Osteoclast differentiation from circulating mononuclear precursors in Paget's disease is hypersensitive to 1,25-dihydroxyvitamin D(3) and RANKL

A characteristic feature of Paget's disease is an increase in the number of osteoclasts in bone. Osteoclasts are formed from mononuclear phagocyte precursors that circulate in the monocyte fraction of peripheral blood. These cells require the presence of RANK ligand (RANKL)-expressing osteoblastic cells and human macrophage colony-stimulating factor (M-CSF) to form osteoclasts in vitro. To determine the role of osteoclast differentiation from circulating precursors in Paget's disease, we cultured monocytes from Paget's patients and gender- and age-matched normal controls with no evidence of bone disease for up to 21 days in the presence of UMR 106 cells and various concentrations of M-CSF (1-25 ng/mL) and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] (10(-10) to 10(-7) mol/L). Relative to controls, there was a significant increase in the extent of osteoclast differentiation from pagetic monocytes as assessed by expression of tartrate-resistant acid phosphatase (TRAP), vitronectin receptor (VNR), and lacunar bone resorption. Serial dilution experiments (2 x 10(5) to 2 x 10(2) cells/well) showed no difference in the concentration of osteoclast precursors in the peripheral blood. In Paget's patients with high serum alkaline phosphatase (sAP) levels, increased sensitivity to the osteoclastogenic effect of 1,25(OH)(2)D(3) was noted. Osteoclast differentiation did not occur when M-CSF was substituted by interleukin-6 (IL-6) and soluble IL-6 receptor (sIL-6R), and these factors did not stimulate osteoclast differentiation in the presence of M-CSF. In this in vitro coculture system, osteoclast formation was inhibited by osteoprotegerin in a dose-dependent manner. In the presence of RANKL (5-30 ng/mL) and M-CSF (25 ng/mL), osteoclast formation and bone resorption were significantly increased in cultures of monocytes from patients with high and low sAP levels as compared with normal controls. Our findings suggest that the increase in osteoclast numbers seen in Paget's disease results not from an increase in the number of circulating precursors in peripheral blood but rather from an increased sensitivity of osteoclast precursors to the humoral factors, 1,25(OH)(2)D(3) and RANKL, which regulate osteoclast formation.     

RANKL coordinates cell cycle withdrawal and differentiation in osteoclasts through the cyclin-dependent kinase inhibitors p27KIP1 and p21CIP1.

The coordination of cell cycle progression and osteoclast differentiation by RANKL signaling was studied. Experiments with mouse genetic models revealed that RANKL promoted cell cycle withdrawal of osteoclast precursors dependent on the cyclin kinase inhibitor p27-KIP1, but that both p27-KIP1 and p21-CIP1 were required for osteoclast differentiation. These cyclin inhibitors may directly regulate osteoclast differentiation in addition to regulating cell cycle withdrawal. INTRODUCTION: RANKL stimulates mononuclear precursor cells of the myeloid lineage to differentiate into multinuclear osteoclasts, thus providing a system to study the fundamental problem of coordination of cell cycle progression with cell differentiation. MATERIALS AND METHODS: Mice that lack expression of functional cyclin inhibitors p27KIP1and p21CIP1 were used to study cell cycle progression and differentiation of osteoclast precursors in vitro and in vivo. RESULTS AND CONCLUSIONS: Experiments with cells derived from p27KIP1- and p21CIP1-deficient mice indicated that p27KIP1 function alone was necessary for RANKL-mediated cell cycle withdrawal by osteoclast precursors, but osteoclasts from mice with single mutations in either of these two genes differentiated normally. In contrast, p21/p27 double knockout mice developed osteopetrosis, with fewer osteoclasts that exhibited lower TRACP activity and abnormal cell morphology present in long bone. Moreover, isolated osteoclast progenitors from p21/p27 double knockout mice were defective in RANKL-mediated differentiation in vitro, expressing low levels of osteoclast-specific genes like TRACP and cathepsin K. Taken together, these data suggest p27KIP1 and p21CIP1 play roles in osteoclast differentiation in response to RANKL signaling distinct from their roles in promoting cell cycle withdrawal.     

