Ternary oxovanadium(IV) complexes of ONO-donor Schiff base and polypyridyl derivatives as protein tyrosine phosphatase inhibitors: synthesis, characterization, and biological activities

Theoretical, antioxidant, antidiabetic and in silico molecular docking and pharmacokinetics studies of heteroleptic oxovanadium(IV) complexes of thiosemicarbazone-based ligands and diclofenac

A series of new heteroleptic oxovanadium(IV) complexes with the general formula [VOL1-6(Dcf)] (1-6), where L1-6 = thiosemicarbazone (TSC)-based ligands and Dcf = diclofenac have been synthesized and characterized. The spectral studies along with the density functional theory calculations evidenced the distorted square-pyramidal geometry around oxovanadium(IV) ion through imine nitrogen and thione sulfur atoms of TSC moiety, and two asymmetric carboxylate oxygen atoms of diclofenac drug. The complexes were evaluated for in vitro antioxidant activity using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2'-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide (H2O2) and superoxide radical scavenging assays with respect to the standard antioxidant drugs butylated hydroxyanisole (BHA) and rutin. The in vitro antidiabetic activity of the complexes was tested with enzymes such as α-amylase, α-glucosidase and glucose-6-phosphatase. The complexes containing methyl substituent showed higher activity than that containing the nitro substituent due to the electron-donating effect of methyl group. The in silico molecular docking studies of the oxovanadium(IV) complexes with α-amylase and α-glucosidase enzymes showed strong interaction via hydrogen bonding and hydrophobic interactions. The dynamic behavior of the proposed complexes was analyzed by molecular dynamics (MDs) simulations, which revealed the stability of docked structures with α-amylase and α-glucosidase enzymes. The in silico physicochemical and pharmacokinetics parameters, such as Lipinski's 'rule of five', Veber's rule and absorption, distribution, metabolism and excretion (ADME) properties predicted non-toxic, non-carcinogenic and safe oral administration of the synthesized complexes.Communicated by Ramaswamy H. Sarma.

Vanadium Complexes with Thioanilide Derivatives of Amino Acids: Inhibition of Human Phosphatases and Specificity in Various Cell Models of Metabolic Disturbances

In the text, the synthesis and characteristics of the novel ONS-type vanadium (V) complexes with thioanilide derivatives of amino acids are described. They showed the inhibition of human protein tyrosine phosphatases (PTP1B, LAR, SHP1, and SHP2) in the submicromolar range, as well as the inhibition of non-tyrosine phosphatases (CDC25A and PPA2) similar to bis(maltolato)oxidovanadium(IV) (BMOV). The ONS complexes increased [14C]-deoxy-D-glucose transport into C2C12 myocytes, and one of them, VC070, also enhanced this transport in 3T3-L1 adipocytes. These complexes inhibited gluconeogenesis in hepatocytes HepG2, but none of them decreased lipid accumulation in the non-alcoholic fatty liver disease model using the same cells. Compared to the tested ONO-type vanadium complexes with 5-bromosalicylaldehyde and substituted benzhydrazides as Schiff base ligand components, the ONS complexes revealed stronger inhibition of protein tyrosine phosphatases, but the ONO complexes showed greater activity in the cell models in general. Moreover, the majority of the active complexes from both groups showed better effects than VOSO4 and BMOV. Complexes from both groups activated AKT and ERK signaling pathways in hepatocytes to a comparable extent. One of the ONO complexes, VC068, showed activity in all of the above models, including also glucose utilizatiand ONO Complexes are Inhibitors ofon in the myocytes and glucose transport in insulin-resistant hepatocytes. The discussion section explicates the results within the wider scope of the knowledge about vanadium complexes.

Enzyme PTP-1B Inhibition Studies by Vanadium Metal Complexes: a Kinetic Approach

The medical field now needs more novel drugs to treat obesity and type-2 diabetes mellitus (T2D) than ever before. Obesity and T2D are both characterized by resistance to the hormones leptin and insulin. PTP-1B is a promising target for drug growth, as strong genetic, pharmacological, and biochemical evidence points to the possibility of treating diabetes and obesity by blocking the PTP-1B enzyme. Studies have also found that PTP-1B is overexpressed in patients with diabetes and obesity, suggesting that inhibiting PTP-1B may be a useful technique in their care. There are no clinically used PTP-1B inhibitors, despite the fact that numerous naturally occurring PTP-1B inhibitors have demonstrated great therapeutic promise. This is most likely due to their low activity or lack of selectivity. It is still important to look for more effective and focused PTP-1B inhibitors. A few organovanadium metal complexes were synthesized and characterized, and binding studies on vanadium complexes with PTP-B were also performed using fluorescence emission spectroscopy. Additionally, we theoretically (molecular modeling) and experimentally (enzyme kinetics) examined the PTP-1B inhibitory effects of these vanadium metal complexes and found that they have excellent PTP-1B inhibitory properties.

