Correlation of geographic distributions of haptoglobin alleles with prevalence of multiple sclerosis (MS) - a narrative literature review

Mild Systemic Inflammation Increases Erythrocyte Fragility

There is growing evidence that inflammation impairs erythrocyte structure and function. We assessed the impact of mild systemic inflammation on erythrocyte fragility in three different settings. In order to investigate causation, erythrocyte osmotic fragility was measured in mice challenged with a live attenuated bacterial strain to induce low-grade systemic inflammation; a significant increase in erythrocyte osmotic fragility was observed. To gather evidence that systemic inflammation is associated with erythrocyte fragility in humans, two observational studies were conducted. First, using a retrospective study design, the relationship between reticulocyte-based surrogate markers of haemolysis and high-sensitivity C-reactive protein was investigated in 9292 healthy participants of the UK Biobank project. Secondly, we prospectively assessed the relationship between systemic inflammation (measured by the urinary neopterin/creatinine ratio) and erythrocyte osmotic fragility in a mixed population (n = 54) of healthy volunteers and individuals with long-term medical conditions. Both human studies were in keeping with a relationship between inflammation and erythrocyte fragility. Taken together, we conclude that mild systemic inflammation increases erythrocyte fragility and may contribute to haemolysis. Further research is needed to assess the molecular underpinnings of this pathway and the clinical implications in inflammatory conditions.

Relation between haptoglobin polymorphism and oxidative stress status, lipid profile, and cardiovascular risk in sickle cell anemia patients

OBJECTIVE

The haptoglobin (Hp) gene located on chromosome 16q22 exhibits a polymorphism that can impact its capacity to inhibit the deleterious oxidative activity of free hemoglobin. We aimed to determine the influence of Hp polymorphism on oxidative stress, lipid profile, and cardiovascular risk in Cameroonian sickle cell anemia patients (SCA patients).

METHOD

The Hp genotypes of 102 SCA patients (SS), 60 healthy individuals (AA), and 55 subjects with sickle cell trait (AS) were determined by allele-specific PCR, and the blood parameters were assessed using standard methods.

RESULTS

Hp2-2 genotype was significantly (P < .05) present in SS (54%) than in AS (42%) and AA (38%). Levels of catalase and cell reactive protein were higher, while levels of total antioxidant capacity, triglycerides, low-density lipoprotein cholestetol, blood pressure, Framingham score, and body mass index were lower in the SCA patients. These parameters appeared to be unrelated to the haptoglobin genotypes. SCA patients with Hp1-1 genotype presented a higher oxidative stress index (0.53 ± 0.31) than those with Hp2-1 (0.33 ± 0.18). Lipid profile and cardiovascular risk were not significantly different between various Hp genotypes in SCA patients.

CONCLUSION

Haptoglobin polymorphism did not affect lipid profile, cardiovascular risk, and oxidative stress status of SCA patients. Nevertheless, SCA patients with Hp1-1 genotype tended to be more prone to oxidative stress than those with Hp2-1.

Haptoglobin Gene Polymorphism among Sickle Cell Patients in West Cameroon: Hematological and Clinical Implications

Haptoglobin is a protein involved in protecting the body from the harmful effects of free hemoglobin. The haptoglobin gene exhibits a polymorphism, and the different genotypes do not have the same capacity to combat the free hemoglobin effects. The present study aimed at determining the polymorphic distribution of haptoglobin in sickle cell patients (SCPs) from West Cameroon and their impact on the hematological parameters, as well as clinical manifestations of the disease severity. Haptoglobin genotype of 102 SCPs (SS) and 115 healthy individuals (60 AA and 55 AS) was determined by allele-specific polymerase chain reaction, and the complete blood count was determined using the AutoAnalyser. Results showed that the genotype Hp2-2 was significantly (p < 0.05) represented in SS patients (54%) than in controls AA and AS (27% and 29%, respectively), while Hp2-1 was mostly found (p < 0.05) in AS (42%) and AA (38%), against 15% in SS. The allelic distribution in SS patients was Hp²: 0.613, Hp^1S: 0.304, and Hp^1F: 0.084. In AA and AS controls, the proportions of the Hp¹ and Hp² alleles were similar (around 0.5 each), with 0.282 for Hp^1S and 0.218 for Hp^1F in AS and 0.283 for Hp^1S and 0.258 for Hp^1F in AA. The distribution of the haptoglobin genotypes did not reveal any significant difference across hematological parameters and clinical manifestations of disease severity in SCP and controls. SCP with Hp1S-1F genotype presented the highest level of hemoglobin. Although Hp2-2 was more frequent in SS patients, it appeared not to be related to the hematological parameters and to the disease's severity. Further investigations are necessary to explore the impact of Hp polymorphism such as antioxidant, lipid profile, and functionality of some tissues in SCP in Cameroon.