AMP kinase acts as a negative regulator of RANKL in the differentiation of osteoclasts

IntroductionAMP-activated protein kinase (AMPK) has been reported to stimulate differentiation and proliferation of osteoblasts, but the role of AMPK in the physiology of osteoclasts has not been investigated.MethodOsteoclasts were differentiated from mouse BMM?s. TRAP-positive multinucleated cells were considered to be osteoclasts using TRAP staining, and resorption area was determined by incubation of cells on dentine discs. Signaling pathways were investigated using Western blotting and RT-PCR.ResultsRANKL induced phosphorylation/activation of AMPK-α in BMM?s and stimulated formation of TRAP-positive multinucleated cells. Pharmacological inhibition of AMPK with compound C and siRNA-mediated knockdown of AMPK-α1, the predominant α-subunit isoform in BMM?s, increased RANKL-induced formation of TRAP-positive multinucleated cells and bone resorption via activation of the downstream signaling elements p38, JNK, NF-κB, Akt, CREB, c-Fos, and NFATc1. STO-609, an inhibitor of CaMKK, completely blocked the RANKL-induced activation of AMPK-α, but KN-93, an inhibitor of CaMK, did not. siRNA-mediated TAK1 knockdown also blocked RANKL-induced activation of AMPK-α. The AMPK activators metformin, (?)-epigallocatechin-3-gallate, berberine, resveratrol, and α-lipoic acid dose-dependently suppressed formation of TRAP-positive multinucleated cells and bone resorption.ConclusionAMPK negatively regulates RANKL, possibly by acting through CaMKK and TAK1. Thus, the development of AMPK activators may be a useful strategy for inhibiting the resorption of bone that is stimulated under RANKL-activated conditions.     

异甘草素抑制RANKL/RANK/TRAF6信号通路对骨质疏松大鼠成骨细胞分化的影响

目的 探究异甘草素对骨质疏松(OP)大鼠成骨细胞分化的影响是否与调控核因子-κB受体活化体配体(RANKL)/核因子-κB受体活化体(RANK)/肿瘤坏死因子受体相关因子6(TRAF6)信号通路有关。方法 采用去势法建立绝经后OP大鼠模型,造模2周后将大鼠随机分为模型组、阳性组(戊酸雌二醇0.09 mg/kg)、异甘草素低(10 mg/kg)、中(20 mg/kg)、高(40 mg/kg)剂量组,每组10只,另取10只大鼠作为假手术组。给药结束后采用ELISA法检测大鼠血清中碱性磷酸酶(ALP)、雌二醇(E₂)水平;Micro-CT扫描观察骨微结构指标;HE染色观察股骨组织病理学;免疫组化法检测大鼠股骨Runt相关转录因子2(Runx2)蛋白表达;Western Blot法检测大鼠股骨RANKL、RANK、TRAF6蛋白表达。结果 与模型组比,阳性组与异甘草素各剂量组大鼠骨组织病变明显减轻,可见新生骨小梁;ALP[(107.94±9.83)U/L、(75.27±7.51)U/L、(89.35±9.14)U/L、(106.33±10.02)U/L比(53.79±5....     

Osteoclast differentiation in ectopic bone formation induced by recombinant human bone morphogenetic protein 2 (rhBMP-2)

