DNA-modified Prussian blue nanozymes for enhanced electrochemical biosensing

Prussian blue nanoparticles exhibit the potential to be employed in bioanalytical applications due to their robust stability, peroxidase-like catalytic functionality, straightforward synthesis, and biocompatibility. An efficient approach is presented for the synthesis of nucleic acid-modified Prussian blue nanoparticles (DNA-PBNPs), utilizing nanoparticle porosity to adsorb nucleic acids (polyT). This strategic adsorption leads to the exposure of nucleic acid sequences on the particle surface while retaining catalytic activity. DNA-PBNPs further couple with functional nucleic acid sequences and aptamers through complementary base pairing to act as transducers in biosensors and amplify signal acquisition. Subsequently, we integrated a copper ion-dependent DNAzyme (Cu2+-DNAzyme) and a vascular endothelial growth factor aptamer (VEGF aptamer) onto screen-printed electrodes to serve as recognition elements for analytes. Significantly, our approach leverages DNA-PBNPs as a superior alternative to traditional enzyme-linked antibodies in electrochemical biosensors, thereby enhancing both the efficiency and adaptability of these devices. Our study conclusively demonstrates the application of DNA-PBNPs in two different biosensing paradigms: the sensitive detection of copper ions and vascular endothelial growth factor (VEGF). These results indicate the promising potential of DNA-modified Prussian blue nanoparticles in advancing bioanalytical sensing technologies.

Ethylene Glycol-Manipulated Syntheses of Calcium Carbonate Particles and DNA Capsules toward Efficient ATP-Responsive Cargo Release

Cargo molecule-encapsulated DNA capsules synthesized with a solid sacrificial template have elicited significant interest in the last decade and have been used for active materials in applications ranging from biosensors to drug delivery. However, the correlation between template properties and the subsequent assembly and triggered release behavior of the resultant carriers remain uninvestigated. In this study, ethylene glycol (EG) was added during the CaCO3 precipitation synthesis to yield particles of various sizes and surface properties, and the adenosine triphosphate (ATP)-responsive release characteristics of the fabricated DNA capsules affected by these particle properties were investigated. The geometry, crystallization, and surface morphology of the CaCO3 particles co-precipitated at various EG concentrations were characterized. We discuss the integrity of cross-linking hybridization, fluorescent molecule internalization, degree of leakage, and release efficiency of the resulting DNA capsules and their relevance brought by particle properties. To achieve efficient encapsulation and cargo release, the surface roughness of the CaCO3 particles was explored and was deemed a key determinant of the compactness of the DNA shell after template removal. This effect was particularly strong in CaCO3 particles in connection with high EG concentrations. The DNA capsules fabricated using 83% EG exhibited low leakage, high loading, and moderate release efficiencies as well as a greater apparent association constant with ATP due to their small particle size and the high-integrity DNA shells.

Hybridization chain reaction-assisted enzyme cascade genosensor for the detection of Listeria monocytogenes

Foodborne diseases caused by pathogens may threaten public health and the social economy. We demonstrated a method for identifying pathogenic Listeria monocytogenes using DNA logic operations. To achieve accurate species distinguishing, three specific sequences of Listeria monocytogenes genomic DNA were screened out and used as the feature sequences. Three complementary probes with tag modification were designed as sensing elements and exert affinity for magnetic beads, glucose oxidase (GOx), and horseradish peroxidase (HRP). To obtain a digital output (YES/NO answer) for rapid determination, a Boolean logic function was employed. Three sensing probes enabled the recognition of the target sequence (input) and the formation of a target DNA/probe hybrid. Through magnetic separation and affinity binding events, the target DNA/probes hybrid led to the construction of GOx/HRP enzyme cascade, which produced a visualized color signal (output) in the presence of substrates, glucose, and 3, 3', 5, 5'-tetramethylbenzidine (TMB). A hybridization chain reaction (HCR) was coupled with this sensing scaffold to increase the binding of the enzyme cascade and amplify the output signal. The logical functional biosensor showed high selectivity of Listeria monocytogenes over other Listeria species. This sensing platform provides a simple, sensitive, and highly specific method for detecting Listeria monocytogenes.

Stimuli-responsive hydrogel microcapsules for the amplified detection of microRNAs

A method for the synthesis of DNA-based acrylamide hydrogel microcapsules loaded with quantum dots as a readout signal is introduced. The shell of DNA-acrylamide hydrogel microcapsules is encoded with microRNA-responsive functionalities, being capable of the detection of cancer-associated microRNA. The microRNA-141 (miR-141), a potential biomarker in prostate cancer, was employed as a model target in the microcapsular biosensor. The sensing principle of the microcapsular biosensor is based on the competitive sequence displacement of target miR-141 with the bridging DNA in the microcapsule's shell, leading to the unlocking of DNA-acrylamide hydrogel microcapsules and the release of the readout signal provided by fluorescent quantum dots. The readout signal is intensified as the concentration of miR-141 increases. While miR-141 was directly measured by DNA-acrylamide hydrogel microcapsules, the linear range for the detection of miR-141 is 2.5 to 50 μM and the limit of detection is 1.69 μM. To improve the sensitivity of the microcapsular biosensor for clinical needs, the isothermal strand displacement polymerization/nicking amplification machinery (SDP/NA) process was coupled to the DNA-acrylamide hydrogel microcapsule sensor for the microRNA detection. The linear range for the detection of miR-141 is improved to the range of 10² to 10⁵ pM and the limit of detection is 44.9 pM. Compared to direct microcapsular biosensing, the detection limit for miR-141 by microcapsules coupled with strand-displacement amplification is enhanced by four orders of magnitude.

Single and Bilayer Polyacrylamide Hydrogel-Based Microcapsules for the Triggered Release of Loads, Logic Gate Operations, and Intercommunication between Microcapsules

A method to assemble loaded stimuli-responsive DNA-polyacrylamide hydrogel-stabilized microcapsules is presented. The method involves coating substrate-loaded CaCO₃ microparticles, functionalized with nucleic acid promoter units, and cross-linking DNA-modified polyacrylamide chains on the microcapsules, using the hybridization chain reaction (HCR) to yield the DNA-cross-linked hydrogel coating. Dissolution of the CaCO₃ particles generated the substrate-loaded hydrogel-protected microcapsules. The microcapsule-hydrogel shells include engineered stimuli-responsive oligonucleotide cross-linkers that control the stiffness of the hydrogel shells, allowing the triggered release of the loads. One approach includes the incorporation of cofactor-dependent DNAzyme units into the cross-linked hydrogel layers (cofactor = Mg²⁺ ions, Zn²⁺ ions, or histidine) as stimuli-responsive units. Cleavage of the cross-linking DNAzyme substrates by the respective cofactors yields hydrogel coatings with a reduced stiffness and higher porosity that allow the release of the loads. A further approach involved the application of the HCR process to assemble the bilayer hydrogel microcapsules that are unlocked by two cooperative triggers. Bilayer microcapsules consisting of a K⁺ ions-stabilized G-quadruplex/18-crown-6-ether (CE) responsive layer and a Mg²⁺ ion DNAzyme-responsive layers are presented. Unlocking and locking of the G-quadruplex cross-linked layer by 18-crown-6-ether and K⁺ ions, respectively, in the presence of Mg²⁺ ions allow the switchable controlled release of the load. In addition, the intercommunication of two kinds of stimuli-responsive bilayer hydrogel microcapsules carrying two different loads (tetramethylrhodamine-dextran, TMR-D, and CdSe/ZnS quantum dots) is demonstrated. The intercommunication process involves the stimuli-triggered generation of "information transfer" strands from one microcapsule to another that activate the release of the loads.

