Quercetin Attenuates Brain Oxidative Alterations Induced by Iron Oxide Nanoparticles in Rats

A comprehensive and systematic review of the potential neuroprotective effect of quercetin in rat models of spinal cord injury

CONTEXT

Spinal cord injury (SCI) is a potentially fatal neurological disease with severe complications and a high disability rate. An increasing number of animal experimental studies support the therapeutic effect of quercetin, which is a natural anti-inflammatory and antioxidant bioflavonoid.

OBJECTIVE

This paper reviewed the therapeutic effect of quercetin on a rat SCI model and summarized the relevant mechanistic research.

DATA SOURCES

PubMed, EMBASE, Web of Science, Science Direct, WanFang Data, SinoMed databases, the China National Knowledge Infrastructure, and the Vip Journal Integration Platform were searched from their inception to April 2023 for animal experiments applying quercetin to treat SCI.

STUDY SELECTION

Based on the PICOS criteria, a total of 18 eligible studies were included, of which 14 were high quality.

RESULTS

In this study, there was a gradual increase in effect based on the Basso, Beattie, and Bresnahan (BBB) score after three days (p < 0.0001). Furthermore, gender differences also appeared in the efficacy of quercetin; males performed better than females (p = 0.008). Quercetin was also associated with improved inclined plane test score (p = 0.008). In terms of biochemical indicators, meta-analysis showed that MDA (p < 0.0001) and MPO (p = 0.0002) were significantly reduced after quercetin administration compared with the control group, and SOD levels were increased (p = 0.004). Mechanistically, quercetin facilitates the inhibition of oxidative stress, inflammation, autophagy and apoptosis that occur after SCI.

CONCLUSIONS

Generally, this systematic review suggests that quercetin has a neuroprotective effect on SCI.

Effectiveness of Flavonoid-Rich Diet in Alleviating Symptoms of Neurodegenerative Diseases

Over the past decades, there has been a significant increase in the burden of neurological diseases, including neurodegenerative disorders, on a global scale. This is linked to a widespread demographic trend in which developed societies are aging, leading to an increased proportion of elderly individuals and, concurrently, an increase in the number of those afflicted, posing one of the main public health challenges for the coming decades. The complex pathomechanisms of neurodegenerative diseases and resulting varied symptoms, which differ depending on the disease, environment, and lifestyle of the patients, make searching for therapies for this group of disorders a formidable challenge. Currently, most neurodegenerative diseases are considered incurable. An important aspect in the fight against and prevention of neurodegenerative diseases may be broadly understood lifestyle choices, and more specifically, what we will focus on in this review, a diet. One proposal that may help in the fight against the spread of neurodegenerative diseases is a diet rich in flavonoids. Flavonoids are compounds widely found in products considered healthy, such as fruits, vegetables, and herbs. Many studies indicated not only the neuroprotective effects of these compounds but also their ability to reverse changes occurring during the progression of diseases such as Alzheimer's, Parkinson's and amyotrophic lateral sclerosis. Here, we present the main groups of flavonoids, discussing their characteristics and mechanisms of action. The most widely described mechanisms point to neuroprotective functions due to strong antioxidant and anti-inflammatory effects, accompanied with their ability to penetrate the blood-brain barrier, as well as the ability to inhibit the formation of protein aggregates. The latter feature, together with promoting removal of the aggregates is especially important in neurodegenerative diseases. We discuss a therapeutic potential of selected flavonoids in the fight against neurodegenerative diseases, based on in vitro studies, and their impact when included in the diet of animals (laboratory research) and humans (population studies). Thus, this review summarizes flavonoids' actions and impacts on neurodegenerative diseases. Therapeutic use of these compounds in the future is potentially possible but depends on overcoming key challenges such as low bioavailability, determining the therapeutic dose, and defining what a flavonoid-rich diet is and determining its potential negative effects. This review also suggests further research directions to address these challenges.