Osteoclast differentiation in the process of ectopic bone formation induced by recombinant human bone morphogenetic protein 2 (rhBMP-2) was examined to clarify the relationship between osteoclast development and rhBMP-2-induced bone formation. A combination of rhBMP-2 with a porous microsphere (PMS) and blood clot was implanted subcutaneously on the bilateral chest muscles of rats. Tartrate-resistant acid phosphatase (TRAPase) activity, cathepsin K (cath K), and calcitonin receptor (CTR), as markers of osteoclasts and their precursors, were examined using enzyme and immunohistochemical analysis up to 7 days after implantation. Mononuclear cells positive for TRAPase, cath K, and CTR first appeared on day 3 in connective tissue surrounding the PMS after implantation of rhBMP-2. Simultaneously, alkaline phosphatase activity became detectable in mesenchymal cells in the connective tissue. Electron microscopy demonstrated some mononuclear cells with abundant mitochondria and poorly developed rough endoplasmic reticulum in the proximity of mesenchymal cells. However, there was no evidence of cartilage or bone matrix formation on day 3. Osteoclasts in various stages of development, classified by the pattern of immunoreactivity for cath K, were observed by day 7. The polarized intracellular distribution of cath K was found only in osteoclasts attached to bone matrix. In conclusion, we have demonstrated for the first time the appearance of osteoclast precursors before bone matrix formation induced by rhBMP-2, suggesting that bone matrix is not a prerequisite for osteoclast precursor recruitment. Furthermore, we suggest that differentiation into polarized functional osteoclasts is accomplished when the osteoclasts attach to the bone matrix.     

Proliferation-coupled osteoclast differentiation by RANKL: Cell density as a determinant of osteoclast formation

Although it is widely recognized that the osteoclast differentiation induced by RANKL is linked to the anti-proliferative activity of the cytokine, we report here that RANKL in the presence of M-CSF actually stimulates DNA synthesis and cell proliferation during the early proliferative phase (0–48 h) of osteoclastogenesis ex vivo, while the same cytokine exerts an anti-proliferative activity in the latter half (48–96 h). A tracing of the individual cells using Fucci cell cycle indicators showed that waves of active DNA synthesis in the S phase during the period 0–48 h are followed by cell-cycle arrest and cell fusion after 48 h. Inhibition of DNA synthesis with hydroxyurea (HU) during the first half almost completely inhibited osteoclastogenesis; however, the same HU-treated cells, when re-plated at 48 h at increasing cell densities, exhibited restored osteoclast formation, suggesting that a sufficient number of cells, rather than prior DNA synthesis, is the most critical requirement for osteoclast formation. In addition, varying either the number of bone marrow macrophages at the start of osteoclastogenic cultures or pre-osteoclasts halfway through the process had a substantial impact on the number of osteoclasts that finally formed, as well as the timing of the peak of osteoclast formation. Thus, caution should be exerted in the performance of any manipulative procedure, whether pharmacological or genetic, that affects the cell number prior to cell fusion. Such procedures can have a profound effect on the number of osteoclasts that form, the final outcome of “differentiation”, leading to misinterpretation of the results.     

