Protein kinase Cε mediates salutary effects on electrical coupling induced by ischemic preconditioning

BACKGROUND: Ischemic preconditioning delays the onset of electrical uncoupling and prevents loss of the primary ventricular gap junction protein connexin 43 (Cx43) from gap junctions during subsequent ischemia. OBJECTIVE: To test the hypothesis that these effects are mediated by protein kinase C epsilon (PKCepsilon), we studied isolated Langendorff-perfused hearts from mice with homozygous germline deletion of PKCepsilon (PKCepsilon-KO). METHODS: Cx43 phosphorylation and distribution were measured by quantitative immunoblotting and confocal microscopy. Changes in electrical coupling were monitored using the 4-electrode technique to measure whole-tissue resistivity. RESULTS: The amount of Cx43 located in gap junctions, measured by confocal microscopy under basal conditions, was significantly greater in PKCepsilon-KO hearts compared with wild-type, but total Cx43 content measured by immunoblotting was not different. These unanticipated results indicate that PKCepsilon regulates subcellular distribution of Cx43 under normal conditions. Preconditioning prevented loss of Cx43 from gap junctions during ischemia in wild-type but not PKCepsilon-KO hearts. Specific activation of PKCepsilon, but not PKCdelta, also prevented ischemia-induced loss of Cx43 from gap junctions. Preconditioning delayed the onset of uncoupling in wild-type but hastened uncoupling in PKCepsilon-KO hearts. Cx43 phosphorylation at the PKC site Ser368 increased 5-fold after ischemia in wild-type hearts, and surprisingly, by nearly 10-fold in PKCepsilon-KO hearts. Preconditioning prevented phosphorylation of Cx43 in gap junction plaques at Ser368 in wild-type but not PKCepsilon-KO hearts. CONCLUSION: Taken together, these results indicate that PKCepsilon plays a critical role in preconditioning to preserve Cx43 signal in gap junctions and delay electrical uncoupling during ischemia.     

Regulation of mucosal structure and barrier function in rat colon exposed to tumor necrosis factor alpha and interferon gamma in vitro: A novel model for studying the pathomechanisms of inflammatory bowel disease cytokines

Objective. In Inflammatory bowel disease (IBD), elevated cytokines are responsible for disturbed intestinal transport and barrier function. The mechanisms of cytokine action have usually been studied in cell culture models only; therefore the aim of this study was to establish an in vitro model based on native intestine to analyze distinct cytokine effects on barrier function, mucosal structure, and inherent regulatory mechanisms. Material and methods. Rat colon was exposed to tumor necrosis factor alpha (TNFα) and interferon gamma (IFNγ) in Ussing chambers. Transepithelial resistance (R^t) and ³H-mannitol fluxes were measured for characterization of the paracellular pathway. Transcellular transport was analyzed by horseradish peroxidase (HRP) flux measurements. Expression and distribution of tight junction proteins were characterized in immunoblots and by means of confocal laser-scanning microscopy (LSM). Results. Colonic viability could be preserved for 20 h in a specialized in vitro set-up. This was sufficient to alter mucosal architecture with crypt surface reduction. R^t was decreased (101±10 versus 189±10 Ω·cm²) with a parallel increase in mannitol permeability after cytokine exposure. Tight junction proteins claudin-1, -5, -7, and occludin decreased (45±10%, 16±7%, 42±8%, and 42±13% of controls, respectively), while claudin-2 increased to 208±32%. Occludin and claudin-1 translocated from the plasma membrane to the cytoplasm. HRP flux increased from 0.73±0.09 to 8.55±2.92 pmol·h^?1·cm^?2. Conclusions. A new experimental IBD model with native colon in vitro is presented. One-day exposure to TNFα and IFNγ alters mucosal morphology and impairs epithelial barrier function by up-regulation of the paracellular pore-former claudin-2 and down-regulation of the barrier-builders claudin-1, -5, and -7. These alterations resemble changes seen in IBD and thus underline their prominent role in IBD pathogenicity.     

