Deciphering the binding behavior and interaction mechanism of apigenin and α-glucosidase based on multi-spectroscopic and molecular simulation studies.

This study investigated the molecular mechanism underlying the binding interaction between apigenin (API) and α-glucosidase (α-glu) by a combination of experimental techniques and computational simulation strategies. The spontaneously formation of stable API-α-glu complex was mainly driven by hydrogen bonds and hydrophobic forces, leading to a static fluorescence quenching of α-glu. The binding of API induced secondary structure and conformation changes of α-glu, decreasing the surface hydrophobicity of protein. Computational simulation results demonstrated that API could bind into the active cavity of α-glu via its interaction with active residues at the binding site. The important roles of key residues responsible for the binding stability and affinity between API and α-glu were further revealed by MM/PBSA results. In addition, it can be found that the entrance of active site tended to close after API binding as a result of its interaction with gate keeping residues. Furthermore, the structural basis for the binding interaction behavior of API was revealed and visualized by weak interaction analysis. The findings of our study revealed atomic-level mechanism of the interaction between API, which might shed light on the development of better inhibitors.

Identification of key phenolic compounds for alleviating gouty inflammation in edible chrysanthemums based on spectrum-effect relationship analyses.

Edible chrysanthemum is a common food resource for tea and functional foods with potential benefits for human health. Studies have indicated that chrysanthemum has the potential effect on inflammatory diseases, while the effects on gouty inflammation remain underexplored. The present study aimed to investigate the anti-gout activity and characterize the active ingredients of chrysanthemums by using metabolite profiles, in vitro experiments, and spectrum-effect analysis. Results showed that 'Boju' (BJ), 'Hangbaiju' (HBJ), and 'Huaiju' (HJ) exhibited regulatory effects on monosodium urate (MSU)-induced inflammation. At the dose of 50 µg/mL, the inhibitory rates of IL-1ß secretion were 24.53 %, 14.36 %, and 38.10 %, respectively. A total of 32 phenolic compounds were identified or preliminarily assigned in UPLC-Q/TOF-MS analysis. And seven phenolics related to anti-gout activity were identified by spectrum-effect relationships. According to ADME (absorption, distribution, metabolism, excretion) evaluation and experiments verification, luteolin, acacetin-7-O-glucoside, and apigenin-7-O-glucoside were critical constituents potentially associated with the reduction of inflammation in gout. Additionally, these phenolics might be suitable as quality control indicators. This study clarified the anti-gout properties of different cultivars of chrysanthemums and active compounds, providing a theoretical basis for its scientific utilization in functional foods.

Protective effects of di-caffeoylquinic acids from Artemisia selengensis Turcz leaves against monosodium urate-induced inflammation via the modulation of NLRP3 inflammasome and Nrf2 signaling pathway in THP-1 macrophages.

Artemisia selengensis Turcz (AST) as a common vegetable is rich in di-caffeoylquinic acids (di-CQAs) and has been reported to possess multiple health benefits. However, whether di-CQAs from AST leaf extracts (ASTE) could alleviate gout inflammation is still unknown. Herein, this study explored the inhibitory mechanism of ASTE on gout inflammation in THP-1 macrophages. Results suggested that ASTE suppressed the secretion and mRNA levels of inflammatory cytokines including interleukin-18, interleukin-1ß, interleukin-6, and tumor necrosis factor-α. Pretreatment with ASTE inhibited lipopolysaccharide-induced of IκBα degradation, p65 phosphorylation and up-regulation of Nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome proteins. Moreover, ASTE inhibited monosodium urate-induced the up-regulation of active caspase-1 and interleukin-1ß, promoted nuclear factor E2-related factor2 (Nrf2) to translocate into the nucleus, reducing the generation of MSU-induced reactive oxygen species. These results suggested that ASTE alleviated gout inflammation via inhibiting NLRP3 inflammasome activation and activating Nrf2 signaling pathway. PRACTICAL APPLICATIONS: Artemisia selengensis Turcz (AST) as a common vegetable in China belongs to genus Artemisia, which are rich in di-caffeoylquinic acids. This study aimed to investigate the effect of ASTE on alleviating gout inflammation and whether NLRP3 inflammasome and Nrf2 signaling pathways are involved in the protection of ASTE against gout inflammation. Our findings are significant for developing di-CQAs from AST by-products as an effective functional food for preventing gout.

Structure-activity relationship and mechanism of flavonoids on the inhibitory activity of P-glycoprotein (P-gp)-mediated transport of rhodamine123 and daunorubicin in P-gp overexpressed human mouth epidermal carcinoma (KB/MDR) cells.

