Evaluation of novel 111In-labeled gonadotropin-releasing hormone peptides for human prostate cancer imaging

The purpose of this study was to evaluate the tumor targeting and imaging properties of novel ¹¹¹In-labeled gonadotropin-releasing hormone (GnRH) peptides for human prostate cancer. Three new 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-linker-d-Phe-(d-Lys⁶-GnRH) peptides with different hydrocarbon linkers were designed to evaluate their effects on GnRH receptor binding affinities. The Aoc (aminooctanoic acid) linker was better than βAla (3-aminopropanoic acid) and Aun (aminoundecanoic acid) linkers in retaining strong receptor binding affinity. DOTA-Aoc-d-Phe-(d-Lys⁶-GnRH) exhibited 6.6 ± 0.1 nM GnRH receptor binding affinity. ¹¹¹In-DOTA-Aoc-d-Phe-(d-Lys⁶-GnRH) exhibited fast tumor uptake and urinary clearance in DU145 human prostate cancer-xenografted nude mice. The DU145 tumor lesions could be clearly visualized by single photon emission computed tomography (SPECT)/CT using ¹¹¹In-DOTA-Aoc-d-Phe-(d-Lys⁶-GnRH) as an imaging probe, providing an insight into the design of new GnRH peptides for prostate cancer in the future.     

Discovery of simplified N2-substituted pyrazolo[3,4-d]pyrimidine derivatives as novel adenosine receptor antagonists: Efficient synthetic approaches,biological evaluations and molecular docking studies

In the present study, a molecular simplification approach was employed to design novel bicyclic pyrazolo[3,4-d]pyrimidine (PP) derivatives from tricyclic pyrazolo[4,3-e]-1,2,4-triazolo-[1,5-c]pyrimidines (PTP) as promising human A₃ adenosine receptor (hA₃AR) antagonists. All the target compounds were synthesized using novel and efficient synthetic schemes and the structure–activity relationship studies of these PPs were explored through the synthesis of a series of PTP analogues with various substituents. Substituents with different lipophilicity and steric hindrance (e.g., alkyl and aryl–alkyl) functions were introduced at N² position of the pyrazole ring, while acyl groups with different electronic properties were introduced at C⁶ position of the bicyclic nucleus to probe both electronic and positional effects. Most of the synthesized derivatives of the PP series presented good affinity at the hA₃AR, as indicated by the low micromolar range of K_i values and among them, compound 63 with N² neopentyl substituents showed most potent hA₃AR affinity with K_i value of 0.9 μM and high selectivity (hA₁AR/hA₃AR = >111 & hA_2AAR/hA₃AR = >111) towards other adenosine receptor subtypes. Interestingly, small isopropyl groups at N² position displayed high affinity at another receptor subtype (hA_2AAR, e.g., compound 55, with K_i hA_2AAR = 0.8 μM), while they were less favorable at the hA₃AR. Molecular docking analysis was also performed to predict the possible binding mode of target compounds inside the hA₃AR and hA_2AAR. Overall, PP derivatives represent promising starting points for new AR antagonists.     

Succinic acid production from sucrose and molasses by metabolically engineered E. coli using a cell surface display system

To achieve sucrose-metabolizing capability, different sucrose utilization operons have been introduced into E. coli that cannot utilize sucrose. However, these engineered strains still suffer from low growth rates and low sucrose uptake rates. In this study, cell surface display system was adopted in engineered E. coli AFP111 for succinic acid production from sucrose and molasses directly. Invertase (CscA) from E. coli W was successfully anchored to outer membrane by fusion with OmpC anchoring motif, and the displayed CscA showed high extracellular activity. Compared with the sucrose permease system, the cell surface display system consumed less ATP during sucrose metabolism. When less ATP was consumed by AFP111/pTrcC-cscA, the succinic acid productivity from sucrose was 23% higher than that by AFP111/pCR2.1-cscBKA that having the sucrose permease system. As a result, 41 g L⁻¹ and 36.3 g L⁻¹ succinic acid were produced by AFP111/pTrcC-cscA from sucrose and sugarcane molasses respectively at 34 h in 3-L fermentor during dual-phase fermentation. In addition, 79 g L⁻¹ succinic acid was accumulated with recovered AFP111/pTrcC-cscA cells at the end of dual-phase fermentation in 3-L fermentor, and the overall yield was 1.19 mol mol⁻¹ hexose.     

