18 research outputs found
Danicamtiv increases myosin recruitment and alters cross-bridge cycling in cardiac muscle
Background: Modulating myosin function is a novel therapeutic approach in patients with cardiomyopathy. Danicamtiv is a novel myosin activator with promising preclinical data that is currently in clinical trials. While it is known that danicamtiv increases force and cardiomyocyte contractility without affecting calcium levels, detailed mechanistic studies regarding its mode of action are lacking.
Methods: Permeabilized porcine cardiac tissue and myofibrils were used for X-ray diffraction and mechanical measurements. A mouse model of genetic dilated cardiomyopathy was used to evaluate the ability of danicamtiv to correct the contractile deficient.
Results: Danicamtiv increased force and calcium sensitivity via increasing the number of myosins in the on state and slowing cross-bridge turnover. Our detailed analysis showed that inhibition of ADP release results in decreased cross-bridge turnover with cross bridges staying attached longer and prolonging myofibril relaxation. Danicamtiv corrected decreased calcium sensitivity in demembranated tissue, abnormal twitch magnitude and kinetics in intact cardiac tissue, and reduced ejection fraction in the whole organ.
Conclusions: As demonstrated by the detailed studies of Danicamtiv, increasing myosin recruitment and altering crossbridge cycling are 2 mechanisms to increase force and calcium sensitivity in cardiac muscle. Myosin activators such as Danicamtiv can treat the causative hypocontractile phenotype in genetic dilated cardiomyopath
Robust collaborative passenger flow control on a congested metro line: A joint optimization with train timetabling
With the rapid increase in residents in megacities, the passenger demand of metro systems is rising sharply and steadily, bringing immense pressure to train operations. To improve the service quality, this paper discusses systematically investigating a joint optimization of the robust passenger flow control strategy and train timetable on a congested metro line. A deterministic model for train timetabling and passenger flow control at each station is first developed to make a trade-off between operation efficiency and service fairness. Then, the uncertain passenger demand is further considered at each station, and three integer linear programming models are formulated to derive the robust passenger flow control strategies. The first two models are related to the technique of Light Robustness, in which the uncertainty is handled by inserting expected protection levels at stations or on trains. In addition, with a stochastic scenario set that characterizes the uncertain passenger information, the last model aims to find a solution that is feasible for all involved scenarios, and thus, reduces the impact of the uncertainty in metro systems. To improve the computational efficiency of large-scale instances, a customized decomposition-based algorithm is developed. Finally, some real-world case studies based on the operation data of the Beijing metro Batong line are conducted to verify the performance and effectiveness of the proposed approaches
A Distributionally Robust Optimization Method for Passenger Flow Control Strategy and Train Scheduling on an Urban Rail Transit Line
Regular coronavirus disease 2019 (COVID-19) epidemic prevention and control have raised new requirements that necessitate operation-strategy innovation in urban rail transit. To alleviate increasingly serious congestion and further reduce the risk of cross-infection, a novel two-stage distributionally robust optimization (DRO) model is explicitly constructed, in which the probability distribution of stochastic scenarios is only partially known in advance. In the proposed model, the mean-conditional value-at-risk (CVaR) criterion is employed to obtain a tradeoff between the expected number of waiting passengers and the risk of congestion on an urban rail transit line. The relationship between the proposed DRO model and the traditional two-stage stochastic programming (SP) model is also depicted. Furthermore, to overcome the obstacle of model solvability resulting from imprecise probability distributions, a discrepancy-based ambiguity set is used to transform the robust counterpart into its computationally tractable form. A hybrid algorithm that combines a local search algorithm with a mixed-integer linear programming (MILP) solver is developed to improve the computational efficiency of large-scale instances. Finally, a series of numerical examples with real-world operation data are executed to validate the proposed approaches
Preparation of a Magnetic Molecularly Imprinted Graphene Composite Highly Adsorbent for 4‑Nitrophenol in Aqueous Medium
In
this article, a type of magnetic molecularly imprinted graphene
composite as a highly efficient adsorbent was prepared by forming
a molecularly imprinted sol–gel polymer on the surface of magnetic
graphene. The magnetic Fe<sub>3</sub>O<sub>4</sub> nanoparticles were
first deposited on a graphene sheet to prepare the magnetic graphene
(MGR). Using the obtained magnetic graphene as a supporting matrix,
4-nitrophenol (4-NP) as template, phenyltriethoxysilane and tetramethoxysilane
as functional monomers, a magnetic molecularly imprinted graphene
composite (MGR@MIPs) was subsequently formed after the sol–gel
polymerization and extraction of 4-NP. The preparation conditions
(concentrations of monomer and template, and reaction time) were optimized.