血吸虫可溶性虫卵抗原诱发脑血管内皮细胞缝隙连接蛋白Cx37mRNA及蛋白的表达

目的 通过观察血吸虫可溶性虫卵抗原(SEA)孵育培养的脑血管内皮细胞缝隙连接(GJ)蛋白的表达和分布,探讨脑动脉GJ在脑血吸虫病病理发生中的作用。方法 使用血吸虫SEA孵育培养幼兔脑基底动脉血管内皮细胞,实验分对照组、SEA 1～5组：加入SEA（质量浓度分别为10.0％、5.0％、3.3％、2.5％、2.0％）,应用逆转录—聚合酶链式反应(RT-PCR)技术测定兔脑血管内皮细胞GJ蛋白Cx37 mRNA的表达;应用Western 印迹技术测定兔脑血管内皮细胞GJ蛋白Cx37蛋白的表达。结果 对照组和SEA 1 ～5组的GJ蛋白Cx37 mRNA水平分别为0.239±0.037、0.260±0.043、0.218±0.310、0.647±0.040、0.419±0.036、0.513±0.038;其中SEA 3～5组的GJ蛋白Cx37 mRNA水平高于对照组（P均＜0.05）。对照组和SEA 1～5组GJ 蛋白Cx37蛋白表达分别为0.401±0.045、0.485±0.048、0.749±0.052、1.119±0.063、1.015±0.057、0.605±0.047,其中SEA 2 ～5组Cx37蛋白表达高于对照组（P均＜0.05）。结论 血吸虫SEA孵育培养的兔脑血管内皮细胞GJ蛋白Cx37 mRNA及其蛋白水平高于对照组,提示GJ蛋白在SEA及其分泌物浸润脑动脉沉积于脑组织,从而在诱发脑血吸虫病的病理发生机制中可能起重要的作用。     

Decreased intercellular coupling improves the function of cardiac pacemakers derived from mouse embryonic stem cells

The aim of this study was to determine if embryonic stem cell derived cardiomyocyte aggregates (ESdCs) can act as pacemakers in spontaneously active cardiomyocyte preparations when their connexin isoform expression is tuned toward a more sinus nodal phenotype. Using microelectrode array recordings (MEAs), we demonstrate that mouse ESdCs establish electrical coupling with spontaneously active cardiomyocyte preparations (HL-1 monolayer) and obtain pacemaker dominance. WT- and Cx43(−/−)-ESdCs comparably established intercellular coupling with cardiac host tissue (Cx43(−/−): 86% vs. WT: 91%). Although both aggregates had a 100% success rate in pacing quiescent cardiac preparations, Cx43(−/−)-ESdCs had an increased likelihood of gaining pacemaker dominance (Cx43(−/−): 40% vs. WT: 13%) in spontaneously active preparations. No differences in size, beating frequency, V_m, or differentiation were detected between WT- and Cx43(−/−)-ESdCs but the intercellular coupling resistance in Cx43(−/−)-ESdCs was significantly increased (Cx43(−/−): 1.2nS vs. WT: 14.8nS). Lack of Cx43 prolonged the time until Cx43(−/−)-ESdCs established frequency synchronization with the host tissue. It further hampered the excitation spread from the cardiomyocyte preparation into the ESdC. However rectifying excitation spread in these co-cultures could not be unequivocally identified. In summary, ESdCs can function as dominant biological pacemakers and Cx43 expression is not a prerequisite for their electrical integration. Maintenance of pacemaker dominance depends critically on the pacemaker's gap junction expression benefiting those with increased intercellular coupling resistances. Our results provide important insight into the design of biological pacemakers that will benefit the use of cardiomyocytes for cell replacement therapy.     

反流性食管炎黏膜上皮中紧密连接蛋白及白细胞介素-6的表达

目的 观察反流性食管炎(RE)大鼠食管黏膜中紧密连接蛋白(闭锁蛋白、跨膜蛋白、胞质附着蛋白-1和连接粘附因子-1)的分布和表达,以阐述紧密连接蛋白在RE发病机制中的作用.方法 雄性8周龄Wistar大鼠220只,分成假手术对照组(10只)、酸反流组(70只)、碱反流组(70只)和酸碱混合反流组(70只).动物于术后3、6、9、14 d分批处死,取食管中、下段评估成模率.以透射电镜成像法观察紧密连接形态学的变化.分别用免疫组化法、Western印迹法和RT-PCR法检测白细胞介素(IL)-6、紧密连接蛋白及其mRNA的表达.结果 造模成功率为100%.显微镜下观察发现随着RE的发展,黏膜厚度增加.电镜下可见细胞间隙增宽,桥粒明显减少.模型组IL-6和紧密连接蛋白的表达明显高于对照组,但随着基底层细胞增殖改变的加重,单个细胞间紧密连接蛋白的表达逐渐降低.随着RE病程的发展,IL-6和紧密连接蛋白及其mRNA的表达逐渐增强.结论 紧密连接蛋白高表达参与了RE的发病机制,是RE发生、发展的早期分子事件.其表达可能在RE的病理过程中具有正调节的协同作用,而IL-6是RE发展演进过程中的致炎因子.     