Quercetin counteracts monosodium glutamate to mitigate immunosuppression in the thymus and spleen via redox-guided cellular signaling

BACKGROUND

Chronic inflammation brought on by oxidative stress can result in several immunopathologies. Natural compounds with antioxidant characteristics, like quercetin, have shown effectiveness in reducing oxidative damage and regulating the immune response.

PURPOSE

The commonly used food additive monosodium glutamate (M) causes immunosuppression by disrupting redox equilibrium and inducing oxidative stress. The goal of this work is to examine the therapeutic potential of quercetin against immunotoxicity brought on by M, revealing the molecular route implicated in such immunopathology by targeting the thymus and spleen, to support the development of future anti-inflammatory and antioxidant therapies.

STUDY DESIGN AND METHODS

M-fed rats were employed as an immunotoxicity model and were supplemented with quercetin for four weeks. Hematological and biochemical parameters were measured; H&E staining, immunohistochemistry, flow cytometry, real-time quantitative PCR, and western blotting were performed.

RESULTS

Based on the findings, TLR4 was activated by M to cause oxidative stress-mediated inflammation, which was alleviated by the supplementation of quercetin by modulating redox homeostasis to neutralize free radicals and suppress the inflammatory response. To prevent M-induced inflammation, quercetin demonstrated anti-inflammatory functions by blocking NF-kB activation, lowering the production of pro-inflammatory cytokines, and increasing the release of anti-inflammatory cytokines. By normalizing lipid profiles and lowering the potential risk of immunological deficiency caused by M, quercetin also improves lipid metabolism. Additionally, it has shown potential for modifying insulin levels, suggesting a possible function in controlling M-induced alteration in glucose metabolism. The addition of quercetin to M enhanced the immune response by improving immunoglobulin levels and CD4/CD8 expression in the thymus and spleen. Additionally, quercetin inhibited apoptosis by controlling mitochondrial caspase-mediated cellular signaling, suggesting that it may be able to halt cell death in M-fed rats.

CONCLUSION

The results of this study first indicate that quercetin, via modulating redox-guided cellular signaling, has a promising role in reducing immune disturbances. This study illuminates the potential of quercetin as a safe, natural remedy for immunopathology caused by M, including thymic hypoplasia and/or splenomegaly, and paves the way for future anti-inflammatory and antioxidant supplements.

Quercetin-loaded nanoemulsions prevent Scopolamine-induced neurotoxicity in male rats

Quercetin (QCT) is well-known as a neuroprotective agent due to its antioxidant capacities and reinstating mitochondrial functions. Scopolamine is commonly used as a model to induce Alzheimer's disease (AD-like) symptoms. The current study develops QCT-loaded nanoemulsion (QCT-NE) accompanied by evaluating its neuro-therapeutic effectiveness against SCO-induced neurotoxicity in male rats. The QCT-NE was prepared by the spontaneous emulsification technique and characterized by using particle size, zeta potential, drug loading, in vitro drug release behavior, and stability studies. In vivo studies were done on adult Wistar rats by applying the Morris water maze (MWM) test to study spatial memory and learning. The levels of lipid peroxidation and reduced glutathione were quantitatively determined to reveal the potential mechanism of SCO-induced oxidative stress. Finally, histological studies were performed using staining techniques. The QCT-NE particle size, zeta potential, polydispersity index (PDI), and DL were obtained at 172.4 ± 16.8 nm, -29 ± 0.26 mV, 0.3 ± 0.07, and 81.42 ± 9.14 %, respectively. The QCT and more effectively QCT-NE reduced the elevation of neurobehavioral abnormalities in the MWM test in SCO-exposed rats. The results of oxidative status showed that SCO significantly could increase the LPO and decrease the GSH levels in the rat's brain. However, QCT-NE treatment was more effective than free QCT to inhibit oxidative damage and was well correlated with histopathological findings. Taken together, QCT-NE, compared to QCT, was superior in ameliorating SCO-induced AD-like symptoms due to its better neuroprotective activity and can be considered a novel supplementary therapeutic agent in AD management.

