Binding Of Genistein Research Articles

Salivary gland protective and antiinflammatory effects of genistein in Sjögren’s syndrome by inhibiting Xist/ACSL4-mediated ferroptosis following binding to estrogen receptor-alpha

BackgroundSjögren’s syndrome (SS) is an autoimmune disease with limited effective treatment options. This study aimed to explore the underlying mechanism by which genistein–estrogen receptor alpha (ERα) complex targets X-inactive specific transcript (Xist) then leads to the inhibition of ferroptosis by regulating acyl-CoA synthetase long-chain family member 4 (ACSL4) expression in salivary gland epithelial cells (SGECs) to attenuate SS.MethodsThe effects of genistein treatment on the progression and underlying mechanism of SS were investigated using nondiabetic obese (NOD)/LtJ mice in vivo and Interferon-γ (IFNγ)-treated SGECs in vitro. Water intake and saliva flow rate were measured to evaluate the severity of xerostomia. Hematoxylin–eosin staining, real-time quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay were conducted to examine the pathological lesions. Western blotting and immunohistochemistry analysis were used to evaluate the protein expression. RNA sequencing and RNA fluorescence in situ hybridization were employed to verify the relationship between Xist and ACSL4. Surface plasmon resonance, molecular docking, and molecular dynamics were used to investigate the binding between genistein and ERα. Furthermore, a chromatin immunoprecipitation assay was used to analyze ERα–XIST promoter interactions. The levels of malondialdehyde, glutathione, Fe2+, and mitochondrial changes were measured to evaluate ferroptosis of SGECs.ResultsIn NOD/LtJ mice, a ferroptosis phenotype was observed in salivary glands, characterized by downregulated Xist and upregulated X chromosome inactivation gene Acsl4. Genistein significantly alleviated SS symptoms, upregulated the Xist gene, and downregulated Acsl4 expression. Genistein upregulated Xist expression in the salivary gland of NOD/LtJ mice via the ERα signaling pathway. It downregulated Acsl4 and ferroptosis in the salivary glands of NOD/LtJ mice. IFNγ-treatment induced inflammation and ferroptosis in SGECs. Genistein binding to ERα upregulated XIST, and aquaporin 5 expression, downregulated ACSL4, and SS antigen B expression, and reversed ferroptosis in SGECs. Genistein mitigated inflammation and ferroptosis in SGECs by upregulated-XIST-mediated ACSL4 gene silencing.ConclusionsGenistein binding to ERα targets Xist, leading to inhibiting ferroptosis by regulating ACSL4 expression in SGECs. This finding provides evidence for genistein as a treatment for SS and identifies Xist as a novel drug target for SS drug development, offering great promise for improving SS outcomes.Graphical

Structural mechanism of human oncochannel TRPV6 inhibition by the natural phytoestrogen genistein

Calcium-selective oncochannel TRPV6 is the major driver of cell proliferation in human cancers. While significant effort has been invested in the development of synthetic TRPV6 inhibitors, natural channel blockers have been largely neglected. Here we report the structure of human TRPV6 in complex with the plant-derived phytoestrogen genistein, extracted from Styphnolobium japonicum, that was shown to inhibit cell invasion and metastasis in cancer clinical trials. Despite the pharmacological value, the molecular mechanism of TRPV6 inhibition by genistein has remained enigmatic. We use cryo-EM combined with electrophysiology, calcium imaging, mutagenesis, and molecular dynamics simulations to show that genistein binds in the intracellular half of the TRPV6 pore and acts as an ion channel blocker and gating modifier. Genistein binding to the open channel causes pore closure and a two-fold symmetrical conformational rearrangement in the S4–S5 and S6-TRP helix regions. The unprecedented mechanism of TRPV6 inhibition by genistein uncovers new possibilities in structure-based drug design.

Genistein binding protein targets in dental pathogens.

Oral pathogens have created a menace in recent years due to biofilm formation and antimicrobial drug resistance. The current treatment strategy works well with antibiotics. However, constant use of antibiotics creates a selective pressure, which increases adaptability of the pathogens. Therefore, it is of interest to analyze the potential targets of genistein in dental pathogens using computer aided prediction tools.

