Patient-Derived Blood-Brain Barrier Model for Screening Copper Bis(thiosemicarbazone) Complexes as Potential Therapeutics in Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent cause of dementia characterized by a progressive cognitive decline. Addressing neuroinflammation represents a promising therapeutic avenue to treat AD; however, the development of effective antineuroinflammatory compounds is often hindered by their limited blood-brain barrier (BBB) permeability. Consequently, there is an urgent need for accurate, preclinical AD patient-specific BBB models to facilitate the early identification of immunomodulatory drugs capable of efficiently crossing the human AD BBB. This study presents a unique approach to BBB drug permeability screening as it utilizes the familial AD patient-derived induced brain endothelial-like cell (iBEC)-based model, which exhibits increased disease relevance and serves as an improved BBB drug permeability assessment tool when compared to traditionally employed in vitro models. To demonstrate its utility as a small molecule drug candidate screening platform, we investigated the effects of diacetylbis(N(4)-methylthiosemicarbazonato)copper(II) (CuII(atsm)) and a library of metal bis(thiosemicarbazone) complexes─a class of compounds exhibiting antineuroinflammatory therapeutic potential in neurodegenerative disorders. By evaluating the toxicity, cellular accumulation, and permeability of those compounds in the AD patient-derived iBEC, we have identified 3,4-hexanedione bis(N(4)-methylthiosemicarbazonato)copper(II) (CuII(dtsm)) as a candidate with good transport across the AD BBB. Furthermore, we have developed a multiplex approach where AD patient-derived iBEC were combined with immune modulators TNFα and IFNγ to establish an in vitro model representing the characteristic neuroinflammatory phenotype at the patient's BBB. Here, we observed that treatment with CuII(dtsm) not only reduced the expression of proinflammatory cytokine genes but also reversed the detrimental effects of TNFα and IFNγ on the integrity and function of the AD iBEC monolayer. This suggests a novel pathway through which copper bis(thiosemicarbazone) complexes may exert neurotherapeutic effects on AD by mitigating BBB neuroinflammation and related BBB integrity impairment. Together, the presented model provides an effective and easily scalable in vitro BBB platform for screening AD drug candidates. Its improved translational potential makes it a valuable tool for advancing the development of metal-based compounds aimed at modulating neuroinflammation in AD.

Identification of (E)-1-((1H-indol-3-yl)methylene)-4-substitute-thiosemicarbazones as potential anti-hepatic fibrosis agents

Liver fibrosis remains a global health challenge due to its rapidly rising prevalence and limited treatment options. The orphan nuclear receptor Nur77 has been implicated in regulation of autophagy and liver fibrosis. Targeting Nur77-mediated autophagic flux may thus be a new promising strategy against hepatic fibrosis. In this study, we synthesized four types of Nur77-based thiourea derivatives to determine their anti-hepatic fibrosis activity. Among the synthesized thiourea derivatives, 9e was the most potent inhibitor of hepatic stellate cells (HSCs) proliferation and activation. This compound could directly bind to Nur77 and inhibit TGF-β1-induced α-SMA and COLA1 expression in a Nur77-dependent manner. In vivo, 9e significantly reduced CCl4-mediated hepatic inflammation response and extracellular matrix (ECM) production, revealing that 9e is capable of blocking the progression of hepatic fibrosis. Mechanistically, 9e induced Nur77 expression and enhanced autophagic flux by inhibiting the mTORC1 signaling pathway in vitro and in vivo. Thus, the Nur77-targeted lead 9e may serve as a promising candidate for treatment of chronic liver fibrosis.

Solvent-Induced Formation of Novel Ni(II) Complexes Derived from Bis-Thiosemicarbazone Ligand: An Insight from Experimental and Theoretical Investigations

In this work, we report solvent-induced complexation properties of a new N₂S₂ tetradentate bis-thiosemicarbazone ligand (H₂L^I), prepared by the condensation of 4-phenylthiosemicarbazide with bis-aldehyde, namely 2,2'-(ethane-1,2-diylbis(oxy)dibenzaldehyde, towards nickel(II). Using ethanol as a reaction medium allowed the isolation of a discrete mononuclear homoleptic complex [NiL^I] (1), for which its crystal structure contains three independent molecules, namely 1-I, 1-II, and 1-III, in the asymmetric unit. The doubly deprotonated ligand L^I in the structure of 1 is coordinated in a cis-manner through the azomethine nitrogen atoms and the thiocarbonyl sulfur atoms. The coordination geometry around metal centers in all the three crystallographically independent molecules of 1 is best described as the seesaw structure. Interestingly, using methanol as a reaction medium in the same synthesis allowed for the isolation of a discrete mononuclear homoleptic complex [Ni(L^II)₂] (2), where L^II is a monodeprotonated ligand 2-(2-(2-(2-(dimethoxymethyl)phenoxy)ethoxy)benzylidene)-N-phenylhydrazine-1-carbothioamide (HL^II). The ligand L^II was formed in situ from the reaction of L^I with methanol upon coordination to the metal center under synthetic conditions. In the structure of 2, two ligands L^II are coordinated in a trans-manner through the azomethine nitrogen atom and the thiocarbonyl sulfur atom, also yielding a seesaw coordination geometry around the metal center. The charge and energy decomposition scheme ETS-NOCV allows for the conclusion that both structures are stabilized by a bunch of London dispersion-driven intermolecular interactions, including predominantly N-H∙∙∙S and N-H∙∙∙O hydrogen bonds in 1 and 2, respectively; they are further augmented by less typical C-H∙∙∙X (where X = S, N, O, π), CH∙∙∙HC, π∙∙∙π stacking and the most striking, attractive long-range intermolecular C-H∙∙∙Ni preagostic interactions. The latter are found to be determined by both stabilizing Coulomb forces and an exchange-correlation contribution as revealed by the IQA energy decomposition scheme. Interestingly, the analogous long-range C-H∙∙∙S interactions are characterized by a repulsive Coulomb contribution and the prevailing attractive exchange-correlation constituent. The electron density of the delocalized bonds (EDDB) method shows that the nickel(II) atom shares only ~0.8|e| due to the σ-conjugation with the adjacent in-plane atoms, demonstrating a very weak σ-metalloaromatic character.

Cellular Uptake of the ATSM-Cu(II) Complex under Hypoxic Conditions

The Cu(II)-diacetyl-bis (N4-methylthiosemicarbazone) complex (ATSM-Cu(II)) has been suggested as a promising positron emission tomography (PET) agent for hypoxia imaging. Several in-vivo studies have shown its potential to detect hypoxic tumors. However, its uptake mechanism and its specificity to various cancer cell lines have been less studied. Herein, we tested ATSM-Cu(II) toxicity, uptake, and reduction, using four different cell types: (1) mouse breast cancer cells (DA-3), (2) human embryonic kidney cells (HEK-293), (3) breast cancer cells (MCF-7), and (4) cervical cancer cells (Hela) under normoxic and hypoxic conditions. We showed that ATSM-Cu(II) is toxic to breast cancer cells under normoxic and hypoxic conditions; however, it is not toxic to normal HEK-293 non-cancer cells. We showed that the Cu(I) content in breast cancer cell after treatment with ATSM-Cu(II) under hypoxic conditions is higher than in normal cells, despite that the uptake of ATSM-Cu(II) is a bit higher in normal cells than in breast cancer cells. This study suggests that the redox potential of ATSM-Cu(II) is higher in breast cancer cells than in normal cells; thus, its toxicity to cancer cells is increased.

Building up PtII -Thiosemicarbazone-Lysine-sC18 Conjugates

Three chiral tridentate N^N^S coordinating pyridine-carbaldehyde (S)-N4-(α-methylbenzyl)thiosemicarbazones (HTSCmB) were synthesised along with lysine-modified derivatives. One of them was selected and covalently conjugated to the cell-penetrating peptide sC18 by solid-phase peptide synthesis. The HTSCmB model ligands, the HTSCLp derivatives and the peptide conjugate rapidly and quantitatively form very stable PtII chlorido complexes [Pt(TSC)Cl] when treated with K2 PtCl4 in solution. The Pt(CN) derivatives were obtained from one TSCmB model complex and the peptide conjugate complex through Cl- →CN- exchange. Ligands and complexes were characterised by NMR, IR spectroscopy, HR-ESI-MS and single-crystal XRD. Intriguingly, no decrease in cell viability was observed when testing the biological activity of the lysine-tagged HdpyTSCLp, its sC18 conjugate HdpyTSCL-sC18 or the PtCl and Pt(CN) conjugate complexes in three different cell lines. Thus, given the facile and effective preparation of such Pt-TSC-peptide conjugates, these systems might pave the way for future use in late-stage labelling with Pt radionuclides and application in nuclear medicine.

