Purification of human haptoglobin 1-1, 2-1, and 2-2 using monoclonal antibody affinity chromatography

Tangential flow filtration of haptoglobin

Haptoglobin (Hp) is a plasma glycoprotein that scavenges cell-free hemoglobin (Hb). Hp has various potential therapeutic applications, but it has been mainly studied for treatment of acute hemolytic conditions that can arise from situations such as massive blood transfusion, infusion of stored red blood cells, severe burns, trauma, sepsis, radiation injury, and others. Therefore, Hp may also be beneficial during chronic hemolytic disease states such as hereditary spherocytosis, nocturnal hemoglobinuria, sickle-cell anemia, and malaria. Various methods have been developed to purify Hp from plasma or plasma fractions. However, none of these methods have exploited the large molecular weight (MW) range distribution of Hp polymers to easily isolate Hp from other plasma proteins. The present study used tangential flow filtration (TFF) to isolate polymeric Hp from plasma proteins using human Fraction IV (FIV) as the starting material. After removal of insoluble material from a suspension of FIV paste, the protein mixture was clarified on a 0.2 μm hollow fiber (HF) TFF filter. The clarified protein solution was then bracketed based on protein MW using HF filters with MW cut-offs (MWCOs) of 750, 500, and 100 kDa. Using untreated FIV, the Hp purity of the main bracket was ~75% with a total Hb binding capacity (HbBC) yield of 1.2 g starting from 500 g of FIV paste. However, pretreatment of FIV with fumed silica to remove lipoproteins increased Hp purity to >95% with a HbBC yield of 1.7 g per 500 g of FIV. Taken together this study provides a novel and scalable method to purify Hp from plasma or plasma fractions.

Haptoglobin phenotype influences the effectiveness of diet-induced weight loss in middle-age abdominally obese women with metabolic abnormalities

BACKGROUND & AIMS

Haptoglobin (Hp) is associated with risks of obesity and cardiometabolic dysfunction; however, the role of the Hp phenotype in diet-induced weight loss remains to be elucidated. This study investigated whether the Hp phenotype contributes to inter-individual variations in body weight reduction as well as changes in the metabolic profile.

METHODS

Secondary data analysis from a randomized controlled trial. In total, 151 abdominally obese Taiwanese women with ≥2 metabolic components were randomized to each of four dietary programs [calorie restriction (CR), calorie restriction plus fish oil supplementation (CRF), calorie restricted meal replacement (CRMR), and calorie restricted meal replacement with fish oil supplementation (CRMRF)] for 12 weeks. Abdominal obesity was defined as a waist circumference (WC) ≥ 80 cm in women. Hp phenotyping was performed by plasma gel electrophoresis.

RESULTS

The prevalence of the Hp 1-1, 2-1, and 2-2 phenotypes were 12.58%, 41.06% and 46.35%, respectively. The mean age was 50.59 ± 12.22 years, and mean reduction in the percent body weight was 4.7% ± 3.8%. The Hp 1-1 phenotype exhibited significant decreases in the WC, body fat mass, plasma insulin levels, free hemoglobin and homeostatic model assessment of insulin resistance (HOMA-IR) compared to the Hp 2-1 or Hp 2-2 phenotypes after adjusting for the baseline age, WC, metabolic syndrome (MetS), and dietary programs (all adjusted p < 0.05). A greater improvement in the prevalence of central obesity and, to a lesser extent, MetS was also found in women with the Hp 1-1 phenotype.

CONCLUSIONS

Obese women with the Hp 1-1 phenotype might obtain greater benefits in terms of reducing abdominal fat and improving insulin sensitivity in response to hypocaloric diet-induced weight reduction. The findings from this study support potential gene-diet interactions affecting weight loss. This trial was registered at ClinicalTrials.gov as NCT01768169.

CLINICAL TRIAL REGISTRY

This trial was registered at ClinicalTrials.gov as NCT01768169.

