Annexin II stimulates RANKL expression through MAPK.

We report that AX-II, in addition to inducing GM-CSF expression, also increases membrane-bound RANKL synthesis by marrow stromal cells and does so through a previously unreported MAPK-dependent pathway. Thus, both GM-CSF and RANKL are required for AX-II stimulation of OCL formation. INTRODUCTION: Annexin II (AX-II) is an autocrine/paracrine factor secreted by osteoclasts (OCLs) that stimulates human OCL formation and bone resorption in vitro by inducing bone marrow stromal cells and activated CD4+ T cells to produce granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF in turn increases OCL precursor proliferation and further enhances OCL formation. However, the induction of GM-CSF by AX-II cannot fully explain its effects on OCL formation. In this study, we tested the capacity of AX-II to induce the expression of RANKL and the corresponding signaling pathways AX-II employs in human marrow stromal cells to induce RANKL. We also showed that both GM-CSF and RANKL are required for OCL formation induced by AX-II. MATERIALS AND METHODS: Real-time RT-PCR and Western blot analysis were used to detect RANKL and osteoprotegerin (OPG) mRNA and protein expression in unfractionated human bone marrow mononuclear cells stimulated with AX-II. Soluble RANKL in the conditioned medium was analyzed by ELISA. Activation of the MAPK pathway by AX-II was tested by Western blot. The effects of OPG and anti-GM-CSF on AX-II-induced OCL formation were also examined. RESULTS AND CONCLUSION: In addition to upregulating GM-CSF mRNA, AX-II increased RANKL mRNA expression dose-dependently in unfractionated human bone marrow mononuclear cells and modestly increased soluble RANKL in unfractionated human bone marrow mononuclear cell conditioned medium. However, AX-II markedly increased membrane-bound RANKL on human bone marrow stromal cells. Treatment of marrow stromal cells with AX-II activated MAP-kinase (ERKs) and PD 98059 abolished the effect but did not block the increase in GM-CSF. Interestingly, OPG, a natural decoy receptor for RANKL, or anti-GM-CSF partially inhibited OCL formation by AX-II in human bone marrow cells, and the combination of OPG and anti-GM-CSF completely blocked AX-II-induced OCL formation. These data show that AX-II stimulates both the proliferation and differentiation of OCL precursors through production of GM-CSF and RANKL respectively.     

Hyaluronan increases RANKL expression in bone marrow stromal cells through CD44.

HA activates CD44 to stimulate RANKL expression in bone marrow stromal cells. HA stimulation of RANKL is blocked by anti-CD44 antibody and is absent in cells from CD44(-/-) mice. CD44(-/-) mice exhibit thicker cortical bone and a smaller medullary cavity, but indices of bone resorption are not affected. INTRODUCTION: Hyaluronan (HA), the major nonprotein glycosaminoglycan component of the extracellular matrix in mammalian bone marrow, functions in part through its receptor, CD44, to stimulate a series of intracellular signaling events that lead to cell migration, adhesion, and activation. To determine whether HA activation of CD44 influences RANKL and osteoprotegerin (OPG) expression and whether CD44 is functionally important in bone metabolism, we studied whole bone and bone marrow stromal cells (BMSCs) from wildtype and CD44(-/-) mice. MATERIALS AND METHODS: BMSCs from wildtype and CD44(-/-) mice at 7 weeks of age were cultured and treated with either HA or anti-CD44 antibody. The levels of mRNA of RANKL, OPG, CD44, alkaline phosphatase (ALP), osteocalcin (OC), and alphaI collagen (COLL) were determined by quantitative real-time RT-PCR. Levels of RANKL and CD44 protein were measured by immunoblotting, and expression of CD44 in whole bone was determined by immunohistochemical staining. Double immunofluorescence staining and confocal microscopy were used to study colocalization of Cbfa1, CD44, and HA. Tibias were imaged using muCT, and cancellous and cortical parameters were measured. Osteoblast and osteoclast surface in the distal femoral metaphysis and osteoclast on the endocortical surface at the tibio-fibular junction were measured using quantitative histomorphometry. Differences were analyzed using ANOVA and the Newman-Keuls test. RESULTS: Addition of HA dose-dependently increased RANKL mRNA (3.6-fold) and protein (3-fold) levels in BMSCs. Stimulation of RANKL by HA could be blocked with anti-CD44 antibody. Treatment of cells with HA or anti-CD44 antibody had no significant effect on OPG mRNA levels. Both CD44 and HA localized on the plasma membrane in cells expressing Cbfa1. HA localization on the cell membrane disappeared when cells were preincubated with anti-CD44 antibody. Compared with control mice, cortical bone of CD44(-/-) was thicker, and medullary area was smaller at both 7 and 17 weeks, but at 7 weeks, indices of bone resorption were normal. At 17 weeks of age, tibial mass of CD44(-/-) mice was higher than control mice. CD44(-/-) animals expressed less RANKL in whole bone (-30%) and in BMSCs (-50%). Cells from CD44(-/-) animals failed to respond to either HA or CD44 antibody treatment. CONCLUSIONS: HA can increase RANKL expression in BMSCs through CD44.     