Synthesis, characterization, molecular docking and biological evaluation of Schiff Base derivatives of cefpodoxime

Synthesis of new Cefpodoxime derivatives via Schiff Bases mechanism and the efficiency of their antimicrobial and antiviral activities were addressed. They were analyzed for structural validation by using spectroscopic techniques using FTIR, ¹HNMR, and ¹³CNMR. Molecular docking against IBV Virus papain-like protease (PLPro) was done with Auto dock tools against compounds having excellent IC₅₀ values against IBV (Corona Class) virus. All derivatives showed strong zone of inhibition ranges from (55 ± 2.0 to 70 ± 0.8 mm) against E. coli. Compounds 1,2,4 and 6 derivatives showed remarkable activity against Stenotrophomonas maltophilia and Serratia marcescens. But For most the newly synthesized derivatives C¹ (64 ± 1.60), C³ (32 ± 0.80), and C⁸ (64 ± 1.60) showed potential IC₅₀ values against two variants of Corona class viruses i.e. Avian Influenza (H9) and Avian corona (IBV) viruses. The current study revealed that newly synthesized Schiff Bases possessed strong anti-viral potential. Further studies may make a breakthrough in medical sciences to tackle latest challenges such as Corona Virus Diseases.

Synthesis, In Vitro, and Computational Studies of PTP1B Phosphatase Inhibitors Based on Oxovanadium(IV) and Dioxovanadium(V) Complexes

One of the main goals of recent bioinorganic chemistry studies has been to design and synthesize novel substances to treat human diseases. The promising compounds are metal-based and metal ion binding components such as vanadium-based compounds. The potential anticancer action of vanadium-based compounds is one of area of investigation in this field. In this study, we present five oxovanadium(IV) and dioxovanadium(V) complexes as potential PTP1B inhibitors with anticancer activity against the MCF-7 breast cancer cell line, the triple negative MDA-MB-231 breast cancer cell line, and the human keratinocyte HaCaT cell line. We observed that all tested compounds were effective inhibitors of PTP1B, which correlates with anticancer activity. [VO(dipic)(dmbipy)]·2 H2O (Compound 4) and [VOO(dipic)](2-phepyH)·H2O (Compound 5) possessed the greatest inhibitory effect, with IC50 185.4 ± 9.8 and 167.2 ± 8.0 nM, respectively. To obtain a better understanding of the relationship between the structure of the examined compounds and their activity, we performed a computer simulation of their binding inside the active site of PTP1B. We observed a stronger binding of complexes containing dipicolinic acid with PTP1B. Based on our simulations, we suggested that the studied complexes exert their activity by stabilizing the WPD-loop in an open position and limiting access to the P-loop.

Interaction and Inhibition of a Ganoderma lucidum Proteoglycan on PTP1B Activity for Anti-diabetes

Protein tyrosine phosphatase 1B (PTP1B) is a key negative regulator of insulin and an effective target for the treatment of type 2 diabetes (T2D). A natural hyperbranched proteoglycan extracted from Ganoderma lucidum, namely, Fudan-Yueyang G. Lucidum (FYGL), was demonstrated capable of inhibiting the activity of PTP1B. Here, to identify the effective active components of FYGL, three different components, the polysaccharide FYGL-1, proteoglycans FYGL-2, and FYGL-3, were isolated from FYGL, and then, the protein moiety of FYGL-3 was further separated, namely, FYGL-3-P. Their abilities to enhance the glucose uptake in cells and inhibit the activity of PTP1B were compared. The inhibitory mechanisms were systematically explored by spectroscopic methods and MD simulations. The results showed that FYGL-3 and FYGL-3-P significantly enhanced the insulin-provoked glucose uptake in insulin-resistant HepG2 cells, detected by the glucose oxidase method. Also, the FYGL-3-P protein moiety in FYGL played an essential role in inhibiting the activity of PTP1B. A strong, enthalpy-driven, and multitargeted interaction by electrostatic forces between PTP1B and FYGL-3-P dramatically inhibited the catalytic activity of PTP1B. These results provided deep insights into the molecular mechanisms of FYGL inhibiting the activity of PTP1B and structurally helped researchers seek natural PTP1B inhibitors.