Acetylated oligopeptide and N-acetylcysteine protect against iron overload-induced dentate gyrus hippocampal degeneration through upregulation of Nestin and Nrf2/HO-1 and downregulation of MMP-9/TIMP-1 and GFAP

Iron accumulation in the brain causes oxidative stress, blood-brain barrier (BBB) breakdown, and neurodegeneration. We examined the preventive effects of acetylated oligopeptides (AOP) from whey protein on iron-induced hippocampal damage compared to N-acetyl cysteine (NAC). This 5-week study used 40 male albino rats. At the start, all rats received 150 mg/kg/day of oral NAC for a week. The 40 animals were then randomly divided into four groups: Group I (control) received a normal diet; Group II (iron overload) received 60 mg/kg/day intraperitoneal iron dextran 5 days a week for 4 weeks; Group III (NAC group) received 150 mg/kg/day NAC and iron dextran; and Group IV (AOP group) received 150 mg/kg/day AOP and iron dextran. Enzyme-linked immunosorbent assay, spectrophotometry, and qRT-PCR were used to measure MMP-9, tissue inhibitor metalloproteinase-1 (TIMP-1), MDA, reduced glutathione (GSH) levels, and nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) gene expression. Histopathological and immunohistochemical detection of nestin, claudin, caspase, and GFAP was also done. MMP-9, TIMP-1, MDA, caspase, and GFAP rose in the iron overload group, while GSH, Nrf2, HO-1, nestin, and claudin decreased. The NAC and AOP administrations improved iron overload-induced biochemical and histological alterations. We found that AOP and NAC can protect the brain hippocampus from iron overload, improve BBB disruption, and provide neuroprotection with mostly no significant difference from healthy controls.

In diabetic male Wistar rats, quercetin-conjugated superparamagnetic iron oxide nanoparticles have an effect on the SIRT1/p66Shc-mediated pathway related to cognitive impairment

BACKGROUND

Quercetin (QC) possesses a variety of health-promoting effects in pure and in conjugation with nanoparticles. Since the mRNA-SIRT1/p66Shc pathway and microRNAs (miRNAs) are implicated in the oxidative process, we aimed to compare the effects of QC and QC-conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) on this pathway.

METHODS

Through the use of the chemical coprecipitation technique (CPT), SPIONs were synthesized, coated with dextran, and conjugated with quercetin. Adult male Wistar rats were given intraperitoneal injections of streptozotocin to look for signs of type 1 diabetes (T1D). The animals were randomized into five groups: the control group got deionized water (DI), free QC solution (25 mg/kg), SPIONs (25 mg/kg), and QCSPIONs (25 mg/kg), and all groups received repeat doses administered orally over 35 days. Real-time quantitative PCR was used to assess the levels of miR-34a, let-7a-p5, SIRT1, p66Shc, CASP3, and PARP1 expression in the hippocampus of diabetic rats.

RESULTS

In silico investigations identified p66Shc, CASP3, and PARP1 as targets of let-7a-5p and miR-34a as possible regulators of SIRT1 genes. The outcomes demonstrated that diabetes elevated miR-34a, p66Shc, CASP3, and PARP1 and downregulated let-7a-5p and SIRT1 expression. In contrast to the diabetic group, QCSPIONs boosted let-7a-5p expression levels and consequently lowered p66Shc, CASP3, and PARP1 expression levels. QCSPIONs also reduced miR-34a expression, which led to an upsurge in SIRT1 expression.

CONCLUSION

Our results suggest that QCSPIONs can regulate the SIRT1/p66Shc-mediated signaling pathway and can be considered a promising candidate for ameliorating the complications of diabetes.

Anti-amyloid potential of some phytochemicals against Aβ-peptide and α-synuclein, tau, prion, and Huntingtin protein

Some molecules self-assemble to create complex structures through molecular self-assembly. Hydrogel preparation, tissue repair, and therapeutic drug delivery are a few applications of molecular self-assembly. However, the self-assembly of amino acids, peptides, and proteins forms amyloid fibrils, resulting in various disorders, most notably neurodegenerative ailments. Examples include the self-assembly of phenylalanine, which causes phenylketonuria; Aβ, which causes Alzheimer's disease; the tau protein, which causes both Alzheimer's and Parkinson's diseases; and α-synuclein, which causes Parkinson's illness. This review provides information related to phytochemicals of great significance that can prevent the formation of, or destabilize, amino acid, peptide, and protein self-assemblies.

