Health effects of quercetin: from antioxidant to nutraceutical

Quercetin, a member of the flavonoids family, is one of the most prominent dietary antioxidants. It is ubiquitously present in foods including vegetables, fruit, tea and wine as well as countless food supplements and is claimed to exert beneficial health effects. This includes protection against various diseases such as osteoporosis, certain forms of cancer, pulmonary and cardiovascular diseases but also against aging. Especially the ability of quercetin to scavenge highly reactive species such as peroxynitrite and the hydroxyl radical is suggested to be involved in these possible beneficial health effects. Consequently, numerous studies have been performed to gather scientific evidence for these beneficial health claims as well as data regarding the exact mechanism of action and possible toxicological aspects of this flavonoid. The purpose of this review is to evaluate these studies in order to elucidate the possible health-beneficial effects of the antioxidant quercetin. Firstly, the definitions as well as the most important aspects regarding free radicals, antioxidants and oxidative stress will be discussed as background information. Subsequently, the mechanism by which quercetin may operate as an antioxidant (tested in vitro) as well as the potential use of this antioxidant as a nutraceutical (tested both ex vivo and in vivo) will be discussed.     

Protection by tetrahydroxystilbene glucoside against neurotoxicity induced by MPP+: the involvement of PI3K/Akt pathway activation

Recent studies indicate that there is interaction between the glutamatergic neurotransmitters system and lead neurotoxicity. Previously, we have demonstrated the potential effects of glutamate in lead-induced cell death in PC12 cells and the protective role of the novel thiol antioxidant, N-acetylcysteine amide (NACA). The current study (1) investigated the potential effects of glutamate on lead exposed CD-1 mice, (2) evaluated the protective effects of NACA against glutamate and lead toxicity in CD-1 mice, and (3) compared the results with N-aceytylcysteine (a well-known thiol antioxidant). Oxidative stress parameters, including glutathione (GSH), oxidized glutathione (GSSG), GSH/GSSG, and malondialdehyde (MDA) levels, were evaluated. Blood and tissue lead levels, glutamate/glutamine (Glu/Gln) ratios, GS activity, and phospholipase-A₂ (PLA₂) were also analyzed. Results indicated that lead and glutamate decreased GSH levels in the red blood cells, brains, livers, and kidneys. Exposure to glutamate and lead elevated the MDA levels and PLA₂ activity. NACA and N-acetylcysteine (NAC) provided protection against the detrimental effects of lead by decreasing the blood and tissue lead levels, restoring intracellular GSH levels, and decreasing the MDA levels. NACA and NAC also increased the GS activity thereby decreasing Glu/Gln levels. However, NACA appeared to have better chelating and antioxidant properties than NAC, due to its higher liphophilicity and its ability to cross the blood-brain barrier.     

PI3K/AKT信号通路在心房颤动中的研究进展

心房颤动（房颤）作为最常见的快速性心律失常,目前主要的治疗手段为抗凝、控制心室率、维持窦性心律。然而房颤的发生机制尚未阐明,上述治疗仍具有一定的局限性。磷脂酰肌醇3-激酶（PI3K）/蛋白激酶（AKT）信号转导通路是参与房颤发生发展的重要通路,其可以通过介导心房纤维化、炎症反应、氧化应激、神经内分泌功能调节参与房颤发生发展的病理生理过程。深入研究PI3K/AKT信号转导通路在房颤中的作用,可为房颤的预防、治疗及预后评估提供有价值的指导。     

PTEN mediates serum deprivation-induced cytotoxicity in H9c2 cells via the PI3K/AKT signaling pathway

The pathogenesis of acute myocardial infarction (AMI) is associated with cardiomyocyte necrosis and apoptosis. Numerous studies have determined the regulatory effects of Phosphatase and tensin homolog (PTEN) cell proliferation and apoptosis in other cell types. However, the potential role of PTEN in cardiomyocyte is unclear. In this study, we used H9c2 cells cultured under serum deprivation to simulate the apoptosis process of myocardial infarction. Small interference RNA (siRNA) of PTEN was used to knock down the expression of PTEN. Cell viability was determined by CCK-8. Cell proliferation was examined by Edu staining, and the protein expression was analyzed by Western blot. We also evaluated the generation of ROS, the degree of DNA damage, and cell apoptosis using immunofluorescence assay. As a result, we observed that serum deprivation in H9c2 cells increased PTEN expression. Functionally, the PTEN knockdown experiment using siRNA inhibited serum deprivation-induced cell apoptosis, ROS production, and DNA damage, whereas increased cell proliferation. All these effects could be reversed by phosphatidylinositol 3-kinase (PI3K) inhibitor, which indicated the PI3K/protein kinase B (AKT) might be the critical component of the PTEN effects during serum deficiency. In conclusion, our study indicated the role of the PTEN/PI3K/AKT pathway in serum deprivation-induced cytotoxicity in H9c2 cells.     

