Disturbed Cyclical Stretch of Endothelial Cells Promotes Nuclear Expression of the Pro-Atherogenic Transcription Factor NF-κB

Exposure of endothelial cells to low and multidirectional blood flow is known to promote a pro-atherogenic phenotype. The mechanics of the vessel wall is another important mechano-stimulus within the endothelial cell environment, but no study has examined whether changes in the magnitude and direction of cell stretch can be pro-atherogenic. Herein, we developed a custom cell stretching device to replicate the in vivo stretch environment of the endothelial cell and examined whether low and multidirectional stretch promote nuclear translocation of NF-κB. A fluid–structure interaction model of the device demonstrated a nearly uniform strain within the region of cell attachment and a negligible magnitude of shear stress due to cyclical stretching of the cells in media. Compared to normal cyclical stretch, a low magnitude of cyclical stretch or no stretch caused increased expression of nuclear NF-κB (p = 0.09 and p < 0.001, respectively). Multidirectional stretch also promoted significant nuclear NF-κB expression, comparable to the no stretch condition, which was statistically higher than the low (p < 0.001) and normal (p < 0.001) stretch conditions. This is the first study to show that stretch conditions analogous to atherogenic blood flow profiles can similarly promote a pro-atherogenic endothelial cell phenotype, which supports a role for disturbed vessel wall mechanics as a pathological cell stimulus in the development of advanced atherosclerotic plaques.     

Transforming Growth Factor-β–Independent Role of Connective Tissue Growth Factor in the Development of Liver Fibrosis

We previously identified transforming growth factor (TGF)-β signaling as a fibronectin-independent mechanism of type I collagen fibrillogenesis following adult liver injury. To address the contribution of TGF-β signaling during the development of liver fibrosis, we generated adult mice lacking TGF-β type II receptor (TGF-βIIR) from the liver. TGF-βIIR knockout livers indeed showed a dominant effect in reducing fibrosis, but fibrosis still remained approximately 45% compared with control and fibronectin knockout livers. Unexpectedly, this was accompanied by significant up-regulation of connective tissue growth factor mRNA levels. Organized type I collagen networks in TGF-βIIR knockout livers colocalized well with fibronectin. We provide evidence that elimination of TGF-βIIR is not sufficient to completely prevent liver fibrosis. Our results indicate a TGF-β–independent mechanism of type I collagen production and suggest connective tissue growth factor as its potent mediator. We advocate combined elimination of TGF-β signaling and connective tissue growth factor as a potential therapeutic target by which to attenuate liver fibrosis.Liver fibrosis is defined as an abnormal response to persistent liver injury, characterized by the excessive accumulation of collagenous extracellular matrices (ECMs).^{1, 2} Liver fibrosis affects tens of millions of people worldwide and is of great clinical significance because normal liver architecture is disrupted and liver function is ultimately impaired. Because there is no effective treatment of liver fibrosis, many patients develop progressive liver cirrhosis, eventually requiring a liver transplant.^{3, 4}There is a long-standing concept that cells in culture cannot form a collagen fibril network without the ECM glycoprotein fibronectin.⁵ We recently established an adult mouse model lacking liver fibronectin and demonstrated that fibronectin-null livers, in fact, formed collagen fibril networks similarly to wild-type mice in response to carbon tetrachloride–induced chronic liver injury. The networks were found to be nucleated by type V collagen, induced by elevated local transforming growth factor (TGF)-β bioavailability.⁶ Therefore, we identified two mechanisms of collagen fibrillogenesis in response to liver injury: both fibronectin and TGF-β–signaling mediated.Early in the fibrogenic process, inflammatory cytokines are important in initiating repair following injury. TGF-β acts as a fibrogenic master cytokine and plays a pivotal role in the progression of a variety of chronic fibrotic diseases by promoting myofibroblastic differentiation, stimulating synthesis of ECMs, and down-regulating ECM degradation.⁷ In TGF-β–mediated signaling, ligand TGF-βs bind to TGF-β type I and type II receptors that form heterotetrameric complexes. On ligand binding, downstream Smad signaling pathways are initiated. Activated (phosphorylated) Smads translocate to the nucleus where they are involved in the regulation of gene expression.^{8, 9} Currently, several monoclonal antibodies and small molecules targeting TGF-β are in the process of clinical application for chronic fibrotic diseases, including liver fibrosis.¹⁰ However, these studies were initiated without knowledge of how TGF-β signaling exerts its action in the development of liver fibrosis.Elevated TGF-β activity in chronic fibrotic diseases is often accompanied by elevated expression of a matricellular protein, connective tissue growth factor (CTGF/CCN2).¹¹ The manifestation of CTGF/CCN2 functions in vivo involves cooperative interactions with costimulatory factors in the microenvironment, such as TGF-β and fibronectin. One hypothesis arising from the in vivo models is that fibrosing liver injuries are exacerbated by the action of TGF-β–mediated CTGF/CCN2.¹² Here, we addressed the extent to which fibrosis is dependent on the TGF-β/CTGF/CCN2 axis in chronic liver injury using an adult mouse model lacking liver TGF-β type II receptors (TGF-βIIR).     