Synthesis, structure and in vitro biological properties of a new copper(II) complex with 4-{[3-(pyridin-2-yl)-1H-pyrazol-1-yl]methyl}benzoic acid

The new copper(II) complex dichloridobis(4-{[3-(pyridin-2-yl-κN)-1H-pyrazol-1-yl-κN²]methyl}benzoic acid)copper(II) methanol sesquisolvate hemihydrate, [CuCl₂L₂]·1.5CH₃OH·0.5H₂O, (1), has been synthesized from CuCl₂·2H₂O and the ligand 4-{[3-(pyridin-2-yl)-1H-pyrazol-1-yl]methyl}benzoic acid (L, C₁₅H₁₁N₃O₂). The complex was characterized by elemental analysis, Fourier transform IR spectroscopy, electrospray ionization mass spectrometry and single-crystal X-ray diffraction. Two chloride ligands and two bidentate L ligands coordinate the Cu^II centre in 1 in a Jahn-Teller-distorted octahedral geometry of rather unusual configuration: a chloride substituent and a pyrazole N atom of an N,N'-chelating ligand occupy the more distant axial positions. Classical O-H...O hydrogen bonds and O-H...Cl interactions link neighbouring complex molecules and cocrystallized methanol molecules into chains that propagate parallel to the b direction. The title compound shows intriguing bioactivity: the effects of 1 on the enzymatic activity of protein tyrosine phosphatase 1B (PTP1B) and on the viability of human breast cancer cells of cell line MCF7 were evaluated. Complex 1, with an IC₅₀ value of 0.51 µM, can efficiently inhibit PTP1B activity. An enzyme kinetic assay suggests that 1 inhibits PTP1B in a noncompetitive manner. A fluorescence titration assay indicates that 1 has a strong affinity for PTP1B, with a binding constant of 4.39 × 10⁶ M^-1. Complex 1 may also effectively decrease the viability of MCF7 cells in an extent comparable to that of cisplatin (IC₅₀ = 6.3 µM). The new copper complex therefore represents a promising PTP1B inhibitor and an efficient antiproliferation reagent against MCF7 cells.

Syntheses, crystal structures, and biological evaluations of new dinuclear platinum(ii) complexes with 1,2,4-triazole derivatives as bridging ligands

A series of new dinuclear platinum(ii) complexes with the general formula [Pt₂(μ-HL)₄] (1-4), where H₂L is 4-[(5-chloro-2-hydroxy-benzylidene)-amino]-3-R-1,2,4-triazole-5-thione: R = H (1), methyl (2), ethyl (3) and propyl (4), were synthesized and characterized. The X-ray crystal structures of 2, 3 and 4 reveal that the two platinum atoms form a paddlewheel core with four chelating triazole ligands as bridges, revealing a radically different structure than those of the traditional anticancer platinum(ii) complexes. These complexes show higher in vitro antiproliferative activity against human liver hepatocellular carcinoma (HepG2) and human breast adenocarcinoma (MCF7) than human lung cancer (A549) and human normal hepatocyte (HL-7702) cell lines. In particular, 3 exhibits antiproliferative activity (IC₅₀ = 5.5 μM) against HepG2 cells comparable to that of cisplatin. Different from the traditional anticancer platinum(ii) complexes with high DNA affinity, 3 binds very weakly to DNA. Upon comparison, it exhibits potent inhibiting activity against protein tyrosine phosphatases 1B (PTP1B, IC₅₀ = 16 μM) through possible binding to its active sites and its binding constant is 5.28 × 10⁴ M^-1. The results suggest that the antiproliferative mechanism of 3 against HepG2 cells may be different from that of cisplatin.