The as-prepared MGR@MIPs was characterized by FTIR, VSM, SEM, and
TEM images. Under the optimized conditions, the obtained MGR@MIPs
exhibited ultrafast adsorption kinetics (2 min to achieve the equilibrium
state), large binding capacity (142 mg/g), and high selectivity toward
4-NP (the imprinting factor α is 4.25). In addition, a high
saturation magnetization of MGR@MIPs was demonstrated, which allows
easy separation from solution by applying an external magnetic field.
Meanwhile, MGR@MIPs can be regenerated and reused in successive six
cycles with slight loss in adsorption capacity. Finally, MGR@MIPs
was successfully used as a highly adsorbent material for the determination
and separation of 4-NP in real samples combining with high-performance
liquid chromatography (HPLC)
Propylene Glycol-Linked Amino Acid/Dipeptide Diester Prodrugs of Oleanolic Acid for PepT1-Mediated Transport: Synthesis, Intestinal Permeability, and Pharmacokinetics
In our previous studies, ethylene
glycol-linked amino acid diester
prodrugs of oleanolic acid (OA), a Biopharmaceutics Classification
System (BCS) class IV drug, designed to target peptide transporter
1 (PepT1) have been synthesized and evaluated. Unlike ethylene glycol,
propylene glycol is of very low toxicity in vivo. In this study, propylene
glycol was used as a linker to further compare the effect of the type
of linker on the stability, permeability, affinity, and bioavailability
of the prodrugs of OA. Seven diester prodrugs with amino acid/dipeptide
promoieties containing l-Val ester (<b>7a</b>), l-Phe ester (<b>7b</b>), l-Ile ester (<b>7c</b>), d-Val-l-Val ester (<b>9a</b>), l-Val-l-Val ester (<b>9b</b>), l-Ala-l-Val ester (<b>9c</b>), and l-Ala-l-Ile ester
(<b>9d</b>) were designed and successfully synthesized. In situ
rat single-pass intestinal perfusion (SPIP) model was performed to
screen the effective permeability (<i>P</i><sub>eff</sub>) of the prodrugs. <i>P</i><sub>eff</sub> of <b>7a</b>, <b>7b</b>, <b>7c</b>, <b>9a</b>, <b>9b</b>, <b>9c</b>, and <b>9d</b> (6.7-fold, 2.4-fold, 1.24-fold,
1.22-fold, 4.15-fold, 2.2-fold, and 1.4-fold, respectively) in 2-(<i>N</i>-morpholino)Âethanesulfonic acid buffer (MES) with pH 6.0
showed significant increase compared to that of OA (<i>p</i> < 0.01). In hydroxyethyl piperazine ethanesulfonic acid buffer
(HEPES) of pH 7.4, except for <b>7c</b>, <b>9a</b>, and <b>9d</b>, <i>P</i><sub>eff</sub> of the other prodrugs
containing <b>7a</b> (5.2-fold), <b>7b</b> (2.0-fold), <b>9b</b> (3.1-fold), and <b>9c</b> (1.7-fold) exhibited significantly
higher values than that of OA (<i>p</i> < 0.01). In inhibition
studies with glycyl-sarcosine (Gly-Sar, a typical substrate of PepT1), <i>P</i><sub>eff</sub> of <b>7a</b> (5.2-fold), <b>7b</b> (2.0-fold), <b>9b</b> (3.1-fold), and <b>9c</b> (2.3-fold)
had significantly reduced values (<i>p</i> < 0.01). Compared
to the apparent permeability coefficient (<i>P</i><sub>app</sub>) of OA with Caco-2 cell monolayer, significant enhancement of the <i>P</i><sub>app</sub> of <b>7a</b> (5.27-fold), <b>9b</b> (3.31-fold), <b>9a</b> (2.26-fold), <b>7b</b> (2.10-fold), <b>7c</b> (2.03-fold), <b>9c</b> (1.87-fold), and <b>9d</b> (1.39-fold) was also observed (<i>p</i> < 0.01). Inhibition
studies with Gly-Sar (1 mM) showed that <i>P</i><sub>app</sub> of <b>7a</b>, <b>9b</b>, and <b>9c</b> significantly
reduced by 1.3-fold, 1.6-fold, and 1.4-fold (<i>p</i> <
0.01), respectively. These results may be attributed to PepT1-mediated