IN VITRO ANTI-NEUROINFLAMMATORY EFFECT OF GENISTEIN (4',5,7-TRIHYDROXYISOFLAVONE) ON MICROGLIA HMC3 CELL LINE, AND IN SILICO EVALUATION OF ITS INTERACTION WITH ESTROGEN RECEPTOR-β

Objective: This study was aimed to evaluate the role of genistein or 4',5,7-trihydroxyisoflavone as a phytoestrogen in the treatment of estrogen deficiency-induced neuroinflammatory. The specific objectives of this study were to determine the anti-neuroinflammatory effect of genistein through measurement of MHC II and Arg1 expressions on microglia HMC3 cell line, as well as to prove that the effect occurs in an ER-dependent manner, through the measurement of free-ERβ expression.
 Methods: The cells were cultured in 24-well microplates, induced with 10 ng IFN-γ, and incubated for 24 h to activate the cell to M1 phenotype which has pro-inflammatory characteristics. Genistein with a concentration of 50 μM was added to the cells. The expression of MHC II, Arg1, and free-ERβ as markers was tested through an immunocytochemistry method and measured using the CLSM instrument. In silico approach was also conducted to determine the interaction between genistein and ERβ, compared to 17β-estradiol. Genistein structure was prepared with Avogadro 1.0.1, and molecular docking was done using PyRx 0.8 software. Biovia Discovery Studio Visualizer 2016 was used to visualize the structure of genistein against 3OLS protein. The physicochemical characteristics of genistein were analyzed using the SwissADME web tool.
 Results: Genistein can decrease MHC II expression and increase Arg1 expression in microglia HMC3 cells compared to negative controls (p<0.005), with expression value of 472.577±26.701 AU and 114.299±6.578 AU. But, genistein cannot decrease the free-ERβ expression in cells (p<0.005). The results of in silico analysis showed that genistein is an ERβ agonist.
 Conclusion: Genistein shows anti-neuroinflammatory effects by decreasing the MHC II expression and increasing Arg1 expression in the microglia HMC3 cell line. However, this effect does not occur through the binding of genistein to ERβ, but it is likely to occur through the binding of genistein with other types of ER.

Identification of Small-Molecule Regulators of Testicular Receptor 4 via a Drug Repurposing Screening.

The testicular receptor 4 (TR4) is a nuclear receptor implicated in multiple pathological processes, including cancer development, chemotherapy, and radiotherapy resistance. However, no effective TR4 small-molecule regulator is available to date. Here, we assessed a physical-interaction-based surface plasmon resonance imaging assay for discovery of TR4 regulators. We screened 1018 FDA-approved drugs and obtained 126 drugs with KD values below 10–6 M. The dual-luciferase-based biological assay verified four activatory compounds and two inhibitory compounds against TR4. Among them, nilotinib exhibited the most potent inhibitor, with an EC50 of 1.05 μM, while genistein represented the most potent activator, with an EC50 of 2.42 μM. Both drugs were predicted to bind in the ligand binding pocket of TR4. The circular dichroism spectroscopic assay revealed differed conformation changes upon nilotinib or genistein binding. These results established our combined physical and biological approaches as a highly effective way to identify and develop new TR4 regulators.

Genistein inhibits radiation-induced invasion and migration of glioblastoma cells by blocking the DNA-PKcs/Akt2/Rac1 signaling pathway

Background and purposeRadiotherapy is the most important therapeutic measure against glioblastoma multiforme (GBM), which is regarded as the most common and highly lethal type of brain cancer. Nevertheless, most relapses originate in the close vicinity of the irradiated target volume. Genistein is a natural product that can suppress the invasive potential of cancer cells. In this study, DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-proficient and -deficient GBM cells were selected for in vitro and in vivo studies to investigate the inhibiting effects of genistein on radiation-induced invasion and migration and the corresponding mechanism. Materials and methodsGBM cell lines with or without genistein pre-treatment were irradiated with X-rays. Cell survival was determined using colony formation assay and the rate of cellular proliferation was analyzed with a real-time cell electronic sensing system. For in vitro study, invasion and migration abilities were evaluated via wound-healing and transwell assays, while protein expression was determined with western blotting. Genistein interaction with DNA-PKcs was estimated with pull-down, recombinant and binding assays. For in vivo study, cells were stereotactically injected into NOD-SCID mice to establish tumors. Hematoxylin and eosin and immunohistochemistry were used to assess the invasive potential of GBM. ResultsX-ray irradiation enhanced the migration and invasion of DNA-PKcs-positive but not DNA-PKcs-negative GBM cells. It also activated the DNA-PKcs/Akt2/Rac1 signaling pathway, which contributed to GBM malignant progression by aggravating GBM cell invasive potential. The study successfully demonstrated that genistein can specifically bind to DNA-PKcs and block the DNA-PKcs/Akt2/Rac1 pathway, thereby effectively inhibiting radiation-induced invasion and migration of GBM cells in vitro and in vivo. The present study emphasized that radiation-induced invasive potential is initiated by DNA-PKcs, which is a well-known double strand breaks (DSB) repair protein, and determined the exact site for genistein binding to DNA-PKcs. ConclusionDNA-PKcs is not only a potential target for cancer therapy, but also a reliable biomarker for predicting radiation-induced invasion and migration of GBM cells. Thus, genistein might serve as a novel therapeutic strategy for treating GBM.

