OPG/RANKL/RANK信号通路在非酒精性脂肪性肝病进展中的作用

非酒精性脂肪性肝病(NAFLD)已成为全球范围内最常见的肝脏疾病,在现有基础上更好诊断、治疗NAFLD也愈发迫切。骨保护素(OPG)/NF-κB受体活化因子(RANKL)/NF-κB受体活化因子受体(RANK)信号通路是参与骨代谢平衡的重要信号通路。分别介绍了OPG、RANKL、RANK及OPG/RANKL/RANK系统,简述了OPG/RANKL/RANK信号通路通过激活NF-κB调节炎症因子生成,促使NAFLD发展的研究现状。指出OPG/RANKL/RANK系统可作为NAFLD治疗的潜在新靶点。     

脂肪组织对骨代谢的调节关系

骨代谢的调节是一个复杂的过程,其本质是调节成骨细胞和破骨细胞的活动。通过破骨细胞吸收旧骨和成骨细胞形成新骨这两个相互偶联又相互制约的骨转换过程,骨组织不断地进行骨重建,以对自身进行新陈代谢~([1])。成骨细胞分泌核转录因子(NF)-κB受体活化因子配体(RANKL),破骨细胞分泌NF-κB受体活化因子(RANK)。RANKL与RANK结合后,传递信号,激活NF-κB,从而促进破骨细胞增     

破骨细胞功能调控与骨吸收抑制剂

骨质疏松症是骨强度下降导致骨折危险性升高的一种骨骼疾病。破骨细胞是人体唯一的骨吸收细胞,与骨质疏松症的发生密切相关,近年来对于破骨细胞与骨吸收有了较深入的研究,并研发了多种抗骨吸收的靶向药物。本文结合国内外研究简述破骨细胞与核因子κB受体活化因子配体(receptor activator for nuclear factor-κB ligand,RANKL)/核因子κB受体活化因子(receptor activator for nuclear factor-κB,RANK)/骨保护素(orthopantomography,OPG)信号通路、Wnt/β-catenin信号通路、细胞因子、组织蛋白酶K和Src激酶之间的关系,并对新型骨吸收抑制剂RANKL的单克隆抗体Denosumab、Wnt信号传导拮抗剂Romosozumab、肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)拮抗剂、白细胞介素-6 (interleukin-6,IL-6)受体拮抗剂Tocilizumab、组织蛋白酶K抑制剂Odanacatib、Src激酶抑制剂Saracatinib等进行综述,为骨质疏松症的防治提供相关依据。     

维持性血液透析患者血清RANKL、OPG及FGF21与冠状动脉钙化的关系

目的 探讨维持性血液透析(maintenance hemodialysis,MHD)患者血清核因子NF-κB受体活化因子配体(receptor activator of NF-κB ligand,RANKL)、骨保护素(osteoprotegerin,OPG)及成纤维细胞生长因子21(fibroblast growth...     

TRPV4离子通道在RANKL诱导的破骨细胞分化中的作用

破骨细胞(osteoclast,OC)来源于血液单核-巨噬细胞系统,其以多核细胞形式发挥作用。破骨细胞在分化过程中受多种信号通路的调控,其中,由核因子受体活化因子(receptor activator of nuclear factor-κB,RANK)及其配体(receptor activator of NF-κB ligand,RANKL)以及骨保护素(osteoprotegefin,OPG)组成的RANK-RANKL-OPG系统起到关键作用,而该通路的调控效应主要通过Ca2+-NFATc1信号轴实现。瞬时感受器电位香草酸受体4(transient receptor potential vanilloid 4,TRPV4)是瞬时感受器电位通道(transient receptor potential,TRP)超家族的成员,该通道介导的钙离子内流维持了破骨细胞内钙离子浓度,确保了RANKL介导的NFATc1调控的基因转录,在破骨细胞的终末期分化中发挥着关键作用。因此,全面了解TRPV4离子通道将有助于临床更好地分析各种骨代谢性疾病的病因及发病机制,进而为治疗提供理论依据。     

携带人护骨素基因的腺相关病毒在关节炎大鼠膝关节转导的初步研究

护骨素(OPG)是一种分泌型糖蛋白和缺乏跨膜结构域的肿瘤坏死因子受体超家族成员,主要通过与NF-кB受体活化因子配体(RANKL)结合而发挥骨保护作用.OPG不仅抑制破骨细胞生成,还抑制破骨细胞的骨吸收功能.各种上游因子如甲状旁腺激素、前列腺素、TNF、IL等最终均通过改变RANKL/OPG的比率而发挥作用,血清RANKL/OPG对早期类风湿关节炎的骨破坏具有预测作用[1].     