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.

The protean role of haptoglobin and haptoglobin genotypes on vascular complications in diabetes mellitus

Introduction and background Haptoglobin (Hp) is considered to be an antioxidant and protective against cardiovascular complications. Polymorphisms in the Hp gene interact with diabetes mellitus to affect the risk of vascular complications. Methods We review the updated literature about the protean role of Hp and Hp genotypes spanning genomics, molecular, translational and clinical studies. We searched Pubmed, SCOPUS and Google Scholar for all articles using the keywords: haptoglobin and/or haptoglobin polymorphism and diabetes. We review the diverse Hp genotypes, phenotypes and the impact on diabetes complications, including lessons from animal models and in vitro models. We describe the clinical studies on the associations of Hp genotypes with vascular complications in type 1 and type 2 diabetes comprehensively. We review the studies looking at vitamin E supplementation in a personalized manner in Hp2-2 diabetes individuals. Results and conclusion Hp genotypes have evolved as a result of deletions in the traditional Hp genes. The Hp genotypes have been associated with microvascular and macrovascular complications in type 1 diabetes mellitus but the association in type 2 diabetes is more consistent with cardiovascular complications. A preferential benefit of vitamin E and other antioxidants in the Hp2-2 genotype for cardiovascular complications in type 2 diabetes has been seen presumably secondary to interaction with high-density lipoprotein function. Hence, the Hp genotype can be used to personalize antioxidant therapeutics in diabetes patients. These results need to be corroborated in large, global, pragmatic, prospective, cardiovascular outcome trials in type 2 diabetes patients.

Haptoglobin Phenotype Among Arab Patients With Mental Disorders

BACKGROUND

Depression, schizophrenia and panic disorder are common mental disorders in the community and hospitalized patients. These mental disorders negatively affect life quality and even expectancy of life. Haptoglobin (Hp) phenotype (Hp 1-1, 1-2, or 2-2) is associated with risk for cardiovascular diseases, but its association with psychiatric disorders, a growing concern in the modern society, has not been studied thoroughly. The aim of the study was to examine whether Hp phenotype is associated with common mental disorders such as depression, schizophrenia, and panic disorder.

METHODS

The study included 92 Arab patients with mental disorders, and among them 44 suffered from schizophrenia (mean age 39 ± 1.5 years), 17 from depression (mean age 44.5 ± 3.1 years), 31 from panic disorder (mean age of 44.9 ± 2.7 years), and 206 healthy Arab control subjects with a mean age of 42.6 ± 0.9 years. Beck's depression inventory assessment and Hamilton depression scale were administered for depression and panic disorder diagnosis. Schizophrenia was evaluated with positive and negative affect schedule (Panas) test. All mental disorders were evaluated by clinical review. Blood analysis for Hp phenotype was performed. Diagnosis was made using the Diagnostic and Statistical Manual of Mental Disorders axis to correlate depression with Hp phenotype.

RESULTS

In mentally healthy controls, 10.7% were Hp 1-1, 38.8% Hp 2-1, and 50.5% Hp 2-2. In patients with the studied psychiatric disorders, Hp phenotype was comparable to healthy subjects; 8.7% were Hp 1-1, 50% Hp 2-1, and 41.3% Hp 2-2. When Hp phenotyping was analyzed in the psychiatric subgroups, Hp 2-1 was more common among depressed and schizophrenic patients, as compared with healthy subjects (58.8% and 52.3% vs. 38.8%). In patients who suffer from panic disorder, Hp phenotype distribution was 6.5% Hp 1-1, 41.9% Hp 2-1, and 51.6% Hp 2-2, suggesting a lower prevalence among Hp 1-1 phenotype.

CONCLUSIONS

Arab patients who carry Hp 2-1 phenotype may be at risk to develop depression or schizophrenia more than the general healthy population. In contrast, Hp 1-1 subjects have a lower prevalence of panic disorder.

