Imran Haq

Blood fibrinogen as a biomarker of chronic obstructive pulmonary disease

Background Chronic obstructive pulmonary disease (COPD) is a multicomponent condition that is characterised by airflow obstruction that is not fully reversible and is a major global cause of morbidity and mortality. The most widely used marker of disease severity and progression is FEV1. However, FEV1 correlates poorly with both symptoms and other measures of disease progression and thus there is an urgent need for other biological markers to better characterise individuals with COPD. Fibrinogen is an acute phase plasma protein that has emerged as a promising biomarker in COPD. Here we review the current clinical evidence linking fibrinogen with COPD and its associated co-morbidities and discuss its potential utility as a biomarker. Methods Searches for appropriate studies were undertaken on PubMed using search terms fibrinogen, COPD, emphysema, chronic bronchitis, FEV1, cardiovascular disease, exacerbation and mortality. Results There is strong evidence of an association between fibrinogen and the presence of COPD, the presence and frequency of exacerbations and with mortality. Fibrinogen is associated with disease severity but does not predict lung function decline, a measure used as a surrogate for disease activity. The role of fibrinogen in identifying inflammatory co morbidities, particularly cardiovascular disease, remains unclear. Fibrinogen is reduced by p38 mitogen-activated protein kinase inhibitors in individuals with stable disease and by oral corticosteroids during exacerbations. Conclusions Fibrinogen is likely to be a useful biomarker to stratify individuals with COPD into those with a high or low risk of future exacerbations and may identify those with a higher risk of mortality.

Systemic elastin degradation in chronic obstructive pulmonary disease

Background Development of emphysema and vascular stiffness in chronic obstructive pulmonary disease (COPD) may be due to a common mechanism of susceptibility to pulmonary and systemic elastin degradation. Objectives To investigate whether patients with COPD have evidence of systemic elastin degradation in the skin. Methods The authors measured cutaneous elastin degradation using immunohistochemistry (percentage area of elastin fibres) in sun-exposed (exposed) and non-sun-exposed (non-exposed) skin biopsies in 16 men with COPD and 15 controls matched for age and cigarette smoke exposure. Quantitative PCR of matrix metalloproteinase (MMP)-2, -9, -12 and tissue inhibitor of metalloproteinase-1 mRNA and zymography for protein expression of MMP-2 and -9 were performed on homogenised skin. Arterial stiffness and emphysema severity were measured using carotid-femoral pulse wave velocity and quantitative CT scanning. Results Skin elastin degradation was greater in exposed and non-exposed skin of patients with COPD compared with controls (exposed, mean (SD); 43.5 (12.1)% vs 26.3 (6.9)%, p<0.001; non-exposed 22.4 (5.2)% vs 18.1 (4.3)%, p=0.02). Cutaneous expression of MMP-9 mRNA and proMMP-9 concentrations was increased in exposed skin of COPD patients (p=0.004 and p=0.02, respectively) and was also associated with increased skin elastin degradation (r=0.62, p<0.001 and r=0.47, p=0.01, respectively). In the entire cohort of ex-smokers, cutaneous elastin degradation was associated with emphysema severity, FEV1 and pulse wave velocity. Conclusions Patients with COPD have increased skin elastin degradation compared with controls, which is related to emphysema severity and arterial stiffness. Systemic elastin degradation due to increased proteolytic activity may represent a novel shared mechanism for the pulmonary, vascular and cutaneous features of COPD.