Schiff Bases of Pioglitazone Provide Better Antidiabetic and Potent Antioxidant Effect in a Streptozotocin-Nicotinamide-Induced Diabetic Rodent Model

Pioglitazone is a Food and Drug Administration-approved thiazolidinedione (TZD) derivative and peroxisome proliferator-activated receptor gamma (PPARγ) agonist and used for the treatment of diabetes mellitus (DM). However, this drug is still associated with many adverse effects. In the present study, four new Schiff bases of pioglitazone (P1-P4) were synthesized and characterized using FTIR, ¹HNMR, ¹³CNMR, mass spectrometry, and elemental analysis. For preliminary screening, the in vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and in vitro alpha-amylase antidiabetic inhibitory assay were performed. Further, P3 was used to investigate in vivo antioxidant and in vivo antidiabetic effects in a streptozotocin-nicotinamide-induced diabetic rat model. Diabetic rats were administered with an i.p dose of pioglitazone 10 mg/kg body weight for 21 days. Moreover, biochemical parameters and antioxidants were quantified from liver and kidney tissues of rodents. In the DPPH assay, compound P3 showed superior antioxidant effects. Using the in vitro α-amylase inhibitory assay, P3 exhibited potent effects as compared to other groups, that is, 93% inhibition, while pioglitazone showed 81% inhibition. Enzymatic and nonenzymatic antioxidants showed significant changes in P3 (10 mg/kg)-treated groups (p < 0.001). Similarly, compound P3 produced significant and better results in comparison to pioglitazone in the rodent model. This study confirmed potent antidiabetic and superior antioxidant potential of the newly synthesized Schiff base (P3), which could ultimately account for insulin sensitization and for cellular protection and hence provide a potential clue for dual therapeutics.

Exploring Serum Transferrin Regulation of Nonferric Metal Therapeutic Function and Toxicity

Serum transferrin (sTf) plays a pivotal role in regulating iron biodistribution and homeostasis within the body. The molecular details of sTf Fe(III) binding blood transport, and cellular delivery through transferrin receptor-mediated endocytosis are generally well-understood. Emerging interest exists in exploring sTf complexation of nonferric metals as it facilitates the therapeutic potential and toxicity of several of them. This review explores recent X-ray structural and physiologically relevant metal speciation studies to understand how sTf partakes in the bioactivity of key non-redox active hard Lewis acidic metals. It challenges preconceived notions of sTf structure function correlations that were based exclusively on the Fe(III) model by revealing distinct coordination modalities that nonferric metal ions can adopt and different modes of binding to metal-free and Fe(III)-bound sTf that can directly influence how they enter into cells and, ultimately, how they may impact human health. This knowledge informs on biomedical strategies to engineer sTf as a delivery vehicle for metal-based diagnostic and therapeutic agents in the cancer field. It is the intention of this work to open new avenues for characterizing the functionality and medical utility of nonferric-bound sTf and to expand the significance of this protein in the context of bioinorganic chemistry.

A Ce(iii) complex potently inhibits the activity and expression of tyrosine phosphatase SHP-2

Four new Ce(iii) complexes 1-4 with tridentate NNO-donor Schiff base ligands have been designed and successfully synthesized. These complexes were characterized by elemental analysis, IR, and ESI-MS, with formulas of [Ce(HL1)2(NO3)3]·2CH3OH (1), [Ce(L2)2(NO3)]·3H2O (2), [Ce(HL3)(L3)(NO3)Br]·H2O (3) and [Ce(L4)2(NO3)]·3H2O (4), in which ligands HL1-HL4 are respectively N'-[(1E)-pyridin-2-ylmethylidene]pyrazine-2-carbohydrazide (HL1), 2-(1-(salicyloylhydrazono)ethyl)pyrazine (HL2), N'-[(1E)-pyridin-2-ylmethylidene]pyridine-2-carbohydrazide (HL3) and 2-(1-(salicyloylhydrazono)ethyl) pyridine (HL4). X-ray single crystal diffraction analysis indicates that complex 1 crystallizes in the monoclinic system with the space group C2/c and the structure of complex 1 consists of a monomeric Ce(iii) species with a Ce(iii) moiety bonded to two tridentate Schiff base ligands, three nitrates and solvents. These complexes effectively inhibit the enzyme activities of PTPs (SHP-1, SHP-2, TCPTP and PTP1B), among which complex 3 shows the most potent inhibition of SHP-2 with the lowest IC50 value of 0.61 μM and displays obvious selectivity towards SHP-2. Its inhibition potency against SHP-2 was approximately 17, 4, and 5 fold higher than that against SHP-1, TCPTP and PTP1B, respectively. Further study discloses that complex 3 inhibits SHP-2 in a competitive manner. Fluorescence measurements indicate that complex 3 tightly binds to SHP-2 with a molar ratio of 1 : 1 and a binding constant of 5.45 × 105 M-1. Western blot experiments show that complex 3 promotes the phosphorylation of the SHP-2 substrate by the combination of the inhibition of the activity and expression of SHP-2. Moreover, complex 3 decreases the survival rate of A549 cells to 35.12% at 100 μM and induces apoptosis with an apoptosis rate of 12.06% at 50 μM. All these results suggest that complex 3 is a potential bi-functional inhibitor of the activity and expression of tyrosine phosphatase SHP-2.

