Animal cells connected by nanotubes can be electrically coupled through interposed gap-junction channels

Tunneling nanotubes (TNTs) are recently discovered conduits for a previously unrecognized form of cell-to-cell communication. These nanoscale, F-actin–containing membrane tubes connect cells over long distances and facilitate the intercellular exchange of small molecules and organelles. Using optical membrane-potential measurements combined with mechanical stimulation and whole-cell patch-clamp recording, we demonstrate that TNTs mediate the bidirectional spread of electrical signals between TNT-connected normal rat kidney cells over distances of 10 to 70 μm. Similar results were obtained for other cell types, suggesting that electrical coupling via TNTs may be a widespread characteristic of animal cells. Strength of electrical coupling depended on the length and number of TNT connections. Several lines of evidence implicate a role for gap junctions in this long-distance electrical coupling: punctate connexin 43 immunoreactivity was frequently detected at one end of TNTs, and electrical coupling was voltage-sensitive and inhibited by meclofenamic acid, a gap-junction blocker. Cell types lacking gap junctions did not show TNT-dependent electrical coupling, which suggests that TNT-mediated electrical signals are transmitted through gap junctions at a membrane interface between the TNT and one cell of the connected pair. Measurements of the fluorescent calcium indicator X-rhod-1 revealed that TNT-mediated depolarization elicited threshold-dependent, transient calcium signals in HEK293 cells. These signals were inhibited by the voltage-gated Ca²⁺ channel blocker mibefradil, suggesting they were generated via influx of calcium through low voltage-gated Ca²⁺ channels. Taken together, our data suggest a unique role for TNTs, whereby electrical synchronization between distant cells leads to activation of downstream target signaling.Cell-to-cell communication plays an important role in physiological processes of multicellular organisms. Diverse signaling pathways have been documented for the exchange of molecular information between cells. These include (i) the direct interaction of cell-surface molecules, (ii) the secretion of signaling molecules and their receptor-mediated uptake by target cells, and (iii) the direct transport of molecules through gap junctions. In addition to the exchange of signaling molecules, cells also communicate via electrical signals, where electrical coupling of cells via gap junctions is crucial for information processing and synchronization. Recent studies implicate electrical signaling in developmental processes, such as the establishment of left-right pattern in embryos (1), tail regeneration of Xenopus (2), and wound healing (2).Some years ago, a new route of intercellular communication, based on the formation of tunneling nanotubes (TNTs) or similar structures that connect cells over long distances, was identified (3, 4). These membrane tubes, typically 50 to 200 nm in diameter with lengths up to several cell diameters, contain F-actin and, as a characteristic property, lack contact to the substratum (5). Subsequently, a growing number of cell types have been shown to form and use TNTs for the exchange of diverse cellular components, such as endocytic vesicles, mitochondria, plasma membrane proteins, and cytoplasmic molecules (6, 7). Pathogens, such as HIV (8, 9) and prions (10), have also been found to spread via TNT-like structures. The increasing number of functions attributed to TNTs (6, 7, 11), in conjunction with the recent finding that these structures exist in vivo (12), suggests important roles in intercellular communication of TNTs under physiological conditions.The question arises as to whether, in addition to the exchange of molecules, TNTs also convey electrical signals between distant cells. The demonstration that artificial membrane nanotubes with a similar diameter as TNTs are efficient conductors of electrical currents (13) suggests that TNTs may also accomplish electrical cell-to-cell coupling. To investigate this theory, we combined optical membrane-potential measurements and electrophysiological methods to analyze electrical signals between TNT-connected cell pairs. Our results demonstrate that TNTs can mediate electrical coupling between distant cells and provide evidence that gap junctions participate in this long-distance coupling. Furthermore, we show that the electrical signals transferred from one cell to another are sufficient to induce a transient calcium elevation in the recipient cell by activating low voltage-gated Ca²⁺ channels.     

Lack of association between the chemokine receptor 5 polymorphism CCR5delta32 in rheumatoid arthritis and juvenile idiopathic arthritis

Background  

The chemokine receptor CCR5 has been detected at elevated levels on synovial T cells, and a 32 bp deletion in the CCR5 gene leads to a non-functional receptor. A negative association between the CCR5Δ32 and rheumatoid arthritis (RA) has been reported, although with conflicting results. In juvenile idiopathic arthritis (JIA), an association with CCR5 was recently reported. The purpose of this study was to investigate if the CCR5Δ32 polymorphism is associated with RA or JIA in Norwegian cohorts.     

Cerebral blood flow findings in moyamoya disease in adults

Three adult patients with moyamoya disease are described. They presented with intracerebral hematoma, cerebral infarction and subarachnoid hemorrhage, respectively. Subarachnoid hemorrhage is rare in moyamoya and is usually the result of aneurysm rupture. No aneurysm was found in our patient. Regional cerebral blood flow (rCBF) and the cerebral perfusion reserve assessed by the acetazolamide test, were significantly reduced in all three patients. The areas with most reduced baseline rCBF and most impaired vasoreactivity did not always correspond to the site of the vascular accident, indicating that these CBF changes were at least in part due to the moyamoya disease and/or its underlying causes, and not solely to the vascular accidents.     

Do the same hypothalamic neurons project to both amygdala and cerebellum?