肝硬化合并肝性骨病的研究进展

骨质疏松症是肝硬化患者一种常见的骨骼系统并发症。症状多不明显,如果不及时治疗,易导致骨折并影响生活质量。本文对肝硬化合并骨质疏松症的病因及发病机制、诊断、治疗等方面的研究进展进行综述。骨质疏松症诊断采用双能X线吸收法检测骨密度,根据骨密度诊断骨质疏松症和骨量减少。骨质疏松症的病因有病毒性肝炎肝硬化、胆汁淤积性肝病和酒精性肝硬化。发病机制考虑为胰岛素生长因子-1、细胞因子、维生素D和钙的缺乏,核因子-κB受体活化因子(receptor activation of nuclear factor-κB,RANK)、核因子-κB受体活化因子配体(the receptor of nuclear factor-κB ligand,RANKL)、骨保护素系统(osteoprotegerin,OPG)、高胆红素血症、糖皮质激素、性腺功能低下,维生素K缺乏和遗传多态性等多种因素共同作用的结果。建议所有肝性骨病患者补充维生素D和钙,治疗骨质疏松症的药物包括双膦酸盐、降钙素和激素替代治疗,必要时行肝移植术。双膦酸盐类药物已成为预防和治疗骨质疏松症的主要药物。建议肝硬化尤其是胆汁淤积性肝硬化患者每年采用双能X线吸收法检测骨密度。     

新型抗骨质疏松症生物制剂对肌肉的影响及其机制

骨骼和肌肉受共同的遗传因素、内分泌、信号通路及力学机制相互调控,因此骨质疏松症和肌肉减少症息息相关。近年来,骨质疏松治疗药物取得长足进展,新型抗骨质疏松症生物制剂包括地舒单抗、特立帕肽及罗莫佐单抗等,能够有效增加骨密度、降低骨折风险。新近研究显示,抗骨质疏松生物制剂可能通过Wnt/β-联环素通路和核因子κB受体活化因子(receptor activator of nuclear factor kappa B,RANK)-核因子κB受体活化因子配体(receptor activator of nuclear factor-kappa B ligand, RANKL)-骨保护素(osteoprote-gerin, OPG)通路等,提高肌肉含量、增强肌力,因此可能对肌肉减少症具有潜在的益处。     

OPG/RANKL/RANK系统在风湿性疾病中的研究进展

OPG/RANKL/RANK系统是近年来发现的在破骨细胞(osteoclast,OC)分化过程中的一个重要信号传导通路,包括:RANKL(ligand of receptor-activator of NF-KB),或称为破骨细胞分化因子(osteoclast differentiatioc factor, ODF);其受体是位于破骨细胞细胞膜上的RANK(receptor activator of NF-KB);骨保护素(osteoprotegerin,OPG)是RANKL的假性受体.     

Toll样受体，核因子-κB与肿瘤

Toll样受体（TLRs）是新近发现的存在于哺乳动物细胞表面，在天然免疫中发挥重要作用的一种细胞跨膜蛋白受体，亦是病原模式识别受体之一。核因子-κB（NF-κB）是广泛存在于哺乳动物细胞中的一种重要转录调控因子，与多种基因启动子中含有的κB序列结合，发挥转录因子作用，激活多种与细胞生长或凋亡相关的细胞因子转录。TLRs通过对病原相关分子模式（PAMPs）进行模式识别，经一系列信号传导分子最终激活NF-κB。近年来一些研究发现，多种肿瘤细胞表面表达TLRs,TLRs介导的信号通路可能参与肿瘤的发生、发展。TLRs／NF-κB通路在肿瘤生物学上的这种新功能为肿瘤的治疗提供了新的策略。     

CLINICAL Review #: the role of receptor activator of nuclear factor-kappaB (RANK)/RANK ligand/osteoprotegerin: clinical implications