Hormonal stimulation of Ca2+ and Mg2+ transport in the cortical thick ascending limb of Henle's loop of the mouse: evidence for a change in the paracellular pathway permeability

Recent studies from our laboratory have shown that in the cortical thick ascending limb of Henle's loop of the mouse (cTAL) Ca²⁺ and Mg²⁺ are reabsorbed passively, via the paracellular shunt pathway. In the present study, cellular mechanisms responsible for the hormone-stimulated Ca²⁺ and Mg²⁺ transport were investigated. Transepithelial voltages (PD_te) and transepithelial ion net fluxes (J _Na, J _Cl, J _K, J _Ca, J _Mg) were measured in isolated perfused mouse cTAL segments. Whether parathyroid hormone (PTH) is able to stimulate Ca²⁺ and Mg²⁺ reabsorption when active NaCl reabsorption, and thus PD_te, is abolished by luminal furosemide was first tested. With symmetrical lumen and bath Ringer's solutions, no Ca²⁺ and Mg²⁺ net transport was detectable, either in the absence or in the presence of PTH. In the presence of luminal furosemide and a chemically imposed lumen-to-bath directed NaCl gradient, which generates a lumen-negative PD_te, PTH slightly but significantly increased Ca²⁺ and Mg²⁺ net secretion. In the presence of luminal furosemide and a chemically imposed bath-to-lumen-directed NaCl gradient, which generates a lumen-positive PD_te, PTH slightly but significantly increased Ca²⁺ and Mg²⁺ net reabsorption. In view of the observed small effect of PTH on passive Ca²⁺ and Mg²⁺ movement, a possible interference of furosemide with the hormonal response was considered. To investigate this possibility, Ca²⁺ and Mg²⁺ transport was first stimulated with PTH in tubules under control conditions. Then active NaCl reabsorption was abolished by furosemide and the effect of PTH on J _Ca and J _Mg measured. In the absence of PD_te and under symmetrical conditions, no Ca²⁺ and Mg²⁺ transport was detectable, either in the presence or absence of PTH. In the presence of a bath-to-lumen-directed NaCl gradient, Ca²⁺ and Mg²⁺ reabsorption was significantly higher in the presence than in the absence of PTH. Finally, when active NaCl transport was not inhibited by furosemide, but reduced by a bath-to-lumen-directed NaCl gradient, PTH strongly increased J _Ca and J _Mg, whereas only a small increase in PD_te was noted. In conclusion, these data suggest that PTH exerts a dual action on Ca²⁺ and Mg²⁺ transport in the mouse cTAL by increasing the transepithelial driving force for Ca²⁺ and Mg²⁺ reabsorption through hormone-mediated PD_te alterations and by modifying the passive permeability for Ca²⁺ and Mg²⁺ of the epithelium, very probably at the level of the paracellular shunt pathway.     

Ultrastructure of melanocytes in the dark cell area of human vestibular organs: Functional implications of gap junctions,isolated cilia,and annulate lamellae

Background: It is known that melanocytes exist in almost all parts of the inner ear, such as the cochlear duct, stria vascularis, Reissner's membrane, modiolus, vestibular organs in the region surrounding the cristae and maculae, semicircular canals, and pars rugosa of the endolymphatic sac. But there have been few studies using human materials, because of the difficulty of obtaining materials. We attempted to investigate the detailed ultrastructure of melanocytes in the vestibular organs of human inner ear. Methods: Eight surgical specimens obtained from patients with vestibular schwannoma were studied by light microscopy and electron microscopy. Results: Melanocytes were found in the subepithelial layer of the dark cell area. Melanocytes had round or spindle-shaped nuclei and clear cytoplasm with brown pigment granules. Besides melanocytes, there were melanophages, fibroblasts, and small blood vessels. Through electron microscopy we found melanocytes with round-shaped melanosomes in various stages of pigmentation, well-developed Golgi apparatus and endoplasmic reticulum in the cytoplasm, and many cytoplasmic processes. Gap junctions were occasionally found between the cytoplasmic processes. And there were pinocytotic vesicles just under the limiting membrane of melanocytes, and intermediate filaments were abundant in the cytoplasm. Isolated cilia of melanocytes, annulate lamellae, and fusiform banded structures in the connective tissue area around melanocytes were found. Conclusions: Melanocytes in human vestibular organs actively synthesize melanosomes. Frequent findings of isoalted cilia and fusiform banded structures and the incidental existence of annulate lamellae may be an indicator of this metabolically activated state of melanocytes. Moreover, monitoring environmental changes by isolated cilia, melanocytes in the human inner ear could act not only as one cell but also as a group to achieve their physiological functions by means of information transmission through gap junctions. © 1994 Wiley-Liss, Inc.     