The possibility that individual hypothalamic cells project to the cerebellum (as hypothalamo-cerebellar fibers) and amygdala (hypothalamo-amygdaloid fibers) by means of collaterals, was studied by means of retrograde transport of Fast blue (FB) and Rhodamine (R)-labeled latex microspheres. Our findings show that R-labeled latex microspheres are well-suited for double labeling studies in combination with other retrograde fluorescent tracers. Neurons retrogradely labeled from cerebellum or from amygdala were found in the same hypothalamic nuclei, and they were often located adjacent to each other. Some additional animals were injected with a third tracer, Nuclear yellow (NY), in the spinal cord. The spinal projecting neurons were located in the same regions as cells retrogradely labeled with FB and R. All projections are bilateral with an ipsilateral preponderance. Some neurons were double-labeled, and all combinations of double-labeling (FB/R, NY/R, FB/NY) were found. This shows that some hypothalamic neurons may project to both cerebellum and amygdala, some to the spinal cord and amygdala, and others to cerebellum and the spinal cord. No triple labeled neurons were observed.     

European health inequality through the ‘Great Recession’: social policy matters

This paper investigates the association between the Great Recession and educational inequalities in self‐rated general health in 25 European countries. We investigate four different indicators related to economic recession: GDP; unemployment; austerity and a ‘crisis’ indicator signifying severe simultaneous drops in GDP and welfare generosity. We also assess the extent to which health inequality changes can be attributed to changes in the economic conditions and social capital in the European populations. The paper uses data from the European Social Survey (2002–2014). The analyses include both cross‐sectional and lagged associations using multilevel linear regression models with country fixed effects. This approach allows us to identify health inequality changes net of all time‐invariant differences between countries. GDP drops and increasing unemployment were associated with decreasing health inequalities. Austerity, however, was related to increasing health inequalities, an association that grew stronger with time. The strongest increase in health inequality was found for the more robust ‘crisis’ indicator. Changes in trust, social relationships and in the experience of economic hardship of the populations accounted for much of the increase in health inequality. The paper concludes that social policy has an important role in the development of health inequalities, particularly during times of economic crisis.     

A Polyprotein-Expressing Salmonid Alphavirus Replicon Induces Modest Protection in Atlantic Salmon (Salmo Salar) Against Infectious Pancreatic Necrosis

Vaccination is an important strategy for the control and prevention of infectious pancreatic necrosis (IPN) in farmed Atlantic salmon (Salmo salar) in the post-smolt stage in sea-water. In this study, a heterologous gene expression system, based on a replicon construct of salmonid alphavirus (SAV), was used for in vitro and in vivo expression of IPN virus proteins. The large open reading frame of segment A, encoding the polyprotein NH2-pVP2-VP4-VP3-COOH, as well as pVP2, were cloned and expressed by the SAV replicon in Chinook salmon embryo cells (CHSE-214) and epithelioma papulosum cyprini (EPC) cells. The replicon constructs pSAV/polyprotein (pSAV/PP) and pSAV/pVP2 were used to immunize Atlantic salmon (Salmo salar) by a single intramuscular injection and tested in a subsequent IPN virus (IPNV) challenge trial. A low to moderate protection against IPN was observed in fish immunized with the replicon vaccine that encoded the pSAV/PP, while the pSAV/pVP2 construct was not found to induce protection.     

The novel colorectal cancer biomarkers CDO1, ZSCAN18 and ZNF331 are frequently methylated across gastrointestinal cancers

We have previously shown that gastrointestinal cancers display similar epigenetic aberrations. In a recent study, we identified frequently methylated genes for cholangiocarcinoma (CDO1, DCLK1, SFRP1 and ZSCAN18), where one of these genes, DCLK1, was also confirmed to be highly methylated in colorectal cancer. The aim of the present study was to determine whether these four genes, in addition to one gene found to be methylated in colon cancer cell lines (ZNF331), are commonly methylated across gastrointestinal malignancies, as well as explore their role as potential biomarkers. Quantitative methylation specific PCR (qMSP) of colorectal cancer (n = 164) and normal colorectal mucosa (n = 106) samples showed that all genes were frequently methylated in colorectal cancer (71–92%) with little or no methylation in normal mucosa (0–3%). Methylation of minimum two of these five genes identified 95% of the tumors with a specificity of 98%, and an area under the receiver operating characteristics curve (AUC) of 0.98. For gastric (n = 25) and pancreatic (n = 20) cancer, the same panel detected 92% and 90% of the tumors, respectively. Seventy‐four cancer cell lines were further analyzed by qMSP and real time RT‐PCR. In addition to the previously reported DCLK1, a high negative correlation between promoter DNA methylation and gene expression was observed for CDO1, ZNF331 and ZSCAN18. In conclusion, the high methylation frequency of these genes in colorectal‐ as well as in gastric‐, pancreatic‐ and bile duct cancer confirmed an epigenetic similarity between gastrointestinal cancer types, and simultaneously demonstrated their potential as biomarkers, particularly for colorectal cancer detection.     

Social inequalities in "sickness": does welfare state regime type make a difference? A multilevel analysis of men and women in 26 European countries

In comparative studies of health inequalities, public health researchers have usually studied only disease and illness. Recent studies have also examined the sickness dimension of health, that is, the extent to which ill health is accompanied by joblessness, and how this association varies by education within different welfare contexts. This research has used either a limited number of countries or quantitative welfare state measures in studies of many countries. In this study, the authors expand on this knowledge by investigating whether a regime approach to the welfare state produces consistent results. They analyze data from the European Union Statistics on Income and Living Conditions (EU-SILC); health was measured by limiting longstanding illness (LLSI). Results show that for both men and women reporting LLSI in combination with low educational level, the probabilities of non-employment were particularly high in the Anglo-Saxon and Eastern welfare regimes, and lowest in the Scandinavian regime. For men, absolute and relative social inequalities in sickness were lowest in the Southern regime; for women, inequalities were lowest in the Scandinavian regime. The authors conclude that the Scandinavian welfare regime is more able than other regimes to protect against non-employment in the face of illness, especially for individuals with low educational level.