Receptor-mediated transcytosis has been widely studied as a possible strategy to transport neurotherapeutics across the blood-brain barrier (BBB). Monoclonal antibodies directed against the transferrin receptor (TfR) have been proposed as potential carrier candidates. A better understanding of the mechanisms involved in their cellular uptake and intracellular trafficking is required and could critically contribute to the improvement of delivery methods. Accordingly, we studied here the trafficking of gold nanoparticles (AuNPs) coated with the 8D3 anti-transferrin receptor antibody at the mouse BBB. 8D3-AuNPs were intravenously administered to mice and allowed to recirculate for a range of times, from 10 min to 24 h, before brain extraction and analysis by transmission electron microscope techniques. Our results indicated a TfR-mediated and clathrin-dependent internalization process by which 8D3-AuNPs internalize individually in vesicles. These vesicles then follow at least two different routes. On one hand, most vesicles enter intracellular processes of vesicular fusion and rearrangement in which the AuNPs end up accumulating in late endosomes, multivesicular bodies or lysosomes, which present a high AuNP content. On the other hand, a small percentage of the vesicles follow a different route in which they fuse with the abluminal membrane and open to the basal membrane. In these cases, the 8D3-AuNPs remain attached to the abluminal membrane, which suggests an endosomal escape, but not dissociation from TfR. Altogether, although receptor-mediated transport continues to be one of the most promising strategies to overcome the BBB, different optimization approaches need to be developed for efficient drug delivery.

The small intestinal epithelium is a highly dynamic system continuously renewed by a process involving cell proliferation and differentiation. The intestinal epithelium constitutes a permeability barrier regulating the vectorial transport of ions, water, and solutes. Morphological changes during cell differentiation, as well as changes in the activity of brush-border enzymes and the expression of transport proteins, are well established. However, little is known about the arachidonic acid (AA) cascade underlying epithelial cell differentiation or its role in the development of epithelial barrier function. The main purpose of this study was to examine the activity of the high-molecular-weight phospholipases A 2 (PLA 2 ) and cyclooxygenase (COX) pathway during differentiation, with particular emphasis on paracellular permeability. PLA 2 activity, AA release, COX-2 expression, prostaglandin E 2 (PGE 2 ) production, and paracellular permeability were studied in preconfluent, confluent, and differentiated Caco-2 cell cultures. Our results show that Caco-2 differentiation induces a decrease in both calcium-independent PLA 2 activity and COX-2 expression and, consequently, a decrease in AA release and PGE 2 synthesis in parallel with a reduction in paracellular permeability. Moreover, the addition of PGE 2 to differentiated cells, at concentrations similar to those detected in nondifferentiated cultures, induces the disruption of epithelial barrier function. These results suggest that AA release by calcium-independent PLA 2 , COX-2 expression, and subsequent PGE 2 release are important for the maintenance of paracellular permeability in differentiated Caco-2 cells.-Martín-Venegas, R., S. RoigPérez, R. Ferrer, and J. J. Moreno. Arachidonic acid cascade and epithelial barrier function during Caco-2 cell differentiation.

dl-Methionine or its corresponding hydroxy analogue, DL-2-hydroxy-(4-methylthio) butanoic acid (DLHMB), are commonly added to commercial animal diets to satisfy the TSAA requirement. The utilization of DLHMB as a supplementary source of Met begins with its conversion to L-Met via a 2-step mediated process. L-Methionine can then be transsulfurated to L-Cys, which, in turn, can be catabolized to taurine (TAU). In the present study, the capacity of the chicken small intestine to convert DLHMB to L-Met and to use this amino acid as a source for L-Cys and TAU production was evaluated. The appearance of Met in the serosal compartment of everted sacs incubated with DLHMB is higher in the presence of an H(+) gradient (mucosal pH 5.5 vs. 7.4). Serosal Cys and TAU concentration was compared in everted sacs incubated at a mucosal pH of 5.5 with DLHMB or L-Met, and the results show significantly higher values after incubation with the hydroxy analogue. Regional comparisons indicate no significant differences in the appearance of serosal Met and Cys, although lower values were obtained for TAU in the duodenum than in the jejunum and ileum. The profile of non-S amino acids was also determined and revealed no significant differences between DLHMB- and L-Met-incubated sacs. In conclusion, Cys and TAU content in chicken enterocytes is higher when DLHMB is used as a Met source.

Corpora amylacea(CA) in the human brain are granular bodies formed by polyglucosan aggregates that amass waste products of different origins. They are generated by astrocytes, mainly during aging and neurodegenerative conditions, and are located predominantly in periventricular and subpial regions. This study shows that CA are released from these regions to the cerebrospinal fluid and are present in the cervical lymph nodes, into which cerebrospinal fluid drains through the meningeal lymphatic system. We also show that CA can be phagocytosed by macrophages. We conclude that CA can act as containers that remove waste products from the brain and may be involved in a mechanism that cleans the brain. Moreover, we postulate that CA may contribute in some autoimmune brain diseases, exporting brain substances that interact with the immune system, and hypothesize that CA may contain brain markers that may aid in the diagnosis of certain brain diseases.

