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OBJECTIVE: Recently, we reported increased cardiovascular disease mortality among supplemental vitamin C users with type 2 diabetes in a prospective cohort study. Because vitamin C may cause oxidative stress in the presence of redox active iron, we hypothesized that non-transferrin-bound iron (NTBI), a form of iron susceptible to redox activity, may be present in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: We measured serum NTBI levels using high-performance liquid chromatography in 48 patients with known diabetes (at least 5 years duration since diagnosis), 49 patients with newly diagnosed diabetes, and 47 healthy control subjects (frequency matched on age and sex). RESULTS: NTBI was commonly present in diabetes: 59% in newly diagnosed diabetes and 92% in advanced diabetes. Mean NTBI values varied significantly between the three groups, with the highest values being observed in patients with known diabetes and the lowest in the control subjects (0.62 +/- 0.43 vs. 0.24 +/- 0.29 vs. 0.04 +/- 0.13 micromol/l Fe). Serum total iron or percent transferrin saturation were very similar among the three groups, yet NTBI was strongly associated with serum total iron (r = 0.74, P < 0.01) and percent transferrin saturation (r = 0.70, P < 0.01) among the patients with known diabetes. CONCLUSIONS: Consistent with our hypothesis, these data demonstrate the common existence of NTBI in type 2 diabetic patients with a strong gradient with severity. Prospective cohort studies are required to clarify the clinical relevance of increased NTBI levels. [ABSTRACT FROM AUTHOR]

In vitro screening of gallium-68( 68 Ga)-siderophores in pathogens relevant to infections is valuable for determining species specificity, their effect on cell viability, and potential clinical applications. As the recognition and internalization of siderophores relies on the presence of receptor- and/or siderophore-binding proteins, the level of uptake can vary between species. Here, we report in vitro uptake validation in Escherichia coli with its native siderophore, enterobactin (ENT) ([ 68 Ga]Ga-ENT), considering different experimental factors. Compared with other reporting methods of uptake, '% Added dose/10 9 CFU/mL (% AD/10 9 CFU/mL),' considering the total viable count, showed a better comparison among microbial species. Later, in vitro screening with [ 68 Ga]Ga-desferrioxamine B (DFO-B) showed high uptake by Staphylococcus aureus and S. epidermidis; moderate uptake by Pseudomonas aeruginosa; poor uptake by E. coli, Candida albicans, and Aspergillus fumigatus; and no uptake by Enterococcus faecalis and C. glabrata. Except for S. epidermidis, [ 68 Ga]Ga-DFO-B did not reduce the cell viability., Competing Interests: Declaration of competing interest There are no competing interests from any authors., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Gallium-68-labeled siderophores as radiotracers have gained interest for the development of in situ infection-specific imaging diagnostics. Here, we report radiolabeling, in vitro screening, and in vivo pharmacokinetics (PK) of gallium-68-labeled schizokinen ([ 68 Ga]Ga-SKN) as a new potential radiotracer for imaging bacterial infections. We radiolabeled SKN with ≥95% radiochemical purity. Our in vitro studies demonstrated its hydrophilic characteristics, neutral pH stability, and short-term stability in human serum and toward transchelation. In vitro uptake of [ 68 Ga]Ga-SKN by Escherichia coli , Pseudomonas aeruginosa , Staphylococcus aureus , and S. epidermidis , but no uptake by Candida glabrata , C. albicans , or Aspergillus fumigatus , demonstrated its specificity to bacterial species. Whole-body [ 68 Ga]Ga-SKN positron emission tomography (PET) combined with computerized tomography (CT) in healthy mice showed rapid renal excretion with no or minimal organ uptake. The subsequent ex vivo biodistribution resembled this fast PK with rapid renal excretion with minimal blood retention and no major organ uptake and showed some dissociation of the tracer in the urine after 60 min postinjection. These findings warrant further evaluation of [ 68 Ga]Ga-SKN as a bacteria-specific radiotracer for infection imaging.

The iron(III) binding properties of citrate and rhizoferrin, a citrate containing siderophore, are compared. Citrate forms many oligonuclear complexes, whereas rhizoferrin forms a single mononuclear complex. The α-hydroxycarboxylate functional group, which is present in both citrate, and rhizoferrin, has a high affinity and selectivity for iron(III) under most biological conditions. The nature of the toxic form of iron found in the blood of patients suffering from many haemoglobinopathies and haemochromatosis is identified as a mixture of iron(III)citrate complexes. The significance of the presence of this iron pool to patients suffering from systemic iron overload is discussed. The wide utilisation of the α-hydroxycarboxylate functional group in siderophore structures is described, as is their photo-induced decarboxylation leading to the release of iron(II) ions. The importance of this facile dissociation to algal iron uptake is discussed., (© 2024. The Author(s).)

