Haptoglobin genotype-dependent differences in macrophage lysosomal oxidative injury

Monocyte/Macrophage Heterogeneity during Skin Wound Healing in Mice

Monocytes (Mos)/macrophages (Mϕs) orchestrate biological processes critical for efficient skin wound healing. However, current understanding of skin wound Mo/Mϕ heterogeneity is limited by traditional experimental approaches such as flow cytometry and immunohistochemistry. Therefore, we sought to more fully explore Mo/Mϕ heterogeneity and associated state transitions during the course of excisional skin wound healing in mice using single-cell RNA sequencing. The live CD45+CD11b+Ly6G- cells were isolated from skin wounds of C57BL/6 mice on days 3, 6, and 10 postinjury and captured using the 10x Genomics Chromium platform. A total of 2813 high-quality cells were embedded into a uniform manifold approximation and projection space, and eight clusters of distinctive cell populations were identified. Cluster dissimilarity and differentially expressed gene analysis categorized those clusters into three groups: early-stage/proinflammatory, late-stage/prohealing, and Ag-presenting phenotypes. Signature gene and Gene Ontology analysis of each cluster provided clues about the different functions of the Mo/Mϕ subsets, including inflammation, chemotaxis, biosynthesis, angiogenesis, proliferation, and cell death. Quantitative PCR assays validated characteristics of early- versus late-stage Mos/Mϕs inferred from our single-cell RNA sequencing dataset. Additionally, cell trajectory analysis by pseudotime and RNA velocity and adoptive transfer experiments indicated state transitions between early- and late-state Mos/Mϕs as healing progressed. Finally, we show that the chemokine Ccl7, which was a signature gene for early-stage Mos/Mϕs, preferentially induced the accumulation of proinflammatory Ly6C+F4/80lo/- Mos/Mϕs in mouse skin wounds. In summary, our data demonstrate the complexity of Mo/Mϕ phenotypes, their dynamic behavior, and diverse functions during normal skin wound healing.

Single cell analysis of M. tuberculosis phenotype and macrophage lineages in the infected lung

In this study, we detail a novel approach that combines bacterial fitness fluorescent reporter strains with scRNA-seq to simultaneously acquire the host transcriptome, surface marker expression, and bacterial phenotype for each infected cell. This approach facilitates the dissection of the functional heterogeneity of M. tuberculosis-infected alveolar (AMs) and interstitial macrophages (IMs) in vivo. We identify clusters of pro-inflammatory AMs associated with stressed bacteria, in addition to three different populations of IMs with heterogeneous bacterial phenotypes. Finally, we show that the main macrophage populations in the lung are epigenetically constrained in their response to infection, while inter-species comparison reveals that most AMs subsets are conserved between mice and humans. This conceptual approach is readily transferable to other infectious disease agents with the potential for an increased understanding of the roles that different host cell populations play during the course of an infection.

Hemolysis Derived Products Toxicity and Endothelium: Model of the Second Hit

Vascular diseases are multifactorial, often requiring multiple challenges, or ‘hits’, for their initiation. Intra-vascular hemolysis illustrates well the multiple-hit theory where a first event lyses red blood cells, releasing hemolysis-derived products, in particular cell-free heme which is highly toxic for the endothelium. Physiologically, hemolysis derived-products are rapidly neutralized by numerous defense systems, including haptoglobin and hemopexin which scavenge hemoglobin and heme, respectively. Likewise, cellular defense mechanisms are involved, including heme-oxygenase 1 upregulation which metabolizes heme. However, in cases of intra-vascular hemolysis, those systems are overwhelmed. Heme exerts toxic effects by acting as a damage-associated molecular pattern and promoting, together with hemoglobin, nitric oxide scavenging and ROS production. In addition, it activates the complement and the coagulation systems. Together, these processes lead to endothelial cell injury which triggers pro-thrombotic and pro-inflammatory phenotypes. Moreover, among endothelial cells, glomerular ones display a particular susceptibility explained by a weaker capacity to counteract hemolysis injury. In this review, we illustrate the ‘multiple-hit’ theory through the example of intra-vascular hemolysis, with a particular focus on cell-free heme, and we advance hypotheses explaining the glomerular susceptibility observed in hemolytic diseases. Finally, we describe therapeutic options for reducing endothelial injury in hemolytic diseases.

Meta-analysis of the association of the haptoglobin genotype with cardiovascular outcomes and the pharmacogenomic interactions with vitamin E supplementation

Objectives

The objectives of the study were to compile and summarize the data from all of the clinical trials designed to examine the association between haptoglobin (Hp) genotype and incidence of cardiovascular (CV) events in patients with diabetes mellitus (DM) and to assess the impact of vitamin E treatment on CV outcomes according to the Hp genotype.

