Background Tiotropium has been shown to improve lung function, quality of life, and exacerbations and reduce mortality when compared with placebo in COPD. It remains unclear whether benefits are seen ...when tiotropium is used in conjunction with inhaled corticosteroids (ICSs) plus long-acting β-agonists (LABAs). Methods We performed a retrospective cohort study using a National Health Service database of patients with COPD in Tayside, Scotland, between 2001 and 2010 that is linked with databases regarding hospital admissions, pharmacy prescriptions, and death registries. The impact of the addition of tiotropium (Tio) to ICS + LABA therapy on all-cause mortality, hospital admissions for respiratory disease, and emergency oral corticosteroid bursts was evaluated. Adjusted hazard ratios (HRs) were calculated by Cox regression after inclusion of the following covariates: cardiovascular and respiratory disease, diabetes, smoking, age, sex, and deprivation index. Results A total of 1,857 patients were given ICS + LABA + Tio, and 996 were given ICS + LABA. Mean follow-up was 4.65 years. The adjusted HR for all-cause mortality for ICS + LABA + Tio vs ICS + LABA was 0.65 (95% CI, 0.57-0.75; P < .001). Adjusted HRs for hospital admissions and oral corticosteroid bursts were 0.85 (95% CI, 0.73-0.99; P = .04) and 0.71 (95% CI, 0.63-0.80; P < .001), respectively. Conclusions The study suggests that the addition of tiotropium to ICSs and LABA therapy may confer benefits in reducing all-cause mortality, hospital admissions, and oral corticosteroid bursts in patients with COPD. Triple therapy is widely used in the real-life management of COPD, with only limited scientific support. The study supports the use of triple therapy in COPD and provides a platform for randomized controlled trials specifically addressing this topic.
•Discordant SHBG measurement was investigated by multiple ELISAs.•Discordance not due to heterophile antibodies.•SHBG affected by glycan removal and modification.•Glycosylation may influence SHBG ...immunoassays.
A discordance between sex hormone-binding globulin (SHBG) measurements by 2-site ELISAs was investigated using pairings of various “in house” SHBG antibodies together with a concordant control. The 2-site monoclonal ELISAs used the same base coat (11F11) and discordance was observed with one top coat monoclonal antibody (7H9) and also when a polyclonal SHBG antibody was paired with the basecoat antibody (11F11). Sialidase treatment of the discordant sample and purified SHBG revealed increased levels using 7H9 whereas there was no change in SHBG in the concordant sample. Conversely, following sialidase treatment, the discordant sample showed no change in SHBG measured using the other monoclonal antibody pairings whereas the SHBG levels in the concordant sample declined following sialidase using the same monoclonal antibody pairings. This implicated glycosylation as a factor in antibody recognition and synthetic peptides spanning the two N-linked and one O-linked glycosylation regions showed that SHBG recognition by monoclonal antibody 7H9 could be disrupted by a peptide spanning the O-linked glycosylation site. Hence rather than immunoassay discordance being attributed to heterophile antibodies or other circulating antibodies here it can be likely attributed to glycosylation affecting antibody recognition and hence the measurement of SHBG.
Calprotectin, the major neutrophil protein, is a critical alarmin that modulates inflammation and plays a role in host immunity by strongly binding trace metals essential for bacterial growth. It has ...two cysteine residues favourably positioned to act as a redox switch. Whether their oxidation occurs in vivo and affects the function of calprotectin has received little attention. Here we show that in saliva from healthy adults, and in lavage fluid from the lungs of patients with respiratory diseases, a substantial proportion of calprotectin was cross-linked via disulfide bonds between the cysteine residues on its S100A8 and S100A9 subunits. Stimulated human neutrophils released calprotectin and subsequently cross-linked it by myeloperoxidase-dependent production of hypochlorous acid. The myeloperoxidase-derived oxidants hypochlorous acid, taurine chloramine, hypobromous acid, and hypothiocyanous acid, all at 10 μM, cross-linked calprotectin (5 μM) via reversible disulfide bonds. Hypochlorous acid generated A9-A9 and A8-A9 cross links. Hydrogen peroxide (10 μM) did not cross-link the protein. Purified neutrophil calprotectin existed as a non-covalent heterodimer of A8/A9 which was converted to a heterotetramer - (A8/A9)
- with excess calcium ions. Low level oxidation of calprotectin with hypochlorous acid produced substantial proportions of high order oligomers, whether oxidation occurred before or after addition of calcium ions. At high levels of oxidation the heterodimer could not form tetramers with calcium ions, but prior addition of calcium ions afforded some protection for the heterotetramer. Oxidation and formation of the A8-A9 disulfide cross link enhanced calprotectin's susceptibility to proteolysis by neutrophil proteases. We propose that reversible disulfide cross-linking of calprotectin occurs during inflammation and affects its structure and function. Its increased susceptibility to proteolysis will ultimately result in a loss of function.