Molecular Typing of “Candidatus Bartonella ancashi,” a New Human Pathogen Causing Verruga Peruana

A recently described clinical isolate, “Candidatus Bartonella ancashi,” was obtained from a blood sample of a patient presenting with verruga peruana in the Ancash region of Peru. This sample and a second isolate obtained 60 days later from the same patient were molecularly typed using multilocus sequence typing (MLST) and multispacer sequence typing (MST). The isolates were 100% indistinguishable from each other but phylogenetically distant from Bartonella bacilliformis and considerably divergent from other known Bartonella species, confirming their novelty.     

Immobilization-Induced Cartilage Degeneration Mediated Through Expression of Hypoxia-Inducible Factor-1α, Vascular Endothelial Growth Factor,and Chondromodulin-I

Immobilization results in thinning of the articular cartilage and cartilage degeneration, although the exact mechanisms are not clear yet. Hypoxia is thought to contribute to the degeneration of articular cartilage. We investigated the roles of hypoxia inducible factor (HIF)-1α, vascular endothelial growth factor (VEGF), and the newly cloned antiangiogenic factor, chondromodulin-I (ChM-1), in cartilage degeneration in immobilized joints. Male Wistar rats (n = 30, 12-week-old) were divided randomly into the control group (n = 10), immobilization group (n = 10), and continuous passive motion (CPM) group (n = 10). In the immobilization group, the ankle joints were fixed in full plantar flexion with plaster casts for 4 weeks. In the CPM group, the ankle casts were removed during the immobilization period and the ankle joints were subjected to CPM. Significant thinning of the articular cartilage was noted in the immobilization group but not in the control or CPM group. In the immobilized group, vascular channels were found in the area between the calcified cartilage zone and the subchondral bone. The densities of HIF-1α—and VEGF-immunostained cells were higher in the immobilized group than the other two groups. In contrast, low expression of ChM-1 was detected in the articular cartilage of the immobilized group compared with the control and CPM group. Our results showed that immobilization induces thinning of the articular cartilage and appearance of vascular channel, in areas with balanced expression of HIF-1α/VEGF and ChM-1.     

The Orientating Reflex: The “Targeting Reaction” and “Searchlight of Attention”

A concept of the orientating reflex is presented, based on the principle of vector coding of cognitive and executive processes. The orientating reflex is a complex of orientating reactions of motor, autonomic, and subjective types, accentuating new and significant stimuli. Two main systems form the orientating reflex: the targeting reaction and the searchlight of attention. In the visual system, the targeting reaction ensures that the image of the object falls onto the fovea; this is mediated by involvement of premotor neurons which are excited by saccade command neurons in the superior colliculi. The searchlight of attention is activated as a result of resonance within the gamma frequency range, selectively enhancing cortical detectors and involving the reticular nucleus of the thalamus. Novelty signals arise in novelty neurons of the hippocampus. The synaptic weightings of neocortical detectors for hippocampal novelty neurons is initially characterized by high efficiency, which assigns a significant level of excitation of these neurons to the new stimulus. During repeated stimulation, the synaptic weightings of all the detectors representing a given stimulus decrease, with the result that the novelty signal becomes weaker. When the stimulus changes, it acts on other detectors, whose weightings for novelty neurons remain high, which strengthens the novelty signal. Decreases in the synaptic weightings on repetition of a standard stimulus form a trace of this stimulus in the novelty neurons – this is the neural model of the stimulus. The novelty signal is determined by the non-concordance of the new stimulus with this neural model, which is formed under the influence of the standard stimulus. The greater the difference between the new stimulus and the previously formed neural model, the stronger the novelty signal.     

Inhibition of Collagen Synthesis and Regulation of Cell Motility in Vascular Smooth Muscle Cells by Suppression of Connective Tissue growth Factor Expression Using RNAInterference

1 IntroductionVascular smooth muscle cell (VSMC) hyperplasia plays an important role in both chronic and acute pathologies including atherosclerosis and restenosis. Recent studies have shown that connective tissue growth factor (CTGF) is a novel growth factor involved in the development and progression of atherosclerosis. However, previous data about the role of CTGF on the VSMC is conflicting. Hishikawa et al demonstrated that CTGF could act as a growth inhibitor in human VSMC; but …     

The “Heart” of depression during early adolescence

This study examined the concurrent associations linking youths’ parasympathetic nervous system activity, specifically baseline respiratory sinus arrhythmia (RSA) and respiratory sinus arrhythmia reactivity (RSAR; vagal withdrawal), with youth depression risk in a community sample of young adolescents. Youth gender was examined as a moderator of associations. Participants included 100 youth (53% boys; M age = 11.05 years, SD = 0.33; 43% ethnic minorities), along with their mothers and teachers. Youth and mothers participated in a laboratory protocol involving a peer problem-solving conversation, during which youths’ physiological activity was measured. Youth reported on their depressive symptoms. Teachers reported on youth depression risk via internalizing symptoms and emotion regulation (e.g., emotion lability/negativity). Results from regression analyses revealed that youths’ vagal withdrawal during the mother-youth peer problem conversation was associated with lower youth-reported depressive symptoms. Further, gender moderated the associations linking youth baseline RSA and RSAR with youth depression risk. Specifically, among girls but not boys, higher baseline RSA was associated with lower depressive symptoms and emotion lability/negativity, and higher RSAR (i.e., vagal withdrawal) was linked with lower internalizing symptoms. Findings contribute to the relatively small literature linking youth parasympathetic functioning with depression risk, and point to specific implications for girls.