Topical tissue nano-transfection mediates non-viral stroma reprogramming and rescue

Although cellular therapies represent a promising strategy for a number of conditions, current approaches face major translational hurdles, including limited cell sources and the need for cumbersome pre-processing steps (for example, isolation, induced pluripotency). In vivo cell reprogramming has the potential to enable more-effective cell-based therapies by using readily available cell sources (for example, fibroblasts) and circumventing the need for ex vivo pre-processing. Existing reprogramming methodologies, however, are fraught with caveats, including a heavy reliance on viral transfection. Moreover, capsid size constraints and/or the stochastic nature of status quo approaches (viral and non-viral) pose additional limitations, thus highlighting the need for safer and more deterministic in vivo reprogramming methods. Here, we report a novel yet simple-to-implement non-viral approach to topically reprogram tissues through a nanochannelled device validated with well-established and newly developed reprogramming models of induced neurons and endothelium, respectively. We demonstrate the simplicity and utility of this approach by rescuing necrotizing tissues and whole limbs using two murine models of injury-induced ischaemia.

Mimicking Peroxidase Activities with Prussian Blue Nanoparticles and Their Cyanometalate Structural Analogues

Nanoparticles composed of Prussian Blue, PB, and the cyanometalate structural analogues, CuFe, FeCoFe, and FeCo, are examined as inorganic clusters that mimic the functions of peroxidases. PB acts as a superior catalyst for the oxidation of dopamine to aminochrome by H₂O₂. The oxidation of dopamine by H₂O₂ in the presence of PB is 6-fold faster than in the presence of CuFe. The cluster FeCo does not catalyze the oxidation of dopamine to aminochrome. The most efficient catalyst for the generation of chemiluminescence by the oxidation of luminol by H₂O₂ is, however, FeCo, and PB lacks any catalytic activity toward the generation of chemiluminescence. The order of catalyzed chemiluminescence generation is FeCo ≫ CuFe > FeCoFe. The clusters PB, CuFe, FeCoFe, and FeCo mimic the functions of NADH peroxidase. The catalyzed oxidation of NADH by H₂O₂ to form NAD⁺ follows the order PB ≫ CuFe ∼ FeCoFe, FeCo. The efficient generation of chemiluminescence by the FeCo-catalyzed oxidation of luminol by H₂O₂ is used to develop a glucose sensor. The aerobic oxidation of glucose in the presence of glucose oxidase, GOx, yields gluconic acid and H₂O₂. The chemiluminescence intensities formed by the GOx-generated H₂O₂ relate to the concentration of glucose, thus providing a quantitative readout signal for the concentrations of glucose.

pH- and ligand-induced release of loads from DNA-acrylamide hydrogel microcapsules

Herein, a method to construct stimuli-responsive DNA-acrylamide-based hydrogel microcapsules has been presented. This method involves the use of polyacrylamide chains modified with predesigned nucleic acid hairpin units and optionally single-strand tethers that provide the required hybridization and recognition functions to yield substrate-loaded stimuli-responsive hydrogel-based microcapsules. The synthesis of the microcapsules involves the loading of CaCO3 microparticles with the respective load substrates and the functionalization of the CaCO3 template particles with nucleic acid promoter units. In the presence of the hairpin-modified acrylamide chains, the promoter units induce the hybridization chain reaction (HCR), which leads to the formation of a hydrogel coating, which, after the dissociation of the CaCO3 cores, yields substrate-loaded stimuli-responsive hydrogel microcapsules. One of the microcapsule systems includes, in the hairpin-modified acrylamide constructs, and in the subsequent HCR-generated hydrogel shells, the caged sequences of anti-ATP or anti-cocaine aptamers. In the presence of ATP or cocaine, the duplex-caged aptamer sequences are separated via the formation of ATP- or cocaine-aptamer complexes, which results in the partial separation of the microcapsules and the release of the loads. The second type of microcapsule is cooperatively stabilized by bridges generated by HCR and pH-sensitive duplex units. Under acidic conditions, the pH-sensitive bridges dissociate via the formation of i-motif structures, which results in an increase in the fluidity of the microcapsule shells and the release of the loads. Preliminary studies indicate that ATP- or pH-responsive microcapsules loaded with the anticancer drug, doxorubicin, have a selective cytotoxic effect on MDA-MB-231 cancer cells.

Mimicking Horseradish Peroxidase Functions Using Cu2+-Modified Carbon Nitride Nanoparticles or Cu2+-Modified Carbon Dots as Heterogeneous Catalysts

Cu²⁺-functionalized carbon nitride nanoparticles (Cu²⁺-g-C₃N₄ NPs), ∼200 nm, and Cu²⁺-carbon dots (Cu²⁺-C-dots), ∼8 nm, act as horseradish peroxidase-mimicking catalysts. The nanoparticles catalyze the generation of chemiluminescence in the presence of luminol/H₂O₂ and catalyze the oxidation of dopamine by H₂O₂ to form aminochrome. The Cu²⁺-g-C₃N₄-driven generation of chemiluminescence is used to develop a H₂O₂ sensor and is implemented to develop a glucose detection platform and a sensor for probing glucose oxidase. Also, the Cu²⁺-C-dots are functionalized with the β-cyclodextrin (β-CD) receptor units. The concentration of dopamine, at the Cu²⁺-C-dots' surface, by means of the β-CD receptor sites, leads to a 4-fold enhancement in the oxidation of dopamine by H₂O₂ to yield aminochrome compared to that of the unmodified C-dots.

Mimicking Horseradish Peroxidase and NADH Peroxidase by Heterogeneous Cu2+-Modified Graphene Oxide Nanoparticles

Cu²⁺-ion-modified graphene oxide nanoparticles, Cu²⁺-GO NPs, act as a heterogeneous catalyst mimicking functions of horseradish peroxidase, HRP, and of NADH peroxidase. The Cu²⁺-GO NPs catalyze the oxidation of dopamine to aminochrome by H₂O₂ and catalyze the generation of chemiluminescence in the presence of luminol and H₂O₂. The Cu²⁺-GO NPs provide an active material for the chemiluminescence detection of H₂O₂ and allow the probing of the activity of H₂O₂-generating oxidases and the detection of their substrates. This is exemplified with detecting glucose by the aerobic oxidation of glucose by glucose oxidase and the Cu²⁺-GO NP-stimulated chemiluminescence intensity generated by the H₂O₂ product. Similarly, the Cu²⁺-GO NPs catalyze the H₂O₂ oxidation of NADH to the biologically active NAD⁺ cofactor. This catalytic system allows its conjugation to biocatalytic transformations involving NAD⁺-dependent enzyme, as exemplified for the alcohol dehydrogenase-catalyzed oxidation of benzyl alcohol to benzoic acid through the Cu²⁺-GO NPs-catalyzed regeneration of NAD⁺.