PTP1b Inhibition, A Promising Approach for the Treatment of Diabetes Type II

BACKGROUND

Diabetes Mellitus (DM), is a metabolic disorder characterized by high blood glucose levels. The main types of diabetes mellitus are Diabetes mellitus type I, Diabetes mellitus type II, gestational diabetes and Diabetes of other etiology. Diabetes type II, the Non Insulin Dependent Type (NIDDM) is the most common type, characterized by the impairment in activation of the intracellular mechanism leading to the insertion and usage of glucose after interaction of insulin with its receptor, known as insulin resistance. Although, a number of drugs have been developed for the treatment of diabetes type II, their ability to reduce blood glucose levels is limited, while several side effects are also observed. Furthermore, none of the market drugs targets the enhancement of the action of the intracellular part of insulin receptor or recuperation of the glucose transport mechanism in GLUT4 dependent cells. The Protein Tyrosine Phosphatase (PTP1b) is the main enzyme involved in insulin receptor desensitization and has become a drug target for the treatment of Diabetes type II. Several PTP1b inhibitors have already been found, interacting with the binding site of the enzyme, surrounding the catalytic amino acid Cys215 and the neighboring area or with the allosteric site of the enzyme, placed at a distance of 20 Å from the active site, around Phe280. However, the research continues for finding more potent inhibitors with increased cell permeability and specificity.

OBJECTIVE

The aim of this review is to show the attempts made in developing of Protein Tyrosine Phosphatase (PTP1b) inhibitors with high potency, selectivity and bioavailability and to sum up the indications for favorable structural characteristics of effective PTP1b inhibitors.

METHODS

The methods used include a literature survey and the use of Protein Structure Databanks such as PuBMed Structure and RCSB and the tools they provide.

CONCLUSION

The research for finding PTP1b inhibitors started with the design of molecules mimicking the Tyrosine substrate of the enzyme. The study revealed that an aromatic ring connected to a polar group, which preferably enables hydrogen bond formation, is the minimum requirement for small inhibitors binding to the active site surrounding Cys215. Molecules bearing two hydrogen bond donor/acceptor (Hb d/a) groups at a distance of 8.5-11.5 Å may form more stable complexes, interacting simultaneously with a secondary area A2. Longer molecules with two Hb d/a groups at a distance of 17 Å or 19 Å may enable additional interactions with secondary sites (B and C) that confer stability as well as specificity. An aromatic ring linked to polar or Hb d/a moieties is also required for allosteric inhibitors. A lower distance between Hb d/a moieties, around 7.5 Å may favor allosteric interaction. Permanent inhibition of the enzyme by oxidation of the catalytic Cys215 has also been referred. Moreover, covalent modification of Cys121, placed near but not inside the catalytic pocket has been associated with permanent inhibition of the enzyme.

Identification of novel imidazole flavonoids as potent and selective inhibitors of protein tyrosine phosphatase

A series of imidazole flavonoids as new type of protein tyrosine phosphatase inhibitors were synthesized and characterized. Most of them gave potent protein phosphatase 1B (PTP1B) inhibitory activities. Especially, compound 11a could effectively inhibit PTP1B with an IC₅₀ value of 0.63 μM accompanied with high selectivity ratio (9.5-fold) over T-cell protein tyrosine phosphatase (TCPTP). This compound is cell permeable with relatively low cytotoxicity. The high binding affinity and selectivity was disclosed by molecular modeling and dynamics studies. The structural features essential for activity were confirmed by quantum chemical studies.

