compounds widely occurring throughout the plant kingdom. They are biologically active and have many medical applications. Flavonoids reveal chemopreventive, anticarcinogenic, and antioxidant properties, as well as being able to modulate the immune system response and inhibit inflammation, angiogenesis, and metastasis. Polyphenols are also believed to reverse multidrug resistance via various mechanisms, induce apoptosis, and activate cell death signals in tumor cells by modulating cell signaling pathways. The main limitation to the broader usage of flavonoids is their low solubility, poor absorption, and rapid metabolism. To tackle this, the combining of flavonoids with nanocarriers could improve their bioavailability and create systems of wider functionalities. Recently, interest in hybrid materials based on combinations of metal nanoparticles with flavonoids has increased due to their unique physicochemical and biological properties, including improved selectivity toward target sites. In addition, flavonoids have further utilities, even in the initial step of preparation of metal nanomaterials. The review offers knowledge on multiple possibilities of the synthesis of flavonoid-metal nanoparticle conjugates, as well as presents some of their features such as size, shape, surface charge, and stability. The flavonoid-metal nanoparticles are also discussed regarding their biological properties and potential medical applications.

Purification, Identification and Evaluation of Antioxidant Peptides from Pea Protein Hydrolysates

Food-derived antioxidant peptides can be explored as natural antioxidants due to their potential health benefits. In this study, antioxidant peptides were isolated and purified from pea protein hydrolysates (PPH). The DPPH and ABTS radical scavenging activities were used as indexes to purify the antioxidant peptides by a series of purification steps including ultrafiltration, ion exchange chromatography, G25 gel filtration chromatography, and reversed-phase chromatography. Three novel antioxidant peptides YLVN, EEHLCFR and TFY were identified, which all exhibited strong antioxidant activity in vitro. EEHLCFR showed stronger DPPH scavenging activity with an IC50 value of 0.027 mg/mL. YLVN showed stronger ABTS scavenging activity with an IC50 value of 0.002 mg/mL and higher ORAC values of 1.120 ± 0.231 μmol TE/μmol, which is even better than that of GSH. Three novel antioxidant peptides significantly elevated LO2 cells viability even at the concentration of 0.025 mg/mL, and cell viability enhanced to 53.42 ± 1.19%, 55.78 ± 1.03%, and 51.09 ± 1.06% respectively, compared to that of H2O2 injury group (48.35 ± 0.96%), and prevented the accumulation of ROS by enhancing the activities of antioxidant enzymes in H2O2-induced oxidative stress LO2 cells. The molecular docking results showed that the potential molecular mechanism of the three novel antioxidant peptides may be in high correlation with the activation of the Keap1-Nrf2 pathway by occupying the Keap1-Nrf2 binding site. These results demonstrate that the three novel antioxidant peptides are potential natural antioxidants that can be devoted to medicine or functional food ingredients.

Flavonoids as Potential Wound-Healing Molecules: Emphasis on Pathways Perspective

Wounds are considered to be a serious problem that affects the healthcare sector in many countries, primarily due to diabetes and obesity. Wounds become worse because of unhealthy lifestyles and habits. Wound healing is a complicated physiological process that is essential for restoring the epithelial barrier after an injury. Numerous studies have reported that flavonoids possess wound-healing properties due to their well-acclaimed anti-inflammatory, angiogenesis, re-epithelialization, and antioxidant effects. They have been shown to be able to act on the wound-healing process via expression of biomarkers respective to the pathways that mainly include Wnt/β-catenin, Hippo, Transforming Growth Factor-beta (TGF-β), Hedgehog, c-Jun N-Terminal Kinase (JNK), NF-E2-related factor 2/antioxidant responsive element (Nrf2/ARE), Nuclear Factor Kappa B (NF-κB), MAPK/ERK, Ras/Raf/MEK/ERK, phosphatidylinositol 3-kinase (PI3K)/Akt, Nitric oxide (NO) pathways, etc. Hence, we have compiled existing evidence on the manipulation of flavonoids towards achieving skin wound healing, together with current limitations and future perspectives in support of these polyphenolic compounds as safe wound-healing agents, in this review.

Blood orange juice intake modulates plasma and PBMC microRNA expression in overweight and insulin-resistant women: impact on MAPK and NFκB signaling pathways

Blood orange consumption presents potential health benefits and may modulate epigenetic mechanisms such as microRNAs (miRNAs) expression. MiRNAs are non-coding RNAs responsible for post-transcriptional gene regulation, and these molecules can also be used as biomarkers in body fluids. This study was designed to investigate the effect of chronic blood orange juice (BOJ) intake on the inflammatory response and miRNA expression profile in plasma and blood cells in overweight women. The study cohort was comprised of twenty women aged 18-40 years old, diagnosed as overweight, who consumed 500 mL/d of BOJ for four weeks. Clinical data were collected at baseline and after 4 weeks of juice consumption, e.g., anthropometric and hemodynamic parameters, food intake, blood cell count, and metabolic and inflammatory biomarkers. BOJ samples were analyzed and characterized. Additionally, plasma and blood cells were also collected for miRNA expression profiling and evaluation of the expression of genes and proteins in the MAPK and NFκB signaling pathways. BOJ intake increased the expression of miR-144-3p in plasma and the expression of miR-424-5p, miR-144-3p, and miR-130b-3p in peripheral blood mononuclear cells (PBMC). Conversely, the beverage intake decreased the expression of let-7f-5p and miR-126-3p in PBMC. Computational analyses identified different targets of the dysregulated miRNA on inflammatory pathways. Furthermore, BOJ intake increased vitamin C consumption and the pJNK/JNK ratio and decreased the expression of IL6 mRNA and NFκB protein. These results demonstrate that BOJ regulates the expression of genes involved in the inflammatory process and decreases NFкB-protein expression in PBMC.

Protective Effects of PEP-1-GSTA2 Protein in Hippocampal Neuronal Cell Damage Induced by Oxidative Stress

Glutathione S-transferase alpha 2 (GSTA2), a member of the glutathione S-transferase family, plays the role of cellular detoxification against oxidative stress. Although oxidative stress is related to ischemic injury, the role of GSTA2 against ischemia has not been elucidated. Thus, we studied whether GSTA2 prevents ischemic injury by using the PEP-1-GSTA2 protein which has a cell-permeable protein transduction domain. We revealed that cell-permeable PEP-1-GSTA2 transduced into HT-22 cells and markedly protected cell death via the inhibition of reactive oxygen species (ROS) production and DNA damage induced by oxidative stress. Additionally, transduced PEP-1-GSTA2 promoted mitogen-activated protein kinase (MAPK), and nuclear factor-kappaB (NF-κB) activation. Furthermore, PEP-1-GSTA2 regulated Bcl-2, Bax, cleaved Caspase-3 and -9 expression protein levels. An in vivo ischemic animal model, PEP-1-GSTA2, markedly prevented the loss of hippocampal neurons and reduced the activation of microglia and astrocytes. These findings indicate that PEP-1-GSTA2 suppresses hippocampal cell death by regulating the MAPK and apoptotic signaling pathways. Therefore, we suggest that PEP-1-GSTA2 will help to develop the therapies for oxidative-stress-induced ischemic injury.