Programmed pH-Responsive Microcapsules for the Controlled Release of CdSe/ZnS Quantum Dots

Two methods for the preparation of pH-responsive all-DNA microcapsules loaded with CdSe/ZnS quantum dots (QDs) are discussed. One approach involves the construction of DNA microcapsules composed of nucleic acid layers that include, at pH 7.2, "dormant" C-G·C(+) triplex sequences. The formation of the C-G·C(+) triplex structures at pH 5.0 leads to the cleavage of the microcapsules and to the release of the QDs. A second approach involves the synthesis of CdSe/ZnS QD-loaded DNA microcapsules, stabilized at pH 7.2 by T-A·T interlayer triplex bridges. The dissociation of the bridges at pH 9.0 separates the bridging triplex units, resulting in the degradation of the microcapsules and to the release of the QDs. The programmed pH-stimulated release of luminescent QDs, emitting at 620 and 560 nm, from the C-G·C(+) or T-A·T triplex-responsive microcapsules is demonstrated by subjecting the QD-loaded microcapsule mixtures to pH 5.0 or pH 9.0, respectively.

Nucleoapzymes: Hemin/G-Quadruplex DNAzyme-Aptamer Binding Site Conjugates with Superior Enzyme-like Catalytic Functions

A novel concept to improve the catalytic functions of nucleic acids (DNAzymes) is introduced. The method involves the conjugation of a DNA recognition sequence (aptamer) to the catalytic DNAzyme, yielding a hybrid structure termed "nucleoapzyme". Concentrating the substrate within the "nucleoapzyme" leads to enhanced catalytic activity, displaying saturation kinetics. Different conjugation modes of the aptamer/DNAzyme units and the availability of different aptamer sequences for a substrate provide diverse means to design improved catalysts. This is exemplified with (i) The H2O2-mediated oxidation of dopamine to aminochrome using a series of hemin/G-quadruplex-dopamine aptamer nucleoapzymes. All nucleoapzymes reveal enhanced catalytic activities as compared to the separated DNAzyme/aptamer units, and the most active nucleoapzyme reveals a 20-fold enhanced activity. Molecular dynamics simulations provide rational assessment of the activity of the various nucleoapzymes. The hemin/G-quadruplex-aptamer nucleoapzyme also stimulates the chiroselective oxidation of L- vs D-DOPA by H2O2. (ii) The H2O2-mediated oxidation of N-hydroxy-L-arginine to L-citrulline by a series of hemin/G-quadruplex-arginine aptamer conjugated nucleoapzymes.

Deterministic transfection drives efficient nonviral reprogramming and uncovers reprogramming barriers

Safety concerns and/or the stochastic nature of current transduction approaches have hampered nuclear reprogramming's clinical translation. We report a novel non-viral nanotechnology-based platform permitting deterministic large-scale transfection with single-cell resolution. The superior capabilities of our technology are demonstrated by modification of the well-established direct neuronal reprogramming paradigm using overexpression of the transcription factors Brn2, Ascl1, and Myt1l (BAM). Reprogramming efficiencies were comparable to viral methodologies (up to ~9-12%) without the constraints of capsid size and with the ability to control plasmid dosage, in addition to showing superior performance relative to existing non-viral methods. Furthermore, increased neuronal complexity could be tailored by varying BAM ratio and by including additional proneural genes to the BAM cocktail. Furthermore, high-throughput NEP allowed easy interrogation of the reprogramming process. We discovered that BAM-mediated reprogramming is regulated by AsclI dosage, the S-phase cyclin CCNA2, and that some induced neurons passed through a nestin-positive cell stage.

FROM THE CLINICAL EDITOR

In the field of regenerative medicine, the ability to direct cell fate by nuclear reprogramming is an important facet in terms of clinical application. In this article, the authors described their novel technique of cell reprogramming through overexpression of the transcription factors Brn2, Ascl1, and Myt1l (BAM) by in situ electroporation through nanochannels. This new technique could provide a platform for further future designs.

Adenosine Triphosphate-Triggered Release of Macromolecular and Nanoparticle Loads from Aptamer/DNA-Cross-Linked Microcapsules

The synthesis of stimuli-responsive DNA microcapsules acting as carriers for different payloads, and being dissociated through the formation of aptamer-ligand complexes is described. Specifically, stimuli-responsive anti-adenosine triphosphate (ATP) aptamer-cross-linked DNA-stabilized microcapsules loaded with tetramethylrhodamine-modified dextran (TMR-D), CdSe/ZnS quantum dots (QDs), or microperoxidase-11 (MP-11) are presented. In the presence of ATP as trigger, the microcapsules are dissociated through the formation of aptamer-ATP complexes, resulting in the release of the respective loads. Selective unlocking of the capsules is demonstrated, and CTP, GTP, or TTP do not unlock the pores. The ATP-triggered release of MP-11 from the microcapsules enables the MP-11-catalyzed oxidation of Amplex UltraRed by H2O2 to the fluorescent product resorufin.

Magnetic tweezers-based 3D microchannel electroporation for high-throughput gene transfection in living cells

A novel high-throughput magnetic tweezers-based 3D microchannel electroporation system capable of transfecting 40 000 cells/cm(2) on a single chip for gene therapy, regenerative medicine, and intracellular detection of target mRNA for screening cellular heterogeneity is reported. A single cell or an ordered array of individual cells are remotely guided by programmable magnetic fields to poration sites with high (>90%) cell alignment efficiency to enable various transfection reagents to be delivered simultaneously into the cells. The present technique, in contrast to the conventional vacuum-based approach, is significantly gentler on the cellular membrane yielding >90% cell viability and, moreover, allows transfected cells to be transported for further analysis. Illustrating the versatility of the system, the GATA2 molecular beacon is delivered into leukemia cells to detect the regulation level of the GATA2 gene that is associated with the initiation of leukemia. The uniform delivery and a sharp contrast of fluorescence intensity between GATA2 positive and negative cells demonstrate key aspects of the platform for gene transfer, screening and detection of targeted intracellular markers in living cells.

Providing instrumental social support is more beneficial to reduce mortality risk among the elderly with low educational level in Taiwan: a 12-year follow-up national longitudinal study

BACKGROUND

To evaluate whether the effects of providing or receiving social support are more beneficial to reduce mortality risk among the elderly with different educational levels.

METHODS

In this long-term prospective cohort study, data were retrieved from the Taiwan Longitudinal Study on Aging. This study was initiated from 1996 until 2007. The complete data from 1492 males and 1177 females aged ≥67 years were retrieved. Participants received financial, instrumental, and emotional support, and they actively provided instrumental and emotional support to others and involved in social engagement. Education attainment was divided into two levels: high and low. The low education level included illiterate and elementary school. The high education level included junior high school to senior high school and above college. Cox regression analysis was used to examine the association between providing or receiving social support on mortality with different educational levels.