Structure–activity relationships of truncated adenosine derivatives as highly potent and selective human A3 adenosine receptor antagonists

On the basis of potent and selective binding affinity of truncated 4′-thioadenosine derivatives at the human A₃ adenosine receptor (AR), their bioisosteric 4′-oxo derivatives were designed and synthesized from commercially available 2,3-O-isopropylidene-d-erythrono lactone. The derivatives tested in AR binding assays were substituted at the C2 and N⁶ positions. All synthesized nucleosides exhibited potent and selective binding affinity at the human A₃ AR. They were less potent than the corresponding 4′-thio analogues, but showed still selective to other subtypes. The 2-Cl series generally were better than the 2-H series in view of binding affinity and selectivity. Among compounds tested, compound 5d (X = Cl, R = 3-bromobenzyl) showed the highest binding affinity (K_i = 13.0 ± 6.9 nM) at the hA₃ AR with high selectivity (at least 88-fold) in comparison to other AR subtypes. Like the corresponding truncated 4′-thio series, compound 5d antagonized the action of an agonist to inhibit forskolin-stimulated adenylate cyclase in hA₃ AR-expressing CHO cells. Although the 4′-oxo series were less potent than the 4′-thio series, this class of human A₃ AR antagonists is also regarded as another good template for the design of A₃ AR antagonists and for further drug development.     

Linker modification reduced the renal uptake of technetium-99m-labeled Arg-Ala-Asp-conjugated alpha-melanocyte stimulating hormone peptide

The purpose of this study was to examine the biodistribution of ^99mTc-RAD-Arg-(Arg¹¹)CCMSH in B16/F1 melanoma-bearing C57 mice to determine whether the replacement of the Lys linker with an Arg linker could decrease the renal uptake of ^99mTc-RAD-Arg-(Arg¹¹)CCMSH. ^99mTc-RAD-Arg-(Arg¹¹)CCMSH exhibited rapid and high tumor uptake (17.98 ± 4.96% ID/g at 2 h post-injection) in B16/F1 melanoma-bearing C57 mice. As compared to ^99mTc-RAD-Lys-(Arg¹¹)CCMSH, the replacement of the Lys linker with an Arg linker dramatically decreased the renal uptake of ^99mTc-RAD-Arg-(Arg¹¹)CCMSH by 68%, 62%, 73% and 64% at 0.5, 2, 4 and 24 h post-injection, respectively. Flank B16/F1 melanoma lesions were clearly imaged at 2 h post-injection using ^99mTc-RAD-Arg-(Arg¹¹)CCMSH as an imaging probe.     

Replacement of the Lys linker with an Arg linker resulting in improved melanoma uptake and reduced renal uptake of Tc-99m-labeled Arg-Gly-Asp-conjugated alpha-melanocyte stimulating hormone hybrid peptide

The purpose of this study was to reduce the non-specific renal uptake of Arg-Gly-Asp (RGD)-conjugated alpha-melanocyte stimulating hormone (α-MSH) hybrid peptide through structural modification or l-lysine co-injection. The RGD motif {cyclic(Arg-Gly-Asp-DTyr-Asp)} was coupled to [Cys^3,4,10, d-Phe⁷, Arg¹¹] α-MSH_3-13 {(Arg¹¹)CCMSH} through the Arg linker (substituting the Lys linker) to generate a novel RGD-Arg-(Arg¹¹)CCMSH hybrid peptide. The melanoma targeting and pharmacokinetic properties of ^99mTc-RGD-Arg-(Arg¹¹)CCMSH were determined in B16/F1 melanoma-bearing C57 mice. The effect of l-lysine co-injection on the renal uptake was determined through the co-injection of l-lysine with ^99mTc-RGD-Arg-(Arg¹¹)CCMSH or ^99mTc-RGD-Lys-(Arg¹¹)CCMSH. Replacement of the Lys linker with an Arg linker exhibited a profound effect in reducing the non-specific renal uptake of ^99mTc-RGD-Arg-(Arg¹¹)CCMSH, as well as increasing the tumor uptake of ^99mTc-RGD-Arg-(Arg¹¹)CCMSH compared to ^99mTc-RGD-Lys-(Arg¹¹)CCMSH. ^99mTc-RGD-Arg-(Arg¹¹)CCMSH exhibited high tumor uptake (21.41 ± 3.74% ID/g at 2 h post-injection) and prolonged tumor retention (6.81 ± 3.71% ID/g at 24 h post-injection) in B16/F1 melanoma-bearing mice. The renal uptake values of ^99mTc-RGD-Arg-(Arg¹¹)CCMSH were 40.14–64.08% of those of ^99mTc-RGD-Lys-(Arg¹¹)CCMSH (p <0.05) at 0.5, 2, 4 and 24 h post-injection. Co-injection of l-lysine was effective in decreasing the renal uptakes of ^99mTc-RGD-Arg-(Arg¹¹)CCMSH by 27.7% and ^99mTc-RGD-Lys-(Arg¹¹)CCMSH by 52.1% at 2 h post-injection. Substitution of the Lys linker with an Arg linker dramatically improved the melanoma uptake and reduced the renal uptake of ^99mTc-RGD-Arg-(Arg¹¹)CCMSH, warranting the further evaluation of ¹⁸⁸Re-labeled RGD-Arg-(Arg¹¹)CCMSH as a novel MC1 receptor-targeting therapeutic peptide for melanoma treatment in the future.     