Daucosterol confers protection against T-2 toxin induced blood-brain barrier toxicity through the PGC-1α-mediated defensive response in vitro and in vivo

T-2 toxin is a common environmental pollutant and contaminant in food and animal feed that represents a great challenge to human and animal' health throughout the world. Using natural compounds to prevent the detrimental effects of T-2 toxin represents an attractive strategy. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a critical regulator in various cellular processes. Recently, PGC-1α activation has been reported to confer protection against neurological injuries. We aimed to identify a potent PGC-1α activator from plants as a chemopreventive compound and to demonstrate the efficacy of the compound in attenuating T-2 toxin-induced blood-brain barrier (BBB) toxicity. We identified daucosterol, which binds directly to the 71-74 (-1100 to -1000 bp) position of the second promoter of human PGC-1α by hydrogen bonding. An in vitro and in vivo T-2 toxin induced BBB injury model revealed that this compound can protect against this injury by increasing transepithelial/transendothelial electrical resistance, reducing sodium fluorescein (NaF) infiltration and increasing the expression of tight junction-related proteins (zonula occludens-1 (ZO-1), occludin (OCLN), claudin-5 (CLDN5)) expression. In conclusion, we identified daucosterol as representing a novel of PGC-1α activators and illustrated the mechanism of specific binding site. Furthermore, we have demonstrated the feasibility of using natural compounds targeting PGC-1α as a therapeutic approach to protect humans from environmental insults that may occur daily such as lipopolysaccharide.

A Comparative Analysis of Neuroprotective Properties of Taxifolin and Its Water-Soluble Form in Ischemia of Cerebral Cortical Cells of the Mouse

Cerebral ischemia, and, as a result, insult, attacks up to 15 million people yearly in the world. In this connection, the development of effective preventive programs and methods of therapy has become one of the most urgent problems in modern angiology and pharmacology. The cytoprotective action of taxifolin (TAX) in ischemia is well known, but its limitations are also known due to its poor solubility and low capacity to pass through the hematoencephalic barrier. Molecular mechanisms underlying the protective effect of TAX in complex systems such as the brain remain poorly understood. It is known that the main cell types of the brain are neurons, astrocytes, and microglia, which regulate the activity of each other through neuroglial interactions. In this work, a comparative study of cytoprotective mechanisms of the effect of TAX and its new water-soluble form aqua taxifolin (aqTAX) was performed on cultured brain cells under ischemia-like conditions (oxygen-glucose deprivation (OGD)) followed by the reoxygenation of the culture medium. The concentration dependences of the protective effects of both taxifolin forms were determined using fluorescence microscopy, PCR analysis, and vitality tests. It was found that TAX began to effectively inhibit necrosis and the late stages of apoptosis in the concentration range of 30-100 µg/mL, with aqTAX in the range of 10-30 µg/mL. At the level of gene expression, aqTAX affected a larger number of genes than TAX; enhanced the basic and OGD/R-induced expression of genes encoding ROS-scavenging proteins with a higher efficiency, as well as anti-inflammatory and antiapoptotic proteins; and lowered the level of excitatory glutamate receptors. As a result, aqTAX significantly inhibited the OGD-induced increase in the Ca²⁺ levels in the cytosol ([Ca²⁺]_i) in neurons and astrocytes under ischemic conditions. After a 40 min preincubation of cells with aqTAX under hypoxic conditions, these Ca²⁺ signals were completely inhibited, resulting in an almost complete suppression of necrotic death of cerebral cortical cells, which was not observed with the use of classical TAX.