Synthesis, characterization, and cytotoxic and antimicrobial activities of mixed-ligand hydrazone complexes of variable valence VOz+ (z = 2, 3)

Mixed-ligand complexes of VO²⁺ and VO³⁺ motifs incorporating a family of hydrazone ligands were reported, which exhibited promising cytotoxic activity against lung cancer cell line and antimicrobial activity against four pathogenic bacterial stains.

Vanadyl as a Stable Structural Mimic of Reactive Ferryl Intermediates in Mononuclear Nonheme-Iron Enzymes

The iron(II)- and 2-(oxo)glutarate-dependent (Fe/2OG) oxygenases catalyze an array of challenging transformations via a common iron(IV)-oxo (ferryl) intermediate, which in most cases abstracts hydrogen (H•) from an aliphatic carbon of the substrate. Although it has been shown that the relative disposition of the Fe-O and C-H bonds can control the rate of H• abstraction and fate of the resultant substrate radical, there remains a paucity of structural information on the actual ferryl states, owing to their high reactivity. We demonstrate here that the stable vanadyl ion [(V^IV-oxo)²⁺] binds along with 2OG or its decarboxylation product, succinate, in the active site of two different Fe/2OG enzymes to faithfully mimic their transient ferryl states. Both ferryl and vanadyl complexes of the Fe/2OG halogenase, SyrB2, remain stably bound to its carrier protein substrate (l-aminoacyl-S-SyrB1), whereas the corresponding complexes harboring transition metals (Fe, Mn) in lower oxidation states dissociate. In the well-studied taurine:2OG dioxygenase (TauD), the disposition of the substrate C-H bond relative to the vanadyl ion defined by pulse electron paramagnetic resonance methods is consistent with the crystal structure of the reactant complex and computational models of the ferryl state. Vanadyl substitution may thus afford access to structural details of the key ferryl intermediates in this important enzyme class.

Synthesis and characterization of oxidovanadium complexes as enzyme inhibitors targeting dipeptidyl peptidase IV

Two oxidovanadium(IV) complexes carrying Schiff base ligands obtained from the condensation of 4,5-dichlorobenzene-1,2-diamine and salicylaldehyde derivatives were synthesised and characterised, including their X-ray crystallographic structures. They were evaluated as dipeptidyl peptidase IV (DPP-IV) inhibitors for the treatment of type 2 diabetes. These compounds were moderate inhibitors of DPP-IV, with IC₅₀ values of ca. 40μM. In vivo tests showed that complexes 1 and 2 could lower significantly the level of glucose in the blood of alloxan-diabetic mice at doses of 22.5mgV·kg^-1 and 29.6mgV·kg^-1, respectively. Moreover, molecular modeling studies suggested that the oxidovanadium complexes 1 and 2 could fit well into the active-site cleft of the kinase domain of DPP-IV. To the best of our knowledge, this is the first report of vanadium complexes capable of inhibiting DPP-IV.

A dioxidovanadium (V) complex of NNO-donor Schiff base as a selective inhibitor of protein tyrosine phosphatase 1B: Synthesis, characterization, and biological activities

A new dioxidovanadium (V) complex, VO₂(HPPCH) (1) (H₂PPCH = N'-picolinoylpyridin-1-ium-2-carbohydrazonate) has been synthesized and characterized by elemental analysis, IR, X-ray diffraction analysis and electrospray ionization mass spectra. Complex 1 crystallized in the monoclinic system with space group P2₁/c. It potently inhibited PTP1B with IC₅₀ of 0.13 μM, about 7, 15 and 125-fold stronger against PTP1B than over TCPTP, SHP-1 and SHP-2, displaying obvious selectivity against PTP1B. Western blotting analysis indicated that complex 1 effectively increased the phosphorylation of PTP1B substrates, especially the phosphorylation of IR/IGF 1R and IRS-1. It exhibited lower cytotoxicity than positive control VOSO₄. These results make complex 1 a promising candidate for novel anti-diabetic drug development.