Synthesis of Palladium(II) Complexes via Michael Addition: Antiproliferative Effects through ROS-Mediated Mitochondrial Apoptosis and Docking with SARS-CoV-2

Metal complexes have numerous applications in the current era, particularly in the field of pharmaceutical chemistry and catalysis. A novel synthetic approach for the same is always a beneficial addition to the literature. Henceforth, for the first time, we report the formation of three new Pd(II) complexes through the Michael addition pathway. Three chromone-based thiosemicarbazone ligands (SVSL1-SVSL3) and Pd(II) complexes (1-3) were synthesized and characterized by analytical and spectroscopic tools. The Michael addition pathway for the formation of complexes was confirmed by spectroscopic studies. Distorted square planar structure of complex 2 was confirmed by single-crystal X-ray diffraction. Complexes 1-3 were subjected to DNA- and BSA-binding studies. The complex with cyclohexyl substituent on the terminal N of thiosemicarbazone (3) showed the highest binding efficacy toward these biomolecules, which was further understood through molecular docking studies. The anticancer potential of these complexes was studied preliminarily by using MTT assay in cancer and normal cell lines along with the benchmark drugs (cisplatin, carboplatin, and gemcitabine). It was found that complex 3 was highly toxic toward MDA-MB-231 and AsPC-1 cancer cells with IC50 values of 0.5 and 0.9 μM, respectively, and was more efficient than the standard drugs. The programmed cell death mechanism of the complexes in MDA-MB-231 cancer cells was confirmed. Furthermore, the complexes induced apoptosis via ROS-mediated mitochondrial signaling pathway. Conveniently, all the complexes showed less toxicity (≥50 μM) against MCF-10a normal cell line. Molecular docking studies were performed with VEGFR2, EGFR, and SARS-CoV-2 main protease to illustrate the binding efficiency of the complexes with these receptors. To our surprise, binding potential of the complexes with SARS-CoV-2 main protease was higher than that with chloroquine and hydroxychloroquine.

Pyrazole Incorporated New Thiosemicarbazones: Design, Synthesis and Investigation of DPP-4 Inhibitory Effects

Dipeptidyl peptidase-4 (DPP-4) inhibition has been recognized as a promising approach to develop safe and potent antidiabetic agents for the management of type 2 diabetes. In this context, new thiosemicarbazones (2a-o) were prepared efficiently by the reaction of aromatic aldehydes with 4-[4-(1H-pyrazol-1-yl)phenyl]thiosemicarbazide (1), which was obtained via the reaction of 4-(1H-pyrazol-1-yl)phenyl isothiocyanate with hydrazine hydrate. Compounds 2a-o were evaluated for their DPP-4 inhibitory effects based on a convenient fluorescence-based assay. 4-[4-(1H-pyrazol-1-yl)phenyl]-1-(4-bromobenzylidene)thiosemicarbazide (2f) was identified as the most effective DPP-4 inhibitor in this series with an IC₅₀ value of 1.266 ± 0.264 nM when compared with sitagliptin (IC₅₀ = 4.380 ± 0.319 nM). MTT test was carried out to assess the cytotoxic effects of compounds 2a-o on NIH/3T3 mouse embryonic fibroblast (normal) cell line. According to cytotoxicity assay, compound 2f showed cytotoxicity towards NIH/3T3 cell line with an IC₅₀ value higher than 500 µM pointing out its favourable safety profile. Molecular docking studies indicated that compound 2f presented π-π interactions with Arg358 and Tyr666 via pyrazole scaffold and 4-bromophenyl substituent, respectively. Overall, in vitro and in silico studies put emphasis on that compound 2f attracts a great notice as a drug-like DPP-4 inhibitor for further antidiabetic research.

Expansion of Human Pluripotent Stem Cell-derived Early Cardiovascular Progenitor Cells by a Cocktail of Signaling Factors

Cardiovascular progenitor cells (CPCs) derived from human pluripotent stem cells (hPSCs) are proposed to be invaluable cell sources for experimental and clinical studies. This wide range of applications necessitates large-scale production of CPCs in an in vitro culture system, which enables both expansion and maintenance of these cells. In this study, we aimed to develop a defined and efficient culture medium that uses signaling factors for large-scale expansion of early CPCs, called cardiogenic mesodermal cells (CMCs), which were derived from hPSCs. Chemical screening resulted in a medium that contained a reproducible combination of three factors (A83-01, bFGF, and CHIR99021) that generated 1014 CMCs after 10 passages without the propensity for tumorigenicity. Expanded CMCs retained their gene expression pattern, chromosomal stability, and differentiation tendency through several passages and showed both the safety and possible cardio-protective potentials when transplanted into the infarcted rat myocardium. These CMCs were efficiently cryopreserved for an extended period of time. This culture medium could be used for both adherent and suspension culture conditions, for which the latter is required for large-scale CMC production. Taken together, hPSC-derived CMCs exhibited self-renewal capacity in our simple, reproducible, and defined medium. These cells might ultimately be potential, promising cell sources for cardiovascular studies.

Imaging of changes in copper trafficking and redistribution in a mouse model of Niemann-Pick C disease using positron emission tomography

Niemann-Pick C disease (NPC) is an autosomal recessive lysosomal storage disorder resulting from mutations in the NPC1 (95% of cases) or NPC2 genes. Disturbance of copper homeostasis has been reported in NPC1 disease. In this study we have used whole-body positron emission tomography (PET) and brain electronic autoradiography with copper-64 (64Cu), in the form of the copper(II) bis(thiosemicarbazonato) complex 64Cu-GTSM, to image short-term changes in copper trafficking after intravenous injection in a transgenic mouse model of NPC1 disease. 64Cu-GTSM is taken up in all tissues and dissociates rapidly inside cells, allowing monitoring of the subsequent efflux and redistribution of 64Cu from all tissues. Significantly enhanced retention of 64Cu radioactivity was observed in brain, lungs and blood at 15 h post-injection in symptomatic Npc1-/- transgenic mice compared to wildtype controls. The enhanced retention of 64Cu in brain was confirmed by electronic autoradiography, particularly in the midbrain, thalamus, medulla and pons regions. Positron emission tomography imaging with 64Cu in selected chemical forms could be a useful diagnostic and research tool for the management and understanding of NPC1 disease.

Copper complexes containing thiosemicarbazones derived from 6-nitropiperonal: Antimicrobial and biophysical properties

A series of four thiosemicarbazones from 6-nitropiperonal along with the corresponding copper complexes were synthesized. The biophysical characteristics of the complexes were investigated by the binding to DNA and human serum albumin. The binding to DNA is moderate; the binding constants run from (0.49-7.50)×10⁴M^-1. In relation to HSA, the complexes interact strongly with binding constants on the order of 10⁵M^-1. The complexes also display antioxidant behavior as determined by the ability to scavenge diphenylpicrylhydrazyl (dpph) and nitric oxide radicals. The antimicrobial profiles of the compounds, tested against a panel of microbes including five of the ESKAPE pathogens (Staphylococcus aureus, MRSA, Escherichia coli, Klebsiella pneumoniae, MDR, Acinetobacter baumannii, Pseudomonas aeruginosa) and two yeasts (Candida albicans and Cryptococcus neoformans var. grubii), are also described. The compounds contain a core moiety that is similar to oxolinic acid, a quinolone antibiotic that targets DNA gyrase and topoisomerase (IV). The binding interaction between the complexes and these important antibacterial targets were studied by computational methods, chiefly docking studies. The calculated dissociation constants for the interaction with DNA gyrase B (from Staphylococcus aureus) range from 4.32 to 24.65μM; the binding was much stronger to topoisomerase IV, with dissociation constants ranging from 0.37 to 1.27μM.

3-[(E)-(acridin-9'-ylmethylidene)amino]-1-substituted thioureas and their biological activity

This paper describes the synthesis of a novel series of acridine thiosemicarbazones through a two-step reaction between various isothiocyanates and hydrazine followed by treatment with acridin-9-carbaldehyde. The properties of this series of seven new derivatives are studied using NMR and biochemical techniques, and the DNA-binding properties of the compounds are determined using spectrophotometric studies (UV-vis absorption, fluorescence, and circular/linear dichroism) and viscometry. The binding constants K are estimated as being in the range of 2.2 to 7.8×10⁴M^-1 and the percentage of hypochromism was found to be 22.11-49.75% (from UV-vis spectral titration). Electrophoretic experiments prove that the novel compounds demonstrate moderate inhibitory effects against Topo I activity at a concentration of 60×10^-6M.

Association between hypoxic volume and underlying hypoxia-induced gene expression in oropharyngeal squamous cell carcinoma

BACKGROUND

Hypoxia imaging is a promising tool for targeted therapy but the links between imaging features and underlying molecular characteristics of the tumour have not been investigated. The aim of this study was to compare hypoxia biomarkers and gene expression in oropharyngeal squamous cell carcinoma (OPSCC) diagnostic biopsies with hypoxia imaged with 64Cu-ATSM PET/CT.