Kaempferol-induced GPER upregulation attenuates atherosclerosis via the PI3K/AKT/Nrf2 pathway

ContextThe effect of kaempferol, a regulator of oestrogen receptors, on atherosclerosis (AS) and the underlying mechanism is elusive.ObjectiveTo explore the effect and mechanism of kaempferol on AS.Methods and materialsIn vivo, C57BL/6 and apolipoprotein E (APOE)^–/– mice were randomly categorized into six groups (C57BL/6: control, ovariectomy (OVX), high-fat diet (HFD); APOE^–/–: OVX-HFD, OVX-HFD + kaempferol (50 mg/kg) and OVX-HFD + kaempferol (100 mg/kg) and administered with kaempferol for 16 weeks, intragastrically. Oil-Red and haematoxylin–eosin (HE) staining were employed to examine the effect of kaempferol. In vitro, human aortic endothelial cells (HAECs) were pre-treated with or without kaempferol (5, 10 or 20 μM), followed by administration with kaempferol and oxidized low-density lipoprotein (ox-LDL) (200 μg/mL). The effect of kaempferol was evaluated using flow cytometry, and TdT-mediated dUTP Nick-End Labelling (TUNEL).ResultsIn vivo, kaempferol (50 and 100 mg/kg) normalized the morphology of blood vessels and lipid levels and suppressed inflammation and apoptosis. It also activated the G protein-coupled oestrogen receptor (GPER) and PI3K/AKT/nuclear factor-erythroid 2-related factor 2 (Nrf2) pathways. In vitro, ox-LDL (200 μg/mL) reduced the cell viability to 50% (IC₅₀). Kaempferol (5, 10 or 20 μM) induced-GPER activation increased cell viability to nearly 10%, 19.8%, 30%, and the decreased cellular reactive oxygen species (ROS) generation (16.7%, 25.6%, 31.1%), respectively, consequently attenuating postmenopausal AS. However, the protective effects of kaempferol were blocked through co-treatment with si-GPER.ConclusionsThe beneficial effects of kaempferol against postmenopausal AS are associated with the PI3K/AKT/Nrf2 pathways, mediated by the activation of GPER.     

Crocetin attenuates the oxidative stress,inflammation and apoptosis in arsenic trioxide-induced nephrotoxic rats: Implication of PI3K/AKT pathway

Arsenic trioxide (ATO)-induced renal toxicity through oxidative stress and apoptosis restricts the therapeutic action of acute myelogenous leukemia. Crocetin (Crt) possesses antioxidant and antiapoptosis properties, and has certain renal protective effects, but it has not been reported that it has protective effect on renal injury caused by ATO. The current study explored the effects and mechanisms of Crt on kidney damage induced by ATO. Fifty Sprague-Dawley rats were randomly divided into five groups. Adult rats were given Crt concurrently with ATO for 1 week. On the 8th day, rats were killed and blood and kidney tissues were collected. Histopathological changes were measured, and kidney tissues and serum were used to determine renal function and antioxidant enzyme activity. In addition, the protein expression levels of P-PI3K, PI3K, P-AKT, AKT, CytC, Bax, Bcl-2 and Caspase-3 were determined via western blot analysis. Results revealed ATO induced renal morphological alterations and activated serum BUN and CRE. Compared with the control group, ROS, MDA, IL-1β, TNF-α, protein carbonyls (PC), lipid hydroperoxides (LOOH) and arsenic concentration levels were found to be significantly increased and SOD, CAT, GSH-Px, GSH and total sulphydryl groups (TSH) levels were attenuated in the ATO group. Crt markedly reduced oxidative stress in ATO-induced nephrotoxicity. Further, ATO induced apoptosis by significantly enhancing CytC, Bax and Caspase-3 and inhibiting Bcl-2. Administration with Crt markedly improved the expression of apoptosis factor. Moreover, Crt treatment stimulated the expressions of P-PI3K, PI3K, P-AKT, AKT induced by ATO. This study indicates Crt could prevent renal injury caused by ATO through inhibiting oxidative stress, inflammation and apoptosis, and its mechanism may be related to activation of PI3K/Akt signaling pathway.     