Relationships of Haptoglobin Phenotypes with Systemic Inflammation and the Severity of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is caused by chronic inflammation. Many inflammatory mediators induce the low grade systemic inflammation of COPD. Haptoglobin (Hp) is synthesized in the liver and by lung epithelial and alveolar macrophage cells. However, associations of the serum concentration and phenotype of Hp with COPD are unclear. Therefore, we explored the association of the Hp concentration and Hp phenotype with the inflammatory response and COPD disease severity. We included healthy subjects and COPD patients. The Hp phenotype was categorized by SDS native-PAGE, and concentrations were determined by ELISA. In this trial Hp concentrations in COPD groups were significantly higher than those in healthy controls. There was a significant negative correlation between the Hp concentration and FEV₁(%) (p < 0.001), while IL-6 and 8-isoprostane were positively correlated with the Hp concentration. As to the Hp phenotype, there were significant negative correlations between the FEV₁ and both Hp2-1 and Hp2-2; IL-6 and 8-isoprostane were significantly positively correlated with Hp2-1 and Hp2-2. The ROC curve analysis of the Hp concentration was significantly higher than CRP. Hp concentrations and phenotype were positively correlated with the severity of COPD, especially Hp2-2. In the future, Hp can be considered a novel biomarker for identifying COPD.

Plasma haptoglobin level can augment NT-proBNP to predict poor outcome in patients with severe acute decompensated heart failure

To evaluate the use of plasma haptoglobin (Hp) levels and N-terminal pro-B-type natriuretic peptide (NT-proBNP) in predicting survival in patients with severe acute decompensated heart failure (AHF). Management of AHF is challenging. Identifying markers associated with patient prognosis in this disease is clinically important. In this prospective observational study, plasma Hp and NT-proBNP levels were measured. Receiver operating characteristic (ROC) curves were used to identify cut-offs of Hp and NT-proBNP with the greatest specificity and sensitivity for predicting overall survival and cardiovascular-related survival. The cut-off values were tested in patients with AHF (n=41). The cut-off value with the greatest specificity and sensitivity with respect to overall survival and for cardiovascular-related survival for Hp was 177. 1 ng/mL for both outcomes and for NT-proBNP was 34 246.0 pg/mL and 11 848.5 ng/mL, respectively. Using these cut-off values, this study found that patients with lower baseline Hp levels (<177. 1 ng/mL) or higher baseline NT-proBNP (≥34 246 pg/mL) were more likely to have shorter overall survival. Similarly, patients with <177. 1 ng/mL of Hp and ≥11 848.5 pg/mL of NT-proBNP had the highest risk of death related to cardiovascular disease. Our findings indicate that Hp and NT-proBNP using specific cut-off values for AHF can be used to determine risk of survival in these patients.

Elevated Plasma Haptoglobin Level as a Potential Marker for Poor Prognosis in Acute Cerebral Infarction

Background: Relationship between peripheral circulation concentration of haptoglobin (Hp) and risk of cerebrovascular disease has not been well investigated so far. The aim of the study was to reveal the prognostic significance of Hp on acute cerebral infarction. Methods: A total of 200 patients with acute cerebral infarction and 200 controls were included. Research data were collected from their medical records. Blood samples were obtained on admission. Hp phenotyping was performed using a native polyacrylamide gel electrophoresis. Plasma Hp levels were determined using enzyme-linked immunosorbent assays. The patients were followed up yearly, and endpoint was overall death. Results: Plasma levels of Hp were significantly elevated in the patients than in the controls (p < 0.001). Three-year overall death in the follow-up period was associated with the high plasma level of Hp (Hazard ratio [HR] 2.33, 95% CI 1.74–3.12). But, 3-year overall death was not related to Hp phenotyping (Hp 2–1 vs. 1–1: HR 1.07, 95% CI 0.66–1.73; Hp 2–2 vs. 1–1: HR 1.08, 95% CI 0.67–1.74). Conclusion: Peripheral circulation concentration of Hp might be an independent prognostic factor for acute cerebral infarction. But there was no relationship between Hp phenotyping and prognosis in this disease.

Higher post-acute myocardial infarction plasma haptoglobin level is associated with poor long-term overall survival

AIM

To evaluate the association of post-acute myocardial infarction (AMI) plasma haptoglobin (Hp) levels with long-term overall survival in AMI patients.