METHODS

64Cu-ATSM imaging, molecular and clinical data were obtained for 15 patients. Primary tumour SUVmax, tumour to muscle ratio (TMR) and hypoxic volume were tested for association with reported hypoxia gene signatures in diagnostic biopsies. A putative gene signature for hypoxia in OPSCCs (hypoxic volume-associated gene signature (HVS)) was derived.

RESULTS

Hypoxic volume was significantly associated with a reported hypoxia gene signature (rho=0.57, P=0.045), but SUVmax and TMR were not. Immunohistochemical staining with the hypoxia marker carbonic anhydrase 9 (CA9) was associated with a gene expression hypoxia response (rho=0.63, P=0.01). Sixteen genes were positively and five genes negatively associated with hypoxic volume (adjusted P<0.1; eight genes had adjusted P<0.05; HVS). This signature was associated with inferior 3-year progression-free survival (HR=1.5 (1.0-2.2), P=0.047) in an independent patient cohort.

CONCLUSIONS

64Cu-ATSM-defined hypoxic volume was associated with underlying hypoxia gene expression response. A 21-gene signature derived from hypoxic volume from patients with OPSCCs in our study may be linked to progression-free survival.

Letter to the Editor: "Analysis of the Interaction of Dp44mT with Human Serum Albumin and Calf Thymus DNA Using Molecular Docking and Spectroscopic Techniques"

n/a.

A Novel Diphenylthiosemicarbazide Is a Potential Insulin Secretagogue for Anti-Diabetic Agen

Insulin secretagogues are used for treatment of type 2 diabetes. We attempted to discover novel small molecules to stimulate insulin secretion by using in silico similarity search using sulfonylureas as query, followed by measurement of insulin secretion. Among 38 compounds selected by in silico similarity search, we found three diphenylsemicarbazides and one quinolone that stimulate insulin secretion. We focused on compound 8 (C8), which had the strongest insulin-secreting effect. Based on the structure-activity relationship of C8-derivatives, we identified diphenylthiosemicarbazide (DSC) 108 as the most potent secretagogue. DSC108 increased the intracellular Ca²⁺ level in MIN6-K8 cells. Competitive inhibition experiment and electrophysiological analysis revealed sulfonylurea receptor 1 (SUR1) to be the target of DSC108 and that this diphenylthiosemicarbazide directly inhibits ATP-sensitive K⁺ (K_ATP) channels. Pharmacokinetic analysis showed that DSC108 has a short half-life in vivo. Oral administration of DSC108 significantly suppressed the rises in blood glucose levels after glucose load in wild-type mice and improved glucose tolerance in the Goto-Kakizaki (GK) rat, a model of type 2 diabetes with impaired insulin secretion. Our data indicate that DSC108 is a novel insulin secretagogue, and is a lead compound for development of a new anti-diabetic agent.

Imaging of hypoxia in mouse atherosclerotic plaques with (64)Cu-ATSM

INTRODUCTION

Cardiovascular disease is the leading cause of death in the United States. The identification of vulnerable plaque at risk of rupture has been a major focus of research. Hypoxia has been identified as a potential factor in the formation of vulnerable plaque, and it is clear that decreased oxygen plays a role in the development of plaque angiogenesis leading to plaque destabilization. The purpose of this study is to demonstrate the feasibility of copper-64 labeled diacetyl-bis (N(4)-methylthiosemicarbazone) ((64)Cu-ATSM), a positron-emitting radiopharmaceutical taken up in low-oxygen-tension cells, for the identification of hypoxic and potentially unstable atherosclerotic plaque in a mouse model.

METHODS

(64)Cu-ATSM PET was performed in 21 atherosclerotic apolipoprotein E knockout (ApoE(-/-)) mice, 6 of which were fed high-fat diet (HFD) while the others received standard-chow diet (SCD), and 13 control wild type mice fed SCD. 4 SCD ApoE(-/-) mice and 4 SCD wild type mice also underwent (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) imaging one day prior to (64)Cu-ATSM PET.

RESULTS

(64)Cu-ATSM uptake was increased in the aortic arch in SCD ApoE(-/-) mice (average aortic arch/muscle (A/M) standardized uptake value ratio 7.5-30min post injection: (5.66±0.23) compared to control mice (A/M SUV ratio 7.5-30min post injection (3.87±0.22), p<0.0001). HFD ApoE(-/-) mice also showed similarly increased aortic arch uptake on PET imaging in comparison to control mice. Immunohistochemistry in both HFD and SCD ApoE(-/-) mice revealed noticeable hypoxia by pimonidazole stain in atherosclerosis which was co-localized to macrophage by CD68 staining. Autoradiography assessment demonstrated the presence of hypoxia by (64)Cu-ATSM uptake correlated with pimonidazole uptake within the ex vivo atherosclerotic aortic arch specimens. A significant increase in (18)F-FDG uptake in the SCD ApoE(-/-) mice in comparison to controls was also observed at delayed time points.

CONCLUSION

This pre-clinical study suggests that (64)Cu-ATSM is a potential PET tracer for hypoxia imaging in atherosclerosis.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

While studies in humans are necessary for conclusive data, in the long term, a (64)Cu-ATSM PET imaging strategy could help facilitate the study of plaque biology in human patients.

In Vitro Characterization of the Pharmacological Properties of the Anti-Cancer Chelator, Bp4eT, and Its Phase I Metabolites

Cancer cells have a high iron requirement and many experimental studies, as well as clinical trials, have demonstrated that iron chelators are potential anti-cancer agents. The ligand, 2-benzoylpyridine 4-ethyl-3-thiosemicarbazone (Bp4eT), demonstrates both potent anti-neoplastic and anti-retroviral properties. In this study, Bp4eT and its recently identified amidrazone and semicarbazone metabolites were examined and compared with respect to their anti-proliferative activity towards cancer cells (HL-60 human promyelocytic leukemia, MCF-7 human breast adenocarcinoma, HCT116 human colon carcinoma and A549 human lung adenocarcinoma), non-cancerous cells (H9c2 neonatal rat-derived cardiomyoblasts and 3T3 mouse embryo fibroblasts) and their interaction with intracellular iron pools. Bp4eT was demonstrated to be a highly potent and selective anti-neoplastic agent that induces S phase cell cycle arrest, mitochondrial depolarization and apoptosis in MCF-7 cells. Both semicarbazone and amidrazone metabolites showed at least a 300-fold decrease in cytotoxic activity than Bp4eT towards both cancer and normal cell lines. The metabolites also lost the ability to: (1) promote the redox cycling of iron; (2) bind and mobilize iron from labile intracellular pools; and (3) prevent ⁵⁹Fe uptake from ⁵⁹Fe-labeled transferrin by MCF-7 cells. Hence, this study demonstrates that the highly active ligand, Bp4eT, is metabolized to non-toxic and pharmacologically inactive analogs, which most likely contribute to its favorable pharmacological profile. These findings are important for the further development of this drug candidate and contribute to the understanding of the structure-activity relationships of these agents.

Donor-acceptor binding interaction of 1-(naphthalene-1-yl)-2,4,5-triphenyl-1H-imidazole with semiconductor nanomaterials

The dynamics of photoinduced electron injection from 1-(naphthalene-1-yl)-2,4,5-triphenyl-1H-imidazole (NTI) to pristine ZnO, Mn-doped TiO2 and BaTiO3 nanoparticles have been studied by absorption, fluorescence and lifetime spectroscopic methods. Both the absorption and fluorescence results suggest the association between the nanoparticles and NTI. The calculated free energy change (ΔGet) confirms the electron injection from NTI to nano semiconductors. The critical energy transfer distance between NTI and the nanoparticles have been deduced. The emission of NTI is enhanced by pristine ZnO and quenched by Mn-doped TiO2 and BaTiO3 nanoparticles which are likely due to change of LUMO and HOMO levels of NTI on its association with nano semiconductors. The strong adsorption of the NTI on the surface of ZnO nanocrystals is likely due to the chemical affinity of the nitrogen atom of the NTI to the zinc ion on the surface of nanocrystals. Electron injection from photoexcited NTI to the CB(S(∗)→S(+)+eCB(-)) is likely to be the reason for the fluorescence enhancement.

Comparison of intratumoral FDG and Cu-ATSM distributions in cancer tissue originated spheroid (CTOS) xenografts, a tumor model retaining the original tumor properties

INTRODUCTION

The intratumoral distributions of [(18)F]FDG and [(64)Cu]Cu-ATSM have been reported to be similar in adenocarcinomas but different in squamous cell carcinoma (SCC) in clinical studies. In the present study, we compared the intratumoral distributions of these two tracers in cancer tissue originated spheroid (CTOS) xenografts derived from adenocarcinoma and SCC, which retain the histological characteristics of the original tumors, and in cancer cell line xenografts of corresponding origin, to investigate the underlying mechanism of the distinct FDG and Cu-ATSM distribution patterns in adenocarcinoma and SCC.