RESULTS

The average age of the participants in 1996 was 73.0 (IQR=8.0) years, and the median survival following years (1996-2007) of participants was 10.3 (IQR=6.7) years. Most participants were low educational level including illiterate (39.3%) and elementary school (41.2%). Participants with high educational level tend to be younger and more male significantly. On the contrary, participants with low educational level tend to have significant more poor income, more depression, more cognition impairment, more with IADL and ADL disability than high educational level. Most participants received instrumental support from others (95.5%) and also provided emotional support to others (97.7%). Providing instrumental support can reduce 17% of mortality risk among the elderly with a low level of education after adjusting several covariates [Hazard ratio (HR) = 0.83; 95% confidence interval (CI) = 0.70-0.99; p = 0.036].

CONCLUSIONS

Providing instrumental social support to others confer benefits to the giver and prolong life expectancy among the elderly with low educational levels.

Improved activity of immobilized antibody by paratope orientation controller: probing paratope orientation by electrochemical strategy and surface plasmon resonance spectroscopy

Electrochemical method and surface plasmon resonance (SPR) spectroscopic analysis are utilized herein to investigate antibody immobilization without and with orientation control for site-positioning paratopes (antigen binding site) of the antibody molecules. Biotin and its antibody were selected in current study as model. Such an approach employed thiophene-3-boronic acid (T3BA) as paratope orientation controller, (i) enabled site orientation of the antibody molecules reducing the hiding of paratopes, and (ii) maintained the activity of the captured antibodies, as confirmed by electrochemical and SPR analysis. Anti-biotin antibody (a glycoprotein) was covalently bound to a self-assembled monolayer of T3BA modified on a nanogold-electrodeposited screen-printed electrode through boronic acid-saccharide interactions, with the boronic acid units specifically binding to the glycosylation sites of the antibody molecules. The immunosensor functioned based on competition between the analyte biotin and biotin-tagged, potassium hexacyanoferrate(II)-encapsulated liposomes. The current signal produced by the released liposomal Fe(CN)6(4-), measured using square wave voltammetry, yielded a sigmoidally shaped dose-response curve that was linear over eight orders of magnitude (from 10(-11) to 10(-3)M). Furthermore this biosensing system fabricated based on T3BA approach was found to possess significantly improved sensitivity, and the limit of detection toward biotin was calculated as 0.102 ng mL(-1) (equivalent to 6 μL of 4.19 × 10(-10)M biotin).

Simulation of single DNA molecule stretching and immobilization in a de-wetting two-phase flow over micropillar-patterned surface

We investigate single DNA stretching dynamics in a de-wetting flow over micropillars using Brownian dynamics simulation. The Brownian dynamics simulation is coupled with transient flow field computation through a numerical particle tracking algorithm. The droplet formation on the top of the micropillar during the de-wetting process creates a flow pattern that allows DNA to stretch across the micropillars. It is found that DNA nanowire forms if DNA molecules could extend across the stagnation point inside the connecting water filament before its breakup. It also shows that DNA locates closer to the top wall of the micropillar has higher chance to enter the flow pattern of droplet formation and thus has higher chance to be stretched across the micropillars. Our simulation tool has the potential to become a design tool for DNA manipulation in complex biomicrofluidic devices.

Effect of phenethyl isothiocyanate on Ca2+ movement and viability in MDCK canine renal tubular cells

The effect of the natural compound phenethyl isothiocyanate (PEITC) on cytosolic Ca2+ concentrations ([Ca2+]i) and viability in MDCK renal cells is unknown. This study explored whether PEITC changed [Ca2+]i in MDCK cells using the Ca2+-sensitive fluorescent dye fura-2. PEITC at 200–700 μM increased [Ca2+]i in a concentration-dependent manner. The signal was reduced by removing extracellular Ca2+. PEITC-induced Ca2+ influx was inhibited by nifedipine, econazole, SK&F 96365 and protein kinase C modulators. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) or 2,5-di- tert-butylhydroquinone (BHQ) inhibited PEITC-induced rise in [Ca2+]i. Incubation with PEITC also inhibited TG or BHQ-induced rise in [Ca2+]i. Inhibition of phospholipase C with U73122 abolished PEITC-induced rise in [Ca2+]i. At 15–75 μM, PEITC decreased viability. The cytotoxic effect of PEITC was enhanced by chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid/acetoxymethyl ester. Annexin V-FITC data suggest that 20 and 50 μM PEITC induced apoptosis. At 10 and 15 μM, PEITC did not increase reactive oxygen species (ROS) production. Together, in renal tubular cells, PEITC-induced rise in [Ca2+]i by inducing phospholipase C-dependent Ca2+ release from endoplasmic reticulum and Ca2+ entry via store-operated Ca2+ channels. PEITC induced apoptosis in a concentration-dependent, ROS/Ca2+-independent manner.

Nanochannel electroporation delivers precise amounts of biomolecules into living cells

Many transfection techniques can deliver biomolecules into cells, but the dose cannot be controlled precisely. Delivering well-defined amounts of materials into cells is important for various biological studies and therapeutic applications. Here, we show that nanochannel electroporation can deliver precise amounts of a variety of transfection agents into living cells. The device consists of two microchannels connected by a nanochannel. The cell to be transfected is positioned in one microchannel using optical tweezers, and the transfection agent is located in the second microchannel. Delivering a voltage pulse between the microchannels produces an intense electric field over a very small area on the cell membrane, allowing a precise amount of transfection agent to be electrophoretically driven through the nanochannel, the cell membrane and into the cell cytoplasm, without affecting cell viability. Dose control is achieved by adjusting the duration and number of pulses. The nanochannel electroporation device is expected to have high-throughput delivery applications.

Formation and finite element analysis of tethered bilayer lipid structures

Rapid solvent exchange of an ethanolic solution of diphytanoyl phosphatidylcholine (DPhyPC) in the presence of a mixed self-assembled monolayer (SAM) [thiolipid/β-mercaptoethanol (βME) (3/7 mol/mol) on Au] shows a transition from densely packed tethered bilayer lipid membranes [(dp)tBLMs], to loosely packed tethered bilayer lipid membranes [(lp)tBLMs], and tethered bilayer liposome nanoparticles (tBLNs) with decreasing DPhyPC concentration. The tethered lipidic constructs in the aqueous medium were analyzed by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Finite element analysis (FEA) was applied to interpret spectral EIS features without referring to equivalent circuit modeling. Using structural data obtained earlier from neutron reflectometry and dielectric constants of lipid bilayers, we reproduced experimentally observed features of the electrochemical impedance (EI) spectra of complex surface constructs involving small pinhole defects, large membrane-free patches, and bound liposomes. We demonstrated by FEA that highly insulating (dp)tBLMs with low-defect density exhibit EI spectra in the shape of a perfect semicircle with or without low-frequency upward "tails" in the Cole-Cole representation. Such EI spectra were observed at DPhyPC concentrations of >5 × 10(-3) mol L(-1). While AFM was not able to visualize very small lateral defects in such films, EI spectra unambiguously signaled their presence by increased low frequency "tails". Using FEA we demonstrate that films with large diameter visible defects (>25 nm by AFM) produce EI spectral features consisting of two semicircles of comparable size. Such films were typically obtained at DPhyPC concentrations of <5 × 10(-3) mol L(-1). At DPhyPC concentrations of <1.0 × 10(-3) mol L(-1) the planar bilayer structures were replaced by ellipsoidal liposomes with diameters ranging from 50 to 500 nm as observed in AFM images. Despite the distinct surface morphology change, the EI curves exhibited two semicircle spectral features typical for the large size defects in planar tBLMs. FEA revealed that, to account for these EI features for bound liposome systems (50-500 nm diameter), one needs to assume much lower tBLM conductivities of the submembrane space, which separates the electrode surface and the phospholipid bilayer. Alternatively, FEA indicates that such features may also be observed on composite surfaces containing both bound liposomes and patches of planar bilayers. Triple semicircular features, observed in some of the experimental EI curves, were attributed to an increased complexity of the real tBLMs. The modeling demonstrated that such features are typical for heterogeneous tBLM surfaces containing large patches of different defectiveness levels. By integrating AFM, EIS, and FEA data, our work provides diagnostic criteria allowing the precise characterization of the properties and the morphology of surface supported bilayer systems.

