Denosumab effects on serum levels of the bone morphogenetic proteins antagonist noggin in patients with transfusion-dependent thalassemia and osteoporosis

INTRODUCTION

Noggin is an antagonist of bone morphogenetic proteins (BMPs) and has a strong effect on osteogenesis. Osteoporosis is a common complication of transfusion dependent beta-thalassemia (TDT) and denosumab has been recently emerged as a promising therapeutic option. This was a post hoc investigation of serum noggin levels among TDT patients with osteoporosis who participated in a randomized, placebo-control, phase 2b study.

METHODS

Patients received either 60 mg denosumab (n = 32) or placebo (n = 31) every 6 months for 12 months. Noggin was measured, for the first time in thalassemia patients, at baseline and at 12 months, using a recently developed high sensitivity fluorescent immunoassay.

RESULTS

Both groups showed a significant increase in noggin serum levels (denosumab p < 0.001; placebo p < 0.0001). Interestingly, the increase was higher in the placebo group. Furthermore, we observed a strong correlation between noggin and wrist bone mineral density (r = -0.641, p = 0.002) only in the denosumab group.

CONCLUSION

In conclusion, higher noggin levels reflected more BMP inhibition, since our assay detects free bioactive noggin, which in turn impaired bone formation in placebo group. Therefore, denosumab possibly regulates noggin and favours bone turnover in TDT patients with osteoporosis through a novel mechanism of action.

Circulating noggin levels following treatment with denosumab or teriparatide in postmenopausal women with low bone mass

OBJECTIVES

Noggin inactivates bone morphogenetic proteins (BMPs), possibly exerting negative effects on the skeleton.We aimed to compare the effect of agents with opposite impact on bone turnover on noggin circulating levels.

METHODS

In this observational, open label, non-randomized clinical study postmenopausal women with low bone mass were treated with either denosumab (n=30) or teriparatide (n=30). Serum samples were obtained at baseline, three and twelve months after treatment initiation. Prevalent fractures were recorded at baseline and lumbar spine bone mineral density (LS BMD) was measured at baseline and twelve months. Measured parameters included noggin, BMP-2, BMP-4, procollagen type 1 N-terminal propeptide (P1NP) and C-terminal cross-linking telopeptide of type 1 collagen (CTx).

RESULTS

Noggin levels remained unchanged after either denosumab or teriparatide treatment. Baseline noggin levels were not different between women with vs. without previous anti-osteoporotic treatment, or between those with vs. without vertebral or non-vertebral fractures and were not correlated with age or LS BMD. At twelve months, noggin levels were positively correlated with P1NP within the denosumab (r_s= 0.47; p=0.014), whereas negatively within the teriparatide group (r_s= -0.43; p=0.019).

CONCLUSIONS

In postmenopausal women with low bone mass noggin levels were not correlated with bone parameters at any time point, except with P1NP at 12 months, and remained stable with both denosumab and teriparatide treatment.

Noggin levels in nonalcoholic fatty liver disease: the effect of vitamin E treatment

AIM

The evaluation of (a) noggin levels in patients with simple steatosis (SS) vs. nonalcoholic steatohepatitis (NASH) vs. controls, and (b) the effect of combined spironolactone plus vitamin E vs. vitamin E monotherapy on noggin levels in biopsy-proven patients with nonalcoholic fatty liver disease (NAFLD).

METHODS

In the case-control study, 15 patients with SS, 16 with NASH, and 24 controls were included. In the randomized controlled trial, NAFLD patients were assigned to vitamin E (400 IU/d) or spironolactone (25 mg/d) plus vitamin E for 52 weeks.

RESULTS

Noggin levels were lower in SS (5.8 ± 1.5 pmol/l) and NASH (8.7 ± 2.4 pmol/l) patients than in controls (13.7 ± 2.7 pmol/l; p for trend = 0.040), but were similar in SS and NASH patients. After adjustment for potential cofounders, log(noggin) remained different between groups. Log(noggin) levels similarly increased post-treatment in both groups: log(noggin) was not different between groups (p = 0.20), but increased within groups over time (p < 0.001), without a significant group × time interaction (p = 0.62). Log(noggin) significantly increased at month 2 post-treatment (p = 0.008 vs. baseline) and remained stable thereafter.