METHODS

CTOSs derived from colon adenocarcinoma and lung SCC and cell lines established from colon adenocarcinoma and lung SCC, which were used for comparison, were subcutaneously transplanted into immunodeficient mice. One hour after administering [(14)C]FDG and [(64)Cu]Cu-ATSM, the intratumoral distributions were compared in the xenografts by using dual-tracer autoradiography. Adjacent sections were evaluated for necrosis, vasculature anatomy, Ki-67 antigen, and pimonidazole adducts using hematoxylin and eosin and immunohistochemical staining.

RESULTS

There was a higher regional overlap of high FDG and Cu-ATSM accumulations in the adenocarcinoma CTOS xenografts than in the SCC CTOS xenografts, while the overlap in the adenocarcinoma cell line xenograft was lower than that observed in the SCC cell line. High FDG accumulation occurred primarily in proximity to necrotic or pimonidazole adduct positive regions, while high Cu-ATSM accumulation occurred primarily in live cell regions separate from the necrotic regions. The adenocarcinoma CTOS xenograft had the stereotypical glandular structure, resulting in more intricately mixed regions of live and necrotic cells compared to those observed in the SCC CTOS or the cell line xenografts.

CONCLUSION

Tumor morphological characteristics, specifically the spatial distribution of live and necrotic cell regions, appeared to be one of the most critical factors determining the regional overlap of FDG and Cu-ATSM distributions in adenocarcinoma.

Cytotoxic behavior and spectroscopic characterization of metal complexes of ethylacetoacetate bis(thiosemicarbazone) ligand

Reaction of Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ion with 2,4-dihydrazino-thioamido-1-ethoxybutane led to the formation of mono and binuclear complexes. These complexes have been characterized by elemental analyses, IR, UV-Vis spectra, magnetic moments, molar conductances, (1)H NMR and mass spectra (ligand and its Zn(II) complex), thermal analyses (DTA and TGA) and ESR measurements. The IR data suggest the involvement of sulfur and azomethane nitrogen atoms in coordination to the central metal ion .The Molar conductances of the complexes in DMF are commensurate with their non-ionic character. The ESR spectra of Cu(II) complexes show axial type symmetry (d(x2-y2)) ground state with covalent bond character. On the basis of spectral studies, octahedral or tetrahedral geometry has been assigned to the metal complexes. Complexes have been tested invitro against tumor cells and number of microorganisms in order to assess their antitumor and antimicrobial properties.

Synthesis, spectral and electrochemical studies of binuclear Ru(III) complexes containing dithiosemicarbazone ligand

Synthesis of several new octahedral binuclear ruthenium(III) complexes of the general composition [(EPh3)2(X)Ru-L-Ru(X)(EPh3)2] containing benzene dithiosemicarbazone ligands (where E=P or As; X=Cl or Br; L=binucleating ligands) is presented. All the complexes have been fully characterized by elemental analysis, FT-IR, UV-vis and EPR spectroscopy together with magnetic susceptibility measurements. IR study shows that the dithiosemicarbazone ligands behave as dianionic tridentate ligands coordinating through the oxygen atom of the deprotonated phenolic group, nitrogen atom of the azomethine group and thiolate sulphur. In DMF solution, all the complexes exhibit intense d-d transition and ligand-to-metal charge transfer (LMCT) transition in the visible region. The magnetic moment values of the complexes are in the range 1.78-1.82 BM, which reveals the presence of one unpaired electron on each metal ion. The EPR spectra of the liquid samples at LNT show the presence of three different 'g' values (gx≠gy≠gz) indicate a rhombic distortion around the ruthenium ion. All the complexes exhibit two quasi-reversible one electron oxidation responses (Ru(III)-Ru(III)/Ru(III)-Ru(IV); Ru(III)-Ru(IV)/Ru(IV)-Ru(IV)) within the E1/2 range of 0.61-0.74 V and 0.93-0.98 V respectively, versus Ag/AgCl.

P-glycoprotein efflux pump plays an important role in Trypanosoma cruzi drug resistance

Drug resistance in protozoan parasites has been associated with the P-glycoprotein (Pgp), an energy-dependent efflux pump that transports substances across the membrane. Interestingly, the genes TcPGP1 and TcPGP2 have been described in Trypanosoma cruzi, although the function of these genes has not been fully elucidated. The main goal of this work was to investigate Pgp efflux pump activity and expression in T. cruzi lines submitted to in vitro induced resistance to the compounds 4-N-(2-methoxy styryl)-thiosemicarbazone (2-Meotio) and benznidazole (Bz) and to verify the stability of the resistant phenotypes during the parasite life cycle. We observed that the EC50 values for the treatment of epimastigotes with 2-Meotio or Bz were increased at least 4.7-fold in resistant lines, and this phenotype was maintained in metacyclic trypomastigotes, cell-derived trypomastigotes, and intracellular amastigotes. However, in epimastigotes, 2-Meotio resistance is reversible, but Bz resistance is irreversible. When compared with the parental line, the resistant lines exhibited higher Pgp efflux activity, reversion of the resistant phenotypes in the presence of Pgp inhibitors, cross-resistance with Pgp modulators, higher basal Pgp ATPase activity, and overexpression of the genes TcPGP1 and TcPGP2. In conclusion, the resistance induced in T. cruzi by the compounds 2-Meotio and Bz is maintained during the entire parasite life cycle. Furthermore, our data suggest the participation of the Pgp efflux pump in T. cruzi drug resistance.

Coordination behavior of ligand based on NNS and NNO donors with ruthenium(III) complexes and their catalytic and DNA interaction studies

Reactions of 2-acetylpyridine-thiosemicarbazone HL(1), 2-acetylpyridine-4-methyl-thiosemicarbazone HL(2), 2-acetylpyridine-4-phenyl-thiosemicarbazone HL(3) and 2-acetylpyridine-semicarbazone HL(4) with ruthenium(III) precursor complexes were studied and the products were characterized by analytical and spectral (FT-IR, electronic, EPR and EI-MS) methods. The ligands coordinated with the ruthenium(III) ion via pyridine nitrogen, azomethine nitrogen and thiolate sulfur/enolate oxygen. An octahedral geometry has been proposed for all the complexes based on the studies. All the complexes are redox active and display an irreversible and quasireversible metal centered redox processes. Further, the catalytic activity of the new complexes has been investigated for the transfer hydrogenation of ketones in the presence of isopropanol/KOH and the Kumada-Corriu coupling of aryl halides with aryl Grignard reagents. The DNA cleavage efficiency of new complexes has also been tested.

Synthesis, characterization, biological screenings and interaction with calf thymus DNA of a novel azomethine 3-((3,5-dimethylphenylimino)methyl)benzene-1,2-diol

The novel azomethine, 3-((3,5-dimethylphenylimino)methyl)benzene-1,2-diol (HL) was synthesized and characterized by elemental analysis, FT-IR, (1)H, (13)C NMR spectroscopy and single crystal analysis. The title compound has been screened for its biological activities including enzymatic study, antibacterial, antifungal, cytotoxicity, antioxidant and interaction with CTDNA, and showed remarkable activities in each area of research. The titled compound interacts with DNA via two binding modes: intercalation and groove binding. In intercalation the compound inserts itself into the base pairs of DNA and the compound-DNA complex is stabilized by π-π stacking. Interaction via groove binding may be due to hydrogen bonding to bases, typically to N3 of adenine and O2 of thymine. The synthesized compound was also found to be an effective antioxidant of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and gives percent inhibition (%I) of 90.7 at a concentration level of 31.3μg/mL.

Assessment of tumor hypoxia by 62Cu-ATSM PET/CT as a predictor of response in head and neck cancer: a pilot study

OBJECTIVE

In radiotherapy and chemotherapy tumor hypoxia is recognized as a major obstacle to effective treatment. We undertook a pilot study in patients with locally advanced head and neck cancer to determine whether there is a relationship between tumor uptake of (62)Cu-ATSM and response to chemoradiotherapy.