Synthesis of organic nitrates of luteolin as a novel class of potent aldose reductase inhibitors

Aldose reductase (AR) plays an important role in the design of drugs that prevent and treat diabetic complications. Aldose reductase inhibitors (ARIs) have received significant attentions as potent therapeutic drugs. Based on combination principles, three series of luteolin derivatives were synthesised and evaluated for their AR inhibitory activity and nitric oxide (NO)-releasing capacity in vitro. Eighteen compounds were found to be potent ARIs with IC₅₀ values ranging from (0.099 ± 0.008) μM to (2.833 ± 0.102) μM. O⁷-Nitrooxyethyl-O^3′,O^4′-ethylidene luteolin (La1) showed the most potent AR inhibitory activity [IC₅₀ = (0.099 ± 0.008) μM]. All organic nitrate derivatives released low concentrations of NO in the presence of l-cysteine. Structure–activity relationship studies suggested that introduction of an NO donor, protection of the catechol structure, and the ether chain of a 2-carbon spacer as a coupling chain on the luteolin scaffold all help increase the AR inhibitory activity of the resulting compound. This class of NO-donor luteolin derivatives as efficient ARIs offer a new concept for the development and design of new drug for preventive and therapeutic drugs for diabetic complications.     

Antiproliferative,antiandrogenic and cytotoxic effects of novel caffeic acid derivatives in LNCaP human androgen-dependent prostate cancer cells

Caffeic acid and its naturally occurring derivative caffeic acid phenethyl ester (CAPE) have antiproliferative and cytotoxic properties in a variety of cancer cell lines without displaying significant toxicity toward healthy cells, and are considered to be potential anticancer agents. However, little is known about their effects on prostate cancer cells. We synthesized and evaluated the effects of caffeic acid, CAPE (2) and 18 synthetic derivatives on cell viability and androgen-dependent cell proliferation, subcellular localisation and expression of androgen receptor (AR) and secretion of prostate-specific antigen (PSA) in LNCaP human hormone-dependent prostate cancer cells. Several synthetic derivatives of CAPE were strong, concentration-dependent cytotoxic agents in LNCaP cells with IC₅₀ values in the 6.8–26.6 μM range, potencies that were up to five-fold greater than that of CAPE (33.7 ± 4.0 μM). A number of caffeic acid derivatives were inhibitors of androgen-stimulated LNCaP cell proliferation with concomitant inhibition of DHT-stimulated PSA secretion. Compound 24 was the most cytotoxic and antiproliferative caffeic acid derivative (IC₅₀ values of 6.8 ± 0.3 and 2.4 ± 0.8 μM, respectively) inhibiting DHT-stimulated cell proliferation and PSA secretion statistically significantly at concentrations as low as 0.3 μM. Exposure to DHT increased cytoplasmic and nuclear AR levels and co-treatment with increasing concentrations of compound 24 or CAPE (2), notably, further increased these levels. In conclusion, a number of synthetic derivatives of caffeic acid are potent inhibitors of androgen-dependent prostate cancer cell proliferation and viability, acting, at least in part, via an antiandrogenic mechanism that involves increased nuclear accumulation of (presumably inactive) AR.     