Histological and biochemical evaluation of the effects of silver nanoparticles (AgNps) versus titanium dioxide nanoparticles (TiO2NPs) on rat parotid gland

The unlimited use of nanoparticles (NPs) results in toxic impacts on different tissues. The current study aimed to compare the adverse effects of AgNPs and TiO2NPs on the parotid gland of adult male albino rats as regards the histopathological, immunohistochemical, and biochemical changes, exploring the possible underlying mechanisms and the degree of improvement after cessation of administration. Fifty-four adult male albino rats were divided into control group (I), AgNPs-injected group (II), and TiO2NPs-injected group (III). We measured the levels of tumor necrosis factor-alpha (TNF-α) and interleukin (IL-6) in the serum, and levels of MDA and GSH in parotid tissue homogenate. Quantitative real-time polymerase-chain reaction (qRT-PCR) was used to measure the expression levels of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC1-α), nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4), mouse double minute 2 (MDM2), Caspase-3 Col1a1, and Occludin. Parotid tissue sections were examined by light microscope (Hematoxylin & Eosin and Mallory trichrome stains), electron microscope, and immunohistochemical examination of CD68 and anti-caspase-3 antibodies. Both NPs severely affected the acinar cells and damaged the tight junction between them by enhancing expression of the inflammatory cytokines, inducing oxidative stress, and disturbing the expression levels of the studied genes. They also stimulated fibrosis, acinar cell apoptosis, and inflammatory cells infiltration in parotid tissue. TiO2NPs effects were less severe than AgNPs. Cessation of exposure to both NPs, ameliorated the biochemical and structural findings with more improvement in TiO2NPs withdrawal. In conclusion: AgNPs and TiO2NPs adversely affected the parotid gland, but TiO2NPs were less toxic than AgNPs.

Salvianolic acid A alleviates atherosclerosis by inhibiting inflammation through Trc8-mediated 3-hydroxy-3-methylglutaryl-coenzyme A reductase degradation

BACKGROUND

Atherosclerosis is the most prevalent cardiovascular disease and remains the major contributor to death and mortality globally. Salvianolic acid A (SalA) is a water-soluble phenolic acid that benefits atherosclerosis. However, the mechanisms of SalA protecting against atherosclerosis remain unclear.

PURPOSE

We aimed to determine whether SalA prevents atherosclerosis by modulating 3-Hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) degradation via the ubiquitin-proteasomal pathway.

METHODS

The animal and cellular models of atherosclerosis were established by subjecting apolipoprotein E (ApoE) knockout mice to a high-fat diet (HFD) and exposing human umbilical vein endothelial cells (HUVECs) to oxidized low-density lipoprotein (ox-LDL), respectively.

RESULTS

Our results showed that similar to atorvastatin, SalA suppressed atherosclerotic plaque formation, improved serum lipid accumulation, and reduced cholesterol levels in HFD-fed ApoE^-/- mice. Moreover, SalA protected HUVECs from ox-LDL-caused cell viability reduction and lipid accumulation. The mechanism study revealed that SalA reduced the production of proinflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6, and augmented the generation of the anti-inflammatory cytokine IL-10 in ApoE^-/- mice and HUVECs, accompanied by increased HMGCR ubiquitination and degradation via translocation in renal carcinoma on chromosome 8 (Trc8), insulin-induced gene (Insig)1 and Insig2. Furthermore, the knockdown of Trc8 abolished the SalA-induced HMGCR degradation and anti-atherosclerosis activity.

CONCLUSION

SalA rescues atherosclerosis by inhibiting inflammation through the Trc8-regulated degradation of HMGCR. These findings underscore Trc8 as a potential target of atherosclerosis.

Natural Products and Neuroprotection 3.0

In recent years, we have been witnessing a dramatic rise in the incidence of neurodegenerative diseases, a phenomenon partly associated with the increase in life expectancy [...].

