Protective Potential of Adiponectin and Quercetin on Alleviating Bisphenol-A-Induced Toxicity in Muscle Cells Through the KEAP1/NRF2 Pathway

Background: Bisphenol A (BPA) is a toxic environmental estrogenic compound which exerts its detrimental effects by increasing oxidative stress and decreasing levels of antioxidants. This study aimed to evaluate beneficial effect of adiponectin and quercetin in reducing BPA-induced oxidative stress by assessing the Prooxidant-antioxidant balance (PAB) assay, catalase activity and KEAP1/NRF2 expression in muscle cells.Methods and Results: L6 rat muscle cells were exposed to BPA (50 an100 μM) with and without treatment with different concentrations of adiponectin (10 and 100 ng/ml) and quercetin (10 and 25 ng/ml) for 24 and 48 hours. Cell viability was assessed using MTT assay, and the PAB was evaluated with the ELISA at 540 nm. Catalase level was also evaluated in all groups. Furtheremore, the expression of KEAP1/Nrf2 genes was assessed using qRT-PCR. The results showed a significant reduction in L6 cells survival after being treated with 100 μM BPA. Adiponectin and quercetin treatment also increased cell survival compared to BPA-treated cells. It was also found that PAB increased with BPA exposure, and quercetin treatment significantly reduced it compared to BPA treatment. The catalase activity was reduced in BPA-treated cells, which was significantly increased by treatment with adiponectin and quercetin. A significant decrease in Nrf2 gene expression was observed in BPA-treated cells compared to the control group. It was further found that cell treatment with quercetin and adiponectin significantly increased the expression of Nrf2 gene compared to the control group.Conclusions: Taking together, our results implied that adiponectin and quercetin could modulate BPA-induced oxidative stress in muscle cells through KEAP1/Nrf2 pathway. Accordingly, it can be concluded that adiponectin in low dose and quercetin, may have significant impact in reducing toxicity due to BPA.

Regulatory Effects of Quercetin on M1/M2 Macrophage Polarization and Oxidative/Antioxidative Balance

Macrophage polarization plays essential and diverse roles in most diseases, such as atherosclerosis, adipose tissue inflammation, and insulin resistance. Homeostasis dysfunction in M1/M2 macrophage polarization causes pathological conditions and inflammation. Neuroinflammation is characterized by microglial activation and the concomitant production of pro-inflammatory cytokines, leading to numerous neurodegenerative diseases and psychiatric disorders. Decreased neuroinflammation can be obtained by using natural compounds, including flavonoids, which are known to ameliorate inflammatory responses. Among flavonoids, quercetin possesses multiple pharmacological applications and regulates several biological activities. In the present study, we found that quercetin effectively inhibited the expression of lipocalin-2 in both macrophages and microglial cells stimulated by lipopolysaccharides (LPS). The production of nitric oxide (NO) and expression levels of the pro-inflammatory cytokines, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, were also attenuated by quercetin treatment. Our results also showed that quercetin significantly reduced the expression levels of the M1 markers, such as interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β, in the macrophages and microglia. The M1 polarization-associated chemokines, C–C motif chemokine ligand (CCL)-2 and C-X-C motif chemokine ligand (CXCL)-10, were also effectively reduced by the quercetin treatment. In addition, quercetin markedly reduced the production of various reactive oxygen species (ROS) in the microglia. The microglial phagocytic ability induced by the LPS was also effectively reduced by the quercetin treatment. Importantly, the quercetin increased the expression levels of the M2 marker, IL-10, and the endogenous antioxidants, heme oxygenase (HO)-1, glutamate-cysteine ligase catalytic subunit (GCLC), glutamate-cysteine ligase modifier subunit (GCLM), and NAD(P)H quinone oxidoreductase-1 (NQO1). The enhancement of the M2 markers and endogenous antioxidants by quercetin was activated by the AMP-activated protein kinase (AMPK) and Akt signaling pathways. Together, our study reported that the quercetin inhibited the effects of M1 polarization, including neuroinflammatory responses, ROS production, and phagocytosis. Moreover, the quercetin enhanced the M2 macrophage polarization and endogenous antioxidant expression in both macrophages and microglia. Our findings provide valuable information that quercetin may act as a potential drug for the treatment of diseases related to inflammatory disorders in the central nervous system.