Adiponectin stimulates RANKL and inhibits OPG expression in human osteoblasts through the MAPK signaling pathway.

Our study indicates that recombinant adiponectin induced RANKL and inhibited OPG expression in human osteoblasts through the AdipoR1/p38 MAPK pathway, and these responses contributed to the adiponectin-induced osteoclasts formation in the co-culture of osteoblast and peripheral blood monocytes systems. These findings showed that adiponectin increased osteoclast formation indirectly through stimulating RANKL and inhibiting OPG production in osteoblasts. It also suggests the pharmacological nature of recombinant adiponectin that indirectly induces osteoclasts formation. INTRODUCTION: Recently, adiponectin has emerged as an element in the regulation of bone metabolism, but the mechanism remains. This study was undertaken to investigate the action of adiponectin on osteoclastogenesis through revealing RANKL and osteoprotegerin (OPG) expression in osteoblasts and osteoclast formation. MATERIALS AND METHODS: Real-time quantitative PCR and ELISA were used to detect RANKL and OPG mRNA and protein expression in cultured human osteoblasts. The involved signal pathway was studied using mitogen-activated protein kinase (MAPK) inhibitor and adiponectin receptor 1 (AdipoR1) siRNA. The effects of recombinant adiponectin on osteoclasts formation also were examined in the co-culture systems of osteoblast and peripheral blood monocytes (PBMCs) systems or purified CD14 + PBMCs cultures. RESULTS: Our study showed that recombinant adiponectin induced RANKL and inhibited OPG mRNA expression in human osteoblasts in a dose- and time-dependent manner. Adiponectin also increased soluble RANKL and decreased OPG secretion in osteoblasts conditioned media. Suppression of AdipoR1 with siRNA abolished the adiponectin-regulated RANKL and OPG mRNA expression in osteoblasts. Furthermore, pretreatment of osteoblasts with the MAPK inhibitor SB203580 abolished adiponectin-regulated RANKL and OPG mRNA expression. Adiponectin induced osteoclast formation in the co-culture systems of osteoblast and PBMCs systems, and OPG entirely blocked this response. However, adiponectin had no direct effect on the differentiation of osteoclast precursor purified CD14 + PBMCs. CONCLUSIONS: These data indicate that recombinant adiponectin induced RANKL and inhibited OPG expression in human osteoblasts through the AdipoR1/p38 MAPK pathway, and these responses contributed to the adiponectin-induced osteoclast formation in the co-culture of osteoblast and PBMCs systems. These findings showed that adiponectin increased osteoclast formation indirectly through stimulating RANKL and inhibiting OPG production in osteoblasts. It suggests the pharmacological nature of recombinant adiponectin that indirectly induces osteoclasts formation.     

Metabolic acidosis and alkalosis.

The factors controlling renal bicarbonate reabsorption and acid excretion under normal conditions and in the presence of metabolic acidosis and alkalosis are reviewed. The methods used to assess distal acidification and its limitations are also discussed. Measurement of urinary pCO2 in maximally alkaline urine (pH greater than 7.8) is a very useful qualitative method to assess distal acidification. The finding of a low urinary pCO2 in maximally alkaline urine indicates a distal acidification defect. We propose that both the secretory and gradient defect types of distal renal tubular acidosis are associated with a low urinary pCO2 when the urine is maximally alkaline. Sodium sulfate and neutral phosphate infusion may allow distinction between a secretory and gradient defect. Sodium sulfate lowers urine pH in the gradient defect but fails to produce the same response in the secretory defect. Neutral phosphate infusion when urine pH (6.8-7.4) is close to the pK of phosphate (6.8) results in an increase in urinary pCO2 in the gradient defect but not in the secretory defect. The mechanisms of generation, maintenance and treatment of metabolic alkalosis are also discussed.     

Relationship between serum RANKL and RANKL in bone

It is now well accepted that the molecule receptor activator of NF??B ligand (RANKL) and osteoprotegerin play key roles in regulating physiological and pathological bone turnover. There are a large number of published reports of circulating RANKL levels in both health and pathology. However, interpretation of these data has been elusive, and the relationship between circulating RANKL and RANKL levels in bone is still not clear. This review explores this subject, documenting the possible origins of circulating RANKL and suggesting additional information that is required before serum RANKL levels can provide useful diagnostic or research information.     