Genistein: Its Role in Breast Cancer Growth and Metastasis.

Genistein being a phytoestrogen imitates the characteristics of estrogen, which can be useful to treat conditions by reducing the estrogen levels at the time of menopause, osteoporosis and high risk for breast cancer. The superior binding of genistein to ERβ might help in reducing breast malignancy risk. Genistein induces cell cycle arrest, anti-metastatic properties and ultimately affects the breast cancer cell growth by multiple mechanisms. Genistein-mediated anti-proliferative or anti-growth effects are usually observed at higher concentrations. These signaling pathways involve the decrease of NF-κB, HIF-1α, VEGF, and an increase of tumor suppressor p21. This will provide further insight into understanding the biology of transcription factors NF-κB, and HIF-1α in breast cancer.

Characterization of a UGT84 Family Glycosyltransferase Provides New Insights into Substrate Binding and Reactivity of Galloylglucose Ester-Forming UGTs.

Galloylated plant specialized metabolites play important roles in plant-environment interactions and in the promotion of human and animal health. The galloylation reactions are mediated by the formation of galloylglucose esters from gallic acid and UDP-glucose, catalyzed by the plant UGT84 family glycosyltransferases. To explore and exploit the structural determinants of UGT84 activities, we performed homology modeling and substrate docking of PgUGT84A23, a galloylglucose ester-forming family 84 UGT, as well as sequence comparisons of PgUGT84A23 with other functionally characterized plant UGTs. By employing site-directed mutagenesis of candidate amino acids, enzyme assays with analogous substrates, and kinetic analysis, we elucidated key amino acid sites for PgUGT84A23 substrate binding and reactivity. The galloylglucose ester-forming UGT84s have not been shown to glycosylate genistein (an isoflavonoid) in vivo. Unexpectedly, amino acids highly conserved among UGT84s that affect specifically the binding of genistein but not gallic acid or other tested sugar acceptors were identified. This result suggests that genistein may resemble the substrate profile for the enzyme ancestor of the galloylglucose ester-forming UGTs and recruited during transition from a general to a more specialized defense function. Overall, a better understanding of the structure-function relationship of UGT84s will facilitate enzyme engineering for the production of pharmaceutically and industrially valuable glycosylated compounds.

Genistein Binding to Copper(II)-Solvent Dependence and Effects on Radical Scavenging.

Genistein, but not daidzein, binds to copper(II) with a 1:2 stoichiometry in ethanol and with a 1:1 stoichiometry in methanol, indicating chelation by the 5-phenol and the 4-keto group of the isoflavonoid as demonstrated by the Jobs method and UV-visible absorption spectroscopy. In ethanol, the stability constants had the value 1.12 × 1011 L2∙mol−2 for the 1:2 complex and in methanol 6.0 × 105 L∙mol−1 for the 1:1 complex at 25 °C. Binding was not detected in water, as confirmed by an upper limit for the 1:1 stability constant of K = 5 mol−1 L as calculated from the difference in solvation free energy of copper(II) between methanol and the more polar water. Solvent molecules compete with genistein as demonstrated in methanol where binding stoichiometry changes from 1:2 to 1:1 compared to ethanol and methanol/chloroform (7/3, v/v). Genistein binding to copper(II) increases the scavenging rate of the stable, neutral 2,2-diphenyl-1-picrylhydrazyl radical by more than a factor of four, while only small effects were seen for the short-lived but more oxidizing β-carotene radical cation using laser flash photolysis. The increased efficiency of coordinated genistein is concluded to depend on kinetic rather than on thermodynamic factors, as confirmed by the small change in reduction potential of −0.016 V detected by cyclic voltammetry upon binding of genistein to copper(II) in methanol/chloroform solutions.