Background

The Hp genotype could serve as a predictive biomarker to DM patients who may benefit from vitamin E therapy.

Methods

The electronic databases MEDLINE, PubMed, EMBASE and the Cochrane Library for Central Register of Clinical Trials were searched systematically using the following MESH terms: "haptoglobin genotype", "diabetes mellitus" and "cardiovascular events".

Results

Overall, 13 studies fit the inclusion criteria for this analysis, yielding a large study population that included 6,161 patients without Hp 2-2 and 4,684 patients with Hp 2-2. The analysis of these studies showed that the incidence of CV events in DM patients with the Hp 2-2 genotype was significantly increased as compared to non-Hp 2-2 patients in all three subgroups of case-control (OR: 2.2, 95% CI: 1.3-3.6; P=0.003), cohort (OR: 1.3, 95% CI: 1.2-1.5; P=0.001) and randomized controlled trials (OR: 1.6, 1.2-2.2; P=0.005). Among patients with the Hp 2-2 genotype, administration of vitamin E was associated with lower rates of CV events (OR: 0.66, 95% CI: 0.45-0.95; P=0.025). Further investigation into the association between Hp 2-2 and myocardial infarction, stroke, mortality and end-stage renal disease was also performed.

Conclusion

The Hp genotype is a risk factor for CV events in patients with DM, and administration of vitamin E appears to offer a low cost and accessible means of reducing CV events and mortality in this population.

Haptoglobin Genotype Is a Determinant of Hemoglobin Adducts and Vitamin E Content in HDL

Haptoglobin (Hp) is an abundant hemoglobin- (Hb-) binding serum protein and a constituent of the HDL proteome. In man, there exists a common polymorphism at the Hp locus with two common alleles defined by the presence (Hp 2 allele) or absence (Hp 1 allele) of a 1.7 kb in-frame partial duplication of exons 3 and 4 of the Hp gene. Numerous studies have demonstrated that the Hp 2-2 genotype is associated with a 3-5-fold increase in vascular disease among individuals with diabetes mellitus (DM). Increased Hp-Hb complex has been shown to be associated with the HDL of Hp 2-2 DM individuals. Hb-associated HDL has been proposed to result in the oxidation of HDL and the consumption of antioxidants in HDL, such as vitamin E, rendering the HDL further susceptible to oxidation. In this study, we set out to identify proteins which become cross-linked to Hb in HDL and to measure vitamin E in HDL as a function of the Hp genotype. We report on the identification of a novel 72 kd Hb reactive species which is cross-linked to HDL and demonstrate that vitamin E in HDL is decreased in Hp 2-2 DM individuals.

Identification of a protein associated with the activity of cytokine-induced killer cells

Cytokine-induced killer cells (CIKs) adoptive immunotherapy for efficient antitumor ability is used clinically, but details regarding the proteins associated with CIK activity remain unclear. In the current study, the cytotoxicity of CIKs on hepatoma was identified to be significantly downregulated by 1.61-fold following gentamincin treatment. Further research revealed that a differentially expressed protein (P43) was significantly downregulated by 1.22-fold using one-dimensional gel electrophoresis analysis. Of these, the P43 was identified as human haptoglobin using liquid chromatography-mass spectrometry. Western blotting demonstrated that the haptoglobin specifically reacted with rabbit anti-human-haptoglobin. Furthermore, western blotting results verified that the haptoglobin was significantly downregulated by 1.17-fold compared with the control group. In addition, the expression of haptoglobin mRNA was significantly downregulated by 1.73-fold following gentamincin treatment. Taken together, the results of the present study demonstrated that the expression of haptoglobin protein was associated with the activity of CIKs, and the results will be beneficial to the further investigation of CIK activity-enhancement mechanism.

Haptoglobin 2-2 Phenotype Is Associated With Increased Acute Kidney Injury After Elective Cardiac Surgery in Patients With Diabetes Mellitus

BACKGROUND

Recent studies reported an association between the 2-2 phenotype of haptoglobin (Hp 2-2) and increased cardiorenal morbidity in nonsurgical diabetic patients. Our goal was to determine whether the Hp 2-2 phenotype was associated with acute kidney injury (AKI) after elective cardiac surgery in patients with diabetes mellitus.

METHODS AND RESULTS

We prospectively enrolled 99 diabetic patients requiring elective cardiac surgery with cardiopulmonary bypass. Haptoglobin phenotypes were determined by gel electrophoresis. Cell-free hemoglobin, haptoglobin, and total serum bilirubin were quantified as hemolysis markers. The primary outcome was postoperative AKI, as defined by the Acute Kidney Injury Network classification. The incidence of AKI was significantly higher in Hp 2-2 patients compared with patients without this phenotype (non-Hp-2-2; 55.6% versus 27%, P<0.01). The need for renal replacement therapy was also significantly higher in the Hp 2-2 group (5 patients versus 1 patient, P=0.02). Thirty-day mortality (3 versus 0 patients, P=0.04) and 1-year mortality (5 versus 0 patients, P<0.01) were also significantly higher in patients with the Hp 2-2 phenotype. In multivariable analysis, Hp 2-2 was an independent predictor of postoperative AKI (P=0.01; odds ratio: 4.17; 95% confidence interval, 1.35-12.48).