Effect of thimerosal on Ca2+ movement and viability in human oral cancer cells

The effect of thimerosal on cytosolic free Ca2+ concentrations ([Ca2+]i ) in human oral cancer cells (OC2) is unclear. This study explored whether thimerosal changed basal [Ca2+]i levels in suspended OC2 cells using fura-2. Thimerosal at concentrations between 1and 50 μM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca 2+. Thimerosal-induced Ca2+ influx was not blocked by L-type Ca2+ entry inhibitors and protein kinase C modulators (phorbol 12-myristate 13-acetate [PMA] and GF109203X). In Ca2+-free medium, 50 μM thimerosal failed to induce a [Ca2+]i rise after pretreatment with thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor). Inhibition of phospholipase C with U73122 did not change thimerosal-induced [Ca2+]i rises. At concentrations between 5 and 10 μM, thimerosal killed cells in a concentration-dependent manner. The cytotoxic effect of 8 μM thimerosal was potentiated by prechelating cytosolic Ca2+ with the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetate/acetomethyl (BAPTA/ AM). Flow cytometry data suggested that 1—7 μM thimerosal-induced apoptosis in a concentration-dependent manner. Collectively, in OC2 cells, thimerosal-induced [Ca2+]i rises by causing phospholipase C-independent Ca2+ release from the endoplasmic reticulum and Ca2+ influx through non—L-type Ca2+ channels. Thimerosal killed cells in a concentration-dependent manner through apoptosis.

Novel modeling concept for evaluating the effects of cadmium and copper on heterotrophic growth and lysis rates in activated sludge process

A new modeling concept to evaluate the effects of cadmium and copper on heterotrophic growth rate constant (mu(H)) and lysis rate constant (b(H)) in activated sludge was introduced. The oxygen uptake rate (OUR) was employed to measure the constants. The results indicated that the mu(H) value decreased from 4.52 to 3.26 d(-1) or by 28% when 0.7 mg L(-1) of cadmium was added. Contrarily the b(H) value increased from 0.31 to 0.35 d(-1) or by 11%. When adding 0.7 mg L(-1) of copper, the mu(H) value decreased to 2.80 d(-1) or by 38%. The b(H) value increased to 0.42 d(-1) or by 35%. After regression, the inhibitory effect was in a good agreement with non-competitive inhibition kinetic. The inhibition coefficient values for cadmium and copper were 1.82 and 1.21 mg L(-1), respectively. The relation between the b(H) values and heavy metal concentrations agreed with exponential type well. The heavy metal would enhance b(H) value. Using these data, a new kinetic model was established and used to simulate the degree of inhibition. It was evident that not only the inhibitory effect on mu(H) but also that the enhancement effect on b(H) should be considered when heavy metal presented.

Interaction of polybrominated diphenyl ethers (PBDEs) with anaerobic mixed bacterial cultures isolated from river sediment

The degradation of flame retardant polybrominated diphenyl ethers (PBDE), including tetra-brominated diphenyl ether (BDE-47), penta-brominated diphenyl ether (BDE-99 and -100), and hexa-brominated diphenyl ether (BDE-153 and -154), by anaerobic bacterial mixed cultures isolated from river sediment was investigated. The effects of PBDEs on changes of anaerobic bacterial community in sediment culture were also studied. Sediments were collected from Er-Jen River and Nan-Kan River basins, which were both heavily polluted rivers in Taiwan, and bacteria from the sediment samples were enriched before the experiment was conducted. Into the anaerobic bacterial mixed cultures, 0.1 microg/mL of PBDEs was added followed by incubation under 30 degrees C for 70 days. Residues of PBDE were determined by gas chromatography with electron capture detector (GC-ECD), and the changes of bacterial community were analyzed by denaturing gradient gel electrophoresis (DGGE). Less than 20% of PBDEs were degraded after 70 days of incubation in all samples except for BDE-47 from the Nan-Kan River sediment. In that culture, BDE-47 was found to have notably degraded. In particular, after 42 days of incubation; BDE-47 was degraded, suddenly and sharply, to a negligible level on Day 70, and the result was confirmed by a repeated experiment. An interesting result was that although BDE-47 was degraded fast in the Nan-Kan River sediment, the bacterial communities did not shift significantly as we had speculated at Day 70. From UPGMA dendrograms, PBDEs changed the composition of bacterial communities, and the extents varied with the variety of PBDE congeners. By the amendment with BDE-153 or -154, bacterial communities would be changed immediately and irreversibly throughout the rest of the incubation period. No significant difference in degradation of PBDEs was observed between sediment bacteria from Er-Jen River and Nan-Kan River. However, the results verified the persistence of PBDEs in the environment.

Analysis of heart donation for cardiac transplantation at the National Taiwan University Hospital: Fifteen-year cases review

The demand for organ transplantation is disparate to the supply of organ donors. The organ shortage is a limitation for transplantation. This study analyzed the status of heart donors at the National Taiwan University Hospital (NTUH) from July 1987 through November 2001 using registry records. One hundred ninety-four total heart donors yielded about 25 donors per year in the late era (years of 1995-2001). The majority of heart donors were men (78.4%) of O blood type (46.9%) with a mean age of 29.8 (SD = 11.9) years. Though head injury was the main source of heart donors (78.4%), cerebrovascular accident patients have increased (15%) since 1995. However, the number of donors from head injury decreased in the year of 1997, when Taiwan passed a law to force motorcycle drivers to wear safety helmets. The average interval from brain death to donation was 75.4 (SD = 71.2) hours. One hundred fifty-six (80.4%) of the 194 donor hearts came from outside hospitals. However, the majority of heart transplantations (166 cases, 85.6%) were done at the NTUH. Implementing a program for a smooth donation and organ procurement processes should provide better donor management in cardiac transplantation.