CONCLUSIONS

Lower noggin levels were observed in NAFLD patients than in controls. Noggin levels increased similarly by either combined low-dose spironolactone plus vitamin E or vitamin E monotherapy.

TRIAL REGISTRATION

NCT01147523.

A Screening Approach for Identifying Gliadin Neutralizing Antibodies on Epithelial Intestinal Caco-2 Cells

Celiac disease (CD) is a chronic inflammatory condition caused by the ingestion of gliadin-containing food in genetically susceptible individuals. Undigested peptides of gliadin exert various effects, including increased intestinal permeability and inflammation in the small intestine. Although many therapeutic approaches are in development, a gluten-free diet is the only effective treatment for CD. Affecting at least 1% of the population in industrialized countries, it is important to generate therapeutic options against CD. Here, we describe the establishment of a high-throughput screening (HTS) platform based on AlphaLISA and electrical cell–substrate impedance sensing (ECIS) technology for the identification of anti-inflammatory and barrier-protective compounds in human enterocytes after pepsin-trypsin-digested gliadin (PT-gliadin) treatment. Our results show that the combination of these HTS technologies enables fast, reliable, simple, and label-free screening of IgY antibodies against PT-gliadin. Using this platform, we have identified a new chicken anti-PT-gliadin IgY antibody as a potential anti-CD agent.

Novel avian single-chain fragment variable (scFv) targets dietary gluten and related natural grain prolamins, toxic entities of celiac disease

BACKGROUND

Celiac disease (CD) is a chronic, small intestinal inflammatory disease mediated by dietary gluten and related prolamins. The only current therapeutic option is maintenance of a strict life-long gluten-free diet, which implies substantial burden for CD patients. Different treatment regimes might be feasible, including masking of toxic celiac peptides with blocking antibodies or fragments thereof. The objective of this study was therefore to select and produce a recombinant avian single-chain fragment variable (scFv) directed against peptic-tryptic digested gliadin (PT-Gliadin) and related celiac toxic entities.

RESULTS

Gluten-free raised chicken of same age were immunized with PT-Gliadin. Chicken splenic lymphocytes, selected with antigen-coated magnetic beads, served as RNA source for the generation of cDNA. Chicken VH and VL genes were amplified from the cDNA by PCR to generate full-length scFv constructs consisting of VH and VL fragments joined by a linker sequence. ScFv constructs were ligated in a prokaryotic expression vector, which provides a C-terminal hexahistidine tag. ScFvs from several bacterial clones were expressed in soluble form and crude cell lysates screened for binding to PT-Gliadin by ELISA. We identified an enriched scFv motif, which showed reactivity to PT-Gliadin. One selected scFv candidate was expressed and purified to homogeneity. Polyclonal anti-PT-Gliadin IgY, purified from egg yolk of immunized chicken, served as control. ScFv binds in a dose-dependent manner to PT-Gliadin, comparable to IgY. Furthermore, IgY competitively displaces scFv from PT-Gliadin and natural wheat flour digest, indicating a common epitope of scFv and IgY. ScFv was tested for reactivity to different gastric digested dietary grain flours. ScFv detects common and khorasan wheat comparably with binding affinities in the high nanomolar range, while rye is detected to a lesser extent. Notably, barley and cereals which are part of the gluten-free diet, like corn and rice, are not detected by scFv. Similarly, the pseudo-grain amaranth, used as gluten-free alternative, is not targeted by scFv. This data indicate that scFv specifically recognizes toxic cereal peptides relevant in CD.

CONCLUSION

ScFv can be of benefit for future CD treatment regimes.