This study was aimed to investigate the inhibitory activity of flavonoids on P-glycoprotein (P-gp). Effects of 39 flavonoids on the cellular uptake (CU) of rhodamine123 (Rho) and daunomycin (DNR) were investigated in both parental KB and P-gp overexpressed KB/MDR cells. The inhibition mechanism of selected flavonoids was further investigated by measuring the ATPase activity and expression level of P-gp. Twelve flavonoids improved the uptake of Rho (↑RhoF) and nineteen flavonoids increased the uptake of DNR (↑DNRF) in KB/MDR cells with nine flavonoids overlapped. Structure-activity relationship (SAR) indicated that 8-OCH3, and 2'-OH have a negative effect on Rho and DNR transport. Whereas 5-OH, 5-OCH3, 6-OH, 7-OCH3, 3'-OH, and 4'-OH, are essential for inhibition of flavonoids on P-gp and reversing the resistance of Rho and DNR. Eleven selected flavonoids significantly induced the basal P-gp-ATPase activity but much lower than that induced by verapamil. Tangeretin, galangin, kaempferol, quercetin, and morin significantly reversed the ATPase activity stimulated by verapamil. Six of eleven flavonoids significantly decreased P-gp expression, whereas three flavonoids slightly increased P-gp expression. These results provide valuable information that flavonoids can effectively reverse multidrug resistance of P-gp-mediated transport of nutraceutical and drugs by co-administration.

Lactobacillus casei-fermented blueberry pomace augments sIgA production in high-fat diet mice by improving intestinal microbiota.

Intestinal secretory immunoglobulin A (sIgA)-improving function of Lactobacillus casei-fermented blueberry pomace (FBP) was investigated in this study. Male C57BL/6 mice were fed with control diet (CD) or high-fat diet (HFD) with or without FBP supplementation. Expressions of sIgA-associated genes/proteins were evaluated by quantitative polymerase chain reaction (qPCR), western blot and enzyme-linked immunosorbent assay (ELISA). Commensal microbiota in Peyer's patches (PPs) and caecal contents were analyzed by 16S rRNA Illumina sequencing and qPCR, respectively. FBP improved sIgA production in HFD mice at mRNA and protein levels. Akkermansia and Lactobacillus in PPs of HFD mice were statistically increased by FBP. Beneficial microbiota and short-chain fatty acids (SCFAs) in caecal contents were positively correlated with caecal immunoglobulins in HFD mice. FBP showed an ability to modulate intestinal microbiota, which improved sIgA production in HFD mice, warranting the potential use of berry by-products as functional ingredients in improving the intestinal immune barrier of HFD individuals.

Fermented blueberry pomace ameliorates intestinal barrier function through the NF-κB-MLCK signaling pathway in high-fat diet mice.

The barrier-improving functions of fermented blueberry pomace (FBP) and its potential mechanism were investigated in this study. Polyphenols and the approximate composition of FBP were evaluated according to the National Standard of the People's Republic of China and the UPLC-MS system. Male C57BL/6 mice were fed a control diet (CD) or a high-fat diet (HFD) with or without FBP supplementation. Oxidative stress, inflammation, histological morphology and the expression of functional proteins in the small intestine of mice were evaluated using the enzyme linked immunosorbent assay (ELISA), quantitative polymerase chain reaction (qPCR) and western blotting. The content of protein, fat, soluble dietary fiber, insoluble dietary fiber and carbohydrates (non-dietary fiber) was 114.5 ± 1.5 g kg-1, 5.0 ± 0.2 g kg-1, 48.0 ± 0.1 g kg-1, 360.3 ± 2.2 g kg-1 and 423 g kg-1 (by difference), respectively. Thirty-six polyphenols were identified in FBP. FBP improved the growth of mice and attenuated hepatic and intestinal oxidative stress. Intestinal inflammation was significantly reduced through the decrease of tumor necrosis factor-alpha (TNF-α) and myeloperoxidase (MPO) as well as an increase of interleukin-10 (IL-10). FBP supplementation significantly improved the intestinal morphology and barrier function, potentially by mediating the NF-κB-MLCK signaling pathway. The supplementation of FBP in HFD mice enhanced the intestinal barrier function. This suggested that polyphenol-rich by-products might provide a similar health effect in HFD individuals.

Quantitative Structure⁻Activity Relationships for the Flavonoid-Mediated Inhibition of P-Glycoprotein in KB/MDR1 Cells.