Metabolic acidosis in a context of acute severe asthma

In a context of asthma, lactic acidosis may occur during beta2-agonist therapy. Several cases have been reported during its administration by intravenous and/or inhaled route. This side-effect seems rather unknown and the mechanism for compensation of metabolic acidosis by hyperventilation may worsen dyspnoea and mislead clinicians. Other causes of lactic acidosis such as a major hypoxemia, a cardiovascular collapse or sepsis may also be experienced in this context and must be ruled out before attributing the lactic acidosis to beta2-agonist treatment. We report the case of a 50-year-old man hospitalized for an acute major asthma, who received a salbutamol continuous infusion associated with inhaled terbutaline. A serum lactate level of 13 mmol/l was noted eight hours after the introduction of the bronchodilator treatment. After reducing doses of beta2-agonists, the evolution was favourable, regarding both respiratory and metabolic aspects, with a rapid decrease of the serum lactate level, which finally returned to normal level after 32 hours of hospitalization.     

Metabolic acidosis in dextran-induced anaphylactic reactions

Results of arterial blood gas and acid-base balance analyses were analyzed in 50 patients suffering from dextran-induced anaphylactic reactions. Metabolic acidosis was always present in severe cases, leading to cardiac arrest, and also frequently found in those with less severe reactions with only slightly impaired circulation. Bronchospastic respiratory signs were frequently encountered but acidosis was noted to develop even without these symptoms. The severity of the acidosis was generally underestimated during treatment. Arterial PO2 and PCO2 were not significantly affected during these reactions.     

Metabolic acidosis and respiratory acidosis impair gastro-pyloric motility in anesthetized pigs

Acidosis impairs smooth muscle function in various organs. However, the effects of acidosis on the gastroduodenal tract are unknown while its dysfunction has potential perioperative harmful consequences. We investigated the effects of metabolic (MA) and respiratory acidosis (RA) on upper gut motility in tracheally ventilated pigs whose anesthesia was induced with halothane and maintained with alpha-chloralose-urethane administration (IV). Increased dead space and perfusion of hydrochloric acid 1 N (150 mL over 30 min) were used to induce RA and MA, respectively. Measurements of fundic tone using an electronic barostat, antro-pyloroduodenal phasic motility with perfused manometry and antro-duodenal electric control activity by electromyography were used to evaluate gastroduodenal function. Acidosis increased the fundic tone as reflected by a decrease in barostat volumes from 275+/-83 to 194+/-88 mL for MA and from 278+/-93 to 236+/-106 mL for RA. Pyloric and duodenal basal tones were not affected by either acidosis. A decrease in pyloric contraction amplitude from 95+/-24 to 62+/-26 mm Hg during MA and from 94+/-26 to 64+/-20 mm Hg during RA was observed. Both acidosis altered antral control activity that became dysrhythmic. Acidosis could be implicated in perioperative complications, such as gastroparesis, emesis, and regurgitation of gastric contents. IMPLICATIONS: Metabolic and respiratory acidosis mainly affects gastric antral rhythms and has a major effect on fundic tone. Acidosis could be implicated in perioperative complications, such as gastroparesis, emesis, and regurgitation of gastric contents.     

Metabolic acidosis and malnutrition in dialysis patients

Acidosis is a classic uremic toxin that causes protein catabolism, mainly by selective breakdown of skeletal muscle protein. However, the importance of acidosis is often overlooked in dialysis patients. In the presence of acidosis, there is activation of the ubiquitin-proteasome machinery as well as the branched-chain keto acid dehydrogenase, resulting in catabolism of muscle protein. Acidosis acts synergistically with other catabolic factors, such as inflammatory cytokines and insulin resistance, in inducing protein catabolism. There is ample laboratory evidence showing that correction of acidosis prevents the up-regulation of the ubiquitin-proteasome machinery and reduces protein degradation. Randomized control trials further show that acidosis in dialysis patients can be treated successfully by a higher dialysate bicarbonate or lactate concentration, or by oral bicarbonate supplement. Correction of mild acidosis in dialysis patients is effective in improving nutritional status and reducing the duration of hospitalization.     