Senolytic effects of quercetin in an in vitro model of pre-adipocytes and adipocytes induced senescence

The dysfunction of adipose tissue with aging and the accumulation of senescent cells has been implicated in the pathophysiology of chronic diseases. Recently interventions capable of reducing the burden of senescent cells and in particular the identification of a new class of drugs termed senolytics have been object of extensive investigation. We used an in vitro model of induced senescence by treating both pre-adipocytes as well as mature adipocytes with hydrogen peroxide (H2O2) at a sub-lethal concentration for 3 h for three consecutive days, and hereafter with 20 uM quercetin at a dose that in preliminary experiments resulted to be senolytic without cytotoxicity. H2O2 treated pre-adipocytes and adipocytes showed typical senescence-associated features including increased beta-galactosidase activity (SA-ß-gal) and p21, activation of ROS and increased expression of pro-inflammatory cytokines. The treatment with quercetin in senescent pre-adipocytes and adipocytes was associated to a significant decrease in the number of the SA-β-gal positive cells along with the suppression of ROS and of inflammatory cytokines. Besides, quercetin treatment decreased miR-155-5p expression in both models, with down-regulation of p65 and a trend toward an up-regulation of SIRT-1 in complete cell extracts. The senolytic compound quercetin could affect AT ageing by reducing senescence, induced in our in vitro model by oxidative stress. The downregulation of miRNA-155-5p, possibly through the modulation of NF-κB and SIRT-1, could have a key role in the effects of quercetin on both pre-adipocytes and adipocytes.

Quercetin promotes bone marrow mesenchymal stem cell proliferation and osteogenic differentiation through the H19/miR-625-5p axis to activate the Wnt/β-catenin pathway

Background Quercetin and H19 can promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). However, whether quercetin regulates H19 expression to promote osteogenic differentiation of BMSCs is unclear. Methods BMSC proliferation, matrix mineralization, and alkaline phosphatase (ALP) activity were assessed using the Cell Counting Kit-8, ALP assay kit, and alizarin red staining kit, respectively. Expression of H19, miR-625-5p, BMP-2, osteocalcin, and RUNX2 were measured by qRT-PCR; β-catenin protein level was measured by western blotting. Results Quercetin promoted BMSC proliferation, enhanced ALP activity, and upregulated the expression of BMP-2, osteocalcin, and RUNX2 mRNAs, suggesting that it promoted osteogenic differentiation of BMSCs. Moreover, quercetin increased H19 expression, while the effect of quercetin on BMSCs was reversed by silencing H19 expression. Additionally, miR-625-5p, interacted with H19, was downregulated during quercetin-induced BMSC osteogenic differentiation, which negatively correlated with H19 expression. Silencing miR-625-5p expression promoted BMSC proliferation and osteogenic differentiation, whereas miR-625-5p overexpression weakened the effect of quercetin on BMSCs. Finally, quercetin treatment or downregulation of miR-625-5p expression increased β-catenin protein level in BMSCs. Upregulation or downregulation of miR-625-5p or H19 expression, respectively, inhibited β-catenin protein level in quercetin treated-BMSCs. Conclusion H19 promotes, while miR-625-5p inhibits BMSC osteogenic differentiation. Quercetin activates the Wnt/β-catenin pathway and promotes BMSC osteogenic differentiation via the H19/miR-625-5p axis.

Beneficial Effect of Quercetin on Erythrocyte Properties in Type 2 Diabetic Rats

Diabetes mellitus is characterized by tissue oxidative damage and impaired microcirculation, as well as worsened erythrocyte properties. Measurements of erythrocyte deformability together with determination of nitric oxide (NO) production and osmotic resistance were used for the characterization of erythrocyte functionality in lean (control) and obese Zucker diabetic fatty (ZDF) rats of two age categories. Obese ZDF rats correspond to prediabetic (younger) and diabetic (older) animals. As antioxidants were suggested to protect erythrocytes, we also investigated the potential effect of quercetin (20 mg/kg/day for 6 weeks). Erythrocyte deformability was determined by the filtration method and NO production using DAF-2DA fluorescence. For erythrocyte osmotic resistance, we used hemolytic assay. Erythrocyte deformability and NO production deteriorated during aging—both were lower in older ZDF rats than in younger ones. Three-way ANOVA indicates improved erythrocyte deformability after quercetin treatment in older obese ZDF rats only, as it was not modified or deteriorated in both (lean and obese) younger and older lean animals. NO production by erythrocytes increased post treatment in all experimental groups. Our study indicates the potential benefit of quercetin treatment on erythrocyte properties in condition of diabetes mellitus. In addition, our results suggest potential age-dependency of quercetin effects in diabetes that deserve additional research.

