Mechanosensory signalling in astrocytes

Mechanosensitivity is a well-known feature of astrocytes, however, its underlying mechanisms and functional significance remain unclear. There is evidence that astrocytes are acutely sensitive to decreases in cerebral perfusion pressure and may function as intracranial baroreceptors, tuned to monitor brain blood flow. This study investigated the mechanosensory signalling in brainstem astrocytes, as these cells reside alongside the cardiovascular control circuits and mediate increases in blood pressure and heart rate induced by falls in brain perfusion. It was found that mechanical stimulation-evoked Ca2+ responses in astrocytes of the rat brainstem were blocked by (i) antagonists of connexin channels, connexin 43 (Cx43) blocking peptide Gap26, or Cx43 gene knockdown; (ii) antagonists of TRPV4 channels; (iii) antagonist of P2Y1 receptors for ATP; and (iv) inhibitors of phospholipase C or IP3 receptors. Proximity ligation assay demonstrated interaction between TRPV4 and Cx43 channels in astrocytes. Dye loading experiments showed that mechanical stimulation increased open probability of carboxyfluorescein-permeable membrane channels. These data suggest that mechanosensory Ca2+ responses in astrocytes are mediated by interaction between TRPV4 and Cx43 channels, leading to Cx43-mediated release of ATP which propagates/amplifies Ca2+ signals via P2Y1 receptors and Ca2+ recruitment from the intracellular stores. In astrocyte-specific Cx43 knockout mice the magnitude of heart rate responses to acute increases in intracranial pressure was not affected by Cx43 deficiency. However, these animals displayed lower heart rates at different levels of cerebral perfusion, supporting the hypothesis of connexin hemichannel-mediated release of signalling molecules by astrocytes having an excitatory action on the CNS sympathetic control circuits.SIGNIFICANCE STATEMENTThere is evidence suggesting that astrocytes may function as intracranial baroreceptors that play an important role in the control of systemic and cerebral circulation. To function as intracranial baroreceptors, astrocytes must possess a specialized membrane mechanism that makes them exquisitely sensitive to mechanical stimuli. This study shows that opening of connexin 43 hemichannels leading to the release of ATP is the key central event underlying mechanosensory Ca2+ responses in astrocytes. This astroglial mechanism plays an important role in the autonomic control of heart rate. These data add to the growing body of evidence suggesting that astrocytes function as versatile surveyors of the CNS metabolic milieu, tuned to detect conditions of potential metabolic threat, such as hypoxia, hypercapnia and reduced perfusion

Adherens junctions remain dynamic

One of the four principal categories of cell-cell junctions that hold together and shape distinct tissues and organs in vertebrates, adherens junctions (AJs) form cell-cell contacts that connect transmembrane proteins with cytoskeletal actin filaments to provide architectural strength, aid in morphogenesis, and help to maintain proper tissue homeostasis. The classical organization of AJs, consisting of transmembrane cadherins and cytoplasmically attached β-catenins and α-catenins assembled together into a multiprotein complex, was once thought obligatory to craft a robust and stable connection to actin-based cytoskeletal elements, but this architecture has since been challenged and questioned to exist. In a stimulating paper published in a recent issue of BMC Biology, Millán et al. provide convincing evidence that in confluent vascular endothelial cells a novel dynamic vascular endothelial (VE)-cadherin-based AJ type exists that interacts with and physically connects prominent bundles of tension-mediating actin filaments, stress fibers, between neighboring cells. Stress fibers were known previously to link to integrin-based focal adhesion complexes but not to cell-cell adhesion mediating AJs. These new findings, together with previous results support the concept that different AJ subtypes, sharing the same transmembrane cadherin types, can assemble in various configurations to either increase barrier function and promote physical cell-cell adhesion, or to lessen cell-cell adhesion and promote cell separation and migration

Forming a three-dimensional porous organic network via solid-state explosion of organic single crystals

Solid-state reaction of organic molecules holds a considerable advantage over liquid-phase processes in the manufacturing industry. However, the research progress in exploring this benefit is largely staggering, which leaves few liquid-phase systems to work with. Here, we show a synthetic protocol for the formation of a three-dimensional porous organic network via solid-state explosion of organic single crystals. The explosive reaction is realized by the Bergman reaction (cycloaromatization) of three enediyne groups on 2,3,6,7,14,15-hexaethynyl-9,10-dihydro-9,10-[1,2]benzenoanthracene. The origin of the explosion is systematically studied using single-crystal X-ray diffraction and differential scanning calorimetry, along with high-speed camera and density functional theory calculations. The results suggest that the solid-state explosion is triggered by an abrupt change in lattice energy induced by release of primer molecules in the 2,3,6,7,14,15-hexaethynyl-9,10-dihydro-9,10-[1,2]benzenoanthracene crystal lattice

Evaluation of macrophage migration inhibitory factor as an imaging marker for hepatocellular carcinoma in murine models