Objective
To identify risk alleles relevant to the causal and biologic mechanisms of antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV).
Methods
A genome‐wide association study ...and subsequent replication study were conducted in a total cohort of 1,986 cases of AAV (patients with granulomatosis with polyangiitis Wegener's GPA or microscopic polyangiitis MPA) and 4,723 healthy controls. Meta‐analysis of these data sets and functional annotation of identified risk loci were performed, and candidate disease variants with unknown functional effects were investigated for their impact on gene expression and/or protein function.
Results
Among the genome‐wide significant associations identified, the largest effect on risk of AAV came from the single‐nucleotide polymorphism variants rs141530233 and rs1042169 at the HLA–DPB1 locus (odds ratio OR 2.99 and OR 2.82, respectively) which, together with a third variant, rs386699872, constitute a triallelic risk haplotype associated with reduced expression of the HLA–DPB1 gene and HLA–DP protein in B cells and monocytes and with increased frequency of complementary proteinase 3 (PR3)–reactive T cells relative to that in carriers of the protective haplotype. Significant associations were also observed at the SERPINA1 and PTPN22 loci, the peak signals arising from functionally relevant missense variants, and at PRTN3, in which the top‐scoring variant correlated with increased PRTN3 expression in neutrophils. Effects of individual loci on AAV risk differed between patients with GPA and those with MPA or between patients with PR3‐ANCAs and those with myeloperoxidase‐ANCAs, but the collective population attributable fraction for these variants was substantive, at 77%.
Conclusion
This study reveals the association of susceptibility to GPA and MPA with functional gene variants that explain much of the genetic etiology of AAV, could influence and possibly be predictors of the clinical presentation, and appear to alter immune cell proteins and responses likely to be key factors in the pathogenesis of AAV.
•The reactive centre loop of human corticosteroid-binding globulin (CBG) is cleaved by chymotrypsin.•Cleavage is rapid and total CBG levels are unaffected.•Following cleavage cortisol is ...released.•This is a new mechanism for cortisol release from its binding globulin.
Corticosteroid-binding globulin (CBG) binds more than 90% of circulating cortisol and is a non-inhibitory member of the family of serine protease inhibitors (SERPINS) with an exposed elastase sensitive reactive centre loop (RCL). At sites of inflammation neutrophil activation can release elastase which may cleave the RCL and result in cortisol release from CBG. The RCL sequence also has two theoretical chymotrypsin cleavage sites and we used a monoclonal antibody with specificity for the RCL to investigate chymotrypsin cleavage of CBG. Here we show, for the first time, rapid chymotrypsin cleavage of the RCL of CBG, resulting in undetectable levels of intact CBG, whereas total CBG levels were unchanged. Coincident with both chymotrypsin and elastase cleavage there was an increase in the free cortisol fraction of serum to levels similar to when CBG had been inactivated by heat indicating total cortisol release from CBG. These findings demonstrate a new mechanism for cortisol release from its binding globulin.
The measurement of vitamin D-binding protein (VDBP) by immunoassay has been confounded by variable antibody recognition of the Gc1s, Gc1F and Gc2 phenotypes. This has led to spurious conclusions ...regarding vitamin D status in different ethnic groups. In order to overcome these problems there is a requirement for VDBP antibodies that are unaffected by phenotype status. Here we report the generation and testing of three monoclonal antibodies to VDBP which recognise linear epitopes and are unaffected by vast molar excesses of synthetic peptides spanning these phenotypic domains. These IgG1 kappa antibodies were purified and biotinylated to allow suitable pairings to develop a sandwich ELISA for circulating VDBP. The VDBP ELISA is unaffected by actin and confirms that VDBP levels are significantly reduced in sepsis patients and non-sepsis intensive care patients compared to normal healthy subjects. Levels of VDBP along with total 25OH vitamin D3 can be used to calculate free 25OH vitamin D3 levels and these compare well with consensus values determined independently. The VDBP ELISA meets acceptable performance criteria and as such can be used in conjunction with total 25OH vitamin D3 to determine the free 25OH vitamin D3 status in various cohorts.
