Freeze-fracture studies of muscle plasma membranes in myopathic patients with hypo-and hyperthyroidism

To examine the influence of thyroid hormone on the skeletal muscle plasma membrane, we analyzed the changes in ultrastructural architecture and membrane area complexed with digitonin of muscle plasma membrane in myopathic patients with hypo-and hyperthyroidism by the conventional freeze-fracture (F-F) technique and F-F cytochemistry using the sterol-specific ligand digitonin. The densities of flask-shaped invaginations, which are mainly thought to correspond to caveolae, intramembranous particles, and orthogonal arrays, and the changes of digitoninreacted membrane areas in the muscle plasma membranes in three patients with hypothyroid myopathy and one patient with both myasthenia gravis and hyperthyroidism were compared with those in age-matched controls. In the conventional F-F study, the muscle plasma membrane of hypothyroid patients showed increased invagination density, whereas that of the hyperthyroid patient was normal ultrastructurally. In the F-F cytochemistry study, however, the ratio of digitonin-reacted membrane areas versus fractured membrane areas was not different between hypothyroid patients and controls, whereas that of the hyperthyroid patient was lowered in comparison with that of control. These results suggest that thyroid hormone may alter the biochemical properties and ultrastructural architecture of muscle plasma membrane.This study was presented at the 29th annual meeting of the Clinical Electron Microscopy Society of Japan, Sapporo, October 2–3, 1997     

Role of O2-sensitive K and Ca channels in the regulation of the pulmonary circulation: Potential role of caveolae and implications for high altitude pulmonary edema

High altitude pulmonary edema (HAPE) is a potentially fatal complication in response to exposure to low O₂ at high altitudes. Hypoxia, by causing pulmonary vasoconstriction, increases pulmonary vascular resistance and pulmonary arterial pressure, both of which are features in the pathogenesis of HAPE. Uneven hypoxic pulmonary vasoconstriction is thought to be responsible for increased capillary pressure and leakage, resulting in edema. O₂-sensitive ion channels are known to play pivotal roles in determining vascular tone in response to hypoxia. K⁺, Ca²⁺ and Na⁺ channels are ubiquitously expressed in both endothelial and smooth muscle cells of the pulmonary microvasculature, subfamilies of which are regulated by local changes in P_O2. Hypoxia reduces activity of voltage-gated K⁺ channels and down-regulates their expression leading to membrane depolarization, Ca²⁺ influx in pulmonary artery smooth muscle cells (by activating voltage-dependent Ca²⁺ channels) and vasoconstriction. Hypoxia up-regulates transient receptor potential channels (TRPC) leading to enhanced Ca²⁺ entry through receptor- and store-operated Ca²⁺ channels. Altered enrichment of ion channels in membrane microdomains, in particular in caveolae, may play a role in excitation–contraction coupling and perhaps in O₂-sensing in the pulmonary circulation and thereby may contribute to the development of HAPE. We review the role of ion channels, in particular those outlined above, in response to low O₂ on vascular tone and pulmonary edema. Advances in the understanding of ion channels involved in the physiological response to hypoxia should lead to a greater understanding of the pathogenesis of HAPE and perhaps in the identification of new therapies.     

Caveolin的生物学功能及其在疾病中的作用

Caveolae由胆固醇、鞘脂及蛋白质组成.Caveolin是Caveolae的标记蛋白,参与胞吞和胞内运输作用、胆固醇运输、信号传导、血管生成等过程,与病原体感染、阿尔茨海默病、糖尿病、肌肉病变、肿瘤、心肺疾病等有密切关系.     

小凹及小凹蛋白1：胆固醇逆向转运与炎症应答的共同分子平台

脂质紊乱和炎症反应在动脉粥样硬化的发生发展中发挥了重要的作用。其中胆固醇的逆向转运能力是决定动脉粥样硬化进程与转归的关键。大量文献及研究结果显示,小凹以及小凹蛋白1既在荷脂细胞胆固醇流出中发挥转运中心和关键分子作用,也在炎症反应中发挥介导抗炎的信号转导作用。因此,小凹以及小凹蛋白1可能是荷脂细胞胆固醇逆向转运和炎症应答的共同分子平台。     