METHODS

Seventeen patients were studied using PET/CT with (62)Cu-ATSM and (18)F-FDG prior to the initiation of radiotherapy and chemotherapy. All patients had locally advanced head and neck cancer (stage III or IV). Tumor uptake in all patients was measured by region of interest analysis using the maximal standardized uptake value (SUVmax). A total dose of 50.4-70.2 Gy (median 70.2 Gy) was delivered in 29-39 fractions (median 39 fractions) to tumor. In patients with (non CR) and without (CR) residual/recurrent tumors at 2-year post irradiation, the statistical significance of the differences in tumor (62)Cu-ATSM SUVmax, T/M ratio, (18)F-FDG SUVmax and tumor volume were analyzed using Student's t test and Welch test. The relationship between clinical outcome and (62)Cu-ATSM/(18)F-FDG uptake patterns was analyzed using Kruskal-Wallis test. The correlation between SUVmax of (62)Cu-ATSM and (18)F-FDG was compared by Spearman's rank correlation test.

RESULTS

Two of the 17 patients that were enrolled in our study were excluded from the final analysis. Of the 15 remaining patients, 9 patients were free of disease and 6 patients had residual/recurrent tumors. The SUVmax differed significantly (p < 0.05) between patients with or without residual/recurrent tumor on (62)Cu-ATSM PET/CT. Six of the 10 patients with tumors SUVmax >5.00 had residual/recurrent tumor, whereas all of the 5 patients with tumors SUVmax <5.00 were free of disease. There was no significant difference in FDG uptake between patients with and without residual/recurrent tumor.

CONCLUSIONS

The results of this pilot study suggested that (62)Cu-ATSM uptake may be a predictive indicator of tumor response to chemoradiotherapy in patients with locally advanced head and neck cancer.

Synthesis and spectral feature of benzophenone-substituted thiosemicarbazones and their Ni(II) and Cu(II) complexes

The ligational behavior of 2-hydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone N-substituted thiosemicarbazones towards Ni(II) and Cu(II) ions has been investigated. The isolated complexes were identified by elemental analyses, molar conductance, magnetic moment, IR, UV-vis and ESR spectral studies. The IR spectra indicated that the investigated thiosemicarbazones lost the N(2) proton or the N(2) and OH protons and act as mononegative or binegative tridentate ligands. The ligands containing methoxy group facilitate the deprotonation of OH by resonance more than the SH. Most of the Ni(II) complexes measured subnormal magnetic moments due to square-planar+tetrahedral configuration and supported by the electronic spectra. The percentage of square-planar to tetrahedral was calculated and found in agreement with the ligand splitting energy (10Dq). Also, Cu(II) complexes measured subnormal values due to the interaction between copper centers; the lower the value the higher the interaction. It was found that the substitutent has a noticeable effect on the distortion of the complex. The ESR spectra of some solid Cu(II) complexes at room temperature exhibit g(parallel)>g( perpendicular)>2.0023 confirming a square-planar structure.

Fluorimetric detection of boron by azomethine-H in micellar solution and sol-gel

Mixtures of boron and azomethine-H in solution result in slow complexation. Addition of sodium dodecyl sulfate (SDS), polyethylene glycol dodecyl ether (Brij-35), 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (TritonX-100), and cetyltrimethyl ammonium bromide (CTAB) result in considerable decrease in complexation time and enhancement in signal of peak in solution and also sol-gel. The fluorescence of the complex is monitored at an emission wavelength of 486 nm with excitation at 416 nm. The presence of 1x10(-3) mol L(-1) SDS decreased the complexation time up to 10 min in solution and 20 min in sol-gel for above 0.25 microg B mL(-1) and 30 min in solution and 35 min in sol-gel for below 0.25 microg B mL(-1). However, the photostability did not change by adding micelle in both media. The proposed method shows a linear response toward boron in the concentration range of 0.05-10 microg mL(-1) and is selective for boron over a large number of electrolytes and cations. The detection limit was 7 microg L(-1). This method has been used for the detection of boron in environmental water samples and fruit juices with satisfactory results.

Synthesis, spectral characterization and eukaryotic DNA degradation of thiosemicarbazones and their platinum(IV) complexes

The condensation products of acetophenone (or its derivatives), salicylaldehyde and o-hydroxy-p-methoxybenzophenone with thiosemicarbazide and ethyl- or phenyl-thiosemicarbazide are the investigated thiosemicarbazones. Their reactions with H(2)PtCl(6) produced Pt(IV) complexes characterized by elemental, thermal, mass, IR and electronic spectral studies. The coordination modes were found mononegative bidentate in the acetophenone derivatives and binegative tridentate in the salicylaldehyde derivatives. The complexes were analyzed thermogravimetrically and found highly stable. Some ligands and their complexes were screened against Sarcina sp. and E. coli using the cup-diffusion technique. [Pt(oHAT)(OH)Cl] shows higher activity against E. coli than the other compounds. The degradation power of the tested compounds on the calf thymus DNA supports their selectivity against bacteria and not against the human or related eukaryotic organisms.

Chelators at the cancer coalface: desferrioxamine to Triapine and beyond

The importance of iron and copper in cancer biology has been well established. Iron plays a fundamental role in cellular proliferation and copper has been shown to be a significant cofactor for angiogenesis. Early observations with the chelator used for the treatment of iron overload, desferrioxamine, showed that it had promise as an anticancer agent. These results sparked great interest in the possibility of developing more effective iron chelators for cancer therapy. The recent entry into clinical trials of the iron-binding drug, Triapine, provides evidence of the potential of this antitumor strategy. Likewise, chelators originally designed to treat disorders of copper overload, such as penicillamine, trientine, and tetrathiomolybdate, have also emerged as potential anticancer drugs, as they are able to target the key angiogenic cofactor, copper. In this review, we will discuss the development of these and other chelators that show potential as anticancer agents.

Study on synthesis, structure, and DNA-binding of lanthanide complexes with 2-carboxylbenzaldehyde thiosemicarbazone

2-Carboxylbenzaldehyde thiosemicarbazone (HL), and its three lanthanide (III) complexes, LnL(3) x 4H(2)O [Ln(III)=La, Sm, Eu], have been synthesized in water. The complexes were characterized by elemental analyses, molar conductivity and IR spectra. The crystal structure of [Sm(2)L(6)(CH(3)OH)(4)] x 7.5CH(3)OH x 0.5H(2)O obtained from methanol solution was determined by X-ray diffraction analysis, crystallized in the triclinic system, space group P-1, Z=1, a=12.217 (2)A, b=14.706 (2)A, c=15.035 (2)A, alpha=111.84(1) degrees , beta=103.47(1) degrees , gamma=104.24(1) degrees , R(1)=0.0290. It has symmetrical (mu-OCO)(2), (mu-O)(2) and disamarium(III) units. The coordination geometry of each Sm(III) ion is a distorted tetradecahedron with nine oxygen atoms. In addition, the DNA-binding properties of the ligand and its complexes have been investigated by absorption, fluorescence, and viscosity measurements. The experimental results indicate that the ligand and the Sm-complex can bind to DNA, but the other two complexes cannot; the binding affinity of the Sm-complex is higher than that of the ligand and the intrinsic binding constant K(b) of the complex is 3.22 x 10(5)M(-1).

The synergistic interaction of gemcitabine and cytosine arabinoside with the ribonucleotide reductase inhibitor triapine is schedule dependent

Gemcitabine and ara-C have multiple mechanisms of action: DNA incorporation and for gemcitabine also ribonucleotide reductase (RNR) inhibition. Since dCTP competes with their incorporation into DNA, dCTP depletion can potentiate their cytotoxicity. We investigated whether additional RNR inhibition by Triapine (3-AP), a new potent RNR inhibitor, enhanced cytotoxicity of gemcitabine and ara-C in four non-small-cell-lung-cancer (NSCLC) cell lines, using the multiple-drug-effect analysis. Simultaneous and sequential exposure (preexposure to 3-AP for 24h) in a constant molar ratio of 3-AP and gemcitabine was antagonistic/additive in all cell lines. Preexposure to 3-AP at an IC(25) concentration for 24h before variable concentrations of gemcitabine was synergistic. RNR inhibition by 3-AP resulted in a more synergistic interaction in combination with ara-C, which does not inhibit RNR. Two cell lines with pronounced synergism (SW1573) or antagonism (H460) for gemcitabine/3-AP, were evaluated for accumulation of the active metabolites, dFdCTP and ara-CTP. Simultaneous exposure induced no or a small increase, but ara-CTP increased after pretreatment with 3-AP, 4-fold in SW1573 cells, but not in H460 (<1.5 fold). Ara-C and gemcitabine incorporation into DNA were more pronounced (about 2-fold increased) for sequential treatment in SW1573 compared to H460 cells (<1.5 fold). This was not related to the activity and expression of deoxycytidine kinase and the M2 subunit of RNR. In conclusion, RNR inhibition by 3-AP prior to gemcitabine or ara-C exposure stimulates accumulation of the active metabolites and incorporation into DNA. The combination 3-AP/Ara-C is more synergistic than 3-AP/gemcitabine possibly because gemcitabine already inhibits RNR, but ara-C does not.