METHODS AND RESULTS

Patients who were diagnosed of AMI were recruited and their Hp phenotypes and plasma levels were determined. According to previously reported cutoff point for Hp level (288.4ng/ml), patients were classified as higher Hp group (>288.4ng/ml) and lower Hp group (≤288.4ng/ml). The primary outcome was overall survival. This study recruited and followed a total of 117 patients for a median of 11.0 (3.2-17.6) years. Higher Hp group had 46 patients (39.3%) and lower Hp group had 71 patients (60.7%). Twelve patients had Hp 1-1 (10.3%), 50 with Hp 2-1 (42.7%), and 55 with Hp 2-2 (47.0%). The lower Hp group had significantly better overall survival (174.1 [51.6-212.5] vs. 106.5 [22.2-209.1], P=0.037). There was no significant difference in overall survival between the three phenotype groups (P=0.477). Multivariate regression analysis revealed that increased age (adjusted HR=1.06, 95% CI: 1.03-1.10, P<0.001) and higher Hp level (adjusted HR=1.65, 95%=1.02-2.67, P=0.040) were significantly associated with poor overall survival.

CONCLUSION

Higher post-AMI plasma Hp level was independently associated with poor overall survival in AMI patients. No significant difference in overall survival was noted between three Hp phenotype groups. Acute phase Hp level might reflect the severity of oxidative stress during inflammation process.

Plasma haptoglobin concentrations are elevated in patients with coronary artery disease

Inflammation underlies the development and progression of coronary artery plaques. Haptoglobin (Hp) is an acute phase protein, the synthesis of which is increased during inflammation. The aim of this study was to investigate plasma Hp concentrations and phenotype in patients with coronary artery disease (CAD). We recruited 359 patients with fixed luminal stenosis ≥50% in at least one coronary artery (CAD group) and 83 patients with luminal stenosis ≤40%, normal ejection fraction, and normal regional wall motion (control group). Plasma Hp concentrations were measured using a phenotype-specific enzyme-linked immunosorbent assay. Hp phenotype was determined by native polyacrylamide gel electrophoresis. Plasma lipid concentrations were measured. Plasma Hp concentrations were significantly higher in the CAD compared with the control group (262.4±144.2 vs 176.0±86.7 ng/mL, P<0.001); however, there was no between group difference in the distribution of Hp phenotype (1-1 = 7.5% vs 7.2%; 2-1 = 40.4% vs 42.2%; 2-2 = 52.1% vs 50.6%). Stepwise multivariate logistic regression revealed that high Hp concentrations (odds ratio [OR] = 5.865), male sex (OR = 3.689), hypertension (OR = 2.632), diabetes mellitus (OR = 3.300), and low-density lipoprotein concentrations (OR = 1.480) were independently associated with CAD (all P<0.05). Hp phenotype was not associated with CAD. Plasma Hp concentrations were significantly correlated with the severity of luminal stenosis (r = 0.236, P<0.001). Our findings suggest that plasma Hp concentrations may be elevated in patients with CAD. There does not appear to be any relationship between Hp phenotype and CAD.

Selection of genes for gene-environment interaction studies: a candidate pathway-based strategy using asthma as an example

BACKGROUND

The identification of gene by environment (GxE) interactions has emerged as a challenging but essential task to fully understand the complex mechanism underlying multifactorial diseases. Until now, GxE interactions have been investigated by candidate approaches examining a small number of genes, or agnostically at the genome wide level.

PRESENTATION OF THE HYPOTHESIS

In this paper, we propose a gene selection strategy for investigation of gene-environment interactions. This strategy integrates the information on biological processes shared by genes, the canonical pathways to which they belong and the biological knowledge related to the environment in the gene selection process. It relies on both bioinformatics resources and biological expertise.

TESTING THE HYPOTHESIS

We illustrate our strategy by considering asthma, tobacco smoke as the environmental exposure, and genes sharing the same biological function of "response to oxidative stress". Our filtering strategy leads to a list of 28 pathways involving 182 genes for further GxE investigation.

IMPLICATIONS OF THE HYPOTHESIS

By integrating the environment into the gene selection process, we expect that our strategy will improve the ability to identify the joint effects and interactions of environmental and genetic factors in disease.