Evaluation of cellular uptake, cytotoxicity and cellular ultrastructural effects of heteroleptic oxidovanadium(IV) complexes of salicylaldimines and polypyridyl ligands

Searching for prospective vanadium-based drugs for cancer treatment, a new series of structurally related [V^IVO(L-2H)(NN)] compounds (1-8) was developed. They include a double deprotonated salicylaldimine Schiff base ligand (L-2H) and different NN-polypyridyl co-ligands having DNA intercalating capacity. Compounds were characterized in solid state and in solution. EPR spectroscopy suggests that the NN ligands act as bidentate and bind through both nitrogen donor atoms in an axial-equatorial mode. The cytotoxicity was evaluated in human tumoral cells (ovarian A2780, breast MCF7, prostate PC3). The cytotoxic activity was dependent on type of cell and incubation time. At 24h PC3 cells presented low sensitivity, but at 72h all complexes showed high cytotoxic activity in all cells. Human kidney HEK293 and ovarian cisplatin resistant A2780cisR cells were also included to evaluate selectivity towards cancer cells and potency to overcome cisplatin resistance, respectively. Most complexes showed no detectable interaction with plasmid DNA, except 2 and 7 which depicted low ability to induce single strand breaks in supercoiled DNA. Based on the overall cytotoxic profile, complexes with 2,2´-bipyridine and 1,10-phenanthroline ligands (1 and 2) were selected for further studies, which consisted on cellular distribution and ultrastructural analyses. In the A2780 cells both depicted different distribution profiles; the former accumulates mostly at the membrane and the latter in the cytoskeleton. Morphology of treated cells showed nuclear atypia and membrane alterations, more severe for 1. Complexes induce different cell death pathways, predominantly necrosis for 1 and apoptosis for 2. Complexes alternative mode of cell death motivates the possibility for further developments.

Antimicrobial metal-based thiophene derived compounds

A novel series of thiophene derived Schiff bases and their transition metal- [Co(II), Cu(II), Zn(II), Ni(II)] based compounds are reported. The Schiff bases act as tridentate ligands toward metal ions via azomethine-N, deprotonated-N of ammine substituents and S-atom of thienyl moiety. The synthesized ligands along with their metal complexes were screened for their in vitro antibacterial activity against six bacterial pathogens (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus and Bacillus subtilis) and for antifungal activity against six fungal pathogens (Trichophytonlongifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata). The results of antimicrobial studies revealed the free ligands to possess potential activity which significantly increased upon chelation.

A Spectroscopy Approach for the Study of the Interaction of Oxovanadium(IV)-Salen Complexes with Proteins

Oxovanadium(IV)-salen complexes bind with bovine serum albumin (BSA) and ovalbumin (OVA) strongly with binding constant in the range 10(4)-10(7) M(-1) at physiological pH (7.4) confirmed using UV-visible absorption, fluorescence spectral and circular dichroism (CD) study. CD results show that the binding of oxovanadium(IV) complexes induces the conformational change with the loss of α-helicity in the proteins. Docking studies indicate that mode of binding of oxovanadium(IV)-salen complexes with proteins is hydrophobic in nature.

A novel one-dimensional chain built of vanadyl ions and pyrazine-2,5-dicarboxylate

Stand in line – a vanadium salt and a pyrazine ligand self-assemble to a linear coordination polymer.

Design, synthesis and pharmacological evaluation of novel vanadium-containing complexes as antidiabetic agents

Based on the data about structure and antidiabetic activity of twenty seven vanadium and zinc coordination complexes collected from literature we developed QSAR models using the GUSAR program. These QSAR models were applied to 10 novel vanadium coordination complexes designed in silico in order to predict their hypoglycemic action. The five most promising substances with predicted potent hypoglycemic action were selected for chemical synthesis and pharmacological evaluation. The selected coordination vanadium complexes were synthesized and tested in vitro and in vivo for their hypoglycemic activities and acute rat toxicity. Estimation of acute rat toxicity of these five vanadium complexes was performed using a freely available web-resource (http://way2drug.com/GUSAR/acutoxpredict.html). It has shown that the selected compounds belong to the class of moderate toxic pharmaceutical agents, according to the scale of Hodge and Sterner. Comparison with the predicted data has demonstrated a reasonable correspondence between the experimental and predicted values of hypoglycemic activity and toxicity. Bis{tert-butyl[amino(imino)methyl]carbamato}oxovanadium (IV) and sodium(2,2'-Bipyridyl)oxo-diperoxovanadate(V) octahydrate were identified as the most potent hypoglycemic agents among the synthesized compounds.

Protein tyrosine phosphatase inhibition by metals and metal complexes

SIGNIFICANCE

Protein tyrosine phosphatases (PTPs) play essential roles in controlling cell proliferation, differentiation, communication, and adhesion. The dysregulated activities of PTPs are involved in the pathogenesis of a number of human diseases such as cancer, diabetes, and autoimmune diseases.

