Porcine arterivirus activates the NF-kappaB pathway through IkappaB degradation

Nuclear factor-kappaB (NF-kappaB) is a critical regulator of innate and adaptive immune function as well as cell proliferation and survival. The present study demonstrated for the first time that a virus belonging to the Arteriviridae family activates NF-kappaB in MARC-145 cells and alveolar macrophages. In porcine reproductive and respiratory syndrome virus (PRRSV)-infected cells, NF-kappaB activation was characterized by translocation of NF-kappaB from the cytoplasm to the nucleus, increased DNA binding activity, and NF-kappaB-regulated gene expression. NF-kappaB activation was increased as PRRSV infection progressed and in a viral dose-dependent manner. UV-inactivation of PRRSV significantly reduced the level of NF-kappaB activation. Degradation of IkappaB protein was detected late in PRRSV infection, and overexpression of the dominant negative form of IkappaBalpha (IkappaBalphaDN) significantly suppressed NF-kappaB activation induced by PRRSV. However, IkappaBalphaDN did not affect viral replication and viral cytopathic effect. PRRSV infection induced oxidative stress in cells by generating reactive oxygen species (ROS), and antioxidants inhibited NF-kappaB DNA binding activity in PRRSV-infected cells, suggesting ROS as a mechanism by which NF-kappaB was activated by PRRSV infection. Moreover, NF-kappaB-dependent expression of matrix metalloproteinase (MMP)-2 and MMP-9 was observed in PRRSV-infected cells, an observation which implies that NF-kappaB activation is a biologically significant aspect of PRRSV pathogenesis. The results presented here provide a basis for understanding molecular pathways of pathology and immune evasion associated with disease caused by PRRSV.     

ECM molecules mediate both Schwann cell proliferation and activation to enhance neurite outgrowth

Tissue engineering using a combination of biomaterials and cells represents a new approach to nerve repair. We have investigated the effect that extracellular matrix (ECM) molecules have on Schwann cell (SC) attachment and proliferation on the nerve conduit material poly-3-hydroxybutyrate (PHB), and SC influence on neurite outgrowth in vitro. Initial SC attachment to PHB mats was unaffected by ECM molecules but proliferation increased (laminin > fibronectin > collagen). SCs seeded onto ECM-coated culture inserts suspended above a monolayer of NG108-15 cells determined the effect of released diffusible factors. The effect of direct contact between the two cell types on ECM molecules was also investigated. In both systems SCs enhanced neurite number per cell and percentage of NG108-15 cells sprouting neurites. NG108-15 cells grown in direct contact with SCs had significantly longer neurites than those exposed to diffusible factors when seeded on laminin or fibronectin. Diffusible factors released from SCs cultured on ECM molecules appear to initiate neurite outgrowth, whereas SC-neuron contact promotes neurite elongation. SC proliferation was maximal on poly-D-lysine-coated surfaces, but these cells did not influence neurite outgrowth to the levels of laminin or fibronectin. This suggests that ECM molecules enhance cell number and activate SCs to release neurite promoting factors. Addition of ECM molecules to PHB nerve conduits containing SCs is likely to provide benefits for the treatment of nerve injuries.     

Glial cells: old cells with new twists

Based on their characteristics and function – migration, neural protection, proliferation, axonal guidance and trophic effects – glial cells may be regarded as probably the most versatile cells in our body. For many years, these cells were considered as simply support cells for neurons. Recently, it has been shown that they are more versatile than previously believed – as true stem cells in the nervous system – and are important players in neural function and development. There are several glial cell types in the nervous system: the two most abundant are oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. Although both of these cells are responsible for myelination, their developmental origins are quite different. Oligodendrocytes originate from small niche populations from different regions of the central nervous system, while Schwann cells develop from a stem cell population (the neural crest) that gives rise to many cell derivatives besides glia and which is a highly migratory group of cells.     