Introduction of d-Phenylalanine enhanced the receptor binding affinities of gonadotropin-releasing hormone peptides

The purpose of this study was to examine whether the introduction of d-Phe could improve the GnRH receptor binding affinities of DOTA-conjugated d-Lys⁶-GnRH peptides. Building upon the construct of DOTA-Ahx-(d-Lys⁶-GnRH1) we previously reported, an aromatic amino acid of d-Phe was inserted either between the DOTA and Ahx or between the Ahx and d-Lys⁶ to generate new DOTA-d-Phe-Ahx-(d-Lys⁶-GnRH) or DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) peptides. Compared to DOTA-Ahx-(d-Lys⁶-GnRH1) (36.1 nM), the introduction of d-Phe improved the GnRH receptor binding affinities of DOTA-d-Phe-Ahx-(d-Lys⁶-GnRH) (16.3 nM) and DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) (7.6 nM). The tumor targeting and pharmacokinetic properties of ¹¹¹In-DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) was determined in MDA-MB-231 human breast cancer-xenografted nude mice. Compared to ¹¹¹In-DOTA-Ahx-(d-Lys⁶-GnRH1), ¹¹¹In-DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) exhibited comparable tumor uptake with faster renal and liver clearance. The MDA-MB-231 human breast cancer-xenografted tumors were clearly visualized by single photon emission computed tomography (SPECT) using ¹¹¹In-DOTA-Ahx-d-Phe-(d-Lys⁶-GnRH) as an imaging probe, providing a new insight into the design of new GnRH peptides in the future.     

Synthesis and evaluation of 18F-labeled CJ-042794 for imaging prostanoid EP4 receptor expression in cancer with positron emission tomography

The potent and selective prostanoid EP4 receptor antagonist CJ-042794 was radiolabeled with ¹⁸F, and evaluated for imaging EP4 receptor expression in cancer with positron emission tomography (PET). The fluorination precursor, arylboronic acid pinacol ester 4, was prepared in 4 steps with 42% overall yield. ¹⁸F-CJ-042794 was synthesized via a copper-mediated ¹⁸F-fluorination reaction followed by base hydrolysis, and was obtained in 1.5 ± 1.1% (n = 2) decay-corrected radiochemical yield. PET/CT imaging and biodistribution studies in mice showed that ¹⁸F-CJ-042794 was excreted through both renal and hepatobiliary pathways with significant retention in blood. The EP4-receptor-expressing LNCaP prostate cancer xenografts were clearly visualized in PET images with 1.12 ± 0.08%ID/g (n = 5) uptake value and moderate tumour-to-muscle contrast ratio (2.73 ± 0.22) at 1 h post-injection. However, the tumour uptake was nonspecific as it could not be blocked by co-injection of cold standard, precluding the application of ¹⁸F-CJ-042794 for PET imaging of EP4 receptor expression in cancer.     

Role of iron plaque in Cd uptake by and translocation within rice (Oryza sativa L.) seedlings grown in solution culture

A hydroponics culture experiment was conducted to investigate the effect of iron plaque on Cd uptake by and translocation within rice seedlings grown under controlled growth chamber conditions. Rice seedlings were pre-cultivated for 43 days and then transferred to nutrient solution containing six levels of Fe (0, 10, 30, 50, 80 and 100 mg L⁻¹) for 6 days to induce different amounts of iron plaque on the root surfaces. Seedlings were then exposed to solution containing three levels of Cd (0, 0.1 and 1.0 mg L⁻¹) for 4 days. In order to differentiate the uptake capability of Cd by roots with or without iron plaque, root tips (white root part without iron plaque) and middle root parts (with iron plaque) of pre-cultivated seedlings treated with 0, 30 and 50 mg L⁻¹ Fe were exposed to ¹⁰⁹Cd for 24 h. Reddish iron plaque gradually became visible on the surface of rice roots but the visual symptoms of the iron plaque on the roots differed among treatments. In general, the reddish color of the iron plaque became darker with increasing Fe supply, and the iron plaque was more homogeneously distributed all along the roots. The Fe concentrations increased significantly with increasing Fe supply regardless of Cd additions. The Cd concentrations in dithionite–citrate–bicarbonate (DCB)-extracts and in shoots and roots were significantly affected by Cd and Fe supply in the nutrient solution. The Cd concentrations increased significantly with increasing Cd supply in the solution and were undetectable when no Cd was added. The Cd concentrations in DCB-extracts with Fe supplied tended to be higher than that at Fe₀ at Cd_0.1, and at Cd_1.0, DCB-Cd with Fe supplied was significantly lower. Cd concentrations in roots and shoots decreased with increasing Fe supply at both Cd additions. The proportion of Cd in DCB-extracts was significantly lower than in roots or shoots. Compared to the control seedlings without Fe supply, the radioactivity of ¹⁰⁹Cd in shoots of seedlings treated with Fe decreased when root tips were exposed to ¹⁰⁹Cd and did not change significantly when middle parts of roots were exposed. Our results suggest that root tissue rather than iron plaque on the root surface is a barrier to Cd uptake and translocation within rice plants, and the uptake and translocation of Cd appear to be related to Fe nutritional levels in the plants.     