Mixed Inhibition of cPEPCK by Genistein, Using an Extended Binding Site Located Adjacent to Its Catalytic Cleft.

Cytosolic phosphoenolpyruvate carboxykinase (cPEPCK) is a critical enzyme involved in gluconeogenesis, glyceroneogenesis and cataplerosis. cPEPCK converts oxaloacetic acid (OAA) into phosphoenol pyruvate (PEP) in the presence of GTP. cPEPCK is known to be associated with type 2 diabetes. Genistein is an isoflavone compound that shows anti-diabetic and anti-obesitic properties. Experimental studies have shown a decrease in the blood glucose level in the presence of genistein by lowering the functional activity of cPEPCK, an enzyme of gluconeogenesis. Using computational techniques such as molecular modeling, molecular docking, molecular dynamics simulation and binding free energy calculations, we identified cPEPCK as a direct target of genistein. We studied the molecular interactions of genistein with three possible conformations of cPEPCK—unbound cPEPCK (u_cPEPCK), GTP bound cPEPCK (GTP_cPEPCK) and GDP bound cPEPCK (GDP_cPEPCK). Binding of genistein was also compared with an already known cPEPCK inhibitor. We analyzed the interactions of genistein with cPEPCK enzyme and compared them with its natural substrate (OAA), product (PEP) and known inhibitor (3-MPA). Our results demonstrate that genistein uses the mechanism of mixed inhibition to block the functional activity of cPEPCK and thus can serve as a potential anti-diabetic and anti-obesity drug candidate. We also identified an extended binding site in the catalytic cleft of cPEPCK which is used by 3-MPA to inhibit cPEPCK non-competitively. We demonstrate that extended binding site of cPEPCK can further be exploited for designing new drugs against cPEPCK.

Analysis of binding interaction of genistein and kaempferol with bovine α-lactalbumin

The fluorescence quenching measurements and docking studies were used for investigating the binding of kaempferol and genistein as functional food ingredients to bovine α-lactalbumin (BLA) as a natural vehicle for bioactive ions and molecules. The closeness of the tryptophan residues to the bound ligands than to the tyrosine residues and the considerable change in microregion of the tryptophan residues in BLA is observed upon the binding of the genistein and kaempferol to BLA by synchronous fluorescence. The essential parameters which describe the characteristics of the binding such as the thermodynamic parameters, the binding constants and the binding stoichiometry were obtained from the fluorescence quenching measurements. The extent of vicinity of the bound ligands to the tryptophan residues of BLA was estimated by Förster's distance. The major role of hydrogen bonds in stabilizing the final ligand–protein complexes was concluded from the thermodynamic parameters which were calculated in different temperatures. The results of docking studies indicated that kaempferol and gnistein come closer to the Trp-60 than to other tryptophans and bind to BLA by three and five hydrogen bonds, respectively. The calculated distances between bound ligands and tryptophans obtained by docking studies were in agreement with fluorescence resonance energy transfer results. These findings can reveal that BLA can not only carry the metal ions, but also has binding affinity for natural polyphenolic compounds.

The influence of common metal ions on the interactions of the isoflavone genistein with bovine serum albumin

The interaction of genistein with bovine serum albumin (BSA) has been characterized via UV–vis, fluorescence spectroscopy and Circular Dichroism (CD) measurements under physiological conditions. In this study, we have investigated the effect of some common metal ions on the binding of genistein with BSA using fluorescence studies. The fluorescence data reveal that the binding affinity of genistein to BSA increases in presence of certain metal ions. The possibility of non-radiative energy transition from the donor tryptophan to the acceptor genistein has been observed in absence and presence of metal ions. The observed similarities in the values of efficiency of energy transfer (E) and the separation between the donor and acceptor (r) in both the cases may be correlated with the complexation between the genistein and metal ions, which is also observed from the UV–vis studies. The changes in enthalpy (ΔH°) and entropy (ΔS°) of the interaction were found to be −14.64kJmol−1 and +42.75Jmol−1K−1 respectively. These values indicate the involvement of electrostatic interactions along with a hydrophobic association that results in a positive entropy change. CD analysis shows that there is a slight increase in the% α-helical content of BSA on binding with genistein at lower molar ratios. Warfarin and ibuprofen displacement studies in accordance with the molecular docking show that genistein binds to site I (subdomain IIA) of BSA.