Exploiting the PI3K/AKT pathway for cancer drug discovery

Evolving studies with several different targeted therapeutic agents are demonstrating that patients with genomic alterations of the target, including amplification, translocation and mutation, are more likely to respond to the therapy. Recent studies indicate that numerous components of the phosphatidylinositol-3-kinase (PI3K)/AKT pathway are targeted by amplification, mutation and translocation more frequently than any other pathway in cancer patients, with resultant activation of the pathway. This warrants exploiting the PI3K/AKT pathway for cancer drug discovery.     

槲皮素的降压作用及其机制研究

槲皮素是一种天然多酚黄酮类化合物,富含于苹果、洋葱、浆果等食物中,与心血管疾病负相关。最近动物和人类试验均表明,槲皮可以降低高血压个体的血压,机制可能涉及抗氧化应激、抑制血管紧张素转化酶(ACE)活性,以内皮依赖性和非依赖性方式改善血管内皮功能等。本综述将系统阐述槲皮素的降压作用及其相关机制。     

Role of PI3K/AKT/mTOR signaling pathway in DBP-induced apoptosis of testicular sertoli cells in vitro

Dibutyl phthalate (DBP) has significant male reproductive toxicity, and the Sertoli cells are the target cells of DBP. This study was to investigate the injury effect induced by DBP on rat testicular Sertoli cells in vitro. MTT results showed that DBP can significantly reduce the survival rate of Sertoli cells; Hoechst staining results showed that the Sertoli cells treated with DBP emerged with typical morphological characteristics of apoptosis, nuclear condensation and chromatin condensation; flow cytometry results showed that DBP significantly increased the apoptotic rate of Sertoli cells, and dose-dependent; Western blotting showed that the expression of PTEN protein in Sertoli cells was significantly higher than that in the control group after treated with different concentrations of DBP for 24 h, while the expression of p-PI3K1, p-AKT, p70S6K and 4E-BP1 protein in the PI3K/AKT/mTOR signal pathway were significantly decreased. It is speculated that PTEN/PI3K/AKT/mTOR signaling pathway plays an important role in DBP-induced apoptosis of testicular Sertoli cells in rats.     

PI3K/AKT信号通路在银屑病发病机制中的研究进展

银屑病是一种免疫介导的多因素炎症性皮肤病,以表皮角质形成细胞异常增殖、毛细血管扩张、中性粒细胞浸润为主要病理表现。磷脂酰肌醇3-激酶（phosphatidylinositol 3-kinase,PI3K）/蛋白激酶B（protein kinase B,AKT）信号通路在表皮细胞增殖、细胞自噬、血管生成、脂质代谢等过程中...     

Toxic response of nickel nanoparticles in human lung epithelial A549 cells

Nickel nanoparticle (Ni NP) is increasingly used in modern industries such as catalysts, sensors and electronic applications. Due to wide-spread industrial applications the inhalation is the primary source of exposure to Ni NPs. However, data demonstrating the effect of Ni NPs on the pulmonary system remain scarce. The present study was designed to examine the toxic effect of human lung epithelial A549 cells treated with well characterized Ni NPs at the concentrations of 0, 1, 2, 5, 10 and 25 μg/ml for 24 and 48 h. Mitochondrial function (MTT assay), membrane leakage of lactate dehydrogenase (LDH assay), reduced glutathione (GSH), reactive oxygen species (ROS), membrane lipid peroxidation (LPO) and caspase-3 activity were assessed as toxicity end points. Results showed that Ni NPs reduced mitochondrial function and induced the leakage of LDH in dose and time-dependent manner. Ni NPs were also found to induce oxidative stress in dose and time-dependent manner indicated by depletion of GSH and induction of ROS and LPO. Further, activity of caspase-3 enzyme, marker of apoptosis was significantly higher in treated cells with time and Ni NPs dosage. The results exhibited significant toxicity of Ni NPs in human lung epithelial A549 cells which is likely to be mediated through oxidative stress. This study warrants more careful assessment of Ni NPs before their industrial applications.     