transport and their differential affinity toward PepT1. According
to the permeability and affinity, <b>7a</b> and <b>9b</b> were selected in the pharmacokinetic studies in rats. Compared with
group OA, <i>C</i><sub>max</sub> for group <b>7a</b> and <b>9b</b> was enhanced to 3.04-fold (<i>p</i> < 0.01) and 2.62-fold (<i>p</i> < 0.01), respectively.
AUC<sub>0→24</sub> was improved to 3.55-fold (<i>p</i> < 0.01) and 3.39-fold (<i>p</i> < 0.01), respectively.
Compared to the ethylene glycol-linked amino acid diester prodrugs
of OA in our previous work, results from this study revealed that
part of the propylene glycol-linked amino acid/dipeptide diester prodrugs
showed better stability, permeability, affinity, and bioavailability.
In conclusion, propylene glycol-linked amino acid/dipeptide diester
prodrugs of OA may be suitable for PepT1-targeted prodrugs of OA to
improve the oral bioavailability of OA
Redox-triggered mitoxantrone prodrug micelles for overcoming multidrug-resistant breast cancer
Orally delivered polycurcumin responsive to bacterial reduction for targeted therapy of inflammatory bowel disease
Inflammatory bowel disease (IBD) such as Crohn’s disease and ulcerative colitis is a chronic autoimmune disease affecting nearly five million people worldwide. Among all drug delivery system, oral administration is the most preferable route for colon-specific targeting and the treatment of IBD. Herein, an amphiphilic curcumin polymer (PCur) composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic curcumin (Cur) linked by disulfide bond was synthesized and characterized. The sufficient solubility, nano-scaled size and close to the neutral surface potential of PCur lead to preferential accumulation of the active drug in the inflamed regions of the gut. Moreover, PCur showed limited drug release and enhanced robustness under the physiological pH of the gastrointestinal tract (GIT), and a significantly elevated release was observed when responding to a bacterial reduction in the colon. Furthermore, cellular studies confirmed PCur had low cytotoxicity and increased transmembrane permeability, resulting in improved oral bioavailability evidenced by in vivo pharmacokinetics of rats. Finally, with DSS-induced murine model of IBD, we demonstrated that orally administered PCur ameliorated the inflammatory progression in the colon and could protect mice from IBD. In conclusion, it is illustrated that the developed PCur conjugate could potentially be employed as a colon-specific candidate for IBD treatment
Orally delivered polycurcumin responsive to bacterial reduction for targeted therapy of inflammatory bowel disease
Redox-triggered mitoxantrone prodrug micelles for overcoming multidrug-resistant breast cancer
<p>Multidrug resistance (MDR) severely hinders the efficient chemotherapeutic treatments of cancer. d-α-Tocopherol polyethylene 1000 succinate (TPGS) based drug delivery system holds the potential of re-sensitizing resistant cancer cells. In this study, a TPGS prodrug containing both TPGS and mitoxantrone (MTO) via a disulphide bond was synthesised and assembled into micelle (TSMm) with a monodispersed diameter of 46.50 ± 1.12 nm. The disulphide bonds within the micelles could be cleaved in response to a high concentration of intracellular glutathione (GSH) after entering the tumour cells, leading a rapid release of MTO. <i>In vitro</i> cytotoxicity study showed TSMm significantly inhibited the