CONTEXT: Receptor activator of nuclear factor-kappaB ligand (RANKL), receptor activator of nuclear factor-kappaB (RANK), and osteoprotegerin (OPG) play a central role in bone remodeling and disorders of mineral metabolism. EVIDENCE ACQUISITION: A PubMed search was conducted from January 1992 until 2007 for basic, observational, and clinical studies in subjects with disorders related to imbalances in the RANK/RANKL/OPG system. EVIDENCE SYNTHESIS: RANK, RANKL, and OPG are members of the TNF receptor superfamily. The pathways involving them in conjunction with various cytokines and calciotropic hormones play a pivotal role in bone remodeling. Several studies involving mutations in the genes encoding RANK and OPG concluded in the discovery of a number of inherited skeletal disorders. In addition, basic and clinical studies established a consistent relationship between the RANK/RANKL/OPG pathway and skeletal lesions related to disorders of mineral metabolism. These studies were a stepping stone in further defining the role of the RANK/RANKL/OPG pathway in osteoporosis, rheumatoid arthritis, bone loss associated with malignancy-related skeletal diseases, and its relationship to vascular calcifications. Subsequently, the further understanding of this pathway led to the development of new therapeutic modalities including the human monoclonal antibody to RANKL and recombinant OPG as a target for treatment of postmenopausal osteoporosis and multiple myeloma. CONCLUSIONS: The RANK/RANKL/OPG system mediates the effects of calciotropic hormones and, consequently, alterations in their ratio are key in the development of several clinical conditions. New agents with the potential to block effects of RANKL have emerged for treatment of postmenopausal osteoporosis and malignancy-related skeletal disease.     

Molecular mechanisms underlying osteoclast formation and activation

Osteoporosis is one of the leading causes of morbidity in the elderly and is characterized by a progressive loss of total bone mass and bone density. Bone loss in osteoporosis is due to the persistent excess of osteoclastic bone resorption over osteoblastic bone formation. Receptor activator of NFkappaB ligand (RANKL) critically regulates both osteoclast differentiation and activation. TRAFs appear to be central coupling molecules in the signal transduction pathways that regulate osteoclastogenesis, cathepsin K is the major mediator of osteoclastic bone resorption, and sex steroids and aging also affect osteoclastogenesis and osteoclast activity. However, bone homeostasis depends upon the intimate coupling of bone formation and bone resorption, wherein both osteoclasts and osteoblasts exert vital stimulatory and inhibitory effects upon each other via molecules such as RANKL, TGFbeta, PDGF, BMP2, and Mim-1. This review will highlight some of the major features of the complex circuit of cytokines, growth factors, and hormones that underlies the formation and function of osteoclasts and the dynamic equilibrium that marks the interaction between osteoclasts and osteoblasts.     

RANKL and RANK as novel therapeutic targets for arthritis

The TNF-family molecule receptor activator of nuclear factor kappa B (NFkappaB) ligand (RANKL) (OPGL, TRANCE, ODF) and its receptor activator of NFkappaB (RANK) are key regulators of bone remodeling and regulate T cell/dendritic cell communications, and lymph node formation. Moreover, RANKL and RANK are expressed in mammary gland epithelial cells and control the development of a lactating mammary gland during pregnancy. Genetically, RANKL and RANK are essential for the development and activation of osteoclasts and bone loss in response to virtually all triggers tested. Inhibition of RANKL function via the natural decoy receptor osteoprotegerin (OPG, TNFRSF11B) prevents bone loss in postmenopausal osteoporosis and cancer metastases. Importantly, RANKL appears to be the pathogenetic principle that causes bone and cartilage destruction in arthritis, and OPG treatment prevents bone loss at inflamed joints and has partially beneficial effects on cartilage destruction in all arthritis models studied so far. Modulation of these systems provides a unique opportunity to design novel therapeutics to inhibit bone loss and crippling in arthritis.     

Pulsed electromagnetic field stimulates osteoprotegerin and reduces RANKL expression in ovariectomized rats

Pulsed electromagnetic field (PEMF) has been shown to increase bone mineral density in osteoporosis patients and prevent bone loss in ovariectomized rats. But the mechanisms through which PEMF elicits these favorable biological responses are still not fully understood. Receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG) are cytokines predominantly secreted by osteoblasts and play a central role in differentiation and functional activation of osteoclasts. The purpose of this study was to investigate the effects of PEMF on RANKL and OPG expression in ovariectomized rats. Thirty 3-month-old female Sprague–Dawley rats were randomly divided into three groups: sham-operated control (Sham), ovariectomy control (OVX), and ovariectomy with PEMF treatment (PEMF). After 12-week interventions, the results showed that PEMF increased serum 17β-estradiol level, reduced serum tartrate-resistant acid phosphatase level, increased bone mineral density, and inhibited deterioration of bone microarchitecture and strength in OVX rats. Furthermore, PEMF could suppress RANKL expression and improve OPG expression in bone marrow cells of OVX rats. In conclusion, this study suggests that PEMF can prevent ovariectomy-induced bone loss through regulating the expression of RANKL and OPG.     