Different genes interact with particulate matter and tobacco smoke exposure in affecting lung function decline in the general population

BACKGROUND

Oxidative stress related genes modify the effects of ambient air pollution or tobacco smoking on lung function decline. The impact of interactions might be substantial, but previous studies mostly focused on main effects of single genes.

OBJECTIVES

We studied the interaction of both exposures with a broad set of oxidative-stress related candidate genes and pathways on lung function decline and contrasted interactions between exposures.

METHODS

For 12679 single nucleotide polymorphisms (SNPs), change in forced expiratory volume in one second (FEV(1)), FEV(1) over forced vital capacity (FEV(1)/FVC), and mean forced expiratory flow between 25 and 75% of the FVC (FEF(25-75)) was regressed on interval exposure to particulate matter <10 µm in diameter (PM10) or packyears smoked (a), additive SNP effects (b), and interaction terms between (a) and (b) in 669 adults with GWAS data. Interaction p-values for 152 genes and 14 pathways were calculated by the adaptive rank truncation product (ARTP) method, and compared between exposures. Interaction effect sizes were contrasted for the strongest SNPs of nominally significant genes (p(interaction)<0.05). Replication was attempted for SNPs with MAF>10% in 3320 SAPALDIA participants without GWAS.

RESULTS

On the SNP-level, rs2035268 in gene SNCA accelerated FEV(1)/FVC decline by 3.8% (p(interaction) = 2.5×10(-6)), and rs12190800 in PARK2 attenuated FEV1 decline by 95.1 ml p(interaction) = 9.7×10(-8)) over 11 years, while interacting with PM10. Genes and pathways nominally interacting with PM10 and packyears exposure differed substantially. Gene CRISP2 presented a significant interaction with PM10 (p(interaction) = 3.0×10(-4)) on FEV(1)/FVC decline. Pathway interactions were weak. Replications for the strongest SNPs in PARK2 and CRISP2 were not successful.

CONCLUSIONS

Consistent with a stratified response to increasing oxidative stress, different genes and pathways potentially mediate PM10 and tobacco smoke effects on lung function decline. Ignoring environmental exposures would miss these patterns, but achieving sufficient sample size and comparability across study samples is challenging.

Proteomic analysis of plasma samples from patients with acute myocardial infarction identifies haptoglobin as a potential prognostic biomarker

Prognosis of clinical outcome following myocardial infarction is variable and difficult to predict. We have analyzed the plasma proteome of thirty patients with acute myocardial infarction to search for new prognostic biomarkers. Proteomic analyses of blood samples were performed by 2-D-DiGE after plasma depletion of albumin and immunoglobulins G. New York Heart Association (NYHA) class determined at 1-year follow-up was used to identify patients with heart failure. Principal component analysis and hierarchical clustering of proteomic data revealed that patients could be separated into 3 groups. The 22 differentially expressed proteins involved in this grouping were identified as haptoglobin (Hp) and respective isoforms. The 3 groups of patients had distinct Hp isoforms: patients from group 1 had the α1-α1, patients from group 2 the α2-α1, and patients from group 3 the α2-α2 genotype. This classification was also associated with different total plasma levels of Hp. The presence of the α2 genotype and low plasma levels of Hp was associated with a higher NYHA class and therefore with a detrimental functional outcome after myocardial infarction. A plasma level of Hp below 1.4g/L predicted the occurrence of heart failure (NYHA 2, 3, 4) at 1-year with 100% sensitivity.

A dual-functional E. coli vector for expressing recombinant protein with high solubility and antigen presentation ability

A dual-functional Escherichia coli expression vector capable of producing soluble recombinant proteins with high immunogenicity in animals is introduced. This vector expresses polypeptides fused to a PTD-J-domain peptide. The J-domain peptide is derived from murine Hsp40 by using optimized codons for E. coli. The association of the J-domain to the nucleotide binding domain of the DnaK chaperone increases the probability that the fused polypeptide will be folded by the DnaK and hence increases the solubility of the recombinant protein. The PTD-J-domain can also enhance the immunogenicity of the fused chicken IGF-I polypeptide as well as an oligo-peptide derived from haptoglobin in rodents, possibly via the association with either the extracellular or intracellular Hsp70 proteins.