Potential role of ferric hemoglobin in MS pathogenesis: Effects of oxidative stress and extracellular methemoglobin or its degradation products on myelin components

There is a well-documented relationship between cerebral vasculature and multiple sclerosis (MS) lesions: abnormal accumulations of iron have been found in the walls of the dilated veins in cerebral MS plaques. The source of this iron is unknown, but could be related to the recognized phenomenon of capillary and venous hemorrhages leading to blood extravasation. In turn, hemorrhaging leading to hemolysis results in extracellular release of hemoglobin, a reactive molecule that could induce local oxidative stress, inflammation, and tissue damage. Our previous studies with a reduced form of hemoglobin (oxyHb) have demonstrated its ability to cause extensive lipid and protein oxidation in vitro, which would result in membrane destabilization. Here, we investigated in further detail the mechanism by which the more abundant oxidized form of extracellular hemoglobin (metHb), and dissociated hemin, cause direct oxidative damage to myelin components, specifically membrane-mimetic lipid vesicles and myelin basic protein (MBP), a highly-abundant protein in the CNS. Oxidation of lipids was assessed by the formation of conjugated diene/triene and malondialdehyde, and oxidation of MBP was demonstrated by the bityrosine formation and by the change in protein mass. Our results show that metHb causes oxidative damage to MBP and myelin lipids, partly by transferring its hemin moiety to protein and lipid, but mostly as an intact protein possibly via formation of a ferryl radical. These results elucidating the mechanism of extracellular hemoglobin-induced oxidative damage to myelin components support the need for further research into vascular pathology in MS pathogenesis, to gain insight into the role of iron deposits and/or in stimulation of different comorbidities associated with the disease.

Free serum haemoglobin is associated with brain atrophy in secondary progressive multiple sclerosis

Background A major cause of disability in secondary progressive multiple sclerosis (SPMS) is progressive brain atrophy, whose pathogenesis is not fully understood. The objective of this study was to identify protein biomarkers of brain atrophy in SPMS. Methods We used surface-enhanced laser desorption-ionization time-of-flight mass spectrometry to carry out an unbiased search for serum proteins whose concentration correlated with the rate of brain atrophy, measured by serial MRI scans over a 2-year period in a well-characterized cohort of 140 patients with SPMS. Protein species were identified by liquid chromatography-electrospray ionization tandem mass spectrometry. Results There was a significant (p<0.004) correlation between the rate of brain atrophy and a rise in the concentration of proteins at 15.1 kDa and 15.9 kDa in the serum. Tandem mass spectrometry identified these proteins as alpha-haemoglobin and beta-haemoglobin, respectively.  The abnormal concentration of free serum haemoglobin was confirmed by ELISA (p<0.001). The serum lactate dehydrogenase activity was also highly significantly raised (p<10^-12) in patients with secondary progressive multiple sclerosis. Conclusions An underlying low-grade chronic intravascular haemolysis is a potential source of the iron whose deposition along blood vessels in multiple sclerosis plaques contributes to the neurodegeneration and consequent brain atrophy seen in progressive disease. Chelators of free serum iron will be ineffective in preventing this neurodegeneration, because the iron (Fe²⁺) is chelated by haemoglobin.

Free serum haemoglobin is associated with brain atrophy in secondary progressive multiple sclerosis

Background A major cause of disability in secondary progressive multiple sclerosis (SPMS) is progressive brain atrophy, whose pathogenesis is not fully understood. The objective of this study was to identify protein biomarkers of brain atrophy in SPMS. Methods We used surface-enhanced laser desorption-ionization time-of-flight mass spectrometry to carry out an unbiased search for serum proteins whose concentration correlated with the rate of brain atrophy, measured by serial MRI scans over a 2-year period in a well-characterized cohort of 140 patients with SPMS. Protein species were identified by liquid chromatography-electrospray ionization tandem mass spectrometry. Results There was a significant (p<0.004) correlation between the rate of brain atrophy and a rise in the concentration of proteins at 15.1 kDa and 15.9 kDa in the serum. Tandem mass spectrometry identified these proteins as alpha-haemoglobin and beta-haemoglobin, respectively.  The abnormal concentration of free serum haemoglobin was confirmed by ELISA (p<0.001). The serum lactate dehydrogenase activity was also highly significantly raised (p<10^-12) in patients with secondary progressive multiple sclerosis. Conclusions An underlying low-grade chronic intravascular haemolysis is a potential source of the iron whose deposition along blood vessels in multiple sclerosis plaques contributes to the neurodegeneration and consequent brain atrophy seen in progressive disease. Chelators of free serum iron will be ineffective in preventing this neurodegeneration, because the iron (Fe²⁺) is chelated by haemoglobin.