Neuroprotective Potentials of Flavonoids: Experimental Studies and Mechanisms of Action

Neurological and neurodegenerative diseases, particularly those related to aging, are on the rise, but drug therapies are rarely curative. Functional disorders and the organic degeneration of nervous tissue often have complex causes, in which phenomena of oxidative stress, inflammation and cytotoxicity are intertwined. For these reasons, the search for natural substances that can slow down or counteract these pathologies has increased rapidly over the last two decades. In this paper, studies on the neuroprotective effects of flavonoids (especially the two most widely used, hesperidin and quercetin) on animal models of depression, neurotoxicity, Alzheimer's disease (AD) and Parkinson's disease are reviewed. The literature on these topics amounts to a few hundred publications on in vitro and in vivo models (notably in rodents) and provides us with a very detailed picture of the action mechanisms and targets of these substances. These include the decrease in enzymes that produce reactive oxygen and ferroptosis, the inhibition of mono-amine oxidases, the stimulation of the Nrf2/ARE system, the induction of brain-derived neurotrophic factor production and, in the case of AD, the prevention of amyloid-beta aggregation. The inhibition of neuroinflammatory processes has been documented as a decrease in cytokine formation (mainly TNF-alpha and IL-1beta) by microglia and astrocytes, by modulating a number of regulatory proteins such as Nf-kB and NLRP3/inflammasome. Although clinical trials on humans are still scarce, preclinical studies allow us to consider hesperidin, quercetin, and other flavonoids as very interesting and safe dietary molecules to be further investigated as complementary treatments in order to prevent neurodegenerative diseases or to moderate their deleterious effects.

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.

Assessment of the potential toxic effect of magnetite nanoparticles on the male reproductive system based on immunological and molecular studies

Magnetite nanoparticles (MNPs) are the most conventional type of iron oxide nanoparticles used in the food industrial processes, removal of heavy metals, and biomedical applications in vivo or in vitro. Until now, there is no sufficient information that can confirm its effect on the body's immune system and reproductive health in males. The purpose of this research is to estimate the immunotoxic and reproductive toxic effects of MNPs in male rats. This study included 36 adult male albino rats divided into three groups. The experimental groups were intraperitoneally injected with MNPs at doses of 5 and 10 mg/kg body weight 3 times/week for 60 days, while the control group was injected with saline solution. MNPs caused a significant decrease in the body weight change of the high-treated group. MNPs produced changes in the lymphocyte proliferation rate which referred to a significant immunotoxic effect measured by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-di-phenyltetrazolium bromide reduction method. The testicular tissue of male-treated rats showed some moderate and severe degenerative changes. The sperm parameters of count, motility, and viability were significantly decreased. Sperm morphological abnormalities were detected in all treated animals. MNPs produced a significant decrease in testosterone levels, increased the level of malondialdehyde, impaired the activity of the antioxidant enzymes and induced testicular DNA damage. In conclusion, MNPs affected the normal immune state in male rats and facilitated the generation of reactive oxygen species subsequently triggering testicular oxidative stress damages. All these consequences had a negative impact on male reproductive health.

Cancer metabolism control by natural products: Pyruvate kinase M2 targeting therapeutics

Glycolysis is the primary source of energy for cancer growth and metastasis. The shift in metabolism from mitochondrial oxidative phosphorylation to aerobic glycolysis is called the Warburg effect. Cancer progression due to aerobic glycolysis is often associated with the activation of oncogenes or the loss of tumor suppressors. Therefore, inhibition of glycolysis is one of the effective strategies in cancer control. Pyruvate kinase M2 (PKM2) is a key glycolytic enzyme overexpressed in breast, prostate, lung, colorectal, and liver cancers. Here, we discuss published studies regarding PKM2 inhibitors from natural products that are promising drug candidates for cancer therapy. We have highlighted the potential of natural PKM2 inhibitors for various cancer types. Moreover, we encourage researchers to evaluate the combinational effects between natural and synthetic PKM2 inhibitors. Also, further high-quality studies are needed to firmly establish the clinical efficacy of natural products.