芒柄花素抑制RANKL诱导破骨细胞分化的实验研究

目的:建立RANKL诱导的破骨细胞体外研究模型,阐述活血化瘀中药鸡血藤有效组分芒柄花素(formononetin,FO)调控小鼠骨髓单核-巨噬细胞(BMMs)向破骨细胞分化和功能的影响,探讨其抑制破骨细胞分化的分子机制。方法:取20只4~6周龄清洁级C57/BL6小鼠,雌雄各10只,体重(20±2)g,无菌条件下分离出股骨和胫骨内BMMs,用α-MEM培养基进行体外培养和增殖。BMMs在加入M-CSF和不同浓度的芒柄花素(5~50?滋M)分别培养4 d后进行细胞增殖与毒性的CCK8检测。将生长状态良好的BMMs依次加入M-CSF和RANKL诱导破骨细胞分化,对照组无特殊处理,DMSO对照组加入DMSO溶剂,各观察组分别加入不同浓度芒柄花素(1~20?滋M),分别进行培养6 d后进行抗酒石酸酸性磷酸酶(TRAP)染色,对破骨细胞的进行计数和统计分析。分别在破骨细胞培养的1、2 d收取总蛋白和磷酸化蛋白,Western blot检测破骨细胞分化中关键转录因子NFATc1和c-Fos的表达以及磷酸化蛋白ERK表达;在培养的4 d提取RNA,Real-Time PCR检测破骨细胞相关基因CTSK、TRAP、MMP9和Car2的活性。结果:CCK8检测结果提示芒柄花素能够剂量依赖性地抑制BMMs的活性,在≤20?滋M的安全浓度范围内对BMMs细胞生长无明显毒性效应(P=0.278>0.05)。TRAP染色结果发现芒柄花素在(1~20?滋M)浓度范围内能够剂量依赖性的抑制破骨细胞的生成,尤其是10?滋M能够显著抑制破骨细胞的生成(P=0.000<0.05)。Western blot检测表明芒柄花素(10?滋M)能显著抑制破骨细胞分化关键蛋白NFATc1和c-Fos的表达,而对磷酸化蛋白ERK的表达未见明显的作用。在破骨细胞功能上,Real-Time PCR检测芒柄花素(10?滋M)能著抑制破骨细胞功能相关基因CTSK(P=0.000<0.05)、TRAP(P=0.000<0.05)、MMP9(P=0.000<0.05)和Car2(P=0.000<0.05)的表达。结论:鸡血藤有效组分芒柄花素能够抑制原代骨髓单核-巨噬细胞向破骨细胞增殖和分化,并下调破骨细胞骨吸收功能相关蛋白和基因的表达,可能是其防治股骨头坏死中骨破坏及塌陷的机制之一。     

Safety of cyclin-dependent kinase4/6 inhibitor combined with palliative radiotherapy in patients with metastatic breast cancer

IntroductionCyclin-dependent kinase (CDK)4/6 inhibitor is a first-line therapy for metastatic ER+/HER2-breast cancer. However, there are limited data on safety of combined radiotherapy (RT) and CDK4/6 inhibition.MethodsWe conducted a retrospective study of women with metastatic breast cancer who received palliative RT within 14 days of CDK4/6 inhibitor use. The primary endpoint was toxicity per Common Terminology Criteria for Adverse Events v5. Secondary endpoints were pain response and local control based on clinical assessment and imaging.ResultsThirty patients underwent 36 RT courses with palbociclib (n = 34 courses, 94.4%) or abemaciclib (n = 2, 5.6%). RT was delivered before, concurrently or after CDK4/6 inhibitors in 7 (19.4%), 8 (22.2%), and 21 (58.3%) of cases with median 3.5 days from RT to closest CDK4/6 inhibitor administration. Median RT dose was 30Gy (range 8–40.05Gy). Treated sites included brain (n = 5, 11.6%), spine (n = 19, 44.2%), pelvis (n = 9, 20.9%), other bony sites (n = 6, 14.0%) and others (n = 4, 9.3%). No acute grade ≥3 non-hematologic toxicity occurred. No increased hematologic toxicity was attributable to RT with grade 3 hematologic toxicities rates 16.7%, 0%, and 6.7% before, during, and 2 weeks after RT completion. All but one patient (29/30) achieved symptom relief. Local control rates were 94.4%, 91.7% at 6 and 12 months.ConclusionsThe use of RT within 2 weeks of CDK4/6 inhibitors had low acceptable toxicity and high efficacy, suggesting that it is safe for palliation of metastatic breast cancer.     

The cyclin-dependent kinase inhibitor p57Kip2 regulates cell cycle exit, differentiation, and migration of embryonic cerebral cortical precursors

