A novel pH-sensitive liposome formulation containing oleyl alcohol

AbstractpH-sensitive liposomes are designed to undergo acid-triggered destabilization. First generation pH-sensitive liposomes, based on the cone-shaped lipid dioleoylphosphatidylethanolamine (DOPE), have been shown to lose fusogenicity in the presence of serum. Here, we report the design and evaluation of novel serum-resistant pH-sensitive liposome formulations that are based on the composition of egg phosphatidylcholine (PC), cholesteryl hemisuccinate (CHEMS), oleyl alcohol (OAlc), and Tween-80 (T-80). When loaded with the fluorescent probe calcein, these liposomes exhibited excellent stability at pH 7.4 and underwent rapid destabilization upon acidification as shown by calcein dequenching and particle size increase. Adjusting the mole percentages of T-80 and OAlc in the formulation could regulate the stability and pH-sensitive properties of these liposomes. Liposomes with a higher T-80 content exhibited greater stability but were less sensitive to acid-induced destabilization. Meanwhile, formulations with a higher OAlc content exhibited greater content release in response to low pH. The pH-triggered liposomal destabilization did not produce membrane fusion according to an octadecylrhodamine B chloride (R18) lipid-mixing assay. Compared to DOPE-based pH-sensitive liposomes, the above formulations showed much better retention of their pH-sensitive properties in the presence of 10% serum. These liposomes were then evaluated for intracellular delivery of entrapped cytosine-β-d-arabinofuranoside (araC) in KB human oral cancer cells, which have elevated folate receptor (FR) expression. The FR, which is amplified in many types of human tumors, has been shown to mediate the internalization of folate-derivatized liposomes into an acidic intracellular compartment. FR-targeted OAlc-based pH-sensitive liposomes, entrapping 200 mM araC, showed ∼17-times greater FR-dependent cytotoxicity in KB cells compared to araC delivered via FR-targeted non-pH-sensitive liposomes. These data indicated that pH-sensitive liposomes based on OAlc, combined with FR-mediated targeting, are promising delivery vehicles for membrane impermeable therapeutic agents

Regularized Semiparametric Estimation for Ordinary Differential Equations

<div><p>Ordinary differential equations (ODEs) are widely used in modeling dynamic systems and have ample applications in the fields of physics, engineering, economics, and biological sciences. The ODE parameters often possess physiological meanings and can help scientists gain better understanding of the system. One key interest is thus to well estimate these parameters. Ideally, constant parameters are preferred due to their easy interpretation. In reality, however, constant parameters can be too restrictive such that even after incorporating error terms, there could still be unknown sources of disturbance that lead to poor agreement between observed data and the estimated ODE system. In this article, we address this issue and accommodate short-term interferences by allowing parameters to vary with time. We propose a new regularized estimation procedure on the time-varying parameters of an ODE system so that these parameters could change with time during transitions but remain constants within stable stages. We found, through simulation studies, that the proposed method performs well and tends to have less variation in comparison to the nonregularized approach. On the theoretical front, we derive finite-sample estimation error bounds for the proposed method. Applications of the proposed method to modeling the hare–lynx relationship and the measles incidence dynamic in Ontario, Canada lead to satisfactory and meaningful results. Supplementary materials for this article are available online.</p></div

Data_Sheet_1_Green physical activity for leisure connects perceived residential greenspace and mental well-being.docx

Physical activity serves as a pivotal mediator in previous theoretical frameworks that link greenspace and human health. However, it remains unclear whether the domain of physical activity within and around greenspaces can alter the pathway. The present study recruited 668 participants online and examined a conceptual framework that explores the associations between residential greenspace and mental well-being, with a particular focus on the mediation effect of green physical activity (physical activity undertaken in and around greenspaces). Moreover, socio-demographic characteristics, including gender, age, household income, education status, marital status, and student status, were controlled for during the examination. The investigated green physical activities included leisure activities, transportation walking, and transportation cycling, and they were measured by a pre-established questionnaire. Meanwhile, mental well-being was measured by the WHO-5 well-being index, and residential greenspace was indicated by self-reported perceived greenspace and mean Normalized Difference Vegetation Index (NDVI) values within 500 meters (m) of residential radius. We found that both perceived greenspace (B = 1.852, p 500 m (B = 3.230, p = 0.038) were positively associated with mental well-being. However, only perceived greenspace, not NDVI 500 m, exhibited positive associations with the three green physical activity items. Furthermore, only green physical activity for leisure (B = 0.223, p  0.05), mediated the relationship between perceived greenspace and mental well-being. Our findings reinforce previous studies on “greenspace-health” frameworks and underline the importance of leisure physical activity in promoting mental well-being.</p

CPDT and SF block Nrf2 ubiquitination.