Osteoclastogenesis inhibitory factor (OCIF)/osteoprotegerin (OPG)

Osteoclastogenesis inhibitory factor (OCIF) was isolated from the conditioned medium of human embryonic lung fibroblasts. OCIF is a novel member of the tumor necrosis factor receptor superfamily and identical with Osteoprotegerin (OPG) discovered by the Amgen researchers. Consequently, through the identification of receptor activator of NF-kappaB ligand (RANKL) as a target molecule of OCIF/OPG, it was demonstrated that RANKL is a crucial factor in the differentiation, maturation, and activation of osteoclasts. Discovery of OCIF/OPG and RANKL has broken new ground in the field of bone physiopathology. Moreover, OCIF/OPG not only contributes to the field of basic science but also is anticipated as a novel therapeutic candidate for the treatment of primary and secondary osteoporosis through a series of pre-clinical and clinical studies. Because OCIF/OPG and RANKL have been proven to be involved in the onset and development of many metabolic bone diseases besides osteoporosis, OCIF/OPG is also expected as a therapeutic candidate for the treatment of such bone diseases.     

RANKL protein is expressed at the pannus-bone interface at sites of articular bone erosion in rheumatoid arthritis

OBJECTIVES: Receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) have been demonstrated to be critical regulators of osteoclast generation and activity. In addition, RANKL has been implicated as an important mediator of bone erosion in rheumatoid arthritis (RA). However, the expression of RANKL and OPG at sites of pannus invasion into bone has not been examined. The present study was undertaken to further elucidate the contribution of this cytokine system to osteoclastogenesis and subsequent bone erosion in RA by examining the pattern of protein expression for RANKL, OPG and the receptor activator of NF-kappaB (RANK) in RA at sites of articular bone erosion. METHODS: Tissues from 20 surgical procedures from 17 patients with RA were collected as discarded materials. Six samples contained only synovium or tenosynovium remote from bone, four samples contained pannus-bone interface with adjacent synovium and 10 samples contained both synovium remote from bone and pannus-bone interface with adjacent synovium. Immunohistochemistry was used to characterize the cellular pattern of RANKL, RANK and OPG protein expression immediately adjacent to and remote from sites of bone erosion. RESULTS: Cellular expression of RANKL protein was relatively restricted in the bone microenvironment; staining was focal and confined largely to sites of osteoclast-mediated erosion at the pannus-bone interface and at sites of subchondral bone erosion. RANK-expressing osteoclast precursor cells were also present in these sites. OPG protein expression was observed in numerous cells in synovium remote from bone but was more limited at sites of bone erosion, especially in regions associated with RANKL expression. CONCLUSIONS: The pattern of RANKL and OPG expression and the presence of RANK-expressing osteoclast precursor cells at sites of bone erosion in RA contributes to the generation of a local microenvironment that favours osteoclast differentiation and activity. These data provide further evidence implicating RANKL in the pathogenesis of arthritis-induced joint destruction.     

Lipopolysaccharide-induced osteoclastogenesis in Src homology 2-domain phosphatase-1-deficient viable motheaten mice

Osteoclasts are hemopoietic cells that participate in bone resorption and remodeling. Receptor activator of nuclear factor-kappaB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) are critical for development of osteoclasts. The Toll-like receptor (TLR) family shares some of the downstream signaling with RANK. The TLR4 ligand, lipopolysaccharide (LPS), is reported to accelerate bone lysis; however, signaling via TLRs has never been reported to induce osteoclastogenesis without RANKL. In this study we showed that significant numbers of mature osteoclasts were generated from protein tyrosine phosphatase Src homology 2-domain phosphatase-1-defective Hcph(me-v)/Hcph(me-v) (me(v)/me(v)) bone marrow cells in the presence of M-CSF and LPS without addition of RANKL in culture. This M-CSF plus LPS-induced osteoclastogenesis was not inhibited by an anti-TNFalpha antagonistic antibody or by osteoprotegerin, a decoy receptor for RANKL. The replacement of RANKL by TLR ligands only occurred with LPS. Other ligands, a peptidoglycan for TLR2 or an unmethylated CpG oligonucleotide for TLR9, did not support osteoclast generation. The osteoclast precursors as well as RANKL-responsive osteoclast precursors were present in the Kit-positive cell-enriched fraction of bone marrow cells. Although me(v)/me(v) bone marrow cells required a comparable concentration of RANKL or TNFalpha as wild-type cells for the initiation of osteoclastogenesis, the numbers of multinucleated osteoclasts in me(v)/me(v) bone marrow cultures were significantly increased by the equivalent dose of RANKL or TNFalpha in the presence of M-CSF. These results indicate that a defect of Src homology 2-domain phosphatase-1 function not only accelerates physiological osteoclast development by RANKL/RANK, but also acquires a novel pathway for osteoclastogenesis by LPS.     

