Altered expression of claudin family proteins in Alzheimer’s disease and vascular dementia brains

Claudins (Cls) are a multigene family of transmembrane proteins with different tissue distribution, which have an essential role in the formation and sealing capacity of tight junctions (TJs). At the level of the blood–brain barrier (BBB), TJs are the main molecular structures which separate the neuronal milieu from the circulatory space, by a restriction of the paracellular flow of water, ions and larger molecules into the brain. Different studies suggested recently significant BBB alterations in both vascular and degenerative dementia types. In a previous study we found in Alzheimer’s disease (AD) and vascular dementia (VaD) brains an altered expression of occludin, a molecular partner of Cls in the TJs structure. Therefore in this study, using an immunohistochemical approach, we investigated the expression of Cl family proteins (Cl‐2, Cl‐5 and Cl‐11) in frontal cortex of aged control, AD and VaD brains. To estimate the number of Cl‐expressing cells, we applied a random systematic sampling and the unbiased optical fractionator method. We found selected neurons, astrocytes, oligodendrocytes and endothelial cells expressing Cl‐2, Cl‐5 and Cl‐11 at detectable levels in all cases studied. We report a significant increase in ratio of neurons expressing Cl‐2, Cl‐5 and Cl‐11 in both AD and VaD as compared to aged controls. The ratio of astrocytes expressing Cl‐2 and Cl‐11 was significantly higher in AD and VaD as compared to aged controls. The ratio of oligodendrocytes expressing Cl‐11 was significantly higher in AD and the ratio of oligodendrocytes expressing Cl‐2 was significantly higher in VaD as compared to aged controls. Within the cerebral cortex, Cls were selectively expressed by pyramidal neurons, which are the ones responsible for cognitive processes and affected by AD pathology. Our findings suggest a new function of Cl family proteins which might be linked to response to cellular stress.     

TELOCYTES IN ENDOCARDIUM: Electron Microscope Evidence

The term TELOCYTES was very recently introduced, for replacing the name Interstitial Cajal‐Like Cells (ICLC). In fact, telocytes are not really Cajal‐like cells, they being different from all other interstitial cells by the presence of telopodes, which are cell‐body prolongations, very thin (under the resolving power of light microscopy), extremely long (tens up to hundreds of micrometers), with a moniliform aspect (many dilations along), and having caveolae. The presence of telocytes in epicardium and myocardium was previously documented. We present here electron microscope images showing the existence of telocytes, with telopodes, at the level of mouse endocardium. Telocytes are located in the subendothelial layer of endocardium, and their telopodes are interposed in between the endocardial endothelium and the cardiomyocytes bundles. Some telopodes penetrate from the endocardium among the cardiomyocytes and surround them, eventually. Telopodes frequently establish close spatial relationships with myocardial blood capillaries and nerve endings. Because we may consider endocardium as a ‘blood–heart barrier’, or more exactly as a ‘blood–myocardium barrier’, telocytes might have an important role in such a barrier being the dominant cell population in subendothelial layer of endocardium.     

Co‐ordinated autophagy with resveratrol and γ‐tocotrienol confers synergetic cardioprotection

This study compared two dietary phytochemicals, grape‐derived resveratrol and palm oil‐derived γ‐tocotrienol, either alone or in combination, on the contribution of autophagy in cardioprotection during ischaemia and reperfusion. Sprague‐Dawley rats weighing between 250 and 300 g were randomly assigned to one of the following groups: vehicle, ischaemia/reperfusion (I/R), resveratrol + I/R, γ‐tocotrienol + I/R, resveratrol +γ‐tocotrienol + I/R. For resveratrol treatments, the rats were gavaged with resveratrol (2.5 mg/kg) for 15 days while for γ‐tocotrienol experiments the rats were gavaged with γ‐tocotrienol (0.3 mg/kg) for 30 days. For the combined resveratrol +γ‐tocotrienol experiments, the rats were gavaged with γ‐tocotrienol for 15 days, and then gavaging continued with resveratrol along with γ‐tocotrienol for a further period of 15 days. After 30 days, isolated perfused hearts were subjected to 30 min. of global ischaemia followed by 2 hrs of reperfusion. Our results showed for the first time that at least in part, the cardioprotection (evidenced from the ventricular performance, myocardial infarct size and cardiomyocyte apoptosis) with resveratrol and γ‐toctrienol was achieved by their abilities to induce autophagy. Most importantly, resveratrol and γ‐tocotrienol acted synergistically providing greater degree of cardioprotection simultaneously generating greater amount of survival signal through the activation of Akt‐Bcl‐2 survival pathway. Autophagy was accompanied by the activation of Beclin and LC3‐II as well as mTOR signalling, which were inhibited by either 3‐methyl adenine (3‐MA) or Wortmannin. The autophagy was confirmed from the results of transmission electron microscopy and light microscopy as well as with confocal microscopy. It is tempting to speculate that during ischaemia and reperfusion autophagy along with enhanced survival signals helps to recover the cells from injury.     

The chemical form of mitochondrial iron in Friedreich's ataxia

Friedreich's ataxia (FRDA) results from cellular damage caused by a deficiency in the mitochondrial matrix protein frataxin. To address the effect of frataxin deficiency on mitochondrial iron chemistry, the heavy mitochondrial fraction (HMF) was isolated from primary fibroblasts from FRDA affected and unaffected individuals. X-ray absorption spectroscopy was used to characterize the chemical form of iron. Near K-edge spectra were fitted with a series of model iron compounds to determine the proportion of each iron species. Most of the iron in both affected and unaffected fibroblasts was ferrihydrite. The iron K-edge from unaffected HMFs were best fitted with poorly organized ferrihydrite modeled by frataxin whereas HMFs from affected cells were best fitted with highly organized ferrihydrite modeled by ferritin. Both had several minor iron species but these did not differ consistently with disease. Since the iron K-edge spectra of ferritin and frataxin are very similar, we present additional evidence for the presence of ferritin-bound iron in HMF. The predominant ferritin subunit in HMFs from affected cells resembled mitochondrial ferritin (MtFt) in size and antigenicity. Western blotting of native gels showed that HMF from affected cells had 3-fold more holoferritin containing stainable iron. We conclude that most of the iron in fibroblast HMF from both affected and unaffected cells is ferrihydrite but only FRDA affected cells mineralize significant iron in mitochondrial ferritin.     