Evidence of tandem repeat and extra thiol-groups resulted in the polymeric formation of bovine haptoglobin: a unique structure of Hp 2-2 phenotype

Human plasma Hp is classified as 1-1, 2-1, and 2-2. They are inherited from two alleles Hp 1 and Hp 2, but there is only Hp 1 in almost all the animal species. Hp 2-2 molecule is extremely large and heterogeneous associated with the development of inflammatory-related diseases. In this study, we expressed entire bovine Hp in E. coli as a alphabeta linear form. Interestingly, the antibodies prepared against this form could recognize the subunit of native Hp. In stead of a complicated column method, the antibody was able to isolate bovine Hp via immunoaffinity and gel-filtration columns. The isolated Hp is polymeric containing two major molecular forms (660 and 730 kDa). Their size and hemoglobin binding complex are significantly larger than that of human Hp 2-2. The amino-acid sequence deducted from the nucleotide sequence is similar to human Hp 2 containing a tandem repeat over the alpha chain. Thus, the Hp 2 allele is not unique in human. We also found that there is one additional -SH group (Cys-97) in bovine alpha chain with a total of 8 -SH groups, which may be responsible for the overall polymeric structure that is markedly different from human Hp 2-2. The significance of the finding and its relationship to structural evolution are also discussed.

Immunochemical property of human haptoglobin phenotypes: determination of plasma haptoglobin using type-matched standards

OBJECTIVES

Haptoglobin (Hp) phenotypes 1-1, 2-1, and 2-2 are associated with inflammatory diseases. Since their biochemical structures are rather heterogeneous, it is necessary to accurately determine the plasma Hp levels.

DESIGN AND METHODS

Immunodiffusion, immunoturbidimetric, and noncompetitive ELISA were conducted to determine the differences in immunoreactivity among Hp phenotypes and to verify that such difference may significantly affect the outcome of Hp determinations. A novel ELISA using phenotype-matched calibrators was performed to compared with a commercial GenWay ELISA kit using a single calibrator in normal healthy males.

RESULTS

In immunodiffusion and immunoturbidimetric assays, the immunoreactivity of Hp 1-1 was markedly higher than 2-1 and 2-2, while an opposite result was observed using an ELISA. The latter was primarily due to the repeated antigenic epitopes in polymeric 2-1 and 2-2. Thus, Hp levels could be significantly over- or underestimated depending on the method. An accurate ELISA could be achieved when using each type-specific Hp calibrator matched to each type subject. We show the mean levels of Hp 1-1 subjects (n=16; 184+/-42 mg/dL) to be significantly and differentially greater than 2-1 (n=28; 153+/-55 mg/dL) (p<0.05) and 2-2 (n=24; 93+/-54 mg/dL) (p<0.01) subjects.

CONCLUSIONS

Due to the diverse immunochemical structure among the Hp types, phenotyping should be performed in all the patients and a type-matched Hp calibrator should be used in clinical Hp determination.

Antioxidant nature of bovine milk beta-lactoglobulin

Heating is necessary for processing milk in the dairy industry, which evidently produces a conformational change in beta-lactoglobulin (beta-LG). beta-Lactoglobulin, a major protein that accounts for approximately 10 to 15% of total milk proteins, is a globular protein consisting of 162 AA with a relative molecular mass of 18.4 kDa. The purpose of the present study was to determine the antioxidant role of beta-LG in milk and the possible mechanism involved. We showed that beta-LG is a mild antioxidant whose potency is less than that of vitamin E and probucol (the latter being an antioxidant used for clinical therapy). The conversion of the beta-LG monomer to dimer was responsible, in part, for the mode of action in protecting low-density lipoproteins against copper-induced oxidation. Cross-linking the free thiol groups of beta-LG by heating (100 degrees C for 2 min), or chemically modifying the beta-LG by carboxymethylation to block the thiol groups resulted in a substantial loss of antioxidant activity. The data suggest that Cys-121 plays an essential role in the antioxidant nature of beta-LG. By using an anti-LG antibody affinity column to deplete the beta-LG from milk, we observed from the lost antioxidant activity that beta-LG contributes approximately 50% of the total activity. Because beta-LG is extremely sensitive to thermal denaturation, to maintain its antioxidant nature, dairy products consumed daily should not be overheated in order to maintain its antioxidant nature.