Palliative Effect of Resveratrol against Nanosized Iron Oxide-Induced Oxidative Stress and Steroidogenesis-Related Genes Dysregulation in Testicular Tissue of Adult Male Rats

The nano-sized iron oxide (Fe₂O₃-NPs) is one of the most used engineered nanomaterials worldwide. This study investigated the efficacy of natural polyphenol resveratrol (RSV) (20 mg/kg b.wt, orally once daily) to alleviate the impaired sperm quality and testicular injury resulting from Fe₂O₃-NPs exposure (3.5 or 7 mg/kg b.wt, intraperitoneally once a week) for eight weeks. Spermiograms, sexual hormonal levels, oxidative stress indicators, and lipid peroxidation biomarker were assessed. Moreover, the steroidogenesis-related genes mRNA expressions were evaluated. The results showed that RSV substantially rescued Fe₂O₃-NPs-mediated sperm defects. Additionally, the Fe₂O₃-NPs-induced depressing effects on sperm motility and viability were markedly counteracted by RSV. Moreover, RSV significantly restored Fe₂O₃-NPs-induced depletion of testosterone, follicle-stimulated hormone, luteinizing hormone, and testicular antioxidant enzymes but reduced malondialdehyde content. Furthermore, the Fe₂O₃-NPs-induced downregulation of steroidogenesis-related genes (3 β-HSD, 17 β-HSD, and Nr5A1) was significantly counteracted in the testicular tissue of RSV-treated rats. These findings concluded that RSV could limit the Fe₂O₃-NPs-induced reduced sperm quality and testicular injury most likely via their antioxidant activity and steroidogenesis-related gene expression modulation.

Effects of Flavonoid Supplementation on Nanomaterial-Induced Toxicity: A Meta-Analysis of Preclinical Animal Studies

Background

Nanomaterials, widely applied in various fields, are reported to have toxic effects on human beings; thus, preventive or therapeutic measures are urgently needed. Given the anti-inflammatory and antioxidant activities, supplementation with flavonoids that are abundant in the human diet has been suggested as a potential strategy to protect against nanomaterial-induced toxicities. However, the beneficial effects of flavonoids remain inconclusive. In the present study, we performed a meta-analysis to comprehensively explore the roles and mechanisms of flavonoids for animals intoxicated with nanomaterials.

Methods

A systematic literature search in PubMed, EMBASE, and Cochrane Library databases was performed up to April 2022. STATA 15.0 software was used for meta-analyses.

Results

A total of 26 studies were identified. The results showed that flavonoid supplementation could significantly increase the levels of antioxidative enzymes (superoxide dismutase, catalase, glutathione, glutathione peroxidase, and glutathione-S-transferase), reduce the production of oxidative agents (malonaldehyde) and pro-inflammatory mediators (tumor necrosis factor-α, interleukin-6, IL-1β, C-reactive protein, immunoglobulin G, nitric oxide, vascular endothelial growth factor, and myeloperoxidase), and alleviate cell apoptosis (manifested by decreases in the mRNA expression levels of pro-apoptotic factors, such as caspase-3, Fas cell surface death receptor, and Bax, and increases in the mRNA expression levels of Bcl2), DNA damage (reductions in tail length and tail DNA%), and nanomaterial-induced injuries of the liver (reduced alanine aminotransferase and aspartate aminotransferase activities), kidney (reduced urea, blood urea nitrogen, creatinine, and uric acid concentration), testis (increased testosterone, sperm motility, 17β-hydroxysteroid dehydrogenase type, and reduced sperm abnormalities), and brain (enhanced acetylcholinesterase activities). Most of the results were not changed by subgroup analyses.

Conclusion

Our findings suggest that appropriate supplementation of flavonoids may be effective to prevent the occupational detriments resulting from nanomaterial exposure.