The chemical nature of intracellular labile iron pools (LIPs) is described. By virtue of the kinetic lability of these pools, it is suggested that the isolation of such species by chromatography methods will not be possible, but rather mass spectrometric techniques should be adopted. Iron-sensitive fluorescent probes, which have been developed for the detection and quantification of LIP, are described, including those specifically designed to monitor cytosolic, mitochondrial, and lysosomal LIPs. The potential of near-infrared (NIR) probes for in vivo monitoring of LIP is discussed.

An aromatic substrate for hydroxylation by hydroxyl radicals ( • OH) was investigated. The probe, N,N '-(5-nitro-1,3-phenylene)- bis -glutaramide, and its hydroxylated product do not bind either iron(III) or iron(II), and so they do not interfere with the Fenton reaction. A spectrophotometric assay based on the hydroxylation of the substrate was developed. The synthesis and purification methods of this probe from previously published methodologies were improved upon, as well as the analytical procedure for monitoring the Fenton reaction through its use, enabling univocal and sensitive • OH detection. The assay was utilised to demonstrate that the iron(III) complexes of long-chain fatty acids lack Fenton activity under biological conditions.

Tumour-targeted near-infrared (NIR) optical imaging is an emerging tool for the detection of malignant tissues. This modality can be useful in both diagnosis and intraoperative visualisation, to help defining tumour margins and allow a more precise removal of all the cancerous mass during surgery. In this context, we have developed a series of NIR fluorescent probes that target the prostate-specific membrane antigen (PSMA), an established biomarker overexpressed in prostate cancer. Four new NIR imaging agents were prepared by conjugating the well-known urea-based PSMA targeting module to the NIR fluorophore Cy7.5, with linkers of 7, 10, 17 and 24 atoms. The affinity of each probe for PSMA was assessed through competitive binding and IC 50 measurement in prostate cancer cells, using a previously reported PSMA-targeted NIR probe (i.e. PSMA-IRDye800CW) as reference. The NIR probe PSMA-Cy7.5&#95;2 demonstrated a high affinity for PSMA (i.e. IC 50 = 58.8 nM) and was further studied in mouse xenograft models of prostate cancer, to assess its ability to image PSMA positive tumour tissues. While PSMA-Cy7.5&#95;2 out-performed PSMA-IRDye800CW in vitro, its tumour accumulation in vivo was not as evident. Further micellar aggregation studies indicated that the relatively higher hydrophobic property of PSMA-Cy7.5&#95;2 may lower its bioavailability and tissue distribution following systemic injection, limiting its ability of targeting PSMA tumour in vivo. Nevertheless, the excellent binding capability of PSMA-Cy7.5&#95;2 renders this probe a valid lead for further structural optimisation to develop imaging analogues with high affinity and specificity for PSMA, as required for effective NIR fluorescence-guided applications pre-clinically and clinically., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Expression of the cellular transmembrane receptor αvβ6 integrin is mostly restricted to malignant epithelial cells in a wide variety of carcinomas, including pancreatic and others derived from epithelial tissues. Thus, this protein is considered an attractive target for tumour imaging and therapy. Two different 68 Ga hexadentate tris (3,4-hydroxypyridinone) (THP) chelators were produced in this study and coupled to the αvβ6 integrin-selective peptide cyclo (FRGDLAFp(NMe)K) via NHS chemistry. Radiolabelling experiments confirmed a high radiochemical yield of the two PET probes. In addition, cellular binding studies showed high binding affinities in the nanomolar range. The two integrin αvβ6-peptide-THP synthesized and radiolabeled in this study will facilitate in vivo monitoring of transmembrane receptor αvβ6 integrin by using the advantage of THP chemistry for rapid, efficient and stable gallium chelation.