白杨素通过PI3K/AKT信号通路抑制LPS诱导的软骨细胞自噬

Aim To explore the effect of chrysin on chondrocyte autophagy in rat chondrocyte osteoarthritis model induced by lipopolysaccharide and its mechanism. Methods Normal articular cartilage cells of 10 SPF SD rats were isolated and cultured in vitro, and the autophagy of rat chondrocytes was induced by LPS. The experiment was divided into blank control group, LPS group, chrysin (CHR) group and LPS + CHR group, the activity of cells in each group was detected by CCK-8 method, the mitochondrial membrane potential of cells in each group was detected by Rhodaminel23, and the protein expression of PI3K, AKT, p-PI3K, p-AKT, Beclin-1 and LC3 II in cells of each group was detected by reactive oxygen species, Western blot method of DCFH-DA. Results Chrysin could inhibit the autophagy induced by LPS, especially when the concentration of chrysin was 10 mmol · L^-1. Chrysin could inhibit the increase of reactive oxygen species (ROS) induced by LPS induced by LPS, inhibit the decrease of mitochondrial membrane potential after injury, and inhibit the expression of Beclin-1 and LC3 II protein and the phosphorylation of PI3K and AKT. Conclusions Chrysin may inhibit autophagy by inhibiting PI3K/AKT signaling pathway and down-regulating the expression of autophagy proteins Beclin-1 and LC3 II, thus protecting chondrocytes. © 2021 Publication Centre of Anhui Medical University. All rights reserved.     

Targeting PI3K/AKT/mTOR pathway in non small cell lung cancer

While PI3K/AKT/mTOR pathway is altered in a variety of cancers including non small cell lung cancer, abnormalities in this pathway are more common in squamous cell lung carcinoma than in adenocarcinoma of the lung. Moreover, aberrant activation of PI3K/AKT/mTOR pathway is one of the mechanisms of acquired resistance to EGFR-TK inhibitors in patients with adenocarcinoma carrying EGFR activating mutations.     

The PTEN/PI3K/AKT signalling pathway in cancer, therapeutic implications

PTEN/PI3K/AKT constitutes an important pathway regulating the signaling of multiple biological processes such as apoptosis, metabolism, cell proliferation and cell growth. PTEN is a dual protein/lipid phosphatase which main substrate is the phosphatidyl-inositol,3,4,5 triphosphate (PIP3), the product of PI3K. Increase in PIP3 recruits AKT to the membrane where it is activated by other kinases also dependent on PIP3. Many components of this pathway have been described as causal forces in cancer. PTEN activity is lost by mutations, deletions or promoter methylation silencing at high frequency in many primary and metastatic human cancers. Germ line mutations of PTEN are found in several familial cancer predisposition syndromes. Activating mutations which have been reported for PI3K and AKT, in tumours are able to confer tumourigenic properties in several cellular systems. Additionally, the binding of PI3K to oncogenic ras is essential for the transforming properties of ras. In summary, the data strongly support the view of the PTEN/PI3K/AKT pathway as an important target for drug discovery.     

基于FOXO3a介导的PI3K/AKT信号通路研究大补元煎改善卵巢储备功能作用及机制

目的 探讨大补元煎含药血清经FOXO3a介导的磷脂酰肌醇激酶(PI3K)/蛋白激酶B(AKT)信号通路对卵巢储备功能减退改善的作用及机制.方法 取36只健康SD大鼠随机分为空白组(6只)、模型组(6只)、大补元煎高剂量组(6只)、大补元煎中剂量组(6只)、大补元煎低剂量组(6只)和西药组(6只),均注射环磷酰胺75 m...     

Isoindolone derivative QSN-IOc induces leukemic cell apoptosis and suppresses angiogenesis via PI3K/AKT signaling pathway inhibition

Aim： 2-（4,6-Dimethoxy-l,3-dioxoisoindolin-2-yl） ethyl 2-chloroacetate （QSN-IOc） is one of isoindolone derivatives with antiproliferative activity against human umbilical vein endothelial cells （HUVECs）. The aim of this study was to investigate its antitumor activity in vitro and anti-angiogenic effects in vitro and in vivo. Methods： K562 leukemic cells and HUVECs were used for in vitro studies. Cell viability was examined using MTT assay. Cell apoptosis and mitochondrial transmembrane potential （Δψm） were detected with flow cytometry. Tube formation and migration of HUVECs were studied using two-dimensional Matrigel assay and wound-healing migration assay, respectively. VEGF levels were analyzed with RT-PCR and Western blotting. A zebrafish embryo model was used for in vivo anti-angiogenic studies. The molecular mechanisms for apoptosis in K562 cells and antiangiogenesis were measured with Western blotting. Results： In antitumor activity studies, QSN-IOc suppressed the viability of K562 cells and induced apoptosis in dose- and time- dependent manners. Furthermore, QSN-IOc dose-dependently decreased the Δψm in K562 cells, increased the release of cytochrome c and the level of Bax, and decreased the level of Bcl-2, suggesting that QSN-10c-induced apoptosis of K562 cells was mediated via the mitochondrial apoptotic pathway. In anti-angiogenic activity studies, QSN-IOc suppressed the viability of HUVECs and induced apoptosis in dose dependent manners. QSN-IOc treatment did not alter the Δψm in HUVECs, but dose-dependently inhibited the expression of VEGF, inhibited the tube formation and cell migration in vitro, and significantly suppressed the number of ISVs in zebrafish embryos in vivo. Furthermore, QSN-IOc dose-dependently suppressed the phosphorylation of AKT and GSK313 in both HUVECs and K562 cells. Conclusion： QSN-IOc is a novel antitumor compound that exerts both antitumor and anti-angiogenic effects via inhibiting the PI3K/ AKT/GSK313 signaling pathway.     

