Dexamethasone stimulates expression of C-type Natriuretic Peptide in chondrocytes

Background  

Growth of endochondral bones is regulated through the activity of cartilaginous growth plates. Disruption of the physiological patterns of chondrocyte proliferation and differentiation – such as in endocrine disorders or in many different genetic diseases (e.g. chondrodysplasias) – generally results in dwarfism and skeletal defects. For example, glucocorticoid administration in children inhibits endochondral bone growth, but the molecular targets of these hormones in chondrocytes remain largely unknown. In contrast, recent studies have shown that C-type Natriuretic Peptide (CNP) is an important anabolic regulator of cartilage growth, and loss-of-function mutations in the human CNP receptor gene cause dwarfism. We asked whether glucocorticoids could exert their activities by interfering with the expression of CNP or its downstream signaling components.     

Peptide YY selectively stimulates expression of the colonocytic phenotype

Peptide YY (PYY) is produced by colonic mucosal endocrine cells and modulates gastrointestinal endocrine activity through specific Y-receptors. The direct effects of PYY on intestinal mucosal growth and differentiation remain uncharacterized. The abundance of PYY in colonic mucosa suggests that PYY acts locally to maintain colonocytic differentiation. We tested this hypothesis in human Caco-2 intestinal epithelial cells, which express alkaline phosphatase (AP) and dipeptidyl dipeptidase (DP), brush-border enzymes differentially concentrated in large and small intestinal mucosa, respectively. The effects of PYY on enzyme specific activity were compared with those of pancreatic polypeptide, neuropeptide-Y, vasoactive intestinal peptide, pentagastrin, bombesin, and selective Y1- and Y2-receptor agonists. Brush-border enzyme activity was assessed by AP and DP specific activity in cell lysates quantitated spectrophotometrically following synthetic substrate digestion. PYY, neuropeptide-Y, pancreatic polypeptide, and vasoactive intestinal peptide (10⁻⁷ mol/L) stimulated AP activity. PYY brought about the greatest increase (38.0%±11.0%, n=48). Only PYY decreased DP specific activity (7.9%±2.2%, n=48). The Y2-agonist but not the Y1-agonist mimicked these PYY effects (increasing AP 28.3%±3.5% and decreasing DP 10.4%±3.6%). These data suggest that PYY promotes differentiation toward a colonocytic phenotype in Caco-2 intestinal epithelial cells and that this effect may be mediated through the Y2-receptor subtype.     

Thyroxine stimulates transglutaminase activity in articular chondrocytes

OBJECTIVES: Thyroid hormones induce features of the hypertrophic phenotype in mature articular chondrocytes as well as in growth plate chondrocytes. Hypertrophic chondrocytes are responsible for extracellular matrix mineralization, with formation of bone mineral in growth plate cartilage and pathologic calcium crystals in aging articular cartilage. Elevated activity levels of the two transglutaminase (Tgase) enzymes (type II Tgase and Factor XIIIA (FXIIIA)) have recently been described as additional features of hypertrophic growth plate chondrocytes. Because Tgases may participate in pathologic mineralization in aging cartilage, we explored the effects of thyroid hormones on Tgase activity in articular chondrocytes. METHODS: Adult porcine articular chondrocytes were incubated with or without 250-750nM L-thyroxine (T4) or 10-100 nM 3,3',5-tri-iodothyronine (T3). Tgase activity was measured with a standard radiometric assay. The effects of thyroid hormones on protein and mRNA levels of type II Tgase and FXIIIA were determined. As Tgase activity can be stimulated by proteases, endoproteinase levels were also measured. The mechanisms of these effects were explored. RESULTS: T4 (750 nM) or T3 (100 nM) stimulated Tgase activity by twofold in articular chondrocytes at 4h and increased the percentage of Tgase activity in the extracellular matrix. Chondrocytes rapidly converted T4 to T3, but the time course suggests similar mechanisms for T4 and T3. T4-induced Tgase activity was suppressed with cycloheximide and protein kinase C inhibitors. The effects of T4 on type II Tgase and FXIIIA levels were modest, but T4 strongly induced endoproteinase activity in chondrocytes. CONCLUSIONS: We report in this study that thyroid hormones increase Tgase activity in articular chondrocytes via a non-genomic mechanism, which may involve increased endoproteinase secretion.     

Low-intensity ultrasound stimulates proteoglycan synthesis in rat chondrocytes by increasing aggrecan gene expression.