Association of MMP-12 polymorphisms with severe and very severe COPD: A case control study of MMPs - 1, 9 and 12 in a European population

BackgroundGenetic factors play a role in chronic obstructive pulmonary disease (COPD) but are poorly understood. A number of candidate genes have been proposed on the basis of the pathogenesis of COPD. These include the matrix metalloproteinase (MMP) genes which play a role in tissue remodelling and fit in with the protease - antiprotease imbalance theory for the cause of COPD. Previous genetic studies of MMPs in COPD have had inadequate coverage of the genes, and have reported conflicting associations of both single nucleotide polymorphisms (SNPs) and SNP haplotypes, plausibly due to under-powered studies.MethodsTo address these issues we genotyped 26 SNPs, providing comprehensive coverage of reported SNP variation, in MMPs- 1, 9 and 12 from 977 COPD patients and 876 non-diseased smokers of European descent and evaluated their association with disease singly and in haplotype combinations. We used logistic regression to adjust for age, gender, centre and smoking history.ResultsHaplotypes of two SNPs in MMP-12 (rs652438 and rs2276109), showed an association with severe/very severe disease, corresponding to GOLD Stages III and IV.ConclusionsThose with the common A-A haplotype for these two SNPs were at greater risk of developing severe/very severe disease (p = 0.0039) while possession of the minor G variants at either SNP locus had a protective effect (adjusted odds ratio of 0.76; 95% CI 0.61 - 0.94). The A-A haplotype was also associated with significantly lower predicted FEV1 (42.62% versus 44.79%; p = 0.0129). This implicates haplotypes of MMP-12 as modifiers of disease severity.

Fungal Recognition Enhances Mannose Receptor Shedding through Dectin-1 Engagement

The mannose receptor (MR) is an endocytic type I membrane molecule with a broad ligand specificity that is involved in both hemostasis and pathogen recognition. Membrane-anchored MR is cleaved by a metalloproteinase into functional soluble MR (sMR) composed of the extracellular domains of intact MR. Although sMR production was initially considered a constitutive process, enhanced MR shedding has been observed in response to the fungal pathogen Pneumocystis carinii. In this work, we have investigated the mechanism mediating enhanced MR shedding in response to fungi. We show that other fungal species, including Candida albicans and Aspergillus fumigatus, together with zymosan, a preparation of the cell wall of Saccharomyces cerevisiae, mimic the effect of P. carinii on sMR production and that this effect takes place mainly through β-glucan recognition. Additionally, we demonstrate that MR cleavage in response to C. albicans and bioactive particulate β-glucan requires expression of dectin-1. Our data, obtained using specific inhibitors, are consistent with the canonical Syk-mediated pathway triggered by dectin-1 being mainly responsible for inducing MR shedding, with Raf-1 being partially involved. As in the case of steady-state conditions, MR shedding in response to C. albicans and β-glucan particles requires metalloprotease activity. The induction of MR shedding by dectin-1 has clear implications for the role of MR in fungal recognition, as sMR was previously shown to retain the ability to bind fungal pathogens and can interact with numerous host molecules, including lysosomal hydrolases. Thus, MR cleavage could also impact on the magnitude of inflammation during fungal infection.

Unravelling the twists and turns of the serpinopathies.

Members of the serine protease inhibitor (serpin) superfamily are found in all branches of life and play an important role in the regulation of enzymes involved in proteolytic cascades. Mutants of the serpins result in a delay in folding, with unstable intermediates being cleared by endoplasmic reticulum‐associated degradation. The remaining protein is either fully folded and secreted or retained as ordered polymers within the endoplasmic reticulum of the cell of synthesis. This results in a group of diseases termed the serpinopathies, which are typified by mutations of α1‐antitrypsin and neuroserpin in association with cirrhosis and the dementia familial encephalopathy with neuroserpin inclusion bodies, respectively. Current evidence strongly suggests that polymers of mutants of α1‐antitrypsin and neuroserpin are linked by the sequential insertion of the reactive loop of one molecule into β‐sheet A of another. The ordered structure of the polymers within the endoplasmic reticulum stimulates nuclear factor‐kappa B by a pathway that is independent of the unfolded protein response. This chronic activation of nuclear factor‐kappa B may contribute to the cell toxicity associated with mutations of the serpins. We review the pathobiology of the serpinopathies and the development of novel therapeutic strategies for treating the inclusions that cause disease. These include the use of small molecules to block polymerization, stimulation of autophagy to clear inclusions and stem cell technology to correct the underlying molecular defect.