In order to develop the tyrosinase inhibitors with potential application in food industry, a series of stilbene-hydroxypyridinone hybrids were prepared. Among these compounds, 1h was found to possess the most potent tyrosinase inhibitory effect on both monophenolase and diphenolase activities, with IC 50 values of 2.72 μM and 15.86 μM, respectively. The inhibitory effect of 1h on monophenolase activity was 4.6 times that of kojic acid. An inhibition kinetic assay indicated that 1h was a mixed-type and reversible inhibitor. The copper-binding and reducing ability assays, molecular docking study, intrinsic and ANS-binding fluorescence assays indicated that copper coordination and reduction is likely to be the causative mechanism for 1h-induced inhibition on tyrosinase. The results of color measurement and browning index determination indicated that treatment with 1h retarded effectively the browning of freshly-cut apples during their storage. Meanwhile, PPO and POD activities in apple slices were found to be effectively inhibited., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Background: Tyrosinase inhibitors find potential application in food, cosmetic and medicinal products, but most of the identified tyrosinase inhibitors are not suitable for practical use because of safety regulations or other problems. For the purpose of development of novel tyrosinase inhibitors that meet the requirement for practical application, a novel stilbene analogue (SA) was designed., Results: SA was found to possess a potent inhibitory effect against both mono- and diphenolase activities of mushroom tyrosinase, with IC 50 values of 1.56 and 7.15 μmol L -1 , respectively. Compared with a natural tyrosinase inhibitor - kojic acid - the anti-tyrosinase effect of SA was significantly improved. Analysis of inhibition kinetics indicated that SA was a reversible and competitive-noncompetitive mixed-type inhibitor. SA was also found to possess more potent antioxidant activities (DPPH, superoxide anion radical and hydroxyl radical scavenging ability) than those of kojic acid. Cell viability studies revealed that SA was non-toxic to two cell lines. Furthermore, an anti-browning test demonstrated that SA effectively delayed the blackening of shrimp., Conclusion: SA has potential as an anti-browning agent in foods. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

Intravenous iron-carbohydrate complex preparations (IVIPs) are non-interchangeable pro-drugs: their pharmacokinetics (PK) varies determined by semi-crystalline iron core and carbohydrate shell structures, influences pharmacodynamics (PD) and thus efficacy and safety. Examining PK/PD relationships of 3 IVIPs we identify a two-pathway model of transient NTBI generation following single dose administration. 28 hypoferremic non-anemic patients randomized to 200mg iron as ferric carboxymaltose (Fe-carboxymaltose), iron sucrose (Fe-sucrose), iron isomaltoside 1000 (Fe-isomaltoside-1000), n=8/arm, or placebo, n=4, on a 2-week PK/PD study, had samples analysed for total serum iron, IVIP-iron, transferrin-bound iron (TBI) by HPLC-ICP-MS, transferrin saturation (TSAT), serum ferritin (s-Ferritin) by standard methods, non-TBI (NTBI) and hepcidin as published before. IVIP-dependent increases in these parameters returned to baseline in 48-150h, except for s-Ferritin and TSAT. NTBI was low with Fe-isomaltoside-1000 (0.13µM at 8h), rapidly increased with Fe-sucrose (0.8µM at 2h, 1.25µM at 4h), and delayed for Fe-carboxymaltose (0.57µM at 24h). NTBI AUCs were 7-fold greater for Fe-carboxymaltose and Fe-sucrose than for Fe-isomaltoside-1000. Hepcidin peak time varied, but not AUC or mean levels. s-Ferritin levels and AUC were highest for Fe-carboxymaltose and greater than placebo for all IVIPs. We propose 2 mechanisms for the observed NTBI kinetics: rapid and delayed NTBI appearance consistent with direct (circulating IVIP-to-plasma) and indirect (IVIP-to-macrophage-to-plasma) iron release based on IVIP plasma half-life and s-Ferritin dynamics. IVIPs generate different, broadly stability- and PK-dependent, NTBI and s-Ferritin signatures, which may influence iron bioavailability, efficacy and safety. Longer-term studies should link NTBI exposure to subsequent safety and efficacy parameters and potential clinical consequences.

Glutamate carboxypeptidase II (GCP(II)), also known as the prostate-specific membrane antigen (PSMA), is a transmembrane zinc(II) metalloenzyme overexpressed in prostate cancer. Inhibitors of this receptor are used to target molecular imaging agents and molecular radiotherapy agents to prostate cancer and if the affinity of inhibitors for GCP(II)/PSMA could be improved, targeting might also improve. Compounds containing the dipeptide OH-Lys-C(O)-Glu-OH (compound 3), incorporating a urea motif, have high affinity for GCP(II)/PSMA. We hypothesized that substituting the zinc-coordinating urea group for a thiourea group, thus incorporating a sulfur atom, could facilitate stronger binding to zinc(II) within the active site, and thus improve affinity for GCP(II)/PSMA. A structurally analogous urea and thiourea pair (HO-Glu-C(O)-Glu-OH - compound 5 and HO-Glu-C(S)-Glu-OH - compound 6) were synthesized and the inhibitory concentration (IC 50 ) of each compound measured with a cell-based assay, allowing us to refute the hypothesis: the thiourea analogue showed 100-fold weaker binding to PSMA than the urea analogue., (Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