Recent Progress in the Hesperetin Delivery Regimes: Significance of Pleiotropic Actions and Synergistic Anticancer Efficacy

BACKGROUND

In the plant kingdom, flavonoids are widely distributed with multifunctional immunomodulatory actions. Hesperetin (HST) remains one of the well-studied compounds in this domain, initially perceived in citrus plants as an aglycone derivative of hesperidin (HDN).

OBSERVATIONS

Natural origin, low in vivo toxicity, and pleiotropic functional essence are the foremost fascinations for HST use as an anticancer drug. However, low aqueous solubility accompanied with a prompt degradation by intestinal and hepatocellular enzymes impairs HST physiological absorption.

MOTIVATION

Remedies attempted herein comprise the synthesis of derivatives and nanocarrier (NC)-mediated delivery. As the derivative synthesis aggravates the structural complexity, NC-driven HST delivery has emerged as a sustainable approach for its sustained release. Recent interest in HST has been due to its significant anticancer potential, characterized via inhibited cell division (proliferation), new blood vessel formation (angiogenesis), forceful occupation of neighboring cell's space (invasion), migration to erstwhile physiological locations (metastasis) and apoptotic induction. The sensitization of chemotherapeutic drugs (CDs) by HST is driven via stoichiometrically regulated synergistic actions. Purpose and Conclusion: This article sheds light on HST structure-function correlation and pleiotropic anticancer mechanisms, in unaided and NC-administered delivery in singular and with CDs synergy. The discussion could streamline the HST usefulness and long-term anticancer efficacy.

Cytoprotective Properties of a New Nanocomplex of Selenium with Taxifolin in the Cells of the Cerebral Cortex Exposed to Ischemia/Reoxygenation

The neuroprotective effect of the natural antioxidant taxifolin (TAX) is well known for ischemic pathologies. However, the limitations of taxifolin application are described-poor solubility, low ability to penetrate the blood-brain barrier, and side effects from high doses for stroke therapy. We proposed the problem of targeted delivery of taxifolin and achievement effective concentrations could be solved by developing a nanocomplex of selenium nanoparticles (SeNPs) with taxifolin (Se-TAX). In this study, we developed a selenium-taxifolin nanocomplex based on selenium nanoparticles with a 100 nm size. It was shown that TAX, SeNPs, and Se-TAX were all able to suppress the production of ROS in neurons and astrocytes under exposure to exogenous H₂O₂ and ischemia-like conditions. However, the Se-TAX nanocomplex appeared to be the most effective, displaying a lower working concentration range and negligible pro-oxidant effect compared with pure SeNPs. The mechanism of Se-TAX beneficial effects involved the activation of some antioxidant enzymes and the suppression of ROS-generating systems during OGD/reoxygenation, while TAX and "naked" SeNPs were less effective in regulating the cellular redox status. Naked SeNPs inhibited a global increase in Ca²⁺ ions in cytosol, but not OGD-induced hyperexcitation of the neuroglial network, while Se-TAX suppressed both [Ca²⁺]i rise and hyperexcitation. The effect of TAX at similar doses appeared exclusively in inhibiting OGD-induced hyperexcitation. Analysis of necrosis and apoptosis after OGD/reoxygenation revealed the highest efficiency of the Se-TAX nanocomplex as well. Se-TAX suppressed the expression of proinflammatory and proapoptotic proteins with simultaneous activation of protective genes. We conclude that the Se-TAX nanocomplex combines the antioxidative features taxifolin and the antiapoptotic effect of nanoselenium, involving the regulation of Ca²⁺ dynamics.

Interdisciplinary Approaches to Deal with Alzheimer's Disease-From Bench to Bedside: What Feasible Options Do Already Exist Today?

Alzheimer's disease is one of the most common neurodegenerative diseases in the western population. The incidence of this disease increases with age. Rising life expectancy and the resulting increase in the ratio of elderly in the population are likely to exacerbate socioeconomic problems. Alzheimer's disease is a multifactorial disease. In addition to amyloidogenic processing leading to plaques, and tau pathology, but also other molecular causes such as oxidative stress or inflammation play a crucial role. We summarize the molecular mechanisms leading to Alzheimer's disease and which potential interventions are known to interfere with these mechanisms, focusing on nutritional approaches and physical activity but also the beneficial effects of cognition-oriented treatments with a focus on language and communication. Interestingly, recent findings also suggest a causal link between oral conditions, such as periodontitis or edentulism, and Alzheimer's disease, raising the question of whether dental intervention in Alzheimer's patients can be beneficial as well. Unfortunately, all previous single-domain interventions have been shown to have limited benefit to patients. However, the latest studies indicate that combining these efforts into multidomain approaches may have increased preventive or therapeutic potential. Therefore, as another emphasis in this review, we provide an overview of current literature dealing with studies combining the above-mentioned approaches and discuss potential advantages compared to monotherapies. Considering current literature and intervention options, we also propose a multidomain interdisciplinary approach for the treatment of Alzheimer's disease patients that synergistically links the individual approaches. In conclusion, this review highlights the need to combine different approaches in an interdisciplinary manner, to address the future challenges of Alzheimer's disease.

Anti-Oxidative, Anti-Inflammatory and Anti-Apoptotic Effects of Flavonols: Targeting Nrf2, NF-κB and p53 Pathways in Neurodegeneration

Neurodegenerative diseases are one of the leading causes of disability and death worldwide. Intracellular transduction pathways that end in the activation of specific transcription factors are highly implicated in the onset and progression of pathological changes related to neurodegeneration, of which those related to oxidative stress (OS) and neuroinflammation are particularly important. Here, we provide a brief overview of the key concepts related to OS- and neuroinflammation-mediated neuropathological changes in neurodegeneration, together with the role of transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB). This review is focused on the transcription factor p53 that coordinates the cellular response to diverse genotoxic stimuli, determining neuronal death or survival. As current pharmacological options in the treatment of neurodegenerative disease are only symptomatic, many research efforts are aimed at uncovering efficient disease-modifying agents. Natural polyphenolic compounds demonstrate powerful anti-oxidative, anti-inflammatory and anti-apoptotic effects, partially acting as modulators of signaling pathways. Herein, we review the current understanding of the therapeutic potential and limitations of flavonols in neuroprotection, with emphasis on their anti-oxidative, anti-inflammatory and anti-apoptotic effects along the Nrf2, NF-κB and p53 pathways. A better understanding of cellular and molecular mechanisms of their action may pave the way toward new treatments.