Sandwich ELISA for proANP 1-98 facilitates investigation of left ventricular dysfunction

Proatrial natriuretic peptides are proposed to be sensitive and specific markers for various stages of heart deficiency. Here we present a rapid and specific sandwich immunoassay for the measurement of proANP 1-98 in biological fluids like plasma, serum urine. No sample preparation prior to the assay is necessary. Polyclonal antibodies specific for distinct epitopes of proANP 1-98, predicted to be highly immunogenic, were raised in sheep and purified by immunoaffinity chromatography prior to use in the assay. Antigen binding sites of the antibodies were determined by epitope mapping with a set of peptide fragments. The capture antibody, specific for proANP 16-23, is coated directly onto microtiter plates. Recombinant proANP 1-98 is used as a standard. The biotinylated detection antibody, specific for proANP 80-88, is incubated simultaneously with 20microl of sample for 150 min. Signal is generated with a streptavidin-HRPO-conjugate and TMB as substrate. The detection limit of the assay is 50 pmol/l; intraassay CVs are below 5%, interassay CVs are lower than 10%. Dilution curves show good linearity, recovery of synthetic peptide ranged between 85% and 91%. Reference values from healthy volunteers range from 0 to 2000 pmol/l in human plasma. We conclude this assay is a easy to handle, quick and reliable method for routine measurement of proANP 1-98 and the presented manuscript describes the procedure and performance of this ELISA in detail.

Evaluation of big endothelin-1 concentrations in serum and ventricular cerebrospinal fluid after early surgical compared with nonsurgical management of ruptured intracranial aneurysms

OBJECT

Whereas the removal of subarachnoid blood is possible during early-stage aneurysm surgery, this cannot be achieved in aneurysms treated by endovascular means. The levels of potential spasmogens in the cerebrospinal fluid (CSF) in patients receiving endovascular treatment might therefore be higher, with the potential for more severe post-subarachnoid hemorrhage (SAH) vasospasm.

METHODS

Serum and CSF concentrations of big endothelin (ET)-1 were serially measured in patients with SAH receiving one of the following treatments: 1) early (within 72 hours of SAH) aneurysm surgical treatment (15 patients), 2) early endovascular treatment (17 patients), or 3) no intervention in the acute phase (12 patients). In patients suffering delayed infarctions higher levels of big ET-1 CSF were demonstrated than in those without infarctions (p = 0.01). In patients in whom surgery was performed in the acute phase lower big ET-1 CSF concentrations were demonstrated than in those who received embolization treatment or no treatment (p = 0.02). Subgroup analysis demonstrated that in patients receiving early endovascular treatment, higher big ET-1 CSF concentrations were revealed than in those undergoing early aneurysm surgery; this was true for patients with (microsurgerytreated, 1.84 +/- 0.83 pg/ml; and embolization-treated 2.19 +/- 0.54 pg/ml) and without (microsurgery-treated 1.76 +/- 0.61 pg/ml; and embolization-treated 2.01 +/- 0.48 pg/ml) delayed infarctions.

CONCLUSIONS

Among patients with SAH who received treatment during the acute phase, those undergoing early aneurysm surgery were shown to have lower big ET-1 CSF levels than those receiving embolization and no treatment (that is, the nonsurgical treatment groups). The clinical significance of this finding remains to be established in future clinical trials, because in the present study the trend toward lower levels of big ET-1 CSF in the microsurgically treated group was not paralleled by a lower delayed stroke rate or an improvement in neurological outcome.

Enzyme immunoassays for fragments (epitopes) of human proatrial natriuretic peptides

Several peptides derived from the N-terminal sequence of pro-atrial natriuretic peptide (proANP) have been tested successfully as markers of heart disease. We have developed specific and sensitive competitive enzyme immunoassays for fragments [1-30] and [31-67] of proANP. Antisera were raised in sheep against synthetic peptides predicted to be highly immunogenic. Binding specificity was determined by epitope mapping. Microtiter plates were coated with antibody specific for the Fc region of sheep IgG to capture the affinity-purified specific anti-proANP antibodies in an oriented and reproducible form. Synthetic proANP calibrators or diluted samples were incubated simultaneously with biotinylated peptide and binding was quantitated using streptavidin-peroxidase and TMB. Immunoreactive proANP could be measured in diluted plasma, serum and urine. The detection limits of the proANP[1-30] and proANP[31-67] assays were 2.5 and 10 pmol/l respectively. The linearity of samples diluted beyond the recommended assay conditions was good. Recoveries of added standard peptides ranged from 102 to 112%. Circulating concentrations of immunoreactive proANP in 115 healthy subjects ranged from 0.11 to 0.47 nmol/l proANP[1-30] and 0.18 to 0.79 nmol/l proANP[31-67]. In patients with cardiac disease, proANP levels were increased significantly. The reference interval of proANP[31-67] in urine was 0.09 to 1.7 nmol/l, several-fold higher than proANP[1-30] (<O.03 to 1.1 nmol/l). After storage for 6 months at -20 degrees C there was no detectable decrease in immunoreactivity.