Cyclooxygenase-2 is over-expressed in Chinese esophageal squamous cell carcinoma, and correlated with NF-kappaB: an immunohistochemical study

BACKGROUND: Cyclooxygenase-2 (COX-2), the inducible isoform of the key enzyme in the synthesis of prostaglandins, has been found to be over-expressed in several human cancers. The aim of the present study was to investigate immunohistochemical expression of COX-2 in esophageal squamous cell carcinoma (SCC) and relationship with clinicopathological parameters and NF-kappaB. METHODS: Expression of COX-2 and NF-kappaB was investigated in 69 cases of esophageal SCC by immunohistochemistry and the correlation of COX-2 expression with clinicopathological features and NF-kappaB staining was examined. RESULTS: Thirty-one esophageal SCC (31/69, 44.9%) had positive expression of COX-2. COX-2 was expressed significantly higher in well-differentiated tumors (16/23, 69.6%) than that in moderate (13/34, 38.2%) and poor (2/12, 16.7%) differentiation (P = 0.034). COX-2 expression was increasingly progressive with the advance of the clinical stages significantly (P = 0.045). The correlation between COX-2 (47/99, 47.5%) and NF-kappaB/p50 (54/99, 54.5%) immunostaining was statistically significant (P = 0.030). CONCLUSIONS: COX-2 is over-expressed in esophageal SCC, especially in a well differentiation, correlated with tumor progression, and possibly regulated by NF-kappaB.     

Herpes simplex virus 2 modulates apoptosis and stimulates NF-kappaB nuclear translocation during infection in human epithelial HEp-2 cells

Virus-mediated apoptosis is well documented in various systems, including herpes simplex virus 1 (HSV-1). HSV-2 is closely related to HSV-1 but its apoptotic potential during infection has not been extensively scrutinized. We report that (i) HEp-2 cells infected with HSV-2(G) triggered apoptosis, assessed by apoptotic cellular morphologies, oligosomal DNA laddering, chromatin condensation, and death factor processing when a translational inhibitor (CHX) was added at 3 hpi. Thus, HSV-2 induced apoptosis but was unable to prevent the process from killing cells. (ii) Results from a time course of CHX addition experiment indicated that infected cell protein produced between 3 and 5 hpi, termed the apoptosis prevention window, are required for blocking virus-induced apoptosis. This corresponds to the same prevention time frame as reported for HSV-1. (iii) Importantly, CHX addition prior to 3 hpi led to less apoptosis than that at 3 hpi. This suggests that proteins produced immediately upon infection are needed for efficient apoptosis induction by HSV-2. This finding is different from that observed previously with HSV-1. (iv) Infected cell factors produced during the HSV-2(G) prevention window inhibited apoptosis induced by external TNFalpha plus cycloheximide treatment. (v) NF-kappaB translocated to nuclei and its presence in nuclei correlated with apoptosis prevention during HSV-2(G) infection. (vi) Finally, clinical HSV-2 isolates induced and prevented apoptosis in HEp-2 cells in a manner similar to that of laboratory strains. Thus, while laboratory and clinical HSV-2 strains are capable of modulating apoptosis in human HEp-2 cells, the mechanism of HSV-2 induction of apoptosis differs from that of HSV-1.     

Normal and neoplastic Schwann cells in fish

Summary Peripheral nerve sheath (PNS) neoplasms, primarily neurofibromas, schwannomas and maliganant schwannomas, are among the most common tumors in fishes. Model systems involving PNS tumors in fishes are also valuable because mammalian models of PNS tumors are rare. Schwann cells, the primary cell type suspected of neoplastic transformation in these tumors, have been difficult to culture. We describe techniques for culturing normal and neoplastic Schwann cells from fish. We also present methods for preparing cells on culture dishes for electron microscopy which are especially useful when specific cells in a culture must be located for ultrastructural examination.Abbreviations PNS peripheral nerve sheath - SC Schwann cells     

Ginsenosides compound K and Rh2 inhibit tumor necrosis factor-α-induced activation of the NF-κB and JNK pathways in human astroglial cells