Intake of Products Containing Anthocyanins, Flavanols, and Flavanones, and Cognitive Function: A Narrative Review

The purpose of this review is to examine human research studies published within the past 6 years which evaluate the role of anthocyanin, flavanol, and flavanone consumption in cognitive function, and to discuss potential mechanisms of action underlying any observed benefits. Evidence to date suggests the consumption of flavonoid-rich foods, such as berries and cocoa, may have the potential to limit, or even reverse, age-related declines in cognition. Over the last 6 years, the flavonoid subgroups of anthocyanins, flavanols, and flavanones have been shown to be beneficial in terms of conferring neuroprotection. The mechanisms by which flavonoids positively modulate cognitive function are yet to be fully elucidated. Postulated mechanisms include both direct actions such as receptor activation, neurotrophin release and intracellular signaling pathway modulation, and indirect actions such as enhancement of cerebral blood flow. Further intervention studies conducted in diverse populations with sufficient sample sizes and long durations are required to examine the effect of consumption of flavonoid groups on clinically relevant cognitive outcomes. As populations continue to focus on adopting healthy aging strategies, dietary interventions with flavonoids remains a promising avenue for future research. However, many questions are still to be answered, including identifying appropriate dosage, timeframes for intake, as well as the best form of flavonoids, before definitive conclusions can be drawn about the extent to which their consumption can protect the aging brain.

Isorhamnetin Promotes Estrogen Biosynthesis and Proliferation in Porcine Granulosa Cells via the PI3K/Akt Signaling Pathway

Isorhamnetin is a natural flavonoid widely distributed in fruits and vegetables. However, the roles of isorhamnetin involved in steroidogenesis, proliferation, and apoptosis in ovarian granulosa cells (GCs) are poorly understood. We found that isorhamnetin promoted the secretion of estrogen and inhibited the secretion of progesterone and testosterone by modulating steroidogenesis-associated proteins and mRNA such as CYP19A1, StAR, and 3β-HSD in ovarian GCs. Mechanistically, isorhamnetin stimulated the expression of the proliferating cell nuclear antigen and C-myc and promoted the proliferation of GCs via the PI3K/Akt signaling pathway. Furthermore, isorhamnetin increased the protein expression of CyclinB, CyclinD, CyclinE, and CyclinA, thereby raising the ratio of S-phase cells in response to GC proliferation. Changes in the expression of apoptosis-associated proteins (Bcl2, Bax, and cytochrome c) and intracellular reactive oxygen species levels showed that isorhamnetin inhibited GC apoptosis. Collectively, these findings indicate that isorhamnetin regulates steroidogenesis through the activation of PI3K/Akt, which promotes proliferation, inhibits apoptosis, and alleviates oxidative stress.

An Up-to-Date Review on Citrus Flavonoids: Chemistry and Benefits in Health and Diseases

Flavonoids, the main class of polyphenols, are characterized by the presence of 2-phenyl-benzo-pyrane nucleus. They are found in rich quantities in citrus fruits. Citrus flavonoids are classified into flavanones, flavones, flavonols, polymethoxyflavones and anthocyanins (found only in blood oranges). Flavanones are the most abundant flavonoids in citrus fruits. In many situations, there are structure-function relationships. Due to their especial structures and presence of many hydroxyls, polymethoxies and glycoside moiety, the flavonoids have an array of multiple biological and pharmacological activities. This article provides an updated overview of the differences in chemical structures of the classes and members of citrus flavonoids and their benefits in health and diseases. The review article also sheds light on the mechanisms of actions of citrus flavonoids in the treatment of different diseases, including arthritis, diabetes mellitus, cancer and neurodegenerative disorders as well as liver, kidney and heart diseases. The accumulated and updated knowledge in this review may provide useful information and ideas in the discovery of new strategies for the use of citrus flavonoids in the protection, prevention and therapy of diseases.

Effects of carbonized process on quality control, chemical composition and pharmacology of Typhae Pollen: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Carbonized Typhae Pollen (CTP), a processed product of Typhae Pollen after stir-fried, is a well-known Traditional Chinese Medicine (TCM) with functions of removing blood stasis and hemostasis.

AIM OF REVIEW

The aim of this study is to summarize and discuss up-to-date information on quality control of CTP, and effects of carbonized process on phytochemistry and biological activities. We hope this review could provide feasible insights for further studies of CTP on its material basis and pharmacological effect mechanism.

MATERIAL AND METHODS

The information of TP before and after carbonized process was collected from online databases (PubMed, CNKI, Google Scholar, Baidu Xueshu, Web of Science, SpringerLink, Wiley Online Library, SciFinder and Chemical book). Meanwhile local books, published and unpublished Ph.D., MSc. dissertations were also taken into consideration.

RESULTS

A total of 27 Ph.D., MSc. dissertations and 208 articles were collected from online database, from which 122 compounds of TP were collected, but only two researches focused on the chemical compositions of CTP. Introductions of new technologies and intelligent processing equipment developments are considered as two main solutions to the quality control of CTP. CTP is a well-known ethnic medicine in China with a fantastic efficacy in curing bleeding caused by blood stasis. Flavonoids were reported as the main active compounds for removing blood stasis while the enhanced hemostatic activity were consistent with flavonoid aglycones. Modern pharmacological researches showed that CTP has wound healing activity, effects on blood vessels, antithrombotic activity, hemostatic activity, antioxidant activity and immunomodulatory activity.

CONCLUSIONS

Although CTP has been widely used in clinic, there are some problems blocking its further development. Unknown mechanism and uncertain active compounds might be the main reasons for few rules on controlling the quality of CTP. It is necessary to investigate the mechanisms and the relationship between carbonized process and the changes in constituents as well as pharmacological effects. This is essential to promote the safe clinical use of CTP.