One candidate for the cytosolic labile iron pool is iron(II)glutathione. There is also a widely held opinion that an equivalent cytosolic labile heme pool exists and that this pool is important for the intracellular transfer of heme. Here we describe a study designed to characterise conjugates that form between heme and glutathione. In contrast to hydrated iron(II), heme reacts with glutathione, under aerobic conditions, to form the stable hematin-glutathione complex, which contains iron(III). Thus, glutathione is clearly not the cytosolic ligand for heme, indeed we demonstrate that the rate of heme degradation is enhanced in the presence of glutathione. We suggest that the concentration of heme in the cytosol is extremely low and that intracellular heme transfer occurs via intracellular membrane structures. Should any heme inadvertently escape into the cytosol, it would be rapidly conjugated to glutathione thereby protecting the cell from the toxic effects of heme.

Iron is known not only for its importance in cellular and metabolic pathways but also for its role in causing cellular toxicities such as production of reactive oxygen species and growth of pathogens. The inability of the human body to physiologically excrete excess iron highlights the need to develop a cheap yet effective iron chelator. This study provides initial evidence of the therapeutic and prophylactic properties of 3-hydroxypyridin-4-one (HPO) chelators in murine collagen-induced arthritis. To determine whether these chelators would be effective on human cells, we tested a panel of different HPO chelators and identified 7-diethylamino-N-((5-hydroxy-6-methyl-4-oxo-1,4-dihydropyridin-3-yl)methyl)-N-methyl-2-oxo-chromen-3-carboxamide (CP655) as the most effective compound targeting human CD4+ T cells. Treatment with CP655 causes significant inhibition of cell proliferation and production of inflammatory cytokines such as interferon-γ and interleukin-17. Microarray analysis revealed dysregulation in cell cycle-related genes following CP655 treatment. This was validated by flow cytometry demonstrating a G1/S phase block caused by CP655. Finally, mechanistic experiments revealed that the chelator may be causing an upregulation of the cell cycle inhibitor protein CDKN1A (p21) as a possible mechanism of action. In conclusion, this study demonstrates that HPO chelators could prove to have therapeutic potential for diseases driven by excessive T cell proliferation., (© 2020 The Authors. Immunity, Inflammation and Disease published by John Wiley & Sons Ltd.)

In an attempt to synthesise new tyrosinase inhibitors, we designed and synthesised a series of chalcone-hydroxypyridinone hybrids as potential tyrosinase inhibitors adopting strategic modifications of kojic acid. All the newly synthesised compounds were characterised by NMR and mass spectrometry. Initial screening of the target compounds demonstrated that compounds 1a , 1d , and 1n had relatively strong inhibitory activities against tyrosinase monophenolase, with IC 50 values of 3.07 ± 0.85, 2.25 ± 0.8 and 2.75 ± 1.19 μM, respectively. The inhibitory activity against monophenolase was 6- to 8-fold higher than that of kojic acid. Compounds 1a , 1d , and 1n also showed inhibition of diphenolase, with IC 50 values of 17.05 ± 0.07, 11.70 ± 0.03 and 19.3 ± 0.28 μM, respectively. The inhibition kinetics of diphenolase indicates that compounds 1a and 1d induce reversible inhibition on tyrosinase. Finally, we found that copper coordination should be one of the important inhibitory mechanism of these compounds in tyrosinase.

The occurrence and progression of Parkinson's disease (PD) has been associated with the observation of elevated iron concentrations in the substantia nigra pars compacta (SNpc). While the reasons for the impact of elevated iron concentrations remain unclear, one hypothesis is that the presence of labile iron induces the oxidation of dopamine (DA) to toxic quinones such as aminochrome (DAC) and reactive oxygen species (ROS). As such, one of the proposed therapeutic strategies has been the use of iron chelators such as deferiprone (DFP) (which is recognized to have limitations related to its rapid degradation in the liver) to reduce the concentration of labile iron. In this study, a detailed investigation regarding the novel iron chelator, CN128, was conducted and a kinetic model developed to elucidate the fundamental behavior of this chelator. The results in this work reveal that CN128 is effective in alleviating the toxicity induced by iron and DA to neurons when DA is present at moderate concentrations. When all the iron is chelated by CN128, the formation of DAC and the oxidation of DA can be reduced to levels identical to that in the absence of iron. The production of H 2 O 2 is lower than that generated via the autoxidation of the same amount of DA. However, when severe leakage of DA occurs, the application of CN128 is insufficient to alleviate the associated toxicity. This is attibuted to the less important role of iron in the production of toxic intermediates at high concentrations of DA. CN128 is superior to DFP with regard to the reduction in formation of DAC and elevation in DA concentration. In summary, the results of this study suggest that prodromal application of the chelator CN128 could be effective in preventing the onset and slowing the early stage development of PD symptoms associated with oxidants and toxic intermediates resulting from the iron-mediated oxidation of the neurotransmitter dopamine with CN128 likely to be superior to DFP in view of its greater in vivo availability and less problematic side effects.