Ginsenosides, the main component of Panax ginseng, have been known for the anti-inflammatory and anti-proliferative activities. In this study, we investigated the molecular mechanisms responsible for the anti-inflammatory effects of ginsenosides on activated astroglial cells. Among 13 different ginsenosides, intestinal bacterial metabolites Rh₂ and compound K (C-K) showed a significant inhibitory effect on tumor necrosis factor-α (TNF-α)-induced expression of intercellular adhesion molecule-1 in human astroglial cells. Pretreatment with C-K or Rh₂ suppressed TNF-α-induced phosphorylation of IκBα kinase and the subsequent phosphorylation and degradation of IκBα. Additionally, the same treatment inhibited TNF-α-induced phosphorylation of MKK4 and the subsequent activation of the JNK-AP-1 pathway. The inhibitory effect of ginsenosides on TNF-α-induced activation of the NF-κB and JNK pathways was not observed in human monocytic U937 cells. These results collectively indicate that ginsenoside metabolites C-K and Rh₂ exert anti-inflammatory effects by the inhibition of both NF-κB and JNK pathways in a cell-specific manner.     

Neurotrophic factors increase tumor necrosis factor-alpha-induced nuclear translocation of NF-kappaB in rat PC12 cells

Neurotrophic factors regulate neuronal survival and differentiation and control neurite outgrowth by binding to tyrosine kinase receptors, the Trks, and a tumor necrosis factor (TNF) receptor-like molecule, p75 neurotrophin receptor. A proinflammatory cytokine, TNF, also affects survival and apoptotic death in neuronal cells. However, it is still unclear whether neurotrophic factors and TNF co-operate the intracellular signaling. Using green fluorescent protein-tagged NF-kappaB1 (GFP-NF-kappaB1), we examined here the effects of TNF-alpha and neurotrophic factors on the nuclear translocation of NF-kappaB in PC12 cells. TNF-alpha induced gradually the translocation of GFP-NF-kappaB1 from the cytoplasm to the nucleus within 60 min. Pretreatment of lactacystin which is a proteasome-specific inhibitor suppressed significantly the nuclear translocation of GFP-NF-kappaB1 after TNF-alpha stimulation. In addition, we found that co-stimulation of TNF-alpha and neurotrophic factors such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) increased greatly the nuclear translocation of GFP-NF-kappaB1 whereas neither NGF nor BDNF itself induced the translocation. These results suggested that there is a close correlation between the signaling pathways via TNF receptors and neurotrophin receptors for the NF-kappaB activation, and that NGF and BDNF enhance TNF-alpha-induced nuclear translocation of NF-kappaB.     

Models and methods to study Schwann cells

Schwann cells (SCs) are fundamental components of the peripheral nervous system (PNS) of all vertebrates and play essential roles in development, maintenance, function, and regeneration of peripheral nerves. There are distinct populations of SCs including: (1) myelinating SCs that ensheath axons by a specialized plasma membrane, called myelin, which enhances the conduction of electric impulses; (2) non‐myelinating SCs, including Remak SCs, which wrap bundles of multiple axons of small caliber, and perysinaptic SCs (PSCs), associated with motor axon terminals at the neuromuscular junction (NMJ). All types of SCs contribute to PNS regeneration through striking morphological and functional changes in response to nerve injury, are affected in peripheral neuropathies and show abnormalities and a diminished plasticity during aging. Therefore, methodological approaches to study and manipulate SCs in physiological and pathophysiological conditions are crucial to expand the present knowledge on SC biology and to devise new therapeutic strategies to counteract neurodegenerative conditions and age‐derived denervation. We present here an updated overview of traditional and emerging methodologies for the study of SCs for scientists approaching this research field.     