Flavonoids as an Intervention for Alzheimer's Disease: Progress and Hurdles Towards Defining a Mechanism of Action

Attempts to develop a disease modifying intervention for Alzheimer's disease (AD) through targeting amyloid β (Aβ) have so far been unsuccessful. There is, therefore, a need for novel therapeutics against alternative targets coupled with approaches which may be suitable for early and sustained use likely required for AD prevention. Numerous in vitro and in vivo studies have shown that flavonoids can act within processes and pathways relevant to AD, such as Aβ and tau pathology, increases in BDNF, inflammation, oxidative stress and neurogenesis. However, the therapeutic development of flavonoids has been hindered by an ongoing lack of clear mechanistic data that fully takes into consideration metabolism and bioavailability of flavonoids in vivo. With a focus on studies that incorporate these considerations into their experimental design, this review will evaluate the evidence for developing specific flavonoids as therapeutics for AD. Given the current lack of success of anti-Aβ targeting therapeutics, particular attention will be given to flavonoid-mediated regulation of tau phosphorylation and aggregation, where there is a comparable lack of study. Reflecting on this evidence, the obstacles that prevent therapeutic development of flavonoids will be examined. Finally, the significance of recent advances in flavonoid metabolomics, modifications and influence of the microbiome on the therapeutic capacity of flavonoids in AD are explored. By highlighting the potential of flavonoids to target multiple aspects of AD pathology, as well as considering the hurdles, this review aims to promote the efficient and effective identification of flavonoid-based approaches that have potential as therapeutic interventions for AD.

Citrus flavonoids and their antioxidant evaluation

The antioxidant ability is the link and bridge connecting a variety of biological activities. Citrus flavonoids play an essential role in regulating oxidative stress and are an important source of daily intake of antioxidant supplements. Many studies have shown that citrus flavonoids promote health through antioxidation. In this review, the biosynthesis, composition and distribution of citrus flavonoids were concluded. The detection methods of antioxidant capacity of citrus flavonoids were divided into four categories: chemical, cellular, animal and clinical antioxidant capacity evaluation systems. The modeling methods, applicable scenarios, and their relative merits were compared based on these four systems. The antioxidant functions of citrus flavonoids under different evaluation systems were also discussed, especially the regulation of the Nrf2-antioxidases pathway. Some shortcomings in the current research were pointed out, and some suggestions for progress were put forward.

Exploring the multimodal role of phytochemicals in the modulation of cellular signaling pathways to combat age-related neurodegeneration

Neurodegeneration is the progressive loss of neuronal structures and functions that lead to copious disorders like Alzheimer's (AD), Parkinson's (PD), Huntington's (HD), amyotrophic lateral sclerosis (ALS), and other less recurring diseases. Aging is the prime culprit for most neurodegenerative events. Moreover, the shared pathogenic factors of many neurodegenerative processes are inflammatory responses and oxidative stress (OS). Unfortunately, it is very complicated to treat neurodegeneration and there is no effective remedy. The rapid progression of the neurodegenerative diseases that exacerbate the burden and the concurrent absence of effective treatment strategies force the researchers to investigate more therapeutic approaches that ultimately target the causative factors of the neurodegeneration. Phytochemicals have great potential to exert their neuroprotective effects by targeting various mechanisms, such as OS, neuroinflammation, abnormal protein aggregation, neurotrophic factor deficiency, disruption in mitochondrial function, and apoptosis. Therefore, this review represents the molecular mechanisms of neuroprotection by multifunctional phytochemicals to combat age-linked neurodegenerative disorders.

Antithrombotic activity of flavonoids and polyphenols rich plant species

Cardiovascular diseases represent one of the most notable health problems of the modern civilization. Stroke and heart attack often lead to lethal outcome; essential problem underneath being thrombus formation. Prophylactic approaches include acetylsalicylic acid and clopidogrel therapy on the level of primary hemostasis, i.e., primary clot formation. In the last five years, in the USA, health care expenses related to cardiovascular diseases have increased 50 %, to over 350 billion dollars. Thus, application of plant species and medicinal plants rich in polyphenols in prevention of thrombus formation are of interest. This is supported by the fact that the number of publications on antiaggregatory effect of polyphenols has doubled in the last decade. In this review we focus on antiaggregatory effect of most abundant polyphenols - flavonoids, the effect of plant extracts rich in polyphenols (propolis, species Salvia sp., Calamintha nepeta L., Lavandula angustifolia Mill., Melissa officinalis L, Mentha x piperita L., Ocimum basilicum L., Origanum vulgare L., Rosmarinus officinalis L.) on platelet aggregation, association of chemical composition and antioxidant properties with the observed biological effect, and possible clinical significance of the published results.

Cortico-hippocampal memory enhancing activity of hesperetin on scopolamine-induced amnesia in mice: role of antioxidant defense system, cholinergic neurotransmission and expression of BDNF

Alzheimer disease (AD) is an age related neurodegenerative disease causing severe cognitive and memory decline in elderly people. Flavonoids play neuroprotective role by inhibiting and/or modifying the self-assembly of the amyloid-β (Aβ) or tau peptide into oligomers and fibrils. This study sought to investigate the effect of hesperetin (HPT) on scopolamine-induced memory impairments in mice. Mice were orally pretreated with HPT (1, 5 or 50 mg/kg) or vehicle (normal saline; 10 ml/kg) for 3 consecutive days. One hour post-treatment on day 3, scopolamine (3 mg/kg, i.p.) was administered 5 min before locomotor activity (open field test) and memory function (novel object recognition test (NORT) for 2 consecutive days and Morris water maze task (MWM) for 5 consecutive days). Levels of oxidative stress markers / brain derived neurotrophic factors (BDNF) and acetylcholinesterase activity were determined in the hippocampus and prefrontal cortex after completion of MWM task. Scopolamine caused no significant change in mice exploration of the familiar or novel object in the test session whereas the HPT-treated mice spent more time exploring the novel object more than familiar object in NORT. Scopolamine also increased the escape latency in acquisition phase and decreases time spent in target quadrant in probe phase which were ameliorated by the pretreatment with HPT. Scopolamine-induced alteration of oxidant-antioxidant balance, acetylcholinesterase activity and neurogenesis in the hippocampus and prefrontal cortex were attenuated by HPT treatment. This study showed that HPT ameliorated non-spatial/spatial learning and memory impairment by scopolamine possibly through enhancement of antioxidant defense, cholinergic and BDNF signaling.

Impediment of selenite-induced cataract in rats by combinatorial drug laden liposomal preparation

Cataract is the leading cause of blindness globally with surgery being the only form of treatment. But cataract surgery is accompanied by complications, chiefly intra-ocular infections. Hence, preventive nanoformulations may be extremely beneficial. In the present study, novel chitosan-coated liposomal formulations encapsulating a combination of drugs, lanosterol and hesperetin were prepared and characterized. The combinatorial liposomes were prepared by thin film evaporation active extrusion method. The characterization of liposomes was done by transmission electron microscopy, zeta potential, encapsulation efficiency, stability, cytotoxicity and in vitro release studies. The main difference between the chitosan-coated and uncoated combinatorial liposomes is the release of drugs as indicated by the in vitro release studies. The slow and sustained release of the drugs from chitosan-coated ones as against the burst release from uncoated indicates an increased retention time for combinatorial drugs in cornea. This leads to a delay in progression of cataract as seen from in vivo studies. Cytotoxicity studies indicate no cell toxicity of the coating of chitosan or the combination of drugs. Stability studies indicate that there were almost no changes in size, zeta potential and polydispersity index values of the combinatorial liposomes upon storage at room temperature for 60 days. Another important study is the estimation of antioxidant defense system. The estimated values of glutathione reductase, malondialdehyde and chief antioxidant enzymes point toward an upregulation of antioxidant defense system. From the results, it may be concluded that novel chitosan-coated combinatorial liposomes are effective in delaying or preventing of cataract.