Background: Microorganisms produce siderophores in order to scavenge iron from the environment and this study focuses on the characterization of the two siderophores secreted by Bacillus megaterium. The general biological properties and pharmacokinetics following oral application of these compounds are reported., Methods: Under optimized culture conditions, the siderophores were harvested, purified by chromatography and identified using LC-MS and NMR. Two dihydroxamate siderophores were isolated, schizokinen (MW = 420) and schizokinen imide (MW = 402)., Results: Both compounds demonstrate strong antioxidant activity and were found to be relatively nontoxic to both human hepatocellular carcinoma (Huh7) and peripheral blood mononuclear cells. The siderophores possess a strong affinity for iron(III) and decrease the levels of the labile iron pool (LIP) in iron-loaded cells in a concentration-dependent manner. Schizokinen, was detected as both the free siderophore and the iron complex in the plasma and urine of rats after oral gavage., Conclusions: However, the bioavailability was low and thus schizokinen, like deferoxamine, has no potential as an orally active iron chelator for the treatment of systemic iron overload., General Significance: By virtue of the high affinity of schizokinen for tribasic metals, this siderophore does have considerable potential for the chelation of gallium(III) and the development of clinical diagnostic reagents., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Deferoxamine, deferiprone, and deferasirox are used for the treatment of systemic iron overload, although they possess limitations due to lack of oral activity, lower efficacy, and side effects. These limitations led to a search for an orally active iron chelator with an improved therapeutic index. The lower efficacy of deferiprone is due to rapid glucuronidation, leading to the formation of a nonchelating metabolite. Here, we demonstrate that the influence of metabolism can be reduced by introducing a sacrificial site for glucuronidation. A log P -guided investigation of 20 hydroxpyridinones led to the identification of CN128. The Fe(III) affinity and metal selectivity of CN128 are similar to those of deferiprone, the log P value is more lipophilic, and its iron scavenging ability is superior. Overall, CN128 was demonstrated to be safe in a range of toxicity assessments and is now in clinical trials for the treatment of β-thalassemia after regular blood transfusion.

A concise and high-yielding double aza -Michael reaction is presented as an atom-efficient method to access chiral 2-substituted 4-piperidone building blocks from divinyl ketones. The piperidones were further converted into analogues of donepezil, an acetylcholinesterase inhibiting drug used in the treatment of Alzheimer's disease. The donepezil analogues were obtained as inseparable diastereomeric mixtures with resolved stereochemistry in position 2 of the piperidine ring. Biological evaluation of the acetylcholinesterase inhibition by these analogues provides a new insight into structure-activity relationship studies with regard to donepezil's piperidine moiety toward stereochemical enhancement., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

The iron(iii) affinity constants for schizokinen and its imide derivative are reported for the first time. Surprisingly, schizokinen possesses a higher affinity for iron(iii) than desferrioxamine B; log KFeIII (FeL), 36.2 and 30.6, respectively. This increase in value is associated with the substitution of one hydroxamate function by an α-hydroxycarboxylate grouping. By virtue of the similarity of siderophore-iron(iii) complexes and siderophore-gallium(iii) complexes, schizokinen (which is a Gram positive siderophore) has potential for 68Ga PET-based imaging.

Iron chelation therapy, either subcutaneous or orally administered, has been used successfully in various clinical conditions. The removal of excess iron from various tissues, e.g., the liver spleen, heart, and the pituitary, in beta thalassemia patients, has become an essential therapy to prolong life. More recently, the use of deferiprone to chelate iron from various brain regions in Parkinson's Disease and Friederich's Ataxia has yielded encouraging results, although the side effects, in <2% of Parkinson's Disease(PD) patients, have limited its long-term use. A new class of hydroxpyridinones has recently been synthesised, which showed no adverse effects in preliminary trials. A vital question remaining is whether inflammation may influence chelation efficacy, with a recent study suggesting that high levels of inflammation may diminish the ability of the chelator to bind the excess iron.