Regulation of cardiolipin biosynthesis by fatty acid transport protein-1 IN HEK 293 cells

Cardiolipin (CL) is a major phospholipid involved in energy metabolism mammalian mitochondria and fatty acid transport protein-1 (FATP-1) is a fatty acid transport protein that may regulate the intracellular level of fatty acyl-Coenzyme A's. Since fatty acids are required for oxidative phosphorylation via mitochondrial oxidation, we examined the effect of altering FATP-1 levels on CL biosynthesis. HEK-293 mock- and FATP-1 siRNA transfected cells or mock and FATP-1 expressing cells were incubated for 24 h with 0.1 mM oleic acid bound to albumin (1:1 molar ratio) then incubated for 24 h with 0.1 mM [1,3-³H]glycerol and radioactivity incorporated into CL determined. FATP-1 siRNA transfected cells exhibited reduced FATP-1 mRNA and increased incorporation of [1,3-³H]glycerol into CL (2-fold, p < 0.05) compared to controls indicating elevation in de novo CL biosynthesis. The reason for this was an increase in [1,3-³H]glycerol uptake and increase in activity and mRNA expression of the CL biosynthetic enzymes. In contrast, expression of FATP-1 resulted a reduction in incorporation of [1,3-³H]glycerol into CL (65%, p < 0.05) indicating reduced CL synthesis. [1,3-³H]Glycerol uptake was unaltered whereas activity of cytidine-5′-diphosphate-1,2-diacyl-sn-glycerol synthetase (CDS) and CDS-2 mRNA expression were reduced in FATP-1 expressing cells compared to control. In addition, in vitro CDS activity was reduced by exogenous addition of oleoyl-Coenzyme A. The data indicate that CL de novo biosynthesis may be regulated by FATP-1 through CDS-2 expression in HEK 293 cells.     

Arsenic accumulation by aquatic macrophyte coontail (Ceratophyllum demersum L.) exposed to arsenite,and the effect of iron on the uptake of arsenite and arsenate

In this study, the aquatic macrophyte Ceratophyllum demersum L. (coontail or hornwort) was tested for its efficiency of arsenic (As) uptake under laboratory conditions. Our results revealed that the solution pH had a significant effect on As accumulation by C. demersum (p < 0.001). The accumulation was highest at pH 5 and decreased as pH values increased. Plants that were exposed to various concentrations of arsenite (As(III)) for 24 and 48 h, exhibited tolerance and toxic responses, respectively. As accumulation by C. demersum depended on the concentrations of As(III) and the duration of exposure (p < 0.001). At 40 μM after 24 h, plants accumulated 227.5 μg As g⁻¹ dw and showed no visible symptoms of toxicity. However, after 48 h, As level reached 302.4 μg g⁻¹ dw and biomass production decreased significantly. Toxic effects were evident by plant necrosis and negative biomass production, leading to a decrease in the amount of accumulated As. Also, the addition of iron (Fe) into the nutrient solutions (0.18 mM) had contrasting effects on the uptake of 2 As species – the uptake of As(III) was enhanced by the presence of Fe, but the uptake of arsenate (As(V)) was considerably inhibited.     

Synthesis and evaluation of copper-64 labeled benzofuran derivatives targeting β-amyloid aggregates

In vivo imaging of β-amyloid (Aβ) aggregates consisting of Aβ(1–40) and Aβ(1–42) peptides by positron emission tomography (PET) contributes to the diagnosis and therapy for Alzheimer’s disease (AD). Because ⁶⁴Cu (t_1/2 = 12.7 h) is a radionuclide for PET with a longer physical half-life than ¹¹C (t_1/2 = 20 min) and ¹⁸F (t_1/2 = 110 min), it is an attractive radionuclide for the development of Aβ imaging probes that are suitable for routine use. In the present study, we designed and synthesized two novel ⁶⁴Cu labeled benzofuran derivatives and evaluated their utility as PET imaging probes for Aβ aggregates. In an in vitro binding assay, 6 and 8 showed binding affinity for Aβ(1–42) aggregates with a K_i value of 33 and 243 nM, respectively. In addition, these probes bound to Aβ plaques deposited in the brain of an AD model mouse in vitro. In a biodistribution experiment using normal mice, these probes showed low brain uptake (0.33% and 0.36% ID/g) at 2 min post-injection. Although refinement to enhance brain uptake is needed, [⁶⁴Cu]6 and [⁶⁴Cu]8 demonstrated the feasibility of developing novel PET probes for imaging Aβ aggregates.     