Urinary and plasma urodilatin measured by a direct RIA using a highly specific antiserum

Urodilatin (95–126) (URO) appears to play a major physiologic role in fluid homeostasis and produces major changes when administered intravenously. Here we describe a monospecific, high-affinity antiserum against URO with no cross-reactivity (&lt;0.01%) against the structural highly homologous atrial natriuretic peptide 99-126 (ANP-99-126), ANP analogs, and related peptides such as brain natriuretic peptide. A competitive RIA was developed, based on this antiserum. Urine samples with or without ethanol extraction and plasma samples without pretreatment were analyzed by the RIA, which had a detection limit of 10.5 ng/L, a linear measuring range between 10.5 and 1000 ng/L, and recoveries of 93–102% in urine and 90–104% in plasma. The intraassay CVs were 8.2% and 8.1% for urine samples with 269 and 669 ng/L URO; the interassay CV was 9.7% at 839 ng/L. Using this assay, we present URO data for urine from healthy volunteers receiving low and routine sodium diets and from clinical urine specimens; we also present pharmacokinetic data for URO in plasma from patients suffering from bronchial asthma and treated by URO infusion.

Urinary and plasma urodilatin measured by a direct RIA using a highly specific antiserum

Urodilatin (95-126) (URO) appears to play a major physiologic role in fluid homeostasis and produces major changes when administered intravenously. Here we describe a monospecific, high-affinity antiserum against URO with no cross-reactivity (<0.01%) against the structural highly homologous atrial natriuretic peptide 99-126 (ANP-99-126), ANP analogs, and related peptides such as brain natriuretic peptide. A competitive RIA was developed, based on this antiserum. Urine samples with or without ethanol extraction and plasma samples without pretreatment were analyzed by the RIA, which had a detection limit of 10.5 ng/L, a linear measuring range between 10.5 and 1000 ng/L, and recoveries of 93-102% in urine and 90-104% in plasma. The intraassay CVs were 8.2% and 8.1% for urine samples with 269 and 669 ng/L URO; the interassay CV was 9.7% at 839 ng/L. Using this assay, we present URO data for urine from healthy volunteers receiving low and routine sodium diets and from clinical urine specimens; we also present pharmacokinetic data for URO in plasma from patients suffering from bronchial asthma and treated by URO infusion.

Validation of endothelin (ET) immunoreactivity in human bile by HPLC. Comparison of biliary ET concentration in liver transplant recipients with values obtained during cholecystectomy

High endothelin (ET) concentrations were recently detected in human bile after orthotopic liver transplantation (OLT). In the present study we compared biliary ET/big-ET levels measured by radioimmunoassay (RIA) in liver graft recipients (n = 37) with levels measured in non-transplant patients during cholecystectomy (n = 38) to clarify the influence of transplantation on the levels of biliary ET peptides. HPLC elution profiles of biliary ET were analyzed for characterization of ET peptide composition and validation of RIA analysis in bile extracts. Mean ET/big-ET levels in the common bile duct after OLT were significantly elevated (ET, 20.9 +/- 15; big-ET, 39.2 +/- 19 fmol/ml) compared to levels in non-transplant patients (ET, 5.7 +/- 4.9; big-ET, 12 +/- 8 fmol/ml). Highest ET/big-ET levels were measured in the gall bladder during cholecystectomy (ET, 61.7 +/- 41; big-ET, 75 +/- 28 fmol/ml). ET and big-ET levels were correlated by linear regression. HPLC analysis reveals the presence of high levels of ET/big-ET in human bile. Biliary ET mostly represents ET-1. High biliary ET levels after OLT appear to be derived from active endothelial secretion and probably reflect hepatic endothelial stress after preservation/ reperfusion. High biliary ET levels could be involved in the mediation of functional cholestatic syndromes after OLT.