A new series of 3-substituted 4-methylene-quinazolinthiones and 4-methylene-quinazolinones were synthesized in moderate to excellent yield through a simple reaction of 2-aminoacetophenones with isocyanates or isothiocyanates. The reaction shows good tolerance of many important functional groups in the presence of air and water under metal-free conditions. Only water is produced as a coproduct, rendering this "green" methodology a highly versatile and eco-friendly alternative to the existing methods for the construction of the quinazolinone/quinazolinthione framework. We have interpreted the reaction mechanism by use of quantum chemical calculations on the basis of state-of-the-art computational methods SMD-B3LYP-D3(BJ)/BS1//B3LYP/BS1.

Perilla frutescens is cultivated in East Asian countries including Thailand, and the nutlets (single-seeded fruits) are used as traditional and medicinal food. Perilla nutlets extracted by ethyl acetate (EA), 80% ethanol (Eth), and hot water (HW) sequentially were chemically characterized using high-resolution accurate liquid chromatography-mass spectrometry with the main compounds detected assigned as rosmarinic acid and derivatives of the flavones apigenin and luteolin, with the more diverse chemical composition observed with the Eth extract. All extracts showed dose-dependent free-radical scavenging activity, with the Eth extract the most potent (IC 50  = 3.43 mg/ml for ABTS • scavenging and 0.27 mg/ml for DPPH • scavenging). The Eth extract also inhibited AAPH-induced hemolysis (IC 50  = 0.07 mg/ml) more potently than did the HW (IC 50  = 0.38 mg/ml) and EA extracts (IC 50  = 1.63 mg/ml). An MTT test revealed all the extracts were noncytotoxic at concentrations up to 200 μg/ml. Only the Eth and EA extracts showed protective effects against the generation of reactive oxygen species and lipid peroxidation in FeCl 3 -induced HuH7 cells in a dose-dependent manner. Our findings suggest the Eth extract of Thai perilla nutlets, containing rosmarinic acid and flavones and their derivatives, may have potential to provide protection against oxidative stress in hepatic disorders., (© 2019 John Wiley & Sons, Ltd.)

An efficient method for the synthesis of 3-functionalized quinolines from commercially available acetophenones and anthranil has been described. Selectfluor propels the C(sp 3 )-H bond activation of the acetophenones and aza-Michael addition of anthranil resulting in annulated 3-acylquinolines in moderate to high yields. DMSO acts not only as a solvent but also as a one carbon donor in the reaction., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The prototype tris(1,6-dimethyl-3-hydroxypyridin-4-one) chelator for gallium-68, THPMe, has shown great promise for rapid and efficient kit-based 68Ga labelling of PET radiopharmaceuticals. Peptide derivatives of THPMe have been used to image expression of their target receptors in vivo in preclinical and clinical studies. Herein we describe new synthetic routes to the THP platform including replacing the 1,6-dimethyl-3-hydroxypyridin-4-one N1-CH3 group of THPMe with O (tris(6-methyl-3-hydroxypyran-4-one, THPO) and N1-H (tris(6-methyl-3-hydroxypyridin-4-one), THPH) groups. The effect of these structural modifications on lipophilicity, gallium binding and metal ion selectivity was investigated. THPH was able to bind 68Ga in extremely mild conditions (5 min, room temperature, pH 6, 1 μM ligand concentration) and, notably, in vivo, when administered to a mouse previously injected with 68Ga acetate. The 67Ga radiolabelled complex was stable in serum for more than 7 days. [68Ga(THPH)] displayed a log P value of -2.40 ± 0.02, less negative than the log P = -3.33 ± 0.02 measured for [68Ga(THPMe)], potentially due to an increase in intramolecular hydrogen bonding attributable to the N1-H pyridinone units. Spectrophotometric determination of the Ga3+/Fe3+ complex formation constants for both THPMe and THPH revealed their preference for binding Ga3+ over Fe3+, which enabled selective labelling with 68Ga3+ in the presence of a large excess of Fe3+ in both cases. Compared to THPMe, THPH showed significantly reduced affinity for Fe3+, increased affinity for Ga3+ and improved radiolabelling efficiency. THPO was inferior to both THPH and THPMe in terms of labelling efficiency, but its benzylated precursor Bn-THPO (tris(6-methyl-3-benzyloxypyran-4-one)) provides a potential platform for the synthesis of a library of THP compounds with tunable chemical properties and metal preferences.