Omapatrilat versus lisinopril: efficacy and neurohormonal profile in salt-sensitive hypertensive patients

Omapatrilat, a vasopeptidase inhibitor, simultaneously inhibits neutral endopeptidase and ACE. The efficacy and hormonal profile of omapatrilat and lisinopril were compared in salt-sensitive hypertensive patients. On enrollment, antihypertensive medications were withdrawn, and patients received a single-blind placebo. On day 15, salt-sensitivity determinations were made. Salt-sensitive hypertensive patients returned within 5 to 10 days for baseline evaluations of ambulatory diastolic blood pressure, ambulatory systolic blood pressure, and atrial natriuretic peptide. Salt-sensitive hypertensive patients were randomized to receive double-blind omapatrilat (n=28) or lisinopril (n=33) at initial doses of 10 mg for 1 week, increasing to 40 and 20 mg, respectively, for an additional 3 weeks. Ambulatory blood pressure and urinary atrial natriuretic peptide were assessed at study termination. Both omapatrilat and lisinopril significantly reduced mean 24-hour ambulatory diastolic and systolic blood pressures; however, omapatrilat produced significantly greater reductions in mean 24-hour ambulatory diastolic blood pressure (P=0.008), ambulatory systolic blood pressure (P=0.004), and ambulatory mean arterial pressure (P=0.005) compared with values from lisinopril. Both drugs potently inhibited ACE over 24 hours. Omapatrilat significantly (P<0.001) increased urinary excretion of atrial natriuretic peptide over 0- to 24-hour (3.8-fold) and 12- to 24-hour (2-fold) intervals; lisinopril produced no change. Omapatrilat significantly (P<0.001) increased urinary excretion of cGMP over the 0- to 24- and 4- to 8-hour intervals compared with that from lisinopril. Neither drug had a diuretic, natriuretic, or kaliuretic effect. In conclusion, in salt-sensitive hypertensive patients, omapatrilat demonstrated the hormonal profile of a vasopeptidase inhibitor and lowered ambulatory diastolic and systolic blood pressures more than lisinopril.

The cardiovascular actions of omapatrilat in spontaneously hypertensive rats

Omapatrilat is a newly developed vasopeptidase inhibitor that inhibits both angiotensin-converting enzyme (ACE) and neutral endopeptidase and has potent antihypertensive efficacy. However, the specific effect of omapatrilat on cardiac function and left ventricular hypertrophy with hypertension remains controversial. Therefore, we investigated the effect of omapatrilat on blood pressure, cardiac hypertrophy, and cardiac function in spontaneously hypertensive rats (SHR). Studies were performed in SHR that received vehicle (n = 9), omapatrilat (n = 10), or fosinopril (ACE inhibitor, n = 7) by daily gavage for 56 days. Systolic blood pressure (SBP) and mean blood pressure (MBP) were measured by tail plethysmography. Left ventricular fractional shortening and left ventricular mass were measured by echocardiography at day 56. Omapatrilat and fosinopril significantly decreased SBP and MBP from day 1 through day 56, and omapatrilat markedly reduced SBP and MBP compared with fosinopril from day 21 to day 56. Although both omapatrilat and fosinopril decreased left ventricular mass and left ventricular mass-to-body weight ratio with increased LV fractional shortening, omapatrilat had a more potent effect on the reduction of left ventricular mass and improvement of cardiac function. This study shows that in SHR, omapatrilat mediated a potent and stable antihypertensive effect and a reduction in left ventricular mass with improvement of cardiac function, compared with ACE inhibition alone.

Pharmacodynamics and pharmacokinetics of omapatrilat in heart failure

The purpose of this study was to determine the pharmacodynamics and pharmacokinetics of omapatrilat, administered orally (25 mg) or intravenously (10 mg) in 19 New York Heart Association class II and class III congestive heart failure (CHF) patients versus 17 healthy controls matched for age, race, gender, and weight. The plasma concentrations of atrial natriuretic peptide (ANP) increased by approximately 20% and 30% in CHF and control subjects, respectively, at 4 hours after intravenous or oral omapatrilat administration. Similar elevation in the cyclic guanosine monophosphate concentration (25% to 35%) and ANP urinary excretion (21 ng/24 h to 22 ng/24 h) was seen in all treatment groups after omapatrilat administration. Angiotensin-converting enzyme activity was > 90% inhibited at 4 hours after dosing and remained approximately 60% to 70% inhibited at 24 hours after dosing. The levels of endothelin-1 and endothelin-2 remained unchanged after oral or intravenous administration of omapatrilat. The maximal reduction in seated blood pressure compared with baseline was similarfor CHF and control subjects. Clinical pharmacokinetic parameters were similar in both groups after intravenous dosing, but maximum concentration and area under the concentration-time curve were elevated in CHF patients compared with controls after oral dosing. Omapatrilat was well tolerated; differences in systemic exposure and metabolism between CHF patients and controls did not appear to be clinically significant.

Omapatrilat: neurohormonal and pharmacodynamic profile when administered with furosemide

Pharmacodynamic effects of combination therapy with omapatrilat and furosemide were evaluated. Two groups of 13 healthy subjects each received furosemide 20 mg dailyfor 15 days coadministered with either placebo on days 6 to 15 or omapatrilat 10 mg on days 6 to 10 and 25 mg on days 11 to 15. In the omapatrilat group, urinary excretion of atrial natriuretic peptide increased, and greater blood pressure reductions were seen compared with placebo. Concomitant omapatrilat treatment did not affect the acute diuresis, natriuresis, and kaliuresis observed with chronic administration of furosemide. Neither effective renal plasma flow nor glomerularfiltration rate changed in either treatment group. No clinically significant safety issues were observed. Daily coadministration of omapatrilat 10 or 25 mg with furosemide 20 mg does not affect the pharmacodynamics offurosemide at steady state.

Oral bioavailability and disposition of [14C]omapatrilat in healthy subjects

The objective of this study was to determine the absolute oral bioavailability and disposition of omapatrilat. This single-dose, randomized, crossover study of 20 mg intravenous and 50 mg oral [14C]omapatrilat was conducted in 12 healthy male subjects to determine the disposition and oral bioavailability of omapatrilat, an orally active vasopeptidase inhibitor. Blood samples were collected up to 120 hours, and the excreta were collected over 168 hours postdose. Plasma concentrations of omapatrilat were determined by a validated LC/MS/MS procedure. Radioactivity in blood, plasma, urine, and feces was determined by liquid scintillation counting. Urinary excretion of radioactivity averaged 80% and 64% of intravenous and oral doses, respectively; < 1% of oral dose was excreted unchanged in urine. The absolute oral bioavailability of omapatrilat averaged 31%. Total body clearance of omapatrilat (80 L/h) exceeded liver plasma flow. Apparent steady-state volume of distribution of omapatrilat (21 L/kg) was extremely high compared with total body water. Omapatrilat undergoes substantial presystemic first-pass metabolism after oral administration. Omapatrilat is eliminated primarily by metabolism, and its metabolites are eliminated primarily in urine. Extrahepatic organs may be involved in the elimination of omapatrilat. Plasma concentrations of omapatrilat exhibit a prolonged terminal elimination phase, which represents elimination from a deep compartment.