Matrix metalloproteinase-12 (MMP-12) SNP affects MMP activity, lung macrophage infiltration and protects against emphysema in COPD

Background Recent genetic and animal studies have implicated matrix metalloproteinase-12 (MMP-12) in the pathogenesis of chronic obstructive pulmonary disease (COPD). It has previously been shown that individuals homozygous for the A/A allele of rs652438 in MMP-12 are over-represented among patients with severe COPD (n=1517). A study was undertaken to examine the functional basis of these findings. Methods rs652438 A and G variants were generated by site-directed mutagenesis and transfected into COS7 cells where they were expressed. Casein zymography and a specific FRET activity assay were used to compare MMP-12 activity between alleles. Cell migration was examined using a transwell assay. Patients from two COPD cohorts were genotyped for rs652438 and associated with inflammatory cell number in bronchoalveolar lavage fluid (n=10) and induced sputum (n=262); the emphysema score (n=1428) was assessed by CT scanning. Results Mean MMP activity was 2.95-fold higher by zymography (p=0.0049) and 3.45-fold higher by FRET assay (p=0.0001) for the A allele than the G allele. Mean migration of COS7 cells expressing the A allele was 2.31-fold greater than for those expressing the G allele (p=0.0001). Macrophage numbers were greater in bronchoalveolar lavage fluid (1.28-fold increase, p=0.033) and induced sputum (1.58-fold increase, p=0.083) of A/A individuals compared with A/G heterozygotes. The presence of the A allele was dose-dependently associated with increased emphysema (p=0.016). Conclusions The rs652438 SNP alters MMP-12 activity with the A allele being more active, which is associated with increased macrophage infiltration and emphysema in the lungs of patients with COPD. These findings further implicate MMP-12 and this SNP in COPD.

Circulating polymers in α1-antitrypsin deficiency

To the Editor: Most individuals carry two wild-type M alleles of the SERPINA1 gene which encodes α1-antitrypsin. 95% of severe deficiency of α1-antitrypsin is associated with the Z allele (Glu342Lys; denoted PiZZ in the homozygote), and with the retention and polymerisation of α1-antitrypsin within hepatocytes [1]. These polymers are contained within periodic acid–Schiff-positive, diastase-resistant inclusions that are associated with neonatal hepatitis, cirrhosis and hepatocellular carcinoma. The concomitant lack of circulating α1-antitrypsin predisposes the Z α1-antitrypsin homozygote to early-onset emphysema. Polymers of α1-antitrypsin form within the lung as a result of local inflammation and exposure to cigarette smoke [2]. They have also been identified in the skin of an individual with α1-antitrypsin deficiency and panniculitis [3] and in a renal biopsy from an individual with α1-antitrypsin deficiency and vasculitis [4]. It is unknown whether these polymers form locally or are deposited in these tissues from a circulating source, and whether extrahepatic polymers are associated with any disease phenotypes. We have assessed whether polymers of α1-antitrypsin are present within serum, from where they originate, and whether they are associated with clinical features in individuals with PiZZ α1-antitrypsin deficiency. In this investigation we used ELISA with the anti-α1-antitrypsin polymer monoclonal antibody (2C1) [5] to assess the presence of polymers in the plasma of 1) 518 individuals with PiZZ α1-antitrypsin deficiency; 2) an individual with α1-antitrypsin deficiency who underwent liver transplantation; and 3) 293 individuals with a mixture of α1-antitrypsin phenotypes. The specificity of the 2C1 antibody was confirmed by using it to immunoprecipitate polymers from the plasma of individuals with and without a positive signal …

A single-chain variable fragment intrabody prevents intracellular polymerization of Z α1-antitrypsin while allowing its antiproteinase activity