Acute genistein treatment mimics the effects of estradiol by enhancing place learning and impairing response learning in young adult female rats

Endogenous estrogens have bidirectional effects on learning and memory, enhancing or impairing cognition depending on many variables, including the task and the memory systems that are engaged. Moderate increases in estradiol enhance hippocampus-sensitive place learning, yet impair response learning that taps dorsal striatal function. This memory modulation likely occurs via activation of estrogen receptors, resulting in altered neural function. Supplements containing estrogenic compounds from plants are widely consumed despite limited information about their effects on brain function, including learning and memory. Phytoestrogens can enter the brain and signal through estrogen receptors to affect cognition. Enhancements in spatial memory and impairments in executive function have been found following treatment with soy phytoestrogens, but no tests of actions on striatum-sensitive tasks have been made to date. The present study compared the effects of acute exposure to the isoflavone genistein with the effects of estradiol on performance in place and response learning tasks. Long–Evans rats were ovariectomized, treated with 17β-estradiol benzoate, genistein-containing sucrose pellets, or vehicle (oil or plain sucrose pellets) for 2days prior to behavioral training. Compared to vehicle controls, estradiol treatment enhanced place learning at a low (4.5μg/kg) but not high dose (45μg/kg), indicating an inverted pattern of spatial memory facilitation. Treatment with 4.4mg of genistein over 2days also significantly enhanced place learning over vehicle controls. For the response task, treatment with estradiol impaired learning at both low and high doses; likewise, genistein treatment impaired response learning compared to rats receiving vehicle. Overall, genistein was found to mimic estradiol-induced shifts in place and response learning, facilitating hippocampus-sensitive learning and slowing striatum-sensitive learning. These results suggest signaling through estrogen receptor β and membrane-associated estrogen receptors in learning enhancements and impairments given the preferential binding of genistein to the ERβ subtype and affinity for GPER.

Genistein Binding Mode to Doubly Nicked Dumbbell DNA. Dynamic and Diffusion Ordered NMR Study

New genistein derivatives were synthesized, which are fairly well soluble in water, with respect to parent genistein, and thus facilitate study of the interaction with dumbbell DNA dodecamer, mimicking the biological target for topoisomerase II inhibitors. A pulsed field gradient spin echo NMR experiment was used to check the binding and to estimate the association constants and its pH dependence of genistein with dumbbell DNA. Experimental restraints based on nuclear Overhauser spectroscopy spectra were used to calculate the NMR structure in solution in case of 6,8-disubstituted genistein with dimethylaminomethyl groups and were used in molecular modeling calculations. The structure is dynamic, and 10 molecular dynamics runs yield a family of conformations that essentially differ in a depth of inclusion of genistein into a nick. The paper experimentally shows evidence for binding, intercalation in the nick is proposed as a mode of genistein binding, and a model of the event is provided.

The Covalent Binding of Genistein to the Non-prosthetic-heme-moiety of Bovine Lactoperoxidase Leads to Enzymatic Inactivation

Objective Genistein, a major soy isoflavone metabolite (SIF), inactivates oxidation activity of bovine lactoperoxidase (LPO). Modification of the heme moiety of LPO by nitrogen-containing compounds has been shown to inactivate LPO. In contrast, SIF mediated inactivation of LPO does not involve a heme modification and the mechanism of SIF inhibition is poorly understood. Methods After inactivation of LPO by genistein in the presence of H 2O 2, trypsin-digested LPO peptide fragments were collected and analyzed by MALDI-TOF-MS to characterize the chemical binding of genistein(s) to LPO. Results The heme moiety of LPO was not modified by genistein. A covalent binding study showed that 3H-genistein bound to LPO with a ratio of ∼12 to 1. After HPLC analysis and peak collection, trypsin-digested peptide fragments were analyzed by MALDI-TOF-MS. The 3H-genistein co-eluted peptide fragments (RT=24 min) were putatively identified as 199IVGYLDEEGVLDQNR214 with two bound genistein molecules or a genistein dimer (2 259 Da), 486TPDNIDIWIGGNAEPMVER504 with two bound genistein molecules or a genistein dimer (2 663 Da), and 161ARWLPAEYEDGLALPFGWTQR182 with three bound genistein molecules or a genistein trimer (3 060 Da). The fragment with a mass of 1 792 Da (RT=36 min) was identified as 132CDENSPYR139 with three genistein molecules or a genistein trimer. Conclusions The results suggest that LPO was inactivated by irreversible covalent binding of genistein or genistein polymers to particular peptide fragments constituting regions of the outward domain. No genistein interaction with the prosthetic heme moiety of LPO was observed.