<p>NBT-II cells were co-transfected for 24 h with expression plasmids for Nrf2 (pEF/Nrf2), Keap1 (pcDNA1/Keap1) or ubiquitin (pMT107-His-Ub, a polyhistidine-tagged ubiquitin expression plasmid), followed by treatment for 6 h with MG132 (25 µM), MG132 (25 µM) plus CPDT (50 µM), or MG132 (25 µM) plus SF (8 µM), from which cytoplasmic and nuclear samples were prepared and analyzed by IB of various proteins. For detection of ubiquitinated Nrf2, the samples were prepared under denatured conditions and then subjected to IP with anti-Nrf2, followed by IB with an anti-His-HRP-conjugated antibody (for detection of ubiquitinated Nrf2). Equal amounts of nuclear and cytoplasmic proteins were used. The arrow points to the Ub band.</p

CPDT and SF stimulate Nrf2 transactivation activity by stabilizing its protein.

<p>(<b>A</b>) Chemical structure of CPDT and SF. RT-4 cells and NBT-II cells were treated with CPDT (50 µM), SF (8 µM) or vehicle (0.1% DMSO) for 6 or 24 h. (<b>B</b>) Whole cell lysates were then prepared for IB or (<b>C</b>) total RNA was isolated for RT-PCR analysis. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was used as a control.</p

CPDT and SF block Nrf2 degradation mainly in the nucleus, but do not dissociate the Nrf2-Keap1 complex or the ubiquitination complex.

<p>RT-4 cells and NBT-II cells were treated with vehicle, CPDT (50 µM) or SF (8 µM) for 6 h, from which cytosols and nuclear extracts were prepared and were subjected to analysis by IB or IP followed by IB. The loading amount of the nuclear sample was about half of the cytoplasmic sample for both IP and IB. (<b>A</b>) IB of indicated proteins. GAPDH and lamin A were used to confirm the purity of the cytosols and nuclear extracts, respectively. (<b>B</b>) Cytosols and nuclear extracts were subjected to IP with anti-Keap1, followed by IB of the indicated proteins.</p

The paradigm of chemical activation of Nrf2.

<p>The Keap1-mediated Nrf2 ubiquitination and proteasomal degradation exist in both cytoplasm and nucleus. Nrf2 activators block Nrf2 ubiquitination by causing conformational change of Keap1 through reaction with its critical cysteine residues (C273 and C288), and this process occurs primarily in the nucleus. Keap1 is shown as a monomer in this model, but a previous study suggests that Nrf2 may be associated with Keap1 homodimer <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035122#pone.0035122-McMahon1" target="_blank">[43]</a>.</p

CPDT and SF block only Keap1-mediated Nrf2 degradation and require key cysteine residues of Keap1.

<p>(<b>A</b>) Murine embryonic fibroblasts (MEF), including wild type MEF (Keap1^+/+) and MEF with Keap1 knockout (Keap1^−/−), were treated with vehicle, MG132 (25 µM), CPDT (50 µM) or SF (8 µM) for 6 h. Cells were then harvested for IB of Nrf2 and GAPDH. (<b>B</b>) RT-4 cells were transfected with either a control siRNA or a specific Keap1-targeting siRNA for 48 h, followed by treatment with vehicle, MG132 (25 µM), CPDT (50 µM) or SF (8 µM) for 6 h. Cells were then harvested for IB of Nrf2, Keap1 and GAPDH. (<b>C</b>) MEF with knockout of both Keap1 and Nrf2 were mock transfected or transfected with expression vectors of Nrf2 (pEF/Nrf2) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035122#pone.0035122-Alam1" target="_blank">[42]</a> with or without Keap1 (wild type or one of three Keap1 mutants, all cloned to pcDNA3) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035122#pone.0035122-Zhang6" target="_blank">[32]</a> for 48 h, followed by treatment with vehicle, CPDT (50 µM) or SF (8 µM) for 6 h. Whole cell lysates were then prepared for IB.</p

Rh-Catalyzed [3 + 2] Cycloaddition of 1‑Sulfonyl-1,2,3-triazoles: Access to the Framework of Aspidosperma and Kopsia Indole Alkaloids

A Rh­(II)-catalyzed dearomative intramolecular [3 + 2] dipolar cycloaddition involving the indolic C2–C3 carbon–carbon double bond has been developed. The reaction was launched from the triazole moiety within the substrate and proceeded efficiently under mild conditions. A wide range of functional groups could be tolerated. These features render the current reaction a highly useful tool for the synthesis of polycyclic indole alkaloids, as showcased by a rapid assembly of the core structure of Aspidosperma and the related alkaloids

5‑Methylation of Cytosine in CG:CG Base-Pair Steps: A Physicochemical Mechanism for the Epigenetic Control of DNA Nanomechanics

van der Waals density functional theory is integrated with analysis of a non-redundant set of protein–DNA crystal structures from the Nucleic Acid Database to study the stacking energetics of CG:CG base-pair steps, specifically the role of cytosine 5-methylation. Principal component analysis of the steps reveals the dominant collective motions to correspond to a tensile “opening” mode and two shear “sliding” and “tearing” modes in the orthogonal plane. The stacking interactions of the methyl groups globally inhibit CG:CG step overtwisting while simultaneously softening the modes locally via potential energy modulations that create metastable states. Additionally, the indirect effects of the methyl groups on possible base-pair steps neighboring CG:CG are observed to be of comparable importance to their direct effects on CG:CG. The results have implications for the epigenetic control of DNA mechanics