Mitochondrial labile iron (LI) is a major contributor to the susceptibility of skin fibroblasts to ultraviolet A (UVA)-induced oxidative damage leading to necrotic cell death via ATP depletion. Mitochondria iron overload is a key feature of the neurodegenerative disease Friedreich's ataxia (FRDA). Here we show that cultured primary skin fibroblasts from FRDA patients are 4 to 10-fold more sensitive to UVA-induced death than their healthy counterparts. We demonstrate that FRDA cells display higher levels of mitochondrial LI (up to 6-fold on average compared to healthy counterparts) and show higher increase in mitochondrial reactive oxygen species (ROS) generation after UVA irradiation (up to 2-fold on average), consistent with their differential sensitivity to UVA. Pre-treatment of the FRDA cells with a bespoke mitochondrial iron chelator fully abrogates the UVA-mediated cell death and reduces UVA-induced damage to mitochondrial membrane and the resulting ATP depletion by a factor of 2. Our results reveal a link between FRDA as a disease of mitochondrial iron overload and sensitivity to UVA of skin fibroblasts. Our findings suggest that the high levels of mitochondrial LI in FRDA cells which contribute to high levels of mitochondrial ROS production after UVA irradiation are likely to play a crucial role in the marked sensitivity of these cells to UVA-induced oxidative damage. This study may have implications not only for FRDA but also for other diseases of mitochondrial iron overload, with the view to develop topical mitochondria-targeted iron chelators as skin photoprotective agents.

Chelation therapy has become an important therapeutic approach for some diseases. In attempt to identify clinically useful chelators, four hexadentate ligands were synthesized by conjugating the corresponding bidentate ligands (3-hydroxypyridin-4-one (3,4-HOPO), 3-hydroxypyridin-2-one (3,2-HOPO), 1-hydroxypyridin-2-one (1,2-HOPO), and 3-hydroxypyran-4-one) each with a free amino group to a tripodal acid. Their pKa values and affinities for iron(iii) were investigated. The pFe3+ values of the hexadentate pyridinones 1 (3,4-HOPO), 3 (3,2-HOPO) and 4 (1,2-HOPO), and the pyranone 2 was found to follow the sequence 1 > 4 ≫ 3 > 2, which is different to the pFe3+ value sequence of the corresponding bidentate forms (3,4-HOPO ≫ 3,2-HOPO > 1,2-HOPO > 3-hydroxypyranone). Hexadentate 3,4-HOPOs and 1,2-HOPOs have the greatest potential as iron scavenging agents.

Melanosis developed in shrimp ( Penaeus vannamei ) is mainly initiated by polyphenoloxidase (PPO), thus understanding of the characteristics of PPO in shrimp is important for controlling the melanosis of shrimp. The shrimp cephalothorax turns black most rapidly amongst all the tissues during the chilled storage. Crude PPO extracted from this cephalothorax has an optimal pH of 6.0 and an optimal temperature of 50 °C. PPO is relatively stable under neutral and weak alkaline conditions (pH 5.5-9.0) and the temperature range of 25-35 °C. The kinetic parameters K m and V max were recorded as 3.02 mM and 54.3 U/mg of protein, respectively, using L-Dopa as a substrate. The molecular weight of PPO was estimated as 200-220 kDa by an activity staining test. A hydroxypyridinone derivative, 5-hydroxy-1-octyl-4-oxo-1,4-dihydropyridine-2-carbaldehyde O-ethyl oxime, was demonstrated to efficiently inhibit the PPO, indicating that this compound might find application as a shrimp preservative., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest.

Iron chelators have recently attracted interest in the field of photodynamic therapy (PDT) owing to their role in enhancement of intracellular protoporphyrin IX (PpIX) generation induced by 5-aminolevulinic acid (ALA) via the biosynthetic heme cycle. Although ALA is widely used in PDT, cellular uptake of ALA is limited by its hydrophilicity. In order to improve ALA delivery and enhance the PpIX production, several dendrimers incorporating both ALA and 3-hydroxy-4-pyridinone (HPO) were synthesized. The ability of the dendrimers to enter cells and be metabolized to the PpIX photosensitizer was studied in several human cancer cell lines. The dendrimers were found to be significantly more efficient than ALA alone in PpIX production. The higher intracellular PpIX levels showed a clear correlation with enhanced cellular phototoxicity following light exposure. Dendritic derivatives are therefore capable of efficiently delivering both ALA and HPO, which act synergistically to amplify in vitro PpIX levels and enhance PDT efficacy.