Olfactory Stimulation with Volatile Aroma Compounds of Basil (Ocimum basilicum L.) Essential Oil and Linalool Ameliorates White Fat Accumulation and Dyslipidemia in Chronically Stressed Rats

We explored the physiological effects of inhaling basil essential oil (BEO) and/or linalool and identified odor-active aroma compounds in BEO using gas chromatography/mass spectrometry (GC-MS) and GC-olfactometry (GC-O). Linalool was identified as the major volatile compound in BEO. Three groups of rats were administered BEO and linalool via inhalation, while rats in the control group were not. Inhalation of BEO for 20 min only reduced the total weight gain (190.67 ± 2.52 g) and increased the forced swimming time (47.33 ± 14.84 s) compared with the control group (219.67 ± 2.08 g, 8.33 ± 5.13 s). Inhalation of BEO for 5 min (392 ± 21 beats/min) only reduced the pulse compared with the control group (420 ± 19 beats/min). Inhalation of linalool only reduced the weight of white adipose tissue (5.75 ± 0.61 g). The levels of stress-related hormones were not significantly different among the groups. The total cholesterol and triglyceride levels decreased after inhalation of BEO for 20 min (by more than -10% and -15%, respectively). Low-density lipoprotein cholesterol levels were lowered (by more than -10%) by the inhalation of BEO and linalool, regardless of the inhalation time. In particular, BEO inhalation for 20 min was associated with the lowest level of low-density lipoprotein cholesterol (53.94 ± 2.72 mg/dL). High-density lipoprotein cholesterol levels increased after inhalation of BEO (by more than +15%). The atherogenic index and cardiac risk factors were suppressed by BEO inhalation. Animals exposed to BEO and linalool had no significant differences in hepatotoxicity. These data suggest that the inhalation of BEO and linalool may ameliorate cardiovascular and lipid dysfunctions. These effects should be explored further for clinical applications.

Biological Effect of Quercetin in Repairing Brain Damage and Cerebral Changes in Rats: Molecular Docking and In Vivo Studies

This study examined the protective effect of quercetin against high-altitude-induced brain damage in rats. A molecular docking study was performed to investigate the potential effect of quercetin in reducing brain damages through its ability to target the oxidative stress enzymes. Biomarker assessment screening assays were also performed then followed by in vivo studies. Three groups of rats were divided into the control group, an untreated animal model group with induced brain damage, and finally, the quercetin treated group that received quercetin dose equal to 20 mg/kg of their body weights. Molecular docking studies and biomarker assessment screening assays proved the potential effect of quercetin to affect the level of representative biomarkers glutathione (GSH), glutathione reductase (GR), glutathione-S-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA). Additionally, the protective effect of quercetin against high altitude, low pressure, and low oxygen was also investigated by exploring the brain histopathology of experimental rats. Brain damage was observed in the untreated animal model group. After treatment with quercetin, the cerebral edema in the brain tissues was improved significantly, confirming the protective effects of quercetin. Therefore, quercetin can be used as a natural food additive to protect from the highaltitude-induced brain damage.

Quercetin attenuates neurotoxicity induced by iron oxide nanoparticles

Iron oxide nanoparticles (IONPs) have been proposed as targeted carriers to deliver therapeutic molecules in the central nervous system (CNS). However, IONPs may damage neural tissue via free iron accumulation, protein aggregation, and oxidative stress. Neuroprotective effects of quercetin (QC) have been proven due to its antioxidant and anti-inflammatory properties. However, poor solubility and low bioavailability of QC have also led researchers to make various QC-involved nanoparticles to overcome these limitations. We wondered how high doses or prolonged treatment with quercetin conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) could improve cognitive dysfunction and promote neurogenesis without any toxicity. It can be explained that the QC inhibits protein aggregation and acts against iron overload via iron-chelating activity, iron homeostasis genes regulation, radical scavenging, and attenuation of Fenton/Haber-Weiss reaction. In this review, first, we present brain iron homeostasis, molecular mechanisms of iron overload that induced neurotoxicity, and the role of iron in dementia-associated diseases. Then by providing evidence of IONPs neurotoxicity, we discuss how QC neutralizes IONPs neurotoxicity, and finally, we make a brief comparison between QC and conventional iron chelators. In this review, we highlight that QC as supplementation and especially in conjugated form reduces iron oxide nanoparticles neurotoxicity in clinical application.