体外培养Schwann细胞缺氧模型的建立

目的:建立体外培养Schwann细胞的缺氧模型。方法:取体外培养Schwann细胞,置于通入体积分数为5%CO2和95%N2的有机玻璃盒中继续缺氧培养10、15和20min,用H-E染色观察细胞形态,MTT比色试验检测细胞的活力。结果:缺氧10min组细胞形态及活力与正常组无明显差异;而缺氧15min组的细胞突起回缩,活力为缺氧前的66·3%;缺氧20min组的细胞多数死亡,活力仅为缺氧前的20·6%。结论:本方法可以成功建立有效、简便、易行的Schwann细胞缺氧模型。     

An electron microscope study of quantitative relationships between axon and Schwann cell sheath in myelinated fibres of peripheral nerves

Summary The quantitative relationships between the crossectional area of the Schwann cell sheath (myelin included) and that of its related axon were studied by electron microscopy in the nerve fibres of the spinal roots of lizard (Lacerta muralis). In both ventral and dorsal roots the cross-sectional area of the Schwann cell sheath (myelin included) was found to be directly proportional to that of its related axon (correlation coefficients between 0.88 and 0.92). The ratio between the cross-sectional area of the Schwann cell sheath (myelin included) and that of its related axon tends to diminish as the cross-sectional area of the latter increases. Thus, under normal conditions, in myelinated fibres of the spinal roots of the lizard a quantitative balance exists between the nerve tissue and its associated glial tissue. This result agrees with those previously obtained in the spinal ganglia of the lizard, gecko, cat and rabbit. Some of the mechanisms probably involved in the control of the quantitative balance between nerve tissue and its associated glial tissue in peripheral nerves are presented and discussed.     

Activation of non-canonical NF-kappaB pathway mediated by STP-A11, an oncoprotein of Herpesvirus saimiri

Although Saimiri Transforming Protein (STP)-A11, an oncoprotein of Herpesvirus saimiri, has been known to activate NF-kappaB signaling pathway, the detailed mechanism has not been reported yet. We herein report that STP-A11 activates non-canonical NF-kappaB pathway, resulting in p100 processing to p52. In addition, translocation of p52 protein (NF-kappaB2) into the nucleus is observed by the expression of STP-A11. STP-A11-mediated processing of p100 to p52 protein requires proteosome-mediated proteolysis because MG132 treatment clearly blocked p52 production in spite of the expression of STP-A11. Analysis of STP-A11 mutants to activate NF-kappaB2 pathway discloses the requirement of TRAF6-binding site not Src-binding site for STP-A11-mediated NF-kappaB2 pathway. Blockage of STP-A11-mediated p52 production using siRNA against p52 enhanced a chemotherapeutic drug-mediated cell death, suggesting that p52 production induced by the expression of STP-A11 would contribute to cellular transformation, which results from a resistance to cell death.     

雪旺细胞增殖的研究进展

随着周围神经组织工程学的发展,雪旺细胞的研究越来越受到重视。在周围神经损伤后,雪旺细胞对周围神经再生过程中的形态和功能的修复起着不可替代的作用,因此雪旺细胞的增殖情况对于周围神经损伤后的修复就尤为重要。其增殖速度的提高可大大改善神经桥接体移植的存活率,为临床神经移植术的成功赢得宝贵的时间。本文从雪旺细胞的功能、增殖机制及其影响因素入手,为雪旺细胞的临床应用提供理论依据。     

施万细胞的层黏连蛋白表达变化及两者关系的初步研究

目的:观察层黏连蛋白(laminin,LN)在坐骨神经发育过程中的表达情况,以及LN和施万细胞(Schwann cells,SCs)的相互关系。方法:取E14、E17、P1和成年SD大鼠坐骨神经,免疫荧光组织化学染色检测LN表达情况;体外培养大鼠来源的SCs,经过外源性LN处理后,免疫荧光细胞化学染色检测LN、nidogen、type IVcollagen等细胞外基质成分的表达,酸性磷酸酶法检测SCs的黏附能力。结果:E17大鼠坐骨神经SCs有LN阳性免疫反应;经过外源性LN处理后,SCs有LN、nidogen、type IV collagen阳性免疫反应,且黏附能力增加。结论:在E17大鼠中,SCs开始分泌LN;LN具有促进SCs合成细胞外基质成分,并在其黏附过程中发挥作用。