Administration of Quercetin Ameliorates Lipopolysaccharide Induced Neuroinflammation and Oxidative Stress in Adult Zebrafish

Background: Quercetin is a natural flavonoid which is known to have numerous pharmacological activities such as antioxidative, anti-inflammatory and neuroprotective effects against various neurological disorders. Lipopolysaccharide (LPS) is a potent endotoxin, reported to cause various neurological disorders such as Alzheimer’s Disease (AD), Parkinson’s Disease (PD), Multiple Sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS), Stroke (Brain Attack), Meningitis. Aim: The present study was designed to investigate the possibility thatquercetin ameliorates LPS induced oxidative stress and neuroinflammation in adult zebrafish. Materials and methods: Zebrafish (weighing 470-530 mg) were treated with single injection of LPS (1 mg/kg) intraperitoneally (i.p.) followed by post treatment for 7 days with quercetin (50 and 100 mg/kg; i.p.). After sacrificed, brain was harvested and subjected for biochemical, molecular and histological analyses. Results: Results revealed post treatment with quercetin was able to ameliorate the behavioral abnormalities as in novel diving test- time spent in top zone (TSTZ), and number of entries in top zone was significantly more as compared to time spent in bottom zone (TSBZ). In light-dark chamber test- time spent in light zone (TSLZ), and number of entries in light zone was significantly more as compared to time spent in dark compartment (TSDC). Additionally, results of histopathology (H & E stain) studies showed less disruption in neuronal cells as compared to LPS treated group. Moreover, results of molecular analysis implies that quercetin treatment significantly decrease TNF-α and IL-1β level as compared to LPS treated animals. Further, results of biochemical analysis reveal that quercetin reduce the level of LPO, nitrite, AChEs and increases anti-oxidant GSH. Conclusion: Quercetin treatment helps to prevent oxidative damage and neuroinflammation in LPS treated adult zebrafish.

Quercetin attenuates lipopolysaccharide-induced myocardial cell apoptosis via modulation of cAMP-Epac pathway

Purpose: To investigate the effects and mechanism of action of quercetin (QUE) on sepsis-induced apoptosis of myocardial cells in vitro. Methods: Lipopolysaccharide (LPS) was used to induce apoptosis H9c2 myocardial cells. Apoptosis of H9c2 cells was determined by propidium iodide staining. Knock down of Epac1 was achieved using small interfering RNA (SiEpac1). The levels of associated proteins (Epac1 and Rap1) were evaluated by western blotting. Results: Lipopolysaccharide promoted apoptosis of H9c2 cells and inhibited the activity of cAMP-Epac pathway (p < 0.001 vs. control). Quercetin inhibited caspase 3 activity and apoptosis (p < 0.05 vs. LPS) induced by LPS via activation of cAMP-Epac1 signaling pathway. Moreover, Epac1 knockdown decreased the anti-apoptosis effect of Que, which indicates that Que attenuated apoptosis partly via cAMP-Epac pathway. Conclusion: Que attenuated LPS-induced apoptosis in myocardial cells via activation of cAMP-Epac1 pathway. Therefore, quercetin treatment may serve as a promising strategy in the treatment of sepsisinduced myocardial injury.