Cell autonomous apoptosis defects in acid sphingomyelinase knockout fibroblasts

A body of evidence suggests that stress-induced sphingomyelin hydrolysis to the second messenger ceramide initiates apoptosis in some cells. Although studies using lymphoblasts from Niemann-Pick disease patients or acid sphingomyelinase (ASMase)-deficient mice have provided genetic support for this hypothesis, these models have not been universally accepted as definitive. Here, we show that mouse embryonic fibroblasts (MEFs) prepared from asmase mice manifest cell autonomous defects in apoptosis in response to several stresses. In particular, asmase(-/-) MEFs failed to generate ceramide and were totally resistant to radiation-induced apoptosis but remained sensitive to staurosporine, which did not induce ceramide. asmase(-/-) MEFs were also partially resistant to tumor necrosis factor alpha/ actinomycin D and serum withdrawal. Thus, resistance to apoptosis in asmase(-/-) MEFs was not global but rather stress type specific. Most importantly, the sensitivity to stress could be restored in the asmase(-/-) MEFs by administration of natural ceramide. Overcoming apoptosis resistance by natural ceramide is evidence that it is the lack of ceramide, not ASMase, that determines apoptosis sensitivity. The ability to rescue the apoptotic phenotype without reversing the genotype by the product of the enzymatic deficiency provides proof that ceramide is obligate for apoptosis induction in response to some stresses.

Weight-correction formula for maternal serum screening for Down syndrome in Taiwan

BACKGROUND AND PURPOSE

This study examined the relationship between maternal weight and serum marker concentrations (alpha-fetoprotein [AFP] and human chorionic gonadotropin [hCG]) to develop a weight-correction formula for second-trimester Down syndrome screening in Taiwan.

METHODS

We conducted a prospective observational study based on data from 18, 016 pregnant Taiwanese women who participated in a second-trimester Down syndrome screening program at Taiwan Adventist Hospital. The relationship between maternal weight and the multiple of median (MoM) concentrations of serum markers was analyzed using two methods; one involved all the observational data (all point method), while the other involved only the median concentrations at various gestational ages (median regression method). In each method, several statistical approaches were used, including simple-linear, reciprocal, quadratic, and log-transformation linear regression.

RESULTS

The correlation between maternal body weight and serum marker concentrations using the all point regression method was very poor, while the median regression method achieved a good fit. The reciprocal regression analysis had the best fit between AFP MoM concentration and maternal weight, while the best fit between hCG MoM concentration and maternal weight was achieved with quadratic regression analysis.

CONCLUSION

The present study has developed a race-specific weight-correction formula for Taiwanese women. This formula is expected to be helpful in second-trimester Down syndrome screening programs in Taiwan.

Quantitative structure-activity relationships for the pre-steady-state inhibition of cholesterol esterase by 4-nitrophenyl-N-substituted carbamates

4-Nitrophenyl-N-substituted carbamates (1-6) are the pseudo-substrate inhibitors of porcine pancreatic cholesterol esterase. Thus, the first step of the inhibition (Ki step) is the formation of the enzyme inhibitor tetrahedral adduct and the second step of the inhibition (kc) is the formation of the carbamyl enzyme. The formation of the enzyme inhibitor tetrahedral adduct is further divided into two steps, the formation of the enzyme-inhibitor complex with the dissociation constant, KS, at the first step and the formation of the enzyme-inhibitor tetrahedral adduct from the complex at the second step. The two-step mechanism for the formation of the enzyme-inhibitor tetrahedral adduct is confirmed by the pre-steady-state kinetics. The results of quantitative structure-activity relationships for the pre-steady-state inhibitions of cholesterol esterase by carbamates 1-6 indicate that values of -logKs and logk2/k-2 are correlated with the Taft substituent constant, sigma*, and the rho* values from these correlations are -0.33 and 0.1, respectively. The negative rho* value for the -logKS-sigma*-correlation indicates that the first step of the two-step formation of the enzyme-inhibitor tetrahedral adduct (KS step) is the formation of the positive enzyme inhibitor complex. The positive rho* value for the logk2/k-2 -sigma*-correlation indicates that the enzyme inhibitor tetrahedral adduct is more negative than the enzyme inhibitor complex. Finally, the two-step mechanism for the formation of the enzyme inhibitor tetrahedral adduct is proposed according to these results. Thus, the partially positive charge is developed at nitrogen of carbamates 1-6 in the enzyme-inhibitor complex probably due to the hydrogen bonding between the lone pair of nitrogen of carbamates 1-6 and the amide hydrogen of the oxyanion hole of the enzyme. The second step of the two-step formation of the enzyme-inhibitor tetrahedral adduct is the nucleophilic attack of the serine of the enzyme to the carbonyl group of carbamates 1-6 in the enzyme-inhibitor complex and develops the negative-charged oxygen in the adduct.

Binary/ternary combined effects of vitamin K3 with other antitumor agents in nasopharyngeal carcinoma CG1 cells

Nasopharyngeal carcinoma (NPC) is a prevalent cancer in Taiwan. To improve the treatment of NPC, we have extensively searched for effective combination chemotherapies. Our previous studies indicated that vitamin K3 (VK3) inhibits the growth of NPC CG1 cells in vitro. In this study, we further studied the binary/ternary combined effects of VK3 with other anticancer drugs against NPC cells. The antitumor effects of different VK3 combinations against CG1 cells were determined by using MTT assay, and the combined effects were evaluated by a taibologram, a modified isobolographic method being developed in our laboratory for the analyses of binary/ternary combinations of anticancer agents. Binary combinations of VK3 with doxorubicin (DOX), vinblastine (VBL), or 5-fluorouracil (5-FU) result in synergistic effects. For three-drug combinations, a remarkable synergy was found in the combination of VK3, VBL, and 5-FU. These in vitro results will provide useful information not only for further mechanistic studies and but also for future clinical trials of VK3-based cancer chemotherapy of NPC.

Comparison of the pharmacokinetics of fosinoprilat with enalaprilat and lisinopril in patients with congestive heart failure and chronic renal insufficiency

AIMS

To compare the serum pharmacokinetics of fosinoprilat with enalaprilat and lisinopril after 1 and 10 days of dosing with fosinopril, enalapril and lisinopril.

METHODS

Patients with congestive heart failure (CHF, NYHA Class II-IV) and chronic renal insufficiency (creatinine clearance </=30 ml min-1 ) were randomized to receive fosinopril, enalapril or lisinopril in two parallel-group studies. In the first study 24 patients were treated with 10 mg fosinopril (n=12 patients) or 2.5 mg enalapril (n=12) every morning for 10 consecutive days. In the second study 31 patients were treated with 10 mg fosinopril (n=16 patients) or 5 mg lisinopril (n=15) every morning for 10 consecutive days. Samples of blood were collected for determination of pharmacokinetic parameters. The area under the curve (AUC) between the first and last days of treatment and the accumulation index (AI) were the primary outcome measures.