Physical and spectroscopic studies on novel vanadyl complexes of some substituted thiosemicarbazides

Complexes of V(IV)O with N(4) ethyl and/or phenyl thiosemicarbazides have been prepared to study the role of substituents, on the two sides of thiosemicarbazide moiety, on the behavior of the complex formation. The study of ligands in solution reflected the dependence of their ionization values on the nature of the function groups neighboring the active sites. Two main (octahedral and square-pyramid) structures have been characterized for the solid complexes by the well known methods. There is some similarity between the structure and the color of the obtained complexes. Three modes of chelation were suggested for the investigated complexes. Complete disappearance of the nitrile group during the complex formation with cyano ligands is attributed to the promotion of water molecules to the cyano group. The intensity and position of the VO band in the IR spectra reflect not only the nature of the ligand but also the geometry of the complex formed. Some complexes were isolated as binuclear and confirmed by ESR spectra. The end product on thermal degradation of most complexes was VO(2).

Palladium(II) complexes of 2-benzoylpyridine-derived thiosemicarbazones: spectral characterization, structural studies and cytotoxic activity

Palladium(II) complexes of 2-benzoylpyridine thiosemicarbazone (H2Bz4DH) and its N4-methyl (H2Bz4M) and N4-phenyl (H2Bz4Ph) derivatives were obtained and fully characterized. [Pd(2Bz4DH)Cl] (1) crystallizes in the monoclinic space group P21/c with a=11.671(1), b=10.405(1), c=13.124(1), beta=115.60(1) degrees and Z=4; [Pd(2Bz4M)Cl] (2) in the monoclinic space group P21/c with a=9.695(1), b=15.044(1), c=10.718(1) A, beta=105.38(1) degrees and Z=4 and [Pd(2Bz4Ph)Cl] (3) in the triclinic space group P1 with a=9.389(1), b=13.629(1), c=15.218(1) A, alpha=70.25(1), beta=73.46(1), gamma=83.57(1) degrees and two independent molecules per asymmetric unit (Z=4). All complexes show a quite similar planar fourfold environment around palladium(II). A negatively charged organic molecule acts as a tridentate ligand and binds to the metal through the pyridine nitrogen, the imine nitrogen and the sulfur atom. A chloride ion occupies the fourth coordination site. The planar complexes stack nearly parallel to one another in the lattice conforming a layered crystal structure. The cytotoxic activity of the thiosemicarbazones and their metal complexes was tested against the MCF-7, TK-10 and UACC-62 human tumor cell lines. The ligands exhibit lower values of GI50 and LC50 than the complexes, H2Bz4Ph being the most active with GI50<0.003 microM; LC50=13.4 microM; GI50=9.3 microM, LC50=12.9 microM; GI50<0.003, LC50=13.8 microM in the MCF-7, TK-10 and UACC-62 cell lines, respectively. Among the complexes, [Pd(2Bz4Ph)Cl] (3) exhibited the lowest values of GI50 in the three studied cell lines.

A DFT investigation of conformational geometries and interconversion equilibria of phenylthiosemicarbazone and its complexation with zinc

The geometrical structures of phenylthiosemicarbazone (HAPhTSC) conformers have been obtained by geometry optimizations using density functional theory (DFT) calculations at the B3LYP/6-31G(d) and B3LYP/6-311G(d,p) levels of theory. Six thioamino and 24 thioimino tautomers of HAPhTSC have been found. Six tautomerization reactions between thioamino and thioimino tautomers occurring via transition states and their corresponding activation energies have been obtained. Conformational pathways for tautomerizations and interconversions of HAPhTSC conformers have been presented. Tautomerization between the most stable species of thioamino (Atttcc) and its thioimino (Itttcct) tautomer is an endothermic reaction, Delta H(0)=18.17 kcal mol(-1) and its log K=-13.74, at 298.15 K. Thermodynamic quantities of tautomerizations, interconversions of HAPhTSC conformers and their equilibrium constants are reported. The geometry of the zinc complex with HAPhTSC, found as a Zn(HAPhTSC)2Cl2 structure, has been obtained using B3LYP/6-31G(d) calculations. Binding of the Zn(HAPhTSC)2Cl2 complex is an exothermic and spontaneous reaction. [figure]. Conformational notation defined as a name consisting of a letter "A" for A thioamino tautomer followed by "c" for cis or "t" for trans isomerism of five dihedral angles of chi(C4-C3-C2-N3), phi(C3-C2-N3-N2), psi(C2-N3-N2-C1), theta;(N3-N2-C1-N1) and omega(N2-C1-N1-H2), serially, or a letter "I" for B thioimino tautomer followed by "c" for cis or "t" for trans isomerism of six dihedral angles of chi(C4-C3-C2-N3), phi(C3-C2-N3-N2), psi(C2-N3-N2-C1), theta(N3-N2-C1-N1), omega(N2-C1-N1-H2) and delta (N2-C1-S-H1), serially.

Spectrofluorimetric determination of both hydrogen peroxide and -O-O-H in polyethylene glycols (PEGs) using 2-hydroxy-1-naphthaldehyde thiosemicarbazon (HNT) as the substrate for horseradish peroxidase (HRP)

2-Hydroxy-1-naphthaldehyde thiosemicarbazon (HNT) had been synthesized and used as a new kind of substrate for horseradish peroxidase (HRP) in spectrofluorimetric determination of hydrogen peroxide (H(2)O(2)). The oxidation reaction of HNT with H(2)O(2) under the catalysis of HRP was studied in detail. The possible reaction mechanism was discussed. Under optimum experimental conditions, the oxidized product of HNT had excitation and emission maxima at 260 and 450 nm, respectively. The linear range of this method was 1.30 x 10(-9)-1.25 x 10(-5) mol l(-1) with a detection limit of 3.89 x 10(-10) mol l(-1). The effect of interferences, surfactants and organic solvents on the determination of H(2)O(2) had been investigated. A study to prove the existence of -O-O-H in PEGs was carried out. The proposed method was successfully applied to the determination of -O-O-H in polyethylene glycols.

Platinum(II) and palladium(II) complexes with 2-acetyl pyridine 4N-ethyl thiosemicarbazone able to overcome the cis-platin resistance. Structure, antibacterial activity and DNA strand breakage

The reactions of Pd(II) and Pt(II) with 2-Acetyl Pyridine N(4)-Ethyl-Thiosemicarbazones, HAc4Et and 2-Acetyl Pyridine N(4)-1-(2-pyridyl)-piperazinyl Thiosemicarbazone, HAc4PiPiz and 2-Formyl Pyridine N(4)-1-(2-pyridyl)-piperazinyl Thiosemicarbazone, HFo4PiPiz afforded the complexes, [Pd(Ac4Et)], 1, [Pd(HAc4Et)2]Cl2, 2 and [Pd(Ac4Et)2], 3 [Pt(Ac4Et)], 4, [Pt(HAc4Et)2]Cl2, 5, [Pt(Ac4Et)2], 6 and [Pd(Fo4PipePiz)Cl], 7, [Pd(Fo4PipePiz)2], 8, [Pd(Ac4PipePiz)Cl], 9 and [Pd(Ac4PipePiz)2], 10. The crystal structure of the complex [Pt(Ac4Et)2], 6 has been solved. The platinum(II) atom is in a square planar environment surrounded by two cis nitrogen atoms and two cis sulfur atoms. The ligands are not equivalent, one being tridentate with (N,N,S) donation, the other being monodentate using only the sulfur atom to coordinate to the metal. The tridentate ligand shows a Z, E, Z configuration while the monodentate ligand shows an E, E, Z. Inter-molecular hydrogen bonds stabilize the structure, while the crystal packing is determined by pi-pi, and Pt-C interactions. The antibacterial effect of Pd(II) and Pt(II) complexes were studied in vitro. The complexes were found to have effect on Gram(+) bacteria, while the same complexes showed no bactericidal effect on Gram(-) bacteria. The effect of the Pd(II) and Pt(II) complexes on the in vitro DNA strand breakage was studied by agarose gel electrophoresis. The complexes 1-6 were found to exhibit a cytotoxic potency in a very low micromolar range and to be able to overcome the cisplatin resistance of A2780/Cp8 cells.

Flexible docking of an acetoxyethoxymethyl derivative of thiosemicarbazone into three different species of dihydrofolate reductase

Dihydrofolate reductases (DHFR) of human, Candida albicans and E coli were docked with their original ligands of X-ray crystal complex using QXP (Quick eXPlore), a docking program. Conditions to reproduce the crystal structures within the root mean square deviation (rmsd) of 2.00 A were established. Applying these conditions, binding modes and species-specificities of a novel antibacterial compound, N4-(2-acetoxyethoxymethyl)-2-acetylpyridine thiosemicarbazone (AATSC), were studied. As the results, the docking program reproduced the crystal structures with average rmsd of six ligands as 0.91 A ranging from 0.49 to 1.45 A. The interactions including the numbers of hydrogen bonds and hydrophobic interactions were the same as the crystal structures and superposition of the crystal and docked structures almost coincided with each other. For AATSC, the results demonstrated that it could bind to either the substrate or coenzyme sites of DHFR in all three species with different degrees of affinity. It confirms the experimentally determined kinetic behavior of uncompetitive inhibition against either the inhibitor or the coenzyme. The docked AATSC overlapped well with the original ligands and major interactions were consistent with the ones in the crystal complexes. The information generated from this work should be useful for future development of antibacterial and antifungal agents.