Modulation of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Activity and Genistein Binding by Cytosolic pH

Potentiators are molecules that increase the activity of the cystic fibrosis transmembrane conductance regulator (CFTR). Some potentiators can also inhibit CFTR at higher concentrations. The activating binding site is thought to be located at the interface of the dimer formed by the two nucleotide-binding domains. We have hypothesized that if binding of potentiators involves titratable residues forming salt bridges, then modifications of cytosolic pH (pH(i)) would alter the binding affinity. Here, we analyzed the effect of pH(i) on CFTR activation and on the binding of genistein, a well known CFTR potentiator. We found that pH(i) does modify CFTR maximum current (I(m)) and half-activation concentration (K(d)): I(m) = 127.7, 185.5, and 231.8 μA/cm(2) and K(d) = 32.7, 56.6 and 71.9 μm at pH 6, 7.35, and 8, respectively. We also found that the genistein apparent dissociation constant for activation (K(a)) increased at alkaline pH(i), near cysteine pK (K(a) = 1.83, 1.81 and 4.99 μm at pH(i) 6, 7.35, and 8, respectively), suggesting the involvement of cysteines in the binding site. Mutations of cysteine residues predicted to be within (Cys-491) or outside (Cys-1344) the potentiator-binding site showed that Cys-491 is responsible for the sensitivity of potentiator binding to alkaline pH(i). Effects of pH(i) on inhibition by high genistein doses were also analyzed. Our results extend previous data about multiple effects of pH(i) on CFTR activity and demonstrate that binding of potentiators involves salt bridge formation with amino acids of nucleotide-binding domain 1.

Genistein, a competitive PDE1–4 inhibitor, may bind on high-affinity rolipram binding sites of brain cell membranes and then induce gastrointestinal adverse effects

The affinities of genistein on phosphodiesterase (PDE)1–4 and cause of gastrointestinal adverse effects of genistein remain unclear. Female BALB/c mice were actively sensitized by intraperitoneal injections of ovalbumin and challenged by aerosolized ovalbumin (1%). After secondary challenge, aerosolized methacholine (6.25–50 mg/ml) induced increases of enhanced pause (P enh) values in conscious mice in a concentration-dependent manner. Genistein (30–100 μmol/kg, i.p.) markedly inhibited methacholine (12.5–50 mg/ml)-induced increase of P enh value in the sensitized and challenged mice. In addition, genistein significantly reduced total inflammatory cells, macrophages, lymphocytes, neutrophils, and eosinophils in bronchoalveolar lavage fluid, with the exception that lymphocytes and neutrophils were not significantly inhibited by genistein at the lowest dose (10 μmol/kg). Genistein also markedly attenuated the release of cytokines, including interleukin (IL)-2, IL-4, IL-5, interferon (IFN)-γ and tumor necrosis factor (TNF)-α. Genistein competitively inhibited PDE1–4, with a K i value ranging from 4.3 to 13.7 μM. Genistein (3–300 μM) concentration-dependently displaced 2 nM [ 3H]-rolipram bound on high-affinity rolipram binding sites of brain cell membranes. The therapeutic ratio of genistein was calculated to be 7.9. Genistein (100 μmol/kg, s.c.) significantly shortened xylazine/ketamine-induced anesthesia, suggesting that genistein administered at a higher dose may have gastrointestinal adverse effects. In conclusion, owing to the low therapeutic ratio of genistein, the gastrointestinal adverse effects may be induced via the binding of genistein on high-affinity rolipram binding sites of brain cell membranes, when it is used for a long term or at higher doses for treating allergies, asthma or chronic obstructive pulmonary disease.