Neuroprotection of multifunctional phytochemicals as novel therapeutic strategy for neurodegenerative disorders: antiapoptotic and antiamyloidogenic activities by modulation of cellular signal pathways

In neurodegenerative disorders, including Alzheimer's and Parkinson's disease, neuroprotection by diet and natural bioactive compounds has been proposed to prevent the onset and progress of neurodegeneration by modification of pathogenic factors. Plant food-derived phytochemicals protect neurons via targeting oxidative stress, mitochondrial dysfunction, neurotrophic factor deficit, apoptosis and abnormal protein accumulation. This review presents the molecular mechanism of neuroprotection by phytochemicals: direct regulation of mitochondrial apoptotic machinery, modification of cellular signal pathways, induction of antiapoptotic Bcl-2 protein family and prosurvival neurotrophic factors, such as brain- and glial cell line-derived neurotrophic factor, and prevention of protein aggregation. Multitargeted neuroprotective agents are under development based on the structure of blood–brain barrier-permeable phytochemicals to ameliorate brain dysfunction and prevent neurodegeneration.

PEP‑1‑glutaredoxin 1 protects against hippocampal neuronal cell damage from oxidative stress via regulation of MAPK and apoptotic signaling pathways

Oxidative stress is known to be a primary risk factor for neuronal diseases. Glutaredoxin (GLRX)‑1, a redox‑regulator of the thioredoxin superfamily, is known to exhibit an important role in cell survival via various cellular functions. However, the precise roles of GLRX1 in brain ischemia are still not fully understood. The present study investigated whether transduced PEP‑1‑GLRX1 protein has protective effects against oxidative stress in cells and in an animal model. Transduced PEP‑1‑GLRX1 protein increased HT‑22 cell viability under oxidative stress and this fusion protein significantly reduced intracellular reactive oxygen species and levels of DNA damage. In addition, PEP‑1‑GLRX1 protein regulated RAC‑a serine/threonine‑protein kinase and mitogen‑activated protein kinase signaling, in addition to apoptotic signaling including B cell lymphoma (Bcl)‑2, Bcl‑2 associated X, apoptosis regulator, pro‑caspase‑9 and p53 expression levels. In an ischemic animal model, it was verified that PEP‑1‑GLRX1 transduced into the Cornu Ammonis 1 region of the animal brain, where it markedly protected against ischemic injury. These results indicate that PEP‑1‑GLRX1 attenuates neuronal cell death resulting from oxidative stress in vitro and in vivo. Therefore, PEP‑1‑GLRX1 may exhibit a beneficial role in the treatment of neuronal disorders, including ischemic injury.

Effects of pulsed electric field on intracellular antioxidant activity and antioxidant enzyme regulating capacities of pine nut (Pinus koraiensis) peptide QDHCH in HepG2 cells

Effects of pulse electric field (PEF) on antioxidant activity of pine nut (Pinus koraiensis) peptide were discussed using H₂O₂-induced HepG2 cells and changes of peptide structures were measured by MIR, NMR and CD spectra. Using HPLC-MS/MS, a novel peptide was identified as QDHCH. After PEF treatment the DPPH and ABTS radical inhibition, and CAA values of QDHCH were increased to 85.13%±0.17%, 95.45%±0.12%, and 4670.10μmol of quercetin equivalents/100g. The PEF-treated QDHCH has better protective oxidative stress inhibitory of 74.22±3.70%, and the T-SOD, CAT, GSH-Px and GSH-Rx activities in cells were significantly increased by 91.92, 7.98, 18.5 and 18.79U/mg prot, while the MDA content was decreased to 8.45±0.71U/mg prot compared with H₂O₂ damaged group. In addition, the hydroxyl radical scavenging activity of QDHCH was increased by 10.53%; the basic structure was not changed by PEF, while the influenced secondary structures may induce the antioxidant activity improvement in HepG2 cells.

Synthesis and antioxidant evaluation of desmethylxanthohumol analogs and their dimers

Four ring-closed analogs of natural prenylated chalcone desmethylxanthohumol (1) and their dimers were synthesized from the commercially available 1-(2,4,6-trihydroxyphenyl)ethan-1-one in five and six linear steps, respectively. The structures of the eight new derivatives were confirmed using¹H NMR, ¹³C NMR and HRMS. The antioxidant activity of the new chalcone derivatives were evaluated in a PC12 cell model of H₂O₂-induced oxidative damage. The SAR studies suggested that the catechol motif was essential for the antioxidant activity. Moreover, the dimers showed better antioxidant activity than their corresponding monomers did. Among them, compound 14d was the most potent and increased PC12 cell viability from 25% to 85%. Flow cytometric analysis showed that compound 14d, the most potent compound, decreased the apoptotic PC12 cell percentage and significantly reduced the LDH release and 8-OHdG generation but increased the GSH levels in H₂O₂-treated PC12 cells. Furthermore, compound 14d had a higher FRAP value than that of gallic acid. It also reduced the stable ABTS⁺ free radical with a lower EC₅₀ than that of gallic acid.

Protective Effects of Costunolide against Hydrogen Peroxide-Induced Injury in PC12 Cells

Oxidative stress-mediated cellular injury has been considered as a major cause of neurodegenerative diseases including Alzheimer’s and Parkinson’s diseases. The scavenging of reactive oxygen species (ROS) mediated by antioxidants may be a potential strategy for retarding the diseases’ progression. Costunolide (CS) is a well-known sesquiterpene lactone, used as a popular herbal remedy, which possesses anti-inflammatory and antioxidant activity. This study aimed to investigate the protective role of CS against the cytotoxicity induced by hydrogen peroxide (H₂O₂) and to elucidate potential protective mechanisms in PC12 cells. The results showed that the treatment of PC12 cells with CS prior to H₂O₂ exposure effectively increased the cell viability. Furthermore, it decreased the intracellular ROS, stabilized the mitochondria membrane potential (MMP), and reduced apoptosis-related protein such as caspase 3. In addition, CS treatment attenuated the cell injury by H₂O₂ through the inhibition of phosphorylation of p38 and the extracellular signal-regulated kinase (ERK). These results demonstrated that CS is promising as a potential therapeutic candidate for neurodegenerative diseases resulting from oxidative damage and further research on this topic should be encouraged.