Ex vivo cell labeling with 64Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) for imaging cell trafficking in mice with positron-emission tomography

We have used copper-64-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (64Cu-PTSM) to radiolabel cells ex vivo for in vivo positron-emission tomography (PET) imaging studies of cell trafficking in mice and for eventual application in patients. 2-[18F]-Fluoro-2-deoxy-d-glucose (FDG) cell labeling also was evaluated for comparison. 64Cu-PTSM uptake by C6 rat glioma (C6) cells increased for 180 min and then stabilized. The labeling efficiency was directly proportional to 64Cu-PTSM concentration and influenced negatively by serum. Label uptake per cell was greater with 64Cu-PTSM than with FDG. However, both 64Cu-PTSM- and FDG-labeled cells showed efflux of cell activity into supernatant. The 64Cu-PTSM labeling procedure did not interfere significantly with C6 cell viability and proliferation rate. MicroPET images of living mice indicate that tail-vein-injected labeled C6 cells traffic to the lungs and liver. In addition, transient splenic accumulation of radioactivity was clearly detectable in a mouse scanned at 3.33 h postinfusion of 64Cu-PTSM-labeled lymphocytes. In contrast, the liver was the principal organ of tracer localization after tail-vein administration of 64Cu-PTSM alone. These results indicate that in vivo imaging of cell trafficking is possible with 64Cu-PTSM-labeled cells. Given the longer t(1/2) of 64Cu (12.7 h) relative to 18F (110 min), longer cell-tracking periods (up to 24-36 h) should be possible now with PET.

Synthesis, cytotoxicity, and antitumor activity of copper(II) and iron(II) complexes of (4)N-azabicyclo[3.2.2]nonane thiosemicarbazones derived from acyl diazines

A series of thiosemicarbazones (TSCs) (bearing a (4)N-azabicyclo[3.2.2]nonane moiety) derived from 3-acylpyridazines, 4-acetylpyrimidines, and 2-acetylpyrazines (1-8) were synthesized as potential antitumor agents. TSCs 1-8 exhibited potent cytotoxic activity against human acute lymphoblastic leukemia CCRF-CEM cells (IC(50) = 0.05-0.77 microM) and colon adenocarcinoma HT-29 cells (IC(50) = 0.011-2.22 microM). Copper II complexes of TSCs 1-8 showed significant improvement in cytotoxic activity against HT-29 cells (IC(50) = 0.004-1.51 microM) by a factor of 3. However, complexation of ligands 1, 2, 4, and 6 with Fe(II) results in lowering of cytotoxic activity by a factor of approximately 7. In clonogenic assays involving human tumor cells of different tumor origins, compounds 5, 7, 8, and their copper complexes 5Cu(II), 7Cu(II), and 8Cu(II) exhibited remarkable cytotoxic activities with mean IC(50) values of 6, 0.18, 1, 1, 0.37, and 0.37 nM, respectively. In particular, the compounds were highly effective against human colon carcinoma and large and small cell lung carcinoma cells. The TSC derivative 5 was evaluated in vivo in nude mice bearing LXFL 529 human large cell lung carcinoma cells. With respect to antitumor activity, application of 30 mg/kg/d resulted in moderate inhibition (42%) of tumor growth. No effect on tumor growth was observed at a dose of 10 mg/kg/d. However, a dose of 40 or 60 mg/kg/d resulted in 50 and 75% death, respectively, in the treated mice, indicating the high toxicity of these compounds. Using human liver microsomes, compound 5 was found to be rapidly and highly metabolized in vitro. In actual fact, only 2% of the unmetabolized compound could be detected in the incubation medium after 5 min. The IC(50) for cell proliferation (0.006-0.022 microM) elicited by these compounds is much lower than that of the inhibition of [(14)C]cytidine incorporation into DNA (0.18-3.32 microM). These compounds are also noncell cycle specific agents. Interestingly, compounds 5, 5Cu(II), and 8 were found to be potent inducers of apoptosis in Burkitt's lymphoma cells.

Biological activity of complexes derived from pyridine-2-carbaldehyde thiosemicarbazone

Biological studies on [Fe(L)2](NO3).0.5H2O (1), [Fe(L)2][PF6] (2), [Co(L)2](NCS) (3), [Ni(HL)2]Cl2.3H2O (4) and Cu(L)(NO3) (5), where HL=C7H8N4S, pyridine-2-carbaldehyde thiosemicarbazone, have been carried out. The crystal structure of compound 3 has been solved. It consists of discrete monomeric cationic entities containing cobalt(III) ions in a distorted octahedral environment. The metal ion is bonded to one sulfur and two nitrogen atoms of each thiosemicarbazone molecule. The thiocyanate molecules act as counterions. The copper(II) and iron(III) complexes react with reduced glutathione and 2-mercaptoethanol. The reaction of compound 1 with the above thiols causes the reduction of the metal ion and bis(thiosemicarbazonato)iron(II) species are obtained. The redox activity, and in particular the reaction with cell thiols, seems to be related to the cytotoxicity of these complexes against Friend erithroleukemia cells and melanoma B16F10 cells.

The development of (99m)Tc-analog of Cu-DTS as an agent for imaging hypoxia

Works on dithiosemicarbazone (DTS) derivatives radiolabeled with divalent Cu (Cu-62, Cu-64) indicate its potentiality as an ischemic tissue detecting agent. Development of analogous derivatives labeled with the more accessible technetium-99m (Tc) is most desirable. Various synthesized DTS derivatives are radiolabeled with a novel approach, using a macromolecular Sn(II)-complex under an anaerobic condition at pH 3.4-4.5 and stabilization by ascorbate solution at pH 6.7-7.0. Characterization of Tc-DTS derivatives done by various analytical methods (TLC, HPLC, EP, PC) and by in vivo studies in normal mice and in rats myocardial LAD (left anterior descent coronary artery) occlusion model. Among tested DTS, only Tc-ATSE, Tc-ATSM and Tc-ATSM(2) showed distinctive characteristics, with the latter presenting high myocardium uptake in regions of ischemia in LAD rat myocardium model. Potentiality of the Cu-DTS mimetic agent, Tc-ATSM(2) as an ischemia-damaged myocardium agent is discussed.

Synthesis, crystal structure, spectral properties and cytotoxic activity of platinum(II) complexes of 2-acetyl pyridine and pyridine-2-carbaldehyde N(4)-ethyl-thiosemicarbazones

The reactions of Na2PtCl4 with pyridine-2-carbaldehyde and 2-acetyl pyridine N(4)-ethyl-thiosemicarbazones, HFo4Et and HAc4Et respectively, afforded the complexes [Pt(Fo4Et)Cl], [Pt(HFo4Et)2]Cl2, [Pt(Fo4Et)2] and [Pt(Ac4Et)Cl], [Pt(HAc4Et)2]Cl2 x 2H2O, [Pt(Ac4Et)2]. The new complexes have been characterized by elemental analyses and spectroscopic studies. The crystal structure of the complex [Pt(Ac4Et)Cl] has been solved. The anion of Ac4E coordinates in a planar conformation to the central platinum(II) through the pyridyl N, azomethine N and thiolato S atoms. Intermolecular hydrogen, non-hydrogen bonds, pi-pi and weak Pt-pi contacts lead to aggregation and a supramolecular assembly. The cytotoxic activity for the platinum(II) complexes in comparison to that of cisplatin and thiosemicarbazones was evaluated in a pair of cisplatin-sensitive and -resistant ovarian cancer cell lines A2780 and A2780/Cp8. The platinum(II) complexes showed a cytotoxic potency in a very low micromolar range and were found able to overcome the cisplatin resistance of A2780/Cp8 cells.