平滑肌细胞caveolae在自发性高血压大鼠肾叶间动脉收缩功能改变中的作用研究

目的探讨平滑肌细胞caveolae在自发性高血压大鼠(spontaneously hypertensive rat,SHR)肾叶间动脉对血管紧张素Ⅱ(angiotensinⅡ,AngⅡ)的收缩反应改变中的作用及其机制。方法采用Wistar Kyoto(WKY)大鼠作为对照组,SHR为实验组(两组大鼠均为Wistar京都种大鼠),分别对SHR和WKY大鼠采用血管环张力描记技术检测肾叶间动脉对AngⅡ的收缩反应,采用甲基-β-环糊精(methyl-beta-cyclodextrin,MCD)孵育以减少平滑肌细胞caveolae含量,采用电镜观察caveolae数量,采用荧光实时定量PCR(quantitative real-time PCR,qRT-PCR)及蛋白免疫印迹(Western blot)法检测血管紧张素受体1型(qngiotensin type 1 receptor,AT1R)的基因和蛋白表达,采用免疫沉淀和Westernblot检测caveoin-1与AT1R的结合。结果与WKY组大鼠相比,SHR组肾叶间动脉对AngⅡ的收缩反应强度及敏感性均明显增加(P0.05),平滑肌细胞caveolae数量显著增加(P0.05),MCD孵育可使SHR组肾叶间动脉对AmgⅡ的收缩强度部分恢复,使其敏感性恢复正常。与WKY组相比,SHR组肾叶间动脉的AT1R蛋白表达显著增加(P0.05),AngⅡ作用后caveolin-1与AT1R的结合显著增强(P0.05),MCD孵育后AT1R的蛋白表达降低,但仍高于WKY组,而caveolin-1与AT1R的结合恢复正常水平。结论平滑肌细胞caveolae增加参与介导SHR肾叶间动脉对AngⅡ收缩反应改变,其可能通过增加平滑肌ATIR含量以及caveolin-1与AT1R的结合而增强收缩反应强度及敏感性。     

小凹蛋白在清道夫受体AI介导的巨噬细胞源性泡沫细胞形成过程中的作用

目的:研究小凹蛋白在清道夫受体AI介导的巨噬细胞源性泡沫细胞形成过程中的作用. 方法:用75 mg/L氧化型低密度脂蛋白(ox-LDL)与巨噬细胞共同孵育不同时间. 清道夫受体AI反义寡核苷酸、P38阻断剂SB202190预处理巨噬细胞,然后给予75 mg/L ox-LDL处理24 h. Western blot法检测清道夫受体AI和小凹蛋白的表达. 高效液相色谱法检测细胞内胆固醇的含量,油红O染色观察细胞内脂滴的形成情况. 结果:经75 mg/L ox-LDL处理巨噬细胞不同时间,ox-LDL呈时间依赖性促进清道夫受体AI的表达,而呈时间依赖性抑制小凹蛋白的表达. 用清道夫受体AI反义寡核苷酸抑制清道夫受体AI的表达,小凹蛋白的表达明显增加. 该组细胞内胆固醇含量为(119±7) mg/g,与ox-LDL处理组比较显著减少(P＜0.01),细胞内脂滴亦明显减少. P38MAPK抑制剂SB202190能明显抑制清道夫受体AI的表达,而增加小凹蛋白的表达. SB202190处理组细胞内胆固醇含量为(173±14) mg/g,与ox-LDL处理组比较显著减少(P＜0.01),细胞内脂滴亦明显减少. 结论:小凹蛋白与清道夫受体AI协同参与了ox-LDL诱导的巨噬细胞泡沫化的形成过程.     