Objective. Macrophage migration inhibitory factor (MIF) is considered as an important mediator in the pathogenesis of neoplasia. The aim of the present study was to evaluate whether MIF could be used as a marker for hepatocellular carcinoma (HCC) detection. Material and methods. Biodistribution and whole-body autoradiography studies of 131I-labeled anti-MIF monoclonal antibody (McAb) and 131I-labeled control IgG were performed. The HCC-bearing mice were injected with 3.7 MBq of each agent and killed at 24, 48, and 72 h postinjection (p.i.). The organs, blood, and HCC tissues were removed from model mice, weighed, and counted using a gamma-counter. The expression of MIF mRNA and protein within HCC tissues was confirmed by RT-PCR and immunohistochemistry. Results. HCCs in model mice could be adequately visualized at 24 h p.i. The target-to-non-target (T/NT) ratios were 6.72 ± 1.09 (24 h), 9.85 ± 0.81 (48 h), and 12.31 ± 0.57 (72 h) for 131I-labeled anti-MIF McAb group, whereas in the control group of 131I-IgG, T/NT ratios were 4.65 ± 0.63 (24 h), 6.12 ± 0.60 (48 h), and 8.23 ± 0.35 (72 h) (p < 0.05). MIF mRNA expression was twofold higher in the HCC tissues than in the healthy liver tissues. MIF protein expression was much higher in the HCC tissues than in controls. Conclusions. Our findings suggested that 131I-anti-MIF McAb could be rapidly and specifically localized in tumors. Thus, MIF could be used as a marker for HCC tumor detection

Prognostic Value of FDG-PET in Patients with Oropharyngeal Carcinoma Treated with Concurrent Chemoradiotherapy

Purpose: The purpose of this study was to evaluate the predictive value of 2-deoxy-2-[F-18] fluoro-D-glucose-positron emission tomography (FDG-PET) following concurrent chemoradiotherapy (CRT) on survival in patients with carcinoma of the oropharynx (OPC). Methods: Eighteen patients with primary OPC who underwent PET pre- and post-CRT were evaluated prospectively for survival. The prognostic performance of post-CRT PET and CT for recurrence was compared. Results: Patients with positive post-CRT PET exhibited significantly lower 2-year cause-specific survival and disease-free survival (50 % vs. 91%, PG0.05 and 0 % vs. 83%, PG0.0001); however, patients with positive post-CRT CT did not exhibit any significant difference (67 % vs. 83%, P= 0.416 and 50 % vs. 75%, P=0.070). Other factors, such as clinical and pre-CRT PET variables, also did not indicate any significant difference. The accuracy of prediction of residual and local recurrence for post-CRT PET and CT (local%/regional%) was 83%/94 % and 83%/78%, respectively. Conclusion: OPC patients with positive post-CRT PET exhibit poor survival. The prognostic accuracy of post-CRT PET is superior to that of CT. The results of post-CRT FDG-PET should be included in the management of the OPC patients

Rapid Suppression of Activated Rac1 by Cadherins and Nectins during De Novo Cell-Cell Adhesion

Cell-cell adhesion in simple epithelia involves the engagement of E-cadherin and nectins, and the reorganization of the actin cytoskeleton and membrane dynamics by Rho GTPases, particularly Rac1. However, it remains unclear whether E-cadherin and nectins up-regulate, maintain or suppress Rac1 activity during cell-cell adhesion. Roles for Rho GTPases are complicated by cell spreading and integrin-based adhesions to the extracellular matrix that occur concurrently with cell-cell adhesion, and which also require Rho GTPases. Here, we designed a simple approach to examine Rac1 activity upon cell-cell adhesion by MDCK epithelial cells, without cell spreading or integrin-based adhesion. Upon initiation of cell-cell contact in 3-D cell aggregates, we observed an initial peak of Rac1 activity that rapidly decreased by ∼66% within 5 minutes, and further decreased to a low baseline level after 30 minutes. Inhibition of E-cadherin engagement with DECMA-1 Fab fragments or competitive binding of soluble E-cadherin, or nectin2alpha extracellular domain completely inhibited Rac1 activity. These results indicate that cadherins and nectins cooperate to induce and then rapidly suppress Rac1 activity during initial cell-cell adhesion, which may be important in inhibiting the migratory cell phenotype and allowing the establishment of initially weak cell-cell adhesions

Splash!: a prospective birth cohort study of the impact of environmental, social and family-level influences on child oral health and obesity related risk factors and outcomes

Background: Dental caries (decay) is the most prevalent disease of childhood. It is often left untreated and can impact negatively on general health, and physical, developmental, social and learning outcomes. Similar to other health issues, the greatest burden of dental caries is seen in those of low socio-economic position. In addition, a number of diet-related risk factors for dental caries are shared risk factors for the development of childhood obesity. These include high and frequent consumption of refined carbohydrates (predominately sugars), and soft drinks and other sweetened beverages, and low intake of (fluoridated) water. The prevalence of childhood obesity is also at a concerning level in most countries and there is an opportunity to determine interventions for addressing both of these largely preventable conditions through sustainable and equitable solutions. This study aims to prospectively examine the impact of drink choices on child obesity risk and oral health status.Methods/Design: This is a two-stage study using a mixed methods research approach. The first stage involves qualitative interviews of a sub-sample of recruited parents to develop an understanding of the processes involved in drink choice, and inform the development of the Discrete Choice Experiment analysis and the measurement instruments to be used in the second stage. The second stage involves the establishment of a prospective birth cohort of 500 children from disadvantaged communities in rural and regional Victoria, Australia (with and without water fluoridation). This longitudinal design allows measurement of changes in the child&rsquo;s diet over time, exposure to fluoride sources including water, dental caries progression, and the risk of childhood obesity.Discussion: This research will provide a unique contribution to integrated health, education and social policy and program directions, by providing clearer policy relevant evidence on strategies to counter social and environmental factors which predispose infants and children to poor health, wellbeing and social outcomes; and evidence-based strategies to promote health and prevent disease through the adoption of healthier lifestyles and diet. Further, given the absence of evidence on the processes and effectiveness of contemporary policy implementation, such as community water fluoridation in rural and regional communities it&rsquo;s approach and findings will be extremelyinformative.<br /