The RANKL/OPG system and bone mineral density in patients with chronic liver disease

BACKGROUND/AIMS: Osteopenia and osteoporosis are common complications of chronic liver disease (CLD). Receptor activator of nuclear factor kappaB ligand (RANKL) and osteoprotegerin (OPG) regulate osteoclastogenesis and bone remodelling, and are involved in several inflammatory diseases. This study investigated the activation state of the RANKL/OPG system and its association with bone loss in CLD. METHODS: Serum levels of OPG and sRANKL were determined in 193 patients with CLD and 56 age- and gender-matched healthy controls. Cellular sources of OPG and RANKL were determined immunohistochemically. Dual-energy x-ray absorptiometry was performed to determine bone mineral density (BMD) of lumbar spine and femoral neck. RESULTS: sRANKL serum levels were significantly elevated in non-cirrhotic, but not cirrhotic patients compared to healthy controls. OPG serum levels were elevated 1.6-fold in non-cirrhotic and 2.8-fold in cirrhotic CLD patients. RANKL+ cells were mainly confined to portal fields, while OPG was broadly expressed. In the cirrhotic subgroup (87 patients) we observed a significantly higher OPG/sRANKL ratio in patients with osteopenia or osteoporosis of the lumbar spine and femoral neck region (T-score < -1) compared to those with normal BMD (T-score > or = -1). CONCLUSIONS: CLD is associated with alterations in RANKL/OPG serum levels, which could modulate bone loss in CLD.     

Receptor activator of nuclear factor kappaB ligand and osteoprotegerin regulation of bone remodeling in health and disease

Osteoclasts and osteoblasts dictate skeletal mass, structure, and strength via their respective roles in resorbing and forming bone. Bone remodeling is a spatially coordinated lifelong process whereby old bone is removed by osteoclasts and replaced by bone-forming osteoblasts. The refilling of resorption cavities is incomplete in many pathological states, which leads to a net loss of bone mass with each remodeling cycle. Postmenopausal osteoporosis and other conditions are associated with an increased rate of bone remodeling, which leads to accelerated bone loss and increased risk of fracture. Bone resorption is dependent on a cytokine known as RANKL (receptor activator of nuclear factor kappaB ligand), a TNF family member that is essential for osteoclast formation, activity, and survival in normal and pathological states of bone remodeling. The catabolic effects of RANKL are prevented by osteoprotegerin (OPG), a TNF receptor family member that binds RANKL and thereby prevents activation of its single cognate receptor called RANK. Osteoclast activity is likely to depend, at least in part, on the relative balance of RANKL and OPG. Studies in numerous animal models of bone disease show that RANKL inhibition leads to marked suppression of bone resorption and increases in cortical and cancellous bone volume, density, and strength. RANKL inhibitors also prevent focal bone loss that occurs in animal models of rheumatoid arthritis and bone metastasis. Clinical trials are exploring the effects of denosumab, a fully human anti-RANKL antibody, on bone loss in patients with osteoporosis, bone metastasis, myeloma, and rheumatoid arthritis.     

RANK ligand and osteoprotegerin: paracrine regulators of bone metabolism and vascular function

In 1997, investigators isolated a secreted glycoprotein that blocked osteoclast differentiation from precursor cells, prevented osteoporosis (decreased bone mass) when administered to ovariectomized rats, and resulted in osteopetrosis (increased bone mass) when overexpressed in transgenic mice. Since then, the isolation and characterization of the protein named osteoprotegerin (OPG) has stimulated much work in the fields of endocrinology, rheumatology, and immunology. OPG functions as a soluble decoy receptor for receptor activator of nuclear factor-kappaB ligand (RANKL, or OPG ligand) and shares homologies with other members of the tumor necrosis factor receptor superfamily. OPG acts by competing with the receptor activator of nuclear factor-kappaB, which is expressed on osteoclasts and dendritic cells for specifically binding to RANKL. RANKL is crucially involved in osteoclast functions and bone remodeling as well as immune cell cross-talks, dendritic cell survival, and lymph node organogenesis. More recently, emerging evidence from in vitro studies and mouse genetics attributed OPG an important role in vascular biology. In fact, OPG could represent the long sought-after molecular link between arterial calcification and bone resorption, which underlies the clinical coincidence of vascular disease and osteoporosis, which are most prevalent in postmenopausal women and elderly people.