Hard corona (HC) protein, i.e., the environmental proteins of the biological medium that are bound to a nanosurface, is known to affect the biological fate of a nanomedicine. Due to the size, curvature, and specific surface area (SSA) 3-factor interactions inherited in the traditional 3D nanoparticle, HC-dependent bio-nano interactions are often poorly probed and interpreted. Here, the first HC-by-design case study in 2D is demonstrated that sequentially and linearly changes the HC quantity using functionalized graphene oxide (GO) nanosheets. The HC quantity and HC quality are analyzed using NanoDrop and label-free liquid chromatography-mass spectrometry (LC-MS) followed by principal component analysis (PCA). Cellular responses (uptake and cytotoxicity in J774 cell model) are compared using imaging cytometry and the modified lactate dehydrogenase assays, respectively. Cellular uptake linearly and solely correlates with HC quantity (R 2 = 0.99634). The nanotoxicity, analyzed by retrospective design of experiment (DoE), is found to be dependent on the nanomaterial uptake (primary), HC composition (secondary), and nanomaterial exposure dose (tertiary). This unique 2D design eliminates the size-curvature-SSA multifactor interactions and can serve as a reliable screening platform to uncover HC-dependent bio-nano interactions to enable the next-generation quality-by-design (QbD) nanomedicines for better clinical translation., (© 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Hydroxypyridinones (HOPOs) form outstanding building blocks for the development of a variety of agents in the field of metal chelation. The pyridinone ring is easily synthesized and readily converted into tetradentate, hexadentate, and octadentate chelators. There is considerable potential for the control of the stereochemistry of the resulting metal complex and hence the properties of these multidentate molecules. Their ability to rapidly bind hard metals in aqueous media has facilitated the development of efficient applications in both biological and medical contexts. In this Review, an in-depth analysis of the synthetic methodologies for HOPO-based ligands is presented, as well as the many aspects to achieve optimal biological activity. Recent advances and current challenges for the future application of HOPO structures are outlined. The present flourishing development of drug candidates and diagnostic agents based on this chemical scaffold opens access to many new applications in analytical, environmental, and clinical science.

Macromolecular chelators have potential applications in the medical area, for instance, in treatment of iron overload-related disorders and in the treatment of external infections. In this investigation, several novel iron(III)-selective hydroxypyridinone hexadentate-terminated first and second generation dendrimeric chelators were synthesized using a convergent strategy. Their iron chelating ability was demonstrated by UV/Visible spectrometry and high resolution mass spectrometry (HRMS). The iron binding affinities were also investigated by the competition with a fluorescent iron chelator CP691. The result indicated that these dendrimers possesses a high affinity for iron with a very high pFe 3+ value, which is close to that of an isolated hexadentate unit. These dendrimeric chelators were found to exhibit inhibitory effect on the growth of both Gram-positive and Gram-negative bacteria., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Certain xenobiotics, such as paraquat, are sequestered into the lungs from the systemic circulation by the polyamine transporter system (PTS). The aim of this study was to investigate whether ion-pairing a drug (theophylline) with a PTS substrate (spermine) provides a means of using this active transport mechanism to target drug delivery to the lungs. Fourier transform infrared spectroscopy showed that two of the amine groups of spermine interact with C-N 7 and C 6 ═O of theophylline, leaving two free amines to interact with the PTS. In A549 cells, which possess a functional PTS (spermidine K m and V max , 0.6 ± 0.3 μM and 1.8 ± 0.3 pmol·min -1 per 10 5 cells, respectively), uptake of the theophylline-spermine ion-pair was increased 1.8-fold compared to free theophylline at 37 °C, but not at 4 °C. In an isolated perfused rat lung model (IPL) a 3.6-fold increase in lung theophylline concentration was observed after vascular administration of the ion-pair compared to free theophylline. Theophylline was cleared from the IPL with similar kinetics irrespective of whether it was delivered as the free drug or an ion-pair, although lung levels remained elevated after washout following delivery as an ion-pair. In vitro simulation of the theophylline-spermine break down demonstrated that a drop in pH from 9.6 to 7.4, such as that undergone by the ion-pair in biological matrices, induces rapid and almost complete dissociation of the ion-paired species. However, infusion of the ion-pair formulations via the vasculature provides almost immediate delivery to the pulmonary capillary bed permitting PTS-mediated active sequestering of ion-paired theophylline into the lungs.