Synthesis, anticancer activity and docking of some substituted benzothiazoles as tyrosine kinase inhibitors

Protein tyrosine kinases occupy a central position in the control of cellular proliferation and its inactivation might lead to the discovery of a new generation anticancer compounds. Substituted benzothiazoles have been found to mimic the ATP-competitive binding of genistein and quercetin to tyrosine kinase. A series of novel 2-phenyl-1,3-benzothiazoles were synthesized and characterised by IR, 1H NMR and mass spectroscopy. All the compounds were tested for their anticancer activity against MCF-7 breast cancer cell line with the MTT assay. Most of the compounds showed moderate to good anti-breast cancer activity. Anticancer activity varied with substitution on the benzothiazole nucleus with halogens and at 4 position, substitution of the 2-phenyl moiety with methyl and methoxy groups was also explored. Among the compounds tested with MTT assay, mono fluoro substitution on benzothiazole nucleus and 4′-methyl variations at 2-phenyl position demonstrated highest percent growth inhibition of MCF-7 cells. Docking studies of the synthesised compounds was done on EGFR using GRIP batch docking method to study their observed activity.

Conformational differences between the wild type and V30M mutant transthyretin modulate its binding to genistein: Implications to tetramer stability and ligand-binding

Transthyretin (TTR) is a tetrameric beta-sheet-rich transporter protein directly involved in human amyloid diseases. It was recently found that the isoflavone genistein (GEN) potently inhibits TTR amyloid fibril formation (Green et al., 2005) and is therefore a promising candidate for TTR amyloidosis treatment. Here we used structural and biophysical approaches to characterize genistein binding to the wild type (TTRwt) and to its most frequent amyloidogenic variant, the V30M mutant. In a dose-dependent manner, genistein elicited considerable increases in both mutant and TTRwt stability as demonstrated by high hydrostatic pressure (HHP) and acid-mediated dissociation/denaturation assays. TTR:GEN crystal complexes and isothermal titration calorimetry (ITC) experiments showed that the binding mechanisms of genistein to the TTRwt and to V30M are different and are dependent on apoTTR structure conformations. Furthermore, we could also identify potential allosteric movements caused by genistein binding to the wild type TTR that explains, at least in part, the frequently observed negatively cooperative process between the two sites of TTRwt when binding ligands. These findings show that TTR mutants may present different ligand recognition and therefore are of value in ligand design for inhibiting TTR amyloidosis.

Genistein Arrests Cell Cycle Progression of A549 Cells at the G2/M Phase and Depolymerizes Interphase Microtubules through Binding to a Unique Site of Tubulin

Genistein (4',5,7-trihydroxyisoflavone), an isoflavone, is a major constituent of soyfoods. It has potential antiproliferative activity against several tumor types. We have examined the effect of genistein on cellular microtubules as well as its binding with purified tubulin in vitro. Cell viability experiments using human non-small lung epithelium carcinoma cells (A549) indicated that the IC(50) value for genistein is 72 microM. Flow cytometry experiments demonstrated that genistein arrested cell cycle progression at the G(2)/M phase, but mitotic index data showed that genistein did not arrest cell cycle progression at mitosis. Immunofluorescence studies using an anti-alpha-tubulin antibody demonstrated a significant depolymerization of the interphase microtubules in a dose-dependent manner, and this was confirmed by the Western blot experiment using genistein-treated A549 cells. In vitro polymerization of purified tubulin into microtubules was inhibited by genistein with an IC(50) value of 87 microM. Genistein binding to tubulin quenched protein tryptophan fluorescence in a time- and concentration-dependent manner. Binding of genistein to tubulin was slow, taking approximately 45 min for equilibration at 37 degrees C. The association rate constant was 104.64 +/- 20.63 M(-1) s(-1) at 37 degrees C. The stoichiometry of genistein binding to tubulin was nearly 1:1 (molar ratio) with a dissociation constant of 15 microM at 37 degrees C. It was interesting to note that genistein did not recognize either the colchicine site or the vinblastine binding site of tubulin. Surprisingly, genistein inhibited ANS binding and competed for its binding site of tubulin with a K(i) of 20 microM as determined from a modified Dixon plot. Hence, we conclude that one of the mechanisms of antiproliferative activity of genistein is depolymerization of microtubules through binding of tubulin.