Soil nitrate accumulation explains the nonlinear responses of soil CO2 and CH4 fluxes to nitrogen addition in a temperate needle-broadleaved mixed forest

The responses of soil-atmosphere carbon (C) exchange fluxes to growing atmospheric nitrogen (N) deposition are controversial, leading to large uncertainty in the estimated C sink of global forest ecosystems experiencing substantial N inputs. However, it is challenging to quantify critical load of N input for the alteration of the soil C fluxes, and what factors controlled the changes in soil CO₂ and CH₄ fluxes under N enrichment. Nine levels of urea addition experiment (0, 10, 20, 40, 60, 80, 100, 120, 140 kg N ha⁻¹ yr⁻¹) were conducted in the needle-broadleaved mixed forest in Changbai Mountain, Northeast China. Soil CO₂ and CH₄ fluxes were monitored weekly using the static chamber and gas chromatograph technique. Environmental variables (soil temperature and moisture in the 0–10 cm depth) and dissolved N (NH₄⁺-N, NO₃⁻-N, total dissolved N (TDN), and dissolved organic N (DON)) in the organic layer and the 0–10 cm mineral soil layer were simultaneously measured. High rates of N addition (≥60 kg N ha⁻¹ yr⁻¹) significantly increased soil NO₃⁻-N contents in the organic layer and the mineral layer by 120%-180% and 56.4%-84.6%, respectively. However, N application did not lead to a significant accumulation of soil NH₄⁺-N contents in the two soil layers except for a few treatments. N addition at a low rate of 10 kg N ha⁻¹ yr⁻¹ significantly stimulated, whereas high rate of N addition (140 kg N ha⁻¹ yr⁻¹) significantly inhibited soil CO₂ emission and CH₄ uptake. Significant negative relationships were observed between changes in soil CO₂ emission and CH₄ uptake and changes in soil NO₃⁻-N and moisture contents under N enrichment. These results suggest that soil nitrification and NO₃⁻-N accumulation could be important regulators of soil CO₂ emission and CH₄ uptake in the temperate needle-broadleaved mixed forest. The nonlinear responses to exogenous N inputs and the critical level of N in terms of soil C fluxes should be considered in the ecological process models and ecosystem management.     

Short and long-term uptake of Hg in white lupin plants:Kinetics and stress indicators

The intrinsic characteristics of white lupin regarding biomass production and tolerance to abiotic stresses could make it a good candidate to be used in degraded mine soils containing mercury (Hg), but white lupin behaviour in response to Hg has to be previously evaluated. With this aim, kinetic parameters of Hg uptake in short and long-term experiments, and Hg resistance of white lupin plants using several stress indicators were studied. The plants were grown with increasing Hg doses in nutrient solutions (0, 5 and 10 μM). Hg uptake showed an active component in Hg influx, suggesting the existence of a low affinity root transporter that can be used for Hg uptake into white lupin root cells. K_m and V_max values obtained for the saturable component were 217.7 ± 27.6 μM and 3.78 ± 0.18 μmol Hg g FW^?1 h^?1. Hg accumulation was concentration–time-dependent, showing a saturable behaviour for the lower doses but a linear behaviour for the highest ones. A high ability of Hg absorption by white lupin was observed both in short and long-term uptake experiments. The highest Hg dose reduced biomass production especially in the shoots. Moreover, increases in chlorophylls, malondialdehyde, total thiols and phenols were observed in Hg-stressed plants. The enhancement of total thiols and phenols levels in roots reduced oxidative stress for the 5 μM dose, but not for higher Hg levels. The deleterious effect of Hg was less marked in root tissues, in spite of their accumulation of very high Hg amounts (99%) because of, at least in part, a combined increase in total thiols and phenolics able to minimize oxidative stress. Our results suggested that phenolic content in roots could be used as a new and easy-to-use indicator of Hg presence. On the whole, white lupin showed a certain ability to survive in Hg-contaminated media and it would be possible to include it in combined decontamination strategies.     

