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

Identification of potential molecular mechanisms and small molecule drugs in myocardial ischemia/reperfusion injury

Myocardial ischemia/reperfusion (MI/R) injury is a complex phenomenon that causes severe damage to the myocardium. However, the potential molecular mechanisms of MI/R injury have not been fully clarified. We identified potential molecular mechanisms and therapeutic targets in MI/R injury through analysis of Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were found between MI/R injury and normal samples, and overlapping DEGs were found between GSE61592 and GSE67308. Gene Ontology (GO) and pathway analysis were performed for overlapping DEGs by Database for Annotation, Visualization and Integration Discovery (DAVID). Then, a network of protein-protein interaction (PPI) was constructed through the Search Tool for the Retrieval of Interacting Genes (STRING) database. Potential microRNAs (miRNAs) and therapeutic small molecules were screened out using microRNA.org database and the Comparative Toxicogenomics database (CTD), respectively. Finally, we identified 21 overlapping DEGs related to MI/R injury. These DEGs were significantly enriched in IL-17 signaling pathway, cytosolic DNA-sensing pathway, chemokine signaling, and cytokine-cytokine receptor interaction pathway. According to the degree in the PPI network, CCL2, LCN2, HP, CCL7, HMOX1, CCL4, and S100A8 were found to be hub genes. Furthermore, we identified potential miRNAs (miR-24-3p, miR-26b-5p, miR-2861, miR-217, miR-4251, and miR-124-3p) and therapeutic small molecules like ozone, troglitazone, rosiglitazone, and n-3 polyunsaturated fatty acids for MI/R injury. These results identified hub genes and potential small molecule drugs, which could contribute to the understanding of molecular mechanisms and treatment for MI/R injury.

Haptoglobin: From hemoglobin scavenging to human health

Haptoglobin (Hp) belongs to the family of acute-phase plasma proteins and represents the most important plasma detoxifier of hemoglobin (Hb). The basic Hp molecule is a tetrameric protein built by two α/β dimers. Each Hp α/β dimer is encoded by a single gene and is synthesized as a single polypeptide. Following post-translational protease-dependent cleavage of the Hp polypeptide, the α and β chains are linked by disulfide bridge(s) to generate the mature Hp protein. As human Hp gene is characterized by two common Hp1 and Hp2 alleles, three major genotypes can result (i.e., Hp1-1, Hp2-1, and Hp2-2). Hp regulates Hb clearance from circulation by the macrophage-specific receptor CD163, thus preventing Hb-mediated severe consequences for health. Indeed, the antioxidant and Hb binding properties of Hp as well as its ability to stimulate cells of the monocyte/macrophage lineage and to modulate the helper T-cell type 1 and type 2 balance significantly associate with a variety of pathogenic disorders (e.g., infectious diseases, diabetes, cardiovascular diseases, and cancer). Alternative functions of the variants Hp1 and Hp2 have been reported, particularly in the susceptibility and protection against infectious (e.g., pulmonary tuberculosis, HIV, and malaria) and non-infectious (e.g., diabetes, cardiovascular diseases and obesity) diseases. Both high and low levels of Hp are indicative of clinical conditions: Hp plasma levels increase during infections, inflammation, and various malignant diseases, and decrease during malnutrition, hemolysis, hepatic disease, allergic reactions, and seizure disorders. Of note, the Hp:Hb complexes display heme-based reactivity; in fact, they bind several ferrous and ferric ligands, including O₂, CO, and NO, and display (pseudo-)enzymatic properties (e.g., NO and peroxynitrite detoxification). Here, genetic, biochemical, biomedical, and biotechnological aspects of Hp are reviewed.

Association of Urine Haptoglobin With Risk of All-Cause and Cause-Specific Mortality in Individuals With Type 2 Diabetes: A Transethnic Collaborative Work

OBJECTIVE

Haptoglobin is an acute-phase reactant with pleiotropic functions. We aimed to study whether urine haptoglobin may predict risk of mortality in people with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We employed a transethnic approach with a cohort of Asian origin (Singapore) (N = 2,061) and a cohort of European origin (France) (N = 1,438) included in the study. We used survival analyses to study the association of urine haptoglobin with risk of all-cause and cause-specific mortality.