RESULTS

All three angiotensin converting enzyme (ACE) inhibitors exhibited a significant increase in AUC between the first and last days of treatment in both studies. The difference between the AI for fosinoprilat (1.41) and enalaprilat (1.96) was statistically significant (95% CI: 1.05, 1.84). Similarly, the difference between the AI for fosinoprilat (1.21) and lisinopril (2.76) was statistically significant (95% CI: 1.85, 2.69). All three ACE inhibitors completely inhibited serum ACE for 24 h. All treatments were well tolerated.

CONCLUSIONS

Fosinoprilat exhibits significantly less accumulation than enalaprilat or lisinopril in patients with CHF and renal insufficiency, most probably because fosinoprilat is eliminated by both the kidney and liver, and increased hepatic elimination can compensate for reduced renal clearance in patients with kidney dysfunction.

Molecular recognition by acetylcholinesterase at the peripheral anionic site: structure-activity relationships for inhibitions by aryl carbamates

Substituted phenyl-N-butyl carbamates (1-9) are potent irreversible inhibitors of Electrophorus electricus acetylcholinesterase. Carbamates 1-9 act as the peripheral anionic site-directed irreversible inhibitors of acetylcholinesterase by the stop-time assay in the presence of a competitive inhibitor, edrophonium. Linear relationships between the logarithms of the dissociation constant of the enzyme inhibitor adduct (Ki), the inactivation constant of the enzyme-inhibitor adduct (k2), and the bimolecular inhibition constant (k(i)) for the inhibition of Electrophorus electricus acetylcholinesterase by carbamates 1-9 and the Hammett substituent constant (sigma), are observed, and the reaction constants (ps) are -1.36, 0.35 and -1.01, respectively. Therefore, the above reaction may form a positive charged enzyme-inhibitor intermediate at the peripheral anionic site of the enzyme and may follow the irreversible inactivation by a conformational change of the enzyme.

Reversal of radiation resistance in LNCaP cells by targeting apoptosis through ceramide synthase

Cell lines derived from human prostate cancer are regarded as relatively resistant to both radiation-induced clonogenic death and apoptosis. Here we attempted to modulate the response of LNCaP prostate cancer cells to radiation therapy (XRT) by pretreatment with 12-O-tetradecanoylphorbol acetate (TPA), a known apoptogenic agent in LNCaP cells. Using plateau-phase cultures, we investigated the response of these cells to XRT, TPA, and a combination of XRT and TPA. LNCaP irradiation did not result in ceramide generation or apoptosis. However, pretreatment with TPA enabled XRT to generate ceramide via activation of the enzyme ceramide synthase and signal apoptosis. Apoptosis was abrogated by the competitive inhibitor of ceramide synthase, fumonisin B1. Furthermore, when transplanted orthotopically into the prostate of nude mice, LNCaP cells produced tumors that recapitulated the responses of LNCaP cells in vitro. XRT or TPA failed to signal apoptosis in LNCaP tumors, whereas a combination of the two resulted in substantial (20-25%) apoptosis within 24 h. There was an additional benefit associated with this regimen because TPA pretreatment protected the adjacent rectum from radiation-induced apoptosis. This represents the first description of signaling-based therapy designed to overcome one form of radiation resistance expressed preferentially in LNCaP human prostate cancer cells.

Ataxia telangiectasia-mutated gene product inhibits DNA damage-induced apoptosis via ceramide synthase

DNA double-stranded breaks (dsb) activate surveillance systems that identify DNA damage and either initiate repair or signal cell death. Failure of cells to undergo appropriate death in response to DNA damage leads to misrepair, mutations, and neoplastic transformation. Pathways linking DNA dsb to reproductive or apoptotic death are virtually unknown. Here we report that metabolic incorporation of 125I-labeled 5-iodo-2'deoxyuridine, which produces DNA dsb, signaled de novo ceramide synthesis by post-translational activation of ceramide synthase (CS) and apoptosis. CS activation was obligatory, since fumonisin B1, a fungal pathogen that acts as a specific CS inhibitor, abrogated DNA damage-induced death. X-irradiation yielded similar results. Furthermore, inhibition of apoptosis using the peptide caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone did not affect CS activation, indicating this event is not a consequence of induction of apoptosis. ATM, the gene mutated in ataxia telangiectasia, is a member of the phosphatidylinositol 3-kinase family that constitutes the DNA damage surveillance/repair system. Epstein-Barr virus-immortalized B cell lines from six ataxia telangiectasia patients with different mutations exhibited radiation-induced CS activation, ceramide generation, and apoptosis, whereas three lines from normal patients failed to manifest these responses. Stable transfection of wild type ATM cDNA reversed these events, whereas antisense inactivation of ataxia telangiectasia-mutated gene product in normal B cells conferred the ataxia telangiectasia phenotype. We propose that one of the functions of ataxia telangiectasia-mutated gene product is to constrain activation of CS, thereby regulating DNA damage-induced apoptosis.

Fosinopril: pharmacokinetics and pharmacodynamics in Chinese subjects

This study examined thepharmacokinetics and pharmacodynamics of fosinopril (IVand oral) in Chinese subjects to determine whether they were different from a group of somewhat heavier and older Western control subjects previously published using the same methods. It was an open-label, randomized, balanced, two-way crossover study comparing oral and IV pharmacokinetics in 12 healthy Chinese subjects in a clinic in Taiwan. Each subject received 10 mg of oral fosinopril or 7.5 mg of IV fosinoprilatin a randomized sequence with sampling for fosinoprilat concentrations over 48 hours. Standard pharmacokinetics, including AUC, Cmax Tmax, T 1/2, Vss, bioavailability, total clearance, and renal and nonrenal clearance, were determined as well as pharmacodynamic effects on angiotensin-converting enzyme (ACE) activity. Following oral administration of 10 mg fosinopril, AUC0-T and AUCinf were 1,556 +/- 586 ng x hr/mL and 1,636 +/- 620 ng x hr/mL, respectively; T 1/2 was 17.4 +/- 11.4 hr; Cmax was 183.4 +/- 59.4 ng/mL; and median Tmax was 4.0 hr, with > 99% protein binding. Following IV administration of 7.5 mg fosinoprilat, AUC0-T and AUCinf were 7,727 +/- 2,638 ng x hr/mL and 7,816 +/- 2,693 ng x hr/mL, respectively; T 1/2 was 13.0 +/- 5.2 hr; and median Tmax was 4.0 hr, with 99.5% +/- 0.22% protein binding and a Vss of 5,850 +/- 2,780 mL. Bioavailability was 22.3% +/- 7.9%. Percent urinary excretion was 7.6% +/- 2.6% after oral dosing and 42.6% +/- 6.1% after IV dosing. After IV, dosing total clearance was 1,088 +/- 439 mL/hr, renal clearance was 472 +/- 213 mL/hr, and nonrenal clearance was 617 +/- 246 mL/hr. ACE inhibition was essentially complete through 12 hours and markedly reduced through 24 hours. Compared to a somewhat heavier and older previously reported control group, pharmacokinetic values were similar except for a slightly lower AUC and total clearance in Chinese and a statistically significantly lower nonrenal clearance. Pharmacodynamic effects on ACE activity were essentially identical. There is no reason to expect significant differences in fosinopril dosing or effect in a Chinese population compared to a Western population.