Neurodegenerative diseases: From available treatments to prospective herbal therapy

Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and many others represent a relevant health problem with age worldwide. Efforts have been made in recent years to discover the mechanism of neurodegenerative diseases and prospective therapy that can help to slow down the effects of the aging and prevent these diseases. Since pathogenesis of these diseases involves multiple factors therefore the important task for neuroscientists is to identify such multiple factors and prevent age-associated neurodegenerative diseases. For these neurodegenerative diseases yet we have only palliative therapies and none of them significantly capable to slow down or halt the underlying pathology. Polyphenolic compounds such as flavonoids present in vegetables and fruits are believed to have anti-aging properties and reduce the risk of neurodegenerative diseases. Despite their abundance, investigations into the benefits of these polyphenolic compounds in human health have only recently begun. Preclinical and clinical studies have demonstrated the potential beneficial effects of flavonoids in neurons. Although clinical trials on the effectiveness of dietary flavonoids to treat human diseases are limited but various animal models and cell culture studies have shown a great promise in developing these compounds as suitable therapeutic targets. In this review, we elaborate the neuroprotective properties of flavonoids especially their applications in prevention and intervention of different neurodegenerative diseases. Their multi-target properties may allow them to be potential dietary supplement in prevention and treatment of the age-associated neurodegenerative diseases.

Tualang Honey Attenuates Noise Stress-Induced Memory Deficits in Aged Rats

Ageing and stress exposure may lead to memory impairment while oxidative stress is thought to be one of the underlying mechanisms involved. This study aimed to investigate the potential protective effects of Tualang honey supplementation on memory performance in aged rats exposed to noise stress. Tualang honey supplementation was given orally, 200 mg/kg body weight for 28 days. Rats in the stress group were subjected to loud noise, 100 dB(A), 4 hours daily for 14 days. All rats were subjected to novel object recognition test for evaluation of memory performance. It was observed that the rats subjected to noise stress exhibited significantly lower memory performance and higher oxidative stress as evident by elevated malondialdehyde and protein carbonyl levels and reduction of antioxidant enzymes activities compared to the nonstressed rats. Tualang honey supplementation was able to improve memory performance, decrease oxidative stress levels, increase brain-derived neurotrophic factor (BDNF) concentration, decrease acetylcholinesterase activity, and enhance neuronal proliferation in the medial prefrontal cortex (mPFC) and hippocampus. In conclusion, Tualang honey protects against memory decline due to stress exposure and/or ageing via enhancement of mPFC and hippocampal morphology possibly secondary to reduction in brain oxidative stress and/or upregulation of BDNF concentration and cholinergic system.

Citrus fruits as a treasure trove of active natural metabolites that potentially provide benefits for human health

Citrus fruits, which are cultivated worldwide, have been recognized as some of the most high-consumption fruits in terms of energy, nutrients and health supplements. What is more, a number of these fruits have been used as traditional medicinal herbs to cure diseases in several Asian countries. Numerous studies have focused on Citrus secondary metabolites as well as bioactivities and have been intended to develop new chemotherapeutic or complementary medicine in recent decades. Citrus-derived secondary metabolites, including flavonoids, alkaloids, limonoids, coumarins, carotenoids, phenolic acids and essential oils, are of vital importance to human health due to their active properties. These characteristics include anti-oxidative, anti-inflammatory, anti-cancer, as well as cardiovascular protective effects, neuroprotective effects, etc. This review summarizes the global distribution and taxonomy, numerous secondary metabolites and bioactivities of Citrus fruits to provide a reference for further study. Flavonoids as characteristic bioactive metabolites in Citrus fruits are mainly introduced.

Neuroprotective effect of Citrus unshiu immature peel and nobiletin inhibiting hydrogen peroxide-induced oxidative stress in HT22 murine hippocampal neuronal cells

BACKGROUND

Oxidative stress-induced cell damage is common in the etiology of several neurobiological disorders, including Alzheimer's disease and Parkinson's disease. In a case study, nobiletin-rich Citrus reticulata peels could prevent the progression of cognitive impairment in donepezil-preadministered Alzheimer's disease patients.

OBJECTIVE

In this study, we investigated the effects and underlying mechanism of nobiletin and Citrus unshiu immature peel (CUIP) water extract, which contains nobiletin as a major compound, on hydrogen peroxide-induced oxidative stress in HT22 cells, a murine hippocampal neuronal model.

MATERIALS AND METHODS

HT22 cells were treated with hydrogen peroxide in the presence or absence of various concentrations of CUIP and nobiletin. Cytotoxicity and apoptotic protein levels were measured by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and Western blotting.

RESULTS

Pretreatment with CUIP and nobiletin inhibited cell death due to hydrogen peroxide. Hydrogen peroxide-induced the expression of phospho-Jun N-terminal kinases (p-JNK) and p-p38 proteins in HT22 cells; however CUIP and nobiletin suppressed p-JNK and p-p38 without changing JNK or p38. Regarding apoptosis, caspase 3, B-cell lymphoma 2 (Bcl-2), and Bax protein expression was determined. CUIP and nobiletin suppressed caspase 3 and Bax expression, but they induced Bcl-2 expression in HT22 cells.

CONCLUSION

These results show that CUIP and nobiletin can protect against hydrogen peroxide-induced cell death in HT22 neurons via mitogen-activated protein kinases and apoptotic pathways.

Effects of hesperetin on platelet-derived growth factor-BB-induced pulmonary artery smooth muscle cell proliferation

Hesperetin is a natural flavonoid, which has been reported to exert various biological activities and positive health effects on mammalian cells. The present study aimed to investigate the effects of hesperetin on the proliferation of primary cultured rat pulmonary artery smooth muscle cells (PASMCs), and to elucidate the possible underlying molecular mechanisms. The results of the present study indicated that hesperetin was able to inhibit the proliferation and DNA synthesis of platelet‑derived growth factor‑BB (PDGF‑BB)‑induced PASMCs in a dose‑ and time‑dependent manner, without exerting cell cytotoxicity. In addition, hesperetin blocked the progression of the cell cycle from G0/G1 to S phase, which was correlated with the decreased mRNA expression levels of cyclin D1, cyclin E, cyclin‑dependent kinase (CDK)2 and CDK4, and the increased mRNA expression levels of p27. Furthermore, the anti‑proliferative effects of hesperetin were associated with suppression of the AKT/glycogen synthase kinase (GSK)3β and p38 signaling pathway, but were not associated with the extracellular signal‑regulated kinases 1/2 and c‑Jun N‑terminal kinases signaling pathways. These results suggested that hesperetin may inhibit PDGFa‑BB‑induced PASMC proliferation via the AKT/GSK3β signaling pathway, and that it may possess therapeutic potential for the treatment of pulmonary vascular remodeling diseases.