P-glycoprotein (P-gp) serves as a therapeutic target for the development of inhibitors to overcome multidrug resistance (MDR) in cancer cells. In order to enhance the uptake of chemotherapy drugs, larger amounts of P-gp inhibitors are required. Besides several chemically synthesized P-gp inhibitors, flavonoids as P-gp inhibitors are being investigated, with their advantages including abundance in our daily diet and a low toxicity. The cytotoxicity of daunorubicin (as a substrate of P-gp) to KB/MDR1 cells and the parental KB cells was measured in the presence or absence of flavonoids. A two-dimensional quantitative structure-activity relationship (2D-QSAR) model was built with a high cross-validation coefficient (Q2) value of 0.829. Descriptors including vsurf_DW23, E_sol, Dipole and vsurf_G were determined to be related to the inhibitory activity of flavonoids. The lack of 2,3-double bond, 3'-OH, 4'-OH and the increased number of methoxylated substitutions were shown to be beneficial for the inhibition of P-gp. These results are important for the screening of flavonoids for inhibitory activity on P-gp.

Isoflavone biochanin A, a novel nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element activator, protects against oxidative damage in HepG2 cells.

Isoflavones are one group of the major flavonoids and possess multiple biological activities due to their antioxidant properties. However, a clear antioxidant mechanism of dietary isoflavones is still remained to be answered. In this study, the effects of isoflavones on the nuclear factor E2-related factor 2 (Nrf2)-antioxidant response element (ARE) signaling pathway and the underlying molecular mechanisms were investigated. Results showed that isoflavones are potential Nrf2-ARE activators while their activities were structure dependent. Biochanin A (BCA), an O-methylated isoflavone with low direct antioxidant activity, can effectively protect HepG2 cells against tert-butyl hydroperoxide (t-BHP)-induced oxidative damage via activation of the Nrf2 signaling, and thereby the induction of downstream cytoprotective enzymes including NAD(P)H quinone oxidoreductase-1, heme oxygenasae-1, and glutamate-cysteine ligase catalytic subunit. A molecular docking study revealed that BCA could directly bind into the pocket of Kelch-like erythroid cell-derived protein with CNC homology (ECH)-associated protein 1 (Keap1), a cytoplasmic suppressor of Nrf2, to facilitate Nrf2 activation. The upstream mitogen-activated protein kinase (MAPK) pathways were also involved in the activation of Nrf2 signaling. These findings indicate that the protective actions of dietary isoflavones against oxidative damage may be at least partly due to their ability to enhance the intracellular antioxidant response system by modulating the Nrf2-ARE signaling pathway.

Structure affinity relationship and docking studies of flavonoids as substrates of multidrug-resistant associated protein 2 (MRP2) in MDCK/MRP2 cells.

This study was aimed to determine the relationship of flavonoid structures to their affinity for an important efflux transporter, multidrug-resistant associated protein 2 (MRP2). The cellular uptake (CU) of 35 flavonoids was investigated in MRP2 overexpression MDCK/MRP2 cells. Resulting data identified 8 flavonoids as MRP2 substrates based on their high CUMK with MK-571 in MDCK/MRP2 cells. Also, three substrates showed better CUMD in MDCK cells than did CUMRP in MDCK/MRP2 cells. Docking analyses showed a good correlation (R = 0.926, p = 0.003) between efflux-fold of flavonoid substrates and their docking S_scoring with the MRP2 model, indicating consistency between in silico and in vitro approaches. A structure affinity relationship (SAR) study indicated that 3-OH, 5-OH, 6-OH, 3'-OH, and 4'-OCH3 substituents were favourable while, 8-OCH3, 2'-OH, 3'-OCH3, 4'-OH and 5'-OH were unfavourable for flavonoid affinity to MRP2. Our study provides valuable information for dietary application of flavonoids with specific structures for high absorption.

Establishment and Use of Human Mouth Epidermal Carcinoma (KB) Cells Overexpressing P-Glycoprotein To Characterize Structure Requirements for Flavonoids Transported by the Efflux Transporter.

This study was aimed to determine the mechanism for flavonoid poor absorption related to P-glycoprotein (P-gp). The cellular uptake (CU) of 40 flavonoids was investigated in P-gp overexpressing KB/multidrug-resistant (MDR) cells. A total of 9 flavonoids, including 5,7,3',4'-tetramethoxyflavone, with a significant ( p < 0.05) CUKBE (2.90 ± 0.146 µmol/g) higher than CUKBP (1.57 ± 0.129 µmol/g) were identified as P-gp substrates. Besides, 8 substrates, including tangeretin, showed a significant ( p < 0.05) CUKB (9.72 ± 1.09 µmol/g) higher than its CUKBP (7.36 ± 0.692 µmol/g). A total of 7 of 17 flavonoid substrates stimulated the P-gp efflux of rhodamine 123, and most substrates increased P-gp expression in KB/MDR cells. Docking analyses showed a good correlation ( R = 0.764; p < 0.01) between efflux fold and S_scoring of flavonoids to the P-gp model, indicating consistency between in silico and in vitro results. A structure-affinity relationship exhibited that 3-OH, 5-OH, 3'-OCH3, and 4'-OCH3 are crucial for flavonoids binding to P-gp. These results provide valuable information for finding a solution to improve the absorption of flavonoids.