混合细胞共微囊化对肝细胞功能的支持作用

目的观察大鼠肝细胞、转基因肝星状细胞株HGF／CFSC和／或大鼠骨髓来源Thy-1^＋β2M^-细胞（BDTC）共微囊化对肝细胞生物学活性的支持,及腹腔移植混合细胞微囊对急性肝衰竭大鼠肝功能的改善作用。方法利用微囊发生器制备含肝细胞或混合细胞的微囊,依微囊内包裹细胞种类不同,分为微囊化肝细胞组、微囊化肝细胞＋CFSC／HGF组）和微囊化肝细胞＋CFSC／HGF＋BDTC组,通过观察囊内细胞形态和体外培养测定培养液中白蛋白和尿素的分泌,判断各组囊内肝细胞活性和功能的维持;将90％肝大部切除所致的急性肝衰竭大鼠按照移植微囊种类不同分为空囊对照组和上述3个实验组（每组10只）,观察腹腔植入后不同时间大鼠的一般状况、存活时间、血生化改变、肝组织再生及微囊化移植物的组织学特征。结果与单独肝细胞微囊者相比,混合细胞微囊内肝细胞存活时间超过1倍,培养液中白蛋白分泌和尿素合成量明显增加（均P〈0．01）;与对照组相比,微囊化肝细胞或微囊化混合肝细胞移植后,急性肝衰竭大鼠的肝功能显著改善、存活率明显提高（10／10 vs 1／10）,其肝组织再生完全;移植21—42d时,部分微囊附着于肝脏表面并出现血管化,微囊表面存在不同程度的纤维化,微囊内仍有存活的细胞,以微囊化混合肝细胞组优于微囊化肝细胞组。结论混合细胞共微囊化能明显改善囊内肝细胞的存活寿命、形态和功能的维持,微囊化混合肝细胞腹腔移植对促进急性肝衰竭大鼠的肝功能恢复具有显著作用。     

VDAC and ERα interaction in caveolae from human cortex is altered in Alzheimer's disease

Voltage-dependent anion channel (VDAC) is a mitochondrial porin also found in the neuronal membrane (pl-VDAC), where its function may be related to redox homeostasis and apoptosis. Murine models have evidenced pl-VDAC into caveolae in a complex with estrogen receptor alpha (mERα), which participates in neuroprotection against amyloid beta (Aβ), and whose integration into this hydrophobic domain remains unclear. Here, we have demonstrated in caveolae of human cortex and hippocampus the presence of pl-VDAC and mERα, in a complex with scaffolding caveolin-1 which likely provides mERα stability at the plasma membrane. In Alzheimer's disease (AD) brains, VDAC was accumulated in caveolae, and it was observed in dystrophic neurites of senile plaques, whereas ERα was expressed in astrocytes surrounding the plaques. Together with previous data in murine neurons demonstrating the participation of pl-VDAC in Aβ-induced neurotoxicity, these data suggest that the channel may be involved in membrane dysfunctioning observed in AD neuropathology.     

小窝与心脏细胞信号转导研究概况

随着近年生物学技术的进展,人们对小窝结构及小窝蛋白的研究逐渐深入。研究发现,小窝蛋白是小窝的标志性蛋白,小窝含有丰富胆固醇的膜微区,是许多重要的信号转导的枢纽,对维持细胞功能及细胞的生物学行为起关键性的影响,进而与机体的生理病理学变化相关。在心脏细胞上,对小窝及小窝蛋白的研究有助于探索心脏疾病的发生发展。本文简述了近年来心脏细胞上信号转导与小窝关系的研究概况。     

Patients with long bone fracture have altered Caveolin-1 expression in their peripheral blood mononuclear cells

Introduction  Fracture triggers a cascade of systemic and local responses including inflammatory mediator signaling, chemotaxis, osteogenic cell recruitment, differentiation and proliferation at the fracture site. Early signaling between immune cells and repair cells in fracture repair is not well understood. Caveolin-1, a 21–24 kDa membrane protein plays key roles in transmembrane signaling. This study was to investigate the expression of caveolin-1 in human peripheral blood mononuclear cells (PBMNCs) following long bone fracture. Methods  PBMNCs were obtained from healthy volunteers or fracture patients at three time points following fracture by density-gradient-centrifugation procedure. Caveolin-1 gene expression and protein characterization was examined by semi-quantitative RT-PCR, immunocytochemistry and Western blot analysis. Results  Caveolin-1 mRNA and protein was expressed at low levels in the PBMNCs of non-fracture samples. In contrast, caveolin-1 expression was greatly increased in the PBMNCs of fracture patients 9–12 days and reduced at 16–21 days following long bone fracture. Conclusion  The identification of caveolin-1 in PBMNCs and osteoblasts makes this cellular domain a new focus for further investigation. We speculate that caveolin-1 expression in PBMNCs and osteoblasts play an important role in signal transduction during the early stages of fracture healing and may be an indicator for normal or abnormal fracture repair.