Lineage specific evolution of the VNTR composite retrotransposon central domain and its role in retrotransposition of gibbon LAVA elements

Background

VNTR (Variable Number of Tandem Repeats) composite retrotransposons - SVA (SINE-R-VNTR-Alu), LAVA (LINE-1-Alu-VNTR-Alu), PVA (PTGR2-VNTR-Alu) and FVA (FRAM-VNTR-Alu) - are specific to hominoid primates. Their assembly, the evolution of their 5’ and 3’ domains, and the functional significance of the shared 5’ Alu-like region are well understood. The central VNTR domain, by contrast, has long been assumed to represent a more or less random collection of 30-50 bp GC-rich repeats. It is only recently that it attracted attention in the context of regulation of SVA expression.

Results

Here we provide evidence that the organization of the VNTR is non-random, with conserved repeat unit (RU) arrays at both the 5’ and 3’ ends of the VNTRs of human, chimpanzee and orangutan SVA and gibbon LAVA. The younger SVA subfamilies harbour highly organized internal RU arrays. The composition of these arrays is specific to the human/chimpanzee and orangutan lineages, respectively. Tracing the development of the VNTR through evolution we show for the first time how tandem repeats evolve within the constraints set by a functional, non-autonomous non-LTR retrotransposon in two different families - LAVA and SVA - in different hominoid lineages. Our analysis revealed that a microhomology-driven mechanism mediates expansion/contraction of the VNTR domain at the DNA level.Elements of all four VNTR composite families have been shown to be mobilized by the autonomous LINE1 retrotransposon in trans. In case of SVA, key determinants of mobilization are found in the 5’ hexameric repeat/Alu-like region. We now demonstrate that in LAVA, by contrast, the VNTR domain determines mobilization efficiency in the context of domain swaps between active and inactive elements.

Conclusions

The central domain of VNTR composites evolves in a lineage-specific manner which gives rise to distinct structures in gibbon LAVA, orangutan SVA, and human/chimpanzee SVA. The differences observed between the families and lineages are likely to have an influence on the expression and mobilization of the elements.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1543-z) contains supplementary material, which is available to authorized users.     

Enhanced cortical excitability in grapheme-color synesthesia and its modulation

Synesthesia is an unusual condition characterized by the over-binding of two or more features and the concomitant automatic and conscious experience of atypical, ancillary images or perceptions. Previous research suggests that synesthetes display enhanced modality-specific perceptual processing, but it remains unclear whether enhanced processing contributes to conscious awareness of color photisms. In three experiments, we investigated whether grapheme-color synesthesia is characterized by enhanced cortical excitability in primary visual cortex and the role played by this hyperexcitability in the expression of synesthesia. Using transcranial magnetic stimulation, we show that synesthetes display 3-fold lower phosphene thresholds than controls during stimulation of the primary visual cortex. We next used transcranial direct current stimulation to discriminate between two competing hypotheses of the role of hyperexcitability in the expression of synesthesia. We demonstrate that synesthesia can be selectively augmented with cathodal stimulation and attenuated with anodal stimulation of primary visual cortex. A control task revealed that the effect of the brain stimulation was specific to the experience of synesthesia. These results indicate that hyperexcitability acts as a source of noise in visual cortex that influences the availability of the neuronal signals underlying conscious awareness of synesthetic photisms.     

Histamine and H1 -histamine receptors faster venous circulation

The study has analysed the action of histamine in the rabbit venous system and evaluated its potential role in contraction during increased venous pressure. We have found that a great variety exists in histamine sensitivity and H(1) -histamine receptor expression in various types of rabbit veins. Veins of the extremities (saphenous vein, femoral vein, axillary vein) and abdomen (common iliac vein, inferior vena cava) responded to histamine by a prominent, concentration-dependent force generation, whereas great thoracic veins (subclavian vein, superior vena cavas, intrathoracic part of inferior vena cava) and a pelvic vein (external iliac vein) exhibited slight sensitivity to exogenous histamine. The lack of reactivity to histamine was not due to increased activity of nitric oxide synthase (NOS) or heme oxygenase-1. H(1) -histamine receptor expression of veins correlated well with the histamine-induced contractions. Voltage-dependent calcium channels mediated mainly the histamine-induced force generation of saphenous vein, whereas it did not act in the inferior vena cava. In contrast, the receptor-operated channels were not involved in this response in either vein. Tyrosine phosphorylation occurred markedly in response to histamine in the saphenous vein, but not in the inferior vena cava. Histamine induced a prominent ρ kinase activation in both vessels. Protein kinase C and mitogen-activated protein kinase (MAPK) were not implicated in the histamine-induced intracellular calcium sensitization. Importantly, transient clamping of the femoral vein in animals caused a short-term constriction, which was inhibited by H(1) -histamine receptor antagonist in vivo. Furthermore, a significantly greater histamine immunopositivity was detected in veins after stretching compared to the resting state. We conclude that histamine receptor density adapts to the actual requirements of the circulation, and histamine liberated by the venous wall during increased venous pressure contributes to the contraction of vessels, providing a force for the venous return.