CONCLUSIONS

Hp 2-2 phenotype is an independent predictor of postoperative AKI and is associated with decreased short and long-term survival after cardiac surgery in patients with diabetes mellitus.

Hp: an inflammatory indicator in cardiovascular disease

Over the past decade significant advancement has occurred in the biological and pathological role that Hp has in cardiovascular disease. Hp is an acute-phase protein with a role in the neutralization and clearance of free heme. Iron has tremendous potential for initiating vascular oxidation, inflammation and exacerbating coronary atherosclerosis. Hp genotype has been linked as a prognostic biomarker of acute myocardial infarction, heart failure, restenosis and cardiac transplant rejection. The increased understanding of Hp as a biomarker has provided new insights into the mechanisms of inflammation after cardiac injury and support the concept that Hp is not only an important antioxidant in vascular inflammation and atherosclerosis, but also an enhancer of inflammation in cardiac transplant.

Pharmacogenomic interaction between the Haptoglobin genotype and vitamin E on atherosclerotic plaque progression and stability

OBJECTIVE

Homozygosity for a 1.7 kb intragenic duplication of the Haptoglobin (Hp) gene (Hp 2-2 genotype), present in 36% of the population, has been associated with a 2-3 fold increased incidence of atherothrombosis in individuals with Diabetes (DM) in 10 longitudinal studies compared to DM individuals not homozygous for this duplication (Hp 1-1/2-1). The increased CVD risk associated with the Hp 2-2 genotype has been shown to be prevented with vitamin E supplementation in man. We sought to determine if there was an interaction between the Hp genotype and vitamin E on atherosclerotic plaque growth and stability in a transgenic model of the Hp polymorphism.

METHODS AND RESULTS

Brachiocephalic artery atherosclerotic plaque volume was serially assessed by high resolution ultrasound in 28 Hp 1-1 and 26 Hp 2-2 mice in a C57Bl/6 ApoE(-/-) background. Hp 2-2 mice had more rapid plaque growth and an increased incidence of plaque hemorrhage and rupture. Vitamin E significantly reduced plaque growth in Hp 2-2 but not in Hp 1-1 mice with a significant pharmacogenomic interaction between the Hp genotype and vitamin E on plaque growth.

CONCLUSIONS

These results may help explain why vitamin E supplementation in man can prevent CVD in Hp 2-2 DM but not in non Hp 2-2 DM individuals.

Modeling hemoglobin and hemoglobin:haptoglobin complex clearance in a non-rodent species-pharmacokinetic and therapeutic implications

Background: Haptoglobin (Hp) prevents hemoglobin (Hb) extravasation and attenuates Hb induced tissue oxidation and vasoconstriction. Small animal models such as mouse, rat and guinea pig appear to demonstrate proof-of-concept for Hb neutralization by Hp in diverse pre-clinical conditions. However, these species differ significantly from humans in the clearance of Hb:Hp and demonstrate long persistence of circulating Hb:Hp complexes.

Objective: The focus of this study is to understand Hb:Hp clearance in a non-rodent species. In contrast to rodents, dogs maintain high plasma Hp concentrations comparable to humans and demonstrate more rapid clearance of Hb:Hp when compared to rodent species, therefore dogs may represent a relevant species to evaluate Hb:Hp pharmacokinetics and cellular clearance.

Results: In this study we show, that like human macrophages, dog peripheral blood monocyte derived macrophages express a glucocorticoid inducible endocytic clearance pathways with a high specificity for the Hb:Hp complex. Evaluating the Beagle dog as a non-rodent model species we provide the first pharmacokinetic parameter estimates of free Hb and Hb:Hp complexes. The data demonstrate a significantly reduced volume of distribution (Vc) for Hb:Hp compared to free Hb, increased maximum plasma concentrations and areas under plasma concentration time curves (Cmax and AUC). Significantly reduced total body clearance (CL) and a longer terminal half-life (t_1/2) of approximately 12 h were also observed for the Hb:Hp complex. Distribution and clearance were identical for dimeric and multimeric Hb:Hp complexes. We found no significant effect of a high-dose glucocorticoid treatment protocol on Hb:Hp pharmacokinetic parameter estimates.

Conclusion: Collectively, our study supports the dog as a non-rodent animal model to study pharmacological and pharmacokinetic aspects of Hb clearance systems and apply the model to studying Hp as a therapeutic in diseases of hemolysis.