Dietary quercetin ameliorates TPT-induced hepatic oxidative damage and apoptosis in zebrafish

The objective of this study was to determine the effects of quercetin on oxidative stress and apoptosis induced by TPT in zebrafish. 240 fish were divided into 4 groups with three repeats. D1: fish fed with the basal diet as the control group. D2: fish fed with basal diet and exposed in 10 ng/L TPT. D3: fish fed diets containing 100 mg/Kg quercetin and exposed in 10ng/L TPT. D4: fish fed diets containing 100 mg/Kg quercetin. The results showed that quercetin could ameliorate oxidative stress, which decreased MDA, NO levels and improved antioxidant enzyme activities. The key apoptotic gene expressions, including caspase3, Bax and caspase9 mRNA expression were significantly induced by TPT exposure as compared with the control group, while notably decreased the Bcl-2 gene. However, dietary quercetin prevented a significant increase in Bax, caspase3 and caspase9 mRNA levels induced by TPT exposure, but increased Bcl-2 mRNA levels. The results of our study also demonstrated that 10 ng/L TPT significantly up-regulated TNF-α, IL-1β, IL-8, and NF-kB p65 gene expression and down-regulated IL-10 and IkB expression compared to the control group. However, TPT-induced inflammation was significantly mitigated in the quercetin treatment group. In conclusion, our findings suggested that quercetin might alleviate hepatic oxidative damage and apoptosis induced by TPT.

Quercetin Antagonizes Glucose Fluctuation Induced Renal Injury by Inhibiting Aerobic Glycolysis via HIF-1α/miR-210/ISCU/FeS Pathway

Background and Objective: Glucose fluctuation (GF) has been reported to induce renal injury and diabetic nephropathy (DN). However, the mechanism still remains ambiguous. Mitochondrial energy metabolism, especially aerobic glycolysis, has been a hotspot of DN research for decades. The activation of HIF-1α/miR210/ISCU/FeS axis has provided a new explanation for aerobic glycolysis. Our previous studies indicated quercetin as a potential therapeutic drug for DN. This study aims to evaluate levels of aerobic glycolysis and repressive effect of quercetin via HIF-1α/miR210/ISCU/FeS axis in a cell model of GF.Methods: The mouse glomerular mesangial cells (MCs) were exposed in high or oscillating glucose with or without quercetin treatment. Cell viability was measured by CCK8 assay. Aerobic glycolysis flux was evaluated by lactate acid, pH activity of PFK. Apoptosis level was confirmed by Annexin V-APC/7-AAD double staining and activity of caspase-3. TNF-α and IL-1β were used to evaluate inflammation levels.Results: GF deteriorated inflammation damage and apoptosis injury in MCs, while quercetin could alleviate this GF-triggered cytotoxicity. GF intensified aerobic glycolysis in MCs and quercetin could inhibit this intensification in a dose-dependent manner. Quercetin prevented activities of two FeS-dependent metabolic enzymes, aconitase, and complex I, under GF injury in MCs. The mRNA expression and protein contents of HIF-1α were increased after GF exposure, and these could be alleviated by quercetin treatment. Knockdown of ISCU by siRNA and Up-regulating of miR-210 by mimic could weaken the effects of quercetin that maintained protein levels of ISCU1/2, improved cell viability, relieved inflammation injury, decreased apoptosis, and reduced aerobic glycolysis switch in MCs.Conclusion: Quercetin antagonizes GF-induced renal injury by suppressing aerobic glycolysis via HIF-1α/miR-210/ISCU/FeS pathway in MCs cell model. Our findings contribute to a new insight into understanding the mechanism of GF-induced renal injury and protective effects of quercetin.

Quercetin Inhibits Biofilm Formation by Decreasing the Production of EPS and Altering the Composition of EPS in Staphylococcus epidermidis

Staphylococcus epidermidis is an opportunistic pathogen, and its biofilm formation ability is an important virulent factor. Quercetin, a typical flavonoid ubiquitously used in dietary supplementation, is known for its antioxidant property, but its anti-biofilm activity against S. epidermidis remains unknown. In this study, the anti-biofilm activity of quercetin was investigated using S. epidermidis ATCC35984, a strong biofilm-positive strain. An attempt was made to disclose the mechanisms of the anti-biofilm activity of quercetin. S. epidermidis exhibited a less cell surface hydrophobicity after quercetin treatment. Also, quercetin effectively inhibited S. epidermidis cells from adhering to the glass slides. Quercetin downregulated the intercellular adhesion (ica) locus and then polysaccharide intercellular adhesin (PIA) production was reduced. Therefore, S. epidermidis cells became less hydrophobic, which supported quercetin’s anti-biofilm effect. Our study suggests that quercetin from plants be given further attention as a potential anti-biofilm agent against the biofilm formation of S. epidermidis, even biofilm infections of other bacteria.