Attenuation of tert-Butyl Hydroperoxide ( t-BHP)-Induced Oxidative Damage in HepG2 Cells by Tangeretin: Relevance of the Nrf2-ARE and MAPK Signaling Pathways.

The current study evaluates the protective effects of tangeretin, a representative polymethoxyflavone (PMF) mainly isolated from the peels of citrus fruits, against tert-butyl hydroperoxide ( t-BHP)-induced oxidative damage in HepG2 cells and the potential mechanisms of this protection. Tangeretin suppressed t-BHP-induced oxidative damage, as evaluated by cell viability, reactive-oxygen-species (ROS) levels, lactate dehydrogenase (LDH) leakage and glutathione (GSH) levels. Further mechanistic studies showed that tangeretin up-regulated the expression of heme oxygenase 1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). Moreover, tangeretin induced antioxidant-responsive-element (ARE)-dependent luciferase activation, nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nuclear translocation, and mitogen-activated-protein-kinase (MAPK) phosphorylation. Results in the study indicate that the protective effects of tangeretin may be at least partly due to its capacity to up-regulate the antioxidant enzymes NQO1 and HO-1 via the MAPK-Nrf2-ARE signaling pathway. Tangeretin may play an effective protective role in liver injury.

Structure characteristics for intestinal uptake of flavonoids in Caco-2 cells.

Flavonoids are a large group of polyphenols and widely distributed in plant foods. Flavonoids exhibit various biological activities, such as anti-cancer, antioxidant and anti-inflammatory while poor oral bioavailability has been considered as a major hurdle in their use as functional foods. Cellular uptake and efflux of flavonoid implicates their bioavailability. To investigate the cellular uptake and efflux of flavonoids, 27 flavonoids were measured for their cellular uptake in Caco-2 cells with (CUV) and without (CU) the inhibitor of P-glycoprotein (P-gp) verapamil. Then, a quantitative structure-absorption relationship (QSAR) model containing 21 compounds as training set was obtained from their corresponding CU. The model showed good robustness and predictivity with a high cross-validation coefficient (Q2) value of 0.809 and Log of the octanol/water partition coefficient (SlogP) and atomic charge on carbon 5 (QC5) were related to flavonoid uptake. The CUV of some flavonoids were significantly (p<0.05 or p<0.01) higher than their CU, suggesting that specific flavonoids are pumped out by P-gp. The structure-affinity relationship of flavonoids as substrates of P-gp was determined with the presence of 4'-OCH3, 3'-OCH3 and the absence of 3'-OH, 3-OH and 4'-OH favorable for the affinity of flavonoids. These results provide valuable information for screening flavonoids with good absorption and low affinity with transporters.

Electromagnetic radiation at 900 MHz induces sperm apoptosis through bcl-2, bax and caspase-3 signaling pathways in rats.

BACKGROUND: The decreased reproductive capacity of men is an important factor contributing to infertility. Accumulating evidence has shown that Electromagnetic radiation potentially has negative effects on human health. However, whether radio frequency electromagnetic radiation (RF-EMR) affects the human reproductive system still requires further investigation. Therefore, The present study investigates whether RF-EMR at a frequency of 900 MHz can trigger sperm cell apoptosis and affect semen morphology, concentration, and microstructure. METHODS: Twenty four rats were exposed to 900 MHz electromagnetic radiation with a special absorption rate of 0.66 ± 0.01 W/kg for 2 h/d. After 50d, the sperm count, morphology, apoptosis, reactive oxygen species (ROS), and total antioxidant capacity (TAC), representing the sum of enzymatic and nonenzymatic antioxidants, were investigated. Western blotting and reverse transcriptase PCR were used to determine the expression levels of apoptosis-related proteins and genes, including bcl-2, bax, cytochrome c, and capase-3. RESULTS: In the present study, the percentage of apoptotic sperm cells in the exposure group was significantly increased by 91.42% compared with the control group. Moreover, the ROS concentration in exposure group was increased by 46.21%, while the TAC was decreased by 28.01%. Radiation also dramatically decreased the protein and mRNA expression of bcl-2 and increased that of bax, cytochrome c, and capase-3. CONCLUSION: RF-EMR increases the ROS level and decreases TAC in rat sperm. Excessive oxidative stress alters the expression levels of apoptosis-related genes and triggers sperm apoptosis through bcl-2, bax, cytochrome c and caspase-3 signaling pathways.