Switching cell penetrating and CXCR4-binding activities of nanoscale-organized arginine-rich peptides

Arginine-rich protein motifs have been described as potent cell-penetrating peptides (CPPs) but also as rather specific ligands of the cell surface chemokine receptor CXCR4, involved in the infection by the human immunodeficiency virus (HIV). Polyarginines are commonly used to functionalize nanoscale vehicles for gene therapy and drug delivery, aimed to enhance cell penetrability of the therapeutic cargo. However, under which conditions these peptides do act as either unspecific or specific ligands is unknown. We have here explored the cell penetrability of differently charged polyarginines in two alternative presentations, namely as unassembled fusion proteins or assembled in multimeric protein nanoparticles. By this, we have observed that arginine-rich peptides switch between receptor-mediated and receptor-independent mechanisms of cell penetration. The relative weight of these activities is determined by the electrostatic charge of the construct and the oligomerization status of the nanoscale material, both regulatable by conventional protein engineering approaches.     

Nephrotoxicity and Kidney Transport Assessment on 3D Perfused Proximal Tubules

Proximal tubules in the kidney play a crucial role in reabsorbing and eliminating substrates from the body into the urine, leading to high local concentrations of xenobiotics. This makes the proximal tubule a major target for drug toxicity that needs to be evaluated during the drug development process. Here, we describe an advanced in vitro model consisting of fully polarized renal proximal tubular epithelial cells cultured in a microfluidic system. Up to 40 leak-tight tubules were cultured on this platform that provides access to the basolateral as well as the apical side of the epithelial cells. Exposure to the nephrotoxicant cisplatin caused a dose-dependent disruption of the epithelial barrier, a decrease in viability, an increase in effluent LDH activity, and changes in expression of tight-junction marker zona-occludence 1, actin, and DNA-damage marker H2A.X, as detected by immunostaining. Activity and inhibition of the efflux pumps P-glycoprotein (P-gp) and multidrug resistance protein (MRP) were demonstrated using fluorescence-based transporter assays. In addition, the transepithelial transport function from the basolateral to the apical side of the proximal tubule was studied. The apparent permeability of the fluorescent P-gp substrate rhodamine 123 was decreased by 35% by co-incubation with cyclosporin A. Furthermore, the activity of the glucose transporter SGLT2 was demonstrated using the fluorescent glucose analog 6-NBDG which was sensitive to inhibition by phlorizin. Our results demonstrate that we developed a functional 3D perfused proximal tubule model with advanced renal epithelial characteristics that can be used for drug screening studies.     

Validación psicométrica de la Escala de gravedad de fatiga en médicos residentes mexicanos

Resident physicians are continually exposed to fatigue, which can lead to work, academic and personal problems, so it is important to have reliable and valid instruments to measure it. One of the most used is Fatigue Severity Scale, but, there are versions with different number of items in different populations. Therefore, the purpose of this work was to translate, adapt culturally relevant and compare versions with different numbers of items, to identify the most appropriate in Mexican resident physicians. With three different groups of participants; first one for translation by seven expert judges in the language, second for psychometric validation with 100 resident physicians, and third for confirmatory factor analysis and invariance test by type of program (specialty and high specialty) with 182 resident physicians. Distribution, discrimination, reliability and factor structure of the scale were tested in an exploratory and confirmatory analysis, leaving a final scale of 6 items with good fit (X²[9] = 9,39, p = 0,40; CFI = 0,99; RMSEA = 0,02), with a reliability = 0,91 and strict factorial invariance by type of residence program.