A Robust Nanoparticle Platform for RNA Interference in Macrophages to Suppress Tumor Cell Migration

Macrophages are one of the most abundant immune cells in the solid tumor and their increased density is associated with the specific pathological features of cancers, including invasiveness, metastasis, immunosuppression, neovascularization, and poor response to therapy. Therefore, reprogramming macrophage behavior is emerging as a promising therapeutic modality for cancer treatment. RNA interference (RNAi) technology is one of the powerful strategies for the regulation of macrophage activities by silencing specific genes. However, as polyanionic biomacromolecules, RNAi therapeutics such as small interfering RNA (siRNA) cannot readily cross cell membrane and thus specific delivery vehicles are required to facilitate the cytosolic siRNA delivery. Herein, we developed a robust nanoparticle (NP) platform for efficient siRNA delivery and gene silencing in macrophages. This NP platform is composed of biodegradable poly (ethylene glycol)-b-poly (-caprolactone) (PEG-b-PCL), poly (-caprolactone)-b-poly (2-aminoethyl ethylene phosphate) (PCL-b-PPEEA), and PCL homopolymer. We chose CC-chemokine ligand 18 (CCL-18) as a proof of concept therapeutic target and our results demonstrate that the CCL-18 silencing in macrophages can significantly inhibit the migration of breast cancer cells. The successful regulation of the macrophage behavior demonstrated herein shows great potential as an effective strategy for cancer therapy

A C-elegans stretch receptor neuron revealed by a mechanosensitive TRP channel homologue

The nematode Caenorhabditis elegans is commonly used as a genetic model organism for dissecting integration of the sensory and motor systems(1). Despite extensive genetic and behavioural analyses that have led to the identification of many genes and neural circuits involved in regulating C. elegans locomotion behaviour(1), it remains unclear whether and how somatosensory feedback modulates motor output during locomotion. In particular, no stretch receptors have been identified in C. elegans, raising the issue of whether stretch-receptor-mediated proprioception is used by C. elegans to regulate its locomotion behaviour. Here we have characterized TRP-4, the C. elegans homologue of the mechanosensitive TRPN channel. We show that trp-4 mutant worms bend their body abnormally, exhibiting a body posture distinct from that of wild-type worms during locomotion, suggesting that TRP-4 is involved in stretch-receptor-mediated proprioception. We show that TRP-4 acts in a single neuron, DVA, to mediate its function in proprioception, and that the activity of DVA can be stimulated by body stretch. DVA both positively and negatively modulates locomotion, providing a unique mechanism whereby a single neuron can fine-tune motor activity. Thus, DVA represents a stretch receptor neuron that regulates sensory - motor integration during C. elegans locomotion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62770/1/nature04538.pd

Insights into the release of triclosan from microplastics in aquatic environment assessed with diffusive gradient in thin-films

Organic chemicals associated with microplastics (MPs) can be released and thus pose potential risks during weathering processes. However, the thermodynamics and kinetics of their release processes still need to be better understood. Herein, the adsorption and desorption kinetics of triclosan on polystyrene (PS) and polyvinyl chloride (PVC) were investigated by using both batch experiments and diffusive gradients in thin-films (DGT) technique. The pseudo-second-order model fitted the data best, implying that both intraparticle diffusion and external liquid film diffusion influence the adsorption and desorption processes. DGT continuously accumulated triclosan from MP suspensions but slower than theoretical values, indicating some restrictions to desorption. The DGT-induced fluxes in Soils/Sediment (DIFS) model, employed to interpret DGT data, gave distribution coefficients for labile species (K ) of 5000 mL g (PS) and 1000 mL g (PVC) and the corresponding response times (T ) were 10 s and 1000 s, respectively. Higher K but smaller T for PS than PVC showed that more triclosan adsorbed on PS could be rapidly released, while there were some kinetic limitations for triclosan on PVC. A novel finding was that pH and ionic strength individually and interactively affected the supply of triclosan to DGT. This is the first study to quantify interactions of organics with MPs by using DGT, aiding our understanding of MPs' adsorption/desorption behavior in the aquatic environment

Cellular Mechanism Underlying Hydrogen Sulfide Mediated Epithelial K+ Secretion in Rat Epididymis

As a novel gasotransmitter, hydrogen sulfide (H2S) elicits various physiological actions including smooth muscle relaxation and promotion of transepithelial ion transport. However, the pro-secretory function of H2S in the male reproductive system remains largely unclear. The aim of this study is to elucidate the possible roles of H2S in modulating rat epididymal intraluminal ionic microenvironment essential for sperm storage. The results revealed that endogenous H2S-generating enzymes cystathionine β-synthetase (CBS) and cystathionine γ-lyase (CSE) were both expressed in rat epididymis. CBS located predominantly in epithelial cells whilst CSE expressed primarily in smooth muscle cells. The relative expression level of CBS and CSE escalated from caput to cauda regions of epididymis, which was paralleled to the progressively increasing production of endogenous H2S. The effect of H2S on epididymal epithelial ion transportation was investigated using short-circuit current (ISC), measurement of intracellular ion concentration and in vivo rat epididymal microperfusion. Our data showed that H2S induced transepithelial K+ secretion via adenosine triphosphate-sensitive K+ (KATP) channel and large conductance Ca2+-activated K+ (BKCa) channel. Transient receptor potential vanilloid 4 (TRPV4) channel-mediated Ca2+ influx was implicated in the activation of BKCa channel. In vivo studies further demonstrated that H2S promoted K+ secretion in rat epididymal epithelium. Inhibition of endogenous H2S synthesis caused a significant decrease in K+ concentration of cauda epididymal intraluminal fluid. Moreover, our data demonstrated that high extracellular K+ concentration actively depressed the motility of cauda epididymal sperm in a pH-independent manner. Collectively, the present study demonstrated that H2S was vital to the formation of high K+ concentration in epididymal intraluminal fluid by promoting the transepithelial K+ secretion, which might contribute to the maintenance of the cauda epididymal sperm in quiescent dormant state before ejaculation

Connexin43 Modulates Cell Polarity and Directional Cell Migration by Regulating Microtubule Dynamics

Knockout mice deficient in the gap junction gene connexin43 exhibit developmental anomalies associated with abnormal neural crest, primordial germ cell, and proepicardial cell migration. These migration defects are due to a loss of directional cell movement, and are associated with abnormal actin stress fiber organization and a loss of polarized cell morphology. To elucidate the mechanism by which Cx43 regulates cell polarity, we used a wound closure assays with mouse embryonic fibroblasts (MEFs) to examine polarized cell morphology and directional cell movement. Studies using embryonic fibroblasts from Cx43 knockout (Cx43KO) mice showed Cx43 deficiency caused cell polarity defects as characterized by a failure of the Golgi apparatus and the microtubule organizing center to reorient with the direction of wound closure. Actin stress fibers at the wound edge also failed to appropriately align, and stabilized microtubule (Glu-tubulin) levels were markedly reduced. Forced expression of Cx43 with deletion of its tubulin-binding domain (Cx43dT) in both wildtype MEFs and neural crest cell explants recapitulated the cell migration defects seen in Cx43KO cells. However, forced expression of Cx43 with point mutation causing gap junction channel closure had no effect on cell motility. TIRF imaging revealed increased microtubule instability in Cx43KO cells, and microtubule targeting of membrane localized Cx43 was reduced with expression of Cx43dT construct in wildtype cells. Together, these findings suggest the essential role of Cx43 gap junctions in development is mediated by regulation of the tubulin cytoskeleton and cell polarity by Cx43 via a nonchannel function