We evaluated the effect of low intensity-pulsed ultrasound stimulation on rat chondrocytes in vitro using two different 1.0-MHz ultrasound signals with spatial and temporal average intensities of 50 or 120 mW/cm2. The pulses had a duration of 200 microseconds and were repeated every millisecond, with corresponding average peak-pressure amplitudes of 230 or 360 kPa, respectively. Cells were stimulated one, three, or five times for 10 minutes each day starting the third day after plating. One group of cells was exposed to sham ultrasound as a control. The cultures were evaluated for cell proliferation (by [3H]thymidine incorporation and DNA measurement), steady-state mRNA levels of alpha1(I) and alpha1(II) procollagens and aggrecan (by Northern blotting), and proteoglycan synthesis (by [35S]sulfate incorporation). The results revealed that ultrasound causes increases in the level of aggrecan mRNA (p < 0.05) and in proteoglycan synthesis (p < 0.03) after three and five treatments. Expression of mRNA for alpha1(II) procollagen increased over time, but ultrasound had no stimulatory effect. Expression of mRNA for alpha1(I) procollagen was initially low and remained unchanged with time. Although cell proliferation increased with time in both groups, there was no statistically significant difference between the cultures treated with ultrasound and the controls (p = 0.1). The in vitro results support our previous in vivo findings that low-intensity ultrasound stimulates aggrecan mRNA expression and proteoglycan synthesis by chondrocytes, which may explain the role of ultrasound in advancing endochondral ossification, increasing the mechanical strength of fractures, and facilitating fracture repair.     

Renal Response to Atrial Natriuretic Peptide in Nephrotic Syndrome

In six patients with nephrotic syndrome of various aetiology,the increase in absolute and fractional sodium excretion (FE_Na)after a bolus injection of 100 µg -human atrial natriureticpeptide (ANP) was not different from the effect in normal healthysubjects at comparable sodium levels. Glomerular filtrationrate rose in normals as well as in patients. In two patients,however, baseline sodium excretion was very low and the natriureticresponse to ANP was proportionally blunted. The high baselinesodium reabsorption and blunted response to ANP may be explainedas due either to an intrinsic renal defect or to a circulatoryhypovolaemia. The finding of a low plasma ANP in these two patients,however, suggests involvement of a hypovolaemic component.     

心脏手术病人心肌组织心钠素含量的测定

为探讨心脏手术病人心肌组织心钠素含量变化与心脏病的关系。应用放射免疫分析方法对３７例心脏手术病人心肌组织心钠素的含量进行测定。结果风湿性心脏病病人心肌组织心钠素含量明显高于先天性房、室间隔缺损者。证实心功能不同，心肌组织心钠素含量不同，在病理状态下，心室亦分泌心钠素。     

地塞米松促进大鼠颅骨成骨细胞向脂肪细胞转分化

目的 研究在不同浓度地塞米松作用下,体外培养的大鼠颅骨成骨细胞能否转分化为脂肪细胞,以进一步探讨糖皮质激素性骨质疏松症发病的具体机制.方法 将原代培养的大鼠颅骨成骨细胞分为四组,分别用含不同浓度的地塞米松(0 mol/L、10-8 mol/L、10-7 mol/L、10-6mol/L)的DMEM(H)培养基培养.于作用后第7天、21 d,采用倒置相差显微镜观察细胞形态的变化,进行细胞化学染色(茜素红钙结节染色、油红O染色),并采用实时荧光定量RT-PCR检测PPARγ-2、LPL及ALP基因mRNA的表达.结果 在10-6、10-7mol/L的地塞米松作用下,大鼠成骨细胞矿化能力减弱,胞浆中出现脂滴,RT-PCR结果显示脂肪细胞标志基因PPAR(γ)-2、LPL mRNA表达增高,成骨细胞标志基因ALP mRNA表达减少.而10-8mol/L地塞米松对成骨细胞的分化有促进作用.结论 长期、大剂量应用糖皮质激素可促进大鼠颅骨成骨细胞转分化为成熟的脂肪细胞,这可能是糖皮质激素性骨质疏松症的发病机制之一.     

氨基末端B型利钠肽前体检测临床研究进展

目前氨基末端B型利钠肤前体正广泛应用于临床试验和心血管研究中,近年的研究显示心衰与氨基末端B型利钠肽前体水平升高有关.现主要就近年来关于氨基末端B型利钠肽前体作为危险因子和预测因素在心血管方面的研究进展进行综述.     