Construction and use of two alpha-human atrial natriuretic peptide-fragment affinity chromatography columns in the isolation of C- and N-terminal epitope-specific antibodies for use in a prototype alpha-hANP biosensor

Two alpha-human atrial natriuretic peptide (alpha-hANP) based affinity chromatography columns were produced by covalently immobilizing the C- and N-terminal epitopes of alpha-hANP. The stationary phase was made from a controlled-pore-glass bead solid support, which was silanized and treated with sulphosuccinimidyl 4-(maleimidomethyl)cyclohexyl carboxylate before the individual fragments were immobilized by substitution at their thiol groups. These columns were used to isolate alpha-hANP-specific antibodies from a goat anti-alpha-hANP serum, which were then further sorted according to their epitope specifity. These C- and N-terminal epitope-specific antibodies were in turn used as components in the construction of an alpha-hANP biosensor based on an enzyme-linked immunosorbent assay (ELISA) sandwich principle. Initial in vitro testing of the sensor using a physiological alpha-hANP solution showed a reproducible response to the peptide. There is to date no other equally fast, sensitive and precise method available to detect this peptide. This alpha-hANP sensor may prove to be an invaluable aid in human medicine as a monitor of patient status during transplant surgery, for example, an area inaccessible to radioimmunoassay and normal ELISA techniques.

Characterization of antibodies against human N-terminal parathyroid hormone by epitope mapping

Two polyclonal antisera from goat and mouse and two monoclonal antibodies against human parathyroid hormone (1-34) were characterised by epitope mapping. Hexapeptides were synthesized on polystyrene pins, the sequences of which overlapped and represented the entire sequence of hPTH(1-34). Binding of antibodies to these hexapeptides was determined and antigenic determinants thus characterized. At least one predominant binding sequence was detected in the region of hPTH(7-14).

Radioimmunoassay of immunoreactive C-terminal big-endothelin(22-38)

Endothelin, a potent endogenous vaso-constrictor, is derived from its biosynthetic precursor by proteolytic degradation. The last step cleaves big-endothelin(1-38) to endothelin(1-21) and a C-terminal fragment. We have developed a radioimmunoassay for this peptide, based on an antiserum recognizing the C-terminal sequence big-endothelin(22-38) and cross-reacting with intact big-endothelin. To test for the presence of immunoreactive big-endothelin(22-38) in plasma, samples were extracted by passage through C18 silica cartridges, and desorption with methanol/water volume fraction 0.8. The yields of this purification and concentration procedure were about 70%. In 15 healthy persons we found concentrations of 1-11 pmol/l, which is about 10-fold higher than the reference levels reported for endothelin(1-21) or big-endothelin(1-38). Thus, endothelin-derived peptides containing the big-endothelin(22-38) sequence, but different from intact big-endothelin, do circulate in human blood. If a sufficiently tight correlation to levels of circulating endothelin(2-21) can be proven, this would facilitate studies on the physiological role of endogenous endothelin.

Immobilization of alpha-human atrial natriuretic peptide on insoluble supports and affinity purification of specific antibodies from a polyclonal goat anti-alpha-human atrial natriuretic peptide serum

alpha-Human atrial natriuretic peptide (alpha-hANP) was covalently coupled via single attachment onto two different insoluble matrices. Controlled-pore glass-alpha-hANP matrices were well suited for the purification of monospecific antibodies, whereas Enzacryl AA-alpha-hANP did not withstand the inevitable chemical and physical stresses during affinity purification.

Determination of alpha-human atrial natriuretic peptide (alpha-hANP) in urine using combination HPLC with RIA strongly indicates non-immunoreactive metabolites

Employing HPLC coupled with RIA, it was shown that alpha-human atrial natriuretic peptide is excreted in urine. Freshly collected urine had to be acidified to obtain reproducible results. When prepurified urine was subjected to HPLC (ion exchange and reversed phase) the subsequent quantification of alpha-hANP immunoreactive material in the eluate showed 10- to 30-fold greater amounts of alpha-hANP after treatment with HPLC; substances with the same elution parameters as synthetic alpha-hANP were detected, but they gave no response in the RIA.

