SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Vesicle

169

Triggering receptor expressed on myeloid cells-2 (TREM2) is a microglial surface receptor involved in phagocytosis. Clearance of apoptotic debris after stroke represents an important mechanism to re-attain tissue homeostasis and thereby ensure functional recovery. The role of TREM2 following stroke is currently unclear.

Concepts: Immune system, Inflammation, Apoptosis, Anti-inflammatory, Vesicle, Knockout mouse

163

The surface behaviour of swimming amoebae was followed in cells bearing a cAR1-paGFP (cyclic AMP receptor fused to a photoactivatable-GFP) construct. Sensitized amoebae were placed in a buoyant medium where they could swim toward a chemoattractant cAMP source. paGFP, activated at the cell’s front, remained fairly stationary in the cell’s frame as the cell advanced; the label was not swept rearwards. Similar experiments with chemotaxing cells attached to a substratum gave the same result. Furthermore, if the region around a lateral projection near a crawling cell’s front is marked, the projection and the labelled cAR1 behave differently. The label spreads by diffusion but otherwise remains stationary in the cell’s frame; the lateral projection moves rearwards on the cell (remaining stationary with respect to the substrate), so that it ends up outside the labelled region. Furthermore, as cAR1-GFP cells move, they occasionally do so in a remarkably straight line; this suggests they do not need to snake to move on a substratum. Previously, we suggested that the surface membrane of a moving amoeba flows from front to rear as part of a polarised membrane trafficking cycle. This could explain how swimming amoebae are able to exert a force against the medium. Our present results indicate that, in amoebae, the suggested surface flow does not exist: this implies that they swim by shape changes.

Concepts: Protein, Cell membrane, Organelle, Cell biology, Vesicle

149

30

Transport between compartments of eukaryotic cells is mediated by coated vesicles. The archetypal protein coats COPI, COPII, and clathrin are conserved from yeast to human. Structural studies of COPII and clathrin coats assembled in vitro without membranes suggest that coat components assemble regular cages with the same set of interactions between components. Detailed three-dimensional structures of coated membrane vesicles have not been obtained. Here, we solved the structures of individual COPI-coated membrane vesicles by cryoelectron tomography and subtomogram averaging of in vitro reconstituted budding reactions. The coat protein complex, coatomer, was observed to adopt alternative conformations to change the number of other coatomers with which it interacts and to form vesicles with variable sizes and shapes. This represents a fundamentally different basis for vesicle coat assembly.

Concepts: Cell nucleus, Cell, Cell membrane, Endoplasmic reticulum, Cell biology, Vesicle, COPII, COPI

28

In this study, a novel amphiphilic copolymer designed as N-octyl-N-phthalyl-3,6-O-(2-hydroxypropyl) chitosan (OPHPC) were synthesized and then conjugated with folic acid (FA-OPHPC) to produce a targeted drug carrier for tumor-specific drug delivery. OPHPC and FA-OPHPC were characterized by FT-IR, (1)H NMR, (13)C NMR and elemental analysis. Paclitaxel (PTX) loaded OPHPC micelles (PTX-OPHPC) with well-defined spherical shape and homogeneous distribution exhibited drug-loading rate ranging from 33.6% to 45.3% and entrapment efficiency from 50.5% to 82.8%. In the cellular uptake studies, PTX-OPHPC brought about a significantly higher amount of PTX accumulated in human breast adenocarcinoma cell line (MCF-7 cells) compared with Taxol. Moreover, the cellular uptake of PTX in PTX loaded FA-OPHPC micelles (PTX-FA-OPHPC) was 3.2-fold improved in comparison with that of PTX-OPHPC. The results revealed that OPHPC micelle might be a promising drug carrier for promoting PTX cellular uptake and FA-OPHPC micelle could be used as a potential tumor-targeted drug vector.

Concepts: Breast cancer, Lung cancer, Chemotherapy, Vesicle, Taxane, Paclitaxel, Docetaxel, MCF-7

28

Rlyso, a highly selective and sensitive pH sensor, can stain lysosomes with a novel lysosome-locating group, methylcarbitol. Rlyso was successfully used to detect lysosomal pH changes during apoptosis or induced by chloroquine while avoiding the “alkalizing effect” on lysosomes of current lysosomal probes with nitrogen-containing sidechains.

