RNA interference in immune cells by use of osmotic delivery of siRNA

Entanglement of polymer chains in hypertonic medium enhances the delivery of DNA and other biomacromolecules into cells

HYPOTHESIS

Most experimental procedures applied in modern biology involve cargo delivering into cells. One of the ways to cargo introduction is osmotic-mediated intracellular vesicle swelling. However, its widespread use was hindered due to cargo size (<10 nm) and cell-type-related restrictions. We addressed the issue of the composition of colloidal loading solution to enhance the efficiency of cellular delivery.

EXPERIMENTS

We examined the effectiveness of colloidal loading solutions of varied compositions, including various types and sizes of polymers building osmotic pressure. We used confocal imaging coupled with fluorescence correlation spectroscopy to evaluate the introduction of polymers, proteins, nanoparticles, and DNA plasmids (cargos of sizes 1-175 nm) to cells representing eight cell lines: cancer, normal, epithelial, and mesenchymal ones.

FINDINGS

We found that cellular delivery effectiveness strongly correlates with the size and concentration of osmotic pressure building polymers and not with the high value of the osmotic pressure itself. We show that polymer solutions at the entangled regime of concentrations enhance the delivery of large biomacromolecules even of size 200 nm (DNA plasmids) into cells, including MDA-MB-231 cells - so far resistant to the osmotic procedure. We show that the colloid loading medium based on entangled polymer chains is a versatile cargo delivery tool for molecular biology.

Specific Silencing of Microglial Gene Expression in the Rat Brain by Nanoparticle-Based Small Interfering RNA Delivery

Microglia are the major innate immune cells in the brain and are essential for maintaining homeostasis in a neuronal microenvironment. Currently, a genetic tool to modify microglial gene expression in specific brain regions is not available. In this report, we introduce a tailor-designed method that uses lipid and polymer hybridized nanoparticles (LPNPs) for the local delivery of small interfering RNAs (siRNAs), allowing the silencing of specific microglial genes in the hypothalamus. Our physical characterization proved that this LPNP-siRNA was uniform and stable. We demonstrated that, due to their natural phagocytic behavior, microglial cells are the dominant cell type taking up these LPNPs in the hypothalamus of rats. We then tested the silencing efficiency of LPNPs carrying a cluster of differentiation molecule 11b (CD11b) or Toll-like receptor 4 (TLR4) siRNA using different in vivo and in vitro approaches. In cultured microglial cells treated with LPNP-CD11b siRNA or LPNP-TLR4 siRNA, we found a silencing efficiency at protein expression levels of 65 or 77%, respectively. In line with this finding, immunohistochemistry and western blotting results from in vivo experiments showed that LPNP-CD11b siRNA significantly inhibited microglial CD11b protein expression in the hypothalamus. Furthermore, following lipopolysaccharide (LPS) stimulation of cultured microglial cells, gene expression of the TLR4 downstream signaling component myeloid differentiation factor 88 and its associated cytokines was significantly inhibited in LPNP-TLR4 siRNA-treated microglial cells compared with cells treated with LPNP-scrambled siRNA. Finally, after LPNP-TLR4 siRNA injection into the rat hypothalamus, we observed a significant reduction in microglial activation in response to LPS compared with the control rats injected with LPNP-scrambled siRNA. Our results indicate that LPNP-siRNA is a promising tool to manipulate microglial activity locally in the brain and may serve as a prophylactic approach to prevent microglial dysfunction-associated diseases.

Intracellular build-up RNAi with single-strand circular RNAs as siRNA precursors

We herein report a new approach for RNA interference, so-called “build-up RNAi” approach, where single-strand circular RNAs with a photocleavable unit or disulfide moiety were used as siRNA precursors.

Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies, and Concepts

Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo types-small molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery.

Cationic copolymer augments membrane permeabilizing activity of an amphiphilic peptide

Membrane disruptive peptides (also called membrane fusogenic peptides) have been employed for cytosolic delivery of macromolecules such as nucleic acids and proteins. We reported previously that the cationic graft copolymer, poly(allylamine)-graft-dextran (PAA-g-Dex), augments membrane disruptive activity of the negatively charged E5 peptide. Strong membrane disruptive activity was observed in the presence of the copolymer at both acidic and neutral pH. In this paper, activities of E5/PAA-g-Dex mixture were further explored. Membrane permeabilization activity of E5/PAA-g-Dex was dependent on concentrations of both E5 and PAA-g-Dex, indicating that a complex between E5 and PAA-g-Dex produced the activity. Since the activity of peptide/PAA-g-Dex was peptide sequence-specific, we reasoned that PAA-g-Dex activated membrane-permeabilization activity by facilitating folding of E5 into its active conformation. The membrane permeabilization activity of E5/PAA-g-Dex resulted in transportation of bovine serum albumin into HL-60 cells with less cellular toxicity than digitonin, a naturally occurring surfactant used for delivery of macromolecules into cells.