•A monoclonal antibody 2-sites ELISA for vitamin D-binding protein is described.•The ELISA is unaffected by common phenotype peptides and actin.•Lower levels are shown in sepsis and ICU patients.•Calculated free vitamin D correlate with levels measured directly.
In normal plasma free cortisol accounts for less than 6% of the total with 80–90% bound to corticosteroid-binding globulin (CBG) and the remainder associated albumin. However little is known about ...the distribution of free cortisol in plasma where CBG is inactivated or in congenital CBG deficiency.
Here we describe ligand binding experiments revealing that while free cortisol in unstressed individuals is less than 6% of total cortisol this rises markedly to 25% when CBG is totally inactivated by heat. Similar elevations of the free cortisol fraction were noted in a patient with a rare genetically determined complete lack of CBG (mean 32% on frequent circadian sampling). Following heat inactivation of CBG or in the congenital absence of CBG, there is a shift in cortisol binding from CBG to albumin. That this shift occurs is further supported by experiments adding
3H-cortisol to physiological human serum albumin solutions, where 25% of cortisol remained in the free fraction.
Taken together the data provide strong evidence that when CBG is inactivated or congenitally absent then more than 25% of the total cortisol appears in the free fraction with the remainder associated with albumin. The proportion of free cortisol measured in plasma thus reflects a simple measure of functional corticosteroid-binding globulin.
The predominant carrier of cortisol in circulation is corticosteroid-binding globulin (CBG) which is a non-functional member of the family of serine protease inhibitors. Corticosteroid-binding ...globulin possesses an exposed elastase sensitive loop and upon cleavage it adopts a “relaxed” conformation promoting the delivery of cortisol to sites of inflammation. Recently we have developed monoclonal antibodies which recognise only the intact exposed elastase loop, including an N-glycosylation site, which, in concert with another monoclonal antibody to CBG, offered the potential for the determination of intact and total CBG which may both be present in circulation. Here we validate these parallel ELISAs and show that like total CBG there is little diurnal variation of intact plasma CBG. Furthermore in a normal reference population the majority of CBG is in the intact or active form but a significant level of apparently cleaved CBG is evident. In some subjects there is gross discordance between total CBG and intact CBG implying a predominance of apparently cleaved CBG in circulation and this significantly affects calculated free cortisol levels. Gross differences in total and intact CBG levels may not be due to differences in N-glycosylation affecting antibody binding as CBG levels are unaffected by PNGase F treatment.
► ELISAs measure both total and intact or “active” CBG in plasma ► These can be used to study CBG structure and function ► Active CBG may comprise 65–70% of total CBG in normal subjects ► There is no diurnal variation of intact or “active” CBG
Supplementation provides the best means of improving vitamin D status; however, individual responses vary partly owing to genetics. The aim of this study was to determine whether 28 single nucleotide ...polymorphisms (SNPs) in six key vitamin D pathway genes (GC, DHCR7, CYP2 R1, CYP24 A1, CYP27 B1, VDR) were associated with differences in response to supplementation.
Participants (N = 313; n = 160 vitamin D, n = 153 placebo) were part of VIDARIS (Vitamin D and Acute Respiratory Infections Study), a double-blind, randomized controlled trial involving oral monthly supplementation of either vitamin D
(200 000 IU each for the first 2 mo, thereafter 100 000 IU monthly) or placebo for 18 mo. Circulating 25-hydroxyvitamin D (25OHD) concentrations at baseline and 2, 6, 12, and 18 mo, and vitamin D binding protein (Gc-globulin) and calculated free 25(OH)D concentrations at baseline and 2 mo were obtained. Multiple regression was used to model associations between genetic variants and 25(OH)D, Gc-globulin, and free 25(OH)D concentrations.
SNPs within GC, CYP2 R1, and CYP27 B1 were associated with 25(OH)D concentrations following supplementation. However, only two GC gene SNPs (rs2282679, rs1155563) were significant after adjustment for multiple testing. This effect disappeared after more than 2 mo of supplementation. None of the SNPs were significantly associated with Gc-globulin concentrations; however, there was a significant interaction with one SNP in DHCR7 (rs12785878), which was associated with reduced free 25(OH)D concentrations in the supplemented arm.
Only variants of GC were associated with 25(OH)D concentrations after supplementation. This effect was modest and disappeared after >2 mo of supplementation, suggesting it may be time/dose-dependent and saturable.
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