The Effect of Renal Transplantation on Plasma Atrial Natriuretic Peptide

The changes in plasma atrial natriuretic peptide (ANP) werestudied in four adult patients after cadaveric renal transplantation.In three patients who achieved good renal function, the correctionof volume overload, as reflected by reduction in weight andright atrial pressure, was associated with a steady fall inplasma ANP and a parallel decrease in both fractional excretionof sodium and plasma cyclic guanosine monophosphate. The fourthpatient. with severe acute rejection, developed severe peripheraloedema, and fractional sodium excretion remained low despitehigh values of ANP.     

Retinoic acid stimulates pyrophosphate elaboration by cartilage and chondrocytes

Abnormal metabolism of extracellular inorganic pyrophosphate (PPi) by articular cartilage contributes to calcium pyrophosphate dihydrate (CPPD) crystal formation and the resultant arthritis known as CPPD deposition disease. The factors causing excess PPi elaboration in affected cartilage remain poorly defined. Retinoic acid (RA), a naturally occurring vitamin A metabolite, promotes cartilage degeneration and mineralization, two correlates of CPPD crystal deposition. RA was examined as a potential modifier of cartilage PPi elaboration. All-trans RA (200–1000 nM) increased PPi levels in culture medium of normal porcine cartilage and chondrocytes 2–3-fold over control values at 96 hours of incubation (P < 0.01). IGF1 and anti-EGF antibody diminished the effects of RA on PPi elaboration. RA modestly increased activity of the PPi-generating ectoenzyme NTPPPH in culture medium (P < 0.01). As some RA effects are mediated through increased activity of TGF\, a known PPi stimulant, we examined the effect of anti-TGF\ antibody on RA-induced PPi elaboration. PPi levels in medium were reduced from 30 ± 7 fxM in cartilage cultures with 500 nM RA to 14 ± 4 ΜM PPi in cartilage cultures with RA and anti-TGF\. Anti-TGF\ antibody, however, had no significant effect on RA-induced PPi elaboration in chondrocyte cultures. Thus, RA, along with TGF\ and ascorbate, can now be included in the list of known PPi stimulants. All three of these factors promote mineralization in growth plate cartilage. These data support a central role for TGF\ in CPPD disease, and provide further evidence linking processes of normal and pathologic calcification in cartilage.     

兔一侧全肺切除术后血浆心钠素变化及意义

目的　探讨心钠素(ANP)与肺切除术后心肺并发症的相关关系。　方法　将30只兔随机分为3组。组Ⅰ12只,行左全肺切除术;组Ⅱ12只,行右全肺切除术;对照组6只,不行肺切除。3组术前、术后测血气分析,ANP,心肌酶和心电图监测,均不吸氧。　结果　组Ⅰ和组Ⅱ术后30分钟pH下降,动脉血氧分压(PaO     

Effect of Ultrafiltration on Plasma Concentrations of Atrial Natriuretic Peptide in Haemodialysis Patients

We have investigated the influence of body fluid volume statuson plasma levels of immunoreactive atrial natriuretic peptide(irANP) in eight uraemic patients on chronic haemodialysis,including two diabetics with severely impaired reflex controlof the heart. IrANP was significantly higher in volume-expandeduraemic patients (36±16 pg/ml) than in a group of sevenage and sex-matched normal subjects (14±2 pg/ml), andfell consistently, approaching the normal range after the removalof 2.0–4.3 litres of isotonic plasma ultrafiltrate (byisolated ultrafiltration). Plasma levels of the hormone werestrictly related to right atrial pressure. The irANP responseto ultrafiltration in the two diabetics was similar to thatof the other uraemic patients. The results suggest that theelevated irANP levels found in volume-expanded uraemic patientsdepend largely on fluid overload per Se. The preserved irANPresponse to ultrafiltration of the two diabetics with severeautonomic neuropathy indicates that in chronic renal failureirANP secretion may be regulated independently from autonomicinfluences.     

Changes of Plasma Atrial and Brain Natriuretic Peptide Levels During Hemodialysis