Impact of TREM-2 gene silencing on inflammatory response of endotoxin-induced acute lung injury in mice

Acute lung injury (ALI) is one of the critical clinical respiratory diseases, of which infection is the main cause and the first risk factor. This study investigated the impact of triggering receptor of myeloid cells expression (TREM)-2 gene silencing on inflammatory response of endotoxin-induced ALI in mice. Lentivirus-mediated TREM-2-shRNA was transfected into healthy male C57BL/6 mice, and the lipopolysaccharide-induced ALI model was established. The immunohistochemistry, immunofluorescence, fluorescence quantitative PCR, western blot, and ELISA were applied to detect the pathological changes of lung tissue and expressions of TREM-2, tumor necrosis factor-α (TNF-α), and interleukin 10 (IL-10) in bronchoalveolar lavage fluid. The lentivirus group, saline control group, ALI model group, blank control group, and negative control group were set up at the same time. Results found that, in lentivirus group, the pathological change of lung tissue was significantly lighter than ALI model group (P < 0.05), and the expression of TREM-2 was significantly reduced compared with all control groups (P < 0.05). The levels of TNF-α and IL-10 were significantly increased than all control groups (P < 0.05), while above indexes in negative control group and blank control group showed no significant difference with ALI group (P > 0.05). This study indicates that TREM-2 has a protective effect on inflammatory response of endotoxin-induced ALI in mice, which has provided new potential targets for prevention and treatment of ALI.

Gene delivery into hepatocytes with the preS/liposome/DNA system

Gene delivery into human hepatocytes remains a critical issue for the development of liver-directed gene therapy. Gene delivery based on non-viral vectors is an attractive approach relative to viral vectors. In this report, novel delivery system of preS/liposome/DNA virus-like particle (VLP) was developed for gene transfection into hepatocytes in vivo and in vitro. Plasmid pCMVbeta, expressing beta-galactosidase, was encapsulated with cationic liposome, and then the histidine-tagged preS domain of hepatitis B virus was coated on the surface of liposome/DNA to form preS/liposome/ DNA VLP. Transfection efficiencies of preS/liposome/DNA, liposome/DNA, naked DNA and preS were analyzed using several different human cell lines. The highest transfection efficiency was found using preS/liposome/DNA VLP as the transfection reagent in human hepatocyte (HH) cell line. Results show that preS domain of hepatitis B virus coated on liposome/DNA can be used for highly efficient gene transfection into human hepatocytes. Moreover, the target characteristic of preS/liposome/DNA was analyzed in vivo. After preS/liposome/DNA VLP was injected into immunocompromised (Nude) mice via the tail vein, most of beta-galactosidase was expressed in the liver; however, no significant target expression was found with the injection of liposome/ DNA or naked DNA. Our results show that preS/liposome/DNA VLP can be used as a novel liver-specific gene delivery system.

The expression of exogenous genes in macrophages: obstacles and opportunities

Over the past three decades many techniques for expressing exogenous genes in a variety of cells and cell lines have been developed. Exogenous gene expression in macrophages has lagged behind that of other nonhematopioetic cells. There are many reasons for this, but most are due to technical difficulties associated with transfecting macrophages. As professional phagocytes, macrophages are endowed with many potent degradative enzymes that can disrupt nucleic acid integrity and make gene transfer into these cells an inefficient process. This is especially true of activated macrophages which undergo a dramatic change in their physiology following exposure to immune or inflammatory stimuli. Viral transduction of these cells has been hampered because macrophages are end-stage cells that generally do not divide; therefore, some of the vectors that depend on integration into a replicative genome have met with limited success. Furthermore, macrophages are quite responsive to "danger signals," and therefore several of the original viral vectors that were used for gene transfer induced potent anti-viral responses in these cells making these vectors inappropriate for gene delivery. Many of these difficulties have been largely overcome, and relatively high efficiency gene expression in primary human or murine macrophages is becoming more routine. In the present chapter we discuss some of the gene expression techniques that have met with success and review the advantages and disadvantages of each.

Toll gates to periodontal host modulation and vaccine therapy

Toll-like receptors (TLRs) are central mediators of innate antimicrobial and inflammatory responses and play instructive roles in the development of the adaptive immune response. Thus when stimulated by certain agonists, TLRs serve as adjuvant receptors that link innate and adaptive immunity. However, when excessively activated or inadequately controlled during an infection, TLRs may contribute to immunopathology associated with inflammatory diseases, such as periodontitis. Moreover, certain microbial pathogens appear to exploit aspects of TLR signalling in ways that enhance their adaptive fitness. The diverse and important roles played by TLRs suggest that therapeutic manipulation of TLR signalling may have implications in the control of infection, attenuation of inflammation, and the development of vaccine adjuvants for the treatment of periodontitis. Successful application of TLR-based therapeutic modalities in periodontitis would require highly selective and precisely targeted intervention. This would in turn necessitate precise characterization of TLR signalling pathways in response to periodontal pathogens, as well as development of effective and specific agonists or antagonists of TLR function and signalling. This review summarizes the current status of TLR biology as it relates to periodontitis, and evaluates the potential of TLR-based approaches for host-modulation therapy in this oral disease.

Toll-like receptor 4 siRNA attenuates LPS-induced secretion of inflammatory cytokines and chemokines by macrophages

Toll-like receptor 4 (TLR4) is critical for activation of macrophages by Lipopolysaccharide (LPS). In this study, we investigated the silencing effects of TLR4-specific 21-nt small interfering RNAs (siRNA) on TLR4 expression in RAW264.7 cells. It was found that treatment with TLR4 siRNA down-regulated the TLR4 mRNA and protein expression in macrophage RAW264.7 cells, and reduced the sensitivity of the cells to LPS stimulation. Our findings also demonstrate that treatment with TLR4 siRNA significantly decreased the tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein 2 (MIP-2) expression induced by LPS. TLR4 siRNA treatment also impaired the signalling of mitogen-activated protein kinases (MAPK) induced by LPS in RAW264.7 cells. These data suggest that inhibition of TLR4 expression by TLR4 siRNA may be therapeutically beneficial in controlling the overall responses of immune cells to LPS.