壮骨止痛方通过RANKL/RANK信号通路抑制骨吸收的机制研究

目的 探讨壮骨止痛方调控骨吸收及破骨活动干预去势大鼠骨质疏松症的疗效和作用机制,为临床治疗绝经后骨质疏松症提供实验依据。方法 40只SD大鼠按照完全随机原则分为ZGZTF组、EV组、OVX组、SHAM组。除SHAM组之外余下均按国内外常用PMOP模型构建方法造模。术后第7天分别给予中药、雌二醇和蒸馏水灌胃。末次取材后检测大鼠右侧股骨骨密度,HE染色法观察各组大鼠胫骨骨组织病理形态变化,ELISA检测血清E2、RANKL水平,免疫组化法分析RANK、TRAP、CTSK的蛋白表达。结果 与OVX组相比,ZGZTF组大鼠骨密度有所升高,胫骨股骨骨组织微结构得到改善,骨小梁连续性稍恢复,骨髓腔缩小,脂肪空泡减少。血清中E2表达上调,RANKL水平下调（P＜0.05）,骨组织RANK、TRAP、CTSK蛋白表达下调（P＜0.05）。结论 壮骨止痛方可以降低去势大鼠骨组织相关的破骨因子的表达。抑制破骨细胞过度分化,改善骨耦联失衡,达到治疗绝经后骨质疏松症的疗效。     

Estradiol rapidly inhibits osteoclastogenesis and RANKL expression in bone marrow cultures in postmenopausal women: a pilot study

Summary We examined RANKL expression and OCL formation in cultured bone marrow cells from eight postmenopausal women in response to E₂. E₂ treatment inhibited the ability of hematopoietic cells to form OCLs in response to RANKL, and decreased RANKL production. These changes are likely involved in the ability of E₂ to influence the development of osteoporosis. Introduction Estrogen (E₂) deficiency at menopause increases osteoclast (OCL) formation and bone resorption, predisposing women to osteoporosis. We examined receptor activator of NF-kappa B-ligand (RANKL) expression and in vitro OCL formation in cultured bone marrow cells from eight postmenopausal women before and after 3 weeks of E₂ therapy and three untreated premenopausal women. Methods TRAP staining and resorption pit assay determined OCL number and function. Flow cytometry measured the distribution of marrow cell types and expression of RANKL in the macrophage-enriched fraction (R1) and a lymphocyte-enriched fraction (R2). Results RANKL (3–100 ng/ml) produced a dose-dependent increase in in vitro OC formation and E₂ therapy significantly (p < 0.01) inhibited OCL formation by 33 to 50%. A small proportion of marrow cells bound anti- RANKL Ab (0.2–4.3%). There was no effect of E₂ on the percentage of cells binding the anti-RANKL Ab in the R1 fraction. In the R2 fraction E₂ treatment decreased the percentage of cells binding anti-RANKL Ab by 68 ± 9% (p < 0.01). Conclusion Three weeks of E₂ treatment had a dual action. It inhibited the ability of hematopoietic cells to form OCLs in response to RANKL, and decreased the production of RANKL in cells of the bone marrow. The observed changes in the osteoclastic potential of bone marrow cells are likely involved in the ability of E₂ to regulate bone mass and influence the development of osteoporosis. *Taxel and Kaneko both shared equally in this work. Supported by grants from the NOF, NIA (R03) and GCRC #M01RR06192.     

Metabolic acidosis and vascular calcification: using blueprints from bone to map a new venue for vascular research

Vascular calcification is an important problem in patients with chronic kidney disease. The pathobiology of vascular calcification is complex and is intricately related to bone remodeling. Mendoza et al. report that experimental metabolic acidosis prevents calcitriol-induced vascular calcification in uremic animals. To fully understand the effect of acidosis on the vasculature, a comprehensive and integrated approach that simultaneously examines the effect of metabolic acidosis on bone and vasculature is needed.     

牛蒡苷元通过OPG/RANKL信号通路介导对去卵巢大鼠骨量流失的保护作用

目的探讨牛蒡苷元(AGN)对去卵巢大鼠骨强度和骨量的影响,并探索可能的机制。方法本研究中通过双侧去卵巢建立骨质疏松大鼠模型;随后随机分为假手术组(Sham)、去卵巢组(OVX)以及牛蒡苷元组(AGN),每组10只;其中牛蒡苷元组大鼠接受牛蒡苷元[40 mg/(kg.d)]治疗12周;待治疗结束后使用Micro-CT、Masson染色切片、骨代谢指标、骨生物力学检测以及蛋白质印迹观察治疗效果以及可能的机制。结果治疗12周后,与OVX组相比,Micro-CT和Masson染色切片结果显示AGN组的大鼠骨小梁数量和骨密度得到明显改善。AGN组大鼠BMD、TV/BV、Tb.N、Tb.Th和Tb.Sp较OVX组明显改善(P0.05)。治疗12周时,AGN组极限载荷和刚度较OVX组显著增加(P0.05),而AGN组骨代谢指标AKP和TRACP水平显著降低(P0.05),差异有统计学意义(P0.05)。和OVX组比较,AGN组OPG表达水平明显上调,而RANKL表达水平显著下调,差异有统计学意义(P0.05)。表明AGN组的大鼠OPG/RANKL信号通路被激活。结论牛蒡苷元可以通过OPG/RANKL信号通路介导对去卵巢大鼠骨骼的保护作用。