Flavonoid-based therapies in the early management of neurodegenerative diseases

During the past several years, there has been enormous progress in the understanding of the causative factors that initiate neuronal damage in various neurodegenerative diseases, including Alzheimer disease, Parkinson disease, multiple sclerosis, amyotrophic lateral sclerosis, and Huntington disease. Preventing neuronal damage and neuronal death will have a huge clinical benefit. However, despite major advances in causative factors that trigger these neurodegenerative diseases, to date there have been no therapies available that benefit patients who suffer from these diseases. Because most neurodegenerative diseases are late-onset and remain asymptomatic for most of the phases, the therapies initiated in advanced stages of the disease have limited value to patients. It may be possible to prevent or halt the disease progression to a great extent if therapies start at the initial stage of the disease. Such therapies may restore neuronal function by reducing or even eliminating the primary stressor. Flavonoids are key compounds for the development of a new generation of therapeutic agents that are clinically effective in treating neurodegenerative diseases. Regular consumption of flavonoids has been associated with a reduced risk of neurodegenerative diseases. In addition to their antioxidant properties, these polyphenolic compounds exhibit neuroprotective properties by their interaction with cellular signaling pathways followed by transcription and translation that mediate cell function under both normal and pathologic conditions. This review focuses on human intervention studies as well as animal studies on the role of various flavonoids in the prevention of neurodegenerative diseases.

Neuroprotective effects of macranthoin G from Eucommia ulmoides against hydrogen peroxide-induced apoptosis in PC12 cells via inhibiting NF-κB activation

Oxidative stress-mediated cellular injury has been considered as a major cause of neurodegenerative diseases including Alzheimer and Parkinson diseases. The scavenging of reactive oxygen species (ROS) mediated by antioxidants may be a potential strategy for retarding the disease's progression. Macranthoin G (MCG), isolated from Eucommia ulmoides, is a derivative from chlorogenic acid methyl ester and caffeic acid. This study is aimed to investigate the protective role of MCG against the cytotoxicity induced by hydrogen peroxide (H2O2) and to elucidate potential protective mechanisms in rat pheochromocytoma (PC12) cells. The results showed that the treatment of PC12 cells with MCG prior to H2O2 exposure effectively increased the cell viability, and stabilized the mitochondria membrane potential (MMP); furthermore, it enhanced the antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and the levels of intracellular glutathione (GSH); it also decreased the malondialdehyde (MDA) content, intracellular ROS, caspase-3 activation, as well as cell apoptosis. In addition, the MCG treatment minimized the cell injury by H2O2 via down-regulation of the NF-κB pathway as well as activation of phosphorylation of IκBα, p38, and the extracellular signal-regulated kinase (ERK). These results showed that that MCG is promising as a potential therapeutic agent for neurodegenerative diseases induced by oxidative damage and should be encouraged for further research.

Flavonoids in modulation of cell survival signalling pathways

Flavonoids, a family of polyphenols, generally found in various fruits and vegetables, as well as in many plant beverages such as tea, pomegranate juice, raspberry, blueberries, and red wine. Recently, studies on flavonoids have attracted scientific attention as a potential nutritional strategy to prevent a broad range of chronic disorders. Many studies suggest that consumption of these flavonoids in sufficient amount plays neuroprotective, cardioprotective, anti-inflammatory, and chemopreventive roles. While there has been a major focus on the antioxidant properties, there is an emerging view that flavonoids and their in vivo metabolites do not act only as conventional antioxidants but may also exert modulatory actions on cellular system through direct action on various signalling pathways. These pathways include phosphoinositide 3-kinase, Akt/protein kinase B, mitogen-activated protein kinase, tyrosine kinases, and protein kinase C. Various inhibitory or stimulatory actions of flavonoids on these pathways greatly affect cellular functions by altering the phosphorylation state of targeted molecules. In addition, flavonoids also modulate various gene expressions through activation of various transcription factors. Thus, the present review will bestow a breathing overview regarding the prime role of flavonoids in modulation of survival signalling pathways at cellular system.

Neuroprotective and anti-inflammatory effects of the flavonoid-enriched fraction AF4 in a mouse model of hypoxic-ischemic brain injury

We report here neuroprotective and anti-inflammatory effects of a flavonoid-enriched fraction isolated from the peel of Northern Spy apples (AF4) in a mouse of model of hypoxic-ischemic (HI) brain damage. Oral administration of AF4 (50 mg/kg, once daily for 3 days) prior to 50 min of HI completely prevented motor performance deficits assessed 14 days later that were associated with marked reductions in neuronal cell loss in the dorsal hippocampus and striatum. Pre-treatment with AF4 (5, 10, 25 or 50 mg/kg, p.o.; once daily for 3 days) produced a dose-dependent reduction in HI-induced hippocampal and striatal neuron cell loss, with 25 mg/kg being the lowest dose that achieved maximal neuroprotection. Comparison of the effects of 1, 3 or 7 doses of AF4 (25 mg/kg; p.o.) prior to HI revealed that at least 3 doses of AF4 were required before HI to reduce neuronal cell loss in both the dorsal hippocampus and striatum. Quantitative RT-PCR measurements revealed that the neuroprotective effects of AF4 (25 mg/kg; p.o.; once daily for 3 days) in the dorsal hippocampus were associated with a suppression of HI-induced increases in the expression of IL-1β, TNF-α and IL-6. AF4 pre-treatment enhanced mRNA levels for pro-survival proteins such as X-linked inhibitor of apoptosis and erythropoietin following HI in the dorsal hippocampus and striatum, respectively. Primary cultures of mouse cortical neurons incubated with AF4 (1 µg/ml), but not the same concentrations of either quercetin or quercetin-3-O-glucose or its metabolites, were resistant to cell death induced by oxygen glucose deprivation. These findings suggest that the inhibition of HI-induced brain injury produced by AF4 likely involves a transcriptional mechanism resulting from the co-operative actions of various phenolics in this fraction which not only reduce the expression of pro-inflammatory mediators but also enhance pro-survival gene signalling.