间隙连接蛋白43与胎膜早破的相关性

胎膜早破(premature rupture of membranes,PROM)是产科最常见的早产原因之一,可诱发新生儿呼吸窘迫综合征、绒毛膜羊膜炎、胎盘早剥、败血症等不良结局.间隙连接通讯是细胞间最常见的信息交互及物质交换途径,其功能主要由间隙连接蛋白实现,间隙连接蛋白43(Connexin43,Cx43)是间隙连...     

Cell mediated calcification in collagen gel cultures of fetal rat calvaria cells. Loss of gap junctions precedes calcification

Summary To analyze the mechanism of initiation of cell-mediated calcification in hard tussue and its relationship to the frequency of gap junctions, enzymatically isolated cells from fetal rat calvaria cultured in collagen gels were observed ultrastructurally over a time course. Calcification was observed at 2–3 weeks after the initiation of culture when the seeding cellularity and the concentration of β-glycerophosphate were sufficiently high. In the collagen gels, round cells (R), spindle or stellate cells (S), and fat cells (F) were characterised morphologically. The ultrastructural features of initial calcification could be classified into 4 subtypes: 1) a large mass greater than 10 μm in diameter (Type I), 2) deposition associated with dead R cells or matrix vesicles (Type II), 3) intracellular deposition (Type III), and 4) other than Types I–III (Type IV). Type II was the most frequent (44.5%) and Type III was the least (6.8%). Gap junction was observed frequently between 1) R cells, 2) S cells, 3) between R cells and S cells. The frequency of gap junctions in collagen gels decreased statistically (X²-test; p<0.001), when calcification was initiated. This cell culture system can be regarded as a useful model to analyze the initiation of cell mediated calcification in hard tissue. Gap junctions might function in cell communication and a decrease in their numbers could lead to cell death and, subsequently to calcification.     

全反式维甲酸对肝癌细胞连接蛋白基因表达及细胞间隙连接通讯功能的影响

目的 观察肝癌细胞株SMMC-7721和BEL-7404经全反式维甲酸(ATRA)诱导前后CX26、CX32、CX43基因在转录水平的改变以及对细胞间隙连接功能的影响。方法 分别用常规培养基和含ATRA浓度为10～mol／L的培养基培养SMMC-7721和BEL-7404两种肝癌细胞株细胞,于药物诱导细胞24、48、72h时,收集各组细胞并提取总mRNA,RT-PCR法检测CX26、CX32、CX43基因表达的情况。通过染料传输实验,观察细胞间隙连接通讯功能的变化。结果 SMMC-7721细胞和BEL-7404细胞在ATRA处理前没有CX26 mRNA和CX32 mRNA的表达,但均有CX43 mRNA的表达。经ATRA处理后出现CX26 mRNA和CX32 mRNA的表达。经ATRA处理后SMMC-7721细胞间隙连接通讯功能增强,而且随ATRA作用时间延长,细胞间隙连接通讯功能增强越明显。BEL-7404细胞经ATRA处理24、48、72h后细胞间隙连接通讯功能没有明显的改变。结论 全反式维甲酸能够在转录水平上调CX26、CX32基因在肝癌细胞SMMC-7721和BEL-7404中的表达。肝癌细胞SMMC-7721在CX26、CX32基因转录水平上调的同时伴有细胞间隙连接通讯功能的增强。肝癌细胞BEL-7404在CX26、CX32基因转录水平上调的同时不伴有细胞间隙连接通讯功能的增强。这说明两种细胞的间隙连接通讯功能调节机制不同。