Mounting evidence indicates cyclin-dependent kinase (CDK) inhibitors (CKIs) of the Cip/Kip family, including p57(Kip2) and p27(Kip1), control not only cell cycle exit but also corticogenesis. Nevertheless, distinct activities of p57(Kip2) remain poorly defined. Using in vivo and culture approaches, we show p57(Kip2) overexpression at E14.5-15.5 elicits precursor cell cycle exit, promotes transition from proliferation to neuronal differentiation, and enhances process outgrowth, while opposite effects occur in p57(Kip2)-deficient precursors. Studies at later ages indicate p57(Kip2) overexpression also induces precocious glial differentiation, suggesting stage-dependent effects. In embryonic cortex, p57(Kip2) overexpression advances cell radial migration and alters postnatal laminar positioning. While both CKIs induce differentiation, p57(Kip2) was twice as effective as p27(Kip1) in inducing neuronal differentiation and was not permissive to astrogliogenic effects of ciliary neurotrophic factor, suggesting that the CKIs differentially modulate cell fate decisions. At molecular levels, although highly conserved N-terminal regions of both CKIs elicit cycle withdrawal and differentiation, the C-terminal region of p57(Kip2) alone inhibits in vivo migration. Furthermore, p57(Kip2) effects on neurogenesis and gliogenesis require the N-terminal cyclin/CDK binding/inhibitory domains, while previous p27(Kip1) studies report cell cycle-independent functions. These observations suggest p57(Kip2) coordinates multiple stages of corticogenesis and exhibits distinct and common activities compared with related family member p27(Kip1).     

A novel strategy for inhibiting growth of human pancreatic cancer cells by blocking cyclin-dependent kinase activity

Pancreatic cancers frequently carry mutations in the Kras, p53, and p16 genes, which regulate cell proliferation. Transition from G1 to S phase of the cell cycle requires activation of cyclin-dependent kinase 2 (Cdk2), which is inhibited by olomoucine and roscovitine. The purpose of this study was to determine whether olomoucine and roscovitine can block Cdk2 kinase activity and inhibit proliferation of four human pancreatic cancer cell lines with various genetic alterations. Human pancreatic carcinoma cell lines BxPC-3, PANC-1, Capan-2, and CAV were treated with olomoucine or roscovitine. Cdk2 kinase activity was determined using histone H1 as the substrate. Cell cycle distribution was analyzed by DNA flow cytometry. Cell numbers were quantitated by Coulter counter. Olomoucine and roscovitine blocked Cdk2 activity in all four pancreatic cancer cell lines. Both compounds also inhibited cell proliferation in a dose-dependent fashion. Roscovitine was at least threefold more potent than olomoucine for both Cdk2 activity and cell proliferation. We have shown that Cdk inhibitors, olomoucine and roscovitine, block proliferation of human pancreatic cancer cells regardless of their mutations in Kras, p53, or pl 6 genes. These compounds represent a novel therapeutic strategy with potential therapeutic benefits for pancreatic cancers. Supported by grants from the National Institutes of Health (K08 CA64191, R01 DK48345), the John S ealy Memorial Endowment Fund, and the Walls Medical Research Foundation. Presented at the Thirty-Eighth Annual Meeting of The Society for Surgery of the Alimentary Tract, Washington, D.C., May 11–14, 1997.     

ATRA attenuate proteinuria via downregulation of TRPC6 in glomerulosclerosis rats induced by adriamycin

Objective: In this research, we explored the molecular mechanism of proteinuria in glomerulosclerosis rats and the protective effects of ATRA.

Methods: This research set up three groups: SHO group, GS group, and ATRA group (15?mg/(kg d), Sigma, St. Louis, MO). The serum creatinine (Scr), urea nitrogen (BUN), and 24-h proteinuria were detected 12?weeks after administration of ATRA. The pathological and ultrastructure changes were observed under light microscope and transmission electron microscope. The protein expression of TGF-β₁ and Col-IV in glomerulus was detected by immunohitochemistry method. The mRNA and the protein expression of glomerular TRPC6 were detected by RT-PCR and Western blot.

Results: In the rat model of GS, the expressions of TRPC6 were significantly elevated compared with the normal rat group; however, the use of ATRA down-regulated the expression of TRPC6 in the glomeruli and attenuated glomerulosclerosis and proteinuria. Scr and BUN were also improved by the treatment of ATRA.

Conclusions: Our results demonstrated that ATRA could ameliorate glomerulosclerosis and proteinuria in GS, which may be related to suppressed expression of TRPC6.     