Bradyzide, a potent non-peptide B(2) bradykinin receptor antagonist with long-lasting oral activity in animal models of inflammatory hyperalgesia

Bradyzide is from a novel class of rodent-selective non-peptide B(2) bradykinin antagonists (1-(2-Nitrophenyl)thiosemicarbazides). Bradyzide has high affinity for the rodent B(2) receptor, displacing [(3)H]-bradykinin binding in NG108-15 cells and in Cos-7 cells expressing the rat receptor with K(I) values of 0.51+/-0.18 nM (n=3) and 0.89+/-0.27 nM (n=3), respectively. Bradyzide is a competitive antagonist, inhibiting B(2) receptor-induced (45)Ca efflux from NG108-15 cells with a pK(B) of 8.0+/-0.16 (n=5) and a Schild slope of 1.05. In the rat spinal cord and tail preparation, bradyzide inhibits bradykinin-induced ventral root depolarizations (IC(50) value; 1.6+/-0.05 nM (n=3)). Bradyzide is much less potent at the human than at the rodent B(2) receptor, displacing [(3)H]-bradykinin binding in human fibroblasts and in Cos-7 cells expressing the human B(2) receptor with K(I) values of 393+/-90 nM (n=3) and 772+/-144 nM (n=3), respectively. Bradyzide inhibits bradykinin-induced [(3)H]-inositol trisphosphate (IP(3)) formation with IC(50) values of 11.6+/-1.4 nM (n=3) at the rat and 2.4+/-0.3 microM (n=3) at the human receptor. Bradyzide does not interact with a range of other receptors, including human and rat B(1) bradykinin receptors. Bradyzide is orally available and blocks bradykinin-induced hypotension and plasma extravasation. Bradyzide shows long-lasting oral activity in rodent models of inflammatory hyperalgesia, reversing Freund's complete adjuvant (FCA)-induced mechanical hyperalgesia in the rat knee joint (ED(50), 0.84 micromol kg(-1); duration of action >4 h). It is equipotent with morphine and diclofenac, and 1000 times more potent than paracetamol, its maximal effect exceeding that of the non-steroidal anti-inflammatory drugs (NSAIDs). Bradyzide does not exhibit tolerance when administered over 6 days. In summary, bradyzide is a potent, orally active, antagonist of the B(2) bradykinin receptor, with selectivity for the rodent over the human receptor. British Journal of Pharmacology (2000) 129, 77 - 86

Synthesis and characterization of complexes of p-isopropyl benzaldehyde and methyl 2-pyridyl ketone thiosemicarbazones with Zn(II) and Cd(II) metallic centers. Cytotoxic activity and induction of apoptosis in Pam-ras cells

It is known that metallic complexes of methyl 2-pyridyl ketone thiosemicarbazone (HL1) and p-isopropyl benzaldehyde thiosemicarbazone (HL2) may have potential antitumor activity. We have prepared complexes of HL1 and HL2 with Zn(II) and Cd(II). The cytotoxic activity shown by these compounds against cell lines sensitive and resistant to cis-diamminedichloroplatinum(II) (cis-DDP) indicates that coupling of HL1 and HL2 to Zn(II) and Cd(II) centers may result in metallic complexes with important biological properties since they display IC50 values in a microM range similar to that of the antitumor drug cis-DDP. Moreover, it is interesting to note that the Zn/HL2 complex exhibits specific cytotoxic activity against Pam-ras cells (cis-DDP resistant cells which over-express the H-ras oncogene) with an in vitro therapeutic index of 3.26 versus 0.78 for cis-DDP. Treatment of Pam-ras cells with the IC50 value of the Zn/HL2 compound induces a 'DNA ladder' (fragmentation of genomic DNA in nucleosome units) indicative of apoptosis in this ras-transformed cell line. In contrast, a 'DNA smear' (non-specific fragmentation of genomic DNA) is observed in Pam 212 normal cells treated with the IC50 of this compound. The analysis by circular dichroism (CD) spectroscopy of the interaction of the Zn/HL2 compound with calf thymus DNA (CT DNA) indicates that it produces stronger alterations on the double helix conformation than cis-DDP. So, these results suggest that Zn/HL2 may be considered a potential antitumor agent.

Antiproliferative effects of melatonin and CGP 52608

The antiproliferative effects of melatonin and CGP 52608, an exogenous ligand for RZR/ROR receptors, are compared in the present paper. Both compounds exerted similar inhibitory effects on the proliferation of neoplastic cells in mouse colonic adenocarcinoma, DU 145 human prostate cancer, MCF-7 human breast carcinoma, and rat diethylstilbestrol-induced prolactinoma. Although it has been suggested that melatonin may influence the proliferation of tumor cells via RZR/ROR receptors, it cannot be excluded that the antiproliferative effects of melatonin and CGP 52608 are unrelated and mediated by different intracellular mechanisms.

An early stage mechanism of the age-associated mitochondrial dysfunction in the brain of SAMP8 mice; an age-associated neurodegeneration animal model

In order to characterize the early stage of mitochondrial dysfunction, we investigated the redox state and oxidative phosphorylation of the brain mitochondria from 2-month-old Senescence-accelerated mouse (SAM)P8 and SAMR1 mice; SAMP8 mice exhibit various signs of age-associated neurodegeneration and rapid mitochondrial dysfunction, although SAMR1 mice do not. The redox state was estimated as the reduction rate of Cu-pyruvaldehyde-bis (N4-methylthiosemicarbazone) (Cu-PTSM), the reduction of which is closely related to the electron leakage from the mitochondrial electron transport system in the brain, using electron spin resonance spectrometry (ESRS). The oxidative phosphorylation was measured polarographically. The SAMP8 mouse brain mitochondria demonstrated higher redox state and a higher activity of mitochondrial respiration with lower respiration control ratio than the mitochondria of SAMR1 mouse brains. This indicates that an inefficient hyperactive state can exist in the mitochondrial electron transport system before the age-associated mitochondrial dysfunction develops.

Novel tetranuclear orthometalated complexes of Pd(II) and Pt(II) derived from p-isopropylbenzaldehyde thiosemicarbazone with cytotoxic activity in cis-DDP resistant tumor cell lines. Interaction of these complexes with DNA

The reaction of p-isopropylbenzaldehyde thiosemicarbazone [p-is.TSCN], 1, with palladium(II) acetate and potassium tetrachloroplatinate yielded two tetrameric orthopalladated isomers, [Pd(p-is.TSCN)]4 (complexes 2 and 3), and the platinum analogue [Pt(p-is.TSCN)]4 (complex 4), respectively. All of these complexes contain the thiosemicarbazone bonded as a terdentate ligand to the metallic atom, through the thiol sulfur, the azomethinic nitrogen and the ortho carbon of the p-isopropylphenyl ring to which the imine group is attached to as deduced from the study of the IR, NMR, and XRD spectra of complexes 2 and 4. Complexes 2 and 4 crystallize in the centrosymmetric monoclinic space group C2/c, with Z = 8. Unit cell parameters for complex 2 are as follows: a = 25.742(5) A, b = 19.560(4) A, c = 24.199(5) A, beta = 101.70(3)o. Unit cell parameters for complex 4 are as follows: a = 25.8728(19) A, b = 19. 5053(14) A, c = 24.0899(16) A, beta = 101.305(2)o. As can be deduced from the NMR study, the palladated isomers 2 and 3 interconvert in DMSO which may be a consequence of the existence in both complexes of a flexible eight-membered ring with alternating Pd-S atoms. The testing of the cytotoxic activity of these compounds against several human and murine cell lines sensitive and resistant to cisplatin (cis-DDP) suggests that compounds 2, 3, and 4 may be endowed with important anticancer properties since they elicit IC50 values in the microM range as does the clinically used drug cis-DDP, and, moreover, they display cytotoxic activity in tumor lines resistant to cis-DDP. The analysis of the interaction of these novel tetrameric cyclometalated compounds with DNA suggests that they form DNA interhelical cross-links.

Equilibrium and kinetic studies of iron(II) and iron(III) complexes of some alpha (N)-heterocyclic thiosemicarbazones. Reduction of the iron(III) complexes of 2-formylpyridine thiosemicarbazone and 2-acetylpyridine thiosemicarbazone by cellular thiol-like reducing agents

alpha (N)-heterocyclic thiosemicarbazones have been shown to possess antitumor properties in mammalian cells through the inhibition of DNA synthesis; the ability to provide the inhibitory action is probably due to coordination of iron. This paper deals with equilibrium and kinetic studies involving 2-formylpyridine thiosemicarbazone (HFPT) and 2-acetylpyridine thiosemicarbazone (HAPT) coordinated to Fe(II) and Fe(III) cations in aqueous solution. The formation constants of all species present in equilibrium were determined. Kinetic measurements of the reduction of the Fe(III) complex of both ligands by thiolic reducing agents, that can act as structural models of cellular thiols, i.e., N-acetyl-L-cysteine (ACCIS) and dithiothreitol (DTT), were carried out. The experimental data lead to a rate law of the type v = k1[A] + k2[A] [B], where [A] represents the concentration of the complex and [B] that of the reducing agent, indicating the coexistence of two reaction pathways. One pathway depends only on the complex concentration and occurs even in the absence of the reducing agent, and the other involves both the complex and ACCIS or DTT.