Enhanced Transport and Permeation of a Polymeric Nanocarrier across the Retina by Mixing with ATP upon Intravitreal Injection

The outer part of the retina pigment epithelium (RPE) in the retina is the main site of neovascularization associated with retinal diseases. However, various obstacles interrupt the delivery of medicines across the RPE, mainly due to the well-developed tight junctions in the RPE. Currently, there is no practical formulation to overcome this issue. In this study, we demonstrated that simple mixing with adenosine tetraphosphate (ATP) has the potential to greatly enhance the transport and permeation of a polymeric nanocarrier across the retina via intravitreal administration. Chitosan-functionalized, pluronic-based nanocarrier (NC), which can deliver various biomolecules efficiently, was used as a polymeric nanocarrier. Mixing with ATP facilitated the diffusion of the nanocarrier in the vitreous humor by reducing the electrostatic interaction between NC and negatively charged glycosaminoglycans (GAGs) in the vitreous humor. Mixing with ATP also allowed the penetration of NC across the whole retina, and it resulted in a great increase (approximately nine times) in the transport of NC across the retina, as well as spreading it throughout the whole retina upon intravitreal administration in a mouse model. This enhanced permeation across the retina was specific to ATP but not to GTP, suggesting the possibility of P2Y receptor-mediated tight junction disruption by ATP.

Chronic stress and corticosterone exacerbate alcohol-induced tissue injury in the gut-liver-brain axis

Alcohol use disorders are associated with altered stress responses, but the impact of stress or stress hormones on alcohol-associated tissue injury remain unknown. We evaluated the effects of chronic restraint stress on alcohol-induced gut barrier dysfunction and liver damage in mice. To determine whether corticosterone is the stress hormone associated with the stress-induced effects, we evaluated the effect of chronic corticosterone treatment on alcoholic tissue injury at the Gut-Liver-Brain (GLB) axis. Chronic restraint stress synergized alcohol-induced epithelial tight junction disruption and mucosal barrier dysfunction in the mouse intestine. These effects of stress on the gut were reproduced by corticosterone treatment. Corticosterone synergized alcohol-induced expression of inflammatory cytokines and chemokines in the colonic mucosa, and it potentiated the alcohol-induced endotoxemia and systemic inflammation. Corticosterone also potentiated alcohol-induced liver damage and neuroinflammation. Metagenomic analyses of 16S RNA from fecal samples indicated that corticosterone modulates alcohol-induced changes in the diversity and abundance of gut microbiota. In Caco-2 cell monolayers, corticosterone dose-dependently potentiated ethanol and acetaldehyde-induced tight junction disruption and barrier dysfunction. These data indicate that chronic stress and corticosterone exacerbate alcohol-induced mucosal barrier dysfunction, endotoxemia, and systemic alcohol responses. Corticosterone-mediated promotion of alcohol-induced intestinal epithelial barrier dysfunction and modulation of gut microbiota may play a crucial role in the mechanism of stress-induced promotion of alcohol-associated tissue injury at the GLB axis.

Blood-brain barrier associated tight junction disruption is a hallmark feature of major psychiatric disorders

Major psychiatric disorders affect 25% of the population. While genetic and environmental risk factors have been identified, the underlying pathophysiology of conditions, such as schizophrenia, bipolar disorder and major depression remains largely unknown. Here, we show that endothelial associated tight junction components are differentially regulated at the blood-brain barrier (BBB) in distinct neuroanatomic regions of human donor brain tissues. Previous studies have shown associations between BBB disruption and the development of psychiatric behaviours in rodents. Using immunohistochemistry and qRT-PCR, we show that the expression of claudin-5 is reduced in the hippocampus of individuals diagnosed with major depression or schizophrenia. We also show that levels of tight junction mRNA transcripts, including claudin-5, claudin-12 and ZO-1 correlate with disease duration and age of onset of a range of psychiatric disorders. Together, these data show that BBB associated tight junction disruption and dysregulation is a common pathology observed across the major psychiatric disorders. Targeting and regulating tight junction protein integrity at the BBB could, therefore, represent a novel therapeutic strategy for these conditions.

Role of ERK activation in H. pylori-induced disruption of cell-cell tight junctions

BackgroundTight junctions, a network of claudins and other proteins, play an important role in maintaining barrier function and para-cellular permeability. H. pylori, the major etiological agent of various gastroduodenal diseases, is known to cause tight junction disruption. However, the molecular events that triggered cell-cell tight junction disruption in H. pylori-infected cells, remain largely elusive.Materials and MethodsTrans-epithelial electrical resistance (TEER) and FITC-Dextran permeability measurement were performed to determine the barrier function in H. pylori 88-3887-infected polarized MKN28 cells. For visualization of tight junction protein localization, immunofluorescence and immunoblotting techniques were used. To examine the role of ERK activation in tight junction disruption, U0126, a MEK inhibitor, was employed. To further support the study, computational analyses of H. pylori-infected primary gastric cells were carried out to decipher the transcriptomic changes.ResultsThe epithelial barrier of polarized MKN28 cells when infected with H. pylori displayed disruption of cell-cell junctions as shown by TEER & FITC-dextran permeability tests. Claudin-4 was shown to delocalize from host cytoplasm to nucleus in H. pylori-infected cells. In contrast, delocalization of claudin-4 was minimized when ERK activation was inhibited. Interestingly, transcriptomic analyses revealed the upregulation of genes associated with cell-junction assembly and ERK pathway forming a dense interacting network of proteins.ConclusionTaken together, evidence from this study indicates that H. pylori regulates ERK pathway triggering cell-cell junction disruption, contributing to host pathogenesis. It indicates the vital role of ERK in regulating key events associated with the development of H. pylori-induced gastroduodenal diseases.