Ginsenoside Rb1 Prevents MPP(+)-Induced Apoptosis in PC12 Cells by Stimulating Estrogen Receptors with Consequent Activation of ERK1/2, Akt and Inhibition of SAPK/JNK, p38 MAPK

Ginsenoside Rb1 shows neuroprotective effects in various neurons, including dopaminergic cells. However, the precise mechanisms of action are uncertain. In this paper, we examine whether Rb1 has a neuroprotective effect on MPP(+)-induced apoptosis and attempt to clarify the signaling pathway in PC12 cells. Apoptosis of PC12 cells was determined by DNA fragmentation assay, the activation of caspase-3, or by the inactivation of Bcl-xL. Rb1 inhibited MPP(+)-induced caspase-3 activation and DNA fragmentation and activated Bcl-xL in MPP(+)-treated PC12 cells. These antiapoptotic effect was abrogated in PC12 cells transfected with estrogen receptor siRNA. Levels of DNA fragmentation were increased by wortmannin or PD 98059, while they were decreased by SB 203580 or SP 600125 in MPP(+)-treated PC12 cells. Rb1 increased phosphorylation levels of ERK1/2 or Akt in MPP(+)-treated PC12 cells, while it reduced phosphorylated p38 or SAPK/JNK. The increased phosphorylation of ERK/1/2 or Akt by Rb1 was abrogated by estrogen receptor siRNA. Rb1-induced inhibition of SAPK/JNK or p38 phosphorylation was also abolished by estrogen receptor siRNA. These results suggest that ginsenoside Rb1 protects PC12 cells from caspase-3-dependent apoptosis through stimulation of estrogen receptor with consequent activation of ERK1/2 and Akt and inhibition of SAPK/JNK and p38.

Pollen Typhae total flavone improves insulin-induced glucose uptake through the β-arrestin-2-mediated signaling in C2C12 myotubes

Defects in insulin-stimulated glucose uptake in skeletal muscle result from the dysfunction of insulin signaling including the phosphatidylinositol-3 kinase (PI3K) pathway and a novel β-arrestin-2-mediated signaling, which leads to insulin resistance (IR). Pollen Typhae, a Chinese herb, has been used for thousands of years in traditional Chinese medicine, and has the potential to inhibit the development of IR. We have previously reported that Pollen Typhae total flavone (PTF), the extract from Pollen Typhae, ameliorates high-glucose- and high-insulin-induced impairment of glucose uptake in 3T3-L1 adipocytes, but the mechanisms remain unclear. The objective of this study was to investigate the effects of PTF on glucose uptake, and to explore the underlying mechanisms in C2C12 myotubes. PTF improved insulin-stimulated glucose uptake in a dose- and time-dependent manner in C2C12 myotubes, and prevented palmitate-induced IR. Furthermore, PTF enhanced the basal gene expression of Src and Akt2, elevated the protein expression of β-arrestin-2, Src and Akt, increased the phosphorylation of insulin receptor-β at Tyr1150/1151 and Akt at Thr308/Ser473 in an insulin-dependent manner, but had no effects on the protein expression of PI3K-p85 or the activity of PI3K. Inhibition of Src but not PI3K restrained PTF-induced phosphorylation of Akt and glucose uptake. Our findings indicate that PTF improves insulin-induced glucose uptake via the β-arrestin-2-mediated signaling in C2C12 myotubes.

Anti-aging effects of hesperidin on Saccharomyces cerevisiae via inhibition of reactive oxygen species and UTH1 gene expression

This study used a replicative lifespan assay of K6001 yeast to screen anti-aging food factors in commercial flavonoids. Hesperidin derived from the Citrus genus extended the lifespan of yeast at doses of 5 and 10 µM as compared with the control group (p<0.01, p<0.01). Reactive oxygen species (ROS), real-time PCR (RT-PCR), and lifespan assays of uth1 and skn7 mutants with the K6001 background were used to study the anti-aging mechanisms in yeast. The results indicate that hesperidin significantly inhibits the ROS of yeast, and UTH1 gene expression, and that SKN7 gene are involved in hesperidin-mediated lifespan extension. Further, increases in the Sir2 homolog, SIRT1 activity, and SOD gene expression were confirmed at doses of 5 (p<0.01) and 10 µM (p<0.05). This suggests that Sir2, UTH1 genes, and ROS inhibition after administration of hesperidin have important roles in the anti-aging effects of yeast. However, the aglycon hesperetin did not exhibit anti-aging effects in yeast.

Neuroprotective effects of citrus flavonoids

Recent attention has been given to the influence of dietary factors on health and mental well-being. Oxidative stress is associated with many diseases including neurodegenerative disorders. Dietary flavonoids exert cardioprotective, chemopreventive, and neuroprotective effects. The biological activities of flavonoids have been attributed to their antioxidant, anti-inflammatory, and signaling properties. A clear understanding of the mechanisms of action, as either antioxidants or signaling molecules, is crucial for the application of flavonoids as interventions in neurodegeneration and as brain foods. Citrus flavonoids exert little adverse effect and have low or no cytotoxicity to healthy, normal cells. The main citrus flavonoids can also traverse the blood-brain barrier; hence, they are promising candidates for intervention in neurodegeneration and as constituents in brain foods. In this review, we discuss the bioactivity, multiple neuroprotection mechanisms, and antioxidant and signaling properties of citrus flavonoids. Receptor-mediated neuroprotective actions and parallel signaling pathways are also explored. Finally, the induction of cellular defense proteins against oxidative stress and neurotoxicity by hesperetin, a main and widespread citrus flavonoid, are also discussed. It is suggested that citrus fruits, which are rich in abundant sources of hesperetin and other flavonoids, are promising for the development of general food-based neuroprotection and brain foods.

Effect of hesperetin against oxidative stress via ER- and TrkA-mediated actions in PC12 cells

Hesperetin is known to activate estrogen receptors (ERs). Estrogen-mediated neuroprotection could be via both ER and tyrosine kinase receptor (Trk) signaling. This study tested whether hesperetin protected PC12 cells from hydrogen peroxide induced oxidative damage via ER- and/or TrkA-mediated actions. Hesperetin (0.1, 1, and 50 μM) inhibited cell viability decreases and reactive oxygen species, intracellular calcium level, and caspase-3 activity increases in H(2)O(2)-induced PC12 cells. Such actions were significantly (p < 0.05) suppressed by ICI 182,780 (an ER antagonist) or K252a (a TrkA antagonist) at low concentrations (0.1 or 1 μM) only. Hesperetin also stimulated the activation of Akt, ERK, and CREB as well as induced brain-derived neurotrophic factor, PPARγ coactivator 1α (PGC-1α), and seladin-1 (selective Alzheimer's disease indicator-1) via both ER and TrkA in the cells. This study demonstrates that the neuroprotective effects of hesperetin, at low concentrations, are attributed to its stimulation on receptor signaling. Moreover, ER and TrkA are known to be expressed in most Alzheimer's disease (AD) vulnerable brain regions. This study thus suggests that hesperetin might have potential for intervention in neurodegenerative disorders, particularly for AD.