Cationic poly(amidoamine) promotes cytosolic delivery of bovine RNase A in melanoma cells, while maintaining its cellular toxicity

Ribonucleases are known to cleave ribonucleic acids, inducing cell death. RNase A, a member of the ribonuclease family, generally displayed poor in vitro activity. This has been attributed to factors such as low intracellular delivery. Poly(amidoamine)s have been used to promote the translocation of non-permeant proteins to the cytosol. Our objective was to demonstrate that poly(amidoamine)s could potentially promote the delivery of RNase A to selected cell line. Interactions of three cationic poly(amidoamine)s (P1, P2 and ISA1) with wild-type bovine RNase A were investigated using gel retardation assays, DLS and microcalorimetry. Although the polymers and the protein are essentially cationic at physiological pH, complexation between the PAAs and RNase A was observed. The high sensitivity differential scanning calorimetry (HSDSC) thermograms demonstrated that the thermal stability of the protein was reduced when complexed with ISA1 (Tmax decreased by 6.5 °C) but was not affected by P1 and P2. All the polymers displayed low cytotoxicity towards non-cancerous cells (IC50 > 3.5 mg mL?1). While RNase A alone was not toxic to mouse melanoma cells (B16F1), P1 was able to promote cytosolic delivery of biologically active RNase A, increasing cell death (IC50 = 0.09 mg mL?1)

Signalling and trafficking of the cysteinyl leukotriene receptors in intestinal epithelial cells

Inflammation is a response to injury or pathogen invasion. A large proportion of the bodie's immune system is centred in the gastrointestinal tract (GI). Prolonged inflammatory conditions of the GI have been suggested to increase the risk for developing colon cancer. The cysteinyl leukotrienes (CysLTs), LTC4, LTD4 and LTE4 are inflammatory mediators that can bind to four known receptors, two of which are the CysLT1R and CysLT2R. Inhibitors of the CysLT1R are currently used in the clinic as asthma medication. LTD4 has been shown to induce cell proliferation, survival and migration in intestinal epithelial cells (Int407) via the CysLT1R. These mechanisms are often used by cancer cells to surive and spread. Furthermore, increased expression of the CysLT1R in colon cancer patient material is correlated with a poorer survival prognosis. Conversley, increased expression of the CysLT2R is correlated with a better survival prognosis. The aim of this thesis was therefore to explore the signalling and trafficking of the cysLT1R and CysLT2R. Our results demonstrate that LTD4 via the CysLT1R can activate the enzyme cPLA2-alpha. This enzyme releases arachidonic acid, the precursor of CysLTs, from the cell membranes, upon activation. One major regulatory mechanism of GPCRs is the internalization from cell membrane upon activation. We demonstrate how LTD4 mainly internalizes CysLT1R and accumulates this receptor at the nuclear membrane and that LTC4 internalizes both the CysLT1R and CysLT2R. This information is valuable in developing potential drugtargets aqainst CysLT1 and CysLT2 in cancer and inflammation

The Possible "Proton Sponge " Effect of Polyethylenimine (PEI) Does Not Include Change in Lysosomal pH.

Polycations such as polyethylenimine (PEI) are used in many novel nonviral vector designs and there are continuous efforts to increase our mechanistic understanding of their interactions with cells. Even so, the mechanism of polyplex escape from the endosomal/lysosomal pathway after internalization is still elusive. The “proton sponge ” hypothesis remains the most generally accepted mechanism, although it is heavily debated. This hypothesis is associated with the large buffering capacity of PEI and other polycations, which has been interpreted to cause an increase in lysosomal pH even though no conclusive proof has been provided. In the present study, we have used a nanoparticle pH sensor that was developed for pH measurements in the endosomal/lysosomal pathway. We have carried out quantitative measurements of lysosomal pH as a function of PEI content and correlate the results to the “proton sponge ” hypothesis. Our measurements show that PEI does not induce change in lysosomal pH as previously suggested and quantification of PEI concentrations in lysosomes makes it uncertain that the “proton sponge ” effect is the dominant mechanism of polyplex escape

Ligand-Induced Tyrosine Phosphorylation of Cysteinyl Leukotriene Receptor 1 Triggers Internalization and Signaling in Intestinal Epithelial Cells

Leukotriene D(4) (LTD(4)) belongs to the bioactive lipid group known as eicosanoids and has implications in pathological processes such as inflammation and cancer. Leukotriene D(4) exerts its effects mainly through two different G-protein-coupled receptors, CysLT(1) and CysLT(2). The high affinity LTD(4) receptor CysLT(1)R exhibits tumor-promoting properties by triggering cell proliferation, survival, and migration in intestinal epithelial cells. In addition, increased expression and nuclear localization of CysLT(1)R correlates with a poorer prognosis for patients with colon cancer

Time dependency behavior of granular materials

Theory of elasticity is the most used assumption in pavement design. Highway materials are neither elastic nor homogenous. Therefore there is a need for models which are based on more realistic assumptions. UGM shows time dependency in nature. This is reflected in a viscous response close to the surface and an elastic response deeper down the construction. Time dependencies of soils are relatively studied phenomena and well known to researchers but not fully regarded as a problem in civil engineering. A limited number of models are suggested to describe time related deformation of soils and unbound granular materials in particular. In this study a large box, 800*800 mm is used where the confining pressure will increase with depth from the surface as in real constructions. The behavior of some granular materials subjected to dynamic loadings is studied. The results indicate that the time of loading affects the permanent deformation