Objectives. The purpose of this study was to evaluate the effect of hemodialysis on the plasma concentration of atrial and brain natriuretic peptides, and to determine the two-dimensional echocardiographic parameters affecting the changes of plasma atrial and brain natriuretic peptide levels in patients with chronic renal failure. Background. Brain natriuretic peptide has been found in human cardiac tissue and increases in patients with congestive heart failure. However, the factors that stimulate the secretion of plasma brain natriuretic peptide have not yet been fully clarified. Methods. In 15 patients with chronic renal failure, plasma atrial and brain natriuretic peptide levels and two-dimensional echocardiographic parameters were measured before and after each session of hemodialysis. Results. Plasma atrial natriuretic peptide levels significantly decreased from 367 ± 537 pg/mL to 138 ± 167 pg/mL after hemodialysis (p < 0.01). However, plasma brain natriuretic peptide levels did not significantly change after hemodialysis. Left atrial dimension significantly decreased (41.1 ± 6.6 vs. 36.3 ± 6.2 mm, p < 0.01) and left ventricular end-diastolic dimension slightly decreased after hemodialysis (57.0 ± 10.3 vs. 55.7 ± 9.9 mm, p < 0.05). The decrease of left atrial dimension was greater than that of left ventricular end-diastolic dimension (4.9 ± 1.6 vs. 1.3 ± 0.6 mm, p < 0.05). Plasma brain natriuretic peptide levels significantly correlated with fractional shortening both before and after hemodialysis (r = 0.65, p < 0.05). Conclusion. Plasma atrial natriuretic peptide levels significantly decreased as the right and left atrial overloads decreased, and plasma brain natriuretic peptide levels did not significantly decrease after hemodialysis. Plasma brain natriuretic peptide levels were not significantly influenced by acute hemodynamic change, such as hemodialysis. However, plasma brain natriuretic peptide levels were significantly correlated with basic cardiac function.     

Diagnostic Value of N-Terminal Pro-Brain Natriuretic Peptide in Pleural Effusions of Cardiac Origin

IntroductionThe diagnosis of cardiogenic pleural effusion (PE) is often difficult to make. The objective of our study was to evaluate the diagnostic usefulness of N-terminal pro-brain natriuretic peptide (NT-proBNP) levels in PE patients with heart failure, in pleural fluid (PF) and serum (S), and to compare the cholesterol in pleural fluid (CHOL PF) and in serum (CHOL S) with the Light criteria.Patients and methodsAll the biomarkers were evaluated in 398 PF (26.9% transudates). The area under the curve (AUC) quantified the overall diagnostic precision. The diagnostic precision of the different parameters was also assessed using the ROC curves.ResultsThe AUC of the ROC for pleural fluid NT-proBNP was 0.894, with no significant differences with CHOL PF (0.914) or with the Light criteria (0.896). The sensitivity, specificity, the positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 85.1% (94.1% for CHOL PF), 79.9% (90.2% for the Light criteria), 4.24 (7.27 for the Light criteria) and 0.19 (0.07 for CHOL PF), respectively. The combination of NT-proBNP in PF ≥ 276 pg/ml and CHOL PF ≤ 57 mg/dL managed to classify the highest number of PE correctly (sensitivity 97.8%, specificity 85.4%).ConclusionsThe diagnostic yield of NT-proBNP in cardiogenic PE is not superior to the CHOL PF or the Light criteria, although it could be diagnostic in transudates of another origin.     

Comparative Effects of Haemodialysis and Haemofiltration on Plasma Atrial Natriuretic Peptide

The effects of 4 h haemodialysis (15 patients) or 4 h haemofiltration(five patients) on plasma concentrations of atrial natriureticpeptide (ANP) were compared by means of a sensitive radioreceptorbinding assay, and related to accompanying changes in body weight,blood pressure and plasma renin activity. Before dialysis, plasmaANP concentrations were considerably elevated: haemodialysisgroup 10–484 pmol/l (mean 156 pmol/l); haemofiltrationgroup 72–320 pmol/l (mean 170 pmol/l). Although plasmaconcentrations of ANP fell markedly with treatment in both groups:post-haemodialysis 2–187 pmol/l (mean 67 pmol/l); post-haemofiltration47–135 pmol/l (mean 79 pmol/l), after treatment it remainedabove the normal range in 14 of the 20 patients. Pretreatmentplasma ANP was related to systolic blood pressure (r=0.459;P<0.05) but bore no relationship to mean or diastolic bloodpressure, or plasma renin activity. The fall in plasma ANP concentrationduring treatment correlated with the postural blood pressuredrop after dialysis (r=0.505; P<0.05), but was unrelatedto changes in weight or plasma renin activity with haemodialysisor haemofiltration. Plasma ANP concentrations rose rapidly againin the 60 min after dialysis treatment, without change in bodyweight. These results show that high levels of biologically active ANPcirculate in end-stage renal disease. The fact that these arenot reduced to normal by haemodialysis or haemofiltration, despiterestoration to normovolaemic or hypovolaemic state, suggeststhat the increased levels of ANP in end-stage renal failureare due to both hypervolaemia and other factors, which may includeoccult cardiac dysfunction and loss of renal clearance.