RESULTS

A total of 365 and 525 deaths were registered in the Singapore cohort (median follow-up 7.5 years [interquartile range 3.5-12.8]) and French SURDIAGENE cohort (median follow-up 6.8 years [interquartile range 4.3-10.5], respectively. Singapore participants with urine haptoglobin in quartiles 2 to 4 had higher risk for all-cause mortality compared with quartile 1 (unadjusted hazard ratio [HR] 1.47 [95% CI 1.02-2.11], 2.28 [1.62-3.21], and 4.64 [3.39-6.35], respectively). The association remained significant in quartile 4 after multiple adjustments (1.68 [1.15-2.45]). Similarly, participants in the French cohort with haptoglobin in quartile 4 had significantly higher hazards for all-cause mortality compared with quartile 1 (unadjusted HR 2.67 [2.09-3.42] and adjusted HR 1.49 [1.14-1.96]). In both cohorts, participants in quartile 4 had a higher risk of mortality attributable to cardiovascular disease and infection but not malignant tumor.

CONCLUSIONS

Urine haptoglobin predicts risk of mortality independent of traditional risk factors, suggesting that it may potentially be a novel biomarker for risk of mortality in patients with type 2 diabetes.

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.

Mendelian randomization analysis to assess a causal effect of haptoglobin on macroangiopathy in Chinese type 2 diabetes patients

Background

Haptoglobin (Hp) functions as an antioxidant by binding with haemoglobin. We investigated whether serum Hp has a causal effect on macroangiopathy via Mendelian randomization (MR) analysis with common variants of the Hp gene in Chinese patients with type 2 diabetes.

Methods

A total of 5687 type 2 diabetes patients were recruited and genotyped for the Hp gene. Clinical features and vascular imaging tests were applied to diagnose macroangiopathy. The association between common Hp genotypes and macroangiopathy was analyzed in the whole population. Serum Hp levels were measured by enzyme-linked immunosorbent assay in a subset of 935 patients. We individually analyzed the correlations among Hp levels, Hp genotypes and macroangiopathy. Further, 8-hydroxy-2′-deoxyguanosine (8-OHdG), an oxidative marker of DNA damage, was examined to evaluate the levels of oxidative stress.

Results

Common Hp genotypes were correlated with macroangiopathy (OR = 1.140 [95% CI 1.005–1.293], P = 0.0410 for the Hp 1 allele). Serum Hp levels were associated with both common Hp genotypes (P = 3.55 × 10⁻³¹) and macroangiopathy (OR = 2.123 [95% CI 1.098–4.102], P = 0.0252) in the subset of 935 patients. In the MR analysis, the directional trends of the observed and predicted relationships between common Hp genotypes and macroangiopathy were the same (OR 1.357 and 1.130, respectively). Furthermore, common Hp genotypes and Hp levels were associated with serum 8-OHdG levels (P = 0.0001 and 0.0084, respectively).

Conclusions

Our study provides evidence for a causal relationship between serum Hp levels and macroangiopathy in Chinese type 2 diabetes patients by MR analysis.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0662-7) contains supplementary material, which is available to authorized users.

Erythrocyte-heme proteins and STEMI: implications in prognosis

The role of erythrocytes in thrombus formation has been often neglected, but some studies have highlighted their active role in thrombotic events. Free-haemoglobin (Hb) has shown to induce oxidative-stress damage. Herein we have investigated the coordinated changes in heme-related proteins in patients with acute-coronary-syndromes (ACS), their association to ongoing thrombosis and their impact on patients' prognosis. The serum proteome of STEMI-patients (N=27) within the first 6h after event-onset and 3d after were compared to controls (N=60). Changes in heme-metabolism were characterized in a second STEMI-group by a dual proteomic approach analyzing in-vivo aspirated coronary thrombi at PCI (N=24) and the associated peripheral-blood changes (N=10). A third STEMI-group (N=132) was studied to analyze the impact of the observed changes in prognosis at 6-months-follow-up. The haptoglobin/hemopexin(Hpg/Hpx)-scavenging-system revealed a time-dependent response after STEMI with an early increase in Hpg circulating levels in the acute phase (P=0.01) and a late increase in Hpx levels 3d after (P=0.045). Beta-Hb content in coronary thrombi was directly correlated with systemic beta-Hb and Hpg (R=0.804,P=0.0029; R=0.859,P=0.0007) levels. The presence of a fully-occlusive thrombus was associated to higher circulating levels of beta-Hb (P=0.03) and unbound-Hpg (P=0.03). ELISA validation demonstrated a decreased survival rate at 6-months follow-up in STEMI-patients with lower Hpg plasma levels at admission (P=0.027). Our results show active Hb-release form erythrocytes in ACS. This release is followed by a systemic early increase in Hpg levels and a late increase in Hpx levels that can co-ordinately help to prevent systemic pro-oxidative effects. The Hb-scavenging ability of haptoglobin is related to patients' prognosis.