growth of resistant breast tumour cells MDA-MB-231/MDR comparing to either free MTO or disulphide-free prodrug micelle (TCMm). In addition, TSMm could sustain favourable intracellular retention and cause the depletion of ATP activity, leading to the preferential transportation of MTO into the nucleus and the reversal of MDR. <i>In vivo</i> imaging also verified that TSMm was specifically targeted to the tumour regions at 24 h post injection. Finally, TSMm has significantly stronger antitumor activity in xenograft nude mice with negligible side effects. Hence, TSMm can serve as promising prodrug candidates to strengthen the reversal of MDR in tumours with less side effects.</p
Ethylene Glycol-Linked Amino Acid Diester Prodrugs of Oleanolic Acid for PepT1-Mediated Transport: Synthesis, Intestinal Permeability and Pharmacokinetics
The purposes of this study were to expand the structure
of parent
drugs selected for peptide transporter 1 (PepT1)-targeted ester prodrug
design and to improve oral bioavailability of oleanolic acid (OA),
a Biopharmaceutics Classification System (BCS) class IV drug. Through
an ethoxy linker the carboxylic acid group of OA was conjugated with
the carboxylic acid group of different amino acid promoieties to form
six diester prodrugs. The effective permeability (<i>P</i><sub>eff</sub>) of prodrugs was screened by in situ rat single-pass
intestinal perfusion (SPIP) model in two buffers with different pH
(6.0 and 7.4) as PepT1 employs a proton-gradient as the driving force.
Compared to OA, 2.5-fold, 2.3-fold, 2.2-fold, 2.1-fold, and 1.9-fold
enhancement of <i>P</i><sub>eff</sub> in buffer with pH
6.0 was observed for l-Phe ester (<b>5c</b>), l-Val ester (<b>5a</b>), l-Lys ester (<b>5e</b>), d-Phe ester (<b>5d</b>), and d-Val ester
(<b>5b</b>), respectively. Furthermore, <i>P</i><sub>eff</sub> of <b>5a</b>, <b>5c</b>, <b>5d</b> and <b>5e</b> in pH 6.0 was significantly higher than that in pH 7.4
(<i>p</i> < 0.01), respectively. These results showed
that the H<sup>+</sup> concentration of perfusion solution had great
effect on the transport of the prodrugs across intestinal membrane.
For the further evaluation of affinity to PepT1, inhibition studies
were performed by coperfusing 0.1 mM prodrug with 50 mM glycyl-sarcosine
(Gly-Sar, a typical substrate of PepT1). It turned out that the <i>P</i><sub>eff</sub> of <b>5a</b>, <b>5b</b>, <b>5c</b> and l-Tyr ester (<b>6f</b>) significantly
reduced in the presence of Gly-Sar (1.7-fold, 2.2-fold, 1.9-fold,
and 1.4-fold, respectively). We supposed that it may be attributed
to PepT1 mediated transport of these prodrugs. <b>5a</b> and <b>6f</b> were selected as the optimal target prodrugs for oral absorption <i>in vivo</i>. Following intragastric administration of 300 mg/kg
(calculated as OA) <b>5a</b>, <b>6f</b> and OA in three
groups of rats, compared with group OA, <i>C</i><sub>max</sub> for the group of <b>5a</b> and <b>6f</b> was enhanced
by 1.56-fold and 1.54-fold, respectively. <i>F</i><sub>app</sub> of group <b>5a</b> and <b>6f</b> was 2.21- and 2.04-fold
increased, respectively, indicating that <b>5a</b> and <b>6f</b> had better oral absorption than OA. The combined results
also suggest that diester prodrugs which conjugated two carboxylic
acid groups of proper amino acid promoieties and parent drug through
a linker can be used for PepT1-targeted prodrug design. With this
strategy, oral bioavailability of OA in rats could be improved significantly