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We recently demonstrated that PGE2 induces the disruption of the intestinal epithelial barrier function. In the present study, our objectives were to study the role of PGE2 receptors (EP1-EP4) and the signaling pathways involved in this event. Paracellular permeability (PP) was assessed in differentiated Caco-2 cell cultures from D-mannitol fluxes and transepithelial electrical resistance (TER) in the presence of different PGE 2 receptor agonists (carbacyclin, sulprostone, butaprost, ONO-AE1-259, ONO-AE-248, GR63799, and ONO-AE1-329) and antagonists (ONO-8711, SC-19220, AH-6809, ONO-AE3-240, ONO-AE3-208, and AH-23848). The results indicate that EP1 and EP4 but not EP2 and EP3 might be involved in PP regulation. These effects were mediated through PLC-inositol trisphosphate (IP 3)-Ca 2ϩ and cAMP-PKA signaling pathways, respectively. We also observed an increase in intracellular Ca 2ϩ concentration ([Ca 2ϩ ]i) strengthened by cAMP formation indicating a cross talk interaction of these two pathways. Moreover, the participation of a conventional PKC isoform was shown. The results also indicate that the increase in PP may be correlated with the redistribution of occludin, zona occludens 1 (ZO-1), and the perijunctional actin ring together with an increase in myosin light chain kinase activity. Although the disruption of epithelial barrier function observed in inflammatory bowel disease (IBD) patients has been traditionally attributed to cytokines, the present study focused on the role of PGE2 in PP regulation, as mucosal levels of this eicosanoid are also increased in these inflammatory processes. paracellular permeability; intestine; tight junctions; eicosanoids; arachidonic acid cascade THE STRUCTURAL INTEGRITY OF the epithelium is maintained by three distinct adhesion systems: tight junctions (TJ), adherent junctions, and desmosomes. Of these, TJ are the most apical component and are the rate-limiting step for paracellular permeability (PP). In addition, TJ constitute the interface (fence) between apical and basolateral membrane domains (32). TJ are multiprotein complexes composed of transmembrane proteins associated with the cytoskeletal perijunctional ring of actin and myosin and with cytosolic proteins involved in cell signaling and vesicle trafficking. Five transmembrane proteins of the junctional complex have been identified in recent years: occludin, the claudin family, tricellulin, crumbs, and junctional adhesion molecules. These proteins are associated with a wide spectrum of cytosolic proteins, of which zona occludens (ZO) 1, ZO-2, ZO-3, AF6, and cingulin are described as forming the nexus with cytoskeletal proteins (42). PGE 2 is an inflammatory mediator that has pleiotropic effects on signal transduction and exerts its biological action through binding to four specific membrane receptor subtypes, EP 1 , EP 2 , EP 3 , and EP 4 , which are widely distributed and have different tissue expression. PGE 2 stimulation leads to activation of different G proteins, depending on the type of EP subtype engaged, i...

Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that causes inflammation, necrosis, and diarrhea in pigs, as well as being an important source of food-borne diseases in humans. Probiotics and prebiotics are promising alternatives to antibiotics to control and prevent intestinal infections. The present work investigated a recently developed ␤-galactomannan (␤GM) prebiotic compared to the proven probiotic Saccharomyces cerevisiae var. boulardii on porcine ileum intestinal epithelial cells (IECs) of the IPI-2I line and monocyte-derived dendritic cells (DCs) cocultured in vitro with Salmonella. We observed that both S. cerevisiae var. boulardii and ␤GM inhibited the association of Salmonella with IECs in vitro. Our data indicated that ␤GM has a higher ability than S. cerevisiae var. boulardii to inhibit Salmonella-induced proinflammatory mRNA (cytokines tumor necrosis factor alpha [TNF-␣], interleukin-1␣ [IL-1␣], IL-6, and granulocyte-macrophage colony-stimulating factor [GM-CSF] and chemokines CCL2, CCL20, and CXCL8) and at protein levels (IL-6 and CXCL8). Additionally, ␤GM and S. cerevisiae var. boulardii induced some effects on DCs that were not observed on IECs: ␤GM and S. cerevisiae var. boulardii showed slight upregulation of mRNA for TNF-␣, GM-CSF, and CCR7 receptor on porcine monocyte-derived dendritic cells (DCs). Indeed, the addition of ␤GM or S. cerevisiae var. boulardii on DCs cocultured with Salmonella showed higher gene expression (mRNA) for TNF-␣, GM-CSF, and CXCL8 compared to that of the control with Salmonella. In conclusion, the addition of ␤GM inhibits Salmonella-induced proinflammatory profiles in IECs but may promote DC activation, although associated molecular mechanisms remain to be elucidated.

Cyclooxygenases (COXs) and lipoxygenases (LOXs) are important enzymes that metabolize arachidonic and linoleic acids. Various metabolites generated by the arachidonic acid cascade regulate cell proliferation, apoptosis, differentiation, and senescence. Hydroxyoctadecadienoic acids (HODEs) are synthesized from linoleic acid, giving two enantiomeric forms for each metabolite. The aim was to investigate the effect of 13-HODE enantiomers on nondifferentiated Caco-2 cell growth/apoptosis. Our results indicate that 13(S)-HODE decreases cell growth and DNA synthesis of nondifferentiated Caco-2 cells cultured with 10% fetal bovine serum (FBS). Moreover, 13(S)-HODE showed an apoptotic effect that was reduced in the presence of a specific peroxisome proliferator-activated receptor-γ (PPARγ) antagonist. In addition, we observed that 13(S)-HODE but not 13(R)-HODE is a ligand to PPARγ, confirming the implication of this nuclear receptor in 13(S)-HODE actions. In contrast, 13(R)-HODE increases cell growth and DNA synthesis in the absence of FBS. 13(R)-HODE interaction with BLT receptors activates ERK and CREB signaling pathways, as well as PGE2 synthesis. These results suggest that the proliferative effect of 13(R)-HODE could be due, at least in part, to COX pathway activation. Thus both enantiomers use different receptors and have contrary effects. We also found these differential effects of 9-HODE enantiomers on cell growth/apoptosis. Therefore, the balance between (R)-HODEs and (S)-HODEs in the intestinal epithelium could be important to its cell growth/apoptosis homeostasis.