Mutant Z α1‐antitrypsin (E342K) accumulates as polymers within the endoplasmic reticulum (ER) of hepatocytes predisposing to liver disease, whereas low levels of circulating Z α1‐antitrypsin lead to emphysema by loss of inhibition of neutrophil elastase. The ideal therapy should prevent polymer formation while preserving inhibitory activity. Here we used mAb technology to identify interactors with Z α1‐antitrypsin that comply with both requirements. We report the generation of an mAb (4B12) that blocked α1‐antitrypsin polymerization in vitro at a 1:1 molar ratio, causing a small increase of the stoichiometry of inhibition for neutrophil elastase. A single‐chain variable fragment (scFv) intrabody was generated based on the sequence of mAb4B12. The expression of scFv4B12 within the ER (scFv4B12KDEL) and along the secretory pathway (scFv4B12) reduced the intracellular polymerization of Z α1‐antitrypsin by 60%. The scFv4B12 intrabody also increased the secretion of Z α1‐antitrypsin that retained inhibitory activity against neutrophil elastase. MAb4B12 recognized a discontinuous epitope probably located in the region of helices A/C/G/H/I and seems to act by altering protein dynamics rather than binding preferentially to the native state. This novel approach could reveal new target sites for small‐molecule intervention that may block the transition to aberrant polymers without compromising the inhibitory activity of Z α1‐antitrypsin.—Ordóñez, A., Pérez, J., Tan, L., Dickens, J. A., Motamedi‐Shad, N., Irving, J. A., Haq, I., Ekeowa, U., Marciniak, S. J., Miranda, E., Lomas, D. A. A single‐chain variable fragment intrabody prevents intracellular polymerization of Z α1‐antitrypsin while allowing its antiproteinase activity. FASEB J. 29, 2667‐2678 (2015). www.fasebj.org

An integrative approach combining ion mobility mass spectrometry, X‐ray crystallography, and nuclear magnetic resonance spectroscopy to study the conformational dynamics of α1‐antitrypsin upon ligand binding

Native mass spectrometry (MS) methods permit the study of multiple protein species within solution equilibria, whereas ion mobility (IM)‐MS can report on conformational behavior of specific states. We used IM‐MS to study a conformationally labile protein (α1‐antitrypsin) that undergoes pathological polymerization in the context of point mutations. The folded, native state of the Z‐variant remains highly polymerogenic in physiological conditions despite only minor thermodynamic destabilization relative to the wild‐type variant. Various data implicate kinetic instability (conformational lability within a native state ensemble) as the basis of Z α1‐antitrypsin polymerogenicity. We show the ability of IM‐MS to track such disease‐relevant conformational behavior in detail by studying the effects of peptide binding on α1‐antitrypsin conformation and dynamics. IM‐MS is, therefore, an ideal platform for the screening of compounds that result in therapeutically beneficial kinetic stabilization of native α1‐antitrypsin. Our findings are confirmed with high‐resolution X‐ray crystallographic and nuclear magnetic resonance spectroscopic studies of the same event, which together dissect structural changes from dynamic effects caused by peptide binding at a residue‐specific level. IM‐MS methods, therefore, have great potential for further study of biologically relevant thermodynamic and kinetic instability of proteins and provide rapid and multidimensional characterization of ligand interactions of therapeutic interest.

Increased ERK signalling promotes inflammatory signalling in primary airway epithelial cells expressing Z α1-antitrypsin

Overexpression of Z α1-antitrypsin is known to induce polymer formation, prime the cells for endoplasmic reticulum stress and initiate nuclear factor kappa B (NF-κB) signalling. However, whether endogenous expression in primary bronchial epithelial cells has similar consequences remains unclear. Moreover, the mechanism of NF-κB activation has not yet been elucidated. Here, we report excessive NF-κB signalling in resting primary bronchial epithelial cells from ZZ patients compared with wild-type (MM) controls, and this appears to be mediated by mitogen-activated protein/extracellular signal-regulated kinase, EGF receptor and ADAM17 activity. Moreover, we show that rather than being a response to protein polymers, NF-κB signalling in airway-derived cells represents a loss of anti-inflammatory signalling by M α1-antitrypsin. Treatment of ZZ primary bronchial epithelial cells with purified plasma M α1-antitrypsin attenuates this inflammatory response, opening up new therapeutic options to modulate airway inflammation in the lung.