Concepts: Phagocytosis, PH, Lysosome, Vesicle

28

2-Demethoxy-2,3-ethylenediamino hypocrellin B (EDAHB) is a diamino-substituted hypocrellin B (HB) with high absorption of red light and high quantum yield of both singlet oxygen ((1)O(2)) and superoxide anions (O(2)(-)). Here we reported the cellular uptake, subcellular location, and cytotoxicity of EDAHB, as well as EDAHB-mediated photodynamic therapy (PDT) efficiency, and cell apoptosis. Results showed that EDAHB accumulated in HeLa cells rapidly up to 1h, with a subsequent decrease in the rate of uptake. EDAHB distributed with well-defined spots throughout the cytoplasm of the cells. EDAHB showed a much higher photopotentiation factor than HB. The phototoxicity of EDAHB to HeLa cells occurred via a mitochondria/caspase apoptosis pathway. This study showed EDAHB to be a promising candidate of photosensitizer for anti-tumor PDT.

Concepts: Protein, Oxygen, Cell, Apoptosis, Cell culture, Vesicle, Singlet oxygen, Photodynamic therapy

28

Double emulsion has been used most often in formulation of hydrophilic drugs by nanoparticles of biodegradable polymers, which has disadvantages such as low drug loading and low drug encapsulation efficiency due to the drug loss in the process. The drug release may be too fast for sustained chemotherapy. We developed in this research a d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) prodrug micelle system with cisplatin as a model hydrophilic drug. We demonstrated that such a system can successfully deliver the model hydrophilic drug with a low critical micelle concentration (CMC) of only 5.01mg/L, a high drug load of 4.95% (w/w) and a pH-responsive drug release kinetics and higher cellular uptake in comparison with the original drug and the TPGS-cisplatin prodrug itself. The cell viability experiment showed great enhancement of the cisplatin chemotherapy, which is demonstrated by the IC50 value reduced from 3.95, 0.98, 0.19 for cisplatin to 1.36, 0.51, 0.08μg/mL for the TPGS prodrug micelle formulation after 24, 48, 72h culture with the HepG2 hepatocarcinoma cells, respectively. Furthermore, such a TPGS prodrug micellar formulation showed significant neuroprotective effects for the cisplatin chemotherapy, which is demonstrated by the greatly increased IC50 value for the SH-SY5Y neuroblast-like cells in comparison between cisplatin and the TPGS prodrug micelle formulation. The TPGS prodrug micelles can also be generalized to become a new strategy for codelivery of hydrophilic and hydrophobic drugs and/or imaging agents.

Concepts: Pharmacology, Hydrophobic effect, Surfactant, Micelle, Vesicle, Cisplatin, Colloidal chemistry, Critical micelle concentration

28

We present a microfluidic array that allows lab-on-a-chip-based studies on hundreds of giant vesicles through immobilization, engineering and release of the vesicles. Real-time observations of the vesicular response are reported. This trap-and-release system is also used to efficiently narrow the size distribution of the vesicle population. In addition, it can be applied to a wide range of deformable objects.

Concepts: Scientific method, Vesicle

27

2-Hydroxy-propyl-β-cyclodextrin (HPβCD), a cholesterol scavenger, is currently undergoing Phase 2b/3 clinical trial for treatment of Niemann Pick Type C-1 (NPC1), a fatal neurodegenerative disorder that stems from abnormal cholesterol accumulation in the endo/lysosomes. Unfortunately, the extremely high doses of HPβCD required to prevent progressive neurodegeneration exacerbates ototoxicity, pulmonary toxicity and autophagy-based cellular defects. We present unexpected evidence that a poly (ethylene glycol) (PEG)-lipid conjugate enables cholesterol clearance from endo/lysosomes of Npc1 mutant (Npc1(-/-)) cells. Herein, we show that distearyl-phosphatidylethanolamine-PEG (DSPE-PEG), which forms 12-nm micelles above the critical micelle concentration, accumulates heavily inside cholesterol-rich late endosomes in Npc1(-/-) cells. This potentially results in cholesterol solubilization and leakage from lysosomes. High-throughput screening revealed that DSPE-PEG, in combination with HPβCD, acts synergistically to efflux cholesterol without significantly aggravating autophagy defects. These well-known excipients can be used as admixtures to treat NPC1 disorder. Increasing PEG chain lengths from 350 Da-30 kDa in DSPE-PEG micelles, or increasing DSPE-PEG content in an array of liposomes packaged with HPβCD, improved cholesterol egress, while Pluronic block copolymers capable of micelle formation showed slight effects at high concentrations. We postulate that PEG-lipid based nanocarriers can serve as bioactive drug delivery systems for effective treatment of lysosomal storage disorders.

Concepts: Lysosomal storage disease, Polymer, Neurodegeneration, Neurodegenerative disorders, Micelle, Vesicle, Ethylene glycol