Acute inhalation toxicity of cerium oxide nanoparticles in rats

The aim of the present study was to assess the acute toxic potential of cerium oxide nanoparticles (CeO₂ NPs) in rats when exposed through the head and nose inhalation route. The rats were exposed to CeO₂ NPs and the resultant effects if any, to cause cytotoxicity, oxidative stress and inflammation in the lungs were evaluated on a 24 h, 48 h and 14 day post exposure period. Our results showed a significant decrease in the cell viability, with the increase of lactate dehydogenase, total protein and alkaline phosphatase levels in the bronchoalveolar lavage fluid (BALF) of the exposed rats. Total leukocyte count and the percentage of neutrophils in BALF were elevated within 24 h of post exposure. The concentrations of pro-inflammatory cytokines (IL-1β, TNF-α, and IL-6) were significantly increased in the BALF and in the blood throughout the observation period. The level of malondialdehyde was elevated with the decreased levels of intracellular reduced glutathione (GSH) in the lung after exposure. The alveolar macrophages (AMs) and neutrophils overloaded with phagocytosed CeO₂ NPs were observed along with non-phagocytosed free CeO₂ NPs that were deposited over the epithelial surfaces of the bronchi, bronchiole and alveolar regions of lungs within 24 h of post exposure and were consistent throughout the observation period. A well distributed, multifocal pulmonary microgranulomas due to impairment of clearance mechanism leading to biopersistence of CeO₂ NPs for an extended period of time were observed at the end of the 14 day post exposure period. These results suggest that acute exposure of CeO₂ NPs through inhalation route may induce cytotoxicity via oxidative stress and may lead to a chronic inflammatory response.     

PI3K/AKT/mTOR信号通路参与自身免疫性

自身免疫性疾病（autoimmune disease,AD）是机体因自身抗原免疫耐受障碍而对自身抗原产生免疫反应,从而引起机体组织损伤的一类疾病。近年研究发现,磷脂酰肌醇-3-激酶/蛋白激酶B/雷帕霉素靶蛋白（phosphatidylin ositol 3-kinase/protein kinase B/mechanistic target ofrapamycin kinase,PI3K/AKT/mTOR）信号通路与AD发病密切相关,其主要参与免疫细胞增殖分化、炎性细胞因子分泌、自噬及氧化应激等过程。本文重点概述PI3K/AKT/mTOR信号通路参与AD发病机理的研究进展。     

PI3K/Akt通路在缺氧活化钙敏感受体介导的A549细胞转移中的作用

目的探讨PI3K/Akt信号通路在缺氧活化钙敏感受体(calcium sensing receptor,Ca SR)介导的A549及A549/DDP细胞转移中的作用。方法将处于对数生长期的A549及A549/DDP细胞随机分为对照组、缺氧组、缺氧+Gd Cl_3(Ca SR激动剂)组、缺氧+NPS2143(Ca SR抑制剂)组、缺氧+LY294002(PI3K通路抑制剂)+Gd Cl_3组。应用Western blot分析不同处理情况下,Ca SR、MMP-2及p-Akt蛋白在A549、A549/DDP细胞的表达水平;采用细胞划痕及Transwell小室方法,检测不同处理因素对细胞迁移和侵袭能力的影响;应用ELISA法,分析不同处理因素对A549及A549/DDP细胞分泌MMP-2蛋白的影响。结果与对照组比较,缺氧能够增强A549及A549/DDP细胞Ca SR的表达,增强细胞迁移能力,提高细胞及培养液中MMP-2蛋白表达水平、促进Akt蛋白的磷酸化,NPS2143能减弱缺氧的作用,Gd Cl_3放大缺氧的作用,而LY294002抑制缺氧和Gd Cl_3的上述作用。结论缺氧活化Ca SR促进A549及A549/DDP细胞转移,其机制可能涉及PI3K/Akt通路。