RECENT ADVANCES

Many PTPs have emerged as potential new targets for novel drug discovery. PTP inhibitors have attracted much attention. Many PTP inhibitors have been developed. Some of them have been proven to be efficient in lowering blood glucose levels in vivo or inhibiting tumor xenograft growth.

CRITICAL ISSUES

Some metal ions and metal complexes potently inhibit PTPs. The metal atoms within metal complexes play an important role in PTP binding, while ligand structures influence the inhibitory potency and selectivity. Some metal complexes can penetrate the cell membrane and selectively bind to their targeting PTPs, enhancing the phosphorylation of the related substrates and influencing cellular metabolism. PTP inhibition is potentially involved in the pathophysiological and toxicological processes of metals and some PTPs may be cellular targets of certain metal-based therapeutic agents.

FUTURE DIRECTIONS

Investigating the structural basis of the interactions between metal complexes and PTPs would facilitate a comprehensive understanding of the structure-activity relationship and accelerate the development of promising metal-based drugs targeting specific PTPs.

Correlation of insulin-enhancing properties of vanadium-dipicolinate complexes in model membrane systems: phospholipid langmuir monolayers and AOT reverse micelles

We explore the interactions of V(III) -, V(IV) -, and V(V) -2,6-pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood-glucose-lowering effects of these compounds on STZ-induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2-ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self-assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the V(III) -phospholipid interactions result in a slight decrease in DPPC molecular area, whereas V(IV) and V(V) -phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of V(III) - and V(IV) -dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of V(IV) complexes in reverse micelles indicate that the neutral and smaller 1:1 V(IV) -dipic complex penetrates the interface, whereas the larger 1:2 V(IV) complex does not. UV/Vis spectroscopy studies of the anionic V(III) -dipic complex show only minor interactions. These results are in contrast to behavior of the V(V) -dipic complex, [VO2 (dipic)](-) , which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that V(III) -, V(IV) -, and V(V) -dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds' efficacy at lowering elevated blood glucose levels in diabetic rats.

2-[(E)-(4-Bromo-phenyl)imino-methyl]-4-chloro-phenol

In the title compound, C13H9BrClNO, the dihedral angle between the substituted benzene rings is 44.25 (11)°. There are strong intra-molecular O-H⋯N hydrogen bonds, which generate S(6) rings, and also inter-molecular Cl⋯Cl [3.431 (3) Å] and Br⋯ Br [3.846 (1) Å] contacts. The crystal packing a C-H⋯O and C-H⋯π inter-actions.

Raft localization of type I Fcε receptor and degranulation of RBL-2H3 cells exposed to decavanadate, a structural model for V2O5

Vanadium oxides (VOs) have been identified as low molecular weight sensitizing agents associated with occupational asthma and compromised pulmonary immunocompetence. Symptoms of adult onset asthma result, in part, from increased signal transduction by Type I Fcε receptors (FcεRI) leading to release of vasoactive compounds including histamine from mast cells. Exposure to (VOs) typically occurs in the form of particles which are insoluble. Upon contact with water or biological fluids, (VOs) form a series of soluble oxoanions, one of which is decavanadate, V10O28(6-) abbreviated V10, which is structurally related to a common vanadium oxide, that is vanadium pentoxide, V2O5. Here we investigate whether V10 may be initiating plasma membrane events associated with activation of FcεRI signal transduction. We show that exposure of RBL-2H3 cells to V10 causes a concentration-dependent increase in degranulation of RBL-2H3 and, in addition, an increase in plasma membrane lipid packing as measured by the fluorescent probe, di-4-ANEPPDHQ. V10 also increases FcεRI accumulation in low-density membrane fragments, i.e., lipid rafts, which may facilitate FcεRI signaling. To determine whether V10 effects on plasma membrane lipid packing were similarly observed in Langmuir monolayers formed from dipalmitoylphosphatidylcholine (DPPC), the extent of lipid packing in the presence and absence of V10 and vanadate was compared. V10 increased the surface area of DPPC Langmuir monolayers by 6% and vanadate decreased the surface area by 4%. These results are consistent with V10 interacting with this class of membrane lipids and altering DPPC packing.