Acute regulation of NHE3 by protein kinase A requires a multiprotein signal complex

Biochemical and cellular experiments in fibroblasts have established the requirement for a member of the PDZ motif Na(+)/H(+) exchanger regulatory factor family of proteins (NHERF and NHERF2) in cAMP-mediated phosphorylation and inhibition of NHE3 activity. NHERF interacts with the actin cytoskeleton through the scaffolding protein ezrin to target a multiprotein signal complex to the plasma membrane. Recent experiments have focused on elements of this model. First, using specific antibodies, NHERF was identified in the renal proximal tubule, where it colocalized with ezrin and NHE3. NHERF2 was seen in glomeruli, the renal vasculature, and collecting duct cells, where it colocalized with ROMK. This distinct nephron localization suggests different physiologic roles for NHERF and NHERF2. Second, the signal-complex model of protein kinase A regulation of NHE3 developed in fibroblasts has been extended to epithelial cells by the development of a dominant-negative opossum kidney cell line expressing an ezrin binding domain-deficient truncation of NHERF. Preliminary studies indicate that these cells have normal basal Na+/H+ exchanger activity but a blunted inhibitory response to cAMP. Third, biochemical, biophysical, and cell experiments have indicated that NHERF binds to itself in a head-to-head configuration, raising the possibility that dimerization may alter the availability of active NHERF. The potential role of the NHERF proteins in the kidney has been expanded by recent studies indicating their involvement in the membrane targeting, trafficking, sorting, and regulation of a range of other transporters, receptors, and signaling proteins. NHERF and related PDZ-containing proteins may serve as adapters for regulation of renal transporters.     

Androgen downregulation of miR-760 promotes prostate cancer cell growth by regulating IL6

Prostate cancer(PCa)is one of the most common malignancies in Western countries.Studies have shown that androgen contributes to the progression of PCa,but how a...     

TNF-stimulated arginine transport by human vascular endothelium requires activation of protein kinase C.

OBJECTIVE: The authors determined the endothelial arginine transport mechanism and the potential role of a tumor necrosis factor (TNF)-alpha-mediated signal transduction pathway involving protein kinase C (PKC) in regulating this transport in cultured endothelial cells. SUMMARY BACKGROUND DATA: The vascular endothelium metabolizes arginine to generate nitric oxide (NO), and an increase in NO production can be stimulated by several cytokines. The mechanism(s) responsible for the accelerated arginine transport are poorly understood. METHODS: Arginine transport was assayed in confluent human umbilical vein endothelial cells in the presence of TNF +/- the PKC inhibitor chelerythrine chloride. RESULTS: Carrier-mediated arginine transport was accomplished by two Na(+)-independent transporters, System y+ (80% of total transport) and System b0,+ (20% of transport). Tumor necrosis factor (0.1-2 ng/mL) increased System y(+)-mediated arginine transport in a time- and dose-dependent manner by augmenting System y+ transport maximal capacity (control Vmax = 1325 +/- 60 pmol/mg protein/minute vs. TNF Vmax = 3015 +/- 110 pmol/mg protein/minute, p < 0.01) without affecting transporter affinity (control Km = 30 +/- 1.4 microM vs. 34 +/- 1.3 microM arginine, p = NS). Stimulation was maximal at the 8-hour time point and was inhibited by both actinomycin D and cycloheximide. In addition, inhibition of PKC with chelerythrine abrogated the TNF-augmented arginine transport. Similarly, incubation of cells with the direct PKC activator TPA (phorbol ester 12-myristate 13-acetate) stimulated System y(+)-mediated arginine transport nearly fivefold, secondary to an increase in transporter Vmax (TPA Vmax = 5349 +/- 310 pmol/mg protein/minute, p < 0.001 vs. control), with no change in Km. This TPA-induced stimulation of arginine transport also was blocked by chelerythrine CI, actinomycin D, and cycloheximide. Incubation of TNF-stimulated cells with two NO synthase inhibitors did not reduce transport activity, suggesting that the arginine transporter and the NO synthase enzyme may, in part, be independently regulated.