Design and synthesis of N6-substituted-4′-thioadenosine-5′-uronamides as potent and selective human A3 adenosine receptor agonists

On the basis of a bioisosteric rationale, 4′-thionucleoside analogues of IB-MECA (N⁶-(3-Iodo-benzyl)-9-(5′-methylaminocarbonyl-β-d-ribofuranosyl)adenine), which is a potent and selective A₃ adenosine receptor (AR) agonist, were synthesized from d-gulonic acid γ-lactone. The 4′-thio analogue (5h) of IB-MECA showed extremely high binding affinity (K_i = 0.25 nM) at the human A₃AR and was more potent than IB-MECA (K_i = 1.4 nM). Bulky substituents at the 5′-uronamide position, such as cyclohexyl and 2-methylbenzyl, in this series of 2-H nucleoside derivatives were tolerated in A₃AR binding, although small alkyl analogues were more potent.     

Y-shaped bis-arylethenesulfonic acid esters: Potential potent and membrane permeable protein tyrosine phosphatase 1B inhibitors

Known PTP1B inhibitors with bis-anionic moieties exhibit potent inhibitory activity, good selectivity, however, they are incapable of penetrating cellular membranes. Based upon our finding of a new pharmacophoric group in inhibition of PTP1B and the structural characteristics of the binding pocket of PTP1B, a series of bis-arylethenesulfonic acid ester derivatives were designed and synthesized. These novel molecules, particularly Y-shaped bis-arylethenesulfonic acid ester derivatives, exhibited high PTP1B inhibitory activity, moderate selectivity, and great potential in penetrating cellular membranes (compound 7p, CLog P = 9.73, P_app = 9.6 × 10^-6 cm/s; IC₅₀ = 140, 1290 and 920 nM on PTP1B, TCPTP and SHP2, respectively). Docking simulations suggested that these Y-shaped inhibitors might interact with multiple secondary binding sites in addition to the catalytic site of PTP1B.     

Synthesis and evaluation of ethyleneoxylated and allyloxylated chalcone derivatives for imaging of amyloid β plaques by SPECT

We report radioiodinated chalcone derivatives as new SPECT imaging probes for amyloid β (Aβ) plaques. The monoethyleneoxy derivative 2 and allyloxy derivative 8 showed a high affinity for Aβ(1–42) aggregates with K_i values of 24 and 4.5 nM, respectively. Fluorescent imaging demonstrated that 2 and 8 clearly stained thioflavin-S positive Aβ plaques in the brain sections of Tg2576 transgenic mice. In vitro autoradiography revealed that [¹²⁵I]2 displayed no clear accumulation toward Aβ plaques in the brain sections of Tg2576 mice, whereas the accumulation pattern of [¹²⁵I]8 matched with the presence of Aβ plaques both in the brain sections of Tg2576 mice and an AD patient. In biodistribution studies using normal mice, [¹²⁵I]2 showed preferable in vivo pharmacokinetics (4.82%ID/g at 2 min and 0.45%ID/g at 60 min), while [¹²⁵I]8 showed only a modest brain uptake (1.62%ID/g at 2 min) with slow clearance (0.56%ID/g at 60 min). [¹²⁵I]8 showed prospective binding properties for Aβ plaques, although further structural modifications are needed to improve the blood brain barrier permeability and washout from brain.     

Synthesis and evaluation of N6-substituted apioadenosines as potential adenosine A3 receptor modulators

Adenosine receptors (ARs) trigger signal transduction pathways inside the cell when activated by extracellular adenosine. Selective modulation of the A₃AR subtype may be beneficial in controlling diseases such as colorectal cancer and rheumatoid arthritis. Here, we report the synthesis and evaluation of β-d-apio-d-furano- and α-d-apio-l-furanoadenosines and derivatives thereof. Introduction of a 2-methoxy-5-chlorobenzyl group at N⁶ of β-d-apio-d-furanoadenosine afforded an A₃AR antagonist (10c, K_i = 0.98 μM), while a similar modification of an α-d-apio-l-furanoadenosine gave rise to a partial agonist (11c, K_i = 3.07 μM). The structural basis for this difference was examined by docking to an A₃AR model; the antagonist lacked a crucial interaction with Thr94.