Chlorophyll precursors in the plasma membrane of a cyanobacterium, Anacystis nidulans. Characterization of protochlorophyllide and chlorophyllide by spectrophotometry, spectrofluorimetry, solvent partition, and high performance liquid chromatography

Plasma membranes were isolated and separated from thylakoid membranes by discontinuous sucrose density gradient centrifugation of crude membranes prepared by French pressure cell extrusion of lysozyme-treated Anacystis nidulans. Two distinct populations of chlorophyll-free plasma membrane vesicles were obtained exhibiting buoyant densities of 1.087 and 1.100 g/cm3 as opposed to a uniform density of 1.192 g/cm3 for thylakoid membranes. Plasma and thylakoid membranes were characteristically different also with respect to fatty acid and protein composition, cytochrome oxidase activity, and pigment content as analyzed by spectrophotometry, spectrofluorimetry, and high performance liquid chromatography. Apart from carotenoids, chlorophyll a was the only major photosynthetic pigment detected in thylakoid membranes while plasma membranes contained virtually no chlorophyll a but (besides large amounts of carotenoids) protochlorophyllide a and chlorophyllide a as revealed by solvent partition (between n-hexane and acetone or methanol), room and low temperature fluorescence emission and excitation spectra, and analytical separation and identification by high performance liquid chromatography and comparison with authentic standards. The protochlorophyllide in the plasma membrane could be transformed into chlorophyllide in the dark in vitro by incubating the membrane preparation with NADPH; NADP+ effected the reverse transition.

Light-independent NADPH-protochlorophyllide oxidoreductase activity in purified plasma membrane from the cyanobacterium Anacystis nidulans

A light plasma membrane fraction corresponding to a buoyant density of 1.087 +/- 0.005 g/cm3 and devoid of chlorophyll was prepared and purified from Anacystis nidulans according to a recently published procedure (G.A.Peschek, V.Molitor, M.Trnka, M. Wastyn and W. Erber (1988) Methods Enzymol. 167, 437-449). Besides major amounts of carotenoids the plasma membranes contained a small but significant pool of chlorophyllide a and protochlorophyllide a as verified by room temperature and 77K spectrofluorimetry and analytical separation and identification by high performance liquid chromatography using authentic standards. Incubation of the plasma membranes in strict darkness in the presence of NADPH was accompanied by the gradual and stoichiometric replacement of protochlorophyllide by chlorophyllide, NADP+ effecting the reverse transition. The reaction was completely insensitive to illumination (5-20 w/m2 tungsten light) but abolished after heating of the membranes (90 degrees C, 5 min) or in the presence of 10 mM EGTA, and was specifically stimulated by calcium ions. Our results indicate the occurrence of light-independent NADPH:protochlorophyllide oxidoreductase activity in the plasma membrane of Anacystis nidulans.

Detection of chlorophyllide in chlorophyll-free plasma membrane preparations from Anacystis nidulans

Plasma and thylakoid membranes were isolated and purified from the cyanobacterium Anacystis nidulans. Spectrophotometric examination of acetone extracts gave major absorption bands resulting from carotenoids and chlorophyll a in plasma and thylakoid membranes, respectively. Only a very small absorption peak at 663 nm was detected in acetone extracts of plasma membranes which, in contrast to the corresponding peak from thylakoid membranes, could not be extracted into n-hexane; methanol, on the other hand, was effective with both plasma and thylakoid membranes. Aqueous membrane suspensions excited at 435 nm gave strong fluorescence emission at 662 nm for plasma membranes, but only a very small one for thylakoid membranes which had been adjusted to equal absorbance at 678 nm. Excitation spectra of the 668 nm fluorescence emission peak in acetone extracts of plasma and thylakoid membranes were strikingly different from each other. Finally, high performance liquid chromatography afforded clear-cut preparative separation of the two "chlorophyll-like" pigments in plasma and thylakoid membranes, respectively, and identification by comparison with retention characteristics known from the literature, together with a pure chlorophyll a standard. Our results indicate that the highly fluorescent and polar "chlorophyll-like" pigment in plasma membranes of Anacystis is a chlorophyll precursor, viz. chlorophyllide a.