Cloning and expression of human haptoglobin subunits in Escherichia coli: Delineation of a major antioxidant domain

Human plasma haptoglobin (Hp) comprises alpha and beta subunits. The alpha subunit is heterogeneous in size, therefore isolation of Hp and its subunits is particularly difficult. Using Escherichia coli, we show that alpha1, alpha2, beta, and alpha2beta chain was abundantly expressed and primarily present in the inclusion bodies consisting of about 30% of the cell-lysate proteins. Each cloned subunit retained its immunoreactivity as confirmed using antibodies specific to alpha or beta chain. By circular dichroism, the structure of each expressed subunit was disordered as compared to the native Hp. The antioxidant activity was found to be associated with both alpha and beta chains when assessed by Cu(2+)-induced oxidation of low density lipoprotein (LDL). Of remarkable interest, the antioxidant activity of beta chain was extremely potent and markedly greater than that of native Hp (3.5x), alpha chain (10x) and probucol (15x). The latter is a clinically proved potent compound used for antioxidant therapy. The "unrestricted" structure of beta subunit may therefore render its availability for free-radical scavenge, which provides a utility for the future design of a "mini-Hp" in antioxidant therapy. It may also provide a new insight in understanding the mechanism involved in the antioxidant nature of Hp.

Circulating haptoglobin is an independent prognostic factor in the sera of patients with epithelial ovarian cancer

OBJECTIVE

This study was conducted to evaluate the prognostic significance of haptoglobin levels in the overall survival of patients presenting with various stages of epithelial ovarian cancer.

MATERIALS AND METHODS

We employed an in-house sandwich enzyme-linked immunosorbent assay method to determine the concentrations of preoperative haptoglobin and C-reactive protein (CRP) in sera samples obtained from 66 malignant tumors, 60 benign tumors, and 10 normal healthy women.

RESULTS

Levels of serum haptoglobin significantly correlated with tumor type (P < .001) and International Federation of Gynecology and Obstetrics stage (P < .05). A significant correlation was observed between clinical stage and patient survival (r = 5.99, P = .026). Our data also indicated that elevated serum haptoglobin levels were associated with poor outcome for overall survival using both univariate and multivariate analyses (P = .048 and P = .036 respectively). Using Pearson's correlation, we have noted that serum CRP concentrations significantly correlated with haptoglobin levels (r(2) = 0.22, P < .001). Immunohistochemical findings and Western blot analyses were compatible with sera levels of haptoglobin in which a higher intensity of staining occurred in late-stage epithelial ovarian cancers.

CONCLUSION

This study provides evidence that preoperative serum levels of haptoglobin could serve as an independent prognostic factor in patients presenting with epithelial ovarian cancer.

Gel electrophoresis of polyphenol oxidase with instant identification by in situ blotting

Polyphenol oxidase (PPO) or tyrosinase is an important and ubiquitous enzyme responsible for browning in plants and melanization in animals. The molecular size of the plant PPO is varied among the species and its activity can be enhanced by a variety of anionic detergents. In the present study, we developed a simple method for the first-step identification of PPO in fruit and vegetable extracts. First, 3mm chromatographic paper was immersed in 0.5% (w/v) catechol solution as an immobilized PPO substrate. After running the extract with 10% sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), one side of the glass plate was removed. The plate was immediately laid on top of the dried catechol-paper. A dark-brown band corresponding to PPO was visualized within 1 min and was further confirmed by a conventional Western blot using an antibody prepared against mushroom PPO. It also reveals that some vegetation (such as tomato, radish, and oriental melon) with low or no detectable activity in a conventional enzyme assay actually possessed marked levels of PPO activity when assessed by PAGE-blot. We propose that an inhibitor is associated with PPO in some plants; the inhibitor, however, is dissociated during the electrophoresis. Therefore, in addition to identify the molecular form of PPO, the present technique may explore the existence of PPO inhibitor(s) in plants. The detail of the method with respect to its relevance for searching a natural PPO inhibitor is described and discussed.